Private

FS 3.206

The Future of Mountain Forests

Details

Full Title
FS 3.206: The Future of Mountain Forests
Scheduled
TBA
Location
TBA
Convener
Michael Bahn
Co-Conveners
Stefan Mayr, Ursula Peintner, Rupert Seidl,
Assigned to Synthesis Workshop
---
Thematic Focus
Ecosystems, ES-Forests
Keywords
Forest, Extreme Climatic Events, Drought, Fire

Description

Mountains play an essential role in global biogeochemical cycles, are extraordinarily rich in biological and socio-cultural diversity and fulfil many ecological and socio-economic functions. Climatic changes, which are especially pronounced in mountain regions, are expected to affect mountain forests particularly strongly through extreme climatic events, such as droughts, heatwaves and storms. Extreme climatic events may threaten the vitality of mountain forests and their protective functions and interrelate with further risks, such as forest fires. This session aims at analysing if and how more extreme climatic conditions, and in particular drought, influence the carbon and water balances of trees and forests, change plant stress responses and interactions with microbial communities, and affect ecosystem services. It will especially consider tree growth and water relations, phloem physiology, stress responses, plant-microbe and plant-animal interactions, forest fire, forest carbon cycling, biogenic volatile organic compounds, forest ecosystem services and related topics.

Submitted Abstracts

ID: 3.7759

Uniting Communities to Combat Forest Fire: Awareness, Action, and Prevention around Kedarnath Wildlife Sanctuary, Uttarakhand, Western Himalaya, India

Barkha Bisht
Uniyal, VP; Naithani, Pratibha

Abstract/Description

The increasing frequency and intensity of forest fires, primarily driven by human activities, pose significant threats to ecosystems, communities, and economies worldwide. In India, however, there is still a limited understanding of the causes, extent, and ecological impacts of forest fires. The Himalayan states, particularly Uttarakhand, experience a higher number of fire incidents due to the dominance of pine forests. The recorded incidents rose sharply from 5,351 in 2022–23 to 21,033 in 2023–24 (FSI, 2024). Pine forests, which are highly susceptible to fires due to resin tapping, cover vast areas of the temperate forests in Uttarakhand’s mountainous regions. Additionally, sub-alpine and alpine bushlands are increasingly affected by fires due to human interference. A study assessing the impact of forest fires on biodiversity and community health has been conducted across 20 villages in the Kedarnath Wildlife Sanctuary (KWLS), a biodiversity hotspot known for its rich variety of endangered and endemic flora and fauna. The study examines fire-related effects on vegetation regeneration, biodiversity monitoring, soil properties, and tree mortality, offering crucial insights into the ecological consequences of fire disturbances. Moreover, the study underscores the multidisciplinary nature of forest fire research, integrating ecological, social, and management perspectives to develop a comprehensive understanding of the issue. Given that human activities are a major cause of ignition; community involvement is essential for effective forest fire management. As the first responders, local communities play a pivotal role in both prevention and suppression efforts. The findings highlight the importance of community-based forest fire management, which actively engages local populations in fire prevention, monitoring, and response initiatives. Ultimately, the study emphasizes the urgent need for sustainable forest management practices, prioritizing protective strategies to mitigate the negative impacts of forest fires and enhance long-term ecosystem resilience in Uttarakhand and the western Himalaya.

ID: 3.8259

Phylogenetic Relationship of Ganoderma species in Mezam Division of the Northwest Region, Cameroon

Bih Ndeh Joan

Abstract/Description

Ganoderma P. Karst. is a pathogen responsible for root and stem rot in trees, eventually leading to their death and questioning the future of mountain ecosystems. Due to the morphological resemblance of different species, it is necessary to understand the phylogenetic relationship between Ganoderma species to better conserve them. This research aims to determine the Phylogenetic relationship of Ganoderma species in Mezam Division, Northwest Region, Cameroon. Opportunistic sampling was used to collect samples from nine villages in the region. The sorbitol-CTAB method was used to extract DNA from the ITS and TEF gene regions. The ITS and TEF gene regions were amplified using ITS1, 5.8S, and ITS4 and TEF1-α primers. Their identities were determined in GenBank using BLAST, and a phylogenetic analysis was performed using MEGA version 11. The study identified nine and two distinct Ganoderma species from the ITS and TEF gene regions. This includes Ganoderma applanatum, G. australe, G. brownii, G. cupreum, G. gibbosum, G. lucidum, G. multipileum, G. multiplicatum, and G. weberianum from its ITS gene region, and G. multiplicatum, and G. weberianum from its TEF gene region. G. australe, G. cupreum, G. lucidum, G. multiplicatum, and G. weberianum have been previously described from Cameroon, while G. multipileum, G. applanatum, G. brownii, and G. gibbosum are new records. Ten clades were obtained from the ITS gene regions, and nine from the TEF gene were obtained compared to those from the GenBank. The collected specimens significantly clustered together and formed a monophyletic group with other Ganoderma taxon, including the holotype, with solid support from ML values, implying that they have self-derived characters and that the Mezam division is diverse in terms of Ganoderma species.

ID: 3.8734

Wood formation dynamics in coexisting Scots pine (Pinus sylvestris L.) and juniper (Juniperus communis L.) of different vitality classes

Marion Fink
Ganthaler, Andrea; Kofler, Werner; Gruber, Andreas; Oberhuber, Walter

Abstract/Description

Global warming has a significant impact on the vitality and resilience of mountain forests, with trees showing reduced vitality in response to prolonged heatwaves and decreased soil water availability. This decline in vitality increases the risk of pathogen infestations and recurrent episodes of heat and drought have already led to a higher incidence of tree mortality. Two primary physiological mechanisms that contribute to tree mortality are persistent carbon deficiency and hydraulic failure. The phloem, which is hydraulically connected to the xylem in higher plants, plays critical roles in carbon allocation, signal transduction, and pathogen defense. When phloem formation is impaired, these essential processes are disrupted, leading to reversible or permanent inactivity of the cambium. Consequently, tree vitality declines, increasing the risk of mortality. The objective of this study is to examine the growth dynamics associated with tree vitality in the xylem, and cambium of Scots pine (Pinus sylvestris) and juniper (Juniperus communis) at a dry-mesic site on the Mieminger Plateau (980 m a.s.l., Tyrol, Austria). The study area is characterized by shallow soils with low water holding capacity, which provides ideal conditions for observing trees subjected to recurrent heat and drought episodes. Histological analyses of the xylem formation throughout the growing season offer a high-resolution perspective on cell differentiation. The present study contributes to our understanding of the different sensitivity of radial stem growth in coexisting tree and shrub species under drought, which enables the formulation of future dieback rates, and hence stand development.

ID: 3.8768

Drought effects on alpine conifers: a xylogenetic approach

Tamara Bibbò
Obojes, Nikolaus; Fonti, Patrick

Abstract/Description

Drought is increasingly impacting forests, even in mountainous regions. The Matsch valley, one of the driest areas in South-Tirol, may serve as a model for future conditions in broader Alpine regions. Xylogenetic analysis can assess the precise impact of climate on wood formation. This study aims to understand the relationship between xylem formation and environmental factors to predict the effect of climate change on tree growth. To this end, we sampled four plots along an elevation transect, including four species and 40 trees in total: 20 Larix decidua Mill., 10 Pinus cembra L., 5 Pinus nigra Arnold, and 5 Picea abies L. .These were distributed as follow: 1070 (F1, low elevation), 1715 (F2, mid- elevation), 2100 (F5, high elevation) and 2250 (FL, forest line) meters during the 2023 and 2024 growing seasons. Based on temperature alone, we would expect growing season length – defined as the difference between the start of the enlarging phase and the end of the secondary cell wall thickening-to decrease with increasing elevation. However, lower elevations may experience drought-induced premature growth cessation. We also expected deciduous larch begin growing later than the evergreen spruce or pines as it must first leaf out before growth. Preliminary results from 2023 support these hypotheses. At F1 and F5, larches exhibited a 135-day growing season, though their start and end dates differed by 20 days. Surprisingly, at F2 – where growth was expected to continue longer than at F5 and FL-the growing season ended earlier, suggesting that drought impacts extend up to 1700 m. As expected, the shortest growing season was observed at FL, mainly due to a delayed start of cell enlargement. Pines initiated growth earlier than larches at all sites. However, in F2,the onset difference between larch and spruce was only two days. Black pine has the longest growing season, while Swiss stone pine at FL had the shortest. Across all sites, the start of the growing season showed less variability than its end. To validate these preliminary findings, we conducted a second xylogenesis campaign in 2024 and we will correlate our results with dendrometers, sap flow and wood anatomy data.

ID: 3.8864

Physiological plasticity of green alder (Alnus alnobetula) under experimental drought stress

Andreas Gruber
Diester, Lieselotte; Thiede, Johanna; Wieser, Gerhard; Oberhuber, Walter

Abstract/Description

In the last decades, green alder (Alnus alnobetula (Ehrh.) K. Koch) has spread rapidly across the Alps. Once restricted to north-facing slopes, with high water availability, it is now expanding even into sites with impaired water availability. Observed leaf wilting following an extended drought period on a dry-mesic site at treeline, raised the question, whether the invasive species can adapt to dry conditions or if frequent drought events could limit the species’ expansion. To answer that question, we exposed three-year-old green alder saplings to two experimental drought phases and analyzed the effects on transpiration, photochemical yield and plant vigor. After 8 days of experimental drought transpiration of the plants had come to halt. Maximum photochemical yield (Fv/Fm) was not affected for 10 days, after which it rapidly declined to values near 0.1. After 15 days of drought more than 70 % of the leaves had wilted, but only 10 days after re-irrigation new leaves were sprouting, in the end replacing about 20% of the losses. Both transpiration and Fv/Fm recovered within seven days after re-irrigation, but transpiration values remained significantly below the control level for almost two months, indicating an adaptation or a legacy-effect of drought. Subsequent to the recovery to normal levels of transpiration, the plants were subjected to a second drought period. Drought stress continuously reduced transpiration, until it ceased 14 days after the onset of the drought. Fv/Fm was not affected for 12 days and afterwards did not fall to values lower than 0.7, indicating an adaptation to dry conditions. After 28 days of drought, most of the leaves had wilted and the experiment was terminated. A quarter of the plants measured showed no vital signs by early October, while the rest sprouted at least a few leaves despite the late season. Green alder has shown amazing resprouting vitality even after prolonged drought stress. However, in a warming climate, recurring drought events could delay or halt the spread of the species in exposed areas.

ID: 3.9043

The role of bark insulation for trees in a more fire-prone future

Andreas Bär
Schwarz, Massimiliano; Mayr, Stefan

Abstract/Description

Climate-driven increases in frequencies and intensities of wild fires will affect even relatively humid regions such as the Austrian Central Alps. Higher temperatures in combination with snow-poor winters, lightning activity and more pronounced dry periods favor an increased occurrence of forest fires. During low- to moderate-intensity fires, the resistance of trees is mainly determined by the insulation of their bark, which protects the cambium from lethal temperatures. However, knowledge about fire resistance and bark heat insulation of tree species in Alpine ecosystems is scarce.
We tested the bark insulation of 10 forest tree species in the laboratory by measuring temperature gradients along heat-exposed bark samples. By linking heat transfer parameters, lethal exposure times and bark traits, we were able to demonstrate a strong relationship between bark thickness and cambial temperature responses. Depending on species, also traits like bark density, bark-to-phloem ratio and moisture content considerably contributed to the bark insulation. We further used the obtained dataset to construct cambium mortality models. By integrating species-specific bark traits and allometry data into a semi-infinite solid conduction model, the exposure time necessary for a lethal dose of heat flux to the cambium under different flame temperature scenarios was calculated.
Thick-barked coniferous species like Pinus sylvestris and Larix decidua were found to have the highest capability to prevent critical cambium temperatures from being reached. Mature trees are able to withstand flame temperatures of up to 500 °C for at least 20 minutes. In contrast, it only takes a few minutes of heat exposure until the cambium is killed in thin-barked species such as Picea abies and Fagus sylvatica.
Exact knowledge of the species-specific bark insulation is important to assess the fire resistance of Alpine trees and to enable fire sensitivity assessment in areas of high fire hazards. Implementing cambium mortality models will further help practitioners to better estimate post-fire mortality of injured trees and to improve forest management strategies on fire sites.

ID: 3.9606

Current and future mountain forest ecosystem services under climate change

Laura Barraclough

Abstract/Description

Mountain forests are sharp ecotones characterised by climatic extremes in both temperature and precipitation that play a vital role in human communities both locally and across wider spatial scales through supply of ecosystem services. However, modern anthropogenic climate and environmental change is inducing rapid, complex shifts in mountain forest ecosystems. To break down and understand this complexity, we use the social-ecological system concept which considers the interplay between human and natural systems.
In this study, we aimed to capture dialogue, interactions and collaborations between stakeholders to explore current and future status of ecosystem services in mountain forests in response to changing climate and land management. To achieve this, we hosted an expert stakeholder workshop where we discussed current perceptions and future expectations of forest ecosystem services. The attendees of this event where a heterogenous group of experts from different parts of this system in Tirol, Austria.
Within the workshop and the follow-up survey, stakeholders identified and indicated the relative importance of ecosystem services, as well as their synergies and trade-offs. We used grounded theory methods to analyse workshop audio and written outputs. From our findings, we derived a conceptual model for adaptive pathways based on empirical data, as well as exploring opportunities and tipping points for mountain forest ecosystem service change. This research looks to build stakeholder knowledge and decision making into how future mountain forests will be used and managed.

ID: 3.9952

Responses of montane conifers to drought stress: unravelling metabolic pathways of adaptation

Moritz Stegner
de Vries, Anna; Schmack, Judith; Spielmann, Felix; Wohlfahrt, Georg; Jud, Werner; Karl, Thomas; Schnitzler, Jörg-Peter; Winkler, Barbro; Arc, Erwann; Roach, Thomas; Kranner, Ilse

Abstract/Description

Forest dieback due to increasingly frequent extreme climatic events, including droughts, poses a threat to ecosystem services provided by mountain forests. Yet, which biochemical pathways confer drought resilience or sensitivity in montane conifers is not fully understood. We analysed needles from 3-year-old Pinus sylvestris and Juniperus communis plants under a controlled, drought gradient, using untargeted GC-MS-based metabolite profiling, and targeted LC-MS/MS and HPLC analyses of hormones, antioxidants and lipid peroxidation products. In both species, indole-3-acetic acid (IAA), abscisic acid (ABA) and glutathione (GSH) increased with drought intensity, peaking at moderate drought in pine, but not until severe drought in juniper. Increasing drought severity was accompanied by increased glutathione disulphide (GSSG) concentrations in both species, and a decrease in GSH:GSSG ratio in pine. Lipid peroxidation markers, including trans-2-hexenal and 4-hydroxyhexenal, peaked under moderate drought in pine but accumulated progressively in juniper up to severe drought. Drought induced a steady increase in osmoregulatory sugars and proline in juniper, whereas pine predominantly accumulated amino acids, including serine, leucine and gamma-aminobutyric acid. In addition, drought induced species-specific responses in organic acids linked to the TCA cycle. Under severe drought, citrate and aconitic acid decreased, whereas fumarate and malic acid accumulated in juniper, while no significant changes occurred in pine. Our analysis reveals distinct species-specific metabolic responses to drought intensity, highlighting the complex biochemical mechanisms that may underlie differential resilience to water scarcity in montane conifers. Further effects of drought on primary metabolites and their downstream consequences for tree health are discussed.

ID: 3.10720

The impact of drought on carbonyl sulfide and CO2 fluxes in P. sylvestris and J. communis

Anna De Vries
Spielmann, Felix; Wohlfahrt, Georg; Schmack, Judith; Jud, Werner; Karl, Thomas; Schnitzler, Jörg-Peter; Winkler, Jana Barbro

Abstract/Description

Gross primary productivity (GPP) is a key driver of the current net land carbon sink. However, climate change—along with the increasing frequency of extreme events—may significantly alter GPP, particularly in mountain regions, which are very vulnerable to extreme events like drought. Understanding how the GPP responds to droughts in mountain regions is therefore crucial. Since GPP cannot be measured directly, it must be inferred via proxies or modelling, introducing substantial uncertainties, which limit the ability to predict GPP responses to climate change driven stressors such as drought. A promising proxy of GPP are measurements of carbonyl sulfide (COS) fluxes, as COS is taken up by plants in parallel to CO2 but in contrast to the latter generally not emitted. In this study, we measured COS and CO₂ fluxes of two woody mountain species, Pinus sylvestris and Juniperus communis, under controlled and varying drought conditions (soil water content ranging from 40 % to 2 %). As water stress intensified, the uptake of both COS and CO₂ declined due to reductions in stomatal conductance. These flux responses to drought were of greater magnitude in P. sylvestris than in J. communis. Interestingly, diurnal variations in GPP and autotrophic respiration were more pronounced in semi-stressed plants, which regulated stomatal conductance and closure following an optimality principle, compared to heavily stressed or control groups. The CO₂ uptake velocity decreased more rapidly than COS uptake under increasing stress in both species due to the increasing biochemical limitations of photosynthesis. The main driver of the diurnal cycle of the COS and CO2 exchange was PAR in both species and all stress levels but with increasing light saturation points as drought intensified. Daily means were mostly driven by the water availability. This study provides valuable insights into how mountain species respond to drought stress, improving our understanding of GPP dynamics under extreme conditions, essential for refining carbon cycle models and improving predictions on the impacts of climate change on terrestrial carbon sinks.

ID: 3.10753

Seed germination and seedling establishment in Alpine conifers following a prescribed fire

Zhiyi Chen
Neurauter, Markus; Stegner, Moritz; Peintner, Ursula; Kranner, Ilse; Mayr, Stefan

Abstract/Description

Wildfires, which occur more frequently due to climate change, affect mountain forests, their rejuvenation and afforestation. In this study, we investigated seed germination and seedling establishment of Alpine conifers after a prescribed fire. We hypothesized that fire and post-fire conditions would hinder seedling establishment, particularly in the immediate aftermath of the fire.

Seeds of Picea abies, Pinus cembra, and Larix decidua were sown every ten days over seven weeks in two 3.8 m² plots near the treeline (Praxmar, Tyrol, 1,600 m a.s.l.). One plot remained unburned (control), while in the second plot, the litter was ignited for a prescribed fire. Environmental conditions (air and soil temperature, heat flux, relative humidity, and soil properties) were monitored during and after fire. Seed germination and seedling establishment were assessed over 15 weeks. During the fire (duration 6 min), air temperature reached 650 °C, while soil temperature close to the seeds peaked at 72°C.

Total germination of fire-exposed P. cembra seeds, tested under controlled laboratory conditions, declined to 38.5% (no fire-exposed seeds: 74.0%), whereas P. abies and L. decidua seeds remained slightly affected (decreased from 78.5% to 63.5% and from 74.5% to 74.0%, respectively). However, in the burned plot, fire-exposed P. cembra achieved 15.3% seedling establishment, while no L. decidua and P. abies established by then. P. cembra seeds sown immediately after the fire established up to 29.3% (control plot: 52.0%). Seedling establishment of P. abies and L. decidua sown after the fire was poor in the first post-fire weeks, but reached 14.0% and 4.7% by week 7 (control plot: 23.3% and 7.3%).

The lower establishment in the burned versus control plot was likely due to high soil temperatures (up to 65°C) and increased ion content, leading to lower soil osmotic potential. The relatively high establishment success of P. cembra was probably related to its massive seeds with rich endosperm and thick seed coat, which ensured germination (of seeds not damaged by or sown after fire) and initial growth despite unfavorable environmental conditions. Seedlings of P. abies and L. decidua were more susceptible to temperature and drought conditions post-fire.

ID: 3.10780

Understory eddy covariance measurements in a mountain forest

Alexander Platter
Hammerle, Albin; Wohlfahrt, Georg

Abstract/Description

Terrestrial ecosystems, such as mountain forests, are crucial components of the global carbon cycle, acting as a net CO2 sink. Whether an ecosystem is a source or a sink of carbon depends strongly on how individual components, like soils or different vegetation components, respond to climatic conditions. Understanding these processes and responses under a changing climate is essential for accurate projections of the global carbon cycle and the climate system. While whole-forest CO2 budgets are typically estimated using eddy covariance (EC) above the canopy, partitioning this exchange among different forest components remains challenging. Understory EC measurements within the canopy offer a potential solution. Combined with above-canopy EC systems or soil chambers, this approach allows for partitioning the ecosystem’s total CO2 budget. However, estimating CO2 exchange from understory EC setups is difficult due to frequent violations of ideal atmospheric conditions within the canopy, which are often assumed for standard data processing. This work revisits various aspects of EC data processing in such challenging environments to provide reliable estimates of individual ecosystem components. Data from an above- and within-canopy EC system in Mieming, Tyrol, Austria, are presented, along with results demonstrating the responses of different components to climatic extremes.

ID: 3.11613

Humid climate may ameliorate negative effects of warming on growth and water use in Japanese boreal conifers

Haruhiko Taneda
Miyazawa, Yoshiyuki; Goto, Susumu

Abstract/Description

Previous studies indicated that boreal and mountainous evergreen conifers are vulnerable to increased temperatures due to global warming, resulting in reduced growth and survival rates, but some reports showed that those of the conifers in the regions where oceanic climate influence rather improve. However, these effects of oceanic climate may be species-specific and the physiological mechanisms remain unclear. To assess the ecophysiological details of boreal conifer growth at warm climate, we conducted two transplant experiments using three Japanese boreal conifers, Abies sachalinensis, Picea jezoensis, and Picea glauca. Saplings of these species were planted at three sites: Furano, near their native habitat; Chichibu, a warm inland region; and Chiba, a warm coastal region. In Experiment 1, we measured relative growth rates and survival rates. In Experiment 2, five years after Experiment 1, we measured photosynthesis and stomatal behavior in A. sachalinensis at the three sites. Results from Experiment 1 showed that high mortality of P. jezoensis and red P. glauca were found at the two warmer sites particularly at Chichibu. Relative growth rates (RGR) were the lowest at Chichibu in 2018 when severely hot summer was recorded, while the RGR at Chiba was similar with those at Furano. Notably, the d13C was significantly higher at Chichibu, suggesting that stomatal closure might cause a reduction in their growth. From Experiment 2, we found that three-year growth was higher in the order of Chiba, Furano, and Chichibu. Foliage mass for the last three years was smaller in Chichibu and Chiba trees than in Furano trees but their maximum photosynthetic rate did not differ. Onset of stomatal closure was detected at ~1.0 of VPD and ~-1.0 MPa of leaf water potential at both the individual leaf and branch levels, and these trends did not differ among trees grown at the three sites. Considering the large difference in air humidity in the three sites, we concluded that the boreal conifer growth at warmer sites was strongly influenced by stomatal closure due to high VPD, and high air humidity under the oceanic climate allowed the trees to maintain high stomatal conductance during growing seasons.

ID: 3.12062

Assessing forest landscape naturalness under future climate change and disturbances in the Italian Alps

Marco Mina
Marzini, Sebastian; Albrich, Katharina

Abstract/Description

Mountain forests have been strongly shaped by past human activities. Their current conditions often diverge greatly from the expected natural vegetation in terms of structure and composition. Generally, aiming at higher naturalness levels in forest ecosystems is preferred, as a more natural forest present higher level of ecosystem functioning. However, it is not clear whether a more natural forest landscape would be less prone to natural disturbances and whether they would better support the provision of multiple ecosystem services to human society. In our study, we addressed this question in a large mountain territory in the Italian Alps. We applied a process-based forest landscape model to determined the naturalness of a forest landscape in South Tyrol. We estimated the long-term potential natural vegetation of the region and compared with current forest conditions using a spatially-explicit naturalness index. Successively, we simulated future forest development of both the natural and the current landscape under combination of climate change scenarios and forest disturbances, which allowed us to compare the vulnerability of the two landscapes to future disturbances by analysing stand structure. Our results showed that the current forest presented a low naturalness due to diverging species composition between the current and natural forest landscape, particularly at low elevations. Nevertheless, higher naturalness levels were observed in subalpine forests. Natural disturbances such as wind and bark beetle impacted the natural and current forest landscape differently. While the current landscape showed to be more vulnerable to bark beetle outbreaks, further amplified by climate change, the natural landscape was more prone to wind disturbances, indicating a higher vulnerability of forests in which successional stages development were driven by natural dynamics only. Our study presented a first attempt of assessing forest naturalness using spatially-explicit dynamic modelling. As disturbances are expected to increase in the future, our results showed that aiming at more natural forest ecosystem might not be the best option under anthropogenic climate change. Management interventions should focus on lowering the future forest vulnerability by prioritizing interventions strategically across mountain forest landscapes.

ID: 3.12356

Characterizing drought impact on tree growth and vitality along an elevation gradient in the Alps

Nikolaus Obojes
Bibbò, Tamara

Abstract/Description

Climate change is expected to increase the frequency and intensity of extreme weather events such as droughts. Thus, mountain forests in the European Alps will increasingly be affected by dry periods. However, trees will react differently to meteorological droughts depending on species, the timing of the drought, and site conditions such as elevation, micro topography and soil characteristics. Here we analyze physiological drought indicators derived from multiple years of dendrometer and sap flow measurements on European Larch (Larix decidua) and co-occurring evergreen conifers (Pinus nigra, Picea abies, Pinus cembra) along an elevation gradient in the inner-alpine dry valley of Matsch/Mazia in Northern Italy. We determine the variability of drought reaction of different trees and species within each site and at different elevations. We also compare them with meteorological (SPI, SPEI) and soil moisture-based (REW) drought indicators to check for thresholds which cause a tree response and seasonality effects. Preliminary results show an expected decrease of physiological drought indicators with increasing elevation and a stronger reaction of evergreen conifers compared to European Larch. In the future we plan to combine these results with ongoing xylogenesis and wood anatomy measurements to get a clear picture on the impact of drought on the cellular basis of wood formation. Overall, this study will improve the understanding of drought impact on tree growth and vitality in mountain forests.

ID: 3.12407

Assessing climate change impacts on the water balance of mountain forests based on soil-vegetation-atmosphere transfer modelling – results from Tyrol and Vorarlberg (Austria)

Thomas Zieher
Gadermaier, Josef; Simon, Alois; Huber, Tobias; Katzensteiner, Klaus; Klebinder, Klaus; Englisch, Michael

Abstract/Description

There is abundant scientific evidence that Alpine forests (will) suffer from impacts of climate change. Rising temperatures and drier conditions (will) force current forests and their composition of tree species towards their ecological limits. Developing strategies towards climate-resilient forest management requires reliable estimates of future growth conditions, including plant-available water . Current and future changes of water balance components in forests can be efficiently simulated using soil-vegetation-atmosphere transfer (SVAT) models, reproducing the interactions and fluxes between soil, plants and atmosphere based on physical laws and empirical relationships. In the present study a lumped SVAT model (LWF-Brook90) was employed for assessing the water balance at 2.009 mapped forest sites in Tyrol and Vorarlberg (Austria). The soils were parameterized based on detailed records of soil surveys and results of laboratory tests. For the vegetation, established generic parameterizations of native tree species were used. Serving as an indicator for the site-specific moisture regime, the mean annual sum of the transpiration deficit (Tdef) was computed for current (1991-2020) and future conditions (2036-2065, 2071-2100), considering three selected climate change scenarios. The results were then upscaled using digital mapping techniques to derive maps of Tdef for the different periods and climate change scenarios, ensuring spatial consistency across model runs. Tdef generally shows a distinct, non-linear increase. Depending on the considered climate change scenario, this increase may reduce the resistance of current tree species composition against biotic disturbances or even might exceed their ecological limits, particularly towards the end of the century. The results also show regional patterns of Tdef, mainly due to spatial climate variability, topographic conditions in a mountain environment, and differences in climate model projections. In combination with further site factors controlling tree growth, the project results will have implications on the management of climate-resilient forests.

ID: 3.12536

Exploring resilience components in Mediterranean mountain forests

Concetta Lisella
Santopuoli, Giovanni; Bottero, Alessandra; Antonucci, Serena; Tognetti, Roberto

Abstract/Description

Forests provide several ecosystem services essential for human well-being. However, with ongoing climate change the frequency and intensity of climatic stressors and natural disturbances are increasing, making forests less resilient. Hence, knowledge about forest resilience is essential to understand ecosystem dynamics and adaptation capacity, especially in mountains of the Mediterranean region, which is considered a climate change hotspot. In the last years, resilience components (i.e., the indices of resistance, resilience, and recovery) have been recognized as advantageous indices to assess growth responses to climatic stressors and disturbances to promote climate-smart forestry strategies.
This contribution explores the use of resilience components to: (i) assess the impact of drought in different pine provenances in Mediterranean forest provenance trials (Sardinia, Italy); and (ii) evaluate the radial growth responses to late frost and drought in mixed oak-fir forests in Mediterranean mountains (Apennine, Italy).
Results confirm that resilience components play a crucial role to discriminate growth response to climatic stressors supporting forest managers to implement climate-smart forestry strategies. Furthermore, resilience components can be considered as indicators of climate-smart forestry providing significant insights to the European observatory part of the FORWARDS project, that is a long-term tool for monitoring climate change impacts and support related decision-making processes.

ID: 3.12578

Mountain Pine (Pinus uncinata) Growth in Andorra: A First Empirical Evaluation

Marta Domènech
Claramunt, Bernat; Grande, Gerard; Niell, Manel

Abstract/Description

For the first time, the growth of the mountain pine (Pinus uncinata) in Andorra, has been evaluated. Mountain pine forests are the most representative forest habitat in the country (49% of the total forested area), playing a crucial role in soil protection, snowpack retention, and serving as a significant component of the national carbon sink. For this study, digital dendrometers were installed on 24 trees at different locations and exposures, covering the entire altitudinal gradient of the Ordino Valley (Andorra). The dendrometers and temperature sensors were placed at 1,5 meters and recorded hourly growth data from 2017 to 2023. These data provide the first empirical insights into forest growth in Andorra. The average annual radial growth of black pine was 3,1 mm/year, with a minimum of 0.42 mm/year and a maximum of 6,7 mm/year. Tree growth was analyzed in relation to key environmental variables, including temperature, precipitation, altitude, and exposure and Stand Spacing Index. A significant positive effect of precipitation and south-facing exposure was detected. Compared to other studies, the observed growth rates are slightly higher than expected, which could indicate the impact of global warming on tree recruitment at higher elevations and, particularly, an increase in atmospheric carbon sequestration in the upper forest boundary.

ID: 3.12629

Mixed forest stand and site conditions buffer effects of recurring drought on ectomycorrhizal and soil bacterial and fungal communities in a subalpine spruce and larch forest

Markus Neurauter
Peintner, Ursula; Tunas-Corzon, Alex; Bahn, Michael; Probst, Maraike

Abstract/Description

Climate change is leading to increased frequency and intensity of drought events. It is crucial to understand how they impact mountain ecosystems, which are disproportionally affected by global warming. Here, we sampled soil cores at the end of a long-term experiment with recurring summer drought (8 years) to investigate the soil microbial communities in a subalpine forest (2000 m a.s.l.) in the Austrian Central Alps, which is dominated by spruce and larch. We investigated ectomycorrhizal (ECM) communities by morphotyping of colonized root tips and molecular identification by Sanger sequencing. Additionally, fungal and bacterial soil communities were investigated by amplicon sequencing and relevant soil parameters were measured to obtain a comprehensive, and inclusive, understanding of cumulative effects of drought on soil microbial communities. We hypothesized a decrease in species richness and diversity for drought plots compared to control, as well as changes in the community structure due to the establishment of a more drought tolerant community. Interestingly, for none of the three communities (ECM, bacteria and fungi) declines in richness or diversity were detected. We found significant differences in beta-diversity for bacterial and fungal communities between control and drought plots, however, little variance between communities was explained by the factor drought. For example, random variation in pH across the plots had a larger influence on communities and for ECM no significant effect of drought on beta-diversity at all was detected. The drought also led to significant changes in soil parameters, mainly decreases in nitrogen availability, which indirectly influenced the decline of certain bacterial taxa. Overall, these findings suggest, that soil microbial communities at the site are largely resilient to recurring drought, likely a result of the site being at the upper distribution limit of these forest types and due to buffering effects of mixed forest stands.

ID: 3.12642

Variation in soil CO2 fluxes through forest management

Daniel Agea Plaza
Martínez López, Javier; Alcaraz Segura, Domingo; Zamora Rodríguez, Regino Jesús; García Berro, Ignacio; Aránega Cortés, María; Postma, Thedmer; Romero Freire, Ana; Serrano Ortíz, Penélope

Abstract/Description

The implementation of adaptive management practices, such as thinning and clearing of pine and oak stands, promotes the protection and enhancement of the ecosystem services they provide. These management practices alter soil properties by contributing plant residues, affecting moisture and temperature, altering the activity of decomposing microorganisms, and modifying greenhouse gas (GHG) exchanges between the soil and the atmosphere. Knowing that two-thirds of the total amount of carbon in the biosphere is stored in the soil, it is of vital importance to analyze and understand the processes that contribute to its storage or release into the atmosphere and predict how these management practices modify its behavior. In this study, CO₂ fluxes were measured in oak forests, holm oak forests, and reforested pine stands in Sierra Nevada under two microhabitats: soil covered with thinning residues and bare soil. The measurements, conducted bimonthly between March 2022 and November 2024 using a gas analyzer and portable chamber, were complemented with satellite images (Landsat-8-9 and Sentinel-2), extracting information on various vegetation indices, moisture, albedo, and temperature to attempt to relate them to carbon fluxes along with other meteorological variables measured in the field. As a general result, we highlight that the soil in these forest ecosystems acts as a CO₂ emitter, with the flux varying according to the type of treatment. Environmental variables such as precipitation and temperature are key to predicting soil CO₂ emissions, along with soil temperature values derived from the Thermal index.

ID: 3.12711

Impact of Recurrent Droughts on the Water Use and Growth Dynamics of Larch and Spruce: insights from a long-term experiment in the Austrian Alps

Alex Tunas
Hwang, Bernice; Bär, Andreas; Oberleitner, Florian; Wieser, Gerhard; Oberhuber, Walter; Mayr, Stefan; Bahn, Michael

Abstract/Description

In the face of climate change, droughts are becoming more frequent and intense, exposing trees to ever-increasing physiological stress. Despite extensive research, the effects of recurrent droughts on tree carbon and water relations remain poorly understood, particularly in mountain forests. At a subalpine Long-Term Ecological Research (LTER) site in the Austrian Alps, we investigated the impacts of eight years of recurrent summer droughts on two conifer species—larch (Larix decidua) and spruce (Picea abies). Using comprehensive dendrometer and xylem sap flow data from 2021–2024, encompassing three years of drought followed by one year of recovery, we tested the following hypotheses: (i) recurrent droughts amplify drought responses of radial tree growth dynamics and water use, and (ii) drought history causes lagged responses on growth dynamics and water use during a recovery year, with larch exhibiting greater resilience. Our preliminary findings reveal drought-induced reductions in sap flow, as well as in mean growth rates for both species during the treatment years. Yet, contrary to our expectations, multiple recurrent droughts did not lead to a sustained amplification of the growth and water use sensitivity of trees at this subalpine site. During the recovery year, sap flow did not show legacy effects for either species; however, their growth rates remained consistently suppressed. Thus, our results suggest that although recurrent summer droughts do not have any lagged effects on water use dynamics in a recovery year, drought legacies may lead to reductions in growth.

ID: 3.12723

Trends and drivers of long-term forest evapotranspiration in Switzerland

Marius Floriancic
Hörtnagl, Lukas; Feigenwinter, Iris; Shekhar, Ankit; Buchmann, Nina

Abstract/Description

Evapotranspiration (ET) from forested ecosystems is a major component of the Alpine water cycle, influencing soil moisture, groundwater recharge, and streamflow. ET also modulates local and regional climate through latent heat exchange, affecting temperature and humidity in forest ecosystems. However, long-term measurements of ET are rare, thus the effects of a warming climate on forest ET fluxes remain poorly understood. Here we present a comprehensive analysis of long-term evapotranspiration data from eddy covariance measurements from two different forest sites in Switzerland: a Alpine evergreen coniferous forest (CH-Dav) and a montane mixed deciduous forest (CH-Lae), where H2O fluxes have been measured using eddy covariance (EC) since 1997 and 2005, respectively. Using this long-term data collection we i) analyzed changes in annual and seasonal ET fluxes and ii) assessed the major drivers of ET fluxes across the two forest sites. The subalpine Davos site received slightly higher precipitation and had a lower temperature compared to the Laegeren site, thus soil moisture and vapor pressure deficit were less important drivers of ET at Davos. Instead, ET limitations in Davos were mainly related to lower net radiation. At the montane Laegern site, compound dry events combining soil water deficits and higher VPD forced the trees to downregulate transpiration during the growing season, decreasing forest ecosystem ET fluxes. Analyses of the especially dry years (i.e., 2003 – only Davos, 2015, 2018 and 2022) indicate that the spruce dominated Davos site showed higher ET compared to average years, due to the favorable growing conditions at this typically energy-limited subalpine site. However, we found that even at the Davos site extended dry periods (i.e., as observed in the year 2018) may lead to lower water availability in the soil and thus force spruce trees to down-regulate transpiration. Overall, our results indicate that i) forest ecosystems in drier lower-elevated places are already experiencing frequent periods of ET reduction due to water limitations in the soil and atmospheric demand exceeding trees’ limitations while ii) higher elevation forest ecosystems might become more vulnerable when the durations of dry conditions and high temperatures are extending over longer time periods as projected in a future climate.

ID: 3.12861

Historical forest fires in the high Catalan-Andorran-Occitan Pyrenees: the Desbosiguem! dataset

Oriol Travesset-Baro
Domènech, Marta; Pons, Pere; Fleury, Camille; Quetglas-Morera, Arès; Oliveres, Jordi; Rosas-Casals, Martí

Abstract/Description

Global climatic change will increase the frequency and intensity of forest fires in mountain regions, even affecting areas that have historically been at low risk. This is the case of the Pyrenees, a transboundary mountain region shared by Spain, France and Andorra, where the combination of rising temperatures, longer and more intense droughts and changes in land use, is leading to an increased risk of major forest fires. In this context, fire risk management, biodiversity conservation and the rational use of pasture and forest resources are of key importance. The Desbosiguem! project (01/04/2024-31/03/2027, poctefa.eu/proyectos/efa089-01-id-desbosiguem/), funded by FEDER through the EU’s POCTEFA programme, aims to combine the experience of neighbouring countries Andorra and Spain in managing unproductive environments with the experience of France in restoring and maintaining these areas through grazing, in order to develop integrated solutions for reopening the landscape, restoring pastures and reducing fire risk. One of the outputs of the project is the provision of fire modelling tools to support rural managers in Catalonia, Andorra and Occitanie. The starting point of these modelling tools is the Desbosiguem! dataset, which will be available through the geo-portal of the Pyrenees Climate Change Observatory (opcc-ctp.org/geoportal). It includes the historical forest fires of the high Catalan-Andorran-Occitan Pyrenees, covering the cross-border area formed by the Pallars Sobirà, Cerdanya and Alt Urgell in Catalonia, the Principality of Andorra and Ariège in Occitanie. This contribution describes the Desbosiguem! dataset, the process of data homogenisation from different countries and provides a preliminary analysis of this cross-border dataset.

ID: 3.13088

Multi-frequency Earth Observation for Vegetation Drought Impact monitoring across scales

Mariette Vreugdenhil
Dirnböck, Thomas; Hollaus, Markus; Brunelli, Benedetta; Borlaf-Mena, Ignacio; Reuß, Felix; Iglseder, Anna; Zappa, Luca; Mancini, Francesco; Reimer, Christoph

Abstract/Description

Austria is experiencing a rapid climate warming, particularly in its alpine regions. Due to rising temperatures and changing precipitation, droughts are increasing and placing therefore additional stress on vegetation. It is evident that we need to improve our understanding of how vegetation will respond to a warming climate, climate extremes, and abrupt changes. Therefore, the monitoring of vegetation phenology demands the availability of high-resolution, accurate and reliable datasets over Austrian alpine regions. The Copernicus Sentinel satellites provide high resolution observations which can be used to retrieve vegetation information. Visible and near infrared methods such as the Copernicus Land Monitoring System Sentinel-2 High Resolution Vegetation Phenology and Productivity (HR-VPP) dataset are most used. A novel approach to monitor vegetation dynamics is to use Synthetic Aperture Radar (SAR) backscatter observations which are sensitive to both structure and water content of vegetation. The Copernicus Sentinel-1 satellite operates at C-band providing data over Austria since 2014. Studies have shown its sensitivity to vegetation dynamics as well as soil moisture, snow cover and terrain which might challenge the retrieval of vegetation information over mountainous regions. We will present the first steps in retrieving vegetation dynamics information from SAR observations from Sentinel-1 C-band and SAOCOM L-band across various topographic landscapes in Austria. SAOCOM L-band observations will be investigated in preparation for upcoming L-band missions such as ROSE-L. In addition, preliminary results on the retrieval of vegetation phenology information from Sentinel-1 and the potential of laser scanning derived 3D point cloud data for the description of the vegetation structure will be shown. Specific focus will be over the mountainous Long-term Ecological Research (LTER) site Zöbelboden in the Kalkalpen, Austria, where in situ gross primary production and dendrometer data will be used as reference. Over the LTER sites the Sentinel-1 based data will be compared to the existing HR-VPP dataset from Sentinel-2. The work is part of the EO4VegetationDrought project, funded by the Austrian Research Promotion Agency, where the goal is to bring together multi-frequency satellite Earth Observation datasets and laser scanning, with high quality in situ data from the LTER Sites to improve vegetation monitoring capabilities in Austria.

ID: 3.13132

Modeling forest fires with low computational complexity and NetLogo in the high Catalan-Andorran-Occitan Pyrenees: the Desbosiguem! fire spreading model (DFS model)

Arès Quetglas I Morera
Travesset-Baro, Oriol; Domenech, Marta; Pons, Pere; Fleury, Camille; Oliveres, Jordi; Rosas-Casals, Martí

Abstract/Description

The Desbosiguem! project (01/04/2024-31/03/2027, www.poctefa.eu/proyectos/efa089-01-id-desbosiguem/), funded by FEDER through the EU’s Interreg POCTEFA programme, aims to reshaping unproductive environments in the Pyrenees through grazing, in order to develop integrated solutions for reopening the landscape, restoring pastures and reducing fire risk. In the case of the Pyrenees, the combination of rising temperatures, longer and more intense droughts and changes in land use, increases the risk of major forest fires. With the objective to improve both fire risk management, biodiversity conservation and the rational use of pastures and forest resources, in this project we use NetLogo (ccl.northwestern.edu/netlogo/), a multi-agent programmable modeling environment used by many hundreds of thousands of researchers worldwide (and downloadable free of charge) to implement a cellular automaton that models fire spread in this transboundary mountain region shared by Spain, France and Andorra: the Desbosiguem! fire spreading model (DFS model). Unlike other much more complex (in terms of computational resources and data usage) fire models, the DFS model that we present in this contribution, considers two parameters (input maps): topography and a loose definition of probability of spread based on canopy cover, to define open and closed forest spaces. This low computational complexity and remarkable accuracy in reproducing historical wildfires in the region makes the DFS model a useful decision – support system for evaluating the relative effects of alternative management scenarios.

ID: 3.13612

Fine-scale tree cover changes in Switzerland in 40 years: impacts for biodiversity and carbon storage

Christian Rixen
Frei, Esther; Shipley, Ryan; Bergamini, Ariel; Krumm, Frank; Christian, Ginzler

Abstract/Description

To understand the future of forests, we must have a detailed understanding of past changes due to climate and land use change. And woody encroachment can have important consequences for carbon stocks and mountain biodiversity. The abandonment of agricultural activities results in woody encroachment, converting species rich mosaic habitats like dry meadows, bogs, and fens into expanding forested areas. These habitats, which are particularly important for biodiversity conservation in Switzerland, face imminent threats. Woody vegetation encroachment not only alters habitat structure but also can drive declines in vascular plant species due to associated effects, such as increased shading or altered competition. Our research addresses this complex relationship by integrating high-resolution vegetation height data (1 meter) across Switzerland, as a proxy for woody encroachment, with a comprehensive dataset comprising over 4,000 vegetation surveys from the effectiveness of habitat conservation monitoring (WBS) in Switzerland. We find that although the greatest increases of woody shrub encroachment are occurring along the southern Alps in Ticino and Graubünden, it is also occurring in habitats in the central and northern Alps at a slower pace. We found this has significant consequences on habitats of conservation concern, where plant species diversity decreases even at the initial stages of encroachment. By analyzing the drivers and consequences of agricultural abandonment, our project aims to offer scientific insights for mitigating the adverse impacts on biodiversity associated with land use changes.

ID: 3.13814

Influence of topo-climatic variation and climatically contrasting years on the intra-annual dynamics of spruce incremental response in the Western Sudetes (between the years 2022 and 2024)

Marek Błaś
Myśkow, Elżbieta; Słupianek, Aleksandra; Ojrzyńska, Hanna; Sobik, Mieczysław; Owczarek, Piotr; Opała, Magdalena

Abstract/Description

In the present study, the rate of mid-year spruce growth was analysed at a dozen measurement sites representing diverse topo-climatic conditions in the Western Sudetes (medium-sized mountain barrier straddling the border between Poland and the Czech Republic). For three consecutive growing seasons (2022-2024), air temperature and humidity, atmospheric precipitation, soil moisture, changes in trunk circumference were measured using electronic band dendrometers and cambium dynamics by collecting micro-core at two-week intervals (methodology according to Trephor). The spatial variability of topo-climatic conditions in the Western Sudetes is greatest in the lower subalpine forest (700-900 m a.s.l.). The averaged date of the last spring frost in the Western Sudetes varies from the end of April at sites located on slopes to the end of June in the region of flat-bottomed basins. Closed depressions create optimum conditions for the formation of nocturnal radiation inversions (cold air stagnation), which translates into high frequency and depth of frosts. These can occur even in the optimum summer and cause serious forest damage in the form of freezing of fresh annual growth of trees. Following this, dendrometric measurements and micro-core analysis showed significant differences in the mid-year growth rate of trees between sites. The extreme differences in annual ring width were more than fivefold. The topo-climatic variation was compounded by the specific weather conditions observed in the following three growing seasons. All growing seasons were characterised by a positive temperature anomaly (from +0.8 to +2.3 C) and a negative precipitation anomaly (from -7 to -23% of normal). During periods of spring and summer drought, spruce trees showed premature growth stop or reduced growth rates in all elevation floors. However, the lowest radial growth during dry and warm growing periods was observed in the foothills floor and the highest in the upper forest zone. In summary, the climate-growth correlations highlighted the inter-seasonal influence of climatic conditions, particularly rainfall deficit and soil moisture, on the short-term responses of trees. Thus, in line with the projected increasing frequency of drought in the growing seasons, the forest ecosystems of the Western Sudetes are expected to show lower growth performance.

ID: 3.13968

The new normal: increasing probability of late frost and drought. Effects on juvenile trees.

Jonathan Ehrmann
von Heßberg, Andreas; Wilkens, Vincent; Jentsch, Anke

Abstract/Description

Drought and late frost events are major disturbances within forest ecosystems. Under a climate change regime, their likelihood, frequency and severity are expected to change, which makes it important to investigate their impact on trees. In a potted experiment, we simulated late frost and drought regimes, putting the trees in a cooling truck to simulate a frost night after bud burst and by controlling the watering during drought season. Overall, the experimental design had five late frost levels and eight drought levels with double control groups, which led to 70 groups and 2250 pots in total. 33 forestry-relevant species were tested within the experiment with 10 species relevant for the northern calcareous alps. Goal of this gradient experiment was to examine the threshold at which the disturbances cause irreversible harm to the trees. Both disturbances were analyzed singular, but also the interaction between both. This experiment showed differences in responding to drought and late frost between multiple tree species. For example, early budding trees are more late frost tolerant, whereas the drought tolerance depend more on the origin of the tree. The measurements also indicates that not the drought, but the heat was the cause of leaf damage for the trees.

ID: 3.12866

Unravelling Water Yield Patterns in Lower Shivaliks of Uttarakhand: Scenario-based Analysis of Climate and Land Use Dynamics

Diksha Verma
Kumar, Vishavjit

Abstract/Description

The Himalayan Forest ecosystem plays a crucial role in regulating water resources by serving as natural reservoir and is a reliable source of freshwater for the mountainous and downstream communities. The lower Shivalik range of Himalayas are best suited for the human development with optimum climatic conditions, consequently, threatened by climatic variability and anthropogenic pressures. The dynamics of land use shifts coupled with climatic variability has a significant contribution in oscillating the hydrological flux of the area. However, research on water ecosystem services is limited in capturing the temporal continuum, which is essential to observe water yield distribution pattern. The present study evaluates the spatio-temporal variation in water yield through the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) Annual Water Yield Model across multiple temporal scale (1995, 2005, 2015, and 2022), and identify the primary influencing factors driving the changes by employing geographical detector modelling. The land use change detection reveals a notable shift from dense forests to built-up (3.41%) and agricultural land (4.62%), contributing to altered hydrological patterns. The upward trend in water yield from 3180.41 m³/ha in 1995 to 6808.07 m³/ha in 2022, underscores the influence of land use dynamics and climatic variability on hydrological processes. Precipitation (q= 0.43) and population density (q= 0.25) were the dominant factor for influencing water yield, however, interaction between land use and precipitation was also significantly positively influencing water yield. The results were further substantiated by scenario-based analysis using four scenarios: SI (Baseline 1995), SII (1995 climate and 2022 land use), SIII (2022 climate and 1995 land use), and SIV (Actual conditions of 2022), which revealed that water retention was severely constrained by alterations to the various climate and land use variables. Areas with high rainfall and intact forest cover exhibited stable and consistent water yield, highlighting the significance of preserving natural recharge zones. The findings emphasize on the critical role of forest conservation and sustainable land use planning in maintaining hydrological balance and securing water resources in Himalayas.

ID:

Carbon-dioxide emission from coarse woody debris in a tropical montane forest

Laszlo Nagy
Polli, Laura

Abstract/Description

Coarse woody debris (CWD) consists of standing and suspended dead trees (snag) and fallen trees and branches in contact with the soil. The contribution of CWD to carbon stocks and fluxes varies with temperature and moisture conditions, with temperature limitation increasing in importance with elevation and latitude. Climate change and forest fragmentation will change the rate of decomposition of CWD and the release of CO₂. To project such changes in the contribution of CWD to carbon stocks and CO₂ emissions in tropical montane forests, we quantified CWD (> 2 cm in diameter) on the forest floor in five permanent plots between 1600 and 1950 m a.s.l. in the Atlantic Forest domain (22.5 S).

We measured CO₂ fluxes in the field and in the laboratory at temperatures that span the range of winter and summer soil surface temperatures (5-15°C) experienced by CWD, and at 25°C, simulating a substantial warming. The estimated mean CWD mass on the forest floor ranged from 8.6 to 21.0 Mg ha^-1. Mean CO₂ emission showed relatively low temperature sensitivity between 15 °C (1.1 – 3.0 Mg CO₂ ha^-1 year^-1) and 25 °C (1.4 – 3.6 Mg CO₂ ha^-1 year^-1); the quantity of emitted CO₂ was halved at 5 °C (0.7 – 1.8 Mg CO₂ ha^-1 year^-1). Our results suggest that most temperature related changes in CO₂ emission from CWD decomposition will likely to be caused by increasing minimum temperatures. While a general warming trend has been detected at our study site since the 1970s, caused by an increase in daily maxima, minimum temperatures have not increased, thus there does not appear to be an indication of an immediate increase in CO₂ emission from CWD.

FS 3.204: Transformative changes towards Living Well in mountains: How does it feel?

FS 3.207: Alpine Forest players facing climate change crisis : adaptation, transition and new players

FS 3.206

The Future of Mountain Forests

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