Effects of Historical and Likely Future Scenarios of Land Use on Above- and Belowground Vegetation Carbon Stocks of an Alpine Valley

Evolution of Ecological Patterns of Poyang Lake Wetland Landscape over the Last One Hundred Years Based on Historical Topographic Maps and Landsat Images

Ecological pattern evolution of Poyang Lake wetland, the largest freshwater lake in China, is critical for regional ecological protection and sustainable development of migratory bird habitats; however, this information is still not fully explored. In this study, we quantitatively reconstructed the spatial distribution and landscape ecological pattern of Poyang Lake wetlands in three periods in the past 100 years based on the military topographic map in the 1930s and the Landsat satellite remote sensing image data in 1979 and 2021. Further, use the Fragstats software to analyze the ecological pattern index of wetland reconstruction results. The results show that the wetland area in the Poyang Lake region has experienced a continuous reduction process over the past 100 years, and it decreased from 3857 km2 in the 1930s to 3673 km2 in the 1970s, and then to 3624 km2 in the 2020s. The current wetland area has decreased by about 6.04% compared with the 1930s. The general trend of changes in the spatial pattern of Poyang Lake wetlands is that the surface water decreases and the open land increases. Nevertheless, the trend has certain spatial differences as a large area of wetlands disappeared in the southwest and west of Poyang Lake and the areas with enlarged wetland density values mainly appeared in the northeastern and northern parts of the study area. The NP (number of patches) in the wetlands of Poyang Lake over the past 100 years showed a downward trend during the 1930s–1970s, and an increasing trend during the 1970s–2010s. Due to the increases of constructed wetlands, the number and density of patches also increased, and PD (patch density) reached a maximum value of 0.142 in 2020s. The LPI (largest patch index) has shown a gradual downward trend in the past 100 years. Compared with the 1930s, the wetlands in 2020s dropped by about 26.64%, and the wetlands further showed a trend of fragmentation. The AI index, which indicates the concentration of wetland patches, reached the maximum value in 2020s, but the LSI (landscape shape index) showed a downward trend in general, indicating that the shape of wetland patches has been simplified over the past 100 years. The research results can provide basic data and decision-making basis for Poyang Lake wetland protection, construction of migratory bird reserve and regional sustainable development.

The Influence of Land Use Change on Key Ecosystem Services and Their Relationships in a Mountain Region from Past to Future (1995–2050)

The ecosystem services (ESs) provided by mountain regions can bring about benefits to people living in and around the mountains. Ecosystems in mountain areas are fragile and sensitive to anthropogenic disturbance. Understanding the effect of land use change on ESs and their relationships can lead to sustainable land use management in mountain regions with complex topography. Chongqing, as a typical mountain region, was selected as the site of this research. The long-term impacts of land use change on four key ESs (i.e., water yield (WY), soil conservation (SC), carbon storage (CS), and habitat quality (HQ)) and their relationships were assessed from the past to the future (at five-year intervals, 1995–2050). Three future scenarios were constructed to represent the ecological restoration policy and different socioeconomic developments. From 1995 to 2015, WY and SC experienced overall increases. CS and HQ increased slightly at first and then decreased significantly. A scenario analysis suggested that, if the urban area continues to increase at low altitudes, by 2050, CS and HQ are predicted to decrease moderately. However, great improvements in SC, HQ, and CS are expected to be achieved by the middle of the century if the government continues to make efforts towards vegetation restoration on the steep slopes.

Climate change causes critical transitions and irreversible alterations of mountain forests

Mountain forests are at particular risk of climate change impacts due to their temperature limitation and high exposure to warming. At the same time, their complex topography may help to buffer the effects of climate change and create climate refugia. Whether climate change can lead to critical transitions of mountain forest ecosystems and whether such transitions are reversible remain incompletely understood. We investigated the resilience of forest composition and size structure to climate change, focusing on a mountain forest landscape in the Eastern Alps. Using the individual-based forest landscape model iLand, we simulated ecosystem responses to a wide range of climatic changes (up to a 6°C increase in mean annual temperature and a 30% reduction in mean annual precipitation), testing for tipping points in vegetation size structure and composition under different topography scenarios. We found that at warming levels above +2°C a threshold was crossed, with the system tipping into an alternative state. The system shifted from a conifer-dominated landscape characterized by large trees to a landscape dominated by smaller, predominantly broadleaved trees. Topographic complexity moderated climate change impacts, smoothing and delaying the transitions between alternative vegetation states. We subsequently reversed the simulated climate forcing to assess the ability of the landscape to recover from climate change impacts. The forest landscape showed hysteresis, particularly in scenarios with lower precipitation. At the same mean annual temperature, equilibrium vegetation size structure and species composition differed between warming and cooling trajectories. Here we show that even moderate warming corresponding to current policy targets could result in critical transitions of forest ecosystems and highlight the importance of topographic complexity as a buffering agent. Furthermore, our results show that overshooting ambitious climate mitigation targets could be dangerous, as ecological impacts can be irreversible at millennial time scales once a tipping point has been crossed.

The ecosystem carbon sink implications of mountain forest expansion into abandoned grazing land: The role of subsoil and climatic factors

Woody encroachment is a widespread phenomenon resulting from the abandonment of mountain agricultural and pastoral practices during the last century. As a result, forests have expanded, increasing biomass and necromass carbon (C) pools. However, the impact on soil organic carbon (SOC) is less clear. The main aim of this study was to investigate the effect of woody encroachment on SOC stocks and ecosystem C pools in six chronosequences located along the Italian peninsula, three in the Alps and three in the Apennines. Five stages along the chronosequences were identified in each site. Considering the topsoil (0-30 cm), subsoil (30 cm-bedrock) and whole soil profile, the temporal trend in SOC stocks was similar in all sites, with an initial increment and subsequent decrement in the intermediate phase. However, the final phase of the woody encroachment differed significantly between the Alps (mainly conifers) and the Apennines (broadleaf forests) sites, with a much more pronounced increment in the latter case. Compared to the previous pastures, after mature forest (>62 years old) establishment, SOC stocks increased by: 2.1(mean) ± 18.1(sd) and 50.1 ± 25.2 Mg C·ha^-1 in the topsoil, 7.3 ± 17.4 and 93.2 ± 29.7 Mg C·ha^-1 in the subsoil, and 9.4 ± 24.4 and 143.3 ± 51.0 Mg C·ha^-1 in the whole soil profile in Alps and Apennines, respectively. Changes in SOC stocks increased with mean annual air temperature and average minimum winter temperature, and were negatively correlated with the sum of summer precipitation. At the same time, all other C pools (biomass and necromass) increased by 179.1 ± 51.3 and 304.2 ± 67.6 Mg C·ha^-1 in the Alps and the Apennines sites, respectively. This study highlights the importance of considering both the subsoil, since deep soil layers contributed 38% to the observed variations in carbon stocks after land use change, and the possible repercussions for the carbon balance of large areas where forests are expanding, especially under pressing global warming scenarios.

Historical trajectories in land use pattern and grassland ecosystem services in two European alpine landscapes

Land use and spatial patterns which reflect social-ecological legacies control ecosystem service (ES) supply. Yet, temporal changes in ES bundles associated with land use change are little studied. We developed original metrics to quantify synchronous historical variations in spatial patterns of land use and ES supply capacity, and demonstrated their use for two mountain grassland landscapes. Consistent with other European mountains, land use dynamics from the nineteenth century until the mid-twentieth century resulted in increased landscape heterogeneity, followed by homogenisation. In the persistently grassy landscape of Lautaret in France, landscape multifunctionality-the provision of multiple ES-coincided with greatest landscape heterogeneity and within-patch diversity in ecosystem services in the 1950-1970s. In the more complex Austrian landscape, where since the nineteenth century intensive production has concentrated in the valley and steep slopes have been abandoned, grassland landscape-level multifunctionality and spatial heterogeneity across grasslands have decreased. Increasing spatial heterogeneity across grasslands until the 1970s was paralleled at both sites by increasing fine-grained spatial variability for individual ES, but subsequent landscape simplification has promoted coarse-grained ES patterns This novel analysis of landscape-scale turnover highlighted how spatial patterns for individual ES scale to multiple grassland ES, depending on the nature of land use spatial variability. Under current socio-economic trends, sustaining or re-establishing fine-grained landscapes is often not feasible, thus future landscape planning and policies might focus on managing landscape and regional-scale multifunctionality. Also, the trends towards decreasing cultural ES and increasing regulating ES suggest a contradiction with current social demand and regional policies.

Future impacts of changing land-use and climate on ecosystem services of mountain grassland and their resilience

Although the ecosystem services provided by mountain grasslands have been demonstrated to be highly vulnerable to environmental and management changes in the past, it remains unclear how they will be affected in the face of a combination of further land-use/cover changes and accelerating climate change. Moreover, the resilience of ecosystem services has not been sufficiently analysed under future scenarios. This study aimed to assess future impacts on multiple mountain grassland ecosystem services and their resilience. For a study area in the Central Alps (Stubai Valley, Austria), six ecosystem services were quantified using plant trait-based models for current and future conditions (in 2050 and 2100) considering three socio-economic scenarios. Under all scenarios, the greatest changes in ecosystem services were related to the natural reforestation of abandoned grassland, causing a shift from grassland to forest services. Although the high resilience potential of most ecosystem services will be maintained in the future, climate change seems to have negative impacts, especially on the resilience of forage production. Thus, decision makers and farmers will be faced with the higher vulnerability of ecosystem services of mountain grassland. Future policies should consider both socio-economic and environmental dynamics to manage valuable ecosystem services.

Storylines of combined future land use and climate scenarios and their hydrological impacts in an Alpine catchment (Brixental/Austria)

In this paper, the hydrological impacts of future socio-economic and climatic development are assessed for a regional-scale Alpine catchment (Brixental, Tyrol, Austria). Therefore, coupled storylines of future land use and climate scenarios were developed in a transdisciplinary stakeholder process by means of questionnaire analyses and interviews with local experts from various relevant societal sectors. Resulting future land use maps for each decade were used as spatial input in the hydrological model WaSiM, to which a new module for the consideration of snow-canopy interaction processes has been added. Simulation results for three developed storylines, each combined with a moderate (A1B) and an extreme (RCP8.5) climate future, show that in a warmer and dryer climate the amount of annual simulated streamflow at the gauge of the catchment undergoes a significant reduction. The (mainly natural) reforestation of the catchment - caused by abandonment of previously cultivated areas - leads to additional losses of water by enhanced interception and evapotranspiration processes. Further cultivation of the current mountain pasture areas has a certain potential to attenuate undesirable long-term impacts of climate change on the catchment water balance.

70 Years of Land Use/Land Cover Changes in the Apennines (Italy): A Meta-Analysis

Land use science usually adopts a case study approach to investigate landscape change processes, so we considered a meta-analysis an appropriate tool for summarizing general patterns and heterogeneous findings across multiple case studies over a large geographic area. Mountain landscapes in the Apennines (Italy) have undergone significant variations in the last century due to regional and national socio-economic changes. In this work, we reviewed 51 manuscripts from different databases and examined 57 case studies. We explored heterogeneous data sets, adopting a stepwise approach to select the case studies: Step 1, a general overview of the main studies; Step 2, an analysis of the features of the study sites and of land-use/cover transitions; Step 3, a landscape pattern analysis. We standardized the processing methods to obtain a new set of homogeneous data suitable for comparative analysis. After some pre-processing of the selected paper due to the broad heterogeneity of the data, we calculated common landscape metrics ex novo. We obtained digital images used to perform automatic segmentation with eCognition Developer 64 software. Our review indicated that most case studies were in Central and Southern Italy, 83% were examined at local scale, 77% carried out change detection, but only 38% included both change detection and landscape spatial pattern analysis. The results revealed a clear trend of forest expansion (+78%) and the reduction of croplands (−49%) and grasslands (−19%). We did not find significant changes in the landscape spatial patterns.

Quantification and mapping of the supply of and demand for carbon storage and sequestration service in woody biomass and soil to mitigate climate change in the socio-ecological environment

In this study, the supply of and demand for carbon storage and sequestration of woody biomass in the socio-ecological environment of the Wabe River catchment in Gurage Mountains, Ethiopia, were estimated. This information was subsequently integrated into a map that showed the balance between supply capacities and demand in a spatially explicit manner to inform planners and decision makers on methods used to manage local climate change. Field data for wood biomass and soil were collected, satellite images for land use and land cover (LULC) were classified, and secondary data from statistics and studies for estimation were obtained. Carbon storage, the rate of carbon sequestration and the rate of greenhouse gas (GHG) emissions from diverse sources at different LULCs, was estimated accordingly by several methods. Even though a large amount of carbon was stored in the catchment, the current yearly sequestration was less than the CO₂-eq. GHG emissions. Forest and Enset-based agroforestry emissions exhibited the highest amount of woody biomass, and cereal crop and wetland exhibited the highest decrease in soil carbon sequestration. CO₂-eq. GHG emissions are mainly caused by livestock, nitrogenous fertilizer consumption, and urban activities. The net negative emissions were estimated for the LULC classes of cereal crop, grazing land, and urban areas. In conclusion, without any high-emission industries, GHG emissions can be greater than the regulatory capacity of ecosystems in the socio-ecological environment. This quantification approach can provide information to policy and decision makers to enable them to tackle climate change at the root level. Thus, measures to decrease emission levels and enhance the sequestration capacity are crucial to mitigate the globally delivered service in a specific area. Further studies on the effects of land use alternatives on net emissions are recommended to obtain in-depth knowledge on sustainable land use planning.

Using land use/land cover trajectories to uncover ecosystem service patterns across the Alps

Managing multiple ecosystem services (ES) in agricultural landscapes is a challenging task, especially in regions with complex topographical and agro-ecological conditions. These challenges require ES assessment approaches that go beyond the case study level and provide multi-temporal information at a transnational level. We used a spatiotemporal approach to examine the impact of specific land use/land cover (LULC) trajectories on eight ES for the past 150 years. We show how a spatially explicit ES upscaling procedure, from case study to an Alpine-wide level, based on topographical, agro-ecological and socioeconomic parameters, can improve our understanding of ES dynamics and bundles. Our results indicated that the provision of multiple ES was not stable during the 150 years surveyed, mainly depending on the prevailing land management type and the biophysical conditions. ES bundle mapping enabled us to identify landscapes with consistent socioecological characteristics that are most likely to either enhance or diminish the provision of specific types of services. By introducing a spatiotemporal perspective into ES assessment, we provide clear evidence of the dynamic nature of ES provision and contribute to identifying processes and drivers behind these interactions. Our results emphasize that mountain ES supply is particularly sensitive to long-term LULC change, to biophysical characteristics and to regional socioeconomic conditions. They indicate the benefit of integrating of ES bundles into environmental policies at national and transnational level.

Influence of Land-Use Intensification on Vegetation C-Stocks in an Alpine Valley from 1865 to 2003

The role of ecosystems as carbon (C) sinks or sources is intrinsically related to land-use intensity, which determines the land required for biomass production. Here, we systematically investigate the role of different land-use types including their land-use intensities on vegetation C-stocks (SC_act) in the Stubai valley, located in the Austrian central Alps. After a period of high land-use impacts until 1954, indicated by massive C-depletion, land-use shifted to completely new courses. Polarization into high-intensity low-land areas and extensification at higher altitudes allowed for a tripling of SC_act until 2003. The most important land-use change was the intensification of the livestock sector accompanied by abandonment of extensive grasslands and reduced harvest pressure on forests after WWII. Market integration, abundance of fossil energy carriers, as well as structural change of the economy were important underlying socio-economic drivers of these trends. However, despite this remarkable SC_act increase, SC_act amounted to only 62% of the potential carbon stocks (SC_pot) in 2003. Although conversion of forests to agriculture clearly contributed the lion’s share to this SC-gap, forest management explains roughly one quarter of the SC-difference. We found that time-lags between land-use shifts and the establishment of a new C-climax had fundamental repercussions on recent C-dynamics in the study region. Apparently, the land system is still net-accumulating C, although land-use changes have peaked decades earlier. Our findings are crucial for the understanding of C-dynamics, including the role of land management and time-lags in mountainous regions, which are regarded key areas for terrestrial C-sequestration.

Landscape changes, traditional ecological knowledge and future scenarios in the Alps: A holistic ecological approach

In recent decades, a dramatic landscape change has occurred in the European alpine region: open areas have been naturally recolonized by forests as traditional agricultural and forest activities were reduced and reorganized. Land use changes (LUC) are generally measured through GIS and photo interpretation techniques, but despite many studies focused on this phenomenon and its effects on biodiversity and on the environment in general, there is a lack of information about the transformation of the human-environment connection. The study of Traditional Ecological Knowledge (TEK), such as the ability to recognize wild plants used as medicine or food, can suggest how this connection evolved through time and generations. This work investigates the relationship between the natural forest cover expansion that influences the loss of open areas and the loss of TEK. Different data sources and approaches were used to address the topic in all its complexity: a mix of questionnaire investigations, historical maps, GIS techniques and modelling were used to analyse past land use changes and predict future scenarios. The study area, Trentino, Italy, is paradigmatic of the alpine situation, and the land use change in the region is well documented by different studies, which were reviewed and compared in this paper. Our findings suggest that open area loss can be used as a good proxy to highlight the present state and to produce future scenarios of Traditional Ecological Knowledge. This could increase awareness of the loss of TEK in other Alpine regions, where data on TEK are lacking, but where environmental trends are comparable.

A mobile system for quantifying the spatial variability of the surface energy balance: design and application

We present a mobile device for the quantification of the small-scale (a few square meters) spatial variability in the surface energy balance components and several auxiliary variables of short-statured (<1 m) canopies. The key element of the mobile device is a handheld four-component net radiometer for the quantification of net radiation, albedo and infrared surface temperature, which is complemented with measurements of air temperature, wind speed, soil temperature and soil water content. Data are acquired by a battery-powered data logger, which is mounted on a backpack together with the auxiliary sensors. The proposed device was developed to bridge between the spatial scales of satellite/airborne remote sensing and fixed, stationary tower-based measurements with an emphasis on micrometeorological, catchment hydrological and landscape-ecological research questions. The potential of the new device is demonstrated through four selected case studies, which cover the issues of net radiation heterogeneity within the footprint of eddy covariance flux measurements due to (1) land use and (2) slope and aspect of the underlying surface, (3) controls on landscape-scale variability in soil temperature and albedo and (4) the estimation of evapotranspiration based exclusively on measurements with the mobile device.

On the effects of scale for ecosystem services mapping

Ecosystems provide life-sustaining services upon which human civilization depends, but their degradation largely continues unabated. Spatially explicit information on ecosystem services (ES) provision is required to better guide decision making, particularly for mountain systems, which are characterized by vertical gradients and isolation with high topographic complexity, making them particularly sensitive to global change. But while spatially explicit ES quantification and valuation allows the identification of areas of abundant or limited supply of and demand for ES, the accuracy and usefulness of the information varies considerably depending on the scale and methods used. Using four case studies from mountainous regions in Europe and the U.S., we quantify information gains and losses when mapping five ES - carbon sequestration, flood regulation, agricultural production, timber harvest, and scenic beauty - at coarse and fine resolution (250 m vs. 25 m in Europe and 300 m vs. 30 m in the U.S.). We analyze the effects of scale on ES estimates and their spatial pattern and show how these effects are related to different ES, terrain structure and model properties. ES estimates differ substantially between the fine and coarse resolution analyses in all case studies and across all services. This scale effect is not equally strong for all ES. We show that spatially explicit information about non-clustered, isolated ES tends to be lost at coarse resolution and against expectation, mainly in less rugged terrain, which calls for finer resolution assessments in such contexts. The effect of terrain ruggedness is also related to model properties such as dependency on land use-land cover data. We close with recommendations for mapping ES to make the resulting maps more comparable, and suggest a four-step approach to address the issue of scale when mapping ES that can deliver information to support ES-based decision making with greater accuracy and reliability.

Assessing paleo-biodiversity using low proxy influx

We developed an algorithm to improve richness assessment based on paleoecological series, considering sample features such as their temporal resolutions or their volumes. Our new method can be applied to both high- and low-count size proxies, i.e. pollen and plant macroremain records, respectively. While pollen generally abounds in sediments, plant macroremains are generally rare, thus leading to difficulties to compute paleo-biodiversity indices. Our approach uses resampled macroremain influxes that enable the computation of the rarefaction index for the low influx records. The raw counts are resampled to a constant resolution and sample volume by interpolating initial sample ages at a constant time interval using the age∼depth model. Then, the contribution of initial counts and volume to each interpolated sample is determined by calculating a proportion matrix that is in turn used to obtain regularly spaced time series of pollen and macroremain influx. We applied this algorithm to sedimentary data from a subalpine lake situated in the European Alps. The reconstructed total floristic richness at the study site increased gradually when both pollen and macroremain records indicated a decrease in relative abundances of shrubs and an increase in trees from 11,000 to 7,000 cal BP. This points to an ecosystem change that favored trees against shrubs, whereas herb abundance remained stable. Since 6,000 cal BP, local richness decreased based on plant macroremains, while pollen-based richness was stable. The reconstructed richness and evenness are interrelated confirming the difficulty to distinguish these two aspects for the studies in paleo-biodiversity. The present study shows that low-influx bio-proxy records (here macroremains) can be used to reconstruct stand diversity and address ecological issues. These developments on macroremain and pollen records may contribute to bridge the gap between paleoecology and biodiversity studies.

Multiple ecosystem services of a changing Alpine landscape: past, present and future

In mountain regions, ecosystem services provision is strongly linked to land use, topography and climate, where impacts can be expected under global change. For our study site in the Austrian Alps, we examined the relationship between agricultural activities and multiple ecosystem services on landscape scale from past to future. Modelling of future land-use patterns was based on stakeholder workshops considering different socio-economic and climate scenarios. In the past, land-use intensity was reduced resulting in less forage provision but better regulating services. Future scenarios predict contrasting developments; under conditions of global change, farmers shift the focus of their activities towards tourism, but in times of global economic crisis farming becomes more important again. Developing the local economy facilitates new markets for agricultural products, but projected drought periods will cause an abandonment of farmland. While forest regeneration is valuable for regulating services, it reduces the aesthetic value. Both regulating and cultural services decrease when forage provision is optimized. To ensure multiple ecosystem service provision, agricultural management should be related to ecosystem services and included into land-use policies and agricultural incentives.