Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km² resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e., offset) between in-situ soil temperature measurements, based on time series from over 1200 1-km² pixels (summarized from 8500 unique temperature sensors) across all the world’s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in-situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Global maps of soil temperature.

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km <sup>2</sup> resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km <sup>2</sup> pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world\u27s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Enhancing the resilience capacity of SENSitive mountain FORest ecosystems under environmental change (SENSFOR): COST Action ES1203: SENSFOR Deliverable 5

Treeline ecotones in mountains all over the world are dynamic and in many cases changing due to human impact, but there is considerable regional variation. Nevertheless, pressures on the treeline ecotone can be differentiated in abiotic (e.g. wind, fire, drought, avalanche), biotic (e.g. insects, browsing, pathogens) and anthropogenic ones (e.g. pollution, overgrazing, global warming). There is a need for a set of indicators but it is difficult to find indicators for entire ecosystems. Indicators within treeline ecotones can be subdivided into those indicating impact on vegetation, soil or fauna. There can be natural ecosystem responses, not triggered by human impact. One example is the influence of strong winds on the growth form of trees. However, there can be responses of the ecosystem and the related ecosystem services due to human impact. One example is the erosion due to overgrazing. The ecosystem service for decomposition and thus nutrient cycling would be hampered. The connection between pressures and indicators using the Driver, Pressure, State, Impact, Response (DPSIR) framework can be clarified by showing two examples. The first example is focusing on climate change. Precipitation is one DRIVER with heavy rain events putting PRESSURE on ecotones. In case for steep slopes (STATE), the heavy rain would lead to an IMPACT on the stability of the slope. The ecological RESPONSE to this impact would be the instability of the slope with the INDICATOR of a landslide. The anthropogenic RESPONSE may be a technical solution fixing the slope. The second example is focusing on land use change. Grazing is one DRIVER and overgrazing the PRESSURE. In case there are sandy and dry soils covered by plants used as forage for the animals (STATE) the ecological RESPONSE would be erosion. In this case, the INDICATOR would be the area with bare soil. The anthropogenic RESPONSE could be the reduction of the number of grazing animals. Due to the high vulnerability of treeline ecosystems, the ecological resilience is low. When vegetation is damaged due to natural and/or human impact, erosion removes the soil cover including most of the carbon. Above- and belowground biodiversity is getting reduced, leading to reduced ecosystem services such as carbon sequestration or decomposition providing nutrients. Meanwhile, those policy makers who have to deal with climate change have following the topics on the agenda: biodiversity, land degradation and carbon sequestration. Thus, there is a slim chance, that recommendations to preserve carbon stocks, to prevent soil erosion and to protect biodiversity (including belowground biodiversity) will be accepted by policy makers. On the other hand, most of the stakeholders are not open to be convinced this way. Most probably, economic benefits will weigh more than biodiversity issues in ecotones for the future. In this deliverable, we introduce 18 indicators that help practitioners and scientists to understand changes, sustainability issues and resilience of sensitive mountain forest ecosystems. Our aim is to identify a common set of indicators to monitor and analyze changes in treeline biodiversity and to develop monitoring methodology. Findings are based on literature, previous and in-project scientific work of the SENSFOR working groups and experimental work, testing the practicality of preliminary indicators with forest technicians (Ferranti 2015). 3 It is important to understand that especially social indicators listed here might be related to treeline issues. Conflicts can take place at local level while economic and population structure changes may not have any effect on the condition of forest ecosystems. This means that following indicators do not necessarily indicate the sustainability issues linked to treeline ecotones. However, there can be connections and causalities between these variables and in each case, potential linkages need to be tested for: 1. to identify a common set of monitoring indicators to analyze changes in the treeline ecotone which could be used for monitoring; 2. to create a holistic set of indicators for the vulnerability and resilience of coupled socio-ecological systems on the basis of the DPSIR framework analysis. The following Indicators could be used for monitoring changes in the treeline ecotone: 1. Ecological Indicators are related to plants, the soil and the fauna. Usually, trees, their growth form or seedling production, are in the focus but soil indicators like carbon stock or soil biodiversity are considered less but with increasing tendency; 2. Economic Indicators, a valuable economic indicator may be the reduction of the amount of income of the stakeholders, e.g. due to reduced tourism in high mountain areas, triggered by global warming. Also, the distribution of benefits (in most cases income) among stakeholders could be influenced. 3. Social and Cultural Indicators, an important social indicator is the conflict between people who use the land and those people who would like to protect nature and the ecological ecosystem services. The indicators are explained in detail in the following, considering several case studies in different parts of Europe

Plant functional trait response to environmental drivers across European temperate forest understorey communities

Functional traits respond to environmental drivers, hence evaluating trait-environment relationships across spatial environmental gradients can help to understand how multiple drivers influence plant communities. Global-change drivers such as changes in atmospheric nitrogen deposition occur worldwide, but affect community trait distributions at the local scale, where resources (e.g. light availability) and conditions (e.g. soil pH) also influence plant communities. We investigate how multiple environmental drivers affect community trait responses related to resource acquisition (plant height, specific leaf area (SLA), woodiness, and mycorrhizal status) and regeneration (seed mass, lateral spread) of European temperate deciduous forest understoreys. We sampled understorey communities and derived trait responses across spatial gradients of global-change drivers (temperature, precipitation, nitrogen deposition, and past land use), while integrating in-situ plot measurements on resources and conditions (soil type, Olsen phosphorus (P), Ellenberg soil moisture, light, litter mass, and litter quality). Among the global-change drivers, mean annual temperature strongly influenced traits related to resource acquisition. Higher temperatures were associated with taller understoreys producing leaves with lower SLA, and a higher proportional cover of woody and obligate mycorrhizal (OM) species. Communities in plots with higher Ellenberg soil moisture content had smaller seeds and lower proportional cover of woody and OM species. Finally, plots with thicker litter layers hosted taller understoreys with larger seeds and a higher proportional cover of OM species. Our findings suggest potential community shifts in temperate forest understoreys with global warming, and highlight the importance of local resources and conditions as well as global-change drivers for community trait variation.</p

Combining biodiversity resurveys across regions to advance global change research

More and more ecologists have started to resurvey communities sampled in earlier decades to determine long-term shifts in community composition and infer the likely drivers of the ecological changes observed. However, to assess the relative importance of, and interactions among, multiple drivers joint analyses of resurvey data from many regions spanning large environmental gradients are needed. In this paper we illustrate how combining resurvey data from multiple regions can increase the likelihood of driver-orthogonality within the design and show that repeatedly surveying across multiple regions provides higher representativeness and comprehensiveness, allowing us to answer more completely a broader range of questions. We provide general guidelines to aid implementation of multi-region resurvey databases. In so doing, we aim to encourage resurvey database development across other community types and biomes to advance global environmental change research

Combining biodiversity resurveys across regions to advance global change research

More and more ecologists have started to resurvey communities sampled in earlier decades to determine long-term shifts in community composition and infer the likely drivers of the ecological changes observed. However, to assess the relative importance of, and interactions among, multiple drivers joint analyses of resurvey data from many regions spanning large environmental gradients are needed. In this paper we illustrate how combining resurvey data from multiple regions can increase the likelihood of driver-orthogonality within the design and show that repeatedly surveying across multiple regions provides higher representativeness and comprehensiveness, allowing us to answer more completely a broader range of questions. We provide general guidelines to aid implementation of multi-region resurvey databases. In so doing, we aim to encourage resurvey database development across other community types and biomes to advance global environmental change research