Species traits interact with stress level to determine intraspecific facilitation and competition

Questions Flooding and drought stress are expected to increase significantly across the world and plant responses to these abiotic changes may be mediated by plant–plant interactions. Stress tolerance and recovery often require a biomass investment that may have consequences for these plant–plant interactions. Therefore, we questioned whether phenotypic plasticity in response to flooding and drought affected the balance between competition and facilitation for species with specific adaptations to drought or flooding. Location Utrecht University. Methods Stem elongation, root porosity, root:shoot ratio and biomass production were measured for six species during drought, well-drained and submerged conditions when grown alone or together with conspecifics. We quantified competition and facilitation as the ‘neighbour intensity effect’ directly after the 10-day treatment and again after a seven-day recovery period in well-drained conditions. Results Water stress, planting density and species identity interactively affected standardized stem elongation in a way that could lead to facilitation during submergence for species that preferably grow in wet soils. Root porosity was affected by the interaction between neighbour presence and time-step. Plant traits were only slightly affected during drought. The calculated neighbour interaction effect indicated facilitation for wetland species during submerged conditions and, after a period to recover from flooding, for species that prefer dry habitats. Conclusions Our results imply that changing plant–plant interactions in response to submergence and to a lesser extent to drought should be considered when predicting vegetation dynamics due to changing hydroclimatic regimes. Moreover, facilitation during a recovery period may enable species maladapted to flooding to persist

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

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-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'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

The importance of priority effects for riparian plant community dynamics

Questions The order of plant species arrival can affect recruitment and subsequent plant community development via priority effects, but is often overlooked. Priority effects occur when early-colonizing plant species affect the establishment of later-arriving species, and are hypothesized to depend on species identity and habitat conditions. In riparian ecosystems on the banks of rivers, a strong moisture gradient induces a zonation of plant species with different degrees of adaptation to soil moisture. Further, riparian zones receive seeds during floods and later in the season via wind dispersal. As such, we questioned if recruitment in riparian zones is primarily affected by (1) environmental conditions (i.e. soil moisture), (2) arrival order, and (3) species identity, or an interaction between these factors. Location Riparian zones of tributaries in the Vindel River catchment, northern Sweden. Method We designed a controlled greenhouse experiment and a large-scale field experiment where we sowed five plant species representing different dispersal events and habitat moisture preferences. We sowed seeds in three arrival order treatments (all species simultaneously, species group A phased 3 wk before group B, and vice versa) and under different soil moisture treatments in the greenhouse (dry, dry-after-wet and wet) and under a range of moisture conditions in the field. Results We found strong priority effects as early-arriving species grew bigger and often produced higher seedling densities compared to later-arriving species, both in the greenhouse and after two growing seasons in the field. Priority effects in the greenhouse were strongest in the dry and dry-after-wet treatments and weaker under wet conditions. Consistent but weaker patterns were observed in the field after the first growing season. The relative abundance of species in plant communities assembled without phased arrival interacted with soil moisture and species identity. Priority effects were strongest for species with a low relative abundance (i.e. less competitive species). Conclusions Our findings that priority effects influenced recruitment and interacted with soil moisture suggest that priority effects should be considered when addressing riparian vegetation changes after shifts in flooding regimes. This is especially important because floods will not only affect habitat conditions, but also the phasing of seed arrival

The importance of priority effects for riparian plant community dynamics

Questions The order of plant species arrival can affect recruitment and subsequent plant community development via priority effects, but is often overlooked. Priority effects occur when early-colonizing plant species affect the establishment of later-arriving species, and are hypothesized to depend on species identity and habitat conditions. In riparian ecosystems on the banks of rivers, a strong moisture gradient induces a zonation of plant species with different degrees of adaptation to soil moisture. Further, riparian zones receive seeds during floods and later in the season via wind dispersal. As such, we questioned if recruitment in riparian zones is primarily affected by (1) environmental conditions (i.e. soil moisture), (2) arrival order, and (3) species identity, or an interaction between these factors. Location Riparian zones of tributaries in the Vindel River catchment, northern Sweden. Method We designed a controlled greenhouse experiment and a large-scale field experiment where we sowed five plant species representing different dispersal events and habitat moisture preferences. We sowed seeds in three arrival order treatments (all species simultaneously, species group A phased 3 wk before group B, and vice versa) and under different soil moisture treatments in the greenhouse (dry, dry-after-wet and wet) and under a range of moisture conditions in the field. Results We found strong priority effects as early-arriving species grew bigger and often produced higher seedling densities compared to later-arriving species, both in the greenhouse and after two growing seasons in the field. Priority effects in the greenhouse were strongest in the dry and dry-after-wet treatments and weaker under wet conditions. Consistent but weaker patterns were observed in the field after the first growing season. The relative abundance of species in plant communities assembled without phased arrival interacted with soil moisture and species identity. Priority effects were strongest for species with a low relative abundance (i.e. less competitive species). Conclusions Our findings that priority effects influenced recruitment and interacted with soil moisture suggest that priority effects should be considered when addressing riparian vegetation changes after shifts in flooding regimes. This is especially important because floods will not only affect habitat conditions, but also the phasing of seed arrival

Variation in plant litter decomposition rates across extreme dry environments in Qatar

Decomposition of plant litter is a key process for transfer of carbon and nutrients in ecosystems. Carbon contained in decaying biomass is released to the atmosphere as respired CO2, a greenhouse gas that contributes to global warming. To our knowledge, there have been no studies on litter decomposition in terrestrial ecosystems in the Arabian peninsula. Here we used commercial teabags (green tea, rooibos tea) as standard substrates to study decomposition rates across contrasting ecosystems in Qatar. Teabags were buried under and beside Acacia tortilis trees, in depressions with abundant grass vegetation, in saltmarsh without and with vegetation, under Zygophyllum qatarense in drylands, in natural mangrove and in planted mangrove. There were significant site effects across ecosystems on decomposition rate (k), litter stabilisation factor (S), final weight of green tea and final weight of rooibos tea. Mangrove and depressions with grassland had the smallest amounts of remaining green and rooibos tea after the incubation period (69-82 days), while teabags buried under A. tortilis and in saltmarsh without vegetation had the largest amounts. Thus decomposition rates differ among ecosystems in the desert environment. Further multi-year and site studies are needed to identify factors that influence decomposition rates across sites in extreme environments.The authors wish to thank Marafi Abdelhameed Dafaalla and Mariana Tavelin-Sj�berg for their assistance during laboratory work. The study was partly funded by a grant from Qatar University to JMA (grant QUUG-CAS-DBES-15/16-5). JS conducted her work within the strategic theme Sustainability, sub-theme Water, Climate, and Ecosystems, at Utrecht University and was funded by the Swedish Research Council, Vetenskapsr�det.Scopu