• Energy Research

Climate change is leading to a species redistributions. In the tundra biome, many shrub species are expanding into new areas, a process known as shrubification. However, not all tundra shrub species will benefit from warming. Winner and loser species (those projected to expand and contract their ranges, and/or those that have increased or decreased in cover over time), and the characteristics that may determine success or failure, have not been fully identified. Here, we investigate whether current range sizes are related to plant trait values and intraspecific trait variation by combining 17,921 trait records and distribution data from 62 shrub species across three continents (>30 degrees north). In addition, we determine which traits are associated with species projected by species distribution models to expand or contract their ranges under climate change, and species that have undergone past cover changes over time. Winner and loser shrub species identified from projected range shifts generally differed from those identified from observed past cover change. We found that greater variation in seed mass and specific leaf area were related to larger projected range shifts. Projected winner species generally had greater seed mass values than ‘no change’ and loser species. However, contrary to our expectations, traits’ values and variation were not consistently related to current and projected ranges, and depended upon the future climate scenarios considered in range projections. There were no clear relationships either between cover change over time and trait values or variation. Overall, our findings indicate that abundance changes and projected range shifts will not lead to directional modifications in shrub trait composition or variation with future warming, since winner and loser species share relatively similar trait spaces based on commonly measured traits. Future research could investigate other morpho-physiological traits underpinning climatic preferences, which might better predict future range and abundance changes.

Global change is associated with variable shifts in the annual production of aboveground plant biomass, suggesting localized sensitivities with unclear causal origins. Combining remotely sensed normalized difference vegetation index data since the 1980s with contemporary field data from 84 grasslands on 6 continents, we show a widening divergence in site-level biomass ranging from +51% to -34% globally. Biomass generally increased in warmer, wetter and species-rich sites with longer growing seasons and declined in species-poor arid areas. Phenological changes were widespread, revealing substantive transitions in grassland seasonal cycling. Grazing, nitrogen deposition and plant invasion were prevalent in some regions but did not predict overall trends. Grasslands are undergoing sizable changes in production, with implications for food security, biodiversity and carbon storage especially in arid regions where declines are accelerating.

AbstractLittle is currently known about how climate modulates the relationship between plant diversity and soil organic carbon and the mechanisms involved. Yet, this knowledge is of crucial importance in times of climate change and biodiversity loss. Here, we show that plant diversity is positively correlated with soil carbon content and soil carbon-to-nitrogen ratio across 84 grasslands on six continents that span wide climate gradients. The relationships between plant diversity and soil carbon as well as plant diversity and soil organic matter quality (carbon-to-nitrogen ratio) are particularly strong in warm and arid climates. While plant biomass is positively correlated with soil carbon, plant biomass is not significantly correlated with plant diversity. Our results indicate that plant diversity influences soil carbon storage not via the quantity of organic matter (plant biomass) inputs to soil, but through the quality of organic matter. The study implies that ecosystem management that restores plant diversity likely enhances soil carbon sequestration, particularly in warm and arid climates.

Alpine areas of the tropical Andes constitute the largest of all tropical alpine regions worldwide. They experience a particularly harsh climate, and they are fragmented into tropical alpine islands at various spatial scales. These factors generate unique patterns of continental insularity, whose impacts on biodiversity remain to be examined precisely. By reviewing existing literature and by presenting unpublished data on beta-diversity and endemism for a wide array of taxonomic groups, we aimed at providing a clear, overall picture of the isolation-biodiversity relationship in the tropical alpine environments of the Andes. Our analyses showed that (1) taxa with better dispersal capacities and wider distributions (e.g., grasses and birds) were less restricted to alpine areas at local scale; (2) similarity among communities decreased with spatial distance between isolated alpine areas; and (3) endemism reached a peak in small alpine areas strongly isolated from main alpine islands. These results pinpoint continental insularity as a powerful driver of biodiversity in the tropical High Andes. A combination of human activities and warming is expected to increase the effects of continental insularity in the next decades, especially by amplifying the resistance of the lowland matrix that surrounds tropical alpine islands.

Abstract Soil respiration accounts for ca. three quarters of total ecosystem respiration and is sensitive to temperature and moisture. Plants can influence soil CO2 emissions through specific effects on soil humidity, soil temperature and soil microbial communities. These plant-soil effects mostly come via litter production and root exudates, enhancing soil autotrophic and heterotrophic respiration. We explored how plant species affected soil CO2 emissions in an arid environment. We altered soil temperature in bare soil and under the canopy of four plant species differing in functional type, and measured monthly fluxes to establish seasonal patterns of CO2 release along a 20-month period. We found that soil temperature explained 69% of the annual soil respiration (SR) variance, while soil water content explained 71% of SR variance. When we included plant species identity in the model, soil temperature and soil water content explained 76% and 81% of SR variance, respectively, exemplifying how plant species modulate SR responses as a function of temperature and water availability. Our results demonstrate that plant species influence soil carbon balance and emphasize that species identity matters in dry ecosystems. SR dynamics in dry ecosystems can be accurately modelled with soil water and temperature as predictors, but models are more efficient if plant species identity is considered.