Laura Yahdjian

Soils sustain life and regulate global carbon cycling, yet the processes governing soil organic matter dynamics are inherently complex, involving multiple pathways and positive and negative feedbacks. Traditional concepts such as humus often portrayed soil carbon as a static pool whose persistence was attributed largely to the inherent biochemical recalcitrance of organic substrates. In contrast, current science emphasizes a dynamic system shaped by inputs, biotic and abiotic transformations, protection mechanisms, and fluxes among organic matter pools. Decomponology is a board game that translates this complexity into a tangible and participatory framework. Players explore soil carbon dynamics within soil organic matter by moving carbon tokens among plant litter, particulate, dissolved, and mineral‐associated organic matter pools, including losses through emissions or leaching. Spinning wheels represent probabilistic decomposition pathways mediated by soil biota. Event cards introduce specific examples of carbon movement mediated by soil organisms, as well as environmental variability, disturbances, and management decisions. By making soil processes tangible through play, Decomponology promotes systems thinking and critical engagement with soil–ecosystem interactions, offering an adaptable tool for higher education, science communication, and sustainability discussions.

Increased climate variability is expected to intensify short-term drought events. Plants have evolved stress tolerance strategies involving trade-offs in resource conservation, mycorrhizal collaboration and plant size, yet how these strategies promote drought resistance across different herbaceous plant groups remains unknown. Leveraging 63 globally distributed grassland and shrubland sites from the International Drought Experiment, we identified plant traits linked to drought resistance in 661 populations of 421 species after 1 year of extreme drought. We assessed how traits, site precipitation and drought severity affected cover change across growth forms and lifespans, and how trait–environment interactions influenced drought resistance. Across all species, leaf N (an acquisitive trait) was associated with drought resistance, whereas in forbs, drought resistance was also associated with a conservative root trait and plant size. In addition, interactions among traits mediated drought resistance; root traits predicted performance only in concert with other traits. Environmental variables influenced trait effects on drought resistance, notably for annuals in wetter sites, suggesting that drought-escape strategies in annuals may be advantageous only under mild stress. Our study highlights variability in traits that predict drought resistance across herbaceous plant groups, emphasizing the importance of species context, environmental stress and the selection of traits in research and management.

Drivers of non-native plant success in drylands are poorly understood. Here we identify functional differences between dryland native and non-native perennial plants and assess how biotic, abiotic and anthropogenic factors shape the success of the latter. On the basis of plant community and functional trait data from 98 sites across 25 countries, we report a total of 41 non-native plant species at 31 sites. Non-natives tend towards faster growth strategies than natives. Non-native plant richness is higher at sites with greater grazing pressure and under environmental conditions associated with higher soil fertility, decomposition and fungal richness—conditions that tend to occur in less arid regions—and lower where native plant and herbivore richness are greater. Non-native plant cover correlates positively with grazing pressure and negatively with native plant richness. Taken together, our results suggest that non-native plant success in drylands is facilitated when high grazing pressure coincides with elevated resource availability. Such context-dependence of non-native plant success and linkages with native plant and herbivore diversity highlight the need for managing grazing and conserving biodiversity across the world’s drylands.

Understanding the mechanisms that shape ecosystem resistance to increasing livestock grazing pressure, a major driver of land degradation, is essential for predicting its impacts and informing sustainable land management strategies. This issue is particularly relevant in drylands, which host half of the world’s livestock production and are highly vulnerable to desertification caused by overgrazing. Here we conduct a standardized field survey across 73 dryland sites in 25 countries to simultaneously evaluate how climatic, edaphic, vegetation and grazing-related factors influence ecosystem resistance—defined here as the capacity to maintain vegetation cover under increasing grazing pressure. We found that increasing grazing pressure reduced vegetation cover in 80% of sites, with an average decline of 35%. Plant species richness emerged as the strongest predictor of ecosystem resistance, with higher richness associated with lower vegetation cover loss. Functional trait data indicated that this positive effect was mainly explained by complementarity in trait values among plants, rather than by functional redundancy. Our results indicate that conserving plant diversity is key to strengthening ecosystem resistance and sustaining dryland functioning under intensifying grazing pressure.

Rangelands are vital ecosystems with high biodiversity that provide forage for livestock and help mitigate the negative impacts of climate change. However, they are increasingly threatened by more frequent and intense drought events. Understanding the key factors influencing forage sensitivity to droughts of varying durations is essential for promoting sustainable livestock production. In this study, we analysed data from multiyear drought experiments conducted across nine contrasting rangeland sites, spanning arid to humid environmental conditions. Our findings reveal that climatic variables related to water availability are the primary drivers of forage sensitivity to drought, regardless of its duration. However, biotic factors, such as plant richness and the proportion of grasses, play a particularly important role in determining sensitivity to prolonged droughts. These results offer novel insights into how rangeland forage production responds to droughts of different lengths across diverse environmental gradients. Our study advances the understanding of rangeland vulnerability to climate change and underscores the importance of species diversity in buffering the impacts of drought.

Questions: Biological invasions significantly impact plant communities, affecting and threatening biodiversity at regional and local scales worldwide. The invasion process may be influenced by climate change, particularly by the increasing frequency of extreme droughts. Here we evaluate (1) the level of exotic plant invasion along an aridity gradient and its relationship with environmental variables, and (2) the cumulative effect of prolonged droughts on native plant communities and the invasion of exotic species. Location: Rangelands located along an aridity gradient from the arid Patagonian steppe to the humid Pampa region in Argentina, South America. The study sites (11) encompass a wide range of mean annual precipitation (170–950 mm year ⁻¹ ) and diverse vegetation physiognomic characteristics. Methods: We conducted floristic surveys to assess plant community composition, diversity, and the cover of native and invasive exotic species in (1) 11 sites located along an aridity gradient, and (2) a 4‐year drought simulation experiment established in nine sites. At each experimental site, rain‐out shelters intercepted 50%–60% of incoming rainfall to simulate drought conditions. We then used linear mixed models to analyze the effects of drought on the cover, richness, and dominance of the plant community. Results: Our findings reveal (1) a positive relationship between plant invasion and rangeland humidity at the regional scale. In the humid extreme, invasive exotic species dominated the plant community, whereas in the arid extreme native species were more abundant than invasive exotic species. (2) Experimental droughts reduced native plant cover in arid and semi‐arid rangelands and promoted the cover, dominance, and richness of invasive exotic species in humid counterparts, reducing native species richness. Conclusions: This study suggests a potential intensification of biological invasions in response to increased occurrences of droughts predicted by climate change. Management strategies for invaded humid rangelands are imperative, and early warnings are crucial during dry years in arid and semi‐arid rangelands, where droughts could enhance the abundance of invasive exotic species.

As droughts become longer and more intense, impacts on terrestrial primary productivity are expected to increase progressively. Yet, some ecosystems appear to acclimate to multiyear drought, with constant or diminishing reductions in productivity as drought duration increases. We quantified the combined effects of drought duration and intensity on aboveground productivity in 74 grasslands and shrublands distributed globally. Ecosystem acclimation with multiyear drought was observed overall, except when droughts were extreme (i.e., ≤1-in-100-year likelihood of occurrence). Productivity losses after four consecutive years of extreme drought increased by ~2.5-fold compared with those of the first year. These results portend a foundational shift in ecosystem behavior if drought duration and intensity increase, from maintenance of reduced functioning over time to progressive and profound losses of productivity when droughts are extreme.

Plant biomass tends to increase under nutrient addition and decrease under drought. Biotic and abiotic factors influence responses to both, making the combined impact of nutrient addition and drought difficult to predict. Using a globally distributed network of manipulative field experiments, we assessed grassland aboveground biomass response to both drought and increased nutrient availability at 26 sites across nine countries. Overall, drought reduced biomass by 19% and nutrient addition increased it by 24%, resulting in no net impact under combined drought and nutrient addition. Among the plant functional groups, only graminoids responded positively to nutrients during drought. However, these general responses depended on local conditions, especially aridity. Nutrient effects were stronger in arid grasslands and weaker in humid regions and nitrogen-rich soils, although nutrient addition alleviated drought effects the most in subhumid sites. Biomass responses were weaker with higher precipitation variability. Biomass increased more with increased nutrient availability and declined more with drought at high-diversity sites than at low-diversity sites. Our findings highlight the importance of local abiotic and biotic conditions in predicting grassland responses to anthropogenic nutrient and climate changes.