Drought is intensifying globally with climate change, creating an urgency to understand ecosystem response to drought both during and after these events end to limit loss of ecosystem functioning. The literature is replete with studies of how ecosystems respond during drought, yet there are far fewer studies focused on ecosystem dynamics after drought ends. Furthermore, while the terms used to describe drought can be variable and inconsistent, so can those that describe ecosystem responses following drought. With this review, we sought to evaluate and create clear definitions of the terms that ecologists use to describe post-drought responses. We found that legacy effects, resilience and recovery were used most commonly with respect to post-drought ecosystem responses, but the definitions used to describe these terms were variable. Based on our review of the literature, we propose a framework for generalizing ecosystem responses after drought ends, which we refer to as 'the post-drought period'. We suggest that future papers need to clearly describe characteristics of the imposed drought, and we encourage authors to use the term post-drought period as a general term that encompasses responses after drought ends and use other terms as more specific descriptors of responses during the post-drought period.
The intensification of drought throughout the U.S. Great Plains has the potential to have large impacts on grassland functioning, as has been shown with dramatic losses of plant productivity annually. Yet, we have a poor understanding of how grassland functioning responds after drought ends. This study examined how belowground nutrient cycling responds after drought and whether legacy effects persist postdrought. We assessed the 2-year recovery of nutrient cycling processes following a 4-year experimental drought in a mesic grassland by comparing two different growing season drought treatments—chronic (each rainfall event reduced by 66%) and intense (all rain eliminated until 45% of annual rainfall was achieved)—to the control (ambient precipitation) treatment. At the beginning of the first growing season postdrought, we found that in situ soil CO2 efflux and laboratory-based soil microbial respiration were reduced by 42% and 22%, respectively, in the intense drought treatment compared to the control, but both measures had recovered by midseason (July) and remained similar to the control treatment in the second postdrought year. We also found that extractable soil ammonium and total inorganic N were elevated throughout the growing season in the first year after drought in the intense treatment. However, these differences in inorganic N pools did not persist during the growing season of the second year postdrought. The remaining measures of C and N cycling in both drought treatments showed no postdrought treatment effects. Thus, although we observed short-term legacy effects following the intense drought, C and N cycling returned to levels comparable to nondroughted grassland within a single growing season regardless of whether the drought was intense or chronic in nature. Overall, these results suggest that the key aspects of C and N cycling in mesic tallgrass prairie do not exhibit persistent legacies from 4 years of experimentally induced drought.
1. In grassland ecosystems, large herbivorous animal grazing activity and increasing nitrogen deposition strongly alter microbial community structure and function.
Aims Increasing nitrogen (N) deposition altered plant communities globally, however the changes in species abundances with short-term vs. long-term N enrichment remains unclear. Stoichiometric homeostasis (H) is a key trait predictive of plant species dominance and species responses to short-term global changes. It is unknown whether N enrichment can alter H over time, thereby affecting species responses to long-term N addition.Methods Here we address these two knowledge gaps with three representative species in a long-term N addition experiment and a sand culture experiment.Results The abundance of Leymus chinensis decreased with short-term N addition, and increased with long-term N addition, while Chenopodium glaucum showed opposite pattern. Cleistogenes squarrosa was only favored by 1-year N addition, and depressed by two and more years of N addition. The H values of L. chinensis and C. glaucum decreased signi cantly with long-term N addition however did not change for C. squarrosa. ConclusionThe decrease of H suggested the nutrients use strategy became more progressive, which mediated the responses of species abundances to short-and long-term N addition. We anticipate our research to be a starting point for explaining ecosystems function and process in response to global change from the perspective of species adaptability mediated by H.
The soil microbiome response to global change drivers remains largely unclassified, with current studies showing contrasting results to several global change drivers. One such driver, drought, is increasing in severity and frequency due to climate change. Further, legacy effects, or long-lasting impacts after drought has subsided, could have lasting impacts on the soil microbiome with important consequences for ecosystem functioning. Thus, our study aimed to understand how the soil microbiome responds after a severe, prolonged drought and whether legacy effects persist post-drought. We measured soil microbial community response in a mesic grassland for two years after a four-year experimental drought in a native tallgrass prairie. The experimental drought was imposed either (1) chronically by reducing each growing season rainfall event by 66% or (2) intensely by completely eliminating growing season rainfall until an ~45% reduction in mean annual rainfall (climatic average) was achieved. The bacterial community showed no legacies in the first season post-drought in response to either chronic or intense drought but showed an increased abundance of Verrucomicrobia and decreased richness in both treatments in the second growing season after the drought treatments ended. In the first and second post-drought growing seasons, we found small differences in beta diversity between the control and intense drought treatment for fungal communities but not for the chronic drought treatment. Further, we found that the two main phyla of fungi, Ascomycota and Basidiomycota, showed reduced relative abundance post-drought in the intense drought treatment. Overall, few legacies in soil microbial communities persisted after a four-year experimentally induced drought. However, our results show that the nature of the droughtchronic versus intense-can differentially impact fungal versus bacterial short-term legacies. These results suggest that the soil microbiome is for the most part drought resistant (responds little during drought) and/or resilient (quickly recovers post-drought, since a study at the same site found that drought impacted the bacterial community) in this mesic grassland.
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