Global Change Biology最新文献

Plant health is increasingly threatened by abiotic and biotic stressors linked to anthropogenic global change. These stressors are frequently studied in isolation. However, they might have non-additive (antagonistic or synergistic) interactive effects that affect plant communities in unexpected ways. We conducted a global meta-analysis to summarize existing evidence on the joint effects of climate change (drought and warming) and biotic attack (pathogens) on plant performance. We also investigated the effect of drought and warming on pathogen performance, as this information is crucial for a mechanistic interpretation of potential indirect effects of climate change on plant performance mediated by pathogens. The final databases included 1230 pairwise cases extracted from 117 recently published scientific articles (from 2006) on a global scale. We found that the combined negative effects of drought and pathogens on plant growth were lower than expected based on their main effects, supporting the existence of antagonistic interactions. Thus, the larger the magnitude of the drought, the lower the pathogen capacity to limit plant growth. On the other hand, the combination of warming and pathogens caused larger plant damage than expected, supporting the existence of synergistic interactions. Our results on the effects of drought and warming on pathogens revealed a limitation of their growth rates and abundance in vitro but an improvement under natural conditions, where multiple factors operate across the microbiome. Further research on the impact of climate change on traits explicitly defining the infective ability of pathogens would enhance the assessment of its indirect effects on plants. The evaluated plant and pathogen responses were conditioned by the intensity of drought or warming and by moderator categorical variables defining the pathosystems. Overall, our findings reveal the need to incorporate the joint effect of climatic and biotic components of global change into predictive models of plant performance to identify non-additive interactions.

Leaf respiratory carbon loss decreases independent of temperature as the night progresses. Detailed nighttime measurements needed to quantify cumulative respiratory carbon loss at night are challenging under both lab and field conditions. We provide a simple yet accurate approach to represent variation in nighttime temperature-independent leaf respiratory CO₂ efflux in environments with both stable and fluctuating temperatures, which requires no detailed measurements throughout the night. We demonstrate that the inter- and intraspecific variation in the cumulative leaf respiratory CO₂ efflux at constant temperature, at any length of night, scales linearly with the inter- and intraspecific variation in initial measurement of leaf respiratory CO₂ efflux at the same temperature at the beginning of the night. This approach informs large-scale predictions of cumulative leaf respiratory CO₂ efflux, which is needed to understand plant carbon economy in global change studies as well as in global modeling and eddy covariance monitoring of the land–atmosphere exchange of CO₂.

In drylands, where water scarcity limits vascular plant growth, much of the primary production occurs at the soil surface. This is where complex macro- and microbial communities, in an intricate bond with soil particles, form biological soil crusts (biocrusts). Despite their critical role in regulating C and N cycling in dryland ecosystems, there is limited understanding of the fate of biologically fixed C and N from biocrusts into the mineral soil, or how climate change will affect C and N fluxes between the atmosphere, biocrusts, and subsurface soils. To address these gaps, we subjected biocrust–soil systems to experimental warming and drought under controlled laboratory conditions, monitored CO₂ fluxes, and applied dual isotopic labeling pulses (¹³CO₂ and ¹⁵N₂). This allowed detailed quantification of elemental pathways into specific organic matter (OM) pools and microbial biomass via density fractionation and phospholipid fatty acid analyses. While biocrusts modulated CO₂ fluxes regardless of the temperature regime, drought severely limited their photosynthetic C uptake to the extent that the systems no longer sustained net C uptake. Furthermore, the effect of biocrusts extended into the underlying 1 cm of mineral soil, where C and N accumulated as mineral-associated OM (MAOM_<63μm). This was strongly associated with increased relative dominance of fungi, suggesting that fungal hyphae facilitate the downward C and N translocation and subsequent MAOM formation. Most strikingly, however, these pathways were disrupted in systems exposed to warming, where no effects of biocrusts on the elemental composition of the underlying soil nor on MAOM were determined. This was further associated with reduced net biological N fixation under combined warming and drought, highlighting how changing climatic conditions diminish some of the most fundamental ecosystem functions of biocrusts, with detrimental repercussions for C and N cycling and the persistence of soil organic matter pools in dryland ecosystems.

Disentangling the influences of climate change from other stressors affecting the population dynamics of aquatic species is particularly pressing for northern latitude ecosystems, where climate-driven warming is occurring faster than the global average. Chinook salmon (Oncorhynchus tshawytscha) in the Yukon-Kuskokwim (YK) region occupy the northern extent of their species' range and are experiencing prolonged declines in abundance resulting in fisheries closures and impacts to the well-being of Indigenous people and local communities. These declines have been associated with physical (e.g., temperature, streamflow) and biological (e.g., body size, competition) conditions, but uncertainty remains about the relative influence of these drivers on productivity across populations and how salmon–environment relationships vary across watersheds. To fill these knowledge gaps, we estimated the effects of marine and freshwater environmental indicators, body size, and indices of competition, on the productivity (adult returns-per-spawner) of 26 Chinook salmon populations in the YK region using a Bayesian hierarchical stock-recruitment model. Across most populations, productivity declined with smaller spawner body size and sea surface temperatures that were colder in the winter and warmer in the summer during the first year at sea. Decreased productivity was also associated with above average fall maximum daily streamflow, increased sea ice cover prior to juvenile outmigration, and abundance of marine competitors, but the strength of these effects varied among populations. Maximum daily stream temperature during spawning migration had a nonlinear relationship with productivity, with reduced productivity in years when temperatures exceeded thresholds in main stem rivers. These results demonstrate for the first time that well-documented declines in body size of YK Chinook salmon were associated with declining population productivity, while taking climate into account.

Following old-growth forest loss and subsequent land abandonment, secondary forest grows throughout the Amazon biome. For Amazonas, agricultural colonization was unsuccessful in many regions, leading to the regeneration of secondary forest and carbon storage under favorable climate conditions. Herein, the extent of regeneration in Amazonas and its timescale are investigated, including a granular analysis of its 62 municipalities, based on the MapBiomas dataset from 1985 to 2021. By 2021, 10,495 km² of secondary forest had grown, corresponding to 28% of the lost old-growth forest. After normalization for algorithmic differences, this estimate was 17%–38% lower than prior studies for Amazonas that used earlier versions of the MapBiomas dataset, indicating increased accuracy in landcover assignments for more current versions of the dataset. For the northeastern microregion, representing the 15 municipalities of economic and population dominance in Amazonas, the growth of secondary forest varied from 3.0% to 9.8% of the total land area. For the southern microregion, constituting seven municipalities adjacent to large-scale deforestation of Mato Grosso and Rondônia, regeneration of secondary forest constituted 0.4%–1.2% of the land area. For the remaining interior municipalities, the regeneration was 0.0%–1.9%. Among the municipalities, the median regeneration interval, corresponding to the duration between the loss of old-growth forest and the appearance of secondary forest, ranged from 2 to 7 years. The median regeneration intervals of the interior, northeastern, and southern microregions were 3, 4, and 5 years, respectively. Even as the secular trend of deforestation continues in the Amazon biome and encroaches into the southern border of Amazonas state, the results herein indicate a possible resiliency toward secondary forest for undisturbed land on a timescale of several years, at least for mixed pasture-forest landscapes of kilometer-scale heterogeneity and assuming that a favorable climate persists for regeneration even as global change occurs.

The physical effects of climate warming have been well documented, but the biological responses are far less well known, especially at the ecosystem level and at large (intercontinental) scales. Global warming over the next century is generally predicted to reduce food web complexity, but this is rarely tested empirically due to the dearth of studies isolating the effects of temperature on complex natural food webs. To overcome this obstacle, we used ‘natural experiments’ across 14 streams in Iceland and Russia, with natural warming of up to 20°C above the coldest stream in each high-latitude region, where anthropogenic warming is predicted to be especially rapid. Using biomass-weighted stable isotope data, we found that community isotopic divergence (a universal, taxon-free measure of trophic diversity) was consistently lower in warmer streams. We also found a clear shift towards greater assimilation of autochthonous carbon, which was driven by increasing dominance of herbivores but without a concomitant increase in algal stocks. Overall, our results support the prediction that higher temperatures will simplify high-latitude freshwater ecosystems and provide the first mechanistic glimpses of how warming alters energy transfer through food webs at intercontinental scales.

Climate change is causing an intensification of soil drying and rewetting events, altering microbial functioning and potentially destabilizing soil organic carbon. After rewetting, changes in microbial community carbon use efficiency (CUE), investment in life history strategies, and fungal to bacterial dominance co-occur. Still, we have yet to generalize what drives these dynamic responses. Here, we collated 123 time series of microbial community growth (G, sum of fungal and bacterial growth, evaluated by leucine and acetate incorporation, respectively) and respiration (R) after rewetting and calculated CUE = G/(G + R). First, we characterized CUE recovery by two metrics: maximum CUE and time to maximum CUE. Second, we translated microbial growth and respiration data into microbial investments in life history strategies (high yield (Y), resource acquisition (A), and stress tolerance (S)). Third, we characterized the temporal change in fungal to bacterial dominance. Finally, the metrics describing the CUE recovery, investment in life history strategies, and fungal to bacterial dominance after rewetting were explained by environmental factors and microbial properties. CUE increased after rewetting as fungal dominance declined, but the maximum CUE was explained by the CUE under moist conditions, rather than specific environmental factors. In contrast, higher soil pH and carbon availability accelerated the decline of microbial investment in stress tolerance and fungal dominance. We conclude that microbial CUE recovery is mostly driven by the shifting microbial community composition and the metabolic capacity of the community, whereas changes in microbial investment in life history strategies and fungal versus bacterial dominance depend on soil pH and carbon availability.