Direct Phenological Responses but Later Growth Stimulation upon Spring and Summer/Autumn Warming of Prunus spinosa L. in a Common Garden Environment

Future predictions of forest ecosystem responses are a challenge, as global temperatures will further rise in the coming decades at an unprecedented rate. The effect of elevated temperature on growth performance and phenology of three Prunus spinosa L. provenances (originating from Belgium, Spain, and Sweden) in a common garden environment was investigated. One-year-old seedlings were grown in greenhouse conditions and exposed to ambient and elevated temperatures in the spring (on average 5.6 °C difference) and in the late summer/autumn of 2018 (on average 1.9 °C difference), while they were kept hydrated, in a factorial design. In the following years, all plants experienced the same growing conditions. Bud burst, leaf senescence, height, and diameter growth were recorded. Height and radial growth were not affected in the year of the treatments (2018) but were enhanced the year after (2019), whereas phenological responses depended on the temperature treatments in the year of the treatments (2018) with little carry-over effects in the succeeding years. Spring warming enhanced more height growth in the succeeding year, whereas summer/autumn warming stimulated more radial growth. Spring warming advanced bud burst and shortened the leaf opening process whereas summer/autumn warming delayed leaf senescence and enlarged the duration of this phenophase. These results can help predict the putative shifts in species composition of future forests and woody landscape elements.

Environmental Control of Inter-annual Variability of Net Ecosystem Exchange in Rice-rice Cropping System

Consecutive five-year long eddy covariance measurements in a lowland tropical rice-rice system were used to investigate the impacts of gross primary productivity (GPP), climate drivers and ecosystem responses (i.e. ecosystem respiration, RE) on the inter-annual variability (IAV) of the net ecosystem exchange (NEE), which is directly related to the agricultural productivity and climate change. The IAV of carbon dioxide fluxes in two crop growing phases i.e. dry and wet season along with fallow period were analysed. The respiratory fluxes build up during the non-growing season were lower by net uptake in growing season. Annual cumulative value of NEE was negative (sink) in both the crop growing season. The variability of climate drivers and changes in the ecosystem responses to drivers revealed a large intra-annual as well as inter-annual variability of net ecosystem fluxes. NEE was found to be strongly correlated with GPP and RE and also with other metrological variables such as photosynthetically active radiation (PAR), precipitation, air temperature and soil temperature. The anomalies of NEE, GPP and RE were observed to be less in 2017 and 2018 which may be due to lower temperature anomalies recorded in these years. Further understanding of biological mechanisms is needed which is involved in the variation of climatological variables to improve our ability to predict future IAV of NEE.

Linking species traits and demography to explain complex temperature responses across levels of organization

Microbial communities regulate ecosystem responses to climate change. However, predicting these responses is challenging because of complex interactions among processes at multiple levels of organization. Organismal traits that determine individual performance and ecological interactions are essential for scaling up environmental responses from individuals to ecosystems. We combine protist microcosm experiments and mathematical models to show that key traits—cell size, shape, and contents—each explain different aspects of species’ demographic responses to changes in temperature. These differences in species’ temperature responses have complex cascading effects across levels of organization—causing nonlinear shifts in total community respiration rates across temperatures via coordinated changes in community composition, equilibrium densities, and community–mean species mass in experimental protist communities that tightly match theoretical predictions. Our results suggest that traits explain variation in population growth, and together, these two factors scale up to influence community- and ecosystem-level processes across temperatures. Connecting the multilevel microbial processes that ultimately influence climate in this way will help refine predictions about complex ecosystem–climate feedbacks and the pace of climate change itself.

Viral infections mediate microbial food web controls on the global carbon cycle under warming

Climate warming will likely disrupt the flow of matter and energy within ecosystems, threatening the global carbon balance. Microorganisms are fundamental components of carbon cycling and are thus integral to ecosystem climate responses. However, ecosystem responses to warming are uncertain due to the functional and trophic complexity of microbial food webs. Here, we expose two major black boxes hindering our ability to anticipate ecosystem climate responses: viral infection and predation by microbial predators. We review current knowledge and uncover critical gaps in knowledge about how warming will impact these important top-down controls on the global carbon cycle. Understanding and predicting ecosystem responses to climate change will require disentangling complex direct and indirect responses within microbial food webs.

Metabolic plasticity can amplify ecosystem responses to global warming

Organisms have the capacity to alter their physiological response to warming through acclimation or adaptation, but empirical evidence for this metabolic plasticity across species within food webs is lacking, and a generalisable framework does not exist for modelling its ecosystem-level consequences. Here we show that the ability of organisms to raise their metabolic rate following chronic exposure to warming decreases with increasing body size. Chronic exposure to higher temperatures also increases the sensitivity of organisms to short-term warming, irrespective of their body size. A mathematical model parameterised with these findings shows that metabolic plasticity could account for an additional 60% of ecosystem energy flux with just +2 °C of warming. This could explain why ecosystem respiration continues to rise in long-term warming experiments and highlights the need to embed metabolic plasticity in predictive models of global warming impacts on ecosystems.

Differential Responses of Community Nonstructural Carbohydrate to Drought Manipulation Along a Natural Aridity Gradient

Plant nonstructural carbohydrates (NSC) can reflect community and ecosystem responses to environmental changes such as water availability. Climate change is predicted to increase aridity and the frequency of extreme drought events in grasslands, but it is unclear how community-scale NSC will respond to drought or how such responses may vary along aridity gradients. We experimentally imposed a 4-year drought in six grasslands along a natural aridity gradient and measured the community-weighted mean of leaf soluble sugar (SSCWM) and total leaf NSC (NSCCWM) concentrations. We observed a bell-shape relationship across this gradient, where SSCWM and total NSCCWM concentrations were lowest at intermediate aridity, with this pattern driven primarily by species turnover. Drought manipulation increased both SSCWM and total NSCCWM concentrations at intermediately arid grassland but decreased total NSCCWM concentrations at one site. These differential responses to experimental drought depended on the relative role of species turnover and intraspecific variation in driving SSCWM and total NSCCWM. Specifically, the synergistic effects of species turnover and intraspecific variation driven the responses of leaf NSC concentrations to drought, while their antagonistic effects diminished the effect of drought on plant SSCWM and total NSCCWM concentrations. Plant resource strategies were more acquisitive, via increasing chlorophyllCWM content, to offset reduced NSCCWM concentrations with increasing aridity at drier sites, but more conservative (i.e., decreased plant heightCWM) to reduce NSC consumption at more mesic sites. The relationship between water availability and NSCCWM concentrations may contribute to community drought resistance and improve plant viability and adaptation strategies to a changing climate.