• Energy Research

AbstractThe density of wood is a key indicator of the carbon investment strategies of trees, impacting productivity and carbon storage. Despite its importance, the global variation in wood density and its environmental controls remain poorly understood, preventing accurate predictions of global forest carbon stocks. Here we analyse information from 1.1 million forest inventory plots alongside wood density data from 10,703 tree species to create a spatially explicit understanding of the global wood density distribution and its drivers. Our findings reveal a pronounced latitudinal gradient, with wood in tropical forests being up to 30% denser than that in boreal forests. In both angiosperms and gymnosperms, hydrothermal conditions represented by annual mean temperature and soil moisture emerged as the primary factors influencing the variation in wood density globally. This indicates similar environmental filters and evolutionary adaptations among distinct plant groups, underscoring the essential role of abiotic factors in determining wood density in forest ecosystems. Additionally, our study highlights the prominent role of disturbance, such as human modification and fire risk, in influencing wood density at more local scales. Factoring in the spatial variation of wood density notably changes the estimates of forest carbon stocks, leading to differences of up to 21% within biomes. Therefore, our research contributes to a deeper understanding of terrestrial biomass distribution and how environmental changes and disturbances impact forest ecosystems.

Abstract Understanding and predicting the impact of climate change on population demography, biotic interactions and ecosystem service is central to ecology. Long-term time series analysis of insect populations is crucial for analyzing the effect of climate change on plant–insect interactions in agro-ecological systems; yet such data are often lacking. Here, based on field experiments and the long-term time series of the overwintering adult cotton bollworm Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) collected since 1975, we investigate the dynamic trend of H. armigera, as well as its driving forces and effects on the recruitment of H. armigera and crop yield. Results illustrated a shift to early eclosion of diapausing pupae due to global warming, extending the duration and abundance of adults in the overwintering generation. This then led to more larvae recruited in the first generation, and consequently damages the wheat at early growing stages. Our results suggest that the asynchronous effects of rising global surface temperature on the relative growth rate of spring crops and insect pests could intensify in the future, causing accentuated crop yield loss. To mitigate the adverse herbivore-mediated effect on crop yield in a warming climate, efficient cultivation measures and pest management are necessary, such as planting precocious crops with short growth period and timely control of insect pests.

AbstractUnderstanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, evergreen and deciduous trees. To address these gaps, we conducted a global, ground-sourced assessment of forest leaf-type variation by integrating forest inventory data with comprehensive leaf form (broadleaf vs needle-leaf) and habit (evergreen vs deciduous) records. We found that global variation in leaf habit is primarily driven by isothermality and soil characteristics, while leaf form is predominantly driven by temperature. Given these relationships, we estimate that 38% of global tree individuals are needle-leaved evergreen, 29% are broadleaved evergreen, 27% are broadleaved deciduous and 5% are needle-leaved deciduous. The aboveground biomass distribution among these tree types is approximately 21% (126.4 Gt), 54% (335.7 Gt), 22% (136.2 Gt) and 3% (18.7 Gt), respectively. We further project that, depending on future emissions pathways, 17–34% of forested areas will experience climate conditions by the end of the century that currently support a different forest type, highlighting the intensification of climatic stress on existing forests. By quantifying the distribution of tree leaf types and their corresponding biomass, and identifying regions where climate change will exert greatest pressure on current leaf types, our results can help improve predictions of future terrestrial ecosystem functioning and carbon cycling.