Chlorophyll fluorescence (ChlF) has been used to understand photosynthesis and its response to climate change, particularly with satellite-based data. However, it remains unclear how the ChlF ratio and photosynthesis are linked at the leaf level under drought stress. Here, we examined the link between ChlF ratio and photosynthesis at the leaf level by measuring photosynthetic traits, such as net CO₂ assimilation rate (A_n), the maximum carboxylation rate of Rubisco (V_cmax), the maximum rate of electron transport (J_max), stomatal conductance (g_s) and total chlorophyll content (Chl_t). The ChlF ratio of the leaf level such as maximum quantum efficiency of PSII (F_v/F_m) is based on fluorescence kinetics. ChlF intensity ratio (LD₆₈₅/LD₇₄₀) based on spectrum analysis was obtained. We found that a combination of the stomatal limitation, non-stomatal limitation, and Chl_t regulated leaf photosynthesis under drought stress, while J_max and Chl_t governed the ChlF ratio. A significant link between the ChlF ratio and A_n was found under drought stress while no significant correlation in the control, which indicated that drought stress strengthens the link between the ChlF ratio and photosynthetic traits. These results suggest that the ChlF ratio can be a powerful tool to track photosynthetic traits of terrestrial ecosystems under drought stress.

Ecosystem stability is the key to maintain the normal service function of the earth, but the dimensionalities and drivers of stability are highly controversial. A global study on the components of stability, including temporal stability, resistance, and resilience, was analyzed by gross productive production of 130 flux sites, species richness, and climate variables such as precipitation, air temperature, and shortwave radiation over a 24‐year period from 1991 to 2014. Our results provided global‐scale evidence that ecosystem stability must be analyzed as a multidimensional construct, and biome‐specific dimensionality should be considered in exploring ecosystem stability. The effective dimensionalities of ecosystem stability were significantly different among biomes, showing the least in savannas and the most in wetlands. In addition, the climate was predicted to be more important than biodiversity in regulating ecosystem stability on a global scale. The result showed that climates explained up to 70%, 49%, and 39% of the variation in temporal stability, resistance, and resilience of ecosystem function, respectively, while species richness only explained up to 5%, 20%, −11%. These findings give a comprehensive assessment for stability at the global scale and highlight the key role of climate in regulating ecosystem stability.

Fine particulate matter in the lower atmosphere (PM_2.5) continues to be a major public health problem globally. Identifying the key contributors to PM_2.5 pollution is important in monitoring and managing atmospheric quality, for example, in controlling haze. Previous research has been aimed at quantifying the relationship between PM_2.5 values and their underlying factors, but the spatial and temporal dynamics of these factors are not well understood. Based on random forest and Shapley additive explanation (SHAP) algorithms, this study analyses the spatiotemporal variations in selected key factors influencing PM_2.5 in Zhejiang Province, China, for the period 2000–2019. The results indicate that, while factors influencing PM_2.5 varied significantly during the period studied, SHAP values suggest that there is consistency in their relative importance as follows: meteorological factors (e.g., atmospheric pressure) > socioeconomic factors (e.g., gross domestic product, GDP) > topography and land cover factors (e.g., elevation). The contribution of GDP and transportation factors initially increased but has declined in the recent past, indicating that economic and infrastructural development does not necessarily result in increased PM_2.5 concentrations. Vegetation productivity, as indicated by changes in NDVI, is demonstrated to have become more important in improving air quality, and the area of the province over which it constrains PM_2.5 concentrations has increased between 2000 and 2019. Mapping of SHAP values suggests that, although the relative importance of industrial emissions has declined during the period studied, the actual area positively impacted by such emissions has actually increased. Despite developments in government policy, greater efforts to conserve energy and reduce emissions are still needed. The study further demonstrates that the combination of random forest and SHAP methods provides a valuable means to identify regional differences in key factors affecting atmospheric PM_2.5 values and offers a reliable reference for pollution control strategies.

Photosynthesis is arguably the most important biochemical process on Earth, which is dramatically influenced by environmental conditions. How environmental factors drive stomatal conductance and biochemical processes of leaf photosynthetic rate has not been sufficiently investigated in subtropical China. In this study, we analysed the effects of stomatal and biochemical parameters on the photosynthetic rate of native Masson’s pine (Pinus massoniana Lamb.) and exotic slash pine (Pinus elliottii Engelm.) in response to leaf temperature and vapour pressure deficit (VPD) in subtropical China, based on leaf gas exchange measurements in 2016. Our results showed that there was no significant difference in the light-saturated photosynthetic rate (A_sat) between native Masson’s pine and exotic slash pine. The seasonal patterns of maximum rate of the carboxylation (V_cmax25) were basically consistent with seasonal patterns of A_sat for both species. The positive effect of leaf temperature on A_sat was mainly produced through its positive effect on V_cmax25. Leaf temperature had no significant effect on stomatal conductance. V_cmax25 and g_s simultaneously affected A_sat in response to VPD. Our results highlighted the importance of biochemical processes in limiting leaf photosynthetic rate in response to environmental conditions in subtropical evergreen coniferous plantations.