• Energy Research

AbstractIncreasing drought frequency and severity in a warming climate threaten forest ecosystems with widespread tree deaths. Canopy structure is important in regulating tree mortality during drought, but how it functions remains controversial. Here, we show that the interplay between tree size and forest structure explains drought-induced tree mortality during the 2012-2016 California drought. Through an analysis of over one million trees, we find that tree mortality rate follows a “negative-positive-negative” piecewise relationship with tree height, and maintains a consistent negative relationship with neighborhood canopy structure (a measure of tree competition). Trees overshadowed by tall neighboring trees experienced lower mortality, likely due to reduced exposure to solar radiation load and lower water demand from evapotranspiration. Our findings demonstrate the significance of neighborhood canopy structure in influencing tree mortality and suggest that re-establishing heterogeneity in canopy structure could improve drought resiliency. Our study also indicates the potential of advances in remote-sensing technologies for silvicultural design, supporting the transition to multi-benefit forest management.

Forest canopy structural complexity (CSC) plays a crucial role in shaping forest ecosystem productivity and stability, but the precise nature of their relationships remains controversial. Here, we mapped the global distribution of forest CSC and revealed the factors influencing its distribution using worldwide light detection and ranging data. We find that forest CSC predominantly demonstrates significant positive relationships with forest ecosystem productivity and stability globally, although substantial variations exist among forest ecoregions. The effects of forest CSC on productivity and stability are the balanced results of biodiversity and resource availability, providing valuable insights for comprehending forest ecosystem functions. Managed forests are found to have lower CSC but more potent enhancing effects of forest CSC on ecosystem productivity and stability than intact forests, highlighting the urgent need to integrate forest CSC into the development of forest management plans for effective climate change mitigation.

AbstractChina’s extensive planted forests play a crucial role in carbon storage, vital for climate change mitigation. However, the complex spatiotemporal dynamics of China’s planted forest area and its carbon storage remain uncaptured. Here we reveal such changes in China’s planted forests from 1990 to 2020 using satellite and field data. Results show a doubling of planted forest area, a trend that intensified post-2000. These changes lead to China’s planted forest carbon storage increasing from 675.6 ± 12.5 Tg C in 1990 to 1,873.1 ± 16.2 Tg C in 2020, with an average rate of ~ 40 Tg C yr−1. The area expansion of planted forests contributed ~ 53% (637.2 ± 5.4 Tg C) of the total above increased carbon storage in planted forests compared with planted forest growth. This proactive policy-driven expansion of planted forests has catalyzed a swift increase in carbon storage, aligning with China’s Carbon Neutrality Target for 2060.

AbstractThe relative greenness and wetness of Giant Sequoia (Sequoiadendron giganteum) groves and the surrounding Sierra Nevada, California forests were investigated using patterns in vegetation indices from Landsat imagery for the period 1985–2015. Vegetation greenness (normalized difference vegetation index) and thus forest biomass in groves increased by about 6% over that 30 year period, suggesting a 10% increase in evapotranspiration. No significant change in the surrounding nongrove forest was observed. In this period, local temperature measurements showed an increase of about 2.2°C. The wetness of groves (normalized difference wetness index) showed no overall long‐term trend but responded to changes in annual water‐year precipitation and temperature. The long‐term trends of grove greenness and wetness varied by elevation, with the lower rain‐snow transition elevation zone (1,700–2,100 m) marking a change from an increasing trend at lower elevations to a decreasing trend at higher elevations. The 2011–2015 drought brought an unprecedented drop in grove wetness, over 5 times the 1985–2010 standard deviation, and wetness in SEGI groves dropped 50% more than in nongrove areas. Overall, the wetness and greenness of SEGI groves showed a larger response to the warming climate and drought than nongrove areas. The influence of droughts on the wetness of SEGI groves reflected effects of both the multidecadal increase in forest biomass and the effects of warmer drought‐year temperatures on the evaporative demand of current grove vegetation, plus sufficient regolith water storage of rain and snowmelt to sustain that vegetation through seasonal and multiyear dry periods.

La complejidad de la comunidad de vegetación es un factor crítico que influye en la estabilidad del ecosistema terrestre. China, el país que lidera el mundo en el reverdecimiento de la vegetación como resultado de las actividades humanas, ha experimentado cambios dramáticos en la composición de la comunidad de vegetación durante los últimos 30 años. Sin embargo, la forma en que la complejidad de la comunidad de vegetación de China varía espacial y temporalmente sigue sin estar clara. Aquí, proporcionamos los conjuntos de datos y códigos utilizados para investigar este tema, según lo publicado en "Human-climate coupled changes in vegetation community complexity of China since 1980s" por Su et al. La complexité de la communauté végétale est un facteur critique influençant la stabilité de l'écosystème terrestre. La Chine, le pays leader mondial en matière de verdissement de la végétation résultant des activités humaines, a connu des changements spectaculaires dans la composition des communautés végétales au cours des 30 dernières années. Cependant, la façon dont la complexité de la communauté végétale chinoise varie spatialement et temporellement reste incertaine. Ici, nous avons fourni les ensembles de données et les codes utilisés pour étudier cette question, tels que publiés dans « Human-climate coupled changes in vegetation community complexity of China since 1980s » par Su et al. Vegetation community complexity is a critical factor influencing terrestrial ecosystem stability. China, the country leading the world in vegetation greening resulting from human activities, has experienced dramatic changes in vegetation community composition during the past 30 years. However, how China's vegetation community complexity varies spatially and temporally remains unclear. Here, we provided the datasets and codes used to investigate this issue, as published in "Human-climate coupled changes in vegetation community complexity of China since 1980s" by Su et al. يعد تعقيد مجتمع الغطاء النباتي عاملاً حاسمًا يؤثر على استقرار النظام البيئي الأرضي. شهدت الصين، الدولة الرائدة في العالم في تخضير الغطاء النباتي الناتج عن الأنشطة البشرية، تغييرات جذرية في تكوين مجتمع الغطاء النباتي خلال الثلاثين عامًا الماضية. ومع ذلك، لا يزال من غير الواضح كيف يختلف تعقيد مجتمع الغطاء النباتي في الصين مكانيًا وزمنيًا. قدمنا هنا مجموعات البيانات والرموز المستخدمة للتحقيق في هذه المشكلة، كما نُشرت في "التغيرات المقترنة بالمناخ البشري في تعقيد مجتمع الغطاء النباتي في الصين منذ الثمانينيات" من قبل سو وآخرون.