Browsing by Author "Wang, Lanhui"

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    Divergent trends of ecosystem-scale photosynthetic efficiency between arid and humid lands across the globe
    (Wiley, 2022-09) Wei, Fangli; Wang, Shuai; Fu, Bojie; Wang, Lanhui; Zhang, Wenmin; Wang, Lixin; Pan, Ning; Fansholt, Rasmus; Earth and Environmental Sciences, School of Science
    Aim Widespread greening and an increasing global terrestrial carbon sink over recent decades have been reported. However, the spatio-temporal relationships between vegetation greenness and productivity and the factors influencing this relationship remain unclear. We define a new metric of ecosystem-scale photosynthetic efficiency (EPE) to analyse its spatio-temporal pattern and investigate how potential drivers regulate the greenness–productivity relationship. Location Global. Time period From 2001 to 2016. Major taxa studied Global terrestrial ecosystems. Methods This study used global datasets of leaf area index (LAI) and solar-induced fluorescence (SIF) as proxies of vegetation greenness and ecosystem productivity, respectively, to propose a new metric of SIF/LAI, representing ecosystem-scale photosynthetic efficiency (EPE). We identified the spatial pattern and dynamics of EPE and examined factors influencing EPE. Results The results showed a weaker increase in productivity compared with the global greening rate from 2001 to 2016, suggesting a decline in EPE at the global scale. This decline in EPE indicates a disproportionate increase in terrestrial productivity against the widespread greening. When stratified into areas following an aridity gradient, we found that EPE overall showed upward trends in arid and semi-arid areas, and downward trends in dry sub-humid and humid regions. The EPE was controlled primarily by soil moisture, which promoted or constrained the EPE in xeric and mesic ecosystems, respectively. Moreover, the increase in short vegetation cover and atmospheric water demand contributed positively or negatively to EPE changes in xeric and mesic ecosystems, respectively. Main conclusions Our study shows that greening of the Earth is associated with decreasing EPE, revealing that current rates of carbon sequestration do not increase proportionally to greening of the Earth and highlighting that soil moisture is a key controller of EPE. These results help to reduce the uncertainties in future climate change impacts on vegetation dynamics, thus having implications for sustainable ecosystem management and climate change mitigation.
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    Responses and feedbacks of African dryland ecosystems to environmental changes
    (Elsevier, 2021-02) Wei, Fangli; Wang, Shuai; Brandt, Martin; Fu, Bojie; Meadows, Michael E.; Wang, Lixin; Wang, Lanhui; Tong, Xiaowei; Fensholt, Rasmus; Earth Sciences, School of Science
    Drylands occupy 43% of the African continent and play an important role in the global carbon cycle and in supporting local livelihoods. Understanding how dryland ecosystems respond to environmental changes, both structurally and functionally, is of great significance for sustainable dryland management. In this article, we review the current remote sensing-based knowledge on African dryland ecosystem dynamics and the main drivers of changes. Global CO2 enrichment, changes in rainfall regimes, and a decline in fire activity have collectively driven vegetation greening, woody plant increase and carbon dynamics in African drylands over recent decades, challenging the long-held desertification narrative. Here we also highlight the importance of rainfall–vegetation–fire feedbacks in enhancing dryland ecosystem resilience and predicting future ecosystem responses.