标题：Global vegetation variability and its response to elevated CO2, global warming, and climate variability – a study using the offline SSiB4/TRIFFID model and satellite data
摘要：Abstract. The climate regime shift during the 1980s had asubstantial impact on the terrestrial ecosystems and vegetation at differentscales. However, the mechanisms driving vegetation changes, before and afterthe shift, remain unclear. In this study, we used a biophysical dynamicvegetation model to estimate large-scale trends in terms of carbon fixation,vegetation growth, and expansion during the period 1958–2007, and toattribute these changes to environmental drivers including elevatedatmospheric CO2 concentration (hereafter eCO2), global warming,and climate variability (hereafter CV). Simulated leaf area index (LAI) andgross primary production (GPP) were evaluated against observation-based data.Significant spatial correlations are found (correlations>0.87),along with regionally varying temporal correlations of 0.34–0.80 for LAI and0.45–0.83 for GPP. More than 40% of the global land area showssignificant positive (increase) or negative (decrease) trends in LAI and GPPduring 1958–2007. Regions over the globe show different characteristics in termsof ecosystem trends before and after the 1980s. While 11.7% and 19.3%of land have had consistently positive LAI and GPP trends, respectively,since 1958, 17.1% and 20.1% of land saw LAI and GPP trends, respectively,reverse during the 1980s. Vegetation fraction cover (FRAC) trends,representing vegetation expansion and/or shrinking, are found at the edges ofsemi-arid areas and polar areas. Environmental drivers affect the change inecosystem trend over different regions. Overall, eCO2 consistentlycontributes to positive LAI and GPP trends in the tropics. Global warmingmostly affects LAI, with positive effects in high latitudes and negativeeffects in subtropical semi-arid areas. CV is found to dominate thevariability of FRAC, LAI, and GPP in the semi-humid and semi-arid areas. TheeCO2 and global warming effects increased after the 1980s, while the CVeffect reversed during the 1980s. In addition, plant competition is shown tohave played an important role in determining which driver dominated theregional trends. This paper presents new insight into ecosystemvariability and changes in the varying climate since the 1950s.
