Abstract
The dynamics of aboveground biomass (AGB) are driven by both climate variation and anthropogenic modification, however, few studies have evaluated the relative importance of these two drivers, especially in a heterogeneous landscape. Taking the Mongolian Plateau as a case study and employing the vegetation optical depth retrieval as a proxy of AGB, this study aimed to determine the relative importance of climatic and anthropogenic drivers on the dynamics of AGB in Mongolia (ML) and the Inner Mongolia Autonomous Region (IM), China. Spatial panel data model specific to each agro-ecological zone was employed to fulfill the task. The results revealed that: (1) Since the socio-institutional transition in the early 1990s, AGB declined in most parts of the grazing zone of Mongolia. The reduction of precipitation, the rise of temperature and the intensification of livestock grazing were the major drivers behind it. Ranked by their relative importance, the order in the grazing zone with relatively humid climate was: Precipitation ≈ temperature > livestock grazing; the order in the grazing zone with relatively arid climate was: Precipitation > temperature > livestock grazing; (2) Since the implementation of a series of ecological restoration programs in the early 2000s, AGB increased in most parts of the grazing zone of IM, and the increase of precipitation was the dominant driver behind it; (3) Since the early 2000s, AGB increased in most parts of the grazing-farming zone of IM. The increase of precipitation, the decline of temperature and the intensification of grain production were the major drivers behind it. Ranked by their relative importance, the order was: Precipitation > grain production > temperature; (4) Since the early 2000s, AGB increased in most parts of the farming zone of IM. The increase of precipitation and the intensification of grain production were the major drivers behind it. Ranked by their relative importance, the order was: Grain production > precipitation.
Highlights
Comprising ~40% of the Earth’s total land surface, grasslands store approximately 10% of the organic carbon in global terrestrial ecosystems and support the livelihoods of ~1 billion people worldwide [1,2,3,4]
With respect to anthropogenic drivers, previous studies have mainly focused on the effects of grazing regimes and intensities on the dynamics of aboveground biomass (AGB) in different grassland ecosystems by conducting systematic field investigation [22,23,24] or performing large-scale spatial analysis [25]; on this basis, some recent studies have evaluated the impacts of agricultural expansion and settlement activities on the dynamics of grassland AGB [12,15]
In tthhee GGrraazziing-A zzone, ggrasslands underwenntt a dramaticc, moderaattee aanndd sliigghhtt decrreaassee in AGB that accounted for 11.1%, 30.0% and 58.3% of the territory respectively, aanndd ffeeww ggrraassssllaannds eexxperienced an increase in AGB ((Taabbllee 33))
Summary
Comprising ~40% of the Earth’s total land surface (excluding Greenland and Antarctica), grasslands store approximately 10% of the organic carbon in global terrestrial ecosystems and support the livelihoods of ~1 billion people worldwide [1,2,3,4]. Grassland AGB is spatially and temporally highly variable [12], and climate variation and anthropogenic modification have been identified as the major drivers behind it [13,14,15,16]. Previous studies have investigated the single and combined effects of rising temperature, changing precipitation and radiation on the dynamics of grassland AGB at different spatial and temporal scales. With respect to anthropogenic drivers, previous studies have mainly focused on the effects of grazing regimes and intensities on the dynamics of AGB in different grassland ecosystems by conducting systematic field investigation [22,23,24] or performing large-scale spatial analysis [25]; on this basis, some recent studies have evaluated the impacts of agricultural expansion and settlement activities on the dynamics of grassland AGB [12,15]. Most of the above-mentioned studies just examined the single influence of climatic or anthropogenic factors on the dynamics of grassland AGB, and to date, an integrated framework to assess the relative importance of these two drivers is still seldom reported [7,26]
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