期刊
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
卷 123, 期 1, 页码 3-17出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2017JG004105
关键词
Africa; herbaceous; leaf area index (LAI); phenology; savanna; woody
资金
- NASA Terrestrial Ecology Program [NNX13AK50G]
- Schlumberger Foundation via a Faculty for the Future Graduate Fellowship
- NASA [NNX13AK50G, 471395] Funding Source: Federal RePORTER
Savannas are widespread global biomes covering 20% of terrestrial ecosystems on all continents except Antarctica. These ecosystems play a critical role in regulating terrestrial carbon cycle, ecosystem productivity, and the hydrological cycle and contribute to human livelihoods and biodiversity conservation. Despite the importance of savannas in ecosystem processes and human well-being, the presence of mixed woody and herbaceous components at scales much finer than most medium- and coarse-resolution satellite imagery poses significant challenges to their effective representation in remote sensing and modeling of vegetation dynamics. Although previous studies have attempted to separate woody and herbaceous components, the focus on greenness indices and fractional cover provides little insight into spatiotemporal variability in woody and herbaceous vegetation structure, in particular, leaf area index (LAI). This paper presents a method to partition 1km spatial resolution Moderate Resolution Imaging Spectroradiometer (MODIS) aggregate green leaf area index (LAI(A)) from 2003 to 2015, into separate woody (LAI(W)) and herbaceous (LAI(H)) constituents in both drought seasonal savannas and moist tropical forests of Sub-Saharan Africa (SSA). In our analysis, we use an allometric relationship describing the variation in peak within-canopy woody LAI of dominant tree species (LAI(Wpinc)) across gradients in mean annual precipitation, coupled with independent estimates of woody canopy cover ((w)), to constrain seasonally changing LAI(W). We present the LAI partitioning approach and highlight the broad spatial and temporal patterns of woody and herbaceous LAI across SSA. The long-term average 8day phenologies of woody and herbaceous LAI (averaged across 2003-2015) are available for evaluation, research, and application purposes.
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