Abstract
Accurate estimation of forest biomass C stock is essential to understand carbon cycles. However, current estimates of Chinese forest biomass are mostly based on inventory-based timber volumes and empirical conversion factors at the provincial scale, which could introduce large uncertainties in forest biomass estimation. Here we provide a data-driven estimate of Chinese forest aboveground biomass from 2001 to 2013 at a spatial resolution of 1 km by integrating a recently reviewed plot-level ground-measured forest aboveground biomass database with geospatial information from 1-km Moderate-Resolution Imaging Spectroradiometer (MODIS) dataset in a machine learning algorithm (the model tree ensemble, MTE). We show that Chinese forest aboveground biomass is 8.56 Pg C, which is mainly contributed by evergreen needle-leaf forests and deciduous broadleaf forests. The mean forest aboveground biomass density is 56.1 Mg C ha−1, with high values observed in temperate humid regions. The responses of forest aboveground biomass density to mean annual temperature are closely tied to water conditions; that is, negative responses dominate regions with mean annual precipitation less than 1300 mm y−1 and positive responses prevail in regions with mean annual precipitation higher than 2800 mm y−1. During the 2000s, the forests in China sequestered C by 61.9 Tg C y−1, and this C sink is mainly distributed in north China and may be attributed to warming climate, rising CO2 concentration, N deposition, and growth of young forests.
Highlights
Forests contain about 80% of global terrestrial aboveground biomass (AGB), and play a key role in the global carbon cycle [1,2]
It has been estimated that forest ecosystems have sequestered annually 1.1 Pg of the carbon over the last two decades [3], which is nearly about 16% of the carbon released by fossil fuel CO2 emissions during the same period [4]
During the period 2001–2013, the total AGB of Chinese forests is estimated to be 8.56 Pg C, with an average aboveground biomass density (AGBD) of 56 Mg C ha-1 over a forest area of 153 Mha (Table 2). This total forest C stock is mainly contributed by evergreen needle leaf forests (ENF) and deciduous broadleaf forests (DBF), which account for 41.5% (3.55 Pg C) and 30.4% (2.60 Pg C) of total forest AGB respectively
Summary
Forests contain about 80% of global terrestrial aboveground biomass (AGB), and play a key role in the global carbon cycle [1,2]. It has been estimated that forest ecosystems have sequestered annually 1.1 Pg of the carbon over the last two decades [3], which is nearly about 16% of the carbon released by fossil fuel CO2 emissions during the same period [4]. There is considerable uncertainty about the magnitude of the forest carbon sink, and even larger uncertainty about its location. Much of this uncertainty is attributed by the incomplete information regarding the spatial distribution of carbon stored in biomass [5,6]. It is PLOS ONE | DOI:10.1371/journal.pone.0130143 June 26, 2015
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