Spatio-temporal variation in vegetation biomass and its relationships with climate factors in the Xilingol grasslands, Northern China.
Spatio-temporal variation in vegetation biomass and its relationships with climate factors in the Xilingol grasslands, Northern China.
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DOI：
10.1371/journal.pone.0083824
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
Xu B
中科院分区：
文献类型：
--
作者：
Gao T;Yang X;Jin Y;Ma H;Li J;Yu H;Yu Q;Zheng X;Xu B
了解草地生物量及其动态对研究区域碳循环和草地资源的可持续利用至关重要。以锡林郭勒草原为研究对象，研究了锡林郭勒草原生物量的时空变化特征。利用野外生物量样本和MODIS时间序列数据集，分别建立了归一化植被指数（NDVI）与地上生物量（AGB）和地上生物量（AGB）与地下生物量（BGB）关系的经验模型。我们进一步探索了这些变化的气候控制。结果表明：2001 - 2012年，在19.6×104 km2的总面积上，平均生物量为99.01 Tg (1 Tg=1012 g)，变化趋势不显著；平均生物量密度为505.4 g/m2， AGB为62.6 g/m2， BGB为442.8 g/m2，总体由东北向西南递减，空间异质性较大。AGB的年际变化与生长季降水（GSP）的年际变化基本一致，呈显著正相关（R2=0.82， P<0.001），而与生长季温度（GST）的年际变化呈相反的耦合趋势（R2=0.61， P=0.003）。气候因子也影响AGB的空间分布，随着GSP梯度的增加，AGB逐渐增加（R2=0.76， P<0.0001），而随着GST的增加，AGB逐渐减少（R2=0.70， P<0.0001）。综合GST和GSP影响的湿度指数的改善比单独降水更能解释AGB的变化（R2=0.81， P<0.0001）。AGB与GSP之间的关系可以用幂函数拟合。GSP - agb关系沿GSP梯度的斜率增大可能部分归因于锡林郭勒GST-GSP空间格局。研究结果表明，气候因子与AGB之间的关系可能是尺度依赖的，需要多尺度研究和足够的长期野外数据来检验AGB与气候因子之间的关系。
Knowledge about grassland biomass and its dynamics is critical for studying regional carbon cycles and for the sustainable use of grassland resources. In this study, we investigated the spatio-temporal variation of biomass in the Xilingol grasslands of northern China. Field-based biomass samples and MODIS time series data sets were used to establish two empirical models based on the relationship of the normalized difference vegetation index (NDVI) with above-ground biomass (AGB) as well as that of AGB with below-ground biomass (BGB). We further explored the climatic controls of these variations. Our results showed that the biomass averaged 99.01 Tg (1 Tg=1012 g) over a total area of 19.6×104 km2 and fluctuated with no significant trend from 2001 to 2012. The mean biomass density was 505.4 g/m2, with 62.6 g/m2 in AGB and 442.8 g/m2 in BGB, which generally decreased from northeast to southwest and exhibited a large spatial heterogeneity. The year-to-year AGB pattern was generally consistent with the inter-annual variation in the growing season precipitation (GSP), showing a robust positive correlation (R2=0.82, P<0.001), but an opposite coupled pattern was observed with the growing season temperature (GST) (R2=0.61, P=0.003). Climatic factors also affected the spatial distribution of AGB, which increased progressively with the GSP gradient (R2=0.76, P<0.0001) but decreased with an increasing GST (R2=0.70, P<0.0001). An improved moisture index that combined the effects of GST and GSP explained more variation in AGB than did precipitation alone (R2=0.81, P<0.0001). The relationship between AGB and GSP could be fit by a power function. This increasing slope of the GSP–AGB relationships along the GSP gradient may be partly explained by the GST–GSP spatial pattern in Xilingol. Our findings suggest that the relationships between climatic factors and AGB may be scale-dependent and that multi-scale studies and sufficient long-term field data are needed to examine the relationships between AGB and climatic factors.
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