Assessing the recent grassland greening trend in a long-term context based on tree-ring analysis: A case study in North China
| 作者: |
Liang, E.Y., D. Eckstein, and H.Y. Liu |
| 期刊名称: |
Ecological Indicators |
| 发表年度: |
2009 |
| 卷: |
9 |
| 期: |
6 |
| 联系作者: |
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| 页码: |
1280-1283 |
| 摘要: |
Records of the Normalized Difference Vegetation Index (NDVI) and of the productivity of grassland are not long enough to reliably capture natural variation of the grassland dynamics. Herein, we compared a 20-year long growing-season NDVI time series of a typical steppe in North China, and the first principal component (PC1) of four tree-ring width chronologies (based on 69 trees from 3 Pinus tabulaeformis sites and 1 Picea meyeri site) with climate data. Both variables are significantly correlated to each other and to April-July rainfall as well as relative air humidity. This is why PC1 was taken as an indicator of greenness of vegetation in a typical steppe since 1850. The recent greening trend may have happened several times in the past as part of the moisture-driven natural variability. Periods of low growing-season NDVI values derived from tree rings were validated by historical documents. In spite of the ecological complexity, tree-ring analysis provides a simple and efficient method to mirror the key characteristics of the underlying ecological process that was primarily controlled by moisture availability. Thus, tree-ring width time series, clearly documenting the signals of environmental influences, conveys invaluable information about the steppe greenness dynamics and enables us to put the recent greening trend in a long-term context. (c) 2009 Elsevier Ltd. All rights reserved.
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