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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Net changes in aboveground woody carbon stock in western juniper woodlands, 1946-1998
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Net changes in aboveground woody carbon stock in western juniper woodlands, 1946-1998

机译：1946-1998年，西部杜松林地上木质碳储量净变化

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Although regional increases in woody plant cover in semiarid ecosystems have been identified as a worldwide phenomenon affecting the global carbon budget, quantifying the impact of these vegetation shifts on C pools and fluxes is challenging. Challenges arise because woody encroachment is governed by ecological processes that occur at fine spatial resolutions (1-10 m) and, in many cases, at slow (decadal-scale) temporal rates over large areas. We therefore analyzed time series aerial photography, which exhibits both the necessary spatial precision and temporal extent, to quantify the expansion of western juniper into sagebrush steppe landscapes in southwestern Idaho. We established upper and lower bounds of aboveground woody carbon change across the landscape via two-dimensional spatial wavelet analysis, image texture analysis, and field data collection. Forty-eight 100-ha blocks across a 330,000-ha region were stratified by topography, soil characteristics, and land stewardship for analyses. Across the area we estimate aboveground woody carbon accumulation rates of 3.3 gCm(-2) yr(-1) and 10.0 gCm(-2) yr(-1) using the wavelet and texture method, respectively, during the time period 1946-1998. Carbon accumulation rates were significantly affected by soil properties and were highly dependent on the spatial and temporal scales of analysis. For example, at a 100-ha scale the aboveground carbon accumulation varied from -1.7 to 9.9 gCm(-2) yr(-1), while at the 1-ha scale the range of variability increased to -11 to 22 gCm(-2) yr(-1). These values are an order of magnitude lower than those previously suggested due to woody encroachment, highlighting the need for examining multiple spatial scales when accounting for changes in terrestrial carbon storage.
机译：尽管半干旱生态系统中木本植物覆盖率的区域增加已被认为是影响全球碳预算的全球性现象，但要量化这些植被转移对碳库和通量的影响仍具有挑战性。挑战之所以出现，是因为木质入侵是由生态过程控制的，该过程以良好的空间分辨率（1-10 m）发生，并且在许多情况下，以大面积区域（数十年级）的时间缓慢变化。因此，我们分析了具有必要的空间精度和时间范围的时间序列航空摄影，以量化西部杜松向西南爱达荷州的鼠尾草草原景观的扩展。我们通过二维空间小波分析，图像纹理分析和野外数据收集，确定了景观中地上木质碳变化的上限和下限。通过地形，土壤特征和土地管理进行分层，以分析33万公顷区域中的48个100公顷区块。在整个区域，我们使用小波和纹理方法分别估算了1946-1998年期间地上木质碳的积累速率，分别为3.3 gCm（-2）yr（-1）和10.0 gCm（-2）yr（-1）。 。碳积累速率受土壤性质的影响很大，并且高度依赖于分析的时空尺度。例如，在100公顷规模上，地上碳积累量从-1.7到9.9 gCm（-2）yr（-1）变化，而在1公顷规模上，变异性范围增加到-11至22 gCm（-2）yr（-1）。 2）yr（-1）。由于木质侵蚀，这些值比先前建议的值低一个数量级，这突出说明在考虑陆地碳储量变化时需要检查多个空间尺度。

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