Doctoral Dissertation Research: Spatio-Temporal Dynamics of Woody Plant Encroachment in Semiarid Rangelands of Argentina: Changes in Carbon Stocks, Albedo, and Radiative Forcing

博士论文研究：阿根廷半干旱牧场木本植物侵占的时空动态：碳储量、反照率和辐射强迫的变化

• 批准号: 1130996
• 负责人: Jennifer Swenson
• 金额: $ 1.2万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1130996&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Spatio; Temporal; Doctoral; Dissertation; Research; Spatio; Temporal

This doctoral dissertation research project will analyze the consequences of woody plant encroachment on ecosystem carbon stocks and albedo changes at regional scale in the Western Pampas grasslands, Argentina. Land cover change dynamics alter ecosystem and climate functioning primarily through changes in matter cycles and energy fluxes. Woody plant encroachment in semiarid rangelands is a global process of land cover change driven primarily by changes in land use practices. The widespread increase in woody plant cover alters ecosystem distribution of carbon and other nutrients and influences the radiative balance due to the different reflective properties of grasses, soil and woody plants. Despite the fact that rangelands comprise almost 45% of the global land surface, our understanding of the process of encroachment is limited, in most cases, to fine resolution studies of the northern hemisphere. In this study a space-for-time substitution approach will be used to analyze changes in C stocks in the woody plant, grass, litter and soil organic carbon pools and changes in albedo along an encroachment gradient. Field measurements along this gradient will be scaled up with the use of sub-pixel woody plant cover estimates derived from moderate resolution satellite imaginary. To understand the temporal component of the process of encroachment, woody plant cover change dynamics will be analyzed between 1880, 1960 and 2009. Historical land surveys (1880) will be digitized and sampling and statistical procedures will be used to develop estimates of woody plant cover. Aerial photographs (1960) and high resolution panchromatic satellite images (2009) will be processed using spatial wavelets and texture analysis, and moderate resolution images (2010) using multi-date spectral mixture models, in order to assess the changes in woody plant cover over time. This project will be among the first to investigate spatio-temporal dynamics of woody plant encroachment and its consequences on C stock and albedo at a regional scale in the southern hemisphere. Results will be critical for more complete accounting of C and the radiative forcing associated with woody encroachment in semiarid rangelands across the globe. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

该博士学位论文研究项目将分析木本植物侵占对阿根廷西部邦帕斯草原地区尺度上生态系统碳库存和反照率变化的后果。土地覆盖变化动态改变生态系统和气候功能主要通过物质周期和能量通量的变化。木本植物在半干旱的牧场中的侵占是一个全球的土地覆盖变化过程，主要是由土地利用实践变化驱动的。由于草，土壤和木本植物的反射性不同，木本植物覆盖的广泛增加改变了碳和其他营养的生态系统分布，并影响了辐射平衡。尽管牧场几乎占全球陆地表面的45％，但在大多数情况下，我们对侵占过程的理解是有限的，可以对北半球进行精细的分辨率研究。在这项研究中，将使用一种空间替代方法来分析木质植物，草，垃圾和土壤有机碳池中C种的变化，以及沿侵占梯度的反照率变化。沿该梯度的现场测量将通过使用中像素木质植物的覆盖估计值来缩放，这些植物覆盖估计值来自中等分辨率的卫星假想。为了了解侵占过程的时间成分，将在1880年，1960年至2009年之间分析木质植物覆盖变化动态。历史土地调查（1880）将被数字化，并将使用采样和统计程序来开发木质植物覆盖的估计。航拍照片（1960年）和高分辨率全质卫星图像（2009年）将使用空间小波和纹理分析进行处理，并使用多尽日展混合模型进行中等分辨率的图像（2010），以评估随着时间的推移木质植物覆盖的变化。该项目将是最早研究木本植物侵占的时空动力学及其对C股票和反照率的后果，该动态在南半球的区域尺度上。结果对于更完整的C和全球半干旱牧场中与木质侵占相关的辐射强迫将至关重要。 作为博士学位论文研究改进奖，该奖项还将提供支持，使有前途的学生能够建立强大的独立研究职业。