Integrating measures of grassland function using Remote Sensing

草原提供了重要的全球生态系统服务，对干扰和入侵很敏感，并且容易发生快速的功能崩溃。至关重要的是，草地生态系统是碳汇或碳源，这主要取决于围绕种植和放牧的管理实践。近几十年来，由于强烈的人类活动和气候变化，世界范围内的草地已经退化，这种退化不仅威胁到生态系统，而且对生态系统服务产生负面影响。退化带来的压力强调了了解、评价和监测草地生态系统的必要性。几十年来，研究一直使用遥感工具来确定草地生长和生产力的单独测量。这些指标包括叶面积指数、生物量、冠层高度和盖度、结构异质性以及燃烧和放牧效应。虽然这种方法提高了我们对如何孤立地监测草地群落的特定元素的理解，但在评估牧草和人类利用生态系统服务的群落效应方面继续取得进展的障碍是对草地的维管、非维管、生物和非生物特征的综合评估。现有非光合植被（NPV）和生物土壤结皮（BSC）造成的光学草地遥感不确定性，以及缺乏有效的非光合植被和生物土壤结皮量化方法，制约了草地综合评价的开展。此外，NPV是确定冬季食草动物携带能力（HCC）的关键因素；然而，这是一个遥感研究不足的领域。因此，为了在利用遥感工具进行大尺度草地生态系统监测和保护方面取得下一步的重要进展，我建议将重点放在平衡计分卡和净现值上，并将其与已建立的光谱关系相结合。这将为通过承载力估算在区域尺度、多季节测量、监测和保护方面取得重大进展打开大门。该计划将通过(1)评估净现值（NPV）、平衡计分卡（BSC）和裸土对草地生产力估算的总体影响来解决三个关键的研究空白；(2)建立了基于遥感的混合草原净现值生物量和生态平衡分盖度定量估算方法；(3)利用遥感技术将NPV整合到HCC时空显式估算中。本研究的结果也将有助于理解碳固存（影响气候变化）、草地生态学和草地水文学。

Grasslands provide vital global ecosystem services, are sensitive to disturbance and invasion, and prone to rapid functional collapse. Critically, grassland ecosystems are carbon sinks or sources depending upon management practices largely surrounding cropping and grazing. Grasslands worldwide have been degraded in recent decades due to intense human activity and climate change and this degradation not only threatens ecosystems but negatively affects ecosystem services. The pressures from degradation emphasize the need to understand, evaluate, and monitor grassland ecosystems. For decades, studies have used remote sensing tools to determine solitary measures of grassland growth and productivity. These include leaf area index, biomass, canopy height and cover, structural heterogeneity, and burn and grazing effects. While this approach has advanced our understanding of how to monitor specific elements of the grassland community in isolation, a barrier to continued progress in assessing community effects of herbivory and human use for ecosystem services is a comprehensive assessment of vascular, non-vascular, biotic and abiotic features of grasslands. A comprehensive grassland assessment is hindered by uncertainties of optical grassland remote sensing resulting from existing non-photosynthetic vegetation (NPV) and biological soil crust (BSC), and constrained by lack of an effective approach to quantify NPV and BSC. In addition, NPV is critical for determining herbivore carrying capacity (HCC) in winter; however, it is an understudied field for remote sensing. Thus, to make the next important advance in large scale grassland ecosystem monitoring and conservation using remote sensing tools, I propose to focus on BSC and NPV and integrate this with established spectral relationships. This will open the door to large advances in regional scale, multi-season measurement, monitoring and conservation through carrying capacity estimation. The proposed program will address three critical research gaps by (1) evaluating the total effect of NPV, BSC, and bare soil on estimating grassland productivity; (2) developing an approach for quantitatively estimating NPV biomass and BSC cover using a remote sensing in mixed grasslands; and (3) integrating NPV into spatiotemporally explicit HCC estimation using remote sensing. The results of this research will also contribute to an understanding of carbon sequestration (affecting climate change), grassland ecology, and grassland hydrology.