Integrating measures of grassland function using Remote Sensing

草原提供重要的全球生态系统服务，对干扰和入侵敏感，容易迅速功能崩溃。关键的是，草原生态系统是碳汇或碳源，主要取决于围绕种植和放牧的管理做法。近几十年来，由于强烈的人类活动和气候变化，世界各地的草原已经退化，这种退化不仅威胁到生态系统，而且对生态系统服务产生了负面影响。退化带来的压力强调了了解、评估和监测草原生态系统的必要性。几十年来，研究一直使用遥感工具来确定草原生长和生产力的单独衡量标准。这包括叶面积指数、生物量、冠层高度和盖度、结构异质性以及燃烧和放牧效应。虽然这种方法促进了我们对如何孤立地监测草原群落特定要素的理解，但在评估草食和人类利用生态系统服务的社区影响方面继续取得进展的一个障碍是对草原的维管、非维管、生物和非生物特征的综合评估。由于现有的非光合作用植被(NPV)和生物土壤结皮(BSC)的存在，以及缺乏有效的量化NPV和BSC的方法，阻碍了草地综合评价的光学遥感的不确定性。此外，NPV对于确定冬季草食动物的载量至关重要；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规模草原生态系统监测和保护方面取得下一个重要进展，我建议将重点放在BSC和NPV上，并将其与已建立的光谱关系相结合。这将为区域规模、多季节测量、监测和通过承载能力估计进行养护方面的重大进展打开大门。该计划将通过以下方式解决三个关键研究空白：(1)评估NPV、BSC和裸地对估计草地生产力的总体影响；(2)开发一种利用遥感定量估计混合草原上NPV生物量和BSC盖度的方法；以及(3)利用遥感将NPV整合到时空上显式的HC估计中。这项研究的结果还将有助于理解碳固存(影响气候变化)、草原生态和草原水文学。

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.