Abstract
Grasslands play important roles in ecosystem production and support a large farming and grazing industry. An accurate and efficient way is needed to estimate grassland health and production for monitoring and adjusting management to get sustainable products and other ecosystem services. Previous studies of grasslands have shown varying relationships between productivity and biodiversity, with most showing either a positive or a hump-shaped relationship where productivity peaks at intermediate diversity. In this study, we used airborne imaging spectrometry combined with ground sampling and eddy covariance measurements to estimate the spatial pattern of production and biodiversity for two sites of contrasting productivity in a southern Alberta prairie ecosystem. Resulting patterns revealed that more diverse sites generally had greater productivity, supporting the hypothesis of a positive relationship between production and biodiversity for this site. We showed that the addition of evenness to richness (using the Shannon Index of dominant species instead of the number of dominant species alone) improved the correlation with optical diversity, an optically derived metric of biodiversity based on the coefficient of variation in spectral reflectance across space. Similarly, the Shannon Index was better correlated with productivity (estimated via NDVI (Normalized Difference Vegetation Index)) than the number of dominant species alone. Optical diversity provided a potent proxy for other more traditional biodiversity metrics (richness and Shannon index). Coupling field measurements and imaging spectrometry provides a method for assessing grassland productivity and biodiversity at a larger scale than can be sampled from the ground, and allows the integrated analysis of the productivity–biodiversity relationship over large areas.
Highlights
Grasslands occur on all continents except Antarctica and occupy nearly 25% of the land surface of the Earth [1]
Narrow-band Normalized Difference Vegetation Index (NDVI) yielded a high correlation with green biomass and Net Ecosystem Exchange (NEE)
(Table 1), confirming that NDVI provided a useful metric of productivity for this prairie ecosystem
Summary
Grasslands occur on all continents except Antarctica and occupy nearly 25% of the land surface of the Earth [1]. In North America, the Great Plains is the broad expanse of flat land located east of Remote Sens. 2016, 8, 214 the Rocky Mountains and west of the Mississippi River in the United States and Canada. This land is mainly covered in steppe and grassland, and is often referred to as “prairie.” In the United States, prairie area is 1.62 ˆ 106 km , or 21 percent of the total area of the country [2]. In Canada, prairie area is 5 ˆ 105 km , percent of the total area of the country [3]. In Alberta, approximately 7% of the area is covered by dry mixed grass prairie [4], most of which is found in southern Alberta and is contiguous with the Great Plains.
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