OOS 59-2 - Hyperspectral earth observation data can enhance our understanding of biodiversity-biological invasion relationships

Invasive plants can alter ecosystem composition, structure, and function, which in turn may have significant negative environmental and economic impacts. There is a critical need to monitor biological invasions; however, the crux of the matter is that the degree to which invasive plants affect different ecosystem characteristics is not consistent in space and time, highlighting the need for large scale studies. Optical remote sensing–which measures reflected light from the Earth surface–is capable of capturing several key ecosystem characteristics across large scales. Over the past four years, we have been using imaging spectroscopy and in-situ observations to determine the degree to which invasive plants can affect plant diversity. We have been primarily focusing on Lespedeza cuneata (hereafter L. cuneata), an aggressive invasive plant in grasslands of the U.S. Southern Great Plains.

We collected in-situ data from 900 1 m × 1 m sampling plots at the Joseph Williams Tallgrass Prairie Preserve, OK, USA in summer 2022. These data included species composition, foliage traits associated with plant function (e.g., nitrogen and phosphorus content), and plant height. We also collected airborne hyperspectral data with spatial resolution of 1 m covering the 400–2450 nm range. We then assessed the capability of remote sensing to reveal the impact of biological invasion on grassland diversity.

Our results showed that L. cuneata invasion did not affect taxonomic diversity. This finding can be attributed to the fact that although L. cuneata significantly decreased percent cover of native grasses (graminoids), it did not affect native forbs, which generally represent bulk of the plant diversity in grasslands. L. cuneata invasion, however, significantly affected community traits and functional diversity. Specifically, our results showed that the association between functional diversity and biological invasion was positive across low rates of invasion but plateaued for moderate rates of invasion. Interestingly, our findings indicated that the association between biodiversity and biological invasion is scale-dependent and can also be affected by disturbance history, particularly time since prescribed fire.
Overall, these results indicate that while the addition of one species following biological invasion can minimally affect taxonomic diversity, it can drastically modify functional diversity. This study serves as a showcase of how imaging spectroscopy can advance our understanding of biodiversity-biological invasion associations across large spatial extents.