Assessing diversity of prairie plants using remote sensing

• Author / Creator

  Wang,Ran

• Biodiversity loss endangers ecosystem services and is considered as a global change that may generate unacceptable environmental consequences on the Earth system. Global biodiversity observations are needed to provide a deep understanding of the biodiversity - ecosystem services relationship and conserve the Earth’s biodiversity. Traditionally, in situ biodiversity monitoring is limited in time and space and is usually a costly and time-consuming enterprise. Remote sensing can provide data over a large area in a consistent, objective manner and has been used to detect plant biodiversity in a range of ecosystems based on the varying spectral properties of different species or functional groups. Studies estimating biodiversity using remote sensing can be generally categorized into three types: estimating biodiversity indirectly with habitat mapping; mapping distribution of individuals as a basis for assessing community composition and diversity; and assessing species richness directly from patterns of spectral variation to yield α-diversity. However, key questions remain: 1) can the diversity-productivity relationship be assessed using remote sensing? 2) what drives the variation of optical signal among species or functional groups? and 3) what is the appropriate spectral and spatial scale for biodiversity detection using remote sensing? To answer these questions, a series studies were accomplished at Cedar Creek Ecosystem Science Reserve, Minnesota, where the biodiversity manipulation of prairie plants provided a proper diversity gradient. First, the productivity-biodiversity relationship was tested from a remote sensing perspective. Results indicated that NDVI and biodiversity were positively related, and that the NDVI-biodiversity relationship varied slightly across the growing season and was affected by other factors including canopy structure, short-term water stress, and shifting flowering patterns. Second, proximal remote sensing revealed rapid information loss with increasing pixel size. The best resolution to detect α diversity using spectral diversity at this prairie ecosystem was at a size close to a typical herbaceous plant leaf or single canopy. Furthermore, results from a combination of field spectral measurements and a modeling framework indicated that both species richness and evenness influenced spectral diversity metrics. Species identities also showed substantial effects on spectral diversity metrics at the fine scale. Background (e.g., soil) effects on spectral diversity varied with metrics: spectral diversity metrics based on information theory were sensitive to the background, while background had no effects on classification-based indices at this fine scale. Using full range spectra (400 – 2500nm) slightly increased the species separability over using visible-NIR wavelength only. Additionally, the primary spectral diversity metric, the coefficient of variation of spectral reflectance in space, was also tested in a prairie ecosystem in Southern Alberta to detect the biodiversity in a natural landscape. Overall, the plant optical signal was influenced by both leaf traits and canopy structure, and the ability to use spectral diversity metrics in biodiversity estimation depended on the species richness, evenness, composition, associated spectral properties, sensor characteristics, and the particular spectral diversity metrics selected. This project provides a critical foundation for assessing biodiversity using imaging spectrometry and these findings can be used to guide regional studies of biodiversity estimation using high spatial and spectral resolution remote sensing.

• Subjects / Keywords

  • Imaging spectroscopy
  • Remote sensing
  • Biodiversity
  • Grasslands

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R32805C5N

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.