Axiotis, A. | Search bioRxiv

bioRxiv2024

Imaging spectroscopy reveals topographic variability effects on grassland functional traits and drought responses

Functional traits and their variations are essential indicators of plant metabolism, growth, distribution, and survival and determine how a plant and an ecosystem function. Under the same climatic condition, traits can vary largely between species and within the same species growing in different topographic conditions. When drought stress occurs, plants that grow in these conditions may respond differently as their topography-driven tolerance and adaptability differ. Insights into topographic variability-driven trait variation and drought response can improve our prediction of ecosystem functioning and ecological impacts. Imaging spectroscopy allows accurate detection of plant species, retrieval of functional traits, and characterization of topography-driven and drought impacts on trait variation across space. However, the use of this data in a heterogeneous grassland ecosystem is challenging as species are small, high mixed, spectrally and texturally similar, and highly varied with small-scale variation in topography. In this paper, we introduce the first study that explores the use of high-resolution airborne imaging spectroscopy to characterize the variation of common traits, including chlorophylls (Chl), carotenoids (Car), Chl/Car ratio, water content (WC), and leaf area index (LAI), across topographic gradients and under drought stress at the species level in a heterogeneous grassland. The results reveal that there were significant relationships between functional traits and topographic variability, and the degree of the relationships deferred among species and under different environmental conditions. The results also show that drought-induced trait responses varied significantly within and between species, especially between drought-tolerant invasive species and native species, between lower and upper slope positions. The study contributes greatly to the advancement in understanding biological and ecological processes for a better prediction of ecosystem functioning under stressed environments.

ecology↗

bioRxiv2021

Characterizing the effect of small-scale topographic variability on co-existing native and invasive species in a heterogeneous grassland using airborne hyperspectral remote sensing

O_LICharacterizing the distribution, mechanism, and behaviour of invasive species is crucial to implementing an effective plan for the protection and management of native grassland ecosystems. Hyperspectral remote sensing has been used for mapping and monitoring invasive species at various spatial and temporal scales. However, most studies focus either on invasive tree species mapping or on the landscape-level using low-spatial resolution remote sensing imagery. These low-resolution images are not fine enough to distinguish individual invasive grasses, especially in a heterogeneous environment where invasive species are small, fragmented, and co-existing with native plants with similar color and texture. C_LIO_LITo capture the small yet highly dynamic invasive plants at different stages of the growing season and under various topography and hydrological conditions, we use airborne high-resolution narrow-band hyperspectral imagery (HrHSI) to map invasive species in a heterogeneous grassland ecosystem in southern Ontario, Canada. C_LIO_LIThe results show that there is high spectral and textural separability between invasive species and between invasive and native plants, leading to an overall species classification accuracy of up to 89.6%. The combination of resultant species-level maps and the digital elevation model (DEM) showed that seasonality is the dominant factor that drives the distribution of invasive species at the landscape level, while small-scale topographic variations partially explain local patches of invasive species. C_LIO_LIThis study provides insights into the feasibility of using HrHSI in mapping invasive species in a heterogeneous ecosystem and offers the means to understand the mechanism and behaviour of invasive species for a more effective grassland management strategy. C_LI

ecology↗