Wetland Dynamics Inferred from Spectral Analyses of Hydro-Meteorological Signals and Landsat Derived Vegetation Indices

Abstract

The dynamic response of coastal wetlands (CWs) to hydro-meteorological signals is a key indicator for understanding climate driven variations in wetland ecosystems. This study explored the response of CW dynamics to hydro-meteorological signals using time series of Landsat-derived normalized difference vegetation index (NDVI) values at six locations and hydro-meteorological time-series from 1984 to 2015 in Apalachicola Bay, Florida. Spectral analysis revealed more persistence in NDVI values for forested wetlands in the annual frequency domain, compared to scrub and emergent wetlands. This behavior reversed in the decadal frequency domain, where scrub and emergent wetlands had a more persistent NDVI than forested wetlands. The wetland dynamics were found to be driven mostly by the Apalachicola Bay water level and precipitation. Cross-spectral analysis indicated a maximum time-lag of 2.7 months between temperature and NDVI, whereas NDVI lagged water level by a maximum of 2.2 months. The quantification of persistent behavior and subsequent understanding that CW dynamics are mostly driven by water level and precipitation suggests that the severity of droughts, floods, and storm surges will be a driving factor in the future sustainability of CW ecosystems.

Long-Term Wetland Monitoring Using the Landsat Archive: A Review

“…Changes in wetlands were detected mainly using multi-temporal approaches (77.5%), followed by time-series analyses (18%), e.g., [127,128], and the diachronic approach (5%), e.g., [129,130] (Figure 6). The diachronic approach (change detection by processing two images of different dates) widely used to map LULC, although fast and simple, does not consider the intra-and inter-annual variability of wetland water and vegetation, which leads to errors in wetland area estimation and habitat classification.…”

Immediate and Long-term Responses of Coastal Vegetation to Extreme Storm Events along the Northern Gulf of Mexico

“…Additionally, precipitation may lead to increases in species abundances or shifts in species distributions (Callaway and Sabraw 1994). Wetland vegetation generally responds more to precipitation than wind and temperature (Tahsin et al 2020), which is likely why greenness of wetland vegetation peaks during the spring and summer, as availability of fresh water increases (Tahsin et al 2020). Over longer time scales, increases in precipitation are likely to lead to increases of fresh marsh species, such as Cladium jamaicense, and decreases of salt marsh species, such as Schoenoplectus americanus in seed banks (Jarrell et al 2016).…”

Unveiling the increasingly altered patterns of wetland ecosystem functional diversity in the lower Delta of the Paraná River

“…Due to their robust biological and temporal significance, metrics were estimated from the high-frequency (D 1 ), intra-annual (D 2 ) and annual (D 3 ) components' quadratic sum (Figure 2) (Campos & Di Bella, 2012). The seventh metric was derived from a pixel-wise phase analysis carried out on the Fourier transformed NDVI time-series data (Figure 2), that assesses the Julian day in which the first relative peak of NDVI (dMAX) occurs (Tahsin et al, 2020).…”