Data and code for "Soil as a Reservoir of Multi Annual Rainfall Determining Semiarid Vegetation Productivity"

Soil as a Reservoir of Multi Annual Rainfall Determining Semiarid Vegetation Productivity (Fux, Svoray & Bell, 2024)

AbstractClimate change and natural variability alter rainfall characteristics. In dry environments, these changes affect vegetation productivity, however, studies of remotely sensed data in high resolution temporal are scarce. We quantified daily scale rainfall-productivity relationships by analyzing daily time series of rainfall and NDVI from Landsat and Sentinel imagery from Israel, New Mexico, and SW Australia. Methodologically wise, we found that the representative area size varied from 0.02--0.14 \(Km^2\), depending on the uniformity of vegetation formations. More substantive, herbaceous vegetation showed maximal response to 3--4 months cumulative rainfall, while woody vegetation response is dominated by rainfall accumulated over a year and even longer periods. These results emphasize the water reservoirs' significance upon intermittent rainfall events and may have implications for ecohydrological modeling, conservation biology, and ecosystem management.

Plain Language SummaryDry environments are characterized by high rainfall variability and water scarcity sets it as a limiting factor for vegetation growth. Yet, vegetation response to rainstorms in semiarid regions is not fully understood. Specifically, it is unclear what dominant statistical characteristic of rainstorms dictates vegetation growth. It has been long debated whether daily, seasonal or annual rainfall characteristics are crucial for triggering vegetation’s response. Here, we used high-resolution satellite images and daily rainfall records, from three locations worldwide, to investigate the rainfall-productivity relationship. We found that for most vegetation formations, maximal correlation is obtained for no lag and seasonal, or longer, rainfall accumulation periods. These results suggest that vegetation does not show a significant response to rainfall pulses but rather to accumulated rainfall over longer periods (even years). Thus, accumulated rainfall is likely stored in soil water reservoirs and remains accessible to ecosystems. These results are more pronounced in woody vegetation and should be considered for environmental management policies.

DescriptionThe compressed file contains two folders, one for the characteristic unit size test and one for the rainfall-NDVI cross correlations.The unit size folder contains NDVI images for the dates used to calculate the characteristic unit size, the shape files of the polygons used to delineate the different vegetation types areas and the R code.The rainfall-NDVI cross correlations folder contain the NDVI images for each vegetation type in each region, processed from the original data, and the code for creating the detrended and summed rainfall time series, the detrended NDVI time series and the cross-correlation analyses.The rainfall and the original satellite data are available from the resources listed in the article.