Resource redistribution mediated by hydrological connectivity modulates vegetation response to aridification in drylands
Data files
Dec 19, 2024 version files 132.98 MB
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Breaks_dryad.xlsx
271.35 KB
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DataBase_dryad.csv
132.71 MB
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README.md
5.59 KB
Abstract
Water scarcity poses a significant life constraint in global drylands that determines species adaptations and mosaic of exposed bare areas and vegetation patches. Runoff-water redistribution resulting from this spatial configuration has been suggested as a key process controlling water availability for vegetation and ecosystem functioning. However, the potential of this process to ameliorate the negative impacts of aridification in drylands remains unclear and there is no empirical evidence of its relevance on natural ecosystems under different levels of aridity and disturbance regimes. To address this gap, we analysed temporal series of the Normalized vegetation index (NDVI, a proxy of vegetation functioning) along a regional aridity-disturbance gradient under current and future climatic conditions. We found that mean NDVI increases in areas of runoff water accumulation (calculated using a water redistribution index) until a certain threshold, above which vegetation patches are not able to retain extra runoff water. Once threshold values were identified, we analysed the role of water redistribution on vegetation dynamics by analysing temporal series of monthly NDVI in a space for time substitution approach. The obtained results provided further evidence of the runoff water redistribution on vegetation, triggering a positive feedback between water accumulation and vegetation growth. Results obtained by the combination of the obtained model with climatic data from the 6th IPCC report, suggest that this feedback could ameliorate the expected negative effects of aridification in drylands. However, this effect is partially counterbalance in scenarios of high human disturbance and in areas where vegetation is not able to trap and retain the extra amount of resources given by runoff. Overall, our results provide empirical evidence of the relevance of runoff redistribution as a key process linking vegetation patterns to climate resistance in drylands that underscore its importance in the analysis and modelling of dryland´s responses to aridification.
README: Resource redistribution mediated by hydrological connectivity modulates vegetation response to aridification in drylands
https://doi.org/10.5061/dryad.kwh70rzfk
Description of the data and file structure
We used R software for data analysis. Long term climatic data (average values for the period 1970-2000) were obtained from the Spanish Climate Atlas developed by the Spanish Meteorological Agency (AEMET, http://agroclimap.aemet.es). Daily climatic data for the studied period was obtainded from the climatic network of the Instituto Valenciano de Investigaciones Agrarias (IVIA, http://riegos.ivia.es/listado-de-estaciones) and the Instituto Murciano de Investigación y Desarrollo Agrario y Medioambiental (IMIDA, http://siam.imida.es). Climate predictions for the 6th IPCC report were downloaded from https://esgf-ui.ceda.ac.uk/cog/search/cmip6-ceda/. Digital Elevation Models (DEMs) were obtained from the Instituto Geográfico Nacional (IGN, https://www.ign.es/web/ign/portal). Orthoimages were obtained from National Plan of Aerial Orthophotography from Spain (PNOA, https://pnoa.ign.es/). Aridity values were obtained from Global Aridity Index Database (Trabucco and Zomer, 2018). Global Human Influence Index v2 was obtained from https://sedac.ciesin.columbia.edu/data/set/wildareas-v2-human-influence-index-geographic . NDVI from Sentinel-2 imagery was calculated in Google Earth Engine code editor (https://code.earthengine.google.com/) using the COPERNICUS/S2 image collection.
General Glossary:
GAI: Global aridity index (Trabucco and Zomer, 2018)
ETP: Potential Evapotranspiration (Trabucco and Zomer, 2018)
Tmax: Mean annual maximum temperature (AEMET, http://agroclimap.aemet.es)
Tmean: Mean annual temperature (AEMET, http://agroclimap.aemet.es)
PP: Mean annual precipitation (AEMET, http://agroclimap.aemet.es)
COVER: Vegetation cover (Calculated from PNOA, https://pnoa.ign.es/)
NDVI: Normalized Difference Vegetation Index (Calcutated from Sentinel-2 images).
HI: Global Human Influence Index (https://sedac.ciesin.columbia.edu/data/set/wildareas-v2-human-influence-index-geographic)
retention: retentioni from BalanR, a water redistribution index from (Rodriguez-Lozano et al., 2023)
Dataset description:
POINTID: Identifier of each pixel from SENTINEL-2 images studied
CODE: Identifier of each study area
CodYear: Identifier of each hydrological year studied
NDVI: Normalized Difference Vegetation Index (Calcutated from Sentinel-2 images). Can contain NA due to cloud masking and low data quality removal.
NDVIn-1: NDVI in the previous month. Please note that for the first month of data NDVIn-1 is NA. In addition, it can contain NA due to cloud masking and low data quality removal.
PP_n-1 to PP_9month: Precipitation in the previous month to 9 months before NDVI adquisition. This information was obtained from Instituto Valenciano de Investigaciones Agrarias (IVIA, http://riegos.ivia.es/listado-de-estaciones) and the Instituto Murciano de Investigación y Desarrollo Agrario y Medioambiental (IMIDA, http://siam.imida.es).
Solar: Potential incoming solar radiation calculated with the hemispherical visual basin algorithm with 100% of atmospheric transmissivity in ArcGis 10.1 (Fu, 2000).
Altitude: Altitude (m.a.s.l.) of each study area
COVER: Vegetation cover of each study pixel. Please note that you need to multiply by 100 to obtain the %
Plot_Altitude: Mean altitude of each study plot
Plot_COVER: Mean vegetation cover of each study plot. Please note that you need to multiply by 100 to obtain the %
GAI:Global aridity index (Trabucco and Zomer, 2018)
Plot_PP, Plot_Tmax and Plot_Tmean: Mean annual precipitation, Mean annual maximum temperature and Mean annual temperature (AEMET, http://agroclimap.aemet.es) of each study plot
Plot_HI: Mean Global Human Influence Index (https://sedac.ciesin.columbia.edu/data/set/wildareas-v2-human-influence-index-geographic) of each plot
ETP: Potential Evapotranspiration (Trabucco and Zomer, 2018)
ETP_1month to ETP_9month: Potential Evapotranspiration in the previous month to 9 months before NDVI adquisition. This information was calculated based on potential solar radiation and climatic data from Instituto Valenciano de Investigaciones Agrarias (IVIA, http://riegos.ivia.es/listado-de-estaciones) and the Instituto Murciano de Investigación y Desarrollo Agrario y Medioambiental (IMIDA, http://siam.imida.es).
WB1 to WB9: Water balance from month he previous month to 9 months before NDVI adquisition. This information was calculated based on ETP_1month to ETP_9month and PP_n-1 to PP_9month
class: Identifies the pixels below and above the thresholds (breakpoints).