Temporal and spatial patterns of ecosystem functioning in protected arid areas in southeastern Spain

We characterized the spatial variability and temporal dynamics of the photosynthetic active radiation absorbed (APAR) by the canopy, a descriptor of ecosystem functioning, in Cabo de Gata - Nííjar Natural Park (CGNNP) (Spain). Ecosystem functioning was characterized for five landscape classes using the Normalized Difference Vegetation Index (NDVI) derived from NOAA/AVHRR LAC (1 km ×× 1 km) images. We also used a 19-year time series of NDVI PAL data (8 km ×× 8 km) to analyse the relationship APAR-precipitation inside and outside the park.The vegetation of CGNNP absorbed less than 20%% of the incoming radiation. Plains intercepted 37%% and hills 14%% less photosynthetic active radiation than mountains, the most productive landscape of the park. CGNNP showed a well-defined growing season with a unique peak of APAR. Plains and piedmont, covered by annual vegetation displayed an earlier development of the leaf area index than the shrublands and grasslands typical of the other landscapes. APAR had a significant relationship with the sum of the precipitation of the current and two previous growing seasons, except for the plains. We found that the APAR of the areas more modified by humans (outside the park) showed a lower sensitivity to changes in precipitation than those under protection. The differences were higher if the accumulated precipitation of the previous three growing seasons was considered. The description of such differences in the response of absorbed PAR to water availability are proposed as the base of a monitoring system for semi-arid and arid areas.Abbreviations: ANPP == Above-ground net primary production; APAR == Photosynthetic active radiation absorbed by green vegetation; CGNNP == Cabo de Gata - Nííjar Natural Park; fAPAR == Fraction of incoming photosynthetic active radiation absorbed by green vegetation; NPP == Net primary production; PPT == Precipitation; PUE == Precipitation use efficiency.