Spatial and temporal patterns of herbaceous primary production in semi-arid shrublands: a remote sensing approach

OESTERHELD, M.; PARUELO, J.M.; BLANCO, L.; BIURRUN, F.N.

JOURNAL OF VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 p. 1 - 12

1100-9233

Questions: Can herbaceous above-ground net primary production (ANPP) beestimated from remote sensing when woody and herbaceous plants are inter-mingled? How does herbaceous ANPP change in space and time in an ecosystemdominated by woody species? What are the main controls of herbaceous ANPPto paddock scale?Location: Native plant communities and buffelgrass roller chopped pastures ofthe Arid Chaco, western Argentina (28?32° S, 64?67° W; area: 100 000 km2).Methods: We decomposed normalized difference vegetation index (NDVI)data from MODIS (pixel size: 250 m 9 250 m) into woody (W) and herba-ceous (H) components. We calibrated the relationship between field esti-mates of herbaceous ANPP and the H component of NDVI using linearregression. The regression model fitted was applied to a 10-yr MODIS data-base for four paddocks to estimate herbaceous ANPP. We analysed the rela-tionship between herbaceous ANPP and watering point distance andgrowing season precipitation.Results: The annual integral of NDVI 9 proportion of the herbaceous com-ponent [H/(H + W)] explained 71% and 91% of herbaceous ANPP varia-tion in native plant communities and buffelgrass roller chopped pastures,respectively. The regression model fitted, however, differed (P < 0.05)between the two types of system. The NDVI annual integral explained ahigher proportion of herbaceous ANPP variations than the NDVI annualpeak or the growing season (December?April) integral. For native plantcommunities, herbaceous production increased significantly (P < 0.05) withwatering point distance, and marginally significantly (P < 0.10) with grow-ing season precipitation. For buffelgrass roller chopped pastures, the herba-ceous production increased significantly (P < 0.05) with growing seasonprecipitation.Conclusion: Our model was able to estimate herbaceous ANPP from the decom-position of an NDVI time series that included woody components. Thus, themodel provides the basis for more accurate monitoring of spatial and temporalvariability of herbaceous ANPP in areas where herbaceous and woody plantcomponents co-exist. Applying our models, we detected clear spatial and tempo-ral patterns of herbaceous ANPP. The possibility of describing in a spatially expli-cit way the past 14 yrs of herbaceous ANPP allows designing livestockmanagement strategies and devise alternatives to control degradation processesin the Arid Chaco.