We investigated the use of a satellite-derived vegetation index to detect changes in biomass productivity in different land management regimes in drylands of the Northern Negev. Two well-documented management regimes, conservation and afforestation using a contour trenching technique were monitored. Biomass data on annual vegetation were collected from field survey and compared to a time series of the Normalized Difference Vegetation Index (NDVI). A significant relationship between NDVI and biomass (r = 0.83, P < 0.01) confirmed the applicability of satellite information to monitoring biomass production in this low productivity area. However, a strong positive relationship between NDVI and precipitation (r = 0.96 ± 0.01, P < 0.001) prevented the conventional use of trend analysis to detect changes in biomass productivity. Trends in the NDVI and precipitation use efficiency were similar in both sites due to a rainfall effect. Use of a reference site revealed the magnitude and direction of change in biomass productivity in the different land management regimes. Measures of soil organic matter confirmed these differences between the two managed sites and the reference site. We suggest that the use of abandoned lands for a reference may enhance the ability to detect changes in biomass productivity in drylands.
- Land degradation
- Trend analysis