Assessing the effectiveness of land restoration interventions in dry lands by multitemporal remote sensing – A case study in Ouled Dlim (Marrakech, Morocco)

Atriplex nummularia has been extensively planted in Northern Africa to combat desertification. However, few studies evaluated the effectiveness of these interventions. This study aimed at assessing the dynamic performance of a number of Atriplex plantations located in the Marrakech province in terms of multitemporal dry biomass production. Three SPOT 5 images (2004, 2008 and 2012) and field biomass measurements were integrated to quantify the dry biomass production dynamics of plantations established from 1996 to 2007. Different plant ages covered the whole plant life cycle curve. Vegetation indices were derived from the images and those of 2012 were coupled to the measured biomass of 2012 to formulate biomass models. An analysis of shrub biomass production was conducted in plantations and in adjacent rangelands, covering varying degree of plant development, and an estimate of the economic benefits generated by the plantations in terms of available fodder biomass was performed. The results show that, on average, the plantation sites produced 221 to 361Mgha(-1) of dry biomass more than the surrounding rangelands. The best performing plantations yielded even greater differences, up to more than 7Mgha(-1). It was observed that the most performing plantations, while contributing to mitigating land degradation, have generated economic value and could compensate the economic cost of the intervention even under drought conditions. However, in several cases the plantation performance was far from sustainability, particularly due to poor management (early and/or over grazing), revealing that management is a critical factor for the success of this restoration practice.