Drivers of plant species richness and structure in dry woodland of Prosopis flexuosa

Abstract

Prosopis flexuosa (Fabaceae), a key species in desert environments, provides ecosystem services whereby it mitigates desertification and supports biodiversity conservation. To understand the relative importance of drivers of species diversity and structure of P. flexuosa-dominated woodland at different scales, we propose (1) to assess whether species richness is affected by predictors such as productivity, woodland structure, soil heterogeneity, mammal occurrence, and human activities; (2) to assess whether woodland structure is explained by productivity, soil heterogeneity, mammal occurrence and human activities; (3) to determine whether productivity and human activities affect mammal occurrence. We quantified drivers and indicators of composition and structure of P. flexuosa-dominated woodland in Ischigualasto Provincial Park and its area of impact, using both field- and remotely-based measurements. Plant species richness was positively explained by texture measures of the Soil-Adjusted Total Vegetation Index at 3x3 (0.81 ha) and 5x5 (2.25 ha) moving-window scales, as a surrogate for productivity, and by abundance of trees in the woodland stand (0.15 ha). The structure of P. flexuosa-dominated woodland was positively accounted for by productivity at the 5x5 moving-window scale and by occurrence of exotic species (positively -Bos taurus- and negatively -Lepus europaeus-). Soil heterogeneity and human activities did not affect woodland richness or structure. Occurrence of native species was explained by productivity at the 5x5 moving-window scale (positively for Microcavia maenas and negatively for Dolichotis patagonum), whereas occurrence of native (Lama guanicoe) and exotic (Equus asinus) species was affected by human activities (positively for distance to nearest village and negatively for distance to road, respectively). Understanding the relationships of dry woodland species richness and structure with different drivers is important to its conservation and management. We found that drivers such as productivity, abundance of trees and occurrence of exotic mammal species would affect richness and structure of P. flexuosa-dominated woodland.