Ecological consequences of dead wood extraction in an arid ecosystem

Coarse woody debris (CWD) plays a key role in ecosystems, reducing erosion and affecting soil development, storing nutrients and water, providing a major source of energy and nutrients, serving as a seedbed for plants and as habitat for decomposers and heterotrophs. We asked whether removal of CWD affected the structure and functioning of an arid woodland ecosystem in mid-western Argentina. These woodlands are protected by national laws and inhabited by indigenous local pastoralists who have land rights to use natural resources, including wood for fuel and construction material. We hypothesized that removal of CWD affected negatively the populations of wood-nesting pollinators, the reproductive performance of Prosopis flexuosa (the dominant tree species), plant cover, richness and composition, and nutrient cycling in the soil. We conducted a manipulative experiment consisting of four pairs of 70 m radius circular plots, each pair with an experimental (CWD removal) and a control (no removal) plots. Experimental CWD extraction affected negatively flower visitor abundance, although the magnitude of this effect decreased over time. In contrast, extraction had a significant, positive effect on seed production of P. flextiosa. No significant effects of extraction were found on cover, richness and composition of understory plants and soil properties. Thus, CWD did not have the generally negative effects expected under our hypotheses.