Linking the spatial patterns of organisms and abiotic factors to ecosystem function and management: insights from semi-arid environments
Numerous theoretical and modeling studies have demonstrated the ecological significance of the spatial patterning of organisms on ecosystem functioning and dynamics. However, there is a paucity of empirical evidence that quantitatively shows how changes in the spatial patterns of the organisms forming biotic communities are directly related to ecosystem structure and functioning. In this article, I review a series of experiments and observational studies conducted in semi-arid environments from Spain (degraded calcareous shrubland, steppes dominated by Stipa tenacissima, and gypsum shrublands) to: 1) evaluate whether the spatial patterns of the dominant biotic elements in the community are linked to ecosystem structure and functioning, and 2) test if these patterns, and those of abiotic factors, can be used to improve ecosystem restoration. In the semiarid steppes we found a significant positive relationship between the spatial pattern of the perennial plant community and: i) the water status of S. tenacissima and ii) perennial species richness and diversity. Experimental plantings conducted in these steppes showed that S. tenacissima facilitated the establishment of shrub seedlings, albeit the magnitude and direction of this effect was dependent on rainfall conditions during the first yr after planting. In the gypsum shrubland, a significant, direct relationship between the spatial pattern of the biological soil crusts and surrogates of ecosystem functioning (soil bulk density and respiration) was found. In a degraded shrubland with very low vegetation cover, the survival of an introduced population of the shrub Pistacia lentiscus showed marked spatial patterns, which were related to the spatial patterns of soil properties such as soil compaction and sand content. These results provide empirical evidence on the importance of spatial patterns for maintaining ecosystem structure and functioning in semi-arid ecosystems. Furthermore, they show how taking into consideration the small-scale spatial patterns of organisms and abiotic factors, their restoration can be improved.