Open access publications in the SLU publication database

Abstract

Functional types are becoming central when searching for generalities in community ecology. They may help in identifying the driving factors that shape communities, as well as in formulating ecological rules. In this thesis I show that functional types of mammal species may determine the species’ responses to various environmental gradients, such as of resource availability and disturbance. My data originate from two contrasting regions of the world, the arid savannas of southern and eastern Africa and the boreal forest of central Sweden, and comprise different spatial and temporal scales. Methods include distance sampling technique, wildlife triangle census, small mammal trapping, vegetation survey and GIS-analysis. Mammal community species richness is lower in the boreal forest than on the savanna. The boreal forest ecosystem is also characterized by few species of herbivores, while the number of predators is high. In the savanna the herbivores dominate. In comparison with savannas the boreal forest is a low productive, homogeneous habitat with a high dominance of two tree species and may thus support merely a low diversity of herbivores. However, the predator diversity seems little affected by prey species diversity and is probably more so by biomass of prey. I found indications that the Jarman-Bell principle, formulated for savanna ungulates, also applies to herbivores in the northern boreal forest. It states that due to metabolic constraints, small-sized herbivores, especially foregut fermenters, will dominate in nutrient-rich areas and large-sized herbivores, especially hindgut fermenters, in nutrient poor areas. The results show that under high-nutrient conditions most boreal herbivores belong to the smaller of two mass classes, while there was no pattern under low-nutrient conditions. The smaller herbivores, as well as the foregut fermenters, also contributed to a larger proportion of the metabolic biomass in the nutrient-rich, compared with the nutrient-poor, area. In summary, my results suggest similarities as well as differences between the structuring factors and processes of mammal communities depending on spatial scale and biome. I recommend that future research in community ecology center around multi-species approaches, including multiple functional types, also for questions which are traditionally restricted to few-species relationships.