SECTION IV ECOSYSTEM LEVEL THE ECOSYSTEM LEVEL OF ORGANIZATION INTEGRATES species interactions and community structure with their responses to, and effects on, the abiotic environment. Interactions among organisms are the mechanisms governing energy and nutrient fluxes through ecosystems. | SECTION IV ECOSYSTEM LEVEL THE ECOSYSTEM LEVEL OF ORGANIZATION INTEGRATES X species interactions and community structure with their p responses to and effects on the abiotic environment. ASS X Interactions among organisms are the mechanisms governing energy and nutrient fluxes through ecosystems. The rates and spatial patterns in which individual organisms and populations 1 acquire and allocate energy and nutrients determine the rate and direction of these fluxes see Chapters 4 and 8 . Communities vary in their ability to modify their abiotic environment. The relative abundance of various nutrient resources affects the efficiency with which they are cycled and retained within the ecosystem. Increasing biomass confers increased storage capacity and buffering against changes in resource availability. Community structure also can modify climatic conditions by controlling albedo and hydric fluxes buffering individuals against changing environmental conditions. A major issue at the ecosystem level is the extent to which communities are organized to maintain optimal conditions for the persistence of the community. Species interactions and community structures may represent adaptive attributes at the supraorganismal level that stabilize ecosystem properties near optimal levels for the various species. If so anthropogenic interference with community organization . species redistribution pest control overgrazing deforestation may disrupt stabilizing mechanisms and contribute to ecosystem degradation. Insects affect virtually all ecosystem properties especially through their effects on vegetation detritus and soils. Insects clearly affect primary productivity hence the capture and flux of energy and nutrients. In fact insects are the dominant pathway for energy and nutrient flow in many aquatic and terrestrial ecosystems. They affect vegetation density and porosity hence albedo and the penetration of light wind and precipitation. They affect accumulation and decomposition
