Ecosystem

About: Ecosystem is a research topic. Over the lifetime, 25460 publications have been published within this topic receiving 1291375 citations. The topic is also known as: ecological system & Ecosystem.

The effect of plants on mineral weathering

Abstract: This paper is centered on the specific effects of plants on the soil weathering environment; we attempt to address how to quantify this component of the ecosystem and assess feedbacks between plants and weathering processes that influence the degree and rates of mineral weathering. The basic processes whereby plants directly influence the soil chemical environment is through the generation of weathering agents, biocycling of cations, and the production of biogenic minerals. Plants may indirectly influence soil processes through the alteration of regional hydrology and local soil hydrologic regime which determines the residence time of water available for weathering. We provide a brief review of the current state of knowledge regarding the effects of plants on mineral weathering and critical knowledge gaps are highlighted. We summarize approaches that may be used to help quantify the effects of plants on soil weathering such as state factor analyses, mass balance approaches, laboratory batch experiments and isotopic techniques. We assess the changes in the soil chemical environment along a tropical bioclimatic gradient and identify the possible effects of plant production on the soil mineralogical composition. We demonstrate that plants are important in the transfer of atmospheric carbon dioxide into the mineral weathering cycle and speculate how this may be related to ecosystem properties such as NPP. In the soils of Hawaiian rainforests subjected to deforestation, pasture grasses appear to change the proportion of non crystalline to crystalline minerals by altering the soil hydrologic regime or partitioning silica into more stable biogenic forms. A better understanding of the relationship between soil weathering processes and ecosystem productivity will assist in the construction predictive models capable of evaluating the sensitivity of biogeochemical cycles to perturbations.

Breeding Bird Populations in Relation to Plant Succession on the Piedmont of Georgia

Abstract: Ecological succession, or the orderly change and development of biotic communities and the ecosystems of which they are a part, is one of the important principles of ecology. Plant succession has been subject to much investigation since 1900, but animal succession is less well-known, studies of it being mostly qualitatively descriptive. Due to the great mobility of animals and the general lack of knowledge dealing with taxonomy and life histories of a large part of the fauna, animal succession in terrestrial communities is more difficult to study than plant succession. At present, the most profitable line of approach is to select for study some significant part of the community or a "population" composed of species groups for which good census methods have been worked out. In terrestrial communities, birds are usually conspicuous components, and the territorial behavior of many species makes possible relatively accurate field determinations of population density during the breeding season. Furthermore, community selection by birds is most pronounced during this critical period in their life history. Since animals, as well as plants, may be active agents in bringing about community changes, quantitative data on population size should help in the understanding, prediction, and control of the changes which we designate as "ecological succession. The present paper deals with the breeding bird populations of areas representing seral stages in secondary succession on the upland of the Piedmont physiographic region. A similar study in the Mountain region has been published (Odum 1950) and one for the Coastal Plain is in progress. For aid in the location and botanical description of study areas we are indebted to the following: Dr. Wilbur H. Duncan, Dr. Don L. Jacobs, Depart1 Present address: Dept. of Biology, Mercer University, Macon, Ga. ment of Botany, and Dr. L. W. R. Jackson, School of Forestry, University of Georgia; Dr. Catherine Keever, State Teachers College, Millersville, Pennsylvania; and Mr. Jack Brown, Soil Conservation Service, Athens, Georgia.

Loss of a Harvested Fish Species Disrupts Carbon Flow in a Diverse Tropical River

Abstract: Harvesting threatens many vertebrate species, yet few whole-system manipulations have been conducted to predict the consequences of vertebrate losses on ecosystem function. Here, we show that a harvested migratory detrital-feeding fish (Prochilodontidae: Prochilodus mariae) modulates carbon flow and ecosystem metabolism. Natural declines in and experimental removal of Prochilodus decreased downstream transport of organic carbon and increased primary production and respiration. Thus, besides its economic value, Prochilodus is a critical ecological component of South American rivers. Lack of functional redundancy for this species highlights the importance of individual species and, contrary to theory, suggests that losing one species from lower trophic levels can affect ecosystem functioning even in species-rich ecosystems.

Tundra co2 fluxes in response to experimental warming across latitudinal and moisture gradients

Abstract: Climate warming is expected to differentially affect CO2 exchange of the diverse ecosystems in the Arctic. Quantifying responses of CO2 exchange to warming in these ecosystems will require coordinated experimentation using standard temperature manipula- tions and measurements. Here, we used the International Tundra Experiment (ITEX) standard warming treatment to determine CO2 flux responses to growing-season warming for ecosystems spanning natural temperature and moisture ranges across the Arctic biome. We used the four North American Arctic ITEX sites (Toolik Lake, Atqasuk, and Barrow (USA) and Alexandra Fiord (Canada)) that span 108 of latitude. At each site, we investigated the CO2 responses to warming in both dry and wet or moist ecosystems. Net ecosystem CO2 exchange (NEE), ecosystem respiration (ER), and gross ecosystem photosynthesis (GEP) were assessed using chamber techniques conducted over 24-h periods sampled regularly throughout the summers of two years at all sites. At Toolik Lake, warming increased net CO2 losses in both moist and dry ecosystems. In contrast, at Atqasuk and Barrow, warming increased net CO2 uptake in wet ecosystems but increased losses from dry ecosystems. At Alexandra Fiord, warming improved net carbon uptake in the moist ecosystem in both years, but in the wet and dry ecosystems uptake increased in one year and decreased the other. Warming generally increased ER, with the largest increases in dry ecosystems. In wet ecosystems, high soil moisture limited increases in respiration relative to increases in photosynthesis. Warming generally increased GEP, with the notable exception of the Toolik Lake moist ecosystem, where warming unexpectedly decreased GEP .25%. Overall, the respiration response determined the effect of warming on ecosystem CO2 balance. Our results provide the first multiple-site comparison of arctic tundra CO2 flux responses to standard warming treatments across a large climate gradient. These results indicate that (1) dry tundra may be initially the most responsive ecosystems to climate warming by virtue of strong increases in ER, (2) moist and wet tundra responses are dampened by higher water tables and soil water contents, and (3) both GEP and ER are responsive to climate warming, but the magnitudes and directions are ecosystem-dependent.