46 research outputs found
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Controls Over Nutrient Flow Through Plants and Microbes in Arctic Tundra
Plant growth in arctic tundra is generally strongly limited by nutrient availability, particularly by nitrogen. The purpose of this sub-project of the R4D program was to examine plant N-uptake and the competition for N between plants and microbes in tundra. This competition can be an important control on N-flow and plant uptake but its significance in tundra has not been studied intensively. How the factors controlling the outcome of competition are altered by disturbance has also received very limited study, yet this is important facet of the R4D program. The primary goal for this project in 1990 was to initiate studies on N-partitioning and turnover in tussock tundra and how this is affected by dust deposition. Secondary goals were to examine the effect of differential dust deposition on microbial activity and nutrient cycling processes (mineralization and nitrification), and begin studies on the control of microbial N-uptake. The N-partitioning studies used {sup 15}N injected into Eriophorum tussocks to examine both the short-term (1 day) partitioning of N and the long-term (1 month and 1 year) redistribution of N through the plant-soil system. These experiments were done in both the early season (June) and peak season (July). To examine the effect of dust on N-partitioning tussocks in the heavy dust zone and in a control site were labeled with {sup 15}N and harvested at the end of the growing season. 4 refs., 1 tab
Microbial responses to inorganic nutrient amendment overridden by warming: Consequences on soil carbon stability
A theoretical analysis of microbial eco-physiological and diffusion limitations to carbon cycling in drying soils
Post-harvest nitrogen cycling in clearcut and alternative silvicultural systems in a montane forest in coastal British Columbia
Soil health in agricultural systems
Soil health is presented as an integrative property that reflects the capacity of soil to respond to agricultural intervention, so that it continues to support both the agricultural production and the provision of other ecosystem services. The major challenge within sustainable soil management is to conserve ecosystem service delivery while optimizing agricultural yields. It is proposed that soil health is dependent on the maintenance of four major functions: carbon transformations; nutrient cycles; soil structure maintenance; and the regulation of pests and diseases. Each of these functions is manifested as an aggregate of a variety of biological processes provided by a diversity of interacting soil organisms under the influence of the abiotic soil environment. Analysis of current models of the soil community under the impact of agricultural interventions (particularly those entailing substitution of biological processes with fossil fuel-derived energy or inputs) confirms the highly integrative pattern of interactions within each of these functions and leads to the conclusion that measurement of individual groups of organisms, processes or soil properties does not suffice to indicate the state of the soil health. A further conclusion is that quantifying the flow of energy and carbon between functions is an essential but non-trivial task for the assessment and management of soil health