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Filters: Tags: Nitrogen Cycling (X) > Types: Journal Citation (X)

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1. Plant carbon (C) and nitrogen (N) inputs to soil interact with microbes and abiotic factors like climate and pH to influence soil fertility and plant productivity. Although root exudates and root litter are important factors affecting the cycling of nutrients critical to plant growth, many studies remain focused on effects of above-ground litter inputs. 2. Using two species that co-dominate alpine moist meadows as a model system (the phenolic-rich forb Geum rossii, and the fast-growing grass Deschampsia caespitosa), we asked whether C from G. rossii fine roots could reduce D. caespitosa growth. We hypothesized that root C would indirectly reduce D. caespitosa growth by stimulating soil microbes, thus restricting...
Phosphorus (P) has been proposed to directly limit primary productivity in some temperate grassland ecosystems. Our study of a recovering prairie on Colorado's Front Range suggests that P availability, possibly via regulation of nitrogen (N) fixation, may strongly influence N availability in recovering prairie soils. Consequently, increased P availability could indirectly affect plant growth through the alleviation of N limitation. At our site, concentrations of soil inorganic N were nearly three times higher in plots fertilized with P than in control plots. Subsequent acetylene reduction analyses showed that soil N fixation rates were more than double for P fertilization plots. These results highlight potential...
The forest-alpine tundra ecotone in the Front Range of Colorado typically occurs as a gradual transition from the treeless tundra to the closed canopy coniferous subalpine forest. We evaluated the patterns of snow, deposition inputs, and soil properties at three spatial scales: across the entire ecotone, with distance from tree limit in the transitional krummholz zone, and around individual trees. Snow depth was deepest in the krummholz zone and lowest in the alpine tundra and upwind of trees near tree limit, but was not predictive of most soil properties except for surface litter decomposition. Inorganic deposition ranged from 0.7 to 7.7 g m−2 yr−1 across the ecotone and tended to be higher downwind than upwind...
The growing awareness that plants might use a variety of nitrogen (N) forms, both organic and inorganic, has raised questions about the role of resource partitioning in plant communities. It has been proposed that coexisting plant species might be able to partition a limited N pool, thereby avoiding competition for resources, through the uptake of different chemical forms of N. In this study, we used in situ stable isotope labeling techniques to assess whether coexisting plant species of a temperate grassland (England, UK) display preferences for different chemical forms of N, including inorganic N and a range of amino acids of varying complexity. We also tested whether plants and soil microbes differ in their preference...
Microbiotic crusts are biological soil crusts composed of lichens, cyanobacteria, algae, mosses, and fungi. The biodiversity of these crusts is poorly understood; several cosmopolitan species dominate in most areas, but many species are confined to one or a few sites. Nitrogen fixation by organisms within the crust can be the dominant source of nitrogen input into many ecosystems, although rates of nitrogen input are limited by water availability, temperature, and nitrogen loss from the crust. Photosynthetic rates of the microbiotic crust can be 50% of those observed for higher plants, but the contribution of crusts to carbon cycling is not known. The microbiotic crust binds soil particles together, and this significantly...
Microbiotic crusts are biological soil crusts composed of lichens, cyanobacteria, algae, mosses, and fungi. The biodiversity of these crusts is poorly understood; several cosmopolitan species dominate in most areas, but many species are confined to one or a few sites. Nitrogen fixation by organisms within the crust can be the dominant source of nitrogen input into many ecosystems, although rates of nitrogen input are limited by water availability, temperature, and nitrogen loss from the crust. Photosynthetic rates of the microbiotic crust can be 50% of those observed for higher plants, but the contribution of crusts to carbon cycling is not known. The microbiotic crust binds soil particles together, and this significantly...
The growing awareness that plants might use a variety of nitrogen (N) forms, both organic and inorganic, has raised questions about the role of resource partitioning in plant communities. It has been proposed that coexisting plant species might be able to partition a limited N pool, thereby avoiding competition for resources, through the uptake of different chemical forms of N. In this study, we used in situ stable isotope labeling techniques to assess whether coexisting plant species of a temperate grassland (England, UK) display preferences for different chemical forms of N, including inorganic N and a range of amino acids of varying complexity. We also tested whether plants and soil microbes differ in their preference...
We tested the hypothesis that decomposition in flood-inundated patches of riparian tree leaf litter results in higher plant-available nitrogen in underlying, nutrient-poor alluvium. We used leafpacks (n=56) containing cottonwood (Populus deltoides ssp. wislizenii) leaf litter to mimic natural accumulations of leaves in an experiment conducted on the Yampa River floodplain in semi-arid northwestern Colorado, USA. One-half of the leafpacks were set on the sandy alluvial surface, and one-half were buried 5 cm below the surface. The presence of NO3? and NH4+ presumed to result from a leafpack?s submergence during the predictable spring flood pulse was assessed using an ion-exchange resin bag (IER) placed beneath each...
Experimentally increasing atmospheric CO2 often stimulates plant growth and ecosystem carbon (C) uptake. Biogeochemical theory predicts that these initial responses will immobilize nitrogen (N) in plant biomass and soil organic matter, causing N availability to plants to decline, and reducing the long-term CO2-stimulation of C storage in N limited ecosystems. While many experiments have examined changes in N cycling in response to elevated CO2, empirical tests of this theoretical prediction are scarce. During seven years of postfire recovery in a scrub oak ecosystem, elevated CO2 initially increased plant N accumulation and plant uptake of tracer 15N, peaking after four years of CO2 enrichment. Between years four...