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A major uncertainty in predicting long-term ecosystem C balance is whether stimulation of net primary production will be sustained in future atmospheric CO2 scenarios. Immobilization of nutrients (N in particular) in plant biomass and soil organic matter (SOM) provides negative feedbacks to plant growth and may lead to progressive N limitation (PNL) of plant response to CO2 enrichment. Soil microbes mediate N availability to plants by controlling litter decomposition and N transformations as well as dominating biological N fixation. CO2-induced changes in C inputs, plant nutrient demand and water use efficiency often have interactive and contrasting effects on microbes and microbially mediated N processes. One critical...
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Data were collected on the abundance of plants in a 10-year weeding experiment of garlic mustard, located at Trillium Trails Park in Pennsylvania. Garlic mustard was weeded annually to suppress its abundance, and the impacts of garlic mustard were measured based on the response of the plant community to garlic mustard weeding. Because garlic mustard is known to suppress mycorrhizal fungi, the mycorrhizal status of each plant species was determined and recorded. The experiment was arranged in a blocked design, where plots had subareas with and without garlic mustard removal. Cover of each plant species was measured as the average percent cover recorded in 18 2x2 meter quadrats with garlic mustard removed per plot...
Whole-plant and leaf nitrogen isotope composition are determined by the isotope ratio of the external nitrogen source and physiological mechanisms within the plant. Whole-plant isotope composition can reflect that of the nitrogen source when plant demand exceeds nitrogen supply. Uptake by mycorrhizae can cause the isotope ratio of the plant to deviate from the source. Intra-plant variation in isotope composition can be caused by multiple assimilation events, organ-specific loss of nitrogen, and resorption and reallocation of nitrogen. Future work must address acquisition of organic nitrogen from the soil solution, the role of mycorrhizae, and internal transformations within the plant. Published in Trends in Plant...
In order to better elucidate fixed-C partitioning, nutrient acquisition and water relations of prairie grasses under elevated [CO2], we grew the C4 grass Bouteloua gracilis (H.B.K.) lag ex Steud. from seed in soil-packed, column-lysimeters in two growth chambers maintained at current ambient [CO2] (350 ?L L?1) and twice enriched [CO2] (700 ?L L?1). Once established, plants were deficit irrigated; growth chamber conditions were maintained at day/night temperatures of 25/16�C, relative humidities of 35%/90% and a 14-hour photoperiod to simulate summer conditions on the shortgrass steppe in eastern Colorado. After 11 weeks of growth, plants grown under CO2 enrichment had produced 35% and 65% greater total and root...
In both field and greenhouse studies, cyanobacterial and cyanolichens of cold-temperature deserts often enhance growth and essential uptake by associated herbs. That effect is associated with better seedling establishment and larger seedlings. The following are possible mechanisms for these effects: (1) the microbiota concentrate essential elements in available forms in soil surface layers, (2) the microbial surface covers are usually darker colored than the soil itself and produce warmer soils during cool seasons when soil water is most available, (3) the gelatinous sheaths of several cyanobacterial genera common on alkaline deserts contain chelating compounds, and (4) conditions that favor persistent microbial...
Thermodynamics predict that in calcareous soils where the equilibrium activity of solution orthophosphate (Pso) is controlled by any calcium-phosphate mineral, calcium oxalate (CaC2O4) precipitation will increase Pso by depressing Ca2+ ion activity in soil solution and enhancing dissolution of the P-controlling mineral. Plants and/or associated microflora capable of imparting effective levels of oxalic acid (H2C2O4) to soil solution, may significantly improve their phosphorus nutrition via this mechanism. In previous work, we presented evidence for calcium oxalate (CaC2O4) formation in the rhizosphere of vesicular-arbuscular mycorrhizal (VAM) western wheatgrass (Agropyron smithii Rydb.). Herein, we report on further...
Large intact soil cores of nearly pure stands of Pascopyrum smithii (western wheatgrass, C3) and Bouteloua gracilis (blue grama, C4) were extracted from the Central Plains Experimental Range in northeastern Colorado, USA and transferred to controlled environment chambers. Cores were exposed to a variety of water, temperature and CO2 regimes for a total of four annual growth cycles. Root subsamples were harvested after the completion of the second and fourth growth cycles at a time corresponding to late winter, and were examined microscopically for the presence of mycorrhizae. After two growth cycles in the growth chambers, 54% of the root length was colonized in P. smithii, compared to 35% in blue grama. Field control...


    map background search result map search result map Data on the impacts of garlic mustard from a weeding experiment in Pennsylvania 2006-2016 Data on the impacts of garlic mustard from a weeding experiment in Pennsylvania 2006-2016