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? Rhizodeposition, or the addition of C from roots to soil C pools, is expected to increase if net primary production is stimulated and some excess C is allocated below-ground. We investigated the effects of 5 yrs of elevated CO2 on below-ground C dynamics in a native, C3?C4 grassland ecosystem in Colorado, USA. ? Cylinder harvests following each growing season and monolith excavation at the end of the experiment provided data on root biomass, root C : N ratios, and root and soil ?13C values. We applied an isotopic mixing model to quantify new soil C inputs on elevated and ambient CO2 treatments. ? Root biomass increased by 23% and root C : N ratios increased by 26% after 5 yrs of elevated CO2. Species-specific...
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These tabular data were compiled to document how key plant trait values change during plant development, particularly seedling stages, and in relation to soil moisture. An objective of our study was to answer three main research questions: (1) Do seedling trait values differ across early to late stages of seedling development and do those trajectories vary among plant species and functional types (i.e., forbs vs. grasses)?; (2) Does water availability influence seedling ontogenetic trait variation? and, if so, does this variation affect plant species drought performance?; and (3) Do seedling trait values at early stages of development differ from complied trait database values for species? These data represent key...
Deuterated water absorbed by deep roots of Artemisia tridentata appeared in the stem water of neighboring Agropyron desertorum tussocks. This supports the hypothesis that water absorbed by deep roots in moist soil moves through the roots, is released in the upper soil profile at night, and is stored there until it is resorbed by roots the following day. This phenomenon is termed hydraulic lift. The potential for parasitism of the water stored in the upper soil layers by neighboring plant roots is also shown. The effectiveness of water absorption by deep roots was substantially improved with hydraulic lift as indicated by reductions of 25 to 50% in transpiration on days following experimental circumvention of hydraulic...
Phosphorus and nitrogen uptake capacities were assessed during 36–58 d drying cycles to determine whether the ability of sagebrush (Artemisia tridentata Nutt.) to absorb these nutrients changed as the roots were subjected to increasing levels of water stress. Water was withheld from mature plants in large (6 I) containers and the uptake capacity of excised roots in solution was determined as soil water potentials decreased from −0.03 MPa to −5.0 MPa. Phosphorus uptake rates of excised roots at given substrate concentrations increased as preharvest soil water potentials decreased to −5.0 MPa. Vmax and Km also increased as soil water potentials declined. Declining soil water potentials depressed nitrogen uptake...
Diel soil water potential fluctuations reflected daytime depletion and nocturnal resupply of water in upper soil layers. Transpiration suppression experiments demonstrated that water absorption by roots caused the daytime depletion. The soil water potential data and experimental results suggest that at night water absorbed from moist soil by deeper roots is transported to and lost from roots into drier upper soil layers. The deeper roots appear to absorb and transport water both day and night. Implications for the efficiency of deep roots and water storage, nutrient uptake and water parasitism in upper soil layers are discussed. Published in Oecologia, volume 73, issue 4, on pages 486 - 489, in 1987.
Mature mountain big sagebrush plants near the bottom and midway up a hillside had maximum rooting depths between 183 and 213 cm, @?60 cm deeper than roots of Wyoming big sagebrush plants just below the ridge. Maximum lateral root spread was between 122 and 152 cm. Approximately 60% of total root system weight was located in the surface 30 cm of soil. Total nonstructural carbohydrate concentrations in root decreased from 6.8% in plants at the bottom site to 3.8% in plants at the ridge site. This response could have resulted from an environmental gradient, by a release from competition, or from subspecies differences. Total carbohydrate reserves of individual plant root systems were =7.7 g. Published in Ecology, volume...
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In the arid southwest of North America, winter precipitation penetrates to deep soil layers, whereas summer "monsoon" precipitation generally wets only surface layers. Use of these spatially separated water sources was determined for three dominant tree species of the pinyon-juniper ecosystem at six sites along a gradient of increasing summer precipitation in Utah and Arizona. Mean summer precipitation ranged from 79 to 286 mm, or from 18% to 60% of the annual total across the gradient. We predicted that, along this summer rainfall gradient, populations of dominant tree species would exhibit a clinal off-on response for use of water from upper soil layers, responding at particular threshold levels of summer precipitation...
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The fine roots of trees are concentrated on lateral branches that arise from perennial roots. They are important in the acquisition of water and essential nutrients, and at the ecosystem level, they make a significant contribution to biogeochemical cycling. Fine roots have often been studied according to arbitrary size classes, e.g., all roots less than 1 or 2 mm in diameter. Because of the size class approach, the position of an individual root on the complex lateral branching system has often been ignored, and relationships between the form of the branching root system and its function are poorly understood. The fine roots of both gymnosperms and angiosperms, which formed ectomycorrhizae (EM) and arbuscular mycorrhizae...
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The semi-arid sagebrush steppe ecosystem is one of the largest biomes in North America. The steppe provides critical habitat and forage for wildlife and is economically important to recreation and livestock industries. However, the ecosystem is threatened primarily due to several negative effects associated with expansion of the exotic annual grass Bromus tectorum (cheatgrass). Because of these changes rehabilitation of the habitat is extremely difficult and energy intensive. Restoration of one of the foundation species, Artemisia tridentata (big sagebrush), is a function of seed availability, seed germination, seedling establishment and mature plant survival. Many studies have addressed various aspects of A. tridentata...
A field experiment was established to quantify the effects of different amounts of rainfall on root growth and dry mass of belowground plant parts in three types of grassland ecosystems. Mountain (Nardus grassland), highland (wet Cirsium grassland), and lowland grassland (dry Festuca grassland) ecosystems were studied in 2006 and 2007. Roofs constructed above the canopy of grass stands and gravity irrigation systems simulated three climate scenarios: (1) rainfall reduced by 50%, (2) rainfall enhanced by 50%, and (3) the full natural rainfall of the current growing season. Experimentally reduced amounts of precipitation significantly affected both yearly root increments and total root dry mass in the highland grassland....
    map background search result map search result map Fine root architecture of nine North American trees Rhizodeposition stimulated by elevated CO2 in a semiarid grassland Intra- and Interspecific Variation for Summer Precipitation Use in Pinyon-Juniper Woodlands Root elongation rates for Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) seedlings for Large Rootbox Experiment, Spring 2010. Plant trait and soil moisture data associated with ontogenetic trait shifts - seedlings display high trait variability during early stages of development Plant trait and soil moisture data associated with ontogenetic trait shifts - seedlings display high trait variability during early stages of development Rhizodeposition stimulated by elevated CO2 in a semiarid grassland Intra- and Interspecific Variation for Summer Precipitation Use in Pinyon-Juniper Woodlands Fine root architecture of nine North American trees