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  • 1
    Electronic Resource
    Electronic Resource
    Nitrate deposition in northern hardwood forests and the nitrogen metabolism of Acer saccharum marsh (1996)
    Springer
    Oecologia 108 (1996), S. 338-344 
    Details
    ISSN: 1432-1939
    Keywords: Nitrogen deposition ; Nitrogen uptake ; Nitrate reductase ; 15N ; Acer saccharum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is generally assumed that plant assimilation constitutes the major sink for anthropogenic Nitrate NO 3 − deposited in temperate forests because plant growth is usually limited by nitrogen (N) availability. Nevertheless, plants are known to vary widely in their capacity for NO 3 − uptake and assimilation, and few studies have directly measured these parameters for overstory trees. Using a combination of field and greenhouse experiments, we studied the N nutrition of Acer saccharum Marsh. in four northern hardwood forests receiving experimental NO 3 − additions equivalent to 30 kg N ha−1 year−1. We measured leaf and fine-root nitrate reductase activity (NRA) of overstory trees using an in vivo assay and used 15N to determine the kinetic parameters of NO 3 − uptake by excised fine roots. In two greenhouse experiments, we measured leaf and root NRA in A. saccharum seedlings fertilized with 0–3.5 g NO 3 − −N m−2 and determined the kinetic parameters of NO 3 − and NH 4 + uptake in excised roots of seedlings. In both overstory trees and seedlings, rates of leaf and fine root NRA were substantially lower than previously reported rates for most woody plants and showed no response to NO 3 − fertilization (range = non-detectable to 33 nmol NO 2 − g−1 h−1). Maximal rates of NO 3 − uptake in overstory trees also were low, ranging from 0.2 to 1.0 μmol g−1 h−1. In seedlings, the mean V max for NO 3 − uptake in fine roots (1 μmol g−1 h−1) was approximately 30 times lower than the V max for NH 4 + uptake (33 μmol g−1 h−1). Our results suggest that A. saccharum satisfies its N demand through rapid NH 4 + uptake and may have a limited capacity to serve as a direct sink for atmospheric additions of NO 3 − .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334659
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  • 2
    Electronic Resource
    Electronic Resource
    Populus tremuloides photosynthesis and crown architecture in response to elevated CO2 and soil N availability (1997)
    Springer
    Oecologia 110 (1997), S. 328-336 
    Details
    ISSN: 1432-1939
    Keywords: Key words Carbon allocation  ;  Elevated CO2  ;   Nitrogen  ;  Photosynthesis  ;  Populus tremuloides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We tested the hypothesis that elevated CO2 would stimulate proportionally higher photosynthesis in the lower crown of Populus trees due to less N retranslocation, compared to tree crowns in ambient CO2. Such a response could increase belowground C allocation, particularly in trees with an indeterminate growth pattern such as Populus tremuloides. Rooted cuttings of P. tremuloides were grown in ambient and twice ambient (elevated) CO2 and in low and high soil N availability (89 ± 7 and 333 ± 16 ng N g−1 day−1 net mineralization, respectively) for 95 days using open-top chambers and open-bottom root boxes. Elevated CO2 resulted in significantly higher maximum leaf photosynthesis (A max) at both soil N levels. A max was higher at high N than at low N soil in elevated, but not ambient CO2. Photosynthetic N use efficiency was higher at elevated than ambient CO2 in both soil types. Elevated CO2 resulted in proportionally higher whole leaf A in the lower three-quarters to one-half of the crown for both soil types. At elevated CO2 and high N availability, lower crown leaves had significantly lower ratios of carboxylation capacity to electron transport capacity (V cmax/J max) than at ambient CO2 and/or low N availability. From the top to the bottom of the tree crowns, V cmax/J max increased in ambient CO2, but it decreased in elevated CO2 indicating a greater relative investment of N into light harvesting for the lower crown. Only the mid-crown leaves at both N levels exhibited photosynthetic down regulation to elevated CO2. Stem biomass segments (consisting of three nodes and internodes) were compared to the total A leaf for each segment. This analysis indicated that increased A leaf at elevated CO2 did not result in a proportional increase in local stem segment mass, suggesting that C allocation to sinks other than the local stem segment increased disproportionally. Since C allocated to roots in young Populus trees is primarily assimilated by leaves in the lower crown, the results of this study suggest a mechanism by which C allocation to roots in young trees may increase in elevated CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008813
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  • 3
    Electronic Resource
    Electronic Resource
    Relationships among root branch order, carbon, and nitrogen in four temperate species (1997)
    Springer
    Oecologia 111 (1997), S. 302-308 
    Details
    ISSN: 1432-1939
    Keywords: Key words Fine roots ; Architecture ; Nitrogen ; Turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objective of this study was to examine how root length, diameter, specific root length, and root carbon and nitrogen concentrations were related to root branching patterns. The branching root systems of two temperate tree species, Acer saccharum Marsh. and Fraxinus americana L., and two perennial herbs from horizontal rhizomes, Hydrophyllum canadense L. and Viola pubescens Ait., were quantified by dissecting entire root systems collected from the understory of an A. saccharum-Fagus grandifolia Ehrh. forest. The root systems of each species grew according to a simple branching process, with laterals emerging from the main roots some distance behind the tip. Root systems normally consisted of only 4–6 branches (orders). Root diameter, length, and number of branches declined with increasing order and there were significant differences among species. Specific root length increased with order in all species. Nitrogen concentration increased with order in the trees, but remained constant in the perennial herbs. More than 75% of the cumulative root length of tree seedling root systems was accounted for by short (2–10 mm) lateral roots almost always 〈0.3 mm in diameter. Simple assumptions suggest that many tree roots normally considered part of the dynamic fine-root pool (e.g., all roots 〈2.0 mm in diameter) are too large to exhibit rapid rates of production and mortality. The smallest tree roots may be the least expensive to construct but the most expensive to maintain based on an increase in N concentration with order.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050239
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  • 4
    Electronic Resource
    Electronic Resource
    Fine root growth and demographic responses to nutrient patches in four old-field plant species (1993)
    Springer
    Oecologia 95 (1993), S. 61-64 
    Details
    ISSN: 1432-1939
    Keywords: Root proliferation ; Root demography ; Nutrient heterogeneity ; Root loraging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Proliferation of roots in a nutrient patch can occur either as a result of an increase in root length (morphological response) or by a change in root birth or death rates (demographic responses). In this study we attempted to distinguish between these two mechanisms of response to nutrient patches and to compare the responses of four old-field plant species (two annuals, two perennials). For all four species combined, there were significant increases in root numbers and root length in fertilized patches. Root proliferation in fertilized patches was largely due to increased birth (=branching) rates of new roots. However, there was also a significant increase in root death rates in the fertilized patches which reduced the magnitude of the increase in net root numbers. Plots for individual species suggested they differed in the magnitude and timing of root proliferation in fertilized patches due to differences in root birth and death rates. However, because of the limited sample size in this study, there was only a marginally significant difference among species in root birth rates, and no difference in death rates. Further studies are currently underway to better quantify species differences in the demographic mechanism, as well as magnitude, of response to nutrient patches and if this would affect the ability to exploit small-scale heterogeneity in soil resources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00649507
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  • 5
    Electronic Resource
    Electronic Resource
    Spatial variation in tree root distribution and growth associated with minirhizotrons (1992)
    Springer
    Plant and soil 143 (1992), S. 283-288 
    Details
    ISSN: 1573-5036
    Keywords: Acer saccharum ; fine root ; forest ; minirhizotron ; production ; spatial variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Four minirhizotrons were installed in each of three replicate plots in a deciduous forest dominated by Acer saccharum Marsh. The length growth of tree roots along the surface of the minirhizotrons was measured for a period of one year, and the resulting data were analyzed in nested, averaged and pooled arrangements. The analyses of nested data showed that spatial variation in root growth and abundance among minirhizotrons within plots was greater than variation among plots. Averaging data from minirhizotrons within plots prior to analysis reduced variation about plot means, but extensive intraplot variation invalidates this approach on statistical grounds. Both nested and averaged data failed to account for the contribution of individual roots to the mean, and root production rates were consequently overestimated. Pooling the data from the four minirhizotrons reduced variation about the means, and resulted in a more representative estimate of root production rates. The analysis of composited data can be used to incorporate small-scale variation into a single replicate sample in those circumstances where the activity of the root systems of plant communities is the object of study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007884
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  • 6
    Electronic Resource
    Electronic Resource
    Elevated atmospheric CO2 and feedback between carbon and nitrogen cycles (1993)
    Springer
    Plant and soil 151 (1993), S. 105-117 
    Details
    ISSN: 1573-5036
    Keywords: atmospheric CO2 ; belowground production ; labile soil C ; microbial biomass ; N mineralization ; photosynthesis ; positive feedback
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We tested a conceptual model describing the influence of elevated atmospheric CO2 on plant production, soil microorganisms, and the cycling of C and N in the plant-soil system. Our model is based on the observation that in nutrient-poor soils, plants (C3) grown in an elevated CO2 atmosphere often increase production and allocation to belowground structures. We predicted that greater belowground C inputs at elevated CO2 should elicit an increase in soil microbial biomass and increased rates of organic matter turnover and nitrogen availability. We measured photosynthesis, biomass production, and C allocation of Populus grandidentata Michx. grown in nutrient-poor soil for one field season at ambient and twice-ambient (i.e., elevated) atmospheric CO2 concentrations. Plants were grown in a sandy subsurface soil i) at ambient CO2 with no open top chamber, ii) at ambient CO2 in an open top chamber, and iii) at twice-ambient CO2 in an open top chamber. Plants were fertilized with 4.5 g N m−2 over a 47 d period midway through the growing season. Following 152 d of growth, we quantified microbial biomass and the availabilities of C and N in rhizosphere and bulk soil. We tested for a significant CO2 effect on plant growth and soil C and N dynamics by comparing the means of the chambered ambient and chambered elevated CO2 treatments. Rates of photosynthesis in plants grown at elevated CO2 were significantly greater than those measured under ambient conditions. The number of roots, root length, and root length increment were also substantially greater at elevated CO2. Total and belowground biomass were significantly greater at elevated CO2. Under N-limited conditions, plants allocated 50–70% of their biomass to roots. Labile C in the rhizosphere of elevated-grown plants was significantly greater than that measured in the ambient treatments; there were no significant differences between labile C pools in the bulk soil of ambient and elevated-grown plants. Microbial biomass C was significantly greater in the rhizosphere and bulk soil of plants grown at elevated CO2 compared to that in the ambient treatment. Moreover, a short-term laboratory assay of N mineralization indicated that N availability was significantly greater in the bulk soil of the elevated-grown plants. Our results suggest that elevated atmospheric CO2 concentrations can have a positive feedback effect on soil C and N dynamics producing greater N availability. Experiments conducted for longer periods of time will be necessary to test the potential for negative feedback due to altered leaf litter chemistry. ei]{gnH}{fnLambers} ei]{gnA C}{fnBorstlap}
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010791
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  • 7
    Electronic Resource
    Electronic Resource
    Belowground responses to rising atmospheric CO2: Implications for plants, soil biota and ecosystem processes (1994)
    Springer
    Plant and soil 165 (1994), S. 1-6 
    Details
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009957
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  • 8
    Electronic Resource
    Electronic Resource
    Applications of minirhizotrons to understand root function in forests and other natural ecosystems (1996)
    Springer
    Plant and soil 185 (1996), S. 293-304 
    Details
    ISSN: 1573-5036
    Keywords: decomposition ; minirhizotron ; production ; soil biota ; turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Minirhizotrons have proved useful to understand the dynamics and function of fine roots. However, they have been used comparatively infrequently in forests and other natural plant communities. Several factors have contributed to this situation, including anomalous root distributions along the minirhizotron surface and the difficulty of extracting data from minirhizotron images. Technical and methodological advances have ameliorated some of these difficulties, and minirhizotrons have considerable potential to address some questions of long standing interest. These questions include more fully understanding the role of roots in carbon and nutrient cycling, rates of root decomposition, responses to resource availability and the functional significance of interactions between plant roots and soil organisms. Maximizing the potential for minirhizotrons to help us better understand the functional importance of fine roots in natural plant communities depends upon using them to answer only those questions appropriate to both their inherent strengths and limitations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02257535
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  • 9
    Electronic Resource
    Electronic Resource
    Above- and belowground response of Populus grandidentata to elevated atmospheric CO2 and soil N availability (1994)
    Springer
    Plant and soil 165 (1994), S. 45-51 
    Details
    ISSN: 1573-5036
    Keywords: CO2 ; gas exchange ; nitrogen ; Populus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil N availability may play an important role in regulating the long-term responses of plants to rising atmospheric CO2 partial pressure. To further examine the linkage between above- and belowground C and N cycles at elevated CO2, we grew clonally propagated cuttings of Populus grandidentata in the field at ambient and twice ambient CO2 in open bottom root boxes filled with organic matter poor native soil. Nitrogen was added to all root boxes at a rate equivalent to net N mineralization in local dry oak forests. Nitrogen added during August was enriched with 15N to trace the flux of N within the plant-soil system. Above-and belowground growth, CO2 assimilation, and leaf N content were measured non-destructively over 142 d. After final destructive harvest, roots, stems, and leaves were analyzed for total N and 15N. There was no CO2 treatment effect on leaf area, root length, or net assimilation prior to the completion of N addition. Following the N addition, leaf N content increased in both CO2 treatments, but net assimilation showed a sustained increase only in elevated CO2 grown plants. Root relative extension rate was greater at elevated CO2, both before and after the N addition. Although final root biomass was greater at elevated CO2, there was no CO2 effect on plant N uptake or allocation. While low soil N availability severely inhibited CO2 responses, high CO2 grown plants were more responsive to N. This differential behavior must be considered in light of the temporal and spatial heterogeneity of soil resources, particularly N which often limits plant growth in temperate forests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009961
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  • 10
    Electronic Resource
    Electronic Resource
    Soil Temperature, Matric Potential, and the Kinetics of Microbial Respiration and Nitrogen Mineralization (1999)
    Springer
    Soil Science Society of America journal 63 (1999), S. 575-584 
    Details
    ISSN: 1435-0661
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 2 and inorganic N. First-order kinetic models described the accumulation of CO2 and inorganic N and accounted for 96 to 99% of the variation in these processes. First-order rate constants (k) for net N mineralization significantly increased with temperature, but the k for microbial respiration did not increase in a consistent manner; it was 0.107 wk-1 at 5°C, 0.123 wk-1 at 10°C, and 0.101 wk-1 at 25° C. Matric potential did not significantly influence k for either process. Substrate pools for microbial respiration and net N mineralization declined between -0.01 and -0.30 Mpa, and the decline was greatest at the highest soil temperature; this response produced a significant temperature-matric potential interaction. We conclude that high rates of microbial activity at warm soil temperatures (e.g., 25°C) are limited by the diffusion of substrate to metabolically active cells. This limitation apparently lessens as physiological activity and substrate demand decline at relatively cooler soil temperature (e.g., 5°C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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