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Hong-sheng Liu - One of the best experts on this subject based on the ideXlab platform.
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Effects of shoot removal and soil water content on Root Respiration of spring wheat and soybean
Environmental and Experimental Botany, 2006Co-Authors: Hong-sheng Liu, Yu JiaAbstract:Abstract In an effort to separate soil Respiration into Root-derived Respiration and soil-microbe-derived Respiration under field conditions, removal of the shoot was investigated as a tool to determine the individual contributions. Spring wheat (Triticum aestivum L. cv Longchun 8139) and soybean (Glycine max L. cv Tianchan 2) were grown in the field under a movable rain shelter and subjected to three water regimes: (1) well-watered, (2) moderate drought stress, and (3) severe drought stress. Roots from spring wheat and soybean plants that had either been left intact or subjected to shoot excision were monitored for the efflux of carbon dioxide, the influx of oxygen, and total soluble carbohydrate (TSC), malic acid, and citric acid contents. The Root Respiration rates of shoot-excised and intact plants ranged from 0.88–2.32 and 1.09–2.72 μmol CO2 m−2 s−1 for wheat and 0.42–1.66 and 0.52–2.03 μmol CO2 m−2 s−1 for soybean, respectively, indicating that although shoot removal had an adverse effect on Root Respiration, this technique can be used to measure the Root-derived Respiration under field conditions. The times of shoot removal that had the most dramatic effects on the gas flux rates in plants subjected to well-watered, moderate drought, and severe drought stress treatments were 3, 2, and 1 h for spring wheat, and 3, 1, and 1 h for soybean, respectively. Both crops showed significantly positive relationships between soil water content and TSC content, and between TSC content and the time when the Root Respiration of the shoot-excised plants differed significantly from that of plants with intact shoots. These results suggest that Root Respiration should be measured within 3 h after shoot excision when the plants are under the optimal growth conditions, although the maximum elapsed time should be reduced as the degree of environmental stress increases. Regardless of the water availability, the Root Respiration should be measured as soon as possible after the shoot is removed, since by the time the Root Respiration rate has stabilized, it differs greatly from the rate observed shortly after the shoot has been clipped.
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Photosynthesis, Root Respiration, and grain yield of spring wheat in response to surface soil drying
Plant Growth Regulation, 2005Co-Authors: Hong-sheng LiuAbstract:The aims of this research were to test the influence of surface soil drying on photosynthesis, Root Respiration and grain yield of spring wheat (Triticum aestivum), and to evaluate the relationship between Root Respiration and grain yield. Wheat plants were grown in PVC tubes 120 cm in length and 10 cm in diameter. Three water regimes were employed: (a) all soil layers were irrigated close to field water capacity (CK); (b) upper soil layers (0–40 cm from top) drying (UD); (c) lower soil layer (80–120 cm from top) wet (LW). The results showed that although upper drying treatment maintained the highest Root biomass, Root Respiration and photosynthesis rates at anthesis, the Root Respiration of the former was significantly (P < 0.05) lower than the latter at the jointing stage. There were no differences in water use efficiency or harvest index between plants from the upper drying and well-watered treatment. However, the grain weight for plants in the upper drying treatment was significantly (P< 0.05) higher than that of in well-watered control. The results suggest that reduced Root Respiration rate and the amount of photosynthates utilized by Root Respiration in early season growth may also have contributed to improve crop production under soil drying. Reduced Root activity and Root Respiration rate, in the early growth stage, not only increased the photosynthate use efficiency (Root Respiration rate: photosynthesis ratio), but also grain yield. Rooting into a deeper wet soil profile before grain filling was crucial for spring wheat to achieve a successful seedling establishment and high grain yield.
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Root Respiration, photosynthesis and grain yield of two spring wheat in response to soil drying
Plant Growth Regulation, 2005Co-Authors: Hong-sheng LiuAbstract:The effects of soil water regime and wheat cultivar, differing in drought tolerance with respect to Root Respiration and grain yield, were investigated in a greenhouse experiment. Two spring wheat (Triticum aestivum) cultivars, a drought sensitive (Longchun 8139-2) and drought tolerant (Dingxi 24) were grown in PVC tubes (120 cm in length and 10 cm in diameter) under an automatic rain-shelter. Plants were subjected to three soil moisture regimes: (1) well-watered control (85% field water capacity, FWC); (2) moderate drought stress (50% FWC) and (3) severe drought stress (30% FWC). The aim was to study the influence of Root Respiration on grain yield under soil drying conditions. In the experiment, severe drought stress significantly (p < 0.05) reduced shoot and Root biomass, photosynthesis and Root Respiration rate for both cultivars, but the extent of the decreases was greater for Dingxi 24 compared to that for Longchun 8139-2. Compared with Dingxi 24, 0.04 and 0.07 mg glucose m−2 s−1 of additional energy, equivalent to 0.78 and 1.43 J m−2 s−1, was used for water absorption by Longchun 8139-2 under moderate and severe drought stress, respectively. Although the grain yield of both cultivars decreased with declining soil moisture, loss was greater in Longchun 8139-2 than in Dingxi 24, especially under severe drought stress. The drought tolerance cultivar (Dingxi 24), had a higher biomass and metabolic activity under severe drought stress compared to the sensitive cultivar (Longchun 8139-2), which resulted in further limitation of grain yield. Results show that Root Respiration, carbohydrates allocation (Root:shoot ratio) and grain yield were closely related to soil water status and wheat cultivar. Reductions in Root Respiration and Root biomass under severe soil drying can improve drought tolerant wheat growth and physiological activity during soil drying and improve grain yield, and hence should be advantageous over a drought sensitive cultivar in arid regions.
Andrew J. Burton - One of the best experts on this subject based on the ideXlab platform.
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Adenylate control contributes to thermal acclimation of sugar maple fine-Root Respiration in experimentally warmed soil.
Plant cell & environment, 2017Co-Authors: Mickey P Jarvi, Andrew J. BurtonAbstract:We investigated the occurrence of and mechanisms responsible for acclimation of fine-Root Respiration of mature sugar maple (Acer saccharum) after 3+ years of experimental soil warming (+4 to 5 oC) in a factorial combination with soil moisture addition. Potential mechanisms for thermal respiratory acclimation included changes in enzymatic capacity, as indicated by Root N concentration; substrate limitation, assessed by examining non-structural carbohydrates and effects of exogenous sugar additions; and adenylate control, examined as responses of Root Respiration to a respiratory uncoupling agent (CCCP). Partial acclimation of fine-Root Respiration occurred in response to soil warming, causing specific Root Respiration to increase to a much lesser degree (14 to 26%) than would be expected for a 4 to 5 oC temperature increase (circa 55%). Acclimation was greatest when ambient soil temperature was warmer or soil moisture availability was low. We found no evidence that enzyme or substrate limitation caused acclimation but did find evidence supporting adenylate control. The uncoupling agent caused a 1.4 times greater stimulation of Respiration in Roots from warmed soil. Sugar maple fine-Root Respiration in warmed soil was at least partially constrained by adenylate use, helping constrain Respiration to that needed to support work being performed by the Roots.
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acclimation and soil moisture constrain sugar maple Root Respiration in experimentally warmed soil
Tree Physiology, 2013Co-Authors: Mickey P Jarvi, Andrew J. BurtonAbstract:The response of Root Respiration to warmer soil can affect ecosystem carbon (C) allocation and the strength of positive feedbacks between climatic warming and soil CO2 efflux. This study sought to determine whether fine-Root (<1 mm) Respiration in a sugar maple (Acer saccharum Marsh.)-dominated northern hardwood forest would adjust to experimentally warmed soil, reducing C return to the atmosphere at the ecosystem scale to levels lower than that would be expected using an exponential temperature response function. Infrared heating lamps were used to warm the soil (+4 to +5 °C) in a mature sugar maple forest in a fully factorial design, including water additions used to offset the effects of warming-induced dry soil. Fine-Root-specific Respiration rates, Root biomass, Root nitrogen (N) concentration, soil temperature and soil moisture were measured from 2009 to 2011, with experimental treatments conducted from late 2010 to 2011. Partial acclimation of fine-Root Respiration to soil warming occurred, with soil moisture deficit further constraining specific Respiration rates in heated plots. Fine-Root biomass and N concentration remained unchanged. Over the 2011 growing season, ecosystem Root Respiration was not significantly greater in warmed soil. This result would not be predicted by models that allow Respiration to increase exponentially with temperature and do not directly reduce Root Respiration in drier soil.
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Acclimation and soil moisture constrain sugar maple Root Respiration in experimentally warmed soil
Tree physiology, 2013Co-Authors: Mickey P Jarvi, Andrew J. BurtonAbstract:The response of Root Respiration to warmer soil can affect ecosystem carbon (C) allocation and the strength of positive feedbacks between climatic warming and soil CO2 efflux. This study sought to determine whether fine-Root (
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Adjustment of forest ecosystem Root Respiration as temperature warms.
Journal of integrative plant biology, 2008Co-Authors: Andrew J. Burton, Jerry M. Melillo, Serita D. FreyAbstract:Adjustment of ecosystem Root Respiration to warmer climatic conditions can alter the autotrophic portion of soil Respiration and influence the amount of carbon available for biomass production. We examined 44 published values of annual forest Root Respiration and found an increase in ecosystem Root Respiration with increasing mean annual temperature (MAT), but the rate of this cross-ecosystem increase (Q(10)= 1.6) is less than published values for short-term responses of Root Respiration to temperature within ecosystems (Q(10)= 2-3). When specific Root Respiration rates and Root biomass values were examined, there was a clear trend for decreasing Root metabolic capacity (Respiration rate at a standard temperature) with increasing MAT. There also were tradeoffs between Root metabolic capacity and Root system biomass, such that there were no instances of high growing season Respiration rates and high Root biomass occurring together. We also examined specific Root Respiration rates at three soil warming experiments at Harvard Forest, USA, and found decreases in metabolic capacity for Roots from the heated plots. This decline could be due to either physiological acclimation or to the effects of co-occurring drier soils on the measurement date. Regardless of the cause, these findings clearly suggest that modeling efforts that allow Root Respiration to increase exponentially with temperature, with Q(10) values of 2 or more, may over-predict Root contributions to ecosystem CO2 efflux for future climates and underestimate the amount of C available for other uses, including net primary productivity.
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Field measurements of Root Respiration indicate little to no seasonal temperature acclimation for sugar maple and red pine.
Tree physiology, 2003Co-Authors: Andrew J. Burton, Kurt S. PregitzerAbstract:Increasing global temperatures could potentially cause large increases in Root Respiration and associated soil CO2 efflux. However, if Root Respiration acclimates to higher temperatures, increases in soil CO2 efflux from this source would be much less. Throughout the snow-free season, we measured fine Root Respiration in the field at ambient soil temperature in a sugar maple (Acer saccharum Marsh.) forest and a red pine (Pinus resinosa Ait.) plantation in Michigan. The objectives were to determine effects of soil temperature, soil water availability and experimental N additions on Root Respiration rates, and to test for temperature acclimation in response to seasonal changes in soil temperature. Soil temperature and soil water availability were important predictors of Root Respiration and together explained 76% of the variation in Root Respiration rates in the red pine plantation and 71% of the variation in the sugar maple forest. Root N concentration explained an additional 6% of the variation in the sugar maple trees. Experimental N additions did not affect Root Respiration rates at either site. From April to November, Root Respiration rates measured in the field increased exponentially with increasing soil temperature. For sugar maple, long-term Q10 values calculated from the field data were slightly, but not significantly, less than short-term Q10 values determined for instantaneous temperature series conducted in the laboratory (2.4 versus 2.62.7). For red pine, long-term and short-term Q10 values were similar (3.0 versus 3.0). Sugar maple Root Respiration rates at constant reference temperatures of 6, 18 and 24 degrees C were measured in the laboratory at various times during the year when field soil temperatures varied from 0.4 to 16.8 degrees C. No relationship existed between ambient soil temperature just before sampling and Root Respiration rates at 6 and 18 degrees C (P = 0.37 and 0.86, respectively), and only a very weak relationship was found between ambient soil temperature and Root Respiration at 24 degrees C (P = 0.08, slope = 0.09). We conclude that Root Respiration in these species undergoes little, if any, acclimation to seasonal changes in soil temperature.
Kurt S. Pregitzer - One of the best experts on this subject based on the ideXlab platform.
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Field measurements of Root Respiration indicate little to no seasonal temperature acclimation for sugar maple and red pine.
Tree physiology, 2003Co-Authors: Andrew J. Burton, Kurt S. PregitzerAbstract:Increasing global temperatures could potentially cause large increases in Root Respiration and associated soil CO2 efflux. However, if Root Respiration acclimates to higher temperatures, increases in soil CO2 efflux from this source would be much less. Throughout the snow-free season, we measured fine Root Respiration in the field at ambient soil temperature in a sugar maple (Acer saccharum Marsh.) forest and a red pine (Pinus resinosa Ait.) plantation in Michigan. The objectives were to determine effects of soil temperature, soil water availability and experimental N additions on Root Respiration rates, and to test for temperature acclimation in response to seasonal changes in soil temperature. Soil temperature and soil water availability were important predictors of Root Respiration and together explained 76% of the variation in Root Respiration rates in the red pine plantation and 71% of the variation in the sugar maple forest. Root N concentration explained an additional 6% of the variation in the sugar maple trees. Experimental N additions did not affect Root Respiration rates at either site. From April to November, Root Respiration rates measured in the field increased exponentially with increasing soil temperature. For sugar maple, long-term Q10 values calculated from the field data were slightly, but not significantly, less than short-term Q10 values determined for instantaneous temperature series conducted in the laboratory (2.4 versus 2.62.7). For red pine, long-term and short-term Q10 values were similar (3.0 versus 3.0). Sugar maple Root Respiration rates at constant reference temperatures of 6, 18 and 24 degrees C were measured in the laboratory at various times during the year when field soil temperatures varied from 0.4 to 16.8 degrees C. No relationship existed between ambient soil temperature just before sampling and Root Respiration rates at 6 and 18 degrees C (P = 0.37 and 0.86, respectively), and only a very weak relationship was found between ambient soil temperature and Root Respiration at 24 degrees C (P = 0.08, slope = 0.09). We conclude that Root Respiration in these species undergoes little, if any, acclimation to seasonal changes in soil temperature.
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Root Respiration in north american forests effects of nitrogen concentration and temperature across biomes
Oecologia, 2002Co-Authors: Andrew J. Burton, Kurt S. Pregitzer, Roger W Ruess, Ronald L Hendrick, Michael F AllenAbstract:Root Respiration rates have been shown to be correlated with temperature and Root N concentration in studies of individual forest types or species, but it is not known how universal these relationships are across forest species adapted to widely different climatic and edaphic conditions. In order to test for broad, cross-species relationships, we measured fine Root Respiration, as O2 consumption, over a range of temperatures on excised Root samples from ten forested study sites across North America in 1997. Significant differences existed among study sites in Root Respiration rates, with patterns among sites in Respiration rate at a given temperature corresponding to differences among sites in fine Root N concentrations. Root Respiration rates were highly correlated with Root N concentrations at all measurement temperatures (r2>0.81, P<0.001, for 6, 18 and 24°C). Lower Root Respiration rates in gymnosperms than in angiosperms were largely explained by lower fine Root N concentrations in gymnosperms, and Root N concentrations and Respiration rates (at a given temperature) tended to be lower at warm sites (New Mexico, Florida, and Georgia) than at cool sites with short growing seasons (Michigan and Alaska). Root Respiration rates increased exponentially with temperature at all sites. The Q10 for Root Respiration ranged from 2.4 to 3.1, but there were no significant differences among the forest types. The average Q10s for gymnosperms (Q10=2.7) and angiosperms (Q10=2.6) were almost identical, as were the average Q10s for Roots of ectomycorrhizal species (Q10=2.7) and arbuscular mycorrhizal species (Q10=2.6). In 1998, fine Root Respiration at the study sites was measured in the field as CO2 production at ambient soil temperature. Respiration rates under field conditions were dependent on both ambient soil temperature and Root N concentration. Relationships between Respiration (adjusted for temperature) and Root N concentration for the field measurements were similar to those observed in the 1997 laboratory experiments. For Root Respiration in tree species, it appears that basic relationships with temperature and nitrogen exist across species and biomes.
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Root Respiration in North American forests: effects of nitrogen concentration and temperature across biomes
Oecologia, 2002Co-Authors: Andrew J. Burton, Kurt S. Pregitzer, Roger W Ruess, Ronald L Hendrick, Michael F AllenAbstract:Root Respiration rates have been shown to be correlated with temperature and Root N concentration in studies of individual forest types or species, but it is not known how universal these relationships are across forest species adapted to widely different climatic and edaphic conditions. In order to test for broad, cross-species relationships, we measured fine Root Respiration, as O2 consumption, over a range of temperatures on excised Root samples from ten forested study sites across North America in 1997. Significant differences existed among study sites in Root Respiration rates, with patterns among sites in Respiration rate at a given temperature corresponding to differences among sites in fine Root N concentrations. Root Respiration rates were highly correlated with Root N concentrations at all measurement temperatures (r2>0.81, P
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Measurement carbon dioxide concentration does not affect Root Respiration of nine tree species in the field.
Tree physiology, 2002Co-Authors: Andrew J. Burton, Kurt S. PregitzerAbstract:Inhibition of Respiration has been reported as a short-term response of tree Roots to elevated measurement CO2 concentration ([CO2]), calling into question the validity of Root Respiration rates determined at CO2 concentrations that differ from the soil [CO2] in the Rooting zone. Our objectives were to validate previous observations of a direct CO2 effect on Root Respiration in sugar maple (Acer saccharum Marsh.) and to determine if high [CO2] also inhibited Root Respiration in other tree species. Root Respiration rates for nine common North American tree species were measured in the field at ambient soil temperature at both 350 and 1000 ?l CO2 1-1. No evidence of direct inhibition of Root Respiration by elevated measurement [CO2] was found for any of the species tested. The ratio of Respiration rates at 1000 and 350 ?l CO2 1-1 ranged from 0.97 to 1.07, and the 95% confidence intervals for this ratio included unity for all species tested. Tests of a Respiration cuvette used in earlier experiments suggested that gas leakage from the cuvette/IRGA system created an apparent direct CO2 effect on Respiration of sugar maple Roots when none actually existed. Small sample masses used in those experiments exacerbated the error. Careful attention to the possibility of gas leaks and the avoidance of small sample masses should produce data that will allow researchers to accurately assess whether direct effects of measurement [CO2] exist. Our findings of no direct CO2 effect on Respiration of Roots of a wide variety of species suggest that such effects may be less common than previously thought for tree Roots.
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Variation in sugar maple Root Respiration with Root diameter and soil depth
Tree physiology, 1998Co-Authors: Kurt S. Pregitzer, Michele J. Laskowski, Andrew J. Burton, Veronica C. Lessard, Donald R. ZakAbstract:Root Respiration may account for as much as 60% of total soil Respiration. Therefore, factors that regulate the metabolic activity of Roots and associated microbes are an important component of terrestrial carbon budgets. Root systems are often sampled by diameter and depth classes to enable researchers to process samples in a systematic and timely fashion. We recently discovered that small, lateral Roots at the distal end of the Root system have much greater tissue N concentrations than larger Roots, and this led to the hypothesis that the smallest Roots have significantly higher rates of Respiration than larger Roots. This study was designed to determine if Root Respiration is related to Root diameter or the location of Roots in the soil profile. We examined relationships among Root Respiration rates and N concentration in four diameter classes from three soil depths in two sugar maple (Acer saccharum Marsh.) forests in Michigan. Root Respiration declined as Root diameter increased and was lower at deeper soil depths than at the soil surface. Surface Roots (0-10 cm depth) respired at rates up to 40% greater than deeper Roots, and Respiration rates for Roots < 0.5 mm in diameter were 2.4 to 3.4 times higher than those for Roots in larger diameter classes. Root N concentration explained 70% of the observed variation in Respiration across sites and size and depth classes. Differences in Respiration among Root diameter classes and soil depths appeared to be consistent with hypothesized effects of variation in Root function on metabolic activity. Among Roots, very fine Roots in zones of high nutrient availability had the highest Respiration rates. Large Roots and Roots from depths of low nutrient availability had low Respiration rates consistent with structural and transport functions rather than with active nutrient uptake and assimilation. These results suggest that broadly defined Root classes, e.g., fine Roots are equivalent to all Roots < 2.0 mm in diameter, do not accurately reflect the functional categories typically associated with fine Roots. Tissue N concentration or N content (mass × concentration N) may be a better indicator of Root function than Root diameter.
Yu Jia - One of the best experts on this subject based on the ideXlab platform.
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Effects of shoot removal and soil water content on Root Respiration of spring wheat and soybean
Environmental and Experimental Botany, 2006Co-Authors: Hong-sheng Liu, Yu JiaAbstract:Abstract In an effort to separate soil Respiration into Root-derived Respiration and soil-microbe-derived Respiration under field conditions, removal of the shoot was investigated as a tool to determine the individual contributions. Spring wheat (Triticum aestivum L. cv Longchun 8139) and soybean (Glycine max L. cv Tianchan 2) were grown in the field under a movable rain shelter and subjected to three water regimes: (1) well-watered, (2) moderate drought stress, and (3) severe drought stress. Roots from spring wheat and soybean plants that had either been left intact or subjected to shoot excision were monitored for the efflux of carbon dioxide, the influx of oxygen, and total soluble carbohydrate (TSC), malic acid, and citric acid contents. The Root Respiration rates of shoot-excised and intact plants ranged from 0.88–2.32 and 1.09–2.72 μmol CO2 m−2 s−1 for wheat and 0.42–1.66 and 0.52–2.03 μmol CO2 m−2 s−1 for soybean, respectively, indicating that although shoot removal had an adverse effect on Root Respiration, this technique can be used to measure the Root-derived Respiration under field conditions. The times of shoot removal that had the most dramatic effects on the gas flux rates in plants subjected to well-watered, moderate drought, and severe drought stress treatments were 3, 2, and 1 h for spring wheat, and 3, 1, and 1 h for soybean, respectively. Both crops showed significantly positive relationships between soil water content and TSC content, and between TSC content and the time when the Root Respiration of the shoot-excised plants differed significantly from that of plants with intact shoots. These results suggest that Root Respiration should be measured within 3 h after shoot excision when the plants are under the optimal growth conditions, although the maximum elapsed time should be reduced as the degree of environmental stress increases. Regardless of the water availability, the Root Respiration should be measured as soon as possible after the shoot is removed, since by the time the Root Respiration rate has stabilized, it differs greatly from the rate observed shortly after the shoot has been clipped.
Donald R. Zak - One of the best experts on this subject based on the ideXlab platform.
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Variation in sugar maple Root Respiration with Root diameter and soil depth
Tree physiology, 1998Co-Authors: Kurt S. Pregitzer, Michele J. Laskowski, Andrew J. Burton, Veronica C. Lessard, Donald R. ZakAbstract:Root Respiration may account for as much as 60% of total soil Respiration. Therefore, factors that regulate the metabolic activity of Roots and associated microbes are an important component of terrestrial carbon budgets. Root systems are often sampled by diameter and depth classes to enable researchers to process samples in a systematic and timely fashion. We recently discovered that small, lateral Roots at the distal end of the Root system have much greater tissue N concentrations than larger Roots, and this led to the hypothesis that the smallest Roots have significantly higher rates of Respiration than larger Roots. This study was designed to determine if Root Respiration is related to Root diameter or the location of Roots in the soil profile. We examined relationships among Root Respiration rates and N concentration in four diameter classes from three soil depths in two sugar maple (Acer saccharum Marsh.) forests in Michigan. Root Respiration declined as Root diameter increased and was lower at deeper soil depths than at the soil surface. Surface Roots (0-10 cm depth) respired at rates up to 40% greater than deeper Roots, and Respiration rates for Roots < 0.5 mm in diameter were 2.4 to 3.4 times higher than those for Roots in larger diameter classes. Root N concentration explained 70% of the observed variation in Respiration across sites and size and depth classes. Differences in Respiration among Root diameter classes and soil depths appeared to be consistent with hypothesized effects of variation in Root function on metabolic activity. Among Roots, very fine Roots in zones of high nutrient availability had the highest Respiration rates. Large Roots and Roots from depths of low nutrient availability had low Respiration rates consistent with structural and transport functions rather than with active nutrient uptake and assimilation. These results suggest that broadly defined Root classes, e.g., fine Roots are equivalent to all Roots < 2.0 mm in diameter, do not accurately reflect the functional categories typically associated with fine Roots. Tissue N concentration or N content (mass × concentration N) may be a better indicator of Root function than Root diameter.
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DROUGHT REDUCES Root Respiration IN SUGAR MAPLE FORESTS
Ecological Applications, 1998Co-Authors: Andrew J. Burton, Kurt S. Pregitzer, Gregory P. Zogg, Donald R. ZakAbstract:Soil moisture deficits can reduce Root Respiration, but the effects have yet to be quantified at the stand level or included in models of forest carbon budgets. We studied fine-Root (≤1.0 mm diameter) Respiration in four sugar maple forests for three growing seasons in order to assess the combined effects of temperature, N concentration, and soil moisture on Respiration rates. Fine-Root Respiration at the four sites was exponentially related to soil temperature and linearly related to Root N concentration and soil moisture availability. Most of the variability in Respiration rates was explained by temperature. Differences in soil moisture availability explained temporal variation within sites in Respiration rate at a given temperature, whereas differences among sites in Respiration rates resulted from site-specific differences in fine-Root N concentration. Periodic moisture deficits during 1995 and 1996 were sufficient to cause declines of up to 17% in total growing-season Root Respiration at affected sit...
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effect of measurement co2 concentration on sugar maple Root Respiration
Tree Physiology, 1997Co-Authors: Andrew J. Burton, Kurt S. Pregitzer, Gregory P. Zogg, Donald R. ZakAbstract:Accurate estimates of Root Respiration are crucial to predicting belowground C cycling in forest ecosystems. Inhibition of Respiration has been reported as a short-term response of plant tissue to elevated measurement [CO 2 ]. We sought to determine if measurement [CO 2 ] affected Root Respiration in samples from mature sugar maple (Acer saccharum Marsh.) forests and to assess possible errors associated with Root Respiration measurements made at [CO 2 ]s lower than that typical of the soil atmosphere. Root Respiration was measured as both CO 2 production and O 2 consumption on excised fine Roots (≤ 1.0 mm) at [CO 2 ]s ranging from 350 to > 20,000 μl l −1 . Root Respiration was significantly affected by the [CO 2 ] at which measurements were made for both CO 2 production and O 2 consumption. Root Respiration was most sensitive to [CO 2 ] near and below normal soil concentrations (< 1500 μl l −1 ). Respiration rates changed little at [CO 2 ]s above 3000 μl l −1 and were essentially constant above 6000 μl l −1 CO 2 . These findings call into question estimates of Root Respiration made at or near atmospheric [CO 2 ], suggesting that they overestimate actual rates in the soil. Our results indicate that sugar maple Root Respiration at atmospheric [CO 2 ] (350 μl l −1 ) is about 139% of that at soil [CO 2 ]. Although the causal mechanism remains unknown, the increase in Root Respiration at low measurement [CO 2 ] is significant and should be accounted for when estimating or modeling Root Respiration. Until the direct effect of [CO 2 ] on Root Respiration is fully understood, we recommend making measurements at a [CO 2 ] representative of, or higher than, soil [CO 2 ]. In all cases, the [CO 2 ] at which measurements are made and the [CO 2 ] typical of the soil atmosphere should be reported.
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Latitudinal variation in sugar maple fine Root Respiration
Canadian Journal of Forest Research, 1996Co-Authors: Andrew J. Burton, Kurt S. Pregitzer, Gregory P. Zogg, Donald R. ZakAbstract:A changing global climate may impact the Respiration of fine Roots. While many models adjust fine Root Respiration as temperature increases, the influence of soil nutrient availability and the possibility that Root Respiration may be adapted to local climate are often not addressed. Rates of fine Root Respiration were measured in four sugar maple (Acersaccharum Marsh.) forests located along a latitudinal gradient in Michigan. Root Respiration was measured as O2 consumption at temperatures ranging from 6 to 24 °C on excised fine Root samples in early September, October, and November of 1994. Root Respiration increased exponentially with temperature with an average Q10 of 2.7; there were no differences in Q10 among sites. However, there were differences among sites in mean Respiration rate at a given temperature. This site effect did not indicate ecotypic adaptation to local climate, but rather reflected fine Root N concentration. Respiration at a given temperature was consistently higher in Roots with high...
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Fine Root Respiration in northern hardwood forests in relation to temperature and nitrogen availability
Tree physiology, 1996Co-Authors: Gregory P. Zogg, Donald R. Zak, Andrew J. Burton, Kurt S. PregitzerAbstract:We examined fine-Root (< 2.0 mm diameter) Respiration throughout one growing season in four northern hardwood stands dominated by sugar maple (Acer saccharum Marsh.), located along soil temperature and nitrogen (N) availability gradients. In each stand, we fertilized three 50 x 50 m plots with 30 kg NO(3) (-)-N ha(-1) year(-1) and an additional three plots received no N and served as controls. We predicted that Root Respiration rates would increase with increasing soil temperature and N availability. We reasoned that Respiration would be greater for trees using NO(3) (-) as an N source than for trees using NH(4) (+) as an N source because of the greater carbon (C) costs associated with NO(3) (-) versus NH(4) (+) uptake and assimilation. Within stands, seasonal patterns of fine-Root Respiration rates followed temporal changes in soil temperature, ranging from a low of 2.1 micro mol O(2) kg(-1) s(-1) at 6 degrees C to a high of 7.0 micro mol O(2) kg(-1) s(-1) at 18 degrees C. Differences in Respiration rates among stands at a given soil temperature were related to variability in total net N mineralized (48-90 micro g N g(-1)) throughout the growing season and associated changes in mean Root tissue N concentration (1.18-1.36 mol N kg(-1)). The hypothesized increases in Respiration in response to NO(3) (-) fertilization were not observed. The best-fit model describing patterns within and among stands had Root Respiration rates increasing exponentially with soil temperature and increasing linearly with increasing tissue N concentration: R = 1.347Ne(0.072T) (r(2) = 0.63, P < 0.01), where R is Root Respiration rate ( micro mol O(2) kg(-1) s(-1)), N is Root tissue N concentration (mol N kg(-1)), and T is soil temperature ( degrees C). We conclude that, in northern hardwood forests dominated by sugar maple, Root Respiration is responsive to changes in both soil temperature and N availability, and that both factors should be considered in models of forest C dynamics.
