The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Allen H Goldstein - One of the best experts on this subject based on the ideXlab platform.
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forest thinning and soil Respiration in a ponderosa pine plantation in the sierra nevada
Tree Physiology, 2005Co-Authors: Jianwu Tang, Ye Qi, Laurent Misson, Ming Xu, Allen H GoldsteinAbstract:Soil Respiration is controlled by soil temperature, soil water, fine roots, microbial activity, and soil physical and chemical properties. Forest thinning changes soil temperature, soil water content, and root density and activity, and thus changes soil Respiration. We measured soil Respiration monthly and soil temperature and volumetric soil water continuously in a young ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) plantation in the Sierra Nevada Mountains in California from June 1998 to May 2000 (before a thinning that removed 30% of the biomass), and from May to December 2001 (after thinning). Thinning increased the spatial homogeneity of soil temperature and Respiration. We conducted a multivariate analysis with two independent variables of soil temperature and water and a categorical variable representing the thinning event to simulate soil Respiration and assess the effect of thinning. Thinning did not change the sensitivity of soil Respiration to temperature or to water, but decreased total soil Respiration by 13% at a given temperature and water content. This decrease in soil Respiration was likely associated with the decrease in root density after thinning. With a model driven by continuous soil temperature and water time series, we estimated that total soil Respiration was 948, 949 and 831 g C m − year − in the years 1999, 2000 and 2001, respectively. Although thinning reduced soil Respiration at a given temperature and water content, because of natural climate variability and the thinning effect on soil temperature and water, actual cumulative soil Respiration showed no clear trend following thinning. We conclude that the effect of forest thinning on soil Respiration is the combined result of a decrease in root Respiration, an increase in soil organic matter, and changes in soil temperature and water due to both thinning and interannual climate variability.
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ecosystem Respiration in a young ponderosa pine plantation in the sierra nevada mountains california
Tree Physiology, 2001Co-Authors: Ming Xu, Ye Qi, Terry A Debiase, Allen H GoldsteinAbstract:We estimated total ecosystem Respiration from a ponderosa pine (Pinus ponderosa Dougl. ex Laws.) plantation in the Sierra Nevada Mountains near Georgetown, California, from June to October, 1998. We apportioned ecosystem Respiration among heterotrophic, root, stem and foliage based on relationships for each component that considered microclimate and vegetation characteristics. We measured each Respiration component at selected sampling points, and scaled the measurements up to the ecosystem based on modeled relationships. Over the study period, total mean ecosystem Respiration was 5.7 ± 1.3 μmol m −2 s −1 (based on daily mean), comprising about 67% from soil-surface CO 2 efflux, 10% from stem and branch Respiration and 23% from foliage Respiration. Shrub leaves contributed about 24% to total foliage Respiration, and current-year needles (1998 age class) accounted for 40% of total tree needle Respiration. Root Respiration accounted for 47% of soil-surface CO 2 efflux. We conclude that ecosystem Respiration can be estimated based on daily mean air and soil temperatures through exponential relationships with r 2 values of 0.85 and 0.87, respectively. When based on both air and soil temperatures, about 91% of the variation in total ecosystem Respiration could be explained by a linear regression.
Ming Xu - One of the best experts on this subject based on the ideXlab platform.
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forest thinning and soil Respiration in a ponderosa pine plantation in the sierra nevada
Tree Physiology, 2005Co-Authors: Jianwu Tang, Ye Qi, Laurent Misson, Ming Xu, Allen H GoldsteinAbstract:Soil Respiration is controlled by soil temperature, soil water, fine roots, microbial activity, and soil physical and chemical properties. Forest thinning changes soil temperature, soil water content, and root density and activity, and thus changes soil Respiration. We measured soil Respiration monthly and soil temperature and volumetric soil water continuously in a young ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) plantation in the Sierra Nevada Mountains in California from June 1998 to May 2000 (before a thinning that removed 30% of the biomass), and from May to December 2001 (after thinning). Thinning increased the spatial homogeneity of soil temperature and Respiration. We conducted a multivariate analysis with two independent variables of soil temperature and water and a categorical variable representing the thinning event to simulate soil Respiration and assess the effect of thinning. Thinning did not change the sensitivity of soil Respiration to temperature or to water, but decreased total soil Respiration by 13% at a given temperature and water content. This decrease in soil Respiration was likely associated with the decrease in root density after thinning. With a model driven by continuous soil temperature and water time series, we estimated that total soil Respiration was 948, 949 and 831 g C m − year − in the years 1999, 2000 and 2001, respectively. Although thinning reduced soil Respiration at a given temperature and water content, because of natural climate variability and the thinning effect on soil temperature and water, actual cumulative soil Respiration showed no clear trend following thinning. We conclude that the effect of forest thinning on soil Respiration is the combined result of a decrease in root Respiration, an increase in soil organic matter, and changes in soil temperature and water due to both thinning and interannual climate variability.
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ecosystem Respiration in a young ponderosa pine plantation in the sierra nevada mountains california
Tree Physiology, 2001Co-Authors: Ming Xu, Ye Qi, Terry A Debiase, Allen H GoldsteinAbstract:We estimated total ecosystem Respiration from a ponderosa pine (Pinus ponderosa Dougl. ex Laws.) plantation in the Sierra Nevada Mountains near Georgetown, California, from June to October, 1998. We apportioned ecosystem Respiration among heterotrophic, root, stem and foliage based on relationships for each component that considered microclimate and vegetation characteristics. We measured each Respiration component at selected sampling points, and scaled the measurements up to the ecosystem based on modeled relationships. Over the study period, total mean ecosystem Respiration was 5.7 ± 1.3 μmol m −2 s −1 (based on daily mean), comprising about 67% from soil-surface CO 2 efflux, 10% from stem and branch Respiration and 23% from foliage Respiration. Shrub leaves contributed about 24% to total foliage Respiration, and current-year needles (1998 age class) accounted for 40% of total tree needle Respiration. Root Respiration accounted for 47% of soil-surface CO 2 efflux. We conclude that ecosystem Respiration can be estimated based on daily mean air and soil temperatures through exponential relationships with r 2 values of 0.85 and 0.87, respectively. When based on both air and soil temperatures, about 91% of the variation in total ecosystem Respiration could be explained by a linear regression.
Jianwu Tang - One of the best experts on this subject based on the ideXlab platform.
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Soil Respiration under climate warming: differential response of heterotrophic and autotrophic Respiration
Global Change Biology, 2014Co-Authors: Xin Wang, Jianwu Tang, Ivan A Janssens, Lingli Liu, Shilong Piao, Weixing Liu, Yonggang Chi, Jing WangAbstract:Despite decades of research, how climate warming alters the global flux of soil Respiration is still poorly characterized. Here, we use meta-analysis to synthesize 202 soil Respiration datasets from 50 ecosystem warming experiments across multiple terrestrial ecosystems. We found that, on average, warming by 2 °C increased soil Respiration by 12% during the early warming years, but warming-induced drought partially offset this effect. More significantly, the two components of soil Respiration, heterotrophic Respiration and autotrophic Respiration showed distinct responses. The warming effect on autotrophic Respiration was not statistically detectable during the early warming years, but nonetheless decreased with treatment duration. In contrast, warming by 2 °C increased heterotrophic Respiration by an average of 21%, and this stimulation remained stable over the warming duration. This result challenged the assumption that microbial activity would acclimate to the rising temperature. Together, our findings demonstrate that distinguishing heterotrophic Respiration and autotrophic Respiration would allow us better understand and predict the long-term response of soil Respiration to warming. The dependence of soil Respiration on soil moisture condition also underscores the importance of incorporating warming-induced soil hydrological changes when modeling soil Respiration under climate change.
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tree photosynthesis modulates soil Respiration on a diurnal time scale
Global Change Biology, 2005Co-Authors: Jianwu Tang, Dennis D BaldocchiAbstract:To estimate how tree photosynthesis modulates soil Respiration, we simultaneously and continuously measured soil Respiration and canopy photosynthesis over an oak-grass savanna during the summer, when the annual grass between trees was dead. Soil Respiration measured under a tree crown reflected the sum of rhizosphere Respiration and heterotrophic Respiration; soil Respiration measured in an open area represented heterotrophic Respiration. Soil Respiration was measured using solid-state CO2 sensors buried in soils and the flux-gradient method. Canopy photosynthesis was obtained from overstory and understory flux measurements using the eddy covariance method. We found that the diurnal pattern of soil Respiration in the open was driven by soil temperature, while soil Respiration under the tree was decoupled with soil temperature. Although soil moisture controlled the seasonal pattern of soil Respiration, it did not influence the diurnal pattern of soil Respiration. Soil Respiration under the tree controlled by the root component was strongly correlated with tree photosynthesis, but with a time lag of 7–12 h. These results indicate that photosynthesis drives soil Respiration in addition to soil temperature and moisture.
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forest thinning and soil Respiration in a ponderosa pine plantation in the sierra nevada
Tree Physiology, 2005Co-Authors: Jianwu Tang, Ye Qi, Laurent Misson, Ming Xu, Allen H GoldsteinAbstract:Soil Respiration is controlled by soil temperature, soil water, fine roots, microbial activity, and soil physical and chemical properties. Forest thinning changes soil temperature, soil water content, and root density and activity, and thus changes soil Respiration. We measured soil Respiration monthly and soil temperature and volumetric soil water continuously in a young ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) plantation in the Sierra Nevada Mountains in California from June 1998 to May 2000 (before a thinning that removed 30% of the biomass), and from May to December 2001 (after thinning). Thinning increased the spatial homogeneity of soil temperature and Respiration. We conducted a multivariate analysis with two independent variables of soil temperature and water and a categorical variable representing the thinning event to simulate soil Respiration and assess the effect of thinning. Thinning did not change the sensitivity of soil Respiration to temperature or to water, but decreased total soil Respiration by 13% at a given temperature and water content. This decrease in soil Respiration was likely associated with the decrease in root density after thinning. With a model driven by continuous soil temperature and water time series, we estimated that total soil Respiration was 948, 949 and 831 g C m − year − in the years 1999, 2000 and 2001, respectively. Although thinning reduced soil Respiration at a given temperature and water content, because of natural climate variability and the thinning effect on soil temperature and water, actual cumulative soil Respiration showed no clear trend following thinning. We conclude that the effect of forest thinning on soil Respiration is the combined result of a decrease in root Respiration, an increase in soil organic matter, and changes in soil temperature and water due to both thinning and interannual climate variability.
Ye Qi - One of the best experts on this subject based on the ideXlab platform.
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forest thinning and soil Respiration in a ponderosa pine plantation in the sierra nevada
Tree Physiology, 2005Co-Authors: Jianwu Tang, Ye Qi, Laurent Misson, Ming Xu, Allen H GoldsteinAbstract:Soil Respiration is controlled by soil temperature, soil water, fine roots, microbial activity, and soil physical and chemical properties. Forest thinning changes soil temperature, soil water content, and root density and activity, and thus changes soil Respiration. We measured soil Respiration monthly and soil temperature and volumetric soil water continuously in a young ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) plantation in the Sierra Nevada Mountains in California from June 1998 to May 2000 (before a thinning that removed 30% of the biomass), and from May to December 2001 (after thinning). Thinning increased the spatial homogeneity of soil temperature and Respiration. We conducted a multivariate analysis with two independent variables of soil temperature and water and a categorical variable representing the thinning event to simulate soil Respiration and assess the effect of thinning. Thinning did not change the sensitivity of soil Respiration to temperature or to water, but decreased total soil Respiration by 13% at a given temperature and water content. This decrease in soil Respiration was likely associated with the decrease in root density after thinning. With a model driven by continuous soil temperature and water time series, we estimated that total soil Respiration was 948, 949 and 831 g C m − year − in the years 1999, 2000 and 2001, respectively. Although thinning reduced soil Respiration at a given temperature and water content, because of natural climate variability and the thinning effect on soil temperature and water, actual cumulative soil Respiration showed no clear trend following thinning. We conclude that the effect of forest thinning on soil Respiration is the combined result of a decrease in root Respiration, an increase in soil organic matter, and changes in soil temperature and water due to both thinning and interannual climate variability.
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ecosystem Respiration in a young ponderosa pine plantation in the sierra nevada mountains california
Tree Physiology, 2001Co-Authors: Ming Xu, Ye Qi, Terry A Debiase, Allen H GoldsteinAbstract:We estimated total ecosystem Respiration from a ponderosa pine (Pinus ponderosa Dougl. ex Laws.) plantation in the Sierra Nevada Mountains near Georgetown, California, from June to October, 1998. We apportioned ecosystem Respiration among heterotrophic, root, stem and foliage based on relationships for each component that considered microclimate and vegetation characteristics. We measured each Respiration component at selected sampling points, and scaled the measurements up to the ecosystem based on modeled relationships. Over the study period, total mean ecosystem Respiration was 5.7 ± 1.3 μmol m −2 s −1 (based on daily mean), comprising about 67% from soil-surface CO 2 efflux, 10% from stem and branch Respiration and 23% from foliage Respiration. Shrub leaves contributed about 24% to total foliage Respiration, and current-year needles (1998 age class) accounted for 40% of total tree needle Respiration. Root Respiration accounted for 47% of soil-surface CO 2 efflux. We conclude that ecosystem Respiration can be estimated based on daily mean air and soil temperatures through exponential relationships with r 2 values of 0.85 and 0.87, respectively. When based on both air and soil temperatures, about 91% of the variation in total ecosystem Respiration could be explained by a linear regression.
Daniel Epron - One of the best experts on this subject based on the ideXlab platform.
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Spatial and temporal variations of soil Respiration in a Eucalyptus plantation in Congo
Forest Ecology and Management, 2004Co-Authors: Daniel Epron, Yann Nouvellon, Olivier Roupsard, Welcome Mouvondy, André Mabiala, Laurent Saint-andré, Richard Joffre, Christophe Jourdan, Jean-marc Bonnefond, Paul BerbigierAbstract:Our objectives were to quantify soil Respiration in a 3-year-old Eucalyptus plantation in coastal Congo and to investigate both temporal and spatial variations of this major component of ecosystem Respiration. Soil Respiration exhibited pronounced seasonal variations that clearly reflected those of soil water content, with minimum values below 1.6 μmol m−2 s−1 at the end of the dry season in September and a maximum value of 5.6 μmol m−2 s−1 after re-wetting in December. An empirical model describing the relationship between soil Respiration and soil water content predicts the seasonal variations in soil Respiration reasonably well (R2 = 0.88), even if the effects of soil temperature and soil water content may be confounded since both factors co-vary across seasons. Spatial heterogeneity of soil Respiration was clearly affected by management practices with higher Respiration rate in slash inter-rows which received higher amounts of detritus at the logging stage, and lower Respiration rate in haulage inter-rows used for heavy vehicle traffic. Higher values of soil Respiration were also recorded in the vicinity of trunks than in the middle of the inter-rows. While soil water content is the main determinant of seasonal variation of soil Respiration, it poorly accounts for its spatial variability over the experimental stand, except for days with low soil water content. Soil Respiration was related neither to root biomass nor to soil carbon content, but was positively correlated with both leaf and total aboveground litter (i.e. leaf, bark and woody debris). Plots exhibiting the highest soil Respiration also contained the highest amounts of aboveground litter. Microbial Respiration associated with litter decomposition is likely a major component of soil Respiration, and the spatial heterogeneity in litter fall probably accounts for most of its spatial variability in this Eucalyptus plantation.
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productivity overshadows temperature in determining soil and ecosystem Respiration across european forests
Global Change Biology, 2001Co-Authors: Ivan A Janssens, Harry Lankreijer, Giorgio Matteucci, Andrew S Kowalski, Nina Buchmann, Daniel Epron, Kim Pilegaard, Werner L Kutsch, Bernard Longdoz, Thomas GrunwaldAbstract:Summary This paper presents CO2 flux data from 18 forest ecosystems, studied in the European Union funded EUROFLUX project. Overall, mean annual gross primary productivity (GPP, the total amount of carbon (C) fixed during photosynthesis) of these forests was 1380 ± 330 gC m−2 y−1 (mean ±SD). On average, 80% of GPP was respired by autotrophs and heterotrophs and released back into the atmosphere (total ecosystem Respiration, TER = 1100 ± 260 gC m−2 y−1). Mean annual soil Respiration (SR) was 760 ± 340 gC m−2 y−1 (55% of GPP and 69% of TER). Among the investigated forests, large differences were observed in annual SR and TER that were not correlated with mean annual temperature. However, a significant correlation was observed between annual SR and TER and GPP among the relatively undisturbed forests. On the assumption that (i) root Respiration is constrained by the allocation of photosynthates to the roots, which is coupled to productivity, and that (ii) the largest fraction of heterotrophic soil Respiration originates from decomposition of young organic matter (leaves, fine roots), whose availability also depends on primary productivity, it is hypothesized that differences in SR among forests are likely to depend more on productivity than on temperature. At sites where soil disturbance has occurred (e.g. ploughing, drainage), soil espiration was a larger component of the ecosystem C budget and deviated from the relationship between annual SR (and TER) and GPP observed among the less-disturbed forests. At one particular forest, carbon losses from the soil were so large, that in some years the site became a net source of carbon to the atmosphere. Excluding the disturbed sites from the present analysis reduced mean SR to 660 ± 290 gC m−2 y−1, representing 49% of GPP and 63% of TER in the relatively undisturbed forest ecosystems.
