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Jianwu Tang - One of the best experts on this subject based on the ideXlab platform.
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temperature response of Soil Respiration largely unaltered with experimental warming
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Joanna C Carey, Jianwu Tang, Pamela H Templer, Kevin D Kroeger, Thomas W Crowther, Andrew J Burton, Jeffrey S Dukes, Bridget A Emmett, Serita D Frey, Mary A HeskelAbstract:The respiratory release of carbon dioxide (CO2) from Soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of Soil Respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of Soil Respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of Soil Respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of Soil Respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of Soil Respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, Respiration rates with and without experimental warming follow a Gaussian response, increasing with Soil temperature up to a threshold of ∼25 °C, above which Respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in Soil Respiration, with colder climates being considerably more responsive to increased ambient temperatures compared with warmer regions. Our analysis adds a unique cross-biome perspective on the temperature response of Soil Respiration, information critical to improving our mechanistic understanding of how Soil carbon dynamics change with climatic warming.
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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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continuous measurements of Soil Respiration with and without roots in a ponderosa pine plantation in the sierra nevada mountains
Agricultural and Forest Meteorology, 2005Co-Authors: Jianwu Tang, Laurent Misson, Alexander Gershenson, Weixin Cheng, Allen H GoldsteinAbstract:Abstract Continuous measurements of Soil Respiration and its components help us understand diurnal and seasonal variations in Soil Respiration and its mechanism. We continuously measured CO 2 concentration at various depths in the Soil and calculated surface CO 2 efflux based on CO 2 gradients and diffusivity in a young ponderosa pine plantation in the Sierra Nevada Mountains of California. We determined Soil Respiration both in a control plot that included roots and in a trenched plot that had no roots. The difference between these plots was used to partition Soil Respiration into root Respiration and heterotrophic Respiration. We found that both CO 2 concentration in the Soil and surface CO 2 efflux in the control plot were higher than in the trenched plot. The diurnal range of Soil Respiration in the trenched plot was larger than in the control. We observed dramatic pulses of Soil Respiration in response to rain events in summer and fall during the dry season. We modeled the seasonal variation in Soil Respiration without the pulses using Soil temperature and moisture as driving variables and simulated Soil Respiration pulses using an exponential decay function in response to the volume of rain. Daily mean Soil Respiration peaked at 5.0 μmol m −2 s −1 in the control and at 2.7 μmol m −2 s −1 in the trenched plot in June before the rain pulses. Soil Respiration increased from 4.9 to 8.2 and to 12.1 μmol m −2 s −1 after the first and second rain events in the control, and increased from 2.2 to 4.1 and to 6.6 μmol m −2 s −1 in the trenched plot. After incorporating the pulse effect, the model simulated measured data well. Annual Soil Respiration in 2003 was estimated as 1184 g C m −2 y −1 . The average ratio of root over total Respiration was 0.56 during the growing season and 0.16 during the non-growing season with an annual average of 0.44.
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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.
Shiqiang Wan - One of the best experts on this subject based on the ideXlab platform.
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water and plant mediated responses of Soil Respiration to topography fire and nitrogen fertilization in a semiarid grassland in northern china
Soil Biology & Biochemistry, 2008Co-Authors: Shiqiang WanAbstract:Soil Respiration is one of the major carbon (C) fluxes between terrestrial ecosystems and the atmosphere and plays an important role in regulating the responses of ecosystem and global C cycling to natural and anthropogenic perturbations. A field experiment was conducted between April 2005 and October 2006 in a semiarid grassland in northern China to examine effects of topography, fire, nitrogen (N) fertilization, and their potential interactions on Soil Respiration. Mean Soil Respiration was 6.0% higher in the lower than upper slope over the 2 growing seasons. Annual burning in early spring caused constant increases in Soil Respiration (23.8%) over the two growing seasons. In addition, fire effects on Soil Respiration varied with both season and topographic position. Soil Respiration in the fertilized plots was 11.4% greater than that in the unfertilized plots. Water- and plant-mediation could be primarily responsible for the changes in Soil Respiration with topography and after fire whereas the positive responses of Soil Respiration to N fertilization were attributable to stimulated plant growth, root activity and Respiration. The different mechanisms by which topography, fire, and N fertilization influence Soil Respiration identified in this study will facilitate the simulation and projection of ecosystem C cycling in the semiarid grassland in northern China.
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responses of Soil Respiration to elevated co2 air warming and changing Soil water availability in a model old field grassland
Global Change Biology, 2007Co-Authors: Shiqiang Wan, Richard J Norby, Joanne Ledford, Jake F WeltzinAbstract:Responses of Soil Respiration to atmospheric and climatic change will have profound impacts on ecosystem and global C cycling in the future. This study was conducted to examine effects on Soil Respiration of the concurrent driving factors of elevated atmospheric CO2 concentration, rising temperature, and changing precipitation in a constructed old-field grassland in eastern Tennessee, USA. Model ecosystems of seven old-field species in 12 open-top chambers (4 m in diameter) were treated with two CO2 (ambient and ambient plus 300 ppm) and two temperature (ambient and ambient plus 3 C) levels. Two split plots with each chamber were assigned with high and low Soil moisture levels. During the 19-month experimental period from June 2003 to December 2004, higher CO2 concentration and Soil water availability significantly increased mean Soil Respiration by 35.8% and 15.7%, respectively. The effects of air warming on Soil Respiration varied seasonally from small reductions to significant increases to no response, and there was no significant main effect. In the wet side of elevated CO2 chambers, air warming consistently caused increases in Soil Respiration, whereas in other three combinations of CO2 and water treatments, warming tended to decrease Soil Respiration over the growing season but increase it overmore » the winter. There were no interactive effects on Soil Respiration among any two or three treatment factors irrespective of testing time period. Temperature sensitivity of Soil Respiration was reduced by air warming, lower in the wet than the dry side, and not affected by CO2 treatment. Variations of Soil Respiration responses with Soil temperature and Soil moisture ranges could be primarily attributable to the seasonal dynamics of plant growth and its responses to the three treatments. Using a conceptual model to interpret the significant relationships of treatment-induced changes in Soil Respiration with changes in Soil temperature and moisture observed in this study, we conclude that elevated CO2, air warming, and changing Soil water availability had both direct and indirect effects on Soil Respiration via changes in the three controlling factors: Soil temperature, Soil moisture, and C substrate. Our results demonstrate that the response of Soil Respiration to climatic warming should not be represented in models as a simple temperature response function. A more mechanistic understanding of the direct and indirect impacts of concurrent global change drivers on Soil Respiration is needed to facilitate the interpretation and projection of ecosystem and global C cycling in response to atmospheric and climate change.« less
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substrate regulation of Soil Respiration in a tallgrass prairie results of a clipping and shading experiment
Global Biogeochemical Cycles, 2003Co-Authors: Shiqiang Wan, Yiqi LuoAbstract:[1] Changes in Soil Respiration, one of the major fluxes of global carbon cycling, could significantly slow down or accelerate the increase in atmospheric CO2, with consequent feedbacks to climate change. It is critical to understand how substrate availability regulates Soil Respiration in projecting the response of carbon cycling to changed climate. We conducted a clipping and shading experiment for 1 year in a tallgrass prairie of the Great Plains, United States, to manipulate substrate supply to Soil Respiration. Our results showed that reduced substrate supply under clipping and/or shading significantly decreased Soil Respiration at all the timescales (diurnal, transient, and annual) irrespective of the minor concurrent changes in Soil temperature and moisture. Annual mean Soil Respiration decreased significantly by 33, 23, and 43% for the clipping, shading, and clipping plus shading treatments, respectively. Temperature sensitivity of Soil Respiration decreased from 1.93 in the control plots to 1.88, 1.75, and 1.83 in the clipped, shaded, and clipped plus shaded plots, respectively. Rhizosphere Respiration, Respiration from decomposition of aboveground litter, and Respiration from oxidation of Soil organic matter and dead roots accounted for 30, 14, and 56% of annual mean Soil Respiration, respectively. Rhizosphere Respiration was more sensitive to temperature than the other two components. Our results suggest a critical role of substrate supply in regulating Soil Respiration and its temperature sensitivity.
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acclimatization of Soil Respiration to warming in a tall grass prairie
Nature, 2001Co-Authors: Yiqi Luo, Shiqiang Wan, Dafeng Hui, Linda L WallaceAbstract:The latest report by the Intergovernmental Panel on Climate Change (IPCC) predicts a 1.4–5.8 °C average increase in the global surface temperature over the period 1990 to 2100 (ref. 1). These estimates of future warming are greater than earlier projections, which is partly due to incorporation of a positive feedback. This feedback results from further release of greenhouse gases from terrestrial ecosystems in response to climatic warming2,3,4. The feedback mechanism is usually based on the assumption that observed sensitivity of Soil Respiration to temperature under current climate conditions would hold in a warmer climate5. However, this assumption has not been carefully examined. We have therefore conducted an experiment in a tall grass prairie ecosystem in the US Great Plains to study the response of Soil Respiration (the sum of root and heterotrophic Respiration) to artificial warming of about 2 °C. Our observations indicate that the temperature sensitivity of Soil Respiration decreases—or acclimatizes—under warming and that the acclimatization is greater at high temperatures. This acclimatization of Soil Respiration to warming may therefore weaken the positive feedback between the terrestrial carbon cycle and climate.
Beverly E Law - One of the best experts on this subject based on the ideXlab platform.
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forest Soil Respiration across three climatically distinct chronosequences in oregon
Biogeochemistry, 2005Co-Authors: John L Campbell, Beverly E LawAbstract:To assess the relative influence of edaphoclimatic gradients and stand replacing disturbance on the Soil Respiration of Oregon forests, we measured annual Soil Respiration at 36 independent forest plots arranged as three replicates of four age classes in each of three climatically distinct forest types. Annual Soil Respiration for the year 2001 was computed by combining periodic chamber measurements with continuous Soil temperature measurements, which were used along with site-specific temperature response curves to interpolate daily Soil Respiration between dates of direct measurement. Results indicate significant forest type, age, and type × age interaction effects on annual Soil Respiration. Average annual Soil Respiration was 1100–1600, 1500–2100, and 500–900 g C m−2 yr−1 for mesic spruce, montane Douglas-fir, and semi-arid pine forests respectively. Age related trends in annual Soil Respiration varied between forest types. The variation in annual Soil Respiration attributable to the climatic differences between forest types was 48%(CV). Once weighted by the age class distribution for each forest type, the variation in annual Soil Respiration attributable to stand replacing disturbance was 15%(CV). Sensitivity analysis suggests that the regional variation in annual Soil Respiration is most dependent on summer base rates (i.e. Soil Respiration normalized to a common temperature) and much less dependent on the site-specific temperature response curves (to which annual rates are relatively insensitive) and Soil degree-days (which vary only 10% among plots).
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an analysis of Soil Respiration across northern hemisphere temperate ecosystems
Biogeochemistry, 2005Co-Authors: K A Hibbard, Markus Reichstein, Beverly E Law, J SulzmanAbstract:Over two-thirds of terrestrial carbon is stored belowground and a significant amount of atmospheric CO2 is respired by roots and microbes in Soils. For this analysis, Soil Respiration (Rs) data were assembled from 31 AmeriFlux and CarboEurope sites representing deciduous broadleaf, evergreen needleleaf, grasslands, mixed deciduous/evergreen and woodland/savanna ecosystem types. Lowest to highest rates of Soil Respiration averaged over the growing season were grassland and woodland/savanna 0.1). Yet, previous studies indicate correlations on shorter time scales within site (e.g., weekly, monthly). Estimates of annual GPP from the Biome-BGC model were strongly correlated with observed annual estimates of Soil Respiration for six sites (R2 = 0.84; p < 0.01). Correlations from observations of Rs with NPP, LAI, fine root biomass and litterfall relate above and belowground inputs to labile pools that are available for decomposition. Our results suggest that simple empirical relationships with temperature and/or moisture that may be robust at individual sites may not be adequate to characterize Soil CO2 effluxes across space and time, agreeing with other multi-site studies. Information is needed on the timing and phenological controls of substrate availability (e.g., fine roots, LAI) and inputs (e.g., root turnover, litterfall) to improve our ability to accurately quantify the relationships between Soil CO2 effluxes and carbon substrate storage.
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supply side controls on Soil Respiration among oregon forests
Global Change Biology, 2004Co-Authors: John Campbell, Osbert Jianxin Sun, Beverly E LawAbstract:To test the hypothesis that variation in Soil Respiration is related to plant production across a diverse forested landscape, we compared annual Soil Respiration rates with net primary production and the subsequent allocation of carbon to various ecosystem pools, including leaves, fine roots, forests floor, and mineral Soil for 36 independent plots arranged as three replicates of four age classes in three climatically distinct forest types. Across all plots, annual Soil Respiration was not correlated with aboveground net primary production (R2=0.06, P>0.1) but it was moderately correlated with belowground net primary production (R2=0.46, P<0.001). Despite the wide range in temperature and precipitation regimes experienced by these forests, all exhibited similar Soil Respiration per unit live fine root biomass, with about 5 g of carbon respired each year per 1 g of fine root carbon (R2=0.45, P<0.001). Annual Soil Respiration was only weakly correlated with dead carbon pools such as forest floor and mineral Soil carbon (R2=0.14 and 0.12, respectively). Trends between Soil Respiration, production, and root mass among age classes within forest type were inconsistent and do not always reflect cross-site trends. These results are consistent with a growing appreciation that Soil Respiration is strongly influenced by the supply of carbohydrates to roots and the rhizosphere, and that some regional patterns of Soil Respiration may depend more on belowground carbon allocation than the abiotic constraints imposed on subsequent metabolism.
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belowground carbon allocation in forests estimated from litterfall and irga based Soil Respiration measurements
Agricultural and Forest Meteorology, 2002Co-Authors: Eric A Davidson, Yiqi Luo, Beverly E Law, Kathleen Savage, Paul V Bolstad, Deborah A Clark, Peter S Curtis, David S Ellsworth, Paul J Hanson, Kurt S PregitzerAbstract:Allocation of C to belowground plant structures is one of the most important, yet least well quantified fluxes of C in terrestrial ecosystems. In a literature review of mature forests worldwide, Raich and Nadelhoffer (1989) suggested that total belowground carbon allocation (TBCA) could be estimated from the difference between annual rates of Soil Respiration and aboveground litterfall. Here we analyze new measurements of Soil Respiration and litterfall, including data from the Ameriflux network. Our results generally agree with Raich and Nadelhoffer’s previous work. A regression analysis of data from mature forests produced the following relationship: annual Soil Respiration = 287 + 2.80 × annual litterfall. This regression slope indicates that, on average, Soil Respiration is roughly three times ab oveground litterfall-C, which further implies that TBCA is roughly twice annual aboveground litterfall-C. These inferences are based on the uncertain assumption of Soil C stocks being at steady state. Nevertheless, changes in Soil C would have to be very large to modify the conclusion that TBCA is generally much larger than litterfall. Among only mature temperate hardwood forests, however, the correlation between litterfall and Soil Respiration was poor, and the correlation among years for a single site was also poor. Therefore, the regression cannot be relied upon to provide accurate estimates of Soil Respiration or TBCA for individual sites. Moreover, interannual variation in TBCA, short-term changes in C stocks, or different temporal scales controlling leaf litter production and Soil Respiration may cause important deviations from the global average. The regression slope for data from young forests is steeper, possibly indicating proportionally greater TBCA, but the steady-state assumption is more problematic for young forests. This method
Qinghui Xing - One of the best experts on this subject based on the ideXlab platform.
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precipitation events reduce Soil Respiration in a coastal wetland based on four year continuous field measurements
Agricultural and Forest Meteorology, 2018Co-Authors: Guangxuan Han, Qinghui Xing, Xiaojing Chu, Baoyu Sun, Weimin Song, Jianyang XiaAbstract:Abstract Coastal wetlands are considered as a significant sink for global carbon because their organic-rich Soils. Given exposed to shallow water tables, water from groundwater is transported upward to the root zone through capillary rise, thus Soil moisture in coastal wetlands is relatively high even when there is no precipitation. We expected that as precipitation occurred, the Soils in coastal wetlands might become quickly saturated and lead to the development of anoxic conditions. We further hypothesized that such anoxic conditions might decrease Soil Respiration by limiting oxygen availability and biological activities of roots and microorganisms. Based on continuous automated Soil Respiration data collected in a coastal wetland in the Yellow River Delta over 4 years (2012–2015), the results showed that on the annual scale, cumulative Soil Respiration was 317, 321, 231, and 274 g C m−2 yr-1 for 2012, 2013, 2014, and 2015, respectively, with an average of 286 g C m−2 yr-1. The rate of Soil Respiration increased exponentially with Soil temperature during each year and its two seasons (growing season and non-growing season). In addition, Soil Respiration was significantly related to Soil moisture during the growing season, but was not affected by Soil moisture during the non-growing season. After each precipitation event, Soil Respiration was significantly negatively correlated with Soil moisture under different initial Soil water contents. There was a significant positive correlation between changes in Soil Respiration and changes in Soil moisture following precipitation events. Moreover, the increase of Soil moisture following precipitation events changed the temperature response of Soil Respiration. Our study indicated that precipitation events could decrease Soil Respiration by increasing Soil moisture and inducing anoxic conditions in the coastal wetland. Therefore, we speculate that the continuation of decreasing precipitation and increasing temperature trends in the Yellow River Delta may increase Soil carbon losses in the coastal wetland due to the increase in Soil Respiration.
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vegetation types alter Soil Respiration and its temperature sensitivity at the field scale in an estuary wetland
PLOS ONE, 2014Co-Authors: Qinghui Xing, Rashad Rafique, Junbao Yu, Nate MikleAbstract:Vegetation type plays an important role in regulating the temporal and spatial variation of Soil Respiration. Therefore, vegetation patchiness may cause high uncertainties in the estimates of Soil Respiration for scaling field measurements to ecosystem level. Few studies provide insights regarding the influence of vegetation types on Soil Respiration and its temperature sensitivity in an estuary wetland. In order to enhance the understanding of this issue, we focused on the growing season and investigated how the Soil Respiration and its temperature sensitivity are affected by the different vegetation (Phragmites australis, Suaeda salsa and bare Soil) in the Yellow River Estuary. During the growing season, there were significant linear relationships between Soil Respiration rates and shoot and root biomass, respectively. On the diurnal timescale, daytime Soil Respiration was more dependent on net photosynthesis. A positive correlation between Soil Respiration and net photosynthesis at the Phragmites australis site was found. There were exponential correlations between Soil Respiration and Soil temperature, and the fitted Q(10) values varied among different vegetation types (1.81, 2.15 and 3.43 for Phragmites australis, Suaeda salsa and bare Soil sites, respectively). During the growing season, the mean Soil Respiration was consistently higher at the Phragmites australis site (1.11 mu mol CO2 m(-2) s(-1)), followed by the Suaeda salsa site (0.77 mu mol CO2 m(-2) s(-1)) and the bare Soil site (0.41 mu mol CO2 m(-2) s(-1)). The mean monthly Soil Respiration was positively correlated with shoot and root biomass, total C, and total N among the three vegetation patches. Our results suggest that vegetation patchiness at a field scale might have a large impact on ecosystem-scale Soil Respiration. Therefore, it is necessary to consider the differences in vegetation types when using models to evaluate Soil Respiration in an estuary wetland.
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ecosystem photosynthesis regulates Soil Respiration on a diurnal scale with a short term time lag in a coastal wetland
Soil Biology & Biochemistry, 2014Co-Authors: Dejun Li, Qinghui Xing, Junbao YuAbstract:Although increasing evidence has provided that Soil Respiration is strongly related to recent canopy photosynthesis, doubts remain as to the extent to which primary productivity controls Soil respiratory and the speed of the link between Soil Respiration and photosynthesis. Based on the automated measurements of Soil Respiration and eddy covariance measurements of ecosystem photosynthesis (i.e. gross primary production, GPP) in a coastal wetland, we assessed the speed of link between ecosystem photosynthesis and Soil Respiration on the diurnal scale, and quantified the control of the ecosystem primary production on diurnal Soil Respiration. On the diurnal scale, the time of daily peak Soil Respiration lagged GPP but preceded Soil temperature on both sunny and cloudy days. Daytime Soil Respiration was significantly linearly correlated with GPP with a lag of 1.5 h on sunny days and 1 h on cloudy days, respectively. By taking advantage of the natural shift of sunny and cloudy days without disturbance to the plant-Soil system, our results also indicated that the changes in Soil temperature and GPP together explained 53% of the changes in daytime Soil Respiration rates between sunny days and adjacent cloudy days. Under the same Soil temperature, changes in Soil Respiration rates were strongly correlated with changes in GPP between sunny days and adjacent cloudy days. We therefore conclude that recent canopy photosynthesis regulates Soil Respiration on a diurnal scale with a short-term time lag. Thus, it is necessary to take into account the influence of photosynthesis on Soil Respiration in order to accurately simulate the magnitude and variation of Soil Respiration, especially at short and medium temporal scales. (C) 2013 Elsevier Ltd. All rights reserved.
Allen H Goldstein - One of the best experts on this subject based on the ideXlab platform.
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continuous measurements of Soil Respiration with and without roots in a ponderosa pine plantation in the sierra nevada mountains
Agricultural and Forest Meteorology, 2005Co-Authors: Jianwu Tang, Laurent Misson, Alexander Gershenson, Weixin Cheng, Allen H GoldsteinAbstract:Abstract Continuous measurements of Soil Respiration and its components help us understand diurnal and seasonal variations in Soil Respiration and its mechanism. We continuously measured CO 2 concentration at various depths in the Soil and calculated surface CO 2 efflux based on CO 2 gradients and diffusivity in a young ponderosa pine plantation in the Sierra Nevada Mountains of California. We determined Soil Respiration both in a control plot that included roots and in a trenched plot that had no roots. The difference between these plots was used to partition Soil Respiration into root Respiration and heterotrophic Respiration. We found that both CO 2 concentration in the Soil and surface CO 2 efflux in the control plot were higher than in the trenched plot. The diurnal range of Soil Respiration in the trenched plot was larger than in the control. We observed dramatic pulses of Soil Respiration in response to rain events in summer and fall during the dry season. We modeled the seasonal variation in Soil Respiration without the pulses using Soil temperature and moisture as driving variables and simulated Soil Respiration pulses using an exponential decay function in response to the volume of rain. Daily mean Soil Respiration peaked at 5.0 μmol m −2 s −1 in the control and at 2.7 μmol m −2 s −1 in the trenched plot in June before the rain pulses. Soil Respiration increased from 4.9 to 8.2 and to 12.1 μmol m −2 s −1 after the first and second rain events in the control, and increased from 2.2 to 4.1 and to 6.6 μmol m −2 s −1 in the trenched plot. After incorporating the pulse effect, the model simulated measured data well. Annual Soil Respiration in 2003 was estimated as 1184 g C m −2 y −1 . The average ratio of root over total Respiration was 0.56 during the growing season and 0.16 during the non-growing season with an annual average of 0.44.
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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.
