Carbon and water exchange over a temperate semi-arid shrubland during three years of contrasting precipitation and soil moisture patterns

Jia, Xin; Zha, Tianshan; Gong, Jinnan; Wang, Ben; Zhang, Yuqing; Wu, Bin; Qin, Shugao; Peltola, Heli

doi:10.1016/j.agrformet.2016.07.007

Cited by 119 publications

(61 citation statements)

References 38 publications

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“…Deep rooting can thus reach the groundwater and thus redistribute such waters into the upper soil profile, enabling the tree to utilize both water sources [8,44], so that the riparian forest can grow continuously under hyper-arid climates. In fact, some studies have shown that the annual precipitation could not explain the inter-annual variations of CO 2 fluxes in arid ecosystems [45,46], which has also been confirmed by the present study.…”

Section: Controls On the Carbon Fluxes Of Riparian Forestsupporting

confidence: 79%

Carbon Dioxide Fluxes and Their Environmental Controls in a Riparian Forest within the Hyper-Arid Region of Northwest China

Feng

et al. 2017

Forests

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Abstract:Hyper-arid regions are expected to undergo climatic change, but only a few research works have so far been conducted on the dynamics of carbon dioxide (CO 2 ) fluxes and their consequent responses to various bioclimatic factors, which is mainly attributable to a limited set of flux observations. In this study, the CO 2 fluxes exchanged between the forest and the atmosphere have been measured continuously by the eddy covariance approach from June 2013 to December 2016 in a riparian forest, which is a primary body of natural oases located within the lower reaches of inland rivers in China. The present results revealed that the climatic conditions characterized by relatively high mean air temperatures (T a ) with fluctuating annual precipitation (P) during the prescribed study periods were comparable to the historical mean value. The annual net ecosystem productivity (NEP) ranged from approximately 278 g C m −2 year −1 to 427 g C m −2 year −1 , with a mean value of 334 g C m −2 year −1 . The mean annual ecosystem respiration (Re) and the gross primary productivity (GPP) were found to be 558 and 892 g C m −2 year −1 , respectively. The results also ascertained that the high inter-annual variations in NEP were attributable to Re rather than to GPP, and this result was driven primarily by T a and the groundwater depth under similar eco-physiological processes. In addition, the CO 2 fluxes were also strongly correlated with the soil temperature and photosynthetically active radiation for the present study site. In conclusion, the desert riparian forest is a considerably significant carbon sink, particularly in the hyper-arid regions.

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Section: Controls On the Carbon Fluxes Of Riparian Forestsupporting

confidence: 79%

Carbon Dioxide Fluxes and Their Environmental Controls in a Riparian Forest within the Hyper-Arid Region of Northwest China

Feng

et al. 2017

Forests

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“…Maximum monthly mean leaf area index (LAI) for plant specimens with full leaf expansion was about 0.1 m 2 m −2 (Table 1). Over 60 % of their roots were distributed in the first 60 cm of the soil complex Jia et al, 2016). Five stems of Artemisia ordosica were randomly selected within the plot as replicates for sapflow measurement.…”

Section: Measurements Of Sap Flow Leaf Area and Stomatal Conductancementioning

confidence: 99%

Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, <i>Artemisia ordosica</i>

et al. 2017

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Abstract. The current understanding of acclimation processes in desert-shrub species to drought stress in dryland ecosystems is still incomplete. In this study, we measured sap flow in Artemisia ordosica and associated environmental variables throughout the growing seasons of 2013 and 2014 (May-September period of each year) to better understand the environmental controls on the temporal dynamics of sap flow. We found that the occurrence of drought in the dry year of 2013 during the leaf-expansion and leaf-expanded periods caused sap flow per leaf area (J s ) to decline significantly, resulting in transpiration being 34 % lower in 2013 than in 2014. Sap flow per leaf area correlated positively with radiation (R s ), air temperature (T ), and water vapor pressure deficit (VPD) when volumetric soil water content (VWC) was greater than 0.10 m 3 m −3 . Diurnal J s was generally ahead of R s by as much as 6 hours. This time lag, however, decreased with increasing VWC. The relative response of J s to the environmental variables (i.e., R s , T , and VPD) varied with VWC, J s being more strongly controlled by plant-physiological processes during periods of dryness indicated by a low decoupling coefficient and low sensitivity to the environmental variables. According to this study, soil moisture is shown to control sap-flow (and, therefore, plant-transpiration) response in Artemisia ordosica to diurnal variations in biophysical factors. This species escaped (acclimated to) water limitations by invoking a water-conservation strategy with the regulation of stomatal conductance and advancement of J s peaking time, manifesting in a hysteresis effect. The findings of this study add to the knowledge of acclimation processes in desert-shrub species under droughtassociated stress. This knowledge is essential in modeling desert-shrub-ecosystem functioning under changing climatic conditions.

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“…Wang et al, 2014). The seasonal trends of the measured T a and P can be found in Jia et al (2016). No surface runoffs were observed at the site, indicating the horizontal redistribution of rainfall was mainly through subsurface flows.…”

Section: Micrometeorological and Soil Co 2 Efflux Measurementsmentioning

confidence: 99%

“…On the other hand, a large fluctuation of diurnal and seasonal temperature may drive the microbial communities to shift between those that are warm adapted and those that are cold adapted (Van Gestel et al, 2013), which could largely change soil respiration and its sensitivity to freeze-thaw cycles (Van Gestel et al, 2013;Liu et al, 2016). Both the biotic controls are mixed with the legacy effects of climatic variability over annual and interannual courses (Sala et al, 2012;Jia et al, 2016;Shen et al, 2016), and could affect the C-water simulations cumulatively through the feedbacks between biomass accumulation and soil biogeochemistry (Bradford et al, 2016). This may explain the decreasing trend of model validity from 2013 to 2014 (Figs.…”

Section: Modelling Uncertainties and Future Research Needsmentioning

confidence: 99%

Modelling the diurnal and seasonal dynamics of soil CO<sub>2</sub> exchange in a semiarid ecosystem with high plant–interspace heterogeneity

et al. 2018

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Abstract. We used process-based modelling to investigate the roles of carbon-flux (C-flux) components and plantinterspace heterogeneities in regulating soil CO 2 exchanges (F S ) in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of F S , the modelling considered simultaneously the CO 2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation). The model was parameterized and validated with multivariate data measured during the years 2013-2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO 2 dissolution and delay the emission of CO 2 produced from rooting zone. In addition, an ineligible fraction of respired CO 2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO 2 source to sink due to the activated photosynthesis of biocrust but the restricted CO 2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO 2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant-interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO 2 efflux dynamics in dryland ecosystems.

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Carbon and water exchange over a temperate semi-arid shrubland during three years of contrasting precipitation and soil moisture patterns

Cited by 119 publications

References 38 publications

Carbon Dioxide Fluxes and Their Environmental Controls in a Riparian Forest within the Hyper-Arid Region of Northwest China

Carbon Dioxide Fluxes and Their Environmental Controls in a Riparian Forest within the Hyper-Arid Region of Northwest China

Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, <i>Artemisia ordosica</i>

Modelling the diurnal and seasonal dynamics of soil CO<sub>2</sub> exchange in a semiarid ecosystem with high plant–interspace heterogeneity

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Carbon and water exchange over a temperate semi-arid shrubland during three years of contrasting precipitation and soil moisture patterns

Cited by 119 publications

References 38 publications

Carbon Dioxide Fluxes and Their Environmental Controls in a Riparian Forest within the Hyper-Arid Region of Northwest China

Carbon Dioxide Fluxes and Their Environmental Controls in a Riparian Forest within the Hyper-Arid Region of Northwest China

Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, &lt;i&gt;Artemisia ordosica&lt;/i&gt;

Modelling the diurnal and seasonal dynamics of soil CO&lt;sub&gt;2&lt;/sub&gt; exchange in a semiarid ecosystem with high plant–interspace heterogeneity

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Soil moisture control of sap-flow response to biophysical factors in a desert-shrub species, <i>Artemisia ordosica</i>

Modelling the diurnal and seasonal dynamics of soil CO<sub>2</sub> exchange in a semiarid ecosystem with high plant–interspace heterogeneity