Net ecosystem exchange, evapotranspiration and canopy conductance in a riparian forest

Kochendorfer, John; Castillo, Eugenia González del; Haas, Edwin; Oechel, W. C.; U, Kyaw Tha Paw

doi:10.1016/j.agrformet.2010.12.012

Cited by 48 publications

(33 citation statements)

References 49 publications

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“…The riparian forest in this study was found to be an important carbon sink, with an average NEP of 334 g C m −2 year −1 . This value is comparable with the riparian cottonwood (Populus fremontii S. Watson) forest found in northern California's Central Valley (i.e., 310 g C m −2 year −1 ) [23] and the riparian mesquite woodland situated along the San Pedro River in southeastern Arizona (i.e., 233 g C m −2 year −1 ) [24], USA. By contrast, the Poplar (i.e., Populus sp.)…”

Section: Co 2 Fluxes In the Riparian Forestsupporting

confidence: 58%

“…With potential access to groundwater, the riparian ecosystems maintain a higher level of biodiversity and productivity compared to the surrounding desert environment [23,24]. However, there have been only a few studies that have focused on the carbon sink of riparian forests and their environmental control mechanisms.…”

Section: Co2 Fluxes In the Riparian Forestmentioning

confidence: 99%

“…These studies have shown that the forest ecosystems in arid regions are reasonable potential carbon pools and are sensitive to the changes in environmental conditions. However, little attention has been paid to the riparian forests that are dependent on the groundwater in hyper-arid regions, although the riparian cottonwood (Populus fremontii S. Watson) forest in northern California's Central Valley (310 g C m −2 year −1 ) [23] and the riparian mesquite woodland along the San Pedro River in southeastern Arizona (233 g C m −2 year −1 ) [24], USA remain an exception.…”

Section: Introductionmentioning

confidence: 99%

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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: Co 2 Fluxes In the Riparian Forestsupporting

confidence: 58%

Section: Co2 Fluxes In the Riparian Forestmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…Thus, many studies have been undertaken over several decades to investigate the water use of GDEs in south-western North America (van Hylckama, 1970;Gay and Fritschen, 1979;Sala et al, 1996;Devitt et al, 1998;Goodrich et al, 2000a;Cleverly et al, 2002;Scott et al, 2004;Nagler et al, 2005b). Sunlight is plentiful in the south-western USA; thus, riparian GDEs are strong carbon sinks (Kochendorfer et al, 2011). However, seasonal variability in surface water discharge and aquifer recharge can create cycles of hypoxia and drought stress (Lowry et al, 2011), both of which act to reduce production (Shah and Dahm, 2008).…”

Section: The Gnangara Moundmentioning

confidence: 99%

“…cottonwood, Populus spp.) can be very sensitive to groundwater decline, resulting in reductions of ET, productivity and canopy conductance as a consequence of increases in vapour pressure deficit that are correlated with depth-to-groundwater (Gazal et al, 2006;Kochendorfer et al, 2011). Branch sacrifice, partial crown dieback and mortality commonly occur in Populus following substantial groundwater drawdown (Mahoney and Rood, 1991;Kranjcec et al, 1998;Scott et al, 1999;Rood et al, 2000Rood et al, , 2003Cooper et al, 2003).…”

Section: The Gnangara Moundmentioning

confidence: 99%

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Eamus

Zolfaghar

Villalobos‐Vega

et al. 2015

Hydrol. Earth Syst. Sci.

132

112

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Abstract. Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs.We discuss three methods for identifying GDEs: (1) techniques relying on remotely sensed information; (2) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration; and (3) stable isotope analysis of water sources in the transpiration stream.We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of evapotranspiration (ET) using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the White method to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration versus evaporation (e.g. using stable isotopes) or from groundwater versus rainwater sources.Groundwater extraction can have severe consequences for the structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown. We provide a brief review of two case studies of the impacts of GW extraction and then provide an ecosystem-scale, multiple trait, integrated metric of the impact of differences in groundwater depth on the structure and function of eucalypt forests growing along a natural gradient in depth-to-groundwater. We conclude with a discussion of a depth-to-groundwater threshold in this mesic GDE. Beyond this threshold, significant changes occur in ecosystem structure and function.

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Growing season variability in evapotranspiration, ecosystem water use efficiency, and energy partitioning in switchgrass

Wagle

Kakani

2012

Ecohydrology

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Evapotranspiration (ET), ecosystem water use efficiency (EWUE), and energy partitioning in switchgrass (Panicum virgatum L.) ecosystems are crucial to understand its water and energy balances since switchgrass acreage is expanding for cellulosic biofuels. We measured CO2, H2O, and energy fluxes over a switchgrass field in Chickasha, OK, USA, using eddy covariance method. The objective of this study was to quantify seasonal variations in ET, EWUE, and seasonal distributions of energy partitioning in response to controlling factors. Seasonal (May to mid‐November) cumulative ET (450 mm) was similar to cumulative rainfall (432 mm). During June to September, ET was 1·92 times of rainfall, indicating that the crop experienced severe drought during the mid‐growing season. ET showed clear seasonality with 3–4 mm day−1 during the active growing season (late May and June) to low rates of about 0·5 mm day−1 during the late growing season (November). The ET rate decreased during dry periods. On seasonal scale, more energy was partitioned to sensible heat flux (H) than latent heat (LE) because of drought. Estimation of EWUE by dividing time integrals of gross ecosystem photosynthesis (GEP) by respective H2O fluxes (ET) at monthly time scale provided EWUE from 10·46 (August) to 14·08 g CO2 mm−1 ET (October) with a seasonal average of 12·01 g CO2 mm−1 ET. Seasonal patterns in EWUE were observed with smaller values during drought because of more rapid reduction in carbon assimilation (GEP) than ET. These findings confirm the major role of precipitation in determining water and energy balances in switchgrass. Copyright © 2012 John Wiley & Sons, Ltd.

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Net ecosystem exchange, evapotranspiration and canopy conductance in a riparian forest

Cited by 48 publications

References 49 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

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Growing season variability in evapotranspiration, ecosystem water use efficiency, and energy partitioning in switchgrass

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