scholarly journals Modelling effects of seasonal variation in water table depth on net ecosystem CO<sub>2</sub> exchange of a tropical peatland

2013 ◽  
Vol 10 (8) ◽  
pp. 13353-13398
Author(s):  
M. Mezbahuddin ◽  
R. F. Grant ◽  
T. Hirano
Keyword(s):  
Seasonal Variation ◽  
Water Table ◽  
Co2 Exchange ◽  
Water Table Depth ◽  
Hydrological Processes ◽  
Transfer Scheme ◽  
Predictive Capacity ◽  
Tropical Peatland ◽  
Tropical Peat ◽  
Dry Seasons

Abstract. Seasonal variation in water table depth (WTD) determines the balance between aggradation and degradation of tropical peatlands. Longer dry seasons together with human interventions (e.g. drainage) can cause WTD drawdowns making tropical peatland C storage highly vulnerable. Better predictive capacity for effects of WTD on net CO2 exchange is thus essential to guide conservation of tropical peat deposits. Mathematical modelling of basic eco-hydrological processes under site-specific conditions can provide such predictive capacity. We hereby deploy a mathematical model ecosys to study effects of seasonal variation in WTD on net ecosystem productivity (NEP) of an Indonesian peatland. We simulated lower NEPs (~ –2 g C m–2 d–1) during rainy seasons with shallow WTD, higher NEPs (~ +1 g C m–2 d–1) during early dry seasons with intermediate WTD and again lower NEPs (~ –4 g C mm–2 d–1) during late dry seasons with deep WTD during 2002–2005. These values were corroborated by regressions (P < 0.0001) of hourly modelled vs. eddy covariance (EC) measured net ecosystem CO2 fluxes which yielded R2 > 0.8, intercepts approaching 0 and slopes approaching 1. We also simulated a gradual increase in annual NEPs from 2002 (−609 g C m–2) to 2005 (−373 g C m–2) with decreasing WTD which was corroborated by EC-gap filled annual NEP estimates. These WTD effects on NEP were modelled from basic eco-hydrological processes including microbial and root oxidation-reduction reactions driven by soil and root O2 transport and uptake which in turn drove soil and plant C, N and P transformations within a soil-plant-atmosphere water transfer scheme driven by water potential gradients. This modelling should therefore provide a predictive capacity for WTD management programs to reduce tropical peat degradation.

scholarly journals Modelling effects of seasonal variation in water table depth on net ecosystem CO<sub>2</sub> exchange of a tropical peatland

2014 ◽  
Vol 11 (3) ◽  
pp. 577-599 ◽  
Author(s):  
M. Mezbahuddin ◽  
R. F. Grant ◽  
T. Hirano
Keyword(s):  
Seasonal Variation ◽  
Nutrient Uptake ◽  
Water Table ◽  
Water Table Depth ◽  
Hydrological Processes ◽  
Plant Nutrient ◽  
Predictive Capacity ◽  
Tropical Peatland ◽  
Tropical Peat ◽  
Dry Seasons

Abstract. Seasonal variation in water table depth (WTD) determines the balance between aggradation and degradation of tropical peatlands. Longer dry seasons together with human interventions (e.g. drainage) can cause WTD drawdowns making tropical peatland C storage highly vulnerable. Better predictive capacity for effects of WTD on net CO2 exchange is thus essential to guide conservation of tropical peat deposits. Mathematical modelling of basic eco-hydrological processes under site-specific conditions can provide such predictive capacity. We hereby deploy a process-based mathematical model ecosys to study effects of seasonal variation in WTD on net ecosystem productivity (NEP) of a drainage affected tropical peat swamp forest at Palangkaraya, Indonesia. Simulated NEP suggested that the peatland was a C source (NEP ~ −2 g C m−2 d−1, where a negative sign represents a C source and a positive sign a C sink) during rainy seasons with shallow WTD, C neutral or a small sink (NEP ~ +1 g C m−2 d−1) during early dry seasons with intermediate WTD and a substantial C source (NEP ~ −4 g C m−2 d−1) during late dry seasons with deep WTD from 2002 to 2005. These values were corroborated by regressions (P < 0.0001) of hourly modelled vs. eddy covariance (EC) net ecosystem CO2 fluxes which yielded R2 > 0.8, intercepts approaching 0 and slopes approaching 1. We also simulated a gradual increase in annual NEP from 2002 (−609 g C m−2) to 2005 (−373 g C m−2) with decreasing WTD which was attributed to declines in duration and intensity of dry seasons following the El Niño event of 2002. This increase in modelled NEP was corroborated by EC-gap filled annual NEP estimates. Our modelling hypotheses suggested that (1) poor aeration in wet soils during shallow WTD caused slow nutrient (predominantly phosphorus) mineralization and consequent slow plant nutrient uptake that suppressed gross primary productivity (GPP) and hence NEP (2) better soil aeration during intermediate WTD enhanced nutrient mineralization and hence plant nutrient uptake, GPP and NEP and (3) deep WTD suppressed NEP through a combination of reduced GPP due to plant water stress and increased ecosystem respiration (Re) from enhanced deeper peat aeration. These WTD effects on NEP were modelled from basic eco-hydrological processes including microbial and root oxidation-reduction reactions driven by soil and root O2 transport and uptake which in turn drove soil and plant carbon, nitrogen and phosphorus transformations within a soil-plant-atmosphere water transfer scheme driven by water potential gradients. Including these processes in ecosystem models should therefore provide an improved predictive capacity for WTD management programs intended to reduce tropical peat degradation.

scholarly journals Coupled eco-hydrology and biogeochemistry algorithms enable simulation of water table depth effects on boreal peatland net CO<sub>2</sub> exchange

2017 ◽  
Author(s):  
Mohammad Mezbahuddin ◽  
Robert F. Grant ◽  
Lawrence B. Flanagan
Keyword(s):  
Plant Growth ◽  
Water Table ◽  
Oxygen Transport ◽  
Ecosystem Respiration ◽  
Vascular Plant ◽  
Co2 Exchange ◽  
Water Table Depth ◽  
Net Ecosystem Co2 Exchange ◽  
Predictive Capacity ◽  
Near Surface

Abstract. Water table depth (WTD) effects on net ecosystem CO2 exchange of boreal peatlands are largely mediated by hydrological effects on peat biogeochemistry, and eco-physiology of peatland vegetation. Lack of representation of these effects in carbon models currently limits our predictive capacity for changes in boreal peatland carbon deposits under future drier and warmer climates. We therefore tested whether the effects of WTD variation on net ecosystem CO2 exchange of a Western Canadian boreal fen peatland could be modelled through a process-level coupling of a prognostic WTD dynamic, which arises from equilibrium between vertical and lateral water fluxes, with oxygen transport, which controls energy yields from microbial and root oxidation–reduction reactions, and vascular and non-vascular plant water relations in an ecosystem model ecosys. Ecosys successfully simulated a May–October WTD drawdown by ~ 0.25 m measured in the fen from 2004 to 2008, which was attributed to reduced precipitation relative to evapotranspiration, and reduced lateral recharge relative to discharge. This WTD drawdown hastened oxygen transport to microbial and root surfaces, enabling greater microbial and root energy yields, and peat and litter decomposition, which raised modelled ecosystem respiration (Re) by ~ 0.26 μmol CO2 m−2 s−1 per 0.1 m of WTD drawdown. It also augmented nutrient mineralization, and hence root nutrient availability and uptake, which resulted in improved leaf nutrient (nitrogen) status that facilitated carboxylation, and raised modelled vascular gross primary productivity (GPP) and plant growth. The increase in modelled vascular GPP exceeded declines in modelled non-vascular (moss) GPP due to greater shading from increased vascular plant growth, and moss drying from near surface peat desiccation, thereby causing a net increase in modelled growing season GPP by ~ 0.39 μmol CO2 m−2 s−1 per 0.1 m of WTD drawdown. Similar increases in GPP and Re left no significant WTD effects on modelled seasonal and interannual variations in net ecosystem productivity (NEP). These modelled trends were corroborated against eddy covariance hourly net CO2 fluxes (modelled vs. measured: R2 ~ 0.8, slopes ~ 1 ± 0.1, intercepts ~ 0.05 μmol m−2 s−1), and against other automated chamber, biometric, and laboratory measurements. Modelled drainage as an analog for climate change showed that this boreal peatland would switch from a large carbon sink (NEP ~ 160 g C m−2 yr−1) to carbon neutrality (NEP ~ 10 g C m−2 yr−1) should water table deepened by a further ~ 0.5 m. Therefore, representing the effects of interactions among hydrology, biogeochemistry and plant physiological ecology on ecosystem carbon, water, and nutrient cycling in global carbon models would improve our predictive capacity for changes in boreal peatland carbon sequestration under changing climates.

scholarly journals Coupled eco-hydrology and biogeochemistry algorithms enable the simulation of water table depth effects on boreal peatland net CO<sub>2</sub> exchange

2017 ◽  
Vol 14 (23) ◽  
pp. 5507-5531 ◽  
Author(s):  
Mohammad Mezbahuddin ◽  
Robert F. Grant ◽  
Lawrence B. Flanagan
Keyword(s):  
Plant Growth ◽  
Water Table ◽  
Oxygen Transport ◽  
Vascular Plant ◽  
Co2 Exchange ◽  
Water Table Depth ◽  
Co2 Fluxes ◽  
Net Ecosystem Co2 Exchange ◽  
Predictive Capacity ◽  
Near Surface

Abstract. Water table depth (WTD) effects on net ecosystem CO2 exchange of boreal peatlands are largely mediated by hydrological effects on peat biogeochemistry and the ecophysiology of peatland vegetation. The lack of representation of these effects in carbon models currently limits our predictive capacity for changes in boreal peatland carbon deposits under potential future drier and warmer climates. We examined whether a process-level coupling of a prognostic WTD with (1) oxygen transport, which controls energy yields from microbial and root oxidation–reduction reactions, and (2) vascular and nonvascular plant water relations could explain mechanisms that control variations in net CO2 exchange of a boreal fen under contrasting WTD conditions, i.e., shallow vs. deep WTD. Such coupling of eco-hydrology and biogeochemistry algorithms in a process-based ecosystem model, ecosys, was tested against net ecosystem CO2 exchange measurements in a western Canadian boreal fen peatland over a period of drier-weather-driven gradual WTD drawdown. A May–October WTD drawdown of  ∼  0.25 m from 2004 to 2009 hastened oxygen transport to microbial and root surfaces, enabling greater microbial and root energy yields and peat and litter decomposition, which raised modeled ecosystem respiration (Re) by 0.26 µmol CO2 m−2 s−1 per 0.1 m of WTD drawdown. It also augmented nutrient mineralization, and hence root nutrient availability and uptake, which resulted in improved leaf nutrient (nitrogen) status that facilitated carboxylation and raised modeled vascular gross primary productivity (GPP) and plant growth. The increase in modeled vascular GPP exceeded declines in modeled nonvascular (moss) GPP due to greater shading from increased vascular plant growth and moss drying from near-surface peat desiccation, thereby causing a net increase in modeled growing season GPP by 0.39 µmol CO2 m−2 s−1 per 0.1 m of WTD drawdown. Similar increases in GPP and Re caused no significant WTD effects on modeled seasonal and interannual variations in net ecosystem productivity (NEP). These modeled trends were corroborated well by eddy covariance measured hourly net CO2 fluxes (modeled vs. measured: R2  ∼  0.8, slopes  ∼ 1 ± 0.1, intercepts  ∼ 0.05 µmol m−2 s−1), hourly measured automated chamber net CO2 fluxes (modeled vs. measured: R2  ∼ 0.7, slopes  ∼ 1 ± 0.1, intercepts  ∼ 0.4 µmol m−2 s−1), and other biometric and laboratory measurements. Modeled drainage as an analog for WTD drawdown induced by climate-change-driven drying showed that this boreal peatland would switch from a large carbon sink (NEP  ∼  160 g C m−2 yr−1) to carbon neutrality (NEP  ∼  10 g C m−2 yr−1) should the water table deepen by a further  ∼ 0.5 m. This decline in projected NEP indicated that a further WTD drawdown at this fen would eventually lead to a decline in GPP due to water limitation. Therefore, representing the effects of interactions among hydrology, biogeochemistry and plant physiological ecology on ecosystem carbon, water, and nutrient cycling in global carbon models would improve our predictive capacity for changes in boreal peatland carbon sequestration under changing climates.

scholarly journals CO 2 emissions from an undrained tropical peatland: Interacting influences of temperature, shading and water table depth

2019 ◽  
Vol 25 (9) ◽  
pp. 2885-2899 ◽  
Author(s):  
Alison M. Hoyt ◽  
Laure Gandois ◽  
Jangarun Eri ◽  
Fuu Ming Kai ◽  
Charles F. Harvey ◽  
...  
Keyword(s):  
Water Table ◽  
Water Table Depth ◽  
Tropical Peatland

scholarly journals Representation of Water Table Dynamics in a Land Surface Scheme. Part I: Model Development

2005 ◽  
Vol 18 (12) ◽  
pp. 1861-1880 ◽  
Author(s):  
Pat J-F. Yeh ◽  
Elfatih A. B. Eltahir
Keyword(s):  
Water Table ◽  
Land Surface ◽  
Surface States ◽  
Unconfined Aquifer ◽  
Water Table Depth ◽  
Shallow Water Table ◽  
Transfer Scheme ◽  
Land Surface Scheme ◽  
Soil Model ◽  
Surface Scheme

Abstract Most of the current land surface parameterization schemes lack any representation of regional groundwater aquifers. Such a simplified representation of subsurface hydrological processes would result in significant errors in the predicted land surface states and fluxes especially for the shallow water table areas in humid regions. This study attempts to address this deficiency. To incorporate the water table dynamics into a land surface scheme, a lumped unconfined aquifer model is developed to represent the regional unconfined aquifer as a nonlinear reservoir, in which the aquifer simultaneously receives the recharge from the overlying soils and discharges runoff into streams. The aquifer model is linked to the soil model in the land surface scheme [Land Surface Transfer Scheme (LSX)] through the soil drainage flux. The total thickness of the unsaturated zone varies in response to the water table fluctuations, thereby interactively coupling the aquifer model with the soil model. The coupled model (called LSXGW) has been tested in Illinois for an 11-yr period from 1984 to 1994. The results show reasonable agreements with the observations. However, there are still secondary biases in the LSXGW simulation partially resulting from not accounting for the spatial variability of water table depth. The issue of subgrid variability of water table depth will be addressed in a companion paper.

scholarly journals Carbon dioxide emissions from an <i>Acacia</i> plantation on peatland in Sumatra, Indonesia

2012 ◽  
Vol 9 (2) ◽  
pp. 617-630 ◽  
Author(s):  
J. Jauhiainen ◽  
A. Hooijer ◽  
S. E. Page
Keyword(s):  
Greenhouse Gas ◽  
Co2 Emissions ◽  
Water Table ◽  
Co2 Emission ◽  
Agricultural Land ◽  
Water Table Depth ◽  
Autotrophic Respiration ◽  
Rooting Zone ◽  
Tropical Peat ◽  
Agricultural Conversion

Abstract. Peat surface CO2 emission, groundwater table depth and peat temperature were monitored for two years along transects in an Acacia plantation on thick tropical peat (>4 m) in Sumatra, Indonesia. A total of 2300 emission measurements were taken at 144 locations, over a 2 year period. The autotrophic root respiration component of CO2 emission was separated from heterotrophic emission caused by peat oxidation in three ways: (i) by comparing CO2 emissions within and beyond the tree rooting zone, (ii) by comparing CO2 emissions with and without peat trenching (i.e. cutting any roots remaining in the peat beyond the tree rooting zone), and (iii) by comparing CO2 emissions before and after Acacia tree harvesting. On average, the contribution of autotrophic respiration to daytime CO2 emission was 21% along transects in mature tree stands. At locations 0.5 m from trees this was up to 80% of the total emissions, but it was negligible at locations more than 1.3 m away. This means that CO2 emission measurements well away from trees were free of any autotrophic respiration contribution and thus represent only heterotrophic emissions. We found daytime mean annual CO2 emission from peat oxidation alone of 94 t ha−1 y−1 at a mean water table depth of 0.8 m, and a minimum emission value of 80 t ha−1 y−1 after correction for the effect of diurnal temperature fluctuations, which may result in a 14.5% reduction of the daytime emission. There is a positive correlation between mean long-term water table depth and peat oxidation CO2 emission. However, no such relation is found for instantaneous emission/water table depth within transects and it is clear that factors other than water table depth also affect peat oxidation and total CO2 emissions. The increase in the temperature of the surface peat due to plantation establishment may explain over 50% of peat oxidation emissions. Our study sets a standard for greenhouse gas flux studies from tropical peatlands under different forms of agricultural land management. It is the first to purposefully quantify heterotrophic CO2 emissions resulting from tropical peat decomposition by separating these from autotrophic emissions. It also provides the most scientifically- and statistically-rigorous study to date of CO2 emissions resulting from anthropogenic modification of this globally significant carbon rich ecosystem. Our findings indicate that past studies have underestimated emissions from peatland plantations, with important implications for the scale of greenhouse gas emissions arising from land use change, particularly in the light of current, rapid agricultural conversion of peatlands in the Southeast Asian region.

scholarly journals Temporal and Local Heterogeneities of Water Table Depth under Different Agricultural Water Management Conditions

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2148
Author(s):  
Jonathan A. Lafond ◽  
Silvio J. Gumiere ◽  
Virginie Vanlandeghem ◽  
Jacques Gallichand ◽  
Alain N. Rousseau ◽  
...  
Keyword(s):  
Water Management ◽  
Water Table ◽  
Cropping Systems ◽  
Irrigation Management ◽  
Sprinkler Irrigation ◽  
Water Table Depth ◽  
Management Systems ◽  
Integrated Water Management ◽  
Growing Seasons ◽  
Good Drainage

Integrated water management has become a priority for cropping systems where subirrigation is possible. Compared to conventional sprinkler irrigation, the controlling water table can lead to a substantial increase in yield and water use efficiency with less pumping energy requirements. Knowing the spatiotemporal distribution of water table depth (WTD) and soil properties should help perform intelligent, integrated water management. Observation wells were installed in cranberry fields with different water management systems: Bottom, with good drainage and controlled WTD management; Surface, with good drainage and sprinkler irrigation management; Natural, without drainage, or with imperfectly drained and conventional sprinkler irrigation. During the 2017–2020 growing seasons, WTD was monitored on an hourly basis, while precipitation was measured at each site. Multi-frequential periodogram analysis revealed a dominant periodic component of 40 days each year in WTD fluctuations for the Bottom and Surface systems; for the Natural system, periodicity was heterogeneous and ranged from 2 to 6 weeks. Temporal cross correlations with precipitation show that for almost all the sites, there is a 3 to 9 h lag before WTD rises; one exception is a subirrigation site. These results indicate that automatic water table management based on continuously updated knowledge could contribute to integrated water management systems, by using precipitation-based models to predict WTD.

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