Seasonal Partitioning of Evaporation Between Trees and Understorey in a Widely Spaced Pinus radiata Stand

Whitehead, David; Kelliher, Francis M.; Lane, P. M.; Pollock, Dennis

doi:10.2307/2404448

Cited by 39 publications

(18 citation statements)

References 44 publications

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“…Understory transpiration (E u ) can compensate for diminished transpiration from sparse overstory canopies (Roberts et al, 1982;Whitehead et al, 1994), and this occurred in the present study. Increased understory irradiance led to higher E u after dry-season loss of leaves from tree canopies.…”

Section: Species Effects On Canopy and Understory Transpirationsupporting

confidence: 59%

Evapotranspiration modelled from stands of three broad‐leaved tropical trees in Costa Rica

Bigelow

2001

Hydrological Processes

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Abstract:To examine the impact of tree species on the water cycle in a wet tropical region, annual evapotranspiration (ET) was estimated in Costa Rican plantations of three native, broad-leaved tree species that contrasted strongly in leaf size, leaf area and phenology. Evapotranspiration was estimated using the Penman-Monteith equation for transpiration from the dry canopy, the equilibrium equation for evaporation from the understory and a modified Rutter model of interception for evaporation of water from the canopy when wetted by rainfall. Canopy conductance was estimated from stomatal conductance, leaf area and leaf boundary-layer conductance; canopy storage capacity and filling rate were estimated from throughfall measurements. Micrometeorological instruments were mounted on a scaffolding tower.Mean stomatal conductance, which ranged from 0Ð1 to 0Ð7 mol m 2 s 1 , was similar to boundary-layer conductance, 0Ð1 to 0Ð5 mol m 2 s 1 , indicating decoupling of stomata from atmospheric conditions. Mean canopy conductance varied from 0Ð6 to 0Ð7 mol m 2 s 1 in the 1994 wet season then dropped to 0Ð3-0Ð4 mol m 2 s 1 in stands of the two deciduous species, Cordia and Cedrela, as a result of reduced leaf area during the dry season. Despite increased understory evaporation, dry-season ET from these stands was only 78-81% of ET in stands of the evergreen species, Hyeronima. Maximum canopy water depth varied from 0Ð2 to 2Ð2 mm, causing modelled interception to vary from 6% to 25% of annual ET. Higher dry-season transpiration rates along with high rates of evaporation of intercepted rainfall in all seasons led to 14% higher annual ET in Hyeronima stands (1509 mm) than in stands of the species with lowest ET, Cedrela (1318 mm). Despite lack of strong physiological control on transpiration, tree species in wet tropical plantations can influence hydrological balance.

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Section: Species Effects On Canopy and Understory Transpirationsupporting

confidence: 59%

Evapotranspiration modelled from stands of three broad‐leaved tropical trees in Costa Rica

Bigelow

2001

Hydrological Processes

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“…1b Plenty, 2007). Annual mean discharge at this site is 2.0 m 3 s −1 (1994-1997Bay of Plenty Regional Council). The Puarenga Stream receives a high proportion of flow from groundwater stores and has only moderate seasonality in discharge.…”

Section: Study Areamentioning

confidence: 98%

Effects of hydrologic conditions on SWAT model performance and parameter sensitivity for a small, mixed land use catchment in New Zealand

Abell

Hamilton

2015

Hydrol. Earth Syst. Sci.

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Abstract. The Soil Water Assessment Tool (SWAT) was configured for the Puarenga Stream catchment (77 km 2 ), Rotorua, New Zealand. The catchment land use is mostly plantation forest, some of which is spray-irrigated with treated wastewater. A Sequential Uncertainty Fitting (SUFI-2) procedure was used to auto-calibrate unknown parameter values in the SWAT model. Model validation was performed using two data sets: (1) monthly instantaneous measurements of suspended sediment (SS), total phosphorus (TP) and total nitrogen (TN) concentrations; and (2) high-frequency (1-2 h) data measured during rainfall events. Monthly instantaneous TP and TN concentrations were generally not reproduced well (24 % bias for TP, 27 % bias for TN, and R 2 < 0.1, NSE < 0 for both TP and TN), in contrast to SS concentrations (< 1 % bias; R 2 and NSE both > 0.75) during model validation. Comparison of simulated daily mean SS, TP and TN concentrations with daily mean dischargeweighted high-frequency measurements during storm events indicated that model predictions during the high rainfall period considerably underestimated concentrations of SS (44 % bias) and TP (70 % bias), while TN concentrations were comparable (< 1 % bias; R 2 and NSE both ∼ 0.5). This comparison highlighted the potential for model error associated with quick flow fluxes in flashy lower-order streams to be underestimated compared with low-frequency (e.g. monthly) measurements derived predominantly from base flow measurements. To address this, we recommend that high-frequency, event-based monitoring data are used to support calibration and validation. Simulated discharge, SS, TP and TN loads were partitioned into two components (base flow and quick flow) based on hydrograph separation. A manual procedure (one-at-a-time sensitivity analysis) was used to quantify parameter sensitivity for the two hydrologically separated regimes. Several SWAT parameters were found to have different sensitivities between base flow and quick flow. Parameters relating to main channel processes were more sensitive for the base flow estimates, while those relating to overland processes were more sensitive for the quick flow estimates. This study has important implications for identifying uncertainties in parameter sensitivity and performance of hydrological models applied to catchments with large fluctuations in stream flow and in cases where models are used to examine scenarios that involve substantial changes to the existing flow regime.

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“…The needle boundary layer conductance in the chamber were effectively equal to infinity because of good mixing and the small size of the needles. The three-dimensional position in the tree crown of the fascicles used for the measurements was determined as described earlier and, at the end of the measurement period, the needles were removed and the surface area determined following Whitehead et al (1994a).…”

Section: Tree Gas Exchange and Stand Carbon Dioxide Profile Measurementsmentioning

confidence: 99%

Nitrogen allocation and carbon isotope fractionation in relation to intercepted radiation and position in a young Pinus radiata D. Don tree

Livingston

Whitehead

Kelliher

et al. 1998

Plant Cell & Environment

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The three dimensional distribution of intercepted radiation, intercellular CO 2 concentration (C i ) and late summer needle nitrogen (N) concentration were determined at the tips of all 54 branches in a 6·2-m-tall Pinus radiata D. Don tree growing in a New Zealand plantation. Measurements included above-and below-canopy irradiance, leaf stable carbon isotopic composition (δ 13 C) and tree canopy architecture. The radiation absorption component of the model, MAESTRO, was tested on site and then used to determine the branch tip distribution of intercepted radiation. We hypothesized that in branch tip needles: (i) the allocation of nitrogen and other nutrients would be closely associated with the distribution of intercepted radiation, reflecting carbon gain optimization theory, and (ii) C i would predominantly reflect changes in photosynthetic rate (A) rather than stomatal conductance (g s ), indicating that the increase in A for a given increase in N concentration was larger than the corresponding increase in g s . Needle nitrogen concentration was poorly related to intercepted radiation, regardless of the period over which the latter was calculated. At a given height, there was a large azimuthal variation in intercepted radiation but N concentration was remarkably uniform around the tree canopy. There was, however, a linear and positive correspondence between N concentration and δ 13 C and needle height above ground (r 2 = 0·73 and 0·68, respectively). The very strong linear correspondence between N concentration and C i (r 2 = 0·71) was interpreted, using gas exchange measurements, as supporting our second hypothesis. Recognizing the strong apical control in P. radiata and possible effects of leaf nitrogen storage in an evergreen species, we propose that the tree leader must have constituted a very strong carbon sink throughout the growing season, and that the proximity of branch tip needles to the leader affected their photosynthetic capacity and nutrient concentration, independent of intercepted radiation. This implies an integrated internal determination of resource allocation within the tree and challenges the current convention that resources are optimally distributed according to the profile of intercepted radiation.

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Seasonal Partitioning of Evaporation Between Trees and Understorey in a Widely Spaced Pinus radiata Stand

Cited by 39 publications

References 44 publications

Evapotranspiration modelled from stands of three broad‐leaved tropical trees in Costa Rica

Evapotranspiration modelled from stands of three broad‐leaved tropical trees in Costa Rica

Effects of hydrologic conditions on SWAT model performance and parameter sensitivity for a small, mixed land use catchment in New Zealand

Nitrogen allocation and carbon isotope fractionation in relation to intercepted radiation and position in a young Pinus radiata D. Don tree

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