The Ecohydrology of a pioneer wetland species and a drastically altered landscape

Abstract

Vegetation plays a central role in forming and maintaining an ecosystem's physical conditions, which in turn strongly influence vegetation function. These bidirectional feedbacks may be particularly evident during an ecosystem succession following large‐scale disturbances. Clay settling areas (CSAs) are large elevated impoundments that receive clay slurry as a by‐product of phosphate mining in Florida. As CSAs mature, a limited seed source arrests ecological succession, resulting in the dominance of Salix caroliniana, which is likely further supported by altered abiotic conditions. The dominance of this wetland pioneer species and its interactions with soil and hydrology may largely determine the future ecosystem state. To identify how interactions between groundwater levels, soil water availability, and vegetation response regulate the succession of CSA ecosystems, we measured groundwater levels, vertical soil moisture profiles, soil water potentials, and root biomass allocation and transpiration of S. caroliniana at two sites. Fine soil texture in the CSAs resulted in capillary fringe heights greater than 1 m, which maintained soil moisture near saturation well above the water table. Rooting depths over 1 m in the clay soils provided sufficient water availability, which, along with high residual phosphorus concentrations, explained the dominance and high transpiration rates of S. caroliniana across CSAs. Capillary rise‐induced water availability created wetland soil conditions far upgradient from inundated areas, underscoring the role of soil texture in determining wetland extent. The strong coupling between water table and S. caroliniana transpiration, however, suggests that beyond soil development, this pioneer phreatophyte may also drive succession through systematic dewatering. Copyright © 2011 John Wiley & Sons, Ltd.

Ecosystem specific yield for estimating evapotranspiration and groundwater exchange from diel surface water variation

“…Research on wetland ET has documented substantial deviation from open water evaporation (Ingram, ; Drexler et al ., ; Mitsch and Gosselink, ) due to variability in hydrology, nutrient availability, successional state, and surrounding land use. Rates have been reported that are both markedly higher (Gavin and Agnew, ; Moro et al ., ; McLaughlin et al ., ) and lower (Lafleur and Rouglet, ; Campbell and Williamson, ; Peacock and Hess, ) than potential ET (PET) estimated with climatic models, underscoring the utility of direct empirical estimates.…”

Assessing stand water use in four coastal wetland forests using sapflow techniques: annual estimates, errors and associated uncertainties

“…Finally, a Salix fragilis L. forest in the Czech Republic transpired at a rate of 1.2-4.1 mm day À1 , (Čermák et al, 1984). It is uncertain how much terrestrial stands regulate water use because of soil water deficit seasonally (Rodríguez-Iturbe and Porporato, 2004;McLaughlin et al, 2012). Even periodic soil water deficit is uncommon for coastal forested wetlands (especially those that are tidally influenced), so water supply is not likely to limit transpiration unless salinity is introduced.…”

“…For both modelling protocols, we begin by using a modified biometric model (Čermák et al ., ; McLaughlin et al ., ), where F is determined from Equation , such that stand water use ( S ) at a given time interval relates as follows: where i corresponds to individual trees in the stand, 1 is the first tree in the stand over a specific diameter limit from which F is calculated, 2 is the second tree and so on, A is the ground area occupied by the stand (m 2 ) and ρ is the density of water (0.998 g cm −3 ). Because forest structural data are collected over a known ground area (in m 2 ), S is reported as kg H 2 O per m 2 ground area, which is equivalent to the same value in millimetres (mm).…”

“…For both modelling protocols, we begin by using a modified biometric model (Čermák et al, 2004;McLaughlin et al, 2012), where F is determined from Equation 2, such that stand water use (S) at a given time interval relates as follows:…”

Approximations of stand water use versus evapotranspiration from three mangrove forests in southwest Florida, USA

“…Stand water use (S) is then determined using individual tree forest structural data from each study plot to sum individual tree measurements. We apply calculations from a modified biometric model (Čermák et al, 2004;McLaughlin et al, 2012), with F tree being derived from Equation 1 scaled to a daily values, and S determined as follows:…”