Ecohydrology of root zone water fluxes and soil development in complex semiarid rangelands

Abstract

Abstract:In semiarid complex terrain, the landscape creates spatial niches for different types of vegetation through the effects of aspect, slope and curvature on the water and energy balance at the soil surface. The ecohydrology of rangelands is defined by the interaction of soils, plants and climate occurring on a topographic surface. While these interactions have been studied for subtle terrain, little is known about the controls exerted by terrain position, in particular terrain aspect, on ecosystem processes. Furthermore, differential plant establishment can lead to measurable differences in rates of soil development, which in turn can affect soil hydraulic properties and the surface water balance. In this study, we outline the physical mechanisms affecting plant establishment, soil development and hydrologic fluxes in semiarid complex terrain. We illustrate the interactions between vegetation, root zone water fluxes and soil development using, as an example, a small drainage basin in the Sevilleta National Wildlife Refuge (SNWR), New Mexico. In the study basin, opposing hillslopes are characterized by marked differences in ecosystem composition and soil profile properties, with the north-facing hillslope dominated by one seed juniper (Juniperus monosperma) and the south-facing slope consisting of creosote bush (Larrea tridentata). We assess the effect of terrain aspect on root zone hydrologic fluxes and soil development in the two ecosystems by using soil observations, hydraulic properties from pedotransfer functions (PTFs), and numerical modelling of vadose zone fluxes. Modelling results show marked differences in root zone fluxes in the north-facing juniper and south-facing creosote ecosystems. Differences in the amplitude and frequency of soil water content and pressure correspond to changes in soil profile and vegetation characteristics. For example, soil properties of the calcium carbonate (CaCO 3 ) horizons and differential plant water uptake impact the simulated soil water pressure over an 8-year period in the opposing ecosystems. It is believed that these variations in water fluxes reinforce the development of CaCO 3 horizons present in the soil profiles, leading to a feedback between vegetation establishment, soil water fluxes and geomorphic processes in the catchment. Our results also indicate that soil properties and water fluxes compensate for large differences in evaporative demand and lead to similar actual evapotranspiration (AET) in the opposing slopes.

Semiarid watershed response in central New Mexico and its sensitivity to climate variability and change

“…Our numerical experiments do not focus on the potential uncertainties associated with the model parameters. Instead, we minimize model calibration by selecting effective parameters at HRUscale based on published literature values (e.g., Rawls et al, 1983;Bras, 1990;Dingman, 2002;Federer et al, 2003;Caylor et al, 2005;Gutiérrez-Jurado et al, 2006). Confidence in the model formulation and parameterization was built through two extensive simulation exercises: (1) point-scale comparisons of the simulated soil moisture to observations, and (2) HRU-scale evaluations of the water balance states and fluxes, as reported in detail in Aragón (2008).…”

Effects of woody vegetation on shallow soil moisture at a semiarid montane catchment

“…Competition within plant communities for resources such as soil moisture can significantly impact their composition and structure (Lauenroth et al, 1993;D'Odorico et al, 2007;Segoli et al, 2012). Soil moisture also affects soil processes, such as the development of calcium carbonate horizons (Gutierrez-Jurado et al, 2006). Due to these influences and many others, applications involving soil moisture are abundant and include weather forecasting, flood forecasting, agricultural production, and watershed and land management.…”

Modelling the Potential of Integrated Vegetation Bands (IVB) to Retain Stormwater Runoff on Steep Hillslopes of Southeast Queensland, Australia

“…In native woodlands, rain infiltration rate, soil water storage capacity and soil biological activity can vary with changes in accumulated litter and soil organic matter [5,6]. While these processes occur naturally in many native ecosystems (e.g., [7,8]), they are often impaired in landscapes that support grazing and cropping land uses.…”