Vegetation controls on soil moisture distribution in the Valles Caldera, New Mexico, during the North American monsoon

Abstract

Soil moisture distributions are expected to be closely tied to ecosystem processes in water-limited environments of the southwest United States. Nevertheless, few studies have addressed how soil moisture varies across grassland to forest transitions frequently observed in semiarid mountain settings. In this study, we quantify the vegetation controls on surface soil moisture by sampling a range of different ecosystems present in the Valles Caldera, New Mexico. Soil and atmospheric variables were measured during a 2-week field campaign conducted in late July to early August 2005 during the North American monsoon. Field observations were supplemented by a network of continuous instruments used to assess conditions prior to and after the sampling campaign. Results reveal that soil moisture responds directly to summer precipitation events and is mediated by plant interception, which differs across the grassland-forest continuum. The nature of the spatial and temporal variations in soil moisture changes across the different sampled ecosystems: wetlands, riparian forests, grasslands, ponderosa, deciduous and mixed conifer forests. In particular, statistical analyses of soil moisture distributions indicate that distinct regimes (e.g. probability density functions) exist along the semiarid vegetation gradient, which may not be revealed through simple metrics such as the ecosystem average. Ecosystem differences are further elucidated through comparison of the spatial variations in each vegetation type, indicating higher variability in wetland and grassland sites.

Mountain ecohydrology: quantifying the role of vegetation in the water balance of montane catchments

“…Moving from a focus on snow to summer rainfall, Vivoni et al (2008) describe distributed field observations of precipitation and soil moisture, and relate these to the vegetation communities found along the grassland to forest transition. The study identifies how sharp gradients Liu et al (2008), quantifies the contributions of different water sources to streamflow at larger spatial and longer temporal scales than the work of Vivoni et al (2008) or Lyon et al (2008).…”

“…Liu et al's results identify non-linear thresholds in hydrologic residence time, the redistribution of precipitation within the ecosystem, and thus ecosystem-scale patterns of water availability. Sources of streamflow were related to soil moisture and precipitation, conceptually linking lateral redistribution of water to the work of Lyon et al (2008) and Vivoni et al (2008), but the type of precipitation (rain versus snow), soil type, and subsurface geology resulted in non-linear behaviour in space and time. For example, lateral subsurface flow dominated water redistribution during all seasons in the well-drained soils at higher elevations.…”

“…In the final paper of the issue, Mahmood and Vivoni (2008) present a distributed hydrologic model capable of capturing the spatial and temporal patterns of the summer season soil moisture observations described in Vivoni et al (2008). Simulations capture the high resolution catchment descriptors and hydrometeorological forcings to reproduce observed surface soil moisture in wetland, grassland, and forest ecosystems following a series of convective storm events.…”

Effects of vegetation restoration on the spatial distribution of soil moisture at the hillslope scale in semi-arid regions

“…Understanding the spatial variability of soil moisture and its influencing factors will provide a basis for optimizing the spatial allocation of vegetation restoration efforts. Soil moisture and its spatial variation are closely related to vegetation (Ferreira et al, 2007;Vivoni et al, 2008). This is particularly true for ecosystems in arid and semi-arid environments (Sanchez-Mejia et al, 2014).…”

Seasonal changes in the soil moisture distribution around bare rock outcrops within a karst rocky desertification area (Fuyuan County, Yunnan Province, China)

“…Soil moisture and its spatial variation are closely related to vegetation (Ferreira et al 2007;Vivoni et al 2008). Sufficient soil moisture is an essential condition for normal plants growth, affecting both survival and quality (Breshears et al 1997;Peng et al 2013;Yang et al 2015).…”