| dc.description.abstract | There are few other regions that have been as significantly altered by woody plant encroachment (WPE) as the Southern Great Plains (SGP) of the United States. The transition from an oak savanna to a shrubland mosaic redistributes energy and water as the vertical and horizontal structure of the landscape change. In the POS, where underlying geology and sandy soils allow for groundwater recharge and active subsurface hydrology, the effect of woody shrubs is likely revealed within the near-surface soil matrix and modified by interception losses from the shrub canopy. However, almost no literature exists to detail the effect of woody invasion in the POS, and further there are no established interception losses for many dominating species. The dynamic transformation of the POS also warrants from time to time contemporary ecological description and documentation, for perpetuity sake. This project aims to determine (1) interception losses, and (2) near-surface soil moisture dynamics of yaupon holly (Ilex vomitoria) and other woody invaders of the POS at the Texas A&M University Ecology and Natural Resources Teaching Area. Interception rates are determined by measuring the volume of canopy throughfall in > 9 throughfall devices (TD) per canopy of shrub species and clusters, and then comparing these volumes to an unobstructed rain-gauge after each rain event. Continuous soil moisture is assessed with time-domain-reflectometry (TDR) sensors under 2 shrub clusters compared to 1 open savanna at 10, 20, and 40cm. Interception losses and soil water contents of different vegetation are reported. Contrary to my hypothesis, there is not significantly different soil-moisture contents in the 5-25 cm rooting zone between shrub and grass vegetation types. Therefore, the ecohydrological role of shrubs in this study shows that: First, these evergreen shrubs reduce a significant portion of rainfall to the subcanopy zone, nearly one-third of total rainfall in the case of yaupon holly. And secondly, that woody shrubs excel where deeper water is available for extraction, and in this process might alter sub-surface flows and connectivity across the landscape. The ecology of yaupon in the POS is further examined. | |
