Ecohydrological implications of woody plant encroachment

TitleEcohydrological implications of woody plant encroachment
Publication TypeJournal Article
Year of Publication2005
AuthorsHuxman T.E., Wilcox B.P., Scott R.L., Snyder K.A., Small E.E., Hultine K.R., Pockman W.T., Jackson R.B.
Date PublishedFebruary 1, 2005
ARIS Log Number159653
Keywordsarid, ecohydrological, ecosystems, evapotranspiration, semiarid, woody plant encroachment
AbstractIncreases in the abundance or density of woody plants in historically semiarid and arid grassland ecosystems have important implications for hydrology, ecology, and society. Using a simplified water-balance model, we propose a framework for conceptualizing how woody plant encroachment is likely to affect components of the water cycle within these ecosystems. We focus in particular on streamflow and the partitioning of evapotranspiration into E (evaporation) and T (transpiration). On the basis of this framework, we suggest that streamflow and evaporative processes are affected by woody plant encroachment in different ways, depending on the degree of aridity and the availability of subsurface water. Differences in landscape physiography, climate, and runoff mechanisms mediate the influence of woody plants on hydrological processes. Similarly, encroachment of woody plants can be expected to produce relatively large shifts in the ratio of E to T in semiarid ecosystems, whereas such shifts will be small or negligible in both subhumid and xeric ecosystems. This framework for considering the effects of woody plant encroachment highlights important ecological and hydrological interactions that serve as a basis for predicting other ecological aspects of vegetation change,such as potential changes in carbon cycling within an ecosystem. In locations where woody plant encroachment results in increased T and concurrently the availability of soil water is reduced, increased accumulation of carbon in soils can be predicted. Thus, explicitly considering the ecohydrological linkages associated with vegetation change provides additional information on the consequences of woody plant encroachment.