Water use of grasslands, agroforestry systems and indigenous forests

• DOI: 10.4314/wsa.v37i5.15
• Publication Date: 2011-12-14T07:16:52Z
• Authors: CS Everson; PJ Dye; MB Gush; TM Everson
• Keywords: Water use

The biotic and abiotic components of ecosystems affect each other through complex interactions processes. These dynamic give their distinct identities provide ecosystem services critical to human survival (e.g. water, energy nutrients). However, activities commercial forestry, agriculture) have placed increasing demands on specific services. effect these processes has been the focus numerous Water Research Commission (WRC) studies. Some determined man's impact plant-water use, biomass production (energy) water use efficiency (biomass produced per unit transpired, termed productive green-water use). For example, measurements evapotranspiration (ETa) from different vegetation types showed that annual is strongly related proportion year in which a dense canopy transpiring leaves maintained. Thus, evergreen such as riparian fynbos plantations introduced tree species exhibit relatively high ETa, when compared seasonal grasslands deciduous trees only maintain during summer. Quantification volumes used by types, under differing climatic site conditions, possible At stand scale, allowed partitioning beneficial (transpiration) non-beneficial (evaporation) fluxes. catchment scale quantified proportional allocation balance. Three case studies are presented illustrate this. In Jatropha curcas, daily total evaporation rates December February (summer) clear hot days ranged between 3 mm·d-1 4 mm·d-1. due nature species, was negligible (< 1 mm·d-1) winter (May August). montane grassland KwaZulu-Natal Drakensberg main hydrological fluxes into streamflow dependent wetness year. average wet years (>1 200 mm precipitation) flux equally split (650 mm) runoff (550 mm), while drier became dominating component balance (752 vs. 356 mm, respectively). data provided an important baseline for comparison with impacted (especially forestry). Finally, results variety growth indigenous growing natural forest plantation systems suggest that, substantially less show lower efficiency, grow more slowly. Advantages potentially include management costs, higher product values, wider range non-wood products impact. Their usefulness may be greatest sensitive sites zones, water-stressed catchments, land cleared alien plants, erosion risk, degraded forest) where reduced environmental required.Keywords: evaporation, transpiration, grassland, trees, curcas