Low plant cover retains soil moisture in drylands

By the end of the subtropical alpine summer season, the deep soils of this altiplano still store c. 1/5 of the annual precipitation (Fig. 1). Note that tall fescue exploits in large top soil horizons, whereas low fescue exploits deeper horizons. The poor ground cover (small leaf area) plus (probably) stomatal control prevents this vegetation from exhausting soil moisture.

1 - Low and tall fescue grassland at 4250 m in the NW-Argentinean Andes - rated by precipitation, a semi-desert (c. 300 mm per year).