Influence of Natural Mulch on Forage Production of Differing California Annual Range Sites

Abstract

Manipulation of natural mulch on nine experimental plots in California annual grassland representing a range of mean annual precipitation from 160 to 16 cm provided information useful for grazing management. Peak standing crop correlated highly significantly with precipitation. Response of peak standing crop to five levels of natural mulch ranging from zero to 1,120 kg/ha differed with site. Three types of sites distinguished by mean annual precipitation and plant species composition were identified. On sites with significant numbers of perennial grasses and more than 150 cm of mean annual precipitation, maximum standing crop is reached when more than 1,120 kg/ha of mulch is present on the ground at the beginning of the fall growing season. Peak standing crop results from 840 kg/ha of mulch on sites containing the annuals Bromus mollis and Erodium botrys and with between 100 and 65 cm of mean annual precipitation. Mulch did not significantly influence standing crop in regions dominated by Bromus rubens and Erodium cicutarium and receiving less than 25 cm of mean annual precipitation. Annual grassland response to mulch and grazing is highly site specific, yet the resilience of annual rangelands also allows rapid recovery from overuse.