Grazing effects on spring ecosystem vegetation of California's hardwood rangelands

Three watersheds at the University of California's Sierra Foothill Research and Extension Center (SFREC), Marysville, Calif. were selected to study ca ttle grazing effects on the vegetation surrounding cold-water springs and t heir downslope creeks. Three spring-creek systems from each of 3 watersheds mere randomly assigned to grazing treatments (9 total). Treatments were un grazed, lightly grazed (1,500 kg.ha(-1) residual dry matter), and moderatel y grazed (1,000 kg.ha(-1) residual dry matter) based on degree of use in up land pastures encircling the spring-creek systems. Total herbaceous cover a t springs varied significantly among the 6 years only once (greater in 1994 than all others) covarying with previous gear's rainfall. Grazing intensit y did not affect total herbaceous cover at springs. A year X grazing treatm ent interaction (P<0.05) was detected for total herbaceous cover at spring- fed creeks. Three years after grazing removal, total herbaceous cover on un grazed creek plots surpassed cover at moderately grazed and lightly grazed plots. Moderately grazed plot herbaceous cover declined steadily throughout the first 3 years, while lightly grazed cover remained relatively stable. Plant community composition and stability by year and grazing treatment wer e analyzed with TWINSPAN. With few exceptions, stable plant communities per sisted on sites regardless of grazing intensity or cover changes. Total her baceous cover was sensitive to interannual fluctuations, especially under i ncreased grazing intensities. This attribute renders cover a more useful ga uge of ecosystem health than plant composition as the latter may not provid e evidence of potentially deleterious grazing X climate interactions until after soil erosion or water table characteristics are seriously, perhaps pe rmanently, altered.