• Detecting channel morphology change in California's hardwood rangeland spring ecosystems

      Allen-Diaz, B.; Jackson, R. D.; Fehmi, J. S. (Society for Range Management, 1998-09-01)
      Permanent channel cross-sectional transects perpendicular to flow were used to estimate changes in spring and resultant creek channel morphology. Three cattle grazing treatments (none, light, and moderate) were applied to 2-5 ha pastures containing a perennial spring and resultant creek cohort for 5 years. Grazing effects on the total change in channel morphology were not detected, nor did our method detect channel morphology change over the 5 year study period. Ungrazed springs and creeks were observed to change more than grazed springs and creeks although these differences were not statistically significant. Observed, but not significant, change over time appears related to rainfall patterns. Permanent channel cross-sections, one of the currently recommended methods for monitoring livestock grazing impacts on stream channels, may not be adequate for detecting channel changes in low-flow spring/creek systems.
    • Grazing effects on spring ecosystem vegetation of California's hardwood rangelands

      Allen-Diaz, B.; Jackson, R. D. (Society for Range Management, 2000-03-01)
      Three watersheds at the University of California's Sierra Foothill Research and Extension Center (SFREC), Marysville, Calif. were selected to study cattle grazing effects on the vegetation surrounding cold-water springs and their downslope creeks. Three spring-creek systems from each of 3 watersheds were randomly assigned to grazing treatments (9 total). Treatments were ungrazed, lightly grazed (1,500 kg(.)ha(-1) residual dry matter), and moderately grazed (1,000 kg(.)ha(-1) residual dry matter) based on degree of use in upland pastures encircling the spring-creek systems. Total herbaceous cover at springs varied significantly among the 6 years only once (greater in 1994 than all others covarying with previous year's rainfall. Grazing intensity did not affect total herbaceous cover at springs. A year X grazing treatment interaction (P 0.05) was detected for total herbaceous cover at spring-fed creeks. Three years after grazing removal, total herbaceous cover on ungrazed 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 were analyzed with TWINSPAN. With few exceptions, stable plant communities persisted on sites regardless of grazing intensity or cover changes. Total herbaceous cover was sensitive to interannual fluctuations, especially under increased grazing intensities. This attribute renders cover a more useful gauge of ecosystem health than plant composition as the latter may not provide evidence of potentially deleterious grazing X climate interactions until after soil erosion or water table characteristics are seriously, perhaps permanently, altered.
    • Livestock management strategy affects net ecosystem carbon balance of subhumid pasture

      Oates, L. G.; Jackson, R. D. (Society for Range Management, 2014-01)
      Temperate grasslands are generally considered carbon (C) sinks, but climate and management likely affect whether they accumulate or lose C on an annual time step. The North Central Region of the United States contains highly productive improved pasture that is used exclusively for livestock grazing and mechanical harvest. The objective of this study was to use a net ecosystem carbon balance (NECB) approach to estimate C accumulation or loss in subhumid pastures under four typical livestock management practices: management-intensive rotational grazing (MIRG), continuous grazing (CONT), haymaking (HARV), and land set aside with no harvests (NONE). MIRG lost significantly less C in 2006 than all other treatments, and in 2007 MIRG was the only treatment that had a positive NECB. For 2006, our model resulted in an average change of-236 ± 15 (CONT),-100 ± 24 (MIRG),-391 ± 11 (HARV), and-276 ± 28 (NONE) g C · m-2 · y-1. For 2007, the change was-234 ± 56 (CONT), 106 ± 69 (MIRG),-200 ± 25 (HARV), and-171 ± 38 (NONE) g C · m-2 · y-1. Increased C fixed as net primary production (NPP) and C imported as hay and grain resulted in the MIRG treatment having the most favorable C balance. Even with imported hay and grain, reduced NPP in the CONT treatment led to a less favorable C balance. In the HARV treatment, high biomass removal drove the negative C balance, while the relationship between reduced NPP and heterotrophic respiration alone drove the negative C balance in the NONE treatment. Climate change mitigation services provided from ecosystem C accumulation relative to cultivation may be warranted for pastures, but when all cross-boundary transfers of C are not considered, significant misconceptions can occur regarding how different management strategies affect the NECB of subhumid pasture. © 2014 The Society for Range Management.