Neil K. McDougald

Tree canopy effects on herbaceous production of annual rangeland during drought

Seasonal herbaceous production was measured beneath tree canopies of blue oak (Quercus douglasii Hook & Arn.), interior live oak (Quercus wislizeniiDC), and digger pine (Pinussabiniana Dougl.), and in adjacent open grassland during 2 drought years (1986-87 and 1987-88) at the San Joaquin Experimental Range, California. Early and mid-growing season herbaceous production was variable, with no increase in production beneath the canopies the first year and a 60 to 150 kg/ha increase the second year compared to the herbage produced in open grassland. Peak standing crop was about 1,000 kg/ha greater beneath blue oak canopies than in open grassland in both years. Peak standing crop beneath interior live oak canopies was about 700 and 1,000 kg/ha greater than in open grassland the first and second years of the study, respectively. Peak standing crop beneath digger pine canopies was about 500 kg/ha greater the first year and similar the second year to that of the open grassland.

Spatial and temporal patterns of cattle feces deposition on rangeland

The objective of this study was to identify and model environmental and management factors associated with cattle feces deposition patterns across annual rangeland watersheds in the Sierra Nevada foothills. Daily cattle fecal load accumulation rates were calculated from seasonal fecal loads measured biannually on 40 m2 permanent transects distributed across a 150.5 ha pasture in Madera County, Calif. during the 4 year period from 1995 through 1998. Associations between daily fecal load per season, livestock management, and environmental factors measured for each transect were determined using a linear mixed effects model. Cattle feces distribution patterns were significantly associated with location of livestock attractants, slope percentage, slope aspect, hydrologic position, and season. Transects located in livestock concentration areas experienced a significantly higher daily fecal load compared to transects outside of these concentration areas (P < 0.001). Percent slope was negatively associated with daily fecal load, but this association had a significant interaction with slope aspect (P = 0.02). Daily fecal load was significantly lower during the wet season compared to the dry season (P = 0.002). Daily fecal loading rates across hydrologic positions were dependent upon season. Our results illustrate the opportunities to reduce the risk of water quality contamination by strategic placement of cattle attractants, and provide a means to predict cattle feces deposition based upon inherent watershed characteristics and management factors.

Effect of canopy and grazing on soil bulk density

Abstract This study compared soil surface bulk density between: 1) sites not grazed by cattle > 26 years; 2) sites not grazed for 6 years; 3) sites grazed for 15 years to October residual dry matter levels of > 1100 kg ha−1; 4) sites grazed for 15 years to October residual dry matter levels of 670 to 900 kg ha−1; 5) sites grazed for 15 years to October residual dry matter levels of < 450 kg ha−1; and 6) sites subject to concentrated cattle use (trails, corrals, and supplemental feed-water stations). Sites were collected from across the 1,772 ha San Joaquin Experimental Range (SJER) in Madera County, Calif. to represent canopy cover (open grassland, blue oak (Quercus douglasii Hook and Arn.), live oak (Quercus wislizenii A.DC.), foothill pine (Pinus sabiniana Douglas), wedgeleaf ceanothus (Ceanothus cuneatus (Hook) Nutt.), and ceanothus interspace) and topography (swale, uplands) typical of the rocky coarse sandy loam soils of the southern Sierra Nevada foothill oak savannah. Soil surface (0 to 7.62 cm) bulk density (g cm−3) was determined for 1489 soil cores collected across all available combinations of grazing management, canopy cover and topographic position at the SJER. Soil surface bulk density was 0.23 to 0.30 g cm−3 lower under canopy compared to open grasslands. Bulk density was not different (P > 0.05) between sites not grazed > 26 years and sites not grazed for 6 years. Grazing to residual dry matter levels of > 1100, 670 to 900, and < 450 kg ha−1 created bulk densities which were 0.08, 0.18, and 0.21 g cm−3 greater than non-grazed sites, respectively. Cattle concentration sites had bulk densities 0.37 to 0.47 g cm−3 greater than areas not grazed > 6 or 26 years. For the purpose of maintaining soil surface bulk density current residual dry matter recommendations for sites with canopy cover > 50% appear appropriate, but recommendations for open grasslands need additional review. In particular, residual dry matter level must be directly linked to soil surface infiltration capacity.

Cryptosporidium parvum transport from cattle fecal deposits on California rangelands.

Cryptosporidium parvum is a fecal borne protozoan parasite that can be carried by and cause gastrointestinal illness in humans, cattle, and wildlife. The illness, cryptosporidiosis, can be fatal to persons with compromised immune systems. At question is the potential for C. parvum in cattle fecal deposits on rangeland watersheds to contaminate surface water. First, C. parvum oocysts must be released from fecal deposits during rainfall, becoming available for transport. In 1996, we examined the transport of C. parvum oocysts in overland flow from fecal deposits under natural rainfall and rangeland conditions at the San Joaquin Experimental Range in Madera County, Calif. Our null hypothesis was that C. parvum oocysts are not released from fecal pats and transported 1 m downslope as overland flow with rainfall. Paired plots were located on 10, 20, and 30% slope sites. Each plot was loaded with four, 200 g fecal pats dosed with 10 5 oocysts g -1 . Pats were placed 1.0 m above the base of each plot. Composite runoff samples from each plot were analyzed for oocyst concentration following each of 4 storm events. Oocysts were transported during each storm. Slope was a significant fac tor in oocyst transport, with oocyst transport increasing with slope. Although not significant, there was an apparent flushing effect of oocysts across storms, with the majority transported in the first 2 storms. A pilot rainfall simulation experiment also revealed a flushing phenomenon from pats during individual rainfall events. C. parvum oocysts in fecal pats on rangeland can be transported from fecal deposits during rainfall events, becom ing available for transport to water-bodies. Future studies need to examine surface and subsurface transport of oocysts on range land hillslopes for distances greater than 1 m.

Oak seedling establishment on California rangelands.

Factors responsible for poor recruitment of blue oak (Quercus douglasii H. & A.) and valley oak (Q. lobata Nee) need to be determined on California hardwood rangelands so that management strategies for enhancement of recruitment can be developed. To examine selected factors, exclusive of large herbivore impacts, a series of acorn seeding experiments was initiated in 1985 in 6 counties on representative sites. At each site, the experimental treatments were the factorial combination of herbs vs. no herbs and screen protection vs. no protection. The experimental design was 4 randomized complete blocks of the herb treatments with each main plot split for the 2 levels of protection. Rainfall and edaphic factors were used to help interpret measures of seedling emergence, survival, and growth. Herbaceous plant control for reduction of moisture stress was the most important factor examined. Emergence was significantly improved by control in nearly 80% of blue oak seedings and in 33% of valley oak seedings. Average first year survival, expressed as a percent of acorns sown, was significantly improved with control in seedings of both blue oak (33% vs. 18%) and valley oak (45% vs. 21%). Limited data suggest the difference in survival remains consistent over time as overall survival declines. With few exceptions, the addition of screen protection discouraged predation and significantly enhanced survival and growth. Window screen cages also may have contributed an unmeasured shade effect.

Response of mountain meadows to grazing by recreational pack stock

Abstract Effects of recreational pack stock grazing on mountain meadows in Yosemite National Park were assessed in a 5-year study. Yosemite is a designated wilderness, to be managed such that its natural conditions are preserved. Studies were conducted in 3 characteristic meadow types: shorthair sedge (Carex filifolia Nutt.), Brewers reed grass (Calamagrostis breweri Thurber), and tufted hairgrass [Deschampsia cespitosa (L.) Beauv.]. Horses and mules grazed experimental plots at intensities of 15 to 69% utilization for 4 seasons. In all 3 meadows, grazing caused decreases in productivity. The mean reduction after 4 years of grazing was 18% in the shorthair sedge meadow, 17% in the Brewers reed grass meadow, and 22% in the tufted hairgrass meadow. Grazing also caused shifts in basal groundcover (usually a reduction in vegetation cover and increase in bare soil cover), and changes in species composition. Productivity and vegetation cover decreased as percent utilization increased, while bare soil cover increased as utilization increased. Changes in species composition were less predictably related to differences in grazing intensity. Passive management of grazing is insufficient in wilderness areas that are regularly used by groups with recreational stock. Wilderness managers need to monitor meadow conditions and the grazing intensities that occur. Our study suggests that biomass and ground cover are more sensitive indicators of grazing impact than species composition. Managers must make decisions about maximum acceptable levels of grazing impact and then develop guidelines for maximum use levels, based on data such as ours that relates grazing intensity to meadow response.

Social Associations and Dominance of Individuals in Small Herds of Cattle

Abstract A series of 6 daylight observations was made each summer and again each winter over 2 years to map cattle distribution on a California foothill pasture. Sixty animals were used in the study with no animals appearing in > 1 observation series. During daylight hours, small herds of cows containing between 14 and 16 animals were scan-sampled and videotaped every 15 minutes. A global positioning system was used to record the position of the camera to aid in accurately locating individual animals. Animal locations and individual identifications were then entered into a geographic information system (GIS) by on-screen digitizing using color orthophotographs. Animal positions were determined to be within 5 m of their true location. Association software, ASSOC1, was used to analyze animal positions to determine cattle subgroups and herd units. This position-based grouping was compared with observation-based grouping by researchers. Direct observation also identified dominant herd members. Older animals, up to 16 years of age, were generally dominant over younger animals, and subgroups tended to be composed of animals of similar age. The size of naturally occurring subgroups was between 3 and 6 animals. Some animals exhibited independence in their actions and behaviors compared with subgroup members. ASSOC1 produced grouping results consistent with direct observations. However, accurate interpretation of the ASSOC1 results depended on direct observational data. ASSOC1 identified close association patterns in 3 of the observations that defined the dominant animals in the herd. Forage availability and thermoregulatory needs influenced the distance between associated subgroup members. Distance between animals decreased when animals sought shade in summer or shelter in winter. Computer analysis of spatial data from GPS collars may be able to determine the social structure and identify dominant animals in herd situations. Incorporating knowledge of cattle social behavior should improve management of cattle on the range.

Site Characteristics Determine the Success of Prescribed Burning for Medusahead (Taeniatherum caput-medusae) Control

Abstract Medusahead is one of the most problematic rangeland weeds in the western United States. In previous studies, prescribed burning has been used successfully to control medusahead in some situations, but burning has failed in other circumstances. In this study, trials were conducted using the same protocol at four locations in central to northern California to evaluate plant community response to two consecutive years of summer burning and to determine the conditions resulting in successful medusahead control. During 2002 through 2003 large-scale experiments were established at two low-elevation, warm-winter sites (Fresno and Yolo counties) and two higher elevation, cool-winter sites (Siskiyou and Modoc counties). Plant species cover was estimated using point-intercept transects, and biomass samples were taken in each plot. After 2 yr of burning, medusahead cover was reduced by 99, 96, and 93% for Fresno, Yolo, and Siskiyou counties, respectively, compared to unburned control plots. Other annual grasses were also reduced, but less severely, and broadleaf species increased at all three sites. In contrast, 2 yr of burning resulted in a 55% increase in medusahead at the coolest winter site in Modoc County. In the second season after the final burn, medusahead cover remained low in burned plots at Fresno and Yolo counties (1 and 12% of cover in unburned controls, respectively), but at the Siskiyou site medusahead recovered to 45% relative to untreated controls. The success of prescribed burning was correlated with biomass of annual grasses, excluding medusahead, preceding a burn treatment. It is hypothesized that greater production of combustible forage resulted in increased fire intensity and greater seed mortality in exposed inflorescences. These results demonstrate that burning can be an effective control strategy for medusahead in low elevation, warm-winter areas characterized by high annual grass biomass production, but may not be successful in semiarid cool winter areas. Nomenclature: Medusahead, Taeniatherum caput-medusae (L.) Nevski

Correlation of degree-days with annual herbage yields and livestock gains

On Caiilomia’s winter a~ud r8ngdanda precipitation controls the beginning and end of the growing season while temperature Lirgely controls se8sonai growth tmtes within the growing season. Post-germination accumulated degree-days (ADD) account for the length of the growing season and variation of daily temperature. Simple correlations of ADD and herbage yield or resultant livestock gains were determined at 5 locations in ammal type range in northern California. Degree day values were determined by summing daily degree-days from the beginning of the growing season after germinating rainfail until the ciipphrg or weigh dates. Accumulated degree-days accounted for 74 to 91% of the variation in seasonal herbage yield while accumuiated days (AD) accounted for 64 to 86% of the variation. Together, ADD and AD accounted for 94 and 8696, respectively, of the variation in stocker cattle weights. Regression coefficients relating ADD to herbage yield appear to predict maximum site productivity. A procedure for estimating a seasonai herbage yield profile based on key growth curve intlection points and using shnple field observations with 3 clipping dates and ADD is proposed. Year-to-year variation in range herbage yield has frequently been attributed to variations in precipitation (Sneva and Hyder 1962). However, Duncan and Woodmansee (1978) were unable to show a relationship between herbage yield and precipitation on California annual rangeland. Pitt and Heady (1978) identified 5 annual range weather variables that explained 73% of the variation in March standing crop. Three of these variables were temperature related. Another set of 5 variables explained 90% of the variation in June standing crop. Two of these were temperature variables. The annual range growing season can be partitioned into fail, winter, and spring periods, Fall precipitation and cooling winter temperatures determine the length of the fail growing season. The duration of slow winter growth is variable depending on the beginning and ending dates of the cold season. The length of the rapid spring growth period is also variable depending on the date that warm spring temperatures begin and the date spring soil moisture becomes depleted. Thus, precipitation controls the beginning and end of the whole growing season while temperature controls the end of the fail and beginning of the spring growing season.

Predicting peak standing crop on annual range using weather variables.

Wide yearly fluctuations in peak standing crop on California annual-type range are largely explained by temperature and precipitation patterns. The objective of this study is to improve the predictability of functions relating weather patterns and peak standing crop by including degree-days, dry periods, evaporation, season start dates, and lengths and precipitation as independent variables. Peak standing crop was regressed on these independent variables for the University of California Hopland Field Station (HFS) and San Joaquin Experimental Range (SJER). Fall and winter precipitation, winter degree-days, and longest winter dry period were related to peak standing crop at HFS (R2=0.61). Spring precipitation, growing season degree-days, winter evaporation, and winter and spring start dates were related to peak standing crop at SJER (R2=.72). The relationship of peak standing crop to accumulated precipitation on 20 November using 33 years of data (r2=0.34) was weaker than previously reported for the rst 16 years (r2=0.49). This study suggests that timely prediction of peak standing crop may be possible at HFS but more difficult at SJER.