Hardwood Rangelands Research Articles

The Test of Time: Using Historical Methods to Assess Models of Ecological Change on California’s Hardwood Rangelands

Geographers and environmental scientists use conceptual models to understand ecological processes and support management decisions. Most of these models are based on short-term experiments and field observations, which might not account for longer term forces that shape ecosystems over decades to centuries. How can scholars use historical sources and methods to improve conceptual models of ecological change? In this article, we present the results of a study that employed methods from environmental history and historical geography to assess three conceptual models that researchers have used to study ecological changes on California’s hardwood rangelands: the succession and climax, state and transition, and cyclical replacement models. The succession and climax model fared poorly at all spatial scales. The historical record contained substantial evidence to support the predictions of the state and transition model at the small spatial scale of the plot or field (0.1–100 ha) and the very large spatial scale of the hardwood rangeland bioregion (4 million ha). The cyclical replacement model performed well at the intermediate scale of the landscape or typical cattle ranch (100–10,000 ha). Historical data and methods hold considerable untapped potential for assessing, building on, and improving conceptual models of ecological change in geography and the environmental sciences.

Exploring the Role of Management in the Coproduction of Ecosystem Services from Spanish Wooded Rangelands

The wood pastures or hardwood rangelands of the southwestern Iberian Peninsula are complex social-ecological systems created from the long-term interaction of society and the landscape. Dehesa, oak woodlands managed for grazing, cropping, and other forms of production, is the most common rangeland system and one of the most distinctive landscapes. Traditionally characterized by multifunctional low-intensity management that enhances a wide range of ecosystem services, current management has shifted from the traditional toward more intensified models. This paper assesses the coproduction of ecosystem services on dehesa properties by exploring the relationship between biophysical and sociocultural factors and dehesa management practices. Based on 42 surveys we analyze 16 quantitative indicators using multivariate techniques. The results indicate that there are four main dehesa types as defined by their characteristics and management: large heterogeneous operations with diverse products; small and homogeneous operations focused on a reduced number of products; medium-large properties focused on crop production; and midsized properties with easy public access. Management is the result of the dynamics of interacting biophysical and sociocultural factors that influence manager priorities and investments. Management decisions group around the degree of multifunctionality of the operation, the relative importance of crop production, the degree of grazing pressure in the system, and how restrictive public access policy is. We find that in the study area, interactions between all the previously mentioned elements covary consistently, generating bundles of ecosystem services associated with each of three management models based on the intensity of management.

The Contribution of Amenities to Landowner Income: Cases in Spanish and Californian Hardwood Rangelands

Rangeland economists have noted that people tend to pay far more for ranches and rangelands than can be justified by the potential income from livestock operations alone. This gap in price can be explained when the value of the amenity benefits from owning a ranch and the capital gains from the rangeland investment are integrated as part of the “income” accruing to the landowner. In this paper, we apply an accounting framework that takes such values into account, the Agroforestry Accounting System, to three hardwood rangeland case studies in Andalucía (southern Spain) and three in California. We estimate how commercial operations, private amenities consumed by the landowner, and capital gains contribute to landowner income and rangeland investment profitability in these case studies. Results show that private amenity consumption and capital gains make the greatest contribution to landowner income. When these income components are included in the estimations, total real profitability ranges from 2.7% to 4.5% in the Spanish cases and from 4.5% to 7.8% in the California cases, rates that are competitive with alternative investments. Our results suggest that conservation programs may be strengthened by enhancing or building on amenity benefits to landowners, motivating them to engage in and continue with these programs. In addition, landowner willingness to pay for amenities may increase the cost-efficiency of programs that would enhance the provision of these, or of closely related, amenities.

Blue oak stump sprouting evaluated after firewood harvest in northern Sacramento Valley

Colifornia's hardwood rangelands, an oak-dominated woodland system, cover 10 million acres. More than 80% of these lands are privately owned, with two-thirds grazed by domestic livestock. Public concerns about long-term damage to habitat in areas harvested for firewood — particularly in the northern Sacramento Valley — led to this study of resprouting, to assess long-term trends in oak cover following harvesting and the potential of sprout (coppice) management to sustain woodlands. In field surveys on 103 sample plots at 19 ranches where oak firewood was harvested, we found that 54% of all oak stumps resprouted. Stump diameter, herbicide application, overstory crown cover percentage, and slope and aspect were significant variables in models developed to assess the probability of stump sprouting. Ten-year sprout height and crown growth models were developed, and livestock grazing, residual overstory canopy, herbicide treatment and stump diameter were found to be significant variables. These models can be used to predict stand development following firewood harvest and can be integrated with forage growth, wildlife habitat and residual tree growth models.

Hardwood Rangeland Landowners in California from 1985 to 2004: Production, Ecosystem Services, and Permanence

A longitudinal study of California hardwood rangelands shows significant change in landowner characteristics and goals. Results of three studies spanning 1985 to 2004 were used to develop and evaluate a multiagency research and extension program known as the Integrated Hardwood Range Management Program. Program-sponsored education and research aimed at encouraging landowners to change woodland management has been reflected in a significant reduction in oak cutting and an increase in oak planting. Recent changes have come with the times: landowners were as likely to have consulted land trusts about oaks as Cooperative Extension, and the number engaged in production of crops or livestock continued to decline. On the other hand, the proportion of landowners, including ranchers, reporting that they live in the oak woodland to benefit from ecosystem services such as natural beauty, recreation, and lifestyle benefits significantly increased. Though owners of large properties and ranchers were more strongly against regulation and ‘‘government interference’’ than other respondents, this did not appear to affect oak values and management. Property size remained significantly related to landowner goals, values, and practices, with those producing livestock owning most of the larger properties. There has been a decline in the number of properties being studied due to conversion of some from oak woodland to other uses, though the remaining respondents still own at least 10% of the woodlands. Landowners with conservation easements or those who are willing to consider them, who believe oak recruitment is inadequate, or who use advisory services were significantly less likely to cut oaks and more likely to plant them. Policy, management, and outreach that support synergies between production and conservation activities, and that combine ecosystem service-based income streams that encourage keeping land intact and increased land-use stability, are needed to support conservation of private rangelands.

Homes on the Range: Cooperative Conservation and Environmental Change on California's Privately Owned Hardwood Rangelands

AbstractThis essay describes the conservation history of California's hardwood rangelands: a vast region of oak woodland, grassland, and chaparral vegetation that occurs almost entirely on private ...

Managed grazing and seedling shelters enhance oak regeneration on rangelands

Livestock grazing remains a common practice on California's hardwood rangelands. This can create problems for oak regeneration because grazing has been identified as one of the factors limiting the establishment of certain oak species. Previous research, as well as recent studies at the UC Sierra Foothill Research and Extension Center, suggests that cattle will damage both planted and/or naturally occurring oaks, but damage varies by season with less during the winter when deciduous oaks do not have leaves. Damage is also influenced by the density and distribution of cattle stocking. Oaks taller than 6.5 feet seem relatively resistant to cattle damage in lightly to moderately grazed pastures, but smaller seedlings need protection.

NITROGEN DYNAMICS IN AN ANNUAL GRASSLAND: OAK CANOPY, CLIMATE, AND MICROBIAL POPULATION EFFECTS

Hardwood rangelands in California, which are commonly used for cattle production, are characterized by an oak overstory and annual grass understory. Our goal was to evaluate how canopies influence nitrogen-cycling processes and how tree removal affected these processes. We measured standing ammonium and nitrate pools, gross production and consumption of NH4 and NO3, nitrification potentials, and NOx and N2O emissions in soils under oak canopies and in open grassy areas over a two-year period in areas within the same watershed that were grazed by cattle or fenced to exclude cattle. We also performed a subset of these measurements in open areas and in plots near stumps of oaks in areas that had been clear-cut seven and nine years earlier. Nitrogen turnover was generally higher in canopy area soils than in open area soils, and higher in the grazed area than in the fenced area. Ammonium production was slow following first autumn wet-up, but achieved higher rates during the growing season. By contrast, NO3 pro...

Agroforestry is promising for previously cleared hardwood rangelands

Livestock grazing is the primary economic use of most hardwood rangelands in the coastal foothills of California. But owners of these lands may be able to increase revenues by simultaneously producing two crops, trees and sheep. In 1993, we initiated an agroforestry project at the UC Hopland Research and Extension Center to study the ability of three pine species and one hybrid to grow on cleared hardwood rangelands that are grazed by sheep. This study also evaluated the response of planted seedlings to auger and fertilization treatments. After 8 years, tree survival has been high, growth has been vigorous and damage from sheep minimal. Monterey pine and KMX pine, a cross between Monterey and knobcone pine, had the most growth. These results suggest that some pine species are promising for planting on grazing lands in coastal foothills where oaks and other hardwoods have been removed.

The Effects of Different Sizes of Tree Shelters on Blue Oak (Quercus douglasii) Growth

Abstract Tree shelters have been used effectively in many locations to establish a wide range of tree species including oaks. However, their efficacy in Mediterranean climates like the hardwood rangelands of California has not been thoroughly tested. This study evaluated the field performance of blue oak (Quercus douglasii)—a species that is reported to be regenerating poorly in many locations in the state—protected by several sizes of tree shelters and compared response of directly sown acorns to that of 4-month-old transplants. After five growing seasons, seedlings in all sizes of tree shelters are larger than their unprotected counterparts. Tree shelters have been especially effective in promoting rapid height growth. However, regardless of tree shelter size, when seedlings grew above the tops of the shelters, average height growth diminished and diameter growth increased. Differences among stock types were relatively small, although transplants tended to perform better than directly sown acorns. These results suggest that tree shelters can greatly reduce the time required by seedlings to grow to a size where they are less vulnerable to browsing. As such, they appear to be a promising tool in efforts to regenerate blue oak in California. West. J. Appl. For. 16(4):153-158.

Mapping vineyard expansion provides information on agriculture and the environment

Vineyards are expanding rapidly in California's coastal counties due to a booming wine market. This change in land use has led to public debate over natural habitat removal, overproduction of wine grapes, loss of agricultural diversity, and changing scenery. Using a geographic information system (GIS) to map and analyze vineyard expansion in Sonoma County, approximately 11,600 acres of new vineyards were identified from 1990 through 1997. The total acreage was calculated to be at least 48,000 acres in 1997, 20% more than reported by county agricultural officials. Compared to vineyards established before 1990, a higher percentage of vineyards planted between 1990 and 1997 were located on hillsides that supported oak woodlands. Oak woodlands support a majority of the region's biodiversity, provide ecosystem goods and services, and have aesthetic value. This research was designed to document the effects of recent vineyard expansion on Sonoma County's hardwood rangelands and to provide tools for informed discussion and decision-making by land-use planners, farmers, residents and environmentalists.

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 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.

Ownership and Management Changes on California Hardwood Rangelands: 1985 to 1992

Results of a 1985 survey of California hardwood rangeland landowners were used to develop a multi-agency research and extension program known as the Integrated Hardwood Range Management Program. In 1992, the same properties were re-surveyed. Although the results cannot prove the program is the sole or direct agent of change, program-sponsored education and research aimed at encouraging oak rangeland owners to change oak management practices is reflected in changes in key landowner behaviors. Program-sponsored research showed that intermediate levels of oak canopy cover did not significantly reduce forage production. Concurrently, landowners have significantly reduced the clearing of oaks for forage production. Other significant changes are reduction of cutting of living oaks for any reason, reduced cutting of oaks for fuelwood, increased use of oak promoting practices, and a growing awareness of the need to be concerned about the status of oaks. Landowners who were aware of the resource benefits of having oaks, or who believed oaks were threatened, or who had been in contact with a natural resource advisory service were significantly more likely to carry out oak-promoting practices. Between 1985 and 1992, many properties changed hands: 24% of parcels were sold but remained intact, while an additional 11% were subdivided. As was found in 1985, owners of smaller properties manage for different and more diverse goals than those of larger properties. The changing pattern of hardwood rangeland land ownership will have an impact on education and conservation programs.

Vegetation mapping on hardwood rangelands in California

Spectral Mixture Analysis (SMA) was used to distinguish the fractional abundance of green foliage, dry grass, and soil in Airborne Visible Infrared Imaging Spectrometer (AVIRIS) data. Three maximum...

Impact of firewood harvesting on hardwood rangelands varies with region

Aerial monitoring of hardwood rangelands over a 4-year period revealed that almost 70,000 cords of firewood ware harvested annually on approximately 6,000 acres. This represents less than 0.1% of the total hardwood rangeland in the state. Over 50% of the firewood volume harvested during these 4 years was in Shasta and Tehama counties, although these two counties represent less than 10% of the hardwood rangeland acreage in the state. In Tehama County, tree growth outpaced harvest, but in Shasta County, harvest exceeded growth by 30%. Both counties' governments adopted resolutions calling for a retention of 30% crown cover following firewood harvest. This retention level attempts to balance the needs for profitable livestock management with wildlife habitat needs.

Multiple use management of California's hardwood rangelands : R. B. Standiford & R. E. Howitt, Journal of Range Management, 46(2), 1993, pp 176–182

Multiple use management of California's hardwood rangelands : R. B. Standiford & R. E. Howitt, Journal of Range Management, 46(2), 1993, pp 176–182

Multiple Use Management of California's Hardwood Rangelands

The importance of evaluating multiple resource values on rangelands is demonstrated in this study of California's 3.0 million hectares of oak-covered (Quercus spp.) hardwood rangelands. Production functions are derived for oak tree growth on rangelands for stands with at least 50% of the total tree cover in blue oak (Quercus douglasii Hook. & Arn.) based on oak volume per acre and site index. Forage production is estimated based on oak cover, weather variables, growing period, and site factors from data reported in the literature. Hunting revenue and cost functions are derived from a survey of commercial hunting clubs, and are based on oak cover, hunter success variables, hunter demographics, advertising, livestock density, and club size. The interrelationship of these resource values is shown in output from an optimal control model that incorporates these production functions. Oak trees are gradually cleared for situations where cattle are the only economic product, whereas a residual tree canopy is maintained for cases where firewood and hunting enterprises are considered. In addition, cattle stocking is higher and net profitability is lower for the cattle only management scenario when compared with a multiple use management scenario. The development of these multiple use production functions allows the full range of resource management options to be considered.

Effects of Cattle Grazing on Blue Oak Seedling Damage and Survival

Cattle grazing has been suggested as a principal cause for poor oak recruitment in California's hardwood rangelands. This study evaluated the effects of stock density and season of grazing on blue oak (Quercus douglasii H. & A.) establishment. In December 1989, seven hundred and twenty blue oak seedlings were planted on 3-m centers in 30 plots in 3 annual grassland pastures at the Sierra Foothill Research and Extension Center east of Marysville, Calif. The treatments consisted of 3 seasons X 3 stock densities plus 1 nongrazed control. During January, April, and July of 1990, steers and heifers (mean = 318 kg) were allowed to graze 1 plot per week at low, medium, and high stock densities (2.5, 7.5, and 15.0 head/ha, respectively). Control plots were used to monitor wildlife browsing. One half of all seedling sites received an application of glyphosate prior to transplanting to eliminate grass competition. Browsing and trampling damage were estimated at the end of each treatment. Total damage (sum of browsing and trampling damage), browsing damage, trampling damage, and survival to April 1991 were significantly different for the 9 season and stock density treatments (P < 0.05). Spring and summer grazing tended to be most damaging and resulted in the lowest survival rates. Within each season total damage increased with stock density but survival did not change significantly. Weed control around oak seedlings had no apparent effect on total damage or survival. There were significant differences in browsing damage between seasons but not between control and grazed plots within seasons (P < 0.05). Survival in ungrazed plots was not significantly different (P < 0.05) from the spring and summer grazed plots. Consequently, the contribution of wildlife to reduced blue oak seedling survival in grazed oak woodlands should not be underestimated.

Solving Empirical Bioeconomic Models: A Rangeland Management Application

AbstractAn empirical bioeconomic model was developed for private ranches conducting firewood, cattle, and hunting enterprises on California's hardwood rangelands. Hunting, forage, cattle, and oak firewood production functions were derived. Nonlinear optimal control was used to solve for two state and four control variables to give optimal time pathways for oak density and cattle stocking. Risk was considered through use of chance constraints, rainfall variability, and price expectations. Commercial hunting is shown to be the dominant economic value on these rangelands. Inclusion of stochastics shifts production away from cattle to less risky firewood and hunting enterprises.

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.