Agroforestry on California's Hardwood Rangelands
Hardwood rangelands comprise approximately nine million acres- just under10% of the total land area-in California. In contrast to higher elevationconiferous forests which are often publicly owned, about 80% of the hardwoodrangelands in the state are in private ownership. Since European settlement,the primary agricultural use of these lands has been livestock grazing.The economic rent for this activity is relatively low, in the neighborhoodof $8 to $15 per acre per year. This low rate of return, and fluctuationsin meat and wool prices, have resulted in difficult economic times for someranchers, causing the reduction or loss of equity and ultimately the conversionof some rangelands to residential use.
Simultaneously growing trees on these grazing lands has been suggestedas a possible means of increasing revenue by providing landowners with anannual income from livestock while the trees are maturing. Though forestgrazing is common in California, establishing plantations where trees andlivestock are raised together on rangelands has not been seriously testedin the state. However, such systems have been extensively and successfullyused in New Zealand, Australia, and elsewhere, primarily with Monterey pineplantations and sheep grazing.
The most common trees on typical hardwood rangelands in California arenative oaks. While these species are tremendously important for wildlifeand aesthetics, and there is widespread interest in oak conservation, theygenerally grow slowly and have little economic value, other than for firewood.As such, they are poor candidates for use in an agroforestry system. Whilethe importance of maintaining existing stands of native oaks is well recognized,there are vast areas in the state where trees have either not become established,or have been previously removed. Small plots of these cleared grazing landsmay be suitable for planting one or more species of conifers, which cantolerate relatively harsh rangeland conditions, yet grow much more rapidlythan oaks. Tree crops could be used for a variety of products includingpulp, lumber, biomass, Christmas trees or firewood. If successful, suchplantations could actually promote oak conservation by reducing the demandfor oak firewood, and providing landowners with more income, thus reducingthe pressure to sell and subdivide. However, it is not clear which coniferswill perform well in these environments and whether or not livestock cansimultaneously graze these lands without damaging trees.
To evaluate the potential of four pine taxa (Monterey pine, knobconepine, a hybrid between these two species called KMX, and Coulter pine) togrow on low elevation hardwood rangelands, a study was initiated at theSierra Foothill Research and Extension Center in 1991. Two hundred forty,one-year-old seedlings from each of the four taxa were planted on a 10-footspacing, within a cattle exclosure. Four treatments were evaluated: augeringto a depth of 2 feet and placement of a 21 gram fertilizer tablet; 2) augering,but no fertilization; 3) fertilization, but no augering; 4) no augeringand no fertilization.
After two years, approximately 10 head of cattle were placed in the ploteach spring for several weeks. Immediately after each of these grazing intervals,we assessed each of the trees for evidence of injury from the cattle. Year-endheight and survival of each surviving tree were also measured every year.
Results to date indicate that several pine taxa can survive and grow-atleast initially-on unirrigated hardwood rangelands in California. Aftersix years, most trees were well over 10 feet tall. Once the trees have becomeestablished and are 2-3 feet tall, the pastures they are planted in canalso be grazed by cattle without substantial damage to the trees. Augering2-foot deep holes prior to planting appeared to offer no positive benefit.Fertilization, on the other hand, improved height growth by about 10%.
Agroforestry systems using pines and cattle show promise on California'soak woodlands, especially for Monterey and KMX pines. However, more timeis needed to evaluate the long-term survival and growth rates in these environments,and to determine if the potential benefits of such systems outweigh therisks of droughts, freezes, or diseases such as pitch canker.
prepared and edited by Richard B. Standiford and Pamela Tinnin