A four-year study was conducted to evaluate the effects of treeshelters on the growth and survival of three oak species and Douglas fir growing in a Mediterranean climate. Trees were planted in irrigated and nonirrigated plots, enclosed in treeshelters or tree guards, and measured annually for height and diameter growth. In nonirrigated plots, both treeshelters and tree guards improved oak survival, but generally did not produce significant height or diameter growth increases over unprotected controls. In irrigated plots, plant growth and survival was substantially greater than that in nonirrigated plots. Irrigated trees with protection (shelters or guards) showed substantially greater survival levels than unprotected trees. Height growth was greatest in treeshelters and diameter growth was roughly equivalent for all irrigated treatments. Irrigated trees continued to grow when irrigation was discontinued after three years, and treeshelter trees exhibited little or no lean when shelters were removed. Trees without irrigation in Mediterranean climates should not be expected to exhibit growth enhancement effects from treeshelters equivalent to those found in temperate climates.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD).

No abstract

of the USDA' s Division of Forestry in 1894, wrote in that year' s Book of Agriculture, "in order to harmonize the requirements of the wood lot from a sylvicultural point of view, and the needs of the farmer for wood supplies, the cutting must follow some systematic plan." This astute statement, written over 100 years ago, still rings true today. In those simpler days, a landowner' s primary worries dealt only with the immediate needs of planting, cultivating, and producing a "crop" of trees over time. It is interesting that even with these modest goals, the author spoke eloquently of the need to have a management plan for guidance.In today' s world, landowners need to know many things to be successful forest stewards. It is of the utmost importance to understand the ecological and environmental effects of various management practices. For those seeking economic returns, it is essential to be informed about markets, costs, and regulatory requirements. Landowners today must consider their place in the community and how their activities can influence their neighbors, other species, and other forest users.Simply stated, there is a great deal more to forest stewardship today than just growing, cutting, and marketing trees. Forest stewards must plan activities well in advance, accurately assess resources, manage potential wildland fuel sources, address erosion and water quality issues, and know how to use sound information to make management decisions. For many California forest landowners, economic returns are incidental or unimportant; they may be more interested in forest restoration or enhancement. Nevertheless, these landowners too must consider the effects of their management (or nonmanagement) actions.Forestland management decisions are implemented over a long time span, often exceeding an individual' s lifetime. The impacts of those decisions affect you and your family as well as your neighbors. These decisions also influence the management of nearby lands and may impact streams and water sources hundreds of miles away. Your decisions have repercussions on wildlife, fire protection, water quality, and scenic values. Even if your decision is to do nothing and let the forest take care of itself, that decision impacts a multitude of resources. a Forest in space and timeThe condition of the forest you own or manage today is largely a consequence of historical land use practices. In all but a small percentage of public lands, forestlands throughout the state have been significantly altered by harvest activities in the relatively recent past.The society of the indigenous peoples of California before the appearance of Europeans was essentially a subsistence-based culture very different from the modern market-based culture that dominates today. Understanding these societal differences is important if we are to understand how human intervention has impacted forest conditions. Prior to the California Gold Rush, indigenous Californians manipulated puBLication 8232 uniVersity oF caLiFornia Division of Agriculture and Nat...

Insects are a natural and necessary part of a healthy forest ecosystem; most insect species are actually beneficial. They speed decay of dead vegetation, releasing nutrients for other plants. Many types of wildlife require insects for food. Bees and other insects pollinate forest plants. Some insects prey on other insects that are harmful to plants, keeping pest outbreaks in check. Many insect populations experience a natural "boom-bust" cycle. Every year fertile adults or pupae survive the winter and emerge in the spring. They reproduce and increase in number through the summer and decline again in the winter. Environmental conditions and food availability control their populations. For those that feed on trees (leaves or sugars in the sap), food availability increases when the trees are under stress and are less able to defend against or rebound from insect attack. When susceptible trees are abundant due to prolonged stress, insect populations increase to the extent that food is available. After an initial "boom" period that may last for several generations, the insects reach a level that is no longer sustainable by the available food. The population then "crashes" until the next cycle begins again. The crash may be caused in part by a buildup in the populations of natural enemies of the insects (birds, predatory insects) who themselves are responding to an increased supply of food (insects). When insect outbreaks of this kind are widespread and prolonged, there can be immense amounts of tree mortality. More commonly, tree mortality due to forest insects is localized, limited to a few trees in a small area. In many cases, healthy trees can repel insect attacks or survive them. Insects kill more trees annually than wildfire. However, they usually take their toll on individual trees or small groups of trees, unlike the spectacular large-scale destruction of forest fires. While insects may be the identifi able cause of tree injury and death, the underlying reason for insect damage is that trees are in poor condition due to stress. Stress is caused by drought, competition for resources among trees, or other environmental conditions. Insects challeng e trees constantly, but generally only the stressed or unhealthy trees are success fully attacked and succumb. Maintain ing healthy, vigorously growing trees is the best defense against insects.