Treesearch

Widespread alteration of natural hydrologic patterns by large dams combined with peak demands for power and water delivery during summer months have resulted in frequent aseasonal flow pulses in rivers of western North America. Native species in these ecosystems have evolved with predictable annual flood-drought cycles; thus, their likelihood of persistence may decrease in response to disruption of the seasonal synchrony between stable low-flow conditions and reproduction. We evaluated whether altered flow regimes affected 2 native frogs in California and Oregon (U.S.A.) at 4 spatial and...

How does a highly degraded Hawaiian tropical dry lowland ecosystem dominated by the non-native invasive Megathyrsus maximus (guinea grass) respond to different restoration treatments (three native species outplanting treatments; four native broadcast seed treatments)? What effect do restoration treatments have on invasive and native species groundcover, biomass and physiological activity, and volumetric soil water content? The study was performed at Waianae Kai Forest Reserve, Island of Oahu, Hawaii, USA. The invasive grass M. maximus was suppressed by initial mowing and pre- and post-plant...

Research in the last several years has indicated that the frequency of large fires is on the rise in western US forests. Although fire size and frequency are important, they do not necessarily provide information concerning the effects of fire on ecosystems, as ecosystems differ in ecological and evolutionary relationships with fire. Our study focused on the four National Forests of NW California (Klamath, Mendocino, Shasta-Trinity, and Six Rivers). We assessed: 1) trends and patterns in fire size and frequency from 1910-2008 (all fires >40 ha), and 2) percentage of high-severity in fires...

Genetic improvement of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in New Zealand was initiated in 1955 with large provenance trials established in the late 1950s. These trials showed that material of Oregon and Californian origin was growing faster than other provenances. Additional collections were made to further evaluate provenance performance from these two areas, and in 1996 additional trials were established at four low-altitude sites across New Zealand.Genotype ×environment (GxE) interaction between these sites was found to be important for diameter at breast height (DBH),...

Hawaii and the U.S.-affiliated Pacific islands, including Guam, American Samoa, Commonwealth of Northern Mariana Islands, Federated States of Micronesia, Republic of Palau, and the Marshall Islands (fig. A1-3), contain a high diversity of flora, fauna, ecosystems, geographies, and cultures, with climates ranging from lowland tropical to alpine desert. Forest ecosystems range from equatorial mangrove swamps to subalpine dry forests on high islands, with most other forest life zones between. As a result, associated climate change effects and potential management strategies vary across the...

Castanea sativa Mill. is an ecologically and economically important species in Europe, not only as a forest tree, but also as a fruit tree. It is dramatically threatened by ink disease caused by Phytophthora spp., introduced during the nineteenth century. To limit its impact, C. mollissima and C. crenata, which proved to be tolerant species, were imported from China and Japan to Europe at the beginning of the twentieth century, together with the agent of chestnut blight (Cryphonectria parasitica) which is now spreading throughout Europe. A clonal selection has resulted in the use of a few...

In the 20th century, elms across Europe and North America were devastated by two pandemics of Dutch elm disease (DED), caused by the introduction of two fungal pathogens: Ophiostoma ulmi, followed by O. novo-ulmi. At the end of 1920s, research into a resistance to DED began in Europe and then in the United States. No worthwhile resistance was ever found within the native European or American elms. The Dutch team resorted to hybridizing European elms, from which the first cultivars exhibiting a resistance were obtained during the 1930s, but these clones did not have sufficient resistance to...

The balsam woolly adelgid (BWA; Adelges piceae) and hemlock woolly adelgid (HWA; Adelges tsugae) have had a tremendous impact on native ecosystems with Fraser fir (Abies fraseri (Pursh) Poir), eastern hemlock (Tsuga canadensis (L.) Carrière), and Carolina hemlock (T. caroliniana Engelm. ) in the eastern United States since their introduction from Asia. They have also caused serious economic damage in Christmas tree plantations and nurseries. The Alliance for Saving Threatened Forests is engaged in research to complement other methods of adelgid control through the development of genetically...

Port-Orford-cedar (Chamaecyparis lawsoniana) has suffered high mortality from the pathogen Phytophthora lateralis in portions of its natural range in southwest Oregon and northwest California, as well as in horticultural plantings in North America, and more recently in Europe. A program to develop genetically resistant populations of Port-Orford-cedar is underway. This operational program began in 1996 and utilizes artificial inoculation of the roots of young seedlings (or rooted cuttings) to rate parent trees for resistance. A key step to any such program is to establish field trials: to...

Western white pine (Pinus monticola Douglas ex D. Don) is highly susceptible to the non-native, invasive pathogen Cronartium ribicola, the causative agent of white pine blister rust. The susceptibility of western white pine to blister rust has limited its use in restoration and reforestation throughout much of western North America. Fortunately, some genetic resistance to blister rust exists in western white pine, and several operational programs to select for resistance and develop orchards to produce resistant seed exist. These programs, such as that of the U.S. Department of Agriculture,...