Treesearch

Hawaiian dry forests currently occupy a small fraction of their former range, and worldwide tropical dry forests are one of the most human-altered systems. Many small-scale projects have been successful in restoring native dry forests in abandoned pastures and degraded woodlands by outplanting after invasive species removal, but this is a costly approach. In this project, we tested forest restoration techniques involving broadcasting seeds pretreated to enhance germination and applying herbicide to reduce non-native grass competition. We compared three treatments: broadcast seeding,...

Oceanic islands are good model systems with which to explore factors affecting exotic species diversity. Islands vary in size, topography, substrate type, degree of isolation, native species diversity, history, human population characteristics, and economic development. Moreover, islands are highly vulnerable to exotic species establishment. We used AICc analyses of data on 1132 vascular plant species for 15 countries and 114 islands from the Pacific Island Ecosystems at Risk (PIER) project to examine biological, geographical, and socioeconomic correlates of exotic species richness. PIER...

Variations in disturbance regime strongly influence ecosystem structure and function. A prominent form of such variation is when multiple high-severity wildfires occur in rapid succession (i.e. short-interval (SI) severe fires, or ‘re-burns’). These events have been proposed as key mechanisms altering successional rates and pathways. We utilized a natural experiment afforded by two overlapping wildfires occurring within a 15-year interval in forests of the Klamath–Siskiyou Mountains, Oregon (USA). We tested for unique effects of a SI fire (15-year interval before 2002 fire) by comparing...

Three species of mangrove crabs (Scylla spp.) were captured in live traps in Ngaremeduu Bay on the island of Babeldaob, Republic of Palau. Most were S. serrata, but one individual each of S. olivacea and S. paramamosain was also trapped, establishing existence of a biogeographic gradient in mangrove crab species diversity across the Micronesian archipelago. Species composition of mangrove trees along transects around the bay and along the three major tributaries was similar to that of other Micronesian islands, although trees are smaller in Palau. For 17 months in 1999–2000, crabs were...

Fire is a widespread natural disturbance agent in most conifer-dominated forests. In light of climate change and the effects of fire exclusion, single and repeated high-severity (stand-replacement) fires have become prominent land management issues. We studied bird communities using point counting in the Klamath-Siskiyou ecoregion of Oregon, USA at various points in time after one or two high-severity fires. Time points included 2 and 3 years after a single fire, 17 and 18 years after a single fire, 2 and 3 years after a repeat fire (15 year interval between fires), and >100 years since...

A removal experiment was used to examine the restoration potential of a lowland wet forest in Hawaii, a remnant forest type that has been heavily invaded by non-native species and in which there is very little native species regeneration. All non-native woody and herbaceous biomass (approximately 45% of basal area) was removed in four 100-m² removal plots; plots were followed for a three-year period. Removal plots had a lower leaf area index, higher air temperatures, higher afternoon soil temperatures, and lower relative humidity than control plots. Removal plots had 40% less litterfall...

Pathogen epidemiology, community ecology of host species, and land use history all play major roles in the current distribution of Phytophthora ramorum and the extent of damage this pathogen has caused in California forests (Rizzo and others 2005, Meentemeyer and others 2008b). Research on the community ecology and the interaction of community composition and disease intensity will help enable synthesis of management actions at the stand level and reduce rates of infection, mortality, and fuel accumulation. Disease and mortality of tanoak (Lithocarpus densiflorus) are patchy across...

The Phytophthora ramorum eradication program in effect in Oregon has allowed for the rapid detection of new infection foci, typically before they develop within each stand and expand into adjacent sites. Yet despite gallant efforts, new locations that previously harbored no apparent infection have been identified each year since the original detection in 2001. Multiple factors may influence why and where each new infection occurs including, but not limited to, stand characteristics such as dominant understory and upper canopy vegetation, age and stem density (which influence microclimate...

The important quarantine organism Phytophthora ramorum has been dramatically increasing its host range in the past years and most of the studies concerning P. ramorum focus on these issues. Very little is known about the latency period. For sampling and analyzing potentially infected plant material, detailed information on the latency of the disease is of high importance. In order to provide such a tool for the infection process follow-up, we established a reliable method for the stable genetic transformation of P. ramorum isolates. The transferred genes were the marker gene nptII for...

Phytophthora kernoviae and Phytophthora ramorum, two pathogens recently introduced to the U.K., incite foliar lesions, shoot necrosis, and death of Rhododendron ponticum, an invasive weed pervading U.K. woodlands. In infested woodlands, R. ponticum serves as an epidemiologically important host, supporting sporulation of both pathogens. Bleeding cankers on trunks of European beech (Fagus sylvatica) caused by either P. ramorum or P. kernoviae are often associated with neighboring infected R. ponticum. Rhododendron ponticum has been removed from several woodlands as an inoculum management...