Treesearch

We used aerial photography from 1954 and airborne LiDAR and imaging spectroscopy from 2008 to infer changes in extent and location of tallstature woody vegetation in 127 km2 of subalpine dry forest on the island of Hawaii (Pohakuloa Training Area), and to identify 25.8 km2 of intact woody vegetation for restoration and management. Total cover of woody vegetation was 54.7 km2 in 1954 and 58.6 km2 in 2008. Approximately 28.9 km2 underwent woody vegetation change (22.7%) between 1954 and 2008. Increases in woody vegetation cover occurred in 16.4 km2, and 12.5 km2 represented reduction of...

Anthropogenic S emissions in the Athabasca oil sands region (AOSR) in Alberta, Canada, affect SO4 deposition in close vicinity of industrial emitters. Between May 2008 and May 2009, SO4-S deposition was monitored using open field bulk collectors at 15 sites and throughfall collectors at 14 sites at distances between 3 and 113 km from one of the major emission stacks in the AOSR. At forested plots >90 km from the operations, SO4 deposition was ~1.4 kg SO4-S ha-1 yr-1 for bulk deposition and ~3.3 kg SO4-S ha-1 yr-1 for throughfall deposition. Throughfall SO4 deposition rates in the AOSR...

Non-native forest pathogens can cause dramatic and long-lasting changes to the composition of forests, and these changes may have cascading impacts on community interactions and ecosystem functioning. Phytophthora ramorum, the causal agent of the emergent forest disease sudden oak death (SOD), has a wide host range, but mortality is concentrated in a few dominant tree species of coastal forests in California and Oregon. We examined interactions between P. ramorum and its hosts in redwood and mixed evergreen forest types over an 80,000 ha area in the Big Sur ecoregion of central California,...

Phytopthora borealis and Phytophthora riparia were identified in recent Phytophthora surveys in forest streams in Oregon, California and Alaska are described as new species in Phytophthora ITS Clade 6. They are similar in growth form and morphology to P. gonapodyides and are predominately sterile. They present unique DNA sequences, however, and differ in temperature and growth relations and geographic distribution.

In this contribution we compile existing records from available sources of reliably identified Phytophthora species from forests and forest trees in Oregon, USA. A searchable version of this information may be found in the Forest Phytophthoras of the World Disease Finder (select USA-Oregon). We have included isolations from soil and streams in forests that are often not associated with any specific disease symptoms. Our goal is to inventory forest Phytophthora species, not forest diseases. On the other hand, we have included records from forest trees growing outside the forest, as Christmas...

Resistance to disease is determined by the genetic capacity of a plant to recognize and respond to a pathogen, as modified to varying degrees by the environment in which the interaction occurs. Physical factors such as temperature and moisture can limit the ability of a pathogen to infect and cause disease, and may also influence the response of the host through effects on gene expression and/or by imposing constraints on physiological activities required to deliver an effective defense. Recent research has also drawn attention to the potential for the biotic environment to modulate...

Pitch canker, caused by Fusarium circinatum, is a serious disease affecting Pinus radiata D. Don (Monterey pine) in nurseries, landscapes, and native forests. A typical symptom of pitch canker is canopy dieback resulting from girdling lesions on terminal branches (Gordon et al. 2001). More extensive dieback can result from coalescing lesions on large branches or on the main stem of the tree. The severity of disease depends, in part, on susceptibility of the individual tree. Some will suffer no more than a few infected branch tips, whereas others sustain extensive damage and may ultimately...

Results from previous studies of resistance in Norway spruce (Picea abies (L.) Karst.) to the pathogens Heterobasidion spp. show significant genotypic variation in fungal growth and spore susceptibility among Norway spruce clones. The genetic variation and the heritability are large enough for practical breeding purposes and there is no adverse correlation between Heterobasidion infection and growth traits. There is an economic incentive to use plant materials which are more resistant than those used in reforestation today. Recent research on developing the methods for testing resistance...

Studies on the relationship between rhododendron and Phytophthora ramorum include the influence of wounds on leaf infection and on the development of leaf necrosis (De Dobbelaere et al. 2010; Denman et al. 2005), the influence of the inoculum type (Widmer 2009), and tissue colonization by P. ramorum (Brown and Brasier 2007; Parke and Lewis 2007; Pogoda and Werres 2004). There are only a few studies on the development of the pathogen on the leaf surface (Moralejo and Descals 2011; Moralejo et al. 2006) and there is no information on the infection process on leaves. Therefore the aim of the...

Sudden oak death, caused by Phytophthora ramorum, has resulted in high levels of coast live oak (Quercus agrifolia Nee (CLO) mortality. However, some CLO survive in areas with high disease pressure and may thus be resistant. We tested the hypothesis that such field resistant trees contain constitutively higher levels of phenolics than susceptible trees. Phloem was sampled from the trunks of two groups of trees (one previously inoculated, one naturally infected with P. ramorum) categorized over the course of several years as putatively resistant (PR, no symptoms), in remission (IR, showed...