Treesearch

Eucalyptus is the most widely planted hardwood crop in world-wide tropical and subtropical regions because of its high growth rate, broad adaptability, and multipurpose wood properties. Until the 1970s, the Eucalyptus plantations in Brazil were practically disease free. However, plantations have continued to expand into warmer and more humid areas that are more favorable to pathogen infection. Furthermore, the use of high-yielding genotypes with unknown disease resistance, the implementation of clonal forestry, and the introduction of new management techniques have favored the emergence of...

Research activities aimed at developing resistance to pests (insect, pathogens, mammals) in forest trees can be documented back over 5 decades. While a substantial body of research has been published on resistances in forest trees, not much of this work has made its way into applied tree improvement programs. There are several reasons for this, e.g.: (i) a new or interesting incursion is noticed, and studies are developed that work on materials not related to a breeding program; (ii) adequate infection or artificial inoculation techniques are too expensive and a large enough population...

The different plant defenses existing within a given taxon have been commonly assumed to trade-off among each other because of both evolutionary and physiological reasons. The higher the efficiency of a single defensive trait, the lower selective pressure for other redundant defenses expected. On the other hand, production of multiple defenses might be constrained by the resources required for maintaining, at a time, increased growth and reproductive rates. However, different defensive traits do not need to always be redundant, and plants require the combination of multiple defenses to...

Individual papers are available at https://www.fs.usda.gov/psw/publications/documents/psw_gtr240/ The Fourth International Workshop on the Genetics of Host-Parasite Interactions in Forestry: Disease and Insect Resistance in Forest Trees provided a forum for research and management options and successes which have occurred over the last 30 years (the previous workshop was held in 1980 in Wageningen, The Netherlands). Eighty-eight submissions from oral and poster presentations at the 2011 workshop held in Eugene, Oregon provide a worldwide, comprehensive update on many aspects of research...

1. The objective of this study was to identify longitudinal distribution patterns of large migratory fish species in the Uruguay River basin, southern Brazil, and construct statistical distribution models for Salminus brasiliensis, Prochilodus lineatus, Leporinus obtusidens and Pseudoplatystoma corruscans. 2. The sampling programme resulted in 202 interviews with old residents and fishermen at 167 different sampling sites in the major rivers of the basin. Interviewees were asked whether these fish species were present in the nearby river segment, recently or in the past. The average age of...

Large scale, high-severity fires are increasing in the western United States. Despite this trend, there have been few studies investigating post-fire tree regeneration. We established a study in the footprint of the 2000 Storrie Fire, a 23,000 ha wildfire that occurred in northern California, USA. We used a stratified sampling design to quantify post-fire vegetation dynamics across four levels of burn severity and three forest types on the Lassen National Forest nine and ten years following fire. Within each sampled stand, we recorded tree seedlings, forest overstory, shrub cover, and...

Anthropogenic climatic change can no longer be considered an abstract possibility. It is here, its effects are already evident, and changes are expected to accelerate in coming decades, profoundly altering wilderness ecosystems. At the most fundamental level, wilderness stewards will increasingly be confronted with a trade-off between untrammeled wilderness character and primeval, natural conditions, accompanied by increasing impetus for management intervention. Possible strategic responses to climatic change fall into four broad classes: restraint (do nothing), resilience, resistance...

The walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae, sensu Wood 2007), was first described from specimens collected in 1896 in Grant Co., New Mexico (Blackman 1928). Bright (1981) and Wood & Bright (1992) reported a distribution for P. juglandis that included Arizona, California, and New Mexico in the U.S. and Chihuahua in Mexico. Cranshaw (2011) described the recent expansion of the range of P. juglandis to include the western U.S. states of Colorado, Idaho, Oregon, Utah, and Washington, as well as the eastern U.S. state of Tennessee.

By measuring and analyzing larval head capsule widths, we determined that a northern California population of the walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), has three larval instars. We also developed rules to classify P. juglandis larval instars. Overlap in the ranges of widths among consecutive instars was addressed by fitting a distribution model to the data and determining limits for head capsule width classes and probabilities of instar misclassification. Growth ratios for laboratory and field samples of P. juglandis were consistent with the...

The diurnal flight response of the walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), was assessed during two seasonal periods at two sites in northern California. Males and females flew primarily at dusk in response to aggregation pheromone-baited traps during late June/early July, and the percentage of beetles that flew between sunrise and late afternoon was positively correlated with the temperature at 6 AM of that day. Between late August and early November, the diurnal flight pattern was more varied and generally bimodal, though approx. 42 to 55% of the...