Treesearch

We studied the effects of Cistus albidus leaf leachates on nitrogen-cycling processes in two siliceous soils (granite and schist) and one calcareous soil. We compared those effects with gross N-transformation rates in soils sampled underneath Cistus. Our results show that although phenolic compounds leached from green foliage changed gross N mineralization, their effects on net N rates were eclipsed by the changes produced by polar nonphenolic compounds such as carbohydrates. Plant nonphenolic compounds may drive N cycling under Cistus.

Scientific understanding of how urban trees, forests and green space benefit people has expanded substantially in recent years to include social, environmental and economic domains. Despite increasing scientific evidence, there is a lag in policy response in many municipalities.

As a National Main Street program participant, Athens, Georgia, U.S., has included streetscape tree plantings in economic development efforts. The Main Street program assists downtown merchant groups with physical improvements planning in order to create vital retail environments. If comprehensively managed, the urban forest can be a beneficial long-term improvement. Nonetheless, business people and merchants often have negative perceptions about trees (such as debris and reduced sign visibility) and may influence local policy and budget support for urban forest programs. This study...

Biometric techniques were used to measure net ecosystem production (NEP) across three climatically distinct forest chronosequences in Oregon. NEP was highly negative immediately following stand-replacing disturbance in all forests and recovered to positive values by 10, 20, and 30 years of age for the mild mesic Coast Range, mesic West Cascades, and semi-arid East Cascades, respectively. The response of stand-level NEP to individual disturbance events is greater than that attributable to edaphoclimatic differences between forest type. However, regional age class distributions are such that...

Sets of flow events from four catchments were selected to study how dynamics in the conversion of effective rainfall into streamflow depends on the event size. The approach taken was to optimize parameters of a linear delay function and effective rainfall series concurrently from precipitation streamflow data without imposing a functional form of the precipitation filter a priori. The delay function is an instantaneous unit hydrograph (IUH) having a mathematical form of the two-parameter gamma distribution. Results from two small research catchments (0.18 and 0.63 km2) with subdaily data...

Northern and high-latitude alpine treelines are generally thought to be limited by available warmth. Most studies of tree-growth-climate interaction at treeline as well as climate reconstructions using dendrochronology report positive growth response of treeline trees to warmer temperatures. However, population-wide responses of treeline trees to climate remain largely unexamined. We systematically sampled 1,558 white spruce at 13 treeline sites in the Brooks Range and Alaska Range. Our findings of both positive and negative growth responses to climate warming at treeline challenge the...

This research was conducted to develop a better understanding of the problems and opportunities confronting U.S. wood window manufacturers in the post and beam segment of the Japanese residential construction industry. The specific objectives of this research were to (1) provide a description of the Japanese market for wood windows; (2) survey Japanese builders regarding use and specification of wood windows, both domestic and imported; and (3) recommend strategies for increasing the competitiveness of U.S. wood windows in the Japanese post and beam market. To obtain primary information on...

Alaska birch lumber is often characterized by small knots and other character defects that can reduce its value when graded according to conventional hardwood lumber-grading rules. In this study, 626 boards (2,782 board feet of lumber) were graded; first according to standard National Hardwood Lumber Association (NHLA) rules, and then a second time using an alternative rule that did not consider defects less than 0.5 inch in diameter to be grade-reducing defects. Mill locations included two sites in interior Alaska and two sites in south-central Alaska. With the alternative grading rule,...

Although most North American firms reported a decline in export revenues from Japan over the period 1997 to 1998, some firms experienced increases. This anomaly prompted an investigation into why some firms were successful in increasing their exports while other firms were not. The primary objective of this study was to identify the key characteristics of successful exporters. The study was a census of firms involved in the export of wood building materials to Japan from the Pacific Northwest (Washington, Oregon, and British Columbia). A combination mail/fax survey was used to collect...

Seed movement guidelines for restoration activities are lacking for most native grasses, forbs, and shrubs. The forestry community has decades of experience in establishing seed zones and seed movement guidelines that may be of value to restoration managers. We review the history of seed zone development in forest trees, with emphasis on the Pacific Northwest, and make some suggestions concerning seed transfer guidelines for other native plants.