Treesearch

We assessed spider (Arachnida: Araneae) responses to prescribed fire following stand s tructure treatments in ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) stands in the Cascade Range of California. Stands were logged or left untreated to create three levels of structural diversity. We logged one treatment to minimize old-growth characteristics (low diversity) and one to enhance old-growth characteristics (high diversity) and we used unlogged Research Natural Areas (RNAs) as old-growth, highest-diversity reference stands. We conducted low-intensity prescribed fire on half of...

Coneworms of the genus Dioryctria Zeller include several serious pests of conifer seeds that are notoriously difficult to distinguish as species. We surveyed mitochondrial DNA variation within the abietella species group by sequencing 451 bp of cytochrome oxidase subunit 1 (COI) and 572 bp of cytochrome oxidase subunit 2 (COII) genes from 64 individuals of six major species in the group. In addition to examining phylogenetic relationships within European members of the group, the study focused on the two most damaging species, D. abietivorella Grote from North America and D. abietella...

The majority of Hawaii's lowland wet forests no longer exist, with many of the last remaining patches found on the eastern, windward sides of the largest islands. To better understand successional patterns and invasion in these native systems, we quantified basal area (BA) and densities of woody species and understory cover at nine sites in the Puna district on the Island of Hawaii, representing age gradients of native stand development on both ‘a‘ä and pähoehoe lava flows. On both flow types, BA of native species increased (from 5 to 50 m2/ha) and stem densities decreased (from 3700 to...

Ecological invasions are amajor driver of global environmental change. When invasions are frequent and prolonged, exotic species can become dominant and ultimately create novel ecosystem types. These ecosystems are now widespread globally. Recent evidence from Puerto Rico suggests that exoticdominated forests can provide suitable regeneration sites for native species and promote native species abundance, but this pattern has been little explored elsewhere. We surveyed 46 sites in Hawai’i to determine whether native species occurred in the understories of exotic-dominated forests. Native...

Objectively assessing the performance of a model and deriving model parameter values from observations are critical and challenging in landscape to regional modeling. In this paper, we applied a nonlinear inversion technique to calibrate the ecosystem model CENTURY against carbon (C) and nitrogen (N) stock measurements collected from 39 mature tropical forest sites in seven life zones in Costa Rica. Net primary productivity from the Moderate-Resolution Imaging Spectroradiometer (MODIS), C and N stocks in aboveground live biomass, litter, coarse woody debris (CWD), and in soils were used to...

Plants influence soil carbon (C) formation through the quality and quantity of C released to soil. Soil type, in turn can modify a plant's influence on soil through effects on plant production, tissue quality and regulation of soil C decomposition and stabilization. Wild-type aspen and three transgenic aspen lines expressing reduced stem lignin concentrations and/or increased syringyl (S) to guaiacyl (G) ratio lignin were grown in greenhouse mesocosms containing a sandy loam, a silt loam, or a clay loam soil for 6 months in order to examine the effects of altered lignin biosynthesis and...

This chapter presents a stated preference technique for estimating the public benefits of reducing wildfires to residents of California, Florida, and Montana from two alternative fuel reduction programs: prescribed burning, and mechanical fuels reduction. The two fuel reduction programs under study are quite relevant to people living in California, Florida, and Montana becasue of these state's frequent wildfires. The methodological approach demonstrated here has broad applicability to other fire prone areas of public land as well.

Green mountains wrapped in clouds are a reassuring sight on islands across the Pacific. These forested highlands catch the water that humans depend on, and can preserve a rich diversity of life. Sadly, although green, many island forests are far from healthy. Among the greatest threats to native forests in Hawaii is the invasive tree, strawberry guava.

In the tropics, exotic plants have been widely introduced for industrial timber, for land reclamation and forage crops, and as ornamentals. In spite of the apparent opportunity for naturalization and spread, invasive exotic plants are scarce in many continental tropical forests. We examine several conditions under which exotic species do pose substantial threats to toprical ecosystems or to their management.

Islands support many more species of invasive plants than comparably sized mainland habitats. Analysis of extensive data on the distribution of invasive plants among Pacific islands suggests that the diversity of these species on islands is a function of both environmental characteristics (island size, habitat heterogeneity) and socioeconomic conditions (country identity, per capita gross domestic product, presence of airports with paved runways, human population size and density). The spread and impact of invasive species on islands also are likely affected by the juxtaposition of...