Treesearch

Insects that reproduce sexually must locate a suitable mate, and many species have evolved efÞcient communication mechanisms to Þnd each other. The number of reproductively viable individuals in a population can be an important constraint in the growth of populations. One factor that can affect insect fecundity is the age of mating adults, as fecundity tends to decline with age. Field observations collected annually on Lymantria dispar (L.) from 2001 to 2007 and 2009 consistently revealed a small proportion of egg masses (generally <10% in each year) in which >0 but <5% of eggs were...

The Asian chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera Cynipidae) is an invasive species in chestnut forests and orchards in many parts of the world. Nuts produced by the European chestnut (Castanea sativa Miller) are important in human food and culture, and as a component in food webs in forest ecosystems. Severe infestations are reported to reduce nut yield, although precise data are lacking because of large natural year-to-year variability in yield. The recent colonization of chestnut orchards in north-eastern Italy, where nut yield has been continuously and precisely...

The U.S. state of Maryland needs to monitor land use change in order to address land management objectives. This paper presents a change detection method that, through automation and standard geographic information system (GIS) techniques, facilitates the estimation of landscape change via photointerpretation. Using the protocols developed, we show a net loss of forest land, with losses due primarily to urban development and most gains in forest land coming from agricultural land conversions. This study indicates that about 75,000 photo plots would be needed to estimate land use change in...

Mercury contamination in wildlife has rarely been studied in the Southern Appalachians despite high deposition rates in the region. From 2006 to 2008 we sampled feathers from 458 birds representing 32 species in the Southern Appalachians for total mercury and stable isotope ä ¹⁵N. Mercury concentrations (mean ± SE) averaged 0.46 ± 0.02 ìg g⁻¹ (range 0.01–3.74 ìg g−1). Twelve of 32 species had individuals (7 % of all birds sampled) with mercury concentrations higher than 1 ìg g⁻¹. Mercury concentrations were 17 % higher in juveniles compared to adults (n =...

We examine land use planning outcomes over a 30-year period in the Portland, OR-Vancouver, WA (USA) metropolitan area. The four-county study region enables comparisons between three Oregon counties subject to Oregon’s 1973 Land Use Act (Senate Bill 100) and Clark County, WA which implemented land use planning under Washington’s 1990 Growth Management Act. We describe county-level historical land uses from the mid-1970s to the mid-2000s, including low-density residential and urban development, both outside and inside of current urban growth boundaries. We use difference-in-differences...

The physiological relationship between abiotic stress in plants and polyamines was reported more than 40 years ago. Ever since there has been a debate as to whether increased polyamines protect plants against abiotic stress (e.g., due to their ability to deal with oxidative radicals) or cause damage to them (perhaps due to hydrogen peroxide produced by their catabolism). The observation that cellular polyamines are typically elevated in plants under both short-term as well as long- term abiotic stress conditions is consistent with the possibility of their dual effects, i.e., being protector...

Four rates of aminopyralid (30, 60, 90, and 120 g ae ha-1 [0.4, 0.9, 1.3, and 1.8 oz ae acre-1]) were compared for their ability to reduce abundance of nonnative dicot species and favor native species in an invaded Cascade Mountain meadow near Trout Lake, WA. Treatments were applied in two replicated studies (June 2009 and 2010), and foliar cover and species richness were monitored for two years. First-year control of nonnative dicots from application of 30 g ae ha-1 of aminopyralid (69%) was greater than that of native dicots (29%); whereas, significant control of both species groups...

Closed-canopy, upland hardwood forests with limited understory development provide suboptimal habitat for wild turkey (Meleagris gallopavo) broods and may lead to low recruitment. Various forest management practices have been used to stimulate understory development within upland hardwoods, but evaluation of such practices on cover and food resources for wild turkey broods is incomplete. Therefore, we compared effects of 7 silvicultural treatments (repeated fire, shelterwood harvest, shelterwood harvest with one fire, retention cut, retention cut with repeated fire, retention cut with...

California spotted owls (Strix occidentalis occidentalis) (fig. 1) have been at the forefront of Sierra Nevada management and conservation debates for 25 years because of their strong habitat associations with commercially valuable large trees, snags, and late-successional forests. Initial concerns focused on the effects of timber harvest on large trees and late-successional habitat and potential risks to California spotted owl population viability. In recent years, the debate over Sierra Nevada forest management and California spotted owls has broadened with growing recognition that past...

The major pollutants causing ecological harm in the Sierra Nevada are ozone, which can be toxic to plants, and nitrogen deposition, which can induce undesirable effects on terrestrial and aquatic ecosystems. Other airborne pollutants of concern include black carbon, particulate matter (PM), pesticides, and heavy metals, including mercury. Atmospheric pollutants that are delivered in wet and dry forms cause deposition of nitrogen to forests and other land areas. The highest potential for ozone to injure plants occurs on western, low-elevation slopes that have elevated daytime levels that...