Treesearch

To evaluate impacts of competitive conditions in tree neighborhoods on growth responses as influenced by moisture availability and local environmental conditions, we sampled 102 codominant 40- to 70-year-old coastal Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) in regions with relatively high and low moisture availability. We quantified local environmental conditions (topographic position index, heat load, and soil depth), and the annual basal area increment and climate moisture deficits during two growth periods: a five-year period prior to commercial thinning and years six to 10...

Ecosystem process models can be used to predict forest response to disturbances at a range of scales. Selection of the spatial class of model should depend on the scale of the research or management question, and model type should depend on the ecosystem attributes of interest. In some cases, multiple classes of models could be used to address a single research question, with evaluations at each scale having potential benefits and drawbacks. This study examines two classes of models relative to how fire return intervals impact carbon and species dynamics in a southeastern U.S....

The Round Hickorynut, Obovaria subrotunda, is declining throughout its range, but little life history information exists for the species. We examined host use and glochidial size in Buck Creek (Cumberland River drainage) and the Licking River (Ohio River drainage), Kentucky, and we examined age and growth in Buck Creek. Glochidia of O. subrotunda from Buck Creek metamorphosed on five darter species (Percidae)—Etheostoma baileyi, Etheostoma blennioides, Etheostoma gore, Etheostoma variatum, and Percina stictogaster—but not on 43 other fish species from nine families; host use was broadly...

Two new species of Bimastos Moore are described based on morphological and molecular data. Bimastos nanae n. sp. resembles B. lawrenceae Fender, B. zeteki (Smith and Gittins) and B. welchi (Smith). Bimastos nanae n. sp. differs from these species in the position of the clitellum, size and number and position of thickened septa. Bimastos magnum n. sp. is similar to B. schwerti Csuzdi & Chang and B. palustris Moore in having a fully annular clitellum and male pores on huge porophores. Bimastos magnum n. sp. differs from both species by having a more posterior position of the clitellum (in...

The widespread use of nitrogen chemical fertilizers in modern agricultural practices has raised concerns over hazardous accumulations of nitrogen-based compounds in crop foods and in agricultural soils due to nitrogen overfertilization. Many vegetables accumulate and retain large amounts of nitrites and nitrates due to repeated nitrogen applications or excess use of nitrogen fertilizers. Consequently, the consumption of high-nitrate crop foods may cause health risks to humans. The effects of varying urea–nitrogen fertilizer application rates on VOC emissions from cucumber fruits were...

Floodplain forests provide valuable ecosystem services, yet human activity has degraded many of these riverine systems. Previous investigations of floodplain forest composition have frequently focused on flooding without incorporating successional dynamics; however, their restoration requires understanding both. We investigated floodplain forest composition along both flooding and succession gradients. River meandering builds new floodplain land with a variable microtopography and diverse levels of flood exposure. We compared vegetation to floodplain land ages on chronological sequences....

Globalization has undeniably impacted the Earth’s ecosystems, but it has also influenced how we think about natural systems. Three fourths of the world’s forests are now altered by human activity, which challenges our concepts of native ecosystems. The dichotomies of pristine vs. disturbed as well as our view of native and non-native species, have blurred; allowing us to acknowledge new paradigms about how humans and nature interact. We now understand that the use of militaristic language to define the perceived role of a plant species is holding us back from the fact that novel systems...

The use of indicator species can simplify bird monitoring by reducing the level of specialized skills needed, which increases the potential pool of participants and reduces training costs and complexity. To facilitate monitoring in the humid forests of northeast Central America, we conducted point count surveys for birds across gradients of disturbance in the Cockscomb Basin Wildlife Sanctuary, Belize, and analyzed the association of bird species with remotely sensed metrics of forest condition and anthropogenic disturbance using indicator species analysis. Twenty species exhibited...

Aims. Climate warming in northern ecosystems is triggering widespread permafrost thaw, during which deep soil nutrients, such as nitrogen, could become available for biological uptake. Permafrost thaw shift frozen organic matter to a saturated state, which could impede nutrient uptake. We assessed whether soil nitrogen can be accessed by the deep roots of vascular plants in thermokarst bogs, potentially allowing for increases in primary productivity. Methods. We conducted an ammonium uptake experiment on Carex aquatilis Wahlenb. roots excavated from thermokarst bogs in interior Alaska....