Treesearch

Recent environmental literature contains claims that livestock grazing has caused reduction in species diversity on Western rangelands. Data of species richness (number of species) is presented from inside and outside 24 long-term exclosures in Montana, Utah, and Wyoming. For the average of all exclosures there was no difference between species richness inside and outside the exclosures. Overlap of species (those found both inside and outside of the exclosures) was high (69 to 72 percent), and the species found either inside only or outside only did not reveal any trend related to grazing...

Seasonal riparian seedbed temperatures were measured and germination of Carex utriculata and C. nebrascensis seeds was tested in relation to chilling, perigynia removal, incubation temperature, and light to help guide propagation and direct seeding of these species for riparian restoration. Diurnal temperatures of riparian seedbeds at two sites in Strawberry Valley, Utah, USA ranged from 3.1 to 11.2° C in May to 9.5 to 24.1° C in August when water was generally available for seed germination. Pre-incubation treatments of chilling at 5° C for 7 to 150 days and perigynia removal increased...

Many studies have assessed genetic changes in exotic plant species in their native and introduced ranges, but none have focused on genetic variation in native plant species in response to exotic invasion. We examine characteristics of native plant communities within and outside old (>25 year) invasions of Acroptilon repens (Russian knapweed) and Cardaria draba (hoary cress). We also document genetic variability of 4 native grass populations (Hesperostipa comata [needle and thread], Achnatherum hymenoides [Indian ricegrass], Sporobolus airoides [alkali sacaton], and Poa secunda [Sandberg...

Species in biological communities respond to environmental variation simultaneously across a range of organizational levels. Accordingly, it is important to quantify the effects of environmental factors at multiple levels on species distribution and abundance. Hierarchical methods that explicitly separate the independent and confounded influences of environmental variation across several levels of organization are powerful tools for this task. Our study used a hierarchical approach to partition explained variance in an Oregon Coast Range bird community among plot-, patch-, and landscape-lev...

Multi-scale investigations of species/environment relationships are an important tool in ecological research. The scale at which independent and dependent variables are measured, and how they are coded for analysis, can strongly influence the relationships that are discovered. However, little is known about how the coding of the dependent variable set influences community-level analyses. In this study, we used canonical correspondence analysis to quantify species/environment relationships between environmental factors collected at three spatial scales and the structure of a forest bird...

Habitat loss and fragmentation processes strongly affect biodiversity conservation in landscapes undergoing anthropogenic land use changes. Many attempts have been made to use landscape structure metrics to quantify the independent and joint effects of these processes. Unfortunately, ecological interpretation of those metrics has been plagued by lack of thorough understanding of their theoretical behavior. We explored behavior of 50 metrics in neutral landscapes across a 21-step gradient in aggregation and a 19-step gradient in area using a full factorial design with 100 replicates of each...

In the northeastern United States, pitch pine (Pinus rigida Mill.)-scrub oak (Quercus ilicifolia Wang.) communities are increasingly threatened by development and fire suppression, and prioritization of these habitats for conservation is of critical importance. As a basis for local conservation planning in a pitch pine-scrub oak community in southeastern Massachusetts, we developed logistic-regression models based on multiscale landscape and patch variables to predict hotspots of rare and declining bird and moth species. We compared predicted moth distributions with observed species-occurre...

In riparian meadows, narrow zonation of the dominant vegetation frequently occurs along the elevational gradient from the stream edge to the floodplain terrace. We measured plant species composition and above- and belowground biomass in three riparian plant communities - a priori defined as wet, moist, and dry meadow - along short streamside topographic gradients in two montane meadows in northeast Oregon. The objectives were to: (1) compare above- and belowground biomass in the three meadow communities; (2) examine relations among plant species richness, biomass distribution, water table...

Pine engraver, Ips pini (Say), often use thinning slash, and their populations are known to be influenced by the condition of this material. In our study, we evaluated the importance of three log diameters (5, 10, and 20 cm) and three lengths (60, 120, and 240 cm) on various parameters of bark beetle host attack, development, and emergence. Evaluation of slash colonization in northern Arizona (near Flagstaff) and western Montana (near Missoula) over several years, during both spring and summer reproductive periods, indicated that the size of material selected by pine engraver differed by...

The success or failure of range restoration and revegetation programs depends on procurement of an adequate supply of quality grass, forb, and shrub seed. Rangeland species seed is either grown commercially or collected from wildland stands. Commercially produced seed of numerous grass species is available (Asay and Knowles 1985b; Horton and others 1990; Sours 1983). A few site-specific grass species of limited commercial demand are collected from native stands, but in general the seed of most grasses are grown under cultivation. The latter is not true for many forbs, or most shrubs. Seed...