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941.
In this study, I examined the composition of managed ponderosa pine ( Pinus ponderosa ) forests used by nesting White-headed Woodpeckers ( Picoides albolarvatus ) along the eastern slope of the Cascade Range in Washington. I sampled trees and snags using the point-centered quarter method to assess species composition, tree and snag density, and stand basal area in 16 forest stands containing White-headed Woodpecker nests. All stands had a history of timber management and 2 had been burned and salvage-logged. Mean live-tree density (≥10.16 cm dbh) was 182.3 trees · ha –1 (SE = 13.52), mean snag density (≥10.16 cm dbh) was 11.5 snags · ha –1 (SE = 1.92), and mean stand basal area was 17.2 m 2 · ha –1 (SE = 1.58). Ponderosa pine had the highest importance value (mean = 220.9, SE = 17.25) of any tree species in all but 2 stands. Mean dbh of ponderosa pines was 33.0 cm (SE = 0.26) and ranged from 26.1 to 50.2 cm within stands. Mean density of ponderosa pine was greatest in the 20.3–30.5 cm dbh size class and lowest in the 50.8–61.0 cm and >61.0 cm dbh size classes. Tree density was up to 5.3 times greater than densities believed to be typical of ponderosa pine forests prior to fire suppression. Snag densities were within the range estimated for historical dry forests of the eastern Cascades, yet only 50% of all snags sampled had a dbh >25.4 cm. Although White-headed Woodpeckers are considered strongly associated with old-growth ponderosa pine, my results suggest that they may be more adaptable to using forests dominated by smaller diameter trees. En este estudio, examiné la composición de los bosques manejados de pino ponderosa ( Pinus ponderosa ), utilizados para anidamiento por el pájaro carpintero cabeciblanco ( Picoides albolarvatus ), a lo largo de la vertiente oriental de la cordillera Cascade del Estado de Washington. Muestreé árboles vivos y muertos usando el método de cuadrantes al punto central en 16 rodales con nidos del pájaro carpintero cabeciblanco para evaluar la composición de especies, la densidad de árboles vivos y muertos y el área basal del rodal. Todas las áreas tenían una historia de manejo maderable y 2 habían sido quemadas y taladas para recuperar madera. La densidad promedio de árboles vivos (≥10.16 cm DAP) fue 182.3 árboles · ha –1 (DE = 13.52), la densidad promedio de árboles muertos (≥10.16 cm DAP) fue 11.5 árboles muertos · ha –1 (DE = 1.92) y el área basal promedio de los rodales fue 17.2 m 2 · ha –1 (DE = 1.58). El pino ponderosa tuvo el valor de importancia más alto (promedio = 220.9, DE = 17.25) de las especies de árboles en todos, menos 2 rodales. El DAP promedio de los pinos ponderosa fue 33.0 cm (DE = 0.26) y variaba de 26.1 a 50.2 cm dentro de rodales. La densidad promedio del pino ponderosa fue la mayor en la clase de 20.3–30.5 cm DAP y menor de las clases de 50.8–61.0 cm y >61.0 cm DAP. La densidad de árboles fue hasta 5.3 veces mayor que las consideradas típicas para bosques de pino ponderosa antes de la intervención para prevenir incendios. Las densidades de árboles muertos estuvo dentro del rango estimado para los bosques secos históricos del oriente de la cordillera Cascade, no obstante sólo 50% de los árboles muertos muestreados tuvieron un DAP >25.4 cm. Aunque se considera que los pájaros carpinteros cabeciblancos están estrechamente asociados con bosques primarios de pino ponderosa, mis resultados sugieren que podrían ser más adaptados a usar bosques donde predominan árboles de diámetro menor.  相似文献   
942.
The genus Capnia in North America is reviewed and compared to other genera in the family. The genus is divided into 10 species groups. A key to the 51 species of Capnia in North America is given along with a listing of type localities, type repositories, diagnoses, and distributions. New illustrations of structures bearing characters important for identification and classification are presented. An annotation of the list of Capnia of North America given by Stark, Szczytko, and Baumann (1986) reflecting current generic placement of species is produced. From this list Capnia bakeri and sugluka are moved to Mesocapnia . Capnia barbata Frison is placed in synonymy under Capnia decepta . The movement of cygna (synonym of venosa ), elevata, fibula, manitoba, venosa , and wanica to Capnura (Nelson and Baumann, 1987b) is noted. Capnia disala and ensicala are placed in Paracapnia .  相似文献   
943.
Variation in kit fox ( Vulpes macrotis ) population parameters can be influenced by vegetative cover and the distribution and abundance of other predator and prey species. Dramatic changes to Great Basin Desert habitats, which can potentially impact mammalian species, have occurred in some areas in Utah. We examined kit fox demographics and prey populations from 1999 to 2001 on Dugway Proving Ground (DPG), a U.S. Army facility in Utah, and compared some parameters to historical levels (1956–1958, 1966–1969). Adult survival rates were fairly consistent between 1999 and 2000 and between 1999 and 2001; however, survival was greater in 2001 than in 2000. Reproductive rates ranged from 1.0 to 3.8 pups per female in 1999–2000 and were similar to historical numbers (1.0–4.2 pups per female). We found a decrease in pre-whelping kit fox density from the 1960s (0.12 foxes ? km –2 ) to 1999–2001 (0.04 foxes ? km –2 ); however, densities were similar between the current study and the 1950s (0.08 foxes ? km –2 ). Using 9 years of data, we found density dependence between reproductive rates of the current year and annual fox density from the previous year. Using 7 years of data, we found a slight correlation between kit fox annual density and a 1-year lag in leporid abundance, even though leporid abundance was lower during the present study than it was historically. Compared to historical levels, current small mammal abundance and species composition has changed in several habitats. Kit fox breeding density and annual density were inversely correlated with coyote ( Canis latrans ) density. Changes to the landscape at DPG, especially due to invasion of cheatgrass ( Bromus tectorum ) and addition of artificial water sources, have caused a change in available kit fox habitat and prey species, and have increased the abundance of coyotes, the kit fox's major competitor.  相似文献   
944.
The herbaceous understory stratum contains most of the plant diversity in ponderosa pine ( Pinus ponderosa P. & C. Lawson var. scopulorum Engelm.) forests of the American Southwest and provides critical food and habitat for many wildlife species. During the last century, this stratum has been affected by livestock grazing and by increased dominance of overstory trees. We sampled a unique grazing exclosure to examine the relative importance of long-term livestock grazing (grazed or ungrazed) and habitat (park or tree) on the understory community. We sampled 3 plots of 192 contiguous quadrats (each quadrat 0.5 m 2 ) in each of the 4 treatment combinations, for a total of 2304 quadrats. Species-area curves were generated by aggregating quadrats into nonoverlapping areas at grain sizes of 0.5 to 576 m 2 . The effects of habitat and grazing on species density were evident at very different scales. Species density was higher in park than tree plots at scales ≤32 m 2 but did not differ between habitats at larger scales. Species density differed minimally between grazed and ungrazed treatments at small grains, but grazed plots contained more species than ungrazed plots at larger grains. Grazing treatments differed at smaller grains (to 4–8 m 2 ) than did habitats (to 32 m 2 ), with respect to density of native species and graminoids. Grazed plots had more exotic species than ungrazed plots at all grain sizes, though few exotics were present. Twenty-two species were identified as indicator species associated with habitats and/or grazing treatments. Evaluations of plant community response to treatments would be improved by accounting for the grain at which data have been collected and analyzed and by identifying indicator species associated with various treatments. These data would enable more-informed conservation and management decisions.  相似文献   
945.
The Black Hills of South Dakota and Wyoming are an insular mountain range completely surrounded by the Great Plains. The stonefly (Plecoptera) fauna of the Black Hills was surveyed and zoogeographic affinities examined. Twenty-seven species representing 22 genera and 6 families were found. Fifteen new state records for South Dakota and 2 for Wyoming are presented. Two species are removed from the South Dakota list. An analysis of the North American distribution of each species showed a strong relationship between the Black Hills and the Rocky Mountains, with much weaker relationships between the Black Hills and eastern and northern regions. Results of a logistic regression analysis comparing factors contributing to long-distance dispersal ability against presence/absence in the Black Hills were inconclusive. However, other evidence suggests that the Black Hills fauna is a result of expansion and subsequent vicariance of stonefly populations during Pleistocene climatic oscillations.  相似文献   
946.
The floristic composition of Navajo National Monument is presented. The flora of the monument consists of 293 species of vascular plants, representing 177 genera and 66 families. The species are scattered throughout 12 plant communities found within the monument. The flora is dominated by forbs (60 percent), followed by shrubs (16 percent), grasses (12 percent) and trees (5 percent). Betatakin canyon exhibits the greatest floristic richness with 223 species being represented and 123 species found only in that area. This is due primarily to two factors: (1) the greater variety of habitats available in the area, and (2) the much longer time the area has been protected from grazing and other manmade disturbance.  相似文献   
947.
Graphs allowing interconversion between various physical chemical parameters are presented for five Artemia habitats in the western USA. Both the mean osmosity and its typical yearly range differ greatly among habitats. Consequently, Artemia populations provide an interesting opportunity to study physiological and life history adaptations to differing degrees of habitat stability.  相似文献   
948.
The new, presumably extinct species, Chrysothamnus pulchelloides, is formally described and illustrated. The plant materials came from Holocene packrat middens. Anatomical and phyletic relationships of the fossil species to extant taxa are discussed.  相似文献   
949.
An expression of Centaurium namophilum (Gentianaceae), long confused with C. exaltatum in the Great Basin of the western United States, is described and designated as var. nevadense. It may be separated from the Death Valley region endemic, var. namophilum, by its broader leaves, its diffuse corymbose cyme, the ultimate peduncles that are longer than the flowers, its medium to deep rose pink corolla, and its stamens that equal or exceed the style and are only slightly exserted from the corolla-tube. The var. nevadense occurs from eastern California to western Utah, and from southeastern Oregon and adjacent Idaho south to the northern Mojave Desert of southeastern California. Centaurium exaltatum may be distinguished from the new variety by its broader, more elliptical leaves, dichotomous peduncles, paler pink or bluish and generally four-merous flowers, shorter and more blunt corolla lobes, and a thicker, more included style and stigma.  相似文献   
950.
Reproduction in L. pyromelana infralabialis Tanner is reported. Eggs were measured and weighed and incubation time and hatching reported. Hatchlings were measured and weighed, and feeding was observed.  相似文献   
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