Treesearch

Objective methods to evaluate hardwood competition in young loblolly pine (Pinustaeda L.) plantations are not widely used in the southeastern United States. Ability of common sampling rules to accurately estimate hardwood rootstock attributes at low sampling intensities and across varying rootstock spatial distributions is unknown. Fixed area plot, polyareal plot, and Batcheler's triple-point distance sampling estimators of hardwood rootstock density, total height, and crown area were evaluated using computer simulation. Rootstock age, density, and spatial pattern combinations defined 24...

A total of 22 loci were assayed in several populations of Abies cephalonica, A. borisii regis, A. bornmuelleriana and A. alba using horizontal starch gel electrophoresis. Within and between-population diversity were analyzed as well as between-species diversity. Mean expected heterozygosity was high and ranged between 0.175 and 0.290. The percentage of loci polymorphic was also very high, from 52.9 to 87.5. All populations except the A. borisii regis provenance were either at equilibrium or significantly deficient in heterozygotes, which suggests a certain level of inbreeding. Some alleles...

The fraction of pool volume filled with fine sediment (usually fine sand to medium gravel) can be a useful index of the sediment supply and substrate habitat of gravel-bed channels. It can be used to evaluate and monitor channel condition and to detect and evaluate sediment sources. This fraction (V*) is the ratio of fine-sediment volume to pool water volume plus fine-sediment volume. These volumes are computed for the residual portion of the pool that lies below the elevation of the downstream riffle crest. Fine-sediment thickness is measured by driving a graduated metal probe into a...

Sites in meadows of the Sierra Nevada near Fresno, California, were studied to learn whether Bolander's (Trifolium holanderi Gray.), longstalked (T. longipes Nutt.), carpet (T. monanthum Gray.), and mountain (T. wormskioldii Lehm.) clovers occurred under the same soil acidity, temperature, and water conditions. In selected meadows, along transects within its community, 20 plants of a clover species were randomly selected. Due to a small population, only 10 plants of mountain clover were selected in one community. In soil next to each plant, soil temperature was measured at the l0-cm depth,...

Plant species diversity refers to variety and abundance; it does not necessarily relate to meadow health but may provide information important in an ecosystem context. Monitoring to detect change in diversity usually begins with estimating alpha (within) diversity of plant communities. Because few such estimates exist for meadow site classes or specific sites of the Sierra Nevada, California, we computed Margalef's diversity index (Dm), which stresses species richness, and Simpson's index (Ds), which stresses species dominance, for two sets of frequency data. Frequency was estimated by the...

The concepts and a procedure for evaluating plant community change using the squared Euclidean distance (SED) resemblance function are described. Analyses are based on the concept that Euclidean distances constitute a sample from a population of distances between sampling units (SUs) for a specific number of times and SUs. With different times, the distances will be intracluster or intercluster. Intercluster distances represent a control treatment. If the communities differ between times, the population will contain clusters (regions of high density with short distances between SUs) that...

Forest trees meet human needs and contribute to natural ecosystems in unique and diverse ways. As a source of fuel and fiber, they are important commodities. As dominant members of many natural ecosystems, they play keystone ecological roles in plant and animal communities. As habitat for other organisms, forests are a reservoir of great natural diversity. In themselves, trees contribute taxonomic diversity through a wealth of species, from rare to widespread and through great genetic diversity within species. Forests.purify water and cleanse the atmosphere. And, to increasingly crowded...

Visitors to southern California National Forests are urban dwellers and as a group are culturally diverse. To manage the National Forests for this diverse group of visitors, information is needed on their expectations, preferences, and experiences at recreation sites. To evaluate visitor perceptions of crowding and discrimination, to determine favorite activities, and to determine the potential of visitor displacement from recreational sites, observations and surveys were collected during July and August 1990 in two of the National Forests. Racial and ethnic groups were categorized into...

Growth patterns of vertical stems in nine ponderosa pines from a stand in the southern Sierra Nevada were analyzed for recent changes due to stand dominance position, age, climate, and ozone exposure. Large positive correlations were found between increments in volume growth and basal area at d.b.h. The results indicated that patterns of wood distribution along the bole were associated with age, competitive position, and release from competition. A multiple regression model using winter and spring precipitation adequately explained short-term growth fluctuations during 1920-1955 and...

Relatively little is known about the earthworm fauna of southern California. Some 20 different species of earthworms were collected and identified in a survey of various southern California wildland habitats. The ecology and biology of earthworms are outlined, and the results of the survey are documented. Introduced species belonging to the Lumbricidae family were encountered most often; however, native species, primarily of genera Argilophilus and Diplocardia, are widely distributed. Several of the natives collected are believed to be new species. Habitats for both the native and introduce...