Aspen is considered a keystone species, and aspen communities are critical for maintaining biodiversity in western landscapes. Inventories of aspen stand health across the Eagle Lake Ranger District (ELRD), Lassen National Forest, California, U.S.A., indicate that 77% of stands are in decline and at risk of loss as defined by almost complete loss of mature aspen with little or no regeneration. This decline is due to competition from conifers establishing within aspen stands as a result of modification of natural fire regimes coupled with excessive browsing by livestock. Restoration treatments were implemented in four aspen stands in 1999 using mechanical equipment to remove competing conifers to enhance the growth environment for aspen. Recruitment and establishment of aspen stems were measured in treated stands (removal of competing conifers) and non-treated stands (control) immediately prior to treatment and 2 and 4 years post-treatment. There was a significant increase in total aspen stem density and in two of three aspen regeneration size classes for treated stands compared to controls. Pre-treatment total aspen density was positively associated with total aspen density and density in all size classes of aspen (p < 0.001). The results demonstrate that mechanical removal of conifers is an effective treatment for restoring aspen.

We conducted a field study to determine the relative contributions of aspen (Populus tremuloides), meadow, and conifer communities to local and landscape-level plant species diversity in the Sierra Nevada and southern Cascade Range, northeastern California, USA. We surveyed plant assemblages at 30 sites that included adjacent aspen, conifer, and meadow communities across a 10,000-km 2 region. We statistically investigated patterns in local and landscape-scale plant diversity within and among the three vegetation types. Summing across sites, aspen stands supported more plant species overall and more unique plant species than either meadow or conifer communities. Local richness and diversity did not differ between aspen and meadow plots; conifer forest plots were significantly lower in both measures. Heterogeneity in species composition was higher for aspen forest than for meadows or conifer forest, both within sites and between sites. Plant communities in aspen stands shared less than 25% of their species with adjacent vegetation in conifer and meadow plots. Within aspen forest, we found a negative relationship between total canopy cover and plant diversity. Our results strongly support the idea that plant communities of aspen stands are compositionally distinct from adjacent meadows and conifer forest, and that aspen forests are a major contributor to plant species diversity in the study region. Current patterns of aspen stand succession to conifer forest on many sites in the semiarid western US are likely to reduce local and landscape-level plant species diversity, and may also have negative effects on other ecosystem functions and services provided by aspen forest.

The application, rationale and process of habitat evaluation methods are discussed in the context of present day fisheries management. The need to consider habitat features at site and catchment level is stressed.Development of habitat evaluation techniques for assessing brown trout habitat in Welsh streams is reported, and examples of these approaches are given: qualitative (visual assessment), semi-quantitative (a combination of subjective and quantitative measurements) and quantitative (measurements on transect system). Habitat attribute-fish population models were based on functional linear regressions and multiple regression (for the quantitative method). Quantitative models explained up to 80% of the variance in abundance of medium sized (10-20cm) trout in hard water (>25mgI-' CaCO,), but were less effective when data from soft waters were included. Testing of the qualitative and semi-quantitative methods on independent data demonstrated that the latter was more effective in predicting habitat quality.Survey costs varied considerably but, although the more precise methods were more costly per site. they were the most cost-effective because fewer sites were required for a given level of precision.The problems associated with soft-water sites are discussed in terms of factors affecting site carrying capacity; and selection of methods is briefly considered in the light of current management practise.

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Aspen (Populus tremuloides Michx.) is a disturbance-dependent, fire-resilient, shade-intolerant, clonal species that is in decline throughout western North America. The objective of this study was to examine the effects of intensity and season of browsing on annual height growth of aspen suckers. The goal was to aid development of livestock grazing strategies to restore stands in decline due to excessive livestock browsing. We implemented 33 combinations of intensity and season of browse on aspen suckers in three aspen stands on Eagle Lake Range District, Lassen National Forest, California, USA, during 2003 and 2004. Greatest growth was on suckers with no terminal leader browse and # 25% of biomass removed from branches. Lowest growth occurred when 90% of terminal leader length and 50% of branch biomass was removed. Growth was most negatively affected by browse on terminal leader. Growth was lowest for suckers browsed midseason only and suckers browsed both early and midseason. Occurrence of conifer in the stand overstory significantly reduced sucker growth. Managers should minimize browse on terminal leaders, midseason browse over consecutive years, and repeated browse during a growing season. Resumen Alamo (Populus tremuloides Michx.) es una planta que depende del disturbio, es resistente al fuego, e intolerante a la sombra; clones de estas especies están desapareciendo a trave´s de toda la parte oeste de Norte América. El objetivo de este estudio fue examinar los efectos de intensidad y temporada de ramoneo sobre el aumento anual de la altura de retoñ os de los álamos durante la época de crecimiento. El objetivo fue desarrollar estrategias de pastoreo para restaurar las poblaciones en disminución debido al excesivo ramoneo. Se realizaron 33 combinaciones de intensidad y época de ramoneo sobre los retoñ os de los álamos en tres poblaciones de álamos en Eagle Lake Range District, Lassen National Forest, CA, USA, durante los añ os 2003 y 2004. El mayor crecimiento se obtuvo en retoñ os en que no se ramoneó la hoja terminal y se removió # 25% de la biomasa de las ramas. El menor crecimiento se presentó cuando el 90% de la longitud de la hoja terminal y el 50% de la biomasa de las ramas fue removido. El crecimiento fue negativamente afectado por el ramoneo en hojas terminales. El crecimiento de los retoñ os se afectó mas ligeramente cuando fueron ramoneadas sólo a la mitad de la temporada de crecimiento y los retoñ os ramoneados en al principio y a la mitad de la temporada. La ocurrencia de coníferas en la población en la parte superior redujo significativamente el crecimiento de los retoñ os. Los manejadores deben minimizar el ramoneo en hojas terminales, el ramoneo en la mitad de la temporada en añ os posteriores, y repetir el ramoneo durante una temporada de crecimiento.