Treesearch

Biotic interactions, such as competition and herbivory, can limit plant species ranges to a subset of edaphically suitable habitats, termed the realized niche. Here we explored the role that herbivores play in restricting the niche of serpentine ecotypes of the native California annual Collinsia sparsiflora.We planted seeds from four populations into a range of natural field environments that varied in the presence/absence of naturally occurring C. sparsiflora and in predicted suitability for growth and survival of the serpentine ecotype of C. sparsiflora. Path analysis was then used to...

The major components of the sex pheromone of Dioryctria abietivorella (Groté) (Lepidoptera: Pyralidae) were recently identified as (9Z,11E)-tetradecadien-1-yl acetate (9Z,11E-14:Ac) and a polyunsaturated, long-chain hydrocarbon (3Z,6Z,9Z,12Z,15Z)-pentacosapentaene (C25 pentaene). The optimal ratio of these components and the role of potential minor components were not fully determined in the initial short report on the pheromone's identification. We tested different ratios of the two major components loaded into grey halobutyl rubber septum dispensers, placed in sticky traps deployed in...

Both permanent high marsh pools and the intertidal surfaces of Spartina patens high marshes in southern Maine, USA, proved to be important habitat for resident mummichog Fundulus heteroclitus production. Manipulations of fish movement onto high marsh Surfaces revealed similar growth rates and production among fish that were (1) restricted to pools, (2) had access to known areas of marsh surface, or (3) had free access to the entire marsh, Smaller scale manipulations with marked fish revealed that males with access to the marsh surface accumulated significantly more biomass, often exhibited...

Tropical dry forests are among the Earth's most threatened ecosystems. On the Island of Hawaii the African bunchgrass Pennisetum setaceum (fountain grass) dominates the understorey of the few remaining fragments of native dry forests and is contributing to the degradation of this once diverse ecosystem. In this study, we examined the impacts of Pennisetum on water use and productivity of the dominant native canopy tree, Diospyros sandwicensis. Over a 3-year period, measurements were made on tree growth rates, and physiological and morphological responses of the most common dry forest...

Chance events such as seed dispersal determine the potential composition of plant communities, but the eventual assemblage is determined in large part by subsequent interactions among species. Postcolonization sorting also affects the ultimate composition of communities assembled by people for restoration, horticulture, or conservation. Thus, knowledge of the mechanisms controlling interspecific interactions in plant communities is important for explaining patterns observed in nature and predicting success or failure of utilitarian combinations. Relationships among species, especially...

Forest fires have been burning ‘hot’ across the United States and particularly in the West recent years. So, too, will the debate on post-fire management strategies. In this paper, we present a successful reforestation project after a catastrophic fire in 1992. Sixteen years later, most lands are covered with vigorous young forest stands. These regenerated stands have sequestered a large amount of atmospheric carbon, although not yet to the level of previous stands. Furthermore, these managed stands will provide wood to consumers and support the local economy in the future. In contrast,...

A pear bait monitoring system was used to detect and quantify Phytophthora ramorum propagules in streams that flow through woodland areas with sudden oak death in Santa Cruz County, CA from 2001 to 2007. Stream propagules were detected most frequently or occurred in highest concentrations in winter and spring. The stream propagule concentration was characterized with statistical models using temperature and rainfall variables from 2004 to 2007. The highest concentrations of propagules occurred when stream sampling was preceded by about 2 months with low maximum daily temperatures and by 4...

In California’s oak woodlands, survival and growth of oaks may depend on a symbiosis between oak roots and fungi that form ectomycorrhizas. Ectomycorrhizal (ECM) fungi are major players in carbon (C) and nitrogen (N) utilization and cycling because they facilitate water and nutrient uptake from the soil into the plant. The ECM fungi also benefit because plants supply carbohydrates to their fungal partners. Little is known about the stoichiometry of N and C exchange within ECM plants. It is not known whether N uptake and transfer from ECM fungi to their plant host is related to C flow from...

Results of a 1985 survey of California hardwood rangeland landowners were used to develop a multi-agency research and extension program, known as the Integrated Hardwood Range Management Program. In 1992 and in 2004, owners of the same properties were re-surveyed, regardless of whether or not the properties had changed ownership. Some highlights of the results are reported here. Although the survey cannot prove the program is the sole or direct agent of change, program-sponsored education and research aimed at encouraging oak rangeland owners to change oak management practices is reflected...