Treesearch

Radicinin is a phytotoxic fungal dihydropyranopyran-4,5-dione under evaluation for the development of a target-specific bioherbicide for invasive buffelgrass (Cenchrus ciliaris) control. It has already demonstrated high toxicity on host plants, low toxicity to native plants and no negative effects on zebrafish embryos. To continue these studies at the whole-plant level there is a need to obtain much larger quantities of radicinin, either by optimizing its large-scale production by fungal fermentation or through its total stereoselective synthesis. A rapid and sensitive HPLC method for...

The fungal pathogens Cochliobolus australiensis and Pyricularia grisea have recently been isolated from diseased leaves of buffelgrass (Cenchrus ciliaris) in its North American range, and their ability to produce phytotoxic metabolites that could potentially be used as natural herbicides against this invasive weed was investigated. Fourteen secondary metabolites obtained from in vitro cultures of these two pathogens were tested by leaf puncture assay on the host plant at different concentrations. Radicinin and (10S, 11S)-epi-pyriculol proved to be the most promising compounds. Thus, their...

Previous research has shown that stems of Artemisia tridentata species exhibit extensive lobe formation. Twenty-two stem samples of Artemisia tridentata Nutt. ssp. wyomingensis (ARTRW) and 24 samples of A. t. ssp. tridentata (ARTRT) were investigated to quantify lobe formation characteristics. For samples of both subspecies, lobe formation values were constant for 8.3-cm-diameter stems. For the above samples, ARTRW had 14 xylem rings, while ARTRT had only 5 rings. Three stem samples (33 to 50 cm long) of ARTRW were cut into a series of 8-mm segments. For the 3 stems, the smallest ends had...

Human activities are changing patterns of ecological disturbance globally. In North American deserts, wildfire is increasing in size and frequency due to fuel characteristics of invasive annual grasses. Fire reduces the abundance and cover of native vegetation in desert ecosystems. In this study, we sought to characterize stem growth and reproductive output of a dominant native shrub in the Mojave Desert, creosote bush (Larrea tridentata (DC.) Coville) following wildfires that occurred in 2005. We sampled 55 shrubs along burned and unburned transects 12 years after the fires (2017) and...

Disturbance and regrowth are vital processes in determining the roles of forest ecosystem in the carbon and biogeochemical cycles. Using time series observations, the vegetation change tracker (VCT) algorithm was designed to map the location, timing, and spectral magnitudes of forest disturbance events. While these spectral disturbance magnitudes are indicative of physical changes in tree cover or biomass, their quantitative relationships have yet to be established. This study focuses on estimating disturbance intensity as measured by percent basal area removal using spectral indices from...

An explicit link between the abiotic environment, the biotic components of ecosystems, and resilience to disturbance across multiple scales is needed to operationalize the concept of ecological resilience. To accomplish this, managers must be able to measure the ecological resilience of current conditions and project resilience under future scenarios of landscape change. The goal of this paper is to present metrics and describe a process for using geospatial data, landscape pattern analysis and landscape dynamic simulation modeling to evaluate ecosystem resilience at management scales. The...

Forest management in much of the Sierra Nevada has undergone a significant redirection in recent decades. Prior to this, fire was largely absent from many foresters’ credo; it was neither considered as a tool for management nor viewed as an inherent ecological component for sustaining basic forest processes. Yet fire has been a part of these forests for millennia, and its removal has slowly but markedly changed forests in unintended ways. The cumulative effects of removing fire for over 100 years are manifested in the large and uncharacteristically severe fires that are now happening...

Background: High-severity fire in forested landscapes often produces a post-fire condition of high shrub cover and large loads of dead wood. Given the increasing patch size of high-severity fire and the tendency for these areas to reburn at high severity in subsequent wildfires, post-fire management often targets restoration of these areas. However, these areas are challenging to manage, in part due to limited knowledge of post-fire fuel dynamics over space and time and uncertainties in how specific fuel components such as snags and logs influence future fire severity. In this study, we...

This article tests two hypotheses on whether forest fuel reduction treatments (prescribed burning and mechanical methods) reduce wildfire suppression costs and property damages. Data were collected on fuel treatments, fire suppression costs, and property damage associated with wildfires in United States National Forests over a five-year period throughout the continental United States. The continental U.S. pooled data model results show that overall, prescribed burning reduces suppression cost and both fuel treatment types reduce property damages. Further analysis was done to separate the...

Nonnative, invasive feral pigs (Sus scrofa) modify habitats by disturbing soils and vegetation, which can alter biogeochemical processes. Soil microbial communities drive nutrient cycling and therefore also play important roles in shaping ecosystem structure and function, but the responses of soil microbes to nonnative ungulate removal remains poorly studied. We examined changes in the soil bacterial community over a ~25 year chronosequence of feral pig removal in tropical montane wet forests on the Island of Hawai’i. We extracted bacterial eDNA from soil samples collected inside and...