Treesearch

Ips hauseri Reitter is themost important bark beetle on Picea schrenkiana in southeastKazakhstan, but its biology, ecology, and outbreak dynamics are poorly known. We dendrochronologically reconstructed a 200-year history of disturbances in the Kazakh Tien Shan P. schrenkiana forests. Only localized, low-severity bark beetle events occurred during the reconstructed period, indicating that extensive high-severity bark beetle outbreaks have not occurred historically in the Tien Shan spruce forest, unlike bark beetle outbreaks in spruce forests in North America, Europe, and Russia. Disturbance...

Multiple high-severity insect outbreaks and wildfires dramatically altered the character of the Pinaleño high-elevation forests with notable impacts on ecosystem services. The Pinaleños are a small mountain range positioned close to large population centers, but not so close that any large industry is dependent on their resources, so regional and local impacts of the insect outbreaks to provisional resources were minor. There were qualitative impacts to cultural services, particularly to recreation, but no documented economic impacts. Effects on carbon and fuels were significant, but...

The first Global Drylands Assessment is a thematic study complementing FAO’s Global Forest Resources Assessment (FRA) but differing from it in method and scope. Unlike FRA, which relies on official national statistics, the Global Drylands Assessment was prepared by a consortium of partner institutions and was carried out through visual interpretation of satellite images. The results are reported at the global and regional levels, not the country level.

Mating strategies contributing to a balance between inbreeding and outcrossing are understudied in all but a few model fungal pathogens. This study examined factors that influence the occurrence of the sexual state of Pyrenophora semeniperda. It was consistently found to have functional copies of the MAT1-1 and MAT1-2 idiomorphs essential for sexual reproduction, despite considerable polymorphism in both single nucleotide polymorphisms (SNPs) and number of 18- base minisatellite repeats. The two idiomorphs occurred at approximately equal frequencies across 25 populations on Bromus tectorum...

Radicinin (1), is a fungal dihydropyranopyran-4,5-dione isolated together with some analogues, namely 3-epi-radicinin, radicinol, 3-epi-radicinol, and cochliotoxin (2-5), from the culture filtrates of the fungus Cochliobolus australiensis, a foliar pathogen of buffelgrass (Cenchrus ciliaris), an invasive weed in North America. Among the different metabolites 1 showed target-specific activity against the host plant and no toxicity on zebrafish embryos, promoting its potential use to develop a natural bioherbicide formulation to manage buffelgrass. These data and the peculiar structural...

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...