Vegetation Trends In Whitehorse Yukon, 1984 To 2009

To assess temporal greenness trends at the landscape scale for Whitehorse, Yukon (417 km2), this study derived a Landsat normalized difference vegetation index (NDVI) time-series from 1984 to 2009. Using a greenest annual pixel approach, NDVI trend analysis revealed that 37% of studied area had significant greening (p<0.05) and that only 1% of the studied land area had significant browning. Yearly mean NDVI values declined in drought years and increased in years with greater precipitation. Greening pixels were most prevalent in white spruce (Picea glauca) and subalpine fir (Abies lasiocarpa) dominant forests, suggesting that increased amounts of precipitation and rising temperatures have benefited both species and associated shrub communities. Forests where trembling aspen (Populas tremuloides) are dominant displayed the least greening, which may be explained by the proliferation of aspen serpentine leaf miner (Phyllocnistis populiella), and drought related die-back on south-facing slopes that have become warmer across the study period.

Vegetation Trends In Whitehorse Yukon, 1984 To 2009

To assess temporal greenness trends at the landscape scale for Whitehorse, Yukon (417 km2), this study derived a Landsat normalized difference vegetation index (NDVI) time-series from 1984 to 2009. Using a greenest annual pixel approach, NDVI trend analysis revealed that 37% of studied area had significant greening (p<0.05) and that only 1% of the studied land area had significant browning. Yearly mean NDVI values declined in drought years and increased in years with greater precipitation. Greening pixels were most prevalent in white spruce (Picea glauca) and subalpine fir (Abies lasiocarpa) dominant forests, suggesting that increased amounts of precipitation and rising temperatures have benefited both species and associated shrub communities. Forests where trembling aspen (Populas tremuloides) are dominant displayed the least greening, which may be explained by the proliferation of aspen serpentine leaf miner (Phyllocnistis populiella), and drought related die-back on south-facing slopes that have become warmer across the study period.

Two new species of Ophiostomatales (Sordariomycetes) associated with the bark beetle Dryocoetes alni from Poland

Bark beetles belonging to the genus Dryocoetes (Coleoptera, Curculionidae, Scolytinae) are known vectors of fungi, such as the pathogenic species Grosmannia dryocoetidis involved in alpine fir (Abies lasiocarpa) mortality. Associations between hardwood-infesting Dryocoetes species and fungi in Europe have received very little research attention. Ectosymbiotic fungi residing in Ceratocystiopsis and Leptographium (Ophiostomatales, Sordariomycetes, Ascomycota) were commonly detected in previous surveys of the Dryocoetes alni-associated mycobiome in Poland. The aim of this study was to accurately identify these isolates and to provide descriptions of the new species. The identification was conducted based on morphology and DNA sequence data for six loci (ITS1-5.8S, ITS2-28S, ACT, CAL, TUB2, and TEF1-α). This revealed two new species, described here as Ceratocystiopsis synnematasp. nov. and Leptographium alneumsp. nov. The host trees for the new species included Alnus incana and Populus tremula. Ceratocystiopsis synnemata can be distinguished from its closely related species, C. pallidobrunnea, based on conidia morphology and conidiophores that aggregate in loosely arranged synnemata. Leptographium alneum is closely related to Grosmannia crassivaginata and differs from this species in having a larger ascomatal neck, and the presence of larger club-shaped cells.

Histology of resin vesicles and oleoresin terpene composition of conifer seeds

The seed coats of several conifers contain terpene-filled resin vesicles, which may be involved in the protection of the dormant embryo and the seed storage tissue against herbivores or pathogens. We analyzed the terpenoid composition of seeds from four Abies species (Abies amabilis Douglas ex J. Forbes, Abies balsamea (L.) Mill., Abies grandis (Douglas ex D. Don) Lindl., and Abies lasiocarpa (Hook.) Nutt.), two Thuja species (Thuja plicata Donn ex D. Don and Thuja occidentalis L.), and three Tsuga species (Tsuga canadensis (L.) Carrière, Tsuga mertensiana (Bong.) Carrière, and Tsuga heterophylla (Raf.) Sarg.) and examined histological features of resin vesicles in seeds from one species from each genus. Resin vesicle morphology was generally similar among the species analyzed. The composition of the seed terpenes varied largely between species. The described seed terpene profiles of the nine species will serve as a foundation for future studies into the function of seed terpenes and resin vesicles in the seed coat.