Spatial patterns of primary productivity in the Greater Yellowstone Ecosystem

Landscapes are often heterogeneous in abiotic factors such as topography, climate, and soil, yet little is known about how these factors may influence the spatial distribution of primary productivity. We report estimates of aboveground net primary productivity (ANPP) in 90 sample stands stratified by cover type and elevation class, and use the results to predict ANPP across a portion of the Greater Yellowstone Ecosystem. Tree ANPP was estimated by sampling tree density by species and diameter classes and estimating average annual diameter increment by tree coring. Biomass for current tree diameter and past tree diameter were calculated by species and diameter class for each stand using the dimension analysis software BIOPAK. Shrub ANPP was estimated by calculating current biomass from basal area using BIOPAK and dividing by the assumed average life span of the shrubs. Clipping at the end of the growing season was used to estimate herb ANPP. Differences in ANPP among cover types and elevation classes were examined with analysis of variance. Multiple regression was used to examine relationships between ANPP, and soil parent material, topography, and cover type. The best regression model was used to predict ANPP across the study area.We found ANPP was highest in cottonwood, Douglas-fir, and aspen stands, intermediate in various seral stages of lodgepole pine, and lowest in grassland and sagebrush cover types. Parent material explained significant variation in ANPP in mature and old-growth lodgepole pine stands, with rhyolite ash/loess being the most productive parent material type. ANPP decreased with increasing elevation in most cover types, possibly because low temperatures limit plant growth at higher elevations in the study area. ANPP was not related to elevation in mature and old-growth lodgepole pine stands, due to relatively rapid growth of subalpine fir at higher elevations.A regression model based on cover type and elevation explained 89% of the variation in ANPP among the sample stands. This model was used to generate a spatially continuous surface of predicted ANPP across the study area. The frequency distribution of predicted ANPP was skewed towards lower levels of ANPP, and only 6.3% of the study area had a predicted ANPP level exceeding 4500 kg/ha/yr. Patches high in predicted ANPP were primarily at lower elevations, outside of Yellowstone National Park, and near the national forest/private lands boundary. These patterns of ANPP may influence fire behavior, vertebrate population dynamics, and other ecological processes. The results reinforce the need for coordinated management across ownership boundaries in the Greater Yellowstone Ecosystem.     

Phytophthora pinifolia sp. nov. associated with a serious needle disease of Pinus radiata in Chile

During the course of the past three years, a new disease of Pinus radiata , referred to as 'Daño Foliar del Pino' (DFP) has appeared in the Arauco province of Chile and subsequently spread to other areas. The disease is typified by needle infections, exudation of resin at the bases of the needle brachyblasts and, in younger trees, necrotic lesions in the cambium, which eventually girdle the branches. The disease causes the death of young seedlings and mature trees can also succumb after a few years of successive infection, probably hastened by opportunistic fungi such as Diplodia pinea . Isolations on selective medium for Phytophthora spp. led to the consistent isolation of a Phytophthora sp. from needle tissue. DNA sequence comparisons for the ITS rDNA and cox II gene regions, and morphological observation showed that this oomycete represents a previously undescribed species for which the name Phytophthora pinifolia sp. nov. is provided. This new species is characterized by unbranched sporangiophores, and non-papillate, sub-globose to ovoid sporangia that are occasionally free from the sporangiophore with medium length pedicels. Despite using a number of oospore inducing techniques, oogonia/antheridia were not observed in isolates of P. pinifolia . Pathogenicity trials with P. pinifolia showed that it is pathogenic to P. radiata and causes rapid death of the succulent apical parts of young plants. Phytophthora pinifolia is the first Phytophthora known to be associated with needles and shoots of a Pinus sp. and its aerial habit is well matched with the occurrence and symptoms of DFP in Chile.