Impacts of Swiss needle cast on overstory Douglas-fir forests of the western Oregon Coast Range

Tree-ring analysis was applied to assess the impacts of the fungal disease Swiss needle cast on the radial growth of mature Douglas-fir (Pseudotsuga menziesii) forests in the western Oregon Coast Range. Although considered endemic to the Pacific Northwest, Swiss needle cast has significantly lowered productivity in Douglas-fir forests only in the past 20–30 years. To date, studies on Swiss needle cast impacts have almost exclusively involved young (<30 years) plantation trees. To better describe the history of Swiss needle cast and its impacts on older (>80 years) trees, we extracted tree cores from dominant and codominant Douglas-fir and western hemlock (Tsuga heterophylla) in three even-aged stands in western Oregon. In the least affected stand growth rates of both species did not significantly differ, while at the most severely diseased site Douglas-fir radial growth was reduced by as much as 85%. Growth reductions likely associated with Swiss needle cast were dated to as early as 1950, though the most severe impacts occurred after 1984. An index of Swiss needle cast severity significantly (p < 0.01) related to instrumental records of air temperatures such that warm conditions from March through August were associated with reduced radial growth at the most severely affected site. Overall, this study demonstrates that even mature forests of natural origin are susceptible to severe growth reductions by Swiss needle cast, that warmer spring and summer temperatures are associated with Swiss needle cast impacts, and that the disease appears to be increasing in severity.     

Addressing the interplay of poverty and the ecology of landscapes: a Grand Challenge Topic for landscape ecologists?

We argue for the landscape ecology community to adopt the study of poverty and the ecology of landscapes as a Grand Challenge Topic. We present five areas of possible research foci that we believe that landscape ecologists can join with other social and environmental scientists to increase scientific understanding of this pressing issue: (1) scale and poverty; (2) landscape structure and human well-being; (3) social and ecological processes linked to spatial patterns in landscapes; (4) conservation and poverty, and (5) applying the landscape ecologist’s toolkit. A brief set of recommendations for landscape ecologists is also presented. These include the need to utilize broad frameworks that integrate social and ecological variables, build capacity to do this kind of work through the development of strong collaborations of researchers in developed and developing countries, create databases in international locations where extreme poverty exists, and create a new generation of researchers capable of addressing this pressing social and environmental issue.     

Evaluation of drying methods and toxicity of rayless goldenrod ( Isocoma pluriflora ) and white snakeroot ( Ageratina altissima ) in goats

White snakeroot and rayless goldenrod cause "trembles" and "milk sickness" in livestock and humans, respectively. The toxin in white snakeroot and rayless goldenrod was identified in 1927 and 1930, respectively, as tremetol. It was reported that the toxin in white snakeroot disappears as it is dried and that completely dried plants were incapable of producing trembles or milk sickness. Conversely, it has been reported that the rayless goldenrod toxin was not destroyed by drying and that the plant is toxic either fresh or dry. In this study the concentrations of tremetone, dehydrotremetone, and structurally similar compounds were determined in white snakeroot and rayless goldenrod before and after various drying conditions. Tremetone, dehydrotremetone, and structurally similar compounds in rayless goldenrod and white snakeroot are most stable upon freeze-drying, followed by air-drying, and least stable upon oven-drying (60 °C). Also demonstrated is that tremetone is stable and that dried white snakeroot and rayless goldenrod are capable of inducing toxicosis in livestock.     

A tissue culture method for the rapid propagation of potatoes

A tissue culture method for the rapid propagation of potatoes was studied using 38 varieties. At least 50 plantlets were regeneratedin vitro, in a sequential procedure, from a single isolated shoot tip. Rapid proliferation of shoots was enhanced by shake culture of previously differentiated organogenic cultures. These shoots in turn were used to regenerate complete plantlets by the culture of nodal sectionsin vitro. Culture initiation was more dependent on the variety than culture proliferation. The culture media contained the Murashige-Skoog basal components supplemented with 6-benzylaminopurine, gibberellic acid and naphthalene acetic acid. The system described, whereby high propagation rates can be achieved, was referred to as “multi-meristem” culture in contrast to the 1:1 rate normally obtained by the conventional, “single-meristem” culture. Evaluations of varietal stability, using both biochemical and morphological criteria showed no detectable changes due to thein vitro procedures. It is proposed to utilize the “multi-meristem” propagation technique for the conservation and international distribution of valuable clonal germplasm.     

The Incidence of Aeromonas Species in the Feces of Nondiarrheic Horses

Aeromonas species have been isolated from the feces of diarrheic adult horses and foals. However, Aeromonas species have also been isolated from the feces of approximately 5% of clinically normal adult horses outside the United States. The objectives of this study were to determine whether Aeromonas species can be shed in the feces of nondiarrheic adult horses and identify any effects of season of year, transportation, and hospitalization on possible fecal shedding of Aeromonas species. Feces were cultured for Aeromonas and Salmonella species from 138 nondiarrheic adult horses examined in the hospital and by field services for complaints other than gastrointestinal disease. Fecal Aeromonas and Salmonella species were isolated from 6.5% and 2.2% of nondiarrheic horses, respectively. All Aeromonas isolates were identified as A caviae. There were no apparent effects on time of year, hospitalization, or transport on isolation of Aeromonas species from feces. Isolation of Aeromonas species from diarrheic horses in the absence of other possible enteric pathogens indicates intestinal disease as a result of Aeromonas infection, but Aeromonas species can also occur as copathogens with Salmonella infections.     

Long-term phosphorus fertilisation increased the diversity of the total bacterial community and the phoD phosphorus mineraliser group in pasture soils

Fertilisers, especially nitrogen (N) and phosphorus (P) supplies, are frequently used in agricultural soil management to attain high crop yields. However, the intensive application of these chemical inputs can decrease the quality of agricultural soils and increase the probability of environmental pollution. In this study, the impact of P fertilisation on the diversity of the soil bacterial community was assessed. For this, a culture-independent approach targeting 16 rRNA and phoD genes was used on DNA extracted from pasture soils subjected to three different P fertilisation regimes for a long-term (42 years). As alkaline phosphomonoesterase (ALP) is necessary for mineralisation of organic P, an inverse relationship between the level of potential ALP activity and soil available P was expected. Indeed, a lower ALP activity was observed in soil subjected to higher chemical P fertiliser input. Analysis of the prevalence of three divergent families of ALP (PhoA, PhoD and PhoX) in metagenomic datasets revealed that PhoD is the most frequent ALP in soil samples and was selected as the most representative ALP possessed by the soil bacterial communities. Diversity of the phoD phosphorus mineraliser group, as well as the total bacterial community, was both increased in response to long-term P fertilisation. Specifically, phosphorus fertilisation decreased the relative abundance of certain taxa, including Acidobacteria and Pseudomonas fluorescens. In conclusion, this study shows that P fertilisation affects the microbial diversity of soil ecosystems, which might potentially modulate the soil biogeochemical cycle.