Developmental contributions to phenotypic variation in functional leaf traits within quaking aspen clones

Phenotypic variation in plant traits is strongly influenced by genetic and environmental factors. Over the life span of trees, developmental factors may also strongly influence leaf phenotypes. The objective of this study was to fill gaps in our understanding of developmental influences on patterns of phenotypic trait variation among different-aged ramets within quaking aspen (Populus tremuloides Michx.) clones. We hypothesized that phenotypic variation in leaf functional traits is strongly influenced by developmental cues as trees age. We surveyed eight aspen clones, each with eight distinct age classes ranging from 1 to 160 years in age, and selected three ramets per age class for sample collection. Leaf traits measured included photosynthesis, stomatal conductance, water use efficiency, specific leaf area, and concentrations of N, phosphorus, sucrose, starch, condensed tannins and phenolic glycosides. Using regression analysis, we examined the relationships between ramet age and expression of leaf functional traits. The data showed significant correlations between ramet age and 10 of the 12 phenotypic traits measured. Eight of the phenotypic traits demonstrated a non-linear relationship in which large changes in phenotype occurred in the early stages of ramet development and stabilized thereafter. Water relations, nutrient concentration, leaf gas exchange and phenolic glycosides tended to decrease from early to late development, whereas sucrose, condensed tannin concentrations and water use efficiency increased with ramet age. We hypothesize that ontogenetically derived phenotypic variation leads to fitness differentials among different-aged ramets, which may have important implications for clone fitness. Age-related increases in phenotypic diversity may partially underlie aspen's ability to tolerate the large environmental gradients that span its broad geographical range.     

Feral swine management for conservation of an imperiled wetland habitat: Florida’s vanishing seepage slopes

Only 1% of the original extent of Florida’s seepage slope habitat remains, with Eglin Air Force Base containing some of the largest tracts. Feral swine damage is one of the greatest threats to this wetland habitat. We conducted a multi-year study to evaluate the impacts of sport hunting and supplemental swine removal on damage to seepage slopes. Prior to initiation of removal in 2003, swine damage to seepage slopes in the portion of the base closed to hunting averaged 25.0%, over twice the 10.9% losses in the portion open to hunting. After less than one year of supplemental removal, damage in the closed-to-hunting area dropped to 7.2%. Although supplemental removal was not applied in the open hunting area, damage dropped significantly to 5.6%, statistically indistinguishable from the swine-controlled (closed) portion. After another year of removal, average damage in the closed hunting area dropped further to 5.6%, while the open hunting area dropped to 4.3%, again statistically indistinguishable. Even though removal was only applied to the area closed to hunting, it also produced damage reductions in the open hunting area, as swine were free to move among areas. Declines in damage following implementation of removal corresponded with large drops in swine population indices for the base. Economic valuations of seepage slope damage losses demonstrated substantial benefit-cost ratios for application of removal. Prior to removal, the combined value of swine damage to seepage slopes in areas open and closed to hunting was estimated at $5.3 million. After only 1.7 years of removal, the value of damage losses was reduced by nearly $4 million to $1.5 million. The benefit-cost ratio over the 1.7 years of removal was an impressive 27.5. Moreover, the economic benefits of removal exceeded the costs 55.2-fold for the first year, when management impact would be greatest.     

Effects of shelter belts on fence-line pacing of deer and associated impacts on water and soil quality

Sustainable land use for deer farming requires the maintenance of good soil and water quality, which can be adversely affected by fence‐line pacing. This study tested the hypothesis that the absence or presence of shelter belts (one or two) in paddocks decreases fence‐line pacing and associated soil and water quality impacts. Soils near the fence line and in the rest of the paddock, in paddocks containing zero, one or two shelter belts, were sampled for bulk density and macroporosity (pores >30 μm diameter). Large intact samples (1 × 0.2 × 0.1 m³) were used to generate overland flow via rainfall simulation. The flow was tested for nutrients [phosphorus (P) and nitrogen (N) fractions], suspended sediment (SS), and the faecal indicator bacteria, Escherichia coli. Results showed that bulk density, void volume, SS, particulate P and total P were affected by location (fence line or rest of paddock) but, along with all other measurements except E. coli, were not affected by the number of shelter belts. Thus, the inclusion of shelter had no effect on the concentration of contaminant lost in overland flow or any soil physical or hydrological parameter, but decreased the run‐off of E. coli. The lack of contrast between the location of soils can be partly attributed to the soil type (Brown, NZ soil classification, USDA Taxonomy: Typic Fragiudalf), which when compared with past studies was less erosive and lost less P into solution. Other factors may have been different management or the lesser impact of weaners compared with older hinds and stags on soil properties. Although only E. coli concentrations were decreased by the inclusion of shelter, factors such as improved production and animal welfare weigh heavily in favour of installing and maintaining shelter on deer farms. However, the environmental benefit of shelter should be tested in other farms where factors such as slope, soil, climate and farm management may increase the contrast with no shelter.     

Lymphocyte unresponsiveness to PPD tuberculin in badgers infected with Mycobacterium bovis.

Lymphocyte transformation tests using phytohaemagglutinin and concanavalin A showed that both T and B lymphocytes are functional in tuberculous badgers. Dose response curves indicated that purified protein derivative sensitised lymphocytes were suppressed when cultured in the presence of the antigen.