Seeing the forest for the deer: Do reductions in deer-disturbance lead to forest recovery?

High levels of deer browsing can prevent canopy tree regeneration, but little is known about changes to forest size-structure following long-term deer herd reductions. We monitored changes in forest stand structure and composition in southwestern Ontario, Canada, over 28-years using permanent plots. Our study site was the largest remaining tract of Carolinian (deciduous) forest in Canada (11 km²), a habitat type that contains up to a fifth of Canada’s species at risk and is under intense anthropogenic pressures. We recorded declines in all tree size classes between 1981 and 1996, during which densities of white-tailed deer (Odocoileus virginianus) reached a peak of 55 deer km⁻². Despite significant and sustained deer herd reductions between 1996 and 2009, which reduced deer densities to 7 deer km⁻², there was limited recruitment of small trees and declines in basal area of tree species that were sensitive to deer browsing. Our results suggest that recovery from herbivory is a protracted process during which canopy tree regeneration may continue to decline despite a reduction in browsing pressure due to deer culling. Large declines in canopy-tree densities in Carolinian forests may lead to forest size-structures and herbaceous plant communities that resemble rare oak savanna habitat, creating difficult decisions for conservation managers aiming to protect rare and endangered species within native ecosystems. We recommend that managers protect Carolinian forest stands and encourage canopy tree regeneration by increasing seed sources of native trees. While deer control is essential in reducing forest damage, our results highlight the need to explore other forms of active management to expedite otherwise slow increases in tree density.     

Quantification of historical livestock importation into New Zealand 1860–1979

AIMS: To quantify the numbers of live cattle, sheep and poultry imported into New Zealand and, where possible, their country of origin from 1860 to 1979.

METHODS: Information on the origin and number of live animal importations into New Zealand was collected for cattle, sheep and poultry for the period 1868–1979 from the annual reports compiled by the New Zealand Registrar General's Office, Government Statistician's Office, Census and Statistics Office, Census and Statistics Department, Customs Department and Department of Statistics. Census data from 1851 to 1871 were also used to estimate the livestock population during this period. The number of animals imported and the mean population for each species in a decade were determined, and the major countries of origin were identified.

RESULTS: A large number of cattle (53,384) and sheep (604,525) were imported in the 1860s, and then there was a marked reduction in importations. Live poultry were imported in relatively small numbers (20,701) from 1880 to 1939, then 1,564,330 live poultry were imported between 1960 and 1979. Australia was the predominant country of origin for sheep between 1868 and 1959 (51,347/60,918; 84.3%) and of cattle between 1868 and 1979 (10,080/15,157; 66.5%). Only 6,712 (11.0%) sheep and 3,909 (25.8%) cattle were imported from the United Kingdom over the same periods, and even fewer from other countries.

CONCLUSIONS: The collated data and historical reports show that from 1860 to 1979 Australia has been the main source of livestock introduced into New Zealand. The pattern of importation showed that large numbers of cattle and sheep were initially imported in the 1860s, probably in response to rapid agricultural expansion. Thereafter importations continued at much reduced numbers. In contrast, relatively small numbers of poultry were introduced until the 1960s when large numbers were imported as part of the development of a modern high-production industry. The overall pattern for both cattle and sheep was of a bottleneck event, as initially a relatively limited number of animals arrived from outside populations, followed by population expansion with ongoing but limited immigration (admixture). Investigation into the genetic population structure of New Zealand's cattle and sheep, as well as their host-associated microorganisms, could reflect the impact of these early historical events.     

Impact of a ski basin on a mountain watershed

The input of heavy metals by automobile exhaust pollution associated with the ski basin activities is the primary concern of this paper. Stream, snowpack and lichen samples were collected and analyzed for Pb, Zn, and Cu. Some lichen samples were also analyzed for Ca, Mg, Na, K, Fe, and Mn, as well as Pb, Zn, and Cu. Snowpack samples from roadside areas demonstrated increased levels of Pb and Cu in comparison to areas up to 180 m from the road, but heavy metal levels at more remote areas were comparable to roadside levels. In all snow samples the heavy metals associated with the particulate matter was the major form of all inputs. Heavy metals in streams were also highly correlated with the particulate matter content. Heavy metal inputs to the watershed were greater than stream export, indicating an accumulation of heavy metals by the system. The forest canopy appears to be the major factor in the accumulation of heavy metals, probably due to better interception and impaction of the particulate matter by the canopy.     

Homogenization of the Soil Surface Following Fire in Semiarid Grasslands

Semiarid grasslands accumulate soil beneath plant “islands” that are raised above bare interspaces. This fine-scale variation in microtopographic relief is plant-induced and is increased with shrub establishment. Research found that fire-induced water repellency enhanced local-scale soil erosion that reduced variation in microtopographic relief, suggesting that fire may counteract vegetation-driven, fine-scale spatial soil heterogeneity. This article analyzes longer-term measurements (up to 9 yr) of soil microtopography to evaluate the hypothesis that fire in semiarid grasslands results in more homogenous soil microtopographic relief. Changes in soil microtopographic relief were measured prior to and following a total of five fires at three semiarid grasslands within central New Mexico, United States. The fires included three cool-season prescribed fires, a warm-season prescribed fire, and a warm-season wildfire. Four of the five fires resulted in significantly lower soil microtopographic variation that persisted for up to 4 yr. The duration and magnitude of the soil leveling effect was lowest in the grassland with clay-rich soils, indicating a possible soil texture interaction. Although two grasslands had net soil loss following fires, no net erosion occurred at the third grassland, indicating that redistribution of soils can occur without net erosion. These results show that management with prescribed fire reduces biotic-driven variation in soil microtopographic relief in semiarid grasslands that may help limit the transition to shrubland ecosystems in this region.     

Linkages Between Riparian Characteristics,Ungulate Grazing,and Geomorphology and Nutrient Cycling in Montane Grassland Streams

Catchment characteristics and disturbances control the conditions and processes found in stream ecosystems. We examined nutrient cycling linkages between riparian soils and adjacent streams and the impacts of the removal of ungulate grazing on these ecosystems and processes at six grazing exclosure sites in the Valles Caldera National Preserve, NM, USA. The exclusion of native and domestic ungulate grazers for 3 yr significantly increased the riparian aboveground biomass of standing vegetation (273 ± 155 in grazed vs. 400 ± 178 g ^. m^-2 in exclosures) and litter (58 ± 75 in grazed vs. 110 ± 76 g ^. m^-2 in exclosures) (P = 0.003 and 0.006, respectively). Except for an increase in total soil phosphorous (P) at three of the six sites, soil nutrient values were minimally affected by grazing after five growing seasons. Within the six sites studied, no connection was found between 0–15-cm depth soils, which were P-limited based on stoichiometric ratios, and stream nutrient availability or limitation, which were nitrogen limited. Stream geomorphology was not significantly altered by 5 yr of grazing exclusion. The elimination of grazing suppressed instream nutrient processing with significantly longer NH₄ uptake lengths (P = 0.003). These results suggest the exclusion of ungulate grazing impacts terrestrial characteristics (increased standing vegetative biomass) that are linked to ecosystem services provided by adjacent aquatic ecosystems (reduced N-uptake). Management plans should carefully balance the positive effect of grazing on stream nutrient processing and retention reported here with the well-documented grazing-related loss of other ecosystem services such as decreased fish and aquatic invertebrate habitat and effects on water-quality parameters such as turbidity and water temperature.     

Factors influencing natural water quality and changes resulting from land-use practices

Surface water and precipitation samples were collected from September 1972 through August 1973 on the northern slopes of Mount Taylor in west-central New Mexico. The samples were analyzed for pH, conductivity, silica, Ca, Mg, Na, K, bicarbonate, alkalinity as CaCO₃ sulfate, chloride, nitrate, phosphate, and total solids. The natural water quality was primarily determined by the contact with the different geologic formations. The water originating on or from the basaltic terrain was of better quality and lower in dissolved solids than the water on or from the sedimentary terrain. The effects of grazing, irrigation, water impoundment, vegetation clearing, and road construction upon the natural water quality was determined. Road construction had the greatest effect upon water quality of these land-use practices, but all of the practices had a significant effect on at least one or more of the dissolved constituents.     

Prevalence of Dirofilaria immitis and gastrointestinal helminths in cats euthanized at animal control agencies in northwest Georgia

Cats euthanized at six northwest Georgia animal control agencies were examined for adult Dirofilaria immitis in heart and lung tissue and presence of gastrointestinal helminth ova by fecal flotation. D. immitis were found in 4 of 184 cats (2.1%). The prevalence of feline dirofilariasis in northwest Georgia was lower than that found in other studies conducted in the southeastern United States, but closer to the prevalences occurring in areas of similar topography. Heartworm antigen and antibody tests performed on batched serum samples resulted in low sensitivity and high specificity. Gastrointestinal helminth ova were found in 39.6% of the fecal samples examined and 6.1% of the samples contained two or more species.