Vegetation Composition,Dynamics, and Management of a Bracken–Grassland and Northern–Dry Forest Ecosystem

We investigated differences in vegetation composition and dynamics for two globally rare ecosystems, bracken–grasslands and northern–dry forests of northern Wisconsin. These ecosystems commonly have been viewed as degraded pine barrens. Bracken–grasslands contained a high dominance of exotic species, low native richness, and no obvious prairie species, suggesting logging-era anthropogenic origins. Differences in cover for common plants among ecosystems were examined using Mann-Whitney U tests of equivalence. Cover of all 8 graminoid species, 4 of 5 Ericaceae and Myricaceae species, and 10 of 17 species of forbs were significantly different between ecosystems. Vegetation changes over a 4-year period were examined through detrended correspondence analysis (DCA) and analysis of variance (ANOVA) repeated measures. DCA analyses of community composition failed to detect significant temporal trends within individual management units, although differences were apparent between ecosystems, regardless of sample year. In addition, no apparent patterns could be detected between years when comparing dominant individual species to management history (prescribed fire). This is contrary to what would be expected for a degraded pine barrens and questions the efficacy of using repeated prescribed fire as a management tool in bracken–grasslands. Methods for conservation and restoration of xeric ecosystems of northern Wisconsin have historically relied heavily on single species (e.g., sharp-tailed grouse) wildlife models, without full consideration of other factors. We suggest that stakeholders involved in these restoration projects examine historic processes and reference conditions prior to formulating management goals. Greater attention to the differentiation and individual management needs of pine barrens, northern–dry forests, and bracken–grasslands is needed.     

Urbanization and the Loss of Resource Lands in the Chesapeake Bay Watershed

We made use of land cover maps, and land use change associated with urbanization, to provide estimates of the loss of natural resource lands (forest, agriculture, and wetland areas) across the 168,000 km² Chesapeake Bay watershed. We conducted extensive accuracy assessments of the satellite-derived maps, most of which were produced by us using widely available multitemporal Landsat imagery. The change in urbanization was derived from impervious surface area maps (the built environment) for 1990 and 2000, from which we estimated the loss of resource lands that occurred during this decade. Within the watershed, we observed a 61% increase in developed land (from 5,177 to 8,363 km²). Most of this new development (64%) occurred on agricultural and grasslands, whereas 33% occurred on forested land. Some smaller municipalities lost as much as 17% of their forest lands and 36% of their agricultural lands to development, although in the outlying counties losses ranged from 0% to 1.4% for forests and 0% to 2.6% for agriculture. Fast-growing urban areas surrounded by forested land experienced the most loss of forest to impervious surfaces. These estimates could be used for the monitoring of the impacts of development across the Chesapeake Bay watershed, and the approach has utility for other regions nationwide. In turn, the results and the approach can help jurisdictions set goals for resource land protection and acquisition that are consistent with regional restoration goals.     

Plasticity in physiological traits in conifers: Implications for response to climate change in the western U.S.

Population variation in ecophysiological traits of four co-occurring montane conifers was measured on a large latitudinal gradient to quantitatively assess their potential for response to environmental change. White fir (Abies concolor) had the highest variability, gross photosynthetic rate (Pg), and foliar carbon (C) and nitrogen (N) content. Despite low water use efficiency (WUE), stomatal conductance (gs) of fir was the most responsive to unfavorable environmental conditions. Pinus lambertiana exhibited the least variability in Pg and WUE, and is likely to be the most vulnerable to environmental changes. Pinus ponderosa had an intermediate level of variability, and high needle growth at its higher elevational limits. Pinus Jeffreyi also had intermediate variability, but high needle growth at its southern latitudinal and lower elevational limits. The attributes used to assess tree vigor were effective in predicting population vulnerability to abiotic (drought) and biotic (herbivore) stresses.     

Single-solute and bi-solute sorption of phenanthrene and pyrene onto pine needle cuticular fractions

To better understand interaction mechanisms of pine needles with persistent organic pollutants, single-solute and bi-solute sorption of phenanthrene and pyrene onto isolated cuticular fractions of pine needle were investigated. The structures of cuticular fractions were characterized by elemental analysis, Fourier transform infrared spectroscopy and solid-state ¹³C NMR. Polymeric lipids (cutin and cutan) exhibited notably higher sorption capabilities than the soluble lipids (waxes), while cellulose showed little affinity with sorbates. With the coexistence of the amorphous cellulose, the sorption of cutan (aromatic core) was completely inhibited, so the cutin components (nonpolar aliphatic moieties) dominated the sorption of bulk needle cuticle. By the consumption of the amorphous cellulose under acid hydrolysis, sorption capacities of the de-sugared fractions were dramatically enhanced, which controlled by the exposed aromatic cores and the aliphatic moieties. Furthermore, the de-sugared fractions demonstrated nonlinear and competitive sorption due to the specific interaction between aromatic cores and polycyclic aromatic hydrocarbon.     

Automobile exhaust gas as a source of aqueous phase OH radical in the atmosphere and its effects on physiological status of pine trees

Free radical generation potential of automobile exhaust gas was examined by measuring hydroxyl (OH) radical photo-formation rates in exhaust gas-scrubbing water. Effects of automobile exhausts on physiological status of Japanese red pine trees (Pinus densiflora Sieb. et Zucc.) were also investigated to elucidate the mechanism how the free radicals derived from exhaust gas damage higher plants. Gasoline and diesel exhaust gases were scrubbed into pure water. Potential photo-formation rates of OH radical in aqueous phase (normalized to sun light intensity of clear sky midday on May 1 at 34°N) for gasoline and diesel cars were ave. 51 and 107 μM h⁻¹ m⁻³ of exhaust gas, respectively. Nitrite was a dominant source (ca. 70-90%) of photochemical formation of OH radical in both gasoline and diesel car exhausts. The scrubbed solution of diesel car exhaust gas was sprayed for six times per week to needles of pine tree seedlings in open top chambers. Control, exhaust + mannitol (added as OH radical scavenger), and nitrite + nitrate standard solution (equivalent levels existed in the exhaust gas) were also sprayed. Two months sprays indicated that the sprayed solutions of diesel exhaust and nitrite + nitrate caused a decrease of maximum photosynthetic rate and stomata conductance in pine needles while the control and exhaust + mannitol solution showed no effects on photosynthetic activities of pine needles. These results indicated that OH radicals generated mainly from photolysis of nitrite occurring in the scrubbing solution of exhaust gas are responsible for the decrease of photosynthetic activities of pine needles.     

Inhibitory effect of arachidonic acid on venom acetylcholinesterase

The venom of krait (Bungarus sindanus), an Elapidae snake, contains high level of acetylcholinesterase (AChE) activity. The effect of arachidonic acid on krait (Bungarus sindanus) venom AChE (acetylcholine hydrolase, EC 3.1.1.7) was studied using kinetic methods. This study evaluated for the first time whether arachidonic acid acts as potential AChE inhibitor of krait venom. Kinetic studies, using Line-Weaver Burk and Dixon plots, indicated that the inhibition produced by arachidonic acid was non-competitive, i.e., both k_m and V _max fell with increase in the concentration of arachidonic acid. The concentration of arachidonic acid required to inhibit 50% of enzymatic activity was found to be 1.9?µM while the inhibitory constant (K_i ) was 1.4?µM. The present results suggest that essential fatty acid (arachidonic acid) may also be used as an inhibitor of snake venom AChE.     

渔游蛇精子的超微结构

扫描电镜观察表明,渔游蛇（Ｎａｔｒｉｘ Ｐｉｓｃａｔｅｒ）精子总长度约１１０μｍ,分为头和尾两部分;头部呈前稍尖的细长圆柱形,略变曲,约长８．５μｍ,直径以经约０．６μｍ。尾部又分４段：颈段、中段、主段和末段;其与从不同之处是中段较长,约７３μｍ,占精子总长度的２／３多;线料体型鞘由近５００圈超过５０００个线粒体构成;透射电镜揭示了头部顶体体覆疬于核前约１／２;尾部颈段的结构较复杂,包括连接片的踝     

Conflict,controversy, and compromise: The Concho water snake (Nerodia harteri paucimaculata) versus the Stacy Dam and Reservoir

The Colorado River Municipal Water District (CRMWD) of Big Spring, Texas, planned to construct the Stacy Reservoir and Dam on the Colorado River near Paint Rock, Texas, yet needed a Section 404 permit from the US Army Corps of Engineers pursuant to the Clean Water Act. In 1986 the Concho water snake (Nerodia harteri paucimaculata) was listed as threatened under the Endangered Species Act (ESA). Much of its remaining range included the stretch of the Colorado River that would be flooded by the proposed dam. After initially rejecting CRMWD proposals for mitigation, and informing the Corps of Engineers that it would issue a jeopardy opinion regarding the 404 permit pursuant to Section 7 of the ESA, the US Fish and Wildlife Service reversed its stand. The final biological opinion stated that reasonable and prudent alternatives previously rejected as unfeasible would remove the threat of jeopardy. This paper concludes that experimental management techniques proposed by FWS to allow dam construction do not adequately ensure survival of the Concho water snake and an alternative water source should have been found.     

Integrating Landscape and Metapopulation Modeling Approaches: Viability of the Sharp-Tailed Grouse in a Dynamic Landscape

Abstract:  The lack of management experience at the landscape scale and the limited feasibility of experiments at this scale have increased the use of scenario modeling to analyze the effects of different management actions on focal species. However, current modeling approaches are poorly suited for the analysis of viability in dynamic landscapes. Demographic (e.g., metapopulation) models of species living in these landscapes do not incorporate the variability in spatial patterns of early successional habitats, and landscape models have not been linked to population viability models. We link a landscape model to a metapopulation model and demonstrate the use of this model by analyzing the effect of forest management options on the viability of the Sharp-tailed Grouse (  Tympanuchus phasianellus ) in the Pine Barrens region of northwestern Wisconsin (U.S.A.). This approach allows viability analysis based on landscape dynamics brought about by processes such as succession, disturbances, and silviculture. The landscape component of the model (LANDIS) predicts forest landscape dynamics in the form of a time series of raster maps. We combined these maps into a time series of patch structures, which formed the dynamic spatial structure of the metapopulation component (RAMAS). Our results showed that the viability of Sharp-tailed Grouse was sensitive to landscape dynamics and demographic variables such as fecundity and mortality. Ignoring the landscape dynamics gave overly optimistic results, and results based only on landscape dynamics (ignoring demography) lead to a different ranking of the management options than the ranking based on the more realistic model incorporating both landscape and demographic dynamics. Thus, models of species in dynamic landscapes must consider habitat and population dynamics simultaneously.