Initial effects of light armored vehicle use on grassland vegetation at Fort Lewis, Washington

Sustainable use of military training lands requires understanding and prediction of the effects of military vehicles on vegetation. We examined the initial impacts of an 8-wheeled, light armored vehicle (LAV) on grassland vegetation at Fort Lewis, Washington. The LAV drove replicate spiral paths at two starting velocities, 10.3 and 5.1 m s(-1). The disturbed width (width of ground impacted by the tires) increased as turning radius decreased, but was unaffected by vehicle velocity. An inverse-exponential model predicted disturbed width (r(2)=0.68) at all turning radii for both velocities combined. In low-velocity spirals, and for straight tracking (turning radius>40 m) and moderate turns (radius 20-40 m) in high-velocity spirals, all vegetation damage was imprint (plants flattened by wheels). During sharp (radius <20 m), high-velocity turns, most or all of the disturbed width was scraped free of surface vegetation and soil, which was piled to the outside of each tire track. Total plant cover (all species) was not affected by track curvature in low-velocity spirals, but decreased in the order straight tracking>moderate turns>sharp turns in high-velocity spirals. In low-velocity spirals, post-tracking cover of several plant growth forms (non-native species, perennial species, sod-forming grasses) was similar to pre-tracking cover, but in high-velocity spirals, post-tracking cover of these growth forms decreased in the order straight > or =moderate=sharp. Cover of native species and forbs decreased more in high- than in low-velocity spirals, but was unaffected by curvature. Pre- and post-tracking cover of annual species, bunchgrasses, and shrubs was < or =3%. The most severe vegetation damage caused by operation of wheeled LAVs on grasslands is associated with sharp, high-velocity turns.     

Even Conservation Rules Are Made to Be Broken: Implications for Biodiversity

Despite efforts to enclose and control conservation zones around the world, direct human impacts in conservation areas continue, often resulting from clandestine violations of conservation rules through outright poaching, strategic agricultural encroachment, or noncompliance. Nevertheless, next to nothing is actually known about the spatially and temporally explicit patterns of anthropogenic disturbance resulting from such noncompliance. This article reviews current understandings of ecological disturbance and conservation noncompliance, concluding that differing forms of noncompliance hold differing implications for diversity. The authors suggest that forms of anthropogenic patchy disturbance resulting from violation may maintain, if not enhance, floral diversity. They therefore argue for extended empirical investigation of such activities and call for conservation biologists to work with social scientists to assess this conservation reality by analyzing how and when incomplete enforcement and rule-breaking drive ecological change.     

浅谈阴离子洗涤剂测定中应注意的几个问题

水质监测中,采用亚甲蓝分光光度法测定水中的阴离子,由于方法的选择性较差,干扰因素及操作过程中出现的问题也颇多,本文就阴离子测定中干扰消除及分析操作过程中应注意的问题进行讨论。     

Chemically mediated avoidance of a predatory odonate (Anaxjunius) by American toad (Bufoamericanus) and wood frog (Ranasylvatica) tadpoles

Predators can have significant nonlethal effects on prey by modifying prey behaviour through chemically mediated interactions. We examined behavioural responses of wood frog (Ranasylvatica) and American toad (Bufoamericanus) tadpoles to both direct and indirect chemical signals associated with a predatory odonate (Anaxjunius). In laboratory trials, tadpoles of both species responded strongly to water conditioned with Anax nymphs by decreasing foraging rates, becoming immobile, and moving away from the stimulus. The responses to water conditioned with starved Anax versus Anax that fed on conspecific tadpoles did not differ significantly; these results suggest that tadpoles rely primarily on direct signals to detect odonates. Rana did not respond to water conditioned with conspecific tissue extracts, while Bufo responded with behaviours that were indistinguishable from those of tadpoles exposed to Anax chemicals. In a field experiment, the responses of R. sylvatica tadpoles to Anax chemicals were similar to those of tadpoles observed in the laboratory. Collectively, our data indicate that tadpoles of both species use chemical cues to assess predation risk from other community members. Tadpoles can selectively distinguish members who pose a threat, and only evacuate food patches or reduce foraging rates when in danger. These behaviours appear to be adaptive and are consistent with the predictions of optimality theory. Received: 1 August 1997 / Accepted after revision: 22 November 1997     

Paleoecological Assessment of Watershed History in PRIMENet Watersheds at Acadia National Park, USA

Paleoecological reconstructions of forest stand histories for two upland watersheds at Acadia National Park in Maine were completed to support related watershed chemistry studies. The project hypothesis was that forest type and fire history influence long-term cycling and storage of atmospheric mercury and nitrogen within watersheds. The reconstructions document differences in major vegetation composition and disturbance between the burned and unburned watersheds during the past several centuries. Pollen and charcoal stratigraphies from organic sediment accumulations in forested wet depressions indicate that the present experimental design of contrasting disturbance and forest histories has persisted during recent centuries. The unburned watershed has been dominated by spruce (Picea rubens) and fir (Abies balsamea) for 500 years or more and has not recently burned or been substantially cleared. The burned watershed is dominated by a heterogeneous forest of patchy hardwood, mixed wood, and softwood stands. A large portion of this watershed burned severely in 1947 and probably more than once in the 1800s, and has supported heterogeneous successional forests for 200 years or longer. Overall, these results support the underlying premise that the experimental design of this watershed research can be used to infer landscape controls on biogeochemical processes.     

Dead indoor plants strengthen belief in global warming

Studies have revealed that heuristics and accessible schemas may affect people's judgments about global warming. In two studies, participants were asked to report on beliefs regarding global warming while seated in a room in which a small tree or several trees had been placed. In one experimental condition, the tree possessed its foliage whereas in the other, the branches were bare. It was found that participants were more likely to believe in global warming in presence of the tree without foliage (Study 1), that this belief increased in presence of three rather than one tree without foliage (Study 2), and that other beliefs not related to global warming were not affected by the experimental conditions. These results reveal that surrounding physical cues do affect beliefs about global warming. The spreading activation theory is used to explain these results.     

Restoration of riparian forest using irrigation,artificial disturbance,and natural seedfall

In interior western North America, many riparian forests dominated by cottonwood and willow are failing to reproduce downstream of dams. We tested the hypothesis that establishment is now prevented by absence of the bare, moist substrate formerly provided by floods and channel movement. Along Boulder Creek, a dammed stream in the Colorado plains, we tested the effects of disturbance (sod removal), irrigation, and addition of seed on the establishment of seedings of plains cottonwood (Populus deltoides subsp.monilifera) and peachleaf willow (Salix amygdaloides). In unirrigated, undisturbed plots, mean cottonwood density was 0.03 seedlings/m². Irrigation or disturbance alone produced mean cottonwood densities of 0.39 and 0.75 seedlings/m². Plots that were both irrigated and disturbed produced a mean cottonwood density of 10.3 seedlings/m². The effects of irrigation and disturbance on cottonwood establishment were significant (P<0.005); added seed had no significant effect (P=0.78). The few cottonwood seedlings in unirrigated plots were in low positions susceptible to scour by future moderate flows. We conclude that cottonwood establishment along Boulder Creek is limited by the scarcity of bare, moist sites safe from future scour. Establishment of peachleaf willow was significantly affected only by disturbance; daily sprinkler irrigation did not provide sufficient moisture to increase survival of this species. Our results demonstrate the feasibility of restoring plains cottonwood forests using natural seedfall, even where only widely scattered adult trees are present. Because use of natural seedfall conserves the genetic makeup of the local population, this method may be preferable to the use of imported cuttings.     

Effects of three phamaceuticals on the responses of tadpoles to predator alarm cues

The aim of this study is to measure the effects of two selective serotonin reuptake inhibitors, fluoxetine and sertraline, and one selective serotonin and norepinephrine reuptake inhibitor, venlafaxine, on the swimming and lateralization behaviour of Sclerophrys arabica tadpoles exposed to predator alarm cues. Tadpoles were exposed to the three pharmaceuticals either at 0.5 µg/L or 2.0 µg/L, either individually or as a mixture for 14 days. Control tadpoles and those exposed to high concentration of drugs individually or as a mixture, and those exposed to the low-concertation mixture reduced their swimming speed. Tadpoles exposed to 0.5 µg/L fluoxetine or venlafaxine did not respond to the alarm cues. Tadpoles exposed to the mixture had similar responses to that of the control. Results indicate that these drugs have an additive mode of action. Tadpoles exposed to the low-concentration mixture increased lateralization of movement.     

Tree Structure and Diversity in Human-Impacted Littoral Forests, Madagascar

This research surveyed human-impacted littoral forests in southeastern Madagascar to determine (i) how forest structural features, indicative of human impact, are related to total, utilitarian, and endemic tree diversity; (ii) the distribution, abundance, and demographics of tree species groups (i.e., total, useful, endemic) across the landscape; and (iii) the amount of basal area available per human use category. We also use these data to consider issues of sustainable use and how human impact may influence littoral forest tree community composition across the landscape. Within 22 transects of 400 m² each, we recorded a total of 135 tree species and 2155 individuals. Seventy-nine species (58%) were utilitarian and 56 (42%) were nonutilitarian species. Of the 2155 individuals, 1827 (84%) trees were utilitarian species. We recorded 23 endemic species (17% of the total species) and 17 (74%) of these were utilitarian species. Basal area was significantly correlated with Shannon Weiner Index values for total (r = 0.64, P < 0.01), utilitarian (r = 0.58, P < 0.01), and endemic tree diversity (r = 0.85, P < 0.01). Basal area was significantly correlated with the Simpson’s index values for the endemic species (r = 0.74, P < 0.01). These correlations suggest that endemic tree species, of high global conservation value, may be the species group most influenced by changes in forest structure. Utilitarian species constituted 84% of the total basal area. The use category contributing the highest amount of basal area to the landscape was firewood. The results presented herein demonstrate that the landscape of southeastern Madagascar, commonly perceived as degraded, retains high value for both global conservation purposes and for local livelihoods. Thus, valuable opportunities may exist for developing conservation incentives that leverage both global and local conservation needs.     

Magnetic compass mediates nocturnal homing by the alpine newt, Triturus alpestris

Experiments were carried out to investigate the use of magnetic compass cues in the nocturnal homing orientation of the alpine newt Triturus alpestris. Tests were carried out at a site 9 km to the east–northeast of the breeding pond. Newts were tested at night in an outdoor circular arena that provided an unimpeded view of celestial cues, in one of four symmetrical alignments of an earth-strength magnetic field. In tests carried out under partly cloudy skies newts exhibited homeward magnetic compass orientation. Because the moon was visible in some trials, but obscured by clouds in others, we investigated whether the presence of the moon contributed to the scatter in the distribution of magnetic bearings. When the moon was visible, the distribution of magnetic bearings was more scattered than when the moon was obscured by clouds, although in neither case was the distribution significant due, in part, to the small sample sizes. Moreover, when the moon was visible, newts oriented along a bimodal axis perpendicular to the moon azimuth, suggesting that the presence of the moon may have affected the newts behavior. To provide a more rigorous test of the role of magnetic compass cues when celestial cues were unavailable, nocturnal tests were carried out during the following migratory season under total overcast. In the absence of celestial compass cues, the distribution of magnetic bearings exhibited highly significant orientation in the homeward direction. These findings indicate that newts are able to orient in the homeward direction at night using the magnetic compass as the sole source of directional information. Moon light altered the newts behavior. However, this apparently resulted from the asymmetrical distribution of moon light in the testing arena, rather than the use of an alternative compass.