Studies In Temperate Regions Research Articles

The diversity of insectivorous bat assemblages among habitats within a subtropical urban landscape

AbstractWe investigated the bat (Microchiroptera) diversity of four major habitat types within a large Australian subtropical city (Brisbane, Australia) to determine whether species richness was affected by habitat changes associated with urbanization, as suggested from studies elsewhere. Forty sites, ten in each habitat type (remnant bushland, parkland, low‐density residential and high‐density residential) were surveyed using acoustic bat detectors on six non‐consecutive occasions. Fourteen bat species were recorded. The species accumulation curve of the entire Brisbane bat assemblage reached a plateau at 14 species. The total numbers of species in bushland, parkland, low‐density residential and high‐density residential habitats were 14, 13, 14 and 11 species, respectively. Asymptotic estimates of species richness for each habitat were close or equal to these totals. Mean asymptotic estimated species richness differed significantly among habitats, being lowest in high‐density residential sites and highest in low‐density residential sites. Evenness profiles were similar across habitats, and were not strongly dominated by a few species. Partitioning of diversity components showed that landscape (γ) diversity was mainly determined by the high species richness of low‐density residential and bushland habitats (α diversity), rather than high beta (β) diversity among habitats. These findings contradict those of other studies on bat diversity in which species richness was highest within ‘natural’ areas of the urban landscape and assemblages were dominated by one or two species. This highlights the need for caution in making generalizations based on existing information, which is dominated by studies in temperate regions.

Fate and effects of the insecticide chlorpyrifos in outdoor plankton‐dominated microcosms in Thailand

The fate and effects of the insecticide chlorpyrifos were studied in plankton-dominated, freshwater microcosms in Thailand. Disappearance rates of chlorpyrifos from the water column in the present study were similar to those in temperate regions. Insecticide accumulation in the sediment was relatively small, with the major part in the top layer (depth, 1.5 cm). Application of chlorpyrifos led to significant changes in freshwater biological communities. Clam shrimps (Conchostraca) and the cladoceran Moina micrura were the most susceptible species (no-observed-effect concentration [NOEC], 0.1 microg/L) and macroinvertebrates the most sensitive community (NOEC, 0.1 microg/L). These results are in agreement with those from semifield experiments with chlorpyrifos in temperate regions. The results of an in situ bioassay were used to calculate a NOEC of 0.1 microg/L and a 48-h median lethal concentration of 0.6 microg/L for M. micrura, which are similar to toxicity values reported for Daphnia magna in studies in temperate regions. Overall, these findings support the use of toxicity data from temperate regions for the risk assessment of low-persistent insecticides like chlorpyrifos for aquatic communities in tropical regions.

‘Non-exchangeable’ ammonium in soils from Swedish long-term agricultural experiments: Mobilization and effects of fertilizer application

In intensive agricultural systems, efficient nutrient use is necessary for high crop yields as well as for sustainable environmental management. Recent studies in temperate regions indicate that non-exchangeable NH4 +-N (NEA), which is fixed in clay minerals, may affect crop productivity and soil N dynamics more than previously thought. To estimate the quantity and plant availability of NEA in Swedish soils, ryegrass (Lolium perenne) was grown in a pot experiment using 18 soils that were collected (0–20 cm depth) from two long-term agricultural experiment series at five locations. Initial NEA, total N and soil K contents were measured, as well as NEA content 56, 112 and 168 days after planting of ryegrass. The results show that the soils (0–20 cm) contained 21–217 mg NEA kg−1 sieved soil (5–300 kg NEA ha−1) estimated as corresponding to 0.1–5.1% of the total soil N. Long-term application of farmyard manure (FYM) did not increase contents of soil NEA. Long-term application of K fertilizer increased soil contents of AL-extractable K, but there was no significant correlation with NEA content. Concurrent with ryegrass growth, NEA content decreased on average by 16% between day 0 and day 112, indicating that NEA was released from the soil and taken up by the plants.

Evaluation of macrofaunal effects on leaf litter breakdown rates in aquatic and terrestrial habitats

Abstract Decomposition of the organic matter is a key process in the functioning of aquatic and terrestrial ecosystems, although different factors influence processing rates between and within these habitats. Most patterns were described for temperate regions, with fewer studies in tropical, warmer sites. In this study, we carried out a factorial experiment to compare processing rates of mixed species of leaf litter between terrestrial and aquatic habitats at a tropical site, using fine and coarse mesh cages to allow or prevent colonization by macroinvertebrates. The experiment was followed for 10 weeks, and loss of leaf litter mass through time was evaluated using exponential models. We found no interaction between habitat and mesh size and leaf litter breakdown rates did not differ between fine and coarse mesh cages, suggesting that macroinvertebrates do not influence leaf litter decomposition in either habitat at our studied site. Leaf breakdown rates were faster in aquatic than in terrestrial habitats and the magnitude of these differences were comparable to studies in temperate regions, suggesting that equivalent factors can influence between‐habitat differences detected in our study.

Late Seasonal Breeding of River Otters in Yellowstone National Park

Abstract Seasonal breeding schedules for wild mammals, such as North American river otters (Lontra canadensis), often vary across their range. Previous studies in temperate regions found that river otters typically breed in March and April. Here we report on breeding condition and copulation of otters in June from Yellowstone Lake in Yellowstone National Park. Our findings suggest Yellowstone Lake otters have a relatively long breeding season, extending into June, or their breeding schedule is delayed so that energetically-demanding lactation coincides with spawning runs of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri).

Late-Holocene environmental history of two New England ponds: natural dynamics versus human impacts

Analyses of sedimentary diatoms in two New England ponds reveal limnological changes during the past 2500 years that are related to climatic change, anthropogenic activities and natural disturbance. Deforestation in the lake catchments during the eighteenth and nineteenth centuries temporarily affected diatom assemblages, with subsequent recovery. However, algal communities did not return completely to presettlement conditions as a result of long-term trends in climatic change, small-scale natural disturbances and delayed watershed recovery from acidification. A short-term rise in diatominferred dissolved organic carbon (DOC) in Levi Pond was related to partial removal of vegetation by logging in the catchment, and a similar DOC increase at North Round Pond is correlated with a hurricane and increased aquatic productivity. At Levi Pond, increasing diatom-inferred DOC concentrations during the past c. 2000 years likely reflect a long-term increase in allochthonous organic matter and peat development in the watershed related to moister conditions, supported by corresponding patterns in the stable-isotope, chironomid and pollen records. These results correspond with moisture patterns in adjacent areas inferred from pollen and sediment analyses, suggesting that diatoms in Levi Pond recorded a larger regional trend in increasing moisture. This is the first study in a temperate region that links diatom-inferred DOC concentration to past changes in moisture balance, suggesting that fossil diatoms may be a promising proxy for future palaeohydrological studies in temperate regions. However, more studies are necessary to separate the effects of peatland growth and allochthonous organic-matter input on lake-DOC concentrations.

Primary plant succession on recently deglaciated terrain in the Canadian High Arctic

AbstractAim Primary succession in a high arctic environment was examined to determine whether the patterns conform to models based on studies in temperate regions. The location also presented an unique opportunity to examine a well preserved pre‐Little Ice Age plant community and organically enriched palaeosol that are being released from the glacier along with the glacial and glaciofluvial sediments.Locations The main location was the recently deglaciated terrain of the Twin Glacier foreland at Alexandra Fjord, Ellesmere Island (79° N). The position of the glacier from air photos in 1959 and 1981, and periodic direct monitoring of the position of the terminus since 1980 provided good chronological control. Surveys of succession patterns were also conducted at four other sites in the Alexandra Fiord region of eastern central Ellesmere Island.Methods Vegetation cover of mosses and vascular plants (lichens were not present) was measured in 1994 and 1995 using a stratified random design. twinspan and canonical correspondence analysis were used together to examine successional vegetation patterns in relation to a set of environmental variables. Species richness, total vegetation cover, and a combined set of soil parameters (pH, organic matter content, moisture and fine substrate) were compared between the two principal soil types, palaeosol and glaciofluvial sediment.Results Terrain age accounted for most of the variation in species composition over the study area. The succession followed a directional‐replacement series with four main stages of dominance in at least 44 years: (1) mosses → (2) graminoid‐forb → (3) deciduous shrub‐moss → (4) evergreen dwarf‐shrub‐moss. There was little difference in species richness patterns over time on the palaeosol compared with the glaciofluvial sediment. However, total vegetation cover was significantly higher on palaeosol and there was a significant difference in a combined set of soil parameters between the two soil types, which indicates that palaeosol may provide conditions more favourable for establishment and growth.Main conclusions Directional‐replacement succession is possible in a high arctic oasis environment; however, this mode of succession is probably atypical of much more extensive high arctic environments such as polar deserts. Descriptive results from four other glacier forelands sampled in 1995 on east‐central Ellesmere Island showed directional succession with no species replacement at two sites and non‐directional succession without species replacement at another site. Primary succession in these high arctic sites is strongly controlled by local environmental conditions.

Home Range Size of Sympatric Squirrel Species Inhabiting a Lowland Dipterocarp Forest in Malaysia1

Home range sizes and spatial overlap of four sympatric squirrel species were investigated in a lowland dipterocarp forest in Malaysia using a radio-tracking method. The population density of Callosciurus caniceps was highest and C. notatus was next highest, while C. nigrovittatus and Lariscus insignis were scarce. C. caniceps was larger than C. nigrovittatus and C. notatus while L. insignis was extremely small. For females, home range size was smaller in L. insignis than Callosciurus spp., which may support the body weight hypothesis: larger species have larger home ranges. Among the three Callosciurus species, female C. caniceps had the smallest home range. These differences were accounted for by habitat characteristics rather than by density or body weight; C. caniceps was dominant in bushy areas and used crowded small trees while C. notatus and C. nigrovittatus used large trees in the forest. In this study, home range size did not change seasonally; this differs from studies in temperate regions, possibly because food availability is much less variable among seasons in tropical rain forest. Home range overlap among heterospecific individuals was common but different species seemed to partition space by using different vertical levels of the forest. Consequently, the home range size and spatial overlap of sympatric squirrel species may be affected by habitat diversity in tropical rain forest.

Changes in endogenous ABA level in relation to the dormancy cycle in grapevines grown in a hot climate

SummaryIn warm-winter regions, the need for artificial means to compensate for the lack of natural chilling becomes a dominant factor for maintaining economic production of table grapes. However, in the absence of a reliable method of predicting the time of natural bud break, the application of the dormancy breaking agent hydrogen cyanamide (HC) entails the risk of serious bud damage if the application is mistimed. In several studies in temperate regions, concentrations of endogenous abscisic acid (ABA) were found to increase as the grape buds entered dormancy, and to decrease during winter months towards dormancy release. To assess the possibility of using bud ABA content as a marker for the stage of bud dormancy in grapevines grown in hot regions, we evaluated the dormancy depth of grape buds in the course of the dormancy cycle and monitored their endogenous ABA content in cv. Perlette vines grown in the Jordan Valley. The endogenous ABA content was highest at maximum dormancy. However, the decline in ABA content was not correlated with dormancy release. The involvement of ABA in dormancy induction and maintenance is discussed.

Composition Changes in a Subandean Avifauna after Long‐Term Forest Fragmentation

Abstract: Current understanding of the effects of forest fragmentation is based largely on studies in temperate regions, Australia, and Neotropical lowlands. In contrast, the consequences of anthropogenic forest fragmentation for Andean avifaunas are poorly understood, despite large‐scale habitat loss and fragmentation. I assessed the effects of long‐term fragmentation on a subandean avifauna in Colombia by comparing the occurrence of bird species in forest fragments isolated over 50–90 years with the original avifauna. Prefragmentation bird composition was based on historical records and current species composition in continuous forest. The original avifauna had approximately 139 forest species and 45 species of open habitats. Among forest species, 30% were currently extinct in fragmented forest and 4% were regionally extinct. At least 23 nonforest species colonized the region from the lowlands following deforestation. Species with small geographic ranges and those that were locally scarce or rare throughout their ranges were likely to be locally extinct. Forest raptors, terrestrial insectivores, and large frugivores were highly extinction prone, whereas nectarivores, small frugivores, and aerial insectivores were highly resilient; other guilds were intermediate. Antbirds (Formicariidae, Thamnophilidae), Cotingas, and, especially, Icterids were highly extinction prone. Large body size was not a determinant of vulnerability except among frugivores. Sixty‐two percent of the species of special conservation concern were extinct in fragments. These results suggest that only large forest tracts will ensure the survival of a large proportion of subandean avifaunas. Fragments of mature forest, however, may support a diverse avifauna, including small populations of globally endangered species several decades after isolation. These fragments could play an important role in the restoration of local avifaunas. A good understanding of the mechanisms that allow persistence in such fragments may prove essential for the conservation of those species for which no large tracts of suitable habitat remain.

Laboratory studies on the leaching of aldicarb through a tropical soil from Belize, Central America

Studies in temperate regions indicate that the carbamate insecticide aldicarb and its metabolites leach readily through agricultural soils into groundwater. However, little is known about the fate of this nematicide in tropical regions, where its leaching potential may be even greater because of high annual rainfall and the acidic nature and low organic content of many tropical soils. Examination of the leaching behaviour of aldicarb and its metabolites in columns containing soil from Belize, Central America, indicated that total carbamate residues (TCR) could rapidly reach concentrations > 15 mg L−1 in porewater 1 m below the soil surface within 70 days of application. These values are well in excess of the US EPA Health Advisory level of 0.01 mg L−1. TCR retention within a given depth interval in the soil columns relative to incoming TCR flux was greatest between 0 and 0.1 m, reflecting high organic matter contents in the upper soil. Retention below 0.1 m was relatively consistent with depth, while differences in relative retention between columns were due to a greater duration of leaching for the second column. Aldicarb was rapidly oxidized to aldicarb sulfoxide and aldicarb sulfone in these soils. The high concentration and mobility of TCR in this acidic soil is attributed to the transformation of the parent compound to the sulfoxide metabolite, which has a lower degradation rate and organic carbon partioning coefficient than aldicarb.

Considerations for Tile Drainage-Water Quality Studies in Temperate Regions

Experimental designs of 14 subsurface drainage-water quality studies conducted over the past 18 years are reviewed. To more accurately determine mass contaminant flux and processes, more intense monitoring of drain discharge rate and drainage water quality is needed than in most past studies. A recently installed field scale system of subsurface drainage-water quality plots and associated equipment, capable of intense, year round monitoring, is described and preliminary data showing performance of the system is presented. The material presented should be of interest to those planning and designing drainage-water quality studies, or refitting existing drainage installation for water quality investigations.