Fuel-Reduction Treatment Effects on Avian Community Structure and Diversity

Abstract: We assessed responses of the breeding bird community to mechanical thinning and prescribed surface fire, alone and in combination, between 2000 and 2006 in ponderosa pine (Pinus ponderosa) forests in northern Arizona, USA. Fuel-reduction treatments did not affect species richness or evenness, and effects on density of 5 commonly detected species varied among species. Populations of some species, such as the western bluebird (Sialia mexicana), increased following burning treatments, whereas others, such as the mountain chickadee (Poecile gambeli), decreased in response to thinning treatments. Our results also identified a temporal response component, where avian community composition and structure changed synchronously on all treatments over time. Given the modest effects these small-scale fuel-reduction treatments had on avian composition and the specific density responses of particular species, our results suggest that land managers should consider implementing prescribed surface fire after thinning projects, where appropriate.     

Mitochondrial phylogeny of Arvicolinae using comprehensive taxonomic sampling yields new insights

Comprehensive taxonomic sampling can vastly improve the accuracy of phylogenetic reconstruction. Here, we present the most inclusive phylogenetic analysis of Arvicolinae (Mammalia, Rodentia) to date, combining all published cytochrome  b gene sequences of greater than 1097 bp and new sequences from two monotypic genera. Overall, the phylogenetic relationships between 69 species of voles and lemmings, representing 18 genera and 10 tribes, were studied. By applying powerful modern approaches to phylogenetic reconstruction, such as maximum likelihood and Bayesian analysis, we provide new information on the early pulse of evolution within the Arvicolinae. While the position of two highly divergent lineages, Phenacomys and Ondatra , could not be resolved, the tribe Lemmini, appeared as the most basal group of voles. The collared lemmings (Dicrostonychini) grouped together with all of the remaining tribes. The two previously unstudied monotypic genera Dinaromys and Prometheomys form a moderately well-supported monophyletic clade, possibly a sister group to Ellobius (Ellobiusini). Furthermore, with one exception, all tribes ( sensu Musser & Carleton, 2005) proved to be monophyletic and can thus be regarded as meaningful evolutionary entities. Only the tribe Arvicolini emerged as paraphyletic in both analyses because of the unresolved phylogenetic position of Arvicola terrestris . Steppe voles of the genus Lagurus were solidly supported as a sister group to the Microtus and allies clade.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 825–835.     

Restoration options for potential persistence of submersed aquatic vegetation: combining ecological, hydrodynamic and sediment transport modelling

1. Restoration of shallow turbid lakes to promote growth of submersed aquatic vegetation (SAV) requires knowledge of the environmental factors affecting SAV growth and persistence, and a means to predict the success of SAV reestablishment under different management scenarios to improve these environmental conditions. We used a dynamic ecological modelling approach relating SAV responses to changes in physical and chemical conditions, with information on water level, flow and transparency being provided by hydrodynamic and sediment transport models. 2. The potential persistence of Vallisneria americana was similar under simulated environmental conditions in 1946 and in 1954, as was the potential persistence of Potamogeton pectinatus, indicating that the disappearance of V. americana from Peoria Lake (U.S.A.) previously attributed to an extended spring flood in 1954, may have been related to the combined effects of changes in water level, flow and water transparency as well as possibly other factors. 3. Recent environmental conditions (for 2000) proved not to be conducive for the colonization and persistence potential of V. americana, but would allow colonization by P. pectinatus. The construction of a hypothetical levee along the eastern descending line of the navigation channel in Upper Peoria Lake, which was expected to reduce fetch‐ and navigation‐related turbidity, did not improve the situation for V. americana and overall deteriorated the situation for P. pectinatus. Thus, such a hydraulic alteration, generally considered as beneficial for SAV restoration, may not always be successful. 4. The results of the simulations indicated that the environmental conditions for potential persistence in Peoria Lake were generally less favourable for V. americana than for P. pectinatus. Measures suggested to restore SAV communities in such a lake should aim at reducing concentrations of total suspended solids at the point of inflow by a factor of three to four and limiting fetch‐ and navigation‐related resuspension.     

Productivity and significance of headwater streams: population structure and biomass of the black-bellied salamander (Desmognathus quadramaculatus)

1. Headwater streams are a significant feature of the southern Appalachian landscape, comprising more than 70% of the total stream length in the region. Salamanders are the dominant vertebrate within headwater‐riparian forest ecosystems, but their ecological role is not clearly understood. 2. We studied a population of black‐bellied salamanders (Desmognathus quadramaculatus) at a headwater stream in the southern Appalachian Mountains using radio‐telemetry and mark‐recapture methods. The length and area of headwater streams in the region were estimated using GIS. 3. Home ranges of radio‐tracked salamanders were relatively small (mean = 1.06 m²). Adult salamanders in our telemetry study inhabited edge microhabitats significantly more often than either stream or riparian microhabitats, and the same trend was observed in the mark‐recapture study. 4. We estimated the population density at this site to be 11 294 salamanders ha^?1, amounting to 99.30 kg ha^?1 of biomass, an estimate that is six times greater than reported in previous studies. The majority of this biomass was found within the stream, but 22% was found in the surrounding riparian habitat more than 1 m from the stream. Using headwater stream length and area estimates, we extrapolated biomass estimates for black‐bellied salamanders inhabiting stream and riparian microhabitats across the study region. 5. We report one of the largest estimates of secondary consumer biomass for a headwater ecosystem, attesting to the overall productivity of headwater streams. Headwaters are known to be important for ecological and ecosystem processes and our biomass estimates suggest that salamanders are a critical component to these systems.     

Global assessment of coral bleaching and required rates of adaptation under climate change

Elevated ocean temperatures can cause coral bleaching, the loss of colour from reef‐building corals because of a breakdown of the symbiosis with the dinoflagellate Symbiodinium. Recent studies have warned that global climate change could increase the frequency of coral bleaching and threaten the long‐term viability of coral reefs. These assertions are based on projecting the coarse output from atmosphere–ocean general circulation models (GCMs) to the local conditions around representative coral reefs. Here, we conduct the first comprehensive global assessment of coral bleaching under climate change by adapting the NOAA Coral Reef Watch bleaching prediction method to the output of a low‐ and high‐climate sensitivity GCM. First, we develop and test algorithms for predicting mass coral bleaching with GCM‐resolution sea surface temperatures for thousands of coral reefs, using a global coral reef map and 1985–2002 bleaching prediction data. We then use the algorithms to determine the frequency of coral bleaching and required thermal adaptation by corals and their endosymbionts under two different emissions scenarios. The results indicate that bleaching could become an annual or biannual event for the vast majority of the world's coral reefs in the next 30–50 years without an increase in thermal tolerance of 0.2–1.0°C per decade. The geographic variability in required thermal adaptation found in each model and emissions scenario suggests that coral reefs in some regions, like Micronesia and western Polynesia, may be particularly vulnerable to climate change. Advances in modelling and monitoring will refine the forecast for individual reefs, but this assessment concludes that the global prognosis is unlikely to change without an accelerated effort to stabilize atmospheric greenhouse gas concentrations.     

Effects of fertilization and herbicides on growth of young loblolly pine and infestations of Nantucket pine tip moth（Lepidoptera： Tortricidae）

A 2-year-old pine plantation was selected to receive treatments of fertilizers and herbicides to evaluate effects on Nantucket pine tip moth infestations and the tree growth parameters of height, diameter and volume increment. Nitrogen and phosphorus fertilizers, and hexazinone and sulfometuron methyl herbicides were used in creating six treatments： （i） control; （ii） phosphorus; （iii） nitrogen and phosphorus; （iv） phosphorus and herbicide; （v） nitrogen, phosphorus and herbicide; and （vi） herbicide. Treatments were applied in 1987 and 1988. In 1987, trees treated with nitrogen, phosphorus and herbicide had significantly greater height, diameter and volume growth than trees not receiving fertilizer treatments, but did not have significantly higher tip moth infestations than control trees. Treatments receiving phosphorus only had much lower tip moth infestation rates than other treatments except nitrogen and phosphorus. In 1988, tip moth infestations were uniformly low, with no differences in treatment effects observed.     

Thermodynamics and Kinetics of MTBE Degradation: A Density Functional Theory Study

Computational studies using density functional theory can help define which of a variety of reactions may be involved in the degradation of the fuel oxygenate methyl tert-butyl ether (MTBE). It is shown that hydrolysis of MTBE in the vapor phase or in neutral aqueous media, as well as its unimolecular decomposition, are not significant degradation mechanisms. The acid catalyzed hydrolysis of MTBE is a more feasible degradation pathway and is shown to proceed via tert-butyl carbonium ion formation. Hydrogen abstraction is shown to be the dominant first step in the degradation of MTBE initiated by hydroxyl radicals.     

Comparative vegetative anatomy and systematics of Cymbidium (Cymbidieae: Orchidaceae)

The genus Cymbidium (Orchidaceae) exhibits distinctive ecological diversification and occurs in terrestrial, epiphytic, and lithophytic life forms. One species, Cymbidium macrorhizon , lacks foliage leaves and has a strongly mycoparasitic existence. Correlation between habitat differentiation and anatomical characters was tested for 21 species of Cymbidium and its putative sister groups. Although hypostomaty characterizes the genus, C. canaliculatum shows amphistomaty. Ecological preference of this species indicates that amphistomaty is likely adapted to intensive insolation. Four types of subepidermal foliar sclerenchyma were found. Two forest floor species, C. goeringii and C. lancifolium as well as the mycoparasitic C. macrorhizon , do not have this sclerenchyma. In this genus, development of sclerenchyma is correlated with the degree of epiphytism. Palisade mesophyll evolved in Cymbidium section Cymbidium . As members of this section grow on isolated trees in tropical lowland forests or on rocks, the differentiation of palisade tissue is probably correlated with immigration to high light habitats. With the exception of C. macrorhizon , stegmata were found in leaves and stems of Cymbidium . Furthermore, a few epiphytic species have stegmata in their roots; this is a curious feature rarely found in vascular plants. Subterranean rhizomes characterize terrestrial species, while ageotropic roots are found in some epiphytic species. Cymbidium macrorhizon shows peculiar features such as degeneration of stomata, anomocytic stomata, and lack of stegmata and sclerenchyma. This set of character transformations is probably correlated with the evolution of mycoparasitic existence. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 383–419.     

Velamen and exodermis characters of West African epiphytic orchids in relation to taxonomic grouping and habitat tolerance

The velamen and exodermis of roots of 76 species of epiphytic orchids occurring in West Africa were examined and evaluated for the following characters: number of velamen layers; wall striations and hairs of the velamen; wall thickening and lignification of velamen and exodermal cells; size, and uniformity in shape and size, of velamen and exodermal cells. The term epi-velamen is proposed for the distinctive outermost layer of multi-seriate velamen. High correlation is reported between the number of velamen layers and taxonomic as well as habitat-tolerance groupings, together with lower, but still appreciable, correlation between the other characters evaluated and taxonomic and habitat-tolerance groupings.     

The flowering time of West African orchids*

Induction of flowering in orchids and controlling factors are briefly reviewed and results presented of observations on 121 epiphytic and 22 terrestrial West African orchid species under cultivation in Nigeria, together with field observations and published reports. It is concluded that about 66% of West African epiphytes flower during one fairly consistent period of the year, 21% during two or three periods and 13% over a long and variable period. At least 35% of the epiphytes and perhaps at least 27% of the terrestrials seem directly day-length controlled. Additional species appear indirectly influenced by day-length. Low temperature and temperature fluctuations induce flowering in other species. Moisture influences flowering only in shortening the time required for ontogenetic maturity. Epiphytes at high altitudes bloom earlier than plants in lowlands, and sometimes at different seasons. Possible genetically controlled blooming-time variations are mentioned.