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PubMed2001

Distribution, relative importance and effect of lepidopterous borers on maize yields in the forest zone and mid-altitude of Cameroon.

Geographic distribution, relative importance, and effect of lepidopterous stem and ear borers on maize, Zea mays L., were studied in the humid forest and the mid-altitude zones of Cameroon from 1994 to 1997. Six villages were chosen in the forest zone and grouped into three blocks representing gradients in human population density. A single block with three villages was chosen in the mid-altitude. Farmers' maize fields were surveyed during the vegetative growth phase for Busseola fusca (Fuller) egg batches, and at harvest for number of larvae and pupae by species, plant damage, and ear weight. There was no significant block effect for any of the variables measured, and most of the overall variance (72-99%) was attributed to within-field variability. In the forest zone, the noctuid B. fusca and the pyralid Eldana saccharina (Walker) accounted for >80% of all species in almost all locations, followed by the pyralid Mussidia nigrivenella (Ragonot) and the tortricid Cryptophlebia leucotreta (Meyrick). The noctuid Sesamia calamistis (Hampson) was found in almost all locations during the first season but disappeared in most locations in the second season. B. fusco egg infestation was significantly higher during the second compared with the first season, whereas larval and pupal densities were much higher during the first season. E. saccharina was the predominant species during the second season, when densities increased fourfold. In the mid-altitude, B. fusca was the predominant species. No significant differences in pest densities, plant damage, and ear weight were found between years. Results of stepwise regression of stem and ear damage on pest densities verified the relative importance of the individual species. In the forest zone, ear and stem damage significantly reduced ear weight, whereas in the mid-altitude only stem tunneling was significant.

Altitude↗
PubMed2006

Movement of dengue vectors between the human modified environment and an urban forest in Rio de Janeiro.

The movement of Aedes aegypti (L.) and Aedes albopictus (Skuse) females between sylvatic and urban environments was investigated by marking, releasing, and recapturing adults and by identifying rubidium (Rb)-marked eggs of females that were released after taking a bloodmeal containing RbCI. When released in the forest, Ae. albopictus females flew as far as 1000 m and reached houses within 1 wk. When Ae. albopictus were released close to houses, most females were recaptured near the release point, and Rb-marked eggs were found 1000 m away in the forest only once, 35 d after the release. These differing patterns of movement may suggest a preference of Ae. albopictus for the human-modified environment. Ae. aegypti, however, showed low tendency to disperse into the forest. The capacity of Ae. albopictus females to disperse from a sylvatic into a human-modified environment suggests that this species may play a role in the dissemination of forest-restricted pathogens, such as yellow fever virus.

Aedes↗
PubMed2006

Changes in hardwood forest understory plant communities in response to European earthworm invasions.

European earthworms are colonizing earthworm-free northern hardwood forests across North America. Leading edges of earthworm invasion provide an opportunity to investigate the response of understory plant communities to earthworm invasion and whether the species composition of the earthworm community influences that response. Four sugar maple-dominated forest sites with active earthworm invasions were identified in the Chippewa National Forest in north central Minnesota, USA. In each site, we established a 30 x 150 m sample grid that spanned a visible leading edge of earthworm invasion and sampled earthworm populations and understory vegetation over four years. Across leading edges of earthworm invasion, increasing total earthworm biomass was associated with decreasing diversity and abundance of herbaceous plants in two of four study sites, and the abundance and density of tree seedlings decreased in three of four study sites. Sample points with the most diverse earthworm species assemblage, independent of biomass, had the lowest plant diversity. Changes in understory plant community composition were most affected by increasing biomass of the earthworm species Lumbricus rubellus. Where L. rubellus was absent there was a diverse community of native herbaceous plants, but where L. rubellus biomass reached its maximum, the herbaceous-plant community was dominated by Carex pensylvanica and Arisaema triphyllum and, in some cases, was completely absent. Evidence from these forest sites suggests that earthworm invasion can lead to dramatic changes in the understory community and that the nature of these changes is influenced by the species composition of the invading earthworm community.

Animals↗
PubMed2006

Extinction debt of forest plants persists for more than a century following habitat fragmentation.

Following habitat fragmentation individual habitat patches may lose species over time as they pay off their "extinction debt." Species with relatively low rates of population extinction and colonization ("slow" species) may maintain extinction debts for particularly prolonged periods, but few data are available to test this prediction. We analyzed two unusually detailed data sets on forest plant distributions and land-use history from Lincolnshire, United Kingdom, and Vlaams-Brabant, Belgium, to test for an extinction debt in relation to species-specific extinction and colonization rates. Logistic regression models predicting the presence-absence of 36 plant species were first parameterized using data from Lincolnshire, where forest cover has been relatively low (approximately 5-8%) for the past 1000 years. Consistent with extinction debt theory, for relatively slow species (but not fast species) these models systematically underpredicted levels of patch occupancy in Vlaams-Brabant, where forest cover was reduced from approximately 25% to <10% between 1775 and 1900 (it is presently 6.5%). As a consequence, the ability of the Lincolnshire models to predict patch occupancy in Vlaams-Brabant was worse for slow than for fast species. Thus, more than a century after forest fragmentation reached its current level an extinction debt persists for species with low rates of population turnover.

Belgium↗
PubMed2006

Recovery of forest structure and spectral properties after selective logging in lowland Bolivia.

Effective monitoring of selective logging from remotely sensed data requires an understanding of the spatial and temporal thresholds that constrain the utility of those data, as well as the structural and ecological characteristics of forest disturbances that are responsible for those constraints. Here we assess those thresholds and characteristics within the context of selective logging in the Bolivian Amazon. Our study combined field measurements of the spatial and temporal dynamics of felling gaps and skid trails ranging from <1 to 19 months following reduced-impact logging in a forest in lowland Bolivia with remote-sensing measurements from simultaneous monthly ASTER satellite overpasses. A probabilistic spectral mixture model (AutoMCU) was used to derive per-pixel fractional cover estimates of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), and soil. Results were compared with the normalized difference in vegetation index (NDVI). The forest studied had considerably lower basal area and harvest volumes than logged sites in the Brazilian Amazon where similar remote-sensing analyses have been performed. Nonetheless, individual felling-gap area was positively correlated with canopy openness, percentage liana coverage, rates of vegetation regrowth, and height of remnant NPV. Both liana growth and NPV occurred primarily in the crown zone of the felling gap, whereas exposed soil was limited to the trunk zone of the gap. In felling gaps >400 m2, NDVI, and the PV and NPV fractions, were distinguishable from unlogged forest values for up to six months after logging; felling gaps <400 m2 were distinguishable for up to three months after harvest, but we were entirely unable to distinguish skid trails from our analysis of the spectral data.

Bolivia↗
PubMed2006

Cicada emergence in Southwestern riparian forest: influences of wildfire and vegetation composition.

Annually emerging cicadas are a numerically and ecologically dominant species in Southwestern riparian forests. Humans have altered disturbance regimes that structure these forests such that floods are less common and wildfires occur more frequently than was historically the case. Impacts of these changes on primary consumers such as riparian cicadas are unknown. Because cicadas are consumed by a variety of animal species, disturbances that alter timing of their emergence or abundance could have consequences for species at higher trophic levels. We trapped emerging cicadas (Tibicen dealbatus) in burned and unburned riparian forest plots along the Middle Rio Grande in central New Mexico (USA) to determine effects of wildfire and vegetation structure on their density and phenology. We measured vegetation variables and soil temperature at cicada traps and related these variables to variation in emergence density and phenology. We also experimentally heated soil under emergence traps to examine the relationship between soil temperature and emergence phenology. Emergence density was similar in wildfire and unburned plots, though emergence date averaged earlier in wildfire plots and experimentally heated traps. We identified models containing cottonwood proximity (distance from the nearest cottonwood tree) and cottonwood canopy coverage as the most parsimonious explanations of emergence density at each trap. Model selection results were consistent with the literature and field observations that showed that cottonwood trees are an essential resource for T. dealbatus. Cottonwood canopy was also correlated with low soil temperatures, which are associated with later emergence dates. Failure of cottonwoods to reestablish following wildfire could result in cicadas emerging at lower densities and at earlier dates. For cicadas to emerge at densities and times that provide the greatest benefits to birds and other riparian-obligate secondary consumers, riparian forests should be protected from fire, and native vegetation in wildfire sites should be restored.

Animals↗
PubMed2006

N fertilization effects on denitrification and N cycling in an aggrading forest.

We investigated N cycling and denitrification rates following five years of N and dolomite amendments to whole-tree harvested forest plots at the long-term soil productivity experiment in the Fernow Experimental Forest in West Virginia, USA. We hypothesized that changes in soil chemistry and nutrient cycling induced by N fertilization would increase denitrification rates and the N2O:N2 ratio. Soils from the fertilized plots had a lower pH (2.96) than control plots (3.22) and plots that received fertilizer and dolomite (3.41). There were no significant differences in soil %C or %N between treatments. Chloroform-labile microbial biomass carbon was lower in fertilized plots compared to control plots, though this trend was not significant. Extractable soil NO3- was elevated in fertilized plots on each sample date. Soil-extractable NH4+, NO3-, pH, microbial biomass carbon, and %C varied significantly by sample date suggesting important seasonal patterns in soil chemistry and N cycling. In particular, the steep decline in extractable NH4+ during the growing season is consistent with the high N demands of a regenerating forest. Net N mineralization and nitrification also varied by date but were not affected by the fertilization and dolomite treatments. In a laboratory experiment, denitrification was stimulated by NO3- additions in soils collected from all field plots, but this effect was stronger in soils from the unfertilized control plots, suggesting that chronic N fertilization has partially alleviated a NO3- limitation on denitrification rates. Dextrose stimulated denitrification only in the whole-tree-harvest soils. Denitrification enzyme activity varied by sample date and was elevated in fertilized plots for soil collected in July 2000 and June 2001. There were no detectable treatment effects on N2O or N2 flux from soils under anaerobic conditions, though there was strong temporal variation. These results suggest that whole-tree harvesting has altered the N status of these soils so they are less prone to N saturation than more mature forests. It is likely that N losses associated with the initial harvest and high N demand by aggrading vegetation is minimizing, at least temporarily, the amount of inorganic N available for nitrification and denitrification, even in the fertilized plots in this experiment.

Ammonium Sulfate↗
PubMed2004

Acoustic identification of eight species of bat (mammalia: chiroptera) inhabiting forests of southern hokkaido, Japan: potential for conservation monitoring.

Assessing the impact of forest management on bat communities requires a reliable method for measuring patterns of habitat use by individual species. A measure of activity can be obtained by monitoring echolocation calls, but identification of species is not always straightforward. We assess the feasibility of using analysis of time-expanded echolocation calls to identify free-flying bats in the Tomakomai Experimental Forest of Hokkaido University, Hokkaido, northern Japan. Echolocation calls of eight bat species were recorded in one or more of three conditions: from hand-released individuals, from bats flying in a confined space and from bats emerging from their roost. Sonograms of 171 calls from 8 bat species were analyzed. These calls could be categorized into 3 types according to their structure: FM/CF/FM type (Rhinolophus ferrumequinum), FM types (Murina leucogaster, Murina ussuriensis, Myotis macrodactylus and Myotis ikonnikovi) and FM/QCF types (Eptesicus nilssonii, Vespertilio superans and Nyctalus aviator). Sonograms of the calls of R. ferrumequinum could easily be distinguished from those of all other species by eye. For the remaining calls, seven parameters (measures of frequency, duration and inter-call interval) were examined using discriminant function analysis, and 92% of calls were correctly classified to species. For each species, at least 80% of calls were correctly classified. We conclude that analysis of echolocation calls is a viable method for distinguishing between species of bats in the Tomakomai Experimental Forest, and that this approach could be applied to examine species differences in patterns of habitat-use within the forest.

Acoustics↗
PubMedDate not supplied

Mercury sequestration in forests and peatlands: a review.

Nearly all Hg in vegetation is derived directly from the atmosphere. Mass of Hg in forest vegetation (roughly 0.1 mg m(-2)) is about an order of magnitude smaller than that in the forest floor (1 mg m(-2)) and two orders of magnitude smaller than that in the mineral soil (10 mg m(-2)). Mass of Hg in peat (20 mg m(-2)) is greater than the sum of that in mineral soil and the forest floor; wetlands usually sequester more Hg than associated uplands. The strong relationship of Hg to organic matter, associated with binding by reduced S groups, is fundamental to understanding Hg distribution and behavior in terrestrial systems. The stoichiometry of the Hg-C relationship varies; Hg-S relationships, though less variable, are not constant. Because of the Hg-organic matter link, landscape conditions that lead to differential soil organic matter accumulation are likely to lead to differential Hg accumulation. The ratio of methylmercury (MeHg) to total Hg is generally low in both vegetation (near 1.5%) and soil (<1%), but areas of poorly drained soils and wetlands are sites of MeHg production. The annual emission of anthropic Hg from the 48 contiguous states of the USA (144 Mg) is two orders of magnitude less than the pool of Hg in forests of those states (30,300 Mg). Peatlands, less than 2% of total land area, sequester more than 20 times annual emissions (2930 Mg). If global climate change affects C storage it will indirectly affect Hg storage, having a major effect on the balance between emissions and sequestration and on the global Hg cycle.

Ecosystem↗
PubMedDate not supplied

Biological effects of wood ash application to forest and aquatic ecosystems.

The present review aims to summarize current knowledge in the topic of wood ash application to boreal forest and aquatic ecosystems, and the different effects derived from these actions. Much research has been conducted regarding the effects of wood ash application on forest growth. Present studies show that, generally speaking, forest growth can be increased on wood ash-ameliorated peatland rich in nitrogen. On mineral soils, however, no change or even decreased growth have been reported. The effects on ground vegetation are not very clear, as well as the effects on fungi, soil microbes, and soil-decomposing animals. The discrepancies between different studies are for the most part explained by abiotic factors such as variation in fertility among sites, different degrees of stabilization, and wood ash dosage used, and different time scales among different studies. The lack of knowledge in the field of aquatic ecosystems and their response to ash application is an important issue for future research. The few studies conducted have mainly considered changes in water chemistry. The biotoxic effects of ash application can roughly be divided into two categories: primary and secondary. Among the primary effects is toxicity deriving from compounds in the wood ash and cadmium is probably the worst among these. The secondary effects of wood ash are generally due to its alkaline capacity and a release of ions into the soil and soil water, and finally, watercourses and lakes. Given current knowledge, we would recommend site- and wood ash-specific application practices, rather than broad and general guidelines for wood ash application to forests.

Animals↗
PubMedDate not supplied

Mobility of sulfate in forest soils: kinetic modeling.

Understanding sulfate transport and retention dynamics in forest soils is a prerequisite in predicting SO4 concentration in the soil solution and in lake and stream waters. In this study forest soil samples from the Gårdsjön catchments, Sweden, were used to study SO4 transport in soil columns from the upper three soil horizons (E, Bs, and BC). The columns were leached using a sequential leaching technique. The input solutions were CaSO4 equilibrated with forest floor material. Leaching behavior of SO4 and concentration in the effluent were measured from columns from individual horizons. Sulfate was always retained in the Bs and BC horizons, while the pattern for the E horizon varied. Attempts were also made to model SO4 breakthrough results based on miscible displacement approaches and solute convection-dispersion equation (CDE) in porous media. Several retention mechanisms were incorporated into the CDE to account for possible reversible and irreversible SO4 reactions in individual soil layers. Our modeling efforts were inadequate in describing the mobility of SO4 in the top (E) horizon. Moreover, a linear equilibrium approach was generally inadequate for describing SO4 sorption during transport in the Bs and BC horizons. In contrast, we found that the model provided good descriptions of all breakthrough results when SO4 reactivity was accounted for based on nonlinear equilibrium or first-order kinetic processes. Moreover, based on model parameter estimates, the reactivity or retention of SO4 during transport is concentration dependent. We conclude that sulfate retention during transport in this forest soil is most likely controlled by kinetic reactivity of SO4 of the reversible and irreversible mechanisms.

Adsorption↗
PubMed2006

Land use change effects on forest carbon cycling throughout the southern United States.

We modeled the effects of afforestation and deforestation on carbon cycling in forest floor and soil from 1900 to 2050 throughout 13 states in the southern United States. The model uses historical data on gross (two-way) transitions between forest, pasture, plowed agriculture, and urban lands along with equations describing changes in carbon over many decades for each type of land use change. Use of gross rather than net land use transition data is important because afforestation causes a gradual gain in carbon stocks for many decades, while deforestation causes a much more rapid loss in carbon stocks. In the South-Central region (Texas to Kentucky) land use changes caused a net emission of carbon before the 1980s, followed by a net sequestration of carbon subsequently. In the Southeast region (Florida to Virginia), there was net emission of carbon until the 1940s, again followed by net sequestration of carbon. These results could improve greenhouse gas inventories produced to meet reporting requirements under the United Nations Framework Convention on Climate Change. Specifically, from 1990 to 2004 for the entire 13-state study area, afforestation caused sequestration of 88 Tg C, and deforestation caused emission of 49 Tg C. However, the net effect of land use change on carbon stocks in soil and forest floor from 1990 to 2004 was about sixfold smaller than the net change in carbon stocks in trees on all forestland. Thus land use change effects and forest carbon cycling during this period are dominated by changes in tree carbon stocks.

Agriculture↗
PubMed2006

Chloride effects on nitrogen dynamics in forested and suburban stream debris dams.

Organic debris dams (accumulations of organic material) can function as "hotspots" of nitrogen (N) processing in streams. Suburban streams are often characterized by high flows that prevent the accumulation of organic debris and by elevated concentrations of solutes, especially nitrate (NO(3)(-)) and chloride (Cl(-)). In this study we (1) studied the effects of urbanization on the extent and characteristics of debris dams in large and small streams and (2) evaluated the effects of NO(3)(-) and Cl(-) on rates of N cycle processes in these debris dams. In some suburban streams debris dams were small and rare, but in others factors that reduce the effects of high stream flows fostered the maintenance of debris dams. Ambient denitrification enzyme activity (DEA) in these suburban and forested streams was positively correlated with stream NO(3)(-) concentrations. In laboratory microcosms, DEA in debris dam material from a forested reference stream was increased by NO(3)(-) additions. Chloride additions constrained the response of DEA to NO(3)(-) additions in material from the forested stream, but had no effect on DEA in material from streams with a history of high Cl(-) levels. Chloride additions changed the sign of net N mineralization from negative (consumption of inorganic N) to positive in debris dam material from the forested reference stream, but had no effect on net mineralization in material from streams with a history of exposure to Cl(-). Understanding the factors regulating the maintenance and N cycling activity of organic debris, and incorporating them into urban stream management plans could have important effects on N dynamics in suburban watersheds.

Chlorides↗
PubMed2005

Mosquitoes of the mangrove forests of India: part 2--Sundarbans, West Bengal.

Mosquitoes of 19 species belonging to 9 subgenera and 6 genera, Aedes, Aedeomyia, Anopheles, Armigeres, Culex, and Mansonia, were recorded in Sundarbans mangrove forest in West Bengal, India. With 6 and 5 species, respectively, the 2 genera Culex and Anopheles were found to be more diverse while less than 3 species were recorded in the other 4 genera. Adults were mainly collected resting on walls in the guesthouse, tree holes in the forest, landing on humans in the guesthouse, and in the forest, and in light traps. Larvae were obtained from tree holes in the forest. The list of species recorded is not conclusive due to the restriction in access to most parts of the mangroves due to the presence of tigers. The occurrence of the urban species Cx. quinquefasciatus within the Sajnakhali sanctuary is indicative of the need to monitor environmental changes that result with the introduction of man-made facilities.

Aedes↗
PubMedDate not supplied

Prevalence of geohelminths in savana and forest areas of Côte d'Ivoire.

BACKGROUND: Côte d'Ivoire has large regional variation in intestinal helminth prevalence. STUDY DESIGN: In a large cross-sectional study conducted from 1997 to 1999, stool samples from 6952 children aged 4-15 years were examined for helminth eggs by the Kato/ Katz technique from 24 villages in the savanna (North) and from 21 villages in the forest (West) in Côte d'Ivoire. RESULTS AND CONCLUSION: Ascariasis lumbricoides (0.7%) was the only species present in the savana area. In the forest area, ascariasis occurred most frequently (18.9%), followed by trichuriasis (2%), Strongyloidiasis (0.1%) and oxyuriasis (0.03%). Ascariasis prevalence was not significantly associated with age within each ecological zone, but was significantly higher in boys in the forest zone. This study confirms that in the more arid savanna, the conditions are less suitable for helminth transmission than in the forest zone.

Adolescent↗
PubMed1990

Clinical and subclinical Barmah Forest virus infection in Queensland.

Barmah Forest virus is a mosquito-borne agent (alphavirus) reported to cause both clinical and subclinical infections in New South Wales. This report describes 29 cases of clinical Barmah Forest virus infection diagnosed between July 1988 and March 1989 (21 from Queensland, six from New South Wales and two from Victoria) and provides evidence of extensive subclinical infection with this virus (0.23% of the population per annum) throughout Queensland. It also includes a description of the first isolation of Barmah Forest virus from a patient. Data obtained in the course of the study suggest that Barmah Forest virus infections may not be diagnosed correctly in many instances because of the similarity of the symptoms of this disease to those of epidemic polyarthritis and the small number of laboratories providing the necessary serological services.

Adolescent↗
PubMed1976

Influence of microclimate on the life cycle of the common tick Ixodes ricinus (L.) in thermophilic oak forest.

Under conditions of the South Moravian thermophilic oak forest (Valtice near Breclav), the life cycle of the common tick Ixodes ricinus was studied by continuous recording of main elements of microclimate (temperature and humidity) in three different biotopes: forest, margin of the forest and meadow. Simultaneously conditions and the process of tick hibernation were studied in four soil layers (surface, depths of 10, 20 and 30 cm). Observations made in the winter and vegetation periods were assessed by mathematical-statistical tests. Results obtained in the forest biotope and at its margin are presented in this paper; results from the meadow biotope will be published separately.

Animals↗
PubMed2000

Studies on Anopheles fluviatilis and Anopheles culicifacies sibling species in relation to malaria in forested hilly and deforested riverine ecosystems in northern Orissa, India.

In a malaria-endemic region in northwestern Orissa, India, a longitudinal study was undertaken to delineate information on the sibling species of Anopheles fluviatilis and Anopheles culicifacies and their bionomics and role in malaria transmission in forested and deforested ecosystems. In forested villages, An. fluviatilis sibling species S (97.97%) and T (2.02%) were present. The former was highly anthropophagic (human blood index 0.88). Among the sibling species of An. culicifacies, species B (27.96%), C (71.1%), and B/C heterozygotes (0.94%) were present and were highly zoophagic. In deforested riverine villages An. fluviatilis was nearly absent and An. culicifacies sibling species A (0.48%), B (21.1%), C (77.94%), and B/C heterozygotes (0.48%) were present. In forested villages, the annual parasite incidence (269 cases/1,000) and the slide positivity rate (45%) were significantly higher than those in deforested areas, which had values of 39 cases/1,000 and 27%, respectively. The study showed that the high endemicity of malaria in the forested villages was due primarily to 2 vectors, the high rate of anthropophagy of An. fluviatilis species S, and also the more favorable ecological conditions for this vector.

Animals↗