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PubMed2006

Old-growth forests can accumulate carbon in soils.

Old-growth forests have traditionally been considered negligible as carbon sinks because carbon uptake has been thought to be balanced by respiration. We show that the top 20-centimeter soil layer in preserved old-growth forests in southern China accumulated atmospheric carbon at an unexpectedly high average rate of 0.61 megagrams of carbon hectare-1 year-1 from 1979 to 2003. This study suggests that the carbon cycle processes in the belowground system of these forests are changing in response to the changing environment. The result directly challenges the prevailing belief in ecosystem ecology regarding carbon budget in old-growth forests and supports the establishment of a new, nonequilibrium conceptual framework to study soil carbon dynamics.

Carbon↗
PubMed1998

Changes in the carbon balance of tropical forests: evidence from long-term plots

The role of the world's forests as a "sink" for atmospheric carbon dioxide is the subject of active debate. Long-term monitoring of plots in mature humid tropical forests concentrated in South America revealed that biomass gain by tree growth exceeded losses from tree death in 38 of 50 Neotropical sites. These forest plots have accumulated 0.71 ton, plus or minus 0.34 ton, of carbon per hectare per year in recent decades. The data suggest that Neotropical forests may be a significant carbon sink, reducing the rate of increase in atmospheric carbon dioxide.

Journal Article↗
PubMed1999

Net primary production of a forest ecosystem with experimental CO2 enrichment

The concentration of atmospheric carbon dioxide was increased by 200 microliters per liter in a forest plantation, where competition between organisms, resource limitations, and environmental stresses may modulate biotic responses. After 2 years the growth rate of the dominant pine trees increased by about 26 percent relative to trees under ambient conditions. Carbon dioxide enrichment also increased litterfall and fine-root increment. These changes increased the total net primary production by 25 percent. Such an increase in forest net primary production globally would fix about 50 percent of the anthropogenic carbon dioxide projected to be released into the atmosphere in the year 2050. The response of this young, rapidly growing forest to carbon dioxide may represent the upper limit for forest carbon sequestration.

Journal Article↗
PubMed1999

Positive feedbacks in the fire dynamic of closed canopy tropical forests

The incidence and importance of fire in the Amazon have increased substantially during the past decade, but the effects of this disturbance force are still poorly understood. The forest fire dynamics in two regions of the eastern Amazon were studied. Accidental fires have affected nearly 50 percent of the remaining forests and have caused more deforestation than has intentional clearing in recent years. Forest fires create positive feedbacks in future fire susceptibility, fuel loading, and fire intensity. Unless current land use and fire use practices are changed, fire has the potential to transform large areas of tropical forest into scrub or savanna.

Journal Article↗
PubMed1995

Effects of environmental parameters on the formation and turnover of acetate by forest soils.

The capacity to form acetate from endogenous matter was a common property of diverse forest soils when incubated under anaerobic conditions. At 15 to 20(deg)C, acetate synthesis occurred without appreciable delay when forest soils were incubated as buffered suspensions or in microcosms at various percentages of their maximum water holding capacity. Rates for acetate formation with soil suspensions ranged from 35 to 220 (mu)g of acetate per g (dry weight) of soil per 24 h, and maximal acetate concentrations obtained in soil suspensions were two- to threefold greater than those obtained with soil microcosms at the average water holding capacity of the soil. Cellobiose degradation in soil suspensions yielded H(inf2) as a transient product. Under anaerobic conditions, supplemental H(inf2) and CO(inf2) were directed towards the acetogenic synthesis of acetate, and enrichments yielded a syringate-H(inf2)-consuming acetogenic consortium. At in situ temperatures, acetate was a relatively stable anaerobic end product; however, extended incubation periods induced acetoclastic methanogenesis and sulfate reduction. Higher mesophilic and thermophilic temperatures greatly enhanced the capacity of soils to form methane. Although methanogenic and sulfate-reducing activities under in situ-relevant conditions were negligible, these findings nonetheless demonstrated the occurrence of methanogens and sulfate-reducing bacteria in these aerated terrestrial soils. In contrast to the protracted stability of acetate under anaerobic conditions at 15 to 20(deg)C with unsupplemented soils, acetate formed by forest soils was rapidly consumed in the presence of oxygen and nitrate, and substrate-product stoichiometries indicated that acetate turnover was coupled to oxygen-dependent respiration and denitrification. The collective results suggest that acetate formed under anaerobic conditions might constitute a trophic link between anaerobic and aerobic processes in forest soils.

Journal Article↗
PubMed2000

Molecular analyses of novel methanotrophic communities in forest soil that oxidize atmospheric methane.

Forest and other upland soils are important sinks for atmospheric CH(4), consuming 20 to 60 Tg of CH(4) per year. Consumption of atmospheric CH(4) by soil is a microbiological process. However, little is known about the methanotrophic bacterial community in forest soils. We measured vertical profiles of atmospheric CH(4) oxidation rates in a German forest soil and characterized the methanotrophic populations by PCR and denaturing gradient gel electrophoresis (DGGE) with primer sets targeting the pmoA gene, coding for the alpha subunit of the particulate methane monooxygenase, and the small-subunit rRNA gene (SSU rDNA) of all life. The forest soil was a sink for atmospheric CH(4) in situ and in vitro at all times. In winter, atmospheric CH(4) was oxidized in a well-defined subsurface soil layer (6 to 14 cm deep), whereas in summer, the complete soil core was active (0 cm to 26 cm deep). The content of total extractable DNA was about 10-fold higher in summer than in winter. It decreased with soil depth (0 to 28 cm deep) from about 40 to 1 microg DNA per g (dry weight) of soil. The PCR product concentration of SSU rDNA of all life was constant both in winter and in summer. However, the PCR product concentration of pmoA changed with depth and season. pmoA was detected only in soil layers with active CH(4) oxidation, i.e., 6 to 16 cm deep in winter and throughout the soil core in summer. The same methanotrophic populations were present in winter and summer. Layers with high CH(4) consumption rates also exhibited more bands of pmoA in DGGE, indicating that high CH(4) oxidation activity was positively correlated with the number of methanotrophic populations present. The pmoA sequences derived from excised DGGE bands were only distantly related to those of known methanotrophs, indicating the existence of unknown methanotrophs involved in atmospheric CH(4) consumption.

Bacteria↗
PubMed2005

Characterization of a forest soil metagenome clone that confers indirubin and indigo production on Escherichia coli.

A microbial community analysis of forest soil from Jindong Valley, Korea, revealed that the most abundant rRNA genes were related to Acidobacteria, a major taxon with few cultured representatives. To access the microbial genetic resources of this forest soil, metagenomic libraries were constructed in fosmids, with an average DNA insert size of more than 35 kb. We constructed 80,500 clones from Yuseong and 33,200 clones from Jindong Valley forest soils. The double-agar-layer method allowed us to select two antibacterial clones by screening the constructed libraries using Bacillus subtilis as a target organism. Several clones produced purple or brown colonies. One of the selected antibacterial clones, pJEC5, produced purple colonies. Structural analysis of the purified pigments demonstrated that the metagenomic clone produced both the pigment indirubin and its isomer, indigo blue, resulting in purple colonies. In vitro mutational and subclonal analyses revealed that two open reading frames (ORFs) are responsible for the pigment production and antibacterial activity. The ORFs encode an oxygenase-like protein and a putative transcriptional regulator. Mutations of the gene encoding the oxygenase canceled both pigment production and antibacterial activity, whereas a subclone carrying the two ORFs retained pigment production and antibacterial activity. This finding suggests that these forest soil microbial genes are responsible for producing the pigment with antibacterial activity.

Bacteria↗
PubMed2006

Differential effects of nitrogenous fertilizers on methane-consuming microbes in rice field and forest soils.

The impact of environmental perturbation (e.g., nitrogenous fertilizers) on the dynamics of methane fluxes from soils and wetland systems is poorly understood. Results of fertilizer studies are often contradictory, even within similar ecosystems. In the present study the hypothesis of whether these contradictory results may be explained by the composition of the methane-consuming microbial community and hence whether methanotrophic diversity affects methane fluxes was investigated. To this end, rice field and forest soils were incubated in microcosms and supplemented with different nitrogenous fertilizers and methane concentrations. By labeling the methane with 13C, diversity and function could be coupled by analyses of phospholipid-derived fatty acids (PLFA) extracted from the soils at different time points during incubation. In both rice field and forest soils, the activity as well as the growth rate of methane-consuming bacteria was affected differentially. For type I methanotrophs, fertilizer application stimulated the consumption of methane and the subsequent growth, while type II methanotrophs were generally inhibited. Terminal restriction fragment length polymorphism analyses of the pmoA gene supported the PLFA results. Multivariate analyses of stable-isotope-probing PLFA profiles indicated that in forest and rice field soils, Methylocystis (type II) species were affected by fertilization. The type I methanotrophs active in forest soils (Methylomicrobium/Methylosarcina related) differed from the active species in rice field soils (Methylobacter/Methylomonas related). Our results provide a case example showing that microbial community structure indeed matters, especially when assessing and predicting the impact of environmental change on biodiversity loss and ecosystem functioning.

Biodiversity↗
PubMed1992

Yeasts associated with Drosophila in tropical forests of Rio de Janeiro, Brazil.

The distribution and diversity of yeast species vectored by and from the crop of eight species groups of Drosophila is described for two rain forest sites and an urban wooded area in Rio de Janeiro, Brazil. The typical forest Drosophila groups guarani, tripunctata, and willistoni showed a higher diversity of yeasts than the cosmopolitan melanogaster species group, suggesting different strategies of utilization of substrates. Apiculate yeasts, including Kloeckera apis, Kloeckera javanica, and Kloeckera japonica, were the prevalent species. Geotrichum spp. and Candida citea were also frequent isolates in the forest sites. Similarities between the yeasts from the external surfaces and crops of Drosophila suggested that the feeding substrates were the main source of the yeasts vectored by these flies. Most of the yeasts were strong fermenters and assimilated few compounds, usually sucrose, cellobiose, and glycerol. This indicated a preference of the flies for food sources such as fruits. Some yeasts were primarily isolated from one group of Drosophila; for example, Kloeckera javanica from the melanogaster group, Debaryomyces vanrijiae var. yarrowii from the tripunctata group, and Kluyveromyces delphensis from the willistoni group. These associations and differences in the yeast communities among the fly groups suggested a differentiation of diets and specialization of the yeast-Drosophila association in the tropical forests.

Animals↗
PubMed2005

Biology and management of insect pests in North American intensively managed hardwood forest systems.

Increasing demand for wood and wood products is putting stress on traditional forest production areas, leading to long-term economic and environmental concerns. Intensively managed hardwood forest systems (IMHFS), grown using conventional agricultural as well as forestry methods, can help alleviate potential problems in natural forest production areas. Although IMHFS can produce more biomass per hectare per year than natural forests, the ecologically simplified, monocultural systems may greatly increase the crop's susceptibility to pests. Species in the genera Populus and Salix comprise the greatest acreage in IMHFS in North America, but other species, including Liquidambar styraciflua and Platanus occidentalis, are also important. We discuss life histories, realized and potential damage, and management options for the most economically influential pests that affect these hardwood species. The substantial inherent challenges associated with pest management in the monocultural environments created by IMHFS are reviewed. Finally, we discuss ways to design IMHFS that may reduce their susceptibility to pests, increase their growth and productivity potential, and create a more sustainable environment.

Animals↗
PubMed2006

A global assessment of closed forests, deforestation and malaria risk.

Global environmental change is expected to affect profoundly the transmission of the parasites that cause human malaria. Amongst the anthropogenic drivers of change, deforestation is arguably the most conspicuous, and its rate is projected to increase in the coming decades. The canonical epidemiological understanding is that deforestation increases malaria risk in Africa and the Americas and diminishes it in South-east Asia. Partial support for this position is provided here, through a systematic review of the published literature on deforestation, malaria and the relevant vector bionomics. By using recently updated boundaries for the spatial limits of malaria and remotely-sensed estimates of tree cover, it has been possible to determine the population at risk of malaria in closed forest, at least for those malaria-endemic countries that lie within the main blocks of tropical forest. Closed forests within areas of malaria risk cover approximately 1.5 million km2 in the Amazon region, 1.4 million km2 in Central Africa, 1.2 million km2 in the Western Pacific, and 0.7 million km2 in South-east Asia. The corresponding human populations at risk of malaria within these forests total 11.7 million, 18.7 million, 35.1 million and 70.1 million, respectively. By coupling these numbers with the country-specific rates of deforestation, it has been possible to rank malaria-endemic countries according to their potential for change in the population at risk of malaria, as the result of deforestation. The on-going research aimed at evaluating these relationships more quantitatively, through the Malaria Atlas Project (MAP), is highlighted.

Africa, Central↗
PubMed2005

Knowledge and use of medicinal plants by local specialists in an region of Atlantic Forest in the state of Pernambuco (Northeastern Brazil).

The study of local knowledge about natural resources is becoming increasingly important in defining strategies and actions for conservation or recuperation of residual forests. This study therefore sought to: collect information from local populations concerning the use of Atlantic Forest medicinal plants; verify the sources of medicinal plants used; determine the relative importance of the species surveyed, and; calculate the informant consensus factor in relation to medicinal plant use. Data was obtained using semi-structured forms to record the interviewee's personal information and topics related to the medicinal use of specific plants. The material collected represent 125 plants, distributed among 61 botanical families, with little participation of native plants. This study demonstrated that local people tend to agree with each other in terms of the plants used to treat blood-related problems, but cite a much more diverse group of plants to treat problems related to the respiratory and digestive systems - two important categories in studies undertaken in different parts of the world. The local medicinal flora is largely based on plants that are either cultivated or obtained from anthropogenic zones, possibly due to the use and access restrictions of the legally protected neighboring forest. Despite these restrictions, the species with the highest use-value by this community was Pithecellobium cochliocarpum (Gomez) Macb., a native plant of the Atlantic Forest.

Aged↗
PubMed2006

The ethnoecology of Caiçara metapopulations (Atlantic Forest, Brazil): ecological concepts and questions.

The Atlantic Forest is represented on the coast of Brazil by approximately 7.5% of remnants, much of these concentrated on the country's SE coast. Within these southeastern remnants, we still find the coastal Caiçaras who descend from Native Indians and Portuguese Colonizers. The maintenance of such populations, and their existence in spite of the deforestation that occurred on the Atlantic Forest coast, deserves special attention and analysis. In this study, I address, in particular, the Caiçaras who live on the coast of São Paulo and Rio de Janeiro States, illustrating with examples of coastal inhabitants from other areas, such as Bahia State (NE coast) and of other forested areas (riverine caboclos of the Amazon). The major focus of this study, based on previous research, performed since 1986 in several populations or villages of the Atlantic Forest coast, is to understand the resilience of the Caiçaras, which is analyzed using ecological concepts, such as metapopulation, resilience and adaptive cycles. The Caiçara populations are located on islands (Búzios, Comprida, Grande, Ilhabela, Jaguanum, Gipóia) and on the coast (Bertioga, Puruba, Picinguaba, among others). Information gathered about the Caiçaras regarding the economic cycles of the local regions, along with ecological, historical and economic data available, are used to understand such resilience, and are complemented with comparative examples from the Brazilian Amazon and with variables such as the local restrictions imposed by environmental governmental agencies.

Anthropology, Cultural↗
PubMed2006

What drives conversion of tropical forest in Carrasco Province, Bolivia?

The conversion of closed forest (CCF) in Carrasco Province, Bolivia, was monitored using a series of four midresolution satellite images from 1986 to 2002. The conversion of forests into nonforests from 1986 to 2002 was 1.5% annually. Inclusion of conversions into open forest doubles the annual CCF rate to 3.1%. Five predictors of CCF were tested in a spatial model: land tenure regime, distance from roads, distance from settlements, topography, and soil suitability for farming. Only three out of the five predictors tested were found to be reliable predictors of CCF: land tenure regime, distance from roads, and distance from settlements. University reserve and indigenous land show substantially less CCF than national park and untitled land. In addition the spatial model shows that the greater the distance of forest from roads or settlements, the less CCF. Topography and soil suitability for farming lack predictive power for CCF and are therefore excluded from the spatial model.

Agriculture↗
PubMed2001

The economic importance of products extracted from Amazonian flood plain forests.

Rural people in the Peruvian Amazon practice agriculture and extract a wide range of products from natural forests, rivers and lakes. Their diversified livelihood system includes fish, game, and plant products. In 2 flood-plain villages, data for one year have been collected to compare the economy of local agriculture with the economy of extracted forest products for subsistence as well as for commerce. The study includes both fauna (game and fish) and flora (timber as well as nontimber). The results show that extracted forest products for subsistence, especially fish, are a main factor in the local economy. The daily net income from extraction activities exceeds both income from cultivation and the normal daily wages for unskilled workers, emphasizing the need for thorough socioeconomic investigations before any alternative land-use option is implemented. The average value per ha of natural forest used for extraction is in the order of USD 13 yr-1, and the average extraction area is 113 ha household-1. When yield from agriculture is included in the calculations, the total per ha value of current extraction and agricultural activities increases to USD 21 yr-1.

Agriculture↗
PubMed2003

Distribution of deciduous stands in villages located in coniferous forest landscapes in Sweden.

Termination of fire along with active removal of deciduous trees in favor of conifers together with anthropogenic transformation of productive forest into agricultural land, have transformed northern European coniferous forests and reduced their deciduous component. Locally, however, in the villages, deciduous trees and stands were maintained, and have more recently regenerated on abandoned agricultural land. We hypothesize that the present distribution of the deciduous component is related to the village in-field/out-field zonation in different regions, which emerges from physical conditions and recent economic development expressed as land-use change. We analyzed the spatial distribution of deciduous stands in in-field and out-field zones of villages in 6 boreal/hemiboreal Swedish regions (Norrbotten, Angermanland, Jämtland, Dalarna, Bergslagen, Småland). In each region 6 individual quadrates 5 x 5 km centered on village areas were selected. We found significant regional differences in the deciduous component (DEC) in different village zones. At the scale of villages Angermanland had the highest mean proportion of DEC (17%) and Jämtland the lowest (2%). However, the amounts of the DEC varied systematically in in-field and out-field zones. DEC was highest in the in-field in the south (Småland), but generally low further north. By contrast, the amount of DEC in the out-field was highest in the north. The relative amount of DEC in the forest edge peaked in landscapes with the strongest decline in active agriculture (Angermanland, Dalarna, Bergslagen). Because former and present local villages are vital for biodiversity linked to the deciduous component, our results indicate a need for integrated management of deciduous forest within entire landscapes. This study shows that simplified satellite data are useful for estimating the spatial distribution of deciduous trees and stands at the landscape scale. However, for detailed studies better thematic resolution is needed to determine biologically relevant differences in quality of deciduous stands.

Environmental Monitoring↗
PubMed1989

[Ecologic aspects of tegumentary American leishmaniasis. 7. Phlebotomus vectorial capacity in the primitive forest environment of the Serra do Mar system, Vale do Ribeira region, State of São Paulo, Brazil].

A total of 5,038 specimens, belonging to nineteen species, were obtained during the three consecutive years of phlebotomine catches in forest and peridomiciliary environments of the Itapoan farm. Proportionally, the CDC light trap contributed with 92.2% in the forest and 0.7% in the peridomicile sites while the human bait corresponded to 7.0% in the forest. Generally speaking the outcome of the technique utilized was rather low or presented reduced geometrical averages. The most common species in the area was P. ayrozai, almost always predominant; however, the results with human bait prevent one's ascribing a high degree of anthropophilic properties to it. The implication of the reduced presence of L. intermedia, L. migonei and L. fischeri, even with human bait, is that the conditions for the transmission of the disease to man in the forest environment are inexistent. Consequently, this could indicate that the vectorial function would be performed by a population which has survived the period of devastation. For this reason a new epidemiological pattern, connected with a focus, of L.b. braziliensis seems to exist in Brazil.

Animals↗
PubMedDate not supplied

A mitochondrial DNA phylogeny indicates close relationships between populations of Lutzomyia whitmani (Diptera: Psychodidae, Phlebotominae) from the rain-forest regions of Amazônia and northeast Brazil.

Phylogenetic analysis of all 31 described mitochondrial (cytochrome b) haplotypes of Lutzomyia whitmani demonstrated that new material from the State of Rondônia, in southwest Amazônia, forms a clade within a lineage found only in the rain-forest regions of Brazil. This rain-forest lineage also contains two other clades of haplotypes, one from eastern Amazônia and one from the Atlantic forest zone of northeast Brazil (including the type locality of the species in Ilhéus, State of Bahia). These findings do not favour recognizing two allopatric cryptic species of L. whitmani, one associated with the silvatic transmission of Leishmania shawi in southeast Amazônia and the other with the peridomestic transmission of Le. braziliensis in northeast Brazil. Instead, they suggest that there is (or has been in the recent past) a continuum of inter-breeding populations of L. whitmani in the rain-forest regions of Brazil.

Animals↗