SEARCH · Search PubMed

Results for “forest”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources

PubMed2001

Assessment of environmental impact zones in the Kola Peninsula forest ecosystems.

This paper describes the condition of forest ecosystems subjected to smelter pollution in the Kola peninsula. This assessment is based on the parameters of the biogeochemical cycle. The defoliation index was used to delimit three basic forest states: background, defoliating, sparse. Close to the smelter, due to expansion of the area not covered by vegetation, a fourth type of state, so-called "industrial deserts", has been observed. The concentrations of sulphur, copper and nickel in the precipitation in the forests generally declined with distance from the smelter. The defoliating forests are noted for the highest Ca, Mg, K concentrations in the summer precipitation. In sparse forests and industrial deserts a decrease in the Ca, Mg, K concentrations in the summer precipitation in comparison with the defoliating forests, despite the particle emissions, could be attributed to the reduction in forest biomass. The higher levels of soil and soil leachate carbon and acidity in the defoliating forests was due to higher litterfall and to the higher dissolution of fulvic acids by the acidic precipitation. This increase in organic matter levels affects soil cation exchange capacity and cation saturation. The pine trees demonstrated significant changes in the uptake of elements in all types of forests under pollution. Elevated levels of S, Ni, Cu and K and reduced levels of Mg, Mn and Zn were found in the needles of different age classes.

Acid Rain↗

PubMed2000

Drought disturbance from climate change: response of United States forests.

Predicted changes in climate have raised concerns about potential impacts on terrestrial forest ecosystem productivity, biogeochemical cycling, and the availability of water resources. This review summarizes characteristics of drought typical to the major forest regions of the United States, future drought projections, and important features of plant and forest community response to drought. Research needs and strategies for coping with future drought are also discussed. Notwithstanding uncertainties surrounding the magnitude and direction of future climate change, and the net impact on soil water availability to forests, a number of conclusions can be made regarding the sensitivity of forests to future drought. The primary response will be a reduction in net primary production and stand water use, which are driven by reductions in stomatal conductance. Mortality of small stature plants (i.e. seedlings and saplings) is a likely consequence of severe drought. In comparison, deep rooting and substantial reserves of carbohydrates and nutrients make mature trees less susceptible to water limitations caused by severe or prolonged drought. However, severe or prolonged drought may render even mature trees more susceptible to insects or disease. Drought-induced reductions in decomposition rates may cause a buildup of organic material on the forest floor, with ramifications for fire regimes and nutrient cycling. Although early model predictions of climate change impacts suggested extensive forest dieback and species migration, more recent analyses suggest that catastrophic dieback will be a local phenomenon, and changes in forest composition will be a relatively gradual process. Better climate predictions at regional scales, with a higher temporal resolution (months to days), coupled with carefully designed, field-based experiments that incorporate multiple driving variables (e.g. temperature and CO2), will advance our ability to predict the response of different forest regions to climate change.

Animals↗

PubMed2002

Biogeochemical dynamics following land use change from forest to pasture in a humid tropical area (Rondĵnia, Brazil): a multi-element approach by means of XRF-spectroscopy.

Forest burning for pastures in tropical areas represents an important component of biogeochemical cycles. In order to provide information concerning chemical modifications after forest burning, in this local study the total contents of 29 elements in topsoils were analyzed when forest is changed to pasture land. The work was carried out in 1999 in Rondĵnia state (Brazilian Amazon Basin) focussing on a native forest site and four neighboring pastures established in 1987, 1983, 1972 and 1911 after forest conversion. Chemical fingerprint graphs of the pasture soils related to the forest soil illustrated mainly higher contents for the vast majority of macro- and micro nutrients, but for other elements as well (e.g. Ba, Sr, Cr, Ni, V or Pb). Also increases of pH levels were measured in all pastures, which remained higher than the forest values for decades. After initial increases of most of the elements in pasture of 1987 the decreases of some macro elements (e.g. C, N, K, Mg, S) in pasture 1983 as well as again the enhanced levels in pasture 1972 and 1911 suggest both a persistent leaching of these elements and a function of pasture age where external element inputs exceed outputs. Ash deposition, accumulation of organic matter, animal excreta as well as natural soil conditions are discussed as influencing factors on the element contents of the original forest and the pasture soils. Nevertheless, in this particular area continuous pasturing after forest clearing primarily enriched the soils in elements.

Agriculture↗

PubMed2002

Where will the wood come from? Plantation forests and the role of biotechnology.

Wood is almost as important to humanity as food, and the natural forests from which most of it is harvested from are of enormous environmental value. However, these slow-growing forests are unable to meet current demand, resulting in the loss and degradation of forest. Plantation forests have the potential to supply the bulk of humanity's wood needs on a long-term basis, and so reduce to acceptable limits the harvest pressures on natural forests. However, if they are to be successful, plantation forests must have a far higher yield of timber than their natural counterparts, on much shorter rotation times. To achieve this in reasonable time, biotechnology must be applied to the tree-improvement process, for which large increases in public and private capital investment are needed. However, additional obstacles exist in the form of opposition to plantations, some forest ecocertification schemes, and concerns about aspects of forest biotechnology, especially genetic engineering. It is the intention of this article to explain, in detail, why plantation forests are needed to sustainably meet the world's demand for wood, why they are not being developed fast enough, and why the application of biotechnology to tree improvement is essential to speeding up this process.

Biotechnology↗

PubMed2002

Hurricane impacts on US forest carbon sequestration.

Recent focus has been given to US forests as a sink for increases in atmospheric carbon dioxide. Current estimates of US forest carbon sequestration average approximately 20 Tg (i.e. 10(12) g) year. However, predictions of forest carbon sequestration often do not include the influence of hurricanes on forest carbon storage. Intense hurricanes occur two out of three years across the eastern US. A single storm can convert the equivalent of 10% of the total annual carbon sequestrated by US forests into dead and downed biomass. Given that forests require at least 15 years to recover from a severe storm, a large amount of forest carbon is lost either directly (through biomass destruction) or indirectly (through lost carbon sequestration capacity) due to hurricanes. Only 15% of the total carbon in destroyed timber is salvaged following a major hurricane. The remainder of the carbon is left to decompose and eventually return to the atmosphere. Short-term increases in forest productivity due to increased nutrient inputs from detritus are not fully compensated by reduced stem stocking, and the recovery time needed to recover leaf area. Therefore, hurricanes are a significant factor in reducing short-term carbon storage in US forests.

Biomass↗

PubMed2003

Silvicultural management in maintaining biodiversity and resistance of forests in Europe-boreal zone: case Finland.

The majority of untouched natural boreal forests have been regenerated through large catastrophes, occurring by intervals between 50 and 100 years. Storm and fire will open the landscape, result in a huge amount of dead or dying trees and let the pioneer tree species germinate. These processes are the guideline for Finnish forest management today. The main focus by maintaining the biodiversity in Finnish boreal forest zone is directed to managed forests. Nature-orientated silviculture on stand level is practised. The site type classification, a reflection of the modern concept of biodiversity and developed by Cajander early in 1900s, on the basis of natural vegetation composition of the site, has the central role by choosing tree species, regeneration methods and thinning procedure, and reflects also on the site productivity. The small size of stands, the abundance of natural seedlings in planted stands and the popularity of mixed stands have a positive impact on biodiversity of forests. The protection of small-sized valuable habitats in commercially managed stands, the leaving of retention trees standing and lying in the forest in all phases of the rotation, are activities made for biodiversity. Many insects and fungi are adapted to catastrophes and so they can survive in single stems left on regeneration areas. Maintaining the biodiversity in multifunctional forests is also supported by the new forest legislation and by the criteria of Finnish Forest Certification System.

Conservation of Natural Resources↗

PubMed2003

Silvicultural management in maintaining biodiversity and resistance of forests in Europe-the Mediterranean region.

Outstanding features of Mediterranean forest area are highlighted with a special reference to biodiversity and connections with forest management. The naturally originated and anthropogenic progress of the mosaic-like evolution, as well as the man-induced factors and natural constraints are described. The past and present close linkages between management and biodiversity are then analysed by means of a few, outstanding cases typical of the geographical region. The management shift on increasing economically marginal forest area (abandonment) appears to be the major force currently driving connections with inherent and associated biodiversity. The goals following the new-established environmental roles of forests have shifted towards adaptive management, namely the implementation of locally tailored rules in accordance with prominent forest functions. Key priorities to face up to the new scenarios are then discussed. Economic and policy implications are addressed with reference to multipurpose forestry and the related annual flow of outputs. It is shown the role of water-related services, as well the provision of various non-wood forest products and public goods in addition to wood and other traditional forest outputs. Reference is also made to the dualism between the Northern and the South-Eastern Mediterranean countries due to different level of economic development (and pressure of forest resources) together with very different institutional structures, i.e. public ownership in Southern and South-Eastern Mediterranean countries. Nevertheless, the situation is going to become more harmonious in the medium run by growing economic development, the affirmation of local rights on forest resources, globalisation and, above all, rural out migration and exchanges of peoples confirming the traditional role of the Mediterranean Region at cross road of South-North and Eastern-Western cultures.

Climate↗

PubMed2003

An integrated strategy for sustainable forest-energy-environment interactions in Nigeria.

The Nigerian forests have been subjected to unguarded exploitation over the years. Although there is overwhelming empirical evidence, which show that Nigeria's forest, may soon vanish, available statistics have shown its increasing importance in the energy sector. With increasing population come the attendant demands on the biotic environment through increased land clearing, deforestation, devegetation, decertification, with attendant soil erosion, flooding, sand dune formation, and changes in the micro-climate with consequent loss of biological productivity and associated socio-economic and socio-political problems in the country. There is therefore the need to adopt measures that will shift the attention of the Nigerian populace from the forest to satisfy their energy needs. However, such measures that will address the challenges confronting the forestry, forest-based energy systems and the environment should be consistent with the development needs, resources and priorities of the nation. Hence, for sustainable forest-energy-environment interactions, a holistic and integrated strategy that can be adopted to minimise the observed forest depletion must take cognisance of options from various land use practices, energy and forest sectors. The focus of this paper is on a strategy of options from both the energy and forest sectors. Based on the socio-economic, socio-political and environmental analyses of various options from the energy and forest sectors, the philosophy behind the mosaic approach to sustainable development has been considered in developing the proposed strategy. Policy measures to implement this strategy of options in the national development programs are also suggested.

Conservation of Energy Resources↗

PubMed2001

Estimating the influence of forests on the overall fate of semivolatile organic compounds using a multimedia fate model.

On the basis of recently reported measurements of semivolatile organic compound (SOC) uptake in forest canopies, simple expressions are derived that allow the inclusion of a canopy compartment into existing non-steady-state multimedia fate models based on the fugacity approach. One such model is used to assess how the inclusion of the canopy compartment in the model affects the calculated overall behavior of SOCs with specific physical--chemical properties. The primary effect of the forest is an increase in the net atmospheric deposition to the terrestrial environment, reducing atmospheric concentrations and accordingly the extent of deposition to the agricultural and aquatic environments. This effect was most pronounced for chemicals with log KOA around 9-10 and log KAW -2 to -3; their average air concentrations during the growing season decreased by a factor of 5 when the canopy compartment was included. Concentration levels in virtually all compartments are decreased at the expense of increased concentrations in the forest soil. The effect of the forest lies not in a large capacity for these chemicals but in the efficiency of pumping the chemicals from the atmosphere to the forest soil, a storage reservoir with high capacity from which the chemicals can return to the atmosphere only with difficulty. Because of seasonal variability of canopy size and atmospheric stability, uptake into forests is higher during spring and summer than in winter. The model suggests that this may dampen temperature-driven seasonal fluctuations of air concentrations and in regions with large deciduous forests may lead to a temporary, yet notable dip in air concentrations during leaf development in spring. A sensitivity analysis revealed a strong effect of forest cover, forest composition, and degradation half-lives. A high degradation loss on the plant surface has the effect of preventing the saturation of the small plant reservoir and can cause very significant reductions in atmospheric concentrations of those SOCs for which uptake in the canopy is limited by the size of the reservoir.

Air Movements↗

PubMed2003

Accurate estimation of forest carbon stocks by 3-D remote sensing of individual trees.

Forests are one of the most important carbon sinks on Earth. However, owing to the complex structure, variable geography, and large area of forests, accurate estimation of forest carbon stocks is still a challenge for both site surveying and remote sensing. For these reasons, the Kyoto Protocol requires the establishment of methodologies for estimating the carbon stocks of forests (Kyoto Protocol, Article 5). A possible solution to this challenge is to remotely measure the carbon stocks of every tree in an entire forest. Here, we present a methodology for estimating carbon stocks of a Japanese cedar forest by using a high-resolution, helicopter-borne 3-dimensional (3-D) scanning lidar system that measures the 3-D canopy structure of every tree in a forest. Results show that a digital image (10-cm mesh) of woody canopy can be acquired. The treetop can be detected automatically with a reasonable accuracy. The absolute error ranges for tree height measurements are within 42 cm. Allometric relationships of height to carbon stocks then permit estimation of total carbon storage by measurement of carbon stocks of every tree. Thus, we suggest that our methodology can be used to accurately estimate the carbon stocks of Japanese cedar forests at a stand scale. Periodic measurements will reveal changes in forest carbon stocks.

Automation↗

PubMed2002

Heavy metal concentration in the moss Pleurozium schreberi in the Niepołomice Forest, Poland: changes during 20 years.

The Niepołomice Forest is a large forest complex (110 km2) situated in southern Poland 10 to 30 km to the east of the urban industrial Kraków agglomeration and steelworks, which was built up on the outskirts of the city in 1950. Due to prevailing westerly winds, the forest is affected by pollutants emitted by both the steelworks and the city. The level of heavy metal contamination in the Niepołomice Forest was described using a sensitive bioindicator - the moss Pleurozium schreberi. Mean concentrations of metals in moss collected in the Niepołomice Forest were Cd - 0.71, Cr - 2.4, Cu - 8.6, Fe - 673, Pb - 12.7, and Zn - 61 mg/kg. Concentrations of heavy metals in moss in the Niepołomice Forest decreased in time. As compared with the relatively clean area in north-eastern Poland (Puszcza Białowieska), the concentration of Fe was 2-9 fold and Pb 4-6 fold higher in the Niepołomice Forest in 1975, while in 1998 4 fold and 2 fold, respectively. In both 1975 and 1998 the most polluted by heavy metals was the western part of the Niepołomice Forest (closest to the pollution sources) and the area along the roads inside the forest complex.

Air Pollutants↗

PubMed2002

Preliminary observations on specific adaptations of exophilic ixodid ticks to forests or open country habitats.

Some features of three-host exophilic ticks important for their survival differ at the generic level in relation to the types of their habitat. Ixodes and Haemaphysalis are typical forest genera. Hyalomma is an open country genus, whereas Dermacentor and Rhipicephalus, having some features of forest ticks, are closer to the ticks of open country. Forest ticks encounter rather stable and favorable temperature, humidity and illumination conditions as compared with open country ticks. A few differences determining every-day survival, hostseeking. and reproduction of ticks are considered. (1) Tolerance to desiccation is very low in forest ticks and much greater in ticks of open country. (2) Lack of eyes in forest ticks (having, however, epithelial photoreceptor cells) and formation of eyes as special morphological structures in ticks of open country. (3) Capability of mating and insemination of unfed specimens both on and off hosts in forest ticks (Ixodes) and insemination of partially engorged females only on hosts by fed males in open country ticks. (4) Reciprocal sexual dimorphism where in forest ticks females have a larger body than males and in open country ticks this correlation is opposite. (5) Linear dependence between female weight and number of eggs laid is established in forest ticks after the female weight becomes higher than 50% of mean engorgement weight whereas in open country ticks linear dependence begins to reveal itself much earlier. (6) In forest ticks the compensatory growth occurs only during adult feeding whereas in open country ticks such a growth occurs both during nymphal and adult feeding. The adaptive nature of the above differences and their evolutionary trends have been hypothesized.

Adaptation, Biological↗

PubMed2005

Soil delta15N patterns in old-growth forests of southern Chile as integrator for N-cycling.

Old-growth forests of southern Chile represent an important reserve of temperate (rain) forests in the world. Wetter and colder forest ecosystems appear to be more efficient in conserving and recycling N such that mostly non-plant available N species are lost, which could be indicated by more depleted delta15N values of the soil and plants. Hydrological N loss from the old-growth forests in southern Chile occurs mainly via dissolved organic nitrogen and not via dissolved inorganic N. Forest disturbances (e.g. fire, clear-cutting or enhanced N deposition) cause (abrupt) changes in ecosystem N-cycling processes. In this study, we hypothesized that delta15N signatures of soil profiles under old-growth forests could be used as an integrator for ecosystem N-cycling, and changes of these delta15N profiles could be valuable to assess ecosystem resilience towards disturbances. Six old-growth forests were selected in the phytogeographical region of the Valdivian rain forest in southern Chile. One of the sites has been partly burned in February 2002. First, we observed that ecosystems with higher mean annual precipitation and lower mean annual temperature were relatively more depleted in 15N. Secondly, we found that a forest fire caused a 100-fold increase of the nitrate export and induced an enrichment of the soil delta15N signal in the upper 20 cm.

Chile↗

PubMed1978

Observations on the vegetation of northeastern Mato Grosso II. Forests and soils of the Rio Suiá--Missu area.

The vegetation of the well drained soils along the Suiá--Missu road in the Serra do Roncador region of NE Mato Grosso is Evergreen Seasonal forest of Amazonian type. The area lies close to the meeting place of the Amazonian forest (the hylaea) and the cerrado (savanna) formation of Central Brazil. The structure of the forest is simple: the canopy is at about 18--23 m, and is exceeded by a few scattered emergents; no recognizable strata can be distinguished among the understorey trees and the shrub and herb layers are sparse. Table 1 lists the most important species and gives information on stratification and general distribution. Most of the species appear to have a hylaean centre of distribution but extend into other vegetation types. The forest differs from related communities which lie closer to the cerrado/forest boundary in its greater height and luxuriance, the presence of additional tall tree species, and the great reduction in abundance of a cerrado floristic element. A survey on the Xavantina--São Felix road allowed us to extend previous observations on the distance to which the cerrado tree Pterodon pubescens extends into the forest. The results obtained indicate a considerable extension of forest into cerrado during the life of an individual tree. A characteristic low forest occurs in the flood plain of the Rio Suiá--Missu while Swampy Gallery forests occur on permanently waterlogged soils around the headwaters of streams. The well drained soils of the Suiá--Missu forest are very uniform, deep latosols (oxisols) of very dystrophic nature with pH (in water) between 4.0 and 5.0 (see table 2, p. 203).

Brazil↗

PubMed2006

Tropical forests and the changing earth system.

Tropical forests are global epicentres of biodiversity and important modulators of the rate of climate change. Recent research on deforestation rates and ecological changes within intact forests, both areas of recent research and debate, are reviewed, and the implications for biodiversity (species loss) and climate change (via the global carbon cycle) addressed. Recent impacts have most likely been: (i) a large source of carbon to the atmosphere, and major loss of species, from deforestation and (ii) a large carbon sink within remaining intact forest, accompanied by accelerating forest dynamism and widespread biodiversity changes. Finally, I look to the future, suggesting that the current carbon sink in intact forests is unlikely to continue, and that the tropical forest biome may even become a large net source of carbon, via one or more of four plausible routes: changing photosynthesis and respiration rates, biodiversity changes in intact forest, widespread forest collapse via drought, and widespread forest collapse via fire. Each of these scenarios risks potentially dangerous positive feedbacks with the climate system that could dramatically accelerate and intensify climate change. Given that continued land-use change alone is already thought to be causing the sixth mass extinction event in Earth's history, should such feedbacks occur, the resulting biodiversity and societal consequences would be even more severe.

Biodiversity↗

PubMed2006

Patterns in potassium dynamics in forest ecosystems.

The biotic cycling of potassium (K) in forest systems has been relatively understudied in comparison with nitrogen (N) and phosphorus (P) despite its critical roles in maintaining the nutrition of primary production in forests. We investigated the ecological significance of K in forests from a literature review and data synthesis. We focused on (1) describing patterns of the effects of K availability on aboveground growth and change in foliar tissue of tree species from a variety of forests; and (2) documenting previously unreported relationships between hydrologic losses of K and N in forested watersheds from the Americas. In a review of studies examining tree growth under K manipulations/fertilizations, a high percentage (69% of studies) showed a positive response to increases in K availability in forest soils. In addition, 76% of the tree studies reviewed showed a positive and significant increase in K concentrations in plant tissue after soil K manipulation/fertilization. A meta-analysis on a subset of the reviewed studies was found to provide further evidence that potassium effects tree growth and increased tissue [K] with an effect size of 0.709 for growth and an overall effect size of 0.56. In our review of watershed studies, we observed that concentrations of K typically decreased during growing seasons in streams draining forested areas in the Temperate Zones and were responsive to vegetation disturbance in both temperate and tropical regions. We found a strong relationship (r2 = 0.42-0.99) between concentrations of K and N (another critical plant nutrient) in stream water, suggesting that similar mechanisms of biotic retention may control the flow of these nutrients. Furthermore, K dynamics appear to be unique among the base cations, e.g. calcium, magnesium, and sodium, because the others do not show similar seasonal patterns to K. We suggest that K may be important to the productivity and sustenance of many forests, and its dynamics and ecological significance warrant further study. We suggest that knowledge about the dynamics of this understudied element is imperative for our understanding patterns and processes in forest ecosystems.

Ecosystem↗

PubMed2006

Public timber supply, market adjustments, and local economies: economic assumptions of the Northwest Forest Plan.

The Northwest Forest Plan in the Pacific Northwest sought to stabilize local economies, including local employment and income, by stabilizing the flow of wood fiber from public forests. This is also a common forest management objective in other regions and countries. Because this economic strategy ignores basic market adjustments, it is likely to fail and to unnecessarily damage forest ecosystems. Application of basic economic principles on how markets operate significantly changes the apparent efficacy of efforts to manage local economies by managing timber supply. The emphasis on timber supply tends to ignore the dominant role that the demand for wood fiber and wood products, rather than wood-fiber supply, plays in determining levels of harvest and production. Contemporary economics indicates that markets tend to operate to offset reductions in wood-fiber supply. This significantly moderates the economic cost of reducing commercial timber harvest in the pursuit of environmental objectives. In addition, contemporary economic analysis indicates that the economic links between natural forests and local communities are much broader than simply the flow of commercially valuable logs to manufacturing facilities. At least in the United States, the flow of environmental services from natural forests has increasingly become an amenity that has drawn people and economic activity to forested areas. Attractive site-specific qualities, including those supported by natural forests, can potentially support local economic development even in the face of reduced timber harvests. These market-related adjustments partially explain the Northwest Forest Plan's overestimation of the expected regional impacts associated with reduced federal timber supply and the ineffectiveness of the plan's efforts to protect communities by stabilizing federal timber supply

Conservation of Natural Resources↗

PubMed2006

Remote forest refugia for Fijian wildlife.

On Pacific islands non-native rats and mongooses threaten many native species. In Fiji we compared visitation rates of rats and mongooses at bait stations and measured biomass of leaf-litter invertebrates to assess the relative predation pressure from these species in forest areas at different distances from the forest edge. Forest areas over 5 km from the forest edge had significantly fewer baits encountered by rats or mongooses than did natural forest areas nearer agricultural and urban habitats. Remote forest areas may function as a last refuge for island species threatened by predation from non-native rats and mongooses. The biomass of leaf-litter invertebrates in remote forest areas was higher indicating a refuge effect for some taxa targeted by rats and mongooses. Protection of the few remaining large blocks of natural forests on Pacific islands may be the most cost-effective approach for conserving many island endemics threatened by rats and mongooses. Logging roads can compromise this refuge effect by acting as dispersal routes for rats into natural forests.

Animals↗