Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Potencial for natural forest regeneration from seed bank in an upper Paraná river floodplain, Brazil
Campos, Jo?o Batista;Souza, Maria Concei??o de;
Brazilian Archives of Biology and Technology , 2003, DOI: 10.1590/S1516-89132003000400018
Abstract: the historical process of deforestation was analyzed to evaluate the regeneration potential of forests from soil seed bank of porto rico island (53° 15'w and 22° 45's) in the upper paraná river floodplain. remnant forest fragments were identified and measured and the structure of arboreous vegetation and the composition of the seed bank of the forests and grassland of the island were evaluated. results showed a fast process of deforestation with critical levels of forest: the remaining twice fragments represented only 5.98% of the total surface of the island. disturbance by cattle raised on the island continuously degraded the fragments (backward succession), while expansion of areas with pasture favored severe impoverishment of the seed banks flora. the latter factor, soil compaction, and characteristics of seeds of existing arboreous species in the bank suggested that the immediate reestablishment of vegetation was more conditioned to introduction processes of seeds (by rain and ''flood seed'') than by stock of seeds in the bank.
Potencial for natural forest regeneration from seed bank in an upper Paraná river floodplain, Brazil  [cached]
Campos Jo?o Batista,Souza Maria Concei??o de
Brazilian Archives of Biology and Technology , 2003,
Abstract: The historical process of deforestation was analyzed to evaluate the regeneration potential of forests from soil seed bank of Porto Rico island (53° 15'W and 22° 45'S) in the upper Paraná river floodplain. Remnant forest fragments were identified and measured and the structure of arboreous vegetation and the composition of the seed bank of the forests and grassland of the island were evaluated. Results showed a fast process of deforestation with critical levels of forest: the remaining twice fragments represented only 5.98% of the total surface of the island. Disturbance by cattle raised on the island continuously degraded the fragments (backward succession), while expansion of areas with pasture favored severe impoverishment of the seed banks flora. The latter factor, soil compaction, and characteristics of seeds of existing arboreous species in the bank suggested that the immediate reestablishment of vegetation was more conditioned to introduction processes of seeds (by rain and ''flood seed'') than by stock of seeds in the bank.
Forest Structure, Nutrients, and Pentaclethra macroloba Growth after Deforestation of Costa Rican Lowland Forests  [PDF]
Daniela J. Shebitz,William Eaton
ISRN Ecology , 2013, DOI: 10.1155/2013/414357
Abstract: Succession following deforestation in Neotropical forests has been investigated extensively, yet rarely have studies connected nutrient dynamics with vegetation. This study was conducted in lowland wet forests of Maquenque, Costa Rica. The objectives were (1) to compare carbon (C), nitrogen (N), and phosphorus (P) characteristics and understory vegetation diversity between regenerating forests and primary forests; and (2) to use these variables to evaluate P. macroloba’s successional role. Four 300?m2 plots were established in primary and secondary forests where P. macroloba was the dominant N-fixing tree. Soil and vegetation data were collected from 2008 to 2010. Values of indicators of C, N, and P cycle activity were generally greater in primary than in secondary forest soils. Efficiency of organic C use and the relative contribution of respiration and organic C to soil biomass were also greater in the primary forest. These trends corresponded with greater richness, biomass, and cover of total and leguminous plant species, greater volume of P. macroloba in primary stands, and greater density of P. macroloba in secondary stands. As cleared regions of former primary forest regenerate, P. macroloba is the important dominant N-fixing tree and a critical driver of C, N, and P recuperation and ecosystem recovery. 1. Introduction Tropical forests originally covered up to 99% of the land in Costa Rica [1]. Approximately 90% of the original forests in Costa Rica have been destroyed in recent decades, and approximately 46% of the total area has been converted into cattle pasture [1, 2]. In the Northern Zone of Costa Rica, four decades of deforestation have resulted in the loss of about 70% of the lowland forests [2–7]. The resulting fragmentation has yielded concern among regional scientists regarding whether the remaining primary forests will be able to regenerate at a rate matching the deforestation [7]. Today, tropical forest land is characterized by an expanding proportion of secondary forests [8]. As the area of the secondary forests grows at the cost of primary forests, the secondary forests will have to be managed and used in the future [9]. Rates of recovery for abandoned farmland in tropical areas are accelerated if prior land-use intensity was low, areas recovering are small in size, soils are fertile, and there are remnant forests nearby [10]. However, many areas cleared and used as pasture in Costa Rica have suffered such a severe deterioration of soils that forest successional processes are hindered. Instead of forests returning to the area,
Tropical Deforestation, Community Forests, and Protected Areas in the Maya Forest
David Barton. Bray,Elvira Duran,Victor Hugo. Ramos,Jean-Francois Mas
Ecology and Society , 2008,
Abstract: Community forests and protected areas have each been proposed as strategies to stop deforestation. These management strategies should be regarded as hypotheses to be evaluated for their effectiveness in particular places. We evaluated the community-forestry hypothesis and the protected-area hypothesis in community forests with commercial timber production and strict protected areas in the Maya Forest of Guatemala and Mexico. From land-use and land cover change (LUCC) maps derived from satellite images, we compared deforestation in 19 community forests and 11 protected areas in both countries in varying periods from 1988 to 2005. Deforestation rates were higher in protected areas than in community forests, but the differences were not significant. An analysis of human presence showed similar deforestation rates in inhabited protected areas and recently inhabited community forests, but the differences were not significant. There was also no significant difference in deforestation between uninhabited protected areas, uninhabited community forests, and long-inhabited community forests. A logistic regression analysis indicated that the factors correlated with deforestation varied by country. Distance to human settlements, seasonal wetlands, and degree and length of human residence were significant in Guatemala, and distance to previous deforestation and tropical semideciduous forest were significant in Mexico. Varying contexts and especially colonization histories are highlighted as likely factors that influence different outcomes. Poorly governed protected areas perform no better as a conservation strategy than poorly governed community forests with recent colonists in active colonization fronts. Long-inhabited extractive communities perform as well as uninhabited strict protected areas under low colonization pressure. A review of costs and benefits suggests that community forests may generate more local income with lower costs. Small sample sizes may have limited the statistical power of our comparisons, but descriptive statistics on deforestation rates, logistic regression analyses, LUCC maps, data available on local economic impacts, and long-term ethnographic and action-research constitute a web of evidence supporting our conclusions. Long-inhabited community forest management for timber can be as effective as uninhabited parks at delivering long-term forest protection under certain circumstances and more effective at delivering local benefits.
Effects of Deforestation and Forest Degradation on Forest Carbon Stocks in Collaborative Forests, Nepal  [PDF]
Ram Asheshwar MANDAL,Ishwar Chandra DUTTA,Pramod Kumar JHA,Sidhibir KARMACHARYA
International Journal of Conservation Science , 2012,
Abstract: There are some key drivers that favor deforestation and forest degradation. Consequently, levels of carbon stock are affected in different parts of same forest types. But the problem lies in exploring the extent of the effects on level of carbon stocking. This paper highlights the variations in levels of carbon stocks in three different collaborative forests of same forest type i.e. tropical sal (Shorea robusta) forest in Mahottari district of the central Terai in Nepal. Three collaborative forests namely Gadhanta-Bardibas Collaborative Forest (CFM), Tuteshwarnath CFM and Banke- Maraha CFM were selected for research site. Interview and workshops were organized with the key informants that include staffs, members and representatives of CFMs to collect the socio-economic data and stratified random sampling was applied to collect the bio-physical data to calculate the carbon stocks. Analysis was carried out using statistical tools. It was found five major drivers namely grazing, fire, logging, growth of invasive species and encroachment. It was found highest carbon 269.36 ton per ha in Gadhanta- Bardibash CFM. The findings showed that the levels of carbon stocks in the three studied CFMs are different depending on how the drivers of deforestation and forest degradation influence over them.
Deforestation, land conversion and illegal logging in Bangladesh: the case of the Sal (Shorea robusta) forests  [cached]
Islam K,Sato N
iForest : Biogeosciences and Forestry , 2012, DOI: 10.3832/ifor0578-005
Abstract: Bangladesh, with a forest cover estimated at 17.08% of all land surface area, has experienced massive degradation of its natural resources and a conside-rable change in its land cover. While deforestation in Bangladesh is obviously a complex issue, one important aspect emerges from previous research findings in explaining deforestation: industrialization. This study focuses on the causes of deforestation in Bangladesh, particularly in tropical moist deciduous Sal forests, using multi levels factor analysis framework. Data were collected through questionnaire surveys, formal and informal discussions with local people, expert interviews and literature reviews. The main findings of defore-station framework show that illegal logging and forest land conversion were the ultimate causes of Sal forests deforestation in Bangladesh. Illegal logging is a complex phenomenon and is being patronized by a local syndicate, functio-ning from behind the scenes. On the other hand, land conversion into different commercial activities has direct influence on national policy and the predispo-sing conditions of this country. Therefore, the immediate task of the nation would be to stop illegal logging and land conversion of Sal forests. This can be done by involving all relevant stakeholders in the form of effective forest policy formulation and execution of strict environmental protection law.
Effects of deforestation on the genetic structure of Castanopsis sclerophylla

生态学报 , 2008,
Abstract: Human activities have vital impacts on ecosystems. Deforestation is one of the most common human activities. Deforestation leads to reduced population sizes of the remnant plants, or leads to local extinction. When deforestation stops, population size of remnant plants may increase gradually and some extinct species may appear via seed dispersal. However, genetic composition of the restored populations may be changed due to bottleneck effect or founder effect. Theoretical studies have proven that deforestation has negative impacts on genetic variation, and that rare alleles are especially vulnerable to loss. However, there are few empirical studies concerning the genetic consequences of deforestation on plant species. East China has suffered from serious deforestation, and there is hardly any pristine forest remaining. Zonal vegetation in subtropical areas of East China is constituted largely by evergreen broadleaved forests (EBLFs). Castanopsis sclerophylla is one of the dominant species of EBLFs and is also one of the earliest evergreen plants to recover during the restoration process that follows after deforestation. Therefore, it is an ideal species to check the effects of deforestation on genetic variation. To study the effects of deforestation on genetic variation of Castanopsis sclerophylla, a total of 138 individuals were collected from 5 populations, among them two were from mature forests and three were from restored forests. We used microsatellites to detect the genetic composition. After screening the microsatellite primers available in congener species C. cuspidata var. sieboldii, we got five pairs of primer suitable for C. sclerophylla. Each individual was genotyped at the five microsatellite loci. The five loci revealed 29 alleles in the global population. Mean number of alleles per locus, effective number of alleles per locus and allelic richness of the global population were 5.80, 3.54 and 4.85 respectively. The observed heterozygosity (0.53) was significantly lower than the expected heterozygosity (0.72) (p<0.01). Within-population genetic diversity was high, and no significant difference was found between populations from mature forests and from restored forests. Little genetic differentiation (GST=0.028, FST=0.032) was observed among populations and the calculated gene flow was 8.68. Comparable genetic variation in populations from restored and mature forests indicated that deforestation in this region has not significantly reduced genetic diversity of C. sclerophylla, mainly due to its extensive sprouting. However, the software BOTTLENECK indicated a recent population bottleneck in 3 restored populations, a sign of distinct population decline in recent generations. A recent bottleneck was also observed in 1 mature population, mainly due to recent forest fragmentation.
Biodiversity status of urban remnant forests in Cape coast, Ghana
JP Deikumah, AA Kudom
Journal of Science and Technology (Ghana) , 2010,
Abstract: Cape Coast Metropolis, which is close to Kakum forest, has its native forests being reduced to fragments. Biodiversity in these forest reserves are exposed to the threat of being cleared over night as a result of urbanization. There are reported cases of some rare or potential medicinal plant species that have disappeared from the Cape Coast environ and is worth noting that basic knowledge of the organisms that make up most of the ecosystems in these remnant forests are woefully inadequate. In this study, inventory of vertebrates and invertebrates were undertaken in five remnant forests in Cape Coast. The study sites were surveyed for small terrestrial mammals, large mammals, avifauna, herpetofauna and invertebrates. From the inventory taken, 15604 species of invertebrates belonging to 51 families, 83 species of birds belonging to 30 families were sampled. Furthermore 14 species of mammals belonging to 8 families and 8 species of herpetofauna were also sampled. Although these species were of least concern under IUCN category, it is important to protect these native forests from total destruction. Benefits such as the protection of numerous native pollinators and biological control agents can be derived when these reserves are protected. Furthermore, such reserves can be developed to become biological field stations for research or ecotourism parks which can generate employment and revenue for the community. Conservation of biodiversity is in the interest of generations unborn; not only Ghanaians or Africans but the whole of tomorrow’s mankind.
Multiresolution quantification of deciduousness in West Central African forests  [PDF]
G. Viennois,N. Barbier,I. Fabre,P. Couteron
Biogeosciences Discussions , 2013, DOI: 10.5194/bgd-10-7171-2013
Abstract: The characterization of leaf phenology in tropical forests is of major importance and improves our understanding of earth-atmosphere-climate interactions. The availability of satellite optical data with a high temporal resolution has permitted the identification of unexpected phenological cycles, particularly over the Amazon region. A primary issue in these studies is the relationship between the optical reflectance of pixels of 1 km or more in size and ground information of limited spatial extent. In this paper, we demonstrate that optical data with high to very-high spatial resolution can help bridge this scale gap by providing snapshots of the canopy that allow discernment of the leaf-phenological stage of trees and the proportions of leaved crowns within the canopy. We also propose applications for broad-scale forest characterization and mapping in West Central Africa over an area of 141 000 km2. Eleven years of the Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) data were averaged over the wet and dry seasons to provide a dataset of optimal radiometric quality at a spatial resolution of 250 m. Sample areas covered at a very-high (GeoEye) and high (SPOT-5) spatial resolution were used to identify forest types and to quantify the proportion of leaved trees in the canopy. The dry season EVI was positively correlated with the proportion of leaved trees in the canopy. This relationship allowed the conversion of EVI into canopy deciduousness at the regional level. On this basis, ecologically important forest types could be mapped, including young secondary, open Marantaceae, Gilbertiodendron dewevrei and swamp forests. We show that in west central African forests, a large share of the variability in canopy reflectance, as captured by the EVI, is due to variation in the proportion of leaved trees in the upper canopy, thereby opening new perspectives for biodiversity and carbon-cycle applications.
Carbon budget of tropical forests in Southeast Asia and the effects of deforestation: an approach using a process-based model and field measurements
M. Adachi, A. Ito, A. Ishida, W. R. Kadir, P. Ladpala,Y. Yamagata
Biogeosciences (BG) & Discussions (BGD) , 2011,
Abstract: More reliable estimates of the carbon (C) stock within forest ecosystems and C emission induced by deforestation are urgently needed to mitigate the effects of emissions on climate change. A process-based terrestrial biogeochemical model (VISIT) was applied to tropical primary forests of two types (a seasonal dry forest in Thailand and a rainforest in Malaysia) and one agro-forest (an oil palm plantation in Malaysia) to estimate the C budget of tropical ecosystems in Southeast Asia, including the impacts of land-use conversion. The observed aboveground biomass in the seasonal dry tropical forest in Thailand (226.3 t C ha 1) and the rainforest in Malaysia (201.5 t C ha 1) indicate that tropical forests of Southeast Asia are among the most C-abundant ecosystems in the world. The model simulation results in rainforests were consistent with field data, except for the NEP, however, the VISIT model tended to underestimate C budget and stock in the seasonal dry tropical forest. The gross primary production (GPP) based on field observations ranged from 32.0 to 39.6 t C ha 1 yr 1 in the two primary forests, whereas the model slightly underestimated GPP (26.5–34.5 t C ha 1 yr 1). The VISIT model appropriately captured the impacts of disturbances such as deforestation and land-use conversions on the C budget. Results of sensitivity analysis showed that the proportion of remaining residual debris was a key parameter determining the soil C budget after the deforestation event. According to the model simulation, the total C stock (total biomass and soil C) of the oil palm plantation was about 35% of the rainforest's C stock at 30 yr following initiation of the plantation. However, there were few field data of C budget and stock, especially in oil palm plantation. The C budget of each ecosystem must be evaluated over the long term using both the model simulations and observations to understand the effects of climate and land-use conversion on C budgets in tropical forest ecosystems.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.