Natural Tropical Forests Research Articles

The effects of drought and fire on seed and seedling dynamics in a tropical seasonal forest in Thailand

Seed production and seedling dynamics were studied for 6 years(1992–1997) with particular emphasis on the effects of the drought andfire in a natural tropical seasonal forest at Mae Klong Watershed ResearchStation, Kantchanaburi, western Thailand. The number of seed produced andemerged seedlings varied greatly among years and species. Most tree speciesproduced very few seeds in 1994 and many in 1995 and 1996, particularly,Shorea siamensis Miq. which displayed the most seedinghabit. Some seedlings, Shorea, Dipterocarpus alatus Roxb.,and Dipterocarpus turbinatus Gaertn. f., emerged at theendof the dry season (late April, after the first rain but when soils still have alow soil moisture content), while the majority of seedlings emerged at thebeginning of the rainy season. After a fire disturbed the plot in April 1996,many species increased their seedling emergences, especially Berryaammonilla. Seedlings of most species less than a year old showed arelatively low mortality in the rainy season, but those ofPterocarpusmacrocarpus Kurz had high mortality. The mean survival rate for allseedling species in this forest was quite low (24.1% y−1), anddifferent values existed for the rainy and the dry season (11.5, and 6.1%month−1, respectively). This suggests that different specieshave adaptations related to the season of seedling emergence and resistance todrought in this tropical seasonal forest community. The traits of tree speciesare classified in terms of their traits in the early stages of regeneration;seed and/or seedling bank, resprouting, and drought resistance. Most specieshave adapted to fire and/or drought by resprouting, seed bank, and/or seedlingbank, although the few species which occur mainly in mesic evergreen forestshave less adapted to these environments. The demographic variations in seed andseedling stages may contribute to the coexistence of these species in thisspecies-rich dry tropical forest.

Poverty Alleviation and Tropical Forests—What Scope for Synergies?

This paper explores the “state-of-the-art” of the two-way causal links between poverty alleviation and natural tropical forests. Microimpacts of rising poverty can increase or slow forest loss. At the macrolevel, poverty also has an ambiguous effect, but it is probable that higher income stimulates forest loss by raising demand for agricultural land. The second question is what potential forest-led development has to alleviate a country's poverty, in terms of producer benefits, consumer benefits and economy-wide employment. Natural forests widely serve as “safety nets” for the rural poor, but it proves difficult to raise producer benefits significantly. Urban consumer benefits from forest, an important target for pro-poor agricultural innovation, are limited and seldom favor the poor. Absorption of (poor) unskilled labor is low in forestry, which tends to be capital-intensive. Natural forests may thus lack comparative advantage for poverty alleviation. There are few “win–win” synergies between natural forests and national poverty reduction, which may help to explain why the loss of tropical forests is ongoing. This may have important implications for our understanding of “sustainable forest development” and for the design of both conservation and poverty-alleviation strategies.

Estimation of forest area near deserts — production of Global Bio-Methanol from solar energy

This paper proposes a new synthesis method for methanol as a future alternative fuel, by the combination of carbon supplied from wood and hydrogen supplied from the electrolysis of water using a solar power generation system in the desert. In the developed countries, more than half of the potential forest area has already been converted into other land uses, while existing forests are well organized and available for wood production. In the developing countries, potential forest sites are expected to be available for wood production, even though they are presently grasslands or secondary forests, while natural tropical forests will not be allowed to be converted into artificial forests. The area available for plantations within 500 km distant from deserts was estimated to be 65 Mha in the world, except for the mountain areas. Biomass production from these sites will be converted annually into 980 Mt methanol with hydrogen from the deserts. This amount is equal to 34% of the world's fuel consumption by vehicles.

Potential carbon flux from timber harvests and management in the context of a global timber market.

This paper presents carbon flux estimates arising from the effect of increasing demand on harvests and management of industrial forests in a global timber market. Results are presented for specific regions and the globe. Harvests and management of forests are predicted to store an additional 184 Tg (1 Tg = 1012 grams) of carbon per year in forests and wood products over the next 50 years, with a range of 108 to 251 Tg per year. Although harvests in natural boreal and tropical forest regions will cause carbon releases, new plantation establishment in subtropical emerging regions more than offsets these losses. Unlike many existing studies, these results suggest that harvests and management of North American forests will lead to carbon emissions from that region over the next 50 years. The results are quantitatively sensitive to the assumed growth in demand although the results are qualitatively similar in the sensitivity analysis.

A study on the plant species diversity of tropical natural forest in Bawangling, Hainan Island

A study on the plant species diversity of tropical natural forest in Bawangling, Hainan Island

Forest Resources and Timber Production of Ghana: Current Instruments for Sustainable Development

The decline of the natural tropical high forest has reached a critical stage in Ghana's forestry history. Timber resources are over-exploited, degraded and further production prospects are questionable and of concern to forest management. The objective of this paper is to discuss some of the institutional measures and development instruments being taken in Ghana towards the feasibility of achieving sustainable management of the high forest for timber and other commodity products, as well as conserving other forest resources. This paper, therefore, provides institutional measures and structures, regulatory and economic instruments, currently being taken to ensure effective forest management and increase the productivity of the land and logging. The role of collaborative management approach of both natural reserved and unreserved high forests and to promote integrated farm forestry is explained. Effective management of the high forest resource demands close harmonizing of instruments and mechanisms, both internal and external to forestry, and which encourage stakeholders to participate actively in decision making that affects the resource quality and its production status. Currently, different instruments including regulatory, property rights, motivational, hypothecation, information supply and economic are being applied in Ghana to achieve sustainable forest resource management and timber production. These instruments are not mutually exclusive in their current application, but rather complementary. Thus, an effective mix of instruments is necessary to promote and make feasible, sustainable forestry in Ghana's socioeconomic development objectives.

Influences of Deforestation on Carbon Balance in a Natural Tropical Peat Swamp Forest in Thailand.

The effects of deforestation on carbon balance in a natural tropical peat swamp forest were evaluated by micrometeorological monitoring. The monitoring sites were the primary forest at To-Daeng and the secondary forest at Bacho in Narathiwat Province, Thailand. The concentration gradient method (CG) and the relaxed eddy accumulation method (REA) were used to estimate the CO2 flux above the canopies. We estimated the annual amount of carbon absorption for both sites, using the relationship between CO2 flux and solar radiation for each site. An annual net carbon absorption of 5.32t C ha-1 year-1, was estimated for the primary forest. The accumulation of the released organic matter from the forest into logged-water caused the net carbon absorption in the peat swamp forest. In the secondary forest, annual net carbon absorption was estimated at 5.22 t C ha-1 year-1, which is almost the same range of absorption as the primary forest, because of plant growth in the secondary forest. A greater quantity of net carbon absorption, 9.69t C ha-1 year-1, was expected, assuming that the ground surface remained water-logged throughout the year. On the other hand, assuming it remained dry throughout the year, a net carbon emission of -0.40 t C ha-1 year-1, was expected.

The use of self-incompatibility in the production of hybrid eucalyptus seed by `Aracruz Celulose' in Brazil

Self-incompatibility found in a Eucalyptus grandis clone was used to promote interspecific hybridization between E. grandis and E. urophylla clones. The interspecific hybridization achieved in an open-pollinated commercial seed orchard planted in Espírito Santo, Brazil was evaluated by the multi-locus outcrossing rate (tm) of the seed producing clone, E. grandis. The percentage of outcrossed seeds reached 95.9%. The outcrossing rate of individual trees was quite variable, but was always above 70.0%. Wright's coefficient was negative (F = -0.30) revealing an excess of heterozygous genotypes in the progeny. Genetic parameters confirmed the high degree of hybridization expected in this orchard. The 800-m wide protection belt of native tropical forest that surrounds this orchard has significantly reduced pollen contamination, in comparison to a 400-m wide belt used in another local seed orchard.

Forestry options for sequestering carbon in mexico: Comparative economic analysis of three case studies

Benefit cost analyses for three case studies which avoid carbon emissions and increase carbon sequestration in Mexican forests, a pulp wood plantation, a native temperate forest and a native tropical evergreen forest, are performed. Management of native temperate and tropical forests offer the most promising alternatives for carbon sequestration. The cost effectiveness of commercial plantations critically depends on very high site productivity.

Analyzing the effect of structural variability and canopy gaps on forest BRDF using a geometric-optical model

A geometric-optical reflectance model is presented which estimates the bidirectional reflectance distribution function (BRDF) of forest canopies by modeling four shadowing pattern components (i.e., illuminated crown, illuminated ground, shadowed crown, and shadowed ground. The model represents the forest canopy as a group of discrete tree crowns and uses a deterministic ray tracing procedure to generate a two-dinwnsional scene of shadow pattern components. It provides the type of shadow fraction information used to calculate the reflectance of forests when it is treated as an area-weighted sum of the shadow component reflectances. The model is designed to test the effect of canopy structure parameters on the bidirectional reflectance of forests and can easily be adapted to accommodate different crown shapes, crown sizes, stem densities, and distributions. The model was used to isolate and quantify the effects of crown shape, canopy cover, stein distribution pattern, and canopy gaps on the shadowing pattern and the canopy reflectance, using a set of statistically generated forest scenes and data gathered for a natural tropical lowland forest scene. The illuminated crown component and the illuminated ground component have the greatest impact on the reflectance values in the red and near-infrared region respectively. The red BRDF, mainly influenced by the illuminated ground component, proves to be sensitive to canopy cover, tree pattern distribution, and canopy gaps. The near-infrared BRDF, affected by the illuminated crown component, is sensitive to canopy cover, crown-center height distribution, and crown shape. The sensitivity of the BRDF to canopy gaps and crown clumping was investigated in more detail. Reflectance-measurements close to the hotspot are found to be insensitive to clumping while retaining sensitivity to crown cover. Forward scattering measurements are fcntnd to be more sensitive to gap size and frequency. The spatial effects of plantations, logging, or road features on the BRDF is further analyzed.

Photoinhibition of Photosynthesis in Plants Growing in Natural Tropical Forest Gaps. A Chlorophyll Fluorescence Study

Abstract:Photoinhibition of photosynthesis was monitored by means of chlorophyll a fluorescence in leaves of plants growing in 60–80 m2 light gaps in a moist tropical lowland forest located on Barro Colorado Island in central Panama. In these forest gaps, photon flux density was low (less than 100 μmol photons m−2 s−1) during most of the day, but increased on clear days to 1.7‐1.8 mmol photons m−2 s−1 for 1–2 h during midday. Nine species representing different taxa and life‐forms were examined. Leaves of all species exhibited substantial photoinhibition in situ during high light exposure, as manifested by a decrease in the ratio of variable to maximum fluorescence emission, FV/FM. Recovery (reversion of fluorescence quenching) took place in the shade following high light exposure. The major part of recovery occurred in a fast phase within about 1 h after the high light period. A slow phase of recovery proceeded for another 4–5 h until sunset. After 30–60 min of recovery in the shade, calculated rates of PSII electron transport remained significantly (5–15%) reduced in comparison to rates obtained prior to high light exposure; after about 2 h of recovery, inhibition was negligible. All species responded to the high light periods and following shade periods in a very similar manner. It is concluded that photoinhibition and recovery exhibited by these gap leaves reflect a dynamic regulatory mechanism of thermal energy dissipation that allows plants of different life‐forms to cope with periods of high light in tropical forest gaps.

Influences of tropical forest changes on environmental quality in Hainan province, P.R. of China

This paper analyses the changes of tropical natural forest of Hainan Island from the eve of liberation to now. The annual mean loss of tropical forest areas is 34000 ha with an annual mean rate of decrease of 2.02%, higher than the rate of global deforestation of tropical forest (about 1%). Deforestation of tropical natural forests causes a series of grave consequences on environmental quality: decrease of forest quality; disappearance of wildlife; increase of rare and endangered wilding species; increase of CO 2 in the air causing greenhouse effect; aggravation of soil erosion and land degradation; imbalance of hydrologic cycle; frequent flood and drought. Therefore, conservation and rational utilization of natural tropical forest resources are very important for Hainan Province to maintain a goad eco-environment quality and ecological balance and to develop the local economy.

Regeneration of an Atlantic forest formation in the understorey of a Eucalyptus grandis plantation in south-eastern Brazil

This note aims to provide data indicating the great potential of Eucalyptus plantations for the recuperation of degraded native tropical forests in Brazil. Cultivation of fast-growing Eucalyptus for charcoal, paper or wood production started in Brazil at the beginning of this century and by 1966 400,000 ha were covered with species of this genus. Rapid industrialization in the early 1970s favoured the expansion of this area to 1,052,000 ha in 1973, the world's largest area covered with Eucalyptus plantations at that time (Lima 1987). Current estimates are of nearly 3,900,000 ha (Instituto de Pesquisas Florestais IPEF, pers. comm.). In order to establish these artificial plantations, however, many native forests were cut, mostly in the cerrado and lower-montane Atlantic forest. The widespread substitution of natural heterogeneous forests by introduced forest monocultures produced some dramatic environmental consequences, as witnessed by the frequent problems that the Eucalyptus planters had with pests and diseases (Berti Filho & Fraga 1987, Zanuincio & Lima 1975). It has now become a priority to restore areas of native vegetation amidst Eucalyptus plantations with the joint aims of protecting water sources, sheltering local fauna, and providing alternative resources for pests and a breeding ground for their predators. To provide background data we carried out a survey in 1988 of regeneration of native trees in the understorey of a Eucalyptus grandis Hill ex Maiden plantation. The site was at CAF (Santa Barbara Agro-forestry Company), a charcoal

Forest management options for sequestering carbon in Mexico

This paper identifies and examines economic response options to avoid carbon emissions and increase carbon sequestration in Mexican forests. A “Policy” scenario covering the years 2000, 2010 and 2030 and a “Technical Potential” scenario (year 2030) are developed to examine the potential carbon sequestration and costs of each response option. Benefit-cost analyses for three case studies, including management of a pulpwood plantation, a native temperate forest and a native tropical evergreen forest are presented and discussed. The study suggests that a large potential for reducing carbon emissions and increasing carbon sequestration exists in Mexican forests. However, the achievement of this potential will require important reforms to the current institutional setting of the forest sector. The management of native temperate and tropical forests offers the most promising alternatives for carbon sequestration. The cost effectiveness of commercial plantations critically depends on very high site productivity. Restoration of degraded forest lands; particularly through the establishment of energy plantations, also shows a large carbon sequestration potential.

Simulation of multi-species tropical forest dynamics using a vertically and horizontally structured model

The mutual interaction of forest growth and light conditions causes vertical and horizontal differentiation in the natural forest mosaic. The associated physical processes should be represented in simulation models describing long-term forest dynamics. The FORMIX2 (tropical) forest simulator incorporates the multi-storey canopy layer structure of the natural tropical forest, the basic processes of gap succession dynamics and gap interaction by tree fall and seed dispersal, several functionally different species groups (emergents, main canopy trees, pioneers, woody treelets and forest-floor herbs) and the energy (carbon) balance of assimilation, dissimilation, and increment resulting from the differing light conditions for the various canopy layers in the gap-size areas of a forest mosaic. The vertically and horizontally structured FORMIX2 model produces time-dependent results (average per hectare data) for stem numbers, diameter distributions, basal areas, standing crop and yield, as well as dynamic views of the forest profile and of spatial forest development, as a function of logging method and intensity and silvicultural treatment. The model has been applied in an exploratory investigation to compute the long-term development of (a) virgin forest and (b) logged-over forest in Sabah, using prototypical data. The results obtained agree with empirical data.

History of decline and present status of natural tropical thorn forest in Punjab

Natural tropical thorn forests once formed one of the most remarkable landscapes of the Punjab plains in Pakistan. Before land reclamation following canal irrigation these forests were the main source of firewood supplies for urban and rural populations. They also contributed to the stability of the fragile areas and supported a thriving wildlife. The past distribution and gradual decline of these forests is traced by literature search. The present status of natural tropical thorn forest was appraised by surveying areas formerly under these forests. The comparison indicated that the natural tropical thorn forest system of the Punjab has almost disappeared. The last few remnants are also severely degraded due to overgrazing, felling, wind erosion, desertification, salinity and waterlogging. Although the main emphasis of this study was to identify and conserve the whole complex, Salvadora oleoides is given special attention because of its great ecological and ethnobotanical importance. It was envisaged that this approach would highlight the significance of preserving the indigenous forest as a whole rather than selecting some species and eliminating others.

Tropical forests in transition: ecology of natural and anthropogenic disturbance processes: ed J. G. Goldammer, (Birkhauser, Basel; Advances in Life Sciences), ISBN (hardback) 3 7643 2601 8, 0 8176 2601 8 (USA), price Sfr98.00 (DM114.00), 1992, 270 pp, index

Tropical Forests in Transition: Ecology of Natural and Anthropogenic Disturbance Processes - An Introduction.- Palynological Evidence Relating to Disturbance and Other Ecological Phenomena of Rain Forests.- Holocene Autochthonous Forest Degradation in Southeast Venezuela.- Vegetation, Megaherbivores, Man and Climate in the Quaternary and the Genesis of Closed Rain Forests.- Succession After Disturbance of Lowland Mixed Dipterocarp Forest by Shifting Agriculture in East Kalimantan, Indonesia.- Degradation of a Forest in the Shimba Hills National Reserve, Kenya, as Initiated by Man and Maintained by Wildlife.- Anthropo-Zoogenic Impact on the Structure and Regeneration of a Submontane Forest in Kenya.- Tropical Mountain Ecology in Ethiopia as a Basis of Conservation, Management and Restoration.- Forests for Integrated Land-Use Development in an Eastern Ethiopian Water Catchment.- Geoecological Consequences of Human Impacts on Forests in Sri Lanka.- Structure and Dynamics of the Upper Montane Rain Forests of Sri Lanka.- A Research Perspective on Disturbance and Recovery of a Tropical Montane Forest.- Process-Oriented Models for Simulation of Growth Dynamics of Tropical Natural and Plantation Forests.- A Finite-Element Model to Simulate Spacial Distributions of Populations of Large Mammals.- The Role of the Tropics in the Global Carbon Budget: Impacts and Possible Developments.- Modeling the Response of Terrestrial Vegetation to Climate Change in the Tropics.

Deforestation: effects on vector-borne disease.

This review addresses changes in the ecology of vectors and epidemiology of vector-borne diseases which result from deforestation. Selected examples are considered from viral and parasitic infections (arboviruses, malaria, the leishmaniases, filariases, Chagas Disease and schistosomiasis) where disease patterns have been directly or indirectly influenced by loss of natural tropical forests. A wide range of activities have resulted in deforestation. These include colonisation and settlement, transmigrant programmes, logging, agricultural activities to provide for cash crops, mining, hydropower development and fuelwood collection. Each activity influences the prevalence, incidence and distribution of vector-borne disease. Three main regions are considered--South America, West & Central Africa and South-East Asia. In each, documented changes in vector ecology and behaviour and disease pattern have occurred. Such changes result from human activity at the forest interface and within the forest. They include both deforestation and reafforestation programmes. Deforestation, or activities associated with it, have produced new habitats for Anopheles darlingi mosquitoes and have caused malaria epidemics in South America. The different species complexes in South-East Asia (A. dirus, A. minimus, A. balabacensis) have been affected in different ways by forest clearance with different impacts on malaria incidence. The ability of zoophilic vectors to adapt to human blood as an alternative source of food and to become associated with human dwellings (peridomestic behaviour) have influenced the distribution of the leishmaniases in South America. Certain species of sandflies (Lutzomyia intermedia, Lu. longipalpis, Lu. whitmani), which were originally zoophilic and sylvatic, have adapted to feeding on humans in peridomestic and even periurban situations. The changes in behaviour of reservoir hosts and the ability of pathogens to adapt to new reservoir hosts in the newly-created habitats also influence the patterns of disease. In anthroponotic infections, such as Plasmodium, Onchocerca and Wuchereria, changes in disease patterns and vector ecology may be more difficult to detect. Detailed knowledge of vector species and species complexes is needed in relation to changing climate associated with deforestation. The distributions of the Anopheles gambiae and Simulium damnosum species complexes in West Africa are examples. There have been detailed longitudinal studies of Anopheles gambiae populations in different ecological zones of West Africa. Studies on Simulium damnosum cytoforms (using chromosome identification methods) in the Onchocerciasis Control Programme were necessary to detect changes in distribution of species in relation to changed habitats. These examples underline the need for studies on the taxonomy of medically-important insects in parallel with long-term observations on changing habitats.(ABSTRACT TRUNCATED AT 400 WORDS)

Cluster point sampling in moist tropical forests using large basal area factors

Horizontal point sampling is only occasionally applied under natural tropical forest conditions. Reasons for this include those relating to the complex floristic composition and structure of these forests and to the presence of unacceptable non-sampling errors resulting from missing trees and incorrect borderline tree checking procedures. Concerning the latter, results from this study, based on probabilities and data derived from computer-simulated sampling on each of three 16 ha real tree stem maps (from Surinam, Kalimantan and Thailand), suggest that there is a statistically valid practical solution. Clusters of points using large basal area factors are used to concentrate work and to ensure that less effort is required in checking the ‘in/out’ status of a borderline tree. For a given basal area factor and bulk of sample, there is no significant difference between the various cluster point layouts used — this offering flexibility in execution.

Comparison of Tropical Tree Plantations with Secondary Forests of Similar Age

The structure and dynamics of small plantations of pine (Pinus caribaea; 4 and 18.5 yr old in 1980) and mahogany (Swietenia macrophylla; 17 and 49 yr old in 1980) were compared with those of paired secondary forest stands of similar age and growing adjacent to each other under similar edaphic and climatic conditions. The study was conducted in the Luquillo Experimental Forest between 1980 and 1984. Comparisons included a variety of demographic, production, and nutrient cycling characteristics of stands. Although the small unmanaged plantations had a lower number of species in understory than paired secondary forests, the understory of the older plantations developed high species richness, including many of native tree species. After 17 yr, native tree species invaded the overstory of plantations. After 50 years the species richness in the understory of a mahogany plantation approached that of its paired secondary forest. Plantation understories had important ecological roles, including high nutrient accumulation. Understory plant tissue, particularly leaf litter, had higher nutrient concentration in pine plantations than in paired secondary forests. Understory biomass in plantations accumulated a higher proportion of the total nutrient inventory in the stand than did the understory in paired secondary forests. Plantations had higher aboveground biomass and net aboveground biomass production than paired secondary forests. Higher root densities and biomass were found in secondary forests as were greater depth of root penetration, higher nutrient concentration in roots, and more microsites where roots grow, than paired plantations. These characteristics may improve the capacity of secondary forests relative to that of paired plantations to rapidly recapture nutrients that become available by mineralization and that could otherwise be lost through hydrological or gaseous pathways. Both forest types accumulated nutrients and mass, but secondary forests recirculated nutrients much faster than the plantations, which tended to store the nutrients. Plantations had higher leaf fall and total litterfall, had litterfall with lower nutrient concentrations, accumulated more nutrients in litter, decomposed more litter on an annual basis, exhibited more variation in the spatial distribution of litter mass, and had more month—to—month variation in litter storage than paired secondary forests. Litter of the secondary forests, on the other hand, had a faster nutrient turnover than plantation litter, though plantations retranslocated more nutrients before leaf fall than did secondary forests. Nutrient retranslocation increased with plantation age. Plantations, particularly pine plantations, produced more litter mass per unit nutrient return than did paired secondary forests. Total nutrient storage in soil gave the best correlation with nutrient use efficiency estimated as element: mass ratios in various compartments. Nutrient use efficiency ranked differently among forest pairs, depending upon which nutrient and ecosystem parameters were being compared. Because of high retranslocation of nutrients, and in spite of greater nutrient "need" to produce higher biomass, plantations had nutrient demands on soil similar to paired secondary forests. Among the ecosystem parameters measured, nutrients in leaf fall correlated best with differences in soil nutrients across stands. Nutrient concentrations in understory species appeared to be a sensitive indicator of whole—stand nutrient use efficiency. Some of the observations of the study could be attributed to intrinsic differences between small unmanaged plantations and secondary forests, but many could be explained by species differences (i.e., timing of leaf fall), age of plantation (i.e., accumulation of biomass or species), or the relative importance of angiosperms and gymnosperms (i.e., nutritional quality of litter). The study challenges the conventional dogma with respect to differences between plantations and native successional ecosystems and underscores the dangers of generalizing about all tropical tree plantations or all natural tropical forests, or even extrapolating from one sector of the ecosystem to another.