Potentials and impacts of short-rotation coppice plantation with aspen in Eastern Germany under conditions of climate change

Woody biomass generated in short-rotation coppice (SRC) plantations with aspen (Populus tremula L.) has good properties for bioenergy crop production: annual yields are high, labour input per year is low, and it is ecologically valuable because of the multi-year rotation periods. Eastern Germany has a special advantage in producing bioenergy crops: the former “agricultural cooperatives” built up quite large farms with, compared to Western Germany, comparatively large fields. Therefore, a modelling study of the potential and the impacts of aspen SRC plantations in the five eastern federal states of Germany under the recent climate and future climate projections was conducted. The ecophysiological forest growth model 4C was used to simulate the growth of aspen SRC plantations and their impacts on carbon in soils, and groundwater recharge, on selected suitable areas currently under crops but with marginal site conditions for cropping. A clear signal to enhanced growth condition over the whole area can be seen in the simulation of the mean annual woody biomass yield under conditions of climate change, which increased from 7.47 t DW ha⁻¹ a⁻¹ under the recent climate to 9.26 t DW ha⁻¹ a⁻¹ at the end of the considered future period 2034–2055 under climate change. The mean soil carbon sequestration rate was 0.81 t C ha⁻¹ a⁻¹ under the recent climate and could rise up to 0.93 t C ha⁻¹ a⁻¹ under the assumption of climate change. On the other hand, the mean annual percolation rate, used as an indicator of impacts on the regional water budget, will diminish under future climatic conditions. The results suggest that aspen SRC plantations are a suitable contribution to regional CO₂ mitigation and carbon sequestration under possible change of climate, but that negative impacts on the regional water budget are possible.     

Intensification level of rice farming in Myanmar: implication for its sustainable development

This study aims to estimate the intensification of rice farming in Myanmar particularly due to chemical fertilizer application, using farm-level data obtained from field surveys conducted in the 2000s. Relatively high-input rice farming was found in dry season crop in the delta zone and the double crop in well-irrigated lowlands of the central dry zone. The chemical fertilizer used there was about 88–159 kg NPK (nitrogen, N; phosphate, P₂O₅; and potash, K₂O) ha⁻¹ (76–110 kg nitrogen (N) ha⁻¹), and the average paddy yield ranged from 2.8 to 3.5 ton ha⁻¹. On the other hand, nutrient input in survey sites of rain-fed lowland was between 11 and 53 kg NPK ha⁻¹ (5 and 36 kg N ha⁻¹), and the yield ranged from 1.1 to 2.3 ton ha⁻¹. The national average of paddy yield and nutrient input of fertilizer was roughly estimated to be around 2.4 ton ha⁻¹ and 60 kg NPK ha⁻¹, respectively. A gap was observed between these calculated values and the official statistics. A comparison of fertilizer use efficiency for rice production in Myanmar with that in China and Vietnam has shown that the efficiency in Myanmar has not declined to an inappropriate level even in its intensive ones. Rice production in Myanmar has room for increasing the yield by capital intensification. Nevertheless, considering its sustainability as well as productivity, further intensification in rice farming technology in irrigated lowlands of Myanmar may neither be the best nor the only way.     

Ecologically optimal nitrogen application rates for rice cropping in the Taihu Lake region of China

Excessive nitrogen (N) fertilization in intensive agricultural areas in the Taihu Lake region of East China has resulted in low N utilization efficiency and serious environmental problems, giving rise to the need for an urgent reduction in the N fertilization rate. However, no holistic evaluations of rice (Oryza sativa L.) yield effect and environmental effects of N fertilization have been conducted when recommending an optimal N rate. The current study provides an economic indicator and an evaluation model to account for the environmental effects of different N losses after N fertilizer application in the ecological and economic N rate for one rice season in the Taihu Lake region. Based on the assembled data and economic index, a general economic evaluation model to measure efficiently the cascading costs of the chemical N cycle at the regional scale was developed. Thereafter, fertilizer-stimulated benefit curves and fertilizer-induced cost curves were generated to determine an economically and ecologically optimal N application rate. The results revealed that the maximum net benefits were 3,123 yuan ha⁻¹ at 202 kg N ha⁻¹ for one rice season in the Taihu Lake region. Additional N application up to a rate of 263 kg N ha⁻¹ would increase rice production, but the increase in the total marginal costs would be slightly greater than the increase in marginal benefits. Among the marginal costs, the fertilizer and acidification costs were the greatest expenses, amounting to 1,716 yuan at 263 kg N ha⁻¹, followed by eutrophication and global warming costs. When compared with the conventional N fertilization rate, this recommended rate could decrease the amount of N applied to rice from 10 to 40%, thereby, enabling optimum economic and ecological results.     

Fuelwood consumption in two tribal villages of the Nanda Devi Biosphere Reserve of the Indian Himalaya and strategies for fuelwood sustainability

Fuelwood is the only important source of energy in the mountainous region of the Garhwal Himalaya, India. Since the commercial source of energy is generally beyond the reach of ordinary people due to their poor socio-economic conditions and due to limited supply and lack of communication facilities for transport of LPG, the villages of the inner region of the Garhwal Himalaya depend on their fuel requirement from the forest. In the present study, two villages of the Nanda Devi Biosphere Reserve in Uttarakhand part of the Indian Himalaya i.e. Lata and Dunagiri located at 2,415 and 3,600 m altitudes, respectively, were selected for the study of socio-economic profile and vegetation and for estimation of per capita fuelwood consumption and the degree of disturbance. The study was conducted from 2002–2005. The population of these villages is migratory and belongs to the Bhotiya community, a scheduled tribe consisting of two subgroups known as Tolcha and Marchha. They grow traditional crops as well as cash crops. Important tree species used for fuelwood include Cedrus deodara, Pinus wallichiana, Cupressus torulosa, Taxus wallichiana, Acer indicum, Quercus dilatata and Viburnum cotinifolium. Maximum density among trees was shown by Pinus wallichiana (169.6 trees ha⁻¹) in village Lata and by Cedrus deodara (89.6 trees ha⁻¹) in village Dunagiri. The average per capita consumption of fuelwood in villages Lata and Dunagiri was 4.03 and 4.77 kg capita⁻¹ day⁻¹. Maximum number of trees (29 and 31% lopping for Lata and Dunagiri, respectively) belonged to disturbance class 1 (1–20% lopping) followed by the disturbance class 2 (20–40% lopping). Due to location of these villages in the buffer zone of the biosphere reserve, the fuelwood consumption may cause an adverse impact on the ecological status of this reserve, which urgently requires employing strategies for the conservation and management of this biosphere in terms of fuelwood sustainability e.g. regulation of livestock stock and grazing, using alternative sources of fuels, plantation of multipurpose trees and adoption of ecotourism.     

Agroforestry in the Western Ghats of peninsular India and the satoyama landscapes of Japan: a comparison of two sustainable land use systems

Agroforestry in the Western Ghats (WG) of peninsular India and satoyama in rural Japan are traditional land-use systems with similar evolutionary trajectories. Some of their relevance was lost by the middle of the twentieth century, when modern agricultural technologies and urbanisation engineered shifts in emphasis towards maximising crop production. There has been, however, a resurgence of interest in traditional land-use systems recently, in view of their ability to provide ecosystem services. Both agroforestry and satoyama are thought to be harbingers of biological diversity and have the potential to serve as “carbon forests.” Carbon (C) stock estimates of the sampled homegardens in WG ranged from 16 to 36 Mg ha⁻¹. Satoyama woodlands owing to variations in tree stocking and management conditions indicated widely varying C stocks (2–279 Mg ha⁻¹). Agroforestry and satoyama also differ in nature, complexity, and objectives. While agroforestry involves key productive and protective functions, and adopts ‘intensive management’, the satoyama woodlands are extensively managed; understorey production is seldom a consideration. Differences in canopy architecture (multi-tiered structure of agroforestry vs. the more or less unitary canopy of satoayama) and land ownership pattern (privately owned/managed agroforestry holdings vs. community or local government or privately owned and mostly abandoned satoyamas) pose other challenges in the transfer and application of knowledge gained in one system to the other. Nonetheless, lessons learnt from satoyama conservation may be suitable for common pool resource management elsewhere in Asia, and aspects relating to understorey production in agroforestry may be relevant for satoyama under certain scenarios.     

VALUING ECOSYSTEM SERVICES OF CHILEAN TEMPERATE RAINFORESTS

The Valdivian Rainforest Ecoregion (35°–48° S) in southern South America is among the ecosystems with highest conservation priority worldwide due to its rich diversity, degree of endemism, and critical conservation status. Temperate rainforests in this vast area are essential as source of biological resources and to maintain different ecosystem services which remain largely unmeasured and unvalued. Consequently, the benefits they provide are not reflected in decision-making regarding forest management and conservation. Based on existing studies and results from ongoing research we describe selected ecosystem services and provide estimates of their economic value. Timber benefits for secondary forests expressed as net present stumpage values were US$ 3742 ha⁻¹ and US$ 3093 ha⁻¹ for sustainable forest management (SFM) and unsustainable harvesting, respectively. Timber benefits for old growth forests␣equaled US$ 4546 ha⁻¹ and US$ 5718 ha⁻¹, for SFM and unsustainable harvesting, respectively, using an 8% discount rate. Annual benefits from recreation were US$ 1.6 ha⁻¹ and US$ 6.3 ha⁻¹ for the two most important national parks located in the study area. The annual value of maintaining soil fertility was US$ 26.3 ha⁻¹ using the replacement cost of nutrient losses due to soil erosion. The annual economic value of water supply for human consumption using the production function method was US$ 235 ha⁻¹. These results provide valuable information on the kind and magnitude of values that could be relevant in decision-making concerning conservation and management of native forests in the Valdivian Rainforest Ecoregion.     

Growth, yield and elements content of wheat (Triticum aestivum) grown in composted municipal solid wastes amended soil

A commercial formulation of composted municipal solid wastes (MSW) was used for amending soil at 0, 50, 100, 150, 200 and 250 kg ha⁻¹ in which wheat had been grown (field experiments) and element residues of amended soil and plant parts were enumerated. MSW amendment caused a significant improvement in soil quality. Growth (shoot length, leaf number, leaf area, tiller number, plant dry weight and chlorophyll contents of leaves) and yield (length of panicle, number of panicles per plant and grain yield per plant) of wheat increased gradually up to the MSW-amendment level of 200 kg ha⁻¹. Elements, Ni, Zn, Cu, Cd, Cr, and Pb accumulated in plants from MSW amended soil, but the degree of metal accumulation was the least in seeds in comparison to other plant parts (root, stem and leaf). Moreover, Ni, Zn, Cd and Pb, were in high concentration in all plant parts. It is recorded that the level of 200 kg ha⁻¹ MSW amendment caused better growth and yield of wheat, but progressive levels of metal accumulation in plant parts were recorded due to increase in amendment levels. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Carbon stock variation of Pinus roxburghii Sarg. Forest along altitudes of Garhwal Himalaya, India

The present study was undertaken in Pinus roxburghii forest along three different altitudes i.e., 1100, 1300 and 1500 meter above mean sea level of Garhwal Himalaya to understand the effect of altitudes on carbon stocks (live trees and soil) in Pinus roxburghii forest. Tree density of this forest ranged between 590 tree ha^?1 (upper altitude) to 640 tree ha^?1 (lower altitude). The highest total carbon density (TCD) of above and belowground carbon was 66.33 ± 29.92 Mg ha^?1 at lower altitude followed by 57.64 ± 16.75 Mg ha^?1 in middle altitude and 52.92 ± 6.52 Mg ha^?1 in upper altitude. Soil organic carbon was highest (33.20 ± 2.77 Mg ha^?1) at lower altitude followed by middle (22.61 ± 7.17 Mg ha^?1) and upper altitude (12.65 ± 6.10 Mg ha^?1). Total carbon stock (trees + soil) of Pinus roxburghii forest was maximum (99.53 Mg ha^?1) at lower altitude and minimum (65.57 Mg ha^?1) at upper altitude.     

Characteristics of Carbon Storage and Density in Different Layers of Forest Ecosystems

Characteristics of carbon storage and density in different layers of forest ecosystems should be studied comprehensively and in more detail. Using forest inventory data in combination with field survey data, we explored the characteristics of carbon storage and density in different layers of forest ecosystems in Liaoning Province of China. Results showed that total carbon storage was 813.034 Tg C. The carbon storage of soil layer accounted for 81.0% of the total storage with 658.783 Tg C, followed by those of arbor, litter and shrub layers with 128.403 Tg C (15.8%), 22.723 Tg C (2.8%) and 3.125 Tg C (0.4%), respectively. The average carbon density for the forest ecosystems were 183.571 Mg C ha^–1, with soil layer (148.744 Mg C ha^–1) being the highest one, followed by arbor layer (28.992 Mg C ha^–1), litter layer (5.131 Mg C ha^–1) and shrub-grass layer (0.706 Mg C ha^–1). Carbon storage in different forest ecosystems varied from 1.595 to 319.161 Tg C, while C density ranged from 165.067 to 235.947Mg C ha^–1, with the highest and lowest values being observed in soil layer and shrub-grass layers, respectively, implying that soil is the main body of forest carbon storage. Young-aged forests accounted for a greater proportion of forests in the Province than forests in other age classes; and proper management of forests could increase the carbon sequestration in the forest ecosystems. The comparison with previous estimations of carbon storage for forest ecosystem implied that methods and data used for forest carbon storage estimation affected the results of estimates obviously.     

Controlling non-point-source pollution by rural resource recycling. Nitrogen runoff in Tai Lake valley, China, as an example

Agricultural non-point-source (NPS) pollution is regarded as the dominant contributor to water quality degradation and eutrophication in China. Nitrogen (N) is a primary source of pollution in fresh water bodies. In this work a linear programming model was developed to simulate the effectiveness of different nitrogen runoff control policies, using Pinghu City in Tai Lake valley as an example. Four policy scenarios were tested: a tax at a rate equivalent to 50% of the cost of nitrogen fertilizer (S1); a ban on summer fertilizer applications to make the most use of fertilizer applied in the spring (S2); mandatory substitution of regular fertilizers by controlled-release fertilizers (S3); and a subsidy of US$300 ha⁻¹ (RMB￥150 mu⁻¹) for using compost (S4). The results indicate that all four policies would effectively reduce nitrogen runoff—by 9.8, 26.8, 14.4, and 80.0%, respectively. A subsidy for recycling domestic animal manure and utilizing compost had the most significant effect on the reduction of nitrogen runoff without reducing household income. This research suggests that measures to control agricultural NPS pollution should be combined with a policy to promote recycling of bio-resources and that financial support for NPS pollution control combined with bio-resource recycling should be regarded as one aspect of public investment in regional sustainable development.     

Applications of a hydro-biogeochemical model and long-term simulations of the effects of logging in forested watersheds

We simulated hydrological and biogeochemical responses to logging in a forested watershed to determine the vulnerability and/or resiliency of the forest ecosystems in the Lake Shumarinai Basin in northern Hokkaido, Japan. We used a biogeochemical model (PnET-CN) and a rainfall–runoff model (HYCYMODEL) to predict ecosystem responses. The PnET-CN model simulated well the observed NO₃ ⁻ concentrations in streamwater, particularly at high concentrations during snowmelt; however, the model could not simulate small increases in NO₃ ⁻ during the summer. By considering hydrological processes within the watershed and combining the model with the HYCYMODEL (PnET + HYCYMODEL), the seasonality of streamwater NO₃ ⁻ concentrations was better simulated. Using these models, the long-term effects of logging were simulated for coniferous, deciduous, and mixed forests. NO₃ ⁻ concentrations in streamwater increased in response to the logging disturbance in both coniferous and deciduous forests. In the coniferous forest, NO₃ ⁻ concentrations reached a maximum 10 years after logging, and high concentrations persisted for 30 years. In contrast, NO₃ ⁻ concentrations in the deciduous forest reached a maximum within 3–4 years and recovered to pre-disturbance levels after 15 years. We also used the models to determine the effects of different sizes and types (coniferous, deciduous, and mixed forest) of logging areas on Lake Shumarinai. The model results indicated that large areas of cutting require more than 100 years for complete lake recovery. Whereas the annual discharge to the lake minimally increased, the annual NO₃ ⁻ load greatly increased. Our simulation results elucidate the vulnerability and resiliency of forest ecosystems and provide valuable information for ecosystem management.     

Evaluation of carbon stock variation in Northern Italian soils over the last 70 years

Carbon (C) sequestration in soils is gaining increasing acceptance as a means of reducing net carbon dioxide (CO₂) emissions to the atmosphere. Numerous studies on the global carbon budget suggest that terrestrial ecosystems in the mid-latitudes of the Northern Hemisphere act as a large carbon sink of atmospheric CO₂. However, most of the soils of North America, Australia, New Zealand, South Africa and Eastern Europe lost a great part of their organic carbon pool on conversion from natural to agricultural ecosystems during the explosion of pioneer agriculture, and in Western Europe the adoption of modern agriculture after the Second World War led to a drastic reduction in soil organic carbon content. The depletion of organic matter is often indicated as one of the main effects on soil, and the storage of organic carbon in the soil is a means of improve the quality of soils and mitigating the effects of greenhouse gas emission. The soil organic carbon in an area of Northern Italy over the last 70 years has been assessed In this study. The variation of top soil organic carbon (SOC) ranged from −60.3 to +6.7%; the average reduction of SOC, caused by agriculture intensification, was 39.3%. This process was not uniform, but related to trends in land use and agriculture change. For the area studied (1,394 km²) there was an estimated release of 5 Tg CO₂-C to the atmosphere from the upper 30 cm of soil in the period 1935–1990.     

Strategic assessment of the magnitude and impacts of sand mining in Poyang Lake, China

Planning for the extraction of aggregates is typically dealt with at a case to case basis, without assessing environmental impacts strategically. In this study we assess the impact of sand mining in Poyang Lake, where dredging began in 2001 after sand mining in the Yangtze River had been banned. In April 2008 concern over the impact on the biodiversity led to a ban on sand mining in Poyang Lake until further plans could be developed. Planning will require consideration of both sand extraction in relation to available sediment resources and also environmental impacts within the context of future demand for sand in the lower Yangtze Valley. We used pairs of near-infrared (NIR) Aster satellite imagery to estimate the number of vessels leaving the lake. Based on this we calculated a rate of sand extraction of 236 million m³ year⁻¹ in 2005–2006. This corresponds to 9% of the total Chinese demand for sand. It qualifies Poyang Lake as probably the largest sand mining operation in the world. It also indicates that sand extraction currently dominates the sediment balance of the lower Yangtze River. A positive relation between demand for sand and GDP, revealed by historic data from the USA, suggests that the current per capita demand for sand in China might increase in the near future from 2 to 4 m³ year⁻¹. We review various environmental impacts and question whether it will be possible to preserve the rich biodiversity of the lake, while continuing at the same time satisfying the increasing Chinese demand for sand. Finally we review alternative options for sand mining, in order to relieve the pressure from the Poyang Lake ecosystem.     

Modelling bark beetle disturbances in a large scale forest scenario model to assess climate change impacts and evaluate adaptive management strategies

To study potential consequences of climate-induced changes in the biotic disturbance regime at regional to national scale we integrated a model of Ips typographus (L. Scol. Col.) damages into the large-scale forest scenario model EFISCEN. A two-stage multivariate statistical meta-model was used to upscale stand level damages by bark beetles as simulated in the hybrid forest patch model PICUS v1.41. Comparing EFISCEN simulations including the new bark beetle disturbance module against a 15-year damage time series for Austria showed good agreement at province level (R2 between 0.496 and 0.802). A scenario analysis of climate change impacts on bark beetle-induced damages in Austria’s Norway spruce [Picea abies (L.) Karst.] forests resulted in a strong increase in damages (from 1.33 Mm3 a⁻¹, period 1990–2004, to 4.46 Mm3 a⁻¹, period 2095–2099). Studying two adaptive management strategies (species change) revealed a considerable time-lag between the start of adaptation measures and a decrease in simulated damages by bark beetles.     

Soil management practices for sustainable agro-ecosystems

A doubling of the global food demand projected for the next 50 years poses a huge challenge for the sustainability of both food production and global and local environments. Today’s agricultural technologies may be increasing productivity to meet world food demand, but they may also be threatening agricultural ecosystems. For the global environment, agricultural systems provide both sources and sinks of greenhouse gases (GHGs), which include carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). This paper addresses the importance of soil organic carbon (SOC) for agro-ecosystems and GHG uptake and emission in agriculture, especially SOC changes associated with soil management. Soil management strategies have great potential to contribute to carbon sequestration, since the carbon sink capacity of the world’s agricultural and degraded soil is 50–66% of the historic carbon loss of 42–72 Pg (1 Pg=10¹⁵ g), although the actual carbon storage in cultivated soil may be smaller if climate changes lead to increasing mineralization. The importance of SOC in agricultural soil is, however, not controversial, as SOC helps to sustain soil fertility and conserve soil and water quality, and organic carbon compounds play a variety of roles in the nutrient, water, and biological cycles. No-tillage practices, cover crop management, and manure application are recommended to enhance SOC storage and to contribute to sustainable food production, which also improves soil quality. SOC sequestration could be increased at the expense of increasing the amount of non-CO₂ GHG emissions; however, soil testing, synchronized fertilization techniques, and optimum water control for flooding paddy fields, among other things, can reduce these emissions. Since increasing SOC may also be able to mitigate some local environmental problems, it will be necessary to have integrated soil management practices that are compatible with increasing SOM management and controlling soil residual nutrients. Cover crops would be a critical tool for sustainable soil management because they can scavenge soil residual nitrogen and their ecological functions can be utilized to establish an optimal nitrogen cycle. In addition to developing soil management strategies for sustainable agro-ecosystems, some political and social approaches will be needed, based on a common understanding that soil and agro-ecosystems are essential for a sustainable society.     

Effect of temperature on blood parameters of the salamander <Emphasis Type="Italic">Batrachupems tibetanus</Emphasis> (Schmidt, 1925) (Amphibia: Hynobiidae)

To better understand how Batrachupems tibetanus responds to different temperature regimes in the blood parameters and to estimate the change in plasma cortisol level in this species exposed to different temperatures, the animals were stochastically divided into three groups and exposed respectively to 4.6°C, 14.6°C and 19.6°C for 12 days. The concentrations of glucose, total protein, albumin, triacylglycerol, Ca²⁺, K⁺, Na⁺, Cl⁻, and plasma cortisol level were measured respectively. There was no significant difference between the plasma cortisol level of the control group and the experiment groups. Glucose level at 4.6°C and 19.6°C was significantly lower than glucose level at 14.6°C. The plasma triacylglycerol level was significantly influenced by acclimation temperature. The concentration of total protein, albumin, globulin and the ratio between albumin and globulin were not significantly influenced by temperature when compared with control group. There was no significant change in concentration of Ca²⁺ at different temperatures. The concentration of K⁺ was significantly influenced by temperature. Plasma K⁺ level significantly increased at 19.6°C. The plasma Na⁺ level and Cl⁻ were significantly influenced by temperature. Na⁺: Cl⁻ ratio was significantly influenced by temperature. Therefore, glucose, triacylglycerol, Na⁺ and Cl⁻ levels could be considered as indicators of thermal stress in B. tibetanus; plasma cortisol, albumin, globulin levels, and albumin/globulin ratio are not influenced by temperature.     

Climate and human impact on lowland lake sedimentation in Central Coastal California: the record from c. 650 ad to the present

The limnological record of human impact on catchment land cover and on lake sedimentation during the historical period has been established for Pinto Lake in Central Coastal California. In addition, the sedimentary record of the ‘pre-impact’ condition preserves evidence of a climatic control on the nature of lake sedimentation. Chronological marker horizons have been determined using pollen data in combination with the documented land-use history and introductions of exotic species. Further chronological data have been determined using ¹⁴C and ¹³⁷Cs. The impact of Mexican and Euro-American immigrants and their ‘imported’ land-use practices is clearly reflected in an order of magnitude increase in the rate of lake sedimentation to c. 9 kg m⁻² year⁻¹ (c. 2 cm year⁻¹) between 1770 and 1850. Here, the occurrence of exotic plant species indicates disturbance as early as c. 1769–1797, whilst redwood deforestation between 1844 and 1860 represents the most significant human impact. Changes in the nature of sedimentation prior to this reveal a high degree of sensitivity to changes in precipitation where subtle decreases in lake level and the supply of runoff-derived mineral matter have resulted in two periods of organic lake sedimentation c. 650–900 and 1275–1750. Set against this background condition of high sensitivity, the dramatic impacts of Euro-American settlement are unsurprising. An erratum to this article can be found at     

Human impacts on methane emission from mangrove ecosystems in India

This study deals with the emission of methane in relation to changing environmental conditions and human impact, in three mangrove ecosystems of south India. Time-varying fluxes of methane adopting the close chamber technique were used to estimate CH₄ emission from an unpolluted site (Pichavaram mangroves) and two polluted sites viz. (1) Ennore Creek mangroves (affected by fertilizer effluents and crude oil discharges) and (2) Adyar estuary mangroves (affected by the discharges of organic and industrial wastes), covering monthly and seasonal variations. The results indicate annual average CH₄ emissions of 7.4, 5.02 and 15.4 mg m⁻² h⁻¹ from the sediment–water interface of the Pichavaram, Ennore Creek and Adyar estuary respectively. Emission characteristics obtained at Pichavaram mangroves represent a natural variability with changing physico-chemical factors, whereas the emission characteristics at Ennore Creek and Adyar estuary mangroves show anthropogenic influence. Several environmental factors such as oxygen availability, organic matter, soil physical and chemical properties, in addition to human-mediated interventions have been identified as influencing emission rates in the mangrove ecosystems. Preliminary CH₄ emission estimates for the mangrove ecosystems along the Indian sub- continent and the tropical and subtropical coastline of the world by linear extrapolation based on surface area range from 0.05 to 0.37 and 2.8 to 19.25 Tg CH₄ year⁻¹ respectively. Our results also highlight the impact of human activities on future emission of methane from the mangrove ecosystems. Received: 3 March 1999 / Accepted: 14 September 1999     

Developing sinks for CO<Subscript>2</Subscript> through forestation of temperate coastal barriers: an environmental business

Since the 1940s, some sectors of the sand dune barriers of Buenos Aires Province have been forested to fix the sand in the neighborhoods of resort villages. Man took advantage of the maritime climate and the shallow groundwater to introduce pine forests. Today, these forests reach more than 20 m in height and have developed soils of more than 0.05 m in thickness on former arid sands. Field data were referred to Landsat (TM) composite and Normalized Difference of Vegetation Index, NDVI, images to calculate forest density and covered area. Considering published tables of wood density for each species, the amount of total carbon storage was estimated on 318 t C ha^-1 (Mg=10⁶ g) in biomass and 86 t C ha^-1 in soils. The three areas analyzed at Miramar, Necochea and Claromecó have captured 658,868 t of carbon in the last 50 years. It is estimated that 150,000,000 t C could be sequestered within temperate dune barriers of Argentina, Uruguay and Brazil. Besides this ecological point of view, there is an important socio-economic factor that cannot be excluded.Presented at and revised subsequent to the 4th LOICZ Open Science Meeting, Bahía Blanca, Argentina. October 1999.     

Fertility status and management implications of wetland soils for sustainable crop production in Akwa Ibom State, Nigeria

Fertility status of soils of three wetland types in Akwa Ibom State, Nigeria, was investigated. The wetland types are Inland Valley (IV), Flood Plain (FP) and Mangrove (MG). The soils have silt-clay ratios above 0.15 and 0.25 indicating that they are of young parent materials with low degree of weathering and possible weatherable minerals for plant nutrition. The pH of the soils was near neutral (>6.4) when wet but extremely acid (>3.5) when dried indicating that the soils are potential acid sulphate soils. Organic matter content was high with mean values of 12.59, 6.03 and 3.20% for IV, FP and MG soils, respectively. Total N (nitrogen) was low except in IV soils where the value was above the 0.30% critical level. The C:N ratios were narrow with mean of 20.90, 12.17 and 12.12 for IV, FP and MG soils, respectively. The contents of basic cations [Calcium (Ca), Magnesium (Mg), Potasium (K) and Sodium (Na)] were low while acidic cations [Aluminium (Al) and Hydrogen (H)] were high. The Ca:Mg ratios were below the optimum range of 3:1 to 4:1 required for most crops. The Mg:K ratios were above 1.2, below which yields of crops like corn and soybean may be reduced. Effective cation exchange capacity (ECEC) was below the 20 cmol/kg. Percent base saturation was low (<38) indicating that the soils are potentially less fertile. Exchangeable Al and percent Al saturation were high, above 60% in IV and FP soils. Electrical conductivity was above the critical value of 2 dsm⁻¹ while exchangeable sodium percentage was less than 15. Available Phosphorus (P) and low, <10 ppm and free Fe₂O₃/clay ratios were <0.15. Positive correlation existed between silt and ECEC, implying that silt contributed to nutrient status of the soils. Generally, fertility status of the soil is low and would require maintenance of adequate organic matter, application of lime and organic and inorganic fertilizers, drainage and irrigation if the land is to be used for intensive/sustainable crop production. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.