Site characteristics,growth and nutrition of natural red pine stands in newfoundland

Red pine (Pinus resinosa Ait.) is rare (< 15 000 mature trees) in Newfoundland and is known from only 22 locations in the central region. Red pine occupies 3 major site types in Newfoundland: 1) red pine on medium-textured sands (RP1), 2) red pine on coarse-textured glaciofluvial deposits (RP2), and 3) red pine on Folisols over bedrock (RP3). The succession of red pine site types after cutting is from red pine to Kalmia-black spruce (Picea mariana (Mill.) B.S.P.) for RP1, and to Cladonia-Kalmia-black spruce for types RP2 and RP3. Succession after fire is usually to the pre-fire type, but this depends on the severity of the fire.Although occupying a relatively poor site, red pine at 60–70 years reaches heights in excess of 18 m, dbh in excess of 40 cm, and individual tree volumes greater than 1 m³ were recorded in 75 stemanalyzed fire-killed trees. Black spruce on that same site produces less than one-third that volume in 60 years. Merchantable volume of 140–280 m³ ha^-1 were recorded i.e., Canada Land Inventory (CLI) forest capability class 5 and class 4 ratings. This raises the CLI rating two capability classes if red pine were occupying these poor quality sites over black spruce. In terms of nutrition, even the best growing red pine are nitrogen (N) deficient as shown by foliar analysis. All natural stands have foliar N concentrations below 1.3% which is the critically low level shown in the literature. Immediately after fire, foliar concentrations reach this level but are usually about 1% or less. Most other nutrients are low but are within the generally reported adequate levels in testing for P, K, Ca and Mg.Fire influences soil nutrient availability as pH increases in the RP1 type. Burning temperature also affects soil pH and the understory vegetation. The RP2 type loses more N in hotter burns on this site type and more N is tied up in these ortstein hardpan soils. The pattern of regeneration following wildfire is related to slope, density, age and species mixture of the stand as well as the thickness and composition of the duff layer.     

Interactions of Atmospheric Deposition with Coniferous Canopies in Estonia

Throughfall and open field bulk precipitation were measured at three coniferous sites during 1995–2002 in the framework of ICP Integrated Monitoring and at five coniferous sites during 1996–2002 in the framework of ICP Forests (Level II). The coniferous canopies acted as a sink for nitrate and ammonium and as a source for base cations: Ca²⁺, Mg²⁺ and K⁺. The estimated share of SO₄–S dry deposition from total deposition was 1.5–4 times higher for dormant period compared to growing period. During the study period average annual throughfall and bulk deposition of SO₄–S decreased significantly, 2.8 and 2.3 times, respectively. Throughfall enrichment with base cations increased in the order Mg < Na < Ca < K. Using Na as a tracer ion, average dry deposition and canopy leaching were calculated. Leaching was the dominant process for TF enrichment by potassium. Leaching of base cations occurred during growing as well as dormant period. The calculated internal flux of Ca²⁺ and Mg²⁺ varied in the range of 0.6–2.0 and 0.6–1.2 kg ha⁻¹ per year in spruce and pine stands, respectively. The internal circulation of K⁺ was significantly higher (8.9–10.9 kg ha⁻¹ per year) in spruce stands than in pine stands (2.7–4.4 kg ha⁻¹ per year).     

Effects of chronic ammonium sulfate treatment on the forest at the Bear Brook Watershed in Maine

At the Bear Brook Watershed in Maine (BBWM), the forest tree composition was characterized and the effects of the chronic ammonium sulfate ((NH₄)₂SO₄) treatment on basal area growth, foliar chemistry, and gas exchange were investigated on forest species. The BBWM is a paired watershed forest ecosystem study with one watershed, West Bear (WB), treated since 1989 with 26.6 kg N ha^???1 year^???1 and 30 kg S ha^???1 year^???1applied bimonthly as (NH₄)₂SO₄, while the other watershed, East Bear (EB), serves as a reference. Tree species richness, density, and mortality were found to be similar between watersheds. Basal area increment was estimated from red spruce and sugar maple, showing that, for the first 7 years of treatment, it was significantly higher for sugar maple growing in WB compared to EB, but no differences were observed for red spruce between watersheds. However, the initial higher sugar maple basal area growth in WB subsequently decreased after 8 years of treatment. Foliar chemical analysis performed in trees, saplings, and ground flora showed higher N concentrations in the treated WB compared to the reference EB. But, foliar cation concentrations, especially Ca and Mg, were significantly lower for most of the species growing in WB compared with those growing in EB. For sugar maple, foliar N was higher on WB, but there were no differences in foliar Ca and Mg concentrations between treated and reference watersheds. In addition, only sugar maple trees in the treated WB showed significantly higher photosynthetic rates compared to reference EB trees.     

Persistence and bioaccumulation of oxyfluorfen residues in onion

A field study was conducted to determine persistence and bioaccumulation of oxyflorfen residues in onion crop at two growth stages. Oxyfluorfen (23.5% EC) was sprayed at 250 and 500 g ai/ha on the crop (variety, N53). Mature onion and soil samples were collected at harvest. Green onion were collected at 55 days from each treated and control plot and analyzed for oxyfluorfen residues by a validated high-performance liquid chromatography method with an accepted recovery of 78–92% at the minimum detectable concentration of 0.003 μg g^???1. Analysis showed 0.015 and 0.005 μg g^???1 residues of oxyfluorfen at 250 g a.i. ha^???1 rate in green and mature onion samples, respectively; however, at 500 g a.i.ha^???1 rates, 0.025 and 0.011 μg g^???1 of oxyfluorfen residues were detected in green and mature onion samples, respectively. Soil samples collected at harvest showed 0.003 and 0.003 μg g^???1 of oxyfluorfen residues at the doses 250 and 500 g a.i. ha^???1, respectively. From the study, a pre-harvest interval of 118 days for onion crop after the herbicide application is suggested.     

Influence of the insecticides acetamiprid and carbofuran on arylamidase and myrosinase activities in the tropical black and red clay soils

The objective of this study was to determine the effects of two insecticides, namely, acetamiprid and carbofuran on the enzymatic activities of arylamidase (as glucose formed from sinigrin) and myrosinase (as β-naphthylamine formed from l-leucine β-naphthylamide) in the black and red clay soils collected from a fallow groundnut (Arachis hypogaea L.) fields in the Anantapur District, Andhra Pradesh, India. The study was realized within the framework of the laboratory experiments in which the acetamiprid and carbofuran were applied to the soils at different doses (1.0, 2.5, 5.0, 7.5, 10.0 kg ha^?1). Initially, the physicochechemical properties of the soil samples were analyzed. After 10 days of pesticide application, the soil samples were analyzed for the enzyme activities. Acetamiprid and carbofuran stimulated the arylamidase and myrosinase activities at lower concentrations after 10 days incubation. Striking stimulation in soil enzyme activities was noticed at 2.5 kg ha^?1, persists for 20 days in both the soils. Overall, higher concentrations (5.0–10.0 kg ha^?1) of acetamiprid and carbofuran were toxic or innocuous to the arylamidase and myrosinase activities. Nevertheless, the outcomes of the present study clearly indicate that the use of these insecticides (at field application rates) in the groundnut fields (black and red clay soils) stimulated the enzyme (arylamidase and myrosinase) activities.     

Dispersion and retrievability of water quality indicators during tidal cycles in coastal Salaya, Gulf of Kachchh (West coast of India)

Bacterial indicators in relation to tidal variations were studied at five locations for over 2 days covering three tidal cycles in the southwestern region of Gulf of Kachchh, India. Tidal flow here is predominantly in the east west direction and can transport particles up to 32 km. Tidal amplitude appears to play a prominent role in abundance, distribution, and dispersal of coliform bacteria examined during this study. Shallow depths, clayey sediments, strong currents, and higher tidal amplitudes appear to rise by an order of magnitude in total bacterial abundance up to 2.4×10⁴ ml^???1 due to their resuspension from the churned up sediments. Dispersal of allochthonous microflora far into coastal marine regions appears to be governed by the strong tidal amplitude in this region.     

Estimates of soil erosion using cesium-137 tracer models

The soil erosion was studied by ¹³⁷Cs technique in Yatagan basin in Western Turkey, where there exist intensive agricultural activities. This region is subject to serious soil loss problems and yet there is not any erosion data towards soil management and control guidelines. During the soil survey studies, the soil profiles were examined carefully to select the reference points. The soil samples were collected from the slope facets in three different study areas (Kırtas, Peynirli and Kayısalan Hills). Three different models were applied for erosion rate calculations in undisturbed and cultivated sites. The profile distribution model (PDM) was used for undisturbed soils, while proportional model (PM) and simplified mass balance model (SMBM) were used for cultivated soils. The mean annual erosion rates found using PDM in undisturbed soils were 15 t ha⁻¹ year⁻¹ at the Peynirli Hill and 27 t ha⁻¹ year⁻¹ at the Kırtas Hill. With the PM and SMBM in cultivated soils at Kayışalan, the mean annual erosion rates were obtained to be 65 and 116 t ha⁻¹ year⁻¹, respectively. The results of ¹³⁷Cs technique were compared with the results of the Universal Soil Loss Equation (USLE).     

Three-year monitoring results of nitrate and ammonium wet deposition in Thailand

Wet deposition is one of the important sources of nitrogen input into the ecosystem. It also contributes to rain acidity in some environments. In this study we reported the annual as well as seasonal trends of nitrogen wet deposition at three locations in Thailand: Bangkok, Chiang Mai and Nan. Comparison of nitrogen wet deposition between in rural and in the urban areas was also made. Daily rainfall was measured and monthly rainwater was collected for nitrogen analysis during 1999–2002. The average NO₃ ^– concentration in rainwater collected from the rural sites (60 km from urban area) was around 0.2–0.3 mg L^–1, while that from the urban areas of Chiang Mai and Nan cities it was 0.4–0.5 mg L^–1. NH₄ ⁺ concentration in rainwater showed the similar ranges to that of NO₃ ^– , except at Nan where concentration was not significantly different between the urban and rural sites. On the other hand, the average concentrations of NO₃ ^– were higher at Bangkok site than other sites, while concentration of NH₄ ⁺ was almost the same between Chiang Mai and Bangkok. Wet deposition of NO₃ ^– at the rural sites of Chiang Mai and Nan ranged from 2.1 to 3.2 kg N ha^–1 yr^–1, while at the urban sites this ranged from about 6 kg N ha^–1 yr^–1 in Chiang Mai and Nan Cities to 8.6 kg N ha^–1 yr^–1 in Bangkok. Wet deposition of NH₄ ⁺ at the rural sites of Chiang Mai and Nan was about 2.4 to 3.6 kg N ha^–1 yr^–1 and at the urban sites of Chiang Mai, Nan and Bangkok this was 7.7, 4.9 and 8.1 kg N ha^–1 yr^–1, respectively. Thus, it was concluded that wet deposition of both nitrogen species was significantly higher at the urban sites than at the rural sites.     

RETRACTED ARTICLE: Biomonitoring fallout <Superscript>137</Superscript>Cs in resident and migratory fishes collected along the southern coast of India and assessment of dose

The globally distributed fallout radionuclide ¹³⁷Cs was monitored in 25 resident and 22 migratory fish species collected from some regions of west and east coast of southern India to establish a baseline data. The samples were collected during June 2008 to June 2009. Higher level of ¹³⁷Cs was noted in planktivorous fishes and lower level in herbivores. A significant variation in ¹³⁷Cs was observed between fishes with different feeding habits and different migratory pattern. Oceanodromic migratory fishes displayed higher cesium levels than other migratory types. Similarly, migratory fishes displayed higher ¹³⁷Cs concentration compared to resident fishes. The overall range of ¹³⁷Cs varied from 0.06 to 0.3 Bq/kg in fishes. The biological concentration varied from 55 to 250. The average external dose rate to fishes was calculated to be 2.7 × 10⁻⁷ μGy/h, while the internal dose rate varied from 8.50 × 10⁻⁶ to 5.27 × 10⁻⁵ μGy/h. The hazard quotient for fishes was found to be less than 1. The average intake of ¹³⁷Cs via fishes to the public was calculated to be 3.5 Bq/year and subsequently the committed effective dose was 0.05 μSv/year. The data obtained were less than global average and comparable to those of many regions.     

Sulphate, Nitrogen and Base Cation Budgets at 21 Forested Catchments in Canada, the United States and Europe

To assess the concern over declining base cation levels in forest soils caused by acid deposition, input-output budgets (1990s average) for sulphate (SO₄), inorganic nitrogen (NO₃-N; NH₄-N), calcium (Ca), magnesium (Mg) and potassium (K) were synthesised for 21 forested catchments from 17 regions in Canada, the United States and Europe. Trend analysis was conducted on monthly ion concentrations in deposition and runoff when more than 9 years of data were available (14 regions, 17 sites). Annual average SO₄ deposition during the 1990s ranged between 7.3 and 28.4 kg ha⁻¹ per year, and inorganic nitrogen (N) deposition was between 2.8 and 13.8 kg ha⁻¹ per year, of which 41–67% was nitrate (NO₃-N). Over the period of record, SO₄ concentration in deposition decreased in 13/14 (13 out of 14 total) regions and SO₄ in runoff decreased at 14/17 catchments. In contrast, NO₃-N concentrations in deposition decreased in only 1/14 regions, while NH₄-N concentration patterns varied; increasing at 3/14 regions and decreasing at 2/14 regions. Nitrate concentrations in runoff decreased at 4/17 catchments and increased at only 1 site, whereas runoff levels of NH₄-N increased at 5/17 catchments. Decreasing trends in deposition were also recorded for Ca, Mg, and K at many of the catchments and on an equivalent basis, accounted for up to 131% (median 22%) of the decrease in acid anion deposition. Base cation concentrations in streams generally declined over time, with significant decreases in Ca, Mg and K occurring at 8, 9 and 7 of 17 sites respectively, which accounted for up to 133% (median 48%) of the decrease in acid anion concentration. Sulphate export exceeded input at 18/21 catchments, likely due to dry deposition and/or internal sources. The majority of N in deposition (31–100%; median 94%) was retained in the catchments, although there was a tendency for greater NO₃-N leaching at sites receiving higher (<7 kg ha^-1 per year) bulk inorganic N deposition. Mass balance calculations show that export of Ca and Mg in runoff exceeds input at all 21 catchments, but K export only exceeds input at 16/21 sites. Estimates of base cation weathering were available for 18 sites. When included in the mass balance calculation, Ca, Mg and K exports exceeded inputs at 14, 10 and 2 sites respectively. Annual Ca and Mg losses represent appreciable proportions of the current exchangeable soil Ca and Mg pools, although losses at some of the sites likely occur from weathering reactions beneath the rooting zone and there is considerable uncertainty associated with mineral weathering estimates. Critical loads for sulphur (S) and N, using a critical base cation to aluminium ratio of 10 in soil solution, are currently exceeded at 7 of the 18 sites with base cation weathering estimates. Despite reductions in SO₄ and H⁺ deposition, mass balance estimates indicate that acid deposition continues to acidify soils in many regions with losses of Ca and Mg of primary concern. The U.S. Government's right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright.     

Spatial variability of the shallow groundwater level and its chemistry characteristics in the low plain around the Bohai Sea,North China

To characterize the spatial distribution of groundwater level (GWL) and its chemistry characteristics in the low plain around the Bohai Sea, shallow groundwater depth of 130 wells were determined. Water soluble ions composition, total dissolved solid (TDS), electric conductivity (EC), total hardness (TH), total alkalinity (TA), and total salt content (TS) of 128 representative groundwater samples were also measured. Classical statistics, geostatistical method combined with GIS technique were then used to analyze the spatial variability and distribution of GWL and groundwater chemical properties. Results show that GWL, TDS, EC, TH, TA, and TS all presented a lognormal distribution and could be fitted by different semivariogram models (spherical, exponential, and Gaussian). Spatial structure of GWL, TDS, EC, TH, TA, and TS changed obviously. GWL decreased from west inland plain to the east coastal plain, however, TDS, EC, and TS increased from west to east, TH and TA were higher in the middle and coastal plain area. Groundwater chemical type in the coastal plain was SO₄²⁻·Cl⁻—Na⁺ while chemical types in the inland plain were SO₄²⁻·Cl⁻—Ca²⁺·Mg²⁺ and HCO₃⁻—Ca²⁺·Mg²⁺.     

The use of lichen growth abnormalities as an early warning indicator of forest dieback

Combinations of pollutants including acidic fog and ozone occur at high levels at a number of sites in eastern North America and Europe. Mountainous regions such as the Laurentians (Quebec), Appalachians (N.Y.) and the Green Mountains (Vermont) are especially vulnerable, with both conifers and hardwoods being affected. Ongoing measurements of atmospheric chemistry (e.g. The Chemistry of High Elevation Fog-CHEF project of the Canadian Atmospheric Environment Service) reveal that extreme cloudwater events of less than pH 3.0 and ozone episodes in excess of 100 ppb are common occurrences. The purpose of this study was to gather information about the response of epiphytic lichens to deteriorating air quality at selected locations for which atmospheric chemical data are readily available. A multidisciplinary approach is being used to analyse the lichens.Morphological and cellular aberrations previously documented by the authors to occur in terricolous lichens exposed to simulated acidic rain events will be evaluated for their usefulness are early warning indicators of forest decline. In addition, tissue chemistry of species such as Hypogymnia physodes will be correlated with parameters such as altitude and decline index and compared with published elemental values for lichens from similarly polluted sites in Europe and Scandinavia.     

Assessment of private economic benefits and positive environmental externalities of tea plantation in China

Tea plantations are rapidly expanding in China and other countries in the tropical and subtropical zones, driven by relatively high private economic benefit. However, the impact of tea plantations on the regional environment, including ecosystem services and disservices are unclear. In this study, we developed an assessment framework for determining the private economic benefits and environmental externalities (the algebraic sum of the regulating services and disservices) of tea plantations in China. Our results showed that tea plantations provided private economic benefits of 5,652 yuan ha^?1 year^?1 (7.6 yuan?=?1 USD in 2007) for tea farmers, plus positive environmental externalities of 6,054 yuan ha^?1 year^?1 for the society. The environmental externalities were calculated as the sum of the value of four regulating services, including carbon sequestration (392 yuan ha^?1 year^?1); soil retention (72 yuan ha^?1 year^?1); soil fertility protection (3,189 yuan ha^?1 year^?1) and water conservation (2,685 yuan ha^?1 year^?1), and three disservices, including CO₂ emission (?39 yuan ha^?1 year^?1), N₂O emission (?137 yuan ha^?1 year^?1) and nonpoint source pollution (?108 yuan ha^?1 year^?1). Before the private optimal level, the positive environmental externalities can be maintained by private economic benefits; if a social optimal level is required, subsidies from government are necessary.     

Factors affecting N and P losses from small catchments (Lithuania)

Most of the important factors causing differences in nutrient losses and their interaction were analysed in three small catchments that are located in partially different geographic and climatic conditions in Lithuania. The investigation revealed that climatic factors change the amount and pattern of water discharge over year (larger water discharge during winter in the catchment located closer to the sea), but nutrient leaching is more dependent on land use. Agricultural factors, such as larger cultivated area and excessive fertilisation in one catchment cause larger nitrogen losses (15 kg N ha^–1 year^–1). Large area of non-intensively used grassland leads to very small nitrogen losses (5.7 kg N ha^–1 year^–1) in another catchment. However, larger water discharge combined with loamy sandy soils leads to comparatively high nitrogen losses (12 kg N ha^–1 year^–1). The highest P losses (0.318 kg P ha^–1 year^–1) occurred in the catchment with hilly relief and clay soil texture. In summary, extensive agriculture in the post-Soviet countries has reduced the importance of agricultural activity for the extent of nutrient losses and agricultural factors (cultivation, fertilisation and livestock density) are responsible for the losses only in the region of sufficient agricultural activity (N input – 71.5 kg N ha^–1, livestock density – 0.87 LU ha^–1).     

Separate estimation of N export into baseline N leakage without disturbance and N loss due to insect defoliation in a pine forest watershed in central Japan

Pine wilt disease (PWD) is caused by a non-native pest that has spread extensively throughout Japan. Previous research has indicated that most infected trees have died and the litter deposited has resulted in changes to stream-water chemistry, particularly increased nitrate (NO ₃ ^? ) concentrations. In this study, we divided stream nitrogen (N) export into N loss due to PWD and baseline N leakage without disturbance based on long-term monitoring. The annual N export was 110.0 mol N ha^?1 year^?1 in 1990 and 749.8 mol N ha^?1 year^?1 in 1997, and had decreased to 37.0 mol N ha^?1 year^?1 in 2005. N export under PWD influence was estimated to be 3697 mol N ha^?1, and N loss due to PWD was 2810 mol N ha^?1. N loss due to PWD was three times larger than baseline N leakage for the disturbed period. These changes in plant–herbivore relationships could affect N status in a forest ecosystem. So-called “semi-natural” disturbances related to non-native species invasion and increases of atmospheric N deposition caused by human activity will increase. Long-term monitoring studies of various aspects are necessary to offer insight into this ecosystem.     

Deposition in boreal forests in relation to type, size, number and placement of collectors

Open precipitation and throughfall was collected at a Norway spruce stand in Finland using funnel-type collectors and at a black spruce stand in Canada using trough-type collectors. The presence or absence of a rim on the funnel, funnel diameter (9, 14 and 20 cm) and length of sampling period (1, 2 and 4 weeks) on monthly values were evaluated at the Norway spruce stand, and the number of collectors required for defined levels of accuracy and precision of throughfall loads to be reached and the influence of the spatial arrangement of collectors on solute concentrations was studied at both stands. The presence of a rim had no significant effect on open precipitation and throughfall amounts, but did on throughfall DOC, Ca²⁺, Mg²⁺, K⁺, Na⁺ and Cl⁻ ion loads. Deposition loads increased with decreasing funnel diameter; for open precipitation, this was due to increased catch efficiency while for throughfall the increase was attributed to canopy interaction and leaching of litter trapped in the collectors. Calculated monthly H⁺ loads decreased and those for all other constituents increased with collection period length. Using 15 collectors at the Norway spruce stand would allow throughfall loads to be determined to within 20% of the true mean weekly value with a confidence level of 95% for most solute, but not for NH₄ ⁺–N, NO₃ ⁻–N, Mg²⁺ and SO₄ ²⁻-S. Using 15 trough collectors, the same confidence level at the more heterogeneous black spruce stand would only be achieved for H⁺, Cl⁻, DOC and SO₄ ²⁻-S loads. In both stands, using either random or systematic placements of throughfall collectors gave similar results.     

Computation of groundwater resources and recharge in Chithar River Basin, South India

Groundwater recharge and available groundwater resources in Chithar River basin, Tamil Nadu, India spread over an area of 1,722 km² have been estimated by considering various hydrological, geological, and hydrogeological parameters, such as rainfall infiltration, drainage, geomorphic units, land use, rock types, depth of weathered and fractured zones, nature of soil, water level fluctuation, saturated thickness of aquifer, and groundwater abstraction. The digital ground elevation models indicate that the regional slope of the basin is towards east. The Proterozoic (Post-Archaean) basement of the study area consists of quartzite, calc-granulite, crystalline limestone, charnockite, and biotite gneiss with or without garnet. Three major soil types were identified namely, black cotton, deep red, and red sandy soils. The rainfall intensity gradually decreases from west to east. Groundwater occurs under water table conditions in the weathered zone and fluctuates between 0 and 25 m. The water table gains maximum during January after northeast monsoon and attains low during October. Groundwater abstraction for domestic/stock and irrigational needs in Chithar River basin has been estimated as 148.84 MCM (million m³). Groundwater recharge due to monsoon rainfall infiltration has been estimated as 170.05 MCM based on the water level rise during monsoon period. It is also estimated as 173.9 MCM using rainfall infiltration factor. An amount of 53.8 MCM of water is contributed to groundwater from surface water bodies. Recharge of groundwater due to return flow from irrigation has been computed as 147.6 MCM. The static groundwater reserve in Chithar River basin is estimated as 466.66 MCM and the dynamic reserve is about 187.7 MCM. In the present scenario, the aquifer is under safe condition for extraction of groundwater for domestic and irrigation purposes. If the existing water bodies are maintained properly, the extraction rate can be increased in future about 10 % to 15 %.     

Carbon density and accumulation in agroecosystem of Indo-Gangetic Plains and Vindhyan highlands,India

In agroecosystems, the annual carbon (C) inputs to soil are one of the most promising greenhouse gas mitigation options. Net primary productivity (NPP) provides the inputs of C in ecosystems that can potentially be sequestered in soil organic matter. In this study, we estimates the C density and accumulation rate in rice–wheat agroecosystem at four sites of Indo-Gangetic Plains and Vindhyan highlands through amalgamation of ground truth (GT) and remote sensing (RS) approach. In addition to this, we validated field-measured aboveground net production (ANP) with remotely sensed SPOT-Vegetation data. ANP of the sites ranged from 6.8 to 11.1 and 3.3 to 8.8 t-C ha^?1 year^?1 for GT and RS, respectively. Both estimates (GT and RS) were linearly and significantly related with each other (y?=?1.33x???5.82, R ²?=?0.93, P?=?0.04; where x?=?GT ANP and y?=?RS ANP). For the whole region, total NPP (rice?+?wheat) was ranged from 7.9 to 12.5 t-C ha^?1 year^?1. The C accumulation potential of the present agroecosystems was 9.1 and 1.9 t-C ha^?1 year^?1 in the form of ANP and belowground NPP (BNP), respectively. The aboveground C stock of agroecosystem allocated in foliage (7.8 %), stem (57.6 %), and grain (35.1 %). Survey about the fate of post-harvested materials indicated that aboveground portion of the crop is almost used completely within the year for different purposes including human consumption and cattle feeding. Therefore, only BNP and litter contribute to long-term C sequestration. Since agroecosystem has enormous potential to sequester C, better management of aboveground portion NPP of the crop may enhance C sequestration potential of agroecosystem.     

Vegetation ecology and carbon sequestration potential of shrubs in tropics of Chhattisgarh,India

Tropical forests are well known to have great species diversity and contribute substantial share in terrestrial carbon (C) stocks worldwide. Shrubs are long-neglected life form in the forest ecosystem, playing many roles in the forest and human life. Shrub has great impact on vegetation attributes which in turn modify the C storage and capture. In the present investigation, an attempt has been made to explore the dynamics of shrub species in four fire regimes, viz. high, medium, low, and no fire zones of Bhoramdeo Wildlife Sanctuary of Kawardha forest division (Chhattisgarh), India. The variations in structure, diversity, biomass, productivity, and C sequestration potential in all the sites were quantified. The density and basal area of shrub varied from 1250 to 3750 individuals ha^?1 and 2.79 to 4.92 m² ha^?1, respectively. The diversity indices showed that the value of Shannon index was highest in medium fire zone (3.77) followed by high, low, and no fire zones as 3.25, 3.12, and 2.32, respectively. The value of Simpson’s index or concentration of dominance (Cd) ranged from 0.08 to 0.20, species richness from 0.56 to 1.58, equitability from 1.41 to 1.44, and beta diversity from 1.50 to 4.20, respectively. The total biomass and C storage ranged from 6.82 to 15.71 and from 2.93 to 6.76 t ha^?1, respectively. The shrub density, importance value index (IVI), and abundance to frequency ratio (A/F) significantly correlated between high fire and medium fire zone. The basal area was found to be significantly positively correlated between high fire and medium fire, and low and no fire zones, respectively. Two-way cluster analysis reflected various patterns of clustering due to influence of the forest fire which showed that some species have distant clustering while some have smaller cluster. Principal component analysis (PCA) reflects variable scenario with respect to shrub layer. Ventilago calyculata and Zizyphus rotundifolia showed higher correlation between themselves in terms of basal area (BA). The total shrub production was 1.59–3.53 t ha^?1 year^?1 while the C sequestration potential of 0.71–1.57 t ha^?1 year^?1 under different fire regimes. Shrub community in the medium fire zone reflected higher productivity and higher C sequestration in comparison to other fire zone. Among the different plant parts, the biomass accumulation ratio was highest in the root of shrub community among various fire regimes. Screening of species for restoration and different land-use pattern on the basis of biomass accumulation and carbon sequestering potential would be an effective strategy for decision-making in sustainable forest management.     

Emission of nitrous oxide from rice-wheat systems of Indo-Gangetic plains of India

Nitrous oxide (N₂O) accounts for 5%of the total enhanced greenhouse effect and responsiblefor the destruction of the stratospheric ozone. The rice-wheat cropping system occupying 26 million ha ofproductive land in Asia could be a major source ofN₂O as most of the fertilizer N in this region isconsumed by this system. Emission of N₂O asinfluenced by application of urea, urea plus farm yardmanure (FYM), and urea plus dicyandiamide (DCD), anitrification inhibitor, was studied in rice-wheatsystems of Indo-Gangetic plains of India. Total emissionof N₂O-N from the rice-wheat systems varied between654 g ha^-1 in unfertilized plots and 1570 g ha^-1 in urea fertilized plots. Application of FYM and DCDreduced emission of N₂O-N in rice. The magnitude ofreduction was higher with DCD. In wheat also N₂O-Nemission was reduced by DCD. FYM applied in rice had noresidual effect on N₂O-N emission in wheat. In riceintermittent wetting and drying condition of soilresulted in higher N₂O-N emission than that ofsaturated soil condition. Treatments with 5 irrigationsgave higher emissions in wheat than those with 3irrigations. In rice-wheat system, typical of a farmer'sfield in Indo-Gangetic plains, where 240 kg N isgenerally applied through urea, N₂O-N emission is1570 g ha^-1 (0.38% of applied N) and application ofFYM and DCD reduced it to 1415 and 1096 g ha^-1,respectively.