Effect of the number of meshes in the protective bag circumference on size selectivity of demersal trawl codends

This study investigated the effect of the number of meshes in the protective bag circumference on size selectivity of a demersal trawl codend. Circumferences of 50‐mesh (NMPB50) and 215‐mesh (NMPB215) protective bags rigged on the 44 mm diamond mesh codend were tested. Fishing experiments were carried out on the commercial trawler ‘Hapulo?lu’ between 20 and 27 August 2010, using a modified trawl net. Data were collected using the covered codend method and analyzed using the logistic equation with the maximum likelihood method. Mean selection curves were analyzed and compared using the between‐haul variations model. The mean L₅₀ values of NMPB50 and NMPB215 were, respectively, 16.4 ± 0.1 mm and 16.5 ± 0.1 mm carapace length for deep‐water rose shrimp, 10.7 ± 0.1 cm and 12.2 ± 0.1 cm total length for hake, and 16.0 ± 0.1 cm and 16.7 ± 0.1 cm total length for horse mackerel. In conclusion, increasing the number of meshes around the protective bag resulted in a 14% and 4% increase in the L₅₀ for hake and mackerel, respectively; however, these differences were not statically significant (P > 0.05).     

Production, transportation and milling costs of sweet sorghum as a feedstock for centralized bioethanol production in the upper Midwest

Sweet sorghum has been identified as a possible ethanol feedstock because of its biomass yield and high concentration of readily fermentable sugars. It has found limited use, however, because of poor post-harvest storage characteristics and short harvest window in cooler climates. Previous research (Bennett, A.S., Anex, R.P., 2008. Farm-gate production costs of sweet sorghum as a bioethanol feedstock. Transactions of the ASABE 51(2), 603-613) indicates that fermentable carbohydrates (FC) can be produced at less expense from sweet sorghum than from corn grain. Previous research, however, did not include costs associated with off-farm transportation, storage, or capital costs associated with milling and energy recovery equipment that are required to provide FC suitable for biological conversion. This study includes these additional costs and reevaluates sweet sorghum as a biocommodity feedstock. A total of eight harvest-transport-processing options are modeled, including 4-row self-propelled and 2-row tractor-pulled forage harvesters, two different modes of in-field transport, fresh processing, on-farm ensilage and at-plant ensilage. Monte Carlo simulation and sensitivity analysis are used to account for system variability and compare scenarios. Transportation costs are found to be significant ranging from $33 to $71 Mg (-1) FC, with highest costs associated with at-plant ensilage scenarios. Economies of scale benefit larger milling equipment and boiler systems reducing FC costs by more than 50% when increasing annual plant capacity from 37.9 to 379 million liters. Ensiled storage of high moisture sweet sorghum in bunkers can lead to significant losses of FC (>20%) and result in systems with net FC costs well above those of corn-derived FC. Despite relatively high transport costs, seasonal, fresh processed sweet sorghum is found to produce FC at costs competitive with corn grain derived FC.     

Landscape correlates of forest plant invasions: A high‐resolution analysis across the eastern United States

Aim

Invasive species occurrence is often related to the anthropogenic context of a given area. Quantifying the effects of roads is of particular interest as roads are a major vector for invasion. Our objective was to further quantify the effects of roads on forest plant invasion through a macroscale, high‐resolution investigation to assist effective invasion control and mitigation.

Location

Eastern United States.

Methods

Using invasive plant data from 23,039 forest inventory plots in 13 ecological provinces, we employed logistic regression to relate the odds of invasion to distance from a road, with adjustments for broadscale differences attributable to ecological provinces, and local scale differences in productivity, forest fragmentation and land use.

Results

The overall proportion (P) of invaded plots was 0.58 (0.65 for plots within 50 m of a road), and the highest odds (P/1 ? P) of invasion were found in relatively more productive, fragmented forest in landscapes with more than 10% agriculture or developed land cover. Wald chi‐square statistics indicated the best predictor of the odds of invasion was ecological province, followed by land use, productivity, forest fragmentation and distance from a road. Depending on the province, the adjusted odds of invasion decreased by up to 23% (typically 4%–10%) per 100 m distance from a road. The adjusted probability of invasion approached zero in only three provinces, for the least productive, least fragmented forest that was at least 2,000 m from a road in landscapes with less than 10% agricultural or developed land cover.

Main conclusions

In the eastern United States, the existence of a nearby road is less important than the landscape context associated with the road. A purely road‐mediated effect has little practical meaning because anthropogenic activities and roads are pervasive and confounded.

     

Optimizing the bioindication of forest soil acidity,nitrogen and mineral nutrition using plant species

Soil moisture and nutritional characteristics are frequently assessed using plant species and community bioindication, e.g., the Ellenberg system of species indicator values. This method, based on complete inventories of plant species present in plots, is time-consuming, which could prevent its general use for forest or other natural land management. Our aim was to determine the impact of a reduction in the time spent to carry out a floristic inventory on the quality of soil characteristic assessment using plant bioindication. We compared the measurements of soil pH-H₂O (pH), organic carbon to total nitrogen ratio (C:N) and base saturation (BS) in the 0–5 cm soil layer of 470 plots with the same variables estimated from floristic inventories of increasing duration, using plant indicator values (IV) from the EcoPlant database. The performance of predictions was evaluated by the square of the linear correlation coefficient between measured and predicted values (R²) and the root mean square error (RMSE) of predictions.The number rather than the percentage of total plot species used for the estimations was determinant for the prediction of soil pH quality. Performance of bioindication of pH, BS and C:N reached the maximum R² using the first 20–25 species recorded per plot, corresponding to a 14-min-long floristic inventory in comparison to a mean of 28 min spent to carry out a complete floristic inventory. A precision of prediction of 80% of the maximal precision was obtained after 4–5 min (6–12 inventoried species) for the three studied variables. These results are independent of the nutritional capability of the soils and were similar at the national and local scales. In order to estimate soil nutritional resources by plant bioindication, it is feasible to significantly reduce the time spent on floristic inventories and, thus, their cost. This is especially useful when the goal is to map the soil quality for decision-making in forest management.     

A quantitative approach for understanding small-scale human mesenchymal stem cell culture – implications for large-scale bioprocess development

Human mesenchymal stem cell (hMSC) therapies have the potential to revolutionise the healthcare industry and replicate the success of the therapeutic protein industry; however, for this to be achieved there is a need to apply key bioprocessing engineering principles and adopt a quantitative approach for large-scale reproducible hMSC bioprocess development. Here we provide a quantitative analysis of the changes in concentration of glucose, lactate and ammonium with time during hMSC monolayer culture over 4 passages, under 100% and 20% dissolved oxgen (dO₂), where either a 100%, 50% or 0% growth medium exchange was performed after 72h in culture. Yield coefficients, specific growth rates (h^-1) and doubling times (h) were calculated for all cases. The 100% dO₂ flasks outperformed the 20% dO₂ flasks with respect to cumulative cell number, with the latter consuming more glucose and producing more lactate and ammonium. Furthermore, the 100% and 50% medium exchange conditions resulted in similar cumulative cell numbers, whilst the 0% conditions were significantly lower. Cell immunophenotype and multipotency were not affected by the experimental culture conditions. This study demonstrates the importance of determining optimal culture conditions for hMSC expansion and highlights a potential cost savings from only making a 50% medium exchange, which may prove significant for large-scale bioprocessing.     

Biochemical control of xylan biosynthesis - which end is up?

Xylans are major components of land plant secondary cell walls and are required for normal plant growth and development. Secondary walls also account for the bulk of lignocellulosic biomass, a potential feedstock for large-scale production of biofuels. Glucuronoxylan and arabinoxylan affect the conversion of lignocellulosic biomass to fermentable sugar, a crucial and expensive step in biofuel production. Thus, knowledge of xylan biosynthesis may provide tools to modify secondary cell wall structure and thereby improve the bioprocessing characteristics of biomass. Recent studies have shown that glucuronoxylan structure and biosynthesis are far more complex than previously appreciated and the number of glycosyltransferases implicated in this process continues to increase. New hypotheses regarding the mechanisms of glucuronoxylan biosynthesis challenge some widely held views.     

Forest biomass carbon sinks in East Asia,with special reference to the relative contributions of forest expansion and forest growth

Forests play an important role in regional and global carbon (C) cycles. With extensive afforestation and reforestation efforts over the last several decades, forests in East Asia have largely expanded, but the dynamics of their C stocks have not been fully assessed. We estimated biomass C stocks of the forests in all five East Asian countries (China, Japan, North Korea, South Korea, and Mongolia) between the 1970s and the 2000s, using the biomass expansion factor method and forest inventory data. Forest area and biomass C density in the whole region increased from 179.78 × 10⁶ ha and 38.6 Mg C ha^?1 in the 1970s to 196.65 × 10⁶ ha and 45.5 Mg C ha^?1 in the 2000s, respectively. The C stock increased from 6.9 Pg C to 8.9 Pg C, with an averaged sequestration rate of 66.9 Tg C yr^?1. Among the five countries, China and Japan were two major contributors to the total region's forest C sink, with respective contributions of 71.1% and 32.9%. In China, the areal expansion of forest land was a larger contributor to C sinks than increased biomass density for all forests (60.0% vs. 40.0%) and for planted forests (58.1% vs. 41.9%), while the latter contributed more than the former for natural forests (87.0% vs. 13.0%). In Japan, increased biomass density dominated the C sink for all (101.5%), planted (91.1%), and natural (123.8%) forests. Forests in South Korea also acted as a C sink, contributing 9.4% of the total region's sink because of increased forest growth (98.6%). Compared to these countries, the reduction in forest land in both North Korea and Mongolia caused a C loss at an average rate of 9.0 Tg C yr^?1, equal to 13.4% of the total region's C sink. Over the last four decades, the biomass C sequestration by East Asia's forests offset 5.8% of its contemporary fossil‐fuel CO₂ emissions.     

Economic comparison between conventional and disposables-based technology for the production of biopharmaceuticals

Time to market, cost effectiveness, and flexibility are key issues in today's biopharmaceutical market. Bioprocessing plants based on fully disposable, presterilized, and prevalidated components appear as an attractive alternative to conventional stainless steel plants, potentially allowing for shorter implementation times, smaller initial investments, and increased flexibility. To evaluate the economic case of such an alternative it was necessary to develop an appropriate costing model which allows an economic comparison between conventional and disposables-based engineering to be made. The production of an antibody fragment from an E. coli fermentation was used to provide a case study for both routes. The conventional bioprocessing option was costed through available models, which were then modified to account for the intrinsic differences observed in a disposables-based option. The outcome of the analysis indicates that the capital investment required for a disposables-based option is substantially reduced at less than 60% of that for a conventional option. The disposables-based running costs were evaluated as being 70% higher than those of the conventional equivalent. Despite this higher value, the net present value (NPV) of the disposables-based plant is positive and within 25% of that for the conventional plant. Sensitivity analysis performed on key variables indicated the robustness of the economic analysis presented. In particular a 9-month reduction in time to market arising from the adoption of a disposables-based approach, results in a NPV which is identical to that of the conventional option. Finally, the effect of any possible loss in yield resulting from the use of disposables was also examined. This had only a limited impact on the NPV: for example, a 50% lower yield in the disposable chromatography step results in a 10% reduction of the disposable NPV. The results provide the necessary framework for the economic comparison of disposables and conventional bioprocessing technologies.     

Soil carbon stocks and carbon sequestration rates in seminatural grassland in Aso region,Kumamoto, Southern Japan

Global soil carbon (C) stocks account for approximately three times that found in the atmosphere. In the Aso mountain region of Southern Japan, seminatural grasslands have been maintained by annual harvests and/or burning for more than 1000 years. Quantification of soil C stocks and C sequestration rates in Aso mountain ecosystem is needed to make well‐informed, land‐use decisions to maximize C sinks while minimizing C emissions. Soil cores were collected from six sites within 200 km² (767–937 m asl.) from the surface down to the k‐Ah layer established 7300 years ago by a volcanic eruption. The biological sources of the C stored in the Aso mountain ecosystem were investigated by combining C content at a number of sampling depths with age (using ¹⁴C dating) and δ¹³C isotopic fractionation. Quantification of plant phytoliths at several depths was used to make basic reconstructions of past vegetation and was linked with C‐sequestration rates. The mean total C stock of all six sites was 232 Mg C ha^?1 (28–417 Mg C ha^?1), which equates to a soil C sequestration rate of 32 kg C ha^?1 yr^?1 over 7300 years. Mean soil C sequestration rates over 34, 50 and 100 years were estimated by an equation regressing soil C sequestration rate against soil C accumulation interval, which was modeled to be 618, 483 and 332 kg C ha^?1 yr^?1, respectively. Such data allows for a deeper understanding in how much C could be sequestered in Miscanthus grasslands at different time scales. In Aso, tribe Andropogoneae (especially Miscanthus and Schizoachyrium genera) and tribe Paniceae contributed between 64% and 100% of soil C based on δ¹³C abundance. We conclude that the seminatural, C₄‐dominated grassland system serves as an important C sink, and worthy of future conservation.     

Optimal number of matings in two aphidophagous ladybirds

Abstract.  1. The present study was designed to identify the optimal number of matings required for maximum fecundity and egg viability in two aphidophagous ladybirds, Cheilomenes sexmaculata and Propylea dissecta .
2. For this purpose, ladybirds were subjected to different numbers of matings and the reproductive responses were recorded thereafter.
3. The Gompertz model was used to draw asymptotic graphs for fecundity and per cent egg viability in both ladybird species. Ninety-five per cent and 50% of maximum theoretical fecundity and per cent egg viability were predicted from the model.
4. Ninety-five per cent maximum theoretical fecundity was obtained after 13.25 and 12.95 matings in C. sexmaculata and P. dissecta , respectively; and 8.95 and 11.25 matings were required for 95% maximum theoretical per cent egg viability in C. sexmaculata and P. dissecta , respectively.
5. The results of these experiments clearly support the existence of an optimal number of matings in these two ladybird species leading to maximum adult fitness.     

不同利用方式下潮棕壤交换性钙镁的剖面分布

在水稻田、玉米地、撂荒地和人工林地4种土地利用方式下,对潮棕壤0～150 cm土层中土壤交换性钙(Ca)和交换性镁(Mg)的剖面分布及Ca/Mg的变化进行了比较研究.结果表明：不同利用方式下土壤交换性Ca含量及储量差异不明显;林地各土层的土壤交换性Mg含量均显著高于水稻田（P<0.05）;交换性Mg储量大小依次为林地、玉米地、撂荒地和水稻田（P<0.05）.不同利用方式交换性Ca/Mg随土层深度的增加而降低,40 cm以下土层水稻田Ca/Mg显著高于其他3种利用方式（P<0.05）.土壤生态系统中Mg的优先固持、土壤管理以及植物自身的特性如生物量的循环速率、生物量在地上部分和地下部分的分配、根系的分布等,对土壤剖面中交换性Ca和交换性Mg的构成以及土壤交换性Ca库和Mg库的重建等起到重要作用.     

Spatial and environmental determinants of vascular plant species richness distribution in the Iberian Peninsula and Balearic Islands

Using an exhaustive data compilation, Iberian vascular plant species richness in 50 times 50 UTM grid cells was regressed against 24 explanatory variables (spatial, geographical, topographical, geological, climatic, land use and environmental diversity variables) using Generalized Linear Models and partial regression analysis in order to ascertain the relative contribution of primary, heterogeneous and spatially structured variables. The species richness variation accounted for by these variables is reasonably high (65% of total deviance). Little less than half of this variation is accounted for spatially structured variables. A purely spatial component of variation is hardly significant. The most significant variables are those related to altitude, and particularly maximum altitude, whose cubic response reflects the occurrence of the maximum number of species at the highest altitudes. This result highlighted the importance of Iberian mountains as hotspots of diversity and the relevance of large and small scale historical factors in contemporary plant distribution patterns. Climatic or energy-related variables contributed little, whereas geological (calcareous and acid rocks) and, to a lesser extent, environmental heterogeneity variables (land use diversity and altitude range) seem to be more important.     

Manipulating fertilization: a management tactic against Frankliniella occidentalis on potted chrysanthemum

Fertilization during production of greenhouse chrysanthemum, Dendranthema grandiflora (Tzvelev), will influence Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) populations as well as plant productivity and postproduction longevity. It is essential to include fertilization effects in the development of crop management practices that reduce thrips populations and maintain plant marketability. In this study, we lowered fertilization to reduce thrips population abundance while maintaining plant productivity. We tested fertilization levels below and above the recommended level (375 p.p.m. N) for commercial production. We reduced mean rate of change in F. occidentalis abundance from 0.05 to 0.03 (day⁻¹) and mean number of thrips per plant by 44% by fertilizing with either 188 p.p.m. N (50% of the recommended level) or 568 p.p.m. N (150%) and higher. Fertilization influenced not only the rate of change in thrips abundance but also the production time (from transplanting to flower opening). Lowering fertilization to 50% of the recommended level lengthened mean production time from 84 to 88 days. Plant height, flower size, and flower number were not adversely affected when fertilization was reduced to 50% of the recommended level. Mean postproduction longevity was shortened from 26 to 24 days when plants were fertilized with 50% of the recommended level. Two important advantages of lowering fertilization to 50% of the recommended level were (1) a 44% reduction in mean F. occidentalis abundance and (2) a significant reduction in fertilizer input for the production system. Manipulation of fertilization can be a useful management tactic against F. occidentalis .     

Impacts of management practices on bioenergy feedstock yield and economic feasibility on Conservation Reserve Program grasslands

Perennial grass mixtures planted on Conservation Reserve Program (CRP) land are a potential source of dedicated bioenergy feedstock. Long‐term nitrogen (N) and harvest management are critical factors for maximizing biomass yield while maintaining the longevity of grass stands. A six‐year farm‐scale study was conducted to understand the impact of weather variability on biomass yield, determine optimal N fertilization and harvest timing management practices for sustainable biomass production, and estimate economic viability at six CRP sites in the United States. Precipitation during the growing season was a critical factor for annual biomass production across all regions, and annual biomass production was severely reduced when growing season precipitation was below 50% of average. The N rate of 112 kg ha^?1 produced the highest biomass yield at each location. Harvest timing resulting in the highest biomass yield was site‐specific and was a factor of predominant grass type, seasonal precipitation, and the number of harvests taken per year. The use of N fertilizer for yield enhancement unambiguously increased the cost of biomass regardless of the harvest timing for all six sites. The breakeven price of biomass at the farmgate ranged from $37 to $311 Mg^?1 depending on the rate of N application, timing of harvesting, and location when foregone opportunity costs were not considered. Breakeven prices ranged from $69 to $526 Mg^?1 when the loss of CRP land rental payments was included as an opportunity cost. Annual cost of the CRP to the federal government could be reduced by over 8% in the states included in this study; however, this would require the biomass price to be much higher than in the case where the landowner receives the CRP land rent. This field research demonstrated the importance of long‐term, farm‐scale research for accurate estimation of biomass feedstock production and economic viability from perennial grasslands.     

Land use of drained peatlands: Greenhouse gas fluxes,plant production,and economics

Drained peatlands are hotspots for greenhouse gas (GHG) emissions, which could be mitigated by rewetting and land use change. We performed an ecological/economic analysis of rewetting drained fertile peatlands in a hemiboreal climate using different land use strategies over 80 years. Vegetation, soil processes, and total GHG emissions were modeled using the CoupModel for four scenarios: (1) business as usual—Norway spruce with average soil water table of ?40 cm; (2) willow with groundwater at ?20 cm; (3) reed canary grass with groundwater at ?10 cm; and (4) a fully rewetted peatland. The predictions were based on previous model calibrations with several high‐resolution datasets consisting of water, heat, carbon, and nitrogen cycling. Spruce growth was calibrated by tree‐ring data that extended the time period covered. The GHG balance of four scenarios, including vegetation and soil, were 4.7, 7.1, 9.1, and 6.2 Mg CO₂eq ha^?1 year^?1, respectively. The total soil emissions (including litter and peat respiration CO₂ + N₂O + CH₄) were 33.1, 19.3, 15.3, and 11.0 Mg CO₂eq ha^?1 year^?1, respectively, of which the peat loss contributed 35%, 24%, and 7% of the soil emissions for the three drained scenarios, respectively. No peat was lost for the wet peatland. It was also found that draining increases vegetation growth, but not as drastically as peat respiration does. The cost–benefit analysis (CBA) is sensitive to time frame, discount rate, and carbon price. Our results indicate that the net benefit was greater with a somewhat higher soil water table and when the peatland was vegetated with willow and reed canary grass (Scenarios 2 and 3). We conclude that saving peat and avoiding methane release using fairly wet conditions can significantly reduce GHG emissions, and that this strategy should be considered for land use planning and policy‐making.     

SPRING HAUL-OUT BEHAVIOR OF RINGED SEALS (PUSA HISPIDA) IN KONGSFJORDEN, SVALBARD

Haul‐out behavior of ringed seals (Pusa hispida) was investigated during the spring molting period of 2003 (May–July) in Kongsfjorden, Svalbard, Norway. Hourly counts were conducted on the land‐fast ice in six spatially defined sectors in the inner fjord, from an elevated land‐based vantage point from early May through until the ice began to break up in June, from 0600 to 2200 daily (total counts n= 478). Concomitantly, measurements were made of a variety of weather parameters. Multiple regression analyses revealed that time of day (P < 0.001) and date (P < 0.001) significantly affected the number of ringed seals hauled out on the ice surface. Other factors influencing the number of seals counted on the ice were air temperature (P= 0.011) and wind speed (P < 0.001). Daily peaks occurred in the early afternoon between 1300 and 1400 and the seasonal high (n= 385) was registered during the first week in June, after which the number of seals on the ice in the fjord declined. In addition to the visual counts, 24 ringed seals were equipped with VHF transmitters, and the haul‐out behavior of individuals was monitored from May through July via an automatic recording station. The VHF‐tagged seals exhibited the same diurnal pattern seen in the total counts, with haul‐out most frequent from 1300 to 1400. Pups exhibited short and frequent haul‐outs, whereas longer haul‐out periods were seen in the older age classes; adult females had the greatest number of haul‐out periods that exceeded 24 h. The seasonal peak of haul‐out for the tagged seals preceded the peak seasonal counts by approximately 3 wk. This may reflect significant out‐ and influx of seals from and to the area, a phenomenon warranting further attention because of its implications for assessment studies.     

The Contribution of Agriculture,Forestry and other Land Use activities to Global Warming, 1990–2012

We refine the information available through the IPCC AR5 with regard to recent trends in global GHG emissions from agriculture, forestry and other land uses (AFOLU), including global emission updates to 2012. Using all three available AFOLU datasets employed for analysis in the IPCC AR5, rather than just one as done in the IPCC AR5 WGIII Summary for Policy Makers, our analyses point to a down‐revision of global AFOLU shares of total anthropogenic emissions, while providing important additional information on subsectoral trends. Our findings confirm that the share of AFOLU emissions to the anthropogenic total declined over time. They indicate a decadal average of 28.7 ± 1.5% in the 1990s and 23.6 ± 2.1% in the 2000s and an annual value of 21.2 ± 1.5% in 2010. The IPCC AR5 had indicated a 24% share in 2010. In contrast to previous decades, when emissions from land use (land use, land use change and forestry, including deforestation) were significantly larger than those from agriculture (crop and livestock production), in 2010 agriculture was the larger component, contributing 11.2 ± 0.4% of total GHG emissions, compared to 10.0 ± 1.2% of the land use sector. Deforestation was responsible for only 8% of total anthropogenic emissions in 2010, compared to 12% in the 1990s. Since 2010, the last year assessed by the IPCC AR5, new FAO estimates indicate that land use emissions have remained stable, at about 4.8 Gt CO₂ eq yr^?1 in 2012. Emissions minus removals have also remained stable, at 3.2 Gt CO₂ eq yr^?1 in 2012. By contrast, agriculture emissions have continued to grow, at roughly 1% annually, and remained larger than the land use sector, reaching 5.4 Gt CO₂ eq yr^?1 in 2012. These results are useful to further inform the current climate policy debate on land use, suggesting that more efforts and resources should be directed to further explore options for mitigation in agriculture, much in line with the large efforts devoted to REDD+ in the past decade.     

Agricultural greenhouse gas mitigation potential globally,in Europe and in the UK: what have we learnt in the last 20 years?

Agricultural lands occupy about 40–50% of the Earth's land surface. Agricultural practices can make a significant contribution at low cost to increasing soil carbon sinks, reducing greenhouse gas (GHG) emissions and contributing biomass feedstocks for energy use. Considering all gases, the global technical mitigation potential from agriculture (excluding fossil fuel offsets from biomass) by 2030 is estimated to be ca. 5500–6000 Mt CO₂‐eq. yr^?1. Economic potentials are estimated to be 1500–1600, 2500–2700 and 4000–4300 Mt CO₂‐eq. yr^?1 at carbon prices of up to $US20, 50 and 100 t CO₂‐eq.^?1, respectively. The value of the global agricultural GHG mitigation at the same three carbon prices is $US32 000, 130 000 and 420 000 million yr^?1, respectively. At the European level, early estimates of soil carbon sequestration potential in croplands were ca. 200 Mt CO₂ yr^?1, but this is a technical potential and is for geographical Europe as far east as the Urals. The economic potential is much smaller, with more recent estimates for the EU27 suggesting a maximum potential of ca. 20 Mt CO₂‐eq. yr^?1. The UK is small in global terms, but a large part of its land area (11 Mha) is used for agriculture. Agriculture accounts for about 7% of total UK GHG emissions. The mitigation potential of UK agriculture is estimated to be ca. 1–2 Mt CO₂‐eq. yr^?1, accounting for less than 1% of UK total GHG emissions.     

土地利用变化对土壤有机碳贮量的影响

通过对比分析六盘山林区典型天然次生林(杂灌林、山杨和辽东栎林)与农田、草地及农田、草地与人工林(13、18和25年生华北落叶松)邻近样地土壤有机碳含量和密度及其在土壤剖面上分布的差异,研究了天然次生林变成农田或草地及农田或草地造林后对土壤有机碳贮量的影响,结果表明,土壤有机碳含量方面,农田和草地比天然次生林分别低54％和27％,差异主要在0～50cm土层;农田和草地比人工林分别低42％和26％,差异主要在0～40cm土层,土壤有机碳密度方面,农田和草地比天然次生林分别低35％和14％,差异主要在0～50cm土层;农田比人工林低23％,草地比人工林高4％,差异主要在0～30cm土层．天然次生林和人工林土壤有机碳含量和密度随土层加深而递减的幅度比农田或草地大．这些差异主要由土地利用变化引起的土壤有机碳输入与输出及根系分布的变化所致．结果说明六盘山林区天然次生林破坏变成草地或农田后土壤有机碳含量和密度(主要是0～50cm土层)将下降,而农田中造林后土壤有机碳含量和密度(主要是0～30cm土层)又将增加,草地上造林后土壤有机碳含量增加而密度变化不大。另外,土壤有机碳含量和密度在土壤剖面上的分布也将随土地利用变化而发生改变。     

浙江省森林生物量动态

以浙江省1976至2004年森林资源连续清查资料为数据源,采用基于生物量与蓄积之间关系的生物量转换因子连续函数法,对全省林分生物量和包括林分在内的森林生物量动态进行估计。森林生物量为包括林分、疏林、灌木林、竹林、经济林和四旁树在内的所有林木生物量之和。结果表明,浙江省1976至2004年间森林生物量从1.00828&#215;10^8Mg上升到2.44426&#215;10^8Mg;其中,林分生物量由0.5712&#215;10^8Mg上升到1.51128&#215;10^8Mg。森林生物量和林分生物量的年平均增长速度分别为5.1%和9.1%。在1999至2004年间,森林生物量和林分生物量增长速度均明显加快,分别达到8.6%和10.1%。在1976至2004年间,全省森林面积年均增长速度为1.0%,森林平均生物量从16.50Mg&#183;hm^-2上升到36.59Mg&#183;hm^-2。但是,在森林资源总量不断增加的同时,全省林分质量仍维持较低水平。2004年全省林分单位面积生物量为38.40Mg&#183;hm^-2,远低于全国平均水平（77.40Mg&#183;hm^-2）。研究还表明,利用森林资源连续清查数据和基于单株测树因子的森林生物量模型能够估计大尺度范围内的森林生物量及其动态,但亟待在统一标准下建立和完善覆盖所有树种的生物量模型。