Implications of land use transitions on soil nitrogen in dynamic landscapes in Tanzania

Land use transitions are rated among the leading sources of greenhouse gas emissions in the tropics. They significantly challenge the functioning of ecosystems and affect multi-temporal stability of greenhouse gases such as N₂O and soil properties. Studies on dynamics in nitrogen balances are essential in understanding greenhouse gas emissions such as N₂O and to manage their impacts on productivity. In this study, multi-temporal Landsat images (1975, 1995 and 2012) were classified to determine land use transitions and potential drivers. The classified images were categorized into degraded and non-degraded lands and eighty sampling plots generated within the entire study area. Soil samples were then collected at 0–15, 15–30 and 30–60 cm depths on each plot and soil nitrogen determined. A regression analysis was developed to determine the influence of forest and grassland degradation on soil nitrogen. Results indicated a significant change in major land use and land cover types. Specifically, there was a decrease in areas covered by forests, woodland and grassland, however, area covered by less dense forest increased. Results also indicated variability in mean nitrogen content between degraded and non-degraded areas and depths. Furthermore, levels of degradation influence nitrogen content up to a soil depth of 30 cm. The present study is relevant in the detailed assessment of the extent of damage and threats posed to biodiversity hotspots in sub-Saharan Africa. These results are transferable to other parts of the world characterized by dynamic ecological transformation.     

Towards the implementation of the European Water Framework Directive?: Lessons learned from water quality simulations in an agricultural watershed

The main objective of the European Water Framework Directive (WFD) is the achievement of a good ecological and chemical status of the water environment (water bodies). This status corresponds to the limit value of Germany's Working Group of the Federal States on Water Problems Issues (LAWA) for water quality class II (3 mg/l total nitrogen). The rivers in the intensively cropped Upper Ems River basin (northwestern Germany) show total nitrogen concentrations in excess of 5–10 mg/l. Hence, the objective of our study was to find a land use and land management scenario that would reduce the total nitrogen concentration to meet the WFD requirements for good ecological and chemical status. We developed consecutive land use and management scenarios on the basis of policy instruments such as the support of agro-environmental measures by Common Agricultural Policy and regional landscape development programs. The model simulations were done by using the Soil and Water Assessment Tool (SWAT). Results of SWAT scenario calculations showed that drastic measures, which are unrealistic from a socio-economic point of view, would be needed to achieve the water quality target in the basin (reduction of arable land from 77.2% to 46% [13% organic farming], increase of pasture from 4% to 15%, afforestation from 10% to 21%, increase of protected wetlands from 0% to 9%, etc.). The example shows additionally that the achievement of the WFD targets is only possible with a consideration of regional landscape and land use distinctions. A related problem yet to be addressed is the general lack of measured water quality data with which to calibrate and validate water quality models such as SWAT. This adds considerable uncertainty to already complicated and uncertainty situations. Thus, improved strategies for water quality monitoring, and data accessibility must be established.     

Reducing nutrient loads from dairy farms: a bioeconomic model with endogenous feeding and land use

Growth trends of animal farming pose a threat to water quality around the world. To find cost‐efficient means to reduce nutrient loads from agriculture, detailed information on the abatement measures need to be incorporated in bioeconomic models. This study presents a theoretical framework that covers both animal and crop operations on farms. It describes the farmer decision making problem and incorporates nonlinear functions to capture the economic and biological aspects of the problem. The model is applied to Finnish dairy farms. The abatement cost functions are derived for nitrogen and phosphorus. Results indicate that abatement measures on fields should precede dietary changes.     

Innovation and diffusion of environmental technology: Industrial NOx abatement in Sweden under refunded emission payments

We study the actual process of technical change in the case of NOx abatement from large stationary sources that have been regulated by very forceful policies in Sweden. Considerable progress has been made in lowering aggregate emissions and this paper seeks to disaggregate average industry improvements to study how much of it is due to innovations by first movers, and how much is achieved by adoption and diffusion of technology. We find both factors very important. Innovation has been rapid: the best firms have cut emissions on the order of 70%. In spite of this, reductions have actually been even more rapid for the majority of firms so that the median firms have caught up with best practice. We analyze various characteristics of the technological change observed.     

A field experiment to estimate the effects of anchoring and framing on residents’ willingness to purchase water runoff management technologies

Watersheds throughout the world have been severely polluted by nutrient-laden runoff that comes from industrial, agricultural, and residential sources. Efforts to reduce this runoff have focused on industrial and agricultural sources, while little attention has been paid to encouraging residents to reduce runoff from their properties. To study residents’ willingness to adopt landscaping practices that reduce runoff, we conducted a field experiment in the Delaware River watershed. In the experiment, over three hundred adults participated in a series of random-price auctions that revealed their willingness to pay (WTP) for five products that reduce nutrient runoff. To study how WTP can be influenced by attributes of the choice architecture, we randomized the starting bid values (anchors) and the way in which the external benefits of the five practices were framed. Compared to a neutral framing, a positive framing (using the product can improve water quality) increased average WTP by about one-third, while the estimated effect of a negative framing (failing to use the product can worsen water quality) was also positive, but smaller and not statistically different from zero. The estimated effect on average WTP from the anchor depends on how bids of $0 are modeled, but the results imply that higher anchors lead to higher WTP. Although we believe the magnitudes of our results should be considered suggestive and we recommend replications with higher statistical power, the results add to the evidence base that environmental programs can achieve policy-relevant gains in program performance through a series of small changes to the decision environment.     

Profiling road transport activity: Emissions from 2000 to 2005 in Ireland using national car test data

This work describes a methodology for determining the average vehicle kilometres travelled by the private national car fleet in Ireland and estimating the disaggregated CO₂ and NO_x emissions from private vehicles in the Irish road transport sector for the period 2000–2005 using national car test records. The developed methodology facilitates the calculation of greatly improved estimates for vehicle kilometres under a range of constraint variables and thereby enables the disaggregated analysis of specific vehicle fleet groups and their associated activity patterns to support evidence-based policy development. The results indicate that while older vehicles are contributing significantly to car NO_x emissions; newer cars produce a higher share of CO₂ emissions than older cars in the vehicle fleet.     

P-Phos-钯络合物催化吡啶硼酸的Suzuki偶联反应研究

将双齿膦配体P-Phos应用于钯催化的3-吡啶硼酸的Suzuki反应中,通过对溶剂和碱等反应条件的考察,确定了最佳的催化条件,并对一系列底物进行了普适性拓展。实验表明,该催化剂对大多数卤代芳烃底物起到了良好的催化效果,并且可以实现惰性底物氯代芳烃与吡啶硼酸的高效偶联,产率高达99%。     

华南地区浅圆仓控温气调储粮技术应用新思路

控温和氮气气调储粮技术是绿色环保综合储粮的重要技术,随着20世纪末国家一批新建粮库的竣工投产,国内粮食储藏条件得到改善,尤其是仓房防潮、隔热、控温、气密等仓储性能得到显著提高。中央储备粮广东新沙港直属库借中储粮总公司氮气气调扩大应用项目推广之机率先在国内浅圆仓开展了氮气气调储藏玉米的试验,通过实验,论证了氮气气调对虫害防治、霉菌抑制和脂肪酸值控制方面效果显著,氮气气调储粮技术的应用对改善保管人员工作条件,降低劳动强度,提高工作效率优势明显,初步得出华南地区浅圆仓使用控温和氮气气调综合技术储藏玉米安全可行,社会、经济等综合效益显著。     

松花江河滨湿地N、P净化功能研究

湿地通过植物吸收、湿地底泥的截留吸附和微生物降解来净化农田径流中携带的N、P污染。农田退水期湿地中的N、P含量最大,流经湿地的农田径流,5月TP和TN含量下降到0.022mg/L和0.95mg/L,7月TP和TN含量下降到0.024mg/L和0.93mg/L;不同群落对N、P的吸收净化能力有所不同,修氏苔草群落在5月植物样品中的TP和TN含量分别为9.20mg/L和18.00mg/L,7月植物样品中的TP和TN含量分别为10.65mg/L和19.35mg/L均高于其它植物样品;修氏苔草群落在5月湿地底泥样品中的TP和TN含量分别为0.26mg/L和1.16mg/L,7月湿地底泥样品中的TP和TN含量分别为0.21mg/L和1.06mg/L均低于其它湿地底泥样品,修氏苔草群落对N、P的阻控能力明显高于其它群落。     

微生物对水田化肥氮素利用率的影响

通过改进施肥方法和施用微生物肥料,探讨对稻田土壤微生态环境及氮素转化动态的影响。结果表明,施用微生物肥料后,水稻根际微生态环境得到明显改善;提高水稻植株对化肥氮素的吸收量,增加土壤氮的残留,减少氮肥的挥发损失及反硝化作用。同时肥料深施也能大大减少氮素的损失,增加根际微生物数量,从而提高作物产量。