土壤碳汇补偿困境及对策研究

土壤碳汇是削减碳排放、缓解全球气候变暖的最具经济效益的手段之一,但土壤碳汇依赖于广大农民对土地利用及管理方式的选择,并且这些选择是伴随着成本的。因此,要想调动广大农民的积极性来参与增加土壤碳汇,必须要对使其转变习惯性土地利用及管理方式带来的损失进行补偿,但通过对土壤碳汇补偿的法律基础、补偿标准以及泄漏与风险等方面的研究却显示,土壤碳汇补偿面临多重困境与不确定性,这使得土壤碳汇补偿陷入瓶颈。对此,建议完善土壤碳汇补偿法律法规、建立土壤碳库数据信息系统、建立碳基金和完善国内碳交易市场来化解土壤碳汇补偿困境。     

Derivatives pricing with marked point processes using tick-by-tick data

I propose to model stock price tick-by-tick data via a non-explosive marked point process. The arrival of trades is driven by a counting process in which the waiting time between trades possesses a Mittag–Leffler survival function and price revisions have an infinitely divisible distribution. I show that the partial-integro-differential equation satisfied by the value of European-style derivatives contains a non-local operator in time-to-maturity known as the Caputo fractional derivative. Numerical examples are provided for a marked point process with conditionally Gaussian and with conditionally CGMY price innovations. Furthermore, the infinitesimal generator of the marked point process derived to price derivatives coincides with that of a Lévy process of either finite or infinite activity.     

Complexity and financial stability in a large random economy

I study the limit of a large random economy, in the ideal case of perfect competition, where full information is available to all market participants, and where a set of consumers invests in financial instruments engineered by banks in order to optimize their future consumption. This provides a picture of how unregulated financial innovation pushes an economy towards the ideal limit of complete markets. Hedging new products with existing products allows financial institutions to reduce the associated risk and hence the risk premium. This has the expected consequence that markets, under such ideal conditions, converge to market completeness as the repertoire of financial instruments expands. As markets approach completeness, however, two ‘unintended consequences’ also arise: (i) equilibrium portfolios develop a marked susceptibility to idiosyncratic shocks and/or parameter uncertainty and (ii) hedging engenders divergent trading volumes in the interbank market. Combining these suggests an inverse relation between financial stability and the size of the financial sector, which can be quantified within the present framework. These results suggest that even under perfect competition and symmetric information, the pursuit of market efficiency—in terms of completeness—may erode financial stability. The proliferation of financial instruments exacerbates the effects of market imperfections and, in order to prevent an escalation of perverse effects, markets may require institutional structures that become more and more substantial as their complexity expands.     

不同改良剂对污染土壤中Cd形态影响的研究

采用室内培养试验,研究了4种改良剂对污染土壤中Cd形态的影响。外源添加Cd的土壤中,重金属Cd主要以可交换态Cd的形式存在,所占比例为全量的35.2%~44.0%。施加改良剂可在一定程度上增加土壤pH值,从而影响土壤中Cd的形态分布,其影响效果为改良剂1＞改良剂4＞改良剂3＞改良剂2。施加改良剂并在室温下培养35 d后,土壤中Cd形态分布发生了明显的变化。在1 mg·kg-1和10 mg·kg-1的Cd污染土壤中,可交换态Cd含量降低,残渣态Cd含量增加,而在5 mg·kg-1的Cd污染土壤中,残渣态Cd含量降低,可交换态Cd含量增加;培养过程中碳酸盐结合态Cd和铁锰氧化物结合态Cd含量并未产生较大变化,土壤中有机质结合态Cd所占比例非常小,改良剂施用对其含量的影响也不明显。总体上来讲,改良剂的施用可使土壤Cd由可交换态向残渣态转化,Cd的生物有效性降低。     

Profitability and opportunity of conservation agriculture in acid savannah grasslands of Laos

In north-eastern Laos, the savannah grasslands of the Plain of Jars cover vast areas of potentially cultivable land. However, soil acidity, low inherent fertility, and the absence of alternatives to tillage represent significant constraints to the development of sustainable smallholder agriculture. Our objective was to evaluate the potential for conservation agriculture (CA) to enhance soil productivity and farming system profitability. A three-year rotation of rice/maize/soybean was tested under three fertilization levels and four agricultural systems: one conventional tillage-based (CT) system and three CA systems based on no-tillage with cover crops. After four cropping seasons, our results show that, compared with CT, CA systems led to similar-to-higher grain production, similar-to-higher profits, higher opportunity of livestock system intensification, and higher labour productivity regardless of fertilization levels. While CA represents a relevant alternative to current practices, our results suggest that its contribution to the emergence of a sustainable smallholder agriculture is conditioned by broader institutional transformations, including the enrolment of local manufacturers and traders for deploying no-till implements and seed market channels for cover crops, long-term public support to maintain active research and technical mentoring to farmers, and possibly the integration of ecosystem services in agricultural policy.     

上海市临港新城土壤有机质空间变异分析

以上海市临港新城土壤(20cm～50cm)中有机质为研究对象,利用地统计与GIS技术相结合的方法研究了该地区土壤中有机质的空间分布特征。采取普通克里金(Ordinary Kriging)插值法绘制了土壤有机质的空间分布图。土壤有机质呈现中等程度空间自相关,含量由西向东逐渐增加,沿海周边又有所下降。     

浅谈梯田施工设计及施工方法——原州区张易镇陈沟坡耕地水土流失综合治理试点项目为例

陈沟坡耕地水土流失综合治理试点项目梯田工程建设的有利因素是由于本区域修建梯田是改善农业生产条件的唯一出路等因素。本文针对该项目的梯田施工设计及施工方法进行探讨论证,以供同仁的相互指正学习。     

水土流失防治措施与工程设计

文章结合某煤矿整合建设的实践经验,简要探讨了建设项目水土流失的防治措施。     

重金属对土壤微生物活性的影响

污灌区土壤基础呼吸、土壤酶的活性是判断土壤重金属影响的指标。通过对长春市四间房、季家、西新3座水库周边地区的污灌、清灌土壤的对比研究,从土壤微生物基础呼吸、土壤酶活性的变化。来研究污灌区重金属对土壤的影响,从而来判断污灌区环境质量的优劣。结果表明：污灌水中含有多种重金属污染物,其对土壤基础呼吸起一定的抑制作用。另一方面,污灌水质对土壤酶活性的影响表现为重金属过高呈现抑制,低浓度呈现激活作用。