EFFECTS OF INCREASED DELTA EXPORTS ON SACRAMENTO VALLEY'S ECONOMY AND WATER MANAGEMENT1

ABSTRACT: Exports from the Sacramento‐San Joaquin Delta are an important source of water for Central Valley and Southern California users. The purpose of this paper is to estimate and analyze the effects increased exports to south of Delta users would have on the Sacramento Valley economy and water management if water were managed and reallocated for purely economic benefits, as if there were an ideal Sacramento Valley water market. Current Delta exports of 6,190 thousand acre‐feet per year were increased incrementally to maximum export pumping plant capacities. Initial increases in Delta exports did not increase regional water scarcity, but decreased surplus Delta flows. Further export increases raised agricultural scarcity. Urban users suffer increased scarcity only for exports exceeding 10,393 taf/yr. Expanding exports raises the economic value of expanding key facilities (such as Engle bright Lake and South Folsom Canal) and the opportunity costs of environmental requirements. The study illustrates the physical and economic capacity of the Sacramento Valley to further increase exports of water to drier parts of the state, even within significant environmental flow restrictions. More generally, the results illustrate the physical capacity for greater economic benefits and flexibility in water management within environmental constraints, given institutional capability to reoperate or reallocate water resources, as implied by water markets.     

Bag leakage: The effect of disposable carryout bag regulations on unregulated bags

Leakage occurs when partial regulation of consumer products results in increased consumption of these products in unregulated domains. This article quantifies plastic leakage from the banning of plastic carryout bags. Using quasi-random policy variation in California, I find the elimination of 40 million pounds of plastic carryout bags is offset by a 12 million pound increase in trash bag purchases—with small, medium, and tall trash bag sales increasing by 120%, 64%, and 6%, respectively. The results further reveal 12–22% of plastic carryout bags were reused as trash bags pre-regulation and show bag bans shift consumers towards fewer but heavier bags. With a substantial proportion of carryout bags already reused in a way that avoided the manufacture and purchase of another plastic bag, policy evaluations that ignore leakage effects overstate the regulation's welfare gains.     

Expression and regulation of the shikimic acid pathway gene DHD/SDH in tea plant (Camellia sinensis)北大核心CSCD

3-Dehydroquinic acid dehydrase/shikimate dehydrogenase (DHD/SDH) is the only bifunctional enzyme in the shikimic acid pathway. It can catalyze the generation of shikimic acid and gallic acid. To investigate the expression and regulation patterns of DHD/SDH in tea, we aimed to determine (1) the miRNA-mediated cleavage of DHD/SDH involved in the shikimic acid pathway, (2) the expression pattern of miRNA and their targets, and (3) the expression pattern of three DHD/SDH genes in tea plant (Camellia sinensis) with different hormone treatments via online prediction, RLM-RACE, and qPCR. Based on the miRNAs obtained, we identified four miRNAs that regulated CsDHD/SDH in tea. CsDHD/SDH2 was targeted by miR5180b, miR1510b-5p, and miR24; CsDHD/SDH3 was targeted by miR868-5p. We also found that CsDHD/SDH2 and CsDHD/SDH3 have a similar expression pattern under different hormone treatments, and they were synergistic with each other. CsDHD/SDH1 exhibited an expression pattern opposite to that of the other two homologues, and increased expression of CsDHD/SDH1 reduced the expression of the other two genes. © 2018 Science Press. All rights reserved.     

Abolition of set-aside schemes, associated impacts on habitat structure and modelling of potential effects of cross-farm regulation

In intensively farmed regions, habitat fragmentation represents a major pressure on biodiversity. Depending on its spatial setting, set-aside land can increase size and connectivity of habitats and thus counteract fragmentation. In 2008, the EU-wide set-aside obligation was suspended and a large proportion of set-aside land was re-cultivated. With Denmark as case we apply an indicator to measure the effect of set-aside land on spatial structure of semi-natural habitats in term of habitat size and connectivity. Furthermore, we model effects of a hypothetical spatial regulation, where set-aside land with the greatest benefit for habitat structure is retained as uncultivated, while set-aside land with the least effect is re-cultivated. The model is applied to individual farms and to farm agglomerations of increasing sizes, enabling us to explore potential effects of cross-farm regulation. The novelty of our approach is the application of observed land-uses changes for modelling a hypothetical regulation working on a range of spatial scales. Results show that after abolition of set-aside schemes the effect of set-aside land on habitat structure was more than halved. Modelled spatial regulation considerably reduces impacts. Effects increase with increasing size of farm agglomerations. However, marginal benefits become negligible at agglomeration sizes over 36 km².     

西藏色季拉山川滇高山栎种群的空间格局与调节

川滇高山栎是青藏高原具有代表性的常绿阔叶树种,在藏东南林区大面积连续分布,对高山峡谷地带的水土保持和水源涵养具有重要的防护作用和较大的生态效益.采用聚集度指标、以空间推时间法的Logistic方程和种群调节的乘幂函数拟合分别对西藏色季拉山川滇高山栎种群的空间分布格局、增长与调节规律进行了研究.结果表明,川滇高山栎幼苗多呈聚集分布,随着演替的进展,川滇高山栎种群的聚集强度减小;川滇高山栎种群增长的环境容纳量为15.2085m2hm-2,内禀增长率为0.614;种群最大增长速率出现在胸断面积9.66m2hm-2处,种群在平均胸断面积46.23cm2(均胸径7cm)~198.723cm2(均胸径15.91cm)阶段自疏强度最大.川滇高山栎种群聚集强度随演替过程逐渐减弱,是种群在有限的环境容量中自疏和自我调节特征的明显表现.Logistic方程即反映了生物种群增长速度的变化和环境容量限制的时滞效应这一重要特征,种群调节的幂函数拟合则有效刻画了生物种群在大量繁殖之后,随着个体增大,个体间资源竞争增强,种群内部出现优胜劣汰的自我调节过程.图4表2参32     

流域、区域、生态——湖泊环境治理的战略思考

湖泊富营养化问题是生态问题,是湖泊所在流域环境问题的集中反映,生态问题应该通过生态途径来解决。调控流域水环境的关键在农村,农村环境污染控制主要靠生态治污来解决。只有把流域作为一个完整的生态系统,调整系统中各种因素之间的关系,实现生态系统的平衡,才能从根本上解决湖泊水环境问题。     

Econometric modeling of fisheries with complex life histories: Avoiding biological management failures

Economics of the fishery has focused on the wastefulness of common pool resource exploitation. Pure open access fisheries dissipate economic rents and degrade biological stocks. Biologically managed fisheries also dissipate rents but are thought to hold biological stocks at desired levels. We develop and estimate an empirical bioeconomic model of the Gulf of Mexico gag fishery that questions the presumptive success of biological management. Unlike previous bioeconomic life history studies, we provide a way to circumvent calibration problems by embedding our estimation routine directly in the dynamic bioeconomic model. We nest a standard biological management model that accounts for complex life history characteristics of the gag. Biological intuition suggests that a spawning season closure will reduce fishing pressure and increase stocks, and simulations of the biological management model confirm this finding. However, simulations of the empirical bioeconomic model suggest that these intended outcomes of the spawning closure do not materialize. The behavioral response to the closure appears to be so pronounced that it offsets the restriction in allowable fishing days. Our results indicate that failure to account for fishing behavior may play an important role in fishery management failures.     

基于气候调节的城市通风道探析

近年来,夏季炎热的气候和愈来愈强的热岛效应使城市饱受因挠,而城市设计策略中缺乏有效的生态规划方法来解决目前存在的问题,城市对炎热气候的适应性不足。论文在利用CFD(计算流体动力学)技术进行实例模拟分析的基础上,重点介绍了一种在城市尺度进行节能设计的新方法:在城市中建立多种形式的通风道,提高城市的通风和排热能力,以达到利用自然资源和有效的规划方式降低夏季城市“热岛”温度、节约能源的目的。文中详细论述了通风道的可行性和必要性、营建方式、注意原则等问题,并进行了一系列的计算机风场模拟研究。     

中国化肥资源供需矛盾及调控策略

鉴于中国化肥供需形势不清给产业调控带来不确定性影响,论文分析了化肥资源供需矛盾,并提出了相关调控策略。结果表明,中国化肥供需总量已经接近平衡,氮磷钾化肥的自给率分别达到100%、95%和29%。少部分产品存在缺口,其中氯化钾的自给率为23%,是当前我国惟一紧缺的化肥产品。随着化肥生产向资源产地集中,中国化肥供需时空不平衡有扩大的趋势。部分时间段的供需不平衡异常尖锐,其中10月份至来年3月份全国化肥供应过剩超过900×10⁴t,而部分月份却极端不足,例如7月份两广、东北等地的尿素缺口达200×10⁴t左右,10月份华北地区的磷酸二铵缺口达到100×10⁴t左右,而5、7、8三个月中两广地区的钾肥缺口也超过100×10⁴t。建议国家加强储备工作,储备化肥消费量的15%,其中10%储备在淡季,以减少过剩的压力,而5%储备在旺季,以应对市场供不应求。     

关于消费者对转基因农产品认知的调查

调查发现有不少声称调查前就对转基因农产品“知道一点”,但了解的程度却有很大差别,其实更多的人并不真正了解,在对待基因农产品的态度上表现出相当的规律性：虽然都比较关注对生产转基因农产品给农民带来的收入,但更多的是关注对生态环境和人体健康的影响,希望加强管理。不同年龄、婚姻状态、性别和不同收入水平的人对转基因农产品的认知程度和态度虽然有很大程度的相似性,但也有相当程度的不同。