长江上游生态环境退化与农地利用

本文在指出长江上游生态环境退化及危害的基础上，分析几种不合理的土地利用与生态环境退化的关系，并在分析这些原因的基础上提出合理利用土地，走农地综合利用的几点建议。     

渍害田地下排水技术与江汉平原农业综合开发

江汉平原是全国重点开发区域之一。本文由分析江汉平原的资源优势及其主要后备资源渍害中低产田入手,以科学试验资料为依据,从理论与实践的结合上,阐述了地下排水技术是改造渍害中低产田的治本措施,进而说明了该项技术的推广应用是江汉平原农业综合开发的主体和关键。     

Use of Stress‐Hormone Levels and Habitat Selection to Assess Functional Connectivity of a Landscape for an Amphibian

Abstract: The influence of landscape matrix on functional connectivity has been clearly established. Now methods to assess the effects of different land uses on species’ movements are needed because current methods are often biased. The use of physiological parameters as indicators of the level of resistance to animal movement associated with different land uses (i.e., matrix resistance) could provide estimates of energetic costs and risks to animals migrating through the matrix. To assess whether corticosterone levels indicate matrix resistance, we conducted experiments on substrate choice and measured levels of corticosterone before and after exposure of toads (Bufo bufo) to 3 common substrates (ploughed soil, meadow, and forest litter). We expected matrix resistance and hormone levels to increase from forest litter (habitat of the toad) to meadows to ploughed soil. Adult toads had higher corticosterone levels on ploughed soil than on forest litter or meadow substrates. Hormone levels did not differ between forest litter and meadow. Toads avoided moving onto ploughed soil. Corticosterone levels in juvenile toads were not related to substrate type; however, hormone levels decreased as humidity increased. Juveniles, unlike adults, did not avoid moving over ploughed soil. The difference in responses between adult and juvenile toads may have been due to differences in experimental design (for juveniles, entire body used to measure corticosterone concentration; for adults, saliva alone); differences in the scale of sensory perception of the substrate (juveniles are much smaller than adults); or differences in cognitive processes between adult and juvenile toads. Adults probably had experience with different substrate types, whereas juveniles first emerging from the water probably did not. As a consequence, arable lands could act as ecological traps for juvenile toads.     

大渡河干热河谷农业环境资源的开发模式

大渡河干热河谷光、热资源充裕,雨、热同期,主、支流(沟)纵横交错,为农业灌溉提供了水源;经济林木资源优势相对突出,农业环境资源立体层次丰富。因此,本文提出了开发大渡河干热河谷农业环境资源的4种模式。     

Embarking on the Second Green Revolution for Sustainable Agriculture in India: A Judicious Mix of Traditional Wisdom and Modern Knowledge in Ecological Farming

The Green Revolution in India which was heralded in the 1960‘s was a mixed blessing. Ambitious use of agro-chemicals boosted food production but also destroyed the agricultural ecosystem. Of late Indian farmers and agricultural scientists have realized this and are anxious to find alternatives – perhaps a non-chemical agriculture – and have even revived their age-old traditional techniques of natural farming. Scientists are working to find economically cheaper and ecologically safer alternatives to agro-chemicals. Blue-Green Algae Biofertilizers, Earthworm Vermicomposts (Vermiculture), biological control of pests and herbal biopesticides are showing promise. Saline agriculture and sewage farming are also being promoted in India to augment food production in the face of water scarcity. There is a move to search for alternative foods, which are more nutritious, cheaper and have shorter harvest cycles. Farm and food policy in India has to change its outlook before there can be a second green revolution. This revised version was published online in August 2006 with corrections to the Cover Date.     

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY1

ABSTRACT: We measured annual discharges of water, sediments, and nutrients from 10 watersheds with differing proportions of agricultural lands in the Piedmont physiographic province of the Chesapeake Bay drainage. Flow-weighted mean concentrations of total N, nitrate, and dissolved silicate in watershed discharges were correlated with the proportion of cropland in the watershed. In contrast, concentrations of P species did not correlate with cropland. Organic P and C correlated with the concentration of suspended particles, which differed among watersheds. Thus, the ratio of N:P:Si in discharges differed greatly among watersheds, potentially affecting N, P or Si limitation of phytoplankton growth in the receiving waters. Simple regression models of N discharge versus the percentage of cropland suggest that croplands discharge 29–42 kg N ha^-1 yr^-1 and other lands discharge 1.2–5.8 kg N ha^-1 yr^-1. We estimated net anthropogenic input of N to croplands and other lands using county level data on agriculture and N deposition from the atmosphere. For most of the study watersheds, N discharge amounted to less than half of the net anthropogenic N.     

成都市休闲旅游资源空间分布特征及影响因素

休闲旅游是旅游消费的发展趋势,休闲旅游资源是休闲旅游产业发展的载体与基础。以成都市休闲旅游资源POI数据为基础,运用最近邻层次聚类分析、Ripley's K函数及地理探测器等方法,研究成都市休闲旅游资源空间格局及其影响因素。结果表明:（1）成都市休闲旅游资源整体呈现中心集聚与外围分散的分布模式,康娱类、文化类、专项类以及自然类休闲旅游资源分别表现出以传统商圈、文化中心、绿地公园以及自然景点为依托的布局特征。（2）不同类型休闲旅游资源的特征空间尺度存在差异,康娱类特征空间尺度最大,专项类和文化类特征空间尺度次之,自然类特征空间尺度最小。（3）距市中心距离、游客密度、街道活力、居民密度、资源禀赋、道路密度等是影响成都市休闲旅游资源空间分布的重要因素。（4）在影响因素中,距市中心距离、游客与当地居民密度是主导因素;资源禀赋、街道活力是驱动因素;道路密度、距主干道距离与区域经济是诱发因素;政府行为、重大事件是调节因素,四个维度共同作用,形成成都市休闲旅游资源的空间格局。     

生物炭对华北农田土壤N2O通量及相关功能基因丰度的影响

为了探寻施用生物炭对农田土壤氧化亚氮(N_2O)的减排效果和机制,于2015年3月27日至6月5日,利用盆栽实验研究了施用生物炭(CK,C1:5%,C2:10%,C3:15%,C4:30%)(质量分数)对华北农田土壤N_2O通量、氨单加氧酶(amo A)、亚硝酸盐还原酶(nir S、nir K)以及氧化亚氮还原酶(nos Z)基因丰度的影响.结果表明:(1)施用低量生物炭(5%)能够促进N_2O排放,施用中、高量生物炭可以起到抑制N_2O排放的效果,且生物炭用量为15%时减排效果最佳.(2)实验初期,施用生物炭对土壤硝化反硝化基因丰度影响较大,AOA和nir S基因丰度与生物炭施用量呈极显著正相关关系,nir K基因丰度与生物炭施用量呈显著正相关关系,AOB和nos Z基因丰度与生物炭施用量呈显著负相关关系;实验末期,AOA丰度与生物炭施用量表现为显著负相关关系,AOB丰度与生物炭施用量表现为显著正相关关系.(3)实验初期,N_2O排放通量与AOA、nir S基因呈现极显著的负相关关系,说明在土壤含水量较高的条件下,N_2O的产生受AOA、nir S基因丰度控制调节;实验末期,N_2O排放通量与nos Z基因呈现极显著正相关关系,说明在土壤含水量较低的条件下,N_2O的产生受nos Z基因丰度控制调节.本研究结果表明施用生物炭能够增加硝化反硝化功能基因丰度,并降低N_2O的排放,为华北农田合理施用生物炭提供了一定的理论依据.     

Conservation practices in U.S. agriculture and their impact on carbon sequestration

Increase in the use of conservation practices byagriculture in the United States will enhance soilorganic carbon and potentially increase carbonsequestration. This, in turn, will decrease the netemission of carbon dioxide. A number of studies existthat calibrate the contribution of various individual,site-specific conservation practices on changes insoil organic carbon. There is a general absence,however, of a comprehensive effort to measureobjectively the contribution of these practicesincluding conservation tillage, the ConservationReserve Program, and conservation buffer strips to anchange in soil organic carbon. This paper fills thatvoid. After recounting the evolution of the use ofthe various conservation practices, it is estimatedthat organic carbon in the soil in 1998 in the UnitedStates attributable to these practices was about 12.2million metric tons. By 2008, there will be anincrease of about 25%. Given that there is asignificant potential for conservation practices tolead to an increase in carbon sequestration, there area number of policy options that can be pursued.     

生态农业的给排水循环系统的探讨

生态农业的发展，是经济、社会和环境保护协调发展的产物。作者提出生态农业的给排水循环系统作为现有模式的延伸和补充，让生态农业在经济、社会、环境的协调发展中发挥更大的作用，最大限度地消除农业污染，为农业可持续发展提供技术支持和可靠保证。