西北地区退耕还林还草工程中存在问题与对策

西北地区退耕还林还草工作还存在一些问题。加强退耕还林还草检查验收工作力度和退耕还林还草政策宣传力度，加速退耕工程管理信息化和后续产业建设步伐，切实落实退耕补贴政策，是顺利开展退耕还林还草工程和有效保护退耕成果的重要途径。     

固原市发展退耕还林草后续产业探讨

对固原市退耕还林草后续产业的现状及问题进行了总结,提出了发展退耕还林草后续产业的思路和措施,并根据固原实际,选择了四个产业作为固原市今后重点发展的退耕还林后续产业,为固原市区域经济发展提供借鉴和参考。     

退耕还林(草)政策主要成效及趋势分析--基于西北5省和内蒙古793个退耕农户的统计分析

根据退耕还林（草）县区和调查人员的分布布局,对西北5省和内蒙古793个退耕还林（草）农户进行了问卷调查,分析了退耕还林（草）政策的主要成效及趋势,总结了农户对退耕还林（草）的评价,并提出了结论和政策性建议。研究表明,退耕还林（草）工程显著地改善了研究区域的生态状况,提高了退耕农户的生态意识和生计水平;农户拥护退耕还林（草）政策,有进一步实施退耕还林（草）的意愿;农户对退耕补助依赖性较大,如果降低补助标准,农民毁林复耕的可能性较大;提高补助标准,扩大退耕还林（草）面积,提供技术支持并大力发展后续产业是当前退耕农户的普遍愿望。     

山西省西山地区退耕还林还草后续产业的发展与保障问题分析

本文通过随机抽取5个典型县区的有关数据,从退耕与林草建设的模式入手,利用比较和综合分析的方法,分析了山西省西山地区以林牧业发展为主的退耕还林还草后续产业的现状和趋势,以及后续产业发展的保障性等问题。结果认为,从整体上看,山西省西山地区退耕还林还草后续产业发展过程可分为倒退式发展(2000—2003年)、明显加快发展(2003—2006年)和迅速发展(2006—2009年)3个时段。选定的典型县区总体情况表明,在区域耕地减少、人口增多的情况下,粮食总产量和人均粮食产量均有所增长,表明典型区域耕地质量明显提高和后续产业持续发展的趋势;从典型县区个案情况看,在某一定时段内粮食总产量和人均粮食产量均出现不同幅度的负增长态势,也显示了该区后续产业存在严重的发展问题。最后提出了稳定耕地数量、保障人均粮食拥有量是后续产业发展的根本,以及需要进一步分析的主要问题。     

中国退耕还林还草现状及问题分析

中国退耕还林还草已取得了初步成效,退耕地区生态面貌得到初步改善,农民从退耕还林还草中得到了较多的实惠,农村产业结构逐步趋向合理.但是由于退耕区域布局缺少严密的科学论证,监督检查方面也没有建立科学的监测评价体系,这使退耕还林还草政策效果大打折扣;退耕补偿政策的不合理、不公平性以及退耕地未来收益的不确定性,又使退耕还林还草成果巩固面临潜在威胁.通过深入研究上述问题,提出了完善退耕还林还草政策的若干建议.     

基于GIS的彭阳县退耕还林(草)决策分析

以彭阳县为例,根据退耕还林(草)原则,应用GIS技术的空间分析功能,提取15°坡以上耕地、未利用土地的数据,进行与退耕还林(草)决策相关的坡度、土壤侵蚀、水系等多源数据的GIS叠加分析,确定了彭阳县退耕还林(草)的区域,将退耕还林(草)的任务落实到了具体的地块,并将退耕区域划分为急需退耕区、后续退耕区、规划退耕区三个级别,以指导退耕工作的合理有序进行。     

退耕生态系统碳储量时空动态变化的研究进展

退耕还林还草作为土地利用方式改变的重要形式之一,对退耕生态系统碳储量产生深远影响。从时间、空间以及退耕还林还草模式等方面综述了退耕还林还草对植被碳库和土壤碳库产生的影响,同时探讨了枯落物和根系周转对土壤碳库动态的效应。现有研究表明,退耕生态系统碳储量对退耕时间、空间和模式有不同程度的响应。最后,提出了退耕生态系统碳储量时空动态研究需解决的关键问题。     

基于土地适宜性评估退耕还林还草工程的效果——以科尔沁左翼后旗吉尔嘎朗镇为例

选取科尔沁沙地典型区域为研究对象,运用遥感数据和GIS空间信息技术,基于土地的自然适宜性,对2000─2007年研究区退耕还林还草工程实施情况做出评价,并指出今后退耕任务和需要注意的问题。研究发现:退耕还林还草工程实施以来,吉尔嘎朗镇耕地明显减少,林地、草地明显增加,草地覆盖度显著提高;从7年间实际退耕还林还草方向、数量和空间分布来看,存在许多不合理的地方,主要是还林还草选择不合理,不宜耕作的土地还有很多没有退耕,实际退耕土地只占应退耕土地的28.63%;还有8 172.00 hm2土地应当逐步实现退耕,其中以退耕还林为主,占73.29%。政策方面,建议发展地区优势产业,积极推动农村富余劳动力转移就业,一方面增加农牧民家庭收入,另一方面减小人口对土地的压力,保证生态退耕工程持续见效。     

退耕还林还草工程生态补偿主要关系构建与工程持续运行的对策研究

利用系统和综合理论相关的分析方法,分析了退耕还林还草生态补偿的主要关系和补偿与被补偿的相关内容,构建了退耕还林还草生态补偿之间的量化联系。结果认为：（1）退耕区域和下游（下风向）区域是退耕还林还草工程的直接受益者和间接受益者,国家和退耕区域居民是受损者;（2）生态补偿的关系所包含的内容共分为14项,其中被补偿8项,补偿6项,如果两者量化关系始终处于平衡状态,是退耕还林还草工程生态环境效益持续发展最理想的模式;（3）以流域作为水土保持效益的补偿与被补偿的界限,以上下风的强弱区域作为减沙效益的补偿与被补偿的界限,最后提出了几点相关建议。分析结果可对维护退耕还林还草工程的成果持续发展具有一定的意义。     

宁南山区退耕还林还草工程实施措施研究--以固原市原州区为例

以宁夏南部山区固原市原州区为研究对象，根据区域的自然环境和人文特点，在对以往退耕还林还草工程实施经验的总结与借鉴的基础上，认为退耕还林还草工程的实施必须要遵循“生态优先”和“科学性”的原则，要从工程措施和保障措施两方面人手。首先确定了原州区三个重点退耕区：六盘山外围退耕区、原州区东北部干旱带退耕区、固原市区外围“五山两河”绿化区，然后根据区域不同的立地条件，科学的选择适宜本地的树种、草种，制定了林草配置比例和模式以及相应地技术措施。只有将工程措施与保障措施相互配合，相互协调，才能使得区域生态环境与人民脱贫致富达到“双赢”，保证本区域实现生态、经济和社会的可持续发展。     

中国华北地区近40年物候春季变化

根据华北地区7个观测站物候资料,分析了华北地区1963-1996年及北京1963-2005年物候春季的变化特征及其与气温的关系。结果表明:华北地区的物候春季有明显提早来临的趋势,而造成这一变化的主要因素是本地区近40 a来冬春季气温的明显上升。其中1963-1996年间华北地区1-3月及4月的平均气温分别上升了2.3℃与1.7℃,物候春季起止日期分别提前了9d和4d,因而使得春季长度也延长了5d;北京1963-2003年间1-3月及4月的平均气温分别上升了3.5℃与2.6℃,物候春季的起止日期分别提前了11d和10d,但春季长度没有明显变化。     

Trace metals in precipitation in Sweden

Trace metals (Cd, Cu, Fe, Mn, Pb, and Zn) concentrations in atmospheric precipitation have been routinely monitored in Sweden since the autumn of 1983. Concentrations are highest in southern Sweden and decrease northward. It is postulated that the long range transport of anthropogenic pollutants from the rest of Europe is the major source of Cd, Pb, and Zn in precipitation. Evidence for this hypothesis is that enrichment factors indicate anthropogenic origin, and Swedish atmospheric emissions of Zn and Cd are 2 to 3 times smaller than deposition fluxes. Also, Cd, Pb, and Zn concentrations are correlated in both space and time and are also well correlated with exSO₄ ⁺, a substance known to be of anthropogenic origin transported long distances.     

Patterns in trace elements in lichens

Water, Air, & Soil Pollution - Epiphytic lichens were sampled in a Dutch national monitoring survey, which was carried out twice within 5 yr. The samples were analyzed by neutron activation...     

Sediment denitrification in waterways in a rice-paddy-dominated watershed in eastern China

Purpose

Rice-paddy-dominated watersheds in eastern China are intensively cultivated, and lands with two crops receive as much as 550–600 kg?ha^–1?year^–1 of nitrogen (N), mainly through the addition of N-based fertilizers. However, stream N concentrations have been found to be relatively low. Waterways in the watersheds are assumed to be effective “sinks” for N, minimizing its downstream movement. We directly measured net sediment denitrification rates in three types of waterways (ponds, streams/rivers, and a reservoir) and determined the key factors that control net sediment denitrification. Such information is essential for evaluating the impact of the agricultural N cycle on the quality of surface water.

Materials and methods

The pond–stream–reservoir continuum was sampled every 2 months at nine sites in an agricultural watershed between November 2010 and December 2011. Net sediment N₂ fluxes/net sediment denitrification rates were determined by membrane inlet mass spectrometry and the N₂/Ar technique. A suite of parameters known to influence denitrification were also measured.

Results and discussion

Net denitrification rates ranged between 28.2?±?18.2 and 674.3?±?314.5 μmol N₂–N?m^–2?h^–1 for the streams, 23.7?±?23.9 and 121.2?±?38.7 μmol N₂–N?m^–2?h^–1 for the ponds, and 41.8?±?17.7 and 239.3?±?49.8 μmol N₂–N?m^–2?h^–1 for the reservoir. The mean net denitrification rate of the stream sites (173.2?±?248.4 μmol N₂–N?m^–2?h^–1) was significantly higher (p?<?0.001) than that of the pond sites (48.3?±?44.5 μmol N₂–N?m^–2?h^–1), and the three types of waterways all had significantly higher (p?<?0.01) mean net denitrification rates in summer than in other seasons. Linear regression and linear mixed effect model analysis showed that nitrate (NO₃ ^?–N) concentration in surface water was the primary controlling factor for net sediment denitrification, followed by water temperature. Using monitoring data on NO₃ ^?–N concentrations and temperature of the surface water of waterways and an established linear mixed effect model, total N removed through net sediment denitrification in the pond–stream–reservoir continuum was estimated at 46.8?±?24.0 t?year^–1 from July 2007 to June 2009, which was comparable with earlier estimates based on the mass balance method (34.3?±?12.7 t?year^–1), and accounted for 83.4 % of the total aquatic N. However, the total aquatic N was only 4.4 % of the total N input to the watershed, and thus most of the surplus N in the watershed was likely to be either denitrified or stored in soil.

Conclusions

High doses of N in a rice-paddy-dominated watershed did not lead to high stream N concentrations due to limited input of N into waterways and the high efficiency of waterways in removing N through denitrification.     

天津半干旱地区不同种植年限菜田土壤微生物变化特征的研究

对天津周边半干旱地区不同种植年限的菜田土壤微生物状况调查研究表明 ,该地区土壤微生物以细菌为主 ,夏季微生物总量大大高于冬季 ;随着种菜年限的增加 ,耕层和亚耕层微生物总量都有增加趋势 ,其中细菌和放线菌增加明显 ,真菌有下降趋势 ;真菌类群分析表明 ,少数纤维素分解菌 ,如青霉 (Penicillium)、木霉 (Trichoderma)等为优势菌 ,而糖和木质素分解菌仅占少数。用尖孢镰刀霉 (Fusariumuoxysporum)、大肠杆菌 (Escherichia coli)接种不同种菜年限土壤 ,检测土壤拮抗菌状况发现 ,拮抗菌仅在种植年限长的老菜田的放线菌中发现。表明北方半干旱地区菜田土壤细菌为优势菌 ,主要存在于土壤微孔隙中 ;而适于生活在土壤疏松大孔隙中的真菌数量极少。应注意土壤结构的改良 ,为丰富土壤微生物提供良好的生态环境     

天津半干旱地区不同种植年限菜田土壤微生物变化特征的研究

对天津周边半干旱地区不同种植年限的菜田土壤微生物状况调查研究表明 ,该地区土壤微生物以细菌为主 ,夏季微生物总量大大高于冬季 ;随着种菜年限的增加 ,耕层和亚耕层微生物总量都有增加趋势 ,其中细菌和放线菌增加明显 ,真菌有下降趋势 ;真菌类群分析表明 ,少数纤维素分解菌 ,如青霉 (Penicillium)、木霉 (Trichoderma)等为优势菌 ,而糖和木质素分解菌仅占少数。用尖孢镰刀霉 (Fusariumuoxysporum)、大肠杆菌 (Escherichia coli)接种不同种菜年限土壤 ,检测土壤拮抗菌状况发现 ,拮抗菌仅在种植年限长的老菜田的放线菌中发现。表明北方半干旱地区菜田土壤细菌为优势菌 ,主要存在于土壤微孔隙中 ;而适于生活在土壤疏松大孔隙中的真菌数量极少。应注意土壤结构的改良 ,为丰富土壤微生物提供良好的生态环境     

Trends in soil science in Switzerland

Phytoremediation is an emerging technology based on the use of green plants to remove, contain, inactivate or destroy harmful environmental pollutants. Recent developments in Europe and the USA show that the approach is somewhat different on both sides of the Atlantic. In Europe, phytoremediation has more basically been research driven and, based on the outcomes, applications have been envisaged. By contrast, the approach in the USA is more application and experience driven. In spite of a growing track record of commercial success, more demonstration projects are needed to prove that phytoremediation is effective in order to rigorously measure its underlying economics, and to expand its applications. More fundamental research is also required to better understand the complex interactions between pollutants, soil, plant roots and micro-organisms at the rhizosphere level, to increase the bioavailability of pollutants, to fully exploit the metabolic diversity of plants and, thus, to successfully implement this new green technology.     

沈阳市城市表土中微生物区系变化的初步研究

在沈阳市远郊-近郊-市区等不同城市化水平区内选取林地、草地和路边土几种不同利用方式下的表层土壤,对土壤中的微生物状况进行了初步分析。结果表明,随着城市化水平的提高,土壤中微生物的数量表现为明显的减少趋势。其中变化较大的是细菌,而真菌和放线菌的变化不明显。     

Changes in proteolytic bacteria in paddy soils in response to organic management

Proteolytic bacterial communities, which mineralize organic nitrogen, play a key role in agricultural systems. In this study, alkaline metalloprotease (apr) gene fragments from proteolytic bacteria were investigated in bulk and rhizosphere paddy soil from four fields under organic management (for 2, 3, 5, and 9 years), and from one field under conventional management (for 2 years). We analyzed the abundance and structure of the proteolytic bacterial communities using real-time quantitative PCR and denaturing gradient gel electrophoresis. Our results showed that the abundance of proteolytic bacteria ranged from 1.57?×?10⁸ to 8.02?×?10⁸?copies/g of soil. In addition, the abundance of the proteolytic bacteria in the paddy soils under organic management was significantly higher than those in the paddy soil under conventional management. Moreover, the gene copy numbers in the rhizosphere soils were significantly higher than those in the bulk soils. The abundance of proteolytic bacteria tended to increase with the duration of organic management, with the highest abundance being found in the soil that had been under organic management for 5 years. However, the proteolytic bacteria communities in the paddy soils were not significantly affected by management practices. Phylogeny analysis showed that all gel bands obtained represented genes from Pseudomonas. Additionally, correlation analysis and canonical correspondence analysis showed that C/N, C, and N were important factors that influenced the abundance and community structure of the proteolytic bacteria. These results suggest that proteolytic bacteria are indicators in organic management systems, depolymerize organic N and hence maintain soil sustainability.

Abbreviations: CM: conventional management; OM: organic management; DGGE: denaturing gradient gel electrophoresis; qPCR: real-time quantitative PCR detecting system; COFCC: China organic food certification center; CCA: canonical correspondence analysis