高复种指数区成都市郫都区农田土壤养分特征及其空间变异研究

成都平原属典型的水田农业区,复种指数高,农作物一年两熟或三熟。为探究高土地利用率地区农田土壤养分特征及其空间分布格局,基于成都市郫都区2015年测土配方施肥数据,运用经典统计学和地统计学方法揭示该区域农田土壤养分的描述性统计特征及其空间变异。结果显示:郫都区农田土壤有机质(SOM)、总氮(TN)、碱解氮(AN)、速效磷(AP)、速效钾(AK)含量均值分别为22.35 g·kg^-1、1.15 g·kg^-1、95.38 mg·kg^-1、21.01 mg·kg^-1和104.58 mg·kg^-1,不同土壤类型及不同种植模式农田土壤养分差异总体较小,表明高强度的人类活动使郫都区土壤养分含量变得均一;半方差分析显示,SOM和AK的块金系数分别为0.39和0.62,其空间变异由土壤母质、地形、气候条件等结构性因素和耕作制度、施肥条件等随机性因素共同作用引起;TN、AN和AP的块金系数分别为0.87、0.94和0.97,其空间变异性主要受耕作制度、施肥条件等随机性因素影响;结合已有研究来看,郫都区农田SOM块金系数呈下降趋势而TN、AN和AP块金系数呈增加趋势,表明随着郫都区作物产量与作物复种指数的不断提高,以蔬菜为主的旱作模式代替传统的水旱轮作模式、复合肥代替农家肥等生产方式的改变正在影响着郫都区农田土壤养分的空间分布格局。     

快速城市化地区生态网络构建与优化——以北京市大兴区为例

快速城市化直接导致生境日益破碎化,景观连通性和生态系统稳定性降低,环境不断恶化。构建完善的生态网络能够有效缓解快速城市化带来的系列生态环境问题,是城市生态系统修复、生物多样性保护的重要途径。以北京市大兴区为例,基于2019年6-8月高分辨率遥感影像分类解译提取的土地覆盖数据,应用形态学空间格局分析(MSPA)和景观连通性评价方法识别提取了生态源地,通过构建生态阻力面和运用最小累积阻力模型(MCR)识别了潜在生态廊道并应用重力模型对廊道系统进行了重要性分级,最后采用网络指数对研究区生态网络进行评价和优化,提出了有针对性的生态网络优化对策。结果表明:研究区核心区面积为349.42km²,占研究区总面积的33.73%;生态源地16块,总面积85.15km²,占总面积的8.2%;潜在生态廊道120条、生态节点49个,其中一级生态廊道39条、二级生态廊道81条。在生态网络优化方面,新增4块生态源地、70条规划生态廊道和17个生态节点,规划建设20处"踏脚石",识别修复72个主要生态断裂点。实施这些优化措施后,网络闭合(α)指数、点线率(β)指数、网络连接度(γ)指数均有所提高,表明生态网络连接度得到有效优化。研究区虽具备较丰富的绿地资源,但在快速城市化过程中出现了生态斑块破碎化、分布不均衡、连通性较差等生态问题,生态源地和廊道主要分布在西部、南部永定河流域绿地以及东南部平原造林区,应重点加强研究区中北部的生态建设与修复。生态网络的构建与优化对于该区域生态系统修复、生物多样性保护具有重要意义,也可为其他快速城市化地区生态建设与优化修复、生态空间可持续发展提供参考借鉴。     

北京市密云区乡村生态旅游价值评估

乡村生态旅游价值作为乡村生态产品价值的重要组成部分，合理的评估是建立健全生态产品价值实现机制，践行"绿水青山就是金山银山"的必由之路，同时能为找准乡村振兴着力点，促进乡村经济可持续发展提供决策支持。将北京市密云区乡村生态旅游的研究对象分为民宿酒店、观光园与农家饭店三类，应用旅行费用法(TCM)进行区域旅游价值评估。结果表明：密云区游客客源以北京市为主，导致TCM的分区旅行费用法(ZTCM)中各分区样本量差异过大，而费用分区法(TCIA)克服了此问题，同时与个人旅行费用法(ITCM)相比受个体偏差的影响较小，所以评估结果更合理；TCIA法评估的密云区乡村生态旅游的总价值为42.45亿元，其中费用成本为11.24亿元，时间成本为15.17亿元，剩余价值为16.04亿元。     

Madagascar Fish Eagle productivity in the Tsimembo-Manambolomaty Protected Area and surrounding habitat of western Madagascar

We monitored the productivity of the critically endangered Madagascar Fish Eagle Haliaeetus vociferoides inside and outside of the Tsimembo-Manambolomaty Protected Area (T-M PA), western Madagascar from 2010 to 2015. We recorded 14 breeding pairs inside and 13 outside T-M PA. The T-M PA and surrounding habitat hosted respectively 10 and six breeding polyandrous pairs, composed of one adult female and two adult males. During the six-year study period, 101 eggs were laid in nests in T-M PA of which 60 hatched and 58 young fledged. We recorded 62 eggs laid in nests outside the T-M PA of which 39 hatched and 36 young fledged. Productivity was similar at both sites, inside and outside T-M PA, with 0.84 (58/69) and 0.76 (36/47) fledgling per nesting attempt and 0.69 (58/84) and 0.5 (36/72) fledglings per territorial pair, respectively. Polyandrous pairs have higher productivity compared with normal pairs. Threats to Madagascar Fish Eagles and their habitat were low due to the existence of a community-based resource management system called the Local Management Secured System (GELOSE) inside and outside the T-M PA. This system is based on strengthening local traditional customs and rules, and involving local people in managing their natural resources sustainably along with biodiversity conservation.     

Structural and biochemical insights into the substrate-binding mechanism of a novel glycoside hydrolase family 134 β-mannanase

Mannan is one of the major constituent groups of hemicellulose, which is a renewable resource from higher plants. β-Mannanases are enzymes capable of degrading lignocellulosic biomass. Here, an endo-β-mannanase from Rhizopus microsporus (RmMan134A) was cloned and expressed. The recombinant RmMan134A showed maximal activity at pH?5.0 and 50?°C, and exhibited high specific activity towards locust bean gum (2337?U/mg). To gain insight into the substrate-binding mechanism of RmMan134A, four complex structures (RmMan134A–M3, RmMan134A-M4, RmMan134A-M5 and RmMan134A-M6) were further solved. These structures showed that there were at least seven subsites (?3 to +4) in the catalytic groove of RmMan134A. Mannose in the ?1 subsite hydrogen bonded with His113 and Tyr131, revealing a unique conformation. Lys48 and Val159 formed steric hindrance, which impedes to bond with galactose branches. In addition, the various binding modes of RmMan134A–M5 indicated that subsites ?2 to +2 are indispensable during the hydrolytic process. The structure of RmMan134A–M4 showed that mannotetrose only binds at subsites +1 to +4, and RmMan134A could therefore not hydrolyze mannan oligosaccharides with degree of polymerization ≤4. Through rational design, the specific activity and optimal conditions of RmMan134A were significantly improved. The purpose of this paper is to investigate the structure and function of fungal GH family 134 β-1,4-mannanases, and substrate-binding mechanism of GH family 134 members.     

Zoonotic and non-zoonotic helminths in black rats of rain-fed and irrigated areas of Swat,Khyber Pakhtunkhwa,Pakistan

Present study was conducted to get information on helminth parasites of zoonotic importance among the black rats of district Swat, Pakistan. Two hundred and sixty nine rats were captured from agricultural ecosystem of the district using live captured traps from 2011 to 2013. Captured rats were anesthetized and surveyed for the presence of ectoparasites, then were carefully dissected for investigation of endoparsites. Helminth parasites of 8 species were identified. Presence of parasite was noticed in 23.7% of sampled rats. The infection rates of sampled rats was given in order of their infectivity as Syphacia obvelata 13(4.83%), Aspiculuris tetraptera 13(4.83%), Heterakis spumosa 12 (4.46%), Hymenolepis spp. 9(3.34%), H.diminuta 8(2.97%), Hymenolepis fusa 4(1.48%), Lutziella microacetabularae 4(1.48%) and Lutziella spp. 1 (0.37%). No significant difference (P < 0.4289) was found in prevalence of parasites among areas, crops, crop stages and sex of the host while adult rats were found more infected than sub-adults. S. obvelata and A. tetraptera were the most common species of helminths while Lutziella sp., 1 (0.37%) was found only in one host. Rattus rattus (the black rat) was regarded as the host of helminth parasites of zoonotic importance, therefore the hidden health hazards of this rodent species needed to be considered to prevent infectivity of humans. Current study was concluded that Rattus rattus harbored a wide variety of helminth parasites which shows a hidden risk to inhabitants of the region. Monitoring rats’ population in settle areas and educating the local community about the risk of rat borne parasitic diseases transmission through rats appears to be absolutely essential.