Effects of forest fragmentation on avian breeding activity

Biodiversity declines and ecosystem decay follow forest fragmentation; initially, abundant species may become rare or be extirpated. Underlying mechanisms behind delayed extirpation of certain species following forest fragmentation are unknown. Species declines may be attributed to an inadequate number of breeding adults required to replace the population or decreased juvenile survival rate due to reduced recruitment or increased nest predation pressures. We used 10 years of avian banding data, 5 years before and 4 years after fragment isolation, from the Biological Dynamics of Forest Fragments Project, carried out near Manaus, Brazil, to investigate the breeding activity hypothesis that there is less breeding activity and fewer young after relative to before fragment isolation. We compared the capture rates of active breeding and young birds in 3 forest types (primary forest, fragment before isolation, and fragment after isolation) and the proportion of active breeding and young birds with all birds in each unique fragment type before and after isolation. We grouped all bird species by diet (insectivore or frugivore) and nesting strategy (open cup, cavity, or enclosed) to allow further comparisons among forest types. We found support for the breeding activity hypothesis in insectivorous and frugivorous birds (effect sizes 0.45 and 0.53, respectively) and in birds with open-cup and enclosed nesting strategies (effect sizes 0.56 and 0.44, respectively) such that on average there were more breeding birds in fragments before isolation relative to after isolation. A larger proportion of birds in the community were actively breeding before fragment isolation (72%) than after fragment isolation (11%). Unexpectedly, there was no significant decrease in the number of young birds after fragment isolation, although sample sizes for young were small (n = 43). This may have been due to sustained immigration of young birds to fragments after isolation. Together, our results provide some of the strongest evidence to date that avian breeding activity decreases in response to fragment isolation, which could be a fundamental mechanism contributing to ecosystem decay.     

灭蝇胺及其代谢物三聚氰胺在银耳及银耳培养料中的消解和残留

为了研究灭蝇胺在银耳及银耳培养料中的降解残留规律,建立了同时测定银耳、银耳培养料中灭蝇胺和三聚氰胺残留量的高效液相色谱法,测得灭蝇胺在银耳和银耳培养料中的平均回收率为81.9%—95.5%,三聚氰胺在银耳和银耳培养料中的平均回收率为80.8%—98.6%,相对标准偏差(RSD)均低于9.0%.田间试验结果表明,灭蝇胺在降解过程中可转化为三聚氰胺;灭蝇胺和三聚氰胺在银耳培养料中的降解半衰期分别为5.5 d、34.9 d;推荐剂量低浓度直接对银耳子实体施药,灭蝇胺在银耳中的降解半衰期为5.3 d,银耳采收时灭蝇胺的残留量为0.39 mg.kg-1,三聚氰胺的残留量为0.32 mg.kg-1;菌袋扩穴后按推荐剂量高浓度对菌袋施药,灭蝇胺在银耳中的降解半衰期为5.6 d,银耳采收时灭蝇胺残留量别为0.14 mg.kg-1,三聚氰胺的残留量为0.15 mg.kg-1.两种施药方式,银耳中三聚氰胺的残留量均符合我国残留限量的要求,灭蝇胺的残留量符合日本肯定列表制度要求.     

Land use and land cover dynamics in the Keleta watershed,Awash River basin,Ethiopia

Unprecedented pace and magnitude of land use/land cover (LULC) change in the Ethiopian highlands is a key problem threatening the natural ecosystem and creates vulnerability to an environmental hazard. A combination of remote sensing, field observations and focus group discussions were used to analyze the dynamics and drivers of LULC change from 1985 to 2011 in the Keleta watershed, Ethiopia. Supervised image classification was used to map LULC classes. Focus group discussions and ranking were used to explain the drivers and causes linked to the changes. The result showed rapid expansion of farmland and settlement (36%), shrublands cover shrinking by 50%, while the size of degraded land increased by 45%. Rapid population growth, rainfall variability and soil fertility decline, lack of fuelwood and shortage of cultivation land were ranked as the main causes of LULC change in the watershed according to the focus group discussion. Further effort is needed to improve the creation of new job opportunity, promotion of improved technologies to boost productivity and soil fertility, provide credit facility, extra push on irrigation infrastructure development and soil, water and natural ecosystem conservation practices. Generally, better community-based land resource management will need to ensure sustainable rural livelihoods.     

煤矿灾害预警影响因素仿真分析

针对煤矿灾害预警过程存在的问题,首先运用解释结构模型分析各影响因素之间的相互关系,其次运用系统动力学原理和方法,对影响煤矿灾害预警的各因素进行动态仿真,对比分析各因素水平增加量对预警水平的影响程度,得出灾害预警中不同因素对预警水平的实际作用率。仿真结果有助于煤矿采取针对性的预警管理措施,同时为煤矿安全管理决策提供一个新的思路。     

普光高含硫气田集输管道冲蚀规律及预测模型研究

基于灰色关联分析方法,根据集输管道在线腐蚀监测数据,采用剪切应力表征湍流两相流动对管道内壁的冲刷作用,以湍流强度表征湍流传质强化对腐蚀的影响程度,同时集成普光气田集输管道室内静态腐蚀实验数据,建立了普光气田集输管道动态腐蚀预测模型,为普光气田集输系统腐蚀监测及安全管理提供了依据。     

不同pH的柠檬酸对茶园土壤溶出液中氟组分变化的影响

通过连续流动搅拌法,研究了不同pH的柠檬酸对茶园土壤溶出液中氟组分变化的影响.结果表明,土壤溶出液的pH随溶出时间的延长而逐渐减小.土壤溶出液中的游离态氟和总氟的浓度随时间的延长和柠檬酸pH的升高而逐渐减小,且呈现初始(0—6h)溶出浓度较高,而后(6—10h)逐渐减缓的趋势.土壤氟的溶出过程用一级动力学方程、Elovich方程、扩散方程和双常数方程均有较好的拟合,决定系数(R2)均大于0.90.低pH(pH3.5)条件下,F主要以H-F形态存在,随着pH的升高(pH4.0—5.0),H-F形态的氟减小,Al-F络合态的氟增多,且随时间延长,溶出浓度均降低.反应开始的前1h,Al-F络合物主要以AlF3为主,占氟溶出总量的90%以上;至7h时,AlF+2的溶出量逐渐增大,并逐渐超过AlF3.低pH的柠檬酸促进土壤游离态氟和总氟的溶出,有利于络合态氟的形成,但对Al-F络合物的形态转化没有显著影响.     

施肥与不施肥措施下小麦田的CO2、CH4、N2O排放日变化特征

二氧化碳（CO2）、甲烷（CH4）、氧化亚氮（N2O）是对全球气候变化影响最大的温室气体。由于土壤与大气之间的水热交换需要一定的传导平衡时间,因此土壤温室气体与温湿度之间的关系存在不同的表现形式。目前,有关温室气体研究多集中于季节性排放特征,而关于CO2、CH4、N2O的日变化研究却少见报道。以北京小麦（Triticum aestivuml）农田土壤为研究对象,对施肥和不施肥条件下CO2、CH4、N2O交换通量和气温、土壤温度进行连续观测,来探讨3种温室气体的日变化特征。采用人工静态暗箱法对小麦田土壤进行连续48 h原位观测,每2 h测定1次,每次盖箱时间为30 min。气体样品中的CO2、CH4、N2O用气相色谱仪（Agilent 6890A,FID/ECD）测定。结果表明：施肥与不施肥条件下小麦生育后期麦田土壤CO2、CH4、N2O交换通量具有明显的日变化特征。土壤表现为CH4的吸收汇、CO2和N2O的排放源。CH4的吸收通量、CO2和N2O的排放通量均表现为施肥区＞对照区。CO2、CH4的交换通量的70%以上出现在白天,而施肥区和对照区的N2O白天排放通量分别达到全天的81.8%、91.1%。另外,相关性分析表明,CO2、N2O交换通量的日变化与气温和5 cm地温呈极显著（P＜0.01）或显著（P＜0.05）的正相关关系,且N2O交换通量日变化与10 cm地温呈现极显著的正相关关系,说明温度是影响CO2、N2O交换通量日变化的重要因素;而气温、5 cm地温、10 cm地温对CH4交换通量日变化不存在显著性影响。     

一稻两鸭共作对稻田土壤养分动态的影响

鸭稻共作是有效减少化肥和农药施用的重要技术,对稻田土壤养分消耗具有一定的缓冲和调控作用。但在鸭稻共作有机生产模式中,外源性化肥投入的缺乏常常成为水稻高产的限制因素。为更好地解决有机种植中土壤养分供应的问题,对常规鸭稻共作进行了调整,建立了2种＂一稻两鸭＂共作生态农业模式。通过田间试验对常规稻作、常规鸭稻共作、一稻两鸭轮养及一稻两鸭套养4种种植模式下的土壤养分进行定位监测。结果表明：相对于常规稻作,3种鸭稻共作模式均能在一定程度上提高土壤全钾、全氮的含量,同时减小碱解氮的消耗。与比生产前期相比,生产结束后常规水稻种植模式下土壤有机质含量有所下降,而3种鸭稻共作模式下土壤有机质含量比生产前期均有不同程度的增加。4种种植模式下土壤全磷含量在生产结束后均有不同程度的下降,然而一稻两鸭套养和一稻两鸭轮养模式下土壤全磷含量的降低程度低于常规稻作。早稻生产结束后,一稻两鸭套养和一稻两鸭轮养模式下的土壤全磷含量比常规稻作分别高出13.53%和11.01%。与常规鸭稻共作模式相比,一稻两鸭轮养和套养模式增加了全氮以及全钾有机物的积累,同时减缓了碱解氮、速效磷、速效钾含量的下降。晚稻生产结束后,一稻两鸭套养模式下土壤碱解氮、速效磷和速效钾的含量分别比常规鸭稻共作模式高出3.7%,10.39%和7.59%。产量测定结果表明,早稻时期一稻两鸭套养模式下的水稻产量比常规鸭稻共作模式高12.90%,晚稻时期则比常规鸭稻共作高12.19%。一稻两鸭共作模式中,由于两批鸭子的存在,其排便和中耕作用几乎贯穿于水稻的整个生长发育过程,因此培肥效果与常规鸭稻共作相比有了进一步的提高,对系统内的养分循环利用起到了更好的促进作用。     

林地的水分动态及其对树木生长的影响——以香桂（Cinnamomum subavenium）人工林为例

土地利用变化引起的水分条件变化反过来又会影响植被的生长,然而,森林-水分-植物生长之间相互作用关系的研究还很少。以香桂（Cinnamomum subavenium）人工林为例,在盐亭生态试验站开展观测,研究了无枯落物林地（FB）、有枯落物林地（FL）和裸地（BL）的水分动态（土壤水分、径流组成和径流量）,比较了FB和FL样地树木高、基径、叶面积、比叶面积（SLA）、地上和地下生物量。研究结果表明：①FL样地的土壤含水量最高,其次是FB样地,而BL样地的土壤含水量最低;②地上径流展现了与土壤水分相反的趋势（FLFB〉BL）,3个样地的总径流量则没有表现出一个明确的大小关系。在观测期间,BL、FB和FL的地表径流量分别为284.68、222.93和68.98cm,地下径流分别为57.83、134.00和289.52 cm,总径流量依次为343.16、356.93和358.35 cm;③在观测早期,FL样地和FB样地植物形态学特征、SLA以及地上和地下生物量均没有显著差异（p〉0.05）。在观测期末,虽然两个样地的基径和SLA无显著差异,然而其他指标差异极显著（p〈0.005）。在观测末期,除SLA外,FL样地植物的高、基径、叶面积、地上生物量和地下生物量分别高于FB样地,表明该样地植物生长条件更好。这些结果表明森林改善了自身的水分环境,而水分环境的改善又反过来促进了森林的生长,森林植被-水分条件的这种相互促进作用是森林系统生存策略的一种表现。