Spatial and temporal variation of atmospheric nitrogen deposition in the North China Plain

A monitoring network of nine sites was established to determine the spatial and temporal variation of atmospheric nitrogen (N) deposition in the North China Plain (NCP) over a two-year period. The annual bulk deposition of inorganic N in the North China Plain ranged from 18.4 to 38.5 kg/hm² and averaged 28.0 kg/hm². The concentration of NH₄ -N and NO₃^--N in rainwater averaged 3.76 and 1.85 mg/L, respectively, which were significantly higher than the values at background sites in China (normally less than 0.5 mg/L). Annual bulk deposition of inorganic N in the Beijing area (32.5 kg/hm²) was higher than that in Shandong and Hebei provinces (21.2 kg/hm² on an average). Also bulk N deposition was much greater in Dongbeiwang and Fangshan than in Yanqing and Shunyi counties. Significant spatial variation of bulk deposition was observed in the Beijing area because of variation of precipitation, and 60% of bulk deposition occurred from June to September. Bulk deposition of NH₄ -N was 2.0 times that of NO₃^--N deposition at the rural monitoring sites. However, the situation was reversed at the Beijing Academy of Agricultural-Forestry Sciences (BAAFS), the unique urban monitoring site. The results suggest that reduced N in precipitation is dominant in rural regions, but oxidized N is the major form in urban regions. The positive relationship between inorganic N deposition and precipitation can be fitted by a power equation (r²= 0.67), showing an increase of NH₄ -N and NO₃^--N inputs with increased precipitation. Wet deposition of N accounted for 73% of the bulk deposition, implying that dry deposition of N, particularly NH₄ -N from dust, is important in the North China Plain.     

Multichannel automated chamber system for continuous monitoring of CO2 exchange between the agro-ecosystem or soil and the atmosphere

A multichannel automated chamber system was developed for continuous monitoring of CO₂ exchange at multiple points between agro-ecosystem or soil and atmosphere. This system consisted of an automated chamber subsystem with a CO₂ concentration analyzer and a data logging subsystem. Both subsystems were under the control of a programmable logic controller (PLC). The automated chamber subsystem contained 18 chambers (50 cm × 50 cm × 50 cm) and a compressor. The chamber lids were closed and can be automatically opened. During measurement, one of the 18 chambers was kept closed for three minutes for measuring and the other chambers were kept open to maintain the natural soil conditions to the maximum extent. Environmental variables were simultaneously measured using sensors and recorded by the data logger. The reliability of the multichannel automated chamber system was tested and the results showed that the turbulence of the fans had no significant effect on the CO₂ exchange. The changes in the air and the temperature of soil and soil moisture inside the chambers, caused by the enclosure of the chambers, were not significant. The net ecosystem CO₂ exchange for the wheat ecosystem was ?2.35 μmol·m^?2·s^>?1 and the soil respiration was 3.87 μmol·m^?2·s^>?1 in the wheat field, and 6.61 μmol·m^?2·s^>?1 in the apple orchard.     

云南澜沧景迈古茶园生态系统植物多样性评价

云南澜沧县境内的景迈古茶园是云南省现存面积最大的古茶园.本文应用植物学样地调查和农业生物多样性调查评价(HH-ABA)方法,在景迈古茶园内设置了78个20 m×20 m的样方,对植物多样性进行调查,并就古茶园的管理及资源利用等问题进行了问卷调查和农户访谈.研究结果表明,景迈芒景地区植物地理成分的热带性明显.在景迈古茶园中发现的珍稀濒危保护植物达15种,其中濒危种5个,易危种7个,稀有种3个,含国家三级保护植物11种.从古茶园、天然林、新式茶园3类生态系统的物种多样性分析来看,古茶园与天然林较为接近而比新式茶园高得多,因而在该区生物多样性的维护上起着非常重要的作用.古茶园的物种数按照生活型排序为草本＞乔木＞灌木＞藤本＞附生.与天然林相比,古茶园内乔木和灌木种类的比例减少,草本和附生(寄生)植物的比例大大增加,这与古茶园内乔木郁闭度及茶树的存在密切相关.农业生物多样性分析显示,不同村寨的物种丰富度和物种利用率均存在差异.6个村寨的农业物种丰富度指数的平均值为0.059,高于同纬度地区旱谷地和橡胶林,可见人们在古茶园管理中有意识地保留了可利用的物种.由于不同农户采取的管理措施不同,影响了古茶园内的植物多样性和古茶树的更新,因而使各农户的茶叶经济效益存在差别.古茶园生态系统是自然资源保护与利用相结合的典型例子,建议应当传承并发展当地人民对古茶园的管理经验,由政府、科研机构和农户共同参与,通过示范和培训加强学习指导,对古茶园进行保护和合理的开发利用.     

不同土壤培肥措施对华北高产农田原生动物丰度的影响

为了解华北高产农田生态系统中秸秆还田、有机肥和化肥投入水平等土壤培肥措施对原生动物群落丰度的影响,1999年10月~2000年9月在山东桓台冬小麦套种夏玉米的田间试验中进行了取样分析。田间处理1~处理9,依序为:全还,麦还,全还 化肥1,麦还 化肥1,全还 化肥2,麦还 化肥2,全还 化肥3,麦还 化肥3和全还 化肥1 有机肥处理。应用3级10倍环式稀释培养法对土壤中鞭毛虫、纤毛虫、肉足虫3类群原生动物的丰度进行了测定。结果显示:该研究地块肥力状况良好;土壤鞭毛虫和肉足虫占有绝大比例,分别为总丰度的39.47%和59.22%,纤毛虫仅占1.31%;土壤原生动物丰度在不同培肥处理中表现出相似的季节性动态变化特征;比较不同土壤培肥措施条件下的原生动物丰度水平为:全还>麦还,全还 化肥1 有机肥>麦还 化肥1,麦还 化肥2,麦还 化肥3>全还 化肥1,全还 化肥2,全还 化肥3;化肥对原生动物丰度表现出明显的抑制作用,而有机肥对原生动力丰度表现出明显的促进作用。化肥的施用量水平对土壤原生动物丰度的影响无显著性差异,作物秸秆采取何种还田方式对土壤原生动物丰度的影响也是不显著的,如麦还 化肥培肥地块的原生动物丰度仅略高于全还 化肥。     

An extraction method for nematodes in decomposition studies using the minicontainer-method

The minicontainer-method is a new method developed to study biological processes related to soil litter decomposition. An adaptation of the classical Baermann-funnel technique is described which can be used, in association with the minicontainer method, to investigate the role of Nematoda in litter decomposition. The use of the extraction method is illustrated in a study of the effects of different tillage systems on the decomposition of rye straw and on the nematode density in minicontainers with different mesh sizes of 20 µm, 500 µm and 2 mm. Three tilled plots (conventional deep plough, cultivator and two-layer plough) and an untilled control were compared after periods of 4 weeks and 38 weeks. On both sample dates there were significant main effects of treatment and mesh size on the nematode density, and additionally, after 38 weeks significant treatment x soil depth interactions. After 4 weeks, there were significant main effects of treatment and soil depth on the decomposition, but no mesh size effects, whereas after 38 weeks, all experimental factors had a significant effect on the decomposition of the straw. Due to the small volume of litter substrate used in the minicontainer method, the efficiency of nematode extraction is high and the lack of oxygen in the minicontainers presents no serious problem during the extraction process. The method also allows the simultaneous extraction of a large number of samples within a short period of time. Our results indicate that the method is suitable to study the microdistribution of nematode activity within the soil profile and improves the possible applications of the minicontainer-method.     

北方农牧交错区农业生态系统生产力对气候波动的响应——以准格尔旗为例

气候变化对区域生态系统结构和功能有重大影响。以中国北方农牧交错区的准格尔旗为例,利用气象和《统计年鉴》数据,采用数理统计方法分析准格尔旗1961—2009年降水量、平均气温的波动特征,计算出该地区1961—2009年农业生态系统NPP值和主要农作物的气候产量,论述了准格尔旗农业生态系统生产力对气候波动的响应。结果表明:(1)降水量和平均气温的年际、年内波动均显著。(2)准格尔旗农业生态系统生产力呈现阶段性地波动上升趋势。排除社会、科技等影响,气候生产力对气候波动表现出较强的敏感性,是作物气候生态适应的结果。(3)中国北方雨养旱作区,粮食气候产量受降水量年际波动(特别是7、8月)显著影响;谷子、糜黍、玉米、薯类、大豆和油料等农作物的气候产量与降水量年际波动呈显著正相关;谷子、糜黍的气候产量与生长季降水量年内波动呈显著负相关。集水型生态农业是北方农牧交错区生态环境友好的农业发展模式。(4)谷子、糜黍、薯类、大豆和油料等农作物的气候产量与6、7、8月平均气温年际波动呈显著负相关;生长季平均气温年内波动对谷子、糜黍、大豆和油料等农作物的气候产量有显著负面影响。因此,需要综合采取工程、生物和农业措施,将气候变化对主要农作物气候产量的不利影响降到最低。     

区域农业生态系统健康定量评价

鉴于农业生态系统健康与人类、社会、经济、环境等具有密切的关系 ,从区域尺度出发 ,提出区域农业生态系统健康的概念、评价指标体系及其相应度量方法 ,并采用专家评判标准赋值法对各指标进行了标准量化。认为农业生态系统存在不健康、亚健康和健康 3种状态 ,在这 3种状态下各指标的属性判断值分别是 1、5和 10 ,并以山东省禹城市为例进行了实证分析应用。结果表明 :从 1980年到 2 0 0 0年 ,禹城市农业生态系统总体上表现为由不健康状态经过亚健康状态 ,目前处在向健康状态的过渡阶段 ,综合健康指数由 4上升为 6。其中 ,结构特征在由亚健康状态向健康状态过渡中又转变为亚健康状态 ,是因为资源可供性和结构多样性向不健康状态转变所致 ;生产功能特征表现为由不健康过渡为亚健康进一步向健康状态过渡 ,其中生态效率有向不健康转变的趋势 ;抗逆特征表现为由亚健康向健康过渡的趋势 ,而其中自生产力已表现为不健康状态。评价结果与实际情况基本相符     

化学除草剂对农田生态系统野生植物多样性的影响

农田生物多样性是全球生物多样性的重要组成部分, 除草剂的大量施用对其产生了严重影响。本文综述了化学除草剂对农田生态系统中野生植物多样性的影响, 并分析归纳了其影响机制。除草剂的施用会使敏感植物减少, 抗药性植物增多, 从而改变农田生态系统中的野生植物物种组成, 并使其趋同化, 降低遗传多样性和物种多样性, 以致植物功能群单一化, 群落稳定性下降。除草剂的主要影响机制是杀死植物或改变其生长代谢、抗性、繁殖等, 改变生境, 并与人为因素、环境因素等产生协同影响。不同种类的除草剂影响程度不同, 且不同物种间、不同群落间的响应也存在差异。我国化学除草剂使用量持续增长, 应加强除草剂对野生植物多样性的影响及其机制研究, 重视除草剂使用历史记录和野生植物的长期监测, 以及除草剂使用规范和相关政策法律研究, 更好地保护我国农田生态系统中的生物多样性。