追肥时间对小麦拔节-成熟期氧化亚氮排放的影响

2007～2008年采用3种追肥时间(雨前追肥、雨时追肥和雨后追肥)进行田间试验,观测小麦拔节-成熟期N2O排放,以探讨追肥时间对麦季N2O排放的影响。结果表明,与雨前追肥和雨时追肥相比,雨后追肥小麦拔节-成熟期N2O排放量分别减少37%～67%和22%～46%。各处理小麦产量无显著差异(p>0.05)。土壤水分含量是影响小麦拔节-成熟期N2O排放的关键因素。雨后趁墒追肥能显著减少小麦拔节-成熟期N2O排放且不影响小麦产量,是较为合理的追肥方式。     

耕作措施对华北地区冬小麦田N2O排放的影响

为研究不同耕作措施对冬小麦田N2O排放的影响以及探明N2O排放季节性波动的原因,该研究选取河北栾城县中国科学院农业生态系统试验站不同耕作处理下冬小麦田为研究对象,利用静态箱法测定翻耕秸秆还田（CT）、旋耕秸秆还田（RT）和免耕秸秆还田（NT）下冬小麦田N2O的排放。结果表明,耕作初期72 h翻耕、旋耕及免耕处理N2O排放总量分别为3.83、10.27、10.55 mg/m2。秸秆还田条件下,不同耕作措施冬小麦田N2O季节排放总量为：CT＞RT＞NT。CT、NT处理下N2O排放通量与0～20 cm各层次土壤温度呈极显著正相关。CT、NT处理表层0～5 cm土壤N2O排放通量与土壤充气孔隙度显著性负相关。NT处理土壤具有较高的C/N比,可能有利于减少N2O的排放。因此,华北冬小麦田采用NT能有效减少N2O排放。     

淮北平原四种土地利用类型非生长季土壤呼吸速率

为了探讨杨树人工林撂荒地、农耕地、农林复合模式的林地和农林复合小麦地的4种土地利用方式对温室气体CO2增长及其通量的影响,利用Licor-8100土壤碳通量测定系统对以上4种不同土地利用的土壤呼吸速率变化进行了研究。结果表明：4种土地利用类型的土壤呼吸速率在非生长季冬季的月内变化和日变化不明显,都保持在低的CO2释放水平;不同土地利用类型土壤呼吸速率表现出明显的空间异质性;农林复合小麦地土壤呼吸速率在非生长季与其影响因素的关系在2009年12月份的关系不明显,2010年1月份和2月份随着气温的升高,土壤呼吸速率与温度的相关性逐渐增大,与其他因子的相关性也变大,但增加的幅度较小;4种土地利用类型中,农林复合冬小麦地的CO2平均通量为最小,CO2的释放量比例最小,为22.55%,比农田小麦地、撂荒地和农林复合隔离带林地分别减少3.02%、0.85%和6.00%的CO2释放。农林复合模式的CO2释放量比农田小麦地多释放2.85%,与人工林撂荒地的土壤呼吸速率相同。     

Effect of heat stress on endotoxin flux across mesenteric-drained and portal-drained viscera of dairy goat

This study was designed to evaluate the effect of heat stress on endotoxin flux across mesenteric-drained and portal-drained viscera of dairy goats. Three Saanen first lactation dairy goats were surgically fitted with indwelling catheters in the portal vein, the mesenteric vein and carotid, and were kept in thermal-neutral and then heat stress environment, for examining the effect of heat stress on endotoxin absorption and redox status. Average net absorption of endotoxin (EU/h) across mesenteric-drained viscera (MDV) and portal-drained viscera (PDV) during the whole period of heat stress increased by 279.05% and 227.92% in relation to thermo-neutral period. Plasma concentration of glutathione peroxidase (GSH-Px) and catalase (CAT) in mesenteric and portal vein, and that of superoxide dismutase (SOD) in mesenteric vein, increased significantly during heat stress. Main conclusions were: (i) net absorption of endotoxin in portal vein is mainly from non-mesenteric tissues both in heat stress and in thermo-neutral condition; (ii) heat stress may lead to the significant decrease in plasma SOD, GSH-Px, CAT flux across PDV and MDV, and the significant increase in endotoxin flux across PDV and MDV; and (iii) the increase in gastrointestinal permeability in dairy goats during heat stress may not be induced by the increase in oxidative stress.     

草地生态系统温室气体排放机理及影响因素

草地生态系统是陆地生态系统的主体,已成为人类活动影响较为严重的陆地生态系统之一,其温室气体排放对全球气候变化具重要影响.本研究综述了草地生态系统中主要温室气体CO2、CH4和N2O的排放机理和主要影响因素的研究进展,指出草地生态系统温室气体排放的不确定性是环境、生物和管理因素共同作用的结果.应加强草地生态系统温室气体产...     

高寒退化草地恢复中种子包衣对土壤微生物和植株生长的影响

本研究采用微藻粉末和植物性吸水材料包衣处理两种牧草种子,并接种微生物孢子,观察植株生长和土壤微生物的呼吸量。结果表明,种子包衣并接种孢子时,两种牧草的干物质量（P<0.01）、豆科牧草的根瘤数（P<0.05）和土壤微生物呼吸量（P<0.05）均显著高于对照;植株的干物质量与土壤呼吸量之间呈极显著的正相关（P<0.001）;豆科牧草根瘤数与土壤呼吸量之间也呈极显著的正相关(P<0.001）。植株收获后,在各种处理的土壤上再播种未经过包衣和孢子处理的种子,其植株的干物质量、根瘤数和土壤微生物呼吸量均与第1茬植株有同样的变化趋势。种子包衣和接种微生物,为土壤微生物提供生长所需的条件,提高了土壤微生物的活性,促进了植物生长,土壤微生物活性的提高效应是可延续的。     

秸秆覆盖对鸡舍氨气排放和环境恶臭影响效果研究

本研究观察了利用秸秆覆盖对鸡舍氨气排放以及舍内环境恶臭影响效果.包括2个试验:试验一为实验室模拟,试验二为鸡舍现场测试.试验一分为11个组,鸡粪为对照组,另外分别选取不同类型秸秆材料覆盖鸡粪表面作为处理组,定期测定鸡粪氨气质量浓度,连续6d.结果表明,采用秸秆材料覆盖后各组氨气质量浓度均显著下降(P<0.05),尤其在覆盖初期.从全程来看,经过覆盖后氨气质量浓度始终保持在26mg/m3以下的组为麦秸末组,其次为玉米秸秆末组等.试验二选择在两栋建筑类型一致的肉鸡舍进行,网上平养,每舍3900只9日龄肉鸡.试验鸡舍网下地面采用不清粪、每两天覆盖一薄层玉米秸秆方式,而对照组鸡舍采用每两天清一次粪、不覆盖方式,试验开始两舍环境温度保持在33～35℃,之后连续对比测定环境指标9 d.结果表明,单独秸秆覆盖第1～4天试验鸡舍NH3和CO2质量浓度总体趋势低于对照组鸡舍(P>0.05);第5天开始利用秸秆覆盖并且辅助喷洒微生态茵液,试验组鸡舍NH3和CO2质量浓度与对照组鸡舍相比差异仍不显著(P>0.05),但均低于国家规定的26mg/m3标准.说明现场采用秸秆覆盖鸡粪方式来减少鸡舍氨气排放和环境影响效果,还受到多种因素的影响有待今后进一步深入研究.     

Temperature and photoperiod control of morphology and flowering time in two greenhouse grown Hydrangea macrophylla cultivars

Knowledge of the factors involved, and tools to control morphology and flowering are important in intensive and cost-efficient greenhouse production. Hydrangea macrophylla is an important flowering pot plant in Norway and is produced year-around in greenhouses. Due to problems in scheduling, a study was conducted to compare floral transition and morphology of two commercially important cultivars of Hydrangea (‘Early Blue’ and ‘Schneeball’) under different flower initiating treatments in growth chambers. Plants were grown with high pressure sodium lamps (HPS) at moderate temperature (17 °C) (MT) and high (24 °C) temperature. At high temperature, the effect of (1) irradiance under long day conditions (16 h lighting with 70 or 200 μmol m⁻² s⁻¹), and (2) short day (8 h lighting) was investigated. The short day treatment had similar light integral as the low irradiance long day treatment (SD: 8 h × 140 μmol m⁻² s⁻¹ and LD: 16 h × 70 μmol m⁻² s⁻¹ = 4.0 mol m⁻² d⁻¹). The intention was to test the effect of irradiance and SD on flower transition and morphology under high temperatures. The results clearly showed that MT is the strongest signal for floral transition. MT resulted in a rapid floral transition of the terminal buds and lateral flower buds. A short forcing period was required and the plants became short and compact without any use of chemical growth retardants. At high temperatures only SD had a promotive effect on flower transition and the response was found to be stronger in ‘Schneeball’ than ‘Early Blue’. In general, all the treatments under high temperatures required a long forcing time and the plants tended to be very tall with a low number of lateral flower buds.     

Energy partitioning and evapotranspiration of hot pepper grown in greenhouse with furrow and drip irrigation methods

Studying crop energy partitioning and evapotranspiration for different irrigation methods is important in optimizing efficient water-saving irrigation, developing suitable irrigation scheduling and improving crop water use efficiency. Two experiments were conducted to compare the energy partitioning and evapotranspiration of hot pepper (Capsicum annum L.) between furrow and drip irrigation methods under two adjacent solar greenhouses in northwest China. Results indicate that irrigation method affected the energy partitioning and evapotranspiration of hot pepper plants and these results were corroborated in a greenhouse study. Compared to drip irrigation, furrow irrigation increased daytime average net radiation (R_n), latent (λET) and sensible (H) heat fluxes by 12–29, 37–53 and 9–23%, respectively, but decreased soil heat flux (G) by 7–19%. Furrow irrigation also resulted in higher λET/R_n and lower H/R_n and G/R_n and increased total evapotranspiration by 55.5% and produced a higher crop coefficient. Total evapotranspiration was 562.3 and 361.6 mm over whole growth stage for furrow and drip irrigation methods, respectively. And drip irrigation increased the total yield and water use efficiency by 18.2 and 80.4%, respectively, before late fruit bearing and harvesting stage. In conclusion, drip irrigation is an effective and water-saving irrigation method in hot pepper production to be used in greenhouse.     

北方城市行道树电导率变化的研究

以北方城市常见行道树为试材,研究其不同部位电导率变化情况。结果表明:行道树的树皮和树叶电导率明显不同,在不同采样区也存在较大差异,多数行道树的树皮和树叶电导率在不同采样区间呈现PA>PB>PC的规律性变化;同一树种在不同路段的树皮电导率值与道路车流量变化呈正相关。