山杨、水曲柳种群密度与种群性比的关系

在长白山次生杨桦林及次生针阔混交林中各建立1块5.2 hm²固定样地,于2006-2008年的4-10月观察繁殖器官（花、种子）,据此判断样地内雌雄异株树种山杨和水曲柳成熟植株的性别,研究雌雄异株树种山杨和水曲柳性比与种群密度及林分密度间的关系,并利用随机区块抽样技术,建立种群性比与取样面积、种群密度和林分密度之间的关系,通过GLM模型检验种群性比的密度依赖性。结果表明： 雌雄异株树种山杨和水曲柳雌雄植株数均随着取样面积的增大而呈线性增加; 山杨和水曲柳种群性比具有显著的密度依赖性(P<0.001),种群性比随着林分密度的增大而减小; 次生杨桦林样地中,繁殖植株密度及种群密度与山杨种群性比呈显著负相关,与水曲柳种群性比呈显著正相关,次生针阔混交林样地中,繁殖植株密度和种群密度与山杨性比呈显著正相关,与水曲柳种群性比呈显著负相关。可见,不同林型内山杨和水曲柳种群性比对繁殖植株密度及种群密度反应不同。     

农业旱涝灾害协同防治体制创新探讨

本文基于对中国农业旱涝灾害风险演变趋势的历史考察,透视中国农业旱涝防治措施失灵的现实;通过对农业旱涝防治措施失灵的制度成因分析,指出现行农业旱涝灾害防治制度造成了灾害防治行为分散、防灾投入短缺、农业脆弱性加大等问题,进而导致农业旱涝灾害成灾率居高不下;提出中国应从农业旱涝灾害防治组织体系、灾害防治投入激励机制、防灾协商机制、灾害响应体系等方面,健全农业旱涝灾害协同防治体制,为提高农业灾害防治行为的协同性与有效性提供体制保障。     

Triticale,wheat, and rye growth rates and mineral accumulation at various growth stages

Abstract

Cultivars of triticale, wheat, and rye were grown with different N‐fertilizer rates and sampled at various maturity stages in 1975 to 1977. ‘6TA 131’ triticale, ‘Arthur’ wheat, and ‘Abruzzi’ rye were used as checks. Increasing N fertilizer rates increased dry matter and N accumulation in the above‐ground plant parts. However, after flowering losses of dry matter and N from the plants increased with N fertilizer rates. Triticale and rye generally absorbed more N from the soil than wheat. Triticale and wheat straw had higher P concentrations than rye. The head/straw concentration ratios were: triticale and rye>wheat for P, wheat>triticale and rye for K while Ca and Mg ratios were triticale>wheat>rye.     

华北落叶松人工林土壤微生物数量特征及其与土壤性质的关系

对河北省木兰围场华北落叶松人工林样地的土壤微生物数量、土壤理化性质以及二者之间的相关性进行了研究,结果表明:土壤深度和林分类型均显著影响土壤理化性质,随着土壤深度的增加,基本表现为:土壤含水量和土壤养分质量分数降低,土壤密度增大,落叶松白桦混交林的土壤齐分质量分数显著高于其他样地,表明针阔混交林有利于土壤养分的循环、转...     

多酚类化合物协同抗氧化性研究进展

多酚类化合物是一种大量存在于植物体内的物质,因其具有优良的抗氧化、抗癌、抗衰老等性能而受到研究者们的广泛关注。多项研究表明具有抗氧化性能的物质之间大多具有协同作用,两种或两种以上的物质化合,其抗氧化能力往往强于单一物质的抗氧化能力。近年来,许多研究者将目光聚焦到多酚类物质与小分子物质化合所具有的协同抗氧化能力的研究上并做出多项试验。本文论述了多酚类化合物的抗氧化机理及协同抗氧化机理,并以茶多酚与维生素C、维生素E 化合为例对协同抗氧化进行论述。     

农抗120和百菌清对辣椒炭疽病菌联合毒力的测定

在室内用平皿菌落直径法测定了农抗120、百菌清及其4种不同配比的混剂对辣椒炭疽菌的菌丝抑制作用和毒力。结果表明,农抗120和百菌清对辣椒炭疽病菌EC50值是2777．2mg／L和1090．7mg／L,农抗120的毒力小于百菌清;农抗120与百菌清以4：1～8：1混配增效系数(SR)为2．04～3．93,具有显著的增效作用,其中农抗120与百菌清6：1增效系数最大,达3．93,为最佳配比;农抗120与百菌清6：1混配对9种植物病原真菌的平均抑菌率为84．4％,显著高于农抗120的75．5％和百菌清的66．0％。     

不同NFC/NDF比日粮对奶山羊瘤胃pH值动态变化的影响

试验采用动态pH值连续监测记录系统对瘤胃pH值进行24h连续监测,旨在研究不同非纤维性碳水化合物/中性洗涤纤维比(NFC/NDF比)日粮对奶山羊瘤胃pH值昼夜动态变化的影响。选用6只安装有永久性瘤胃瘘管的关中奶山羊作为试验动物,采用自身对照试验设计,分为4期,每期10d,依次饲喂NFC/NDF比分别为1.02(Ⅰ期)、1.24(Ⅱ期)、1.63(Ⅲ期)、2.58(Ⅳ期)的4种日粮。结果表明,瘤胃pH值随着日粮NFC/NDF比增加而显著降低(P<0.05),瘤胃pH值<5.2、5.5、5.8、6.0的平均持续时间亦随日粮NFC/NDF比增加而延长,分别由Ⅰ期的0、0、2.42和9.40h/d增加到Ⅳ期的0.33、7.50、17.06和20.53h/d;瘤胃pH值<5.5、5.8、6.0的曲线面积亦逐步加大,分别由Ⅰ期的0、0.21和1.43(pH·h)增加到Ⅳ期的1.09、4.84和8.59(pH·h);而且瘤胃pH值下降速率和下降幅度及最低值所持续的时间亦随日粮NFC/NDF比增加而增加。     

Balance and concentration of nitrogen and potassium affect growth and nutrient status in soilless cultivated lisianthus

Purpose: Nitrogen (N) / potassium (K) nutrient balance has been studied for some ornamental plants, however, available information is limited. Here we investigate the optimum N and K balance and concentration for lisianthus production in soilless medium.

Materials and methods: The effect of three N / K balances: 1.43, 2.14 and 4.29, prepared by varying the concentration of N and K, were evaluated in lisianthus grown in soilless medium (volcanic rock).

Results: Plants fertigated with a N / K balance of 2.14 exhibited enhanced height and stem dry weight when compared to plants fertigated with a balance of 4.29, and a higher flower buds count and total dry weight than those fertigated with a balance of 1.43 or 4.29. Plants fertigated with a balance of 2.14 exhibited increased dry weight when N was reduced from 15 to 9?meq?L^?1 and K from 7 to 4.2?meq?L^?1, suggesting that lisianthus does not require high levels of these nutrients. Although shoot N concentration was not correlated with N concentration in the nutrient solution or balance, increasing N in the shoot was associated with higher P and Mg in the plant tissues. In general, P, Ca, and Mg in plant tissues were unaffected by the external N / K balance, however, the internal P and Mg concentrations were positively correlated with shoot dry weight. Shoot K concentration significantly increased when the N / K balance decreased, which is related to the higher concentrations of external K when the balance decreased.

Conclusions: The optimum N / K balance for lisianthus was 2.14. However, there was a concentration effect, as fertigation with solutions containing a N / K balance of 2.14 and an N and K concentration of 9 and 4.2?meq?L^?1 respectively, resulted in plants with the greatest dry weight.