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991.
40种阔叶树树冠的外、中、内层同龄叶中,均以外层叶的气孔密度最高,其次为中层叶,内层叶气孔密度最低。新银合欢和马尖相思幼苗在高光照强度下所形成的叶气孔密度最高,中等光照者次之,低光照者最低。在蓝光照射下形成的叶气孔密度最高,其次为红光照射者,自然漫射光下最低。这说明光照强度和光波长对气孔密度有深刻影响。 相似文献
992.
The endemic midwife toad of Mallorca (Alytes muletensis) is restricted to a small number of breeding populations in the mountainous northwest of the island. The decline of the species has been attributed to the impacts of introduced species such as the viperine snake (Natrix maura) and green frog (Rana perezi), and toads may be surviving only in areas that are suboptimal for these predators. The influence of landscape features (elevation, aspect and maximum slope) on the distribution of toads and associated predators was therefore investigated using GIS. The presence of toads was positively associated with steep slopes. At sites where they occurred with toads, the distribution of predators was negatively associated with elevation. Reproductive success within toad populations was strongly associated with the number of pools at each site, while reproductive success within individual pools was positively associated with elevation. These findings may be used to optimise the design and location of future reintroduction sites. 相似文献
993.
Conservation value of the herbaceous vegetation in hedgerows - does organic farming make a difference? 总被引:1,自引:0,他引:1
The aim was to compare and test differences in the conservation value of hedge bottom vegetation on organic and conventional farms. The studied hedgerows (28 organic and 28 conventional) were on average 14 years old and established in the same way, except that organic hedgerows were established and managed without use of pesticides. We investigated three sample plots of 10 m2 in all hedgerows together with a set of 13 explanatory variables. There were no differences in soil texture between hedgerow types but organic farms had higher pH and lower conductivity. Organic farms had higher total N values, which are explained by a slightly higher content of organic matter. There was highly significant interaction between farming type and neighbouring crop type according to soil phosphate concentration. Significantly more plant species were found in the organic hedgerows. The species compositions in organic hedgerows appeared significantly more similar to semi-natural communities when compared with other plant communities. We conclude that organic farming is slightly superior with regard to conservation of herbaceous diversity of hedgerows in intensively cultivated agricultural landscapes. The possible reasons for this are discussed. 相似文献
994.
Regina Skuodiene Kazimieras Katutis Rita Nekrosiene Regina Repsiene Danute Karcauskiene 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2016,66(8):653-663
ABSTRACTThe research has been conducted for four years in five phytocenoses affected by the processes of naturalization. Two of them are located in non-flooded, relatively abandoned meadows and the remaining - flooded meadows in different parts of the Nemunas delta (Western Lithuania). The aim of the research was to estimate the influence of ecological conditions (humidity regimes, soil agrochemical parameters) on semi-natural meadow productivity. Humidity regimes and nitrogen amount in the soil influenced dry matter (DM) yield of meadow phytocesosis. The biggest DM yield (8.64 ± 0.77 t ha-1) was found in flooded meadow in the central part of the Nemunas delta in Terric Histosol (HSs) soil, which had moderate acidity and was rich in nitrogen. The economic value depended on the prevailing plant species and was the highest in non-flooded meadows. Botanical composition and plant species number depended on agrochemical characteristics of the soil and management activities: the greatest plant species diversity and the best plant population stability were established in flooded meadow in the riverside part of the Nemunas delta behind a levee in soil rich in phosphorus and potassium and low acidity. A similar number of plant species and similar ecological stability parameters were found in non-flooded meadow, whose soil was low in nutrients, but there was intensified farming. 相似文献
995.
研究不同菌材树种、菌材用量对甘孜州野生乌天麻(Gastrodia elata Bl.f.glauca S.Chow)无性繁殖的影响。结果表明,菌材树种对甘孜州野生乌天麻无性繁殖的产量和箭麻折干率均有极显著影响,刺叶栎类材质紧密树种所培养的天麻的产量和折干率极显著高于白桦类材质疏松树种;菌材用量对甘孜州野生乌天麻无性繁殖产量有极显著影响,但对箭麻折干率无影响。 相似文献
996.
997.
采用标本采集鉴定方法对甘肃省天祝藏族自治县内647个蝶类标本进行鉴定。结果表明,该区域中蝶类有绢蝶科(Pamassiidae)的1属4种,粉蝶科(Pieridae)的6属20种,眼蝶科(Satyridae)的12属16种,蛱蝶科(Nymohalidae)的10属12种,灰蝶科(Lycaenidae)的4属5种。蝶类区系组成分析表明,古北东洋界共有物种为13种,占总物种数的22.81%;古北界蝶类物种共44种,占总物种数的77.19%。 相似文献
998.
为探明贵州省不同生态环境水稻3个主要生育期稻田寄生蜂物种组成的异同及多样性特点,采用田间调查的方法在具有不同代表性的4个区域(贵州省榕江县车江乡、绥阳县洋川镇、贵阳市花溪区石板镇和六枝特区平寨镇)进行了调查研究。结果表明:采集到水稻寄生蜂标本5 222号,隶属23科123属224种;各地稻田寄生蜂个体数和丰富度的最高时期出现在乳熟期,除榕江县车江乡稻田寄生蜂的优势度最高时期出现在乳熟期外,其余各地的多样性指数、优势度和均匀度的最高时期均出现在抽穗期-开花期。稻田寄生蜂的多样性取决于其物种数及物种个体数的分布情况。 相似文献
999.
1000.