地震干扰后恢复群落的数量分类与排序

根据对四川王朗自然保护区地震干扰后恢复群落的野外调查数据,运用二元指示种分析(TWINSPAN)和除趋势对应分析(DCA)对该地区恢复群落进行了数量分类与排序。结果显示,可将所调查的植物群落划分为3种群落类型:重度干扰群落(群落E)、中度干扰群落(群落T)和轻度干扰群落(群落F)。排序结果也得到了相同的结论,并显示3种群落分布与一定的环境因子密切相关,群落E与岩石裸露度呈正相关,而与土壤厚度、土壤水分、苔藓盖度及盖度等环境因子呈负相关,群落F则与岩石裸露度呈负相关,而与土壤厚度、土壤水分、苔藓盖度及盖度等环境因子呈正相关。     

植物群落排序方法概述

总结了几十年来植物群落排序研究的成果,探讨了各种排序方法在植物群落分析应用中的优点和不足之处,并对排序的有效性进行了讨论。     

Tree species composition and similarity in semideciduous forest fragments of southeastern Brazil

This study investigates the influence of fragment size on tree species composition, species richness and on individual groups of species within 11 semideciduous forest fragments in southeastern Brazil. We compared same-sized samples of 500 trees from 10 fragments <100 ha, allocated to three size categories, with three 500-tree samples collected in different areas within a large forest, used as a reference forest. The variation in species richness, in the proportion of species/individuals in dispersal modes, and in the proportion of rare species was not related to fragment size. Nonetheless, comparisons between the mean values of these variables of each fragment size categories, using 95% confidence intervals, showed a wider range of variation within the category of small-sized fragments than in the other size categories. NMS ordination plot also suggested the absence of a relationship between fragment area and tree species composition. However, multiple regressions using the scores from the NMS ordination as response variables, and area and disturbance intensities as predictor variables, suggested that the interaction of area and disturbance might be a good predictor of species composition. Pre-existing environmental heterogeneity and geographical proximity also appeared to play a role in the variations of forest composition among the fragments studied. Our results demonstrated the high conservation value of small forest fragments.     

The impact of cropping on weed species composition in rice after fallow across a hydrological gradient in west Africa

In a 5-year experiment, weed species composition in rice was recorded at different positions along the toposequence, from the rain-fed upland to the irrigated valley bottom. A total of 107 species was recorded, 70 of which occurred in more than 1% of the total of 465 samples. Canonical correspondence analysis was used to explore the changes in weed flora over time in the different rice-growing environments. There were substantial differences in the composition of weed flora between the differing environments and years. On the upland sites, there was a pronounced shift from perennial grasses, including Imperata cylindrica (L.) Raeuschel and Pennisetum purpureum Schum., to annual grass weeds, such as Digitaria horizontalis Willd., Chloris pilosa Schum. and Eleusine indica (L.) Gaertn. The forbs Boerhavia spp. and Euphorbia heterophylla L. also increased in abundance, whereas others, such as Aspilia bussei Hoffm. & Muschl. and Laggera aurita (L.f.) Sch. Bip. ex C. B. Clarke, declined. The total number of species in the upland site declined from 30 to 11 between 1992 and 1996 compared with 11 to eight species in the same period in the irrigated lowlands. Although the numbers of species recorded in the lowlands were lower and more stable over time, there was an increase in problem grass weeds, such as Echinochloa crus-pavonis (Kunth.) Schult. in the irrigated lowlands and Leersia hexandra Sw.in the rain-fed lowlands.     

山茶亚科植物过氧化物酶同工酶分析

用聚丙烯酰胺凝胶电泳方法,研究10种山茶亚科植物的过氧化物酶同工酶.结果表明,山茶亚科植物属间、亚属间酶谱差异较大,种间差异次之,种内不同品种间差异较小.采用酶谱距离极点排序法,定量研究了各类型间的酶谱差异,排序结果与前人应用传统方法分类的结果相吻合.因此,酶谱距离的极点排序可用于植物亲缘关系的探讨.     

克拉玛依农业综合开发区外围荒漠植物群落分布的土壤环境排序解释

应用DCA数量排序方法,在群落水平上对克拉玛依农业综合开发区外围荒漠植物群落与土壤环境因子之间的关系进行了分析,并对排序轴进行了逐步回归分析。结果表明,该地区植物群落分为盐穗木群落、梭梭群落和白梭梭群落三个典型群落类型。通过排序分析土壤盐渍化与盐穗木群落相关性较强,梭梭群落与土壤肥力、白梭梭群落与土壤酸碱性具有明显的相关性。在梭梭＋白梭梭群落的过渡带上,土壤各因子含量也随之发生过渡变化,而盐穗木群落与梭梭、白梭梭群落有明显的界线,表现出了恶劣生境下的物种趋同性。综合分析表明了在隐域条件下土壤因子含量与植被格局的一致性,也反映了植被对生境的依赖性。     

3个甜瓜品种不同生育期同工酶谱活性度的Fuzzy评判

根据3个甜瓜品种4个生育期的POD,SOD和EST同工酶酶谱,建立同工酶谱矩阵,并给出反映酶谱活性度的4个主要特征的量化指标。采用Fuzzy综合评判方法,确定这3种酶的同工酶谱在不同生育期的活性度高低。结果表明,3个甜瓜品种上述3种酶的同工酶活性度变化呈现明显的规律,即由高到低的排序为:(1)POD同工酶谱:开花期>幼苗期>座果期>子叶期;(2)SOD同工酶谱:幼苗期>子叶期>开花期>座果期;(3)Est同工酶谱:开花期>座果期>幼苗期>子叶期。     

基于RDA排序的现代农业园土地利用功能分区:以剑河县南明镇为例

为给现代农业园区土地利用功能分区方法提供借鉴,以剑河县南明镇现代农业园区项目为例,通过专家决策与咨询法构建了17个因子的评价体系,采用RDA排序法选出功能分区主导因子,再结合园区内各行政村的主导因子指标数据完成对现代农业园区的土地利用功能分区。结果表明:在现代农业园区中人口密度、土地利用率、土地垦殖率、农林牧渔业总产值等指标可作为园区土地利用功能分区的主导因子;园区内22个行政村可划分为综合服务区、农业生产区、休闲农业区和生态农牧业区4类功能区;功能群的方法(RDA排序)可用于指导现代农业园区土地利用功能分区。     

太行山低山石灰岩区水土保持林地类型研究

通过对太行山低山石灰岩区水保林定性和定量兼有的１３个变量，１７０块标地调查，采用主成分分析方法，对该区的水保林进行排序，结果≤５００ｍ丘陵区可划分为四个类型：灌木盖度〉２０％侧柏，山皂荚乔灌草型，灌木盖度≤２０％侧柏，白草乔草灌云南省 枯落物荆条，酸枣灌草型；无枯