梅州城区植物群落的结构特征

2009年4—10月,采用群落调查法、主成分分析法对梅州城区5种绿地类型65个种植的植物群落进行研究,结果表明：1）各类植物共计43科105属147种（含变种）,其中乔木62种（42．17％）、灌木45种（30．61％）、草本植物31种（21．09％）、藤本植物9种（6．12％）;2）群落垂直结构为乔、灌、草3层复合结构者9个（13．85％）,为乔、草2层结构者34个（52．31％）,乔或草单层结构者12个（18．46％）;3）乔木树种平均胸径16．7cm,其中平均胸径〈10cm者23种（37．09％）,平均胸径10～20cm者29种（46．77％）,平均胸径20～30cm、〉30Cm者分别为5种（均为8．06％）;4）梅州城区植物群落结构的特征,可用乔木高度因子、胸径因子、密度因子及冠幅因子来表述,这4个主因子的方差累积贡献率达到81．55％,可以很好地反映出群落结构的大部分信息;5）梅州市城区乔木层的优势树种是垂榕、大叶榕、大王椰子,次优势种是阿珍榄仁、阴香、海南蒲桃、细叶榕、木棉、麻楝、香樟、洋紫荆,这11个树种分属桑科、棕榈科、使君子科·、樟科、桃金娘科、木棉科、楝科、豆科（云实科）,它们是梅州城市森林的骨干树种和基调树种,决定了梅州城市森林的南亚热带性质的外貌。     

Effect of Vertebrate Grazing on Plant and Insect Community Structure

Abstract: We compared species diversity of plants and insects among grazed and ungrazed areas of Ponderosa pine–grassland communities in Arizona. Plant species richness was higher in two of three grassland communities that were grazed by native elk and deer and domestic cattle than in ungrazed areas inside a series of three large (approximately 40-ha) grazing exclosures. Similarly, plant species richness was higher in grazed areas relative to ungrazed areas at one of two series of smaller (approximately 25-m²) and short-term exclosure sites. Evenness of plant distribution, however, was greater inside ungrazed long-term exclosures but was reduced inside ungrazed short-term exclosures relative to grazed areas. Relative abundances of forbs, grasses, trees, and shrubs, and native and introduced plants did not differ between the long- and short-term grazing exclosures and their grazed counterparts. Relative abundances of some plant species changed when grazers were excluded, however. In contrast, insect species richness was not different between grazed and ungrazed habitats, although insect abundance increased 4- to 10-fold in ungrazed vegetation. Our results suggest that vertebrate grazing may increase plant richness, even in nutrient-poor, semi-arid grasslands, but may decrease insect abundances.     

Acid Precipitation Effects on Forest Habitats: Implications for Wildlife

Abstract: Forests ecosystems, with their stratified structure, provide a diversity of habitats for a variety of animals. The influence of acidic deposition on forests is being studied intensely, and preliminary research indicates that some forest resources are being affected. These effects and the potential for subsequent change in forest structure and function imply that an impact on the wildlife inhabitants is occurring. In most cases, these impacts are not direct, but instead reflect modifications of habitat and changes in trophic relationships. Detecting changes distinguishable from normal spatiotemporal variations in animal populations is difficult. The net result over time may be reductions or shifts in populations and species composition. This paper provides an overview of current information on the impact of acidic deposition on forest resources as it relates to animals.     

Influence of a Large Herbivore Reintroduction on Plant Invasions and Community Composition in a California Grassland

Abstract:  Despite many successful reintroductions of large mammalian herbivores throughout the world, remarkably little attention has focused on how these actions affect native and exotic vegetation at reintroduction sites. One such herbivore is tule elk ( Cervus elaphus nannodes ), which was on the brink of extinction in the mid 1800s, but now has numerous stable populations due to intensive reintroduction efforts. Here, we summarize results from a 5-year exclosure experiment that explored the effects of tule elk on a coastal grassland in northern California. Elk significantly altered the species composition of this community; the response of annual species (dominated heavily by exotic taxa) was dramatically different from perennial species. Elk herbivory increased the abundance and aboveground biomass of native and exotic annuals, whereas it either had no effect on or caused significant decreases in perennials. Elk also decreased the cover of native shrubs, suggesting that these herbivores play an important role in maintaining open grasslands. In addition, elk significantly reduced the abundance and biomass of a highly invasive exotic grass , Holcus lanatus, which is a major problem in mesic perennial grasslands. Our results demonstrate that the successful reintroduction of a charismatic and long-extirpated mammal had extremely complex effects on the plant community, giving rise to both desirable and undesirable outcomes from a management perspective. We suspect that these kinds of opposing effects are not unique to tule elk and that land managers will frequently encounter them when dealing with reintroduced mammals.     

土壤温度上升与森林衰退

土壤温度上升可能会引起土壤产生过量的ＨＮＯ３，而过量的ＨＮＯ３在酸性土壤中将导致Ａｌ（３＋）浓度的升高和盐基阳离子的流失，使养分失调，细根坏死。土壤温度上升还可能会改变土壤有机质动力学、土壤水文学和土壤物理学，从而改变森林生境特征，影响森林的正常生长。     

Influence of Forest Fragmentation on Community Structure of Frogs and Lizards in Northeastern Costa Rica

Abstract:  To better understand responses of reptiles and amphibians to forest fragmentation in the lowland Neotropics, we examined community and population structure of frogs and lizards in the fragmented landscape surrounding La Selva Biological Station in the Sarapiquí region of northeastern Costa Rica. We used diurnal quadrats and nocturnal transects to sample frogs and lizards in nine forest fragments (1–7 ha each) and La Selva (1100 ha). Species richness in all fragments combined was 85% of that found in La Selva with comparable sampling effort. Richness varied from 10 to 24 species among forest fragments, compared with 36 species at La Selva. Lizard density was higher and frog density was lower in forest fragments than in La Selva. Community composition varied among sites and by fragment size class, and species occurrence was nested with respect to fragment area. Isolation and habitat variables did not significantly affect species richness, composition, or nestedness. We classified 34% of species as fragmentation sensitive because they were absent or occurred at low densities in fragments. Nevertheless, the relatively high diversity observed in the entire set of fragments indicates that preserving a network of small forest patches may be of considerable conservation value to the amphibians and reptiles of this region.     

上海海湾国家森林公园1 hm2样地群落结构特征及其动态监测意义

运用生态系统定位监测方法,于2011年在上海市奉贤区海湾国家森林公园内设置面积为100 m×100 m的样地,记录样地内的所有植物种类,定位调查高于1.3m的木本植物,分析其种类组成、区系成分、垂直结构和水平结构.结果表明,1 hm2样地内共记录有维管束植物31科68属73种,其中温带区系成分占总属数的51.8％,热带区系成分占46.4％.高于1.3m的木本植株3 094株,其中常绿树种6种,共1 670株,重要值占48.0％;落叶树种7种,共1 424株,重要值占52.0％.女贞(Ligustrum lucidum)、喜树(Camptotheca acuminata)、椤木石楠(Photinia davidsoniae)、乌桕(Sapium sebiferum)、黄山栾树(Koelreuteria integrifoliola)和香樟(Cinnamomum camphora)的重要值位居前6位,在垂直空间上呈分层结构.在0～50 m尺度范围内,女贞种群均呈集群分布,喜树种群呈均匀-随机-集群分布,椤木石楠和乌桕种群表现为集群-随机-均匀分布,黄山栾树和香樟种群表现为随机-集群-随机分布.从群落结构特征看,样地为以北温带成分、泛热带成分为主的常绿落叶阔叶混交林,表征了该地区自然植被的结构特征.建立长期固定样地可为长三角城市化地区平原地貌上城市森林的发生、发展和演替规律提供长期的数据基础.     

上海市外环林带秋季不同区域土壤动物群落结构

为了解上海市外环林带土壤动物群落的生态特征,于2010年11月对上海市外环林带香樟群落的9个样点进行系统调查.结果表明,共捕获土壤动物5 792头,分属6门12纲26个类群,优势类群有轮虫纲(Rotatoria)、涡虫纲(Turbellaria)、线虫纲(Nematoda)、蜱螨目(Acarina)和弹尾目(Collembola).区域环境及建成年份对土壤动物密度都有着明显影响:城乡结合部土壤动物密度最高,工业区最低;建成年份越早,土壤动物密度越低.在垂直方向上,土壤动物存在明显的表聚性.各样点间群落相似性并没有明显的规律性,但区域环境对土壤动物相似性有一定影响.不同区域土壤动物多样性规律存在明显差异,建成年份与土壤动物群落多样性也具有明显相关性,城区样点建成年份越早,多样性指数越高,而工业区则相反.由此可见,区域环境对土壤动物存在一定影响,而外环林带的建立能够缩小不同区域之间的差异,为土壤动物群落创造适宜的小生境.     

四川道孚县芒苞草生境的植物群落结构和土壤元素含量

芒苞草(Achanthoclamys bracteata P.C.Kao)是分布于横断山区局部狭小区域的一种单型科植物,在指示植物系统进化和地理环境变迁中具有十分重要的作用和地位.对四川省道孚县鲜水河流域的两个芒苞草分布地点(麦粒山和亚卓山)进行了群落学特征和土壤学研究.芒苞草生境群落类型为温性干旱河谷灌丛和草地,上接亚高山云冷杉针叶林.麦粒山芒苞草生境为毛莲蒿-矮嵩草-芒苞草群落;而亚卓山灌丛草地类型为川滇蔷薇-毛莲蒿-西南野古草-芒苞草群落,亚卓山草地则以西南野古草、直芒草、金发藓等为优势种.物种多样性指数以灌丛最高,亚卓山草地物种多样性在中海拔处出现极小值,海拔越高,芒苞草单株重量越轻,中海拔位置处的地上地下生物量比值(2.06±0.17)最大.土壤元素含量以铝和铁最丰富,而磷和钾的含量分别为(8 873.5±1463.3)mg kg-1和(431.1±180.4)mg kg-1,比该区域的平均值低.芒苞草多生长在有岩石出露的地方,在道孚县的分布区域局限在鲜水河河谷地带.芒苞草强烈的生境选择作用以及河谷地带强度较大的人为活动,是威胁芒苞草生存的主要因素.图5表3参24     

Adjusting to Climate Change: Implications of Increased Variability and Asymmetric Adjustment Costs for Investment in Water Reserves

In this paper we study the determination of optimal water storage capacity in a region, taking into account that the supply of the resource, the flow into the reserve, is uncertain, that a measure of the uncertainty, the variance, is likely to increase with climate change, that building capacity is costly, and that the development of water resources may entail alsoenvironmental costs. We find that water storage capacity in the long run ispositivelyrelated to increases in uncertainty if the marginal benefit of water withdrawal isconvexand that, for the case of costly reversibility of investment, a range of inaction for investment appears, and the stability of water storage capacity with respect to changes in variance increases.     

北京典型郊野公园植物组成结构分析

通过对北京典型郊野公园绿地植物的系统调查,分析了其种类构成,计算并论述了公园绿地的植物结构特征,以期能够为北京生态城市建设提供科学依据。调查发现典型郊野公园植物有78科181属299种,占北京市总维管植物种数的12.1%,总体上偏少。乔木和灌木的丰富度指数都在5.0以下,草本的丰富度要大于乔、灌木;植物均匀度指数总体上在0.7以内,乔木要高于灌木和草本;总体说来,郊野公园绿地植物种类偏少、分布不均匀;北京郊野公园建设刚刚起步不久,要在现有基础上不断完善。     

Landsat Thematic Mapper: Detection of Shifts in Community Composition of Coral Reefs

Abstract: We assembled a time series of 20 Landsat thematic mapper images from 1982 to 1996 for Key Largo, Florida, to ascertain whether satellite imagery can detect temporal changes in coral reef communities. Selected reef and control areas were examined for changes in brightness, spectral reflectance, band ratios, spatial texture, and temporal texture (  pixel-to-pixel change over time). We compared the data to known changes in the reef ecosystem of Carysfort Reef and terrestrial sample sites. Changes in image brightness and spectral-band ratios were suggestive of shifts from coral- to algal-dominated community structure, but the trends were not statistically significant. The spatial heterogeneity of the reef community decreased in the early 1980s at scales consistent with known ecological changes to the coral community on Carysfort Reef. An analysis of pixel-scale variation through time, termed temporal texture, revealed that the shallow reef areas are the most variable in regions of the reef that have experienced significant ecological decline. Thus, the process of reef degradation, which alters both the spatial patterning and variability of pixel brightness, can be identified in unclassified thematic mapper images.     

南京朴树林竞争强度及其群落稳定性

选择南京紫金山和老山国家森林公园的朴树林为研究对象,采用Phylomatic和PhyloCom软件构建主要竞争种的系统发育树,并利用Hegyi单木竞争指数模型分别对两地朴树的种内和种间竞争强度进行研究,同时采用改进的M.Godron稳定性测定方法分析群落稳定性.结果表明,朴树受到的种内竞争强度随着林木径级的增大而逐渐减小.紫金山和老山朴树林种内与种间竞争强度由大到小分别依次为麻栎、朴树(种内竞争)、刺槐、毛梾和三角枫以及构树、朴树(种内竞争)、黄檀、刺槐和化香.南京紫金山和老山两地朴树的种内竞争强度均小于种间,这可能与朴树林中优势树种的生物学特性、生境异质性及系统发育相关.两地竞争强度与对象木胸径的关系均符合幂函数关系,当朴树的胸径≥20 cm时,竞争强度变化很小,所得模型能很好地预测朴树种内与种间的竞争强度.研究结果表明南京紫金山和老山两地的朴树林均处于不稳定状态.     

太湖浮游植物群落结构及其与水质指标间的关系

为了探讨太湖浮游植物群落结构时空分布特征、以及太湖浮游植物群落指标与水质指标间的关系,于2013年1月─2013年12月对太湖7个点位浮游植物群落结构和水质指标（水温、透明度、pH、溶解氧、电导率、总氮、总磷、氨氮、高锰酸盐指数、化学需氧量、氟化物、生化需氧量、硝酸盐氮、亚硝酸盐氮、溶解性磷酸盐和叶绿素a）进行月度调查,研究其浮游植物群落结构和湖泊水质的时空分布;并利用Pearson相关性分析浮游植物密度、浮游植物多样性与水质指标间的关系;找出影响太湖浮游植物群落结构的主要水质指标。结果表明：太湖7个点位共获得124种浮游植物物种,其中蓝藻门（Cyanophyta）30种、绿藻门（Bacillariophyta）47种、硅藻门（Chlorophyta）34种、隐藻门（Cryptophyta）3种、裸藻门（Euglenophyta）6种和甲藻门（Dinoflagellate）4种;其中蓝藻门的微囊藻属（Microcystis spp.）为绝对优势种群,优势度为80.8%;太湖浮游植物总密度与蓝藻门密度呈极显著正相关（r=1.000,P＜0.0001）;绿藻门和硅藻门占浮游植物总密度百分比分别和蓝藻门占浮游植物总密度百分比呈极显著负相关（r=-0.497,P＜0.0001;r=-0.814,P＜0.0001）。太湖7个点位水质首要污染物为总氮,其次是总磷和化学需氧量;西太湖污染物浓度最高。从空间上看,太湖浮游植物总密度最高值出现在贡湖湾（远离其入湖口处）,且贡湖湾浮游植物群落多样性相对低于太湖其他点位,同时贡湖湾微囊藻属密度百分比达90.1%,远高于太湖其他点位;从时间上看,太湖浮游植物总密度最高值出现在12月份、其次是6月份;通过浮游植物群落指标与水质指标相关性分析,水温、透明度、总氮、化学需氧量、叶绿素a是影响太湖浮游植物群落结构的主要水质指标。控制太湖入湖口水质污染物浓度排放和修?