北祁连山东段早石炭世棘鱼类、辐鳍鱼类和软骨鱼类--北祁连山东段石炭纪鱼类序列研究之一

对甘肃靖远一带和内蒙古自治区黑山地区早石炭世前黑山组、臭牛沟组和靖远组中三亚纲鱼类微体化石进行了形态学和古组织学研究。这些化石涉及 7个目或亚目 ,含 4属 4种 ,其中有 2新种。文中记述的属均为全球广布的属。建立了 3个早石炭世鱼类组合 ,这是我国早石炭世第一个鱼类组合序列。辐鳍鱼类和软骨鱼类中 2个目的化石均为我国早石炭世鱼类的首次记录     

秦岭百合科部分类群的细胞学研究

对分布于秦岭地区的4属5种百合科植物进行了细胞学研究。结果表明,这5种百合科植物均为二倍体,其核型公式分别为：大花韭(Allium macranthum),2n=14=8m 2sm 4st,“2B”核型;多叶韭(A．plurifoliatum),2n=16=14m 2sm,“2A”核型;山竹花(Disporum cantoniense),2n=16=8sm 8st(2SAT),“3B”核型;假百合(Notholirion bulbuliferum),2n=24=2m 2sm 20t(4SAT),“3B”核型;黄花油点草(Tricyrtis maculata),2n=26=8m 12sm 4st 2t,“3B”核型。除多叶韭和假百合外,其余各种的染色体数目和核型均为秦岭地区的首次报道。     

Dispersal patterns of endemic alpine butterflies with contrasting population structures:<Emphasis Type="Italic"> Erebia epiphron</Emphasis> and<Emphasis Type="Italic"> E. sudetica</Emphasis>

We studied population sizes and mobility of Erebia epiphron and Erebia sudetica, two high mountain butterflies forming endemic subspecies in the Hrubý Jeseník Mountains, Czech Republic. E. epiphron formed two continuous populations containing 100,000 and 4,500 individuals on alpine grasslands. The butterflies moved freely within their habitats, but movements between the two populations were highly unlikely. E. sudetica formed a system of colonies at timberline sites on valley headwalls and in forest clearings. Two such colonies studied in detail contained 4,500 and 450 adults and were interconnected by limited dispersal. The negative exponential function and the sigmoid function (this assumes flat decrease of movements over short distances) were superior to the inverse power function in fitting mobility data for both species. For E. sudetica, the functions describing movements within a habitat differed significantly from total movements, suggesting different behaviours of dispersing individuals. The habitats of E. epiphron are uniform and highly isolated, favouring free within-habitat mobility but prohibiting leaving their boundaries. The habitats of E. sudetica are diverse and disturbance-dependent; leaving such habitats is less risky, and a source-sink model may explain the persistence of the species in the mountains.     

Towards an ecological basis for the conservation of subalpine heath-grassland on the upper ridges of the Vosges

Abstract. The subalpine oligotrophic heath-grasslands, assigned to the Pulsatillo-Vaccinietum and Violo-Nardetum, occurring at the upper ridges in the Vosges at 1100 - 1300 m a.s.l. are of conservational interest because they form natural, mature and stable ecosystems. The Pulsatillo-Vaccinietum is particularly rich in endemic plant species and subspecies due to a local oceanic-subarctic climate and the continuous occurrence of the community throughout the Holocene period, when the association was not affected by changes in the prevailing environmental conditions. After a period of abandonment during and after World War II, agriculture was intensified through mineral fertilization and liming, sometimes mowing, and even ploughing and sowing. Seven pastures were selected to estimate the present plant biodiversity. Losses of biodiversity were assessed on the Kastelberg ridge by diachronic analysis of the vegetation composition and structure over the last 30 years. Species diversity changed in both associations through a decrease in the abundance of oligotrophic, acidophilic species, typical of the mountains of western Europe, and an extension of grassland types of the Violo-Nardetum trifolietosum. Strategies for a return to more natural conditions include the abandonment of fertilization and liming, except locally around farms. Regular mowing is needed in order to decrease the nutrient level of the sites.     

Plant Effects on Spatial and Temporal Patterns of Nitrogen Cycling in Shortgrass Steppe

Because of the water-limited nature and discontinuous plant cover of shortgrass steppe, spatial patterns in ecosystem properties are influenced more by the presence or absence of plants than by plant type. However, plant type may influence temporal patterns of nutrient cycling between plant and soil. Plants having the carbon-3 (C₃) or carbon-4 (C₄) photosynthetic pathway differ in phenology as well as other attributes that affect nitrogen (N) cycling. We estimated net N mineralization rates and traced nitrogen-15 (¹⁵N) additions among plant and soil components during May, July, and September of 1995 in native plots of C₃ plants, C₄ plants, or mixtures of C₃ and C₄. Net N mineralization was significantly greater in C₃ plots than in C₄ plots during both July and September. C₃ plots retained significantly more ¹⁵N in May than did mixed and C₄ plots; these differences in ¹⁵N retention were due to greater ¹⁵N uptake by C₃ plants than by C₄ plants during May. There were no significant differences in total ¹⁵N retention among plant communities for July and September. Soil ¹⁵N was influenced more by presence or absence of plants than by type of plant; greater quantities of ¹⁵N remained in soil interspaces between plants than in soil directly under plants for July and September. Our results indicate that plant functional type (C₃ versus C₄) can affect both the spatial and the temporal patterns of N cycling in shortgrass steppe. Further research is necessary to determine how these intraseasonal differences translate to longer-term and coarser-scale effects of plants on N cycling, retention, and storage. Received 8 December 1997; accepted 6 May 1998.     

浙江天台山甜槠群落研究

以分布在浙江省天台山的甜储群落为对象,分析了群落的特征和性质。甜储群落中,甜储的优势突出,呈单优势群落。群落垂直结构复杂,可分为乔木层、灌木层、草本层,亦有一定数量的层间植物。乔木层的物种多样性指数偏低,这与特定生境所形成的单优势群落有关。各样地间的植物种类具有较高的相似性,群落内种类组成相对一致。群落内优势种群甜储、木荷的年龄结构属稳定型或增长型,它们在各样地的分布格局均呈集群分布。     

广西姑婆山及邻近地区大型真菌物种多样性

姑婆山紧邻南岭生物多样性保护优先区，孕育了丰富的生物资源。为了解该区域大型真菌物种多样性，该文采用随机踏查法对广西姑婆山自治区级自然保护区(以下简称姑婆山)及邻近地区大型真菌资源进行调查采集，并结合形态学和分子生物学方法进行物种鉴定。结果表明：(1)共发现348种大型真菌，隶属于2门6纲17目69科175属，其中包含食用菌40种、药用菌42种、毒菌7种。(2)对该区的物种组成分析表明，优势科为蘑菇科(Agaricaceae)、牛肝菌科(Boletaceae)、粉褶蕈科(Entolomataceae)和锈革菌科(Hymenochaetaceae)等9科；优势属为鹅膏属(Amanita)、靴耳属(Crepidotus)、毛皮伞属(Crinipellis)和粉褶蕈属(Entoloma)等11属。(3)共发现2个中国特有属，即脆孔菌属(Fragiliporia)和臧氏牛肝菌属(Zangia);11个中国特有种，即厚集毛菌(Coltricia crassa)、魏氏集毛菌(C.weii)、丛生粉褶蕈(Entoloma caespitosum)、极细粉褶蕈(E.praegracile)、近薄囊粉褶蕈...     

Effects of species and habitat positional errors on the performance and interpretation of species distribution models

Aim A key assumption in species distribution modelling is that both species and environmental data layers contain no positional errors, yet this will rarely be true. This study assesses the effect of introduced positional errors on the performance and interpretation of species distribution models. Location Baixo Alentejo region of Portugal. Methods Data on steppe bird occurrence were collected using a random stratified sampling design on a 1‐km² pixel grid. Environmental data were sourced from satellite imagery and digital maps. Error was deliberately introduced into the species data as shifts in a random direction of 0–1, 2–3, 4–5 and 0–5 pixels. Whole habitat layers were shifted by 1 pixel to cause mis‐registration, and the cumulative effect of one to three shifted layers investigated. Distribution models were built for three species using three algorithms with three replicates. Test models were compared with controls without errors. Results Positional errors in the species data led to a drop in model performance (larger errors having larger effects – typically up to 10% drop in area under the curve on average), although not enough for models to be rejected. Model interpretation was more severely affected with inconsistencies in the contributing variables. Errors in the habitat layers had similar although lesser effects. Main conclusions Models with species positional errors are hard to detect, often statistically good, ecologically plausible and useful for prediction, but interpreting them is dangerous. Mis‐registered habitat layers produce smaller effects probably because shifting entire layers does not break down the correlation structure to the same extent as random shifts in individual species observations. Spatial autocorrelation in the habitat layers may protect against species positional errors to some extent but the relationship is complex and requires further work. The key recommendation must be that positional errors should be minimised through careful field design and data processing.     

云居山栓皮栎群落特征及多样性研究

栓皮栎群落是我国暖温带和亚热带落叶阔叶林的重要森林群落类型之一,也是赣北珍稀森林群落之一,在森林演替和植物资源利用中占有重要的地位。通过对江西云居山栓皮栎(Quercus variabilis)群落进行实地调查,采用区系分析、生活型谱分析、物种多样性和双向聚类等方法对其群落特征进行了研究,发现云居山自然保护区栓皮栎群落结构简单,层次明显,多样性程度不高。物种调查及区系研究结果显示,云居山栓皮栎群落维管束植物共计43科56属70种,植物区系主要以泛热带、东亚及北美间断、北温带分布为主,表现出从温带区系向热带区系过渡的特征;生活型谱以高位芽植物为主(占70%),其他生活型相对较少,反映出中亚热带森林以高位芽植物为主的特点。群落物种丰富度、多样性指数均为乔木层小于灌木层和草本层,均匀度指数分析表明,乔木层为聚集分布、灌木层和草本层为均匀分布。双向聚类分析表明,调查的5个样地均为栓皮栎群落,以乔木层物种多度可将5个样地分为3类,组成群落的24个主要物种可分为10类。     

山西霍山灌丛空隙草本植物物种多样性与更新

采用物种重要值和物种多样性指数,分析了山西霍山灌丛空隙内主要草本组成及其多样性随灌丛空隙面积梯度的变化规律。结果表明:在自然状况下形成的10 m2的灌丛空隙最多,占51.2%。灌丛空隙内草本植物的重要值高于灌丛下草本,且以10~20 m2的空隙为最高。主要草本可分为3类:(1)对灌丛空隙更新反应不明显的草本,(2)对灌丛空隙有正更新反应的草本,(3)对灌丛空隙有负更新反应的草本。灌丛空隙内的物种丰富度、多样性指数和均匀度指数均高于灌丛下,而生态优势度均小于灌丛下,呈现"单峰型"的变化趋势,且在10~20 m2达到峰值。因此,适宜大小的灌丛空隙是森林生态系统草本层植物多样性维持的重要途径。