Seasonal succession of Cladocerans in a ricefield in Italy

A biological ricefield in northern Italy, without periodic dry spells in its growing cycle and therefore more familiar to naturally humid zones, was studied for its heleoplankton community. The biocoenosis reached a greater level of complexity than reported in literature. In particular, the seasonal succession of Cladocerans, the dominant group throughout the study period, was analyzed. Wlassicsia pannonica (Daday, 1904; Anomopoda Macrothricidae), is new to Italy; its morphology is compared to that of other populations of the same species and its biological cycle is compared with that of other dominant Cladocerans.     

The effect of a seed source on primary succession in a forest ecosystem

An analysis of the Relative Importance Value Index (RIVI) of later successional tree species and the Shannon diversity indexH of all tree and shrub species was undertaken on previously mined sites within a sparsely forested area in central Florida, USA. A comparative analysis of the distance to a seed source and the age of a site suggested that the distance to a seed source was the best predictor (R ²=0.85) of the regeneration of the later successional species and a good predictor of species diversity. Both theRIVI of the later successional species and the diversity index decreased with the distance from the seed source. The lack of a seed source containing climax species resulted in arrested succession at some sites. It is suggested that biological information is the causative means of succession and the dispersal of this information entails spatial dependency while its introduction and development are time dependent processes.Research was part of a project of the Center for Wetlands, University of Florida, Gainesville under contract with the Florida Institute of Phosphate Research. Interactions of Wetlands with Phosphate Mining, H. T. Odum and G. R. Best, principal investigators. B. T. Rushton, J. Butner, G. R. Best, R. S. Schnoes and S. R. Humphrey are thanked for the use of their data.     

Pathways and determinants of early spontaneous vegetation succession in degraded lowland of South China

Continuous and prolonged human disturbances have caused severe degradation of a large portion of lowland in South China, and how to restore such degraded ecosystems becomes an increasing concern. The process and mechanisms of spontaneous succession, which plays an important role in vegetation restoration, have not been adequately examined. To identify the pathways of early spontaneous vegetation succession, 41 plots representing plant communities abandoned over different times were established and Investigated. The communities and indicator species of the vegetation were classified by analyzing the important values of plant species using multivariate analyses. The reaults indicated that the plant species could be classified into nine plant communities repreaenting six succession staages. The pathway and species composition alao changed in the process of succession. We also meaeurad 13 environmental variables of microtopography, soil structure and soil nutrition in each plot to examine the driving forces of auccession and the vegetation-environment relationships. Our resulta ahowed that the environmental variables changed in diverse directions, and that aoil bulk density, soil water capacity and soU acidity were the most important factors.     

Ectomycorrhizal ecology under primary succession on coastal sand dunes: interactions involving Pinus contorta, suilloid fungi and deer

Ectomycorrhizal fungi (EMF) are critical for pine establishment under primary succession. The species of EMF supporting primary successional pine seedlings on coastal sand dunes and mechanisms for their establishment were investigated. Fungi were identified from ectomycorrhizal roots using molecular techniques. Field seedlings were collected from forested and nonforested zones. Laboratory seedlings were grown in soils collected from the same zones, and in sterile soils inoculated with fresh and 1-yr-old dry deer fecal pellets. Suilloid fungi were frequently observed on all seedlings. A diverse group of fungi was available to seedlings in forested zones. A less diverse group of fungi was available to field seedlings in nonforested zones and all laboratory bioassay seedlings. Deer fecal inoculant yielded an average of two EMF per seedling. Both Suillus and Rhizopogon species dominated seedlings inoculated with fresh deer feces, but only Rhizopogon species dominated seedlings inoculated with 1-yr-old feces. Suilloid fungi are dispersed by deer, produce resistant spore banks and are the principle fungi supporting seedlings on the sand dunes.     

西门岛人工秋茄林恢复对大型底栖生物的影响

选择乐清湾西门岛海域相同高程断面不同造林时间的人工红树林(秋茄林)、光滩和互花米草丛,采用空间代替时间的方法,分析我国分布最北界人工红树林造林过程对大型底栖生物的影响.大型底栖动物生活型分布基本表现为幼林(1、4、8a秋茄林)以底上附着型为主,而在光滩、50a秋茄林和互花米草中底下生活类群相对增加.并且穴居型动物只出现在发育成熟的生态系统内.各项指标显示50a老林群落生态稳定性较好,光滩和互花米草丛次之,但优于发育中的秋茄幼林.与以往研究结果不同,50a老林的大型底栖动物生物种类的丰度及群落的物种多样性最高,并不与红树林的发育状况呈负相关,也不比邻近光滩低.结合50a林下滩涂底泥情况,西门岛50a红树林林下滩涂的底质发育要落后于国内天然红树林土壤.这可能与当地红树林造林规模小以及强潮差海域有关.此外,红树林恢复过程中,大型底栖动物生物多样性与生态稳定性之间的线性关系,其适用的系统面积和演替时间的尺度范围有必要做更加深入的探讨.     

内蒙古典型草原不同恢复演替阶段植物养分化学计量学

对内蒙古典型草原不同恢复演替阶段群落土壤养分动态及空间格局、植物养分及其化学计量比时空动态、植物与土壤养分相关性等进行了分析, 以揭示放牧干扰对植物的养分及其化学计量比影响。结果表明: 土壤各养分含量表现为恢复群落略高于严重退化群落, 土壤全氮(STN)/土壤全磷(STP)恢复群落高于严重退化群落, 土壤有机质(SOC)/STN恢复群落低于严重退化群落; 大多数植物叶片C含量在恢复群落最高, 严重退化群落最低, 与恢复演替时间呈正相关, 而植物的全氮(TN)和全磷(TP)含量则是严重退化群落最高, 恢复群落最低, 与退化程度呈正相关, 且TP含量的变幅明显高于TN含量; 植物叶的N:P和C:N表现为严重退化群落最低, 与退化程度呈负相关; 严重退化群落植物相对于P而言, 总体上表现为缺N; 而恢复群落相对于N而言, 更为缺P, 或同时缺N和P; 群落优势种化学计量学特征对群落演替方向有一定的指示作用。     

碱化草地群落恢复演替空间格局动态分析

对松嫩平原碱化草地1989年开始围栏封育的1hm^2样地9a间的空间格局进行了分析,结果表明：（1）不同物种斑块空间格局动态不同,在恢复演替各个阶段中的地位与作用也不同。（2）结论基本上支持了斑块化－稳定性假说。     

滇西北高原碧塔湖滨沼泽植物群落分布与演替

滇西北高原碧塔海湖滨带狭长型沟谷和宽广型沟谷设置了两条沼泽研究样带,研究了沼泽群落种类组成特征、群落分布与演替规律及其驱动因素.结果表明:两条样带总计调查到43种植物,隶属21科35属;群落中均以稀有种占多数,但总体上狭长型沟谷沼泽群落的均匀程度高于宽广型沟谷;α多样性各指数与沼泽水位均呈显著正相关,但β多样性与沼泽水位无相关性;沿水分梯度,沼泽群落呈现出挺水植物群落→沼泽植物群落→沼泽化草甸植物群落的生态序列分布,但是也在局部微地形作用下形成群落复合体;生态序列分布与湖岸特点和沟谷类型有关:狭长型沟谷具有陡坡湖岸,沼泽群落倾向于间断分布,宽广型沟谷具有缓坡湖岸,沼泽群落倾向于连续分布.以水分因子为主、以地形等因子为辅的综合环境因素是决定碧塔海湖滨沼泽群落植物多样性和生态序列分布格局的驱动因素,相应地植物群落演替特点为渐变式演替和跳跃式演替两种模式并存,但演替方向一致.     

晋西吕梁山严村流域撂荒地植物群落替中的物种多样性变化

用ＤＣＡ排序研究了黄土丘陵区撂荒地上植物群落演替的趋势和方向,用６种多样性指数分析了物种丰富度、均匀度和综合多样性在演替过程中的变化。随着演替的进展,物种丰富性显著增高,均匀性逐渐降低,综合多样性逐渐升高。     

Acceleration of vegetation succession on eroded land by reforestation in a subtropical zone

Based on field investigations in the East River basin in Guangdong Province, south China, the processes of vegetation development and vegetation succession on bare slopes with high erosion rates are studied. Different reforestation measures have been applied to the slopes, which have resulted in very different processes of vegetation development and succession. On an experimental plot with burned forest but surviving roots, the vegetation restored naturally and quickly because there was little soil erosion. However, in the plots suffering from long-term severe soil erosion, natural vegetation recovery on these barren slopes is very slow. After 26 years, a barren slope has only been partly colonized by poorly developed vegetation composed of heliophilous herbages and scattered shrubs. On the other hand, plantation of some selected wood species on the slope land has dramatically accelerated the vegetation recovery and succession. The plots were reforested with plantation of Acacia auriculiformis in the early 1980s. Twelve years later, the vegetation cover of the artificial forests reached 90% and an understory vegetation community consisting of local species had naturally developed. Reforestation with suitable strategies may control erosion and greatly accelerate vegetation succession in the eroded slope land in the subtropical zones.     

Early herbaceous succession along a topographical gradient on forest clear-felling sites in mountainous terrain,central Japan

Early successional patterns of herbaceous communities in forest clear-felling sites were investigated along a topographical gradient, which included ridge, slope and valley habitat types, in warm-temperate evergreen forest regions of central Japan for 5 years. Three dominant species with wind-dispersed seeds played a major role in the succession: an annual,Crassocephalum crepidioides, a biennial,Erigeron canadensis, and a perennial,Miscanthus sinensis. Pioneer herbs that have a seed-bank strategy, which are common in old field succession, were not found in the mountainous sites. The persistence of the annual or biennial dominants during the very early stages of secondary succession was different in the three topographical habitat types. In the ridge habitat,M. sinensis dominated from the first year state, andC. crepidioides andE. canadensis were less prominent.Crassocephalum crepidioides andE. canadensis became dominant as one moved down the slope. In the valley habitat,C. crepidioides dominated in the first year stage, was succeeded byE. canadensis in the second year, and thenM. sinensis gradually replaced it in later years. As all three wind-dispersed dominants simultaneously invaded in all the habitat types after clear-felling, the different successional patterns along the topographical gradient might have resulted from differences in the establishment ability and the growth rate of the three dominants depending on the three habitat types.     

沙质海岸防护林入侵植物垂序商陆的防治

垂序商陆的入侵给我国沿海防护林造成了严重危害.本研究在入侵程度相对一致的刺槐林下设置样地,采用物理(刈割、切根)、化学(喷洒无公害除草剂)方法进行控制试验,并以林下紫穗槐发育良好、未进行处理的地段作为对照,探索控制垂序商陆生长的有效方法.结果表明:刈割能快速降低垂序商陆各项生长指标,但次年即恢复至对照水平.1/3切根仅减少了当年地上部分生长量,第3年又恢复至处理前水平,而2/3切根和完全切根处理一次即可有效地清除垂序商陆.精喹禾灵和百草枯仅能杀死其地上部分,次年即恢复至处理前水平,而45g·L-1草甘膦处理的垂序商陆死亡率达到100％,第3年新萌发垂序商陆生长与结实量已明显恢复.紫穗槐发育良好地段的垂序商陆各生长指标始终处于较低的平衡状态.采用紫穗槐替代法是长期控制垂序商陆的有效防治方法.     

土壤-牧草氮素供需状况变化对高寒草甸植被演替与草地退化的影响

在中国科学院海北高寒草甸生态系统定位站 ,选取处于不同退化阶段的具有典型代表意义的草甸草场为研究对象 ,通过对其土壤氮素矿化补给能力、牧草对氮素的需求量的研究 ,探讨土壤 牧草氮素供需状况变化对高寒草甸植被演替与草地退化的影响。结果表明 ,在牧草生长季 5～ 8月 ,高寒草甸土壤的氮素矿化补给量为 15 86 g·m-2 ,而随着高寒草甸退化程度的加重 ,植物群落中优势种群由禾草演替为禾草 苔草 嵩草、嵩草至杂类草 ,其牧草生长需要的总氮量分别为 2 2 86、2 4 87、37 3、14 96g·m-2 ,只有在杂类草草甸阶段 ,其牧草生长对氮素的需求才与其土壤氮素供求相适配 ,可见养分是高寒草甸植被演替与草场退化的重要驱动因子之一。     

Vegetation and soil recovery following Eucalyptus grandis removal in Limpopo Province,South Africa

South African terrestrial ecosystems are invaded by hundreds of alien plant species, and large‐scale clearing based on the passive restoration assumption that cleared areas will recover unaided is underway. This study assessed the recovery of vegetation and soil properties, three years following Eucalyptus grandis clearing using fell‐and‐removal and fell‐and‐stackburn methods at Zvakanaka Farm in Limpopo Province, South Africa. The main aim was to ascertain the extent of vegetation and soil recovery, as well as determining which clearing methods facilitate passive vegetation and soil restoration. Results indicate significantly (p < 0.001) lower native species diversity, cover and composition in cleared than in uninvaded sites. However, the recorded low species diversity and composition in cleared sites were more pronounced in the fell‐and‐stackburn than in the fell‐and‐removal sites. Measured soil physical properties varied, with compaction being higher in fell‐and‐removal, whereas soils were more repellent in fell‐and‐stackburn sites. The study concludes that vegetation and soil recovery, following E. grandis clearing, is complex and involves several interacting factors, which are linked to invasion history and intensity. Therefore, for vegetation and soil properties to recover, following E. grandis removal, the clearing programme should consider active restoration techniques, for example soil manipulation and native plant seeding.     

红树林生物入侵研究概况与趋势

为了掌握目前红树林生物入侵研究实况, 基于ISI Web of Science数据库和HistCite文献分析软件, 我们进行了全面系统的文献检索与分析。结果显示, 国内外有关红树林生物入侵研究文献绝大部分针对植物入侵, 有关动物与微生物的研究寥寥无几; 研究区域集中于中国华南与东南沿海(尤其是珠江口、雷州半岛西侧)和美国东南海岸及夏威夷群岛。无瓣海桑(Sonneratia apetala)是否构成入侵, 一直备受争议, 有待更长远论证, 但须谨慎引种。互花米草(Spartina alterniflora)与微甘菊(Mikania micrantha)是世界性恶草, 生长迅速, 繁殖力强, 竞争与化感作用明显, 二者已在红树林生态系统中爆发入侵, 显著降低了红树林微生境质量, 并改变了底栖生物群落结构。Rhizophora mangle作为外来红树植物入侵夏威夷群岛, 改善了沉积条件, 丰富了底栖生物群落, 但需从全球尺度考察入侵后果。目前, 红树林生物入侵研究才刚起步, 针对性研究局限于入侵对红树林生态系统结构和功能产生的效应。相关入侵机制缺乏探索, 现有防治方法大多只是借鉴其他被入侵系统的防治方法。今后, 红树林生物入侵研究应持续加深入侵现状和入侵效应的探索与评价, 加快开展入侵机制和防治方法的研究应用, 以及对生态系统服务的影响评价。健全红树林生物入侵管理体系, 将在防治红树林生物入侵实践中发挥主导作用。     

基于功能性状的毛乌素沙地不同演替阶段适生植物筛选

沙地生态系统修复是恢复生态学研究的热点问题,适生植物筛选是修复的关键。植物功能性状反映了植物在不同环境中的生存策略,探究沙地植物功能性状及其与环境之间的关系,有助于筛选用于植被恢复的物种,为保护沙地生态系统提供理论依据。以毛乌素沙地为研究区,分析了1983-2015年间沙地典型飞播样地群落演替特征及其对环境因子的响应,建立基于10个植物功能性状的毛乌素沙地潜在种库,进一步筛选飞播恢复下沙地不同演替阶段的适生植物。研究表明:(1)飞播恢复下的毛乌素沙地植物群落分为三个演替阶段:固沙先锋物种群落、沙生植物为主的杂类草群落、中生植物为主的杂类草群落。(2)土壤因子是群落演替的主要驱动力,其中土壤全氮、土壤总有机碳、土壤硝态氮是影响群落演替的关键因素。(3)基于功能性状筛选出29种适生物种用于植被恢复,演替第一阶段可用雾冰藜、猪毛菜等,演替第二阶段可用拂子茅、无芒隐子草等,演替第三阶段可用草地风毛菊、猪毛蒿等。通过物种功能性状特征可以快速选择适合沙地退化生态系统修复的候选物种,为植被恢复提供了一定的理论支持。     

不同带长微喷带灌溉对土壤水分布与冬小麦耗水特性及产量的影响

于2010-2012年度冬小麦生长季,选用高产冬小麦品种济麦22,采用测墒补灌方式,设置40 m(T₄₀)、60 m(T₆₀)和80 m(T₈₀)3种带长的微喷带灌溉处理,研究不同带长微喷带灌溉对土壤水分分布及冬小麦耗水特性和产量的影响.结果表明： 拔节期和开花期采用微喷带补灌,随微喷带带长缩短,灌溉水在土壤中的水平分布均匀系数显著增加.拔节期补灌,T₄₀和T₆₀处理在距畦首0～40 m范围内各小麦行间的0～200 cm土层土壤含水量均无显著差异;T₈₀处理在距畦首38～40 m、58～60 m和78～80 m处各小麦行间的0～200 cm各土层土壤含水量变化规律一致,均表现为随距微喷带的距离增加而减小.T₄₀处理的小麦在拔节至开花期间和开花至成熟期间分别对40～60 cm和20～80 cm土层土壤贮水的消耗量显著高于T₆₀和T₈₀处理,而对深层土壤贮水消耗量和总土壤贮水消耗量、开花期补灌水量、总灌水量和总耗水量显著低于T₆₀和T₈₀处理.随微喷带带长缩短,小麦籽粒产量、产量水分利用效率显著升高,而流量降低,在灌水量一定的情况下,单位时间内的有效灌溉面积减小.综合考虑小麦籽粒产量、水分利用效率和流量,40和60 m是本试验条件下的适宜微喷带带长.