期刊文献+
共找到62篇文章
< 1 2 4 >
每页显示 20 50 100
Diversity and Dynamics of Soil Free-Living Nematode Populations in a Mediterranean Agroecosystem 被引量:22
1
作者 LIANGWen-Ju I.LAVIAN +1 位作者 S.PEN-MOURATOV Y.STEINBERGER 《Pedosphere》 SCIE CAS CSCD 2005年第2期204-215,共12页
To determine the effect of agricultural management on the dynamics and functional diversity of soil nematode communities in a carrot field at Kibbutz Ramat Hakovesh, Israel, soil samples from 0-10 cm and 10-20 cm dept... To determine the effect of agricultural management on the dynamics and functional diversity of soil nematode communities in a carrot field at Kibbutz Ramat Hakovesh, Israel, soil samples from 0-10 cm and 10-20 cm depths were collected during the growing season of carrot. Indices were used to compare and assess the response of soil free-living nernatode communities to agricultural management. Eighteen nematode families and 20 genera were observed during the growing period, with Cephalobus, Rhabditidae, Aphelenchus, Tylenchus, and Dorylaimus being the dominant genera/families. During the planting, mid-season and post-harvest periods the total number of nematodes at both depths was significantly lower (P < 0.01) in the carrot treatment than in the control plots, while during the harvest period at both depths total nematodes and bacterivores were significantly higher in the treatment plots (P < 0.01). The values of the maturity index (MI) at both depths were found to be significantly lower in the treatment plots than in the control plots during the pre-planting period (P < 0.05). Overall, WI, MI and PPI were found to be more sensitive indicators than other ecological indices for assessing the response of nematode communities to agricultural management in a Mediterranean agroecosystem 展开更多
关键词 agricultural management carrot-growing season diversity maturity index nematode community
下载PDF
Forest characteristics,population structure and growth trends of threatened relict Pseudotsuga forrestii in China 被引量:1
2
作者 Cindy Q.Tang Shi-Qian Yao +8 位作者 Peng-Bin Han Jian-Ran Wen Shuaifeng Li Ming-Chun Peng Chong-Yun Wang Tetsuya Matsui Yong-Ping Li Shan Lu Yuan He 《Plant Diversity》 SCIE CAS CSCD 2023年第4期422-433,共12页
Pseudotsuga forrestii is a relict evergreen coniferous tree species in Pinaceae endemic to China.P.forrestii tree numbers have greatly decreased due to deforestation,over-utilization and habitat degradation.Here we cl... Pseudotsuga forrestii is a relict evergreen coniferous tree species in Pinaceae endemic to China.P.forrestii tree numbers have greatly decreased due to deforestation,over-utilization and habitat degradation.Here we clarify P.forrestii community types,structure,species diversity,seedling recruitments and growth trends.We identified four P.forrestii community types:(1)Pseudotsuga forrestii-Quercus guyavifolia-Acer davidii evergreen coniferous and broad-leaved mixed forest;(2)Pseudotsuga forrestii-Pinus yunnanensis-Quercus guyavifolia evergreen coniferous and broad-leaved mixed forest;(3)Pseudotsuga forrestii evergreen coniferous forest;(4)Pseudotsuga forrestii-Abies georgei var.smithii evergreen coniferous forest.P.forrestii forests are characterized by both warm temperate and temperate affinities.Simpson diversity,Pielou evenness,Shannon-Wiener diversity indices ranged from 0.75 to 0.76,0.74-0.81,and 1.62-1.93,respectively,with no significant differences among the four forest types.The forest stratification was multilayered.The canopy layer was generally 10-25 m tall,with the emergent layer reached 25-42 m.DBH and age structures of P.forrestii showed multimodal distributions.Its maximum age P.forrestii was 570 years with a DBH of 143 cm.The growth of annual ring width of P.forrestii was slow,and generally decreased with age,whereas the basal area at the breast height increased with age.Established seedlings/saplings were mainly found in unstable micro-habitats.Regeneration of P.forrestii depends on moderate natural disturbances.Finally,we provide recommendations for P.forrestii conservation. 展开更多
关键词 Pseudotsuga forrestii community structure Species diversity population structure Regeneration Growth trend
下载PDF
Some of the Mechanisms for Coexistence of Tree Species Diversity in Tropical Forests: A Review of Effects of Tree Density Dependence
3
作者 Oladele Fisayo Falade 《Open Journal of Forestry》 2023年第1期132-144,共13页
Tree communities contribute to maintenance of species diversity in tropical forests. Coexistence of many tree species is not without competition. Therefore, coexistence of tree species and size diversities occur seque... Tree communities contribute to maintenance of species diversity in tropical forests. Coexistence of many tree species is not without competition. Therefore, coexistence of tree species and size diversities occur sequentially or simultaneously in tropical natural forests. Understanding coexistence and competition mechanisms of tree species requires knowledge of interactions within and between species. However, many conservation efforts and strategies failed due to inability to identify and maintain functional coexistence mechanisms among tree species in the forest. Also, most trees died because of pressure on their habitats and not because of limiting growth resources. Hence, species identity, minimum distance and size of the neighbouring trees which are responsible for coexistence of competing trees in most tropical forests have not been explicitly reviewed. Therefore, this review evaluated some of the density dependent mechanisms for coexistence of tree species alpha diversity in tropical forests. Many interactive mechanisms are responsible for coexistence tree species in tropical forests. Inter- and intra-specific competitions are the most significant and both facilitate positive and negative density dependence. Therefore, switching from negative to positive density dependence may occur in some situations. Positive and negative density effects regulate species abundance and coexistence through conspecific and heterospecific structures. Aggregates of conspecific and heterospecific neighbours constitute forest spatial structure. Negative density interactions are mutually exclusive and basically ranged from effect of species identity of neighbours, distance to neighbours and tree size of the neighbours to reference trees in the community structures. Some mechanisms shorten distances for heterospecific than conspecific interactions. Conspecific structures improved survival and growth of rare tree species. Interactive mechanisms in tree community and population structures facilitate species diversity and size inequality, respectively. 展开更多
关键词 Tree community Structure Tree Species diversity Tree Species Coexistence Tree populations
下载PDF
Feedback Between Influent Condition Heterogeneity and Diversity of Bacterial Community in Bioreactor at Low Substrate Concentration
4
作者 Hui Feng Wei Wang +3 位作者 Zhiwei Zhao Maoan Du Fuyi Cui Ruisha Shi 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2017年第6期60-66,共7页
In order to investigate the effect of influent condition heterogeneity on diversity of the bacterial community,the degree of microbial resolution and effluent quality,biological treatment of micro-polluted source wate... In order to investigate the effect of influent condition heterogeneity on diversity of the bacterial community,the degree of microbial resolution and effluent quality,biological treatment of micro-polluted source water is proposed. Scanning Electron Microscopy( SEM) analysis reflects that influent conditions change the morphologies of biofilm. Denaturing Gradient Gel Electrophoresis( DGGE) analysis shows differences of H values are due to succession of functional bacterial communities. Microbial resolution values and species identifications reveal organic carbon is the main cause of community differentiation and bacterial migration. 展开更多
关键词 BACTERIAL community diversity BIOREACTOR cluster analysis INFLUENT HETEROGENEITY shannon index
下载PDF
Effects of community succession dynamics on forest biodiversity in eastern mountainous area of Heilongjiang Province
5
作者 孟庆凡 魏嵩 《Journal of Forestry Research》 CAS CSCD 2000年第3期210-212,共3页
Plant, insect and forest structures of 25 forest communities were investigated in Mao'ershan Experimental Forest Farm and Liangshui Experimental Forest Farm during 1994–1995. The paper used continuum index (C i) ... Plant, insect and forest structures of 25 forest communities were investigated in Mao'ershan Experimental Forest Farm and Liangshui Experimental Forest Farm during 1994–1995. The paper used continuum index (C i) as a parameter, to quantitatively describe forest community succession stage. Relationships between the biodiversity and continuum index of forest community were studied. The annual species and family diversities in forest plant community showed nonlinear correlation with continuum index, and the largest diversities were during the middle stage of succession. The diversities of total insect community and herbivorous insect group were negatively related withC i, that of spide group and parasitic insect group was positively related. The pattern diversity and coverage weight diversity index foliage height increased with continuum index. 展开更多
关键词 diversity Continuum index community dynamics
下载PDF
Effect of exclosure ages on woody plant structure,diversity and regeneration potential in the western Tigray region of Ethiopia 被引量:1
6
作者 Tsegay Gebregerges Zewdu K.Tessema Emiru Birhane 《Journal of Forestry Research》 SCIE CAS CSCD 2018年第3期693-703,共11页
Exclosure is a method of rehabilitating degraded lands by protecting them from the interference of animals and from human encroachment, and is used to regenerate native vegetation as a way to reduce soil erosion, incr... Exclosure is a method of rehabilitating degraded lands by protecting them from the interference of animals and from human encroachment, and is used to regenerate native vegetation as a way to reduce soil erosion, increase rain water infiltration and provide fodder and woody biomass in degraded grazing lands. Therefore, we studied woody plant structure, diversity and regeneration potentials in 5-and 10-year grazing exclosures in comparison with open grazed sites in a semi-arid environment. Data on species diversity, abundance, structure, basal area, frequency, density, and regeneration status were collected from 270 sample plots. Forty-one woody species representing 20 families were identified, with 18, 28 and 38 species found in open grazed areas, and in 5-and 10-year grazing exclosures, respectively. The 10-year grazing exclosures had a higher(P <0.05) species richness and plant densities compared to the 5-year grazing exclosures and the open grazed areas. The population structure and regeneration status of woody species in both grazing exclosures showed an inverted J-shape, indicating a healthy regeneration status, whereas hampered regeneration was observed in open grazed areas. The establishment of grazing exclosures had positive effects in restoring woody plant diversity and improving vegetation structure and regeneration potentials of degraded grazing lands. 展开更多
关键词 Basal area diversity Important value index population structure Regeneration status Species composition EXCLOSURES
下载PDF
Stand Structure, Diversity and Regeneration Status of Woody Species in Open and Exclosed Dry Woodland Sites around <i>Molapo</i>Farming Areas of the Okavango Delta, Northeastern Botswana 被引量:2
7
作者 John Neelo Demel Teketay +1 位作者 Keotshephile Kashe Wellington Masamba 《Open Journal of Forestry》 2015年第4期313-328,共16页
Stand structure, diversity and regeneration status of woody species were investigated in open and exclosed dry woodland sites in Island Safari, Shorobe and Xobe, northeastern Botswana. A total of 105, 111 and 130 quad... Stand structure, diversity and regeneration status of woody species were investigated in open and exclosed dry woodland sites in Island Safari, Shorobe and Xobe, northeastern Botswana. A total of 105, 111 and 130 quadrats, measuring 20 × 20 m each, were laid down along parallel line transects in the three sites, respectively, to collect data. A total of 47 species, representing 16 families and 24 genera, were recorded in the study sites. Of these, 33 species representing 13 families and 20 genera, 41 species representing 15 families and 23 genera and 27 species representing 10 families and 14 genera were encountered in Island Safari, Shorobe and Xobe, respectively. The most diverse family was Fabaceae followed by Combretaceae and Tiliaceae at all the three sites. The most diverse genus was Acacia, followed by Combretum and Grewia. The diversity of woody species in the study sites were 2.18, 2.15 and 1.5 in Shorobe, Island Safari and Xobe, respectively, while their corresponding evenness values were 0.6, 0.6 and 0.5, respectively. The mean densities of the woody species encountered in Island Safari, Shorobe and Xobe were 2629, 4271 and 2745 individuals ha&#451, respectively. The five densest species were Colophospermum mopane, Dichrostachys cinerea, Acacia tortilis, Philenoptera violacea and Terminalia prunioides in Island Safari, C. mopane, A. tortilis, A. erioloba, P. violacea and D. cinerea in Shorobe and Acacia mellifera, A. tortilis, P. nelsii, A. luederitzii and A. erubescens in Xobe. The highest important value index values were exhibited by C. mopane, D. cinerea, A. tortilis, P. violacea and T. prunioides in Island Safari, C. mopane, A. erioloba, A. tortilis, P. violacea and C. imberbe in Shorobe, and A. mellifera, A. tortilis, P. nelsii and A. luederitzii in Xobe. The alarming result was the fact that 71%, 80% and 85% of the woody species recorded in Island Safari, Shorobe and Xobe, respectively, exhibited hampered regeneration and, thus, unhealthy population structures. Therefore, there is an urgent need to address the observed unhealthy population structures of the woody species through investigation of the major causes of their hampered regeneration, and also designing measures that will facilitate natural and artificial regeneration of these species at the three study sites. 展开更多
关键词 Anthropogenic Disturbance Area EXCLOSURE Deforestation Density diversity Flood Recession (Molapo) FARMING Important Value index population Structure REGENERATION
下载PDF
The Diversity and Composition of Woody Plants in Chebera Churcura National Park (CCNP), Southern Ethiopia
8
作者 Mezmir Girma Melesse Maryo 《Open Journal of Forestry》 2018年第4期439-458,共20页
National parks harbor the most valuable biological diversities of national and global significance. The study of these diversities assists for the proper resource management. This study was carried out to determine wo... National parks harbor the most valuable biological diversities of national and global significance. The study of these diversities assists for the proper resource management. This study was carried out to determine woody species diversity and composition in CCNP. Systematic sampling was used to collect vegetation data from 67 plots (400 m2 each), which were laid following altitudinal gradient. From each plot presence/absence of woody species, abundance and structural data were recorded. R Program, Sorensen’s similarity, Shannon diversity index were used for vegetation analysis. Our result indicated that a total of 106 plant specimens belonging to 42 families and 90 genera were identified, of which 57.6% were trees, followed by 18.8% shrubs, 7.6% liana and 16% tree/shrub. The three most dominant families were Fabaceae, Rubiaceae and Combretaceae. Five vegetation community types were identified. Millettia ferugenia—Vepris danelii, and, Combrutum molle—Terminalia browni are among others. The tree density and basal area were 426.5 trees/hectare and 30.92 m2/hectare, respectively. The diversity and evenness indices were 3.88 and 0.46 for the study area, respectively. CCNP has more similarity with Bonga and Yayu afromontane forests of Ethiopia. Disturbances caused by the human activities and wild animals such as elephant were major threats to plant biodiversity in CCNP. We recommend floristic as well as ethnobotanical investigations to realize fully the existing plant diversity and their importance. Moreover, national attention should be given to ensure sustainable use of CCNP with its incredible biological resources. 展开更多
关键词 diversity National PARK population Structure Plant community
下载PDF
Macrobenthos Community Structure and Its Relations With Environmental Factors in Three Reservoirs in Tianjin 被引量:1
9
作者 姜巨峰 傅志茹 +4 位作者 李文雯 张韦 孟一耕 钱红 李相普 《Agricultural Science & Technology》 CAS 2014年第6期947-953,969,共8页
[Objective] The aim was to research macrobenthos community structure and its relations with environmental factors in three reservoirs. [Method] Benthic diversity and water quality of Yuqiao Reservoir, Beidagang Reserv... [Objective] The aim was to research macrobenthos community structure and its relations with environmental factors in three reservoirs. [Method] Benthic diversity and water quality of Yuqiao Reservoir, Beidagang Reservoir and Er- wangzhuang Reservoir were investigated in May, July and September 2011, respec- tively. []Result] Of all the 14 sampling sites, 22 species of macroinvertebrates were collected, totally, which included 6 species of aquatic insects, 7 species of Mollusca, 2 species of Crustacean, 7 species of Oligochaeta. The species of macroinverte- brates during May, July and September in Yuqiao reservoir were 11, 8 and 10, respectively. The dominant species were Chironomus sinicus, and Monopylephorus limosus. The average density and biomass of the macrobenthos were 132.43 ind./m2 and 50.09 g/m2. Yuqiao reservoir was mostly at status of premediate polluted, according to the Margalef index, Shannon index and Pielou index. The species of during May, July and September in Beidagang reservoir were 5 5 and 5, respectively. The dominant species were Chironomus sinicus, Penaeus vannamei. The average density and biomass of the macrobenthos were 218 ind./m2 and 2.70 g/m2. Beidagang reservoir was mostly at status of heavy polluted, accord- ing to the Margalef index, Shannon-wiener index, Pielou index. The species of during May, July and September in Erwangzhuang reservoir were 3, 5 and 5, respectively. The dominant species were Monopylephorus limosus, Chi- ronomus sinicus. The average density and biomass of the macrobenthos were 104 ind/m2 and 0.20 g/m2. Erwangzhuang reservoir was mostly at status of intermediate polluted, according to the Margalef index, Shannon index, Pielou index. The density of zoobenthos in Yuqiao Reservoir was positively significantly correlated with TP (P〉 0.05), negatively correlated with NH4+-N (P〉0.05), positively correlated with COD (P〈 0.01), not significantly correlated with other environment factors (P〉0.05). There was no significant correlation between biomass of zoobenthos and environment factors. The density of zoobenthos in Beidagang Reservoir with NH4+-N was positively signif- icantly correlated (P〈0.05), not significantly correlated with other aquatic environment factors (P〉0.05). There was no significant correlation between biomass of zoobenthos and environment factors. The density of zoobenthos in Erwangzhuang Reser- voir with NO3-N was positively significantly correlated (P〈0.05), not significant cor- related with other aquatic environment factors (F〉0.05). The biomass of zoobenthos in Erwangzhuang Reservoir with NH4+-N was positively significantly correlated (P〈 0.05), not significant correlated with other aquatic environment factors (P〉0.05). [Conclusion] It is indicated that this three reservoirs were all eutrophied and polluted, and the eurephication extent change of water in three reservoirs is as follows: Beidagang reservoir〉Erwangzhuang reservoir〉Yuqiao reservoir. 展开更多
关键词 MACROBENTHOS community structure diversity index Water quality as-sessment Large reservoirs TIANJIN
下载PDF
蓖麻SL1×CHCH1 F_(2)群体的主要农艺性状分析
10
作者 王宙 王宏伟 +4 位作者 曹越 王亚 赵宜婷 张宏斌 杨俊芳 《山西农业科学》 2024年第4期34-41,共8页
为了挖掘控制蓖麻产量的数量性状位点(Quantitative trait loci,QTL),为进一步QTL定位研究奠定基础,以农艺性状差异比较大的蓖麻SL1和CHCH1为亲本,杂交获得194份F2群体材料,并对该群体的15个主要农艺性状进行了遗传多样性分析、相关性... 为了挖掘控制蓖麻产量的数量性状位点(Quantitative trait loci,QTL),为进一步QTL定位研究奠定基础,以农艺性状差异比较大的蓖麻SL1和CHCH1为亲本,杂交获得194份F2群体材料,并对该群体的15个主要农艺性状进行了遗传多样性分析、相关性分析、回归分析、主成分分析和聚类分析。结果显示,该群体的15个农艺性状的遗传变异系数为12.80%~56.30%,遗传多样性指数为1.23~2.07,表明该群体间性状差异较大,性状分离明显,表型变异丰富。相关性分析发现,单株产量和单株蒴果总数呈极显著正相关,相关系数最高,为0.940。逐步回归分析发现,影响单株产量的2个重要因素为有效蒴果总数和百粒质量。主成分分析获得4个主要因子,累计贡献率为73.538%。根据综合得分,可将194份群体材料分为3大类,第Ⅰ类材料主要表现为植株高大、粗壮、多穗、单株产量高;第Ⅱ类材料主要表现为株高、单株蒴果总数、单株产量适中;第Ⅲ类材料主要表现为植株较矮、果穗长度较短、有效分枝穗数少、单株产量较低。最后,在该群体里筛选到综合表现较好的5份材料。 展开更多
关键词 蓖麻 F2群体 变异系数 多样性指数 相关性分析 回归分析 聚类分析
下载PDF
Analysis of effect of nicotine on microbial community structure in sediment using PCR-DGGE fingerprinting 被引量:3
11
作者 Ai-dong Ruan Chen-xiao Liu 《Water Science and Engineering》 EI CAS CSCD 2015年第4期309-314,共6页
Solid or liquid waste containing a high concentration of nicotine can pollute sediment in rivers and lakes, and may destroy the ecological balance if it is directly discharged into the environment without any treatmen... Solid or liquid waste containing a high concentration of nicotine can pollute sediment in rivers and lakes, and may destroy the ecological balance if it is directly discharged into the environment without any treatment. In this study, the polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) method was used to analyze the variation of the microbial community structure in the control and nicotinecontaminated sediment samples with nicotine concentration and time of exposure. The results demonstrated that the growth of some bacterial species in the nicotine-contaminated sediment samples was inhibited during the exposure. Some bacteria decreased in species diversity and in quantity with the increase of nicotine concentration or time of exposure, while other bacteria were enriched under the effect of nicotine, and their DGGE bands changed from undertones to deep colors. The microbial community structure, however, showed a wide variation in the nicotine- contaminated sediment samples, especially in the sediment samples treated with high-concentration nicotine. The Jaccard index was only 35.1% between the initial sediment sample and the sediment sample with a nicotine concentration of 0.030 μg/g after 28 d of exposure. Diversity indices showed that the contaminated groups had a similar trend over time. The diversity indices of contaminated groups all decreased in the first 7 d after exposure, then increased until day 42. It has been found that nicotine decreased the diversity of the microbial community in the sediment. 展开更多
关键词 NICOTINE SEDIMENT PCR-DGGE Microbial community structure diversity index
下载PDF
Phylogenetic patterns of shrub communities along the longitudinal and latitudinal gradients on the northeastern Qinghai–Tibetan Plateau 被引量:1
12
作者 XIAO Yuan-ming YANG Lu-cun +3 位作者 NIE Xiu-qing LI Chang-bin XIONG Feng ZHOU Guo-ying 《Journal of Mountain Science》 SCIE CSCD 2020年第5期1106-1114,共9页
Biodiversity distribution patterns are a basic and long-standing but crucial aspect of ecology research.These patterns form the primary source of data used to develop biodiversity protection practices,especially in mo... Biodiversity distribution patterns are a basic and long-standing but crucial aspect of ecology research.These patterns form the primary source of data used to develop biodiversity protection practices,especially in mountain ecosystems.Shrubs comprise one of the main types of vegetation on the Qinghai–Tibetan Plateau,where they serve vital ecological functions.In this study,we used a community phylogenetic approach to examine the distribution patterns of shrub communities along the longitudinal and latitudinal gradients on the northeastern Qinghai–Tibetan Plateau.We observed significant latitudinal trends in both the phylogenetic diversity(PD)and net relatedness index(NRI)values of shrub communities,such that the former decreased and the latter increased with increasing latitude.However,no significant PD,NRI and nearest taxon index(NTI)distribution patterns were observed along a longitudinal gradient.A further analysis revealed that the combination of temperature-related and precipitation-related climate variables most strongly affected the PD,NRI and NTI values of shrub communities,indicating that the latitudinal patterns in the PD,NRI and NTI of a shrub community may be determined mainly by interactions with these climate factors. 展开更多
关键词 Phylogenetic diversity Phylogenetic community structure Shrub communities Qinghai–Tibetan Plateau Net Relatedness index Nearest Taxon index
下载PDF
Presence of Sargassum horneri at Todos Santos Bay, Baja California, Mexico: Its Effects on the Local Macroalgae Community 被引量:1
13
作者 Giuliana I. Cruz-Trejo Silvia E. Ibarra-Obando +2 位作者 Luis E. Aguilar-Rosas Miriam Poumian-Tapia Elena Solana-Arellano 《American Journal of Plant Sciences》 2015年第17期2693-2707,共15页
To describe the annual cycle of Sargassum horneri in Mexican waters, we selected two sites differing in their degree of wave exposure and sediment type: Rincón de Ballenas (RB), and Rancho Packard (RP). From June... To describe the annual cycle of Sargassum horneri in Mexican waters, we selected two sites differing in their degree of wave exposure and sediment type: Rincón de Ballenas (RB), and Rancho Packard (RP). From June 2009 to April 2010 we followed the seasonal changes in S. horneri density and biomass along two intertidal transects per site. The effects of this non-indigenous species on the local macroalgae community were assessed by comparing their species composition, density, biomass, species richness, and diversity index in quadrats with and without S. horneri. There were significant differences in S. horneri density and biomass between sites (P < 0.001). At RB the invasive alga density average was 2 ± 0.94 individual m-2, with a mean biomass of 4 ± 0.95 g DW m-2. At RP, S. horneri density average was 10 ± 0.96 individual m-2, and mean biomass of 102 ± 0.97 g DW m-2. At RB, the invasive alga promoted a significant reduction in the four selected structural variables, and the corticated macrophytes and the foliose functional forms were severely reduced. At RP, there were only marginally significant effects (P = 0.06) of S. horneri presence on the local macroalgae community, and higher density, biomass, and diversity values were found when S. horneri was present. Most of the functional forms were found, even if the invasive alga was present. At both locations, the highest biomass corresponded to the articulated calcareous functional form. These contrasting results could be due to the fact that the native macroalgae community has already been altered by the early invasion of S. muticum, with the most resilient species and functional forms remaining in place. One of the most important changes we noticed is the severe reduction of the canopy forming species at both sites. 展开更多
关键词 ANNUAL Cycle community Structure diversity index Functional Forms INVASIVE ALGA Species Richness
下载PDF
Effect of forest fragment size on tree diversity and population structure of humid subtropical forest of Meghalaya, India 被引量:1
14
作者 Om Prakash Tripathi Khongjee Rangdajied Reynald 《生物多样性》 CAS CSCD 北大核心 2010年第2期208-214,共7页
The present study was conducted in subtropical humid forests of Meghalaya to study the distributional pattern of species, floristic composition, community structure and tree population structure.Forest fragments of va... The present study was conducted in subtropical humid forests of Meghalaya to study the distributional pattern of species, floristic composition, community structure and tree population structure.Forest fragments of varying sizes(0.5 ha, 1 ha, 2 ha and 5 ha) were used in the study.All of the forest fragments are distributed within the same altitudinal range, and had similar rainfall and temperature regimes.Four forest fragments were sampled using random quadrats to analyze the impact of fragment size on tree diversity and population structure.Indices were used to compare the dispersion pattern of plant species, species diversity among fragments, and the heterogeneity and homogeneity of the fragments.A total of 45 tree species were recorded from all the fragments and simple correlation showed that the species richness was positively related to fragment size(n = 4, P<0.05).Other measures such as stand density, basal cover, diversity and dominance indices were unrelated to fragment size.Forest canopy was composed mainly of Castonopsis indica, C.armata, Schima khasiana and Engelhardtia spicata in all of the fragments.A majority of woody tree species were contagiously distributed which made the forest community highly patchy in nature.Low values of Sorensen's similarity index and high values of Whittaker's β-diversity index between the fragments suggest marked difference in the species composition among the fragments.The maximum stand density, basal area, Shannon diversity index and Simpson dominance index was recorded in a 5-ha fragment.Trees in lower girth classes(15-55 cm circumference at breast height, CBH) accounted for 52-86% of stand density in all fragments except in 0.5-ha fragments where middle girth class(55-95 cm CBH) accounted for 47% of the total stand density.The overall density of seedlings, saplings and adult trees formed a pyramidal structure, indicating that the period between the sapling and adult stage was a critical stage in tree life cycles, as the maximum mortality occurred during this period.These groves are mildly/highly disturbed by communities using forests for their timber and fuel wood requirements as well as cattle and goat grazing.Tree regeneration was apparently not limited, as was evidenced by high density of saplings.These human activities may have been responsible for a decrease in tree diversity in the smaller fragments.Large fragments that were less disturbed harbored species not present in small fragments. 展开更多
关键词 生物多样性 相异性指数 生态学 森林
原文传递
CHARACTERISTICS OF SMALL RODENT COMMUNITY IN DIFFERENT AGED CUT-OVER AREAS IN DAILING MOUNTAIN
15
作者 高中信 姜洪海 +1 位作者 高继宏 赵淑琴 《Journal of Northeast Forestry University》 SCIE CAS CSCD 1994年第4期52-57,共6页
The field investigation of small rodent community was made in Liangshui Reserve, Heilongiiang Province, in 1992. Species composition and percentage of each species of the small rodents in different aged clear-cut-over... The field investigation of small rodent community was made in Liangshui Reserve, Heilongiiang Province, in 1992. Species composition and percentage of each species of the small rodents in different aged clear-cut-over areas were analyzed. The change of rodent community was associated with the change of vegetation cover. Forest harvest, which results in change of light, temperature, water and othcr ecological factors, made change of vegetation cover and was the main cause for the change of small rodent community. The small rodents were low in number of species population and diversity index in the inatial stages after clear cutting. The diversity index of rodents in order of different aged cut-over areas were 5-year-old area >20-year-old area > 28-year-old area > 1 -year-old area > 10-year-old area. 展开更多
关键词 Cut-over area Rodent community Forest harvest diversity index
下载PDF
Impact assessment of genetically modified herbicide-tolerant cotton on arthropod communities
16
作者 LI Dongyang ZHU Xiangzhen +5 位作者 ZHANG Kaixin WANG Li ZHANG Rui LIANG Chengzhen LUO Junyu CUI Jinjie 《Journal of Cotton Research》 2022年第2期164-172,共9页
Background:Cotton(Gossypium spp.)is one of the most important economic crops worldwide,and its production plays an important role in the economy of many countries.Genetically modified herbicide-tolerant(GMHT)crops,whi... Background:Cotton(Gossypium spp.)is one of the most important economic crops worldwide,and its production plays an important role in the economy of many countries.Genetically modified herbicide-tolerant(GMHT)crops,which were developed to minimize the losses caused by weeds,have gradually become the most widely adopted genetically modified crops in the world due to their economic and environmental benefits.However,the potential ecological and environmental risks of GMHT crops have attracted extensive attention and controversy.Arthropod communities form a promine nt part of the biodiversity of agroecosystems and are important indicators of environmental health.Elucidating the effects of GMHT crops on the diversity of arthropod communities is necessary to ensure the safety of GMHT crops.Result:In this 2-year study,we investigated the potential impact of GMHT crops on arthropod communities.The GMHT cotton variety GGK2 with glyphosate tolerance and its near-isogenic non-GMHT variety K312 were used for the experimental groups.The Shannon diversity index(H),Simpson diversity index(D),Pielou evenness index(J),and principal co-ordinates analysis(PCoA)of the Bray-Curtis distance were used to evaluate the population dynamics and biodiversity of arthropods in cotton fields.No significant differences were found between GGK2 and K312 in their total abundance of arthropod communities,and biodiversity indexes on most sampling dates.The arthropod composition in the GGK2 and K312 plots was similar.Sampling elates had a significant effect on biodiversity indexes,whereas no clear tendencies related to cotton variety or cotton variety x sampling elates interaction were recorded.In addition,PCoA revealed high similarity between the arthropod communities in the plots of the GMHT cotton variety GGK2 and its near-isogenic variety K312.Conclusion:There was no obvious difference in abundance,diversity indexes of arthropod communities between GMHT cotto n variety GGK2 and its near-isogenic variety K312 under the small-scale plan ting regime. 展开更多
关键词 GMHT crops COTTON Arthropod communities BIOdiversity diversity index PCoA
下载PDF
Phylogenetic Structure of Low Altitude Forest Communities in Baotianman Mountain
17
作者 Jianghao ZHAO Yingying LIU +4 位作者 Xiaoguo BAI Anping LI Yanjiao LI Shiping CHENG Guang QI 《Asian Agricultural Research》 2022年第6期31-36,共6页
[Objectives]The paper was to reveal the phylogenetic structure of low altitude forest communities in Baotianman Mountain.[Methods]Ten 20 m×20 m plots were set at an altitude of 249-796 m in Baotianman Nature Rese... [Objectives]The paper was to reveal the phylogenetic structure of low altitude forest communities in Baotianman Mountain.[Methods]Ten 20 m×20 m plots were set at an altitude of 249-796 m in Baotianman Nature Reserve,in which 62 plant species were found.A phylogenetic tree was established on Phylomatic website,and the community related phylogenetic indexes at low altitude were calculated and analyzed,including net relatedness index(NRI),nearest taxon index(NTI),phylogenetic diversity Faith's PD index,phylogeneticβdiversity PhyloSor index and Dnn index.[Results]The NTI and NRI values of low altitude forest communities were generally greater than 0,showing phylogenetically clustered communities,and habitat filtration was the dominant factor in community construction.Combined with the species abundance matrix of plots,it was found that PD index had a significantly positive correlation with species richness.Phylogeneticβdiversity PhyloSor index was larger in the lower altitude area,which was exactly opposite to Dnn index.In other words,the more similar the community,the closer the distance between species,and the communities were phylogenetically clustered.[Conclusions]The study can provide a scientific basis for forest community management and restoration. 展开更多
关键词 Phylogenetic tree community phylogeny βdiversity index
下载PDF
Does palynological diversity reflect floristic diversity?A case study from Northeast China
18
作者 Yifan CUI Feng QIN +3 位作者 Yan ZHAO Qiaoyu CUI Rongwei GENG Quan LI 《Science China Earth Sciences》 SCIE EI CAS CSCD 2023年第9期2097-2108,共12页
Fossil pollen data can provide important information of past vegetation diversity,on the basis of established relationship between modern palynological and floristic diversity.However,current studies on modern pollen ... Fossil pollen data can provide important information of past vegetation diversity,on the basis of established relationship between modern palynological and floristic diversity.However,current studies on modern pollen assemblages in China have not examined this relationship yet.Herein,we report a case study from Northeast China,aiming to investigate the representation of modern palynological diversity to regional floristic diversity.A total of 87 sets of modern pollen and vegetation data from various vegetation types were applied to assess modern palynological diversity and floristic diversity in Northeast China,and the relationship between palynological and floristic diversity was studied using spatial pattern comparison and correlation analysis.Moreover,to reduce representation bias related to pollen production and dispersal,we calibrated pollen data using the Regional Estimates of Vegetation Abundance from Large Sites(REVEALS)model with Pollen Productivity Estimates(PPEs)and Fall Speeds of Pollen(FSP).The results show that the spatial variations of palynological and floristic richness among vegetation types are similar,and have a good positive correlation(r=0.41,p<0.01).However,palynological evenness presents a different spatial pattern from floristic evenness,with a weaker positive correlation(r=0.21,p>0.05).The calibration on pollen data using REVEALS model minimized the differences in spatial patterns between palynological and floristic diversity,and improved the correlations between them(richness,r=0.50,p<0.01;evenness,r=0.33,p<0.01).Our study indicates that palynological richness in Northeast China could reflect regional floristic richness in general,and the calibration with REVEALS model is recommended for reconstructing past floristic diversity from pollen data. 展开更多
关键词 Northeast China Modern palynological diversity Floristic diversity Richness and evenness community dissimilarity index REVEALS model
原文传递
蒙古栎主要种群表型性状变异分析及多样性研究
19
作者 王娜 杨会娜 肖健 《林业与生态科学》 2023年第3期269-274,共6页
为揭示蒙古栎种群的表型分化程度和变异规律,探索蒙古栎表型变异特点和性状地理分布格局,对来自河北、内蒙古、辽宁、吉林、黑龙江5省6个蒙古栎天然种群的10个表型性状进行差异分析和多样性研究,采用巢式分析、相关性分析及聚类分析对... 为揭示蒙古栎种群的表型分化程度和变异规律,探索蒙古栎表型变异特点和性状地理分布格局,对来自河北、内蒙古、辽宁、吉林、黑龙江5省6个蒙古栎天然种群的10个表型性状进行差异分析和多样性研究,采用巢式分析、相关性分析及聚类分析对种群表型多样性进行系统分析。结果发现,蒙古栎的9个表型性状差异显著,种群表型分化系数为48.12%,种群内表型分化程度略高于种群间表型分化程度;10个表型性状香农指数均大于1.00,性状表现丰富,种群变异系数差别较大,变异幅度为5.0%~51.1%,同一表型性状在不同种群间的变异及同一种群内不同表型性状的变异不同;利用聚类分析将蒙古栎种群分为3类,聚类结果与地理距离不一致。 展开更多
关键词 蒙古栎 种群 表型性状 表型分化系数
下载PDF
披碱草属8种野生牧草居群穗部形态多样性 被引量:23
20
作者 德英 穆怀彬 +2 位作者 刘新亮 赵来喜 王照兰 《草业科学》 CAS CSCD 北大核心 2011年第9期1623-1631,共9页
采用14项穗部性状对披碱草属8种(Elymusspp.)101个野生牧草居群的形态多样性进行研究。结果表明,采自同一地区不同种的各居群之间以及采自不同地区同一种的各居群之间表现型均存在一定的差异。8个披碱草属牧草种间存在差异,14项穗部性状... 采用14项穗部性状对披碱草属8种(Elymusspp.)101个野生牧草居群的形态多样性进行研究。结果表明,采自同一地区不同种的各居群之间以及采自不同地区同一种的各居群之间表现型均存在一定的差异。8个披碱草属牧草种间存在差异,14项穗部性状中,肥披碱草(E.excelsus)有9个性状(穗长、穗宽、小穗长、小穗宽、小穗数、每穗轴小花数、第一外稃芒长、第一颖长、主穗轴第一节间长)均为最大值;黑紫披碱草(E.atratus)的穗宽、第一外稃长、第一颖芒长3个性状均为最小值;变异系数大小依次为第一颖芒长>旗叶与穗基部长度>第一颖长>主穗轴第一节间长>第一颖宽>第一外稃芒长>穗宽>小穗数>每穗轴小花数>小穗宽>穗长>小穗长>第一外稃长>第一内稃长。8个披碱草属牧草居群总遗传多样性指数为垂穗披碱草(E.nutans)>老芒麦(E.sibiricus)=披碱草(E.dahuricus)>麦薲草(E.tangutorum)>肥披碱草>圆柱披碱草(E.cylindricus)>短芒披碱草(E.breviaristatus)>黑紫披碱草;居群平均遗传多样性指数为老芒麦>肥披碱草>垂穗披碱草>披碱草>黑紫披碱草>短芒披碱草>圆柱披碱草>麦薲草;表型分化系数为麦薲草>圆柱披碱草>垂穗披碱草>披碱草>老芒麦>肥披碱草>短芒披碱草>黑紫披碱草;8个披碱草属牧草的多样性是由居群内和居群间多样性共同引起的,不同物种其多样性二者所占的比例是各不相同的。 展开更多
关键词 披碱草属 居群 穗部性状 多样性指数
下载PDF
上一页 1 2 4 下一页 到第
使用帮助 返回顶部