祁连山4种杜鹃在不同海拔梯度上的株丛特征

以分布于祁连山东段的头花杜鹃(Rhododendron.Capitatum)、千里香杜鹃(R.thymifolium)、烈香杜鹃(R.anthopogonoides)和陇蜀杜鹃(R.przewalskii)为对象,研究了其株丛特征与海拔梯度间的关系。随着海拔升高,头花杜鹃、千里香杜鹃和烈香杜鹃的冠基呈降低趋势。随着海拔升高,头花杜鹃与千里香杜鹃的重要值增加,并显著大于其他物种。在海拔3 100m处,杜鹃灌丛群落物种组成和多样性均处于较高水平。随着海拔升高,杜鹃灌丛总盖度逐渐降低。千里香杜鹃的分盖度在海拔3050m较小。头花杜鹃的分盖度在各海拔梯度上均较大。头花杜鹃和千里香杜鹃的植株高度随着海拔升高而逐渐降低。     

三江源区高寒草甸植物群落与土壤理化性质沿海拔梯度的变化特征

为探讨高寒植物群落物种多样性和土壤理化特征随海拔梯度的变化以及相互关系，本研究以不同海拔的典型高寒草甸植被群落为研究对象，综合分析了高寒草地植物群落物种组成、物种多样性及土壤理化性质对海拔梯度变化的响应。结果表明：植物群落在中海拔梯度处物种最丰富，生产力最高；除pH、土壤容重外，土壤环境其他因子含量随海拔梯度增加呈先增加后减少趋势，在中海拔处值最高；物种Margalef指数、Shannon-Weiner指数、Simpson指数和Pielou指数均随海拔升高呈单峰变化；植物群落生物量和群落多样性与土壤理化特征之间均呈正相关关系，与土壤容重、pH值之间存在负相关性，影响植物群落多样性的主要环境因子是土壤水分、速效磷和铵态氮，结果表明不同海拔梯度下的环境差异对研究区内植物群落多样性与土壤理化特征具有显著影响。本研究可为三江源区高寒草甸生态系统的保护恢复措施建设提供科学的参考。     

拉萨河谷山地灌丛草地植物多样性监测方法的比较研究

生物多样性是西藏生态安全监测与评估的重要内容之一.在气候变暖和放牧干扰背景下沿海拔梯度探讨西藏拉萨河谷山地灌丛草地植物群落物种多样性的变化特征,对于该地区草地的保护与可持续利用具有重要意义.以拉萨市林周县白朗村沟域的山地灌丛草地为研究对象,采用常规样方法,重复样线法和Modified-Whittaker样地法3种方法进行系统调查,研究草地群落物种组成及其沿海拔梯度的变化特征.结果表明,1) 3种不同取样方法α多样性的物种丰富度均随海拔的升高呈先增加后降低的趋势,其中50 m样线法效果最好.2) 表征β多样性的Sorensen相似性指数和Bray-Curtis指数均随样地间海拔高差的增大而减小.3) 种-面积关系的截距c,斜率z随海拔的升高呈先增加后降低的趋势,与α,β多样性随海拔梯度的变化特征吻合一致.4) 依据种-面积关系研究结果,山地灌丛草地设置100 m²的样地可覆盖80%左右的植物物种.山地灌丛草地的α和β多样性指数沿海拔梯度均呈先增后减的变化特征,未来研究应注重植物多样性分布格局对山体气候梯度以及放牧干扰变化的响应和适应机制.     

祁连山天涝池流域典型灌丛地上生物量沿海拔梯度变化规律的研究

通过野外样地调查和试验,以祁连山寺大隆林区天涝池流域高山灌丛为研究对象,建立地上生物量与易测因子(冠幅周长和植株高度)之间的关系,对灌丛地上生物量随海拔梯度变化的分布规律进行研究.结果表明:阳坡和阴坡灌丛的平均总地上生物量分别为7375.8 kg·hm-2和3055.6 kg·hm-2;随着海拔高度升高,阳坡与阴坡灌丛地上生物量均呈单峰型曲线变化,其最大值分别分布在海拔3200m和3650m处,分别为12101.6 kg·hm-2和4084.8 kg·hm-2;在4种灌丛植物中,金露梅(Potentillafruticosa)和吉拉柳(Salix gilashanica)地上生物量最大值分别出现在海拔3150m和3650m,鬼箭锦鸡儿(Caragana jubata)和高山绣线菊(Spiraea alpina)最大值分布在海拔3200 m.综上可知,祁连山天涝池流域灌丛地上生物量随海拔升高呈先增加后减小的单峰型曲线变化.     

东祁连山高寒草原柳灌丛—草地群落结构研究

以东祁连山高寒地区柳灌丛群落为研究对象,在海拔3 050～3 450 m内设2样线,每样线沿海拔梯度每50 m设1个16 m×16 m调查样地,采用记名记数法取样调查,对柳灌丛群落的结构、组成进行了系统研究.结果表明,东祁连山高寒柳灌丛群落主要由30种植物构成,其中,灌木植物13种,草本植物17种,立面上该群落由高位芽植物层片、地面芽植物层片和地下芽植物层片组成.     

甘肃尕海湿地不同海拔草地群落组分及物种多样性研究

以青藏高原东部甘肃尕海湖西侧坡地为研究对象,在尕海湖边到坡地顶部(海拔3 485~3 650 m)内,调查了不同海拔梯度上植物群落物种组成和群落特征数据,分析不同海拔草地群落特征、物种生活型变化及人类活动的影响,以期探讨高寒湿地附近草地群落组分与物种多样性对海拔梯度和人为干扰的响应。结果表明,尕海湖西侧坡地共调查到59种被子植物,分别属于20科46属,其区系特征以温带分布为主,且植物生活型和功能型以多年生和非固氮植物为主。在不同海拔梯度上草地群落可分为早熟禾-银莲花群落、羽毛委陵菜-平车前群落、紫花针茅群落、早熟禾-菭草群落、早熟禾-嵩草群落和嵩草-莎草群落。人类活动严重影响着草地群落特征,即在人类活动较弱的区域以禾本科和莎草科为主,而在人类活动较强的区域,由早熟禾为主的高寒草原群落类型演变为羽毛委陵菜-平车前群落和紫花针茅群落。此外,物种多样性指数与海拔间存在明显的负相关,即物种丰富度、物种密度、相邻群落间共有物种数目和相似性指数随海拔升高而逐渐降低。可见,海拔和人类活动强烈影响着高寒草地群落的组成和多样性,尤其人类活动影响更为剧烈。因而,为保证高寒草地生态系统可持续发展和物种多样性的维持,应采取合理有效的保护措施,尽量减少人类活动的影响。     

青南高海拔地区高寒草甸植物群落多样性的研究

根据 42个样地的实地调查资料 ,采用不同的物种多样性指数、丰富度和均匀度测度指标对达日县建设乡高海拔地区高寒草甸的物种多样性进行了分析 ,结果表现为 :草地物种多样性随海拔的升高总体上呈现下降的趋势 ;“黑土滩”物种多样性指数、丰富度和均匀度指数最低 ,草地生物量也最低。苔草、嵩草和灌丛草甸 ,有着较高的物种多样性指数、丰富度和均匀度指数。单子叶和灌丛植物生物量随海拔梯度的变化较为复杂 ,在一定海拔范围内有较高的生物量。双子叶植物生物量随海拔的升高基本呈现下降趋势     

祁连山不同植被类型土壤微生物群落多样性差异

土壤微生物是土壤生态系统的重要组成部分,在生态系统物质循环和能量转化中占有重要的地位。以祁连山中段不同海拔的4种植物群落,即垫状植被(cushion plants,CP)、高寒草甸(alpine meadow,AM)、沼泽化草甸(swamp meadow,SM)和高寒灌丛(alpine shrub,AS)作为实验样地,采用BIOLOG技术,探讨了土壤微生物群落多样性在不用海拔梯度形成的植被条件下的变化特征。结果表明,反映微生物活性的平均颜色变化率(average well color development,AWCD)的大小顺序为:沼泽化草甸高寒草甸高寒灌丛垫状植被,沼泽化草甸土壤微生物群落代谢活性最高;高寒草甸和沼泽化草甸土壤微生物群落碳源利用模式相似,土壤微生物群落的Shannon-Wiener物种丰富度指数(H)与土壤有机碳和全氮显著相关(P0.05),Simpson优势度指数(D)和Mc Intosh指数(U)与土壤全氮显著相关(P0.05);冗余分析表明,土壤有机碳、p H和全氮可能是土壤微生物利用碳源的控制因子。研究结果为进一步探讨高寒草甸与土壤微生物之间的关系奠定了基础。     

高寒草甸湿润与干旱化生境中植物多样性的海拔分布格局

受全球变化和外界干扰的影响,青藏高原高寒草甸生境趋向干旱化。生境变化对物种多样性的海拔分布格局有何影响?本研究以藏东南东达山作为研究地点,沿海拔梯度设置9个样地,在每个样地设置10个1m×1m样方,5个位于湿润生境,5个位于干旱生境,调查样方内的物种组成。将样方中频度≤7的物种确定为偶见种,反之为常见种,分析所有种、偶见种和常见种α、β和γ多样性沿海拔梯度的分布格局。以Cody指数(βC)、倍性分配法(βW)和物种组成相似性随海拔距离的衰减速率(βslope)3种方法测度β多样性。样地中共记录种子植物160种,其中湿润生境132种,干旱生境107种。湿润生境中,所有种和偶见种的α和γ多样性随海拔的增加而下降,而干旱生境中呈现为增加趋势;常见种α和γ多样性在两种生境中均随海拔的增加而略增加。3种β多样性指数的分布格局不一致,湿润生境中βC和βW多样性高于干旱生境,偶见种βC和βW多样性高于常见种。高寒草甸湿润与干旱生境物种多样性的海拔分布格局不同,偶见种多样性高,直接影响物种多样性的海拔分布格局。     

山西关帝山亚高山灌丛、草甸物种多样性的研究

运用12个多样性指数对12个灌丛群落样地和21个草甸群落样地进行了数量分析,结果如下,1)关帝山亚高山灌丛、草甸群落的物种多样性与海拔有较密切的关系,随着海拔的升高,其丰富度指数明显下降;均匀度指数表现为升高趋势;综合多样性指数也呈下降趋势;2)关帝山亚高山灌丛、草甸群落的物种多样性与坡度有较密切的关系,随着坡度的下降,灌丛、草甸的丰富度呈现平缓下降的趋势;均匀度和综合多样性呈现明显上升的趋势;3)在各多样性指数的变化幅度上,灌丛群落较草甸群落明显.     

Heartworm in dogs in Canada in 1983

In late December 1983, 2 800 veterinarians across Canada were sent a questionnaire in order to assess the status of heartworm disease in Canada in 1983 and 26% of them responded. Veterinarians reported that 59 504 dogs were blood-tested to check for microfilariae and 771 dogs (1.30% of those tested) were found with Dirofilaria immitis. Heartworm disease was diagnosed in all provinces except New Brunswick and Newfoundland but most (733) of the cases were in Ontario.

Heartworm disease was found most frequently in companion dogs over three years of age maintained mainly outdoors in rural areas. About 31% of the cases were observed with clinical signs of heartworm disease and 64% had a history of not having left Canada. Southwestern Ontario continues to be the focus of the infection and most of the dogs there had not left the province previously.

     

Heartworm in dogs in Canada in 1985

In late December 1985, 1485 institutional veterinarians and small and mixed animal clinics across Canada were sent a questionnaire in order to assess the status of Dirofilaria immitis in Canada in 1985 and 44% of them responded. Veterinarians reported that 137,300 dogs were blood-tested to check for microfilariae and 1210 dogs were found with heartworm. Another 36 dogs were amicrofilaremic but diagnosed with heartworm disease to give the total number diagnosed in 1985 as 1247 (0.91%).

Heartworm was reported from all provinces except Prince Edward Island, Newfoundland and Saskatchewan but most (1126) of the cases were in Ontario. Southwestern Ontario continued to be the primary focus of the infection in Canada. From Quebec, 91 cases were reported mostly from and around Montreal. From Manitoba, 19 cases were reported from Winnipeg and surrounding areas. Heartworm was found most frequently in companion dogs over three years of age maintained mainly outdoors in rural areas. About 28% of the cases were observed with clinical signs of heartworm disease and 78% had a history of not having left Canada.

     

Heartworm in dogs in Canada in 1988

In late November 1988, 1581 small and mixed animal clinics and institutional veterinarians across Canada were sent a questionnaire in order to assess the status of Dirofilaria immitis in Canada in 1988, and 46% of them responded. Veterinarians reported that 181,577 dogs were blood-tested for heartworm disease and 367 dogs were found with D. immitis microfilariae. Another 60 dogs were amicrofilaremic but diagnosed with heartworm disease to give the total number of cases diagnosed in 1988 as 441 (0.24%).     

Heartworm in dogs in Canada in 1984

In late December 1984, 1853 institutional veterinarians and small and mixed animal clinics across Canada were sent a questionnaire in order to assess the status of Dirofilaria immitis in Canada in 1984 and 35% of them responded. Veterinarians reported that 97,794 dogs were blood-tested to check for microfilariae and 1417 dogs (1.45% of those tested) were found with heartworm. Another 34 dogs were amicrofilaremic, but were diagnosed as having heartworm disease, to give the total number diagnosed in 1984 as 1451 (1.48%). Heartworm was reported from all provinces except Prince Edward Island and Newfoundland but most (1310) of the cases were in Ontario. In Quebec, 126 cases were reported mostly from west of Montreal.

Heartworm was found most frequently in companion dogs over three years of age maintained mainly outdoors in rural areas. About 27% of the cases were observed with clinical signs of heartworm disease and 72% had a history of not having left Canada. Southwestern Ontario continued to be the primary focus of the infection.

     

Heartworm in dogs in Canada in 1989

In late November 1989, 1732 clinics and institutional veterinarians were sent a questionnaire to assess the status of Dirofilaria immitis, and 51.7% responded. Of 247,716 dogs tested, 394 had D. immitis microfilariae and 51 were amicrofilaremic for a total of 445 cases and heartworm prevalence of 0.17%. Most (408) of these dogs had no preventive medication and the prevalence among dogs tested and unprotected was 1.01%. That prevalence was considerably higher in endemic areas. Thirty-seven dogs with heartworm had preventive medication. Heartworm was most frequent in companion dogs over three years of age maintained outdoors in rural areas. About 75% of the cases had never left Canada, 26% had clinical signs and 125 were not treated.

Heartworm was reported from British Columbia, Manitoba, Ontario, Quebec, Nova Scotia and Newfoundland, but 383 cases were in Ontario. South-western Ontario was the primary focus of infection. There were 33 cases in Quebec and 24 in Manitoba, mainly found in and around Metropolitan Montreal and Winnipeg respectively.

     

Heartworm in dogs in Canada in 1987

In late November 1987, 1246 institutional veterinarians and small and mixed animal clinics across Canada were sent a questionnaire in order to assess the status of Dirofilaria immitis in Canada in 1987, and 50% of them responded. Veterinarians reported that 165,428 dogs were blood tested for heartworm disease and 511 dogs were found with D. immitis microfilariae. Another 78 dogs were amicrofilaremic but diagnosed with heartworm disease to give the total number of cases diagnosed in 1987 as 589 (0.35%).     

Heartworm in dogs in Canada in 1986

In late December 1986, 1224 institutional veterinarians and small and mixed animal clinics across Canada were sent a questionnaire in order to assess the status of Dirofilaria immitis in Canada in 1986; 46% of them responded. Veterinarians reported that 150,989 dogs were blood-tested for microfilariae and 869 dogs were found with heartworm. Another 65 dogs were amicrofilaremic but diagnosed with heartworm disease and one was found with heartworm at necropsy to give the total number diagnosed in 1986 as 935 (0.62%).

Heartworm was reported from Manitoba, New Brunswick, Ontario and Quebec, but most (810) of the cases were from Ontario. South-western Ontario continued to be the primary focus of the infection in Canada. There were 103 cases reported from Quebec, mostly from and around Montreal, and 21 cases from Manitoba, from Winnipeg and surrounding areas. Heartworm was found most frequently in companion dogs over three years of age maintained mainly outdoors in rural areas. About 33% of the cases were observed with clinical signs of heartworm disease and 81% had a history of not having left Canada.