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1.
Emiru Birhane Mengsteab Hailemariam Girmay Gebresamuel Tesfay Araya Kiros Meles Hadgu Lindsey Norgrove 《林业研究》2020,31(1):313-323
Poor land use management and practice inhibit the growth and establishment of tree seedlings in dryland areas.We assessed arbuscular mycorrhizal fungi(AM)status of Faidherbia albida(Del.)A.Chev.trees grown on different land uses.We quantified the growth and nutrient uptake of F.albida seedlings inoculated with AM from different sources.These efforts were based on soil and fine root samples from the rhizosphere soils of F.albida trees.AM root colonization was determined using the gridline intersect method.Spores were extracted by the wet sieving and decanting method and identified to genus level.The seedling experiment had a completely randomized onefactorial design with four treatments and five replications.Faidherbida albida seedlings were grown in a greenhouse.All in situ F.albida trees were colonized by AM fungi.AM root colonization of F.albida trees was significantly higher(P<0.0086)in area exclosures than on lands used for grazing or cultivation.Spore abundance was significantly higher(P<0.0014)in area exclosures followed by cultivated land and grazing land.Glomus was the dominant genus in all land-uses.AM-inoculated F.albida seedlings grew better(P<0.05)than non-inoculated controls.Seedlings inoculated with AM from area exclosure had significantly(P<0.05)higher growth and nutrient uptake than those inoculated with AM from grazing and cultivated land.This emphasizes the importance of the native soil AM potential for better establishment of seedlings to achieve optimum plant growth improvement and assist in rehabilitation of degraded arid lands. 相似文献
2.
东北沼泽湿地土壤中氨氧化微生物活性和丰度研究 总被引:1,自引:1,他引:0
为了研究东北典型沼泽湿地——三江湿地和扎龙湿地表层土壤中氨氧化微生物的活性和丰度,采用氯酸盐抑制亚硝酸盐氧化菌(Nitrite-oxidizing bacteria,NOB)和氨苄青霉素抑制氨氧化细菌(Ammonia-oxidizing bacteria,AOB)以及荧光定量PCR的方法,分析了生长季和非生长季氨氧化微生物的活性和丰度的关系。结果表明:在不同类型的湿地土壤中,pH值显著地影响湿地土壤中氨氧化古菌(Ammonia-oxidizing archaea,AOA)的潜在氨氧化活性(Potential ammonia oxidation activity,PAO)(P0.01)。AOA的丰度值与PAO_(AOA+AOB)呈显著正相关(r=0.96,P0.05),而与PAO_(AOA)不存在相关性(P0.05)。三江湿地的毛苔草和小叶章土壤中的PAO_(AOA+AOB)、PAO_(AOA)、AOA丰度与AOB丰度,并无显著差异。研究表明植被的差异并没有影响土壤中氨氧化微生物的潜在氨氧化活性以及氨氧化微生物的丰度,但在抑制AOB活性之后毛苔草土壤中的PAO出现了显著的下降(P0.05),表明AOB在毛苔草土壤中的氨氧化过程中发挥着重要作用。 相似文献
3.
Potential application of baited remote underwater video to survey abundance of west coast rock lobster Jasus lalandii 下载免费PDF全文
L. A. Roberson C. G. Attwood H. Winker A. C. Cockroft D. L. Van Zyl 《Fisheries Management and Ecology》2017,24(1):49-61
The first assessment of the baited remote underwater video system (BRUVs) for monitoring rock lobster Jasus lalandii (Milne‐Edwards) in South Africa was compared to annual ring net and trap survey data. Count data from 58 BRUVs, 36 ring net and 95 trap samples were fitted with generalised additive models using depth, habitat, time and spatial gradient as independent variables. A power analysis was used to determine the number of samples needed per annum to detect a 5 and 10% increase and decrease in population size. The BRUVs outperformed the nets and traps in terms of sampling effort and were better at detecting changes in abundance of lobster than abundance of three fish species. Considering factors such as cost, analysis time, additional data and environmental impact, traps are the most feasible method in deeper waters but BRUVs could replace nets and traps in depths less than 60 m, low‐density areas and marine reserves. 相似文献
4.
选择青藏高原东缘同一生境类型下具有不同交配系统特点和不同传粉者丰度的3种龙胆科植物湿生扁蕾(Gentianopsis paludosa)(自花授粉)、祁连獐牙菜(Swertia przewalskii)(高昆虫访问异花授粉)和线叶龙胆(Gentiana farreri)(低昆虫访问异花授粉)为对象,研究其资源分配特征。结果表明,1)3种植物的花粉胚珠比例(P/O)存在显著差异(P0.05),湿生扁蕾的P/O显著低于另外两种异花授粉植物的(P0.05),祁连獐牙菜的P/O显著低于线叶龙胆的(P0.05);2)3种植物的繁殖分配比例存在差异,湿生扁蕾的繁殖分配比例显著高于另外两种异花授粉植物的(P0.05),线叶龙胆的繁殖分配比例显著高于祁连獐牙菜的(P0.05);3)在繁殖分配比例与个体大小关系上,湿生扁蕾与其个体大小不存在显著相关关系(P0.05),而另外两种异花授粉植物则与其各自个体大小之间存在显著负相关关系(P0.05)。研究表明,交配系统类型和传粉者丰度与植物的资源分配模式有关,尽管3种植物的繁殖绝对投入量都与其个体大小显著正相关(P0.05),但自花授粉植物相对于异花授粉植物具有较高的繁殖分配比例,并且这种较高的繁殖分配比例不受个体大小影响,这种高繁殖投入的资源分配模式可能与自花授粉植物具有繁殖保障,从而降低其繁殖代价有关。 相似文献
5.
We reviewed 199 published data sets (21 species) to assess the relative frequency of various density-dependent processes in salmonids. We examined studies for the presence or absence of density-dependence: in growth, mortality, fecundity and recruitment. Based on data from all studies pooled 71% showed density-dependence in growth, 23% found density-dependence in mortality, 2% detected density-dependence in fecundity and 4% displayed density-dependence in recruitment. Most studies at the population level (e.g. changes in abundance or means of growth, mortality or fecundity) demonstrated density-dependence; however, these studies were not common, likely because they require long time series of data (at least 3–4 times mean generation time for the species). Our review indicated there was no evidence that the probability of finding density-dependent effects differed among the 21 species examined, but the number of studies per species varied substantially (5 [minimum for analysis] – 20+); hence, this finding should be viewed as tentative. Most salmonid species showed evidence of density-dependence in growth; however, few studies examined density-dependent effects on fecundity or recruitment, and further study is needed on these phenomena. There was no evidence that density-dependent effects were restricted to a particular habitat type or geographic region. 相似文献
6.
Di ZENG Tinghao JIN Yuhao ZHAO Chuan YAN Zhibin ZHANG Ping DING 《Integrative zoology》2021,16(1):109-119
Density-dependent non-monotonic species interactions are important in maintaining ecosystem stability and function, but empirical evidences are still rare. Rodents, as both seed dispersers and seed predators, have dual effects on plant regeneration and may result in non-monotonic rodent-plant interactions. According to the non-monotonic models, the relative positive or negative effects of rodents on seedling establishment can be measured based on the positive or negative association of seedling recruitment rate and rodent abundance. In this study, we investigated the fates of acorns of Quercus serrata by tracking tagged seeds on 21 fragmented subtropical islands in the Thousand Island Lake, China. We found that the proportion of germinated seeds of all released seeds showed a dome-shaped association with rodent abundance per seed. The proportion of removed seeds and cached seeds showed a saturated- and a weak dome-shaped association with rodent abundance per seed, respectively. Our results demonstrated a clear empirical evidence that rodent abundance per seed triggered a switch between the relative mutualism and predation in a rodent–seed system. Our study implied that the observed non-monotonic interactions between plants and animals may play a significant role in maintaining biodiversity and ecosystem function. We appeal for more investigations of the complex non-monotonic interactions in various ecosystems. 相似文献
7.
文中研究森林资源丰裕度与经济增长的关系,从森林资源诅咒的存在性检验、传导机制和破解对策3个方面对国内外相关文献进行了梳理总结。结果表明:森林资源诅咒研究已经取得了一定成果,但是现有文献对森林资源诅咒现象的实证研究结果不稳定,会因研究对象、时间、样本以及模型和指标选取的不同而变化;现有研究对森林资源诅咒的传导机制缺乏实证检验,在指标选择和模型构建中尚存在许多不足之处。未来研究需要考虑指标筛选的科学性、计量模型的稳健性以及中介和调节效应的引入等;此外,森林资源丰裕度与经济增长之间的关系可能不是线性关系,因此在建立计量模型时应对模型形式进行优化选择。 相似文献
8.
Md. Milon Sarker Mohammad Belal Hossain Md. Monirul Islam Abu Hena Mustafa Kamal Mohd. Hanafi Idris 《Aquaculture Research》2021,52(1):167-184
Homestead ponds may offer an ideal opportunity in contribution to household income, fish consumption through fish culture. Phytoplankton plays a key indicator in pond productivity. However, the phytoplankton communities in the homestead ponds are nearly undetermined in Bangladesh. This study summarizes the phytoplankton diversity, assemblage and ecological parameters of the homestead ponds in central coastal belt, Bangladesh, based on two seasons. The results revealed that significant differences (p < .05) were found in pH, DO, conductivity, TDS, nitrates, phosphates and sulphates except temperature in monsoon, and transparency in both seasons. A total of 34 phytoplankton genera representatives of five major groups were recorded such as Euglenophyceae (41.5%), Chlorophyceae (30.5%), Cyanophyceae (13%), Dinophyceae (10%) and Bacillariophyceae (5%). A significant difference (p < .05) in phytoplankton abundance was found in both seasons with the highest mean of 186.13 ± 129.34 × 104 cells L?1 in monsoon and the lowest mean of 144.40 ± 107.26 × 104 cells L?1 during winter. The diversity (H'), evenness (J'), richness (d) and dominance (D) ranged from 1.62 to 2.47, 0.52 to 0.97, 0.37 to 1.15 and 0.10 to 0.28 respectively. Based on SIMPER, the most dominant (>10%) genera for dissimilation within stations and seasons were Euglena spp., Phacus spp., Chlorella spp., Strombomonas spp. and Peridinium spp. ANOSIM results stated that 12 genera of phytoplankton were significant contributors based on average dissimilarity. Pearson's correlation coefficient and canonical correspondence analysis (CCA) revealed that phytoplankton abundance, diversity and community were mainly governed by transparency, dissolved oxygen and nitrates. 相似文献
9.
Recruitment declines of walleye, Sander vitreus (Mitchill), observed in some northern Wisconsin lakes have resulted in management actions to evaluate and rehabilitate populations. An effective index for estimating relative abundance of yearling walleye is required. The objectives herein were : (a) to evaluate the relationship between yearling walleye electrofishing CPUE and density in northern Wisconsin lakes; (b) to test for the influence of lake‐specific factors on electrofishing catchability of yearling walleye; and (c) to develop an index whereby electrofishing CPUE can be used to quantify yearling walleye relative abundance. Yearling density was significantly positively related to electrofishing CPUE on a long‐term dataset from Escanaba Lake as well as a dataset including several lakes combined. Electrofishing catchability of yearling walleye was negatively related to lake‐surface area but was not related to other lake‐specific variables. This index can provide an efficient method to continue monitoring natural recruitment and also to evaluate survival of stocked walleye. 相似文献
10.
为切实保护耕地,基于遥感技术对不同耕地演化类型,包括不变耕地、新增耕地、撂荒耕地和退耕耕地进行识别和检测,以民勤县为例,采用2010和2015年2个年份的春、夏、初冬地物景观三季相特点的Landsat TM/OLI数据作为主要数据源。依据不同耕地演化类型的季相变异规律和内部要素特征选取具有物理意义的端元丰度值、丰度值差值建立2年份混合决策树划分不同耕地演化类型。同时对比分析在2010和2015年各自决策树土地利用/覆被分类结果后比较提取的耕地演化类型。结果表明:民勤县大部分耕地未发生变化,新增耕地在各个区域均有一定量的分布且主要分布在下游;退耕耕地大面积分布在坝区;撂荒耕地主要分布在沙漠绿洲过渡带。研究表明通过能够与地物先验知识关联的端元丰度值、特征端元丰度的差值建立决策树可以有效实现不同耕地演化类型的检测。误差矩阵精度评价结果显示,基于混合决策树耕地演化类型提取结果在总体精度上要高于分类后变化检测的结果。 相似文献