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Plant diversity of secondary forests in response to anthropogenic disturbance levels in montane regions of northeastern China 总被引:4,自引:0,他引:4
The effects of anthropogenic disturbances on forest structure and plant diversity of secondary forest ecosystems were evaluated
based on the classification by site factors in the montane regions of northeastern China. Forty-five sample plots containing
720 sub-plots of overstory species (8 m × 8 m), 1,440 quadrats of understory species (2 m × 2 m), and 1,440 quadrats of herbaceous
layer species (1 m × 1 m) were clustered into five groups (G1, G2, G3, G4 and G5) by site variables with Hierarchical Cluster
Analysis. Meanwhile, the disturbance levels corresponding to the five groups were determined according to the factors influencing
human disturbances (D0-G2, D1-G1, D2-G3, D3-G5, and D4-G4). Species diversities of overstory, understory, herbaceous layer
and overall species were evaluated using species number, Margalef index, Pielou index, Shannon–Wiener index, and Simpson index;
and β-diversities (Whittaker index, Cody index). Basal area of stands exhibited a decreasing trend along the disturbance level
due to a gradual increase in the extraction of timber by the human disturbances. The indices of species diversity suggested
that overstory and understory species were distributed evenly among the groups or disturbance levels. There were no absolutely
dominant tree species in the secondary forest ecosystems. The differences in site factors and the current disturbance intensities
were not intense enough to lead to loose changes in overstory and understory species. The species diversity indices exhibited
the maximum values at D3 (G5) for herbaceous layer species; this may suggest that the current disturbance intensities were
intense enough to lead the changes of herbaceous layer species. Three rare and endangered species (Juglans mandshurica, Fraxinus mandshurica and Acanthopanax senticosus) were found within the secondary forests. These rare and endangered species appeared in each clustered group or disturbance
level, which suggested that the current disturbance intensity in the study area was not strong enough to influence the distribution
of rare and endangered species. The current disturbances in the secondary forests may not lead to a decrease in stability
and complexity of the overstory and understory species, but the higher disturbance level may be intense enough to change the
habitat fitness for the herbaceous species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized authors. 相似文献
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本文系统地介绍了互联网上国外动物医学信息资源,包括英文网络数据库、信息网站、机构和研究站点、电子期刊等其它相关网站,为用户快速、准确、全面地获取互联网上重要的和相关的动物医学文献信息资源提供了依据。 相似文献
46.
A network of superconducting gravimeters detects submicrogal coseismic gravity changes 总被引:8,自引:0,他引:8
With high-resolution continuous gravity recordings from a regional network of superconducting gravimeters, we have detected permanent changes in gravity acceleration associated with a recent large earthquake. Detected changes in gravity acceleration are smaller than 10(-8) meters seconds(-2) (1 micro-Galileo, about 10(-9) times the surface gravity acceleration) and agree with theoretical values calculated from a dislocation model. Superconducting gravimetry can contribute to the studies of secular gravity changes associated with tectonic processes. 相似文献
47.
为进一步研究蛋白酶与成熟衰老的关系,试验以‘918’番茄(Lycopersicum esculentum Mill.cv.918)果实为材料,采用改进的含明胶的十二烷基硫酸钠聚丙烯酰胺凝胶电泳方法对番茄果实中的蛋白酶进行检测,结果发现番茄果实中有3个蛋白酶,命名为SP-1、SP-2和SP-3,其活性伴随着果实后熟衰老发生变化。乙烯处理可提高番茄果实蛋白酶SP-2的活性,使SP-1和SP-3活性被提前检出,而1-甲基环丙烯处理对蛋白酶起相反作用。番茄果实蛋白酶受果实后熟衰老和乙烯的双重调控,是衰老相关蛋白酶。该文为进一步研究蛋白酶与果蔬衰老的关系提供参考。 相似文献
48.
Rui A. Gonçalves Tu Do Cam Nguyen Nhu Tri Gonçalo A. Santos Pedro Encarnação Le Thanh Hung 《Aquaculture International》2018,26(3):921-936
Triplicate groups of one hundred Tra catfish (8 g?±?0.2) were fed seven test diets containing increasing levels of AFB1 (0, 50, 100, 250, 500, and 1000 μg AFB1 kg?1). Additionally Mycofix® Secure was added at 1.5% to one diet containing 500 μg AFB1 kg?1. Results showed that Tra catfish are sensitive to AFB1. Reduction in weight gain (P?<?0.05) was observed for fish fed 50 μg AFB1 kg?1 and declined further with increasing levels of AFB1 in the diets. Fish fed diets contaminated with 500 and 1000 μg AFB1 kg?1 showed increased (P?>?0.05) hepatosomatic index (HIS), while an increase in adipose somatic index (ASI) was observed in fish fed 50 μg AFB1 kg?1 and above when compared to the control and Mycofix® diets. After 12 weeks, blood serum analysis revealed higher alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in fish fed the 50, 100, and 250 μg AFB1 kg?1 suggesting occurrence of liver damage. Disease resistance of fish exposed to Edwardsiella ictaluri was also compromised by the presence of AFB1 in the feed and was directly related to the contamination level. Seven days after Edwardsiella ictaluri exposure, survival rates were 50, 41.7, 31.7, and 8.3% for fish fed control, 50, 100, and 250 μg AFB1 kg?1, respectively. This trial shows that AFB1 at a level of 50 μg AFB1 kg?1 and above can affect fish performance and disease resistance. Application of an effective mycotoxin management in the feed seems to be useful to prevent the negative effects of AFB1. 相似文献
49.
2BFM-5型山地免耕播种机的设计与试验 总被引:1,自引:5,他引:1
针对黄土高原丘陵水蚀区残茬覆盖免耕播种及抗旱播种的作业要求,研制了以8.8~11.0?kW手持拖拉机为动力源的2BFM-5型山地免耕播种机。该播种机采用长翼尖角组合式种肥分施开沟器、复合铰链前位双轮仿形机构和螺旋齿槽轮排种器。田间试验表明:该播种机排种均匀性变异系数为35.4%,播深合格率为81.8%,平均种肥间距为44.0?mm,化肥集中在90~100?mm土层范围内,地表可形成宽66~85?mm、深40~52?mm的小垄沟,各项技术性能满足农业种植要求。该播种机适应中国黄土高原丘陵水蚀区缓坡地(<15°)和水平梯田的免耕播种,满足雨养农业区播种技术的“深种浅覆、镇压提墒、集雨抗旱”等要求。 相似文献
50.
东北地区兴安落叶松和红皮云杉球果种实害虫危害调查初报 总被引:6,自引:1,他引:6
1993年4-9月与法国农科院合作,北地区兴安落叶松和红皮云杉球果种实害虫危害调查的初步总结得出:危害兴安落叶松球果的害虫以球果花蝇属为主,共5种,落叶松球果花蝇。贝加尔球果花蝇,黑胸球果花蝇,稀球果花蝇和斯氏球果花蝇。其中斯氏球果花蝇在我国是首次报首为新记录。这几咱花蝇造成的落叶松要被害率,其中有些地区可达100%,平均为63%。以黑胸球果花蝇为绝对优势种,占花蝇种群数量的53%。兴安落叶松种子 相似文献