Taxonomic revision of the seasonal killifish genus Nothobranchius from Zanzibar,East Africa (Cyprinodontoidei: Aplocheilidae)

Nothobranchius guentheri and Nothobranchius melanospilus, the two seasonal killifishes of the genus Nothobranchius occurring in Zanzibar Island, Tanzania, were involved in past taxonomical mistakes and are still misidentified in museum collections. A historical review is herein presented and both species are redescribed on the basis of type material and recent collections. Nothobranchius guentheri, a popular aquarium fish, is endemic to Zanzibar, and N. melanospilus, geographically widespread in East Africa, occurring both in Zanzibar and in continental river basins. These species are distinguished by a series of morphological features not previously reported in the literature, including pre-dorsal length and relative position of the anterior portion of the dorsal-fin skeletal support and vertebrae; number of gill-rakers of the first branchial arch, caudal-fin rays, scales of the longitudinal series, series of scales around caudal peduncle, and vertebrae; frontal squamation; and arrangement and number of neuromasts of the supraorbital series. The present taxonomic revision comprising N. guentheri and N. melanospilus, the oldest species names of the genus in the East African biodiversity hotspot, is important to improve the knowledge of the genus in a region where its taxonomy is still problematic     

海南热带雨林滑坡地质灾害生态型治理措施

探讨了热带雨林滑坡地质灾害的发生机制,提出应在最大限度地减少对热带雨林区内环境的影响下,用生态型措施来治理当地的滑坡地质灾害,以最终实现有效治理滑坡和使生态环境可持续发展的双重目标.     

陕北黄土高原森林地带油松林的主要类型及其动态关系

油松林系陕北黄土高原森林地带的气候顶极群落,共含11个类型,其中分布普遍的是:油松——多花胡枝子——大披针苔林;油松——柔毛绣线菊——大披针苔林;油松——虎椿子——大披针苔林;油松——胡枝子——大披针苔林;油松——杭子稍——大披针苔林;油松——大披针苔林。它们之间的演替关系和起源比较复杂,非单元和单演替顶极。     

斑尾榛鸡南迁及其与花尾榛鸡分布区间断成因探讨

更新世中期斑尾榛鸡的原始种群因冰川作用及相近种花尾榛鸡种群的竞争排挤南廷到青藏高原东部、东南部山地。当时这些地区的森林和适度的冰雪环境适于其生活，定居下来，经久进化。自然力和人类开发作用使东北平原，华北、黄土高原的原始森林消失，再加入类狩猎活动，致使两种榛鸡分布区间断。     

模拟氮磷沉降和凋落物处理对两种林型红松林土壤有机碳组分的影响

【目的】阐明模拟氮(N)磷(P)沉降和凋落物处理对两种林型红松(Pinus koraiensis)林土壤有机碳(SOC)组分的影响,为该地区红松林的合理施肥提供参考。【方法】以黑龙江省伊春市带岭区凉水国家级自然保护区红松人工林与阔叶红松林为对象,每个林型设置3块20 m×30 m样地,每块样地间隔20 m,每块样地内布设12个样方,共计72个样方。每个样方实施两种处理：(1)凋落物处理：2017年10月进行该处理的去除(R)、添加(A)和原状(CK1)3个水平的试验,每个水平设定3个重复;(2)模拟氮磷沉降处理：2018年与2019年的5—10月,每月进行1次该处理的试验,分别使用(NH₄)₂SO₄和(NH₄)₂HPO₄作为氮源和磷源配置成不同质量浓度的液体肥,施肥量设置低剂量(L,N、P添加量均为5 g/m²)、中剂量(M,N添加量为15 g/m²,P添加量为10 g/m²)、高剂量(H,...     

基于改进的随机森林TLD目标跟踪方法

针对TLD算法中采用的随机森林分类器的决策树阈值固定,不能根据目标特征随时调整,影响分类精度和时间开销的问题,引入极端随机森林的思想,提出了基于改进的随机森林TLD目标跟踪方法。该方法用Gini系数度量样本集合的混乱程度,通过比较Gini系数是否超过了给定阈值,判断叶节点何时转变成决策节点进行分裂;再结合TLD算法中的P-N学习框架和在线模型训练更新样本;最终基于改进的TLD算法完成目标跟踪。将本文方法应用于多个视频集进行目标跟踪实验,验证了算法的有效性和稳定性。     

基于纹元森林的视觉词袋模型在图像分类中的应用

引入纹元森林(semantic texton forest,STF)的视觉词袋模型,联合基于金字塔匹配核的支持向量机,实现图像分类.首先对图像进行采样,提取SIFT(scale-invariant feature transform)特征,然后导入纹元森林构造视觉词典,统计视觉单词出现的频率构建语义词袋模型,最后利用支持向量机进行训练得出分类结果.实验在MSRC21(Microsoft research cambridge)图像库上进行,通过优化实验中的关键参数,引入加权的不平衡训练,提高了图像分类精度.实验结果表明,基于纹元森林的视觉词袋模型具有良好的图像分类效果.     

Diversity and species composition of Araneidae,Tetragnathidae and Nephilidae in different levels of disturbed habitats in Trinidad,West Indies

ABSTRACT

An increasing amount of natural vegetation is being cleared in the tropics, prompting the questions of how disturbance influences the fauna, and the possible value of disturbed habitats as a means to conserve biodiversity. Three habitat types experiencing difference levels of disturbance farmland (most disturbed), cocoa plantations, and secondary forest (least disturbed) were examined in this study. Six localities of each of three disturbed habitat types were sampled for the spider families Araneidae, Tetragnathidae and Nephilidae, and compared to previous data from 46 localities of 16 natural habitats. Observed and estimated species richness, evenness and dominance of orb-weaving spiders differed significantly among the disturbed habitat types, with secondary forest having greater diversity than the mean for natural habitats in all these measures. Overall, disturbed habitats were not significantly different from natural habitats in species richness, evenness and dominance, and were therefore of conservation value.     

黄土山地典型覆被类型对土壤水分运动的影响

黄土高原山区土地覆被发生了巨大变化,为研究退耕还林后,覆被类型对黄土高原土壤水分的影响,对典型覆被类型的山区土地开展了不同季节土壤含水率变化监测研究.结果表明,不同深度土壤水分随季节发生了较大的变化,而相同季节不同的覆被类型对降水入渗及土壤水运动也有极大影响,且对土壤水分有效性有显著影响.植树造林有利于林地0～3m土壤水的补给,但仍会出现土壤干层,且下部土壤水的补给明显受到该干层的影响.覆被类型不同,土壤水分的变化趋势不同,当土壤水分改变后,又反作用于植被.土壤水与植被之间存在一个平衡状态,当平衡状态被打破时,直接影响植被的生长,而影响土壤水分的运动.