神农架植被及其生物多样性与垂直分布格局-兼论中国中、北亚热带植被带的划分

本文主要通过样线法和样方法相结合，进行了大量的群落学调查和分析，分别从植物区系、物种多样性的垂直分布格局和森林群落类型三个方面分析了神农架植被的基本特征及其物种多样性，结果表明： 1．神农架地区具有很高的物种丰富度，有高等植物3，479种，隶属于1，010属，202科。 其中，蕨类植物305种，80属，32科;种子植物3，174种，930属，170科，其中裸子植物32种，19属，6科，被子植物3，142种，911属，164科;单子叶植物501种，175属，21科，双子叶植物2，641种，736属，143科。植物区系属的分布区类型中北温带分布型最多，其次为东亚分布、泛热带分布、东亚北美间断分布、旧世界温带分布以及热带亚洲分布。中国特有成分占5.65%，较全国的8.12%低。温热比(温带分布型(8-11)属数与热带分布型(2-7)属数的比值）为1.200，比全国(0.385)高。 调查样方中共出现高等植物784种，隶属于454属，144科，其中蕨类植物41种，32属，16科;种子植物743种，422属，128科，其中裸子植物20种，14属，5科，被子植物723种，408属，123科;单子叶植物86种，58属，11科，双子叶植物637种，350属，112科。属的分布区类型中北温带分布型最多，其次为东亚分布、泛热带分布、东亚北美间断分布、旧世界温带分布以及热带亚洲分布。温热比为1.52，草本层>乔木层>灌木层分别为2.18、1.76和1.14。 2．神农架植被类型多样，具有常绿阔叶林、常绿落叶阔叶混交林、落叶阔叶林、针阔混交林、亚高山针叶林、硬叶常绿阔叶林和亚高山灌丛草甸等自然植被类型。本文，依据乔木物种的重要值将神农架地区的森林植被划分出了69个类型。用Twinspan将调查的森林群落划分为32组，能基本上反映群落间相似的关系。 3．神农架地区具有完整的植被垂直带谱：海拔900 (1300) m以下为常绿阔叶林带;海拔900 (1300) m～1500 (1800)ⅡI为常绿落叶阔叶混交林带;海拔1500 (1800) m-2000 (2200)m为落叶阔叶林带;海拔2000 (2200) m～2400 (2600)m为针阔混交林带：海拔2400 (2600)m以上为亚高山针叶林带。神农架地区植被的垂直带的分化从总体上比较显著，但由于小生境的异质性和人为干扰，垂直带谱又具有一定的模糊性和次生性。南北坡具有一定的差异，但不十分明显，也说明神农架植被的过渡性。 4．神农架物种多样性的垂直分布格局。神农架的物种多样性与海拔的关系，类似于“中间膨胀”规律(mid-altitude bulge)，在中低海拔处生物多样性最高。通过二次多项式回归拟合，得到如下拟合曲线： 1)海拔与总体物种数：y= _14.445x2+ 34.74lx+42.07，Xd=1.203km; 2)海拔与乔木层物种数：y=-6.9707x2+ 21.334x+0.2004，Xdrl.530km; 3)海拔与灌木层物种数：y=-6.1599x2+ 9.9747x+30.991，Xd=0.8 lOkm: 4)海拔与草本层物种数：y= _3.9907x2+ 10.455x+15.35，Xd-1.308km; 5）海拔与乔木层Shannon-Wiener指数：y=_0.3337x2+ 0.9877x+0.2537，Xd' 1.480km; 6)海拔与灌木层Shannon-Wiener指数：y=-0.1938xz+ 0.422lx+1.2103，Xd=1.089km： 7)海拔与草本层Shannon-Wiener指数：y=_0.1072x2+ 0.294lx+0.9954，Xd=1.372km; x为海拔( km)，y为各物种多样性指标，Xd为物种多样性的最大时的海拔。 从这些拟合曲线中可以看出：总体物种多样性在海拔1200m左右的常绿落叶阔叶混交林带最高：乔木层物种多样性在海拔1500m左右的常绿落叶阔叶混交林带与落叶阔叶林的过渡带最高;灌木层物种多样性在海拔800-llOOm左右的常绿阔叶林与常绿落叶阔叶混交林带的过渡带最高;草本层物种多样性在海拔1300-1400m左右的常绿落叶阔叶混交林带最高。 但物种多样性随海拔变化有许多的起伏和波动。这些波动有些反映了群落的垂直带谱随海拔梯度变化的特点，在垂直带谱的过渡区物种多样性往往较高;有些波动反映了一些特殊的生境，有些反映了人为活动的影响，造成了神农架植被的次生性。因此，影响神农架物种多样性垂直分布的因素有：植被本身的性质和特点、过渡带的特点、生境的异质性和人为活动。 5．神农架植被水平地带性的过渡性。海拔1300m以下的植物属的分布区类型的温热比南坡总是比北坡小，而且相差十分显著，反映了神农架作为植被分界线的价值。神农架南坡的基带植被是常绿阔叶林，因此南坡属于中亚热带。北坡的基带植被，虽然也有常绿树种的零星分布，甚至有小块的常绿阔叶林，完全由于小生境所至，分布的主要类型是常绿落叶阔叶混交林，应属于北亚热带。因此，神农架是中、北亚热带重要的过渡地带。神农架地区中北亚热带的具体分界线宜按照分长江干流和汉水的水岭来划界，即猴子石、大窝坑、神农架、神农顶、老君山一线，南坡属于中亚热带，北坡属于北亚热带。 总之，神农架处于我国中、北亚热带的过渡带，具有过渡带的性质，具有很高的物种多样性，拥有完整的植被垂直带谱，具有多种多样的植物群落及其组成的生态系统。而且，具有我国许多特有植物和珍稀濒危保护植物和许多资源植物。因此，神农架植被在我国植被体系中具有重要的地位，是我国生物多样性最丰富的地区之一，是生物多样性保护的关键地区，也应是生物多样性研究的热点地区。 另外，调查分析了黄山和万朝山植被及其物种多样性与垂直分布格局，结果表明： 6．黄山样方中共出现高等植物259种，隶属于263属，110科，其中蕨类植物14种，II属，8科，种子植物345种，152属，105科，其中裸子植物9种，8属，6科，被子植物336种，144属，99科，其中单子叶植物37种，27属，6科，双子叶植物299种，117属，90科。属的分布区类型中北温带分布最多，其次为东亚分布和泛热带分布，再次为东亚北美间断分布、热带亚洲分布以及旧世界温带分布，与神农架和万朝山也较相似，但热带分布的属更多一些。温热比为1.1875，灌木层>草本层>乔木层，分别为1.3818、1.2609和1.2143。 黄山的森林植被类型有针叶林、常绿阔叶林、常绿落叶阔叶混交林、针阔混交林、落叶阔叶林和竹林。Twinspan将调查的森林群落划分为22组，反映群落间相似的关系，比较清楚和适用。依据乔木物种的重要值将森林植被划分出了34个类型。黄山物种多样性的与海拔的关系不十分明显。黄山植被的垂直带谱不是十分明显，将其垂直带谱划分为：海拔1300m(1500m)以下为常绿阔叶林带;海拔1300m(1500m)-1500m(1600m)常绿落叶阔叶混交林 带;1500m(1600m)以上为落叶阔叶林、黄山松林、山地灌木草丛带。垂直带谱在不同坡向上有差别，东、南、西坡的相似性较大，而北坡与其差别较大。 7．万朝山样方中共出现高等植物490种，隶属于339属，124科，其中蕨类植物21种，18属，11科，种子植物469种，321属，113科，其中裸子植物9种，7属，4科，被子植物460种，314属，109科，其中单子叶植物47种，37属，11科，双子叶植物413种，277属，98科。植物属的分布区类型中，北温带分布所占最多，其次为泛热带分布、东亚分布、东亚北美间断分布、旧世界温带分布以及热带亚洲分布，。温热比为1.3366，草本层>乔木层>灌木层，分别为1.5429、1.4063和1.0645。 万朝山的植被类型包括针叶林、落叶阔叶林、针阔混交林和常绿落时阔叶混交林，但没有典型的常绿阔叶林。依据乔木物种的重要值将森林植被划分出了20个类型。万朝山物种多样性与海拔的关系则不十分明显。万朝山的人为干扰比较强，植被的次生性很大，南、北坡物种多样性随海拔升高的起伏较大。

Ecological imbalances in the coastal areas of Pakistan and Karachi Harbour

The marine environment of Pakistan has been described in the context of three main regions : the Indus delta and its creek system, the Karachi coastal region, and the Balochistan coast. The creeks, contrary to concerns, do receive adequate discharges of freshwater. On site observations indicate that freshwater continues flowing into them during the lean water periods and dilutes the seawater there. A major factor for the loss of mangrove forests as well as ecological disturbances in the Indus delta is loss of the silt load resulting in erosion of its mudflats. The ecological disturbance has been aggravated by allowing camels to browse the mangroves. The tree branches and trunks, having been denuded of leaves are felled for firewood. Evidence is presented to show that while indiscriminate removal of its mangrove trees is responsible for the loss of large tracts of mangrove forests, overharvesting of fisheries resources has depleted the river of some valuable fishes that were available from the delta area. Municipal and industrial effluents discharged into the Lyari and Malir rivers and responsible for land-based pollution at the Karachi coast and the harbour. The following are the three major areas receiving land-based pollution and whose environmental conditions have been examined in detail: (l) the Manora channel, located on the estuary of the Lyari river and serving as the main harbour, has vast areas forming its western and eastern backwaters characterized by mud flats and mangroves. The discharge of industrial wastewater from the S.I.T.E. and municipal effluents from the northern and central districts into the Lyari has turned this river into an open drain. This, in turn, has caused a negative impact on the environment of the port, fish harbour, and the adjacent beaches. (2) The Gizri creek receives industrial and municipal effluents from the Malir river as well as from several industries and power stations. The highly degraded discharges from the Malir have negatively impacted the environment in this creek. (3) The coastline between the Manora channel and Gizri creek where the untreated municipal effluents are discharged by the southern districts of Karachi, is responsible for the degraded environment of the Chinna creek, and also of the beaches and the harbour. The Balochistan coast is relatively safe from land-based pollution, mainly because of the lack of industrial, urban or agricultural activity, except the Hingol river system where some agricultural activities have been initiated.

Seasonal dynamics in the occurrence and abundance of Pseudo-nitzschia species in the Maheshkhali channel of the Bay of Bengal, Bangladesh

Occurrence and abundance of Pseudo-nitzschia spp. at the mouth of the Maheshkhali channel of the Bay of Bengal, Bangladesh were studied. Plankton and water samples were collected monthly from the sub-surface water during high tide at daytime from June 2000 to May 2001. Four species of Pseudo-nitzschia, namely P. pungens, P. pseudodelicatissima, P. delicatissima and P. australis were identified and among them the first three were most commonly encountered and they varied seasonally. Pseudo-nitzschia delicatissima was the dominant species during the autumn and winter months, whereas P. pungens was dominant during the summer and spring months. Pseudo-nitzschia pseudodelicatissima exhibited its highest abundance level during the summer. Surface water temperature, salinity, nitrate-nitrogen (N03-N) and phosphate-phosphorus (P04-P) were recorded and their relationship with the occurrence and abundance of Pseudo-nitzschia species were studied. At the mouth of the Maheshkhali channel, Pseudo-nitzschia cell density was highest in late autumn (November) when highest salinity (35 o/oo) and P04-P (3.2 mg/l) concentrations and low temperature (23 °C) were recorded.

Rapid detection of white spot syndrome virus (WSSV) of Penaeus monodon by latex agglutination test using monoclonal antibodies

Latex beads were sensitized with monoclonal antibodies (MAb) rose against VP28 of WSSV. The optimum concentration of MAb required to sensitize the latex beads was 125 µg/ml. The sensitized latex beads were used to detect WSSV from PCR-positive stomach tissue homogenates obtained from infected shrimp. Stomach tissue homogenates from WSSV-infected shrimp agglutinated the sensitized latex beads within 10 minutes, while uninfected samples did not produce any agglutination, although non-specific agglutinations were observed in some samples. The analytical sensitivity, analytical specificity, diagnostic sensitivity and diagnostic specificity of the (LAT) agglutination test were assessed. The analytical sensitivity of the test was 40 ng of purified WSSV (2 µg/ml). The sensitized latex beads did not agglutinate with normal shrimp tissue or MBV-infected tissue homogenate. The test has a diagnostic sensitivity of 70 and 45%, respectively, compared to single-step and nested PCR. The diagnostic specificity of the test was 82%. This test is a simple and rapid on-farm test which can be used to corroborate clinical signs for the detection of WSSV in grow-out ponds.

A Plant Needs Ants like a Dog Needs Fleas: Myrmelachista schumanni Ants Gall Many Tree Species to Create Housing

Hundreds of tropical plant species house ant colonies in specialized chambers called domatia. When, in 1873, Richard Spruce likened plant-ants to fleas and asserted that domatia are ant-created galls, he incited a debate that lasted almost a century. Alth

Studies on the occurrence and growth rates of two intertidal fouling bryozoans in the Mattancherry channel of Cochin harbour, south-west coast of India

Occurrence and growth rates of two species of intertidal fouling bryozoans namely Electra bengalensis (Stoliczka) and Electra crustulanta (Pallas) are presented in this paper. The former was a typically marine form, settling on panels only during the high saline conditions of the pre-monsoon period and were absent during the low salinity conditions of the monsoon period, while the latter appeared to be a typical brackish water form settling on panels during the low saline conditions existing during the monsoon and post-monsoon periods and were totally absent during the pre-monsoon months. Regression co-efficient of the former was higher than that of the latter suggesting more pronounced growth in Electra bengalensis. Maximum growth for this species was noticed during March, April and May (pre-monsoon) while for the other species growth was more or less similar during monsoon and post-monsoon months (June-January) showing that the species was at home in oligohaline and mesohaline waters.