神农架地区米心水青冈萌枝过程的研究

米心水青冈是水青冈属３种多主干的树种之一,萌枝是它的主要更新方式。本文通过样方法和树木年代学方法对神农架地区米心水青冈的萌枝更新过程进行了研究。结果表明,米心水青冈的萌枝现象是普遍存在的,但萌枝数量不同地点差异较大。９丛米心水青冈完整的年轮分析结果表明,它们萌枝的时间不是连续的,而与森林的受干扰有关。根据８３个圆盘和生长锥芯资料,米心水青冈在萌枝后成长为乔木层或林冠层的过程中,径向生长表现为５种模式,这是根株内竞争的结果。萌枝在米心水青冈林的维持和发展过程中,具有重要的生态学作用。     

神农架地区米心水青冈-曼青冈群落的结构与格局研究

 米心水青冈(Fagus engleriana)-曼青冈(Cyclobalanopsis oxyodon)常绿落叶阔叶混交群落是神农架山地植被垂直带谱的重要类型。通过分析乔木层结构及优势种的分布格局,探讨群落的特点及动态。结果表明,群落乔木层可分为3个亚层：第一亚层落叶阔叶树种占优势,势树种为米心水青冈;第二及第三亚层以常绿树种为主,优势种为曼青冈。应用偏离指数、Lloyd的平均拥挤度和聚块性指数及Morisita指数,在8个尺度下对米心水青冈及曼青冈两种优势树种进行格局分析,发现两者总体上均为聚集分布,米心水青冈的聚集强度高于曼青冈。按1～4cm, 4～8cm及8cm以上３个径级对曼青冈分布格局进行比较,各径级间聚集强度相似,没有自疏现象。由于米心水青冈及曼青冈占据乔木层不同的高度,且均不缺乏更新贮备,因此形成稳定共存的群落。     

米心水青冈基因组DNA提取及RAPD反应体系优化

采用4种方法对米心水青冈基因组DNA进行提取,通过比较得出改良CTAB法提出的DNA纯度较高,能够达到扩增要求,因此采用此方法用于正式DNA的提取。适合米心水青冈的RAPD反应体系为：反应体积为25 μL,模板DNA40 ng,引物0.8 μmol·L^-1,Taq聚合酶1.25 U,Mg²⁺浓度2.0 mmol·L^-1,dNTP浓度0.16 mmol·L^-1。适合米心水青冈RAPD扩增程序： 94℃预变性3 min,一个循环,94℃变性30 s,37℃退火1 min,72℃延伸2 min,45个循环。     

数字高程模型在群落内物种共存研究中的应用——以神农架米心水青冈-曼青冈群落的地形模型建立为例

地形是环境异质性产生的原因之一。受技术条件的限制, 以往研究中地形因子只能作为背景因子介入, 无法分析地形的细微变化对植物分布格局的影响。该文将数字高程模型引入群落内物种多样性研究, 以神农架米心水青冈 (Fagusengleriana) _曼青 冈 (Cyclobalanopsisoxyodon) 群落固定样地的地形分析为例, 介绍DEM的建立及地形因素的提取。摸拟 0.96hm2 样地的地形变化, 发现样地总坡向为西偏北 30°, 总坡度为 4 0.0 1°, 最大坡度为74.6°, 最小坡度为 18.2°, DEM的精度为 0.4m。选择群落中 2 4种植物与坡度、坡向及坡位等地形因素进行相关分析, 发现不同的种对地形变化的反应不同。该次研究中, DEM量化了地形数据, 使之可以参与到生物多样性研究中, 为在连续面上分析地形因素对群落内植物分布的影响提供了极大的便利。DEM在小尺度中应用的主要问题是原数据的采集, 该次研究中的地形数据为人工野外测量, 研究规模受到一定限制。     

啮齿动物对米心水青冈种子命运的影响

有性生殖(实生更新)和无性生殖(萌生更新)是植物繁殖的两种关键方式。自然界中,个别物种同时具备两种更新方式,米心水青冈(Fagus engleriana Seem.)就是典型的物种。已有研究表明萌生更新在米心水青冈种群生活史中普遍存在,可使其占据原有生态位(生态位占据假说),但对米心水青冈实生更新的研究却未见报道。为了探索啮齿动物对米心水青冈实生更新的作用机制,笔者在神农架米心水青冈林中通过坚果摆放实验,研究啮齿动物对米心水青冈坚果传播机制的影响。结果显示,鼠类对坚果的原地捕食率高达81.22%;坚果被扩散率低,仅18.56%;坚果在原地平均留存时间为(5.25±5.95)d;坚果扩散距离为(2.63±1.60)m。研究发现,米心水青冈坚果被啮齿动物捕食率极高,贮藏率极低,且坚果被传播距离在同属植物中较小,不利于该物种更新繁殖。萌生更新在很大程度上弥补了米心水青冈实生更新繁殖方式的不足。本研究结果有助于对水青冈属植物繁殖策略的理解。     

四川大巴山米心水青冈（Fagus engleriana）群落的物种多样性特征

四川省大巴山处于秦岭南部的北亚热带,水青冈属植物分布较集中.该处米心水青冈(Fagus engleriana)林分布面积较大,生长良好,保存相对完好,具有重要的地域代表性.分析了米心水青冈群落的物种组成、区系地理成分、物种多样性以及群落自身特征与物种多样性的灰色关联度,得到以下主要结果:(1)在4个样地28个10m×10m群落样方中,一共记录到维管束植物197种,隶属140属、74科. 群落乔木层物种主要由壳斗科、蔷薇科、杜鹃花科、桦木科、槭树科等科组成;灌木层物种主要由蔷薇科、忍冬科、杜鹃花科等科组成;草本层主要由莎草科、菊科、百合科等科植物组成.(2)地理区系成分中,温带成分分别占群落总属数、总种数的65.38%和64.32%,处于主导地位;热带和亚热带成分占总属数、总种数的23.85%、24.32%.(3)群落中物种数目-多度在不同的层次变化趋势不同.(4)群落的物种丰度以灌木层最高、乔木层最低.Shannon指数、Simpson指数、均匀度指数以草本层最高、灌木层最低.(5)乔、灌、草3层的物种多样性均受到乔、灌两层植物的多度与盖度的影响,说明群落自身的特征与群落物种多样性是紧密相关的.     

米心水青冈种群萌条更新与高度生长

萌条是许多木本植物更新的重要方式,尤其是在干扰生境中.有种观点认为萌条需要消耗大量资源,导致其他方面投入减少,据此提出萌条数-高度的权衡假说.对该假说的检验多比较萌条和非萌条同属植物的高度,然而由于生活史以及其他生物学习性的差异,可能使这一比较的基础不成立.在米心水青冈中比较萌条现象不同的个体间高度来检验该假说,结果表明米心水青冈萌条和非萌条个体间的高度不存在显著差异(p=0.873),多茎干和少茎干成体间的高度也没有显著差异(p=0.559),并且个体的高度与茎干数存在显著的正相关,表明在米心水青冈中不存在茎干数-高度的权衡关系,其原因是由于萌条的叶片也具有光合能力,向萌条的资源运输随着萌条的长大而逐渐减少,直至中止.在调查的米心水青冈种群中,多干指数达到96.4%,几乎所有的幼苗、幼树和小树都是通过萌条形成的,表明萌条在种群的更新中起着关键作用.     

天目山米心水青冈群落物种组成特点与萌条更新

由于特定的温湿需求,中国的水青冈多分布于亚热带山地,而分布于欧洲和北美的水青冈则为温带的优势种。本文对浙江天目山自然保护区内米心水青冈群落物种组成特点和更新进行了研究。结果表明：在3个30 m×30 m样方中共发现132种高等植物,分属于51科86属;种-面积关系符合Arrhenius模型,lg S=0.384 lg A+0.6443;log-series模型能很好地模拟米心水青冈群落中乔木层种-多度关系(R²=0.9596);乔木层优势种为壳斗科的米心水青冈、短柄枹、锥栗等;灌木层优势种有伞形绣球、宜昌荚蒾等;草本层优势种为箬竹、苔草等;群落物种多样性较高,而灌木层和草本层物种多样性与乔木层多样性呈负相关;群落结构表明,天目山米心水青冈群落是稳定的顶极群落,萌条更新在米心水青冈群落中十分常见,55%的乔木层物种具有萌条现象;尤其是米心水青冈,萌条数与母株的胸径呈显著的正相关。     

米心水青冈幼苗对光照和养分的响应

在模拟郁闭林下(L1,大约1%～2%的全日照)、林窗(L2,大约18%的全日照)、开阔地(L3,全日照)3个光照水平和每个光照水平下进行施肥(F1)和不施肥(F0)对照的6个实验处理条件下,研究了 2年龄米心水青冈(Fagus engleriana Seem)幼苗在随后的两个生长季里的生长对光照和土壤养分的响应.结果显示:光照和养分对幼苗高度、基径和生物量有显著的影响.经过两个生长季,L1处理下幼苗高度增量极显著地小于L2和L3处理下幼苗高度增量.L1处理下基径和生物量的增量在处理当年秋就极显著地小于L2和L3处理下的增量,并在第二年差异继续扩大.L2和L3处理下的幼苗间的生长没有显著差异.施肥明显地促进了L2和L3处理下的幼苗的生长,但对L1处理下的幼苗没有明显的作用.这些结果说明,虽然2年龄米心水青冈幼苗能够在林下的弱光条件下生存,但生长受到了极大的抑制.幼苗在林窗的中等光照条件下能够与在开阔地全日照条件下生长的一样好或更好,这与许多耐阴的落叶树的响应一样.在比林内光照强度较高的条件下施肥或较高的土壤养分才对米心水青冈幼苗的生长和生存起作用.     

Structures and topographical pattern of the tree layer of Fagus engleriana-Cyclobalanopsis oxyodon community in Shennongjia area, Hubei Province, China

Shennongjia represents an area of considerable plant biodiversity, not only for China but for the whole world. The numerous species are distributed along an altitude gradient. The genus Fagus, commonly known as Beeches, constitutes one of the dominant woody species of the humid temperate forests in China. This paper deals with the community structure of a mixed, broadleaved deciduous-evergreen beech forest dominated by the Fagus engleriana and Cyclobalanopsis oxyodon, which occurs along an altitude gradient range in this area. The community consists of 46 woody species, belonging to 22 families and 27 genera. The tree layer can be divided into three sub-strata. The upper layer is composed of deciduous trees, 80.7% of which is E engleriana. The second and third layers are dominated by the evergreen species, such as C. oxyodon and the Rhododendron hypoglaucum. These species increase from 55.9% in the second layer to 80.5% in the third, and regeneration at that rate allows us to assume that the stability of the community may be guaranteed. The micro-site heterogeneity plays an important role in maintaining species diversity in plant communities. In this research, a terrain surface of 0.96 hm<'2> was simulated using the digital elevation model (DEM) in order to analyze the influence of the topography on plant community structures on a small scale. The slope relief aspect obtained with the DEM showed an accentuated heterogeneity. Semivariance analysis was used to measure the heterogeneity scale. The range and nugget variance of the semivariograms for slope were 285.8 and 280.5, respectively; for aspect, were 21.8 and 498, respectively. The elevated value of the nugget variance suggested that even on a small scale, the topographic variations influenced the species distribution. Twenty-four species were selected to estimate the correlation coefficient between the slope, aspect, and orientation. Then based on the correlation results using the Square Euclidean Distance cluster analysis, the 24 species were divided into four groups.     

The Janzen-Connell effect on the population dynamics of a Fagus engleriana- Cyclobalanopsis oxyodon community in a subtropical zone of China

The Janzen-Connell (J-C) hypothesis provides a mechanism explaining the high species diversity in tropical rainforests. It postulates that predation could cause greater mortality on seeds and seedlings near their parental trees. In this study, we tested the hypothesis in a subtropical zone, a mixed evergreen-deciduous broad-leaved forest dominated by the Fagus engleriana and Cyclobalanopsis oxyodon. The study area was in the Shennongjia region, a key area of biodiversity conserva-tion in both China and the world. The recruitment probability index was used to detect the J-C effect on nine species of the community, which were more than 50 individuals. Six large adults of each species were selected, and the numbers of saplings and adults were counted at the distance intervals of 0-5, 5-10, 10-15, 15-20, and 20-25 m from each focal tree. Two species in saplings stage and six in adult stage supported the J-C hypothesis, but their χ2 was not significant. Three species, the F. engleri-ana, Rhododendron hypoglaucum, and Toona sinensis, showed a strong Hubbell pattern in the adult stage. Because of these results, we reject the J-C hypothesis and conclude that species could recruit near the conspecific trees in subtropical forest. The reasons why the J-C hypothesis fails to explain the species diversity in this community are the shortage of seed-consuming agents of subtropical forest and the influence of microsite topo-graphic variation.     

Variation of Soil Nutrition in a Fagus engleriana Seem.- Cyclobalanopsis oxyodon Oerst. Community Over a Small Scale in the Shennongjia Area, China

Soil nutrition is a key factor influencing species composition in a community, but it has clearly scaledependent heterogeneity. In the present study, geostatistics methods and canonical correspondence analysis （CCA） were used to detect： （i） the variation range of soil spatial heterogeneity; （ii） the influence of topographic factors on the distribution of soil nutrition; and （iii） the relationships between soil chemical properties and species in the community. In all, 23 soil variables were measured, including total N and organic C, AI, Ba, Ca, Cr, Cu, Fe, Ga, Li, Mg, Mn, Na, NH4-N, Ni, NO3-N, Pb, pH, P, Sr, Ti, V, and Zn. Semi-variograms of these variables were calculated and mapped. All indices showed autocorrelatlons, with ranges between 29 and 200 m. When the sample method was larger than these distances, spatial autocorrelations were avoided. The distribution patterns of Ca, Cr, Ga, K, Mg, organic C, P, Pb, and pH, and total N were related to the microtopography and the distribution of these compounds was clumped in water catchments area. The CCA method was used to investigate the relationship between plant species and soil properties in this community. Fagus engleriana Seem., Lindera obtusiloba BI. Mus., and Acer griseum （Franch.） Pax were correlated with organic C, available N, and P.     

History of Disturbance and Regeneration Strategies of Fagus engleriana and Quercus aliena var. acuteserrata Forests in Shennongjia,Hubei Province

Based on plot investigation, stem analysis and radial growth pattern, the authors studied the history of suppression, release and regeneration strategies of Fagus engleriana Seem. and Quercus aliena var. acuteserrata Maxim. forests, which were widely distributed in Shennongjia of Hubei Province. It was found that (85.9 ± 6.9) % of the Fagus engleriana samples showed periods of suppression during their canopy recruitment. The average number of suppression periods was 2.1 ± 0.8, the average total length of suppression time was (47 ± 24.1) a, the length of longest suppression time was 73 a, the average number of periods of release was 1.6±0.7, and the average total length of release time was 23 a. (60.83±17.3)% of the Quercus aliena var. acuteserrata samples showed periods of suppression but without release. Combined with height and radial growth characteristics, these suggest that Fagus engleriana was shade-tolerant species, and its regeneration strategies was release from seedling sprouts in canopy gaps, while Quercus aliena var. acuteserrata was shade-intolerant species, and its regeneration strategies was seedling establishment and growth in large canopy gaps by producing large amount of seeds.     

米心水青冈生长过程中的抑制和释放

米心水青冈生长过程中的抑制和释放江明喜,金义兴,张全发（中国科学院武汉植物研究所,武汉４３００７４）ＳｕｐｐｒｅｓｓｉｏｎａｎｄｒｅｌｅａｓｅｐｅｒｉｏｄｓｉｎｔｈｅｃｏｕｒｓｅｏｆＦａｇｕｓｅｎｇｌｅｒｉａｎａｇｒｏｗｔｈ￥．ＪｉａｎｇＭｉｎｇｘｉ...