横断山区干旱河谷川滇蔷薇生长与繁殖特征的地理空间差异

通过大面积的野外踏查、种群调查和室内实验,分析了横断山区干旱河谷乡土灌木川滇蔷薇在岷江流域、大渡河流域、雅砻江流域和金沙江流域的分布、生长繁殖特征及其在流域间的差异。结果表明,川滇蔷薇广泛分布于四大流域,海拔范围1700m至3700 m,所调查的18个种群生长状况良好,株高2 m以上,明显高于群落中的其他灌木。主成分分析表明,地理位置(流域、纬度、经度、海拔)和土壤(全碳、总有机碳、全氮、pH值)是影响川滇蔷薇生长繁殖的主要因子,其中地理位置的影响更大。生长特征包括株高、地径和冠幅在18个种群间差异显著,但在不同的流域间差异不显著。丛萌生数在种群间差异显著,其差异性较其他生长特征弱,但丛萌生数在不同流域间差异显著:岷江流域显著大于雅砻江流域,金沙江流域显著大于大渡河流域。与生长和无性繁殖相比,有性繁殖特征表现出更强的空间差异性,果实重量、瘦果重量以及种子活力在居群间差异极显著,果实重量和种子活力在不同流域间差异显著,但瘦果重量在流域间的差异不显著。综合分析表明,川滇蔷薇生长和繁殖特征在横断山区干旱河谷存在较强空间差异性,较强无性繁殖是种群持续存活的保证,而有性繁殖及其强烈的空间差异为种群适应多变环境以及地理空间扩展提供了遗传基础。     

岷江干旱河谷多苞蔷薇生长与繁殖特征

通过大面积野外踏查和样方调查,分析了岷江干旱河谷乡土灌木多苞蔷薇种群的分布、生长繁殖特征及其空间差异性.结果表明,多苞蔷薇广泛分布于岷江干旱河谷汶川绵褫至松潘镇江关约170 km长、海拔1 200～2 600 m的空间范围内,其株高、基径、年龄、冠幅、萌蘖株数和结实量的平均值分别为(123.33±3.13) cm、(12.49±0.40) mm、(3.34±0.16) a、(1.30±0.13) m²、(5.07±0.39)株/丛和(171.47±25.90)果/丛.随着海拔高度和纬度增加,其株高、基径、冠幅和结实量增加,而萌蘖株数没有显著变化.多苞蔷薇有性结实和无性萌蘖能力随环境空间变化的不匹配性与其生长密切相关,可能与多变环境下资源分配利用的平衡机制有关;以丛进行年龄统计,多苞蔷薇缺少幼龄个体,种群发展并不稳定,但随海拔高度升高,萌蘖株年龄结构均呈“金字塔”型,且较大龄级的萌株比例略增,显示出良好的种群持续性.综合分析发现,多苞蔷薇生长与繁殖的空间差异性是对干旱河谷长期适应的结果,既为种群持续提供了保证,也为种群扩大奠定了基础.     

岷江上游干旱河谷西康扁桃灌丛生长繁殖特征

以西康扁桃(Amygdalus tangutica (Batal.) Korsh.)为材料,在岷江干旱河谷四川省阿坝藏族羌族自治州茂县至松潘段设置47个调查点进行该物种的自然分布调查;选取4个典型分布点,随机选择20株灌丛,测定西康扁桃的年龄、基径、高度、冠幅等生长指标以及结实量、结实重量等特征指标;并设置5个4 m×6 m的灌木样方,调查西康扁桃的群落结构与物种组成情况。结果显示:西康扁桃广泛分布于岷江上游干旱河谷,并在松潘县南部安宏乡形成优势群落,群落主要由灌木及多年生草本植物组成,物种丰富度较高(43～55种/24 m2);西康扁桃当年结实量较小,平均值为(8.83±2.25)粒/丛;灌丛平均萌生枝数为(7.38±0.46)枝/丛,其中25.68%的萌生枝处于5～10 a的年龄阶段,而果重/枝叶重仅为(0.69±0.16)%,表明其结实能力较低,主要依靠产生萌生枝维持种群稳定;各生长与结实参数关系密切,灌丛年龄、高度是影响结实量的主要因素。研究结果表明,西康扁桃广泛分布于岷江上游干旱河谷内,灌丛有性繁殖贡献率较低,依靠无性繁殖维持群落稳定,亟需开展资源保护。     

岷江上游干旱河谷引种番麻的生态适应性及生物量预测模型

以岷江上游干旱河谷地区引种的番麻为研究对象,通过对不同海拔番麻的株高、冠幅、单株叶片数以及萌芽数等生长指标的调查研究结果,了解其在干旱河谷区的生长分布上限,为该地区与类似地区引种该品种相关物种提供理论依据;同时,利用株高等简单生长指标与番麻生物量的关系进行拟合,建立预测方程.通过高度、冠幅、单株叶片数、萌芽数(株/100m2)等生长指标比较表明,番麻的最适生长区为海拔1400～1500m.在干旱河谷阳坡的生长上限为海拔1800m,往上仅能成活,不能自身繁殖.根据番麻的株高、冠幅、叶片数等简单生长指标与生物量呈显著相关(P＜0.01),分别建立了相应的回归模型,其中地上生物量和单株生物量的最优回归模型R2值均在0.90以上,地下生物量的最优回归模型R2值也在0.75以上.     

岷江干旱河谷黄蔷薇和川滇蔷薇更新能力及其限制因素

植物种子、种子库和幼苗库的研究是种群更新和植被恢复的重要内容.研究了岷江干旱河谷两种乡土灌木(黄蔷薇和川滇蔷薇)的种子、种子库和幼苗库特征.黄蔷薇和川滇蔷薇种子产量较高, 分别为(627±216)和(7832±4347)果/丛,但种子质量较差,饱满率分别为(49.62±1.03)%和(73.83±3.42)%,活力为(32.25±0.67)%和(55.38±2.5)%.黄蔷薇种子产量和活力低于川滇蔷薇,但其种子重量和休眠程度却远高于川滇蔷薇.两种蔷薇土壤种子库的水平和垂直分布格局相似:在水平分布上,离植株基部越近,种子密度越高;在垂直分布上,种子主要分布在地表层.黄蔷薇和川滇蔷薇种子库密度均较高,分别为(560±90)粒m2和(1955±235)粒/m2,但活力种子数量较少,分别为(26±4)粒/m2和(152±18)粒/m2, 处于休眠状态的种子,黄蔷薇(60.6%)较川滇蔷薇(18.4%)高,可萌发的种子,两者分别为(10±1)粒/m2和(124±14)粒/m2.黄蔷薇(65.3%)的种子库中被啮齿动物取食的比例较川滇蔷薇(0.5%)高.两种蔷薇的幼苗密度差异不大,黄薇幼苗密度((4.28±0.49)株/m2)略小于川滇蔷薇((5.24±1.28)株/m2).幼苗组成的总体趋势是高度级低的幼苗所占的比例相对较高,且Ⅰ级幼苗数显著高于较其他级幼苗数.研究表明,两种蔷薇种子存在休眠,能形成持久种子库,种子特征对种子库和幼苗库具有深刻影响.两种蔷薇更新状况不佳,比较而言,黄蔷薇更新较川滇蔷薇好.黄蔷薇更新的主要限制因素是动物对种子的破坏,而川滇蔷薇更新的主要限制因素是幼苗存活定居.     

岷江上游干旱河谷耕地和居民用地的空间特征

以岷江上游干旱河谷耕地和居民用地为对象,用景观格局分析软件FRAGSTATS3.3计算了4个景观格局指数,利用ARCMAP9.0分析了耕地和居民用地与其它景观类型间的空间邻接特征,基于数字高成模型(DEM)研究了耕地和居民用地与海拔及坡度的关系。结果表明:灌木林地是干旱河谷的景观基质;耕地和居民用地斑块的平均面积和密度较小,形状简单;耕地大多在1700~3000m的区域,陡坡耕种比较严重,与灌木林地具有较高的邻接长度和数目;居民用地间隔较远,在低海拔地区分布相对较密,高海拔地区分布比较分散;对居民用地在空间结构影响最大的是耕地的分布。     

岷江干旱河谷主要灌丛类型地上生物量研究

灌丛是岷江干旱河谷主要的植被类型,也是该区相对稳定的生态系统类型。基于岷江干旱河谷主要灌丛大量的样地调查和实验,研究了其地上生物量及分布规律。结果表明:(1)该地区的9个灌丛的地上生物量存在较大差异,对节刺灌丛的地上生物量最大,达11554.2kg·hm-2,其次是子栎灌丛和绣线菊灌丛,分别为7144.7kg·hm-2和7213.1kg·hm-2,而滇紫草灌丛的平均地上生物量最小,仅为1407.2kg·hm-2,其余类型介于它们之间,导致这一结果的原因很多,如群落的优势种、物种组成、海拔、坡向、土壤水分等等;(2)灌丛地上生物量都随海拔升高而增加,并呈现出良好的相关性。(3)干旱河谷中土壤水分也随着海拔升高而增加。在干旱河谷过渡区,灌丛地上生物量与土壤水分间呈现很好的相关性;但是,在其核心区,灌丛地上生物量与土壤水分之间的相关性反而不显著。这主要是由于在干旱河谷的低海拔地区,"焚风"作用相对较强,其土壤水分条件较差,灌丛的生长受到抑制,随着海拔的升高,"焚风"作用不断降低,土壤水分条件逐步得到改善,灌丛的生长状况较好。而在干旱河谷核心区内"焚风"作用较强,其影响的海拔范围更大,因而,导致土壤水分非常低。由此可见,土壤水分是干旱河谷灌丛植被生长的主要限制因素。此外,低海拔地区灌丛植被受人类干扰活动的频     

岷江上游干旱河谷区域空间变化的定量判定

采用遥感和地理信息系统技术,准确界定了岷江上游干旱河谷的范围,在此基础上分析了岷江上游干旱河谷的面积变化及其边界分布海拔的最高上限在垂直方向上的抬升距离。结果表明,干旱河谷面积在不断扩大,由1974年的93140hm2扩大到2000的123078hm2,其中1995～2000年间年变化率较1974～1995年有所降低;岷江上游干旱河谷的边界沿山体向上攀升非常迅速,1974岷江上游干旱河谷边界的最高上限海拔为3128m,1995年为3167m,较1974年抬升了39m;2000年为3181m,与1995年相比沿垂直方向向上抬升了14m。1974到2000年间岷江上游干旱河谷边界最高上限沿垂直方向抬升了53m,大约平均每年抬升2m。为了遏制干旱河谷进一步扩大的趋势,必须加大植被恢复和生态建设力度。     

岷江上游干旱河谷矮探春叶片特征与环境因子的关系

对岷江上游干旱河谷矮探春(Jasminumhumile L.)的叶片形态解剖特征进行了显微观察,分析了海拔梯度上叶片形态与环境因子的关系。结果表明,矮探春叶片呈长椭圆形,叶肉组织分化明显;随着海拔升高,叶面积、厚度、干重、饱和含水量、海绵组织厚度,中脉厚度以及厚角组织厚度/中脉厚度之比(M/C)等呈增大趋势,而栅栏组织厚度/海绵组织厚度之比(P/S)则减小;叶片长/宽比、表皮厚度、栅栏组织厚度和比叶重在海拔梯度上无明显差异。叶面积、干重、饱和含水量、叶厚度和海绵组织厚度等参数两两之间呈显著正相关,而它们与P/S均呈显著负相关。叶面积、干重、海绵组织厚度和M/C等主要受土壤含水量的影响,并随着土壤含水量增加而增大;P/S随着土壤含水量和年降水量增加而减小;叶片厚度、饱和含水量和中脉厚度均随着温和度的降低而增大。岷江上游干旱河谷区土壤水份和生长季温度可能是影响矮探春叶片形态解剖特征的主要因子。     

岷江干旱河谷5种乡土植物的出苗、存活和生长

为了阐明干旱河谷自然条件下乡土植物种子出苗与幼苗定居能力的空间差异性,选择环境适应能力较强的植被恢复物种,试验选择岷江上游干旱河谷水热条件具有明显差异的两个试验地点:四川省茂县撮箕山(南坡)和两河口(北坡),采用4因素随机区组设计,开展大量的野外播种对比试验,研究了微生境类型改变及不同播种处理方式对白刺花(Sophora davidi (Franch.) Skeels.)、小马鞍羊蹄甲(Bauhinia faberi var. microphylla)、岷谷木蓝(Indigofera lenticallata Craib)、落芒草(Oryzopsis munroi Stapf)和川芒(Miscamthus szechuanesis Keng)5种干旱河谷乡土植物种子出苗、幼苗存活及生长的影响.发现:(1)在干旱河谷自然气候条件下,播种后1个月是所有受试植物出苗的高峰期,但是种子出苗率都很低,达不到30%;幼苗存活能力也极低,在播种1个月后所有幼苗死亡数量增加而保存数明显下降;在播种2个后幼苗存活数均为0.相同条件下小马鞍羊蹄甲、岷谷木蓝与落芒草的出苗数量明显高于白刺花和川芒.这说明干旱河谷地区种子出苗与幼苗存活的限制是自然植被更新能力弱,并且恢复困难的主要原因.(2)种子出苗及幼苗存活能力在不同区域之间具有明显的差异,湿润地段种子出苗数量与幼苗保存数量都较大.但是,种子出苗及幼苗存活能力在同一地段灌丛、半灌丛与裸地等不同类型的微生境之间无明显变化.(3)小容器播种能够有效地增加种子出苗率与短期幼苗存活,但是未能提高幼苗最终的存活能力及生长速率;采用保水剂与腐殖质土壤改良措施对种子出苗数与幼苗保存数没有明显影响,因而这些措施不能解除干旱河谷地区极端环境胁迫对幼苗定居的阻碍.     

岷江上游河岸带土地覆盖格局及其生态学解释

针对岷江上游干流河岸带的土地覆盖状况,将该区沿河流主干分为68个样方,结合空间信息及环境因子,对这些样方及流域内的12种土地覆盖类型,采用双向指示种分析法(Two-way indicator species analysis, TWINSPAN)和除趋势典范对应分析法(Detrended canonical correspondence analysis, DCCA)对种类和样方进行分类和排序,以揭示其生态学意义及环境影响因素。结果显示:1)研究区土地覆盖可分为高植被覆盖、中度植被覆盖和低/非植被覆盖3种类别,各类别在流域不同位置分布状况不同,整个流域以中度植被覆盖为主。2)所取样方可分为8个类群,各自拥有相似的土地覆盖组成,呈聚集分布。3)根据土地覆盖特征,河岸带可分为上、中、下3段,流域上段河岸带植被覆盖度较高;中段以中度植被覆盖类型为主,占总面积最大;下段集中了大部分人工土地覆盖类型。4)气温、海拔是影响岷江上游干流河岸带土地覆盖格局的最重要因素,此外降水和人类活动对其也有影响。除干旱河谷区外,顺流自上而下,海拔逐渐降低,水热条件逐渐改善,同时人类干扰强度也逐渐增加,是造成流域3段截然不同的土地覆盖格局的原因。5)干旱河谷特殊的土地覆盖格局是水、热共同作用造成的。总之,岷江上游河岸带土地覆盖呈现出一定的梯度变化特征,自然条件的制约是形成这一格局的主要原因。     

Sexual dimorphism in clonal growth forms and ramet distribution patterns in <Emphasis Type="Italic">Rumex acetosella</Emphasis> (Polygonaceae)

We investigated clonal traits in the dioecious herb Rumex acetosella to characterize sexual dimorphism in clonal forms and to correlate below-ground clonal patterns and above-ground ramet distributions. We recorded creeping root length, branching patterns, ramet and clump (caespitose ramets from the same position on the root) sprouting patterns, and biomass allocations in three females and males. We also estimated the patch size of flowering ramets within a quadrat. No sexual dimorphism was detected in the frequencies of branches and flowering ramets per root length. Male plants allocated proportionally more biomass to below-ground organs. Total root length did not differ between the sexes. Females sprouted more clumps with fewer flowering ramets per root length than males, which sprouted fewer clumps with more flowering ramets, which meant that clump sprouting patterns were phalanx-like in females and guerrilla-like in males. Flowering ramets were aggregately distributed in both females and males and patch sizes were similar between sexes, indicating that the spreader propagations were not found in the guerrilla-like males. We assumed that sexual dimorphism occurred in response to physiological integration for higher reproductive effort in females.     

Demographic response to shading and defoliation in two woodland orchids

Many woodland herbs are long-lived, clonal geophytes that have evolved life histories favoring survival over reproduction. We examined the life history responses of natural populations of two woodland orchid species,Cypripedium calceolus andCephalanthera longifolia to defoliation and heavy shading conducted early in the growing seasons of 2002 and 2003. We asked whether, in view of the importance of growth for the survival of geophytes, treated plants were more likely to exhibit reduced flowering than reduced vegetative growth in the seasons following treatment. We also asked whether plants would suffer reduced ramet performance. Both treatments led to significant declines in flower number per ramet, number of leaves per ramet, and mean ramet height relative to controls inCypripedium. However, inCephalanthera, only shaded plants exhibited significant declines in flower number per ramet, and only defoliated plants exhibited declines in mean ramet height. The number of ramets per plant did not decline relative to controls in either species. Thus, these orchids, especiallyCypripedium, appeared to allocate resources preferentially to vegetative growth functions over sexual reproduction. Per-plant variation in leaf and flower number per ramet, as well as in mean ramet height, consistently declined in response to treatment, significantly so in the case of mean ramet height, suggesting that ramets became more similar within genets. These results suggest both similarities and differences in the ways in whichCephalanthera andCypripedium mobilize resources in response to stress.     

Sexual reproduction and clonal growth in Reinhardtia gracilis (Palmae), an understory tropical palm

Patterns of sexual reproduction and clonal growth were investigated in the understory palm Reinhardtia gracilis var. gracilior over a 3-yr period. R. gracilis is a very abundant clonal palm in the tropical rain forest of Los Tuxtlas, Veracruz, México. Because ramets form clumps, genets are easily identified in the field. Genets were monitored in a 0.5-ha area, and classified by size according to the number of ramets they possessed. In contrast to clonal growth, sexual reproduction was highly dependent on genet size. The probability of reproduction, the number of inflorescences, and the number of fruits produced were positively correlated with genet size. However, neither the probability of producing a ramet, nor the number of ramets produced per genet were correlated with genet size. Over the 3 yr of study, 55% of the genet population had at least one ramet with reproductive structures, while <1% (a single genet in one year) had six ramets with flowers. Thirty-two percent of the mature genets reproduced during each of three consecutive years. In contrast, 58% of the genets produced no new ramets during these 3 yr. No evidence was found of a trade-off between clonal growth and sexual reproduction. Ramet production increases genet size and this in turn increases genet reproductive performance. Clonal growth in this species may be viewed as a growth strategy that tends to maximize genet fitness.     

萌蘖调控对辽东栎留存萌生株生长与结实的影响

比较了不同调控措施对岷江上游辽东栎萌生灌丛生长与结实的影响.结果表明,人为调控对辽东栎萌生灌丛本生长阶段的高生长与有性繁殖有着显著影响.各调控措施对辽东栎灌丛萌生株的基径增长未产生明显影响;保留2支和3支萌生株的丛高生长优势明显.调控丛的新生枝数量、总长度、总生物量较未调控前有较大增加,保留2支萌生株的丛类型增加得尤为显著;叶片数量、叶片总生物量与未调控前相比增加明显,叶片面积按保留萌生株数量由多到少逐渐变小.调控后,每丛保留3支萌生株的丛产生的种子最多,但自然状态丛种子单粒重最大.     

Reproductive demography of ramets and genets in a rhizomatous clonal plant <Emphasis Type="Italic">Convallaria keiskei</Emphasis>

Clonal growth occurring below the ground makes it difficult to identify individuals and demonstrate the demographic features of a focal plant species. In this study, genotypically identified ramets of a rhizomatous clonal herb, Convallaria keiskei Miq., were monitored for their growth, survival, and reproduction from 2003 to 2006. After the monitoring period, their subterranean organs were excavated to explore the underground connections of established ramets and the direction of clonal growth. We then combined data on the fate of the monitored ramets with the information of rhizome connections, clarifying reproductive demography at both the ramet and genet levels. Although each ramet initiated both sexual reproduction (via flowering) and clonal growth, clonal growth tended to precede sexual reproduction. In a surveyed genet, 51.0% of ramets produced flowers and 29.6% generated clonal offspring during the study period. Consequently, we clarified the reproductive demography of C. keiskei: clonal growth tended to precede flowering in a ramet, and a genet can keep reproducing every season at the genet level, despite a ramet not having inflorescence every year.     

Biological Properties,Trunk Anatomy and Growth Patterns of Cycas panzhihuaensis

Cycas panzhihuaensis L. Zhou et S. Y. Yang is a rare and endangered Cycad that grows in dry-hot valley of Jinsha River. The biological properties, trunk anatomy and growth patterns were studied by field investigation and location observation. The results showed as follows: The sex ratio of cones was strongly male based on reproductive episode. There were no significant sexual differences in leaf number, leaf size, trunk size and ramet number. More than 70% of the adult plants produce ramets, with a mean number of ramets per adult plant of about 2.8. The proportion of individuals with ramets and the number of ramets was positively correlated with trunk height. Maximum mean trunk diameter and mean number of leaves were reached when the plant reached 30--40 cm tall. Further increase of leaf width ceased when the plant reached 5 years old. Leaf reached its maximum length when the trunk was 10 cm tall. Growth units of trunk showed a linear relationship with height. The estimated age could be obtained by counting growth units of the trunk. The survival curve of leaves was well described by Deevey type Ⅰ . The survival time of many leaves was two growth units. The rate of leaf mortality abruptly increased after two growth units. Few leaves could survive five units.     

Floral distribution,clonal structure,and their effects on pollination success in a self-incompatible <Emphasis Type="Italic">Convallaria keiskei</Emphasis> population in northern Japan

In plant species, when clonal growth produces a patchy structure and flowering ramets are clustered, the amount of pollen contributing to reproductive success is often regulated by pollinator efficiency and geitonogamy. The spatial population structure may influence reproductive success. We examined the clonal structure, the spatial ramet distribution, and their combined effects on fruit set in a natural population of the insect-pollinated, self-incompatible clonal herb, Convallaria keiskei, in northern Japan. The number of shoots, flowers, and fruits in 1-m² quadrats were counted at every 5 m grid point in an established 100 × 90-m study plot. From all the quadrats where shoots existed, leaf samples were collected for allozyme analysis. Using the two spatial parameters of flowering ramet densities and genotypes, we then constructed individual-based fruit-set models. A total of 236 quadrats contained shoots, and 135 contained flowering ramets, which indicated expanded distribution of this plant throughout the study plot, while shoots, flowers and fruits all showed clustering distributions. Allozyme analysis of 282 samples revealed 94 multilocus genotypes. The largest clone extended to more than 40 m, whereas 56 genotypes were detected in only one sample. Several large clones and many small clones were distributed close to each other. Fine-scale spatial modelling revealed that the neighbouring flower numbers of different genotypes, compared with local genet or flower diversity, more influenced fruit set, in which the range of the neighbour was 14.5 m. These findings indicate that the compatible pollen dispersed by insect pollinators has a significant effect on sexual reproduction, in this C. keiskei population. Consequently, the spatial structure, which includes both genet distribution and clonal expansion by ramets, had a significant effect on pollination success.