木麻黄种子萌发的限制生态因子

成功的天然更新应同时具备三个条件:(1)种源数量充足、质量良好;(2)适宜种子萌发的微生境;(3)幼苗、幼树存活的生态条件。为进一步揭示海南岛木麻黄(Casuarina equisetifolia)海防林自身无法天然更新的障碍因子,该文对影响其天然更新的三个条件之一的种子萌发条件进行了研究,并探讨了不同的生态因子,如木麻黄化感、土壤酸碱度、盐度、温度、基质类型、水分等对木麻黄种子萌发的影响。结果表明:(1)不同浸提物的不同浸提液浓度处理的种子萌发率与CK组无显著性差异。(2)设定范围内的pH、盐度和温度对木麻黄种子萌发率无显著影响。(3)不同浓度梯度PEG溶液处理的木麻黄种子萌发率存在显著性差异,且伴随PEG溶液浓度增加,木麻黄种子萌发率随之锐减。(4)不同基质及浇水频度对种子萌发率也具有显著影响。从综合PEG干旱胁迫、基质及浇水频度的结果可以发现,木麻黄种子抗旱能力较弱,对水分敏感。因此,水分是制约木麻黄种子萌发的主要限制因子,凋落物层及滨海沙土较差的保水性不同程度地制约了种子的萌发。     

福建闽清福建青冈天然林种子雨和种子库

对福建闽清黄楮林自然保护区的福建青冈(Cyclobalanopsis chungii)天然林的种子雨和土壤种子库进行了观测和分析.结果表明,福建青冈种子雨持续2个月,其高峰期在11月下旬～12月上旬,总量为12.44个m~(-2),在种子散布过程中完好种子、虫蛀种子、败育种子、霉烂种子和萌发种子的比例差异明显,其中虫蛀种子是萌发种子的19.44倍.土壤种子库中虫蛀种子占53.79%,与种子雨相比,完好种子和萌发种子数量分别减少2.15个m~(-2)和0.20个m~(-2).土壤种子库种子存活率仅13.51%,动物捕食率达45.90%,说明动物的捕食和搬运是福建青冈种子缺失的原因之一.福建青冈天然林土壤种子库有69种植物种子,但种子数量较少,且分布不均匀,种子库中78.42%种子分布在2～5 cm土层中.福建青冈天然林中实生幼苗少与福建青冈种子本身特性及其生长环境密切相关,福建青冈种子发育成熟后因动物侵扰、虫蛀、霉烂和败育等情况发生,难以在土壤中长期保存,以致福建青冈林分天然更新严重受阻.     

木麻黄原生境种子萌发及幼苗存活的影响因素分析

木麻黄无法天然更新已严重影响了海南岛木麻黄海防林发挥其永续的防护效能。该文以海口木麻黄海防林为原生境试验基地,采用5因素2水平的因子试验设计方法,共设计36个处理组合,探究木麻黄种子萌发及幼苗存活的影响因素及障碍因子。结果表明:(1)木麻黄种子发芽率最高的处理组合为林窗-不浇水-沙土-保水-盖土(GJ0SBM),发芽率为37.33%,显著高于其他处理组合(P<0.05); 平均株高最高的处理组合为林窗-浇水-红土-不保水-不盖土(GJRB0M0),平均株高为6.43 cm/53 d,显著高于其他处理组合(P<0.05); 存活率最高的组合为林窗-浇水-沙土-保水-盖土(GJSBM),存活率为79.00%/73 d,显著高于其他处理组合(P<0.05)。(2)林分光照条件和盖土方式是木麻黄种子发芽率及发芽势的影响因素,保水方式对种子发芽速度有显著影响。(3)林分光照条件是影响木麻黄幼苗株高的影响因素。(4)浇水方式是影响木麻黄幼苗存活率的主要影响因素。综上所述,木麻黄自身无法天然更新的障碍机制不在于种子萌发,而是因为木麻黄幼苗在海南旱季因缺乏必要的水分而无法存活,从而导致其自身无法天然更新。     

海南岛木麻黄海防林天然更新特征及更新树种筛选

天然更新是森林资源再生产的一个重要的生态学过程,良好的天然更新可促进人工林向近自然林的方向转变。为了解海南木麻黄海防林天然更新现状和特征,筛选出自然条件下天然更新良好的树种。该研究在海南岛木麻黄海防林内共计设立临时样地73块,样地总面积为2.51 hm~2,采用典型抽样的调查方法对海南全岛木麻黄海防林天然更新状况进行系统调查,应用天然更新密度及物种丰富度等指标对干、湿不同气候区木麻黄天然更新特征进行比较分析,并应用更新密度、更新指数等指标对天然更新质量较好的树种进行筛选。结果表明:(1)海南岛木麻黄海防林下天然更新质量整体不佳,木麻黄自身虽无法实现天然更新,但局部其他树种天然更新良好,更新良好的比例为15.1%。(2)湿润区天然更新丰富度及物种多样性远优于半干旱区,其中湿润区样地更新树种为28科、50属、59种,半干旱区样地更新的树种为6科、6属、6种。(3)乔木更新情况优于灌木。(4)潺槁木姜子、鸦胆子、台湾相思、榄仁树等具有较强的天然更新性能,适合与木麻黄混交,可以作为木麻黄海防林的混交树种或伴生树种。     

毛红椿天然林种子雨、种子库与天然更新

2008-2011年,调查江西九连山国家级自然保护区毛红椿天然林的种子雨、种子库及林下幼苗数量.结果表明:在毛红椿天然林,种子雨散布时间为10月下旬至12月下旬.2010年不同样地的种子雨强度为虾公塘气象观测站(320.3±23.5粒·m-2)＞虾公塘保护站(284.7±24.2粒·m-2)＞大丘田保护站(251.6±24.7粒·m-2),分别以222.0、34.3和22.6粒·m-2完好种子供土壤萌发更新;毛红椿种子储量取决于结实量、鸟类取食和种子活力等因素,鸟类取食是其种子储量大幅下降的首要因素;由于种子不耐储藏以及大量腐烂,种子有效贮藏期不足1个月.12月天然林种子库平均萌发数≤2株·m-2,次年1月土壤种子库种子量最少,为6.7～11.8粒·m-2,平均仅萌发0.4～0.6株·m-2,与林下实生幼苗分布极少相吻合.毛红椿种子雨储备、种子库种子活力保存及幼苗建成等因素影响其天然更新.     

准噶尔盆地东南缘梭梭种子雨特征

为了研究梭梭种子散布规律,通过布设种子雨收集器结合室内实验分析,对准噶尔盆地东南缘梭梭种子雨特征进行了研究。研究显示:(1)梭梭种子雨的累积密度达到平均189粒/m2,其中有活力种子占约80%;(2)种子散布的高峰集中在11月初到11月15日时间段,其落种量占整个种子雨的65%。其后种子雨密度随时间逐渐减小;(3)整个种子雨过程,不同时期散落的种子雨质量存在差异,表现为不同时期散落种子的萌发率呈现出先增大后减小的趋势;(4)变异函数分析表明,梭梭种子雨在8.12 m的有效变程内,种子雨具有明显的空间格局,其由空间自相关和随机因素引起的空间异质性各占50.0%。准噶尔盆地东南缘梭梭种子雨密度大且质量较高,同时其时空分布异质性较高,这些特征均将影响梭梭种群的分布格局和种群更新。     

花楸树种子散布、萌发与种群天然更新的关系

花楸树是我国东北林区重要的非木质资源树种,其实生天然更新不良.本文通过研究花楸树种子散布、土壤种子库及种子萌发出土过程,分析花楸树实生天然更新的影响因素.结果表明：自然散落的花楸树果实96.1%分布于母株2 m范围内,凋落物层和土壤表层（0～2 cm）的种子数占土壤种子库总数的97.0%;不同季节花楸树土壤种子库种子数量差别很大,当年11月上旬种子数量最多,达(257.7±69.2)粒·m^-2;翌年7月下旬种子数量最少,仅为(2.9±2.9)粒·m^-2;温度不是花楸树种子萌发出土过程的限制因子,0 ℃～5 ℃时幼苗出苗率达(67.5±6.6)%,但对其出苗速率影响显著.土壤含水量为50%时,花楸树出苗率最高,达(74.7±4.2)%;含水量为60%时,幼苗死亡率最低,为(32.6±0.6)%.花楸树种子的散布格局和土壤种子库的时空分布格局影响种子的萌发出土过程,进而影响其种群的天然更新.     

海南岛木麻黄林林下植物天然更新影响因素的研究

木麻黄海防林是海南岛重要的海岸生态屏障,天然更新对其持续发挥防护功能具有重要意义。调查发现海南岛大多数木麻黄林林下天然更新困难,然而却存在局部更新良好的现象。为了探究天然更新存在巨大差异的原因,并为促进海南海防林由人工林向近自然林转化提供一定的理论基础,通过分析不同林地更新质量的差异,研究影响木麻黄海防林林下天然更新的主要影响因素。该研究在海南岛木麻黄海防林中共设置73块临时样地,采用方差分析和相关分析等统计方法,分别研究林地所属气候区、林分条件、土壤因子和凋落物累积量对天然更新质量和密度的影响。结果表明:(1)湿润气候区的木麻黄林下更新要显著优于半干旱区;(2)木麻黄林分密度与更新密度和草本盖度存在显著负相关,但林分条件其他因子对更新影响不大;(3)不同更新质量样地的土壤pH和养分均无显著性差异,但铵态氮对幼苗、有机质对幼树的更新存在一定的促进作用;(4)凋落物的累计整体不利于天然更新的进行。结果说明气候因子、木麻黄林分密度、木麻黄凋落物积累量是木麻黄海防林林下植物天然更新的主要影响因素。     

科尔沁沙地南缘樟子松(Pinus sylvestris var.mongolica)人工林天然更新障碍

针对科尔沁沙地南缘樟子松人工林不能天然更新的特征,从森林天然更新的必要条件出发,通过种子萌发、幼苗存活与生长所需条件的系列试验,探讨了科尔沁沙地南缘樟子松人工林不能天然更新的障碍特征。结果表明,沙地樟子松人工林不能天然更新的主要原因有:(1)由于土壤的干旱胁迫使沙地樟子松人工林中天然下种的种子很少有萌发的机会,尤其是在春季;(2)在水分条件相对充足的季节(秋季),樟子松种子能够萌发,但萌发产生的更新幼苗数量极少,即便这些更新幼苗得以存活,但由于沙地表层(0~5cm)与樟子松共生的外生菌根菌几乎不能存活而导致幼苗根系无法形成菌根,从而致使存活的樟子松幼苗抗旱、抗病能力非常弱,不能越冬,即不能更新。     

灵山湾国家森林公园刺槐林下垂序商陆种子雨时空动态

垂序商陆(Phytolacca americana)的入侵给山东省沿海防护林的生物多样性及乔木更新造成了严重的危害, 为揭示其繁殖特性和扩散机制, 在灵山湾国家森林公园刺槐(Robinia pseudoacacia)林下由林缘至林内60 m设置5个梯度, 采用机械布点法对垂序商陆的结实量、种子雨分布和扩散格局进行了调查。结果表明: 1)垂序商陆的结实量与种子雨量由林缘至林内逐渐减小, 分别为2 273-1 846和1 382-621粒·m^-2, 不同空间种子雨密度占结实密度的60.80%-33.64%, 平均为49.52%, 人为搂割及动物取食是种子雨量损失的主要原因; 2)种子雨始于9月中旬, 林缘种子雨的发生早于林内, 种子雨的平均强度由林缘至林内逐渐减小, 在10月下旬和12月中旬各有一次种子雨高峰, 最大强度分别为32-4和59-5粒·m^-2·d^-1; 3)种子雨由林缘至林内散布范围逐渐减小, 同时随距母株距离的增加而减小, 其中最大散布距离与加权平均距离分别为210-180 cm和94.32-63.03 cm, 整体加权平均距离为81.00 cm。表明垂序商陆种子雨具有明显的时空异质性, 对预测其扩散潜力及群落结构组成趋势有重要的意义。     

盐磷胁迫对木麻黄和台湾相思种子萌发及幼苗生长的影响

恶劣环境下,人工海防林因面临养分胁迫而经营困难。为探讨盐、磷胁迫对主要海防林树种木麻黄和台湾相思种子萌发及生长的影响,该研究分别用不同浓度的NaCl(盐)和KH₂PO₄(磷)溶液处理种子和浇灌幼苗,测定种子萌发和幼苗生长指标。结果表明：(1)高盐胁迫显著抑制种子萌发,对幼苗生长有一定影响,但两种植物影响程度不同;台湾相思种子萌发耐盐性高于木麻黄,前者相对盐害率最大值为23.03%,后者为89.15%;随着盐浓度增加,木麻黄和台湾相思种子的发芽率、发芽势、发芽指数和活力指数均降低,对应最大值分别为38.70%、34.67%、18.70、0.055和76.67%、62.22%、48.46、6.11。(2)两种植物的株高和根长随盐浓度增加而降低,木麻黄和台湾相思株高分别为12.29～6.01 mm和48.27～17.33 mm,根长分别为8.57～1.45 mm和33.41～5.88 mm;台湾相思根、茎、叶生物量及根冠比均随盐浓度的增加逐渐减小,木麻黄各处理差异较小。(3)台湾相思的种子和幼苗较木麻黄更耐低磷环境,二者最适磷浓度存在差异;木麻黄种...     

不同年龄香果树种子雨和种子库及其更新特征

对宝天曼自然保护区香果树种子雨、土壤种子库进行了观测,并进行不同微生境播种实验,研究其种子萌发及幼苗生长动态。结果表明:(1)不同龄级香果树种子雨持续时间及其高峰期有所不同,种子雨强度存在极显著差异。(2)20~50龄级香果树的种子饱满率、土壤种子库中种子密度均显著低于其他龄级,但其不同类型种子的水平和垂直分布规律一致;大约80%的香果树种子在其萌发前消失,剩余种子中以霉烂种子密度最高(9.81粒·m-2),饱满种子密度最低(1.94粒·m-2)。(3)野外育苗实验表明,不同龄级香果树所产饱满种子的萌发率及幼苗存活率差异不显著,其种子萌发率约为16.93%,但仅有3.86%的幼苗寿命超过5个月;不同微生境对香果树幼苗存活率产生显著影响,林窗是其最适宜微生境。研究认为,人工采集香果树种子,于次年4月份在原生境下播种;清理母树冠下和冠缘的地被物,增加林缘空地地被物覆盖度,以减少香果树种子的损失,改善香果树种子萌发和幼苗生长的光照条件,以利于幼苗根系的生长,促进香果树的自然更新。     

Reinvasion of a Riparian Forest Community by an Animal-dispersed Tree Weed Following Control Measures

Patterns of seed dispersal and the effects of mulching upon Celtis sinensis Pers. seedling establishment were investigated following the removal of this tree weed from a riparian forest community. At the commencement of the study there was virtually no representation of C. sinensis in the soil seed bank. However, subsequent rates of seed immigration were high since mature individuals of C. sinensis remained on the boundary of the site. Fruit bats (Pteropus spp.) were the principal dispersal vectors. Seed rain density of C. sinensis was best fitted by an inverse power distribution, with seed densities in excess of 20 m⁻² detected at 70 m from the seed source. Extrapolation from this relationship suggested that a site would have to be more than 350 m from a seed source to reduce the C. sinensis seed rain to less than 1 m⁻². More than 98% of the seed rain occurred below the canopies of the native tree species that remained following the removal of C. sinensis. For these trees, subarboreal C. sinensis seed distributions were not homogeneous, with peak seed densities occurring at different distances from tree trunks in each of the two years that seed distributions were assessed. Mulching with compacted sugar cane trash, corresponding to litter loadings of 6–12 kg m⁻², was imposed early in the study, some weeks before the C. sinensis seed rain commenced. These treatments had no measurable effect upon C. sinensis germination, but substantially reduced seedling survival and had variable effects upon the early growth of seedlings. The potential roles of seed limitation vs establishment limitation are discussed in relation to the management of animal-dispersed invasive species. It is argued that an understanding of the likely levels and patterns of invasion is essential for the formulation of management strategies that can effectively reduce the invasion and impacts of these plants. This revised version was published online in July 2006 with corrections to the Cover Date.     

SEED DISPERSAL OF METROSIDEROS POLYMORPHA (MYRTACEAE): A PIONEER TREE OF HAWAIIAN LAVA FLOWS

Wind dispersal of seeds of Metrosideros polymorpha, the dominant tree of rain forests and the main pioneer of volcanic substrates in Hawaii, was measured on a 20-yr-old lava flow downwind of a M. polymorpha forest. Seed rain was concentrated in December and January, when 74.5% of the annual total was dispersed. Annual seed rain at the forest edge was 63,893 seeds/m², of which 5,580 (8.7%) contained embryos and were potentially viable. Beyond the forest edge, the density of embryo-containing seed decreased to 363, 137, 37, 25, and 20/m² at distances of 25, 50, 100, 150, and 250 m, respectively. In contrast, the density of established M. polymorpha seedlings remained relatively constant beyond 25 m, a fact suggesting that the density of safe sites for germination and establishment was also constant over the same distance. It was concluded that colonization of the lava flow was limited by the density of safe sites, i.e., conditions for establishment, rather than by seed rain, i.e., dispersal, which was more than sufficient to saturate the available safe sites.     

Does proximity to a mature forest contribute to the seed rain and recovery of an abandoned agriculture area in a semiarid climate?

Proximity to forests contributes to the recolonisation of anthropogenic‐disturbed areas through seed input. We evaluated the role of proximity to a mature forest in the recolonisation of an agricultural area that has been abandoned for 18 years and is currently a young forest. Seed rain was monitored at fixed distances from the mature forest. The type of surface recolonisation (germination versus resprouting) and the reproductive season were measured in both forests. The majority of plants recolonising the young forest originated from seed germination. Proximity to the mature forest contributed to the seed rain in the young forest; however, 18 years has not provided sufficient time for the recolonisation of 80 species present in the mature forest. Some species shared between forests differed in their fruiting season and seed dispersal. The seed rain had a total species richness of 56, a total density of 2270 seeds·m^?2·year^?1 and predominance of self‐ and wind dispersal. A significant reduction in seed rain with increasing distance from the mature forest was observed. The young forest contained 35 species not observed in the mature forest, and the floristic similarity between the two forests was 0.5, indicating that the two forests are floristically distinct.     

Relationships among the seed rain,seed bank and vegetation of a Hawaiian forest

Abstract. Hawaiian ecosystems are prone to invasion by alien plant species. I compared the seed rain, seed bank, and vegetation of a native Hawaiian forest to examine the potential role that seed ecology plays in allowing alien species to invade native forest. Absolute cover of seed plants in the forest was 126 %, annual seed rain was 5 713 seeds m^-2 yr^-1, and the mean density of seedlings emerging from the seed bank averaged across four seasons was 1 020/m². The endemic tree Metrosideros polymorpha was the most abundant species in the vegetation, seed rain and winter seed bank. Overall, native seed plants comprised 95 % of the relative cover in the vegetation and 99 % of the seeds in the seed rain, but alien species comprised 67 % of the seeds in the seed bank. Alien species tended to form persistent seed banks while native species formed transient or pseudo-persistent seed banks. Dominance of the seed bank by alien species with persistent seed banks suggests that aliens are favorably placed to increase in abundance in the vegetation if the forest is disturbed.     

灵山湾国家森林公园垂序商陆土壤种子库时空动态及其对防除措施的响应

土壤种子库是植物潜在的种群,对生态系统稳定和未来植被的结构、功能有着举足轻重的影响。垂序商陆(Phytolacca americana)的入侵已对山东省胶南市灵山湾国家森林公园的森林生态系统构成严重危害。为调查该物种在公园内的潜在扩散能力,于2009—2014年调查了刺槐(Robinia pseudoacacia)林、黑松(Pinus thunbergii)林、刺槐黑松混交林和紫穗槐(Amorpha fruticosa)林(灌丛)4种林分类型,以及2009年采用物理和化学控制入侵危害严重的刺槐林内的土壤种子库。结果表明:垂序商陆种子在4种林分中均有发现,在刺槐、黑松林内表现为由林缘至林内逐步降低的趋势。垂序商陆种子只存在于枯落物层和5 cm以上的土壤中,随土层深度的增加而减少,枯落物层土壤种子库由林缘到林内呈递减趋势。与2009年相比,2014年黑松林和灌丛中平均种子库密度分别降低46%和44%,刺槐林和混交林分别增加299%和355%。垂序商陆种子发芽率在10%以下,随土层深度的增加而依次降低。采用物理、化学控制措施的刺槐林内垂序商陆的更新量、结实量、种子库含量均明显高于紫穗槐林的。调查结果表明垂序商陆土壤种子库具有明显的空间异质性,并且保持了较强的繁殖潜力,营造紫穗槐灌丛可以有效控制垂序商陆的扩散,可为经营沿海防护林提供理论指导。     

中亚热带4种森林凋落物量、组成、动态及其周转期

为研究亚热带次生林保护对森林生态系统养分循环等功能过程的影响。采用凋落物直接收集法,比较湘中丘陵区3种次生林(马尾松+石栎针阔混交林、南酸枣落叶阔叶林、石栎+青冈常绿阔叶林)和杉木人工林的凋落物量、组成特征及其周转期。结果表明:4种林分年凋落物量在414.4—818.2 g m-2a-1之间,3种次生林显著高于杉木人工林,3种次生林两两之间差异不显著,落叶对林分凋落物量的贡献最大,占林分凋落物量的59.9%—66.6%。杉木人工林和南酸枣落叶阔叶林的凋落物量月动态变化呈"双峰型",马尾松+石栎针阔混交林、石栎+青冈常绿阔叶林呈"不规则型"。优势树种的凋落物量对其林分凋落物量的贡献随林分树种多样性的增加而下降,杉木、马尾松凋落物量的月动态与其林分凋落物量的月动态基本呈一致变化趋势,但南酸枣、青冈、石栎没有一致的变化趋势。杉木人工林凋落物分解率最低(0.31),周转期最长(3.2 a),南酸枣落叶阔叶林分解率最高(0.45),周转期最低(2.2 a),凋落物的分解速率和周转随林分树种多样性增加而加快。可见,次生林凋落物量大,且分解快,周转期短,有利于养分归还和具有良好地力维持的能力。     

Natural regeneration of Spanish black pine [Pinus nigra Arn. ssp. salzmannii (Dunal) Franco] at contrasting altitudes in a Mediterranean mountain area

Information on plant seed dispersal, natural loss dynamics of seeds and germination are critical for understanding natural regeneration mechanisms. The aim of this study was to assess the effect of different forest stand densities on seedfall, seed predation, and seedling germination of two populations of the endangered Spanish black Pine forests located at lower (Central population) and higher elevation near the limit of the species?? range (peripheral population) in the Cuenca Mountains of Central Spain. The seed predation and germination experiment also included a nested site preparation treatment. Seed fall varied significantly between 2006 and 2005 or 2007 in both populations. During the only mast year of 2006, higher seedfall was observed at lower elevation and in higher density stands. Predation rates were influenced by the seed crop since predators consumed more than 75?% of seeds in years with lower production and less than 15?% in a mast year. Seed germination is influenced by forest habitat, stand density and soil scalping. For common habitat types, and in a high seed production year, better seed germination rates were observed in medium and dense stands (25?C30 and 35?C40?m²?ha^?1, respectively, in terms of basal area). No statistical difference in seed germination rate was found for Spanish black pine forest at its ecological distribution limit between lower and higher densities (15?C20 and 35?C40?m²?ha^?1, in terms of basal area). In both sites, closed stands with soil scalping exhibited higher germination rates.