【作者】 张孟文；

【导师】 吴庆书； 杨小波；

【作者基本信息】 海南大学 ， 植物学， 2012， 硕士

【摘要】 为了了解海桑属植物在海南岛清澜港红树林保护区的分布情况及海南海桑濒危的原因,本文重点研究了海桑属植物所在的红树林群落组成特征、海桑属植物的种群分布特征及濒危植物海南海桑的繁殖生态学特性。关于海桑属的群落特征及分布特点的研究结果表明：海桑属植物群落生长在距低潮线不远的海滩上或至内河、潮水盐度较低地段的低潮滩上,常常为海水淹没；群落中红树植物种类丰富,其中真红树植物有24种,半红树植物20种,优势种为海莲(Bruguiera sexangula)和海桑(Sonneratis caseolaris),海桑属植物主要6种,分别是海桑(S. caseolaris)、杯萼海桑(S. alba)、无瓣海桑(5. apetala)、卵叶海桑(S. ovata)、拟海桑（S. paracaseolaris)、海南海桑(S. hainanensis),其中卵叶海桑、拟海桑已处于濒危状态,海南海桑处于严重濒危状态。关于海南海桑繁殖生态学特性的研究结果表明：(1)海南海桑退化雄蕊数受花部多种因素影响,特别是与花萼直径之间呈极显著负相关,海南海桑的繁育系统为混合交配,其中异交为主,部分自交亲和,传粉过程需要传粉者(蝙蝠、蜜蜂和蚁类)。(2)海南海桑种了空壳率较高,为53.33%,种子需要在光照条件下才能萌发,其适宜温度为30-40℃,最适温度为35℃；盐度在0-7.5‰时种子可萌发,最适盐度为2.5‰。在各环境因子中,盐度与发芽率、发芽势和胚根长之间极显著负相关,表明了种子萌发对盐度的反应敏感,低盐度促进萌发,高盐度抑制萌发。(3)海南海桑幼苗生长最适盐度生态幅在0-5‰之间,低盐度下的幼苗侧根多且较长,而高盐度下侧根则少又短,表明高盐度抑制幼苗根系伸长。(4)自然条件下种子萌发的研究表明,人工散播种子在自然状态下萌发率为0,散播种子遭动物破坏和被搬迁共占观测数的81.5%和18.5%；另外野外调查发现,3株海南海桑母树下都没有见到幼苗,可见自然条件下,海南海桑种子转化到幼苗的过程是很脆弱的环节。综合以上的研究结果,可以发现在文昌清澜港地区的红树林群落中,海桑属植物所在的区域,其群落主要以海桑和海莲组成。6种海桑属植物中卵叶海桑、拟海桑已处于濒危状态,海南海桑更是处于严重濒危状态。结合海南海桑繁殖生态学特性的研究结果,不难发现,海南海桑处在严重濒危状态不仅与林下光照不足导致温度变化及海水盐度过高抑制种子萌发及幼苗生长有关,而且与开花和坐果期间,雄蕊退化和脱落、落蕾落果,导致有效传粉、有效结实低,种子空壳率高、种子的萌发率低及在野外成熟的果实与种子被野生动物啃食密切相关。对此要采取的保护措施有：开花期进行人工异株异花授粉,提高传粉效率,增加坐果率,促进结实。建造小型人工模拟温室,及时采集种子,通过室内育苗扩大种群,并进行盐度等因子的驯化,等幼苗个体生长到一定程度,再移栽至林下进行大而积野外种植,恢复海南海桑种群数目。更多还原

【Abstract】 To investigate the distribution of Sonneratia species and endangered mechanisms for Sonneratia hainanensis in Qinglangang mangrove reserve in Hainan island, the community composition and distribution pattern of Sonneratia population were studied, as well as the breeding characteristics of the endangered species, Sonneratia hainanensis.Results concerning the community composition and distribution of Sonneratia population were as follows:Sonneratia plants usually grew on the coast near low-tide line, or extended to inland river and low tidal beach with low salinity. There were rich mangrove species including24true-mangrove and20semi-mangrove in Qinglan mangrove reserve. The forest community was dominated by Bruguiera sexangula and Sonneratia caseolaris. There were six species attributed to Sonneratia, including S. caseolaris, S. alba, S. apetala, S. ovata, S. paracaseolaris and S. hainanensis. There were three endangered Sonneratia species including S. ovata, S. paracaseolaris and S. hainanensis, with small number of individual tree, especially, S. hainanensis with only3individual trees in the fields.Results concerning breeding characteristics of the endangered species, Sonneratia hainanensis, were as follows:(1) Many factors of floral syndrome made an influence on staminode, which was negatively correlated with calyx diameter. Bagging test results showed that Sonneratia hainanensis was a cross-pollinated species without apomixis, which was partially self-compatible and needs pollinators like bat, bee and ants, etc.(2) Impacts of illumination time, temperature and water salinity on seed germination of mangrove tree, Sonneratia hainanensis, were explored through experiments in laboratory. Results showed that the empty grain rate for Sonneratia hainanensis was53.33%. The seeds did not germinate in the dark condition. The preferable temperature for the seed germination ranged from30to40℃with optimum temperature was35℃. Salinity between0and7.5%o was beneficial to germination. At2.5%o the germination rate, potential germination rate and radicle length were81.33%,72.67%and4.23cm. The results of correlation analysis showed that only salinity, respectively, was much negatively correlated with germination rate, potential germination rate and radicle length. Experiment results indicated that seeds were sensitive to water salinity, that low salinity promoted the seeds germinating while high salinity inhibited it.(3) Salinity between0and5%o was beneficial to seedling growth. Lower salinity was good at growth of lateral root while higher resulted in inhibition of root elongation.(4) The germination rate of Sonneratia hainanensis seeds in natural forest conditions was0, and the proportion of seeds eaten by animals was81.5%, with the seed moved18.5%. No seedlings were found near the parent trees through a field investigation. This probably indicates that the period from seed to seedling was a hard-growth time for Sonneratia hainanensis because of many barriers.According to the above results, it can be concluded that in Qinglan mangrove reserve, the forest is dominated by Sonneratia caseolaris and Bruguier sexangula. S. ovata, S. Paracaseolaris and S. hainanensis are all endangered species, especially there are only3individual trees for S. hainanensis in the study area. The reasons result in severe difficulty in natural regeneration for Sonneratia hainanensis are as follows:(1) light deficiency in understory caused inadequate temperature and higher salinity resulted in inhibition of seeds germinating and seedling growth;(2) there are high fruit-dropping rate and a certain number of stamen which degenerate in the flowering stage;(3) high percentage of empty grains contribute to low germination rate;(4) large amount of fruits and seeds were eaten by animals.Some measures can be done to effectively conserve the endangered plant S. hainanensis,(1) artificially cross pollination can be done to improve pollination rates for S. hainanensis;(2) small greenhouse can be built and natural forest conditions can be simulated to make seed germinate;(3) seedling population can be enlarged in greenhouse, and then trees are transplanted to the fields.更多还原