珍稀植物伯乐树一年生更新幼苗的死亡原因和保育策略
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BGCI中国项目(6206/R4352);国家科技支撑计划项目(2008BAJ10B03-05); 广东省科技攻关计划(2010B020303005);河南科技大学博士科研基金项目(09001495)


Death causes and conservation strategies of the annual regenerated seedlings of rare plant, Bretschneidera sinensis
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    摘要:

    伯乐树(Bretscheneidera sinensis Hemsl.)是我国特有珍稀的孑遗植物和国家一级重点保护野生植物,在研究被子植物的系统发育、古地理和古气候等方面具有重要科学价值。研究发现伯乐树1年生更新幼苗的高死亡率是其天然更新困难的主要原因之一。采用分区试验监测了不同生境下1年生更新幼苗的生长动态;分析了幼苗死亡的共同原因,探讨了土壤酸碱度和不同光照环境对其生长的影响,并提出有效的保育策略以促进其种群更新。结果表明,伯乐树作为多年生木本植物,其根尖并无根毛分化,因此对环境的营养要求较高,并极易受到各种因素影响而导致死亡。1年生更新幼苗死亡的原因主要包括三方面,分别表现在土壤透气性较低时,幼苗易腐烂致死;在夏季炎热天气易受干旱胁迫致死;茎叶内含有黑芥子酶细胞,作为菜青虫发育的必要场所而易被啃噬致死等。幼苗较适于弱酸性土壤(5.0-6.5),并据中国土壤规律主要分布在长江以南地区。不同光环境下对夏季时幼苗的存活率和生长量存在显著区别,表现在全光环境下易造成幼苗的死亡,而极度弱光环境会导致生长迟缓,只有适度遮荫有利于幼苗的形态生长,其中自然遮荫下的生长量各项指标(苗高、地茎、叶片数和侧枝数等)和幼苗成活率达到最优。据此,在保育策略上建议采取适当的水肥管理和适度遮荫等措施,如在大田中遮网1层或在中等郁闭度的林下自然遮荫。

    Abstract:

    Bretschneidera sinensis Hemsl., a tertiary relict tree endemic in China, was listed in National Key Protected Wild Plants (Class I) as a rare species. It is significant for the studies on phylogeny, paleogeography and paleoclimate of angiosperm. It was discovered that natural regeneration of the population was quite difficult and one of the key causes is the high death rate of its annual regenerated seedlings. Site experimentation was conducted to monitor the growth status of annual regenerated seedlings in different habitats, in order to discuss the common death causes of the seedlings and to study the effects of soil pH and different shade treatments on the growth of seedlings, also the effective conservation measures were advised to promote its natural regeneration. Results indicated that, as a perennial tree, the root tip of B. sinensis has no root hair differentiated, so it needed special habitats with enough nutrition and would be caused death easily by many lethal factors. The main death causes of the seedlings consisted of 3 aspects: the decay of root system because of poor permeability of soil, water shortage by drought stress in summer, predation risk by cabbage caterpillar because of the myrosin cell in its stem and leaf which is the necessary development site for the pest, respectively. The seedlings were adapt to weak acidic soil (pH=5.0-6.5), so the species only distributed in the south area of Changjiang river according to the changing rule of the soil properties in China. Also the diverse light intensity differed significantly in the survival rates in hot summer and biomass accumulation of annual regenerated seedlings. Results of light control treatment showed that the natural sunlight would cause the death of seedlings seriously, while severely weak shade conditions would inhibit the biomass accumulation. Only moderate shade treatment was suitable to the growth of seedlings, and the biomass indexes (plant height, basal diameter, number of leaves and number of branches) and the survival rate were all highest under natural shade treatment. Accordingly, suitable water and fertilizer management and moderate shade treatment were recommended to be utilized on the annual regenerated seedlings of B. sinensis as conservation strategies, including using shading net by one layer in the field or natural shade under the forest with middle canopy density.

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乔琦,秦新生,邢福武,陈红锋,刘东明.珍稀植物伯乐树一年生更新幼苗的死亡原因和保育策略.生态学报,2011,31(16):4709~4716

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