红树林群落优势种群自疏过程的生长动态

在深圳福田红树林保护区设置永久样地,经1994、1996、1998和2002年4次调查表明:群落中个体的断枝、死亡现象很明显,样地总面积200 m2中出现的总个体数分别为417、341、196和132个,种群平均密度依次为2.08、1.70、0.98和0.66个/m2;间隔期的死亡率依次为18.2%、42.5%和32.6%.种群个体存在明显的增粗生长,在每2年间隔期,优势种群桐花树(Aegiceras corniculatum(L.)Blanco)、秋茄(Kandelia candel(L.)Druce)和白骨壤(Avicennia marina(Forsk.)Vierh.)的胸径增加最大值分别达3.63 cm、2.45 cm、4.52 cm,且以白骨壤加粗较大.增高生长也很明显,第二次调查时341个个体中,233个出现增高生长,第三次调查时,196个个体中127个出现增高生长;2年间隔期,以桐花树增高生长最普遍,达1.5 m,秋茄增高生长最大的达1.9 m,白骨壤达1.8 m.生物量亦呈明显的相关变化,在逐次间隔调查中,地上部分总生物量依次降低,或稍增加后再次降低,但存活种群个体的平均生物量大多依次增加,4次调查期间单位面积的总生物量分别为7.57 kg/m2、8.36 kg/m2、5.15 kg/m2和7.71 kg/m2,与谭凤仪等(1995b)早期通过标准木等方式的计算结果相似.研究结果证实红树林群落的自疏过程是一种重要的演变过程,以植株、分枝干枯频繁发生为特征;演替过程中,新苗出现很少,而高度(长度)生长、增粗生长、干枯发生等与群落中种群的组成、结构、密度状况等直接相关.

Growth Dynamics and Self-Thinning of the Dominant Populations in the Mangrove Community

Consecutive investigations in 1994, 1996, 1998, and 2002 in the permanent plots established in Futian Mangrove Reserve of Shenzhen, Guangdong Province, revealed that the breaking, drying and death of the individual plants or branches in the mangrove communities were significant and the number of plants in plots covering an area of 200 m² was 417, 341, 196 and 132; the average density of population per square meter is 2.08, 1.70, 0.98 and 0.66; the death rate between the interval of two investigations is 18.2%, 42.5% and 32.6% respectively. The individuals of population exhibit an obvious diameter at breast height (DBH) growth. For example, the maximum increment of individual DBH was up to 3.63, 2.45, and 4.52 cm in the dominant populations Aegiceras corniculatum (L.) Blanco (Ac), Kandelia candel (L.) Druce (Kc), and Avicennia marina (Forsk.) Vierh. (Am), respectively. At the same time, growth of individual height was also prominent. In the second investigation, 233 out of the 341 individuals exhibit a height growth; whereas the number under the third and fourth investigations was 127 out of 196 and 74 out of 132, respectively. During a 2-year interval, the maximum height growth was 1.5 m in Ac, 1.9 m in Kc, and 1.8 m in Am. The biomass also showed a relative change in the mangrove communities. The total biomass of stems and leaves decreased with time but occasionally an increase was found in the second and third investigations and finally a decrease in the fourth investigation. However, the average biomass of the survived individuals usually increased with time. In terms of the total biomass, the results of the four investigations were similar to the previous research in which the data were calculated by the methods of standardized timbers, etc. being 7.57, 8.36, 5.15 and 7.71 kg/m² during 1994, 1996, 1998 and 2002, respectively. The above analysis indicates that self-thinning of mangrove communities is an important evolutionary process, characterized by drying, breaking, and death of individuals/ramifications. During the process of evolution, fewer new seedlings developed, and individual height growth, DBH growth, breaking and death from dryness maybe closely related to the composition, structure, and density of population in the mangrove communities.