拉关木小苗在白骨壤林内及林缘生长实验研究

Growth of Laguncularia racemosa seedlings inside and at the edge of Avicennia marina forests

探讨引进的红树植物拉关木(Laguncularia racemosa)是否对本土红树植物白骨壤林(Avicennia marina)造成入侵风险。通过野外种植实验,将1年生拉关木苗种植在成熟白骨壤林的林内和林缘,每月观察记录并测量其生长指标。结果表明:白骨壤林内和林缘的1年生拉关木苗的月均苗高增量变化趋势相似,均表现为夏季高,冬季低;月均基径增量表现为林内低于林缘,且随着种植时间的延长而降低。白骨壤林内和林缘的拉关木苗野外种植13个月后的苗高增量仅为14.1 cm和13.5 cm,基径增量仅为1.0 mm和1.5 mm,叶片数增量均为负值,分别为-0.4片和-0.7片,可见外来种拉关木苗在厦门海沧湾的白骨壤林内及林缘生长速度缓慢,不具有速生快长特性,因此,外来红树植物拉关木只有在其适宜生长的环境才能表现出速生的特性。种植13个月后,白骨壤林内和林缘拉关木苗的存活率仅为4.7%和5.3%。表明由于光照强度、低温等环境因子的限制,引进种拉关木小苗很难通过自然扩散在厦门本土红树植物白骨壤林内自然更新生长。

In order to assess the invasion risk of fast-growing introduced mangrove species Laguncularia racemosa, field experiments of planting 1-year-old L. racemosa seedlings were used to study the effects of environmental factors of light intensity on their growth inside and at the edge of native mangrove species Avicennia marina forest. Results showed that the average monthly shoot height of 1-year-old L. racemosa seedlings inside and at the edge of the A. marina forests was similar, both high in summer and low in winter;the average monthly shoot diameter of 1- year-old L. racemosa seedlings inside the A. marina forests was lower than that in A. marina forest margins, and the average monthly shoot diameter increment of L. racemosa seedlings decreased with the prolongation of planting time. After planting for 13 months, the seedling height of L. racemosa inside and at the edge of native mangrove species A. marina forest was only 14.1 and 13.5 cm, respectively;and the base diameter increment was only 1.0 and 1.5 mm, respectively. The average monthly number leaves of 1-year-old L. racemosa seedlings inside and at the edge of the A. marina forest decreased to -0.4 and -0.7, respectively. The results indicated that the growth rate of exotic mangrove species L. racemosa was slowly inside and at the edge of Avicennia marina forests in Haitang Bay, Xiamen city;and it did not show fast-growing characteristics. Therefore, the exotic mangrove species L. racemosa can grow fast only in its suitable environment. The survival rate of L. racemosa seedlings inside the A. marina forests was only 4.7%, and that in A. marina forest margin was 5.3%. Due to the limitation of light intensity, low temperature, it is very difficult for L. racemosa seedlings to naturally renew and grow under natural conditions in the natural indigenous A. marina mangrove forest in Xiamen.