间伐修枝对拉关木林下乡土红树植物的影响

Effects of thinning and pruning on native mangrove plants in understory of Laguncularia racemosa forest

关键词:  外来红树, 拉关木, 间伐修枝, 乡土红树, 生态恢复

Key words:  exotic mangrove, Laguncularia racemosa, thinning and pruning, native mangrove, ecological restoration

摘要:

为探究保护区内对外来红树拉关木(Laguncularia racemosa)人工林不采取剧烈扰动生境的皆伐措施,而通过间伐修枝处理使拉关木逐渐退出更替为乡土红树林的新途径的影响,该研究以海南东寨港国家级自然保护区内拉关木林为研究区域,依托保护区对拉关木林进行间伐修枝,研究拉关木林间伐修枝的调控措施对恢复乡土红树群落的生态效应。结果表明:(1)间伐修枝后拉关木残桩萌枝的无性繁殖削弱了处理效果,但一次干预(50%强度的间伐修枝)和两次干预(50%强度的间伐修枝之后追加一次修枝)2种处理之间,拉关木残桩萌枝的效果没有显著差异。(2)间伐修枝能丰富林下灌木层的乡土红树种类,以及促进其生长,并且两次干预比一次干预的促进作用明显,但对草本层红树幼苗自然更新无显著影响。(3)在未间伐、间伐修枝和林缘3种样地中人工种植乡土红树苗木,间伐修枝对红海榄(Rhizophora stylosa)、秋茄(Kandelia obovata)幼苗的存活率有一定的促进作用; 间伐修枝对红海榄的生长有接近林缘条件的效果,但效果有限。综上所述,建议在50%强度间伐修枝的基础上加大间伐强度或修枝频率,在林下适当进行乡土红树植物的人工种植,同时清除拉关木残桩萌生的枝条,这样更有利于拉关木林向乡土红树林的转化。

Abstract:

In order to investigate a new way to replace the exotic mangrove Laguncularia racemosa plantations gradually with native mangrove forests through thinning and pruning without clear-cutting of drastic habitat disturbance in the reserve, we took the exotic mangrove L. racemosa forests introduced in Hainan Dongzhai Harbor National Nature Reserve as the study area, and L. racemosa forests were thinning and pruning relying on the reserve. The purpose was to study the ecological effects of the thinning and pruning of L. racemosa forests on the restoration of native mangrove communities. The results were as follows:(1)Asexual reproduction of L. racemosa stump sprouting after thinning and pruning weakened the treatment effect, and there was no significant difference in the effects of L. racemosa stump sprouting between one intervention(50% intensity of thinning and pruning)and two interventions(50% intensity of thinning and pruning followed by an additional pruning).(2)Both intervention methods enriched native mangrove species and promoted their growth in the understory shrub layer, and the two interventions had a more significant promotion effect than the one intervention. However, there was no significant effect on the natural regeneration of mangrove seedlings in the herbaceous layer.(3)In the experiment of planting native mangrove seedlings in the three plots of non-thinning, thinning and pruning, and forest margin, the survival rates of Rhizophora stylosa and Kandelia obovata seedlings were promoted by the thinning and pruning. The effect of thinning and pruning on the growth of Rhizophora stylosa seedlings was close to the forest margin conditions, but the effect was limited. In conclusion, we suggest increasing the thinning intensity or pruning frequency based on 50% intensity thinning and pruning, carrying out artificial planting of native mangrove plants in the understory appropriately, and removing the sprouting branches from the stumps of Laguncularia racemosa, which is more conducive to the conversion of L. racemosa plantation to native mangrove community.