西双版纳三叶橡胶林树干呼吸特征

Stem respiration characteristics of rubber(Hevea brasiliensis)plantations in Xishuangbanna

采用红外气体分析法(IRGA)为期1a原位监测西双版纳三叶橡胶(Hevea brasiliensis)4个年龄段(7、15、27、40a)的树干呼吸情况,同时对每个年龄段树干监测2种高度(1.3m-割胶部位、2.0m-不割胶部位)和2个方向(南、北面)以及林内空气和树干1cm深温度。结果表明,4个年龄的树干呼吸有相同的季节规律,都是在雨季大于干季。林龄是影响橡胶树树干呼吸的一个重要因素,15、27a树干呼吸速率最大,分别为(4.989±0.278),(4.678±0.268)μmol·m-·2s-1,显著高于40a和7a树,40a树((3.753±0.205)μmo.lm-.2s-1)显著大于7a树((2.299±0.129)μmol·m-·2s-1)。所研究的高度和方向上树干呼吸速率无差异,割胶对树干表层破坏愈合后并不影响树干呼吸。树干呼吸与树干温度呈显著相关性,有良好的自然指数回归关系,Q10值为1.966～3.127,南北面Q10差异不明显,4个年龄段树干呼吸Q10值平均为2.452,大于已监测的热带树种。各年龄段橡胶林的主干(一级分枝以下部分树干)呼吸初步估算表明,7、15、27a和40a橡胶树主干呼吸分别为1.74,5.54,7.53,7.59tC.hm-·2a-1。

Stem respiration is an important component of the carbon budget in forest stands.Some data for temperate and boreal zones were available,while stem respiration in rubber plantation was not found.In the present study,we made in situ chamber measurements of the stem respiration for 4 ages（7,15,27,and 40year-old）of rubber plantations in Xishuangbanna using an infra-red gas analyzer（IRGA）method.LI-820 CO2 gas analyzer was connected to a custom-built polyvinyl chloride（PVC）chamber.The chamber was fastened to the stem surface using thin neoprene gaskets with a strap at sampling time.The stem respiration rates of rubber were measured in the south and north sections at 1.3 m and 2.0 m height from March 2004 to February 2005.Measurements were taken once every month.Temperature at 1 cm depth of stem and air temperature in plantations were recorded concurrently.The tendencies of stem respiration in 4 plantations were in remarkable single-peak patterns with high rates during wet season and low rates during dry season.The stem respiration rates for 7,15,27,and 40year rubber were（2.299±0.129）,（4.989±0.278）,（4.678±0.268）,and（3.753±0.205）μmol·m-2·s-1,respectively.Respiration rates were significantly higher for 15a and 27a trees than 40a and 7a tree（P〈0.05）,and it significantly higher in 40a tree than that in 7a tree.The stem respiration rates of rubber were similar at the same height in north and south sections and it also similar at 1.3 m and 2.0 m of the same section.Relationship between stem respiration rates and temperature were analyzed.There was an exponential correlation between stem respiration rate and stem temperature（P〈0.01）.The Q10 values for stem respiration of 4 age trees varied from 1.966 to 3.127,and the average Q10 value of 4 ages trees was 2.452,which was high compared with the range of Q10 values（1.60-2.38）reported in previous studies in tropical trees and were close to other trees in China（1.96-3.33）.Annual stem respiration rates（except branches）of 7,15,27,and 40year-old forests were estimated and they were 1.74,5.54,7.53,7.59 t C·hm-2·a-1,respectively.