西双版纳不同海拔4种雨林幼苗的光合特性和生物量

Photosynthetic Characteristic and Biomass of Four Species Seedlings of Rain Forest at Different Altitudinal Gradients in Xishuangbanna, China

摘要:

在云南西双版纳勐仑(600 m, 低海拔)、菜阳河(1 100 m, 中海拔)和勐宋(1 600 m, 高海拔)，对热带季节雨林4种主要树种绒毛番龙眼(Pometia tomentosa)、云南玉蕊(Barringtonia macrostachya)、云南肉豆蔻(Myristica yunnanensis)和小叶红光树(Knema globularia)幼苗进行移栽试验，测定幼苗的光合作用和生物量。结果表明，高海拔上的低温使幼苗处于休眠或光系统受到不可恢复的破坏，光合作用几乎停止；4种幼苗的最大净光合速率及生物量均随海拔的增加而下降；低、中海拔上4种幼苗的净光合速率日变化曲线均表现为“双峰型”，低海拔的第一个峰明显高于中海拔。除小叶红光树外，其它幼苗的根生物量分数均随海拔增高而增加。海拔升高，温度降低是限制幼苗光合特性、生物量积累的主要因子，也是某些幼苗在更高海拔雨林群落中消失的潜在原因。此外，幼苗的根生物量分数随海拔上升而增加是其对极限环境温度的一种重要适应特征。

Abstract:

The seedlings of 4 dominant tree species of tropical seasonal rain forest, such as Pometia tomentosa, Barringtonia macrostachya, Myristica yunnanensis and Knema globularia, were transplanted at three altitudinal sites (low 600 m in Menglun; middle 1 100 m in Caiyanghe; high 1 600 m in Mengsong) in Xishuangbanna. The parameters of photosynthesis and biomass of these seedlings were measured. The results showed that the low temperature at high altitude caused dormancy or photosynthetic system destroy. The maximum photosynthesis rate (Pmax) and dry biomass of four seedlings declined significantly along the increment of elevation. The diurnal change pattern of photosynthetic rate of four seedlings at low and middle altitude both showed double-peak type, which the first peak appeared at 11: 00~12: 00 am and the next peak at 4: 00~5: 00 pm, and the first peak was higher significantly at low altitude than that at middle altitude. Except for K. globularia, the root biomass fraction (RMF) of seedlings of the others increased with the increment of altitude. It is concluded that the biomass and photosynthetic rate of these seedlings are mainly limited by temperature, which is the potential reason that these species disappeared in rain forest community at high altitude. Furthermore, It is an important characteristic adapted to limited environmental temperature that RMF of four seedlings increased with the increment of altitude.