海南岛三种低海拔热带林的生物量变化规律

Variation of Biomass among Three Low Elevational Tropical Forests of Bawangling on Hainan Island,China

利用样地调查资料并结合生物量模型,分析了海南岛3种低海拔热带林生物量及其随群落特征的变化规律。结果表明：热带低地雨林总生物量（409 Mg/hm^2）高于热带季雨林（205 Mg/hm^2）和转化季雨林（176 Mg/hm^2）,而热带季雨林具有最高的落叶物种及最低的常绿物种生物量。总生物量在胸径≥40 cm径级内热带低地雨林最高,1～10 cm径级内热带季雨林最高,10～40 cm径级内3种群落无显著差异。热带季雨林中落叶物种生物量在所有径级中均为最高,但常绿物种生物量除1～10 cm径级外均为最低。三种群落在下层（H〈5 m）和中层（5≤H〈15 m）总生物量上没有差异,但热带低地雨林在上层（H≥15 m）总生物量最高。热带季雨林在上、中层中均具有最高的落叶物种生物量及最低的常绿物种生物量。

Vegetation plays a major role in nutrient cycling and energy flux of terrestrial ecosystems,and biomass is an important parameter for characterizing a forest ecosystem.Tropical forests hold large stores of carbon and play a major role in the global carbon cycle.Forest biomass size and regional distribution are factors controlling the global carbon budget,but are also the basis for prediction of future climate change.Forest biomass＇ importance has attracted a great deal of experimental and theoretical attention,while attention is rarely paid to biomass of three low elevational tropical forests in Bawangling of Hainan Island.In order to understand the variation of the aboveground biomass in the three low elevational tropical forests type,i.e.the old-growth tropical lowland rainforest（TLRF）,the transformed monsoon rainforest（TMRF） and the old-growth tropical monsoon rainforest（TMF）,we conducted community investigations by randomly setting three sample plots（each with a size of 50 m×50 m） in each of the forest type.Each plot was divided into 10 m×10 m subplots to identify the species name,and measure the height,diameter at breast height（DBH） of each individual DBH≥1.0 cm.Biomass of the three low elevational tropical forests was estimated by using empirical model.The study showed that total biomass in the TLRF was higher than in the TMF and the TMRF,whereas,the TMF had the highest biomass of the deciduous species and the lowest biomass of the evergreen species.The TLRF had the highest total biomass in the big diameter classes（〉5th diameter class）,the TMF had the highest total biomass in the first diameter classes,however,no significant difference was found in the second,the third and the fourth diameter classes in the total biomass among the three low elevational tropical forests.Total biomass in the TLRF was mainly distributed in the big diameter classes,but total biomass in the TMF and the TMRF was mainly distributed in the middle diameter classes.Deciduous species biomass in the TMF was the highest in all diameter classes,however,its evergreen species biomass was the lowest in most of the diameter classes among the three forest types.In the vertical direction,no significant difference was found between the low and middle layer in total biomass among the three low elevational tropical forests,however,the TLRF had the highest total biomass in the high layer.The TMF had the highest deciduous species biomass in most of the layers except in the lowest layer.Total biomass in the TLRF was mainly distributed in the high layer,however,it was mainly in the middle layer in the TMF and the TMRF.