【作者】 刘万德；

【导师】 臧润国； 蒋有绪；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2009， 博士

【摘要】 随着全球变化的发展,极端气候出现频率将逐渐增加,热带地区的年降水量及其分配格局正在发生明显的变化,主要体现在旱季持续时间和降水变化幅度的显著提高,生境旱化使热带森林面临着严重的威胁。由于众多落叶物种及其独特功能性状的存在,热带季雨林群落具有较强的干旱适应能力,因而,加强热带季雨林群落生态学的研究,对于全球气候变化背景下的热带林生物多样性保育和生态系统经营都具有重要的理论和实践意义。海南岛的热带季雨林分布在与低地雨林相似的低海拔范围内但生境较差的局部区域,通过全部或大部分落叶等调节机制对季节性干旱进行整体适应,同时对群落环境产生明显影响。本文选择海南岛霸王岭林区典型的热带季雨林为主要对象,同时以相似海拔范围内的热带低地雨林及其被干扰后产生的转化季雨林为对照,通过大量的典型样方(合计8.75hm2)调查,研究了热带季雨林的生境、群落组成、结构及多样性特征,分析了群落内组成植物的主要功能性状、物种丰富度与个体多度、种—多度关系和生物量分配等随群落类型和环境条件的变化规律。通过野外试验,分析了季雨林优势树种及相似海拔范围内典型树种幼苗更新的影响因素。本研究的成果将有助于阐明季雨林群落主要特征的产生及物种多样性的调控机制,揭示季雨林主要群落特征对季节性干旱所引发的环境变化的生态适应规律,从而为热带森林的保护、恢复与可持续经营提供科学依据。通过研究得出以下主要结果:1.以野外样方调查数据为基础,对海南岛霸王岭林区热带季雨林分布海拔范围内的热带森林进行了数量分类与排序。结果表明:应用TWINSPAN和DCA可将热带季雨林分布海拔范围内的热带森林划分为3个类型:热带季雨林、热带低地雨林和转化季雨林。DCA排序显示三种森林群落分布与一定的环境因子组合密切相关,热带季雨林与坡度和裸岩面积呈显著正相关,热带低地雨林与海拔和凋落物厚度呈显著正相关,转化季雨林则与海拔呈正相关,而与坡度呈负相关。转化季雨林是介于热带季雨林和热带低地雨林之间的一种群落类型。2.利用热带季雨林群落及其分布海拔范围内的转化季雨林和热带低地雨林群落的野外调查数据,对比分析了热带季雨林群落的组成、结构及多样性特征。结果表明:热带季雨林群落中科、属、种丰富度及乔木物种丰富度低于转化季雨林及热带低地雨林。三种群落类型中低密度种均较多,其中以热带季雨林中最少,热带低地雨林最多。三种群落类型中林分平均胸径、平均高都是热带季雨林<转化季雨林<热带低地雨林,但群落的树木密度则是热带季雨林>转化季雨林>热带低地雨林。物种丰富度及多度在热带季雨林及热带低地雨林和转化季雨林中均随径级和高度级的增加而减小。热带季雨林中落叶物种丰富度及个体多度均显著高于转化季雨林和热带低地雨林。转化季雨林中的落叶物种大都来自于热带季雨林。落叶物种丰富度及个体多度所占比例在热带季雨林群落中最高,而热带低地雨林中最低,转化季雨林则居中。在热带季雨林群落中,落叶物种的丰富度和多度在乔木中所占比例均显著高于灌木和木质藤本植物。3.通过对热带季雨林群落及其分布海拔范围内的转化季雨林和热带低地雨林群落植被和环境的野外调查,分析了热带季雨林分布海拔范围内物种丰富度及多度与环境的关系。单因素相关分析表明,木本植物总物种丰富度分别与林分郁闭度、海拔高度和土壤含水量成正相关,与裸露裸岩面积成负相关,而与坡度没有显著的相关性。落叶物种丰富度则分别与林分郁闭度、海拔高度和土壤水分含量成负相关,而与坡度和裸岩面积成正相关。逐步回归分析表明,总物种丰富度仅与海拔高度有关,回归方程为y = 0 .154x+10.153(R=0.925,P=0.000)。而落叶物种丰富度与裸露裸岩面积和坡度成正相关,与海拔及土壤含水率负相关,逐步回归关系可用方程y =30 .506?0.023(海拔高度) +0.15(1岩石覆盖率)?0.29(2土壤水分含量)+0.15(2坡度)( R=0.989 ,P=0.000)来描述。单因素相关分析表明,木本植物总个体多度则与裸岩面积呈正相关,分别与海拔高度和土壤含水量呈负相关。落叶物种多度则与坡度呈正相关,分别与郁闭度、海拔高度和土壤含水量呈负相关。逐步回归分析表明,木本植物总个体多度及落叶物种个体多度均仅与土壤含水量有关,回归方程分别为y = 3907. 472?100.469x(R=0.846,P=0.000)和y = 1676. 237?59.606x(R=0.870,P=0.000)。4.利用热带季雨林群落及其分布海拔范围内的转化季雨林和热带低地雨林群落调查数据及树木的七种主要功能性状(落叶、具刺、潜在高度、SLA、种子重量、传播方式及木材密度)测定(或查找)数据,分析了热带季雨林群落树木不同功能性状的大小及物种丰富度和多度在各主要功能性状中的分布。结果表明:热带季雨林中落叶与具刺物种丰富度和个体多度均显著高于热带低地雨林和转化季雨林。热带季雨林中树木潜在高度最低,并且在不同潜在高度范围内的物种丰富度及个体多度也最低。三种群落类型在比叶面积较大(>20 m2/kg)时具有相同的物种丰富度和个体多度,但热带季雨林中拥有最大数量的较小比叶面积(<10 m2/kg)的个体多度。热带季雨林中种子重量显著低于热带低地雨林和转化季雨林,但三种群落类型在中等种子重量大小(50mg～200mg)时物种丰富度及个体多度无显著差异,而热带季雨林没有种子重量较大(>200mg)的物种,并且动物传播的物种丰富度及个体多度也低于热带低地雨林和转化季雨林。三种群落类型的木材密度及不同密度大小范围内(除400～600kg/m3外)的物种丰富度及个体多度无显著差异。5.为了分析热带季雨林分布海拔范围内热带森林群落中的树木组配规律,利用6种物种—多度关系模型(分割线段模型、几何级数模型、对数正态模型、Zipf模型和Zipf-Mandelbrot模型、中性理论模型)对热带季雨林群落及热带低地雨林和转化季雨林群落的物种—多度关系进行了模拟。结果发现:热带季雨林中模拟效果最好的是Zipf-Mandelbrot模型,其次为Zipf模型;热带低地雨林中模拟效果最好的是中性理论模型,其次为对数正态分布模型,其余模型模拟效果均较差;转化季雨林中仅有Zipf-Mandelbrot模型模拟效果较好,其余所有模型模拟效果均较差。x 2检验进一步支持了上述结果。我们的研究表明,在海南岛霸王岭热带季雨林分布海拔范围内,中性理论适合于密闭的热带林(热带低地雨林),但却不适用于稀疏的热带林(热带季雨林)或受人为干扰后恢复的密闭的热带林(转化季雨林),而生态位理论则恰好相反,它不适用于密闭的热带林,而适合于稀疏的热带林或受人为干扰后恢复的密闭的热带林。6.通过对热带季雨林优势树种(海南榄仁Terminalia hainanensis)及相似海拔范围内典型树种(青梅Vatica mangachapoi,荷木Schima superba和银珠Peltophorum tonkinense)幼苗的17个月移栽及不同处理(移除地上植被、挖沟、挖沟+移除地上植被处理和对照)试验,分析了热带季雨林优势树种及相似海拔范围内典型树种幼苗更新的影响因素。结果表明:移除地上植被、挖沟、挖沟+移除地上植被处理显著增加了荷木幼苗旱季、雨季及实验期间的存活率,也增加了海南榄仁幼苗旱季及青梅实验期间的幼苗存活率,对银珠幼苗来说,则是移除地上植被增加了其旱季及实验期间的幼苗存活率。此外,移除地上植被和挖沟+移除地上植被处理也增加了荷木、海南榄仁和银珠幼苗的生长率。而土壤水分含量的增高则提高了3种幼苗(青梅,荷木和银珠)存活率及所有幼苗的生长率。高土壤水分含量对应着高的幼苗存活率和生长率。我们的研究表明,地上、地下竞争及水分梯度对热带季雨林分布海拔范围内典型树木幼苗的存活和生长有显著影响,地上、地下竞争及水分梯度是限制幼苗存活与生长的主要因素。7.利用群落野外调查数据及生物量模型,估测了热带季雨林分布海拔范围内不同热带森森林群落类型的生物量大小及其分布特征。结果表明:热带季雨林总生物量(205Mg/hm2)低于热带低地雨林(409 Mg/hm2),而与转化季雨林(176 Mg/hm2)无显著差异,但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。总生物量在大于5径级内热带低地雨林最高,第一径级内热带季雨林最高,第二、第三、第四径级内三种群落无显著差异。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第一径级外均为最低。三种群落在下层(H<5m)和中层(5≤H<15m)总生物量上没有差异,但热带低地雨林在上层(H≥15m)总生物量最高。与其它两个群落类型相比,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。更多还原

【Abstract】 Climate change and biodiversity loss have been increasingly concerned by the whole world.In recent years humans have witnessed increases in the frequency of extreme climatic events and rapid extinction of biodiversiy.The tropical forest regions are experiencing decreased precipitation, increased duration of the drier season and greater variability in precipitation.Tropical forest biodiversity have been greatly impacted by these climatic scenarios. Drought in habitats is one of the most threatening factors to the tropical rain forests. The tropical monsoon rainforest has strong abilities and obvious advantages to adapt to drought stress since it has many deciduous species with special functional traits. Therefore, the ecological studies on tropical monsoon rainforest communities has both theoretical and practical implications for biodiversity conservation and ecosystem management of tropical forests under global climate change. The tropical monsoon rainforest on Hainan Island is a azonal vegetation type, mainly distributed in the similar elevational ranges with the tropical lowland rainforest but in locations where environmental conditions are more stressful, especially in the dry season. The tropical monsoon rainforest adapts to the seasonal droughts by defoliation of all or most of its trees ,which has significant effects on the community environments. In this study, the tropical monsoon rainforest in Bawangling forest region of Hainan Island was selected as the main study object, while two other forest types with similar elevational ranges were selected as comparisons.The two forest types for comparisons are the tropical lowland rainforest and the transformed monsoon rainforest,which is a disclimax recovered from serious disturbed tropical lowland rainforest. Based on the field investigations conducted in totally 8.75 hm2 sample plots ,the environmental feature, composition, structure, diversity, functional traits of plants, species-abundance relationships and biomass for the tropical monsoon rainforest community were studied. Through field seedling experiments, the factors influencing the survival and growth for seedlings of one dominant species(Terminalia hainanensis) in the tropical monsoon rainforest and seedlings of three typical species(Schima superba, , Vatica mangachapoi, and Peltophorum tonkinense) distributed in the similar elevational ranges with the tropical monsoon rainforest were also studied. These results can help us to understand the main features and maintenance mechanism of species diversity of the tropical monsoon rainforest, and explore the ecological adaptations of the tropical monsoon rainforest community to seasonal drought, which could provide scientific basis for the conservation, restoration and sustainable managements of tropical forests. The main results of the study are as follows:1. To analyze the characteristics of the tropical monsoon rainforest and similar elevational forest communities, quantitative classification and ordination were conducted by TWINSPAN and DCA based on field investigation plots. The investigated plots were classified into 3 communities by TWINSPAN and DCA, they are the tropical monsoon rainforest(TMR), the tropical lowland rainforest(TLR) and the transformed monsoon rainforest(TFMR).The results of ordination by the DCA also reflected the basic relationships between plant communities and environmental factors, the distribution of tropical monsoon rain forest was positively related to the slop and the coverage of exposed rock surface, and the distribution of tropical lowland rainforest was positively related to elevation and litter depth , while the distribution of the transformed monsoon rainforest was positively related to elevation and was negatively related to slop. The transformed monsoon rainforest was recognized as a community type between the tropical lowland rainforest and the tropical monsoon rain forest.2.The composition, structure and diversity of the tropical monsoon rain forest, community were analyzed by comparison with the TLR and the TFMR. The results indicated that family, genera and species richness were lower in the TMR than in the TLR and the TFMR. Many low density species existed in the three tropical forests,and it was the lowest in the TMR and the highest in the TLR. The mean DBH and the mean height in the three tropical forests from low to high were the TMR, the TFMR and the TLR, whereas, the stand density in three tropical forests from high to low were the TMR, the TFMR and the TLR. Species richness and abundance decreased with increasing diameter classes and height classes in the three forest types. Both the richness and abundance of deciduous species were the highest in the TMR than in the TFMR and the TLR. Most of the deciduous species in the TFMR were dispersed from the TMR. The percentages of deciduous species richness and abundance were the highest in the TMR, and the lowest in the TLR. In the tropical monsoon rain forest, the percentages of deciduous species richness and abundance in the trees were higher than in the shrubs and in the lianas.3. To explore the relationships between species richness, abundance and environments in the tropical monsoon rain forest and in the similar elevational ranged tropical forests in the study forest region,as, the vegetation investigations and environmental recording were carried out in field sample plots. Single factor correlation and stepwise regression analysis between species richness, abundance and environments were conducted. Single factor correlation analysis showed that the species richness of woody plants was positively correlated with canopy density, elevation and soil water content,repectively and was negatively correlated with the coverage of exposed rock surface. The richness of deciduous species was negatively correlated with canopy density, elevation and soil water content respectively, but positively correlated with slop and the coverage of exposed rock surface respectively.Stepwise regression analysis showed that the species richness of woody plants was only related to elevation( y = 0 .154(elevation)+10.153,R=0.925,P=0.000).The stepwise regression analysis also indicated that the species richness of decious woody plants was positively related to slop and the coverage of exposed rock surface,and negatively related to elevation and soil water ontent( y = 30. 506?0.023(elevation)+0.151(rocky)?0.292(water)+0.152(slop),R=0.989,P=0.000). Single factor correlation analysis showed that the total stem abundance of woody plants was positively correlated with the coverage of exposed rock surface ,and negatively correlated with crown density, elevation and soil water content respectively. The stem abundance of deciduous woody plants was positively correlated with slop,but negatively correlated with crown density,elevation and soil water content respectively. The stepwise regression analysis revealed that both the total stem abundance of woody plants and the stem abundance of the deciduous woody plants were negatively related to the soil water content ( y = 3907. 472?100.46(9water),R=0.846,P=0.000; y = 1676. 237?59.60(6water),R=0.870,P=0.000).4. Based on the field investigation data,major functional traits of trees in the tropical monsoon rain forest and similar elevational forests in the study region were explored.The 7 functional traits included defoliation or evergreen, with or without thorns, potential maximum height, specific leaf area(SLA), seed-mass(SM), dispersal mode and wood density(WD). The results showed that species richness and abundance of deciduous species and species with thorns were higher in the TMR than in the TLR and the TFMR. The value of potential maximum height, species richness/abundance in different range of potential maximum height were the lowest in the TMR. There were no significant difference in species richness and abundance when SLA was higher than 20m2/kg, but the TMR had the highest abundance when SLA was lower than 10m2/kg. SM was lower in the TMR than in the TLR and the TFMR, however, no significant difference was found in the three tropical forests in species richness and abundance when SM was 50～200mg, and no species existed in the TMR when SM value was higher than 200mg. Species richness and abundance of animal dispersal were lower in the TMR than in the TLR and the TFMR. No significant difference were found in species richness and abundance in different WD ranges in the three tropical forests except when the WD was 400～600kg/m3.5. To explore the tree assembly rules in the tropical monsoon rain forest and similar elevational forest communities in the study region, the speices-abundance relationships were studied and simulated with population models ,including the Zipf- Mandelbrot(ZMM), Zipf(ZM), the broken stick model(BSM), the geometric series model(GOM), the lognormal distribution model(LN) and the neutral theory model(NT). We found that the best model to fit the TMR was the Zipf- Mandelbrot(ZMM), and the next was the Zipf(ZM). However, the best model to fit the TLR was the NT, and the next was the LN. Only the ZMM could predict well species-abundance relations in the TFMR. We hypothesized that in the study region,the neutral models fit species-abundance distribution patterns in the closed-canopy old growth forests(such as the TLR),but didn’t fit those patterns both in the open-canopy old-growth forests(such as the TMR) and in the closed-canopy second-growth forests recovered from anthropogenic disturbance(such as the TFMR) , on the contrary, the niche models fit species-abundance distribution patterns in the open-canopied old-growth forests and the closed-canopy second-growth forests recovered from anthropogenic disturbance, but didn’t fit the patterns in the closed-canopy old-growth forests.6. To find the factors affecting the survival and growth of the seedlings, a field seedling treatment experiment was conducted.We measured survival and height growth of 1200 seedlings of of dominant tree species in the tropical monsoon rain forest(Terminalia hainanensis) and three representative tree species distributed in the similar elavational range(Schima superba, , Vatica mangachapoi, and Peltophorum tonkinense)in the study region. The seedlings were planted for 17 months under one of four treatments: removal of aboveground vegetation(R), trenching(T), trenching plus removal of aboveground vegetation(T+R), and a control(C). We found that the treatments of R, T, T+R significantly increased the survival of Schima superba in the dry season, wet season and the whole experiment priod(17 months), increased the survival of Terminalia hainanensis in the dry season and increased the survival of Vatica mangachapoi in the whole experiment priod. Whereas, only the R treatment increased the survival of Peltophorum tonkinense in dry season and the whole experiment priod. Furthermore, the treatments of R and T+R increased the relative growth rates of Schima superba, Terminalia hainanensis, and Peltophorum tonkinense. The soil water content could increase the seedlings survivals of three species() and the seedlings relative growth rates of all the four species. The above- and below-ground competition and soil water content had significant controlling effects on the survival and growth of tree seedlings in the tropical monsoon rain forest.7. Biomass and its allocation in the TMR was studied using the data of field investigations and the biomass estimation models. We found that the total(evergreen+deciduous species) biomass was lower in the TMR than in the TLR, and no significant difference was found between the TMR and the TFMR, whereas, the TMR had the highest biomass of the deciduous species and the lowest biomass of the evergreen species. The TLR had the highest total biomass in the big diameter classes(> 5th diameter class), the TMR had the highest total biomass in the first diameter classes, however, no significant difference were found in the second, the third and the fourth diameter classes in total biomass among the three similar elevational tropical forests. Total biomass in the TLR mainly distributed in the big diameter classes, but total biomass in the TMR and the TFMR mainly distributed in the middle diameter classes. Biomass of deciduous species in the TMR was the highest in all diameter classes, however, its biomass of evergreen species 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(H<5m) and middle(5≤H<15m) layers in total biomass among the three similar elevational tropical forests, however, the TLR had the highest total biomass in the high(H≥15m) layer. The TMR had the highest deciduous species biomass in most of the layers except in the lowest layer. Total biomass in the TLR mainly distributed in the high layer. Compared with the TLR and the TFMR, the TMR had the highest deciduous species biomass and the lowest evergreen species biomass in the high and the middle layers.更多还原