【作者】 陈宏伟；

【导师】 刘勇；

【作者基本信息】 北京林业大学 ， 森林培育， 2008， 博士

【摘要】 人工造林是解决木材生产的主方式,而人类活动对生态系统的影响是当今生态学研究的热点之一,人类活动产生的生态后果如生态系统退化、生物多样性降低、全球变暖等也是人们普遍关心的问题之一。我国的南亚热带地区是生态系统退化比较严重的地区,也是重要的木材生产基地,在这一地区应用乡土树种进行人工造林并对退化山地雨林生态系统进行恢复实验,是解决木材需求、综合整治退化生态系统的有效方式。西南桦既是热带山地、南亚热带地区的珍贵速生树种,也热带地区人工造林的一个主要树种,本文对栽培了半个轮伐期的西南桦人工林与本区域的地带性植被山地雨林生态系统进行比较,对西南桦人工林生物多样性、群落结构、土壤特性等生态学效应进行阶段评估,以评价其作为人工林主要树种的适宜性及造林模式,并研究人类活动对地带性生态系统的影响。本研究采用群落样地调查法调查群落的物种组成和结构。用Braun-Blanquet系统、Raunkiaer系统、物种丰富度指数(S)、Shannon-Wiener指数(H′)和Simpson指数研究植物种多样性特征。根据吴征镒的中国种子植物属的分布区类型划分分析人工林和天然林的区系成分;以各人工林类型的共有种、多样性指数为基础,来判断群落的相似性。采用解析木法、皆伐法和收获法进行生物量的测定。采用常规方法测定土壤理化性质。结果发现:与天然群落相比,西南桦人工林对生态系统的植物物种的生活型谱、物种叶型谱、区系成分、物种多样性等方面的群落学特征影响不大;即使在这些方面有或多或少的差异,这可能也是小环境的异质性造成的。但是人工种植西南桦林对群落的季相外貌、群落的结构、物种组成、物种丰富度以及生物量等方面有较大的影响。1)人工造林使得群落结构简化,西南桦人工林的层次结构有3层,以乔木层占优势,并且有种类多而发达的灌木层,同时,藤本植物欠发达,但是乔木层树种单一,明显仅有一层;山地雨林的层次结构有4层,以乔木层占优势,还有灌木层、草本层和藤本植物,藤本植物种类多,十分发达;乔木层树种丰富,可达38种,乔木层还可分为3层。2)人工造林较大程度地改变了群落的物种组成,根据重要值的大小排列,人工林和天然林的主要物种组成已经完全不同;并且人工林单优树种明显,而天然林就含有较多的优势树种。3)人工造林改变了群落的外貌。西南桦人工林的乔木层在旱季落叶,而山地雨林外貌为高大、常绿、茂密的阔叶林,即使旱季也仍保持林冠葱绿的外貌,乔木层可明显的分为3层,林下比较空旷,灌木植被少见,草本植物分散,另外具有高大的木质藤本植物和附生植物。4)人工造林对群落的物种生活型谱影响不大。西南桦人工林和山地雨林具有相似的物种生活型谱,高位芽植物所占比例最高,达到80%以上,具有相近的地面芽和地下芽比例;但二者生活型谱也有一些差异,西南桦人工林小高位芽比例最高,而中高位芽比例次之,山地雨林则正相反。5)人工造林对群落叶型谱影响不大。西南桦人工林和山地雨林叶型谱基本上相似,都以中型叶为主,但二者也有差异。西南桦人工林的小型叶比例大于山地雨林。6)人工造林对物种丰富度和物种多样性有影响。山地雨林的物种丰富度在各层次中的分布最高,说明天然林在物种上的丰富性。山地雨林的乔木层种类最多。虽然两种林型的物种丰富度有较大的差异,但Simpson指数和Shannon-Wiener指数却相差不大。7)人工造林对群落区系成分影响不大。二者区系成分基本特性相似,但区系的各成分皆略有差异。8)人工林比山地雨林生物量小得多。山地雨林的总生物量远远大于10年生的西南桦人工林,其中灌木层的相对差别尤其巨大。9)4次的观测发现,人工林栽植后,土壤容重一般呈现一个先上升后下降的特点;而土壤非毛管孔隙度、土壤总孔隙度大多呈下降趋势,几年后有不同程度的恢复。各林分类型的土壤阳离子交换量,在年度变化上都呈上升趋势;在0-30cm土层中,土壤盐基饱和度含量一般呈下降趋势;0-60cm土层的人工幼林土壤养分含量多呈下降趋势;有效磷、氮、有效钾均呈下降趋势。综合分析后得出:1)使用乡土树种营造人工林,并且营造乡土树种混交林,在维持大量生物多样性价值的同时,有可能持续经营热带森林,生产木材或其他产品。2)人工林能实现许多天然林所具有的生产和保护功能,但用人工林取代天然植被会简化现有生态系统。3)虽然人工造林可以缩短植被自然恢复的时间以及具有显著的经济价值,但与地带性植被相比,还是有一定的差异。更多还原

【Abstract】 Afforestation is adopted as the main strategy to meet the demand for wood.The impact of human activity on environment is given high priority for research.Meanwhile environmental issues caused by human activities like ecosystem degradation,loss of biodiversity and global warming are worldwide concerned.Southern subtropical areas in China are often severely degraded,but also important timber production bases.Conducting afforestation and degraded rain forest rehabilitation experiments using indigenous species was an effective way to meet timber demand and to restore degraded ecosystem. Betula alnoidis is a fast-growing tree with very high value,widely planted in tropical and southern subtropical mountain areas.This study is to assess the adaptability of Betula alnoidis as a plantation species and suitable silviculture model,and to find out the impacts of human activities on regional ecosystems through a comparison between half-rotation aged Betula alnoidis plantations and the regional vegetation—mountain rain forests with its focus on the aspects of plantation biodiversity, community structure and soil etc.Community plot survey method was adopted to investigate species composition and structure. Braun-Blanquet system,aunkiaer system,S index,Shannon-Wiener H index and Simpson index were used to study the plant biodiversity.Flora composition of both plantation and nature forest was studied based on the seed plant genera distribution type in China by Wu-Zhengyi.Community similarity was estimated by common species and diversity index of the plantations.Biomass was assessed using methods of analytical wood,clear cutting and tree harvesting.Conventional method was used for soil analysis.Results showed that compared with nature community,impacts brought by planting Betula alnoidis were not remarkable in terms of life form spectrum,leaf form spectrum,flora composition and plant diversity in the plantation.Small differences in above aspects might be more likely caused by microenvironments.However remarkable impacts were observed in the plantation in terms of community physiognomy,community structure,species composition,species richness,and biomass accumulation.1) Planting trees made community structure simple.Betula alnoidis plantation had three layers including a dominant arbor layer,a complex and well developed shrub layer and a poorly developed vine layer.The arbor layer contained few species and had a single layer.The mountain rain forest had 4 layers including the dominant arbor layer,shrub layer,grass layer and vine layer.The vine layer was well developed and very rich in species composition,and the arbor layer contained as many as 38 species that could be grouped into 3 layers.2) Sequenced by the important value,main species for the plantation and the nature forest were totally different,and the plantation had one dominant species while the nature forest contained many dominant species.3) Planting trees changed the community physiognomy.The plantation defoliated in dry seasons while the mountain rain forest was tall and dense evergreen broadleaved forest and kept green in dry season.The mountain rain forest’s arbor layer contained 3 layers.Relatively open space under the canopy,rare shrub,sparse grasses,very tall wood vines and rich epiphytes were found in it.4) Afforestation did not change the life form spectrum significantly.The Betula alnoidis plantation and the compared mountain rain forest had similar life form spectrum with phanerophyte accounted for the biggest percentage of above 80%,similar percentages for both hemicryptophyte and cryptophytes.However,some differences were also observed that the biggest part of life form spectrum for the plantation was small phanerophyte,followed by the middle phanerophyte,and that of the mountain rain forest was converse.5) The leaf form spectrum was not significantly changed by afforestation.The Betula alnoidis plantation and the mountain rain forest showed similar leaf form spectrum with some differences that the mountain rain forest had a few small leaves while the plantation did not.6) Species richness and species diversity were changed by afforestation.The rain forest had greater species richness in all layers.The fact indicated the rain forest was rich in species composition.The rain forest also had more layers in arbor layers.Although the two vegetation types had different species richness,the Simpson index and Shannon-Wiener index did not differ remarkably.7) Afforestation changed the flora components slightly.The plantation and the nature rain forest had similar basic components but with slight differences.8) Biomass assessed in the plantation was much lower than that of the mountain rain forest.Biomass in the rain forest was far more than that in the plantation of 12 years,especially for the shrub layer.But the biomass of litterfall collected in the plantation was greater than that of the rain forest for the reason that Betula alnoidis defoliated in dry seasons.9) Four years observation found that soil bulk density tended to increase first, then decrease after planting trees;total soil porosity and non-capillary porosity tended to decrease and after few years they recovered to different degrees;the soil cation exchange capacity for all forest types increased;in the soil of 0-30cm depth,soil salt saturation tended to decrease;nutrient content in the soil of 0-60cm depth in the young stand tended to decline;soil effective P,effective K and N contents all tended to decrease.Based on the above findings,the followings were generalized:1) Mixed species plantations established with indigenous species could maintain biodiversity and produce timber and non-timber products when they were sustainably managed.2) Plantations could also achieve both protection and production functions found in most nature forests.However replacing nature forests with plantations may simplify the ecosystems.3) Although planting trees shortened the time for the nature vegetation to get restored and brought some economic benefits,the plantation was still different from the nature vegetations.更多还原