林下植被对长白山温带森林土壤关键过程的影响

The interaction among different plant spices determines structure and function of the plant community. Understory is an important part of the forest ecosystem. It has the important influence on the stability, productivity and nutrient cycling of the forest ecosystem by changing the forest microclimate, renewal of the species, nutrient utilization and microbial components. The understory vegetation of the temperate forest in the northeast of China is abundant. In present, thinning on understory was the main method of forest management in this region. However, systematic study on the impact of understory tending on the soil ecological process is lacking in the temperate forest. The project will take the Broad-leaved Korean pine (broad-leaved and coniferous mixed forest), larch forest (coniferous forest) and birch forest (broadleaf forest) in Changbai Mountain as research object. By setting different understory removing treatments (control, removing shrub layer, removing herb layer, and removing shrub and herb layers), the project will study the impact of understory on under forest environment (temperature and moisture), the emission of CO2/N2O from soil, dynamic of soil nutrient, litter decomposition, different forms of nitrogen utilization and soil microbes. Inner mechanism of effects of understory on the carbon and nitrogen cycle and the difference in different forest type will be discussed. The results will provide the necessary scientific basis for restoration and reconstruction of the temperate forest and forest sustainable management in Changbai Mountain.

植物间的交互作用决定植物群落结构和功能的发挥。林下植被作为森林生态系统的重要组成部分，它通过改变林内小气候、物种更新、水分与养分利用以及对土壤微生物组成等，对森林生态系统的稳定性、生产力及养分循环具有重要影响。我国东北温带森林的林下植被组成丰富，目前该地区林业经营主要是对林下植被进行抚育，但有关林下植被对温带森林土壤生态过程的影响机制还缺乏系统研究。本项目以长白山原始阔叶红松林（针阔混交林）、落叶松林（针叶林）和白桦林（阔叶林）为研究对象，通过野外设置剔除不同功能群的实验处理（对照、去除灌木层、去除草本层和去除灌草层），研究林下植被对土壤环境（温度和水分）、CO2/N2O排放、土壤养分变化、凋落物分解、不同形态氮素利用以及土壤微生物等方面的影响，明确温带森林的林下植被对土壤碳/氮循环的影响机理，以及其在不同林型间的差异。本研究将为长白山温带森林的恢复重建和可持续经营提供必要的科学依据。

林下灌木层是森林生态系统中不可或缺的组成部分，林业经营管理中，常采用去除林下灌木层的方法来促进森林更新。但林下灌木层的去除不仅影响森林生态系统的物种多样性，还会显著影响生态系统的地上-地下过程。本研究以长白山典型的原始阔叶红松林（针阔混交林）、天然次生的白桦林（阔叶林）和人工补植的落叶松林（针叶林）作为主要的研究对象，探讨林下灌木的去除对土壤性质、林下植被、土壤微生物群落和土壤温室气体排放的短期影响。.主要结果如下：（1）三种林型的土壤全量养分含量差异显著，白桦林土壤养分含量最高，阔叶红松林次之，落叶松林最低。去除灌木5年后，土壤持水量、铵态氮、硝态氮、速效磷、全磷含量均有增大的趋势，而pH呈下降趋势。（2）林下灌木去除5年后，阔叶红松林的林下植被多样性无显著变化，但物种组成发生了变化，且林下生物量减小；（3）三种林型的细菌组成、真菌群落组成均相似，但是相对丰度存在一定差异；灌木去除改变了白桦林的细菌群落组成，对真菌群落组成影响较小。细菌的α-多样性与土壤全量养分（全碳、全氮、全磷）显著正相关和碳氮比负相关，真菌的α-多样性与土壤速效磷含量正相关和pH显著负相关；细菌群落组成与土壤持水量、全碳和硝态氮含量显著相关，真菌群落组成与土壤持水量、全碳、全磷和硝态氮显著相关。（4）林下植被去除显著提高了阔叶红松林土壤CO2排放，显著提高白桦林土壤CH4吸收；林下植被去除减弱了阔叶红松林土壤含水率与CH4的正相关、与N2O的负相关，增强了土壤表层（5cm深）温度与N2O的正相关；林下植被去除减弱了白桦林土壤含水率与CO2、N2O的负相关，增强了与CH4的正相关，未对土壤表层（5cm深）温度与温室气体排放关系产生影响。.研究结果不仅有助于深化认识森林生态系统植物-土壤性质-土壤微生物之间的关系，也为长白山地区林下植被管理提供了科学依据。