贵州茂兰喀斯特森林生物成土研究

Maolan protection zone is one of largest, concentrated, stable, and original karst forest ecosystems on earth, Guizhou province. This region is a natural laboratory, which provides good opportunities to conduct qualitative, quantitative, and oriental researches about karst forest ecosystems. As we know it, the soil-forming rate in karst region is extremely slow, the acid insoluble content of pure carbonate rock is very low with an average value of only about 4%, and the weathering residues are so limited that making formation of 1cm thick soil layer costs the average time range from 8000 to 10000 years. However, this situation could be converted by the process of biological decomposition if the karst ecosystem environment is in a good condition. Therefore, study the biological soil-forming process and its law will have significant meaning in karst region. Currently, the study of biological soil-forming process in karst ecosystem is still a weakness part among karst earth science research fields, and these studies also have obviously regional characteristics. In the view of the present research status, we have designed a program which consisting of three steps. First of all, this program will explore the compositions of litter, biomass and their dynamics in different time and space scales; Secondly, we plan to analyze the dissolution differences among different microhabitats (stone flatland, stone gully, stone crevice, earth flatland, etc), which affected by biological interferences; Finally, this program will summarize the contributions of soil animals and microorganisms to soil-forming process, the nutrient translocation in soils, and the soil-forming rules in karst region. This program will have important and positive meanings in promoting forestry production and rocky desertification control, and advancing the virtuous circle of ecosystem in semitropical karst area of China.

贵州茂兰喀斯特保护区是地球同纬度地区残存下来的一片面积最大、典型和原生性强的喀斯森林生态系统，是研究喀斯特生态特征的天然实验室和难得的定性、定量和定位研究基地。喀斯特地区土壤形成速度极慢，土被不连续，碳酸盐岩的酸不溶物含量低，平均仅为4%左右，风化残余物少，平均形成1cm厚的土层需要8000-10000年，但在良性喀斯特生态环境下，由于有生物作用，加速了成土速率。因此，探讨喀斯特地区生物成土过程及规律有重要的现实意义。研究喀斯特生态系统生物成土过程是喀斯特地球关键带研究领域的薄弱之处，具有明显的区域特色。项目将系统研究茂兰喀斯特森林凋落物的组成、生物量及时空动态规律，探讨土壤动物和微生物群落对喀斯特生物成土过程的贡献，分析不同小生境（石面、石沟、石缝、土面等）生物作用下岩石的溶蚀异同，阐明生物成土过程中微生物群落的响应特征，对促进我国亚热带喀斯特生态系统良性循环及石漠化治理具有重要的意义。

喀斯特山区成土速率缓慢、土层浅薄、生态环境脆弱。碳酸盐岩溶蚀是喀斯特山区主要成土方式。在典型性和原生性强的贵州茂兰喀斯森林自然保护区，对其凋落物的组成、生物量及时空动态规律进行系统研究，探讨了土壤动物和微生物群落对喀斯特生物成土过程的贡献，分析了不同小生境生物作用下岩石的溶蚀异同。得出以下研究结果：①在3种典型原生林树种凋落物中共收集到土壤动物4203只，隶属于3门11纲25目，优势种群为弹尾目和蜱螨目；土壤动物多样性未受凋落物种类的影响；②在凋落物的前期分解过程中，土壤动物显著加剧了凋落物的质量损失，促进了凋落物中养分元素向土壤的转移，加快了森林生态系统物质循环，对茂兰喀斯特森林生物成土具有一定的正效应；③凋落物分解过程中全碳表现为释放，全氮表现出富集趋势；④对受不同干扰程度的土壤进行高通量测序，共检测出土壤真菌4门11纲55目145科361属，干扰程度较小的间伐林土壤真菌群落的丰富度和物种总数相对较高；⑤土壤微生物 PLFA 总含量在原生林土壤中最高，细菌和真菌群落丰度受植被恢复类型和土壤深度的影响较显著，革兰氏阳性菌的相对丰度在荒草地土层中表现最高；⑥6种小生境中土壤pH存在较大差异，石槽中的有机质、总氮、总碳含量及土壤微生物总量显著高于其它小生境；⑦小生境土壤中共检测出细菌25个门，94个纲，244个目，376个科，536个属，643个种；变形菌门、放线菌门分别为低pH、高pH生境土壤优势菌门；pH是影响细菌分布的首要因子；⑧小生境土壤中共检测出7828种功能酶；石洞、石缝生境土壤贫瘠、环境脆弱。⑨埋于生境土面以下的岩石试片溶蚀速率较置于生境表面的高。能谱分析发现试片溶蚀区域元素组成未见显著差异。岩石溶蚀主要受到小生境类型的影响，影响过程可通过土壤含水率、有机质以及微生物等因子体现。这些研究结果为促进我国亚热带喀斯特森林生态系统良性循环及石漠化治理提供了科学依据。