Knowledge Resource Center for Ecological Environment in Arid Area
| 生物土壤结皮演化与高寒嵩草草甸演替的协同 | |
| 其他题名 | Synergistic relationship between biological soil crusts evolution and alpine Kobresia meadow succession |
| 李以康 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 韩发 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 生物土壤结皮（BSCs）是干旱半干旱生态系统主要生物组成部分，对BSCs的大量研究始于上个世纪90年代，并受到高度重视。其形成和发展对陆地生态系统的功能和过程有重要影响，是荒漠生态系统植被演替的基础，扮演了生态系统工程师的重要角色。但其对生态系统功能如种子萌发和水分入渗等的影响还存在很大争议。BSCs随高寒草甸演替而发生、发展、演化和死亡，特别在小嵩草阶段藻结皮的大面积存在，构成这一阶段特色景观，但其与高寒嵩草草甸演替的协同关系及其对系统生态功能的影响尚不明确。本研究于2013年到2016年进行，以青藏高原高寒嵩草草甸生态系统为研究对象，通过野外调查和室内控制实验，对BSCs在高寒嵩草草甸的分布、功能及其与系统的协同演替进行研究，试图：1）明确不同BSCs类型分布特点及其构成成分；2）探究BSCs对高寒草甸种子萌发的生物过滤功能和草甸水分入渗等的影响；3）明晰BSCs随草甸演替的协同过程及影响因素；探讨其协同演化对系统演替和群落构建的影响，以期探究高寒草甸退化演替进程中BSCs的生态地位及其对系统的互馈机制。研究结果如下：1. BSCs在高寒草甸的分布分异：BSCs是高寒草甸生态系统的重要组成部分，在地带性植被禾草矮嵩草草甸和6年生人工草地，分布结皮类型是藓结皮（频度96%）；在矮嵩草草甸，黑斑、菌斑和地衣形成，并在小嵩草阶段得到迅速发展，成为小嵩草阶段的重要地表景观；而杂类草-黑土滩阶段，由于高寒草甸地被层遭到完全破坏，结皮很少存在。植被盖度与藓结皮出现频度极显著相关（p < 0.01）。BSCs在高寒草甸广泛分布，不同退化程度样地，其分布和类型存在较大差别，植被生长和表土稳定性状况导致了BSCs的异质性分布格局。2. 高寒草甸BSCs的物种构成特点：地衣结皮的物种组成反映了干旱半干旱区荒漠的地衣区系特点，即以鳞片状和壳状的土生地衣为主要群落组成，主要属包括石果衣属等，其中Endocarpon pusillum是一个最为常见的地衣。苔藓的优势种为土生对齿藓（Didymodon vinealis），真藓（Bryum argenteum）也是重要组成成分之一；藻结皮以蓝藻和绿藻为主。3. 结皮类型改变对种子萌发的影响：结皮类型对高寒草甸物种萌发具有物种特异性。对种子萌发的具体抑制作用取决于结皮类型和种子；影响种子萌发的主要因子包括结皮类型、种子位置、土壤质地，以及结皮类型和种子位置、物种和种子位置、物种和土壤表层质地、种子与结皮类型和土壤质地的交互作用。藻结皮显著抑制了所有种类种子的萌发（P < 0.05）；而高山豆在土壤表面的萌发率与其在群落中的出现频率显著相关。我们结果证明BSCs可以在种子萌发过程中作为生物过滤因子，取决于BSC的类型。通过对种子萌发的影响，BSCs能够强烈影响高寒草甸逆向演替过程的群落构成。4. 结皮类型演替影响草甸水分入渗及含量：结皮类型演替对草甸水分入渗影响极显著（P < 0.01）。在矮嵩草草甸，藻结皮斑块的形成显著抑制了草甸土壤水分入渗速率（P < 0.01，相比于植被斑块，降低了70%），而藓结皮对草甸土壤水分入渗速率没有显著影响（P > 0.05）。藻结皮去除后，显著提高了草甸的水分入渗速率（提高1.03倍）。3年封育使高寒草甸结皮斑块和植物斑块的水分入渗速率都显著提高（P < 0.05）。恢复样地藻结皮斑块的土壤水分含量依然显著低于植物斑块，说明结皮斑块的形成对草甸土壤水分含量产生很大影响，对其恢复需要更长的时间。降雨过后的草甸藻结皮斑块的含水量依然显著低于植物斑块（P < 0.05）。藻结皮斑块的形成显著降低了草甸的土壤含水量，从而可能对植物生长产生重要影响。5. BSCs与高寒草甸逆向演替过程的协同： BSCs类型随草甸演替而发生相应演化。在高寒草甸的逆向演替进程中，藓结皮在矮嵩草阶段盖度最高（66.7%），随草甸退化演替，盖度显著降低；在矮嵩草阶段，藻结皮和地衣结皮开始繁衍扩展，在小嵩草阶段占据优势地位。藓结皮适于分布在植被生长良好群落盖度高的环境中，而藻结皮的分布极显著受到莎草植物的重要值和群落盖度的影响（P < 0.01），在放牧扰动强烈的小嵩草草甸藻结皮的生长占据绝对优势，地衣结皮的分布与与草甸群落盖度显著负相关，适于生长在植被稀疏的退化草甸中。藓结皮对放牧干扰敏感，放牧扰动下生长退缩，而放牧扰动促进了藻结皮和地衣结皮的生长和分布。放牧家畜的取食造成的群落植被生长退缩而非践踏可能是导致结皮演替的最重要原因。6. BSCs与草甸恢复的协同减牧和封育都使藓结皮的盖度显著增高（P < 0.05），藻结皮和地衣结皮生长受到抑制。高寒草甸退化草地结皮恢复演替的速度较快，在小嵩草草甸开裂期，减牧和封育后藓结皮的年均增长率为原来盖度的80%，而藻结皮的年均退缩速率为原来盖度的30%。相关分析结果表明，群落总盖度和禾草重要值极显著促进了藓结皮的生长分布（P < 0.01），莎草科植物的生长则抑制了藓结皮的生长；藻结皮盖度与莎草重要值极显著正相关（P < 0.01），而与禾草重要值和群落总盖度则负相关。减牧和封育导致了结皮类型的不同演替。本研究具有如下重要的理论和实践意义：（1）明确BSCs是高寒草甸生态系统的重要一环，弥补了以往对高寒草甸生态系统BSCs的研究不足；（2）BSCs与高寒草甸的协同演化，对高寒草甸系统演替有重要影响，其对种子萌发生长的生物过滤作用和对水分入渗的影响研究，深化了高寒草甸的退化演替机理，同时对进行高寒草甸适应性管理和退化草甸的植被恢复也具有重要启示。 （3）藻结皮在小嵩草演替阶段的大面积发展，对种子萌发和水分入渗等生态功能造成很大影响，可能是导致生物多样性减少和草甸干旱化进程的重要因子，因此，如何根据藻结皮的分布状况，判断其对草甸生态功能可能造成的影响，并采取相应措施进行适应性管理，可能这一阶段是采取措施加强管理的关键点。 |
| 英文摘要 | Biological soil crusts(BSCs) are the mainly components of (semi-)arid ecosystem, its formation and development exert important influence on ecosystem function and process, which is the basis of vegetation succession in desert ecosystem, act as the important role of ecosystem engineer. A large number of studies on biological soil crusts began in the last 1990s and were highly valued. But for its impact on ecosystem seed germination and water infiltration, there is still a lot of controversy.The occurrence, development, evolution and death of BSCs along with the process of alpine meadow succession, especially in Kobresia pygmaea meadow cyanobacteria crust large area exists and constituted the characteristics of this stage landscape, but its synergistic relationship with the succession of alpine Kobresia meadow and its effect on the ecological function of the system is still not clear.This research was conducted between 2013 and 2016, and took Qinghai-Tibet Plateau alpime meadow ecosystem as research object, through field investigation and indoor control experiments, research on the succession, distribution and function of BSCs in the process of synergistic succession with alpine Kobresia meadow, we try to: 1) clarify the components and distribution of BSCs; 2) investigate influence of BSCs ecological filter function on alpine meadow seed germination and BSCs formation on meadow water infiltration, 3）detect the synergistic process and influencing factors of BSCs with alpine meadow; and to explore the influence of synergetic evolution on system succession and community construction, in order to explore the ecological status of BSCs during the process of alpine meadow degradation and its mechanism of mutual feedback. The main results as follows:1. Differentiation of BSCs distribution in alpine meadow:BSCs make up an important component of all alpine meadow ecosystem, the distribution of BSCs differed in different alpine meadow stages. In Graminoid- dominated zonal vegetation and 6-year-old artificial grassland, the crust type is moss-crust(occurrence frequency is 96%) and, black patches, white patches and lichen formed in K. pygmaea meadow, and were most abundant in K.humilis meadow and become an important soil surface landscape. But in “Black Soil Type” degraded grassland BSC seldom exist for the reason of mattic epipedon was broken. Community coverage have very significant correlation with moss-crust (p<0.01). BSC are widely distributed in alpine meadows, but in different degrees of degraded meadow, its distribution and species composition varied greatly, vegetation growth and topsoil stability of surface soil led to the heterogeneity distribution of BSCs.2. Characteristic of BSCs species composition in alpine meadow:There are 3 types of crusts in alpine meadow: moss crust, cyanobacteria crust and lichen crust. The species composition of lichen crust reflects the lichen flora characteristics in (semi-) arid desert ecosystem, with scaly and shelly soil lichens to form the main community. The main genus of lichen include Endocarpon, and Endocarpon pusillum is one of the most common species. The dominant species of bryophytes is Didymodon vinealis, and Bryum argenteum is also one of the most important component; Algal crust is dominated by cyanobacteria and green algal.3. Alterations to biological soil crusts with alpine meadow retrogressive succession affect seeds germination:Different BSC type have special effect on alpine meadow plant seed germination. The inhibitory effects of BSCs depended on the crust type and seed species tested. The major factors influencing seed germination were BSC type, seed position, soil texture, and the interactions between BSC type and seed position; species and surface texture; and species, crust type, and surface texture. Cyanobacteria crust significantly inhibited germination of all seeds; Germination rates of T.himalaica on the soil surface were significantly correlated with plant occurrence frequency within the alpine meadow community. Our results clearly demonstrated that BSCs can be biological filters during seed germination, depending on the BSC succession stage. Through their influences on seed germination, BSCs can strongly influence community assemblages throughout alpine meadow retrogressive succession.4. Effects of crust type succession caused by grazing on alpine meadow affect soil water infiltration rate and soil water content:The effect of crust succession on meadow soil water infiltration was very significant(P < 0.01). Our results showed that in Kobresia humilis meadow the formation of cyanobacteria crust patch significantly inhibited soil water infiltration of alpine meadow（P < 0.01）, but moss crust formation nearly have no influence on meadow soil water infiltration (P > 0.05). The removal of cyanobacteria crust significantly increased alpine meadow soil water infiltration(increased by 1.03 times). Three years of fencing resulted in increase of infiltration on crust patch and vegetation patch(P < 0.05). Soil water content in cyanobacteria crust patch significantly lower than that in vegetation patch, and it also showed same tendency in restored meadow, this indicate that crust patch formation exert great influence on meadow soil water content, and its recovery need more time. Though soil water content of meadow after rainfall was very high, the water content of algae crust patch was still significantly lower than that of vegetation patch(P < 0.05）. Cyanobacteria crust patch formation significantly reduced soil water content of meadow soil, which may have important influence on the growth of meadow plants.5. Synergism between BSCs and alpine meadow retrogressive succession process:The BSCs type changes with meadow succession. During the process of alpine meadow retrogressive succession, the coverage of moss-crust is highest than other stages（66.7%）, and significantly decreased with meadow degraded succession; Multify and expand of cyanobacteria and lichen crust began from Kobresia humilis meadow, and dominated in the Kobresia pygmaea meadow stage. Moss crust suitable for distributed in environments where vegetation growth is well covered, and the distribution of cyanobacteria crust was affected significantly by important value of sedge and community coverage, and dominated absolutely in Kobresia pygmaea meadow which was disturbed strongly by grazing, the distribution of lichen crust was negatively correlated with the coverage of meadow community, and suitable for growth in sparse degraded meadow. Moss crust was sensitive to grazing disturb and growth was inhibited by it, but grazing disturb increased the growth and distribution of cyanobacteria and lichen crust. The inhibition of community growth caused by grazing animals feeding rather than trampling may be the most important cause that resulted in crust succession.6. Synergism between BSCs and meadow restoration:The coverage of moss crust was significantly increased by grazing reduction and fencing（P < 0.05）, but the growth of cyanobacteria and lichen crust was inhibited. Crust recovered very quickly in alpine degraded meadow, The results of correlation analysis show that community coverage and important value of Graminoid significantly increased the growth of moss crust, but the growth of Sedge inhibited the growth of moss crust; In cracked turf succession stage of K. pygmaea meadow, the average annual growth rate of moss crust is 80% of the original coverage after grazing reduction and fencing, the average decreasing rate of cyanobacteria crust is 30% of the original coverage. Correlation analysis showed that total community coverage and the important value of Graminoid significantly increased the growth and distribution of moss crust (P < 0.01), but was inhibited by sedge growth; There was a significant positive correlation between the coverage of cyanobacteria crust and the important values of sedge (P < 0.01), but negatively correlated with the important value of Graminoid and the total coverage of community. Grazing reduction and fencing resulted in the different succession status of crust type. This study has the following important theoritical and practical significance:（1）Clarify that BSCs are important part of alpine meadow ecosystem, and make up for the previous research on the BSCs on alpine meadow;（2）Synergistic succession of BSCs and alpine meadow exert important influence on alpine meadow succession, and its ecological filter function on seed germination and effect on water infiltration, which enriched the degradation and succession mechanism of alpine meadow, and also has important implications for the restoration of alpine meadow and the restoration of vegetation in degraded meadows. （3）The large area development of cyanobacteria crust in K.pygmaea meadow, exert important influence on seed germination and water infiltration, may be an important factor leading to biodiversity reduction and meadow drought processes. How to take appropriate measures to carry out adaptive management according to cyanobacteria crust distribution and the influence it may exert on meadow ecosystem function, and perhaps this stage is the key point to take measures to strengthen management. |
| 中文关键词 | 生物土壤结皮 ; 青藏高原 ; 协同演替 ; 种子萌发 ; 水分入渗 |
| 英文关键词 | biological soil crusts Tibetan Plateau cooperative succession seed germination water infiltration |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院西北高原生物研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287930 |
| 推荐引用方式 GB/T 7714 | 李以康. 生物土壤结皮演化与高寒嵩草草甸演替的协同[D]. 中国科学院大学,2017. |
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