宁南山区典型植物茎叶分解过程及其对土壤养分和微生物群落的影响
发布时间：2018-09-03 17:49
【摘要】：国家实施退耕还林还草政策以来,黄土高原植被恢复略见成效,地上枯落的植物茎叶有了大量的积累。植物茎叶的累积和分解可以改变土壤微环境,提高土壤养分含量,增加土壤微生物多样性。作为连接土壤和植被的纽带,植物茎叶在生态系统物质和能量的循环中具有重要的作用。本研究选取该区三种典型草本植被作为研究对象,采用野外分解袋法模拟植物茎叶的分解,对植物茎叶分解过程中自身养分变化以及土壤养分和土壤微生物多样性变化进行分析,研究不同植被及处理对土壤性质的影响特征,为黄土高原植被恢复和生态系统生物多样性恢复提供基础科学依据,主要结论如下:(1)植物茎叶营养元素的释放规律受季节性变化明显,不同处理元素的释放规律差异不显著。植物茎叶中元素的初始含量直接影响其分解速率,BLX的初始氮含量最低,初始木质素和纤维素含量均最高,导致BLX和含有BLX组合的处理茎叶分解速率较低,且含有BLX的处理在分解末期养分损失量均较低。各组合处理的初始氮含量较高,所以在分解过程中氮元素基本处于释放状态。各处理有机碳在分解过程中均出现淋溶、富集、释放的模式,分解前期易溶性物质和易分解碳水化合物的淋失和降解使得有机碳迅速释放,分解后期木质素、纤维素等难溶物质比例增大,使得分解变得缓慢。随着分解时间的进行,不同处理磷元素的释放规律基本一致,基本遵循释放、富集、释放的波动模式。各组合处理和单种植物处理间磷素富集的起始时间不同,单种植物处理中CMC和BLX在分解释放45天后便开始缓慢富集,而各组合处理和TGH在分解释放90天后才开始富集。到分解390天为止,各处理植物茎叶木质素分解不明显,纤维素在分解前90天无明显变化,之后分解迅速,CMC茎叶的分解速率最快且分解量也最大。(2)添加植物处理的土壤养分的变化趋势和空白土壤的变化趋势基本一致,说明植物茎叶分解对土壤养分的影响主要受外界水热条件变化的影响。添加植物处理的土壤养分相对于空白土壤养分都有所增加,说明植物茎叶的分解可以为土壤提供一定的营养物质。各个处理间土壤养分的变化差异不显著,这和植物茎叶自身的化学组成有密切的关系。土壤全氮主要来源于植物茎叶分解所形成的有机物质,因此土壤全氮和有机碳具有相似的变化趋势,土壤全氮和有机碳含量均在分解135天后才达到最高值。土壤速效磷含量受水热条件变化明显,在夏季雨水充足情况下土壤速效磷含量开始缓慢增加。植物茎叶分解初期土壤铵态氮含量有所减少,硝态氮含量有所增加,整个分解过程土壤铵态氮含量变化不明显,植物茎叶的分解对土壤速效氮的影响主要表现为硝态氮含量的变化。(3)土壤酶活性受外界环境因素的影响较大,受植物茎叶分解的影响较小。土壤的初始养分状况会在一定程度上影响土壤酶活性,土壤有机碳、全氮、速效氮等对土壤脲酶、蔗糖酶、纤维素酶、碱性磷酸酶活性有显著影响,土壤速效磷含量与土壤碱性磷酸酶活性呈显著负相关关系。植物茎叶的分解能提高土壤的养分状况,改善土壤环境,植物茎叶分解末期,土壤脲酶、蔗糖酶、纤维素酶活性均有所增加,而土壤碱性磷酸酶活性有所减少,这可能与碱性磷酸酶矿化土壤磷素使无机磷增加有关。植物茎叶混合分解能更好的提高土壤中酶的活性,改善土壤养分状况,但各处理土壤酶活性的增加和减少差异均不显著。(4)土壤微生物生物量受外界环境条件的影响较大,而土壤和植物茎叶的初始养分含量及其化学计量比是导致各处理土壤mbn和mbc含量产生差异的主要原因。外界水热条件充足时,适宜微生物生长繁殖,微生物数量的增加提高了土壤微生物生物质量;分解试验结束时土壤mbn和mbc与植物茎叶和土壤初始养分含量进行相关性分析,结果显示植物茎叶分解试验结束时土壤mbc和mbn含量与土壤和植物茎叶初始全氮、全磷、木质素含量在0.01水平下均呈正相关关系,其中土壤mbn含量与土壤初始全氮含量呈显著正相关关系,相关系数达0.909(p0.01)。分解前期,植物茎叶中易分解有机物质的释放补充了土壤中营养元素含量,加快了土壤微生物的新陈代谢。微生物利用充足的碳源进行自身生长繁殖,同时将枯落物碳同化为生物体碳,导致土壤mbc的增加。随着植物茎叶分解的进行,纤维素、木质素等难分解物质的积累使后期分解速率越来越慢,土壤对微生物的供给不及时,土壤mbc含量就开始降低。同样,植物茎叶的分解和养分的释放加速了土壤的矿化作用,微生物的大量繁殖导致土壤mbn增加,随着植物茎叶分解的进行,土壤中氮素的大量消耗不能满足微生物的生长繁殖,导致土壤mbn的下降。植物茎叶分解后期,各组合处理土壤微生物生物量略高于单种植物处理,但差异不明显,各组合间土壤微生物生物量差异不显著,单种植物间土壤微生物生物量差异也不显著。植物茎叶分解末期,各添加植物样品的处理土壤mbn和土壤mbc含量均略低于空白处理土壤。(5)利用高通量测序技术对不同处理下植物茎叶分解435天后的土壤微生物特征研究发现:添加植物茎叶的处理土壤细菌和真菌的ace指数和chao指数均高于空白处理,simpson指数小于空白处理,shannon指数大于空白处理,且在0.05水平下差异显著,说明植物茎叶的分解能显著提高土壤细菌和真菌的丰度,增加土壤细菌的多样性。在不同的分类水平下,土壤细菌的种类以放线菌、变形菌、绿湾菌门、芽单胞菌为主,这几种细菌的相对丰度占土壤中所有细菌的90%以上,其中放线菌门的相对丰度占40%左右。在门水平下,土壤真菌的种类主要包括:子囊菌门(ascomycota)、担子菌门(basidiomycota)、球囊菌门(glomeromycota)等,这三种门类真菌的相对丰度占土壤中所有真菌的95%以上,其中子囊菌门的相对丰度占50%左右。在纲的分类水平下,座囊菌纲(dothideomycetes)、粪壳菌纲(sordariomycetes)、伞菌纲(agaricomycetes)、盘菌纲(Pezizomycetes)、球囊菌纲(Glomeromycetes)等五种真菌相对丰度占60%-80%。在目的分类水平下,格孢腔菌目(Pleosporales)、盘菌目(Pezizales)、伞菌目(Agaricales)、肉座菌目(Hypocreales)、球囊菌目(Glomerales)等五种真菌相对丰度占75%-85%。细菌中的放线菌门和真菌中的子囊菌门在植物茎叶分解过程中起着非常重要的作用;植物茎叶的分解能够使土壤中真菌的优势种群个体数明显增多;土壤真菌数量与植物茎叶分解前期初始基质含量有关。
[Abstract]:Since the state implemented the policy of returning farmland to forests and grasslands, the vegetation restoration on the Loess Plateau has achieved some results, and a large number of plant stems and leaves have accumulated on the ground. The accumulation and decomposition of plant stems and leaves can change soil microenvironment, increase soil nutrient content, and increase soil microbial diversity. In this study, three typical herbaceous vegetations in this area were selected as the research object, and the decomposition of plant stems and leaves was simulated by field decomposition bag method. The effects of vegetation and treatment on soil properties provide basic scientific basis for vegetation restoration and ecosystem biodiversity restoration in the Loess Plateau. The main conclusions are as follows: (1) The release of nutrient elements from plant stems and leaves is obviously seasonal, but the release of nutrient elements from different treatments is not significantly different. The initial nitrogen content of BLX was the lowest, and the initial lignin and cellulose content were the highest, which led to the lower decomposition rate of stems and leaves of BLX and BLX-containing treatments, and the nutrient loss of BLX-containing treatments at the end of decomposition was lower. The leaching, enrichment and release of organic carbon appeared in the decomposition process. The leaching and degradation of soluble substances and carbohydrates in the early decomposition stage made the organic carbon release rapidly, and the proportion of lignin and cellulose in the late decomposition stage increased, which made the decomposition slow. The initial time of phosphorus enrichment was different between the treatments of each combination and the treatments of single plant. CMC and BLX began to enrich slowly after 45 days of interpretation and release, while the combination treatments and TGH began to enrich slowly after 45 days of interpretation and release. Lignin decomposition was not obvious until 390 days after decomposition. Cellulose did not change significantly 90 days before decomposition. After decomposition, the decomposition rate of CMC stem and leaf was the fastest and the decomposition amount was the largest. (2) The change trend of soil nutrients and the change trend of blank soil were basically the same. The results showed that the effect of decomposition of plant stems and leaves on soil nutrients was mainly affected by the changes of external water and heat conditions. The chemical composition of plant stems and leaves is closely related. Soil total nitrogen mainly comes from the organic matter formed by the decomposition of plant stems and leaves, so soil total nitrogen and organic carbon have similar changing trend. Soil total nitrogen and organic carbon content reach the highest value after 135 days of decomposition. Soil available phosphorus content began to increase slowly in summer when rainwater was sufficient. Soil ammonium nitrogen content decreased and nitrate nitrogen content increased at the initial stage of plant stem and leaf decomposition. Soil ammonium nitrogen content did not change significantly during the whole decomposition process. The effect of plant stem and leaf decomposition on soil available nitrogen content was mainly manifested in nitrate nitrogen content change. (3) The activity of soil enzymes is greatly influenced by environmental factors, and is less affected by the decomposition of plant stems and leaves. The initial nutrient status of soil will affect soil enzyme activity to a certain extent. Soil organic carbon, total nitrogen, available nitrogen and so on have a significant impact on soil urease, invertase, cellulase and alkaline phosphatase activity, and the content of soil available phosphorus and soil available phosphorus content. Soil alkaline phosphatase activity was negatively correlated. Plant stem and leaf decomposition could improve soil nutrient status and soil environment. At the end of plant stem and leaf decomposition, soil urease, sucrase and cellulase activity increased, while soil alkaline phosphatase activity decreased, which might be due to alkaline phosphatase mineralization of soil phosphorus. Mixed decomposition of plant stems and leaves could improve soil enzyme activity and soil nutrient status, but there was no significant difference in the increase and decrease of soil enzyme activity among treatments. (4) Soil microbial biomass was greatly affected by environmental conditions, while the initial nutrient content and stoichiometry of soil and plant stems and leaves were affected by environmental conditions. The ratio of MBN to MBC was the main reason for the difference of MBN and MBC contents in different treatments. At the end of decomposition test, MBC and MBN contents were positively correlated with soil and plant stem and leaf initial total nitrogen, total phosphorus, lignin content at 0.01 level, and soil MBN content was positively correlated with soil initial total nitrogen content, the correlation coefficient was 0.909 (p0.01). at the early decomposition stage, the decomposition of organic matter in plant stem and leaf was easy. The release of nutrients supplemented the content of soil nutrients and accelerated the metabolism of soil microorganisms. Microorganisms used sufficient carbon sources for their own growth and reproduction, and assimilated litter carbon into biological carbon, resulting in the increase of soil mbc. With the decomposition of plant stems and leaves, the accumulation of difficult-to-decompose substances such as cellulose and lignin led to the subsequent growth of soil microorganisms. Similarly, the decomposition of plant stems and leaves and the release of nutrients accelerated the mineralization of soil. The proliferation of microorganisms led to the increase of soil mbn. As the decomposition of plant stems and leaves proceeded, the large amount of nitrogen consumption in soil could not meet the micro-level. The microbial biomass of each combination was slightly higher than that of the single plant treatment at the late stage of plant stem and leaf decomposition, but the difference was not obvious. there was no significant difference in soil microbial biomass between different combinations, and there was no significant difference in soil microbial biomass between individual plants. (5) Soil microbial characteristics after 435 days of decomposition of plant stems and leaves under different treatments were studied by high-throughput sequencing technique. Ace index and Chao index of soil bacteria and fungi in the treatment of plant stems and leaves were higher than those in the blank treatment, and Simpson index was higher. The number of soil bacteria was less than that of blank treatment, and the Shannon index was higher than that of blank treatment, and the difference was significant at 0.05 level, indicating that the decomposition of plant stems and leaves could significantly increase the abundance of soil bacteria and fungi, and increase the diversity of soil bacteria. The relative abundance of several bacteria accounted for more than 90% of all bacteria in the soil, and the relative abundance of actinomycetes accounted for about 40%. The relative abundance of Ascomycetes is about 50%. At the classification level, the relative abundance of five fungi, including dothideomycetes, sordariomycetes, agaricomycetes, Pezizomycetes and Glomeromycetes, accounts for 60%-80%. The relative abundance of five fungi (Pleosporales, Pezizales, Agaricales, Hypocreales, Glomerales) is 75% - 85%. Actinomycetes in bacteria and Ascomycetes in fungi play an important role in the decomposition of plant stems and leaves. The number of dominant soil fungi increased significantly, and the number of soil fungi was related to the initial matrix content in the early stage of plant stem and leaf decomposition.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S158;S154.3
本文编号：2220726
[Abstract]:Since the state implemented the policy of returning farmland to forests and grasslands, the vegetation restoration on the Loess Plateau has achieved some results, and a large number of plant stems and leaves have accumulated on the ground. The accumulation and decomposition of plant stems and leaves can change soil microenvironment, increase soil nutrient content, and increase soil microbial diversity. In this study, three typical herbaceous vegetations in this area were selected as the research object, and the decomposition of plant stems and leaves was simulated by field decomposition bag method. The effects of vegetation and treatment on soil properties provide basic scientific basis for vegetation restoration and ecosystem biodiversity restoration in the Loess Plateau. The main conclusions are as follows: (1) The release of nutrient elements from plant stems and leaves is obviously seasonal, but the release of nutrient elements from different treatments is not significantly different. The initial nitrogen content of BLX was the lowest, and the initial lignin and cellulose content were the highest, which led to the lower decomposition rate of stems and leaves of BLX and BLX-containing treatments, and the nutrient loss of BLX-containing treatments at the end of decomposition was lower. The leaching, enrichment and release of organic carbon appeared in the decomposition process. The leaching and degradation of soluble substances and carbohydrates in the early decomposition stage made the organic carbon release rapidly, and the proportion of lignin and cellulose in the late decomposition stage increased, which made the decomposition slow. The initial time of phosphorus enrichment was different between the treatments of each combination and the treatments of single plant. CMC and BLX began to enrich slowly after 45 days of interpretation and release, while the combination treatments and TGH began to enrich slowly after 45 days of interpretation and release. Lignin decomposition was not obvious until 390 days after decomposition. Cellulose did not change significantly 90 days before decomposition. After decomposition, the decomposition rate of CMC stem and leaf was the fastest and the decomposition amount was the largest. (2) The change trend of soil nutrients and the change trend of blank soil were basically the same. The results showed that the effect of decomposition of plant stems and leaves on soil nutrients was mainly affected by the changes of external water and heat conditions. The chemical composition of plant stems and leaves is closely related. Soil total nitrogen mainly comes from the organic matter formed by the decomposition of plant stems and leaves, so soil total nitrogen and organic carbon have similar changing trend. Soil total nitrogen and organic carbon content reach the highest value after 135 days of decomposition. Soil available phosphorus content began to increase slowly in summer when rainwater was sufficient. Soil ammonium nitrogen content decreased and nitrate nitrogen content increased at the initial stage of plant stem and leaf decomposition. Soil ammonium nitrogen content did not change significantly during the whole decomposition process. The effect of plant stem and leaf decomposition on soil available nitrogen content was mainly manifested in nitrate nitrogen content change. (3) The activity of soil enzymes is greatly influenced by environmental factors, and is less affected by the decomposition of plant stems and leaves. The initial nutrient status of soil will affect soil enzyme activity to a certain extent. Soil organic carbon, total nitrogen, available nitrogen and so on have a significant impact on soil urease, invertase, cellulase and alkaline phosphatase activity, and the content of soil available phosphorus and soil available phosphorus content. Soil alkaline phosphatase activity was negatively correlated. Plant stem and leaf decomposition could improve soil nutrient status and soil environment. At the end of plant stem and leaf decomposition, soil urease, sucrase and cellulase activity increased, while soil alkaline phosphatase activity decreased, which might be due to alkaline phosphatase mineralization of soil phosphorus. Mixed decomposition of plant stems and leaves could improve soil enzyme activity and soil nutrient status, but there was no significant difference in the increase and decrease of soil enzyme activity among treatments. (4) Soil microbial biomass was greatly affected by environmental conditions, while the initial nutrient content and stoichiometry of soil and plant stems and leaves were affected by environmental conditions. The ratio of MBN to MBC was the main reason for the difference of MBN and MBC contents in different treatments. At the end of decomposition test, MBC and MBN contents were positively correlated with soil and plant stem and leaf initial total nitrogen, total phosphorus, lignin content at 0.01 level, and soil MBN content was positively correlated with soil initial total nitrogen content, the correlation coefficient was 0.909 (p0.01). at the early decomposition stage, the decomposition of organic matter in plant stem and leaf was easy. The release of nutrients supplemented the content of soil nutrients and accelerated the metabolism of soil microorganisms. Microorganisms used sufficient carbon sources for their own growth and reproduction, and assimilated litter carbon into biological carbon, resulting in the increase of soil mbc. With the decomposition of plant stems and leaves, the accumulation of difficult-to-decompose substances such as cellulose and lignin led to the subsequent growth of soil microorganisms. Similarly, the decomposition of plant stems and leaves and the release of nutrients accelerated the mineralization of soil. The proliferation of microorganisms led to the increase of soil mbn. As the decomposition of plant stems and leaves proceeded, the large amount of nitrogen consumption in soil could not meet the micro-level. The microbial biomass of each combination was slightly higher than that of the single plant treatment at the late stage of plant stem and leaf decomposition, but the difference was not obvious. there was no significant difference in soil microbial biomass between different combinations, and there was no significant difference in soil microbial biomass between individual plants. (5) Soil microbial characteristics after 435 days of decomposition of plant stems and leaves under different treatments were studied by high-throughput sequencing technique. Ace index and Chao index of soil bacteria and fungi in the treatment of plant stems and leaves were higher than those in the blank treatment, and Simpson index was higher. The number of soil bacteria was less than that of blank treatment, and the Shannon index was higher than that of blank treatment, and the difference was significant at 0.05 level, indicating that the decomposition of plant stems and leaves could significantly increase the abundance of soil bacteria and fungi, and increase the diversity of soil bacteria. The relative abundance of several bacteria accounted for more than 90% of all bacteria in the soil, and the relative abundance of actinomycetes accounted for about 40%. The relative abundance of Ascomycetes is about 50%. At the classification level, the relative abundance of five fungi, including dothideomycetes, sordariomycetes, agaricomycetes, Pezizomycetes and Glomeromycetes, accounts for 60%-80%. The relative abundance of five fungi (Pleosporales, Pezizales, Agaricales, Hypocreales, Glomerales) is 75% - 85%. Actinomycetes in bacteria and Ascomycetes in fungi play an important role in the decomposition of plant stems and leaves. The number of dominant soil fungi increased significantly, and the number of soil fungi was related to the initial matrix content in the early stage of plant stem and leaf decomposition.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S158;S154.3
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1 李鑫;宁南山区典型植物茎叶分解过程及其对土壤养分和微生物群落的影响[D];西北农林科技大学;2016年
，本文编号：2220726
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