【作者】 张倩；

【导师】 徐建明；

【作者基本信息】 浙江大学 ， 土壤学， 2019， 博士

【摘要】 土壤中蕴含着种类极其丰富的微生物,其在元素生物地球化学循环过程调控和生态系统功能维持方面起到了关键作用。对土壤微生物空间分布格局及其形成机制的认识,将有助于人们对陆地生态系统的保护、管理和调控,以应对气候变暖等重大的全球性环境问题。硝化微生物主导的硝化作用作为氮循环的重要组成部分,对提高氮肥利用率有重要影响。针对海拔和温度对土壤硝化过程的影响研究,可以帮助我们更好地了解气候变化对土壤硝化过程及硝化微生物的影响,从而为合理施肥、提高氮肥利用率提供科学依据。因此,本文以中国东部最大的梯田—云和梯田为研究对象,分别对自然土壤和水稻土中细菌、古菌、真菌的多样性及群落组成沿海拔分布模式进行了研究,同时探讨了不同海拔土壤硝化速率和活性硝化微生物的差异以及升温对土壤硝化作用的影响,主要结果如下:(1)两类土壤中细菌多样性及群落组成沿海拔分布模式。自然土壤和水稻土中细菌群落组成差异显著,水稻土中细菌群落间的连结性低于自然土壤,应对环境干扰的反应也不如自然土迅速。两种类型土壤细菌群落组成的海拔差异均非常明显。自然土壤中,细菌多样性随海拔呈单调递减模式,土壤C/N 比是细菌多样性和群落组成的主要驱动因子。而水稻土中,细菌多样性随海拔呈单峰模式,在500米处多样性最高,解磷细菌相对丰度与有效磷含量呈极显著的正相关关系(r=0.800,P<0.001),细菌多样性和群落组成主要与土壤有效磷含量呈显著相关关系,说明解磷菌对整个细菌群落有重要影响。在两类土壤中,细菌群落组成主要由当代环境因子(土壤属性)驱动,同时海拔和地理距离的作用也不容忽视。(2)两类土壤中古菌多样性及群落组成沿海拔分布模式。水稻土中古菌群落间的连结性高于自然土壤,其应对外界干扰的反应也更迅速。自然土壤和水稻土中古菌优势物种分别为:硝化作用相关的Nitrososphaeria纲和产甲烷相关的Methanomicrobia纲。两类土壤中古菌a多样性均随海拔升高而升高,并与土壤理化因子有显著相关关系。自然土壤中,硝态氮含量是土壤古菌群落组成的主要驱动因子,而水稻土中,古菌多样性和群落组成主要与土壤有效磷含量显著相关。(3)两类土壤中真菌多样性及群落组成沿海拔分布模式。与自然土壤相比,水稻土中子囊菌门相对丰度升高,而担子菌门相对丰度降低,真菌网络结构更简单。自然土壤中真菌多样性随海拔升高而递减,并与土壤有机质、铵态氮等呈显著负相关关系,而与硝态氮呈显著正相关关系。水稻土中真菌多样性亦呈现出单调递减的海拔分布模式,且与土壤硝态氮含量、阳离子交换量及机械组成有明显的相关性。自然土壤中,C/N比是真菌群落组成的关键驱动因子,而水稻土壤中,真菌群落组成主要受海拔高度影响。(4)不同海拔土壤硝化速率及活性硝化微生物的差异。土壤硝化速率随海拔升高而增大,伴随着氨氧化细菌(AOB)的显著增加,而氨氧化古菌(AOA)丰度在培养结束时显著下降。经过56天的培养,活性AOB丰度和标记程度均远远高于AOA和亚硝酸盐氧化细菌(NOB),首次通过稳定性同位素核酸探针技术(DNA-SIP)证明了细菌氨氧化在酸性水稻土中的重要作用。活性氨氧化微生物主要由Group 1.1a-associated AOA和Nitrosospira cluster 3 AOB组成,而活性亚硝酸盐氧化菌在不同土壤中由不同的Nitrospira NOB组成,其生态位分异主要由土壤理化性质决定。土壤理化性质(pH、有效磷、土壤氧化还原能力(OXC))对土壤活性硝化群落有重要影响,土壤硝化速率的差异主要由活性微生物相对丰度及群落组成差异造成的。(5)升温对土壤硝化速率及活性硝化微生物的影响。温度越高,土壤硝化速率越强,各温度下硝酸根的产生均伴随着AOB的显著增加,而AOA丰度在培养结束时显著下降。AOA和AOB的生长对温度的响应不同,随着温度升高,氨氧化的主导类群由AOA变为AOB,13C标记的主要NOB由Nitrospira moscoviensis变为Nitrospirajaponica。升温对土壤硝化作用有直接和间接的影响,主要通过改变AOA和AOB的丰度以及AOA和NOB群落结构实现的,而AOB在高温条件下较稳定,,群落结构没有显著变化。更多还原

【Abstract】 Soils harbor diverse microorganisms,which play an important role in the regulation of biogeochemical cycles and the maintaining of ecosystem function.Understanding the spatial distribution of microorganisms and its forming mechanisms will help us protect,manage and regulate the terrestrial ecosystems and cope with global environmental issues such as global warming.Nitrification,as a crucial component of the global nitrogen cycle,is of great importance to improve the utilization rate of nitrogen fertilizer.Researches about the effects of elevation and temperature on soil nitrification process can help us better understand the effects of climate change on nitrification and nitrifying microorganisms in paddy soils,thus providing a scientific basis for rational fertilization and nitrogen utilization.Therefore,this study,based on the biggest terrace in East China,Yunhe terrace,investigated the elevational distribution pattern of bacterial,archaeal and fungal diversity and community structure.At the same time,the differences of soil nitrification activity and active nitrifying microorganisms at different elevations as well as the effects of warming on soil nitrification were also explored.Main results are as follows:(1)The elevational distribution pattern of bacterial diversity and community compisiton in natural and paddy soils.The connectivity between bacterial communities in paddy soils is lower,and their response to environmental disturbances is slower than that of natural soils.Significant differences in bacterial community composition between natural and paddy soils were observed,and bacterial community composition differed significantly among the selected elevations in both natural and paddy soils.In natural soils,there was a monotonic decreasing trend of bacterial diversity and soil C/N ratio was the best predictor of both bacterial diversity and composition.In paddy soils,a Hump-Backed-like trend of bacterial species richness and diversity was found with a ’peak’appeared in elevation 500 m,and the bacterial diversity and composition were most strongly affected by soil available phosphorus(AP)content.There was a very significant positive correlation between the relative abundance of phosphate solubilizing bacteria and soil AP content,implying the great influence of phosphate solubilizing bacteria to the whole bacterial community.The historical effects persistent in soil microbial communities cannot be erased by contemporary disturbance even after a long-term rice cultivation process,although the contemporary factors(soil properties)were more important than the historical factors(elevation and geographic distance)in shaping bacterial community in both natural and paddy soils.(2)The elevational distribution pattern of archaeal diversity and community compisiton in natural and paddy soils.The connectivity between archaeal communities in paddy soils is higher,and their response to environmental disturbances is also faster than that of natural soils.Classes Nitrososphaeria associated with nitrification and Methanomicrobia associated with methane production dominated the archaeal communities in natural and paddy soils,respectively.The archaeal diversity increased with high elevation and also correlated with different soil properties in both kinds of soils.The contents of nitrate content and available phosphorus were the best predictor of archaeal diversity and community in natural and paddy soils,respectively.(3)The elevational distribution pattern of fungal diversity and community compisiton in natural and paddy soils.The relative abundance of Ascomycota increased while Basidiomycota decreased,and the co-occurence network of fungi in paddy soils were simpler compared with natural soils.In natural soils,the diversity of fungi decreased with elevation and was significantly negatively correlated with SOC and ammonium content,while positively correlated with soil nitrate content.In paddy soils,there was also a negative linear elevational distribution pattern of fungal diversity which was significantly correlated with soil nitrate content,CEC and soil texture.Soil C/N ratio and elevation was the best predictor for fungal community in natural and paddy soils,respectively.(4)Difference of nitrification and active nitrifiers in soils with different elevations.Nitrification activity increased from E200 to E600 and then to E1100,accompanied with significant growth of ammonia-oxidizing bacteria(AOB)over the 56-day incubation,while the abundance of archaeal amoA gene declined significantly in all soils during incubation.Active AOB outnumbered ammonia-oxidizing archaea(AOA)and were much more heavily labeled than AOA and nitrite-oxidizing bacteria(NOB)during the incubation,providing the unequivocal evidence for the significant contribution of AOB to nitrification in these acidic paddy soils using DNA-SIP.Active ammonia oxidizing microorganisms were dominated by group 1.1a associated cluster AOA and Nitrosospira cluster 3 AOB,and 13C-NOB was dominated by Nitrospira-like NOB,with distinct phylotypes in different soils,which was driven by soil properties.Soil physiochemical properties(e.g.,pH,available phosphorus(AP)and soil oxidation capacity(OXC))are of great significance in determining the composition of the active nitrifying populations.Soil nitrification activity was influenced by the differences in the relative abundance and community structure of active nitrifiers.(5)Influence of elevated temperature on nitrification and active nitrifiers.Nitrification activity greatly increased with increasing temperature,accompanied by increase in AOB abundance,while the abundance of AOA gradually decreased during incubation.AOA and AOB responded differently to elevated temperatures,and the dominant ammonia oxidizers changed from AOA to AOB with increasing temperature.Dominant 13C-NOB shifted from Nitrospira moscoviensis to Nitrospira japonica at elevated temperatures.Elevated temperature had significant direct and indirect impacts on soil nitrification which were driven by changes in AOA and AOB abundance,as well as the community structure of AOA and NOB,while the composition of AOB was more stable than AOA communities under elevated temperatures without shift.更多还原