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氮添加对干热河谷优势草本植物与土壤微生物群落关联特征的影响
Alternative TitleThe effects of nitrogen addition on the couplings between dominant plants and soil microbial communities in an arid-hot grassland
闫帮国
Subtype博士
Thesis Advisor刘刚才
2017
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline土壤学
Keyword土壤微生物 土壤酶 碳循环 氮循环 磷脂脂肪酸
Abstract自工业革命以来,大气氮沉降日益增加。富氮化不仅改变了植物群落中的物种组成,对土壤微生物群落也有重要影响。富氮化可能会通过影响植物物种组成,进而改变土壤的微生物群落结构和功能。因此,植物物种在土壤生态系统响应富氮化的过程中扮演极为重要的中间角色。但是富氮化对不同植物物种下土壤微生物群落结构、土壤酶活性的变化特征和机制仍不清楚。干热河谷具有独特的气候特征,生态系统极为脆弱,土壤微生物功能对维系当地的植被生长中扮演关键角色。本文研究了氮添加(添加量为5g·m2·yr-1)对干热河谷优势草本植物与土壤微生物群落关联特征的影响。研究结果有助于认识富氮化对土壤生态系统的影响,深化对区域内土壤-植物关系的理解,为合理管理当地生态系统提供了理论基础。主要结论如下: (1) 相对于裸地样方,植物样方的土壤碳氮含量分别高出55.0%和44.2%。植物对土壤理化性质的影响与植物性状有关,养分含量较高的竞争性物种下土壤碳氮含量越高,相反养分含量较低的耐受性物种下的土壤碳氮含量较低。(2) 植物对土壤微生物生物量具有显著影响。种植植物的样方中微生物生物量显著高于裸地,总微生物生物量高出103.5%,真菌高出116.2%,革兰氏阴性菌高出304.8%,革兰氏阳性菌高出124.6%;植物样方的革兰氏阴性菌:阳性菌比例也高于裸地(72.8%)。耐受性植物物种下的微生物生物量低于竞争性物种,拟金茅微生物生物量较其它物种平均值低67.6%。植物样方内土壤水解酶活性显著高于裸地,其中酸性磷酸酶(AP)活性高出239.7%,亮氨酸氨肽酶(LAP)活性高出 95.9%,几丁质酶(NAG) 活性高出219.2%,β-1,4-葡萄糖苷酶(BG) 活性高出 245.4%。植物物种通过其性状的差异影响土壤酶活性,养分含量较高、比叶面积较大的物种下土壤酶活性更高。植物物种对土壤酶效率没有显著影响,植物物种对土壤碳氮磷水解酶化学计量特征也没有影响,表明不同植物下土壤碳氮磷水解酶的耦合特征基本相似。(3) 氮添加下土壤pH从6.26降至5.87,有效氮含量也显著增加。氮添加对微生物生物量没有显著影响,但是显著降低了微生物群落真菌:细菌比。相关分析表明真菌:细菌比与土壤pH紧密相关,表明氮添加可能通过降低土壤pH从而影响了土壤微生物群落结构。氮添加下LAP活性降低了42.9%,过氧化物酶(PER)活性降低了30.8%,但BG和NAG活性没有显著变化。氮添加增加了植物样方上土壤AP活性。氮添加对微生物酶效率的影响与土壤酶活性相似,表现为降低LAP效率和PER效率,提高了酸性磷酸酶效率,表明氮添加可能通过影响土壤酶效率进而影响了土壤酶活性。氮添加增加了ln(BG):ln(LAP),降低了ln(LAP):ln(AP)和ln(BG):ln(AP)。氮添加对土壤酶化学计量学特征的影响与土壤pH和微生物群落结构变化有关。氮添加也改变了土壤酶活性与植物生物量的关系,降低了单位植物生物量下的LAP酶活性,增加了AP活性与植物生物量关系的斜率。氮添加与植物物种交互作用对土壤酶活性没有影响,表明氮添加对不同植物下的土壤酶活性的影响方式较为一致。(4) 氮添加与植物物种对土壤酶活性具有不同的影响途径。结构方程模型分析显示,氮添加通过降低土壤pH,进而改变微生物群落结构,影响了AP、LAP和NAG活性;pH对PER活性具有直接作用,与微生物群落结构无关;pH对BG活性无作用。相反,植物物种通过性状差异影响微生物生物量和土壤碳含量,从而影响了土壤酶活性,其中碳含量对除PER外的其它酶活性均存在显著的作用,而微生物生物量的作用对所有酶活性都是显著的。(5) 氮添加下土壤微生物呼吸降低了26.2%,微生物呼吸速率与植物生物量关系的截距显著降低;氮添加也降低了微生物代谢熵(35.5%)。植物物种也影响了土壤微生物呼吸,这种作用主要由植物性状差异引起,养分含量较高、比叶面积较大的植物物种下土壤微生物呼吸速率较高;植物物种对土壤微生物代谢熵没有作用。(6) 氮添加下惰性碳组分的分解速率降低了28.7%;氮添加对活性碳组分分解速率没有影响。氮添加也改变了惰性碳组分分解速率与植物生物量的关系,表现为单位植物生物量下的惰性碳组分分解速率降低。植物物种通过植物性状显著影响了土壤活性碳组分和惰性碳组分的分解速率。竞争性物种的活性碳组分和惰性碳组分分解速率较高,而耐受种下分解速率较低。微生物生物量、群落结构和酶活性影响了活性碳组分和惰性碳组分的分解速率,惰性碳组分的分解速率与真菌:细菌比显著正相关;活性碳组分分解速率与微生物生物量显著正相关。NAG+BG+LAP活性之和可以解释活性碳组分分解速率57.4%的变异,LAP活性可以解释惰性碳组分分解速率49.0%的变异。(7) 葡萄糖添加(500mg C Kg-1土壤)极大地促进样方的土壤微生物和酶活性,表明样方中存在碳限制。土壤NAG、LAP和AP活性在葡萄糖添加下分别增加了95.6%、68.0%和218.8%,土壤呼吸增加了10.8倍。葡萄糖添加对促进富氮土壤的酶活性促进作用较大,表明葡萄糖添加后出现了氮限制作用。但是,葡萄糖添加对富氮土壤的微生物呼吸速率的促进作用较小。葡萄糖添加与植物交互作用对NAG活性和LAP活性 具有显著影响,表明裸地中存在更严重的碳限制,并影响了土壤酶的活性。葡萄糖添加对AP活性的促进作用与有效氮含量有关,表明AP活性受到土壤碳和氮的序列性限制。葡萄糖添加对碳水解酶的促进作用较小,从而降低了ln(BG):ln(LAP)和ln(BG):ln(AP)。(8) 土壤pH调节实验结果表明,提升土壤pH (增加1.0左右)显著增加了土壤微生物呼吸(74.3%)和土壤LAP活性(25.2%),表明土壤pH是影响微生物呼吸和氮的水解酶活性的重要因素;提升土壤pH使土壤氮净矿化速率增加了62.9%。这里的结果表明土壤pH是控制土壤碳氮循环的重要因素。(9) 通过微生物群落接种实验,将不同植物下的土壤微生物群落与植物物种作交互处理,结果表明来源于不同植物下的微生物生物量存在很大差异,表明植物物种对微生物群落结构的影响可能会对其生长能力和恢复弹性造成影响。与野外田间试验一致,氮添加对土壤微生物群落和植物关系产生显著影响,主要表现为单位植物生物量下土壤微生物生物量的降低。微生物接种来源对土壤亮氨酸胺肽酶效率具有显著影响。研究中没有发现物种与微生物接种之间的交互作用,表明土壤分解微生物和植物物种之间不存在专一的作用。土壤微生物在与新的植物物种配对时可以较好继续发挥其分解功能,有助于植物群落动态下的土壤功能维持。
Other AbstractThe atmospheric nitrogen deposition rates increase rapidly since industrialization. Nitrogen enrichment not only changed species components in plant communities, it also had a great influence on soil microbial communities. Nitrogen enrichment can modify soil microbial community structures and functioning via affecting plant species components. Therefore, plant species play an important role in the response of soil ecosystems to nitrogen deposition. However, the effect of nitrogen enrichment on the relationships between plant species and microbial organisms was far from understood. The arid-hot valley characterized by a unique climate system and a fragile ecosystem. Soil microbial functioning plays a critical role in maintaining local vegetation growth. This dissertation investigated the effects of nitrogen addition (at the rates of 5g·m2·yr-1) on the coupling characters between dominant grass species and soil microbial communities. The results will help us to recognize the impact of nitrogen enrichment on soil ecosystems and deepen our understood of the linkages between soil and plants, providing a theoretical foundation for rational managing the local ecosystems. The results showed as follows:(1) The concentrations of soil carbon and nitrogen beneath planted plots were 55.0% and 44.2% higher than fallow plots. The effects of plants on soil physio-chemical properties were mediated by plant traits. The concentrations of carbon and nitrogen in soils were high beneath competitive species with high nutrient concentrations; by comparison, the concentrations of carbon and nitrogen beneath tolerant species which contain low nutrient concentrations.(2) Plants significantly affect soil microbial biomass. Soil microbial biomass in planted plots was higher by 103.5% than in fallow plots, with fungi by 116.2%, gram-negative (gram-) bacterial by 304.8% and gram-positive (gram+) bacterial by 124.6%. The gram-:gram+ in planted plots was also 72.8% higher than fallow plots. The soil microbial biomass beneath tolerant plant species was lower than competitive species, with 67.6% lower in soils beneath Eulaliopsis binata compared to the average microbial biomass beneath other plant species. Soil hydrolase activities were significantly higher in planted plots than fallow plots, with acid phosphatase (AP) by 239.7%, leucine aminopeptidase (LAP) by 95.9%, β-N-acetyl glucosaminidase (NAG) by 219.2% and β-1,4-glucosidase (BG) by 245.4%. Plant species affected soil enzyme activities and microbial biomass, due to their differences in traits. Soil enzyme activities were relatively high beneath the species with high nutrient concentrations and larger specific leaf area. However, plant species did neither affect soil enzyme efficiencies, nor stoichiometry of enzyme activities, suggesting that the coupling characters of carbon-, nitrogen- and phosphorus- acquisition enzymes were similar beneath different species.(3) Nitrogen addition reduced soil pH from 6.26 to 5.87, but increased soil available nitrogen. Nitrogen addition did not affect soil microbial biomass, but significantly reduced fungi:bacterial ratio. The correlation analyses showed that fungi:bacterial ratio was closely correlated with soil pH, suggesting that nitrogen addition affected soil community structures through reducing soil pH. Nitrogen addition reduced LAP activities by 40.6% and peroxidase (PER) activities by 30.8%, but did not affect the activities of BG and NAG. Nitrogen addition significantly increased AP activities beneath planted plots. Nitrogen addition had similar effects on enzyme efficiencies by decreasing the efficiencies of LAP, PER and increasing the efficiencies of AP, suggesting that nitrogen addition might affect soil enzyme activities via its effects on enzyme efficiencies. Nitrogen addition increased ln(BG):ln(LAP), but decreased ln(LAP):ln(AP) and ln(BG):ln(AP). The effects of nitrogen addition on the stoichiometry of enzyme activities were mediated by soil pH and microbial community structures. Nitrogen addition changed the coupling between enzyme activities and plant biomass with a decreased LAP activities under a given plant biomass and an increased slopes between AP activities and plant biomass. There were no interactions between nitrogen addition and plant species on enzyme activities, indicating that nitrogen addition affected soil enzyme activities beneath different plant species in similar ways. (4) Nitrogen addition and plant species affected soil enzyme activities through different pathways. Structure equation modelling analyses showed that nitrogen addition reduced soil pH which in turn affected activities of AP, LAP and NAG by changing microbial community structures. Soil pH had a direct effect on PER activities and the effect was not linked with microbial community structures. Soil pH did not affect BG activities. By contrast, plant species affected enzyme activities via their effects on soil microbial biomass and soil carbon concentrations, due to their differences in traits. The pathways of soil carbon were significant for all enzymes except for PER. The pathways of soil microbial biomass were significant for all enzymes. (5) Nitrogen addition significantly depressed soil respiration by 20.8% and lowered the intercept of soil microbial respiration rates and plant biomass significantly. The microbial metabolic quotients were also significantly decreased by 26.2% under nitrogen addition. Plant species affected soil microbial respiration, mainly due to the differences in traits. Species with high nutrient and large specific leaf area supported high microbial respiration rates. Plant species did not affect soil microbial metabolic quotients.(6) Nitrogen addition significantly reduced the decomposition rates of resistant carbon pool by 28.7%, but did not affect the decomposition rates of active carbon pool. Nitrogen addition also changed the coupling between the decomposition rates of resistant carbon pool and plant biomass, with decreasing the decomposition rates of resistant carbon pool under a given plant biomass. Plant species significantly affected the decomposition rates of active carbon pool and resistant carbon pool due to the differences in plant traits. The decomposition rates of active carbon and resistant carbon pool were relative high beneath competitive species compared with tolerant species. Soil microbial biomass, community structures and enzyme activities significantly affected the decomposition rates of active carbon and resistant carbon. The decomposition rates of resistant carbon were positively related to fungi:bacterial ratio, and the decomposition rates of active carbon was positively related to soil microbial biomass. The activities of NAG+BG+LAP can explain 57.4% variations in the decomposition rates of active carbon while LAP activities can explain 49.0% variations in the decomposition rates of resistant carbon.(7) Glucose addition (500mg C Kg-1 soil) substantially improved the soil microbial respiration rates and enzyme activities, indicating that there were carbon limitations in plots. The activities of NAG, LAP and AP increased by 95.6%, 68.0% and 218.8% while microbial respiration rates increased by 10.8 times under glucose addition. Enzyme activities of nitrogen enrichment soils increased more greatly than soils without nitrogen enrichment, suggesting that enzyme activities were limited by nitrogen under glucose addition. However, the positive effects of glucose addition on microbial respiration rates in nitrogen-enrichment soil were relatively low compared with in nitrogen-poor soils. The interactions between glucose addition and plantation treatment significantly affected NAG and LAP, suggesting that the enzyme activities were more seriously limited by carbon in fallow plots than planted plots. The positive effect of glucose addition on AP was correlated with soil available nitrogen, indicating that AP activities were serially limited by carbon and nitrogen. The positive effects of glucose addition on carbon acquisition enzymes were relatively low, resulting in the decreases of ln(BG):ln(LAP) and ln(BG):ln(AP). (8) The soil pH adjustment experiment here showed that elevating soil pH (about 1.0) increased soil respiration rates (74.3%) and LAP activities (25.2%), indicating that soil pH play important roles in regulating soil microbial respiration rates and nitrogen acquisition activities. Soil nitrogen net mineralization rates were also increased 62.9% by elevating soil pH. The results here suggest that soil pH is a key factor of controlling cycling of soil carbon and nitrogen. (9) Inoculum origin of microbial organisms ( from plant species) differed greatly in the microbial biomass in the microbe-plant species swap experiment, indicating that plant species effects on soil microbial community structures can affect microbial growth ability and resilience. Nitrogen addition modified soil microbe-plant relationships by reducing microbial biomass at a given plant biomass, which was consistent with the results of the field experiments. Inoculum origin of microbial organisms significantly affected soil LAP efficiencies. The lack of interactions between plant species and inoculum origin of microbes indicated that there was no specificity between the saprophytic microbes and plant species. Soil microbes derived from a given plant species can continue to maintain the decomposition function when matching with a new plant species. This will help the soil functioning under the dynamics of plant communities.
Pages132
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24585
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
闫帮国. 氮添加对干热河谷优势草本植物与土壤微生物群落关联特征的影响[D]. 北京. 中国科学院大学,2017.
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