【作者】 黄懿梅；

【导师】 曲东；

【作者基本信息】 西北农林科技大学 ， 植物营养学， 2008， 博士

【摘要】 植被恢复与土壤质量的相互作用是影响黄土高原植被重建和生态环境持续发展的关键因素。土壤微生物学性质能敏感的反映出土壤质量的变化,由于对土壤结构和养分循环的重要性以及对土壤生态过程的敏感性而日益成为土壤质量评价指标提取的重点。本论文针对土壤学和生态学研究的前沿性科学问题和黄土高原生态环境建设的需求,对黄土丘陵区典型地区—宁南宽谷丘陵区草地植被自然恢复的不同演替阶段、不同土地利用方式下土壤质量微生物指标进行了系统的研究。针对植被恢复过程,采用传统方法对土壤微生物区系、土壤微生物量、土壤微生物呼吸及磷脂脂肪酸图谱分析技术(PLFA)对土壤微生物群落结构和组成多样性进行了研究,阐明了在植被自然恢复过程中土壤微生物性质的演变规律和不同土地利用方式对土壤微生物性质的影响,为黄土高原生态恢复过程中土壤质量的恢复保育提供了理论依据。研究获得以下主要结论:(1)通过PLFA技术确定了云雾山植被自然恢复不同阶段下土壤中35种磷脂脂肪酸的含量,发现磷脂脂肪酸含量与植被恢复过程有着十分密切的关系。随着植被封育时间的延长,土壤中35种磷脂脂肪酸的含量都有所增加,其中,10Me16:0、i15:0和19:1ω11三种脂肪酸含量增加较快;16:0、18:1ω9c、18:1ω11和16:1ω9四种脂肪酸含量显著高于其他种类的脂肪酸,而2OH14:0、3OH14:0和2OH16:0三种脂肪酸含量相对较低。35种磷脂脂肪酸在草地土壤中的含量均明显高于农地土壤。直链脂肪酸18:0在农地土壤中相对含量最高;而在草地土壤中,随着植被封育时间的增加,其含量变化呈降低趋势,尤其在封育23年后,其含量相对较低。比较不同土层中脂肪酸的含量发现,在农地土壤中,18:0的含量在0-10cm土层明显高于10-20cm土层,其余脂肪酸在两个土层中含量差别不大;草地土壤中,10Me16:0和10Me17:0在10-20cm土层中的含量高于0-10cm土层,其余的脂肪酸都是上层高于下层。(2)发现在植被恢复过程中土壤主要微生物类群PLFA具有明显的变化规律。土壤中总的活体微生物、细菌、真菌和放线菌的PLFA含量都随着植被封育时间的增加呈线性增加,在0-10cm土层中,真菌PLFA含量与植被恢复时间的相关性最高;10-20cm土层中,放线菌PLFA含量与植被恢复的相关性最高;革兰氏阴性细菌(G-)和VAM真菌的PLFA含量也随着封育时间的增加呈线性增加;革兰氏阳性细菌(G+)的PLFA含量在0-10cm土层的变化没有明显的规律,在10-20cm土层随植被恢复年限的增加而增加;非特殊标记的直链磷脂脂肪酸含量的变化规律不明显。封育后的草地土壤中总的活体微生物、细菌、真菌、放线菌、革兰氏阳性细菌(G+)、革兰氏阴性细菌(G-)和VAM真菌的PLFA含量都远远高于农地土壤。(3)揭示了植被自然恢复不同阶段土壤中一些基于PLFA分类的生理指标的变化特征。用PLFA (cy17:0和cy19:0)与(16:1ω9和18:1ω11)的比值可反映土壤与环境胁迫的关系。研究发现该比值在农地土壤中高于封育后的草地土壤,在草地土壤中均表现为10-20cm土层的比值高于0-10cm土层,但在不同封育年限没有明显的变化规律。无论草地还是农地,比值均小于0.5的胁迫阈值,说明云雾山的草地土壤不存在明显的环境胁迫。在0-10 cm土层中,真菌和细菌PLFA的比值在农地和草地以及草地的不同封育年限没有明显的区别;而在10-20cm土层中则总体上随着植被恢复年限的增加而增加,说明随着植被自然恢复年限的增加,10-20cm土层中土壤有机质的含量增加,或者易被真菌利用的有机质含量增加。农地土壤中G+/G-PLFA比值略高于草地土壤。在不同恢复年限的草地土壤中,比值的变化没有明显的规律,说明不同营养利用方式的微生物群落的变化不大。(4)植被自然恢复过程中,土壤细菌和放线菌的数量呈抛物线性变化,峰值出现在封育23年左右;真菌的数量则随着植被恢复时间的增加而增大。在植被恢复中,0-20cm土壤细菌数量在植被恢复的23年和58年间出现峰值,夏季细菌数量较大。20-40cm土层则相差不大。两个土层的细菌数量在0-23年的时间段,都表现为随着植被恢复时间的增加而增大,增长率分别为11.6%和59.5%。23年后,随植被恢复年限增加,表现为下降趋势。春季土样中真菌数量总体上表现为增加趋势,植被恢复23年后土壤中真菌增加较快。真菌总体上仍然有着随植被恢复年限的增加而增加的趋势。0-20cm土层中,春季真菌的峰值分别出现在15、58和78年,且逐渐递增;夏季真菌的峰值分别出现在9和78年。20-40cm土层中,两个季节样品中真菌的变化趋势相似,都在植被恢复的73年达到最大,但数值仍然是夏季土样高于春季土样。放线菌数量0-20cm土层中放线菌的峰值在植被恢复的23年样地土壤中,在23年后,基本上呈下降趋势。(5)在植被自然恢复的过程中,土壤微生物量总体表现出随植被恢复时间的增加呈对数增大的趋势,在植被恢复的前23年增加速率较快,23年后增加缓慢。尤其是A280增量和微生物量碳的变化,能够敏感反应出植被恢复对土壤质量的影响。草地开垦后,土壤微生物量明显下降。在以上几个指标中,A280的变化率最大,其次是微生物碳,微生物氮。风干土样在一定程度上也可以反映土壤微生物量的变化,但量值略低于新鲜土样的结果。(6)土壤微生物呼吸随着植被恢复年限的增加呈对数增加趋势,土壤呼吸熵都随植被封育时间的增加呈对数降低趋势。土壤呼吸熵能够更加稳定地反映不同土壤之间的区别。新鲜样的土壤呼吸熵明显低于风干样,0-20cm土层明显低于20-40cm土层。放牧降低了土壤的基础呼吸强度,对土壤呼吸熵影响不明显;而开垦则会使土壤呼吸熵增大。风干土样可以通过预培养后测定土壤的呼吸作用,而且能够更加稳定地反映不同土壤之间的区别。在反映土壤的生物学活性大小上,累积呼吸量比呼吸强度更直观一些。(7)土壤脲酶、碱性磷酸酶、蔗糖酶和脱氢酶的活性总体上都随着封育年限的增加而呈对数增大关系。土壤酶活性对植被恢复的响应可划分为两个明显的阶段,在封育的前23年间,年均增加速率较大,而在23年后,年均增加速率较低。土壤表层这几种酶活性大于表下层,且表层酶活性的增加速率也高于表下层。两层之间的差距也有明显的阶段性,在封育的前15年或23年,差距较大,其后趋于稳定。土壤过氧化氢酶活性变化没有明显的规律。脲酶、蔗糖酶与碱性磷酸酶之间呈极显著相关关系。与封育相比,开垦后的土壤中脱氢酶、蔗糖酶、碱性磷酸酶和脲酶活性,在0-20cm土样中平均下降35.7%、56.1%、60.8%和81.5%;在20-40cm土样中平均下降31.5%、32.9%、51.7%和79.8%。过氧化氢酶活性总体表现为在0-20cm平均增加1.0%;20-40cm平均减少0.7%。(8)对土壤的微生物量测定方法进行了比较和改进。采用熏蒸-280nm紫外法与淹水培养法测定土壤微生物N的两种方法进行对比之后,初步确定风干土测定土壤微生物量时,预培养时间为10天。用熏蒸-280nm紫外法对风干和新鲜样的土壤微生物量测定结果为:新鲜样结果大于风干土,且高一定比例。两种方法在反映土壤微生物量的大小方面基本一致,风干土样在一定程度上也可以用于反映土壤微生物量的大小。在测定的精确度方面,280nm紫外比色法的重复性和平行性较好,且操作简便,误差的产生环节少。因此,可以用操作简便的280nm紫外比色法来测定土壤的微生物量N。更多还原

【Abstract】 Relationship and interaction between soil quality restoration and vegetation rehabilitation are the key factors for vegetation reconstruction and eco-environment sustainable development on the Loess Plateau. Soil microbiological characteristic can reflect the soil quality changes sensitively, also is it very important to soil structure and plant nutrition cycling. Hence, it becomes a focal point to be used as one of soil quality assessment indices. To meet the requirement of eco-environment construction in the Loess Plateau and to explore the hotspot in soil and ecology sciences, responses and evolvements of soil microbial indices in the process of vegetation restoration in Hilly-Gully Loess Plateau were studied systematically in this thesis. Soil samples under the grassland vegetation of different rehabilitation ages and different succession stages of natural recovering as research objects were selected in Hilly-Gully area and Yun-Wu mountain lies in Southern of Ning-xia province. Soil microflora, soil microbial biomass (SMB), soil microbial respiration and several soil enzyme activities were determined by traditional method; and soil microbial community diversity were detected by PLFA method. The evolvement regular pattern of soil microbial properties during the processes of vegetation natural rehabilitation and the influence of different land uses to soil microbial characteristics were found. Which can provide scientific references for vegetation rehabilitation and soil quality care in the Hilly-Gully Loess region, and enrich the theory and method for soil quality management. The results obtained were summarized as follows:(1) The 35 kinds PLFA contents of soil samples under different succession stages of natural recovering vegetation in Yun-Wu mountain were identified by GC-MS, and there has a very close relationship between the content of PLFA and the time of vegetation recovering. The 35 PLFA contents all increased with the increasing of enclosed year in grassland soil, among which, the contents of 10Me16:0, i15:0 and 19:1ω11 increased faster especially; the contents of 16:0、18:1ω9c、18:1ω11 and 16:1ω9 were marked higher than others; the contents of 2OH14:0、3OH14:0 and 2OH16:0 were lower relatively. The contents of the 35 kinds PLFA were all higher in the grassland soil than in agriculture soil clearly. The straight-saturate18:0 was high in agriculture soil, but it decreased relatively with the vegetation time prolong, and it became lower after 23 years enclosure in grassland. Except 10Me16:0 and 10Me17:0, most of PLFA were higher in surface layer (0-10cm) than subsurface layer(10-20cm) soil in grassland. In cultural soil, most of PLFA were no different in two layers, except 18:0 was higher in 0-10cm than 10-20cm. (2) The PLFA contents of total alive microbes, bacteria, fungi, actinomyces increased lineally as the vegetation recovered time increasing. In 0-10cm soil layer, the highest correlation lies between the contents of fungi’s PLFA and the vegetation recovering time; while in 10-20cm soil layer, The contents of actinomyces’s PLFA had the marked positive relevance with recovering year. The contents of G- bacteria and VAM fungi’s PLFA were also increased as the enclosure year prolonged, but G+ bacteria’s PLFA content had no clearly correlation with the enclosure years in 0-10cm layer, same phenomenon observed in straight-saturate PLFA. The PLFA contents of total alive microbes, bacteria, fungi, actinomyces, G+ bacteria, G- bacteria and VAM fungi in grassland soil were all higher than agriculture soil.(3) The ratio of PLFA (cy17:0 and cy19:0) to (16:1ω9and 18:1ω11) was higher in agriculture soil than grassland soil. It was higher in 10-20cm than 0-10cm in grassland soil, but it has no change in different vegetation rehabilitation years. The value of this ratio is less than 0.5 in both grassland soil and agriculture soil. The ratio of PLFA (fungi/bacteria) has no change in 0-10cm layer both in grassland soil and agriculture soil, even in different recovering sites. But it increased in 10-20cm layer soil along with the enclosed year extending. The ratio value of PLFA (G+/G-) was higher in agriculture soil than grassland soil.(4) Bacteria was higher in 23 year and 58 years sites in 0-20 cm during the process of vegetation rehabilitation, meanwhile, it is higher in summer soil samples. The increasing rate of Bacteria were11.6% and 59.5% before 23 years rehabilitation in two layers separately. The amount of Bacteria decreased after 23 years rehabilitation. Fungi have the different trend along with the rehabilitation years, which was increased step by step. The amount of Fungi increased faster after 23 years site than before. In 0-10 cm, fungi has three peaks of high amount in 15, 58 and 78 years sites in spring season, but the high peaks of fungi amount were in 9 year and 78 year sites in 20-40cm layer. The amount of Actinomycetes increased before 23 year site then declined after this time.(5) SMB increased in the process of vegetation rehabilitation, meanwhile, it enhanced very fast before 23 year vegetation rehabilitation then almost keep stable. Especially the changes of A280 and soil microbial biomass carbon (SMBC) can reflected the soil quality sensitively. SMB declined very fast after the grassland cultured, in which the value of⊿ A280 changed most quickly, then SMBC and soil microbial biomass nitrogen (SMBN) followed.(6) The soil basal respiration increased as the logarithm function with the vegetation recovery time extending, but the soil respiratory quotient( qCO2) decreased as the logarithm function with the vegetation recovery time extending. Soil respiratory quotient( qCO2) of fresh soil was lower than air-dried soil. Grazing reduced grassland soil basal respiration, but has no influence to qCO2. Controversially, reclamation increased qCO2 obviously. The air-dried soil can be used to measure the soil basal respiration after pre-incubation, and it can reflect the quality of soil microbial activity more stable. The cumulative respiration (CR) is more direct and clear in reflecting soil microbial activity of different soil than equivalent daily respiration (EDR).(7) The activity of soil invertase, urease, alkaline phosphatase and dehydrogenase were all increase along with the vegetation rehabilitation ages. These enzymes activity responses can be divided into two stages, they increased very quickly before enclosed 23 years and became slower after 23 years. The increasing rate in surface layer of these four enzyme activities is much higher than subsurface layer. Soil catalase activity has no obvious change regular pattern. There has clearly positive correlation among activities of soil invertase, urease, and alkaline phosphatase. Compared to enclosed land, the activity of soil dehydrogenase invertase, alkaline phosphatase and urease decreased 35.7%、56.1%、60.8% and 81.5% in 0-20cm layer after reclamation, also decreased 31.5%、32.9%、51.7% and 79.8% in 20-40cm layer.(8) Two techniques were compared that uses the UV absorbance at 280nm of 0.5M K2SO4 extracts of fumigated and unfumigated soils and fumigation-waterlogged incubation to estimate the concentrations of SMBN. The results showed that the pre-incubation days of air-dried soil to measure SMBN should be 10 days. The result of SMB using the UV absorbance at 280nm in fresh soil was bigger than from air-dried soil, but both results had same regular changing, which showed that air-dried soil can be used to measure SMB. Considering the measured accuracy,The 280nm UV absorbance technique has the advantages as followed, simple steps, less error, less time needed and better repeatability than fumigation/ waterlogged incubation method. So it can be used as the measure method of SMBN.更多还原