认为扰动对高寒草地土壤有机碳及微生物学特征的影响

NWIPB OpenIR

	认为扰动对高寒草地土壤有机碳及微生物学特征的影响
其他题名	The Influence of Artificial Disturbance on the Soil Organic Carbon and Microbiological Properties in Alpine Meadow
	冯瑞章
学位类型	博士
导师	龙瑞军
	2009-05-24
学位授予单位	中国科学院西北高原生物研究所
学位授予地点	西北高原生物研究所
关键词	黄河源区高寒草地人工建植草地有机碳土壤养分微生物生物量微生物多样性土壤酶活性
摘要	黄河源区高寒草地退化与恢复是当今草地生态学研究的热点之一。目前，对于高寒草地退化生态系统的研究，主要集中在人为干扰下草地群落结构稳定性、物种多样性及土壤理化特征方面，同时，对草地退化后鼠类活动，鼠丘、洞的分布和杂类草蔓延也有一些研究，但对人为扰动后(包括退化和人工恢复)土壤不同组分的有机碳和微生物学特征缺乏系统研究。因此，本文以青藏高原黄河源区高寒草地退化和人工恢复过程中的土壤作为研究对象，采用野外调查、室内培养和相关数学分析相结合的方法，分别对未退化（UD）、轻度（LD）、中度（MD）、重度（HD）退化草地及3龄（3-year）和7龄（7-year）垂穗披碱草（E. nutans）人工建植草地不同深度土壤有机碳特征（包括总有机碳、密度分组有机碳、颗粒分组有机碳和易氧化态有机碳）、土壤养分特征（包括全氮、全磷、土壤不同颗粒组分氮、磷）及不同草地5月、7月、8月、10 月四个月份土壤微生物学特征（包括微生物生物量、微生物数量及土壤酶活性）进行研究。探讨了高寒草地退化过程中土壤质量演变的有机碳、养分和微生物机制及人工恢复中土壤—植物系统中的土壤质量恢复机制，为我国青藏高原植被恢复和重建提供土壤学方面的科学依据。主要结果如下： 1. 高寒草地退化后，草地植被盖度、物种丰富度、多样性指数、均匀度指数降低，优良牧草比例减少，毒杂草的优势度逐步增加，地下生物量急剧降低，草地利用价值丧失；在严重退化的“黑土滩”草地上建植单播垂穗披碱草（E. nutans）人工草地后，通过人为调控管理措施，多年利用后其群落组成仍然以E. nutans为优势种，同时一些优良乡土草种大量侵入。 2. 退化后的高寒草地，0-30cm土层的土壤容重和pH值增加，土壤含水量、>0.25mm水稳性团聚体百分数和团聚体平均几何直径显著降低；而人工建植E. nutans于严重退化草地上以后，以上指标呈现相反的变化趋势，土壤物理结构有一定程度的改善。 3. 草地退化导致土壤总有机碳（TOC）含量急剧降低，与未退化草地相比，轻度退化草地各土层TOC含量降低14-36%，中度和重度退化草地TOC含量分别降低38-67%和30-77%。土壤轻组（LFOC）、重组（HFOC）和易氧化态有机碳（EOC）含量及轻组有机碳占总有机碳百分比亦随草地退化逐步降低，包裹态有机碳( IFOC )的含量及占总有机碳的比例变化不明显，而重组有机碳占总有机碳的比例却逐步的增加。建植人工草地以后，土壤总有机碳含量明显升高，利用3年以后，只有表土层的TOC含量较HD增加30%；利用7年以后，土壤总有机碳较建植前的“黑土滩”草地增加17-46%；此时，表土层土壤有机碳水平与中度退化草地接近，且LFOC、HFOC、EOC含量均较建植前的“黑土滩”明显增加。 4. 当高寒草地遭受严重退化时，0-30cm深度土壤有机碳流失量大约为53 Mg ha-1，其中流失的轻组有机碳占总流失有机碳的64%；建植人工草地3年后，TOC储量没有增加，而LFOC储量有一定程度升高，利用7年以后，总有机碳、轻组和重组有机碳储量均有增加，但以LFOC储量增加为主。各草地间粗有机碳(COC)、年轻有机碳(YOC)和稳定有机碳(SOC)的含量及储量分别表现出与LFOC、IFOC和HFOC相对应的变化趋势。 5. 草地由未退化状态演替为严重退化草地后，土壤全氮(TN)、中粗沙组分氮(SCN)、极细沙粒组分氮(SFN)、粘粉粒组分氮(SCSN)含量明显降低；建植人工草地后，它们的含量均有一定程度的增加，利用7年后土壤SSN含量大于中度和重度退化草地。草地退化后氨态氮(NH4+-N)含量明显降低，而硝态氮(NO3--N)的含量有轻微增加；建植人工草地后它们的变化则正好相反。 6. 与未退化草地相比，中度和重度退化草地表层(0-10cm)土壤全磷(TP)含量降低了0.4-15.4%，而轻度退化草地与未退化草地间无差异(P >0.05)；在10-20 cm和20-30cm 土层，LD、MD 和HD全磷含量较未退化草地增加了2.9-27.8 %；建植垂穗披碱草（E. nutans）草地后，7龄草地土壤全磷含量在所有草地中最高。草地退化后，中粗沙组分磷(SCP)含量随草地退化程度加剧而降低，极细沙粒组分磷(SFP)表现与全磷相似的变化趋势，粘粉粒组分磷(SCSP)含量却逐渐升高；建植人工草地后，中粗沙组分磷 (SCP)的含量仅与中度退化草地接近，而SSP含量在所有草地中最高。 7. 从5月份到10月份，微生物生物量碳(MBC)、氮(MBN)和磷(MBP)随月份呈 “降低-升高-降低”趋势，在8份出现微生物生物量C、N和P的最大峰值。草地退化导致土壤MBC、MBN和MBP的明显下降，而人工建植E. nutans草地，是恢复草地微生物生物量的有效途径，人工建植的草地利用7年以后，MBC含量略高于中度退化草地，MBN含量则与轻度退化草接近。不同退化程度的草地中，各土层MBP的大小顺序为： LD>UD>MD>HD，经过人工种植垂穗披碱草7年以后，MBP含量达到所有样地中的最大值。MBC、MBN和MBP均表现随土层深度增加而降低的剖面分布结构。 8. 各草地微生物中，细菌数量占总微生物数量的90%以上。随季节变化，各草地细菌数量的大小顺序为： 5月份>7月份>8月份>10月份，真菌和放线菌则在7月份或者8月份达到最大值，5月份和10月份的数量较少。微生物总数、细菌和真菌随着草地退化程度的加剧而降低，建植人工草地后它们有不同程度的增加，7龄草地土壤表土层总微生物数量和细菌数量明显高于未建植的退化草地，有些土层的微生物数量与中度退化草地之间无显著差异。草地退化后放线菌的数量亦有一定降低，但建植人工草地对它的影响不大。 9. 土壤脲酶、中性磷酸酶、过氧化氢酶和脱氢酶活性均在7月份和8月份较高，5月份和10月份较低。高寒草地由未退化阶段演替为严重退化草地时，各种土壤酶活性均降低，建植E. nutans人工草地7年以后，脲酶和过氧化氢酶活性能恢复到与未退化草地相近的水平，中性磷酸酶活性能达到与轻度退化草地相近的水平，脱氢酶能恢复到与中度退化接近的水平。 10. 土壤各种物理性质、有机碳特征、养分及微生物学间的相关性分析表明，大多数指标之间显著相关，说明高寒草地土壤物理、化学性质的变化对土壤生物学性质具有重要的调控作用，而土壤生物学性质对土壤肥力的演变则具有关键影响。
其他摘要	The degradation and restoration of alpine meadow ecosystem in the source region of Yellow River has become one of the focused problems of modern ecology. Intensive studies concerning the effects of degradation and artificial restoring measures on plant population, characteristics of species, variation of plant diversity and physical and chemical properties of soil quality have been carried out in the alpine region, but very few have focused on soil organic C and microbiological characteristics during the degradation and artificial restoration in alpine meadow. Therefore, this paper systematically studied on the change of soil organic C (included total organic C, easily oxidizable organic C, density fraction organic C and particle fraction organic C), nutrients (included total N, P and particle fraction N, P), and soil microbiological properties (included microbial biomasses, microbial diversity and soil enzyme activities). Soil samples (at depths of 0–10, 10–20 and 20–30 cm) were collected from the undegraded (UD), lightly degraded (UD), moderately degraded (UD), heavily degraded meadow (UD), and three-year-old (3-year) and seven-year-old (7-year) artificial sowed grassland. The evolutive mechanism of soil organic C, nutrients, and microbial properties during the alpine meadow degradation, and biological mechanism between plant and soil system during artificial restoration were discussed. The main study results were as following: 1. When alpine meadow suffered seriously degradation, plant cover, species richness, diversity index and evenness index decreased, the proportion of palatable grasses and under-ground biomass declined sharply, whereas, poisonous weeds dominated the meadow gradually. E. natans establishment practices including ploughing up the soils and application of herbicides killed species (mainly forbs) that previously inhabited in the degraded meadows (control), such that E. natans dominated over re-established grasslands. 2. Alpine meadow degradation increased soil bulk density and promoted the soil shift from weak acidity to weak alkalinity, and soil water content, >0.25mm water-stable aggregates and mean weight diameter decreased gradually with increase of degradation degree. Sowing E. natans on degraded meadows had soil bulk density and pH decreased, soil water content, >0.25mm water-stable aggregates and mean weight diameter increased at depth 0–30 cm in 3- and 7-year old reestablished vegetation. 3. Degradation of alpine meadow resulted in sharply decreased in total soil organic C, compared with UD, LD decreased TOC by 14-36%, MD and HD decreased TOC by 38-67% and 30-77% respectively at three sampling depths. With the alpine meadow converted from UN to HD, the concentration of EOC, LFOC and HFOC, the percentage of EOC to TOC, LFOC to TOC decreased, the HFOC to TOC increased gradually. However, the content of IFOC and percentage of EOC to TOC was not affected by degradation. Total soil organic C (TOC) concentration was higher by 30% in 3-year old seeded soil only at depth 0–10 cm, and by 17–43% in 7-year old reseeded soil at three sampling depths of 0–10, 10–20 and 20–30 cm, than those in the soil under HD. The concentration of LFOC, HFOC and EOC changed as a similar pattern as TOC under different treatments. 4. When the alpine meadow suffered degraded, about 67.5 Mg ha-1 of organic C was lost in heavily degraded alpine meadow at 10-30 cm depths. The organic C of LF accounted for 64% of the total organic C lost. At the early stage of E. nutans established, the stock of total organic C varied slightly, but the store of LFOC enriched significantly. With the increasing of established years, the stocks of TOC, LFOC and HFOC increased markedly, especially for LFOC. The concentrations and stocks of COC, YOC and SOC changed as a similar pattern as LFOC, IFOC and HFOC respectively under different treatments. 5. The degradation of alpine meadow resulted in a significant decrease of soil TN, SCN, SFN, and SCSN in the headwater region of Yellow Rivers. Sowing E. natans on degraded meadows had concentrations of them enriched; after 7 year E. natans growing, the concentration of SSN was higher than that in the HD and MD soils. Soil NH4+-N decreased, and NO3--N increased generally when alpine meadow shifted from healthy conditions to heavily degraded “black soil type”, especially for surface soil (0-10 cm), the country patterns were observed for NH4+-N and NO3--N after E. natans established. 6. Total soil P concentration was decreased by 0.4–15.4% in MD and HD soils and no significantly increased in LD soil compared with the soil UD at 0-10 cm depth, respectively; at 10-20 and 20-30 cm layers, concentration of TP increased by 2.9-27.8% under three degraded meadows than that under non-degraded treatment. The maximum TP concentration was observed in the soil of 7-year re-vegetated grassland at 0-10 cm. SCP decreased with alpine meadow degradation, SFP changed as a similar pattern as TP, and SCSP increased gradually with alpine meadow converted from stage of non-degraded to heavily degraded; SCP in two re-vegetated grassland was increased to the level of it under MD, and the maximum SCSP was also found under 7-year grassland. 7. From May to October, the concentrations of MBC, MBN and MBP changed as the pattern of “decreased- increased - decreased”, the maximum of MBC, MBN and MBP was observed in August generally. Degradation of alpine meadow resulted in the decrease of the content of microbial biomass C, N, and P. Establishment E. nutans on heavily degraded ecosystem is an effective measure to restore soil microbial biomass, the content of MBC was higher than MD treatment slightly, and the content of MBN was increased to the level of LD treatment after 7 year of E. nutans growing. Among different treatment with different degraded degree, the concentration of MBP was changed as: LD > UD > MD > HD, whereas, the maximum MBP was observed in the soil of 7-year re-vegetated grassland. All of the MBC, MBN and MBP decreased with the increasing of soil depth. 8. The amount of soil microbes was different obviously, which was bacteria> antinomies> fungi, the bacteria was the dominant group, accounts for above 90% of total microbes. Bacteria changed with season as: May > August > July > October, and antinomies and fungi had higher activities in July and August. The quantity of total microbes, bacteria and fungi was decreased after alpine meadow degraded, whereas, increased to the level of MD treatment after 7 year of E. nutans growing. The number of antinomies decreased with meadow degradation, but has no significant change after artificial rehabilitation. 9. The higher activities of soil enzymes were observed in May and August. The activities of soil urease, neural phosphatase, catalase and dehydrogenase were generally higher in non-degraded soil than in degraded soils. The concentration of urease and catalase could have increased to the level of non-degraded meadow, neural phosphatase increased to the level of LD, and dehydrogenase increased to the level of MD, after 7year of artificial grassland established. 10. Correlation analysis between soil physical properties, organic C, nutrients and microbiological properties showed that most of parameters correlated with each other significant, which indicated that the changes of soil physical and chemical properties play a critical role to regular biological properties, and biological characteristic influenced soil fertility significantly in alpine region.
页数	149
语种	中文
文献类型	学位论文
条目标识符	http://210.75.249.4/handle/363003/3164
专题	中国科学院西北高原生物研究所
推荐引用方式 GB/T 7714	冯瑞章. 认为扰动对高寒草地土壤有机碳及微生物学特征的影响[D]. 西北高原生物研究所. 中国科学院西北高原生物研究所,2009.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
10001_20051801221501（1064KB）			开放获取	--	请求全文