三峡库区消落带植被对土壤养分的吸收及其淹水释放特征
文献类型：学位论文
| 作者 | 谭秋霞 |
| 学位类别 | 硕士 |
| 答辩日期 | 2013 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 朱波 |
| 关键词 | 三峡库区 消落带 植被 淹水 碳氮磷释放 影响因素 |
| 其他题名 | Nutrient Absorption from Soil by the Herbaceous Vegetation and Release from the Grass Plants under Inundation in the Water-Level Fluctuation Zone of the Three Gorges Reservoir Area |
| 学位专业 | 环境工程 |
| 中文摘要 | 水体富营养化问题已成为全球水环境面临的重要挑战，我国江河、湖泊、水库的富营养化问题日益突出，长江流域的水质也不容乐观，特别是三峡水库建成后，将形成一个巨大的特殊消落带，每年9月底蓄水后消落带植被淹没并开始腐解，导致有机体分解向水体释放碳、氮、磷等养分，该过程是否会成为三峡库区水体富营养化的重要来源还不得而知。本研究借鉴陆地生态系统凋落物分解研究方法，通过对三峡库区消落带植被生物量、土壤和植物养分的采样分析和室内模拟浸泡实验，试图查明消落带植被在淹水后碳氮磷的释放形态、释放量及其主要影响因素，为三峡库区蓄水期间植物淹水后养分释放量提供基础数据，弥补三峡库区生态恢复重建风险评估的不足。主要结论如下： （1）消落带土壤有机质含量范围在13.68~27.10g/kg之间，平均含量为（19.86±3.83）g/kg，全氮含量范围在0.61~1.50g/kg之间，平均含量为（0.99±0.24）g/kg，全磷含量范围在0.34~0.91g/kg之间，平均含量为（0.56±0.15）g/kg，同时，消落带土壤养分含量的区域差异显著。 （2）消落带植被经过反复淹水与出露后，演替成以草本植物为主的植被类型，蓄水对消落带植被群落的影响非常明显，低水位带主要为耐淹的水生植物，高水位带主要为旱生植物。优势物种主要有苍耳、苋菜、铁线蕨、牛毛毡、水蓼、稗子、空心莲子草、苦蒿、狗尾草、狗牙根、马唐、牛鞭草等，优势物种的分布区域和带位差异显著。消落带植被生物量范围为336.48~874.42g/m2，平均生物量为（540.12±8.68）g/m2，地上生物量存在显著的区域差异。消落带内的植被除受土壤及水文条件影响外，还受地形、坡度等多种因素的影响。 （3）消落带主要优势草本植物的全碳含量范围在36.63~45.97%之间，全碳平均含量为（43.52±3.19）%；全氮含量范围在0.51~1.79%之间，平均含量为（1.21±0.54）%；全磷含量范围在0.01~0.63%之间，平均含量为（0.32±0.06）%，不同类型植物的养分含量差异显著。消落带优势草本植被所固定的有机碳量平均为（2327.83±805.57）kg C/hm2，对土壤氮磷的吸收量分别为（51.18±14.77）kg N/hm2和（15.90±4.56）kg P/hm2。消落带植被对碳氮磷的吸收量存在显著的区域和带位差异。消落带优势草本植物对氮的富集系数范围在5.75~22.21之间，平均富集系数为（13.82±3.23），苍耳对氮的富集能力较强，狗尾草对氮的富集能力较弱；对磷的富集系数范围在2.71~6.70之间，平均富集系数为（4.65±1.61），旱生植物（苍耳、狗尾草等）对土壤磷的富集能力较强，水生植物（空心莲子草等）对土壤磷的富集能力较弱。 （4）消落带植物在淹水浸泡过程中干重损失最大为苋菜，最小为铁线蕨，平均干重损失为（51.14±3.47）%。主要优势植物的干重损失顺序为：苋菜>苍耳>空心莲子草>稗子>牛毛毡>水蓼>苦蒿>狗尾草>牛鞭草>铁线蕨，植物干重损失率与其含水量呈显著正相关关系，与N含量呈显著正相关关系，与C/N呈显著负相关关系。 （5）主要优势草本植物在淹水浸泡过程中DOC的释放过程动力学方程为y=alnx+b，不同物种的释放系数（a）差异较大，旱生植物苦蒿等的释放系数较大，水生植物如空心莲子草等释放系数较小。DOC释放量最小水蓼为（6.51±1.62）mg/g，最大苦蒿为（48.54±6.49）mg/g，平均释放量为（18.15±3.92）mg/g，不同草本植物的释放量差异显著。释放量大小为：苦蒿>苍耳>牛毛毡>苋菜>狗尾草>稗子>水蓼>空心莲子草>铁线蕨>牛鞭草。DOC释放量与初始基质的C/N值呈显著正相关关系。平均释放速率最大为苦蒿（10.35mg±2.89）mg/(g?d)，最小为牛鞭草（0.16±0.01）mg/(g?d)，主要优势草本植物的平均释放速率平均值为（1.96±0.34）mg/g.d，不同植物物种间释放速率差异显著，释放速率大小关系为：苦蒿>苍耳>牛毛毡>苋菜>狗尾草>稗子>水蓼>空心莲子草>铁线蕨>牛鞭草。 （6）植物在淹水浸泡过程中总氮（TN）的前期释放较快，后期趋于平稳，符合动力学方程y=alnx+b，不同植物物种间释放系数差异较大，空心莲子草等水生植物的释放系数较小，而苦蒿等旱生植物释放系数较大。TN释放量最大为苍耳（10.32±2.56）mg/g，最小为牛鞭草（0.57±0.15）mg/g；TN的平均释放速率最大为苍耳（0.49±0.03）mg/g.d，最小为铁线蕨（0.016±0.01）mg/g.d，不同物种总氮的平均释放速率差异显著。植物浸泡过程中上覆水的氮素形态变化明显，前期（30d前）有机氮（ON）浓度增加较快，30d后出现净减少并趋于稳定；铵态氮（AN）30d前浓度较高，30d后出现净减少，在整个释放过程中AN浓度波动较大；硝态氮（NN）在15d前的浓度很低，后期浓度增加，且持续升高。植物浸泡过程中氮素释放形态主要以有机氮为主，不同形态氮素的释放量占释放总氮的比例为ON 80.26%，AN 17.68%，NN 1.94%；DN 55.77%，PN44.17%。TN的平均释放量为（4.06±1.90）mg/g，ON（3.11±1.27）mg/g，AN（0.81±0.24）mg/g，NN（0.10±0.02）mg/g，DN (2.32±0.34)mg/g，PN（1.72±0.21）mg/g。植物不同形态氮的释放量与初始基质全氮含量呈显著正相关关系，与C/N呈显著负相关关系。 （7）植物在淹水浸泡过程中TP前期释放快，后期趋于平稳，均符合对数方程(y=alnx+b)，总磷释放峰值浓度最大为狗尾草（33.44±2.71）mg/L，苍耳达到（18.92±1.01）mg/L，其余几种植物均在10mg/L左右，最小为苋菜（2.46±0.23）mg/L。苍耳的释放量最大达到（5.26±0.09）mg/g，最小为苋菜（0.51±0.10）mg/g。苦蒿的释放速率最大(0.11±0.01)mg/g.d，水蓼、苍耳次之，铁线蕨的释放速率最小(0.004±0.001)mg/g.d。植物浸泡过程中上覆水的磷素形态变化明显，有机磷（OP）除苦蒿在第15d时达到释放浓度峰值，其余几种植物在30d达到释放浓度峰值；可溶性磷酸盐（OPP）的释放过程曲线与总磷相似；颗粒态磷（PP）除苦蒿在第15d达到释放峰值，牛鞭草在第60d到达释放峰值，其余几种植物在30d达到释放峰值。释放过程中不同形态磷的占总磷的比例为DP 77.14%，PP 22.82%；OPP和OP占总磷的比例为OPP 64.64%，OP 35.32%。TP释放量为（1.95±0.57）mg/g，OP为（0.68±0.21）mg/g，OPP为（1.22±0.12）mg/g，DP为（1.46±0.23）mg/g，PP为（0.48±0.11）mg/g。消落带优势草本植物在淹水过程中不同形态磷的释放量与初始基质磷含量呈显著正相关关系，与N/P含量呈显著负相关关系。 （8）pH值对植物浸泡过程中养分的释放量存在不同的影响，酸性和碱性条件有利于氮的释放，酸性条件有利于磷的释放，碱性条件有利于DOC的释放，干重损失率为碱性>中性>酸性；扰动可能增加植物在浸泡过程TN和TP的释放量，对DOC的释放量影响较小。温度升高有利于TN、DOC的释放，温度升高有利于植物的腐烂分解。 （9）三峡库区消落带植被在淹水200d后，DOC的单位面积释放量为（234.59±74.11）hm2；TN为（17.97±3.63）kg/hm2、ON为（14.15±2.85）kg/hm2、AN为（3.23±0.65）kg/hm2、NN为（0.52±0.10）kg/hm2、DN为（11.85±2.40）kg/hm2、DON为（8.02±1.68）kg/hm2、PN为（6.04±1.22）kg/hm2；TP为（10.92±3.39）kg/hm2、OP为（4.91±1.53）kg/hm2、OPP为（5.95±1.86）kg/hm2、DP为（8.42±2.62）kg/hm2、PP为（2.49±0.77）kg/hm2、DOP为（2.44±0.76）kg/hm2。不同地区单位面积内养分释放量差异显著。三峡库区消落带(重庆段291.1km2)植被淹水200d内的养分释放负荷为：DOC 6829.03t；TN 523.01t、ON 412.05t、AN 94.02 t、NN 15.23t、DN 345.01t、DON 233.56t、PN 175.82t；TP 317.85t、OP 143.17t、OPP 171.12t、DP 245.10t、PP 72.48t、DOP 71.13t。完全腐烂分解释放负荷为：TN 1489.97t，TP 462.84t。三峡库区消落带植被淹水后养分的释放负荷可能成为三峡库区水体营养物的重要来源，并可能成为影响三峡库区水环境安全的重要因素。 |
| 英文摘要 | Eutrophication has become one of the most important challenges of the global water environment. The eutrophication trend of rivers, lakes, reservoirs in China are prominent. Water quality of the Yangtze River is also influnced by eutrophication, especially in the Three Gorges Reservoir (TGR). TGR runs in the regime of “desilting for clear water storage” in terms of flood control, power generation, shipping and flushing. TGR runs in the low water level at about 145 m (above sea level) to control flood and drainage sediment in the raining season (May – late September); while TGR starts to fill up to the high water level of 175 m (above sea level) in autumn (since late September) to meet need for the power generation. Then, TGR forms a water-lever fluctuation zone (WLFZ) with a fall of 30 meters and an area of 349 km2. After impoundment at the end of September of each year, a large area with vegetation is submerged, organisms begin to decompose with a large quantity of nutrient release to the water. We doubted this process may become an important source of water eutrophication of the Three Gorges Reservoir. This study was conducted through methods of litter decomposition, biomass harvest and plant and soil sample collection from terrestrial ecosystem research. Meanwhile, simulated experiments indoors to identify the characteristic of carbon, nitrogen and phosphorus release from decomposition of plant were conducted to learn nutrient releasing forms, fluxes and impacting factors. The results and conditions are listed as follows: (1) The soil organic matter (SOM) in WLFZ is the range of 13.68~27.10 g/kg with average being (19.86±3.83)g/kg; total nitrogen (TN) content is in the range of 0.62~1.51 g/kg with average being (0.99±0.24) g/kg; total phosphorus (TP) is in the range of 0.35~0.92 g/kg with average being (0.56±0.150) g/kg. (2) Natural vegetation successes to herbaceous vegetation after repeatedly impoundment and dry up. However, water level of WLFZ impacts the vegetation community greatly. In the WLFZ of low water level, vegetation consisted mainly of aquatic plants which had higher submerging tolerance, whereas, in the high level of WLFZ, there were mainly xerophytes plants. Coverage of the dominant species in different water-level was significantly different. The dominant species were Xanthium sibiricum，Amaranth，Adiantumcapillus-veneris，Eleocharisyokoscensis, Polygonumhydropiper, Echinochloacrusgalli (L.)Beauv, Xanthium sibiricumPatrin, AlternantheraphiloxeroidesGriseb, Centaureapicris Pall, Setariaviridis Beauv, Setaria viridis, Cynodon dactylon, Digitaria ciliaris, Hemarthria altissima, and so on. Plant biomass ranged from 336.48 to 874.42 g/m2 with average biomass being (540.12±8.68) g/m2. The aboveground biomass showed significant difference in different region. The vegetation types and soil physico-chemical characteristics in WLFZ were influenced by not only hydrological regimes and soil types, but also topography and slope gradient. (3) The organic carbon contents of dominant plants in WLFZ ranged from 36.63% to 45.97% with the average being (43.52±3.19) %; TN contents were in range of 0.51 to 1.79% with average being (1.21±0.54) %; TP contents were in range of (0.01 to 0.63) % with average being (0.32±0.06)%. There are significant differences for nutrient contents between different plants. Organic carbon in the plants of WLFZ ranged in (2327.83±805.57) kg/hm2; while TN and TP of vegetation absorbed were in range of (51.18±14.77) kg/hm2 and (15.90±4.56)kg/hm2 respectively. The enrichment coefficient of nitrogen ranged in (5.75 to 22.21), with average being (13.82±3.23). Xanthium sibiricum had the highest enrichment coefficient of nitrogen, whereas, SetariaviridisBeauv had the lowest. The enrichment coefficient of phosphorus ranged in (2.71 to 6.70), with average being (4.65±1.61). Xerophyte (such as xanthium sibiricum and setariaviridisBeauv) had the highest enrichment coefficient of phosphorus. Aquatic plants（such as AlternantheraphiloxeroidesGriseb）had the lowest. (4) The maximum plants’ dry weight loss rate under simulated inundation was amaranth, and the minimum was Adiantumcapillus-veneris, with the average being (51.14±3.47) %. The order of dry weight loss rate were as followed Amaranth > Xanthium sibiricum > AlternantheraphiloxeroidesGriseb > Echinochloacrusgalli > Eleocharisyokoscensis > Polygonumhydropiper > Centaureapicris Pall > SetariaviridisBeauv > Hemarthria altissima > Adiantumcapillus-veneris. Plant dry weight loss rate and its water content was significantly positive correlation, positive correlation with the content of total nitrogen, negative correlation with the content of total phosphorus. (5) In the process of flooding simulated, the DOC release process presented an equation as y=alnx+b. Releasing factor (a) of the different species were quite different. Aquatic plants were smaller, xerophyte were lager. The minimum amount of DOC released was Polygonumhydropiper with release quantity of (6.51±1.62) mg/g; the maximum was Centaureapicris Pall with release quantity of (48.54±6.49) mg/g. Average DOC release amount was (18.15±3.92) mg/g. The amount of DOC released and its C/N was significantly positive correlation. The maximum of the average release rate was Centaureapicris Pall in (10.35mg±2.89）mg/(g?d), the minimum was Polygonumhydropiper in (0.16±0.01）mg/(g?d) with average of average release rate (1.96±0.34) mg/(g?d). There were significant differences between different plants. (6) The total nitrogen (TN) released quickly in the early days, and slowly in the late period under immersion experiment condition. The release process conformed the kinetic equation in the form of y=alnx+b. Releasing factor (a) of the different species were quite different. Aquatic plants were smaller, xerophyte were lager. The largest amount of TN released to the overlying water was Xanthium sibiricum in (10.32±2.56) mg/g, while, the smallest was Hemarthria altissima in (0.57±0.15) mg/g under emmersion. The maximum release rate of TN was Xanthium sibiricum in (0.49±0.03) mg/g.d, the smallest was Adiantumcapillus-veneris in (0.016±0.01) mg/g.d. The average release rate showed a significantly difference between plant species. The nitrogen forms released to the overlying water changed rapidly. Organic nitrogen (ON) released quickly in the early days of immersion (30d), and slowly in the late period. The concentrations of ammonium nitrogen (AN) were high in the first 30 days, and slowly decreased in the late days of immersion. The concentrations of nitrate nitrogen (NN) of the overlying water were low in the first 15 days, then increased continuously to the late period of immersion. Different nitrogen forms in the total nitrogen released to the overlying water were in following, ON 80.26%, AN 17.68%, NN 1.94%; DN 55.77%, PN 44.17%. The amounts of TN released were (4.06±1.90) mg/g, ON (3.11±1.27) mg/g, AN (0.81±0.24) mg/g, NN （0.10±0.02）mg/g, DN (2.32±0.34) mg/g, PN (1.72±0.21) mg/g. The amount of nitrogen forms released to the overlying water showed a significant positive correlation with plants’ C/N. Meanwhile, the amount of released nitrogen forms was in a significant negative correlation with total nitrogen contents of the initial experimented plants. (7) The total phosphorus (TP) released quickly in the early days, and slowly in the late period under immersion experiment condition. The release process conformed the kinetic equation in the form of y=alnx+b. Releasing factor (a) of the different species were quite different. The largest peak concentration was SetariaviridisBeauv. (33.44±2.71)mg/L, Xanthium sibiricum (18.92±1.01)mg/L, the smallest was Amaranth (2.46±0.23)mg/L, and the other plants were around 10 mg/L. The largest amount of TP released to the overlying water Xanthium sibiricum (5.26±0.09) mg/g, the smallest was Adiantumcapillus-veneris (0.51±0.10) mg/g. The maximum released rate was Centaureapicris Pall (0.11±0.01)mg/g.d, followed by Polygonumhydropiper and Xanthium sibiricum, the smallest was Adiantumcapillus-veneris (0.004±0.001)mg/g.d. The phosphorus forms released to the overlying water changed rapidly. Organic phosphorus (OP) reached the concentration peak in the first 30d, and Centaureapicris Pall in the first 15d. The release process curves of OPP were similar with TP’s. Particulate phosphorus(PP) reached the concentration peak in the first 30d, centaureapicris in the first 15d and hemarthria in the first 60d. Different phosphorus forms in the total phosphorus released to the overlying water were in following DP 77.14%, PP 22.82%; OPP 64.64%, OP 35.32%. The amount of TP released were (1.95±0.57) mg/g, OP (0.68±0.21)mg/g, OPP (1.22±0.12) mg/g, PP (0.48±0.11) mg/g, DP (1.46±0.23) mg/g. Meanwhile, the amount of released phosphorus forms was in a significant negative correlation with total phosphorus contents of the initial experimented plants. (8) Impacts of pH on nutrient release under immersion were different. Acidic and alkaline conditions were conducive to nitrogen release, while acidic conditions were propitious to phosphorus release. The dry weight loss rate of immersed plants followed pH changed in alkaline>neutral>acidity. The alkaline conditions were conducive to the release of DOC. Human disturbance may increase the amount of TN and TP release in the soaking process. Increasing temperature was in favor of TN and DOC release. (9) The amount of nutrient released from soaded plants were as following: DOC (234.59±74.11) kg/hm2; TN (17.97±3.63) kg/hm2, ON (14.15±2.85) kg/hm2, AN (3.23±0.65) kg/hm2, NN (0.52±0.10) kg/hm2, DN (11.85±2.40) kg/hm2, DON (8.02±1.68) kg/hm2, PN (6.04±1.22) kg/hm2; TP (10.92±3.39) kg/hm2, OP (4.91±1.53)kg/hm2, DP (8.42±2.62)kg/hm2, PP(2.49±0.77)kg/hm2, OPP(5.95±1.86)kg/hm2, DOP(2.44±0.76) kg/hm2 in WLFZ of the Three Gorges Reservior Area in the inundation period of 200 days. However, nutrient release amount were significant differences in different regions. The loadings of nutrient released from plants were as following, DOC 6829.03t; TN 523.01t, ON 412.05t, AN 94.02 t, NN 15.23t, DN 345.01t, DON 233.56t, PN 175.82t; TP 317.85t, OP 143.17t, OPP 171.12t, DP 245.10t, PP 72.48t, DOP 71.13t in WLFZ of the Three Gorges Reservior Area (in Chongqing with area 291.1km2) when inundated in water. The loadings of plants by completely decomposing were TN 1489.97t, TP 462.84t. The nutrient loadings from plants released under flooding period may become an important nutirnt source of the Three Gorges Reservoir. |
| 语种 | 中文 |
| 公开日期 | 2014-08-26 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/7141]  |
| 专题 | 成都山地灾害与环境研究所_山地表生过程与生态调控重点实验室 |
| 推荐引用方式 GB/T 7714 | 谭秋霞. 三峡库区消落带植被对土壤养分的吸收及其淹水释放特征[D]. 北京. 中国科学院研究生院. 2013. |
入库方式： OAI收割
来源：成都山地灾害与环境研究所
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