IMHE OpenIR  > 山地表生过程与生态调控重点实验室
三峡库区消落带土壤-植物系统淹水浸泡的养分释放特征
Alternative TitleCharacteristics of Nutrient Release under Inundation from Soil And Plants in the Water-level Fluctuation Zone of the Three Gorges Reservoir
肖丽微
Subtype博士
Thesis Advisor朱波
2017
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline土壤学
Keyword三峡库区 消落带 土壤-植物 干湿交替 水体富营养化
Abstract三峡水库的运行使得消落带在淹水-落干过程中与水体之间存在大量的物质迁移和交换,成为碳氮磷等营养元素的“源”和“汇”。生长于消落带土壤上的植物生态系统与土壤相互影响,导致消落带在源汇中不断转化,进而影响整个消落带的生态环境。目前,消落带土壤-植物在淹水-落干过程中碳氮磷等营养元素的转化和迁移过程,及其对水体可能造成的污染负荷还缺乏系统的研究。因此,本研究调查了消落带土壤和植被的基本养分特征,开展典型消落带植物的原位分解实验和土壤、植物的室内模拟浸泡实验,得以了解消落带土壤-植物系统在淹水-落干周期中的源汇转化过程,查明典型优势消落带植物的淹水分解特征和土壤-植物退水落干后的养分释放过程及影响因素,估算出消落带土壤和植物淹水期可能造成的污染负荷,为三峡水库的营养源解析和水环境评价提供了基础数据。主要研究结论如下:(1)消落带土壤有机碳含量范围为 5.43~25.22g/kg,平均含量为(12.74±3.82)g/kg;全氮含量范围为 0.23~1.93 g/kg,平均含量为(0.75±0.28)g/kg;全磷含量范围为 0.16~1.28 g/kg,平均含量为(0.63±0.18)g/kg。不同地点土壤养分含量存在显著差异,不同高程土壤养分含量差异不明显。淹水能提高土壤磷的有效性,而落干则会降低有效磷的水平。反复淹水-落干后土壤中全磷含量有所下降,淹水使得土壤 Ca-P 和 Al-P 含量下降明显。O-P 则经过淹水-落干过程活化为 Fe-P后得以释放。消落带在淹水期间,土壤对养分有释放的作用,对碳、氮、磷养分的平均释放量分别为(-6065.8±8251.8)、(-335.4±637.5)、(-403.5±243.3)kg/hm2。(2)不同高程土壤在浸泡过程中上覆水 DOC 在 10-20d 及 90d 出现浓度峰值。150、160、170m 土壤 DOC 的释放量随高程的增加而增加,分别为(0.022±0.003)g/kg、(0.031±0.002)g/kg、(0.061±0.001)g/kg。DOC 的释放主要受控于土壤初始养分的含量。土壤浸泡过程上覆水 TN 浓度逐渐上升, TN 释放量随水位高程的变化为 150m>170m>160m,150、160、170m 处土壤 TN 释放量分别为(0.109±0.004)g/kg、(0.095±0.002)g/kg、(0.105±0.009)g/kg。TN 的释放与自身性质关系不大,主要受到微生物活动的影响,氮主要以 NO3-N 的形式释放。上覆水中 TP 的浓度先快速大幅上升随后逐渐降低,TP 释放量随着土样高程的升高而逐渐降低, 150、 160、 170m 处土壤 TP 释放量分别为(3.83±0.13)mg/kg、(3.81±0.04)mg/kg、(3.39±0.13)mg/kg。TP 的释放量随着土壤碳氮磷养分的增加而增加,与 N/P 显著正相关,主要释放形态为颗粒态。(3)消落带植被在经历淹水-落干循环后,植物优势种多为一年生草本植物。消落带主要优势植物包括狗根、鬼针草、水蓼、马唐、稗草、苍耳、牛鞭草、等。2015 年 9 月消落带淹水前生物量平均为(887.66±197.10)g/m2,随着水位高程增加而减少,与土壤全氮含量显著正相关。消落带植被对碳的富集系数为(38.88±8.16),对氮的富集系数为(10.71±2.67),对磷的富集系数为(4.91±0.70)。2016 年 5 月退水落干后植物残体残存量为(387.30±95.23)g/m2,随水位高程的增加而增加。(4)消落带内植被(植被残体)有机碳含量范围为 335.52~451.27 g/kg,平均含量为(411.21±14.89)g/kg;全氮含量范围为 7.70~20.58 g/kg,平均含量为(11.68±1.98)g/kg;全磷含量范围为 1.11~4.82 g/kg,平均含量为(2.65±0.74)g/kg。在落干期间,植被对养分有吸收的作用,对碳、氮、磷养分的平均吸收量分别为(2294.20±589.78)、(52.01±15.32)、(21.80±5.23)kg/hm2。消落带在淹水期间,植被对养分有释放的作用,对碳、氮、磷养分的平均释放量分别为(-2433.77±865.37)、(-58.02±34.80)、(-20.24±9.82)kg/hm2。(5)植物在浸泡过程中上覆水 DOC 的浓度在 7-10d 出现浓度峰值,120d后保持稳定,8 种消落带典型优势植物种的 DOC 平均释放量为(16.49±8.58)g/kg。不同植物之间 DOC 释放量存在显著差异。各植物浸泡时 TN 浓度在 5d 出现峰值,120d 后浓度保持不变,各植物的 TN 释放平均量为(3.35±1.22)g/kg,不同植物之间存在显著差异。其中苍耳向上覆水中释放 TN 量最大,为(5.06±0.24)g/kg;水蓼最小,仅为(1.16±0.08)g/kg。氮素在上覆水主要以 PN 和 DON为主,随着浸泡的进行,NH4-N 浓度逐渐增加。植物浸泡时 TP 在 15d 出现浓度峰值,90d 后浓度保持不变。TP 的平均释放量为(2.11±1.60)g/kg,不同植物之间存在显著差异,其中苍耳释放量最大,狗牙根、牛鞭草和水蓼的释放量相差较小。TP 的释放以 PO4-P 和 PP 为主,随着浸泡进行,PO4-P 浓度逐渐减小,PP浓度增加升高。植物在浸泡过程中氮磷元素的释放主要受植物体磷含量和初始C/P 的影响。(6)消落带优势植物淹水后分解以 30d 为转折点,前 30d 淹水主要是易溶大分子物质的快速洗脱,30d 以后则为木质素为主的慢速有机化学分解过程。8种植物的分解速率排序为马唐>稗草>牛鞭草>狗牙根>水蓼>苍耳>鬼针草>柳树茎叶。200d 淹水过程中,8 种消落带植物的平均失重速率为(0.36±0.04)%/d,其中前期平均失重速率为(1.99±0.33) %/d,后期平均失重速率较前期低 28 倍,为(0.07±0.04)%/d。植物淹水分解的释放速率与植物初始 C/N 关系明显,其中,在 C/N 为 25-50 时,分解速率随 C/N 增加而上升;C/N 为 50-100 范围时,分解速率随 C/N 增加而下降。植物的干重、有机质、全氮、全磷的损失量均受到植物初始磷含量的制约。完全分解后,植物有机碳、全氮、全磷的平均损失量为(312.40±39.97)g/kg、(6.56±4.65)g/kg、(2.25±1.25)g/kg。其中,苍耳和鬼针草的养分损失量最大,而水蓼和狗牙根的的养分损失相对较小。(7)土壤-植物系统在浸泡过程中,上覆水 DOC 浓度是逐渐增加的,且随着水位高程的增加,系统对 DOC 的释放量逐渐减少,分别为(73.76±41.04)mg/kg、(37.36±15.28)mg/kg、(31.31±23.03)mg/kg。土壤-植物系统浸泡中,TN 的浓度仅在 30-60d 发生快速上升,而后保持不变。各水位高程系统的 TN 释放大小为:150m>160m>170m,平均 TN 释放量为(37.36±15.28)m g/kg。系统中 TN 的释放以 PN 为主,占 80%以上。上覆水中 TP 的浓度变化与 TN 一致,60d 后浓度稳定。各水位高程的土壤-植物系统 TP 释放量为(10.25±1.27) mg/kg、(6.01±2.41)mg/kg、(5.70±2.18)mg/kg。浸泡过程中,PP 浓度增加增加,DP 浓度逐渐减少,最终 PP 占 TP 释放量的 90%以上。土壤-植物系统的浸泡上覆水各养分的浓度变化和释放量与土壤和植物浸泡差异明显,认为植物的根际效应是在研究消落带淹水时养分循环中不可缺乏的部分。(8)浸泡温度升高不利于土壤 TP 和植物 TN、TP 向水体释放。碱性条件能加速土壤养分的释放,而酸性和弱碱性均能促进植物分解,有利于各养分的释放。光照会极大的抑制土壤和植物淹水条件 DOC、TN 和 TP 养分释放。因此认为底层处的土壤和植物对库区水环境的影响更大。通过植物的原位分解网袋法能较好的模拟植物的淹水分解过程,是植物淹水分解动态观测的有效途径。(9)浸泡 200d 后,消落带土壤向水体中释放的有机碳、氮、磷负荷平均为104.63kg/hm2、276.75kg/hm2、9.61kg/hm2;消落带植被向水体中释放的有机碳、氮、磷负荷平均为 153.77kg/hm2、34.02kg/hm2、22.14kg/hm2;消落带土壤向水体中释放的有机碳、氮、磷负荷平均为 130.60kg/hm2、 165.68kg/hm2、 9.91kg/hm2。消落带土壤-植物系统的养分淹水释放已成为三峡水库营养物质的重要来源。
Other AbstractThe operating scheme of the Three Gorges Reservoir (TGR) results in materialsmigration and exchange during flooding and re-drying period between water-level fluctuation zone (WLFZ) and water environment. The mutual effect between soils and plants in the WLFZ makes the role of WLFZ changing from nutrients source to sink, thus affecting the ecological environment of WLFZ. However, transformation and migration process of nutrient in soils and plants in the WLFZ and the pollution load via this process are still not well understood recently. Therefore, this study was conducted by surveying the characteristics of soils and plants in the WLFZ, carrying out the in-situ experiments of plants decomposition, and stimulating the inundated process of soils and plants in laboratory. The objectives of this study were to investigate the translation process of nutrient in soils and plants in the WLFZ, to evaluate the decomposition rates of dominant plant species and nutrients release process from inundated soils and plants, and to estimate pollution loads released by inundated soils and plants in the WLFZ and thus provide a scientific basis for subsequent environmental risk assessment of the TGR. The main results and conclusions are listed below:(1)The contents of soil organic carbon (SOC) in the WLFZ is ranging from 5.43 to 25.22 g/kg, at an average of (12.74±3.82) g/kg; the contents of total nitrogen (TN) is ranging from 0.23 to 1.93 g/kg, at an average of (0.75±0.28) g/kg; the contents of total phosphorus (TP) is ranging from 0.16 to 1.28 g/kg, at an average of (0.63±0.18) g/kg. The content of SOC, TN, and TP differed significantly from different sampling sites and insignificantly from different water-level elevations. The effectiveness of soil phosphorus increased during the flooding period and decreased during the drying period. The STP content decreased after repeated flooding and drying. During the flooding period, contents of soil Ca-P and Al-P reduced and O-P can be excited andchanged to Fe-P. During the flooding period, soils released nutrients and the amount of fixed organic carbon, nitrogen, phosphorus were ( -6065.8±8251.8 ) , (-335.4±637.5),(-403.5±243.3) kg/hm2, respectively.(2) The DOC concentration in the overlying water from inundating soils at different water-level elevations of WLFZ reached its peak at 10-20 d and 90 d. The DOC amounts released by soils at water-level of 150m, 160m, 170m were (0.022±0.003) g/kg, (0.031±0.002) g/kg, (0.061±0.001) g/kg. The release of DOC wasaffected by soil initial nutrients. TN concentration in overlying water during soil inundated increased gradually with an order of 150 m> 170 m> 160 m, and the TN release amounts were (0.109±0.004) g/kg, (0.095±0.002) g/kg, (0.105±0.009) g/kg.The release of TN was affected by microbial activities and NO3-N was the mainform. TP concentration in overlying water during soil inundated increased rapidly at first and then slowed down. The amounts of TP released from soil inundated increased with water-level declined, and the amounts were (3.83±0.13) mg/kg, (3.81±0.04) mg/kg, (3.39±0.13) mg/kg, respectively. TP release amount was positive correlation with soil initial nutrients and significant correlation with N/P. The main form of phosphorus released into overlying water was particulate phosphorus.(3) Natural vegetation success to annual herbaceous plants after repeated flooding and drying. Dominant plants species in the WLFZ were Cynodon dactylon (Linn.) Pers., Bidens bipinnata Linn., Polygonum hydropiper, Digitaria sanguinalis (Linn.) Scop., Echinochloa crusgali (Linn.) Beauv., Xanthium sibiricum Patr exWidder, Hemarthria altissima (Poir.) Stapfet C. E. Hubb., and so on. Average biomass before flooding was (887.66±197.10) g/m2,with a positive relationship with STN and negative relationship with water-level elevation. The enrichment coefficient of organic carbon was (38.88±8.16), the enrichment coefficient of nitrogen was (10.71±2.67), and the enrichment coefficient of phosphorus was (4.91±0.70). The biomass afterflooding was (387.30±95.23) g/m2,with a positive relationship with water-level elevation.(4) The contents of plants organic carbon (TOC) in the WLFZ is ranging from 335.52 to 451.27 g/kg, at an average of (411.21±14.89) g/kg; the contents of total nitrogen (TN) is ranging from 7.70 to 20.58 g kg-1, at an average of (11.68±1.98) g/kg; the contents of total phosphorus (TP) is ranging from 1.11 to 4.82 g/kg, at an average of (2.65±0.74) g/kg. During the drying period, organic carbon, nitrogen and phosphorus were absorbed by plants at an average amount of (2294.20±589.78), (52.01±15.32), (21.80±5.23) kg/hm2. During the flooding period, plants will release nutrients and the amount of fixed organic carbon, nitrogen, phosphorus were (-2433.77±865.37), (-58.02±34.80), (-20.24±9.82) kg/hm2, respectively.(5) The DOC concentration in the overlying water from inundating plants at different water-level of WLFZ reached its peak at 7 to 10 d and stayed stable after 120 d. The average DOC amounts released by eight plant species were (16.49±8.58) g/kg and there were significant differences between plants. TN concentration in overlying water reached its peak at 5 d and stayed stable after 120 d. The average TN release amounts of eight plant species were (3.35±1.22) g/kg and significantly different with each other. Xanthium sibiricum Patr ex Widder. released maximum TN amount of (5.06±0.24) g/kg, while Polygonum hydropiper. released minimum of (1.16±0.08) g/kg. The nitrogen forms released to overlying water were mainly particulate nitrogenand dissolved organic nitrogen. Along with inundating, concentration of NH4-N increased gradually. TP concentration in overlying water reached its peak at 15 d and stayed stable after 90 d. The average TP release amounts of eight plant species were (2.11±1.60) g/kg and significantly different with each other. Xanthium sibiricum Patr ex Widder. released maximum TN amount, while Hemarthria altissima (Poir.) Stapfet C. E. Hubb., Cynodon dactylon (Linn.) Pers. and Polygonum hydropiper. released less. The main form of phosphorus released into overlying water was particulate phosphorus (PP) and PO4-P. Along with plants inundating, concentration of PO4-P decreased and PP increased gradually. The plants initial contents of phosphorus and C/P was pivotal for nitrogen and phosphorus releasing into overlying water via plant inundation.(6) The decomposition process of plant was divided into two stages at 30 d soaking. In the early 30 d, many dissolution materials were discharged rapidly. In the later stage, lignin broke down and plant decomposed slowly by the organic-chemical composition. The order of decomposition rate of eight plant species were as followed Digitaria sanguinalis (Linn.) Scop.> Echinochloa crusgali (Linn.) Beauv.> Hemarthria altissima (Poir.) Stapfet C. E. Hubb.> Cynodon dactylon (Linn.) Pers.> Polygonum hydropiper > Xanthium sibiricum Patr ex Widder> Bidens bipinnata Linn.> Salicaceae. The average dry weight loss rate were (0.36±0.04)% /d,(1.99±0.33)%/d at early stage and (0.07±0.04)% /d at later stage. Decomposition rate of the eight plant species were positively correlated with the plant initial C: N ratios over a range of C/N from 20 to 50. An opposite pattern was observed for C/N values ranging from 50 to 100. The losses of organic carbon, nitrogen, phosphorus in plant dry weight were affected by plant initial TP contents. After completely decomposed, the loss amount of organic carbon, nitrogen, phosphorus in plant dry weight were (312.40±39.97) g/kg, (6.56±4.65) g/kg, (2.25±1.25) g/kg. Xanthium sibiricum Patr ex Widder. and Bidens bipinnata Linn. lost most dry weight nutrient, while Polygonum hydropiper and Cynodon dactylon (Linn.) Pers. lost relatively lessnutrient during decomposition process.(7) The DOC concentration in the overlying water from inundating soil-plants increased gradually. With the increase of water-level elevation, the amount of DOC reduced. The DOC amounts of 150 m, 160 m, 170 m were (73.76±41.04) mg/kg, (37.36±15.28) mg/kg, (31.31±23.03) mg/kg. TN concentration in overlying waterincreased fast at 30 to 60 d and then remained unchanged. The average TN release amounts were (37.36±15.28) mg/kg, as an order of 150 m> 160 m> 170 m. The particulate nitrogen was the main form of nitrogen released into overlying water, accounting for over 80%. The variation of TP concentration in overlying water was in line with TN concentration. The amounts of TP released from soil-plants inundated were (10.25±1.27) mg/kg, (6.01±2.41) mg/kg, (5.70±2.18) mg/kg, respectively. Along with plants inundating, concentration of PP increased gradually and dissolved phosphorus decreased. After 200 d inundation, PP was accounted for TP at over 90%. The variations of nutrient concentration and release amounts in overlying water from soil-plants inundation significantly differed from soils and plants inundation. The discrepancy showed that rhizosphere effect was an inevitable impact on nutrient cycling during WLFZ flooding.(8) The lower the temperature, the higher amount of TN and TP will be released from soil inundation and plant inundation. Alkaline condition of soil inundation can accelerate the release of nutrients and both acidic and alkaline condition of plant inundation can promote plant decomposition and nutrients release. Light wouldgreatly inhibit the release of DOC, TN and TP during soil inundation and plant inundation. Thus, more consideration should be taken on the impact of soils and plants at bottom of WLFZ on water environment. In-situ litterbag experiment simulated the plant soaking decomposition in WLFZ effectively and it can be ahelpful way to observe the dynamic changes during the plants soaking decomposition.(9) After 200 d inundation, the loads of organic carbon, nitrogen, phosphorus of the unit area of soils in WLFZ were 104.63 kg/hm2, 276.75 kg/hm2, 9.61 kg/hm2. And the loads of organic carbon, nitrogen, phosphorus of the unit area of plants were 153.77 kg/hm2, 34.02 kg/hm2, 22.14 kg/hm2. The loads of organic carbon, nitrogen, phosphorus of the unit area of soil-plants were 130.60 kg/hm2, 165.68 kg/hm2, 19.91 kg/hm2.The nutrient loads by soil-plants in the WLFZ during the flooding period may become the main sources of nutrients in the TGR and have an important influence on the water environment of the TGR.
Pages139
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24594
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
肖丽微. 三峡库区消落带土壤-植物系统淹水浸泡的养分释放特征[D]. 北京. 中国科学院大学,2017.
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