Knowledge Resource Center for Ecological Environment in Arid Area
| 生物结皮调节土壤水分和碳平衡的机理 | |
| 其他题名 | Mechanism of Biocrusts Regulating Soil Water and Carbon Balance |
| 欧阳海龙 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 胡春香 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 生物结皮是在干旱区中，主要由藻类(包括蓝藻和真核藻)、地衣、苔藓、菌类等生物体及其分泌物胶结、捆绑土壤颗粒，在土表形成的易剥离生物土壤复合层。结皮对荒漠生态系统的景观过程、土壤理化过程、水分循环、生物地化循环等至关重要。本论文以沙坡头地区(宁夏腾格里沙漠南缘)的和达拉特旗(内蒙古库布齐沙漠东缘)为研究地点，用室内模拟和野外实验相结合，以三个不同演替阶段结皮(藻结皮AC、地衣结皮LC、藓结皮MC)为对象，研究了其在土壤水分平衡和碳平衡中的作用机理，主要结果如下：各结皮自然含水量显著高于流沙，MC和LC较接近，显著高于早期的AC。饱和持水量随演替递增。且不同阶段间差异高于同阶段不同类型间差异。结皮生物及其分泌物、死亡残体对结皮表面粗糙度、内部孔隙度的影响，均影响持水性，且作用强度超过单纯的土壤结构和质地；但各结皮优势生物作用途径不同。无论自然结皮或生物被杀灭结皮，水分蒸发中剩余水占初始饱和水的比例MC > LC > AC。AC1蒸发最快，胶状地衣LC1-1的蒸发慢于非胶状的LC1-2。两MC中生物杀灭前后水分蒸发基本无异。MC结皮生物杀灭前后蒸发变化相对较小。整体上AC和LC中有机体对蒸发作用更大，而MC中土壤质地与结构影响更明显。各强度模拟降水下，结皮渗透时间和渗透吸水量随演替增加。渗透量与模拟降水强度无显著关系(P > 0.05)，而与厚度、粗糙度、粉粘土量、孔隙度、EPS、有机质的量、Chl a量和总生物量显著正相关(P < 0.05)，与砂粒含量、密度显著负相关(P > 0.05)。影响最明显的依次为粉粘土含量、粗糙度、总生物量、厚度、胞外多糖。瞬间少量水分下，各结皮光合活性开启和维持所需水分均较低。Fv/Fm能开始恢复的最低水分条件MC > LC > AC，其中AC2 > AC1，两LC间无显著差异(P > 0.05)，MC2 > MC1。Fv/Fm维持相对稳定值所需最低水分MC > LC > AC，其中AC2 > AC1，LC1-1 > LC1-2，MC2 > MC1。这两水分条件在不同阶段间差异高于同阶段不同类型结皮间。在瞬间少量水分下，AC总能先于LC和MC最早出现正的净光合。而两蓝藻地衣净光合碳输入对水量与持续时间的要求最高。野外实验中非降雨型水分(NRW)日形成量MC>LC2>LC1>AC2>AC1。MC的NRW持续时间和量始终最大，LC次之，AC最低；MC和LC的NRW来自大气比例更高，AC来自土壤比例最高。在NRW积累中，LC和MC来源比例相对稳定，AC来自土壤比例渐增，来自大气的比例降低。最影响结皮日最大NRW的因素依次为光合生物量、沙粒、有机质的量、粗糙度和孔隙度。随演替进行，主要气象因素对NRW积累的影响存在一定的规律和差异。两AC相似，地表温度影响最强，LC1也如此。地下5 cm土温对LC2和MC影响最强。从AC2开始光强作用渐增，到LC2和MC已仅次于地下5 cm土温。随结皮演替，地表温度影响减弱，而地下5 cm土温和空气相对湿度影响渐增。夜间NRW积累过程中适应结皮的光合活性逐渐恢复但模式不同。两AC恢复最早最慢，LC2和MC较晚但一旦开始后较迅速。日出后光合活性均随NRW减少迅速降低。夜间水量积累到一定程度，结皮开始呼吸作用；当水量合适，日出前后光强增加时四种结皮均有一段 (2-3 h)净光合积累，且整个过程能获得净碳收入。AC和LC2日净碳流量与日最大NRW量呈三次方关系， MC日碳流量与日最大NRW量呈二次方关系。室内模拟实验温度范围内(-2.5 ~ 10 °C)水饱和时，各结皮获正Pn的最低光强均随温度增加，且MC > LC > AC2 > AC1。温度和光强共同影响结皮碳交换，各结皮净光合Pn与温度呈负相关，与光强正相关；而总光合Pg与温度和光强均呈正相关。该温度范围内，光强对Pn和Pg的预测力均要高于温度。等效NRW量下，除LC1其他结皮出现正Pn的最低光强也随温度增加，但升高趋势不如水饱和时明显。光强 ≤ 10 μmol m-2 s-1时，各结皮Pn均与温度呈反比而与光强成正比，且对Pn的预测大部来自光强。25-400 μmol m-2 s-1光下，除LC1的Pn仍与温度呈反比而与光强呈正比外，各结皮Pn与温度和光强均呈正比。温度对两AC的Pn的预测力大幅增加而光强预测力降低，LC1中温度预测力也明显增加，而LC2和MC中温度预测力变化不大。光强≤ 10 μmol m-2 s-1时，对Pg的预测主要来自光强。而25-400 μmol m-2 s-1光下，AC1，AC2和LC1的Pg的主要预测力都来自温度，温度对LC2和MC的Pg的预测力有提高但比其他三结皮要弱。两水分下，结皮暗呼吸与水含量和温度均呈负相关。其中水含量和温度对AC2和两LC的暗呼吸分别具有相当程度的预测力。AC1中水含量对暗呼吸的预测力远高于温度，而MC中温度对暗呼吸的预测力要远高于水含量。野外微宇宙实验中，光强直接积极影响温度(气温和地表温度)，温度直接消极影响NRW量，而光强也可直接影响NRW量。最终光强、温度和NRW量共同影响碳交换。两AC的NRW量主要受地表温度影响。影响其碳交换的最强因素是积极作用的气温，其次是消极作用的地表温度，然后才是NRW量，光强影响较弱。LC1的NRW量受地表温度的影响较弱，而主要受气温影响。其碳交换最主要受地表温度影响，其次是气温和光强，尤其是光强的影响在所有结皮中最高，NRW影响仍较弱。LC2和MC的NRW主要受光强和气温的消极影响。而NRW对其碳交换的积极作用显著高于其他三种结皮，但气温的影响显然低于两AC。同时光强对LC2和MC的碳交换有积极影响。 |
| 英文摘要 | Biocrusts, a complex association of soil particles and organisms within the uppermost millimeters of the soil surface, widely distribute in arid regions throughout the world and mainly composed of cyanobacteria, algae, bacteria, fungi, lichens and mosses. Biocrusts play a vital role in many ecological progresses of desert ecosystems, including landscape progress, soil physical and chemical process, water cycle, and biogeochemical cycle. This work carried out a series of laboratory simulation and in situ field experiments in Shapotou regions (southern edge of Tengger Desert, Ningxia) and Dalateqi (eastern edge of Qubqi Desert, Inner Mongolia) studying the action mechanism of three stages of biocrusts (algae crusts-AC for short; lichen crusts-LC and moss crusts-MC) in soil water and carbon balance. The main results are as follow: Natural water content (NWC) of biocrusts is significantly higher than shifting sand. NWCs of MCs and LCs are higher than that of earlier AC. Saturated water content (SWC) increases with successional stages. The difference of SWC among stages is higher than that between biocrusts in the same stage. The influences of biocrust organisms and their excretions, residual body on roughness and porosity, all have impacts on water holding capacities, which is stronger than that of soil structure and texture only. But action pathways of various dominated organisms are different. No matter for natural biocrusts or the ones with killed organisms, after same period, the percentage of remaining water to the initial saturated water keeps the pattern of MC>LC>AC. AC1 always losts water quickest. The water in LC1-1 evaporates more slowly than LC1-2. There is no difference for two MCs. Overall, for evaporation, organisms in ACs and LCs play a more important role than that in MC, while the influences of soil texture and structure are stronger in MC than that in ACs and LCs.It takes longer time and needs more water to infiltrate the crust soil in later successional stages. There is no significant relationship between infiltration capacity with simulated rainfall intensity (P > 0.05), but there is significant positive correlation with physical properties (thickness, roughness, powder, clay content, porosity and and biochemical properties (EPS, organic quality, photosynthetic biomass and total biomass) (P < 0.05), and significantly negative correlate to sand content and density (P > 0.05). The most obvious influencing characteristics of crusts are silt and clay content, roughness, total biomass, thickness and extracellular polysaccharide (EPS). Under the instantaneous water conditions, the water content that biocrusts need to open and maintain photosynthetic activities is not much. The minimum water content under which Fv/Fm can reactivate is in such an order: MC >LC > AC. AC2 needs more than AC1, MC2 needs more than MC1, while there is no significant difference between two lichens (P > 0.05). The minimum water content under which Fv/Fm can remain relatively stable high level is such an order: MC > LC > AC. AC2 needs more than AC1, LC1-1 than LC1-2, MC2 than MC1, respectively. The differences of water threshold among different successional stages are higher than that between crusts in the same stage. Under the instantaneous and small quantity of water condition, the two ACs always obtain positive net photosynthesis earliest and are prior to LCs and MCs. The net carbon input of the two cyanolichens needs the highest water content and the longest duration.During the accumulation process in field experiments, it is found that MC always has the highest NRW and lasts longest, then LC, and AC the lowest and shortest. The NRW of MC and LCs have a higher percentage from atmosphere while ACs have a higher percentage from soil. In the accumulation process, the percentages of different sources are relatively stable for NRW of LC and MC, while the percentage from soil increases gradually and the proportion from atmosphere decreases in ACs. The characteristics that most influence the maximum NRW are photosynthesis biomass, sand content, organic matter amount, roughness and porosity. During the accumulation of NRW, the most important meteorological factors are different and in the following pattern: for ACs and LC1 is surface temperature while for LC2 and MC is 5 cm depth temperature. The effects of light intensity gradually enhanced, for LC2 and MC light intensity has become the second to 5 cm depth soil temperature. Influence of surface temperature weakens gradually with the development and succession of biocrusts, while that of 5 cm depth soil and RH gradually increased. Photosynthetic activities of biocrusts which have adapted recover gradually in different models during the accumulation of NRW in the night. AC recovers earliest but slowest. LC2 and MC recover later but very quickly. Photosynthetic activities decrease rapidly with the reduction of NRW after sunrise. Biocrusts begin respiration when NRW accumulates to a certain degree and are able to have a period of (2-3 h) net photosynthetic accumulation and obtain net carbon income. The daily net carbon flux of ACs and LCs is cubic correlated to daily maximum NRW, while for MC is quadratic with maximum NRW.Under temperature range of simulated experiments (2.5 ~ 10 °C) and saturated soil wate, the minimum light intensity that biocrusts required to gain positive Pn increases with temperature and in such an order: MC>LC>AC2>AC1. Temperature and light intensity affect CO2 exchange together. For all biocrusts, Pn is negatively correlate with temperature and positively correlate with light intensity. Pg is positively correlated with temperature and light intensity. In that temperature range, light intensity has more predictive power on Pn and Pg than temperature. Under equivalent NRW amount, the minimum light intensity that other biocrusts required to gain positive Pn increase with temperature other than LC1, but not so obvious as moisture is saturated. Under light intensity less than 10 μmol m-2 s-1, Pn is inversely proportional to temperature and proportional to light intensity, and the prediction for Pn most come from light intensity. Under light of 25-400 μmol m-2 s-1, Pn of LC1 is still inversely proportional to temperature and proportional to light intensity, while the Pn of other crusts all proportional to temperature and light intensity. Meanwhile, for Pn of AC1 and AC2, the predictive power of temperature increased greatly and that of light intensity reduced sharply; for LC1, the predictive power of temperature also increase significantly; but for LC2 and MC, the predictive power of temperature does not change significantly. When light intensity is not higher than 10 μmol m-2 s-1, the forecast of Pg mainly comes from light intensity. Under 25 - 400 μmol m-2 s-1, for AC1, AC2 and LC1 the forecast of Pg mainly come from temperature and the predictive power of light intensity reduces; for LC2 and MC the predictive power of temperature for Pg improved but still weaker than other crusts.Under the two water conditions, dark respiration is negatively correlated with water content and temperature. For AC2, LC1 and LC2, water content and temperature both have considerable predictive power. For AC1, predictive power of water is far higher than temperature, while for MC the predictive power of temperature is much higher than water.In microcosm experiments, light intensity has directly positive influence on temperature (air and surface temperature), temperature directly and negatively impact NRW, and light intensity also can directly affect NRW amount. Light intensity, temperature and NRW affect carbon exchange together. For ACs, NRW is mainly affected by surface temperature. For their carbon exchange, air temperature has strongest and positive effect, followed by surface temperature with negative effect, then NRW amount, the influence of light intensity is relatively weak. The NRW of LC1 is mainly affected by air temperature. Its carbon exchange is mainly affected by surface temperature, followed by air temperature and light intensity, especially light intensity has the highest influence in all biocrusts, while influence of NRW is still weak. NRW of LC2 and MC is mainly affected by the negative influence of light intensity and air temperature. Among the factors affecting their carbon exchange, the positive effect of NRW is significantly higher than that in other three crusts, but the influence of temperature is obviously less than two ACs. At the same time, light intensity has a positive impact on carbon exchange of LC2 and MC. |
| 中文关键词 | 生物结皮 ; 水分平衡 ; 碳平衡 ; 非降雨型水 |
| 英文关键词 | biocrusts water balance carbon balance non-rainfall water |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 水生生物学 |
| 来源机构 | 中国科学院水生生物研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287839 |
| 推荐引用方式 GB/T 7714 | 欧阳海龙. 生物结皮调节土壤水分和碳平衡的机理[D]. 中国科学院大学,2017. |
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