| 其他摘要 | 湿地硫的生物地球化学过程在湿地生态系统中起着重要作用，是与碳矿化、水体酸化、黄铁矿的形成，金属元素循环以及大气硫释放等一系列重要生态过程联系在一起的。为了更好地了解硫在湿地生态系统中的地位和作用，本论文以三江平原草甸小叶章湿地为研究对象，通过野外定位观测、室内培养、模拟控制试验，研究了小叶章湿地硫的形态分布和转化过程，建立了大气－土壤－植物系统硫的循环模式，探讨了影响湿地硫动态变化的主要因素，揭示了开垦、水位和外源硫输入对湿地硫状况的影响规律。研究得到的主要结论如下： 初步明确了大气向沼泽湿地系统输入SO42-的量具有明显的季节性，与当地大规模的秸秆焚烧活动、降水强度及频次以及该区的风向和地理位置有关。通过大气湿沉降输入到沼泽湿地系统的硫为1.33 kg S.hm-2.a-1，这在为生态系统提供硫营养的同时也有可能引起生态系统的酸化。 典型草甸小叶章和沼泽化草甸小叶章各器官中总硫含量具有明显的季节变化规律，在生长季二者地上各器官中（茎、叶和鞘）总硫含量均呈波动性变化，但总体上呈递减趋势；根中总硫含量呈波动变化，总之，二者各器官中总硫含量的变化与植物的生长节律相一致。二者对硫的积累量均有：根>叶>茎>鞘，可见硫主要在根中累积，即根是硫的重要储库。二者相比，沼泽化草甸小叶章当年累积硫的量高于典型草甸小叶章当年的累积量。 枯落物和根均呈快－慢交替变化的分解模式，夏季高于冬季，这种模式与当地的气候条件相一致。在分解过程中，枯落物和根残体的总硫含量呈波动性变化，枯落物中硫的释放模式为：淋溶－固持－释放，其中C/S是决定其释放模式的主要因素；而根中硫的释放模式为：固持－释放，其C/S也是决定硫释放模式的主要因素。水分条件是影响小叶章枯落物分解的一个重要因素，沿着水位梯度从碟形洼地边沿到中心，分解速率依次增加。枯落物残体中的总硫浓度变化也受到水分条件的制约，枯落物残体中总硫浓度沿着水位梯度从洼地边沿向中心方向依次降低。 草甸小叶章湿地土壤各形态硫含量具有区域和地带性分布特征，硫在土壤中主要以有机硫的形态存在，有机硫在总硫中所占的比例高达90％以上，有利于硫的储存。土壤有机质含量是影响土壤硫状况的主要因素，可以用土壤有机质含量粗略估计土壤总硫和有机硫含量；湿地土壤各形态硫也具有明显的分层性，硫主要在表层富集，这种分布受制于土壤有机质的分布。土壤无机硫和有机硫具有明显的季节变化特征，其中植物的生长过程是影响其季节变化的重要因素；开垦耕作是导致土壤硫含量降低的主要原因，且随着开垦年限的增加，土壤含硫量逐渐减少。弃耕是土壤恢复的一种有效手段，弃耕主要通过增加土壤有机质的积累来增加土壤硫的含量。 草甸小叶章湿地土壤对SO42－的吸附符合Langmuir 方程和Freundrich方程，其吸附能力随土壤深度的增加而增加，并受土壤粘粒、有机质含量和pH值的影响，其吸附率明显高于解吸率，对于延缓土壤的酸化具有一定的意义。土壤有机硫的矿化符合一级动力学方程，不同形态的有机硫具有不同的矿化能力，其中以酯键硫最为活跃，碳键硫次之，未知态硫最小，为评价土壤肥力提供了依据。 生长季沼泽湿地含硫气体的排放具有明显的季节变化和日变化特征，其排放通量受到植物生长过程的影响，在植物生长旺盛期出现H2S排放峰值和COS吸收峰值。在生长季，典型草甸小叶章湿地和沼泽化草甸小叶章湿地中H2S的排放量分别为1.83 mg.m-2和4.76 mg.m-2，二者COS的排放量分别为－3.41 mg.m-2和－4.39 mg.m-2，就其排放总量而言，不同的湿地类型可以是含硫气体的排放源，也可以是其汇。 建立了包括大气硫分室、植物地上、地下硫分室、枯落物硫分室和土壤硫分室的典型沼泽湿地系统硫循环模式。通过对小叶章湿地系统输入输出过程的研究表明，两种小叶章湿地系统硫的输入量均高于输出量，其差值最低分别为0.342 g.m－2和0.338 g.m－2，这表明在两种小叶章湿地生态系统内硫均处于积累状态，硫虽然是植物生长必需的营养元素，但过多的硫积累可能会抑止植物的生长，降低生态系统的生产力，严重时可能引起湿地的酸化，应引起足够的注意。 水位和外源硫输入对湿地植物的地上、地下生物量具有一定的影响。小叶章在0cm水位下生物量最大，表明小叶章适宜生长在湿润条件下；在缺水条件下，施硫可能会对根系产生毒害作用，因此不宜使用。在地表湿润和淹水条件下，施加不同水平的硫，地上、地下生物量的变化没有明显的差异，因此硫的施用量以少量施用为宜。; Biogeochemical processes of sulfur play a critical in the wetland ecosystem and it contact with important ecological process such as carbon mineralization, water acidification, pyrite formation, metal cycle and gaseous sulfur emission and so on. In order to understand the role and action of sulfur in wetland ecosystem better, in this paper, two types Calamagrostis angustifolia Wetlands in Sanjiang Plain, Northeast China were selected as research objects, An in situ investigation in the field, three laboratory incubations and a simulate design were performed to study the distribution and transformation of sulfur in wetland ecosystem, and the main influencing factors to the dynamics of sulfur in wetland were discussed, then the model of sulfur cycle in air-soil ?plant system were established, finally the effects of tillage, water table and sulfur input on sulfur status in wetland were disclosed. The main results were as following: The seasonal variations of sulfur deposition amount to the wetland ecosystem were obvious, which was related with straw setting on fire, intension and frequency of precipitation, wind and geographical location. The total sulfur deposition amount to the wetland ecosystem was 1.33kg S.hm-2.a-1, which was the nutrition to the ecosystem and could also cause the ecosystem acidification. The total sulfur content in different organs of Calamagrostis angustifolia had seasonal changes. The total sulfur content in aboveground organs of Calamagrostis angustifolia were fluctuant, but declined as a whole in the grown season. The total sulfur content in roots was different. Sulfur accumulation amounts in two types Calamagrostis angustifolia wetland were both root > Leaf >Vagina > Stem in growth season, which indicated root was the important sulfur storage Comparatively sulfur accumulation amounts in MMC were much higher than those in TMC The decomposition modes of the litter and root of Calamagrostis angustifolia were both the alternate changes of fast-slow in the two different wetland types, which were correlated with the native climate. The concentrations of sulfur in the litter and root were both fluctuant changes during the decomposition. The released patterns of sulfur in the litter of Calamagrostis angustifolia were both leaching-immobilization-release in typical meadow Calamagrostis angustifolia and marsh meadow Calamagrostis angustifolia, which were regulated by the values of C to S ratios in the remaining matter of the litter. The released patterns of sulfur in the root of Calamagrostis angustifolia were both immobilization-release, which were also regulated by the values of C to S ratios. water conditions were the important factors affecting the decomposition of the Calamagrostis angustifolia litter, the mass remaining rate along the water level gradient from the edge to the center of the dishing billabong were decreased and their corresponding decomposition rates increased along the water gradient, and the concentrations of sulfur in the litter were decreased along the water level gradient from the edge to the center of the dishing billabong. Sulfur in the wetland soil showed a significantly spatial pattern and an obvious layered characters, which was affected by the content of organic matter in the wetland soil. Tillage cause the decline of the sulfur in the soil and the content of sulfur decreased gradually with the increasing of the year of cultivation. Abandonment can increase the contents of sulfur in soil while the increased contents of sulfur were little, which indicated sulfur storeroom in the soil exhaust easily, but resumed difficultly. The adsorption of wetland soil to SO42－ accord with the equation of Langmuir and Freundrich, and the adsorption ability increased with the increased soil depth, which was affected with the clay ,organic matter and pH. The adsorption ability in wetland soil was higher than sorption ability, which can delay the soil acidification. The mineralization of sulfur in wetland soil followed the first order kinetic equation, which were affected by the water condition and temperature. Different fractions of organic sulfur were all mineralized at a certain extent and the mineralization of the ester sulfate was the largest during the incubation period. The seasonal and diurnal variations of H2S and COS emission were both obvious. The H2S and COS emission were both affected by the Calamagrostis angustifolia growth, and the H2S emission peak and COS absorbed peak were observed during the bloom growth time. The emission amount of H2S in TMC and MMC was 1.83 mg.m-2 and 4.76 mg.m-2 respectively, and the emission amount of COS in TMC and MMC was －3.41 mg.m-2and －4.39 mg.m-2 respectively, So emission amount were different in different wetland types. Water table and sulfur input had a certain effects on the biomass of Calamagrostis angustifolia. Sulfur input would contaminate the root when the soil was lacy water, while in the condition of wetness and inundation, sulfur input can increase the biomass of Calamagrostis angustifolia, but increased biomass was no obvious different under different sulfur input, so a small quantity of sulfur was used. The compartment model on the distribution and circulation of sulfur in atmosphere-soil-plant system of Calamagrostis angustifolia wetland ecosystem was established. According to the compartment model, the sulfur balance in Calamagrostis angustifolia wetland ecosystem was calculated and the results showed that the input of sulfur was higher than the output of sulfur in Calamagrostis angustifolia wetland ecosystem, and the minimum differences between input and output in TMC and MMC were 0.342 g.m－2 and 0.338 g.m-2, which indicated that sulfur was accumulated in the Calamagrostis angustifolia wetland ecosystem. Sulfur was one of the necessary nutrient elements to the plant, however, the more sulfur accumulated in the ecosystem, the more the growth of plant would be restrained, the productivity of ecosystem would also be depressed, moreover the wetland would face acidification in the future if sulfur were accumulated too much. |
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