中国典型山地森林生态系统C、N循环模拟研究
文献类型：学位论文
| 作者 | 鲁旭阳
|
| 学位类别 | 博士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院水利部成都山地灾害与环境研究所 |
| 授予地点 | 成都 |
| 导师 | 程根伟 |
| 关键词 | 贡嘎山 峨眉冷杉 C循环 N循环 气候变化 Forest-DNDC 温室气体 |
| 其他题名 | Modelling the C, N cycles of upland forest ecosystems in China |
| 学位专业 | 自然地理学 |
| 中文摘要 | 气候变暖已成为当今全球性的环境问题，气候变暖的主要原因是由于大气中温室气体不断的增加，CO2、N2O、NO、CH4被认为是最重要的温室气体。陆地生态系统C、N循环过程对大气中温室气体浓度的变化起着至关重要的作用，陆地生态系统既可以是大气中主要温室气体CO2、N2O、NO、CH4的源，C、N元素的分解/矿化及转化过程所产生的温室气体通过土壤和植物进入大气，使得大气中温室气体浓度增加；同时陆地生态系统也可以是大气中主要温室气体的汇，例如通过植物的光合作用，陆地生态系统每年从大气吸收高达1220亿吨的C。森林是地球陆地主要的生态系统，森林约占陆地面积的1/3，生物量占整个陆地生态系统生物量的90%，生产量占陆地生态系统的70%，森林生态系统的C、N循环在全球变化中占据重要作用。 本研究选择已在世界各地广泛验证和使用的森林生态系统C、N生物地球化学循环模型Forest-DNDC，以位于青藏高原东缘的中国典型山地贡嘎山森林生态系统为研究对象，探讨气候变化和不同森林管理策略情景下贡嘎山峨眉冷杉林C、N循环特征的变化规律，对比贡嘎山植被垂直带谱中不同类型森林的C、N循环特征的异同，并初步探讨我国不同森林生态系统类型的C、N循环的空间分异规律。主要结论如下： (1)贡嘎山东坡植被垂直带谱海拔1600m的常绿阔叶林GPP(Gross Primary Productivity)、NPP(Net Primary Productivity)以及NEP( Net Ecosystem Productivity)均高于海拔3000m的峨眉冷杉林；两种森林有机土壤库和矿质土壤库土壤每年增加的SOC(Soil Organic Carbon)量均表现为常绿阔叶林明显高于峨眉冷杉林，并且主要是常绿阔叶林的凋落物C年际增加明显高于峨眉冷杉林；但是高的SOC并未带来高的土壤CO2释放。峨眉冷杉林从土壤中吸收的N较多，通过凋落物归还的却比较少，循环系数为0.51；常绿阔叶林从土壤中吸收的N不多，但归还的却较多，循环系数高达0.91；常绿阔叶林年际硝化和矿化的N量较低，通过淋溶和含N气体释放丢失的N量也较低；但土壤的有机N库年际增加的量高于峨眉冷杉林。 (2)峨眉冷杉林的GPP受温度的强烈影响，随着温度的增加而增加，同时，植被的自养呼吸也随之增加，导致NPP随着温度升高而呈下降趋势；随着温度的升高NEP呈下降趋势，并且为负值，由C汇转变为C源；降水量的改变对峨眉冷杉林GPP影响不大，当温度降低时，年际SOC的累积增加，当温度升高时，年际SOC的累积减少；降水量变化对土壤C动态的影响较小；温度的升高促进土壤CO2释放，降水并不是控制土壤CO2释放的关键因子。随着温度和降水量的增加，年际净硝化N和矿化N均增多；无论温度升还是降，土壤N2O释放均增加；随着降水量的增加土壤的NO和N2O增多。 (3)在IPCC报告B1、AlB和A2三种气候情景下，峨眉冷杉林的GPP增加，同时也使自养呼吸和异养呼吸以更高的速度增加，从而造成NPP和NEP的下降，并且在未来气候变化情景下，峨眉冷杉林从净C汇转化为净C源；峨眉冷杉林生态系统中有机土壤层和矿质土壤层中年际累加的SOC在未来气候变化情景下均呈下降趋势，土壤CO2释放呈增加的趋势。随着气候的变化越剧烈，植物从土壤吸收的N量越多，但向土壤中归还的比例越少，在植物体内留存的越多；气候变化使N的硝化和矿化作用增强；随着气候变化程度的加剧向大气中释放的含N温室气体量增加。 (4)轻度收获(收获20%)、中度收获(收获50%)、高度收获(收获80%)条件下，峨眉冷杉林的GPP和对照相比均有不同程度的下降，并且收获的强度越高GPP下降得越多，NPP和对照相比有所增加，其中进行中度收获后NPP增加得最多，NEP变化趋势和NPP相同；森林的收获事件造成了有机土壤层中SOC的流失，并且收获的强度越大，流失的SOC也就越多；森林进行收获后短时间内使土壤CO2释放剧增，随后收获的强度越大土壤CO2释放量就越少。进行不同强度的收获后短时间内峨眉冷杉归还的N量和对照相比显著增加，初期净N硝化和矿化随之增加，随后土壤N逐渐达到平衡；在收获的当年土壤排放N2O和NO气体随着收获强度的增加而呈增加，随后逐渐恢复平衡。 (5)贡嘎山峨眉冷杉成熟林生态系统C储量和活体植物C储量高于其他类型森林生态系统；中龄林C储量远低于成熟林。不同森林NPP表现为热带雨林>亚热带常绿阔叶林>寒温带针叶林>亚高山峨眉冷杉中龄林>温带落叶阔叶辽东栎林，大体上成从南到北逐渐降低的趋势。土壤CO2释放同样呈从南到北逐渐减少的趋势，峨眉冷杉林土壤释放CO2的通量仅次于热带雨林和亚热带季风常绿阔叶林，高于森林土壤CO2释放全国平均水平。贡嘎山峨眉冷杉林N吸收和归还量仅次于鼎湖山季风常绿阔叶林，但循环系数仅为0.50。不同森林土壤N矿化随着纬度的增加而下降，峨眉冷杉林土壤N矿化仅次于西双版纳热带雨林，与常绿阔叶林相当。贡嘎山峨眉冷杉中龄林土壤释放N2O较低，略高于长白山针叶云冷杉林。 |
| 英文摘要 | At present global warming has became the global environmental problem. The sustaining greenhouse gases increasing is the mainly reasons of global warming. Carbon dioxide (CO2), nitrous oxide (N2O), nitric oxide (NO) and methane (CH4) are considered the most important greenhouse gases. The C, N cycles of terrestrial ecosystem plays a vital role in regulating the greenhouse gas concentrations of atmosphere. On the one hand terrestrial ecosystem is the sources of the main atmospheric greenhouse gases CO2, N2O, NO and CH4. Greenhouse gases from the decomposition, mineralization and transformation process go into the atmosphere through the soil and plants and increase the concentration of greenhouse gases. On the other hand terrestrial ecosystem is the important sink of greenhouse gases. Terrestrial ecosystems can absorb as much as 122 billion tons of C from the atmosphere each year through photosynthesis. Forests are the most extensively distributed vegetation type ecosystems in the world and cover approximately one-third of the earth land surface. Forest biomass account the 90% of terrestrial ecosystem biomass and productivity account the 70% of terrestrial ecosystem productivity. The C, N cycles of forest ecosystems play an important role in global change. In this study, the biogeochemical cycle model Forest-DNDC which has been widely used and validated around the world was utilized to modeling the C, N cycles of forest ecosystems in Gongga Mountain which located the eastern edge of Tibetan Plateau. The climate changes and forest management strategies effected on the C, N cycles of the Abies fabri forest ecosystems were discussed and the C, N cycles of different type foerest ecosystems in vertical vegetation spectrum in Gongga Mountain was compared. The spatial distributions of C, N cycles of different type foerest ecosystems in China were also discussed in prssent study. The main conclusions are as follows: (1) The GPP（Gross Primary Productivity）, NPP（Net Primary Productivity）and NEP（Net Ecosystem Productivity）of evergreen broad-leaved forest which located at about 1600m of Gongga Mountain vertical vegetation spectrum were higher than those of Abies fabri forest (3000m). The annual changes of SOC（Soil Organic Carbon）on both forest floor and the mineral soil of the evergreen broad-leaved forest were significantly higher than Abies fabri forest. And this is because the annual increase litter C of evergreen broad-leaved forest was significantly higher than Abies fabri forest. But high SOC did not bring higher soil CO2 emissions. The N uptake of Abies fabri forest was more and the N return was little, the recycling coefficient was 0.51. And the N uptake of evergreen broad-leaved forest was not more but the N return was more, so recycling coefficient was 0.91. The N nitrification, mineralization, leaching and N trace gas emissions of evergreen broad-leaved forest were lower than those of Abies fabri forest. But the annual change of SON accumulation was higher than Abies fabri forest. (2) The GPP of Abies fabri forest was strongly influenced by temperature and increased with temperature increasing. At the same time the autotrophic respiration also increased. So the NPP and NEP decreased with temperature increasing and from C sinks change to a C sources. The GPP, NPP and NEP were influenced little by precipitation. As the temperature decreasing the annual change of SOC increased and as the temperature increasing the annual change of SOC decreased. The effects of precipitation on soil C dynamics were smaller. Temperature increasing promoted the emissions of soil CO2 and the precipitation was not key factor which controlled soil CO2 emissions.With temperature and precipitation increasing the net N nitrification and mineralization were increased. Regardless of the temperature rise or drop the soil N2O emissions increased and soil NO and N2O emissions increased with precipitation increasing. (3) In B1, A1B and A2 three climate scenarios (IPCC report) the GPP of Abies fabri forest increased, but the autotrophic respiration and heterotrophic respiration increased as the higher speed. So resulted in a decline in NPP and NEP and the Abies fabri forest changed from C sink into a net C source in the future. The annual changes of SOC on both forest floor and the mineral soil decreased under future climate change scenarios but soil CO2 emissions increased. With climate changed more severely the plants uptaked more N from soil, but little returned to soil and the most of N were retained in the plant. The net N nitrification, mineralization and soil N2O and NO emissions were increased under climate change scenarios. (4) With mild harvest (20% harvest), moderate harvest (50% harvest) and high harvest (80% harvest) conditions, the GPP of Abies fabri forest was lower than control. And with the higher intensity of harvest the more GPP declined. The NPP increased in comparison to control and it increased the most under moderate harvest. The changes of NEP kept the same trends with NPP. Forest harvest resulted in the SOC decreased, and the greater intensity of harvest, the more SOC declined. After a short time of forest harvest soil CO2 emissions strongly increased. And then soil CO2 emissions decreased with the greater intensity of harvest. In the early stage after harvest the N which returned to soil were significant increasing. The net N nitrification, mineralization and soil N2O and NO emissions were increased with harvests, and then gradually reached balance. (5) The ecosystem C and living plant C stores of the mature Abies fabri forest was higher than that of other forest ecosystems in China. And the C store of the middle aged Abies fabri forest was much lower than the mature forest. The NPP of different forests generally followed the order tropical rain forest＞subtropical evergreen broad-leaved forest＞boreal conifers forest＞subalpine Abies fabri middle-aged forest＞temperate deciduous broad-leaved oak forest. The NPP generally declined gradually from the south to north of China. Soil CO2 emissions kept the same trends. Soil CO2 emissions of Abies fabri middle-aged forest were only lower than those of tropical rain forests and subtropical monsoon evergreen broad-leaved forest, but they were higher than the level of national average. The N uptake and N return of Abies fabri forest were lower than monsoon evergreen broadleaf forest in Dinghu Mountain, but the cycle coefficient was only 0.50. Forest soil N mineralization decreased with the latitude increasing. The N mineralization of Abies fabri forest was only lower than Xishuangbanna tropical rain forest and generally consistented with evergreen broad-leaved forest. Soil N2O emissions of Abies fabri forest were considerable lower, and slightly higher than coniferous spruce-fir forest in Changbai Mountain. |
| 学科主题 | 生态学 |
| 语种 | 中文 |
| 公开日期 | 2010-10-13 |
| 分类号 | X17;S75 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/2177]  |
| 专题 | 成都山地灾害与环境研究所_成都山地所知识仓储（2009年以前） 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 | 鲁旭阳. 中国典型山地森林生态系统C、N循环模拟研究[D]. 成都. 中国科学院水利部成都山地灾害与环境研究所. 2009. |
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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