Knowledge Resource Center for Ecological Environment in Arid Area
| 增温对不同退化程度小嵩草高寒草甸生态系统的影响 | |
| 其他题名 | Effects of warming on different degraded Kobresia pygmaea alpine meadow ecosystems |
| 崔树娟 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 汪诗平 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 高寒草甸是青藏高原最重要的草地生态系统，对整个青藏高原的生态安全起着重要的调节作用，也是青藏高原重要的畜牧业生产基地。由于其高海拔低温的特点，使得其对气候变化异常敏感。近年来，青藏高原气候持续变暖，年平均气温明显上升，以往的研究表明，增温对草地生态系统的影响还存在很大的不确定性；同时青藏高原高寒草甸正在发生不同程度的退化，而不同退化程度草地对增温的响应可能不同，因此研究不同退化程度小嵩草高寒草甸生态系统对增温的响应，对于了解小嵩草高寒草甸生态系统的退化过程以及预测未来气候变化条件下高寒草甸草地生态系统的变化趋势具有重要的理论和现实意义。为研究小嵩草高寒草甸生态系统退化过程以及对未来增温的响应，本论文在藏北那曲地区以西藏大学-中国科学院青藏高原研究所那曲生态环境综合观测研究站（那曲站）为依托，选择未退化、中度退化和重度退化三种不同退化程度的小嵩草高寒草甸进行OTC增温控制实验，实验设置有未退化不增温（ND-NW）、未退化增温（ND-W）、中度退化不增温（MD-NW）、中度退化增温（MD-W）、重度退化不增温(SD-NW)、重度退化增温（SD-W）6个处理，每个处理设置4个重复，在2014-2016年对不同处理下的高寒草甸的植物个体和群落物候、物种组成和多样性、地上净初级生产力和生态系统碳交换特征等进行了观测，旨在回答增温对不同退化程度的高寒草甸生态系统结构和功能的影响，主要研究结果如下：（1）OTC增温显著增加了土壤温度，增温分别显著提高了2014、2015和2016年未退化小嵩草高寒草甸年平均土壤温度0.7、0.8 和 0.8 oC，中度退化0.5、0.6 和 0.8 oC，重度退化1.1、1.1 和 1.0 oC。同时增温显著降低了未退化和中度退化草甸的土壤湿度。无论退化程度如何，增温对土壤可溶性有机碳（DOC）和可溶性有机氮（DON）含量均没有显著影响；但与未退化草甸相比，重度退化土壤中DOC和DON含量分别显著降低了50.2%和43.0%。增温与退化程度对DOC和DON的影响不存在互作效应。（2）对于不同退化程度草甸主要植物个体物候，增温对小嵩草、紫菀和灰绿藜物候的影响因退化程度而异，增温对多裂委陵菜、紫菀、肉果草和灰绿藜的影响因年份而异。对于群落物候而言，2014、2015和2016年增温分别显著推迟了群落物候返青期 4.8、9.7和15天，对其他物候期初始期无显著影响；增温缩短了返青期和整个生长季持续期，2014、2015和2016年增温分别缩短了返青期持续期6.2、7.4和9.8天，分别缩短了生长季4.3、11.3和12.2天。增温和退化程度对植物群落物候的影响不存在交互作用。3年试验期间，不同退化程度下植物群落的返青期、现蕾期、花期初始期和初黄期无显著差异，但与未退化草甸相比，中度退化和重度退化结实期初期推迟，中度退化枯黄期推迟，重度退化枯黄期提前。（3）在草地退化过程中，随着退化程度的加重，原生植被莎草科植物小嵩草的比例逐渐降低，杂类草植物多裂委陵菜的比例先增加后降低，杂类草植物紫菀和灰绿藜的比例逐渐增加；增温降低了未退化和中度退化小嵩草的比例，提高了多裂委陵菜的比例，增温提高了中度退化紫菀和灰绿藜的比例。从物种组成方面来看，增温可能会促进未退化和中度退化小嵩草高寒草甸生态系统的退化。（4）增温对物种丰富度和多样性的影响因退化程度而异，增温显著提高了未退化状态的物种丰富度，2014-2016年物种数目分别增加了2种、4种和3种，但降低了中度退化的物种丰富度，这3年分别减少了1种、2种和3种，增温对重度退化物种丰富度没有显著影响。相似地，增温显著提高了未退化状态的物种多样性指数，但降低了中度退化的物种多样性指数，而对重度退化物种多样性指数没有显著影响。总体上，物种丰富度和物种多样性指数表现为中度退化>未退化>重度退化。 （5）总体上，增温对地上净初级生产力（ANPP）无显著影响。增温与退化程度对ANPP的影响没有交互作用，与未退化草甸相比，中度退化状态下ANPP显著提高，重度退化状态下ANPP显著降低，2015和2016年中度退化状态下ANPP 分别提高了37.3和37.7%；2014、2015和2016年重度退化ANPP分别降低了35.8、44.2和63.8%。（6）总体上，增温对生态系统碳交换特征（GEP、ER和NEE）无显著影响，增温与退化程度对这三者的影响没有互作效应，但不同退化程度GEP、ER和NEE之间有显著差异。与未退化草甸相比，重度退化降低了GEP、ER和NEE；中度退化显著提高了ER，对GEP和NEE无显著影响。与未退化草甸相比，2016年中度退化ER显著提高了的20.7%，重度退化显著降低了GEP52.7%，同时显著降低了ER35.6%。2014、2015和2016年重度退化NEE分别降低了的71.8、63.4 和70.3%。生长季期间三种退化类型草甸均表现为生态系统碳汇，增温未改变其在生长季的碳源/汇功能，与未退化草甸相比，重度退化草甸碳汇能力显著降低。综上所述，在个体水平上，增温降低了未退化和中度退化草甸中原生植被小嵩草的比例，提高了杂类草植物的比例，表明增温将可能加剧这两种小嵩草高寒草甸的植被退化；在群落水平上增温推迟了3种退化程度小嵩草高寒草甸的返青期，缩短了生长季长度，提高了未退化的物种丰富度和多样性，降低了中度退化的物种丰富度和多样性，未改变重度退化的物种丰富度和多样性，未改变ANPP，说明增温可能会导致半干旱区中度退化草甸的进一步退化；但从生态系统水平上，增温未显著改变三种草甸在生长季的碳源汇大小，说明短期增温主要体现在对个体和群落水平的影响上。 |
| 英文摘要 | As the most important ecosystem on Tibetan Plateau, alpine meadow plays an important role in regulating the entire ecological environment of the Tibetan Plateau and acts as a main area of livestock husbandry on Tibetan Plateau. Due to the high altitude and low temperature, alpine meadow is extremely sensitive to climate change. For decades, the Tibetan Plateau has seen a remarkable temperature arising, and there still exists a large uncertainty on how warming affects degradation in alpine meadow. Now days the alpine meadow is facing continuing degradation and the different degraded meadows may have different responses to warming. Therefore, researching the responses of different degraded alpine meadows to warming is very meaningful, which provides important theoretical and practical basis in understanding the degradation process of alpine meadow ecosystems and forecasting changes of alpine meadow ecosystem in the climate change future. In order to study the degradation process of Kobresia pygmaea meadow ecosystem and its response to future warming, in this paper non-degraded (ND), moderately degraded (MD) and severely degraded (SD) Kobresia pygmaea meadows in Naqu Ecological and Environment Observation and Research Station of Tibet University and Institute of Tibetan Plateau Research, Chinese Academy of Sciences in Naqu (Naqu station) were selected to carry out OTC warming experiment. In this study, non-degraded with no-warming (ND-NW), non-degraded with warming (ND-W), moderately degraded with no-warming (MD-NW), moderately degraded with warming (MD-W), severely degraded with no-warming (SD-NW) and severely degraded with warming (SD-W) treatments were set, each of which had four repeats. Then we observed the species and community phenology, vegetation community characteristics, species composition, vegetation community productivity and ecosystem carbon exchange of the six treatments during the period from 2014 to 2016. The results are as follows: (1) OTC significantly enhanced the soil temperature, and reduced the soil water content in ND and MD. Warming enhanced the soil temperature in ND 0.7, 0.8 and 0.8 oC in 2014, 2015 and 2016 respectively, in MD warming enhanced 0.5, 0.6 and 0.8 oC, and in SD warming enhanced 1.1, 1.1 and 1.0 oC. Warming had no significant influence on DOC and DON, and the effects of warming on DOC and DON were not varied with the degradation degrees, but there were significant differences among DOC and DON in different degraded meadows. Compared with ND, MD had no significant influence on DOC and DON, but SD reduced DOC and DON by 50.2% and 43% respectively. (2) The impact of warming didn't differ from degradation degree. Overall, warming delayed the period of emergence of first leaf (EFL) and the EFL was delayed by 4.8, 9.7 and 15 days respectively in 2014, 2015 and 2016. Warming had no significant influence on other phenological event. And warming shortened the duration of leafing (DL) for 6.2, 7.4 and 9.8 days respectively in 2014, 2015 and 2016. Warming shortened the growing season by 4.3, 11.3 and 12.2 days respectively in 2014, 2015 and 2016, respectively.Generally, during the three years, the phenelogical events such as EFL、first budding-set (FBS)、first flowering (FF) and first leaf coloring (FLC) in different degradation degrees didn't have significant differences. The degradation level had a significant effect on first fruiting-set (FFS) and complete leaf coloring (CLC). Compared with ND, the FFS in MD and SD were delayed; and the CLC in MD was delayed and CLC in SD was advanced. The duration of phenological event under different degradation level had significant differences. (3) During the process of grassland degradation, with the degrees of degradation increasing, the ratio of native dominant species Kobresia pygmaea, a kind of cyperaceae plant, was reducing gradually, while the forbs Aster souliei and Chenopodium glaucum were gradually increasing. Warming reduced the proportion of Kobresia pygmaea in ND and MD, but increased the ratio of the forbs Potentilla multifida in ND and MD, and increased the ratio of Aster souliei Franch and Chenopodium glaucum in MD. Generally, from the aspect of species composition, warming will aggravate the degradation of ND and MD alpine meadows.(4) Overall, in terms of the index of species richness and species diversity MD>ND>SD. The impacts of warming on the species richness and diversity in three different degraded alpine meadows differed from the degradation degree. Warming significantly increased the species richness in ND. The warming increased the numbers of species by 2, 4 and 3 in 2014, 2015 and 2016, respectively. But warming reduced the species richness in MD, and the species richness index reduced by 1, 2 and 3 respectively in these three years. Warming didn't have a significant impact on the species richness in severely degraded meadow. Similarly, warming markedly increased the species diversity in ND, but reduced the species diversity in MD. And it had no remarkable influence on the species diversity in SD. (5) The impact of warming on ANPP varied with year, and overall, warming had no significant effect on ANPP. Warming and degradation level didn't have an interaction effect on ANPP. Overall, compared with the ND, the ANPP in MD significantly increased and the ANPP in SD remarkably decreased. The ANPP in MD increased by 37.29 and 37.65% respectively in 2015 and 2016, while the ANPP in SD reduced by 35.75, 44.22 and 63.8% respectively in 2014, 2015 and 2016. (6) Overall, warming had no significant effect on carbon exchange (GEP, ER and NEE), but there were significant differences in GEP, ER and NEE among different degraded levels. Compared with non-degraded meadow, GEP, ER and NEE were declined in the severely degraded meadow, while ER was dramatically improved in the moderately degraded meadow and there was no significant influence in GEP and NEE between ND and MD. Compared with ND, MD significantly increased ER by 20.7% in 2016. In severely degraded meadow, ER was dramatically declined by 35.6%, and GEP declined by 52.7%. In 2014, 2015 and 2016, NEE in SD decreased by 71.8, 63.4 and 70.3% respectively. The three different degraded alpine meadows were carbon sinks in growing season and warming did not change the carbon absorbing function of the alpine meadow.In conclusion, at the individual level, warming reduced the propotion of native species Kobresia pygmaea and increased the ratio of forbs in ND and MD, indicating that warming may aggravate the vegetation degradation of ND and MD; at the community level, warming enhanced the species number and diversity in ND, but decreased the species number and diversity in MD, which suggested that warming may promote the degradation MD in semi-arid area; at the ecosystem level, warming did not change the CO2 fluxes (GEP, ER and NEE) significantly, indicating that the effects of warming were mainly on the species and plant community level. |
| 中文关键词 | 小嵩草高寒草甸 ; 增温 ; 退化 ; 植物群落特征 ; CO2交换 |
| 英文关键词 | Kobresia pygmaea alpine meadow Warming Grassland degradation Phenology Plant community characters CO2 exchange |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院青藏高原研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288042 |
| 推荐引用方式 GB/T 7714 | 崔树娟. 增温对不同退化程度小嵩草高寒草甸生态系统的影响[D]. 中国科学院大学,2018. |
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