Knowledge Resource Center for Ecological Environment in Arid Area
| 藏北高寒草地生物量分配及根系动态 | |
| 其他题名 | Root Dynamics and Biomass Allocation in the Northern Tibetan Plateau Alpine Grasslands |
| 曾朝旭 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 张宪洲 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 藏北高原由于其独特的自然环境和气候条件而被誉为研究气候变暖背景下高寒草地生态系统的理想地区之一。近年来，该地区草地由于本身脆弱的生态环境、气候变化、人口和牲畜数量增多而出现了不同程度的退化。植物地上与地下生物量分配模式是对环境的适应，根冠比和fBNPP(地下净初级生产力占总净初级生产力的比)是陆地碳循环研究的两个重要参数，根系周转是土壤碳的重要来源。因此，有必要对它们的发生模式、动态变化和形成原因进行研究。然而，当前对该地区生物量及分配的研究主要集中于生长旺季时进行一次采样，不足以估算其对陆地碳循环的贡献，特别是地下碳库。本研究选取该地区降水梯度带上四个典型草地(高寒草甸、高寒草甸草原、高寒草原、高寒荒漠草原)进行生长季内生物量及其地上-地下分配和地下根系动态研究。运用收获法动态采集地上地下生物量，并用微根管技术监测根系生长动态，估算其生物量。旨在深入理解藏北高寒草地地上与地下生物量分配模式，以期为定量预测高寒生态系统对气候变化和人类活动干扰的响应提供基础。主要结果如下：(1)该地区地上生物量和地下生物量沿高寒草甸、高寒草甸草原、高寒草原、高寒荒漠草原下降。生长季内地上生物量有明显的“单峰”模式变化。地下生物量随土层加深而明显下降，10 cm深的地下生物量决定着整个根量，能达到(80.09~91.10%)。草甸和荒漠草原拥有较高的根冠比，草甸草原和草原较低；生长季初和季末较高，旺季最低。围栏围封处理对藏北高寒草地生物量及其分配影响不十分明显。(2)通过对该地区地上与地下生物量进行标准主轴分析得出，无论各草地生态系统还是整个藏北地区的生物量地上地下分配均支持异速分配假说。(3)该地区高寒草地地上与地下净初级生产力有明显的差异，沿高寒草甸、高寒草甸草原、高寒草原、高寒荒漠草原依次降低。地上净初级生产力的年变化从东到西逐渐降低，地下净初级生产力和总净初级生产力无明显年变化。在当前放牧水平下，放牧降低地上净初级生产力，未影响地下和总净初级生产力。研究发现藏北高寒草地拥有较高的fBNPP，且年际变异较小。三个生长季高寒草甸、高寒草甸草原、高寒草原、高寒荒漠草原的fBNPP平均值分别为93.83%、76.02%、77.60%和92.01%。地下净初级生产力随土层加深而变小。(4)根系周转率有明显的变化，高寒荒漠草原最高，高寒草甸最低。年变化不明显，放牧不对其产生影响。(5)放牧占有的地上净初级生产力有明显变化，沿高寒草甸至高寒荒漠草原递减。草甸和草甸草原有轻微的年变化，草原和荒漠草原无明显年变化。(6)可食与不可食地上净初级生产力有较明显的差异，前者依次降低，后者是沿此线先升高，再降低，且趋于平缓。三年间两处理下可食与可食性地上净初级生产力未表现出明显的年际差异，并不受放牧影响。(7)微根管法估算2014年生长季内该地区地下生物量随时间推移逐渐增加。相邻两采样间隔间地下生物量净增长量有明显季节变化，生长旺季时较高，生长季初和末期较低。 |
| 英文摘要 | Northern Tibetan Plateau (NTP) is one of the ideal regions of studying how alpine grassland ecosystems will respond and acclimate to climatic changes considering for its unique natural environment and climatic conditions. In recent years, due to the fragile ecological environment, climatic change and the increasing population and livestock, the alpine grasslands showed degradation in different degrees. Plant biomass allocation pattern is an adaptation to local environments. The ratio of root to shoot (R/S) and fraction of BNPP to NPP (fBNPP) are two key parameters of terrestrial carbon cycling. Root turnover is an important source of soil carbon in grasslands. These suggest that, it is necessary to study their patterns, dynamic changes and reasons. However, previous studies about biomass and its above-and belowground allocation were only based on single sampling at the peak of growing season, which cannot be good enough to estimate the alpine grasslands’ contribution to terrestrial carbon cycle, especially its soil carbon. Therefore, to get a more comprehensive knowledge of biomass patterns, its above- and belowground allocation and the root turnover dynamics in NTP , four typical alpine grasslands (alpine meadow, AM; alpine meadow steppe, AMS; alpine steppe, AS; alpine desert steppe, ADS) along the precipitation gradients were selected to conduct a dynamic and continuous observations. Both the traditional harvesting method and minirhizotron technique were used to obtain plant biomass. The objective of this study was to provide a support for quantifying impacts of climatic change and anthropogenic activities disturbance on alpine ecosystems. The major findings were as following:(1)Both aboveground biomass (AGB) and belowground biomass (BGB) decreased from AM to ADS. Aboveground biomass showed a unimodal pattern during the growing seasons. Belowground biomass decreased markedly with increasing soil depth. The BGB in the 0-10 cm soil layer accounted for 80.09-91.10% of the total BGB.Both AM and ADS took a higher root to shoot ratio (R/S) and AMS and AS had a lower value. Meanwhile, it was higher at the start and end of the growing season, and lower at the peak growing season. Grazing exclusion did not impact the biomass and its allocation between above- and belowground. (2) Based on the (standardized major axis) SMA analysis, the allocation between above- and belowground biomass supported the allometric partitioning hypothesis no matter in each grassland ecosystems or in the whole NTP. (3) Both above- and belowground net primary productivity (ANPP and BNPP) decreased from AM to ADS. Meanwhile, the annual variation of ANPP also lowered from AM to ADS, whereas the BNPP and NPP did not show obvious annual variations. Grazing reduced ANPP but did not impact BNPP and NPP at current grazing situations. Thus, all NTP alpine grasslands took higher value of fBNPP, meanwhile all of them were lack of annual variations. The three growing seasons mean value of AM，AMS, AS, and ADS were 93.83%, 76.02%, 77.60%, and 92.01%, respectively. Moreover, BNPP also decreased sharply with soil depths.(4) The root turnover rate of ADS was largest, while that of AM was lowest among the four grassland types. In addition, they did not show obvious annual variation and grazing also did not impact them.(5) Grazing consumption of ANPP exhibited a reduced tendency from AM to ADS. Moreover, both AM and AMS varied slightly with years, whereas, the other two grasslands did not change. (6) Both eatable and uneatable ANPP had an obvious distribution variation, the former decreased, while the latter firstly increased, then decrease and lastly turn to smooth. They were stable among three years and did not influence by grazing. (7) The BGB estimated by minirhizotron technique increased with time during the growing season in 2014. The net root biomass increments between two samplings changed along with season, which showed a higher value at the peak growing season and smaller at the start or the end of growing season. |
| 中文关键词 | 净初级生产力 ; fBNPP ; 异速分配假说 ; 根冠比 ; 根周转 ; 微根管技术 |
| 英文关键词 | net primary productivity fBNPP allometric allocation hypothesis root to shoot ratio root turnover minirhizotron technique. |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院地理科学与资源研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287861 |
| 推荐引用方式 GB/T 7714 | 曾朝旭. 藏北高寒草地生物量分配及根系动态[D]. 中国科学院大学,2017. |
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