| 喀斯特地区凋落物物质循环及其对全球变暖的响应 |
| 熊红福
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| 导师 | 王世杰
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| 2013
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| 学位授予单位 | 中国科学院研究生院
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| 学位授予地点 | 北京
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| 学位名称 | 博士
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| 学位专业 | 地球化学
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| 关键词 | 喀斯特
凋落物
全球变暖
物质循环
土壤养分
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| 摘要 | 凋落物的生物地球化学循环过程在全球气候变暖条件下的改变对生态系统的生长发育、恢复演替以及全球碳平衡具有深远的影响，研究喀斯特地区凋落物物质循环及其对全球气候变暖的响应，对于深入认识喀斯特生态系统碳循环和养分生物地球化学循环具有重要的科学意义。本研究采取空间代替时间的方法，分别选取喀斯特稀灌草丛、藤刺灌丛、灌木林、乔灌过渡林、次生乔木林和原生乔木林6种具有代表性的演替群落，对其凋落物物质归还量、凋落物分解过程中物质释放动态进行了研究；同时采用纬向温度梯度与室内模拟增温相结合的方法研究了凋落物分解过程中物质释放动态对全球气候变暖的响应；此外，设计了相同凋落物在同一小流域内（具有相同气候条件和地质地貌条件）不同演替群落样地的分解，以此探讨土壤理化性质及土壤生物（样地效应）对凋落物分解的影响；设计有凋落物输入和无凋落物输入两种对比处理试验，分析凋落物对土壤物质的贡献。目的是揭示喀斯特地区凋落物物质的积累与释放规律，阐明喀斯特生态系统物质循环的生物地球化学过程与特点，评估喀斯特生态系统自养能力和恢复潜力，为喀斯特地区石漠化治理和生态恢复以及碳收支的估算提供科学依据。通过两年的定位观测研究，主要结果如下： 1 喀斯特地区不同演替群落凋落物量及其物质归还动态 （1）喀斯特稀灌草丛、藤刺灌丛、灌木林、乔灌过渡林、次生乔木林和原生乔木林6种演替群落的年平均凋落物量分别为751.8±53.4、3816.8±7.1、4417.6±145.1、4261.4±145.1、4182.8±25.7和4344.3±557.1 kg ? hm-2，年均凋落物总量表现为：随着群落正向演替的推进，群落凋落物年总凋落量呈现出先升高后缓降最后趋于稳定的变化趋势，处于演替初期阶段的稀灌草丛群落的凋落物量显著低于其他演替群落。6种演替群落叶凋落物占总凋落量的62.2%~74.0%，叶凋落物是群落凋落物的主体，决定了总凋落量的凋落节律，喀斯特原生乔木林、稀灌草丛两种群落总凋落量及叶凋落量呈单峰型，而次生乔木林、乔灌过渡林、藤刺灌丛总凋落量及叶凋落量呈双峰型。相关分析表明，枝凋落量与群落演替阶段显著正相关（相关系数0.923，p=0.009<0.01）。因此，喀斯特地区是否可以用年均枝凋落量的大小来表征植物群落演替阶段的高低，还有待于进一步研究验证。 （2）喀斯特稀灌草丛、藤刺灌丛、灌木林、乔灌过渡林、次生乔木林和原生乔木林6种演替群落凋落物C、N、H、S的归还量主要受各群落凋落物量大小控制，C、N、H、S含量在群落之间的差异对其影响较小。凋落物各凋落组分C、N、H、S含量具有一定差异，C、N、S含量总体上表现为花果等凋落物大于叶凋落物和枝凋落物，H的含量在各组分间差异不显著。 （3）原生乔木林叶凋落物中K、Ca、Mg、Fe、Mn、Zn、Na七种元素的年均含量分别为0.30%、2.46%、0.36%、0.02%、0.02%、0.004%、0.002%，属于Ca﹥K型。七种元素的归还量月动态主要受叶凋落物量的大小控制，其月变化与叶凋落物量月动态基本一致。七种元素的年归还量分别为89.03、13.03、10.01、0.82、0.77、0.14、0.07 kg ? hm-2，大量元素K、Ca、Mg的归还量较大；而微量元素Fe、Mn、Zn、Na的归还量较小，叶凋落物中K、Ca、Mg、Fe、Mn、Zn、Na的年归还量大小主要受元素含量大小决定。 2 喀斯特地区不同演替群落叶凋落物原地分解过程及其物质释放动态 （1）喀斯特藤刺灌丛、灌木林、乔灌过渡林、次生乔木林和原生乔木林5种演替群落叶凋落物两年（2011年4月至2013年3月）原地分解的质量剩余率分别为27%、29%、30%、41%、28%。随着分解时间的推进，质量剩余率出现递减的趋势，C、N、H、S的释放率出现递增的趋势。分解过程中，5种演替群落的分解速率、C、N、H、S的月均释放率在群落水平上均表现为：灌木林、原生乔木林、藤刺灌丛大于次生乔木林和乔灌过渡林。除次生乔木林、乔灌过渡林外（因为次生乔木林、乔灌过渡林主要为壳斗科栎属类革质叶凋落物，分解速率较慢），其余3种演替群落凋落叶的分解速率表现为：随着群落正向演替的推进，分解速率加快。 （2）原生乔木林叶凋落物在22个月（2011年4月至2013年1月）的分解时间里，随着分解时间的推进，叶凋落物中K、Mg含量（浓度）总体上呈现出递减的趋势；而Ca、Fe、Mn、Zn、Na含量（浓度）总体上呈现出递增的趋势。K、Ca、Mg表现为净释放，并呈现出：随着分解时间的推进，其释放率出现递增的趋势；而Fe、Mn、Zn、Na大部分时间表现为富集现象，并呈现出：随着分解时间的推进，其富集程度出现递增的趋势。虽然Ca元素在22个月的分解时间里，其浓度一直递增（富集），但是其释放率不断递增，即在分解期内，从养分总量来看，一直表现为净释放。 3 喀斯特地区凋落物分解的影响因素 温度是影响凋落物分解速率的重要因素，温度升高加快了凋落物的分解，具体表现为：相同叶凋落物在具有较高年均温的茂兰原生乔木林的分解速率大于在普定原生乔木林的分解。C/N（凋落物质量）是控制凋落物分解的另一个因素，凋落物C/N越小其分解速率越快，喀斯特藤刺灌丛、灌木林、乔灌过渡林、次生乔木林和原生乔木林5种演替群落叶凋落物的分解速率与其C/N的大小显著负相关。 |
| 其他摘要 | The biogeochemical cycling change of forest litter which effects by global warming could have profound and complicated effects on plant development， vegetation succession and global carbon balance in terrestrial ecosystems. The research of litter’s material cycling and its responses to global warming in Karst area has scientific significance of understanding carbon cycling and nutrients’ biogeochemical cycling of Karst ecosystem. Adopting the concept of space as a substitute for time，the dynamics of litterfall，its material return quantity and material releasing during litter decomposition in six different successional communities (sparse tussock, thorn-scrub shrubland, low shrubland, shrubby woodland and forest, secondary mixed evergreen and deciduous broadleaved forest, and primary evergreen broadleaved forest) were studied in Karst area in Guizhou Province, China. Based on the method combining latitudinal temperature gradient with experimental temperature gradient，the release dynamics of material during the process of litter decomposition and its responses to global warming were studied in this paper. In addition，the same litter was designed to decompose in different successional communities (in the small watershed with similar climatic attributes and geological condition)，so as to observe the effects on litter decomposition which diferented from the difference of soil physo-chemical characteristics and organism. Remove litter group (no litter input) and unconditional control group (litter input normaly) was designed to observe litter’s contribution to soil nutrients. Objective to find the rule of accumulation and release of litter in Karst area. To elucidate the characteristics of biogeochemical cycling in Karst ecosystem. To evaluate the self-fertility ability and recovery potential of Karst ecosystem. To provide scientific basis for controlling of Karst rocky desertification，ecological restoration and carbon budget in Karst area. The following conclusions were drawn from two years' located observation and analysis: 1 The dynamics of litterfall and its material return quantity of different successional communities in Karst area (1) Results show that the averaged annual litterfall biomass of above six different successional communities were 751.8、3816.8、4417.6、4261.4、4182.8 and 4344.3 kg ? hm-2, respectively. During the forward successional process, litterfall increased during the initial stage, then gradually decreased in medium stage, and tended to be stable in the last stage. The litterfall biomass of sparse tussock which in the early succession was significantly lower than other five successional communities. Litterfall of leaf accounted 62.2%~74.0% of the total litterfall and it was the dominant component. The leaf litterfall showed a consistent monthly dynamic with the total litterfall. The monthly litterfall dynamics of sparse tussock and primary evergreen broadleaved forest exhibited a unimodal distribution, while other three successional communities (thorn-scrub shrubland, shrubby woodland and forest, secondary mixed evergreen and deciduous broadleaved forest) exhibited a bimodal distribution. Litterfall biomass of branch showed relatively high positive correlation with successional stages. Whether the litterfall biomass of branch can be used to characterize the succession stage need to be studied further. (2) In the above six different successional communities，the return amount of litter's C, N, H, S were primarily dominated by its litterfall biomass，the differences of quantity of C, N, H, S between communities has slight influence on return amount. The results showed that there were some differences in the contents of C, N, H, S between different components (the leaf, branch, flower and fruit). |
| 学科领域 | 环境地球化学
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| 语种 | 中文
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| 文献类型 | 学位论文
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| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/5843
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| 专题 | 研究生_研究生_学位论文
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推荐引用方式
GB/T 7714 |
熊红福. 喀斯特地区凋落物物质循环及其对全球变暖的响应[D]. 北京. 中国科学院研究生院,2013.
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