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| 荒漠生态系统凋落物分解的化学计量研究 | |
| 其他题名 | The stoichiometry characteristics during the litter decomposition in a temperature desert |
| 赵红梅 | |
| 出版年 | 2014 |
| 学位类型 | 博士 |
| 导师 | 李彦 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 凋落物分解是生态系统功能的重要过程，与植物养分、生态系统生产力和养分循环密切相关。传统分解模型中，气候因子和凋落物质量能够很好地预测湿润区凋落物的分解速率，但却在预测干旱、半干旱生态系统凋落物的分解方面存在一定问题。近年来，随着全球气候变化及人类活动的加剧，古尔班通古特沙漠的降水和大气N沉降正在发生着显著的改变，这不可避免地影响着凋落物的分解过程，进而影响到了该区生态系统的各个方面。为探讨荒漠植物凋落物分解的控制因素及C:N:P化学计量特征，在古尔班通古特沙漠南缘，选择粗柄独尾草(Eremurus inderiensis)、尖喙牻牛儿苗(Erodium oxyrrhynchum)、沙漠绢蒿(Seriphidium santolinum)以及粗枝猪毛菜(Salsola subcrassa)、芦苇(Phragmites communis)、花花柴(Karelinia caspia)、西伯利亚白刺(Nitraria sibirica)为对象，将其根、茎、叶分开，在2009年–2012年研究了3个水分梯度(冬春增雪、夏季增水和对照)及2个养分梯度(施氮和对照)处理下凋落物的分解。通过比较不同凋落物类型、不同水肥处理下凋落物质量残留率及C、N、P含量等参数的变化，揭示荒漠区植物凋落物的分解特征及控制因素；通过分析凋落物C:N:P比值关系的变化，初步了解荒漠区凋落物养分空间分异以及其生态化学计量特征。 实验数据表明，各组分凋落物的质量损失过程可以用负指数衰减模型较好地拟合。经过近3年的分解，各组分凋落物最终的质量残留率在不同处理下均无显著性差异(p>0.05)。然而，凋落物的初始化学组成与分解速率存在显著相关关系，其中，初始养分含量和C组分能够预测地表凋落物(叶和茎)的分解，相比之下，难降解成分是限制根凋落物分解的主要因子。在荒漠区，植物的生活型与凋落物质量密切相关，快速生长的短命、类短命植物木质素含量较低，其分解速率显著快于多年生草本。在荒漠区凋落物的分解过程，微生物起到了非常重要的作用，从组分来看，叶根凋落物表现为净N释放，而低质量的茎凋落物则表现为不同程度的N固持，这预示叶、根凋落物的快速分解能够加速N素的循环速率，而茎凋落物的缓慢分解则可能有利于N素的保存。 凋落物分解的C:N:P化学计量特征的研究表明，在荒漠区植物凋落物分解过程中，凋落物的N、P损失慢于C损失。并且，凋落物发生N(P)释放的临界C:N(C:P)因凋落物类型而异，初始C:N较高的凋落物，分解过程中的临界C:N也较高。随着C残留率的减少，荒漠区凋落物分解的C:N:P化学计量组成，表现出一致的轨迹线和收敛特性，当C残留率为20%时，5种凋落物C:N:P比值收敛于170:10:1(质量比)，较低的收敛值反映了荒漠区凋落物分解时易发生养分的累积。 本研究表明，在温带荒漠，凋落物初始化学组成是凋落物分解速率的主要控制因素，短时的水分和养分添加对分解的直接影响较小，这将有助于深化了解荒漠植物凋落物的分解过程与植物特性的关系。全球气候变化背景下，荒漠植物凋落物分解对于水氮添加的响应研究，为完整构建荒漠生态系统的C、N循环模型提供了关键的理论依据。以生态化学计量学的角度明确荒漠植物凋落物分解的C:N:P计量特征，为揭示荒漠区养分循环的驱动机制提供了理论和数据支撑。 |
| 英文摘要 | Litter decomposition is an important process and is closely linked to the content of plant nutrients, ecosystem productivity and nutrient cycling. Decomposition rate in mesic ecosystems are generally quite successfully predicted by litter chemical composition and climatic variables. However, these factors controlling decomposition of litter in arid and semi-arid ecosystems remain poorly understood. In arid regions, owing harsh natural climate, such as sporadic rainfall, intense radiation, long drought period and serious soil water loss, the litter decomposition is different from those mesic environments. Recent studies have found that there is a discrepancy between stimulated decomposition rates and measured ones in arid areas. In addition, changes in precipitation patterns and nitrogen deposition in response to global climate change are expected to have a large impact on decomposition rates in arid ecosystems. Here, we used the litterbag method to investigate aboveground and root litter decomposition of Eremurus inderiensis, Erodium oxyrrhynchum, Seriphidium santolinum, Salsola subcrassa, Phragmites communis, Karelinia caspia and Nitraria sibirica in Gurbantunggut Desert, China. The experiments were carried out during 2009–2012 under three manipulated precipitation treatments (snow addition in winter-spring, water addition in summer and no precipitation, respectively) and two manipulated fertilizer treatments (nitrogen added and no nitrogen added, respectively). In this study, we explored decomposition rates and nitrogen dynamics in litter with water additions in different seasons and nitrogen added to evaluate controlling factors of litter decomposition in arid lands. Meanwhile, we measured changes in carbon (C), nitrogen (N) and phosphorus (P) concentrations and mass of desert plants, in order to understand the spatial differentiation and ecological stoichiometry traits of litter nutrient of desert plants in typical temperate desert. The experiment revealed that: (1) Mass loss curves of different litters were well described by an exponential decay model. After three years of decomposition, no significant differences were observed in natural conditions, snow addition in winter-spring, water addition in summer and nitrogen added treatments (p>0.05). The patterns of litter decomposition and nutrient release were mainly controlled by initial chemical composition in the Gurbantunggut Desert. The decomposition rates of ephemeral herb were faster than that of perennial herbs. The content of neutral soluble detergent positively correlated with mass loss and was responsible for the faster rates in the primary decomposition phase. Additionally, both N and P contents and C components affected decomposition of aboveground litter. By contrast, recalcitrant compounds (e.g. lignin content) were more important in predicting decomposition of roots than aboveground litter. Only stem generally exhibited N accumulation, whereas there was no relationship between the initial N content and net N immobilization during decomposition of leaf and root litter. (2) Litters lost N and P in slower rate than C during the decomposition process. There was a similar trajectories and convergence of C:N:P quotients as litter decomposition, with an overall mass ratio of 170:10:1 (mass ratio) when the litters reached 20% original remaining. Also, the estimated critical C:N (C:P) quotient for N (P) released differed among litter types. The litter with the small C:N quotient (e.g. Erodium oxyrrhynchum leaf) showed a relatively small decline in quotient, whereas Eremurus inderiensis stem (with the high C:N quotient) still had relatively large quotient late in decomposition. In conclusion, the decomposition rates and nutrient released in temperature desert were closely linked to initial nutrient and C contents of litters, and water and N addition would not promote decomposition rates. These find improved our understanding of the links between plant litter decompo |
| 中文关键词 | 荒漠生态系统 ; 凋落物分解 ; 凋落物化学组成 ; 质量损失 ; N释放 ; C:N:P ; 生态化学计量 |
| 英文关键词 | Desert ecology Litter decomposition Litter chemistry Mass loss Nitrogen release C:N:P quotients Ecological stoichiometry |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院新疆生态与地理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287426 |
| 推荐引用方式 GB/T 7714 | 赵红梅. 荒漠生态系统凋落物分解的化学计量研究[D]. 中国科学院大学,2014. |
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