【作者】 刘亚迪；

【导师】 范少辉；

【作者基本信息】 中国林业科学研究院 ， 森林培育， 2012， 博士

【摘要】 雷竹（Phyllostachys praecox Z.D. Chu et C.S. Chao f. prevelnalis）是一种优良的栽培笋用竹种，在浙江、江西、江苏、安徽、福建等地广泛栽培。随着以冬季地表增温覆盖和施肥为核心的早产高效栽培技术的实施，雷竹林的竹笋产量和经济产出效益大大提高。但连年林地覆盖和化学肥料的长期大量施用，使得雷竹林林分结构失衡，养分代谢功能失调，竹笋产量和质量大幅度下降，竹林退化现象越来越严重。因此，如何在保证竹林经济效益稳步提升的同时维持竹林系统结构和功能的稳定性，从而实现雷竹林的可持续经营显得至关重要。本研究从雷竹林植被退化的角度入手，选择雷竹原产地浙江省临安市以及重要引种地之一江西省万年县的雷竹试验林，进行雷竹林植被退化等级划分，在对雷竹林植被退化进行科学定位评价的基础上，选择不同退化程度雷竹林进行土壤—植被系统不同组分养分及其化学计量特征研究，探讨土壤—植被系统内土壤、竹叶、竹鞭在抽枝换叶期、行鞭期、笋芽分化期、孕笋出笋期年生长周期内的养分时空动态变化规律，同时兼顾竹叶养分内、外循环规律，细根养分储量在不同退化程度雷竹林养分循环中的特征响应，并通过研究退化雷竹林系统C、N、P养分化学计量特征加以验证，以期得出雷竹林退化的限制性养分元素及其敏感响应期，从而为退化雷竹林修复工作的开展奠定理论基础。具体研究结论如下：1、根据林分结构因子和竹笋产量对不同经营程度雷竹林进行植被退化评价，将雷竹试验林划分为未退化、轻度退化、中度退化和重度退化四类。随退化程度的加重，立竹平均胸径以及竹笋产量呈逐渐降低的趋势，2年生立竹比例逐渐降低，而3年生及其以上老龄竹的比例逐渐升高，重度退化雷竹林的新竹比例最低，仅为18.67%，林分自我更新能力降低。立竹年龄结构、立竹胸径和竹笋产量是响应人工经营雷竹林植被退化程度的主要指标。2、不同退化程度雷竹林土壤—植被系统各组分养分响应特征之间差异显著，不同组分因功能不同表现出不同的养分响应特征。雷竹林土壤养分有效性水平受地表覆盖和施肥等人为经营措施影响显著，随着经营年限的延长，土壤养分含量的累积使得竹林养分代谢水平失衡，植被退化程度加剧。P、Zn养分的富集是竹林退化的显著特征，其中P素大量富集的特点在竹林笋芽分化期明显显现，而抽枝换叶期Zn素的累积是竹林退化程度加剧的又一明显特征。（1）雷竹林土壤有效养分含量随退化程度不同表现出明显的差异性。重度退化雷竹林土壤有机C、有效P、有效Zn含量因经营年限和地表覆盖时间的延长而显著升高，有效Mn呈降低的趋势。轻度退化雷竹林由于未进行地表覆盖，有效P含量在不同生长期均为最低值，分别为抽枝换叶期：54.82mg·kg^-1，行鞭期：50.96mg·kg^-1，笋芽分化期：61.92mg·kg^-1，孕笋出笋期：13.04mg·kg^-1，而重度退化雷竹林在相应的生长期分别为477.19mg·kg^-1、705.83mg·kg^-1、544.63mg·kg^-1、402.92mg·kg^-1，分别是轻度退化雷竹林的8.71、13.85、8.80和30.89倍，可见地表覆盖导致竹林土壤P素显著升高是退化竹林的显著特征。而在雷竹林退化过程中，土壤酸化与土壤P、Zn等养分离子的积累呈显著正相关。（2）土壤中有效P、Zn水平是制约退化雷竹林竹叶、竹鞭中养分含量变化的关键因素。竹叶、竹鞭中P、Zn养分含量均能及时反映退化雷竹林土壤中养分含量的变化，其中笋芽分化期竹叶、竹鞭中P养分含量与土壤中Zn养分含量显著相关，抽枝换叶期竹鞭中Zn素的含量又受土壤中P养分水平的制约，不同生长期养分元素在地上、地下不同营养器官中的分配表现出明显的差异性，退化雷竹林土壤P素大量富集对雷竹林的影响与土壤中Zn素水平的升高有显著正相关关系。（3）叶片养分内、外循环是竹林应对养分胁迫环境的一种适应性机制，同时也是表征竹林退化程度的重要特征。未退化雷竹林生长代谢旺盛，吸收大量养分，以一种“节约保守”型的方式充分利用养分资源，而重度退化雷竹林由于受到P素胁迫的响应表现出“铺张浪费”、“奢侈”型的消费方式，叶片表现出较低的P养分再吸收效率。叶片适应性机制的存在使得养分再吸收效率与土壤中相应养分的有效性水平相关关系不显著。随着退化程度的加重，雷竹林凋落叶量呈逐渐降低的趋势，凋落叶中养分归还量与土壤中有效P、Zn水平呈显著负相关关系。（4）细根（直径≤2mm的根系）生物量及养分储量是表征竹林退化程度的重要指标。随着退化程度的加重，雷竹林细根生物量呈逐渐降低的趋势，未退化雷竹林在孕笋出笋期达到最高值4.68t·hm-2，而重度退化雷竹林此时达到最低值0.95t·hm-2，呈现出明显的退化特征；重度退化雷竹林细根N、P、K、Mn、Zn养分储量显著降低，细根周转速度降低，土壤中有效P、Zn含量的富集是制约细根生产的关键因素。3、雷竹林土壤—植被系统中各组分的C、N、P养分化学计量特征可以真实、有效地反映雷竹林的退化程度以及受养分限制状况。与未退化雷竹林相比，重度退化雷竹林土壤、叶片、细根N∶P化学计量比值显著降低，而凋落叶N∶P在抽枝换叶期和孕笋出笋期显著升高，明显地表现出竹林的退化程度；在笋芽分化期，凋落叶P素化学计量比值转而降低，表现出退化竹林P素过量积累而P养分吸收保存能力显著降低的特征。土壤、叶片的N∶P化学计量比值可以反映退化雷竹林土壤P素富集的特点；叶片、凋落叶中N、P化学计量比值可以明显表征退化雷竹林叶片对N的再吸收水平，而叶片对P的再吸收水平仅在细根N∶P变化中得以体现。4、退化雷竹林限制性养分元素的响应特征为退化雷竹林修复工作的开展提供理论依据。以施肥和地表覆盖为主的早产高效经营技术在实施早期有减缓植被退化、增加竹林经济产出的效果，随着经营年限的延长，养分元素尤其是P素的富集使得植被退化程度加剧。因而在退化竹林的修复过程中，应该适当减少P肥的输入，尤其在竹林生长代谢比较缓慢的笋芽分化期；考虑到土壤酸化对养分含量的影响，可以适当调节土壤酸碱度，从而改善退化竹林遭受土壤养分胁迫的局面；由于P、Zn等养分离子之间存在一定的交互作用，因而在进行竹林养分管理过程中必须兼顾到单一养分含量的变化对其他养分离子含量的影响，合理搭配养分比例，实现雷竹林可持续经营。更多还原

【Abstract】 Phyllostachys praecox Z.D. Chu et C.S. Chao f. prevelnalis, cultivated in Zhejiang,Jiangxi, Jiangsu, Anhui, Fujian province, et al., is an excellent bamboo used for bamboo shoots.With the implementation of cultivation techniques of winter soil-surface mulching andfertilization for early shooting and high yielding, the yield of bamboo shoots and economicoutput efficiency had been greatly increased. However, with the current annual soil-surfacemulching and the long-term application of chemical fertilizer, the stand structure becameirrational, the nutrient metabolism become disorder, the quality and yield of bamboo shootsdecreased substantially. As a result, the phenomenon of degradation became more and moreserious. Therefore, it is crucial to ensure the steady increment of the economic benefit andmaintain the stability of the structure and function in the meantime so as to realize thesustainable management for P. praecox. In this paper, the evaluation of vegetation degradationdegree was conducted for experimental forests of P. praecox in the city of Lin’an, Zhejiangprovince and Wannian County in Jiangxi province. Based on the scientific evaluation ofvegetation degradation, the characteristics of nutrient and its ecological stoichiometry werestudied for different components in the soil vegetation system （SVS） of different degradationdegrees of P. praecox. Temporal-spatial variability of soil, bamboo leaf and bamboo rhizomenutrients was discussed in the annual growth cycle of refoliation and branch developmentperiod, rhizome growing period, bud differentiation period, pregnancy and emergence forshoots period. The response characteristics of internal and external nutrient cyclings forbamboo leaf, nutrient stock of fine root in the nutrient cycling of different degradation degreesof P. praecox were also given consideration, which was tested through the characteristic ofnutrients ecological stoichiometry in the system of different degradation degrees of P. praecox.The aiming of the research was to distinguish the limiting nutrient element and its sensitive responding periods which could lay a theoretical foundation for remediation. The main resultswere as follows:1The evaluation of vegetation degeneration for P. praecox of different degrees ofmanagement was conducted based on the factors of stand structure and bamboo shoot yield.The P. praecox testing forests were classified into four categories in terms of vegetationdegradation degree, namely, non-degraded, light-degraded, moderate-degraded andheavy-degraded. With the increasing of degradation degree, average DBH and bamboo shootyield decreased gradually. The proportion of two-year-old standing bamboo decreased whilethat of three-year-old-and-over standing bamboo increased. The heavy degradation degrees of P.praecox had the lowest proportion of new bamboo which had low self-renewal capacity. Theage structure，average diameter of breast height （DBH） and bamboo shoot yield were mainresponding indexes for different degradation degrees of P. praecox.2There were obvious differences among different degradation degrees of P. praecox forthe nutrients responding characteristics. Different components in SVS showed differentnutrient characteristics for different functions. With the extension of implementation years, theenrichment of nutrients made the metabolism lose balance and the degradation degree becomeaggravating. The enrichment of P, Zn elements was the critical factors for the degradation of P.praecox. The levels of soil available nutrients were affected signicificantly by the cultivationtechniques. The effect of P element appeared obviously in the period of bud differentiationwhile that of Zn element was revealed in the period of refoliation and branch development.（1） Soil available nutrient content show significant difference among different degradationdegrees of P. praecox. Soil organic matter, soil available P and Zn contents were increasedsignificantly while available Mn decreased for heavy-degraded forests with the extension ofyears for soil-surface mulching. Light-degraded forests of P. praecox without soil-surfacemulching had the lowest soil available P content, which were54.82mg·kg^-1in the period ofrefoliation and branch development,50.96mg·kg^-1in the period of rhizome growing,61.92mg·kg^-1in the period of bud differentiation,13.04mg·kg^-1in the period of pregnancy and emergence for shoots, while soil available P content for heavy-degraded forests of P. praecoxwere477.19mg·kg^-1,705.83mg·kg^-1,544.63mg·kg^-1and402.92mg·kg^-1in the correspondingperiods, which were8.71,13.85,8.80and30.89times as much as that for light-degradedforests of P. praecox. Therefore, the significant increment of soil available P content caused bysoil-surface mulching was the distinguishing feature for degraded forests of P. praecox. In theprocess of degradation, soil acidification had the significant positive correlation with theaccumulation of soil available P, Zn and other contents.（2） Soil available P, Zn contents were the key factors to restrict the changing of bambooleaf and bamboo rhizome nutrient contents. P, Zn contents of both bamboo leaf and rhizomecould reflect the changing of soil nutrient contents for different degradation degrees of P.praecox. In the period of bud differentiation, P content of bamboo leaf and rhizome had thesignificant correlation with soil available Zn content, while in the period of refoliation andbranch development, Zn content of bamboo rhizome was restricted by the soil available Pcontent. There was obvious differentiation between the nutrient contents of bamboo leaf andrhizome in different growing periods. The influence of the enrichment of soil P content to thenutrient metabolic level of P. praecox had a significant positive correlation with the high levelof soil Zn.（3） The internal and external nutrient cyclings for bamboo leaf, an adaptive mechanismunder nutrient stressed environments, were also the important feature representing thedegradation degrees of P. praecox. Non-degraded forests, with a large nutrient absorption andexuberant metabolic level, made the best of nutrient resources in a manner of “conservation”;while heavy-degraded forests of P. praecox, which had a low P nutrient resorption efficiency,showed an “extravagance” pattern of consumption under P nutrient stress. The existence ofadaptive mechanism for bamboo resulted in the non-significant correlation between thenutrient resorption efficiency and the corresponding soil nutrient availability level. With theincreasing of degradation degree, the quantity of litter leaf decreased gradually. Nutrient returnof litter leaf had a significant negative correlation with the soil P, Zn content. （4） Fine root biomass and nutrient stock were the vital indicators representing thedegradation degrees of P. praecox. With the increasing of degradation degree, fine root biomassshowed a gradually decreasing trend. Non-degraded forests reached the highest level of4.68t·hm-2while heavy-degraded forests got to the lowest level of0.95t·hm-2in the period ofpregnancy and emergence for shoots, which showed an obvious degradation feature. The N, P,K, Mn, Zn stock of fine root for heavy-degraded forests decreased significantly, which revealeda low rate of fine root turnover. The enrichment of soil available P and Zn contents were thekey restricting indicators for the production of fine root.3C, N, P stoichiometric characteristics for different components in SVS of differentdegradation degrees of P. praecox could reflect the degradation degree and the influence oflimiting nutrient element effectively for P. praecox. Compared with non-degraded forests, N: Pstoichiometric ratios of soil, leaf and fine root for heavy-degraded forests of P. praecox reducedsignificantly, while N: P of litter leaf rose in the periods of refoliation and branch developmentand emergence for shoots, which reflected the degradation degree; however, in the period ofbud differentiation, the stoichiometric characteristic of P element of litter leaf reduced whichrevealed the feature of reduction for P absorption and conservation capacity resulted from theexcessive accumulation of P element in degraded forests. N: P stoichiometric ratios of soil andleaf could reveal the characteristic of P enrichment for soil in degraded forests, while that ofleaf and litter leaf could represent leaf N resorption level of degraded forests. N: Pstoichiometric ratio of fine root gave expression to leaf P resorption level.4The responding characteristics of limiting nutrient element could provide a theoreticalbasis for the management countermeasures of remediation for degraded forests of P. praecox.In the early period of the implementation, cultivation techniques for early shooting and highyielding had effects of slowing down the process of vegetation degradation and increasing theeconomic output. With the extension of implementation years, the enrichment of nutrientsespecially P element made the degradation degree become aggravating. Thus, it is necessary toreduce the input of P fertilizer properly, especially in the period of bud differentiation when the level of growth and metaboly is slow for forests. In view of the effect of the soil acidificationto the changing of soil nutrient content, it is proper to adjust soil pH to improve the situation ofnutrient stress. Meanwhile, the interaction of P, Zn and other elements should be given highconsideration in the process of nutrients formulation management for degraded forests so as torealize the sustainable management for P. praecox effectively.更多还原