【作者】 刘海涛；

【导师】 贾志清；

【作者基本信息】 中国林业科学研究院 ， 水土保持与荒漠化防治， 2012， 博士

【摘要】 退化生态系统恢复的实质是群落演替，植物生理生态学作为生态系统结构与功能关系的研究内容之一，在退化生态系统植被恢复的研究中起着非常重要的作用。为了研究高寒沙地人工乌柳林植被建设对退化生态系统恢复过程的影响以及乌柳本身在当地特殊高寒环境条件下的生理生态特征，本研究从植物生理生态学角度出发，通过对处于不同恢复阶段乌柳的光合生理、水分生理、叶片结构型性状特征以及乌柳林群落结构和林下物种多样性、土壤理化性质等方面进行了系统的比较研究。主要研究结果如下：（1）25和37年生乌柳P_n日变化为双峰曲线，出现了光合“午休”现象；4和11年生乌柳P_n日变化为单峰曲线。11和25年生乌柳P_n和T_r日均值显著高于4和37年生乌柳，4年生乌柳WUEt日均值显著高于其它3个林龄乌柳。采用Michaelis-Menten模型对各林龄乌柳的光响应和CO₂响应参数拟合良好。11年生乌柳α值显著高于其它3个林龄乌柳；4和37年生乌柳R_d值显著高于11和25年生乌柳；11和25年生乌柳Amax值显著高于4和37年生乌柳。叶绿素荧光参数中，11和25年生乌柳Φ_PSⅡ、q_P日均值显著高于4年生乌柳，4年生乌柳NPQ日均值显著高于其它3个林龄乌柳，37年生乌柳NPQ日均值显著高于11年生乌柳。林龄对乌柳的光合能力产生了显著影响：11和25年生乌柳的光合能力较强；4年生乌柳的水分利用效率较高；37年生乌柳的光合能力和水分利用效率均显著降低，植株应已处于生长发育衰退期。（2）各林龄乌柳相对水分亏损无显著差异。37年生乌柳水势日均值显著低于其它3个林龄乌柳，4和11年生乌柳水势日均值显著低于25年生乌柳，37年生乌柳在日尺度上受到了严重的水分胁迫。4年生乌柳失水率显著低于其它3个林龄乌柳，25年生乌柳失水率显著低于11年生乌柳，4和25年生乌柳的抗旱能力较强。4年生乌柳SLA显著低于其它3个林龄乌柳，表明其水分利用效率较高。11年生乌柳N_mass显著高于其它3个林龄乌柳，25年生乌柳N_mass显著高于37年生乌柳，表明11和25年生乌柳的光合能力较强。11年生乌柳P_mass显著高于25和37年生乌柳，4年生乌柳P_mass显著高于25年生乌柳。25年生乌柳N_mass/P_mass显著高于4和11年生乌柳，各林龄乌柳N_mass/P_mass在5.16⁶.28之间，表明乌柳的生长严重受到氮素缺乏的制约。4个林龄乌柳N_mass与P_mass呈显著正相关，P_mass与N_mass/P_mass呈极显著负相关，P_mass与林龄呈显著负相关，N_mass/P_mass与林龄呈显著正相关。林龄对乌柳的水分生理状况和叶片结构型性状产生了显著影响：25年生乌柳的水分条件较好，抗旱能力较强，由叶性状参数反映出的光合能力也较强；11年生乌柳的水分条件较差，抗旱能力较弱，但由叶性状参数所反映出的光合能力却最强；4年生乌柳的水分条件较差，但其抗旱能力较强，由叶性状反映出的水分利用效率也较高；37年生乌柳的水分条件恶劣，抗旱能力较弱，由叶性状反映出的光合能力也最弱，植株应已处于生长发育衰退期。（3）4个林龄乌柳林下重要值较大的物种不尽相同，赖草在各林龄乌柳林下植被群落中均以优势种的地位出现，表明其适应性较强。随着林龄的增加，在流动、半流动沙地中出现的一年生植物逐渐从群落中消失，半灌木、灌木开始出现在林下植被中，群落结构趋于稳定。演替各阶段多年生植物的单种重要值明显大于一年生植物，多年生植物在林下植物群落功能维持中起着重要作用。随演替进展林下植物群落物种丰富度、物种多样性、均匀度、生态优势度指数均表现出逐渐增加的趋势。林龄对乌柳林下的群落结构组成和物种多样性产生了显著影响：随着乌柳林龄的增加，林下植物群落的组成向着均匀化方向发展，物种丰富度和多样性指数不断增加，林下植被群落得到了较好的恢复。（4）在乌柳林生长发育过程中，林下0¹0cm土层土壤含水量逐渐增加，10²0cm土层土壤含水量先减少后增加，0¹0cm土层土壤含水量的变化幅度明显大于10²0cm土层土壤。0¹0cm和10²0cm土层土壤粉粒、有机质、TOC和TN含量随乌柳林恢复年限的增加而增加，在垂直方向上其增幅和含量呈降低趋势。0¹0cm和10²0cm土层土壤沙砾含量和pH值随乌柳林恢复年限的增加而降低，在垂直方向上其降幅呈降低趋势，含量呈升高趋势。土壤pH与TOC、TN呈极显著负相关，TOC与TN呈极显著正相关，土壤中沙砾（1⁰.05mm）含量与有机质、TOC和TN含量呈极显著负相关，粉粒（0.05⁰.002mm）含量与有机质、TOC和TN含量呈极显著正相关。在研究区域，有机质、TOC和TN因土壤颗粒组成变化而积累的定量关系可用线性方程较好的预测，为乌柳林植被恢复过程中不同阶段的土壤碳汇量的估算提供了依据。林龄对乌柳林下土壤环境特征参数产生了显著影响：随着乌柳林龄的增加，林下表层土壤的理化性状逐渐得到改善；乌柳林的建设有利于风沙土的固定和发育，其作用随林龄的增加而增强，随土层深度的增加而降低；沙砾含量的减少和粉粒含量的增加共同导致土壤质地的细粒化，并伴随着土壤碱性的减弱和碳、氮的固存效应。更多还原

【Abstract】 The essentiality of restoration of degraded ecosystem is community succession. Plantphysiological ecology is one of the research content of relation between ecosystem structureand function, playing important roles in the research of vegetation recovery of degradedecosystem. In order to understand the effect of Salix cheilophila plantation on the recoveryprocess of degraded ecosystem and adaptive characters of S. cheilophila plantation to localspecific high-cold climate condition in alpine sandy land, In this study, the physiological andecological characteristics of S. cheilophila vegetation were researched, includingphotosynthetic physiology, water physiology, leaf structure traits, community structure of S.cheilophila plantation, understory species diversity and soil physicochemical properties, themain results are as follows:（1） Four stand ages S. cheilophila showed different diurnal courses of gas exchange. Thediurnal fluctuations of net photosynthetic rate of37-and25-years-old S. cheilophila wererepresented by a bimodal curve, appearing the photosynthetic midday depression.11-and4-years-old S. cheilophila were represented by a unimodal curve. P_nand T_rof11-and25-years-old S. cheilophila was significantly higher that of4-and37-years-old S. cheilophila,while WUEtof4-years-old S. cheilophila was significantly higher that of other three stand ageS. cheilophila. Light response parameters fitting and CO₂response parameters fitting revealedthe initial quantum yield（α） of11-years-old S. cheilophila was significantly higher than that ofother three stand age S. cheilophila, and photosynthetic capacity （Amax） of11-and25-years-oldS. cheilophila were significantly higher than those of4-and37-years-old S. cheilophila,simultaneously, the dark respiratory rate（R_d） were significantly lower than that of4-and37-years-old S. cheilophila, indicating both of them have stronger photosynthetic and organicmatter accumulation ability. Meanwhile, the actual photochemical quantum efficiency （Φ_PSⅡ）and photochemical quenching coefficient （q_P） of11-and25-years-old S. cheilophila weresignificantly higher than that of4-years-old S. cheilophila, indicating both of them havestronger photosynthetic ability. Simultaneously, non-photochemical quenching coefficient（NPQ） of4-years-old S. cheilophila was significantly higher than that of other three stand age S.cheilophila, and NPQ of37-years-old S. cheilophila was significantly higher than that of11-years-old S. cheilophila, suggesting that there were a lot of light energy absorbed of4-and37-years-old S. cheilophila can not be used for photosynthesis, dissipating in the form of heat. The conclusion is that photosynthetic capacity of S. cheilophila shows significant changewith the increase of stand age. The photosynthetic capacity of11-and25-years-oldS.cheilophila is comparatively even higher, and the photosynthetic capacity and waterutilization efficiency of37-years-old S.cheilophila is decreasing obviously, which indicates thatthe plant of37-years-old S.cheilophila is in decline stage of growth and development.（2） The relative water deficit of four ages S. cheilophila had no significant difference. Thedaily mean value of water potential of37-years-old S. cheilophila was significantly lower thatof other three stand ages S. cheilophila, and the daily mean value of water potential of4-and11-years-old S. cheilophila was significantly lower that of25-years-old S. cheilophila, whichindicated that37-years-old S cheilophila suffers serious drought stress. The water losing rate of4-years-old S. cheilophila was significantly lower than that of other three stand ages S.cheilophila, and the water losing rate of25-years-old S. cheilophila was significantly lowerthat of11-year-old S. cheilophila, which indicated that4-and11-years-old S cheilophila havehigher drought resistance capability. Simultaneously, the SLA of4-years-old S. cheilophila wassignificantly lower that of other three stand ages S. cheilophila, implying the water useefficiency of4-years-old S. cheilophila is even higher. The N_massof11-years-old S. cheilophilawas significantly higher that of other three stand ages S. cheilophila, and the N_massof25-years-old S. cheilophila was significantly higher that of37-years-old S. cheilophila,implying photosynthetic capacity of11-and25-years-old S. cheilophila is even higher. TheP_massof11-years-old S. cheilophila was significantly higher that of25-and37-years-old S.cheilophila, and the P_massof4-years-old S. cheilophila was significantly higher that of25-years-old S. cheilophila. The N_mass/P_massof25-years-old S. cheilophila was significantlyhigher that of11-and25-years-old S. cheilophila, meanwhile, the average N_mass/P_masswerebetween5.16and6.28, far below14, which revealed the productivity of S. cheilophila inGonghe basin is nitrogen limited. Correlation analysis indicated that the N_massof four ages S.cheilophila was significantly positively correlated with P_mass, the P_massof four ages S.cheilophila was highly significantly negatively correlated with N_mass/P_mass, the P_massof fourages S. cheilophila was significantly negatively correlated with stand age, and the N_mass/P_massoffour ages S. cheilophila was significantly positively correlated with stand age.The conclusion is that water physiological status and leaf structure type traits of S.cheilophila shows significant change with the increase of stand age. The water physiologicalstatus of11-years-old S.chelophila is better, and drought resistance capability is stronger, andthe photosynthetic capacity reflected by leaf traits is higher. The drought-resistant ability of11-years-old S.chelophila is weaker, but the photosynthetic capacity reflected by leaf traits is the highest.4-years-old S.chelophila reveals stonger drought-resistant ability and waterutilization efficiency through its own adjustment of physiology and leaf traits under worsewater condition. The drought-resistant ability of37-years-old S.chelophila decreasesignificantly as well as photosynthetic capacity reflected by leaf traits, which indicates that theplant of37-years-old S.cheilophila is in decline stage of growth and development.（3） The species of the important value were different in four understory vegetation of S.cheilophila. Leymus decalinus was the dominant species in understory vegetation of differentstand ages of S. cheilophila, which indicated that L. decalinus has strong adaptability. With theincrease of age, some annual species in drifting or semi-drifting sandy land graduallydisappeared from the community, and shrub and subshrub began to appear in the undergrowthvegetation community, implying the structure of undergrowth vegetation community tended tobe stable. During the process of succession, the important value of one perennials species wassignificantly higher than that of annuals, which indicated that perennial plants played animportant role in maintenance of community function. Both aboveground biomass andcoverage of understory communities presented increasing-decreasing-increasing trend in theprocess of vegetation restoration. Simultaneously, the species richness, species diversity,evenness and ecological dominance index of undergrowth vegetation community increasedwith progress of succession, which indicated that structure tended to be stable and ecosystemfunction also strengthened constantly. In early-middle period of vegetation restoration, due tothe poor stability of the soil substrate, low soil nutrients and the competition and shading ofupper Salix cheilophila, the restorative course for understory species diversity were relativelyslow, and primary productivity and coverage of vegetation aslo be in low level. Therefore, inorder to promote development of forest stands and understory species diversity, a selectivecutting for upper layer of S. cheilophila plantation should be carried out in the middle stage ofsuccession. Meanwhile, upper layer of S. cheilophila plantation was in a state of decline in thelater stage of succession, stumping and rejuvenating treatments should be done to improvestability and ecological function of forest stands.The conclusion is that community structure and understoryapecies diversity of S.cheilophila shows significant change. With the increase of stand age of S. cheilophila, thestructure of undergrowth vegetation community tend to be stable, and diversity of species areincreasing, and ecosystem function improve steadly.（4） With the growth of S. cheilophila plantation, soil water content of0¹0cm increasedgradually, while soil water content of10²0cm primarily decreased and then increased, therangeability of0¹0cm soil water content was obviously higher than10²0cm soil water content. The soil silt, organic matter, TOC and TN content of0¹0cm and10²0cm soil layerincreased with the restoration period of S. cheilophila plantation, and the increase amplitudeand the content presented decreasing trend in vertical direction. Simultaneously, soil sandcontent and pH of0¹0cm and10²0cm soil layer decreased with ages increasing of S.cheilophila plantation, and the falling range presented decreasing trend, and the content wastending to rise in vertical direction. The Soil pH was highly significantly negatively correlatedwith TOC and TN. TOC was highly significantly positively correlated with TN. Soil sand（1⁰.05mm） content was highly significantly negatively correlated with organic matter, TOC,and TN content. Soil silt （0.05⁰.002mm） content was highly significantly positivelycorrelated with organic matter, TOC, and TN content. In research area, it could be predicted foraccumulated quantitative relation of organic matter, TOC, TN because of soil particlescomposition by linear equation, which provided scientific basis to estimate soil carbon sink inthe process of S. cheilophila plantation vegetation restoration.The conclusion is that characteristic parameters of forest soil of S. cheilophila showssignificant change. With the increase of stand age of S. cheilophila, the physicochemicalproerty of surface soil layer improved gradually. The increase of the content of silt and thedecrease of the content of sand grains led jointly the fining of soil texture in surface soil layer,the fining of soil texture was accompanied with the soil environment improved and the fixedexisting effect of organic carbon and nitrogen.更多还原