【作者】 唐万鹏；

【导师】 李吉跃；

【作者基本信息】 北京林业大学 ， 森林培育， 2009， 博士

【摘要】 江汉平原是我国南方重要的杨树速生丰产林基地,长期以来江汉平原杨树人工林的一直处于粗放经营状态,栽植密度不合理,定向培育目标不明确,杨树生长潜力尚未充分发挥,加之大面积纯林化经营和长期连栽,导致林木生长减缓、林分生物量降低、生产力下降、地力衰退、病虫害频发等生态经济问题日益凸显。针对江汉平原杨树人工林经营现状、问题及需求,为充分发挥该区域杨树人工林的栽培潜力,实现地力维持及人工林可持续经营,促进区域经济发展,采用野外调查与室内分析相结合以及空间代替时间的研究方法,系统开展了高密度(＞1000株.hm^-2)、中密度(1000～500株.hm^-2)、低密度(＜500株.hm^-2)三种密度状况下杨树人工林的生物量与生产力、主伐年龄、培育年限以及江汉平原杨树人工林最适经营密度研究,并首次全面深入地研究了连栽对江汉平原杨树人工林土壤水分物理性质、化学养分、生物学特性以及对林木生长的影响,具有重要的理论意义和应用价值。研究结果表明:1.中密度与低密度林分林木与各组份生物量的变化规律为“树干＞树枝＞树皮＞树根＞树叶”,高密度林分生物量的变化规律不明显;各组份生物量所占比例在各类密度林分中的变动幅度大小排序为“树叶（7.48%）＞树皮（3.53%）＞树干（2.51%）＞树根（0.97%）＞树枝（0.55%）”。林分密度对净生产力有显著影响,随着林分密度的降低,林分和林分各组分的净生产量也随之降低。在林分各组份中,树干的净生产量最大,高、中、低3组密度林分分别为5.78～15.73t.hm^-2.a^-1、5.03～5.69 t.hm^-2.a^-1和2.58～3.74 t.hm^-2.a^-1。2.对于同龄林分,最适经营密度随着地位指数的增加而减少。立地条件好,初植株行距宜大,保留株数少;立地条件差,初植株行距宜小,保留株数多,结合江汉平原立地条件,大部分地区杨树人工林的造林株行距以大于3.0m×5.0m为宜。3.不同密度类型杨树人工林的主伐年龄与数量成熟龄表现出随着林分密度的减少而逐渐变大的总趋势,而主伐年龄时的最大年均净收益则随林分密度增大而增加;高密度林分主伐年龄为5～7年,以培育纸浆材、刨花板等工业用材为主;中密度林分主伐年龄为8～10年,以培育木芯板、家具等工业用材为主;低密度林分主伐年龄为11～12年,以培育胶合板等工业用材为主。4.各种立地密度组合类型下,高密度林分均不适合培育大径材,Ⅰ类和Ⅱ类立地栽培中密度和低密度林分较好,培育大、中、小径材均较理想;Ⅲ类立地各种密度类型培育不同用途林分总体差别不大。小径材培育年限平均为5～7a,中径材培育年限平均为7～10a,大径材培育年限平均为10～13a以上。5.连栽导致林地土壤变紧实,土壤孔隙度及持水量变小,土壤团聚体稳定性变差。灰色评价表明第二代林地土壤物理性质的关联度值比第一代降低14.80%,土壤物理状况呈恶化趋势。连栽导致N、P、K大量元素下降2.88%～12.20%,且对N影响最大,K次之,P最小;微量元素下降3.52%～53.37%,且对Zn影响最大,其次为Cu、Fe和Mn;土壤微生物总量下降56.05%;土壤磷酸酶、脲酶、蔗糖酶、蛋白酶、过氧化氢酶活性下降1.92%～50.00%,而多酚氧化酶活性增加100.00%。6.连栽条件下,前4年连栽对杨树生长影响并不明显,但从第5年到第9林,第二代林较第一代林胸径减少0.70%～12.05%%,树高减少7.28%～20.41%,材积减少17.78%～27.83%,单株生物量减少7.26%～32.42%。采用层次分析法对连栽杨树人工林的生产力进行综合评价,结果表明第一代人工林生产力高于第二代人工林。更多还原

【Abstract】 Jianghan Plain is an important high-yield poplar plantation basis in southern China.For a long time, however,the poplar plantations in Jianghan Plain were always managed extensively with no clear directive cultivation targets and irrational cultivation densities,so their growth potential playing unfully. At the same time,some ecological and economic problems had become more obvious which included poplar growing slowly,biomass decreasing,productivity dropping,land capability declining and pest taking place frequently resulted by pure stand managing widely and long-term successive planting. According to management situations,questions and demands of poplar plantation in Jianghan Plain,and applying to the methods of field survey,laboratory analysis,random sampling and space replacing time, density control techniques of poplar plantation were researched symatically which included biomass and productivity,felling age,cultivation period and the optimal management density under different density conditions of high density(＞1000 strains.hm^-2),middle density(1000～500 strains.hm^-2)and low density(＜500 strains.hm^-2),and successive planting effects on soil physical,chemical and biological characterristics and growth of poplar plantation were also studies initially in order to applying poplar plantation cultivation potential,maintaining soil fertility,achieving plantation sustainable management and promoting regional economy development.The main results were as follows:1.The biomass of different parts of the stand changed diversely with different stand densitities.In stands with middle,low density,it was the regular pattern that the biomass of stem＞branch＞bark＞root＞leaf.However,there was no obvious regularity in stands with high density.The biomass ratio variation extents of all parts had the same regularity of leaf（7.48%）＞bark（3.53%）＞stem（2.51%）＞root（0.97%）＞branch（0.55%）in regardless of densities.Stand densities also had obvious positive influences on the net productivities,which meaned that net productivities of stands and all parts all decreased with stand densities decreasing.The output of stem was biggest among all parts of stands, which was 5.78～15.73t.hm^-2.a^-1,5.03～5.69 t.hm^-2.a^-1and 2.58～3.74 t.hm^-2.a^-1respectively in stands of high,middle and low densities.2.For stands with the same ages,the optimal management densities decreased with site index increasing.Space between plants should be larger with less poplar remained with better stand conditions; it should be smaller with more poplars remained with general stand conditions.It was suitable for 3.0m×5.0m of space between plants of poplar plantation in most areas of Jianghan plain.3.Harvest cutting ages and quantitative maturity ages of man-made poplar forests with different stand densities showed a general trend of becoming larger with decreasing stand densities;on the other hand,the maximum annual mean net and stand stock per area showed the larger trend with increasing stand densities.The cultivating periods were 5～7 years of high density plantations for paper-making and particle boards,8～10 years of middle density plantations for core boards and furniture,and 11～12 years of low density plantations for plywoods.4.It was not suitable for cultivation of large-diameter timber at every type different site and density. At typeⅠandⅡsite,it was better combination selection to more ideally cultivate large,middle, small-diameter timbers when using categories of middle-density and low-density;however,there were not very large difference among various categories of density at typeⅢsite.The everage cultivating periods were 5～7 years for small-density timbers,7～10 years for middle-density timbers,and 10～13 years for large-density timbers.5.Under successive plantation,the soil became compacter,soil porosity and water-holding capacity became smaller,and the stabilish of soil aggregate became worse.Grey evaluate showed that the relating value of soil physical characteristics in second generation forests was 14.80%less than that in first generation forests,which meaned soil physical conditions worsen.In second generation forests macroelements such as N、P、K decreased by 2.88%～12.20%,and the soil N element suffered the most to successive plantation followed by K and P.it also accounted for that Soil microelements decreased by 3.52%～53.37%with the order of severity of Zn,Cu,Fe,Mn.The quantities of total microbe numbers decreased by 56.05%;and the activities of soil phosphataese,urease,sucrase,proteinase,catalase decreased by 1.92%～50.00%,while the activity of soil polyphenol oxidase increased by 100.00%.6.Comparied with the first generation forests,the influence of successive plantation on poplar growth was not significant in the previous four years,the DBH,height,volume and individual biomass decreased by 0.70%～12.05%,7.28%～20.41%,17.78%～27.83%and 7.26%～32.42%respectively in second generation forests from the fifth year to the ninth year.It showed that the productivity of first generation man-made poplar forest was higher than that of second generation man-made poplar forest by the mothod of AHP.更多还原