【作者】 易志军；

【导师】 吴晓芙； 胡曰利；

【作者基本信息】 中南林学院 ， 生态学， 2002， 博士

【摘要】 本文探讨和揭示了桉树人工林及其退化土壤中林木生长、养分平衡与地力维护的相关理论和规律，重点阐述和验证了桉树人工林生态采伐的时期和季节；林木施肥的重要性与养分吸收的时段和各器官养分储量规律；空间和混交对林木生产力、养分分布及地力维护中时空差异规律；混交中抑制机理和调控措施等问题。并提出了复层混交生态采伐经营模型。 主要结果和结论如下： 1)桉凋落物叶是总凋落物的主要部分，其生物量节律呈双峰曲线。低温和低降雨量与树冠竞争的相互作用结果增大枝、叶凋落物量。冠幅扩展时凋落物量最小。在凋落物产生的林龄和季节高峰期之后采伐可通过凋落物归还林地部分养分。 2)树体器官N浓度显著差异规律是叶＞枝，皮，根＞干；P为叶＞枝，皮＞根＞干；K为叶＞皮，枝＞根，干。总体上N、P和K浓度随林龄增大而递减，其时效对叶和枝最显著，反映早期N、P和K管理的重要性。同龄树木体内养分浓度近相同。每公顷养分储量随林龄增加而增加。在一个轮伐期内桉树养分吸收明显呈3个时段。 3)叶干重占树体总干重的比例随林龄增加而减小，其与干重相反。单株叶干重在2.5a后差异小。2.5a前地上部分NPK储量规律性可确定早期养分供应比例。3.5a前是快速N、P储存期。桉树施肥是维护林地养分平衡外部养分补偿的主要途径。防止地力退化所需养分量是地力养分亏损量；维持地力生产力则是地力养分亏缺量。地力衰退是亏损量不断增加。 4)空间效应对直径、高、单株生物量有促进作用。桉和相思混交抑制了桉树与相思生长，其抑制机理是①树冠不成层竞争导致光资源使用效率降低；②地下细根非协同性且无资源的供给关系。 5)增大空间增加了单株器官尤其是叶和根的生物量，相对降低了分配到干的生物量比例。混交增加单株叶量和每公顷叶量，降低其它器官尤其是枝的生物量；但对根生物量没有显著影响。空间对叶生物量的影响大于混交。 6)混交增加凋落物量；延长了凋落期；增加凋落叶量而减少枝量。混交对肥力参数具有正效应；提高土壤生物活性。 7)混交和增大空间均增加叶和根NPK含量、储量，但空间的效应比混交显著。混交降低了除叶外其它器官PK含量和储量。 8)空间增加了单株平均N、P、K浓度和林分每公顷平均储量；而混交则增加了N而降低了平均P、K浓度和每公顷平均储量。空间对N增加的效应比混交显著。空间增大易消耗林地养分而混交则节约养分。因此，可提出“隔年种植—萌芽—复层混交—生态采伐”经营模型。更多还原

【Abstract】 The objective of the work probed into and opened out the theory and the related laws of tree growth and nutrient balance and site productivity of maintenance in the area of Eucalyptus plantation and its degradation site management. By expatiating and validating, it made clear some topics such as the ecological harvest age and season of Eucalyptus, the importance of tree fertilization and the stage of nutrient uptake and the change of nutrient pools of tree parts, the age and spacing effect of the increasing spacing and the mixed measure on productivity, nutrient distribution and site maintenance, the restraining mechanism between the mixed species and its control. The management model of Eucalyptus plantation, finally, was put forward. Main results and conclusions are as follows:1. Leaf litter, the main contributor of the total annual litter fall, has a rhythm with double peak curve. Reacted with the lower temperature and lower precipitation, canopy competition accelerated the amount of branch and leaf litter fall, which was the lowest as canopy spread. Trees should be harvested after the peak times of season and tree age to return nutrient via litter partially.2. The order of significant difference of tree parts for N-concentration was leaf > branch, bark, root > bolewood, for P leaf > branch, bark > root > bolewood, and for K leaf > bark, branch > root. NPK concentrations, generally, decreased with increasing tree age, the age effects of which were significant on branch and leaf so as to reveal the major role of forepart NPK managements. Trees with same age had almost stable nutrient concentrations. The total nutrient pools per hectare increased with increasing tree age. Three significant difference stage of nutrient uptake of Eucalyptus during one rotation could be divided.3. The proportion of the dry weight of leaves that had small change after 2.5a to total biomass of tree parts decreased with increasing tree age, in reverse to bolewood weight. NPK pool treads of aboveground biomass before 2.5a could be used to account the ratio of nutrient supply, in rapid accumulation of NP before 3.5a. Eucalyptus fertilization was main approach for returning nutrient from exterior setting in order to ensure a balance nutrient system in forest soil. New concepts of the site nutrient losing (SNLo) and the site nutrient lacking (SNLa) were put forward. Amount of SNPLo was equal to that of nutrient for preventing site degradation, SNLa for maintaining site productivity. The essential of site degradation was result from SNLo increasing.4. Spacing effect had the facilitating effects on mean diameter, height and biomassof trees. The mixed stands, Eucalyptus ABL12 X Acacia crassicarpa Cunn, was restrain Eucalyptus growth and Acacia, the mechanism of which was from the no-stratification competition of canopy that lead to reduce the utilization efficiency of light resources, and from soil micro-environment of the no-cooperation and no-supply each other of fine roots between the mixed species.5. Increasing spacing added the biomass of tree parts, especially leaf and root, and relatively reduced the proportion of the allocated biomass to bolewood. However, the mixed measure increased the weights of a tree and per hectare leaves while decreased that of other tree parts, especially for branch, no effect on root biomass. Increasing spacing had more significant effect on leaf biomass than the mixed measure.6. The mixed measure increased the amount of litter than monoculture and enlarged the period of fall and increased the leaf litter but reduced the branch litter. With higher bioactivity, the mixed measure had a more positive effect on soil fertility parameters.7. The mixed measure and increasing spacing separately increased the NPK contents and pools of leaves and roots; however the former had more adding effects on that than the latter. The mixed measure reduced the PK contents and pools of tree parts except leaf,8. Increasing spacing increased average NPK concentrations of a tr更多还原