【作者】 俞元春；

【导师】 叶镜中； 姜志林；

【作者基本信息】 南京林业大学 ， 生态学， 1999， 博士

【摘要】 杉木[Cunninghamia lanceolata(Lamb) Hook]是我国南方最重要的用材树种,近几十年来,由于高度的集约经营、并伴随着某些不合理的营林和栽培措施,如树种单纯,全垦整地,大面积皆伐、在同一林地上连续栽杉等,加上杉木自身生物学特性等原因,致使杉木人工林生产力下降和地力衰退现象普遍存在,已严重影响了杉木人工林的持续经营。因此,如何维护和提高杉林土壤肥力,保持人工林持续速生、丰产,使林地能长期持续利用,已成为我国林业建设,尤其是营林生产中急待解决的重大问题之一。 近年来,虽然有关杉木人工林地力变化及连栽生产力下降的研究较多,然而这些研究都是在不同学科、不同地区范围、不同方面分散进行,学科之间缺乏联系,研究工作缺乏系统性,对不同生长发育时期、不同立地指数杉木人工林的土壤肥力变化和生产力状况缺乏全面、深入的系统研究,加上林业地域上的复杂性,在研究的深度和广度上仍受到一定程度的限制。不同立地指数、不同生长发育时期的杉木人工林是否都存在地力衰退,杉木人工林土壤综合肥力退化发生在林分的什么时期(林龄)尚不十分清楚。鉴于此,本论文通过面上调查和定位观测,全面系统地研究不同栽植代数、不同生长发育时期和不同立地指数杉木人工林的土壤肥力变化和生产力状况,在轮伐期内,炼山、整地等营林措施对杉林土壤养分损耗与功能的影响,以及发展和丰富林下植被、推行林地施肥制度对杉林土壤肥力和长期生产力的影响,为维护和提高杉林土壤肥力,实现林地可持续经营提供科学依据。主要研究结果如下: 1、随着栽植代数的增加,杉木胸径生长逐代递减,树高生长明显衰退,林分蓄积量逐代下降。不同地位指数的林地,连栽后,杉木生长的降低幅度有所不同,16地位指数级的林地,二代中龄林杉木林平均胸径、树高和蓄积量比一代林分别下降了9.27%、12.56%和22.85%;三代林比一代林分别下降26.90%、15.96%和56.15%;14地位指数的林地,连栽后三代林的胸径和蓄积量降低更为明显。不同立地指数(14和16)林地间杉林平均胸径和蓄积量的差异以三代林最大。连栽对杉林生物量也有明显影响,杉木林平均单株总生物量和各器官生物量均随栽植代数逐代下降,16地位指数的二、三代中龄林平均单株总生更多还原

【Abstract】 Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is a most important timber tree in southern China. In the last decades, because of the traditional extensive management and some inappropriate cultivated measures, such as monoculture of a tree species, control burning, over-all site preparation, clear cutting and continuous cropping at the same site, as well as the biological characteristics of Chinese fir itself, the decline of its forest productivity and soil fertility exists in common, which directly affects the sustained-yield management of Chinese fir plantation on site. It is a critical problem nowadays to reveal the’ mechanism of productivity decline of Chinese fir plantations after continuous cropping and to explore techniques for long-term maintenance of the forest productivity.In northern Fujian province, the characteristics of tree growth and soil fertility of the Chinese fir plantations with different rounds of continuous cropping, different ages and different site index have been studied through fixed-size plot observations and extensive investigations. Practicable techniques, such as developing undergrowth and fertilization have also been explored for long-term maintenance of the productivity in Chinese fir plantations. The results obtained are as follows:1. Compared with the first planting, D.B.H, height and volume of the tree in the second and the third plantings in the continuous cropping system of Chinese fir decreased. For example, for the site index 16 stands, compared with those of the first planting, the mean tree height, D.B.H and volume of the second planting decreased by 9.27%, 12.56% and 22.85%, and those of the third planting decreased by 26.90%, 15.96% and 56.15%, respectively. The mean individual biomass of site index 16 stands from the second and the third planting of Chinese fir decreased by 18.45% and 42.94% respectively, compared with those of the first planting. The composition of biomass also changed, the ratio of trunk and bark decreased, but the ratio of branches, leaves and roots increased.2. The physical properties of soil were greatly influenced by the continuous cropping of Chinese fir. Especially in the mid-age stands, the soil volume weight increased, capillary, non-capillary and total porosity of soil under the second and the third plantings decreased, compared with the first one. Soil permeability also became worse. For example, for the site index 16 stand, capillary, non-capillary and total porosity of surface soil (0-20cm) under the second stand decreased by 23.33%, 22.03% and 23.06%, capillary and total porosity of surface soil under the third stand decreased by 43.91% and 27.8%, respectively. For the young plantation, due to the influences of site preparation and tending, the effects of continuous cropping on soil physical properties were not as clear as those in the mid-age stands.3. The greatest effect of continuous cropping on soil nutrient status occurred upon available P. Continuous cropping resulted in decreasing of available P to all of the stands. For example, for the site-index 14 mid-age stand, the concentration of available P in the surface soil of the second and the third plantings decreased by 35.82% and 7.68% respectively. For the site index 16 mid-age stand, the organic matter, total N and hydrolyzable N in soil under the second also plantation decreased by 43.98%, 15.11% and 28.86% respectively. But for the young Chinese fir plantation, except for the available P, most of the other nutrient concentration was not decreased, some were even increased.4. Total contents of Mn and Zn in this region were all lower than their average contents of the whole country, and those of Fe and Cu were relatively high. The contents of available Mn, Cu and Zn were relatively low, and most of soil in this region lacked the available contents of these microelements Mn, Cu, Zn, Along with the increasing continuous cropping of Chinese fir, these shortage could become more serious.5. Along with the increasing continuous cropping of Chinese fir, the acidity of the rhizophere soil was raised, and for the first and the second plantings, O. M. and total N of the rhizophere soil was relatively enriched. But for the third planting, they were relatively lacking. The available P in all of the rhizophere soil decreased.6. For the mid-age and mature continuous cropping plantation, the quantity of soil microbe decreased obviously. The organic carbon may increase in the soils of some continuous plantations, whereas the humic acid and humification coefficient decreased, i.e. continuous cropping resulted in lessening the complication and worsening the quality of soil humus.7. The long-term maintenance of Chinese fir plantation productivity was greatly influenced by ground clearance. Control burning and site preparation led to the decreasing of soil volume weights and the increasing of capillary porosity and total porosity, as well as to the water retaining capacity and soil permeability. Control burning and site preparation could also increase the quantity of microbes, and the contents of available N, P, K. Control burning might promote the survival rate andenhance growth of young Chinese fir trees in a short period. However, owing to the great losses of soil, water and nutrients resulted by control burning, it has been proved that control burning for continuous cropping on the same site is one of the major factors leading to the productivity decline of Chinese fir plantations.8. The type of under growth had clear effects on soil fertility of Chinese fir plantation. Compared with the dicranopteis type undergrowth, the nutrient contents of soil under Chinese fir stand with the pteridophyte type increased. For the same type undergrowth, the more abundant the undergrowth, the higher of nutrient contents in the soil. The contents of available B, Mo, Cu, Zn, in surface soil (0~6cm) under young Chinese fir stand with pteridophyte type undergrowth were higher than those with dicranopteis type undergrowth, but those in subsurface soil (6~30cm) of the former decreased.9. In the northern part of Fujian province, fertilization had some positive effects on the young Chinese fir plantation, but, in general, the effects were not remarkable. P fertilization could increase the biomass of different parts of the tree, In particular, the application of ammonium phosphate in a ditch could increase the amount of laves as well as the total biomass of the tree remarkably. P fertilization could also increase the P concentration and storage in one -year-old leaves and roots. Whether there is fertilization or not, leaf was the major P pool of Chinese fir stands.10. In pot experiment of Chinese fir, P fertilization increased its Fe and N absorption, and N and P associated fertilization increased its Mo absorption, P shortage induced Fe and N shortage, and N shortage induced Mo shortage.11. P utilization percentage by Chinese fir stands in Fujian was much higher than that of the pot experiment in Jiangsu. The highest P utilization percentage occurred with ammonium phosphate, which were 4.06% and 10.04% in pot and field experiment respectively. In the northern part of Fujian province, ammonium phosphate might be the best fertilizer for Chinese fir, and fertilization in a ditch was the best fertilization method.更多还原