【作者】 宋曰钦；

【导师】 翟明普；

【作者基本信息】 北京林业大学 ， 森林培育， 2009， 博士

【摘要】 开展速生纸浆林长期立地生产力维持理论及关键技术的研究,不仅丰富我国森林长期立地生产力研究的内容,促进相关学科的发展,具有一定的理论意义,而且对提高我国纸浆林生产力,确保我国纸浆原料的可持续生产,保障我国制浆、造纸工业的产业安全具有十分重要的实践意义。本文采取时序研究法,以3a、5a、6a、7a共4个不同年龄的三倍体毛白杨纸浆林为对象,研究了地上凋落物、细根周转、湿沉降在林分N、P营养元素循环中的作用及不同年龄林分N、P营养元素循环的特征,以评价三倍体毛白杨纸浆林长期立地生产力的变化;采取网袋法研究了不同因素对落叶、树皮、树枝分解的影响,以确定加快其分解、促进养分释放的措施:同时研究了不同间作物对林地影响、林木与间作物之间关系,以选择能维持立地生产力的合适的间作物种类等内容,得到以下结论:（1）随着年龄的增加,三倍体毛白杨地上凋落物的数量从3a的216.03±59.7gm^-2增加到7a的482.38±101.3gm^-2,通过凋落物归还的N分别为:3a时为18.38±2.46kg.hm^-2a^-1,5a时为21.63±2.25kg.hm^-2a^-1,6a时为39.51±4.61kg.hm^-2a^-1,7a时为38.89±4.89kg.hm^-2a^-1,归还的P分别为:3a时为5.80±0.62kg.hm^-2a^-1,5a时为8.16±0.94kg.hm^-2a^-1,6a时为11.31±1.33kg.hm^-2a^-1,7a时为11.76±1.37kg.hm^-2a^-1;随着年龄的增加,通过细根周转归还的养分也在增加,归还的N分别为:3a时3.85±0.41kghm^-2a^-1,5a时5.22±0.63kghm^-2a^-1,6a时7.62±0.89kghm^-2a^-1,7a时9.17±1.22kghm^-2a^-1;归还的P分别为:3a时0.73±0.07kghm^-2a^-1,5a时1.69±0.09kghm^-2a^-1,6a时1.92±0.31kghm^-2a^-1,7a时1.96±0.21kghm^-2a^-1;从地上凋落物、细根周转、湿沉降三种不同途径归还林地养分所占的比例来看,地上凋落物中的落叶是归还养分主要途径,年龄在3a、5a、6a、7a时,通过落叶归还的N所占比例分别为74.84%、71.96%、78.58%和75.03%,归还的P所占比例分别为85.93%、80.31%、83.04%和83.23%。因此,在维持和提高三倍体毛白杨纸浆林林地长期立地生产力的过程中应加强对落叶的保护和利用,充分发挥落叶在林地自肥中的作用。（2）三倍体毛白杨纸浆林存留的N从3a的212.00kghm^-2增加到7a时的775.6lkghm^-2,存留的P从3a时的109.61kghm^-2增加到7a时的407.15kghm^-2,归还的N从3a的24.56kghm^-2到7a的51.83kghm^-2,在3a、5a、6a、7a4个不同年龄时归还率分别为34.75%、45.85%、48.81%、46.78%,但土壤的N为亏损状态,从3a时亏损0.54%到7a时的1.92%;在3a、5a、6a、7a4个不同年龄时P的归还率则分别为18.47%、29.66%、26.75%、24.29%,土壤的P也为亏损状态,从3a时亏损0.35%到7a时0.52%,无论是N还是P的亏损均表现出增加的趋势;N的周转时间从3a的345.6年缩短到7a的163.8年,P的周转时间从3a的1625.0年缩短到7a的596.1年。因此从N、P养分的变化趋势来看,三倍体毛白杨纸浆林经营可能导致养分缺乏,威胁到长期立地生产力的维持。（3）不同因素在落叶、树皮、枯枝的分解过程中所起的作用不同,林带内与林带间的不同环境、不同年龄对落叶的分解没有产生显著性差异。与棉花叶混合后促进了三倍体毛白杨落叶的分解,混合叶分解50%的天数比三倍体毛白杨落叶少254天,分解95%的天数比三倍体毛白杨落叶少1076天,年分解率比三倍体毛白杨落叶高15.43%。与地表相比,地下环境对不同年龄的落叶、枝条和树皮的分解均产生了显著的促进作用,2a林分的落叶分解50%的时间从地表的499天缩短到地下的291天,4a林分的落叶则从777天缩短到304天,6a林分的落叶从1036天缩短到393天,枝条从771天缩短到338天,树皮从710天缩短到304天;分解95%的时间同样也显著缩短,2a林分的落叶从1853天缩短到1114天,4a林分的落叶从3080天缩短到1157天,6a林分的落叶从4326天缩短到1544天,枝条从3073天缩短到1223天,树皮则从2803天缩短到1072天。因此在生产中如果能对落叶、树枝、树皮进行掩埋可以加快落叶分解,提高养分归还林地的速率。（4）从室内添加不同氮源的结果来看,外加氮源对三倍体毛白杨落叶分解有一定的促进作用,不同氮源之间差异显著,添加铵态氮能显著促进落叶的分解,年分解率可以达到75.28%,而添加硝态氮和混合氮的年分解率分别为55.90%和55.14%,对照为51.14%。（5）从间作1年的结果来看,不同间作物对林地土壤的理化性质产生了不同的影响,间作棉花显著改善了土壤容重,有机质、速效N也有所增加。不同间作物对林木高生长没有产生显著差异,但对胸径生长的影响达到了显著性差异水平,间作棉花在第一年促进了三倍体毛白杨胸径的生长。从不同间作物在造林第一年的产量来看,林木没有对间作物的生长产生影响,各间作物的RCI值均在0附近。因此,综合来看,在造林的第一年,选择棉花作为间作物较为适宜。更多还原

【Abstract】 Carrying out the study on key techniques and theory to maintenance the long-term-site productivity of fast-growth pulp plantation is very important. Not only had it theoretical meanings to enrich contents of the long-term-site productivity study, to promote the development of related disciplines. But also it had practical significance to raise the pulp plantation productivity, to ensure the pulpwood sustainable production, to guarantee our country pulp and paper industry security. In order to assess the change of triploid populus tomentoza pulp plantation long-term-site productivity, The paper studied on effects of aboveground litterfall, fine root turnover and wet dust precipitation in nutrient（N、P） cycling of triploid populus tomentoza pulp plantations at different ages,namely 2a、4a、5a、6a.It studied influence of different factors on decomposition of leaf、tree bark and twig of triploid populus tomentoza to select the operations to accelerate the decomposition and nutrient release. Finally, it studied influence of different intercrops on plantation site productivity and the relationship of intercrops and triploid populus tomentoza to select suitable intercrops. The main results as follows:（1）The aboveground litterfall of triploid populus tomentoza increased along with age from 216.03±59.7gm^-2 at 3a to 482.38±101.3gm^-2 at 7a, The N returned by litterfall wasl8.38±2.46kg.hm^-2a^-1;21.63±2.25kg.hm^-2a^-1;39.51±4.61kg.hm^-2a^-1;38.89±4.89kg.hm^-2a^-1 at 3a、5a、6a、7a respectively. The P returned by litterfall was 5.80±0.62kg.hm^-2a^-1、8.16±0.94kg.hm^-2a^-1, 11.31±1.33kg.hm^-2a^-1、11.76±1.37kg.hm^-2a^-1 at 3a、5a、6a、7a respectively. The nutrient returned by fine root turnover increased along with age, too. The N returned by fine root turnover was 3.85±0.41kghm^-2a^-1、5.22±0.63kghm^-2a^-1,7.62±0.89kghm^-2a^-1,9.17±1.22kghm^-2a^-1 at 3a、5a、6a、7a respectively. The P returned by fine root turnover was 0.73±0.07kghm^-2a^-1、1.69±0.09kghm^-2 a^-1、1.92±0.31kghm^-2a^-1、1.96±0.21kghm^-2a^-1 at 3a、5a、6a、7a respectively. The leaf was the principal pathway to return nutrient（N、P） to soil among litterfall, fine root turnover and wet dust precipitation. The proportion of returned N by leaf was 74.84%、71.96%、78.58%、75.03% at 3a、5a、6a、7a respectively,The proportion of returned P by leaf was 85.93%、80.31%、83.04%、83.23% at 3a、5a、6a、7a respectively. Therefore, it is important to protect and utilize the leaf in order to maintenance and enhance the long-term-site productivity of triploid populus tomentoza pulp plantation.（2）The remained N of triploid populus tomentoza pulp plantation increased from 212.00kghm^-2 at 3a to 775.61kghm^-2 at 7a, the remained P increased from 109.61kghm^-2 at 3a to 407.15kghm^-2 at 7a. The returned N increased from 24.56kghm^-2 at 3a to 51.83kghm^-2 at 7a. The ratio of returned N to absorbed was 34.75%、45.85%、48.81%、46.78% at 3a、5a、6a、7a respectively. But the total N in soil decreased from 0.54% at 3a to 1.92% at 7a. The ratio of returned P to absorbed was 18.47%、29.66%、26.75%、24.29% at 3a、5a、6a、7a respectively, but the total P in soil decreased from 0.35% at 3a to 0.52% at 7a. The turnaround time of N was shortened from 345.6 years at 3a to 163.8 years at 7a, The turnaround time of P was shortened from 1625.0 years at 3a to 596.1 years at 7a. Thus the management of triploid populus tomentoza pulp plantation might cause soil nutrient（N、P） deficiency and threaten site productivity maintenance.（3）The influence of different factors on decomposition of leaf, twig and tree bark was defferent. Neither the circumstance between interior-intermediate of plantation belt nor the leaf brought out by different age’s trees had significance difference. The decomposition of leaf of triploid populus tomentoza was accelerated by mixed with cotton leaf in 1:1 mass ratio. The time of 50% leaf decomposed was shortened 254 days compared to pure triploid populus tomentoza leaf. The time of 95% leaf decomposed was shortened 1076 days compared to pure triploid populus tomentoza leaf. The decomposition ratio at 1 year increased 15.43% compared to pure leaf. The circumstance of underground 10cm promoted decomposition of leaf、twig and tree bark significance. Compared to soilsurface, The time of 50% leaf decomposed under ground 10cm was shortened from 499 days to 291 days of 2a plantation, from 777 days to 304 days of 4a plantation, from 1036 days to 393 days of 6a plantation respectively. The time of 95% leaf decomposed was shortened from 1853 days to 1114 days of 2a plantation, from 3080 days to 1157 days of 4a plantation, from 4326 days to 1544 days of 6a plantation respectively; The time of 50% twig decomposed was shortened from 771 days to 338 days, the time of 95% twig decomposed was shortened from 3073 days to 1223 days. The time of 50% tree bark decomposed was shortened from 710 days to 304 days and the time of 95% tree bark decomposed was shortened from 2803 days to 1072 days. Thus it could accelerate decomposition of leaf、twig and tree bark if they were buried under surface soil during operations such as cultivation、weed eradication.（4）From the result of laboratory experiment, the difference of decomposition rate among different N-resource was significance. The leaf decomposition was accelerated by added ammonium nitrogen, The half leaf decomposition needed 175d by added ammonium nitrogen compared to 301d、316d or 348d by added nitrate nitrogen、mixed N or control respectively. The 95% leaf decomposition needed 781d by added ammonium nitrogen compared to 1397d、1238d or 1627d by added nitrate nitrogen、mixed N or control respectively. The decomposition ratio of one year was 75.28% by added ammonium nitrogen, compared to 55.90%, 55.14% and 51.14% by added nitrate nitrogen, mixed N or control respectively.（5）The different intercrops had different effects on soil physic-chemical characteristics. Soil bulk density、soil organic matter and soil available nitrogen were improved significance by intercropped cotton. There were no significance influence on tree height growth by different intercrops, but tree diameter at breast height was increased significance by intercropped cotton.the yield of different intercrops were not influenced by tree at first year. The RCI（relative competition index） were 0 almostly.Therefore the whole, cotton was suitable intercrop at first year.更多还原