As a basic measure for forest management,pruning has an important impact on the tree trunk shape,wood qulity,etc. At present,in the process of growing fast-growing and high-yielding plantation,afforestation was took i...As a basic measure for forest management,pruning has an important impact on the tree trunk shape,wood qulity,etc. At present,in the process of growing fast-growing and high-yielding plantation,afforestation was took into account,whereas management after planting was ignored,which had much detrimental effect on woodland’s quality and productivity. The paper studied the topic to find a scientific pruning model that could provide a guideline for the management in forest production. The plantation and the intercropping of poplar-crop were pruned in four different levels in Hebei and Shandong province. The levels were respectively light p1 (1/6 crown was pruned),medium p2 (2/6 crown was pruned),strong p3 (3/6 crown was pruned),heavy p4 (4/6 crown was pruned) and the control (unpruned). Heights and diameters at breast height(DBH) were measured. Diameter growth and cutting-area increment in one year from ten parsed trees were counted. The volume growth of trunk (below 9 m) was calculated. The results were:1) the difference of relative growth rate for different pruning treatment was not significant (P<0.05),which demonstrated the nutrition for height growth came from the branches and leaves of the top crown; 2) The difference of relative growth rate of DBH was significant(P<0.01). That is,the greater of pruning intensity,the smaller relative growth in the DBH. 3) The stem growth of parsed disk at different height was fluctuant among the different treatments. From stem base (0.0 m) to 9 m height of the trunk,the stem increase of the lower half reduced along with the increase of pruning intensity,while the growth of the upper half in pruning trees was bigger than that of non-pruning ones. 4) The difference of volume growth rate for different treatments was significant,all of the pruning treatments were bigger than the control. The medium p2 had the biggest growth,and the order was CK<p4<p1<p3<p2,which suggested that reasonable pruning can improve the growth of volume. However an excessive pruning reduced volume growth. 5展开更多
以北极研究为中心,基于CNKI和Web of Sciences Core Collection数据库2000—2017数据,采用CiteSpace,系统展示了中国和国际(含中国)在北极科研领域的发展趋势、前沿、热点和机构合作特征。研究表明,国内的北极研究经历了由气候海冰—航...以北极研究为中心,基于CNKI和Web of Sciences Core Collection数据库2000—2017数据,采用CiteSpace,系统展示了中国和国际(含中国)在北极科研领域的发展趋势、前沿、热点和机构合作特征。研究表明,国内的北极研究经历了由气候海冰—航运—北极治理的研究过程,发文量以北极航运为主导。国际针对北极的研究经历了三个逐步加速阶段:1990、2000和2005,北极八国和德、英、法是北极研究的主力军。北极科技合作仍主要以国家内部合作为主,但科研机构合作频率高度爆发且出现一批以“Helmholtz Centrefor Polar and Marine Research(德国)、The Arctic University of Norway(挪威)、Aarhus University(丹麦)和KoreaPolar Research Institute(韩国)”为代表的北极研究合作爆发单位;北极研究领域多样,呈现出以“arcticocean”、“climate”、“arctic temperature”、“variability”、“sea ice”、“model”等为重点的关键词,表明近年国际北极研究主要热点在气候变化、海冰、洋流等领域,这些领域相互交叉。通过对国内外北极通航经济性的系统综述分析得出:国内外学者均认为与北极海冰有关因素是制约北极通航的关键;国内学者对北极通航的经济效益较为乐观,而国外学者则较为辨证且谨慎。这与研究所考虑的角度有关,国内学者较多考虑北极通航的技术管理、人力资源、能耗、时间和政治等因素,而国外学者在这些因素的基础上,还侧重于贸易需求、通航意愿性和通航对气候的影响等因素。展开更多
人工林的增加大大改善了我国的生态环境,但也同时增加了森林有害生物发生的风险。生态调控技术克服了传统控制策略的不足,是目前森林有害生物管理的最佳策略之一。论文回顾了森林有害生物的管理策略思想的发展历程,简述了生态调控(Ecolo...人工林的增加大大改善了我国的生态环境,但也同时增加了森林有害生物发生的风险。生态调控技术克服了传统控制策略的不足,是目前森林有害生物管理的最佳策略之一。论文回顾了森林有害生物的管理策略思想的发展历程,简述了生态调控(Ecological regulation)策略与森林有害生物可持续控制(Sustainable pest management in forest,SPMF)的理念与核心原则。通过对有害生物的实例研究的概括,从森林生态系统自身特征、调控对象有害物质和森林生态系统的环境条件三个方面,综述了森林有害生物生态调控的相应策略。文章也指出了该策略的发展前景及不足之处。展开更多
文摘As a basic measure for forest management,pruning has an important impact on the tree trunk shape,wood qulity,etc. At present,in the process of growing fast-growing and high-yielding plantation,afforestation was took into account,whereas management after planting was ignored,which had much detrimental effect on woodland’s quality and productivity. The paper studied the topic to find a scientific pruning model that could provide a guideline for the management in forest production. The plantation and the intercropping of poplar-crop were pruned in four different levels in Hebei and Shandong province. The levels were respectively light p1 (1/6 crown was pruned),medium p2 (2/6 crown was pruned),strong p3 (3/6 crown was pruned),heavy p4 (4/6 crown was pruned) and the control (unpruned). Heights and diameters at breast height(DBH) were measured. Diameter growth and cutting-area increment in one year from ten parsed trees were counted. The volume growth of trunk (below 9 m) was calculated. The results were:1) the difference of relative growth rate for different pruning treatment was not significant (P<0.05),which demonstrated the nutrition for height growth came from the branches and leaves of the top crown; 2) The difference of relative growth rate of DBH was significant(P<0.01). That is,the greater of pruning intensity,the smaller relative growth in the DBH. 3) The stem growth of parsed disk at different height was fluctuant among the different treatments. From stem base (0.0 m) to 9 m height of the trunk,the stem increase of the lower half reduced along with the increase of pruning intensity,while the growth of the upper half in pruning trees was bigger than that of non-pruning ones. 4) The difference of volume growth rate for different treatments was significant,all of the pruning treatments were bigger than the control. The medium p2 had the biggest growth,and the order was CK<p4<p1<p3<p2,which suggested that reasonable pruning can improve the growth of volume. However an excessive pruning reduced volume growth. 5
文摘以北极研究为中心,基于CNKI和Web of Sciences Core Collection数据库2000—2017数据,采用CiteSpace,系统展示了中国和国际(含中国)在北极科研领域的发展趋势、前沿、热点和机构合作特征。研究表明,国内的北极研究经历了由气候海冰—航运—北极治理的研究过程,发文量以北极航运为主导。国际针对北极的研究经历了三个逐步加速阶段:1990、2000和2005,北极八国和德、英、法是北极研究的主力军。北极科技合作仍主要以国家内部合作为主,但科研机构合作频率高度爆发且出现一批以“Helmholtz Centrefor Polar and Marine Research(德国)、The Arctic University of Norway(挪威)、Aarhus University(丹麦)和KoreaPolar Research Institute(韩国)”为代表的北极研究合作爆发单位;北极研究领域多样,呈现出以“arcticocean”、“climate”、“arctic temperature”、“variability”、“sea ice”、“model”等为重点的关键词,表明近年国际北极研究主要热点在气候变化、海冰、洋流等领域,这些领域相互交叉。通过对国内外北极通航经济性的系统综述分析得出:国内外学者均认为与北极海冰有关因素是制约北极通航的关键;国内学者对北极通航的经济效益较为乐观,而国外学者则较为辨证且谨慎。这与研究所考虑的角度有关,国内学者较多考虑北极通航的技术管理、人力资源、能耗、时间和政治等因素,而国外学者在这些因素的基础上,还侧重于贸易需求、通航意愿性和通航对气候的影响等因素。
文摘人工林的增加大大改善了我国的生态环境,但也同时增加了森林有害生物发生的风险。生态调控技术克服了传统控制策略的不足,是目前森林有害生物管理的最佳策略之一。论文回顾了森林有害生物的管理策略思想的发展历程,简述了生态调控(Ecological regulation)策略与森林有害生物可持续控制(Sustainable pest management in forest,SPMF)的理念与核心原则。通过对有害生物的实例研究的概括,从森林生态系统自身特征、调控对象有害物质和森林生态系统的环境条件三个方面,综述了森林有害生物生态调控的相应策略。文章也指出了该策略的发展前景及不足之处。
