陕北山地苹果树形改造研究

为促进陕北丘陵沟壑区山地苹果的优质高效生产，本研究将传统稀植果园中主要采用的主干疏层形改造为小冠疏层形、纺锤形或圆柱形、高干开心形和开心形，测定不同树形的树冠透光率、树冠大小、一年生枝和结果枝的数量及组成比例、果实产量和品质等指标，并估算其产值。结果表明:与对照主干疏层形相比，高干开心形和开心形的树冠大而扁，树冠透光率较高。开心形的叶丛枝和短枝占全树枝条的61.21%，树势中庸偏上；主干疏层形、小冠疏层形和高干开心形的叶丛枝和短枝占全树枝条的70.00%以上，树势较弱。开心形的短果枝占结果枝的60.68%，中果枝占28.67%，利于连年优质丰产；主干疏层形的短果枝占结果枝的85.00%，中果枝仅占8.79%，易形成隔年结果。不同树形的果实产量以主干疏层形的最高，其次为开心形；果实品质、均匀度和价格均以开心形的最高，主干疏层形的最低；经济产值以开心形的最高，其次为主干疏层形，高干开心形的最低。综上，建议将陕北丘陵沟壑区山地稀植苹果园的主干疏层形改造为开心形。

Study on the canopy transformation of mountain apple in northern Shaanxi

In order to promote mountain apple quality and efficient production in the hilly-gully region of northern Shaanxi, the trunk and dispersal-stratified canopy used in traditional sparse planting orchard were transformed into small and sparse canopy, spindle or cylinder canopy, high stem and open-center canopy, and open-center canopy in this study. The intracoronal light transmittance, crown size, number of annual branches and fruit-bearing branches and their composition proportion, and fruit yields, fruit quality and fruit output and others of different canopy were monitored and estimated. The results showed that: Compared with the trunk and dispersal-stratified canopy, the crowns of high stem and open-center canopy and open-center canopy trees were large and flat, and their intracoronal light transmittance were higher. The foliage branches and short branches of open-center canopy accounted for 61. 21% of the total annual branches, and the tree vigour was moderate to the upper. The foliage branches and short branches of trunk and dispersal-stratified canopy, small and sparse canopy, and high stem and open-center canopy accounted for more than 70. 00% of the total annual branches, and the tree vigour all were weaker. The short fruit-bearing branches of open-center canopy accounted for 60. 68% of the fruit-bearing branches, and the middle fruit-bearing branches accounted for 28. 67%, which were beneficial to high quality and high yields in consecutive years. The short fruit-bearing branches of trunk and dispersal-stratified canopy accounted for 85. 00%, and the middle fruit-bearing branches accounted for only 8. 79%, which were easy to form alternate bearing. The fruit yields of trunk and dispersal-stratified canopy were the highest among different canopies, and followed by open-center canopy. The fruit quality, fruit uniformity and fruit price of open-center canopy were the highest, and trunk and dispersal-stratified canopy were the lowest. The economic output value of open-center canopy was the highest, followed by trunk and dispersal-stratified canopy, and high stem and the open-center canopy was the lowest. By comprehensive comparison, in the hilly and gully region of northern Shaanxi, the trunk and dispersal-stratified canopy of traditional sparse planting orchard should be transformed into an open-center canopy.