我国4种主要苹果树形冠层结构和辐射三维分布比较研究

树体结构和辐射分布是影响果树冠层光合生产力和果实产量品质的主要因素。本文以"富士"苹果(Malus domestica Borkh.cv.‘Fuji’)为试材,采用田间调查方法,系统研究了我国苹果生产中4种主要树形的树体结构参数以及叶面积密度(LAD)和光合有效辐射(PAR)的三维分布特征。结果表明,开心形树冠的枝量(894×103·hm-2)和叶面积指数(LAI,2.53)最小,其他3种树形中小冠疏层形分别为2 280×103·hm-2、4.14,疏散分层形分别为2 119×103·hm-2、3.98,纺锤形分别为2 190×103·hm-2、3.88。不同树形LAD三维分布各不相同,小冠疏层形苹果树的叶片主要分布在树冠的0.5~1.5 m之间,疏散分层形和纺锤形主要分布在0.5~2.0 m之间,开心形主要分布在1.0~2.0 m之间。通过对不同树形LAD和PAR三维分布比较发现,每种树形的PAR都随树冠深度的增加而降低,在树冠中部LAD最大部位辐射消减最快,PAR的三维分布主要与叶片分布有关。其中开心形树冠的平均PAR最高,分布最均匀。4种树冠内叶片得到的平均相对PAR小冠疏层形为24.85%,疏散分层形为28.84%,纺锤形为27.71%,开心形为37.28%。开心形树冠内低光区的叶片所占比例只有35%,其他树形都超过50%。研究表明,不同相对PAR范围内的叶片比例能够更好地反映果树冠层的辐射情况,开心形树冠在辐射分布上优于其他3种树形。

Tree structure and 3-D distribution of radiation in canopy of apple trees with different canopy structures in China

Tree structure and radiation distribution are critical factors influencing photosynthetic productivity of fruit trees as well as fruit yield and quality.The aim of this study was to determine the parameters of tree structure,leaf area density(LAD) 3-D distribution of photosynthetically active radiation(PAR) within four canopy structures(small-sparse canopy,stratified-disperse canopy,spindle canopy and open-center canopy) of apple tree.The experiment was conducted in ’Fuji’ apple(Malus domestica Borkh.cv.’Fuji’) orchard during 2005~2008 growth seasons.The structure parameters of trees with different canopy structures were determined via direct measurement,and PAR of each apple tree canopy measured by quantum sensors.The results showed that the lowest total shoot number(894×103·hm-2) and leaf area index(LAI,2.53) were in open-center canopy.Total shoot and LAI were 2 280×103·hm-2 and 4.14,2 119×103·hm-2 and 3.98,2 190×103·hm-2 and 3.88 in small-sparse,stratified-disperse and spindle canopies,respectively.3-D distribution of LAD was different among the four canopy structures.LAD vertical distribution yielded a distribution mode with height range of 0~4.0 m,largely occurring within 1.0~3.0 m high.While the highest LAD was within 0.5~2.0 m height range in stratified-disperse and spindle canopy structures,it was 0.5~1.5 m and 1.0~2.0 m in small-sparse and open-center canopy structures,respectively.In all the canopy structures,relative PAR decreased with increasing canopy depth.Rapid relative PAR depression was concentrated in middle canopies where LAD was highest.Relative PAR 3-D distribution pattern in unit cells apparently tracked leaf area distribution.The highest average relative PAR and most uniform distribution were in open-center canopy structure.Percent average relative PAR of leaves were 24.85%,28.84%,27.71% and 37.28% for small-sparse,stratified-disperse,spindle and open-center canopy structures,respectively.While only 35% leaf area was in the low-light region of open-center canopy structure,over 50% was in the low-light region in the other canopy structures.The main aim of tree pruning was to remove useless shoots and leaves,which were easily identified in 3-D plots.Percent leaf areas in different relative PAR ranges reasonably predicted canopy radiation,which was critical in fruit studies.Leaf and PAR distributions were more uniform in open-center than in other canopy structures.This was a distinct advantage of open-centre canopy structure over the other canopy structures.