蒙古栎节子分布规律与疏松节长度预测模型

Spatial and Temporal Distribution Characteristics and Prediction Models of Length of Loose Knot for Mongolian Oak

节子分布影响木材质量,了解蒙古栎节子数量及分布规律是确定修枝的重要依据。以辽宁省夏家堡林场32年生的蒙古栎天然林为研究对象,利用X射线计算机断层扫描技术(CT)对51株蒙古栎(Quercus mongolica)树干进行扫描。结果表明:(1)平均每株蒙古栎有89个节子,根据节子发育部位的不同,将其分为初生节和次生节,初生节又分为包埋节和未包埋节;(2)蒙古栎节子着生高度(H_(I))主要分布在4 m<H_(I)≤8 m范围内,占总数的41%,树干节子着生部位直径(D_(I))在7 cm<D_(I)≤13 cm范围内,分布的节子数量占总数的67.36%;(3)节子形成时间(Y_(E))主要在11 a≤Y_(E)≤20 a范围内,节子死亡时间(Y_(D))主要在16 a≤Y_(D)≤35 a范围内。节子平均寿命为7.55 a,平均愈合时间是4.1 a,其愈合时间随节子直径增加而增长;(4)树干外部特征与疏松节长度之间存在极显著相关性(P<0.01);(5)通过逐步回归分析,筛选出节子着生直径(D_(I))、外部疤痕封口长度(L_(s))、外部疤痕封口宽度(W_(s))、外部疤痕长度(L_(m))4个影响节子变色的关键因子,建立了疏松节长度的多元回归模型:L_(dk)=-1.636+0.36 D_(I)+0.104 L_(s)+0.048 W_(s)+0.061 L_(m)。X射线计算机断层扫描技术可以检测蒙古栎树干内部节子特征。利用X射线计算机断层扫描技术大大提高了节子无损检测数量。利用树干外态特征可以预测疏松节长度。蒙古栎的修枝工作应集中在4 m<H_(I)≤8 m、16 a≤Y_(D)≤35 a。

With the natural forest of 32-a Mongolian oak in Xiajiapu Forest Farm,Liaoning Province,X-ray computed tomography(CT)was used to scan the trunks of 51 Mongolian oak trees.The results showed that:(1)On average,each Mongolian oak tree had 89 knots,which were classified into primary and secondary knots according to their developmental position.(2)The knots were mainly distributed on the trunk at a height of 4 m<H_(I)≤8 m,accounting for 41%of the total number,and the number of knots distributed within the range of 7 cm<D_(I)≤13 cm in trunk diameter accounted for 67.36%of the total number.(3)Knot formation mainly occurred during radial growth at 11 a≤Y_(E)≤20 a,and the time for dead knot formation was mainly at 16 a≤Y_(D)≤35 a.The average lifespan of a knot was 7.55 a,and the average healing time was 4.1 a,which increased with the diameter of the knot.(4)There was a significant correlation(P<0.01)between external trunk characteristics and the length of loose knots.(5)Through stepwise regression analysis,four key factors affecting knot discoloration were screened out:knot attachment diameter(D_(I)),length of external scar closure(L_(s)),width of external scar closure(W_(s)),and length of external scar(L_(m)).A multiple regression model for loose knot length was established as follows:L_(dk)=-1.636+0.36 D_(I)+0.104 L_(s)+0.048 W_(s)+0.061 L_(m).CT can detect the internal characteristics of Mongolian oak knots in the trunk without damage,and it greatly can improve the number of knots detected.The length of loose knots can be predicted by external trunk characteristics.Pruning of Mongolian oak should focus on trees with a height of 4 m<H_(I)≤8 m and radial growth at 16 a≤Y_(D)≤35 a.