中正大學校園小葉欖仁嫁接之變異

Grafting Variation of Terminalia boivinii in National Chung Cheng University Campus

小葉欖仁於台灣各地普遍栽植，為近二十年來頗受民眾喜愛的樹種之一，而目前種植於道路、公園與校園之部份成木，乃早期採嫁接方式繁殖，其砧木為欖仁。隨時間這些嫁接苗長成大樹，明顯出現嫁接變異。除於嫁接處特別腫脹外，砧木會明顯細縮，中央主幹較易傾斜，且樹幹嫁接處上、下部位呈現不同顏色，下部欖仁之樹皮明顯較上部小葉欖仁更為暗褐色。本研究目的係探討小葉欖仁因嫁接所產生之變異，以及預測未來可能引發的問題，並研擬因應對策。本研究採實地調查方法，以中正大學之小葉欖仁為調查對象。研究結果發現胸徑與樹幹細縮百分比以及樹幹粗細離地高差均具顯著正相關，表示樹幹細縮隨樹齡增加而越加嚴重，且樹幹嫁接處與細縮處之間距也越大。另外嫁接處離地高度與樹幹細縮百分比以及樹幹粗細離地高差均具顯著正相關，表示當嫁接位置越高時，樹幹細縮越嚴重，樹幹粗細間距也越大。嫁接處離地高低差與樹幹粗細離地高差具正向相關，嫁接處離地高低差越大，表示嫁接切面越傾斜，其樹幹最粗（嫁接處）與砧木細縮點之間距也越大。建議不要種植主幹嫁接之中大型觀賞喬木，且不要以嫁接主要樹幹方式繁殖，必要時嫁接部位以越低越好，低至根部附近，樹幹未來可能較不會細縮變型太多；另外建議嫁接採平切而不要斜切，中央主幹較易保持直挺特性。至於目前樹幹已明顯細縮之嫁接小葉欖仁，建議以截頂與疏枝方式來降低其株高與樹冠量體外、並加強支柱，以降低無預警時之倒塌對人車所造成的危害。 At present, Terminalia boivinii has been widely planted throughout Taiwan, which was considered as a prevalent and new plant species for the past twenty years. Some of the adult trees were bred from the grafted nursery stocks, those rootstocks is Terminalia catappa. As the times goes by, these grafted stocks have grown into big trees, which also exhibit obvious grafting variation. In addition to particular swelling at the callus, the rootstocks is notably thinned and shrunk, and the tree trunks are no longer straight or upright. Grafted branch would have different bark colors on the upper and lower parts. Since the lower part is Terminalia catappa, its bark is showed distinctly dark brown. The main purpose of this study is to investigate the current growing state of the grafted Terminalia boivinii, understand the variation of grafting on Terminalia boivinii, compare the difference between grafted and non-grafted Terminalia boivinii, and predict the possible problems of grafted stocks. This study was based on on-site investigation, and the research area was at National Chung Cheng University campus. The results showed that the grafted Terminalia boivinii was likely to form buttress, and the size of buttress is much larger, in length, thickness, and height, than non-grafted samples. Terminalia boivinii with rootstock of Terminalia may easily form large buttress. Also, the position of the callus may affect the percentage of trunk thinning and shrinking. Comparison of the diameter of trunk showed that, as the grafting position is lower, the trunk thinning and shrinking is less obvious. The position of callus would affect the thickness and height of the rootstock. When the height difference of the callus of callus (height difference of horizontal cutting is zero), the thickness and height difference of the rootstock is also smaller. The results proved that the grafting produces variation, notably the rootstock thinning and shrinking, which may be more serious as the tree grows. The thinning and shrinking branch on tall Terminalia boivinii may likely to break, thus leading to collapse. Therefore, it is suggested to avoid using grafting to breed landscape trees. If grafting is necessary, the grafting position should be as low as possible so that the root grafting would not have obvious thinning and shrinking. In addition, the grafting should adopt horizontal cutting, instead of oblique cutting, so that the trunks can retain straight and upright. For the grafted Terminalia boivinii whose trunks are obviously thinned and shrunk, it is suggested to cut off the tree top to reduce its height and strengthen its strut, in order to avoid the risk of sudden collapse.

At present, Terminalia boivinii has been widely planted throughout Taiwan, which was considered as a prevalent and new plant species for the past twenty years. Some of the adult trees were bred from the grafted nursery stocks, those rootstocks is Terminalia catappa. As the times goes by, these grafted stocks have grown into big trees, which also exhibit obvious grafting variation. In addition to particular swelling at the callus, the rootstocks is notably thinned and shrunk, and the tree trunks are no longer straight or upright. Grafted branch would have different bark colors on the upper and lower parts. Since the lower part is Terminalia catappa, its bark is showed distinctly dark brown. The main purpose of this study is to investigate the current growing state of the grafted Terminalia boivinii, understand the variation of grafting on Terminalia boivinii, compare the difference between grafted and non-grafted Terminalia boivinii, and predict the possible problems of grafted stocks. This study was based on on-site investigation, and the research area was at National Chung Cheng University campus. The results showed that the grafted Terminalia boivinii was likely to form buttress, and the size of buttress is much larger, in length, thickness, and height, than non-grafted samples. Terminalia boivinii with rootstock of Terminalia may easily form large buttress. Also, the position of the callus may affect the percentage of trunk thinning and shrinking. Comparison of the diameter of trunk showed that, as the grafting position is lower, the trunk thinning and shrinking is less obvious. The position of callus would affect the thickness and height of the rootstock. When the height difference of the callus of callus (height difference of horizontal cutting is zero), the thickness and height difference of the rootstock is also smaller. The results proved that the grafting produces variation, notably the rootstock thinning and shrinking, which may be more serious as the tree grows. The thinning and shrinking branch on tall Terminalia boivinii may likely to break, thus leading to collapse. Therefore, it is suggested to avoid using grafting to breed landscape trees. If grafting is necessary, the grafting position should be as low as possible so that the root grafting would not have obvious thinning and shrinking. In addition, the grafting should adopt horizontal cutting, instead of oblique cutting, so that the trunks can retain straight and upright. For the grafted Terminalia boivinii whose trunks are obviously thinned and shrunk, it is suggested to cut off the tree top to reduce its height and strengthen its strut, in order to avoid the risk of sudden collapse.