Effects of Different Pruning Levels on the Growth Potential of Nauclea Diderrichii (De Wild) Merr

Home , Nauclea diderrichii

Full Length Research Paper Effects of different pruning levels on the growth potential of Nauclea diderrichii (De Wild) Merr. Plantation Asinwa, I.O; Ogunwande, O.A; Adegoke, F.F and Adio, A.F

Forestry Research Institute of Nigeria, P.M.B, 5054. Jericho, Ibadan

Accepted 21 August, 2014

Pruning involves the removal of live and dead branches along lower trunks of forest trees in order to produce clear knot-free timber. Nauclea diderrichii often produce multiple branches (Figure 1) which usually leads to knotty bole when harvested and thus lower the economic values of it. Therefore the study investigated the effects of different levels of pruning on the growth of N. diderrichii. Assessment of effects of different levels of pruning on the growth potentials of N. diderrichii was carried out on two years old plantation of the species. The study was made up of 5 treatments combination replicated 5 times in a randomized complete block design (RCBD). The result revealed that there were significant differences among the treatments at 5% level of probability in the height, girth diameter and number of branches within the period of study. The highest mean growth in height and number of branches was recorded in T1, (184.68cm and 13.38 respectively) while the highest mean girth of 13.86cm was given by T4. The study showed that partial pruning induced optimum growth and development of Nauclea diderrichii which could be vastly used for timber production. It is recommended that partial pruning of 25% and 50% should be applied to Nauclea diderrichii plantation in order to achieve vigorous, clean and straight bole stand of the species.

Keywords: Pruning, Branches, Knot-free, straight bole and Nauclea diderrichii

INTRODUCTION

Pruning is a silvicultural prescription of removing trees have at least some tendency to prune their limbs or branches in order to improve tree form or wood quality parts which are living under compensation point (Costello, 1999). This activity is planned for timber especially when growing in closed canopy but artificial production and almost exclusively for conifer plantations. pruning encourages growth potentials (Gilman, 2001). The purpose of pruning is to nuture trees to a single Nauclea diderrichii (Family: Rubiaceae) is an evergreen straight stem and develops more valuable, knot-free tree that reaches a height of 30-40 m and a diameter of trunks (ANSI, 2001). To improve wood quality and to 0.9-1.5 m; bole cylindrical and slender rising to 20-30 m allow trees to grow a long period, pruning must be done and a broad spherical crown with thick foliage. The early. It is done mainly to permit easy access to the shining leaves are 15 cm long and bigger when young, plantation for thinning and is carried out on all trees and elliptic, acute at the ends, keeled towards the base, and to maximise photosynthetic energy for the development stipulate, with a pair of distinct leafy stipules at the base. of flowers, fruits, and limbs that remain on the plant It is mostly deciduous except at the ends of shoots, and (ANSI, 2000). the nodes are often occupied by ants. Flowers small, Pruning involves the removal of live and dead branches green-white-yellow and tubular, in solitary terminal heads along lower trunks of forest trees in order to produce (unbranched), 3 cm across; stalks only about 1 cm. The clear knot-free timber (Gilman, 2002). In nature, most fruit is yellow, fleshy, in a globose head deeply pitted between the deeply fused calyx lobes(CABI, 2000). Nauclea diderrichii is a semi-heavy wood and of medium hardness (CABI, 2000). Because of its good *Corresponding author’s e-mail: [email protected]. mechanical properties and natural durability, which can be Scholarly J. Agric. Sci. 466

Figure 1: Nauclea diderrichii tree with multiple branches at the lower part of the bole

Figure 2: Experimental Layout enhanced by preservative treatment, it is sought after as as part of an infusion for treating jaundice, bark infusion a timber for outdoor uses (harbour works, railway to treat gonorrhoea; a decoction of leaves is used as a sleepers), buildings (carpentry, floors, facings, indoor and wash for measles (CABI, 2000). outdoor woodwork) and for cabinet making (Dupuy and All woody plants shed branches in response to shading Mille 1993). The wood is also suitable for fence posts and and competition. Branches that do not produce enough bridges as it is moderately termite-resistant and resistant carbohydrates from photosynthesis to sustain themselves to fungi and marine borers. Its bark decoction is die and are eventually shed; the resulting wounds are prescribed for anaemia, stomach-ache and indigestion, sealed by wound wood (callus) Ramos et al, (1998). Asinwa et al. 467

Table 1: Analysis of Variance (ANOVA) table for Mean Height of two years old Nauclea diderrichii plantation subjected to different levels of pruning

SV df SS MS F- cal F-tab Treatments 4 5117.6 1279.40 2.98* 2.53 Blocks 4 5066.08 1266.52 2.94*

Error 66 28,335.78 429.33

Total 74 38,519.46

 = Significant at P < 0.05

Table 2: Follow up test (Duncan) of Analysis of Variance (ANOVA) for Mean Height of two years old Nauclea diderrichii plantation subjected to different levels of pruning

Treatments Mean 1 206.02a 2 189.11a 3 182.3ab 4 158.6b 5 (control) 152.7b

* Means with the same letter are not significantly different (P > 0.05)

Table 3: Analysis of Variance (ANOVA) table for Mean Girth of two years old Nauclea diderrichii plantation subjected to different levels of pruning

SV df SS MS F- cal F-tab Treatments 4 2734.39 683.85 2.67* 2.53 Blocks 4 2787.54 696.89 2.72* Error 66 16,909.86 256.21

Total 74 22431.79

 = Significant at P < 0.05

Branches that are poorly attached may be broken off by consisted of 5 blocks, each demarcated into 4 plots with wind. Branches removed by such natural forces often each plot bearing a different treatment and control. Each result in large, ragged wounds that rarely seal. Pruning plot was measured 12m x 12m with a 3m inter-plot and as a cultural practice can be used to supplement or inter-block boundary. replace these natural processes and increase the Each sapling allotted to different treatment was strength and longevity of plants. N. diderrichii often carefully tagged for proper identification. The study was produce multiple branches (Figure 1) which usually leads made up of 5 treatments combination (including to knotty bole when harvested and thus lower the control).This was replicated 5 times in a randomized economic values of it. Therefore the study investigated complete block design (RCBD). the effects of different levels of pruning on the growth of The treatment combinations were as follows: T1 = N. diderrichii. 100% pruning (total removal of branches), T2 = 75% pruning (removal of three-quarter of the total branches), T3 = 50% pruning (removal of the half of total branches), MATERIALS AND METHODS T4 = 25% pruning (removal of one-quarter of the total branches) and T5 = 0% pruning (Control) Two years old plantation of N. diderrichii (60m x 63m) Base data was collected followed by monthly growth was demarcated into blocks and plots for the assessment assessment. The following parameters were assessed of effects of different levels of pruning on the growth shoot height, girth diameter and number of branches. potentials of N. diderrichii. The layout (Figure 2) Collected data were subjected to Analysis of Variance Scholarly J. Agric. Sci. 468

Table 4: Follow up test (Duncan) of Analysis of Variance (ANOVA) for Mean Girth of two years old Nauclea diderrichii plantation subjected to different levels of pruning/

Treatments Mean 1 3.70a 2 4.10a 3 14.5b 4 15.2b 5 (control) 12.91ab

* Means with the same letter are not significantly different (P > 0.05)

Table 5: Analysis of Variance (ANOVA) table for Number of branches of two years old Nauclea diderrichii plantation subjected to different levels of pruning

SV df SS MS F- cal F-tab Treatments 4 69.68 17.42 4.38* 2.53 Blocks 4 44.48 11.12 2.80* Error 66 262.11 3.97 Total 74 3728.35

* = Significant at P < 0.05

Table 6: Follow up test (Duncan) of Analysis of Variance (ANOVA) for Number of branches of two years old Nauclea diderrichii plantation subjected to different levels of pruning

Treatments Mean 1 14.6a 2 11.9b 3 7.9c 4 7.1c 5 (control) 5.1d

* Means with the same letter are not significantly different (P > 0.05)

Table 7: Average mean Height, Girth and Number of branches during 9 months of study.

Treatments Height (cm) Girth (cm) Number of Branches 1 184.68 4.70 13.38 2 173.03 6.77 10.22 3 167.21 11.86 7.37 4 158.46 13.86 6.18 5 (Control) 150.56 9.02 4.87

(ANOVA). and the least value of 150.56cm was recorded on T5 (Table 7). The highest shoot length produced by the treatment RESULTS AND DISCUSSION with complete pruning might be as result of the fact that shoot growth is dependent upon root potential in water There were significant differences among the treatments and mineral nutrient uptake. While root growth depends at 5% level of probability in the height, girth diameter and upon the above ground stored carbohydrates, the number of branches within the period of study (Table 1, 3 appreciable amount of the stored energy encourages and 5). The highest mean growth in height was recorded new shoot s developments (Coder, 1997). Also, in T1, (184.68cm), this was followed by T2 with 173.03 according to Ramos et al, (1998) Pruning branches of a Asinwa et al. 469

plant increases the growth rate of the remaining branches. Operations—Pruning, Trimming, Repairing, Maintaining, and Removing This invigorating effect of shoot growth and branch Trees, and Cutting Brush—Safety Requirements. (Z133.1). International Society of Arboriculture, Champaign, IL. initiation could be attributed to available carbohydrate American National Standards Institute. (2001). American National and mineral nutrients. Standard for Tree Care Operations—Tree, Shrub, and Other Woody In contrast, T1 gave the least mean girth of 4.70cm; T2 Plant Maintenance—Standard Practices (Pruning). (A300, Part 1). gave 6.77cm while the highest mean girth of 13.86cm National Arborist Association, Manchester, NH. CABI. (2000). Global Forestry Compendium. CD-ROM. CABI was given by T4 (Table 7). The highest number of Calatayud, A., Roca, D., Gorbe, E. and Martynez, P.F. (2008). branches (13.38) was given by T1 followed by T2 with 10.2 Physiological effects of pruning in rose plants cv. Grand Gala. while the least mean number of branches (4.87) was Scientia Horticultural 116:73–79. recorded on T (Table 7). Coder, K.D. (1997). Crown pruning effect on roots. [Online]. 5 www.http://warnell.forestry.uga.edu/warnell/service/library/inde The highest number of branches produced by complete x.php3?docID=146 pruning (T1) is accordance with findings of Lin and Hsu, Costello, L. (1999). Training Young Trees for Structure and Form (2004) that pruning generally increase branching (videocassette). International Society of Arboriculture, Champaign, IL. potential and induce shoot production. This is also similar Florida Chapter of the International Society of Arboriculture. Pruning Specifications. www.floridaisa. org/Specifications.html. Florida to the findings of Calatayud et al., (2008) that Pruning too Chapter, ISA, Sarasota, FL. many branches led to stem sprouting of numerous Dupuy, B and Mille, G. (1993). Timber plantations in the humid tropics branches. In the mere sense, growth and development of of Africa. FAO Forestry. p. 98. plant is being assessed by physiological features such as Gilman, E.F. (2001): Horticopia: Illustrated Pruning and Planting (cd- rom). Horticopia, Inc. Purcellville, VA. Garrett, H.E., W.B. Kurtz, and Shoot height, leaf and branch production as well stem J.P Slusher. 1996. Walnut Agroforestry. University of Missouri- girth. Therefore the least mean girth produced by T1 could Columbia, Cooperative Extension. AgriculturalPublication G5020. 5 p. nd be as a result of more of energy meant for all the growth Gilman, E.F. (2002). An Illustrated Guide to Pruning (2 ed.). Delmar parameters probably being diverted to shoot growth and Publishers, Albany NY. p. 330. Gilman, E.F., and S.J. Lilly. (2002). Best management practices: tree branch production at expense of girth increment. pruning International Society of Arboriculture, Champaign, IL. p. 35. It was observed that partial pruning (25%) enhanced Ramos, D.E., DeJong, T.M., Ryugo, K., Olson, W.H., Reil, W.O., Sibbett, girth development than complete pruning. The fact that G.S., Krueger, W.H. and Synder, R.G. (1998). Pruning and tree the control (T ) had higher girth than complete pruning thinning. p. 147-158. D.E. Ramos (tech. ed). In: Walnut Production 5 Manual. University of California Division of Agriculture and Natural (T1) simply depicts that photosynthate produced by the Resources, Oakland, CA. foliage part of the plants has a crucial influence on the Smith, D.M., Larson, B.C., Kelty, M.J. and Ashton, P.M.S. (1997). The metabolic processes that give rise to stem development. Practice of Silviculture: Applied Forest Ecology. John Wiley and Sons, This corroborates the findings of Gilman, (2001) that Inc. p. 537. stem growth depends on the strategy and levels of pruning as well as cutting position.

CONCLUSION

Different levels of pruning as at period of study showed differences in shoot height, girth and branch production. The study revealed that different pruning levels modified the branch and shoot initiation, which ultimately affects the physiological features of Nauclea diderrichii. In the case of complete pruning, the species gave optimum growth in shoot height and produced numerous branches which are not ideal for stands meant for timber production. On the other hand, partial pruning of 25% and 50% improved girth production. Therefore, it can be concluded from the result of the study that partial pruning induced optimum growth and development of Nauclea diderrichii which could be vastly used for timber production. It is recommended that partial pruning of 25% and 50% should be applied to Nauclea diderrichii plantation in order to achieve vigorous, clean and straight bole stand of the species.

REFRENCES

American National Standards Institute. (2000). Arboricultural