Effect of coppicing levels on the re-growth of Julbernardia globiflora

Oswin C Chibinga, Moses M Nyangito¹, Nashon R K Musimba², Joseph Simbaya and Moses T Daura

Department of Animal Sciences, School of Agricultural Sciences, University of Zambia, P.O Box 32379, Lusaka, Zambia
ochibinga@yahoo.co.uk
¹ Department of Land Resource Management and Agricultural Technology, University of Nairobi, P.O box 29053, Kangemi, Nairobi, Kenya
² South Eastern University College, Kitui, Kenya

Abstract

In most semi-arid communal areas browse plays a critical role as livestock feed in the dry season.  Management practices of browse trees include lopping, coppicing, pruning and pollarding. These practices can increase the amount of fodder harvested from the trees. The idea is to cut away branches for fodder and wood and to improve the potential of the tree to produce more of the desired produce.  This study looks at the effect of coppicing a local important drought tolerant browse tree Julbernardia globiflora. A survey was also conducted to determine intensity of harvesting of Julbernardia globiflora by the local people and its effect on number of shoots produced.  The cutting height, tree circumference and number of shoot sprouting were measured on 51 trees from 5 sites.

The survey indicated that more than 80% of the trees were cut within a height of 100cm while less than 2% were cut at a height above 150cm.  Browse trees with a circumference of 31-40cm (10-13 cm diameter) were cut the most (47.06%) followed by browse trees with a circumference of 20 -30 cm (6.6-9.5 cm diameter) (39.21%).  Browse trees with 5-11 shoots were the highest frequency while trees with 16-20 shoots were the lowest. There was a positive correlation (R² = 0.45) between the cutting height and the number of shoots that sprouted and was statistically significant (P<0.05) The higher the cutting height the more shoots the trees sprouted.  However there was a negative correlation (R²= - 0.02) between the circumference of the lopped trees and the number of shoots that sprouted but the correlation was not significant (P>0.05).

It would therefore be recommended not to cut the browse tree close to the ground (< 20cm) so that there is balance between the requirement of the local people for wood for various uses, the ease of regeneration of the tree on a sustainable basis and the need of animals to easily reach the tree for dry season browse.

Key Words: browse, dry season, regeneration

Introduction

In most semi-arid communal areas browse plays a critical role as livestock feed in the dry season (Sibande 1986, Magadzire 2002, Ndathi 2011).  Dry season feed resources are the major factor affecting long term livestock numbers in the semi-arid region. Livestock nutrition is the major constraint to sustainable livestock production in drylands especially during the dry seasons (Mnene et al 2004 and Kibet et al 2006).  This is because the natural grasses which form the bulk of the feed resource dry up and lose their high nutritive value and digestibility leading to poor animal performance.   Browse trees on the other hand remain green, have higher nutritive value and are still very palatable during the dry season. The leaves, pods and fruits from deciduous browse trees and shrubs are consumed from trees or after they have fallen naturally to the ground (Aregawi et al 2008). Herdsmen can facilitate improved accessibility of leaves, pods and other edible portion of the browse species to livestock during the dry season using sticks or stones or by shaking the browse plants/branches or lopping their branches (Aregawi et al 2008).

Management practices of browse trees include lopping, coppicing, pruning and pollarding. This can increase the amount of fodder harvested from the trees. The idea is to cut away branches for fodder and firewood and to improve the potential of the tree to produce more of the desired produce.

Coppicing is the practice of cutting back a tree to stimulate it to produce new shoots. This method is ideal for producing forage where livestock are not browsing on the tree directly. Coppicing will enhance a bushy regrowth to produce many branches for fodder (Chileshe and Kitalyi 2009).  This practice can help to improve the amount of browse during the dry season or extreme weather conditions because the browse trees can regenerate after coppicing. However, Primefacts (2009) suggests that no more than about 60% of tree/shrub foliage be removed and that some tree/shrubs remain unlopped to avoid permanent damage to the trees.  Julbernardia globiflora coppices well, but trees cut close to the ground (<5cm) produce less coppice growth than plants cut at 1.3 m height (Jimu 2010).  In Zimbabwe lopping of branches is carried out in the late dry season to make browse accessible to livestock.

However, very little is known about the effect of coppicing on indigenous browse tree species in Zambia. This study therefore looked at the effect of coppicing Julbernardia globiflora an important indigenous browse tree in Zambia.

Julbernardia globiflora is a tropical african tree. It is well branched, deciduous, rounded tree, growing to 12m in height. It occurs in mixed deciduous miombo woodland, growing over large areas of the escarpment and the Tonga plateau in Zambia (Chileshe 2009) and is an important browse plant during drought in Southern Zambia (Chibinga et al 2012b). It usually occurs at 250-2000m altitude with an average annual rainfall below 1000 mm.  It is often dorminant or co-dominant in dry miombo woodland usually occurring with Brachystegia sperciformis.  The climate in the Brachystegia-Julbernardia (miombo) woodland region of southern Africa is characterised by a long dry season (7-8 months) during which herbaceous vegetation dries out and the litter of deciduous woody plants accumulate on the ground (Chidumayo 1991) It displays a bright red foliage in late August and then the red colour fades back to green in October/November at the end of the dry season. It has tender leaves which are good for fodder for livestock and is important as an early dry season browse plant. It is a bee forage, yielding honey of very high quality and an important food plant for edible caterpillars.  Wood is used for poles, tool handles, mortars, yokes harnesses and canoes. It is also widely used for fuelwood and charcoal. The bark yields tannin which is used for dyeing.   In Zimbabwe farmers gather Julbernardia globiflora leaf litter from adjacent woodlands to improve soil fertility of their fields; it is sometimes moved to kraals and composited with manure before being applied to fields  (Jimu 2010).

Materials and Methods

This study was carried out in Choma districts in of Southern Zambia. The district was chosen because it is a major ruminant rearing area where browse utilization is very important and is in the drylands of Southern Zambia. The major inhabitants of the study area are the Plateau Tongas who are mainly agro-pastoralists (Chibinga et al 2012a). The area experiences unimodal type of rain lasting from November to April. The annual rainfall is averaging between 600-700mm while the average monthly temperature is 26^oC with a maximum of 32^oC in October and a minimum of 15^oC in June (Chibinga et al 2012a)   Five sites were randomly selected and ten (10) coppiced tress were measured from each site. Coppicing height, tree diameter and number of shoots were measured.  Data were subjected to regression using Minitab Reference Manual release 13 (Minitab 200). 

Results

Trees subjected to different levels of cutting or coppicing by the farmers and trees of different diameters were cut (Table 1).   The high number of trees cut between 50 -100cm height could be attributed to requirement of this browse tree for various household uses. This browse tree has various uses such as timber for building huts, fibre, crafts, firewood and charcoal.  This cutting height is also ideal for livestock such as cattle, goats and sheep in that they can easily reach the shoots that sprout after the cutting.  Cutting the tree higher than 100cm would therefore reduce the amount of wood that would be available for these important uses though it would increase the amount of shoots for browse. Browse trees with a circumference of 31-40cm (10-13 cm diameter) were cut the most because of the high demand of this size or trees mainly for timber for various uses compared to the much smaller and the bigger timber sizes.

Coppicing height

There was a positive correlation (R² = 0.45) (Figure 1) between the cutting height and the number of shoots that sprouted and was statistically significant (P<0.05) (Table 2). The higher the cutting highest the more shoots the trees sprouted.  This results is similar to Jimu 2010 who found that Julbernardia globiflora coppices well, but trees cut close to the ground (<5cm) produce less coppice growth than plants cut at 1.3 m height. Kumar and Tewari 2000 indicated that not more than 2/3 of the crown length should be removed preferably with a gap between successive lopping for better yield and sustainable basis. This positive correlation is because if the tree is cut at a lower height, it has more stress because a lot of its material is removed and it is shaded by other trees and therefore will be less competitive for nutrients.  This will cause it to have less number of shoot.  If the tree is cut at a higher height, it has less stress since less material is removed, it will be more exposed to more light and will therefore form more shoots. Though coppicing at higher height yielded more shoots, it poses a big challenge with regards to feeding animals because most animals would not reach the shoots at this height of more than 2 meters. However an exception can be made for goats because they are able to climb trees in search of browsable material.  For cattle and sheep it would be ideal if the shoots are harvested end fed to the animals.  Severe copping (below 20 cm) though ideal for easy reach of the browse for the animals and good harvest of timber for human use is not good for tree regeneration as seen from the number of shoots.  There is also the danger that shoots from trees coppiced at high intensity could be burnt by uncontrolled bush fires and further delay or even stop their regeneration. 

Figure 1: Relationship between coppicing height and number of shoots of Julbernardia globiflora

Figure 2: Relationship between coppiced tree circumference and number of shoots of Julbernardia globiflora

Coppicing Diameter

There is however a negative correlation (R²= - 0.02) between the circumference of the coppiced trees and the number of shoots that sprout (Figure 2) but this was not statistically significant (p>0.05). This means that the re-sprouting of browse trees does not really depend on the circumference of the tree.  Tree diameter is not as important as the coppicing height as far as re-sprouting is concerned.

Conclusion

• This study showed that coppicing  Julbernardia globiflora  at different levels affects the number of shoots yielded. Coppicing at lower heights though desirable in order to maximize the amount of produce from the tree reduces the number and yield of shoots for animals to browse.   Coppicing at higher heights which produces high number of shoots reduces the amount of tree produce for use by the farmer and then the produced shoots would not be easily reached by the browsing animals.

  
  

• It is therefore recommended to harvest not less than 20 cm from the ground of the browse trees in order to create a balance between the need of humans for timber produce on one hand and the need of regenerated browse for the animals on the other.

Acknowledgements

We are very grateful to the Regional Universities Forum for Capacity Building in Agriculture (RUFORUM) for financial support for this research.

References

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Received 22 January 2016; Accepted 29 January 2016; Published 1 March 2016

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