Memoire Online - Using tree- ring analysis to study the growth performance from saplings to trees for five savanna species in West Africa

This research aimed to establish the growth performance for five tree species from four different wood species families (Table 1). The Samples were collected in 2002 in the Comoé National Park (Côte d'Ivoire, Hennenberg, 2005) and in Central Benin (Orthmann, 2005). At CNP, 10, 8 and 8 samples were respectively collected from D. microcarpum, A. leiocarpa and D. abyssinica. A. leiocarpa was collected at the forest border, D. microcarpum in the savanna and D. abyssinica in the forest. In Benin, six (6) samples were also collected from I. doka, P. erinaceus and A. leiocarpa in open mosaic forest.

TABLE 1- The five tree species investigated in two different sites. UAC: Upper Aguima catchment, CNP: Comoé National Park; Cutting levels (level 1: cut at 0,1m - level 2: cut at 1,3m) and N (tree) means the number of sampled trees.

Site	Species	Family	Foliation pattern	N (tree)	Cutting levels
CNP	Anogeissus leiocarpa (DC.) Guill. & Perr.	Combretaceae	Short deciduous	8	1-2
UAC	Anogeissus leiocarpa (DC.) Guill. & Perr.	Combretaceae	Short deciduous	6	1
CNP	Detarium microcarpum Guill & Perr.	Caesalpiniaceae	Deciduous	10	1-2
CNP	Diospyros abyssinica (Hiern) F. White	Ebenaceae	Evergreen	8	1-2
UAC	Isoberlinia doka Craib and Stapf	Caesalpiniaceae	Brevi-deciduous	6	1-2
UAC	Pterocarpus erinaceus Poir.	Fabaceae	Pronounced deciduous	6	1

The african birch species named Anogeissus leiocarpa (DC.) Guill. & Perr., belong to the family of Combretaceae and ranged from the borders of the sahara up to the outlier humid tropical forests and is found from Senegal to Cameroon in West Africa. The tree of about 20 m of height with light green foliage grows in dry forest s, fringing forests and semi aris savanna areas. The leaves, bark, roots and seeds serve for traditional tanning and its wood is used for house construction and tool handles because of its resistance against insects (Seed leaflet, 2007). The picture 1 shows some of morphological characteristics of the species.

Picture 1a: Flowers - Picture 1b: aspect of the stem - Picture 1c: the tree (Brunken et al., 2008)

Detarium microcarpum Guill. & Perr. from the family of Caesalpiniaceae typically found in high rainfall savanna areas, dry forests and fallow land, on sandy or iron rich hard soils. It can grow up from 10 m to 25 m in height. D. Microcarpum tree is also found in open savanna as a more stunded tree with smaller fruits as showing the picture 2. It has great fruit-bearing potential and is also used as medicinal plant.

Picture 2a: the fruits - Picture 2b: the aspect of the bark - Picture 2c: the tree (Brunken et al., 2008)

Diospyros abyssinica (Hiern) F. White has small, medium or large tree up to 36 m with a
relatively sparse and shortly branched crown. The leaves are altern ate, glossy dark green and
distinctly red when they are young. Its ecological distribution is known as widespread in

tropical Africa from the Guinea Republic to Eritrea southwards to the FZ area an d Angola. It is known for its medicinal use and used to make pestles. The picture 3 shows at left the leaves and at right its trees in forest stand.

Picture 3: Morphological characteristics of Diospyros abyssinica Picture 3a: a leave - Picture 3b: the tree (Brunken et al., 2008)

Isoberlinia doka Craib Stapf is one of several sudanian species of the family of Caesalpiniaceae found in deciduous woodland, tall grass savanna alway s in stands forming open forests with Isoberlinia tomentosa, Burkea africana, Prosopis africana, Uapaca somon etc... The tree has 10 to 20 m of height and the trunk straight 5 m height. The wood is used in marine construction, naval architecture, in paper products, as pulpwood and for office materials. The aspect of the foliage is presented in figure 4.

Picture 4a: the fruits - Picture 4b: the aspect of the bark (Brunken et al., 2008)

Pterocarpus erinaceus is a tropical African deciduous tree of 12 to 15 m (or more) that can be found in open stands, woodland and savanna. The bark is fissured as showing the picture 5.

Its wood is useful for house construction, in carpentry for doors and windows frames. It makes very good charchoal and decorative things.

Picture 5a: the fruits - Picture 5b: the aspect of the bark - Picture 5c: the tree (Brunken et al., 2008)

The dendrometric measurements such as diameter at 10 cm from grou nd, diameter at breast height (DBH) and the total height were made on some of the sampled trees by Orthmann (2005) and Hennenberg (2005). Their mean values were presented in table 2. The cross-sectional wood discs were cutted at 10 cm from ground level and at breast height (DBH) for all tree samples from Ivory Coast. In Benin, at least one stem disc per tree was cutted.

TABLE 2- Some characteristics of the investigated species. MD (1): mean diameter at 10 cm from ground, MD (2): mean DBH, MNR: mean number of ring of samples cutted at 10 cm from ground, MH: mean height and s.d: standard of deviation.

Species	N (trees)	MD (1) #177; sd (mm)	MD (2) #177; sd (mm)	MNR	MH #177; sd (m)
A. leiocarpa (UAC)	6	44 #177; 1.41		6.33 #177; 0.82	1.8 #177; 0.00
A. leiocarpa (CNP)	8	72.62 #177; 4.14	52.12 #177; 1.81	17 #177; 1.41	6.77 #177; 0.52
D. microcarpum	10	79.5 #177; 10.01	52.1 #177; 1.29	13.4 #177; 2.12	3.47 #177; 0.32
D. abyssinica	8	76.62 #177; 12.45	52.75 #177; 2.12	30.25 #177; 2.55	7.00 #177; 0.71
I. doka	6	55.25 #177; 7.91	42.44 #177; 3.50	7.83 #177; 2.40	2.77 #177; 0.55
P. erinaceus	5	42.93 #177; 2.96		8.2 #177; 1.09	2.14 #177; 0.22

The stem discs were labelled and conducted in laboratory (University of Göttingen, Germany). It is useful to note that the most of Comoé National Park samples were really cutted at two levels of height (10 cm from ground and 1.3 m). The missing diameter values were added after measurements on these stem discs with electronic forest compass (Pictures 6 and 7).

Picture 6: Some of the analysed stem discs Picture 7: The used electronic forest compass

Using tree- ring analysis to study the growth performance from saplings to trees for five savanna species in West Africa

3. MATERIAL AND METHODS

3.1 Studied plant species and collection of samples