ABSTRACT

The assessment of recruitment of indigenous tree species and litterfall in three exotic plantations and a bush fallow system was carried out at Forestry Research Institute ofNigeria (FRIN), Umuahia. Litterfall was studied for 12 months in the 21- year old exotic plantations and 11- year old fallow system using a factorial experiment in complete randomized design (CRD) with four replicates. Enumeration of indigenous tree species was carried out in the exotic plantations and the bush fallow system with a 3.5m X 3.5m quadrat. The Pine/Gmelina mixed stand had the highest level of recruitment among the exotic plantations with a total of 140 species with 14 families in occurrence followed by Pine stand with 121 species and 14 families in occurrence while Gmelina stand had the least recruitment with 115 species and 11 families in occurrence. Litterfall was continuous with much of the litter falling between March and April. April 2004 gave significantly the highest litter fall (165.9 gm'2), followed by March 2004 (104.7 gm'2) in the Pine plantation. . No significant differences, however, existed among the mean monthly litter fall values of September, October, November, December (i.e. September - December 2003) and January, February, May, June, July and August 2004 in the pine plantation. September 2003 gave significantly the highest mean monthly litter fall (75.70 gm'2) in the Gmelina plantation. The result of October 2003 was statistically equal to November 2003. No significant differences existed among the mean monthly litter fall values of October, November, December (i.e. October - December 2003) as well as those of January, February, March, April, May, June, July and August 2004. . In the Pine/Gmelina mixed stand, the highest litter fall occurred between the months of September and October. No significant differences, however, existed in the mean monthly litter fall in the Pine/Gmelina mixed stand. In the bush fallow system, the highest mean monthly litter fall (53.10 gm'2) occurred in the month of April 2004. The months of March and June were also statistically equal. December and January were also statistically equal. No significant differences existed among the mean monthly litter fall values of September, October, November, December, January, February, March, May, June, July and August. However, April 2004 gave significantly the highest mean monthly litter fall (165.9 gm'2) among the four plant communities (vegetation types) studied. Significant differences in mean monthly litter fall occurred between the months of September 2003/ March 2004 and the months of November, December, January, February, June, July and August. No significant differences existed among the mean monthly litter fall values of March, September, October and May in the four vegetation types. Pine stand gave significantly the highest (P > 0.05) annual litter fall (10,000 kg/ha) followed by the Pine/Gmelina mixed stand (7094 kg/ha), while the Gmelina stand had the least value among the exotic plantation. The bush fallow system (control) gave the least (5014 kg/ha) annual litter fall. The mineral content of the different plant parts in the studied area is not similar. In the bush fallow system Mg was highest (1.83%), followed jointly by Pine and Gmelina plantations (1.58%) while Pine/Gmelina mixed plantation had the lowest Mg content 1.34 %. Ca was 5.48% in the bush fallow system, Pine/Gmelina mixed plantation (4.66%), while Pine had the least Ca content (3.9%). N was 6.09% in the Pine litter, Gmelina was 3.91% while the bush fallow system had 3.15%. P was 0.62% in Gmelina, 0.57% in Pine while Pine/Gmelina mixed plantation had the lowest with 0.43%. Na was 0.77% in bush fallow system, 0.76% in Gmelina while Pine had the lowest with 0.58%. K was 2.86% in Pine/Gmelina mixed plantation, 2.19% in Gmelina while Pine had the lowest with 0.75%. The highest value of clay (5.5%), which was recorded in the Gmelina plantation portrayed higher level of weathering that has taken place in the soil through organic acids exuded from the roots. This however, must have led to the lowest level of recruitment of indigenous tree species within this plantation. Meanwhile, it was discovered that the highest quantity of litterfall produced by the Pine plantation did not bring about highest recruitment ofthe indigenous tree species.