Woody plant species enumeration in abandoned farmlands within Omuigwe Agrarian Community in Aluu, Rivers State, Nigeria

Abstract

This study was conducted to enumerate woody plant species in abandoned farmlands of different ages in Omuigwe community, ALUU, Rivers State, with a view to ascertaining the impact of different fallow periods on woody species composition and diversity. Four fallow farmlands: FL₁ (1 year old), FL₂ (3 years old), FL₃ (5 years old) and FL₄ (7 years old), were purposively chosen for the study. Tree enumeration was carried out using five 20 m x 20 m quadrats randomly distributed on each fallow land. All woody species found in the quadrats were identified to species level, and the number of individuals counted and recorded for each fallow period. Woody species diversity was measured using Simpson (1-D) and Shannon-Wienner (H') indices while similarity in woody species between fallow lands was computed using Sorensen’s index. Total height and diameter of the woody species were measured using a pole graduated in metres and a caliper respectively. Woody species that contribute to livelihoods in the community were identified through oral interviews with twenty randomly selected Heads of households in the community. A total of twenty-five species belonging to nineteen families were identified as contributing to livelihoods in the community. This information was used to ascertain the number of the key livelihood species among the woody species in the fallow farmlands. Populations of woody species in fallow farmlands among the species identified as contributing to livelihoods in the community were low (20%, 20%, 29% and 20% in FL₁, FL₂, FL₃ and FL₄, respectively). Total woody species population decreased with an increase in the age of fallow land while woody species diversity was slightly higher in FL₃ (1-D = 0.86; H' =2. 21) than in FL₁ (1-D = 0.85; H' = 2.11), FL₂ (1-D = 0.84; H' = 2.10) and FL₄ (1-D = 0.82; H' = 2.10). Woody species diameter and height showed an increasing trend with increase in fallow period with some species and varied significantly (p < 0.05) amongst fallow farmlands in some cases. Similarity in woody species composition between sites was generally low (below 50% except between FL₂ and FL₃ where a similarity of 50% was recorded). Woody species diversity and the populations of woody species contributing to rural livelihoods decreased after a fallow period of five years. Integrated land use system like agroforestry is suggested for effective regeneration and conservation of woody species in the community especially those that contribute to rural livelihoods.

Keywords: Shifting cultivation, fallow period, woody species, rural livelihood, regeneration