An Assessment of the Physico-Chemical Parameters of Mangrove Soils that Support Nypa fruticans and Other Mangrove Species Establishment in the Cameroon Estuary

Abstract

Invasion of Nypa palm into mangroves is a problem in the Cameroon Estuary. Soil variability is one of the dominant features that support Nypa palm establishment. The objective was to characterize the soil under the different mangrove stands; Purely Nypa palm stands (A), mixed stands i.e Nypa palm and other mangrove species (B) and other mangrove species i.e Nypa palm free (C), determine the principal soil characteristic critical for Nypa spread.  9 plots of 20 x 20 m were laid in each of the sites.  27 soil samples were collected in the North, West, South East and Center at a depth of 30 cm in these three sites using a soil auger. The results in the three sites indicated that; soils were acidic (3.87- 4.39), pH values did not significantly differ (alpha >0.05), organic matter was low in A (12.32%) and B (16.35%).Soil Organic Carbon ranged from (4.52 to 7.06%). High percentage of organic carbon content was recorded in C (7.06%). Low percentage of organic carbon was found in A (4.52%). Total nitrogen varied from 1.04 g/kg, 1.70g/kg, 1.80 g/kg in sites C, A and B. In all the mangrove stands, the values of Exchangeable Ca content were below 4.0 cmolkg-1. Soil texture in the three sites were; sandy, clay and silt. Power test showed no significant different in soil types between the three sites (p>0.05). According to the component matrix the factor is positively loaded by soil EC, moisture content, organic matter, organic carbon, N, C/N, CEC, Ca, Mg, K, Na, Clay, Silt, and negatively loaded by the percent sand. This study therefore, suggests that since soil plays key role in Nypa palm establishment, there should be constant monitoring of soil quality to forestall drastic changes that will jeopardize the survival of the mangroves. Nypa palm seedlings should also be physically removed from mangrove forest to prevent colonization. In addition, more mangrove seeds should be planted in deforested mangrove areas to close the window of opportunity for the palms.