© 2019 Aroloye O. Numbere. This open access article is distributed under a Creative Commons Attribution (CC-BY) 3.0 license. American Journal of Environmental Sciences Original Research Paper Effect of Soil Types on Growth, Survival and Abundance of Mangrove (Rhizophora racemosa) and Nypa Palm (Nypa fruticans) Seedlings in the Niger Delta, Nigeria Aroloye O. Numbere Department of Animal and Environmental Biology, University of Port Harcourt, Choba, Nigeria Article history Received: 27-12-2018 Revised: 08-04-2019 Accepted: 23-04-2019 Email: aroloyen@yahoo.com Abstract: The invasion of nypa palm into mangrove forest is a serious problem in the Niger Delta. It is thus hypothesized that soil will influence the growth, survival and abundance of mangrove and nypa palm seedlings. The objective was to compare the growth, survival and abundance of both species in mangroves, nypa palm and farm soils (control). The seeds were planted in polyethylene bags and monitored for one year. Seed and seedling abundance experiment was conducted in the field. The result indicates that there was significant difference in height (F 3, 162 = 4.54, P<0.001) and number of leaves (F 3, 162 = 21.52, P<0.0001) of mangrove seedlings in different soils, but there was no significant difference in diameter (F 3, 162 = 4.54, P = 0.06). Height of mangrove seedling was influenced by highly polluted soil (P = 0.027) while number of leaves was influenced by farm soil (P = 0.0001). On the other hand, mangrove seedlings planted in farm soil were taller (7.8±0.7 cm) than seedlings planted in highly polluted (7.7±0.4 cm), lowly polluted (6.3±1.4 cm) and nypa palm (6.0±0.8 cm) soils whereas Nypa palm seedlings planted in farm soil were the tallest (42±3.4 cm) followed by mangrove-high (38.8±5.8 cm), mangrove-low (34.2±cm) and nypa palm (21.1±1.0 cm) soils. Furthermore, species abundance of the different growth stages of mangrove and nypa palm seedlings were significantly different (F 1, 37 = 3.07, P = 0.04). Nypa palm seedlings outnumbered mangroves (27:1) and had higher overall survival rate (0.48) than mangroves seedlings (0.35) in all soils. This implies that nypa palm has competitive advantage over mangrove in mangrove soil. Keywords: Abundance, Farm Soil, Invasive Species, Mangrove, Nypa Palm, Rhizophora Introduction The growth of seedlings can signify underlying adaptation to environmental conditions. Within different population individuals that find suitable location not only increase their chances of survival to maturity, but also pass on the good genes to the next generation (Duke et al., 1997). Therefore, with time seeds of individuals that show greater competitive ability dominate a given locality. This adaptation by the majority of the individuals to select a favorable soil condition is reflected in the local pattern of seed distribution, abundance and growth. Mangroves are amongst the most widespread marine vascular plants along subtropical and tropical coastlines (Sanchez, 2019). They grow in swampy soils (Feller et al., 2010), which originates from weathered sedimentary rocks (SPDC, 1999). The soil is a mixture of litter at different stages of decomposition (Numbere and Camilo, 2016) and serves as carbon sinks (Ong and Gong, 2013; Tam and Wong, 1995). Nypa palm (Nypa fruticans) on the other hand, is regarded as a member of the mangrove ecosystem and from the nypoid line (Gee, 2001). However, other studies had shown that nypa palm is not a true mangrove (Kathiresan and Bingham, 2001). Nypa palms are invasive species that are deliberately introduced into the Niger Delta to curb coastal erosion (CEDA, 1997; Keay et al., 1964). but have become a major threat to the mangroves. They grow in mangrove soils and have their seeds dispersed across the mangrove forest by tidal currents, signaling readiness for full colonization. During low tides the seeds of the palms settle down on the forest