Decomposition of Entandrophragmacylindricum Tree Prunings in Agroforestry System in Onne, Rivers State

A study was conducted at Swamp Forest Research Station, Onne, Forestry Research Institute of Nigeria, to evaluate the rate of decomposition of E. cylindricumtree prunings. The experiment was a 2x8 factorial in a randomized complete block design with three replications. The first factor comprises two placement methods (surface-placed and soil-incorporated) and the second factor comprises eight biweekly sampling intervals (2 – 16 weeks). The litterbag technique was employed. Results indicated that the Total leaf decomposition (100.0%) of soil incorporated leaf litter was obtained at 16th week after litter placement (WALP). Soil-surface placed had 98.00% at 16th WALP. Leaf half-lives of the soil-surface placed and soil incorporated were 5.08 and 2.10 WALP respectively. The turnover coefficients (k1) of the soil surface-placed and soil -incorporated leaf litter of E. cylindricum were 6.93yr-1 and 17.33 yr-1 respectively. The high rate of fresh leaf decomposition and subsequent release of nutrient make E. cylindricum leaf pruning a good source of organic manure for soil fertility restoration.

How do silicious trichomes influence leaf decomposition by meso- and macrofauna?

<p>Decomposition of plant leaves is influenced by multiple traits, however, discrete structures of Si such as silicious trichomes on the leaf surface have been overlooked, although similarly to defense against insect herbivores, trichomes are thought to protect leaves from decomposers. This study hypothesized that silicious trichomes slow down leaf decomposition by soil meso- and macrofauna. We used two mesh bags (<0.2 mm and 5 mm) and examined ash-free mass loss of green leaves of <em>Broussonetia papyrifera</em> and <em>Morus australis</em>, closely related Moraceae species apparently different in trichome size and density, after 25 days of decomposition in a common garden. We also measured 10 traits of initial leaves and performed microscopic observation of the leaf surface with an energy dispersive X-ray analyzer. Of the leaf traits, trichome density on the lower leaf surface differed greatly between the two species. Our microscopic observation showed that short trichomes densely arranged on the lower leaf surface of <em>B. papyrifera</em> were highly silicified and that some of long trichomes were also composed of calcium. Ash-free mass loss of <em>M. australis</em> was greater in 5-mm mesh bag than in <0.2-mm mesh bag, while that of <em>B. papyrife</em>ra did not differ by mesh size, which represents a suppressive effect of silicious trichomes on decomposition by meso- and macrofauna. The trichomes of <em>B. papyrifer</em>a remained apparently intact on the decomposed surface, supporting a view of their continuously deferring influence on the large decomposers during the experimental period. For the meso- and macro-detritivore community, three taxa (Acari, Collembola and Isopoda) showed high population density in the common garden. Overall, our results suggest that distinct forms of Si bodies in plants such as trichomes are worth considering in better understanding of leaf decomposition by meso- and macrofauna.</p>