Population Structure, Growth Dynamics, Leaf Production and Soil Conditions of Megaphrynium macrostachyum, a Key Non-Wood Forest Product in Central Africa

Abstract

Aims: Megaphrynium macrostachyum is a key non-wood forest product (NWFP) in Central Africa. This study aims to describe the soil characteristics and behaviour of the species Megaphrynium macrostachyum in a fallow land in southeastern Gabon. Methodology: Leaf growth was monitored weekly on a sample of 60 leaves for 10 weeks, after the unrolling of horns. Population structure and leaf production were quantified on 64 m² plots and then extrapolated to the hectare. Soil samples were collected at 30 cm depth. Results: Leaf growth and stem enlargement were observed to take place during the horn stage, while stem elongation became active after this stage. The stem reached its maximum height about 60 days after the leaf had fully unrolled. Within the same population, leaf length and leaf width were less heterogeneous (on average 55.6 ± 5.9 cm and 35.5 ± 4.5 cm, respectively); whereas leaf area, stem diameter and stem height were quite heterogeneous (on average 1475 ± 328.3 cm², 9 ± 2.2 mm and 154 ± 33.3 cm, respectively). Megaphrynium macrostachyum was observed to colonise its environment quite well (148,646 ± 66,623 stems per hectare), thus explaining its high leaf production (104,167 ± 45,271 usable leaves per hectare). The soil sample analysed revealed Megaphrynium macrostachyum to grow in sandy-silty or sandy-silty-clay soils (58.21% sand, 25.69% silt and 16.1% clay), and in soils that are wet (35% relative humidity), acidic (pH 4.01), low in phosphorus (9.38 ppm assimilable phosphorus) and total nitrogen (0.01% total nitrogen), and high in organic matter (19.3% organic matter). Conclusion: The leaf area exploited by local populations is variable. Megaphrynium macrostachyum is less demanding on soil characteristics, with high leaf production. From a cultivation perspective, the horn stage would be decisive.