Abstract
The effects of four silvicultural methods notably Layon, Blanc-Etoc (BE), Martineau and assisted natural regeneration (ANR) have been compared on the dendrometric traits of <i>Pericopsis elata Harms</i> and <i>Entandrophragma cylindricum Sprague</i> planted in 1938 in Yangambi for controlling anthropogenic activities (agricultural deforestation and forest degradation) threatening the species to extinction added to difficult natural regeneration. The sustainable pedo-silvicultural system will preserve Yangambi biosphere reserve. In case of variance analysis significance; the non-parametric test of Kruskal Wallis and the test of Tukey Honest Significant Differences were applied to separate the traits means. Results have revealed that the three plantation methods were significantly different from ANR. BE, Martineau and Layon have determined the Gaussian shape for <i>P. elata</i> diametric structures while Layon, Martineau and ANR presented the inversed J shape for <i>E. cylindricum</i>. BE method convenes for plantations of the two species whose trait values were higher than those of other methods. The difference was significant between the widest average breast height diameter (DBH) of 44.49±10.63cm with the total height mean of 24.46±4.45m for <i>P. elata</i> and DBH of 29.63±11.59cm with the total height mean of 22.04±5.80m for <i>E. cylindricum</i>. The differences were also identified respectively for the two species regarding the basal areas with 25.54±5.6 against 9.474±1.67 m<sup>2</sup>/ha, the aboveground biomasses with 318.81±77.2 against 94.315±11.59t/ha and the loose volumes with 45069.49±12219.30 against 14 471.348±3 645.692m<sup>3</sup>/ha. The Layon method did not have significant effect on the <i>E. cylindricum</i>, but has influenced the DBH, AGB and basal area of <i>P. elata</i>. The least productive method ANR has expressed a convenient natural regeneration inversed J shape for the two species, as related to Yangambi reserve preservation.
Highlights
The importance of the ombrophilous evergreen dense forest of Yangambi is characterized by its role of shading between plants, microbial and animal species, photosynthesizing with vegetal carbonic respiration, purifying atmospheric air, structuring ligneous tissues and moderating climate warming willing to benefit carbon credit [1,2,3]
The analysis of variance presented in table 4 shows the differences between the four silvicultural methods related to each dendrometric parameter of Pericopsis elata
Legend: ANR: assisted natural regeneration, BE: Blanc-Etoc; numbers followed by the same letter a, b and c are not statistically different at 0.5 probability level
Summary
The importance of the ombrophilous evergreen dense forest of Yangambi is characterized by its role of shading between plants, microbial and animal species, photosynthesizing with vegetal carbonic respiration, purifying atmospheric air, structuring ligneous tissues and moderating climate warming willing to benefit carbon credit [1,2,3]. The forest serves through deeper tree roots recycling plant nutriments and controlling water and soil erosions [2, 4]. The shifting is combined with global warming and humidity decrease of denuded soils reducing evaporing surfaces and proportional raining surfaces [5, 8]. This has caused latent hit flux of infrared rays from earth to the atmosphere in increasing temperature by 0.44°C in the Yangambi region [9, 10]. The devastating degradation of Yangambi reserve which sequestrates about 164 Mg C/ha aboveground carbon and 68 Mg C/ha underground carbon, would be negative to the environment by disturbing edaphic, hydrologic, human, plant and animal ecosystems in favoring climate heat [2, 5]
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