The soil seed bank is considered as an important mechanism for the natural regeneration, resilience and conservation of the forests after disturbances. This study evaluates the characteristics of the soil seed bank in...The soil seed bank is considered as an important mechanism for the natural regeneration, resilience and conservation of the forests after disturbances. This study evaluates the characteristics of the soil seed bank in two post-logging plots of Loundoungou-Toukoulaka Forest Management Unit: one plot exploited in 2008 and another exploited in 2021. In each study plot, 40 samples were collected per soil layer (0 - 5 cm, 5 - 10 cm, 10 - 15 cm, 15 - 20 cm and 20 - 25 cm depth). The species diversity and abundance of the soil seed bank were estimated after soil samples were brought to germination. The results demonstrated that 347 seedlings belonging to 37 species in the plot exploited in 2008 and 418 seedlings belonging to 27 species in that exploited in 2021 germinated during 20 weeks of monitoring. The total densities of the seedlings identified were respectively 1446 seedlings/m<sup>2</sup> and 1742 seedlings/m<sup>2</sup>. The plot exploited in 2021 presented a higher proportion of herbaceous species (93.78%) compared to that exploited in 2008 (82.71%). Two pioneer species were recorded in the plot exploited in 2008. These are Macaranga barteri (0.29%) in the 0 - 5 cm layer and Musanga cecropioides (2.31%) up to 20 cm deep. On the other hand, in the plot exploited in 2021, Macaranga spinosa (0.96%) in the 0 - 5 cm layer and M. cecropioides (0.96%) up to 20 cm deep were identified. In the plot exploited in 2008, the 20 - 25 cm layer demonstrated important proportions in woody species (9%), these are in particular Rubiaceae sp.4 and Nauclea diderrichii. While that exploited in 2021, presented 19% of woody species, namely the species of Rubiaceae sp.4, Rubiaceae sp.5 and N. diderrichii, greatly exceeding the proportions obtained in the 15 - 20 cm layer of the two plots. Nonetheless, N. diderrichii was the only commercial species recorded with densities of 108 seedlings/m<sup>2</sup> and 4 seedlings/m<sup>2</sup>, respectively in the plot exploited in 2008 and that exploited in 2021. Commercial tree species are poorly represented in the soil seed bank. Consequently, the study suggests that to improve the natural regeneration of the commercial species, silvicultural interventions based on planting techniques in the exploited plots should be more effective in order to sustainably manage these production forests.展开更多
The belowground biomass is represented by coarse and fine roots. Concentrated in the superficial horizons of the soil, the fine roots play a crucial role in the functioning of a forest ecosystem. However, studies on t...The belowground biomass is represented by coarse and fine roots. Concentrated in the superficial horizons of the soil, the fine roots play a crucial role in the functioning of a forest ecosystem. However, studies on their dynamics in natural forests are almost non-existent in the Republic of Congo. Here, we estimated the biomass, production, turnover and fine root lifespan of two forest strata of a semi-deciduous forest: the <i><span style="font-family:Verdana;">Gilbertiodendron dewevrei</span></i><span style="font-family:Verdana;"> (De Wild.) J. Léonard forest (GF) and the mixed forest (MF) of land. The ingrowth cores method was used to estimate the biomass, production, turnover and lifespan of fine roots. The results of this study revealed that the biomass, production and fine root turnover of the two forest strata studied significantly decreased with increasing soil depth, with an increase in lifespan. The annual fine root biomass of GF (2284.50 ± 37.62 <img src="Edit_990c94b6-013e-4e21-90df-d1388dc0e65f.png" alt="" /></span><span style="font-family:Verdana;"> and 1034.61 ± 14.52 <img src="Edit_dff42540-5a2f-413b-8620-cb500e9961e2.png" alt="" /></span><span style="font-family:Verdana;">) was slightly lower than that of MF (2430.07 ± 40.68 <img src="Edit_66800589-8460-4c37-83b2-2df0f335d75d.png" alt="" /></span><span style="font-family:Verdana;"> and 1043.10 ± 11.75 <img src="Edit_c22f255e-d910-4b49-a6a4-033516044362.png" alt="" /></span><span style="font-family:Verdana;">) in the 0-15 cm and 15-30 cm horizons, respectively. The annual production of fine roots from these latter horizons was respectively 1300.19 ± 32.17 <img src="Edit_5482204b-8e9e-476a-907d-0865bf3a1c99.png" alt="" /></span><span style="font-family:Verdana;"> and 539.18 ± 11.55 <img src="Edit_65a2856e-5322-4fc9-b42a-3ba1176fa992.png" alt="" /></span><span style="font-family:Verdana;"> in GF and 1362.24 ± 39.59 <img src="Edit_9802e464-658d-48eb-9b57-8e746c3e8ef4.png" alt="" /></span><span style="font-family:Verdana;"> and 492.95 ± 14.38 <img src="Edit_51413fca-930c-45b9-a385-2b55d4d2bac8.png" alt="" /></span><span style="font-family:Verdana;"> in the MF. Root turnover was higher in the GF (1.68 ± 0.05 <img src="Edit_ce9d780c-6a46-46c4-aad2-653309318e29.png" alt="" /></span><span style="font-family:Verdana;"> and 1.35 ± 0.03 <img src="Edit_d66d8b7b-c608-4398-9441-e85547f03dea.png" alt="" /></span><span style="font-family:Verdana;">) than in the MF (1.57 ± 0.05 <img src="Edit_cb79094f-88a0-401c-a3e7-06eedb2cef9a.png" alt="" /></span><span style="font-family:Verdana;"> and 1.13 ± 0.02 <img src="Edit_e4f9b6d7-2e2e-44d5-8662-862b8f8ff80e.png" alt="" /></span><span style="font-family:Verdana;">). The lifespan of fine roots increased with the depth of the soil. The difference in fine root dynamics observed between the forest strata studied was influenced by the Evenness index and the above-ground biomass.</span>展开更多
文摘The soil seed bank is considered as an important mechanism for the natural regeneration, resilience and conservation of the forests after disturbances. This study evaluates the characteristics of the soil seed bank in two post-logging plots of Loundoungou-Toukoulaka Forest Management Unit: one plot exploited in 2008 and another exploited in 2021. In each study plot, 40 samples were collected per soil layer (0 - 5 cm, 5 - 10 cm, 10 - 15 cm, 15 - 20 cm and 20 - 25 cm depth). The species diversity and abundance of the soil seed bank were estimated after soil samples were brought to germination. The results demonstrated that 347 seedlings belonging to 37 species in the plot exploited in 2008 and 418 seedlings belonging to 27 species in that exploited in 2021 germinated during 20 weeks of monitoring. The total densities of the seedlings identified were respectively 1446 seedlings/m<sup>2</sup> and 1742 seedlings/m<sup>2</sup>. The plot exploited in 2021 presented a higher proportion of herbaceous species (93.78%) compared to that exploited in 2008 (82.71%). Two pioneer species were recorded in the plot exploited in 2008. These are Macaranga barteri (0.29%) in the 0 - 5 cm layer and Musanga cecropioides (2.31%) up to 20 cm deep. On the other hand, in the plot exploited in 2021, Macaranga spinosa (0.96%) in the 0 - 5 cm layer and M. cecropioides (0.96%) up to 20 cm deep were identified. In the plot exploited in 2008, the 20 - 25 cm layer demonstrated important proportions in woody species (9%), these are in particular Rubiaceae sp.4 and Nauclea diderrichii. While that exploited in 2021, presented 19% of woody species, namely the species of Rubiaceae sp.4, Rubiaceae sp.5 and N. diderrichii, greatly exceeding the proportions obtained in the 15 - 20 cm layer of the two plots. Nonetheless, N. diderrichii was the only commercial species recorded with densities of 108 seedlings/m<sup>2</sup> and 4 seedlings/m<sup>2</sup>, respectively in the plot exploited in 2008 and that exploited in 2021. Commercial tree species are poorly represented in the soil seed bank. Consequently, the study suggests that to improve the natural regeneration of the commercial species, silvicultural interventions based on planting techniques in the exploited plots should be more effective in order to sustainably manage these production forests.
文摘The belowground biomass is represented by coarse and fine roots. Concentrated in the superficial horizons of the soil, the fine roots play a crucial role in the functioning of a forest ecosystem. However, studies on their dynamics in natural forests are almost non-existent in the Republic of Congo. Here, we estimated the biomass, production, turnover and fine root lifespan of two forest strata of a semi-deciduous forest: the <i><span style="font-family:Verdana;">Gilbertiodendron dewevrei</span></i><span style="font-family:Verdana;"> (De Wild.) J. Léonard forest (GF) and the mixed forest (MF) of land. The ingrowth cores method was used to estimate the biomass, production, turnover and lifespan of fine roots. The results of this study revealed that the biomass, production and fine root turnover of the two forest strata studied significantly decreased with increasing soil depth, with an increase in lifespan. The annual fine root biomass of GF (2284.50 ± 37.62 <img src="Edit_990c94b6-013e-4e21-90df-d1388dc0e65f.png" alt="" /></span><span style="font-family:Verdana;"> and 1034.61 ± 14.52 <img src="Edit_dff42540-5a2f-413b-8620-cb500e9961e2.png" alt="" /></span><span style="font-family:Verdana;">) was slightly lower than that of MF (2430.07 ± 40.68 <img src="Edit_66800589-8460-4c37-83b2-2df0f335d75d.png" alt="" /></span><span style="font-family:Verdana;"> and 1043.10 ± 11.75 <img src="Edit_c22f255e-d910-4b49-a6a4-033516044362.png" alt="" /></span><span style="font-family:Verdana;">) in the 0-15 cm and 15-30 cm horizons, respectively. The annual production of fine roots from these latter horizons was respectively 1300.19 ± 32.17 <img src="Edit_5482204b-8e9e-476a-907d-0865bf3a1c99.png" alt="" /></span><span style="font-family:Verdana;"> and 539.18 ± 11.55 <img src="Edit_65a2856e-5322-4fc9-b42a-3ba1176fa992.png" alt="" /></span><span style="font-family:Verdana;"> in GF and 1362.24 ± 39.59 <img src="Edit_9802e464-658d-48eb-9b57-8e746c3e8ef4.png" alt="" /></span><span style="font-family:Verdana;"> and 492.95 ± 14.38 <img src="Edit_51413fca-930c-45b9-a385-2b55d4d2bac8.png" alt="" /></span><span style="font-family:Verdana;"> in the MF. Root turnover was higher in the GF (1.68 ± 0.05 <img src="Edit_ce9d780c-6a46-46c4-aad2-653309318e29.png" alt="" /></span><span style="font-family:Verdana;"> and 1.35 ± 0.03 <img src="Edit_d66d8b7b-c608-4398-9441-e85547f03dea.png" alt="" /></span><span style="font-family:Verdana;">) than in the MF (1.57 ± 0.05 <img src="Edit_cb79094f-88a0-401c-a3e7-06eedb2cef9a.png" alt="" /></span><span style="font-family:Verdana;"> and 1.13 ± 0.02 <img src="Edit_e4f9b6d7-2e2e-44d5-8662-862b8f8ff80e.png" alt="" /></span><span style="font-family:Verdana;">). The lifespan of fine roots increased with the depth of the soil. The difference in fine root dynamics observed between the forest strata studied was influenced by the Evenness index and the above-ground biomass.</span>
