Abstract
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 Gilbertiodendron dewevrei (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 and 1034.61 ± 14.52 ) was slightly lower than that of MF (2430.07 ± 40.68 and 1043.10 ± 11.75 ) 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 and 539.18 ± 11.55 in GF and 1362.24 ± 39.59 and 492.95 ± 14.38 in the MF. Root turnover was higher in the GF (1.68 ± 0.05 and 1.35 ± 0.03 ) than in the MF (1.57 ± 0.05 and 1.13 ± 0.02 ). 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.
Highlights
Each forest ecosystem has five carbon pools: above-ground and below-ground biomass, coarse woody debris, litter and soil
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 biomass amounts for the 0 - 15 cm and 15 - 30 cm horizons are slightly higher in the mixed forest strata, the variance analysis did not reveal significant differences between the two forest strata (Figure 4(c))
Summary
Each forest ecosystem has five carbon pools: above-ground and below-ground biomass, coarse woody debris, litter and soil. They are involved in the absorption of mineral elements and water (Tobner et al, 2013; Meng et al, 2018), in the accumulation of organic matter in the soil (Luizao et al, 1992) and in the flow of mineral elements (Liu et al, 2018; Du et al, 2019) Their net primary production which oscillates between 21% and 67% (Pausch & Kuzyakov, 2018) and their turnover play a key function in the regulation of the carbon flux of forest ecosystems (Peng et al, 2017). Despite their revealed importance in the functioning of the forest ecosystem, the dynamics of fine roots and their influence on the carbon cycle of belowground biomass are little studied (Persch et al, 2015)
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