Fine Root and Soil Nitrogen Dynamics during Stand Development Following Shifting Agriculture in Northeast India

Abstract

Nitrogen (N) dynamics during changes in land use patterns in tropical forests may profoundly affect fine root dynamics and nutrient cycling processes. Variations in fine root biomass and soil N dynamics were assessed in developing stands of increasing ages following shifting agriculture in Mizoram, Northeast India, and comparisons were made with a natural forest stand. Concentrations of soil available N (NH4-N and NO3-N) and the proportion of NH4-N in total available N increased with stand age. The N-mineralization rate also increased with stand age whilst the proportion of nitrification relative to ammonification declined during succession. Fine root biomass and N-mineralization increased, and available N decreased during the monsoon season while this pattern was reversed during the winter season. A greater proportion of fine roots were <0.5 mm diameter in the younger sites, and turnover of fine roots was more rapid in the developing stands compared to the natural forest. Fine root biomass was correlated positively with N-mineralization rate and soil water content. Thus, it can be concluded that the fine root growth was aided by rapid N-mineralization, and both fine root growth and N-mineralization increase as stands redevelop following shifting cultivation disturbance.

Seasonal Variations of Fine Root Dynamics in Rubber-Flemingia macrophylla Intercropping System in Southwestern China

“…We found a clear declining trend in the soil available P and K with the increasing stand age; however, we did not find any apparent trends in available N across stand ages. In contrast, previous studies observed increasing soil N concentrations with the increase in stand age [ 46 , 51 ].…”

“…In the present study, higher fine root biomass under young stand age ( Figure 1 ) can be attributed to increasing N and altered species composition and biomass across stand age [ 25 , 44 ]. A more significant proportion of fine roots in the young stand is an efficient strategy to enhance the absorption of available nutrients by exploring large soil volumes and enabling stand recovery [ 45 , 46 ]. The significant effect of stand age and seasons suggest that environmental variability between different ages and seasons creates distinct effects on the soil N, P, and K concentrations.…”

Tradeoffs and Synergies in Tropical Forest Root Traits and Dynamics for Nutrient and Water Acquisition: Field and Modeling Advances

“…Root dynamics in tropical forests tend to respond strongly to seasonal moisture cycles, with more root production in surface soils being typical during the wet season (Luizao et al, 2007;Rodtassana and Tanner, 2018;Singha et al, 2020). For example, fine root production was greatest during wet periods in an Amazonian rainforest (0-90 cm depth), and this relationship was strongest in surface soils.…”

Quantification of Root Biomass in Post-Mining Areas in the Municipality of Capitão Poço – PA, Brazil

“…By means of the Tukey test at the 5% probability level, the area of native forest did not differ statistically from the area under recovery at depth 0-10 cm, being statistically different in the degraded area at depths 0-10 and 10-20 cm. The fine root biomass in the upper soil layer (0-15 cm) was significantly higher than in the deeper layer (15-60 cm).Although the area under recovery has stopped being explored in less time than the degraded area, the higher proportion of fine roots may be due to the fact that in younger stands there is probably a strategy to produce roots faster after a suffered disturbance, increasing the search for resources within the largest volume of soil possible and thus return organic matter to the soil to increase vegetation growth [24].…”