Fine root vertical distribution and temporal dynamics in mature stands of two enset (Enset ventricosum Welw Cheesman) clones

Quantification of the role of fine roots in the biological cycle of nutrients necessitates understanding root distribution, estimating root biomass, turnover rate and nutrient concentrations, and the dynamics of these parameters in perennial systems. Temporal dynamics, vertical distribution, annual production and turnover, and nitrogen use of fine roots (<= 2 mm in diameter) were studied in mature (5-year-old) stands of two enset (Ensete ventricosum) clones using the in-growth bag technique. Live fine root mass generally decreased with increasing depth across all seasons except the dry period. Except for the dry period, more than 70% of the fine root mass was in the above 0-20 cm depth, and the fine root mass in the upper 0-10 cm depth was significantly higher than in the lowest depth (20-30 cm). Live fine root mass showed a seasonal peak at the end of the major rainy season but fell to its lowest value during the dry or short rainy season. The difference between the peak and low periods were significant (p <= 0.05). Fine root nitrogen (N) use showed significant seasonal variation where the mean monthly fine root N use was highest during the major rainy season. There were significant effects on N use due to depths and in-growth periods, but not due to clones. Enset fine root production and turnover ranged from 2,339 to 2,451 kg ha(-1) year(-1) and from 1.55 to 1.80 year(-1), respectively. Root N return, calculated from fine root turnover, was estimated at 64-65 kg ha(-1) year(-1). Fine root production, vertical distribution and temporal dynamics may be related to moisture variations and nutrient (N) fluxes among seasons and along the soil depth. The study showed that fine root production and turnover can contribute considerably to the carbon and nitrogen economy of mature enset plots.