Fine-roots dynamics, anatomy and carbon-nitrogen concentrations in relation to forest management and soil water content. Case studies in beech(Fagus sylvatica L.) and Turkey-oak (Quercus cerris L.) forests.

Abstract

Uncertainties in estimates of fine root dynamics prevent a proper quantification of net primary productivity and belowground C allocation. Moreover, model studies for estimating carbon budgets are biased by the lack of fine roots datasets at forest stand level. This study shed some lights on fine root dynamics in two different Italian forests. In particular fine-root systems was investigated: 1) in three beech forest stands (Fagus sylvatica L.) located in Southern-Alps in relation to different forest management practices and age 2) in a mature Turkey-oak stand (Quercus cerris L.) located in the Southern Apennines in relation to soil moisture seasonal changes. Data from beech forests showed that conversion from coppice to high forest practice induced considerable variations in fine-root traits. Reduction of stand tree density induced a reduction of total fine-root mass and an increase of both production and turnover rate. Both fine-root production and turnover rate increased in converted stands. When fine-roots Carbon and Nitrogen contents were analyzed, their ratio was significantly lower in converted stands, supporting the finding of a higher turnover rate. A histological study was carried to assess if also anatomical changes occurred due to conversion practices. Anatomy on fine roots showed a higher percentage of xylem cells in conversion stands explaining the lowest carbon concentration. Turkey-oak fine-root biomass and length showed a bimodal pattern with a peak in summer and a peak in autumn. SRL had only one peak in summer. All fine root traits increased during the transition from the wet to dry season. These results indicate a pulse in root growth in order to increase the soil exploitation when soil water content is low. Moreover, during the summer period, Q. cerris change fine-root morphology leading an increase of fine root length per unit mass