Annual and seasonal changes in fine root biomass of a Quercus ilex L. forest

The biomass, production and mortality of fine roots (roots with diameter <2 .5 mm) were studied in a typical Mediterranean holm oak (Quercus ilex L.) f orest in NE Spain using the minirhizotron methodology. A total of 1212 root s were monitored between June of 1994 and March of 1997. Mean annual fine r oot biomass in the holm oak forest of Prades was 71 +/-8 g m(-2) yr(-1). Me an annual production for the period analysed was 260+11 g m(-2) yr(-1). Mor tality was similar to production, with a mean value of 253 +/-3 g m(-2) yr( -1). Seasonal fine root biomass presented a cyclic behaviour, with higher v alues in autumn and winter and lower in spring and summer. Production was h ighest in winter, and mortality in spring. In summer, production and mortal ity values were the lowest for the year. Production values in autumn and sp ring were very similar. The vertical distribution of fine root biomass decr eased with increasing depth except for the top 10-20 cm, where values were lower than immediately below. Production and mortality values were similar between 10 and 50 cm depth. In the 0-10 cm and the 50-60 cm depth intervals , both production and mortality were lower.