4 Discussion
Our findings support the first
hypothesis that the vertical depth of fine roots in woody species
increases with increasing RFC. Plants distributed more than 60% of fine
root biomass in a soil depth above 30 cm and their presence reduced
exponentially with soil depth. With an increase in RFC, fine root
biomass and length density in
most soil layers showed increasing trends, and this increase was highly
noticeable in soil layers below 30 cm. The increase in fine root depth,
average biomass, and length density range of woody species with
increasing RFC were maximum in the second year, but minimum in the
fourth year, which is consistent with our second hypothesis. Fine root
diameter in all species decreased with increasing plant age, and the
thinnest roots were found in soil profiles with 75% RFC. We also found
that fine root depth, biomass, and length density ofA. vestita decreased with
increasing RFC and age, whereas the other three woody species presented
maximum values under 75% RFC and in the last year.