3.2 Vertical distribution of fine roots with different RFC treatments
Plants generally distributed a large proportion of fine roots in the soil layer above 30 cm (more than 60%, Fig. 3 and S1). The vertical distribution of fine root biomass varied significantly between the different RFC treatments and species (P < 0.01, Table S1). Fine root biomass of woody species increased in most soil layers at 50–75% of RFC, and in particular, biomass increased in soil depth below 30 cm (Fig. 3 and S1). Along the RFC gradient, the increasing range of average fine root biomass in woody species was the greatest in the first year (Fig. 2). In 50–75% of RFC, the fine roots of A. vestita were concentrated in the surface layer, whereas those of the other three species were distributed in deep soils (Fig. 3 and S1).
Vertical patterns of fine root length density among RFC treatments, years, and species were similar to those of fine root biomass (Fig. 2, 3, and S2). The fine root specific length, diameter, and tissue density of the four species did not show distinct changes with varying soil profiles (Fig. S3–S5). With the increase in RFC, the average fine root specific length and tissue density increased in all species; however, the average diameter decreased (Fig. 2).