To investigate the effects of herbs'root systems on soil water properties

the root systems of vetiver〔Vetiveria zizanioides(Lin.)Nash〕，bahia grass(Paspalum natatum)

bermuda grass〔Cynodon dactylon(L.)Pers.〕and alfalfa(Medicago sativa L.)were scanned by WinRHIZO

and the correlations between these root systems and soil physical properties and soil water holding capacity were analyzed bySPSS18.0.Results showed that the root length density of herbs decreased as soil depth increased

which canbe simulated by an exponential function.Roots of vetiver and alfalfa were mainly distributed in the 0-20cmsoil layer

but roots of bahia grass and bermuda grass were concentrated in the 0-10cm soil layer.Soil porosity

non-capillary porosity

water capacity and saturated water holding capacity decreased

but soil bulkdensity increased as soil depth increased.The improvement of soil moisture was mainly realized by roots ofdiameters in the ranges of 0.5mm