Background In order to evaluate the effect of soil and water conservation in small watershed management in Beijing mountainous area for many years, and to provide theoretical support for small watershed management and vegetation reconstruction in the future, taking Puwa small watershed of Fangshan District in Beijing as research target, soil physical properties, soil texture, infiltration and soil anti-scourability of all major kinds of soil and water conservation measures were studied.

Methods The sample plots of 7 typical soil and water conservation measures was selected and investigated, and the data were acquired through typical plot survey, test of field soil anti-scourability, and method of single-ring.

Results The soil density increased and soil porosity decreased significantly with the increasing of the soil depth. The soil density, total porosity and capillary porosity varied with the measures consistently. The order of effects on improving soil structure were Quercus liaotungensis secondary forest > Larix principis-rupprechtii and Pinus tabulaeformis mixed forest > terraces with stone banks> Pinus tabulaeformis forest > Larix principis-rupprechtii forest > vitex negundo shrub, while there was no significant effect for Platycladus orientailis forest. The soil particles in this area were mostly rich in powder, and the fractal dimension showed that the permeability of all kinds of soil and water conservation measures was promising. Compared with weed land, the scoured soil amount decreased significantly, the runoff time was prolonged, and the order of the scoured soil amount was as L. principis-rupprechtii and P. tabulaeformis mixed forest (0.82 kg/cm³) < P. orientailis forest (1.14 kg/cm³) < L. principis-rupprechtii forest (1.30 kg/cm³) < Q. liaotungensis secondary forest (3.91 kg/cm³) < P. tabulaeformis forest (5.96 kg/cm³) < vitex negundo shrub (10.88 kg/cm³), and the order of runoff scouring time was as Q. liaotungensis secondary forest (55.65 s/m)> L. principis-rupprechtii and P. tabuliformis mixed forest (46.82 s/m)> L. principis-rupprechtii forest (28.19 s/m)> vitex negundo shrub (22.39 s/m)> P. orientailis forest (17.48 s/m)> P. tabuliformis(16.94 s/m).The amount of soil loss showed a negative correlation with fine sand, medium silt, but a positive correlation with non-capillary porosity, indicating that the effect of non-capillary pore size formed by large diameter roots on soil erosion resistance might be negative.

Conclusions In summary, the soil and water conservation capacity of the mixed forest of L. principis-rupprechtii and P. tabulaeformis shows a great advantage followed by terraces with stone banks which should be the principal consideration of small watershed management.