Taking sixteen forest types in the loess hilly area of eastern Qinghai Province as research objects

the main vegetation types and soil physical properties(soil bulk density and porosity)and chemical properties(organic matter

N

P

and K)are analyzed.The changes in soil water holding capacity and soil fertility are studied.Results show that mixed forest have the minimum soil bulk density and the largest soil capillary porosity

and the mixed forest soil is loosen and porous and has the higher capability of water conservation and soil conservation.The distributions of soil organic matter

N

P

and K for different vegetation types are consistent

following the order of mixed forestconiferous forestbroadleaf forestshrubbarren hills.In different forest types

soil in Larix principis-rupprechii forest has the highest N content

while P and K contents are relatively low.Soil in Populus cathayana has the highest P content

while N and K content are relatively low.Soil in Betula platyphylla Suk—Betulautilis—Sabina przewalskii—Ricea asrerata(5∶2∶2∶1)mixed forest has the highest K content

while N and P contents are relatively low.In terms of comprehensive comparison

mixed forest well promotes the increases in soil organic matter

N

P

and K contents

improves soil nutrient status

and helps to sustain soil fertility.