Time-space effect of soil nutrient and chemical characteristics of Robinia pseudoacia L.plantation forestland in Loess Plateau has been studied.The results shows that: soil organic matter

pH

total N

available N

available P and available K

exchangeable Ca and exchangeable base capacity changes irregularly with tree age

total P and exchangeable Mg changes fluctuantly;Soil organic matter

total N

available N decreases by power function with soil depth

available P tends to decreases

total P

available K

exchangeable Ca

exchangeable Mg and exchangeable base capacity varies irregularly with soil depth

but pH-value changes fluctuantly;Compared with wasteland

soil organic matter

total N

available N

total P

available P

exchangeable Ca

exchangeable Mg and exchangeable base capacity raises respectively by 21.56%~96.8%

34.3%~160.1%

191.5%~238.4%

2.1%~24.1%

19.82%~92.71%

64.21%~80.02%

25%~46.5%

67.2%~89.5%.These showed that Robinia pseudoacia L.plantation can improve the condition of soil nutrient effectively.