Hydro-thermal factors is a key factors affecting the greening on highway slope.By using self-recording hygrometer

self-recording soil thermometer and other instruments

solar radiation

soil temperature and soil moisture were observed on sunny slope

ground

shady slope and central isolation belt along the Langfang-Zhuozhou highway from June 2009to May 2010.Results show that:(1)The diurnal variations of solar radiation under different terrain conditions meet a quadratic curve.There was no significant impact of terrain on direct solar radiation.(2)The monthly variations of soil temperature are in a“cosine curve” shape under different terrain conditions.The soil temperature at 40cm depth was the highest under different terrain conditions;and the soil temperature in central isolation belt was the highest from March to August

whereas the soil temperature on sunny slope was the highest from September to December and from January to February.(3)The monthly variations of soil moisture are in a wave shape under different terrain conditions.The soil moisture in 20-40cm soil layer was the highest under different terrain conditions

and the soil moisture in central isolation belt was the highest at different depths.