Abstract: Based on the data of medlar samples from 6 Provinces in northern China and data of field experiments from 2000 to 2001,soil and meteorologic condition factors associated to the content of medlar ashes(CMA)were analyzed,and relevant models were established.The results showed that coefficient of variation (Cv) of CMA was about 15%.CMA mainly determined by medlar's variety,while environmental factors also played an important role.Those environmental factors include mean relative air humidity and diurnal range of mean air temperature from fruit developing stage of medlar, precipitation days during flowering to autumn,and total Kin soil.According to statistical results,relative air humidity during fruit development was the main factor influncing CMA.CMA increasing exponentially with the increase of relative air humidity.Precipitation days during flowering to Autumn was the key factor for CMA.It increased as logarithm actually with precipitation days.

Key words: Xiaoxing′anling forest region, Forest harvesting, Runoff, Peak flood, Snowmelt runoff amount