Abstract:

The biomass,soil characteristics and root distribution of 26-year-old pure poplar(Populus simonii)stand and poplar-seabuckthorn(Hippophae rhamnoides)mixed stand were measured in Ansai,Shaanxi,Loess Plateau.The results showed that mean height,DBH and stand biomass were 44.8%,32.7% and 139.76% higher in the mixed stand than in the pure stand respectively.Biomass allocation patterns of two forest stands were different remarkably.Total biomass,as well as each of the parts in the mixed stand,was higher than that in the pure stand.Compared with the pure stand,soil bulk density and porosity of each layers in the mixed stand were respectively reduced and increased;soil water content in the mixed stand is higher except in August;and the soil total N content and rapidly P were 5%～69.0% and 22.4%～233.3% higher in the mixed stand,with total P content almost unchanged.Poplars root system in the pure stand(diameter<3.5mm and 3.5～10mm)were mainly distributed over soil 0～30cm,yet those in the mixed stand were distributed deeper and evener.On the contrary,the distribution of the poplar root system(diameter>10mm)in the pure stand was deeper and evener than in the mixed one.Horizontal distribution extent of the poplar root(diameter<3.5mm and 3.5～10mm) in the mixed stand was close to this in the pure one,yet the other one(diameter>10mm)in the former was narrower than the latter.

Key words: Seabuckthorn, Poplar, Mixed stand, Biomass, Soil characteristic, Root distribution