Effects of selective tree species on phytosociology and production of understorey vegetation in mid-Himalayan region of Himachal Pradesh

Characteristic of ground vegetation in Pinus roxburghii, Acacia mollissima, Quercus leucotricophora, Eucalyptus tereticornis, Ulmus villosa and mixed forest plantations were compared with grassland in mid-Himalayan region. Herbage density, basal area and biomass (aboveground and belowground) increased gradually from June till August in all systems. Maximum herbage density (1597 tillers/m²), basal area (63.10 cm²/m²), aboveground (3.61 t/ha) and belowground (4.03 t/ha) biomass was recorded in grassland in the month of August. There was 33.24% (Pinus roxburghii) to 71.19% (U. villosa) decrease in peak aboveground biomass of herbage under trees as compared to grassland. Further, aboveground biomass of herbage under trees accounted for only 0.75% (U. villosa) to 2.47% (Pinus roxburghii) of total aboveground biomass of vegetation in plantations. Total (herb + shrub + tree) biomass (191.30 t/ha), carbon density of vegetation (86.21 t/ha) and soil (49.13 t/ha) was highest in U. villosa plantation. Carbon density (vegetation + soil) in systems decreased in the order: U. villosa (135.34 t/ha) > Mixed forest (97.63 t/ha) > E. tereticornis (96.51 t/ha) > A. mollissima (88.37 t/ha) > Q. leucotricophora (86.72 t/ha) > P. roxburghii (85.94 t/ha) > grassland (45.61 t/ha).