Composition of herbage in Pinus roxburghii Sargent stands: basal area and importance value index

In the present study basal area and Importance Value Index (IVI) attributes of herbage were investigated in chir pine (Pinus roxburghii Sargent) stands of three different ages and also in open grassland in the sub-tropical region of Himachal Pradesh (India) during growing season (June to September). A higher basal area of the herbage was recorded in open grassland as compared to chir pine stands of different ages. Basal area of the vegetation increased gradually from July onwards and its highest values were recorded in September in all the systems. Amongst the chir pine stands basal area of herbage was recorded highest in tree stand followed by pole and sapling stands. IVI and basal area values of different species revealed that only few species were major contributors to the total basal area values of the vegetation at different times. The differences in the basal area of vegetation in the four systems at a particular time and changes as recorded in the basal area with the sampling time were found to be statistically significant.