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Keywords: Applied Sciences
Agriculture & related technologies
Field & plantation crops
Issue Date: 2010
Publisher: Arid Agriculture University Rawalpindi Pakistan
Abstract: Increasing atmospheric carbon dioxide (CO 2 ) concentrations over the last 150 years and the increasingly dramatic effects of climate change on ecosystems and humankind have reinvigorated the need to understand the terrestrial global carbon cycle. Forest ecosystems are of particular importance because they contain up to 82% of the terrestrial plant biomass, which is inter-linked with atmospheric CO 2 levels through the carbon cycle. This importance has been recognized within global agreements like the Kyoto Protocol, which is designed to address climate change. In order to meet the requirements of this and similar agreements, we need reliable estimates of carbon stocks and fluxes. These have so far been lacking for many of the forest ecosystems of Pakistan. I quantified the mean forest carbon stocks (t ha -1 ) for two major forest types in Pakistan and investigated the uncertainty of these estimates at three levels of sampling intensity. Overall, 261 plots of 1 ha each were established in selected four sites, two in sub-tropical pine forests (Ghoragali, 1729 ha and Lehterar, 1254 ha) and two sub- tropical, broad-leaved, evergreen forests (Sohawa, 4048 ha and Kherimurat, 3360 ha) between 2005-08, representing a sampling intensity of 2.5 percent of the total forest area. In mature (~100 years old) pine forest stand at Ghoragali and Lehterar sites, a mean basal area of 30.38 and 26.11 m 2 ha -1 represented mean volume of 243 and 197xv m 3 ha -1 respectively. The average biomass (t ha -1 ) in both sites was 237 and 186 t ha -1 respectively which is equal to 128 and 100 t C ha -1 including soil C. However, on average basis both the forests have 114.5+ 2.26 t ha -1 of carbon stock which comprises of 92 percent in tree biomass and only 8 % in the top soils. In mixed broad-leaved evergreen forests a mean basal area (m 2 ha -1 ) at Kherimurat and Sohawa was 3.06 and 2.65 with stem volume of 12.86 and 11.40 m 3 ha -1 . The average upper and understorey biomass (t ha -1 ) in both sites was 50.93 and 40.43 t ha -1 respectively which is equal to 31.18 and 24.36 t C ha -1 including soil C stocks. This study provides a protocol and valuable baseline data for monitoring biomass and carbon stocks in Pakistan‟s managed and unmanaged sub-tropical forests. Reducing the sampling intensity from the standard 2.5 percent of total forest area to 1.0, 0.5 and 0.25 percent of total forest area did not increase the coefficient of variation or uncertainty associated with the mean estimated forest C in these forests. However, at a sampling intensity of 0.1 percent there was a marked increase in estimate uncertainty. One of the important recommendations of the study is that 1.0 percent sampling intensity is adequate for future studies in sub tropical pine and broadleaved evergreen forests.
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