Abstract:
This paper examines the survivorship patterns of trees and seedlings of four conifer species including Pinus wallichiana, P. roxburghii, Abies pindrow and Cedrus deodara in the forests of Murree hills. The construction of life tables and key-factor analysis allows us to examine the demographic parameters of the four conifer species including their growth, age structure, survival, mortality and mean expectation of further life. The age of the trees of different species ranged between 35-185, 65-125, 30-120 and 45-135 years for Pinus wallichiana, Pinus roxburghii, Cedrus deodara and Abies pindrow respectively. The survivorship curves for conifer tree species were close to Deevy type II curves. However, the slope of survivorship curves for P. wallichiana, P. roxburghii and C. deodara became somewhat steeper in the later part of the curve indicating greater rate of mortality at old age of the trees. Except for P. roxburghii, mean expectation of further life declined in the old-aged trees. Seedling/sapling density was in the order: Pinus wallichiana > Pinus roxburghii > Cedrus deodara > Abies pindrow. The key factor analysis showed that killing power (K) was highest for Pinus wallichiana and Cedrus deodara. The survivorship curves for the seedlings/saplings also showed a pattern close to Deevy type II. Besides natural mortality owing to competition and disease pressure, one of the principal causes of tree loss is illegal logging that is depicted in the form of high mortality. It is concluded that if biological interference and deforestation is not reduced up to sustainable level, it would be a serious threat to the biodiversity, ecosystem and infra structure of that area.
Keywords:
Mortality
,
frequency
,
Fecundity
,
Survivorship
,
Life expectancy