Characterization of the Vegetation Communities Associated with Ancient Juniperus virginiana L. Stands in the Obed Wild and Scenic River Gorge.

Nepal, Bal

ABSTRACT: A vegetational survey of ancient red cedar (Juniperus virginiana L.) stands in the talus areas of the Obed Wall and North Clear Creek (NCC) in the Obed Wild and Scenic River Gorge was conducted during the summers of 2008 and 2009. Altogether, 161 vascular plants, 37 lichens, and 21 bryophytes were recorded from both the Obed Wall and NCC sites. The diversity and abundance of vascular plants were found to be higher at the Obed Wall site than that at the NCC site, while the reverse was true for lichens and bryophytes. Statistical analysis of percent coverage and frequency of vascular plants from systematic sampling revealed significant variations in species composition between the Obed and NCC sites. Thirty-five living red cedar trees were sampled, and their vegetational communities (vascular and non-vascular) in the vicinity were examined. Also, species accumulation curves (SAC) were determined for vascular plants, lichens and bryophytes found in association with red cedars. To determine the species richness of lichen epiphytes associated with red cedars 28 trees were surveyed, where an asymptote was observed in terms of increasing species diversity. However, a minimum of 12 trees were sampled before an asymptote was reached for bryophytes. During the study, an asymptote was not observed for vascular plant diversity even though 35 red cedar trees (a nearly complete census) were surveyed. In December 2007, a dendroecological survey of ancient red cedars was carried out at the Obed Wall and NCC sites. The age-class structure of red cedars showed an inverse J-shaped curve, which represents continuous, balanced recruitment and mortality of these stands. Of the 36 living trees cored, the oldest-living red cedar was found to be 767 years old. A general climatic history of the Obed area was reconstructed back to 1246 A.D. but this is not a precise reconstruction because of the prevalence of false rings.