Diversity and abundance of medicinal plants among different forest-use types of the Pakistani Himalaya

Abstract

Medicinal plants collected in the Himalayan forests are receiving increasing attention at the international level for a number of reasons and they play an important role in securing rural livelihoods. However, these forests have been heavily transformed over the years by logging, grazing and agriculture. This thesis examines the extent to which the diversity and abundance of medicinal plants are affected between forest-use types as a result of such transformations.In northwestern Pakistan we studied old-growth forest, degraded forests (forests degraded by logging, derived woodland, agroforest and degraded sites) and restored forests (re-growth forests and reforestation sites). An approximate map was initially established covering an area of 90 km2 of the studied forest-use types and fifteen and five plots were allocated to five and two forest-use types respectively at altitudes ranging from 2,200 m to 2,400 m asl. The abundance and diversity of medicinal plants were then assessed therein.Of the fifty-nine medicinal plant species (herbs and ferns) encountered, old-growth forest contained the highest number thereof with fifty-five species, followed by re-growth forest with forty-nine species and finally, forest degraded by logging with only forty species. In terms of local use, all these species are employed to cure various diseases (intestinal, stomach etc.), and most of them have a relatively high market value. Species such as Aconitum heterophyllum and Coptis tecta are endemic to the Himalayan region and were found to occur exclusively in old-growth forest. The species composition and abundance in degraded forests differed markedly from that of old-growth forest, with all the degraded forest types having much lower medicinal plant densities and diversities. In addition, medicinal plant density correlated negatively with tree canopy cover in degraded forests, which indicates that species adapted to open conditions dominate in disturbed landscapes.Re-growth forest was somewhat similar to old-growth forest with densities of Bergenia ciliata, Viola canescens and Valeriana jatamansi being highest in old-growth forest and second highest in re-growth forest, which is most probably due to the species adaptation to the deep shade conditions provided by the high tree basal area and tree canopy cover under these forest-use types. Reforestation sites had a higher diversity of medicinal plants across the forest-use types, which may be due to the higher tree diversity under this forest-use type. Both re-growth forest and reforestation sites support the recovery of medicinal plant species such as Paeonia emodi and Podophyllum emodi, which are absent from most of the studied degraded forests and are important to the livelihoods of local people. Moreover, shade adapted medicinal plants can recover strongly under forest re-growth in comparison to reforestation sites, while for sun-adapted or partial shade-adapted species the opposite holds true.In conclusion, a high variation in the abundance and diversity of medicinal plants was found across the studied forest-use types. Old-growth forest is highly diverse and abundant in medicinal plants and is important as a refuge for vulnerable endemics. All forms of degraded forests have the lowest diversity of relatively common medicinal plants, which depends on the type of forest degradation. Forest re-growth and reforestation can facilitate the recovery of medicinal plants, including more economically valuable species that support local livelihoods, which in turn promotes ecological restoration and can pave the way forward to forest expansion in the region.