Comparative study on Population of Earthworms in Different Habitat Types along altitude in Tsholingkhar gewog, Tsirang district, Bhutan

Abstract

Earthworms are one of the very diverse organisms in the environment. The abundance of the earthworms relates to the different land use, human activity, biotic and abiotic factors on nature. The diversity and abundance of earthworms was studied in different habitats; broadleaved forest, chirpine forest, residential area and agriculture land with the aim to understand the variation in earthworm species in those habitats. Between the altitude 650-1450masl. a total of 20 major plots and 100 sub-plots was made to assess the earthworm diversity in selectedhabitat. Physio-chemical analysis of soil was done to know the diversity, abundance and density of earthworms. The result of study does find two orders, five families and seven species of earthworms. They were Amynthasalexandri, Metaphirehoulleti, Perionyx excavatus, Aporrectodeacalciginosa, Dichogastersp., Pontoscolexcorethrurus and Darwidasp. Broadleaved had the highest diversity with Shannon index of 2.04 and the lowest diversity was found in chirpine forest with Shannon index of 1.6. The highest richness was in the broadleaved forest with index of 0.827. Amynthasalexandri was present in all the habitats and it had the highest relative abundance of 28.12%, relative density of 32.80 per m2 and frequency of 25%. The lowest relative density, abundance and frequency was found in Darwida sp. The analysis of variance showed thatthe NPK content in the soil has effect on the density of earthworm along the altitude. In lower altitude at 650 masl. The density of earthworms was more with a high amount of NPK in soil and in higher altitude at 1450masl. the decrease in NPK showed low earthworm density. Pearson correlation showed a positive correlation with soil Physico-chemical parameters and an abundance of earthworms.