TITLE:
Impact of Cardamom Cultivation on the Composition and Dynamics of Soil Seed Banks in a Conservation Forest in Sri Lanka: Implications for Conservation
AUTHORS:
Balram Dhakal
KEYWORDS:
Cardamom Cultivation, Forest Restoration, Knuckles, Soil Seed Bank, Sri Lanka
JOURNAL NAME:
Open Journal of Forestry,
Vol.7 No.3,
May
15,
2017
ABSTRACT: Cultivation of cash
crops, such as cardamom (Elettaria
cardamomum) in the forest understorey is a common practice in many tropical
forests. Over time, cultivation may change forest structure and species
composition, leading to gradual degradation of biodiversity and ecosystem
services. Effective conservation of these forests requires an enhanced
understanding of the demographic processes such as soil seed bank that may
greatly influence future forest composition. We examined how the soil seed bank
structure and composition responds to cardamom cultivation in a high
conservation value Sri Lankan montane rain forest. Soil samples from natural
forest with abandoned cardamom plantations (CP) and adjacent natural forest (NF)
patches without cardamom were collected in dry and wet seasons. Soil samples
were spread out in trays in a shade house and germination was recorded weekly
for 19 weeks. The density of seeds in the soil seed bank was much higher in CP
than NF. While grasses and forbs contributed the highest number and percentage
of seeds in soils of both forest types, their densities in the soil seed bank
were 9 and 2 times greater in the CP than the NF, respectively. Seeds of the
non-native herbs Ageratina riparia and E. cardamomum were 4 and 20 times
greater in the soil of CP, respectively. Seeds of light demanding tree species
such as Macaranga indica were
restricted to soils of CPs. Overstorey tree community of each forest type was
poorly represented in their respective soil seed banks. The high density of
seeds of pioneer trees and non-native herbs in the soil of CPs, combined with
higher light transmission to the ground floor may exacerbate competition for
resources with the seedlings of late successional trees of high conservation
value. To overcome this barrier and enhance conservation value of the forest,
restoration strategies may need to focus on transplanting seedlings of these
species into forest with abandoned cardamom plantations.