Effects of Eucalyptus Plantation on the Physico-Chemical Properties and Litter Decomposition Processes in Soil

Abstract

Plantation of Eucalyptus has been increasing worldwide for the multiple benefits including fast growth, massive biomass production and quick economic returns. However, plantation with Eucalyptus has created debate from ecological concerns such as loss of biodiversity and degradation of soil quality including loss of soil water and nutrients. The general aim of the research was to investigate the ecological effects of plantation with the introduced species Eucalyptus to improve understanding about the plantation, afforestation and management of sustainable forestry program by using this tree species in Bangladesh. Soil and plant materials were collected from different sites such as Tangail, Dinajpur and Dhaka where there were plantations of this species was done along with other tree species such as Acacia (Acacia auriculiformis), Jarul (Lagerstroemia speciosa) and teak (Tectona grandis). Soil was collected at different distance from the tree trunk and depths along the soil column in order to study the physical and chemical properties. At the Madhupur site where Eucalyptus plantation was done beside the plantation with Acacia, pH was significantly (P = 0.0399) affected by depth but not by plantation and their interactions. Electrical conductivity was significantly affected by plantation (P = 0.0001) but not by depth and their interactions. Total P (%) was significantly affected by both plantation (P = 0.0310) and depth (P = 0.0211) but not by their interactions. At the Dinajpur site where Eucalyptus plantation was done beside the plantation with Jarul. Moisture content (P = 0.0001) and organic carbon were significantly (P = 0.03) affected by plantation but not by depth and their interactions. Soil pH was significantly affected by both plantation (P = 0.0001) and depth (P = 0.0029) but not by their interactions. Total phosphorous was significantly affected by both plantation (P = 0.0015) and depth (P = 0.0241) but not by their interactions. N:P was significantly affected by only plantation(P = 0.0494). At the Dr. Muhammad Shahidullah Hall Campus site where Eucalyptus plantation was done beside the plantation of teak, three-way ANOVA statistics showed that pH value was significantly affected by plantation (P = 0214), distance (P = 0.0001) and depth (P = 0.0103) but not by their interactions. Organic carbon content was significantly affected only by the interaction of distance and depth (P = 0.0457) but not by other factors such as plantation, distance and depth. Total P (%) (P = 0.0001) and N:P (P = 0.0047) were significantly affected only by plantation. Litter decomposition study conducted for 12 months showed that mass loss rate of Mahagony (Swetenia mahogoni) was significantly affected by litter type (P = 0.023) and time (P = 0.075) but not by their interactions. In case of teak, mass loss rate was significantly affected by time (P = 0.002) and between time and litter type (P = 0.017) but not by litter type. In case of Axonopus (Axonopus compressus), highly significant (P = 0.001) difference was found between time and litter type (P = 0.035) but not in their interactions. Soil N content was significantly (P = 0.000) affected only by time in teak and only by interaction between time and litter type (P = 0.019) in Mahogony. Litter type effects on N release was absent for each species. Overall, the results of the present study indicated that plantation with Eucalyptus might had potential influence in altering decomposition rate of an ecosystem through mixing of its litter with that of the other plant pecies.