Changes of soil carbon dioxide, methane, and nitrous oxide fluxes in relation to land use/cover management.

Abstract

Conversions of land use/cover are associated with changes in soil properties and biogeochemical cycling, with implications for carbon (C), nitrogen (N), and trace gas fluxes. In an attempt to provide a comprehensive evaluation of the significance of different land uses (Alnus subcordata plantation, Taxodium distichum plantation, agriculture, and deforested areas) on soil features and on the dynamics of greenhouse gas (GHG) fluxes at local scale, this study was carried out in Mazandaran province, northern Iran. Sixteen samples per land use, from the top 10cm of soil, were taken, from which bulk density, texture, water content, pH, organic C, total N, microbial biomass of C and N, and earthworm density/biomass were determined. In addition, the seasonal changes in the fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) were monitored over a year. Our results indicated that the different land uses were different in terms of soil properties and GHG fluxes. Even though the amount of the GHG varied widely during the year, the highest CO2 and CH4 fluxes (0.32mg CO2 m(-2)day(-1) and 0.11mg CH4 m(-2)day(-1), respectively) were recorded in the deforested areas. N2O flux was higher in Alnus plantation (0.18mg N2Om(-2)day(-1)) and deforested areas (0.17mg N2Om(-2)day(-1)) than at agriculture site (0.05mg N2Om(-2)day(-1)) and Taxodium plantation (0.03mg N2Om(-2)day(-1)). This study demonstrated strong impacts of land use change on soil-atmosphere trace gas exchanges and provides useful observational constraints for top-down and bottom-up biogeochemistry models.