Environmental controls and influences of Pinus roxburghii Sarg. (Chir pine) plantation on temporal variation in soil carbon dioxide emission and soil organic carbon stock under humid subtropical region.

Abstract

Soil carbon dioxide emission is a major component of ecosystem respiration, responsible for organic carbon losses from the ecosystem. In Pinus roxburghii Sarg. plantations, higher CO2 emission coincided with maximum soil moisture and soil temperature during the rainy season (4.23µmol CO2m-2s-1) followed by summer season (1.69µmol CO2m-2s-1) and winter season (1.35µmol CO2m-2s-1). The soil CO2 emission rates recorded during the rainy season differed significantly from other seasons (p < 0.05). Multiple linear regression revealed that rainfall was the main dominant factor affecting the soil CO2 emission. A significant positive correlation with minimum air temperature and average air temperature during the lag period, i.e., preceding 15days of data, was recorded. A significant positive correlation was also observed between annual soil CO2 emission rates with soil temperature, soil moisture, air temperature, and rainfall (p < 0.05). Vapor pressure and relative humidity at 14.19h also emerged as additional scientific variables affecting soil CO2 emission with significant positive correlations. Annual soil CO2 emission rates and soil properties were not significantly correlated but were positively correlated with organic carbon, exchangeable potassium and negatively correlated with available nitrogen and phosphorous (p > 0.05). Higher annual average carbon stock, 95.05 t ha-1 in P. roxburghii plantations than the yearly soil CO2 emission, 33.23 t ha-1 indicates that plantations sequester more carbon than the emissions.