[Soil respiration rate and its influencing factors in artificial land-bridge islands system]

It is of great significance to understand the pattern of soil respiration rate in fragmented forests for further revealing terrestrial ecosystem carbon cycling. With different habitats (island vs. mainland, island edge vs. island interior) of the artificial land-bridge island system in Thousand Island Lake (TIL) region as the objects, we analyzed the seasonal dynamics of soil respiration rate and its relationships with soil physicochemical factors. The results showed that: 1) Soil respiration rates varied significantly across different seasons, with an order of summer (3.74 μmol·m^-2·s^-1) > autumn (2.30 μmol·m^-2·s^-1) > spring (1.82 μmol·m^-2·s^-1) > winter (1.40 μmol·m^-2·s^-1). 2) Forest fragmentation had significant effects on soil respiration rate, with soil respiration rate of island (2.37 μmol·m^-2·s^-1) being significantly higher than that of mainland (2.08 μmol·m^-2·s^-1) and the soil respiration rate of island edge (2.46 μmol·m^-2·s^-1) being significantly higher than that of island interior (2.03 μmol·m^-2·s^-1). 3) Soil temperature significantly promoted soil respiration rate, explaining 56.1% of the total variation. 4) There was a significant positive correlation between soil respiration rate and soil total carbon, ammo-nium nitrogen content, and vegetation coverage. The soil total carbon and ammonium nitrogen content of island edge were significantly higher than those of island interior. In all, forest fragmentation promoted soil respiration rate, with soil physicochemical factors as the drivers for its variation.