2. Materials and methods
2.1. Study site description
The study basin (149 km2) is an agriculture-dominant basin
located in the Heilong Jiang province in northeastern China
(47.25N, 134.02E), (Fig. 1). The annual average rainfall is 583 mm,
and most rainfall occurs in the summer. The local agriculture was
developed by converting wetlands into farmlands, which has
created pollution and environmental concerns. Increased N
availability induced by human activities accelerated water quality
degradation and affected soil organic carbon dynamics in wetlands
(Ouyang et al., 2013b).