Objective Exploring the spatial differentiation and formation mechanism of carbon and nitrogen storage in wetland ecosystem along the lakeshore to the highlands will help to reduce the uncertainty of wetland carbon storage estimation.

Method The ecosystem carbon and nitrogen storage (vegetation and soil), and related environmental factors (water level, water level fluctuation amplitude, soil organic matter, total nitrogen and total phosphorus, etc.) of six plant communities (L-Phragmites australis swamp, C-tussock swamp, D-Ledum palustre swamp, LN-Larix olgensis-Sphagnum magellanicum swamp, LX-Larix olgensis-moss swamp and LT-Larix olgensis-Carex schmidtii swamp) distributing along the lakeshore to the highland environmental gradient were simultaneously determined by relative growth equation and carbon/nitrogen analyzer method, to reveal its spatial differentiation law and its formation mechanism.

Result (1) The carbon and nitrogen storage (2.17−69.98 t/ha and 0.058−0.940 t/ha) of the vegetation increased progressively along the environmental gradient from lakeshore to upland (LT ≈ LX > LN > D > C > L), in which the dominant vegetation layer accounted for main position (73.72%−93.37% and 71.57%−85.24%). (2) The soil carbon and nitrogen storage (67.45−243.21 t/ha and 2.44−13.53 t/ha) decreased along the environmental gradient in a step-by-step manner (L > C > D ≈ LN > LX ≈ LT), there were three types of vertical spatial differentiation of carbon stock: first constant and then decreasing (L), first increasing and then decreasing (C, D and LN), and decreasing (LX and LT), and those of nitrogen storage were basically the same as that of carbon stock (only C and LX were slightly different). (3) The carbon and nitrogen storage (122.20−245.38 t/ha and 3.31−13.58 t/ha) of the ecosystem decreased first and then steadily or decreased in a step-by-step manner along the environmental gradient, respectively, the proportion of carbon and nitrogen in soil decreased (50.27%−99.11% and 73.48%−99.57%), but that of vegetation increased (0.89%−49.73% and 0.43%−26.52%). (4) The carbon storage of ecosystems at the lower, middle and upper habitats of the water environmental gradient from lakeshore to upland was promoted by water level, restrained by water level and restrained by water level fluctuation amplitude in turn, while the nitrogen storage was promoted by water level, restrained by water level fluctuation amplitude and promoted by soil total nitrogen in the corresponding habitat.

Conclusion The carbon and nitrogen storage of wetland ecosystem in lakeshore of Yuanchi Lake has obvious spatial differentiation law along the water environmental gradient from lakeshore to upland, and its formation mechanism is that the water level gradient and distribution of vegetation types caused by microtopography determine the carbon and nitrogen storage capacity of each marsh type. Therefore, accurate determination of carbon and nitrogen storage of each marsh type in the lakeshore zone will help to reduce the uncertainty of carbon and nitrogen storage estimation at catchment scale.