Ecosystem Dynamics After Abandonment of Rice Paddy Fields: Does Alien Plant Invasion Enhance Carbon Storage?

Abstract

Ecosystem property and function can be considerably altered by changes in agricultural land use. Despite the expansion of abandoned fields in temperate humid areas worldwide, little is known about how ecosystem C stock and its partitioning change with secondary succession, especially under the invasion of non-native, fast-growing plants. Using a paired-plot approach, we investigated how plant community type (native vs. non-native, the latter represented by Solidago altissima) influences temporal changes in ecosystem C pools in abandoned paddy fields. Thirty-seven plots of control (paddy) and abandoned (2–37 years of succession) pair having similar soil types under the humid temperate climate of Japan were selected for this study. We detected a net loss of ecosystem C in the first 15.2 years, followed by a gradual C gain. Apparent maximal C gain (up to 10 Mg C ha−1) was observed approximately 30 years after abandonment, based on a smooth spline model. The initial C loss was largely attributed to decomposition in mineral-associated soil C, owing presumably to the rapid decay of the C accumulated under temporally anaerobic paddy. While no detectable difference was found in the ecosystem C stock between plots dominated by S. altissima and native plants, the S. altissima-dominated plots showed significantly lower litter C stock. We therefore conclude that, despite the rapid growth and high aboveground biomass of S. altissima, its invasion did not increase ecosystem C storage in the studied region; these findings highlight the absence of ecological benefits associated with S. altissima invasion.