Plant growth in riverine wetland is determined by both elevation (or flooding regime) and soil fertility. In recent years, flooding regimes of rivers have been dramatically changed as global changes and dam constructions in upstream. Meanwhile, most river systems now suffer eutrophication as the increasing nutrient inputs from watershed. However, it remains unclear how these changes would affect primary production, especially the relative importance of each factor.
Question
how these changes would affect primary production, especially the relative importance of each factor
Methods and Results
Here, environmental factors and community biomass were determined for the floodplain Carex meadow (the most widespread vegetation in Poyang Lake) in seven estuaries of five main tributary of Poyang Lake. (1) soil nutrient or community biomass significantly differed among different tributaries. (2) community biomass did not correlate with soil nutrient (N, P) content, but negatively correlated with soil pH and positively correlated with elevation, (3) leaf N or P content did not correlated with soil nutrient and community biomass. (4) soil nutrient content did not correlated with nutrient concentration of river water, suggesting that spatial variations of soil fertility was determined by hydrological factors, rather than amount of N and P inputs
Conclusions
Our results demonstrate that flooding regime or the elevation is the predominant factor in determining primary production, while soil fertility is much inferior. Our study suggest that lowering water level in the recent years will increase primary production of floodplain meadow as the elongated growing season, and thus affect the ecosystem functions.