Plant zonation patterns reflected by the differences in plant growth, biomass partitioning and root traits along a water level gradient among four common vascular plants in freshwater marshes of the Sanjiang Plain, Northeast China

Water level is important in determining plant zonation distribution patterns in freshwater wetlands. However, the role of whole-plants' morphological traits in response to water level gradients in accounting for the distribution of marsh species is far from clear. Four typical dominant vascular plants with different distribution patterns (high-elevation species Deyeuxia angustifolia, mid-elevation species Carex lasiocarpa and Glyceria spiculosa, and low-elevation species Carex pseudocuraica) in freshwater marshes in the Sanjiang Plain of Northeast China were treated with four static water level conditions (-5, 0, +5, and +15 cm relative to the soil surface), and each plant's growth characteristics, biomass allocation and root traits were investigated. With the rising water level, the growth of D. angustifolia performed worse than other species, whereas the total biomass, plant height and relative growth rate (RGR) of C. pseudocuraica increased steadily. Compared with the other three species, C. pseudocuraica showed a distinct pattern with increasing water levels in the biomass allocation to photosynthetic and non-photosynthetic organs, as well as for coarse and fine roots. Flooding stress significantly reduced root diameter and C/N ratio but simultaneously increased the specific root length (SRL), specific root area (SRA) and root nitrogen concentration (RNC) for both coarse roots (1st order, >0.2 mm) and fine roots (2nd and 3rd orders, <0.2 mm). However, these root parameters of C. pseudocuraica exhibited an opposite response with the increase in the water level between such two different branching orders. Our results indicate that wetland plants could acclimate to flooding stress through resource trade-off among different tissues and trait-coordinated variation within the root system. Furthermore, species-specific shifts in above-and below-ground traits could help to better understand and predict the vegetation zonation patterns in temperate freshwater wetlands. (C) 2015 Elsevier B.V. All rights reserved.