Search

Decreases in water level could stimulate emergent plant growth and accelerate lake terrestrialization. To explore the impacts of hydrological variability on detritus accumulation in Lake Baiyangdian, a process-based ecosystem model was applied to investigate how emergent plants affect lake terrestrialization under changing water levels. Results of this study suggested that the accumulation of Phragmites australis ( P. australis) detritus is one of the main factors that promote terrestrialization, accounting for 1.8 mm yr−1 of sediment increase in the lake from 2001 to 2010. Water level and temperature were the primary drivers of detritus accumulation. The impacts of water level variability on detritus accumulation in Lake Baiyangdian were further investigated through scenario analysis. Results demonstrated that both annual and inter-annual water level fluctuations could affect plant detritus accumulation. The scenario with low water level supported relatively high plant productivity and fast plant detritus accumulation, whereas the high water level scenario induced the lowest plant biomass production and slowest detritus accumulation. Enlarged inter-annual water level fluctuations also caused an increase in both plant productivity and detritus accumulation. This study suggests that the terrestrialization processes of lakes can be mitigated through regulating lake water levels to reduce detritus accumulation. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Denitrification is an important process of nitrogen removal in lake ecosystems. However, the importance of denitrification across the entire soil-depth gradients including subsurface layers remains poorly understood. This study aims to determine the spatial pattern of soil denitrification enzyme activity (DEA) and its environmental determinants across the entire soil depth gradients in the raised fields in Baiyang Lake, North China. In two different zones of the raised fields (i.e., water boundary vs. main body of the raised fields), the soil samples from −1.0 m to 1.1 m depth were collected, and the DEA and following environmental determinants were quantified: soil moisture, pH, total nitrogen (TN), ammonia nitrogen (NH-N), nitrate nitrogen (NO-N), total organic carbon (TOC), and rhizome biomass of Phragmites australis. The results showed that the soil DEA and environmental factors had a striking zonal distribution across the entire soil depth gradients. The soil DEA reached two peak values in the upper and middle soil layers, indicating that denitrification are important in both topsoil and subsurface of the raised fields. The correlation analysis showed that the DEA is negatively correlated with the soil depth ( p < 0.05). However, this phenomenon did not occur in the distance to the water edge, except in the upper layers (from 0.2 m to 0.7 m) of the boundary zone of the raised fields. In the main body of the raised fields, the DEA level remained high; however, it showed no significant relationship with the distance to the water edge. The linear regression analysis showed significant positive correlation of the DEA with the soil TN, NO-N, NH-N, and TOC; whereas it showed negative correlation with soil pH. No significant correlations with soil moisture and temperature were observed. A positive correlation was also found between the DEA and rhizome biomass of P. australis. [ABSTRACT FROM AUTHOR]

Macrophyte decomposition can significantly influence aquatic carbon and nutrient cycling, especially in eutrophic shallow lakes, in which incomplete decomposition of detritus may lead to sediment accumulation and accelerate lake aging. In order to explore the role of macrophyte decomposition in lake terrestrialization, six major aquatic plants (two submerged, two floating, and two emergent species) in Lake Baiyangdian were investigated in this study. Detritus of these species were placed at three sites with different pollution intensities to investigate the contributions of plant species, site nutrient condition, and their interactions on detritus decomposition. Detritus decomposition was represented by detritus mass remaining at each sampling time. Results of this study suggest that although decomposition processes are species and site specific, and the effects of species are stronger than site conditions. Initial detritus phosphorus (P)-related indicators were proved to be effective controllers for detritus decay at the later stage of the experiment. Significant interactions between site and species indicate that plant species also influenced site controls on detritus mass loss. Site effects on decomposition were significant for submerged and floating species (P <0.01), and slightly significant for emergent species (P <0.05). A mathematic two-stage decomposition model was developed based on the experimental results using stepwise analysis to analyze effects of detritus quality and site conditions on decomposition. The detritus quality indicators were the main contributors for both early and later stages of detritus decomposition, while the site nutrients only affected decomposition at the later stage. [Copyright &y& Elsevier]