The Relationship of the Processes in the Rhizosphere of Common Reed Phragmites australis, (Cav.) Trin. ex Steudel to Water Fluctuation

Abstract

The Relationship of the Processes in the Rhizosphere of CommonReed Phragmites australis, (CAV.) TRIN. ex STEUDEL to Water Fluctuation key words: water level fluctuation, reed stand, ETS-activity, inorganic nutrients, soil water. AbstractIntermittent Lake Cerknica is characterised by extreme water level fluctuations. It is neither a lake, nor a terrestrial ecosystem. The decomposition processes in the rhizosphere of extended reed stands are essential for the entire ecosystem. The influence of intermittent water regime on the microbial activity and availability of nutrients in the rhizosphere in a terrestrial reed stand was investigated. The measurements revealed a relatively high soil water content, that was not related to underground water table. Mineralization processes in a soil profile were estimated by measuring microbial activity as electron transport system (ETS) activity and by nutrients in soil water. The microbial activity was determined in the whole depth profile. The highest ETS activity of a soil was 0. . The values were not related to underground water table. All forms of nutrients were constantly present, showing no correlation with the soil water content. ANOVA revealed significant decrease of nitrate with depth, but not for nitrite, ammonium and ortho-phosphate. IntroductionThe intermittent Lake Cerknica is characterised by extreme water level fluctuations. A part of the year the area is flooded, but from time to time, usually in summer, it becomes dry. The lake is the locus typicus for intermittent lakes and poljes (karst fields). Wetting and drying occurs seasonally, depending on precipitation. The exchanging of dry and wet periods influences the dynamics of biota and the process of mineralisation (URBANC-BERČIČ and GABERŠČIK, 2001). Common reed (Phragmites australis) is a dominant wetland species in the area. With respect to the water regime three types of reed stands were distinguished: terrestrial, land-water interface, and littoral stands. Stands exhibited significant differences in primary productivity parameters (GABERŠČIK et al., 2000), in the composition and depth of the soil layer, and in the variations of water regime (URBANC-BERČIČ and GABERŠČIK, 2001; URBANC-BERČIČ and GABERŠČIK, in press). Variations of water regime are fundamental for the nutrient cycling in the sediment (BROCK, 1986;BOULTON and BROCK, 1999). Most chemical features depending on aerobic and anaerobic conditions are highly variable. A presence of oxygen in a soil increases the microbial activity and the mineralization rate at the beginning of drying. Later on drying can cause considerable impact on sediment properties by affecting mineral phases and by killing up to 76% of the microbial biomass (QUI and MCCOMB, 1995). These changes reduce the capacity of the sediment to adsorb nutrients, such Internat. Rev. Hydrobiol.

Implication of Nitrifying and Denitrifying Bacteria for Nitrogen Removal in a Shallow Lake

“…NH 4 + is the first form released by the decomposition of organic matter and represents a constant source of N for microorganisms and plants. NH 4 + is then transformed to NO 2 − and NO 3 − in the aerobic zones through the nitrification process . Thus, the positive correlation between NH 4 + contents and amo A‐type nitrifier assemblages in the rhizosphere sediment was significant.…”

Effects of water-level fluctuations on lakes: an annotated bibliography

“…Though most of the efforts are focused on the changes of macrophyte area as controlled by WLF (e.g. Wallsten & Forsgren, 1989;Dienst et al, 2004;Hudon et al, 2005), studies have addressed many different aspects of macrophyte biology and ecology (Wagner & Falter, 2002;Urbanc-Bercic & Gaberscik, 2004;Nishihiro et al, 2004a, b;Paillisson & Marion, 2006;Imamoto et al, 2007). The strong response of wetland vegetation to hydrological conditions underlines their vulnerability to water-level variations resulting from regulation and climate variability (Murphy, 2002).…”

Water Regime Changes and the Function of an Intermittent Wetland

“…The highest ETS-activity was detected at Dujice (0.12-0.23 mg O 2 gDM −1 h −1 ), while at Drvošec and Zadnji kraj, ETS-activities were lower than 0.008 mg O 2 gDM −1 h −1 (Urbanc-Berčič & Gaberščik, 2001). The organic structure of the soil enabled high field-water capacity, supporting undisturbed mineralisation processes even in dryer periods (Urbanc-Berčič & Gaberščik, 2004). It was expected that the ETS-activity of soil would be positively correlated with soil water content, however the correlation was rather weak.…”