Water-level fluctuations as a driver of Phragmites australis primary productivity, litter decomposition, and fungal root colonisation in an intermittent wetland

Abstract

The hypothesis of this study is that the variable hydrological regime of intermittent lakes and wetlands affects the primary productivity, decomposition and root fungal colonisation of Phragmites australis, with effects on the whole ecosystem metabolism. The above-ground biomass of reed stands was monitored in littoral and riparian stands of Lake Cerknica, under different water levels. Leaf and culm litter decomposition was also studied at three locations, from predominantly dry to permanently submerged. Root colonisation by fungi was monitored across two seasons in the littoral reed stand. The primary productivity of the littoral stands was related to a variable degree with water levels and air temperature in July in the current year. In the riparian reeds, only monthly temperatures in October of the previous year were important. The submersion duration of the litter enhanced the decomposition rates. The frequency of fungal colonisation of reed roots was decreasing with the submersion time length. Overall, roots were colonised by arbuscules, hyphae, vesicles, hyphal coils and microsclerotia. The main outcomes of this study deals with the role of intermittent hydrological conditions in determining the structure and functioning of reed-dominated lacustrine wetlands, which are exposed to climate threats.

Arbuscular mycorrhizal fungi in a coastal wetland in Yucatan, Mexico

“…Absence of arbuscules in mycorrhizal roots has been explained as an effect of flooding (Dolinar et al 2016, Wang et al 2016 this may support the results observed in the present work. The absence of arbuscules at some moment of interaction could be interpreted as an inactive mycorrhiza (Dolinar et al 2016, but see Vallino et al 2014) or that the mutualistic exchange of nutrients is absent (Wang et al 2016) at that particular moment; nevertheless, to test any of these hypotheses a physiological experiment is needed.…”

“…The absence of arbuscules in our observation may be due to their ephemeral nature (Smith & Read 2008) and low frequency in field samples; but particularly in wetland plants mycorrhized roots commonly present a reduced number or even total absence of arbuscules (v.g., Dolinar et al 2016, Khan 1993, Sengupta & Chaudhuri 2002. Absence of arbuscules in mycorrhizal roots has been explained as an effect of flooding (Dolinar et al 2016, Wang et al 2016 this may support the results observed in the present work.…”

“…The absence of arbuscules in our observation may be due to their ephemeral nature (Smith & Read 2008) and low frequency in field samples; but particularly in wetland plants mycorrhized roots commonly present a reduced number or even total absence of arbuscules (v.g., Dolinar et al 2016, Khan 1993, Sengupta & Chaudhuri 2002. Absence of arbuscules in mycorrhizal roots has been explained as an effect of flooding (Dolinar et al 2016, Wang et al 2016 this may support the results observed in the present work. The absence of arbuscules at some moment of interaction could be interpreted as an inactive mycorrhiza (Dolinar et al 2016, but see Vallino et al 2014) or that the mutualistic exchange of nutrients is absent (Wang et al 2016) at that particular moment; nevertheless, to test any of these hypotheses a physiological experiment is needed.…”

“…Extensive evidence suggests that arbuscular mycorrhizal (AM) root colonization declines during extended periods of flooding (v.g., Dolinar et al 2016, Miller 2000, Ray & Inouye 2006, Stevens et al 2011, Vallino et al 2014, but see Xu et al 2016). A. wrightii presents fluctuations in the percentage of root colonization associated with the sampling month, however the highest percentage of root colonization was found in February (beginning of the dry season), while the lowest was presented when the site was no longer flooded (April and May); this may be because at the end of the dry season the soil drought may have limited fungal development, these results are in agreement with Bohrer et al (2004) who found the highest mycorrhizal colonization level during the period of highest water table which coincides with the production of new roots in the plants.…”

Preface: Wetlands biodiversity and processes—tools for conservation and management

“…Such organic matter bulk fuels decomposition processes which support the wetland food webs (Á goston-Szabó et al, 2016). In relatively dry areas, the intermittent hydrological regime is the main driver of litter decomposition (Dolinar et al, 2016).…”