Water Level Fluctuations and Air Temperatures Affect Common Reed Habitus and Productivity in an Intermittent Wetland Ecosystem

Abstract

Lake Cerknica is an intermittent wetland ecosystem with extreme water level fluctuations. It hosts extensive reed stands that have colonized different habitat types. Two different stands were compared: a lake stand not directly influenced by the intermittent River Stržen and a riparian stand near River Stržen. Reed productivity (growth and assimilate allocation) was monitored for these reed stand types over 13 years (2007–2019), and this measurement was compared to monthly water levels and air temperatures. Reeds from the lake reed stand were significantly shorter with a lower shoot density, overall biomass production, and ratio of flowering plants. A correlation analysis revealed stronger and more numerous significant correlations between environmental and reed productivity parameters for the lake reed stand compared to the riparian reed stand. The variabilities of the growth and assimilate allocation parameters in the lake reed stand were both mostly explained by the combined water levels for June and July, which explained 47% and 52% of the variability, respectively. The most influential temperatures were in May, which explained 29% and 19% of the variability of growth and assimilate allocation parameters, respectively. For the riparian reed stand, water levels and temperatures out of the vegetation season appeared more important. Therefore, habitats with permanent water are more suitable for reeds than those with fluctuating water. However, fluctuating water conditions are expected to become more common due to climate change.

Original Leaf Colonisers Shape Fungal Decomposer Communities of Phragmites australis in Intermittent Habitats

“…Similarly, Wirsel et al [ 65 ] observed Sclerotinia on the Phragmites material only in flooded sites. Flooding can induce leaf senescence and programmed cell death [ 66 ], which is frequently the case in the studied wetland [ 4 ]. As preventing early senescence is a resistance strategy of plants against necrotrophs [ 67 ], the faster senescence of leaves could speed up nutrient acquisition by necrotrophs and improve their spread in early phases of leaf decomposition.…”

“…The level of herbivory in such wetlands is relatively low, thus the majority of produced biomass is subjected to the decomposition processes [ 2 ]. Phragmites australis is a highly productive cosmopolitan species that forms extensive monoculture stands in many wetlands [ 1 ] and contributes significantly to plant litter production in these ecosystems [ 3 , 4 ]. Leaf litter has multiple functions in the ecosystem.…”

Distribution of Vascular Plant Communities in Slovenian Watercourses

“…The association Potamo crispi-Ranunculetum trichophylli is the only association from this alliance. It encompasses the vegetation of aquatic plants, that is mainly present in rivers on karst poljes with an extremely fluctuating water table [101].…”

Hydrology-Shaped Plant Communities: Diversity and Ecological Function

“…A hydrological gradient and a fluctuating water level present major driving forces, which determine the distribution of different plant communities as well as plant species composition within them. This was evidenced in various aquatic ecosystems, such as wet-meadows [12], marshes [4], intermittent lake [15], flood-forests [11], ponds [10], lakes [3,17], or rivers [6]. Waterlogged or flooded soil can become an inhospitable environment, which excludes the majority of species, while in the remaining species, it triggers the expression of various traits and mechanisms that enable survival despite oxygen shortage in the root zone.…”

“…The contribution of Gaberščik et al [15] analyzes the long-term response of cosmopolitan species Phragmites australis to extreme water level fluctuations. The study was performed in intermittent wetland Lake Cerknica, which is located at the bottom of the Cerkniško polje depression.…”