Ecological changes in the highest temporary pond of western Crete (Greece): past, present and future

Abstract

This study explores the past, present and future ecological changes in the highest Mediterranean temporary pond (Omalos pond) in western Crete, Greece. Data from downcore pollen analysis (including pollen and spores from both aquatic vegetation, and terrestrial herbaceous, arboreal and shrub vegetation), modern vegetation monitoring and existing climate scenarios have been combined to provide a picture of the ecological changes in the pond over the last 13,600 years. Downcore pollen analysis throughout the last 13,600 years indicated the presence of species typical of Mediterranean Temporary Pond (MTP) habitats and suggested relatively drier conditions towards the present. The low number of non-native, cultivated species (such as herbaceous Trifolium and Plantago species) observed over this period suggested relatively low impact from crop agriculture, despite the increasing grazing pressure in the area. In the absence of independent proxies, we cannot reliably distinguish between natural and human-induced changes. The presence of aquatic Isoetes in the palaeo-record indicates the existence of an ephemeral pond in the area as early as the beginning of the Holocene suggesting resilience of the ecosystem over time. However, the degraded state of pollen in depths over 55 cm (i.e. 3600 year BP) increases the uncertainty of the interpretation. Currently, the pond holds 76 plant species belonging to 25 families. Therophytes and chamaephytes were the most frequent, suggesting a typical ephemeral habitat life form spectrum. Species richness was found to increase during spring surveys whereas the highest turnover was observed between summer surveys of consecutive years. Cluster analysis demonstrated a distinct zonation in four vegetation belts from the periphery to the centre of the pond which is typical of these environments. Modelling, based on two IPPC scenarios (A2 and B2), predicted relatively low climate change impacts on the pond's hydroperiod for the next 100 years (i.e. a decrease of 16 and 24 days, respectively). This reduction in the hydroperiod of the pond will have an effect on the physiognomy and spatial extent of vegetation,

Sensitivity of ephemeral wetland swards with Isoetes histrix Bory to environmental variables: implications for the conservation of Mediterranean temporary ponds

“…the Mediterranean basin) are characterized by low annual rainfall and high evapotranspiration, and under these conditions wetland conservation is considered a key global issue (Williams, ). Therophytes (annual species), which are the dominant life forms in the swards, are characterized by short life‐cycles that invest more in seed production than in vegetative development (Zedler, ), indicating adaptation to hot, dry, environmental conditions, including unpredictable changes in the water regime (Ghosn et al , ). Protracted and repeated changes in the hydroperiod length could, however, result in adverse impacts, and a progressive impoverishment in the seed/spore bank of characteristic sward species, with an increase in opportunistic non‐specialized ones (Rhazi et al , ).…”

Can elevated CO2 modify regeneration from seed banks of floating freshwater marshes subjected to rising sea-level?

“…Climate change may present species with interacting environments, so that the overall effect may be more severe than anticipated based on the analysis of singleenvironmental factors (Ghosn et al, 2010). This study empirically tested seed germination and seedling responses to interacting environments, which may be associated with changes in sea level and CO 2 in coastal freshwater marshes.…”

Mediterranean temporary ponds. A disappearing ecosystem

“…Mediterranean temporary ponds are shallow water bodies, which are flooded in winter or in the end of spring for a sufficiently long period, to allow the development of (semi-) aquatic vegetation and animal communities Zacharias et al 2008;Ghosn et al 2010). They dry out in summer for an adequate period, so as to exclude the more commonplace plant and animal communities, which are characteristic of more permanent waters.…”