Ponds

Ponds are one of the environments identified in the Provincial Nature Reserves.

The pond is a small water collection usually located on the valley floor. A ring of dense aquatic vegetation runs along its banks, in some cases concealing the central body of water from view.

The pond almost resembles a miniature lake, and in many cases its origin is precisely linked to the evolution of a pre-existing larger reservoir that has gradually shrunk in size. The differences from the lake are mainly related to the smaller amount of water that the pond accommodates.

Particularly during the summer, when the tributaries and/or springs dry up and evaporation also increases with the rise in temperature, the water level in the pond can drop considerably, often reducing the reservoir to a few separate puddles. Puddles in which warm, poorly oxygenated water stagnates and in which only animal and plant organisms that are well adapted to these situations of water and temperature stress can live.

In the transition zone between water and land, which can be more or less wide depending on the profile of the reservoir, the vegetation consists of reeds or large sedge formations. Further inland, on the other hand, where the water becomes deep, plant species develop whose vegetative body is either entirely submerged or floats freely, or is partly submerged and partly floating. The group of aquatic plants whose leaves float on the surface of the basin forming a striking green carpet is called 'laminarvegetation', also called 'lamineto'. This name derives from the fact that the leaves do not rise far above the surface of the water, but instead develop horizontally so as to form a thin, extensive lamina. The laminar vegetation can expand to such an extent that it almost completely covers the surface of a pond. Some of the laminar species, e.g. the common water lentil(Lemna minor), is completely unattached to the bottom of the pond and thus the leaf floats unanchored, while the roots dangle freely in the water. Most species, however, are firmly rooted to the bottom, often with underground stems (rhizomes) that grow horizontally by branching. The connection between the rhizomes and the leaves and flowers, floating on the water surface, is provided by underwater stems or long petioles and peduncles, as in the case of the white water lily(Nimphaea alba) and the nannufer(Nuphar luteum), the two most conspicuous and beautiful aquatic species. Sometimes, however, the stems and leaves remain largely or even entirely submerged and only the inflorescences emerge during the flowering period; this is the case with theceratophyllum (Ceratophyllum demersum) or the water milfoil(Myriophyllum spp.), which are typical components of the so-called'submerged vegetation'.

When a pond has a certain extent and its banks are characterised by the presence of abundant hygrophilous vegetation, the environment becomes suitable for the presence of water birds. The bank vegetation provides a safe place to take refuge in case of danger, to build nests and raise their offspring; the abundance of water-bound invertebrates provides a rich source of food.

Low-lying ponds commonly host two species of reptiles, which share the name 'water snakes': the collared snake and the taxidermy snake. These snakes are particularly adept at swimming and spend their lives near water, feeding mainly on aquatic prey. They are two species that are completely harmless and very fearful of humans. If disturbed, they flee into the tangle of marsh vegetation or quickly plunge into the water.

Ponds are by far the most important habitats for Amphibians, because the small bodies of water provide the ideal breeding habitat for most species. As a rule, the presence of Amphibians in ponds is limited to spring, sometimes even summer; at other times of the year, these animals live far from water.

Ponds are perhaps by far the richest environments for invertebrate fauna. Many species spend their entire lives in water, others only their juvenile phase. Among the invertebrates in the pond, a great variety of forms and ways of life can be observed; as a whole, they constitute a fundamental element in the balance of the environment.

In the pond, the overall conditions of the environment make the presence of many demanding fish species impossible: the temperature, for example, has very high annual fluctuations. In summer, temperatures exceed 20 °C, while already in autumn, due to the small volume of water, the water cools rapidly and the surface freezes for long periods. Therefore, the more tolerant cyprinids dominate and, among the predators, the pike clearly prevails, which has the important role of controlling the density of the more prolific species.