Truffle fields, special eco-systems
Traditionally in the Périgord, the precious truffle was collected in natural truffle fields, once in impressive quantities. If you consult a cookery book, dating back more than a hundred years, you can read instructions like this: "take a fat poultry, stuff it with truffles up to the crop". Today, this is science fiction! Truffle growing as we know it today is only two centuries old. The Dordogne is currently ranked first in France for the number of mycorrhizal plants, i.e. more than 1,000 hectares per year. The truffle is demanding with three basic needs: a host tree, a calcareous soil (fissured and loose clay-limestone soils) and a good exposure to the sun. In Périgord, the best host tree is the white or pubescent oak. However, truffles are also cultivated around junipers, hazel trees and even lime trees, hornbeams, beeches, poplars, pines... Some plant species are good indicators of truffle soil: false cherry, blackthorn, boxwood, walnut, hazelnut, wild cherry, fig, hawthorn, wild rose, bramble, corm tree... In addition, there are many herbaceous plants in truffle fields, with a high proportion of hawkweed, sedum and small fescue. On the mushroom side, morels and Satan's boletus are usual neighbours. It used to be said that truffle growth was more abundant thanks to the following conditions: the presence of dry stone walls to reflect heat back to the soil, the proximity of ploughed vines to decompact the soil, and sheep to get rid of the tall weeds and smoke the earth. To complete the picture of this ecosystem, we must finally take an interest in the famous truffle fly, which is very useful for digging up the precious black diamond, in truffle fields that are not very productive and scattered. The helomyza tuberivora is a small fly, barely one centimetre long, which looks like a flying ant. It has a remarkable sense of smell which allows it to look for its egg-laying site, as close as possible to a ripe truffle whose larvae will feed if it is not collected. It takes patience and a good eye to spot it when it flies away or lands on the ground, marking the probable location of a truffle. Let's hope that the dog or the pig are more efficient and quicker techniques, to dig on a larger scale!
The wild orchid, a protected species
The French flora counts only 160 species of local orchids. Aquitaine is very well endowed with 65 species, including 44 in the Périgord, which is an exceptional conservatory of these species. These plants are mythical and act as a barometer of the quality of the natural environments where they flourish. Fortunately, they are now attracting the interest of the general public, which could facilitate their protection. Delicate, discreet and fascinating in many ways, they flee cultivated areas to take refuge on limestone soils, causses and natural meadows, whether dry or wet. Their worst enemy is man and especially his practices of "cleaning up" the natural environment; early mowing, logging, systematic mowing of roadsides. The reproduction system of these plants is remarkable. Not only do they produce bulbs, known locally as "couillons" because of their characteristic shape, but they also reproduce sexually, with insects fertilizing them. In this respect, orchids excel in the art of luring and mimicry, to encourage insects to land, believing that they are flirting with their fellow creatures. Six orchids are on the list of protected species in the Dordogne: the large-leaved cephalanthera, the fragrant gymnadenia, the bird's nest orchid, the bee orchid, the marsh orchid and the monkey orchid.
The bestiary of the countryside and rivers
If you like to discover nature, you will need a lot of time to hope to see all the animal species present in the Dordogne, as the bestiary is so vast. The department has a rich biodiversity of remarkable animal and plant species, both on a national and European scale. Many rare and endangered species in other areas remain here, particularly in the Dordogne basin around the aquatic environments. As far as fish are concerned, with around forty species, the Dordogne is a rich river. It serves as a refuge for the great migratory species of Western Europe, such as the European sturgeon, or the European eel. But the Dordogne River is also home to many other sedentary fish species that contribute to the river's piscicultural wealth. Several introduced species have also acclimatised to the waters of the Dordogne, and it is not unusual to encounter carp, pike-perch or catfish during a fishing session. The latter has attracted many fishermen over the last few years who have specialised in this deep-sea species. The quality of the water in the Dordogne coupled with a wide variety of environmental conditions, the presence of invertebrates and fish allow the birds to settle and remain in the area. All these factors guarantee an optimal living environment for prestigious species such as the great horned owl, the kingfisher or the small gravelot. Finally, aquatic mammals are also very numerous along the rivers. Here again, the living environment, climatic conditions and food reserves available to them are the key to their survival. Among the most remarkable, two rare species stand out: the common otter and the European mink. The spotted salamander is common in the Dordogne. The town of Sarlat has made it its emblem. It lives in deciduous woods or mixed forests, near water. Beware of its toxic poison which it can discharge at a meter in case of intense fear. It is to this defense mechanism that it owes its bad reputation.
