Truffle fields, special eco-systems
Traditionally in Périgord, the precious truffle was harvested from natural truffle beds, once in impressive quantities. If you consult a cookery book dating back more than a hundred years, you'll find instructions along the lines of: "Take a plump fowl and stuff it with truffles up to the crop". Today, that's science fiction! Truffle growing as we know it today is only two centuries old. Today, the Dordogne ranks first in France for the number of mycorrhizal plants, with over 1,000 hectares planted each year. Truffles are demanding, with three basic requirements: a host tree, calcareous soil (loose, fissured clay-limestone soils) and good exposure to the sun. In Périgord, the best host tree is the white or pubescent oak. However, truffles are also grown around juniper, hazelnut and even lime, hornbeam, beech, poplar and pine trees... Some plant species are good indicators of truffle-growing soils: false cherry, blackthorn, boxwood, walnut, hazelnut, wild cherry, fig, hawthorn, wild rose, bramble, corm... Herbaceous plants are also abundant in truffle-growing areas, with a high proportion of hawkweed, sedum and small fescue. On the mushroom side, morels and Satan's boletus are regular neighbors. 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 tall weeds and smoke the earth. To complete the picture of this ecosystem, we should also mention the famous truffle fly, which is extremely useful for finding the precious black diamond in scattered, low-productivity truffle fields. The helomyza tuberivora is a small fly, barely a centimetre long, that resembles a flying ant. It has a remarkable sense of smell, which enables it to seek out its egg-laying site as close as possible to a ripe truffle whose larvae will feed on it if it is not collected. Patience and a keen eye are therefore required to spot it when it flies away or lands on the ground, marking the probable location of a truffle. Let's hope that dogs and pigs will be faster and more efficient techniques for digging on a larger scale!
The wild orchid, a protected species
There are only 160 local orchid species in France. Aquitaine is very well endowed, with 65 species, 44 of which can be found in Périgord, an exceptional conservatory for these species. These plants are mythical, serving as a barometer of the quality of the natural environments in which they thrive. Fortunately, they are now attracting the interest of the general public, which could make it easier to protect them. 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 in particular his practices of "cleaning up" the natural environment: early mowing, logging, systematic mowing of roadsides. These plants have a remarkable reproductive system. Not only do they produce bulbs, nicknamed "couillons" locally 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, enticing insects to land in the belief that they are flirting with their fellow species. Six orchids are listed as protected species in the Dordogne: large-leaved cephalanthemum, fragrant gymnadenia, bird's-nest neottie, bee orchid, marsh orchid and monkey orchid.
The bestiary of the countryside and rivers
If you love discovering nature, you're going to need a lot of time to hope to see all the animal species present in the Dordogne, so vast is the bestiary. The department boasts a rich biodiversity of remarkable animal and plant species, both on a national and European scale. Many species that are rare and endangered elsewhere can still be found here, particularly in the Dordogne basin and its aquatic environments. The Dordogne is a rich river for fish, with some forty species. It is a refuge for some of Western Europe's great migratory species, such as the European sturgeon and the European eel. But the Dordogne is also home to many other sedentary fish species that contribute to the river's rich piscicultural diversity. Several introduced species have also acclimatized to the waters of the Dordogne, and it is not uncommon to encounter carp, zander or catfish during a fishing session. In recent years, the latter has attracted many anglers who specialize in this deep-sea species. The quality of the waters in the Dordogne, coupled with a wide variety of environmental conditions and the presence of invertebrates and fish, enable birds to settle in and stay. All these factors guarantee an optimal living environment for prestigious species such as the great horned owl, kingfisher and petit gravelot. Last but not least, aquatic mammals are also very numerous along the rivers. Here again, the living environment, climatic conditions and food reserves available to them are key to their survival. Among the most remarkable are two rare species: the common otter and the European mink. Last but not least, a little-known and sometimes overlooked animal. 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 waterholes. Beware of its toxic poison, which can be discharged from a meter away in case of intense fear. It is to this defense mechanism that it owes its bad reputation.
