The ecological features of chestnut orchards, their agronomic management and architecture strongly depend on species and country. The best soils for chestnut are deep, soft, volcanic in origin, and rich in phosphorus, potassium, and organic matter. The soil pH should be in the range 5.0−6.5; therefore, soils with active limestone are not optimal, because Castanea species are very sensitive to high pH values. Soil permeability is very important. In fact, the crop performs better in well-drained, loam to sandy-loam soils, while heavy, washed out, clayey, stagnant soils which favor root rot must be avoided [6].

Chestnut tolerates cold winters and requires average temperature of 8–15 °C, with a monthly average of 10 °C for at least six months. Castanea sativa is more cold-resistant (−15 to −20 °C) than the Euro-Japanese hybrids. Despite late bud-break (March–April in the Northern Hemisphere), the trees may be prone to spring frosts which damage young shoots. Temperatures of 27−30 °C are necessary during pollination. European and Japanese cultivars require about 800–900 mm/year of rainfall, well distributed during the growing season, while Euro-Japanese hybrids and C. mollissima are much more waterdemanding (1200–1300 mm/year). In temperate climates, sweet chestnut should not be planted above 800–900 m, while for hybrids the maximum altitude is about 500–600 m [5].

Ecological features of a chestnut orchard can be influenced by many natural and anthropogenic parameters, such as soil, climate, rootstock, cultivar, cover crops, irrigation system and fertilization [7]. Concerning soil, an increase in the organic matter content is often obtained through sheep and cattle pasture, outside the harvesting period, or with the use of manure (10–15 tons/ha/year). Mown grass, leaves, husks and the small pruned material are often left on the ground as they provide further enrichment in organic matter. Fertilization of the orchard is every year carried out according to soil conditions and uptakes [8]. Biological or conventional management are both adopted by chestnut growers and could strongly influence the crop ecological features.

The orchard model, traditional or intensive, could also strongly influence the crop ecological features. Traditional orchards are mainly located in mountainous areas while intensive orchards are a relatively recent practice and are usually located in lowlands, quite far from the typical ecological conditions of the species [9]. For all species, except in traditional European chestnut orchards, the general trend is to increase plant density to develop in a relatively short time maximum bearing per unit area. Plantation density can affect the orchard microclimatic conditions and can range from 100 to 550 trees/ha, based on species, variety, genotype-environment interactions and cultural practices. For traditional plantations of C. sativa, spacing ranges from 8–10 m apart in rows and 8–12 m between rows. For the most vigorous Euro-Japanese hybrids the distances range between 7 × 8 m (178 trees/ha) and 8 × 10 m (125 trees/ha). Castanea sativa and the Euro-Japanese hybrids can be cultivated in high density plantations (3 m × 10 m). For C. crenata distances of about 5 × 7 m (285 trees/ha, in deep fertile soils) or 7 × 7 m (204 trees/ha) are recommended. Castanea mollissima, grown in China and the Unites States, is managed in a high or semi-high density scheme, due to the smaller tree size. Planting patterns may be rectangular, squared or triangular, but the first scheme is mostly used because of easier management [3]. Nowadays, many traditional plantations need renewal and recovery after years of abandonment or following the attacks of pests and diseases that have compromised their efficiency.

3. Occurrence of Endophytic Fungi in Chestnuts and Ecological Implications