Valley Loess Plains, and Mississippi Alluvial Plain regions. Tennessee is the most biodiverse inland state, the Great Smoky Mountains National Park is the most biodiverse national park, and the Duck River is the most biologically diverse waterway in North America. The Nashville Basin is renowned for its diversity of flora and fauna. Tennessee is home to 340 species of birds, 325 freshwater fish species, 89 mammals, 77 amphibians, and 61 reptiles. Forests cover about 52% of Tennessee's land area, with oak–hickory the dominant type. Appalachian oak–pine and cove hardwood forests are found in the Blue Ridge Mountains and Cumberland Plateau, and bottomland hardwood forests are common throughout the Gulf Coastal Plain. Pine forests are also found throughout the state. The Southern Appalachian spruce–fir forest in the highest elevations of the Blue Ridge Mountains is considered the second-most endangered ecosystem in the country. Some of the last remaining large American chestnut trees grow in the Nashville Basin and are being used to help breed blight-resistant trees. Middle Tennessee is home to many unusual and rare ecosystems known as cedar glades, which occur in areas with shallow limestone bedrock that is largely barren of overlying soil and contain many endemic plant species. Common mammals found throughout Tennessee include white-tailed deer, red and gray foxes, coyotes, raccoons, opossums, wild turkeys, rabbits, and squirrels. Black bears are found in the Blue Ridge Mountains and on the Cumberland Plateau. Tennessee has the third-highest number of amphibian species, with the Great Smoky Mountains home to the most salamander species in the world. The state ranks second in the nation for the diversity of its freshwater fish species. Climate Most of Tennessee has a humid subtropical climate, with the exception of some of the higher elevations in the Appalachians, which are classified as a cooler mountain temperate or humid continental climate. The Gulf of Mexico is the dominant factor in Tennessee's climate, with winds from the south responsible for most of the state's annual precipitation. Generally, the state has hot summers and mild to cool winters with generous precipitation throughout the year. The highest average monthly precipitation usually occurs between December and April. The driest months, on average, are August to October. The state receives an average of of precipitation annually. Snowfall ranges from in West Tennessee to over in East Tennessee's highest mountains. Summers are generally hot and humid, with most of the state averaging a