The land considered forest includes areas that contain little more than scrub ground cover and others that have been ravaged by unsystematic cutting. More than half of the forests, however, contain mature trees and, owing largely to their inaccessibility, have escaped the reckless harvesting that destroyed many lower elevation forests during the first years of the country's independence. Maquis, a Mediterranean scrub tree, grows to about fifteen or twenty feet, can be extremely dense, and is the most frequent ground cover at low elevations. It withstands dry weather and, although it is of little value as a tree and does not of itself build a rich soil, it stabilizes the alluvial lowlands and provides cover for better humus-producing vegetation. Maquis can survive at slightly higher elevations in sheltered conditions, but it is usually found below 1,000 or 1,300 feet. Most maquis species are evergreen. Deciduous scrub, usually Christ's-thorn, or _shiblijak_, is also common in the lowlands, but it occurs much less frequently than maquis. The oaks are the most important of trees. Oak forests have never reattained the majesty they had during the days of Venice's power when they could be called upon to furnish 400 shiploads of straight oak stems for Venetian fleets, but in 1970 they still constituted nearly half of all forests. The oaks are valuable not only for their economic worth as fuel and lumber but also because the leaves of deciduous varieties and the undergrowth encouraged beneath them are excellent soil builders. Occurring at moderate elevations, however, they have been accessible and overexploited. Lowland oak forests contain poorer species that rarely grow in excess of thirty feet tall, but the thick undergrowth they usually allow provides stability and improves the alluvial soil. The finer and more valuable species occur at middle and higher elevations. Oak forests predominate between 1,000- and 3,000-foot elevations but occur up to about 4,000 feet. Beech trees appear at all elevations between 3,000 feet and the timberline. They predominate in northern areas between about 3,500 and 6,000 feet. In the south they flourish at the same elevations but are usually outnumbered by conifers. Beech is excellent hard wood, and its leaves are among the best of soil builders. The trees generate most of the humus themselves, as their canopies interlace tightly in mature forests, permitting relatively little undergrowth to flourish on the forest floors beneath them. Mature forests have survived in many of the remote, inaccessible areas that beech species prefer. The most copious forests are in cloud forest regions where cloud cover is almost constant, rainfall is frequent, and temperatures do not usually reach the extreme highs.