Complex sentence: Sierra de San Pedro Mártir contains several coniferous species; the most abundant are: pinus ponderosa, pinus ayacahuite, pinus cembroide, firs, Sugar Pine, Jeffrey Pine and cupressus mostly found in the higher elevations.
Split into simpler sentences: Sierra de San Pedro Mártir contains several coniferous species; the most abundant are: pinus ponderosa, pinus ayacahuite and pinus cembroide, principalm. There are also large number of other tree species like firs and cupressus mostly found in the higher elevations.