XVI International Botanical Congess

We studied the changes in chemical and physical properties of soils of different seral stages in the montane cloud forest of Sierra Norte Oaxaca. We analyzed three chronosquences from 15 to >120 years (mature forest). Soils are ultisols derived from schist and are poor in P, and in exchangeable K, Ca, and Mg. Soil organic matter and nitrogen content are high and tend to increase in older woods. Soils are very acidic. Soil pH decreases and interchangeable Al increases in later stages of succession. Consequently, we anticipate problems of Al toxicity and P limitation in plants.