Soil Organic Matter in Secondary Forests of Puerto Rico

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Abstract
Soil organic matter content and loose litter were studied in secondary forests of the subtropical moist- and wet-forest life zones of Puerto Rico to observe patterns due to life zone (climate), type of forest cover, soil group, and topography. Soil organic matter content in the top 23 cm ranged from 8.99 kg/m2 in the moist-forest life zone to 7.30 kg/m2 in the wet-forest life zone, a highly significant difference. Greater amounts of soil organic matter were found under higher timber volumes, but the trend was less pronounced in the wet forest. Significant interactions with life zone were found for organic matter among soil groups (deep volcanic, shallow volcanic, granitic, and limestone) and among forest classes (young secondary, late secondary, abandoned coffee, and active coffee shade). In secondary forests on granitic soils, highly significant differences of 12.98 and 7.32 kg/m2 of organic matter were found in wet and moist forests, respectively. Moreover, highly significant differences were observed by landform and slope in active coffee shade in wet forests, with the lowest values on convex land forms and slopes > 45 percent. Mean loose litter storages in moist and wet forests were not significantly different, nor was there a significant interaction with life zone. Significant differences, however, were detected by timber volume class, soil group, and forest class. Within these highly disturbed wet and moist forests, greater timber volumes tended to be associated with greater loose litter accumulation.