OOS 15-1 - Ecosystem-level attributes of novel dry, moist, and wet forests: A comparison across life zones

Tuesday, August 9, 2016: 1:30 PM
Grand Floridian Blrm H, Ft Lauderdale Convention Center
Ariel E. Lugo, International Institute of Tropical Forestry, USDA Forest Service, Rio Piedras, PR

Novel forest ecosystems are defined by their species composition (novel mixtures of native and non-native species) and by the environmental conditions under which they develop, which reflect a human footprint (e.g., soil degradation or novel disturbance regime).  Many ecologists fear that the functioning of novel ecosystems will be different from that of historic ecosystems resulting in the loss of their capacity to deliver ecological services to people.  To shed some light on this fear, I ask if the ecosystem-level attributes of novel subtropical forests are different from those of historic ones that they replace.  I focus attention on the ecosystem-level attributes of novel dry, moist, and wet forests in the Caribbean by reviewing available literature from the region.  The attributes that I synthesize are species composition (including the relative importance of native and non-native species), structural parameters such as biomass accumulation, primary productivity parameters such as litterfall, and nutrient cycling and stoichiometry of leaves and leaf litter.  The elements included in the analysis are: C, N, S, P, Ca, Mg, K, Na, Mn, Al, and Fe.


The number of non-native tree species that mix with native ones decreases with increasing climate harshness.  More non-native species contribute to the species composition of moist forests than either in wet or dry forests.  A moisture stress index (C/mm) explained over 40 percent of the biomass accumulation in novel forests, with the lowest accumulations in dry forests and higher values in moist and wet conditions.  Most novel forests are young (<30 years), which explains low values for their structural indices, and limits the reliability of comparisons with older historical forests.  Litterfall was higher in novel forests than in historic mature forests.  High net primary productivity accelerates nutrient return to the forest floor of novel forests in all life zones.  The concentration of leaf N and P tend to be higher in novel forests than in historical forests.  Leaf chemistry reflects the ecophysiological characteristics of dominant naturalized species and their relative importance in the forest ecosystem.  Leaf litter chemistry varied with life zone for C, Ca, Mg, Na, and Mn.  I found no anomalies in the functioning of novel forests. Their abundance and ecological attributes increases the availability of N and P, and contributes to the rehabilitation of eroded soils.