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Individual Highlight

Highly Dynamic Urban Forest in San Juan, Puerto Rico.

Photo of The southern part of the San Juan Bay Estuary, a hilly area with soils  derived from volcanic soils, is less densely developed and has higher  tree cover than other parts of the watershed. Tom Brandeis, USDA Forest ServiceThe southern part of the San Juan Bay Estuary, a hilly area with soils derived from volcanic soils, is less densely developed and has higher tree cover than other parts of the watershed. Tom Brandeis, USDA Forest ServiceSnapshot : Between 2001 and 2010, the urban forest in the San Juan Watershed in Puerto Rico was highly dynamic. Nearly 50 percent in trees originally sampled in 2001 had been removed or had died. However, growth of new trees exceeded mortality and resulted in an average increase of 40 trees per acre. The urban forest had a mean diameter growth rate of 0.39 inch per year.

Principal Investigators(s) :
Zipperer, Wayne C. 
Research Location : San Juan, Puerto Rico
Research Station : Southern Research Station (SRS)
Year : 2014
Highlight ID : 738

Summary

In 2010, 87 permanent plots, established in 2001 in the San Juan Watershed in Puerto Rico, were inventoried to assess changes in species composition and structure across urban land uses. Forty-nine percent of the trees (3,670 trees/acre) inventoried in 2001 died, but 64 percent of the trees (7,511 trees/acre) inventoried in 2010 had grown since 2001. Vacant lands had the highest and upland forests had lowest annual mortality rates. Species richness increased from 68 species in 2001 and 85 species in 2010. Natural regeneration in upland and mangrove forests accounted for most of the new stems added. Residential areas had the highest and vacant lands had the lowest richness. Trees grew fastest in residential areas (0.55 inch per year) and slowest in mangrove forests (0.12 inch per year). Overall, growth of non-native and invasive species was best correlated with human population density, whereas growth of native species was best correlated with tree density. Much of vegetation dynamics observed in the San Juan Watershed can be attributed to human activities.

Forest Service Partners

External Partners

  • Dr. Thomas J. Brandeis, FIA, SRS 4801
  • University of Alabama
  • University of Florida