Exploring Stand Structural Complexity’s Drivers: A Cerrado (São Paulo State, Brazil) Case Using Stand Structural Complexity Index (SSCI)

Developing and understanding full potential of new tools for large scale reforestation programs has become essential nowadays. In this framework, stand structural complexity (SSC) has been identified as essential driver for multiple ecosystem services. Using terrestrial laser scanner (TLS) with light detection and ranging (LiDAR), I measured stand structural complexity index (SSCI) among four experimental reforestation sites in early development stage (three to eighteen years old) to identify impact of five potential SSC drivers: (1) water availability, (2) species diversity, (3) functional diversity, (4) tree density and (5) treatment applied on reforested sites. I find that (1) increased water availability enhances SSC as well as species diversity on lower level (up to six species) and (3) functional diversity. Contrastingly, no effect on SSC was observed for (2) high species diversity (twenty to one hundred fourteen species), (4) tree density and (5) treatment. SSC is likely to be enhanced by (1) water availability by promoting shade tolerant species abundance, and niche complementarity can explain positive impact on SSC by both (2) species and (3) functional diversity. On the other hand, competition for resources is likely to explain the limited impact on SSC by (4) increased tree density and (5) treatment. Finally, niche complementarity saturation is likely to explain saturating SSC on high species diversity plots. I conclude that (1) water availability plays a crucial role for improving stand structural complexity, being its main driver, (2) species diversity and (3) functional diversity (on lower level) improves it, but high tree density and species diversity as well as increased treatment play a neglectable role for enhancing stand structural complexity on forest’s early stage. Those results put forward the importance of species mixtures with various functional traits in reforestation programs, and the unnecessity of increasing tree density and treatments (resulting in additional costs) for enhancing stand structural complexity.