Author(s)

Philip Beckschäfer, Philip Mundhenk, Christoph Kleinn, Yinqiu Ji, Douglas W. Yu, Rhett D. Harrison

Chair of Forest Inventory and Remote Sensing, Georg-August-Universitat Gottingen, Gottingen, Germany.
Key Laboratory for Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, China.
State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.
State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China; School of Biological Sciences, University of East Anglia, Norwich, UK.

The horizontal distribution of stems, stand density and the differentiation of tree dimensions are among the most important aspects of stand structure. An increasing complexity of stand structure is often linked to a higher number of species and to greater ecological stability. For quantification, the Structural Complexity Index (SCI) describes structural complexity by means of an area ratio of the surface that is generated by connecting the tree tops of neighbouring trees to form triangles to the surface that is covered by all triangles if projected on a flat plane. Here, we propose two ecologically relevant modifications of the SCI: The degree of mingling of tree attributes, quantified by a vector ruggedness measure, and a stem density term. We investigate how these two modifications influence index values. Data come from forest inventory field plots sampled along a disturbance gradient from heavily disturbed shrub land, through secondary regrowth to mature montane rainforest stands in Mengsong, Xishuangbanna,Yunnan,China. An application is described linking structural complexity, as described by the SCI and its modified versions, to changes in species composition of insect communities. The results of this study show that the Enhanced Structural Complexity Index (ESCI) can serve as a valuable tool for forest managers and ecologists for describing the structural complexity of forest stands and is particularly valuable for natural forests with a high degree of structural complexity.

Forest Structure Index; Structural Complexity; Stem Map; Species Composition; NMDS

Beckschäfer, P. , Mundhenk, P. , Kleinn, C. , Ji, Y. , Yu, D. & Harrison, R. (2013). Enhanced Structural Complexity Index: An Improved Index for Describing Forest Structural Complexity. Open Journal of Forestry, 3, 23-29. doi: 10.4236/ojf.2013.31005.