On the structural complexity of central European agroforestry systems: a quantitative assessment using terrestrial laser scanning in single-scan mode

Agroforestry systems provide important ecosystem functions and services. They have the potential to enrich agricultural monocultures in central Europe with structural elements otherwise absent, which is expected to be accompanied by a surplus of ecosystem functions. Here we used quantitative measures derived from terrestrial laser scanning in single-scan mode to describe the structural complexity, the canopy openness, the foliage height diversity and the understory complexity of four common agroforest systems in central Europe. We accessed silvopasture systems with grazing ponies and cattle as well as fellow deer, short rotation forests with agricultural use between the tree rows, tree orchards with grazing sheep and Christmas tree plantations on which chickens forage. As a reference, we used data for 65 forest sites across Germany, representing different forest types, various dominant tree species, stand ages and management systems. We found that overall stand structural complexity is ranked as follows: forest > silvopasture systems > short rotation forest > tree orchard > Christmas tree plantation. Consequently, if overall structural complexity of an agricultural landscape shall be enriched, there is now strong evidence on how this may be achieved using agroforests. However, if the focus lies on selected structures that serve specific functions, e.g. dense understory to provide animal shelter, specific types of agroforests may be chosen and the ranking in overall structural complexity may be less important.