Species–area relationships in continuous vegetation: Evidence from Palaearctic grasslands
Author(s)
Date Issued
2020
Type
article
Volume
47
Issue
1
Start Page
72
End Page
86
Journal
Abstract
Aim: Species–area relationships (SARs) are fundamental scaling laws in ecology although
their shape is still disputed. At larger areas, power laws best represent SARs.
Yet, it remains unclear whether SARs follow other shapes at finer spatial grains in
continuous vegetation. We asked which function describes SARs best at small grains
and explored how sampling methodology or the environment influence SAR shape.
Location: Palaearctic grasslands and other non‐forested habitats.
Taxa: Vascular plants, bryophytes and lichens.
Methods: We used the GrassPlot database, containing standardized vegetation‐plot
data from vascular plants, bryophytes and lichens spanning a wide range of grassland
types throughout the Palaearctic and including 2,057 nested‐plot series with at
least seven grain sizes ranging from 1 cm2 to 1,024 m2. Using nonlinear regression,
we assessed the appropriateness of different SAR functions (power, power quadratic,
power breakpoint, logarithmic, Michaelis–Menten). Based on AICc, we tested
whether the ranking of functions differed among taxonomic groups, methodological
settings, biomes or vegetation types.
Results: The power function was the most suitable function across the studied taxonomic
groups. The superiority of this function increased from lichens to bryophytes
to vascular plants to all three taxonomic groups together. The sampling method was
highly influential as rooted presence sampling decreased the performance of the
power function. By contrast, biome and vegetation type had practically no influence
on the superiority of the power law.
Main conclusions: We conclude that SARs of sessile organisms at smaller spatial
grains are best approximated by a power function. This coincides with several other