Data from: A new digital method of data collection for spatial point pattern analysis in grassland communities

A major objective of plant ecology research is to determine the underlying
processes responsible for the observed spatial distribution patterns of
plant species. Plants can be approximated as points in space for this
purpose, and thus, spatial point pattern analysis has become increasingly
popular in ecological research. The basic piece of data for point pattern
analysis is a point location of an ecological object in some study region.
Therefore, point pattern analysis can only be performed if data can be
collected. However, due to the lack of a convenient sampling method, a few
previous studies have used point pattern analysis to examine the spatial
patterns of grassland species. This is unfortunate because being able to
explore point patterns in grassland systems has widespread implications
for population dynamics, community-level patterns and ecological
processes. In this study, we develop a new method to measure individual
coordinates of species in grassland communities. This method records plant
growing positions via digital picture samples that have been sub-blocked
within a geographical information system (GIS). Here, we tested out the
new method by measuring the individual coordinates of Stipa grandis in
grazed and ungrazed S. grandis communities in a temperate steppe ecosystem
in China. Furthermore, we analyzed the pattern of S. grandis by using the
pair correlation function g(r) with both a homogeneous Poisson process and
a heterogeneous Poisson process. Our results showed that individuals of S.
grandis were overdispersed according to the homogeneous Poisson process at
0-0.16 m in the ungrazed community, while they were clustered at 0.19 m
according to the homogeneous and heterogeneous Poisson processes in the
grazed community. These results suggest that competitive interactions
dominated the ungrazed community, while facilitative interactions
dominated the grazed community. In sum, we successfully executed a new
sampling method, using digital photography and a Geographical Information
System, to collect experimental data on the spatial point patterns for the
populations in this grassland community.