# An investigation into the spatial patterns of invasive common milkweed (Asclepias syriaca L.) stands through the utilization of drone images

## TL;DR

This study shows that drone imaging can effectively map invasive common milkweed populations, matching ground survey data closely.

## Contribution

The study demonstrates the effectiveness of drone imaging for analyzing spatial patterns of invasive milkweed compared to ground surveys.

## Key findings

- Drone images showed a strong positive correlation with ground survey data for shoot counts (r = 0.9594).
- The average distance between shoots and observed patterns also correlated strongly between methods (r = 0.933 and r = 0.9146).
- Drone imaging is a valuable tool for invasive species management and monitoring treatment effectiveness.

## Abstract

The phenomenon of biological invasions represents one of the most significant threats to biodiversity. A fundamental aspect of combating invasive plant species is the comprehension of the spatial and temporal alterations in their population dynamics. One of the important habitats of the European Union is the Pannon sand grasslands in Hungary, which are primarily threatened by the invasive common milkweed (Asclepias syriaca). The objective of this study was to ascertain the efficacy of drone imaging in examining the spatial patterns of milkweed shoots in comparison to ground survey data. To facilitate comparison, a survey was conducted on 12 milkweed populations in the Fülöpháza area of Kiskunság National Park. In each population, a 12-meter transect (comprising six contiguous 2 m × 2 m quadrats) was designated within which the positions of the shoots were recorded with centimeter accuracy through ground surveys. The individual shoots were marked on images captured from an altitude of 20 m using a drone. The results indicated that the number of shoots identified in the drone images was slightly lower than in the ground surveys; however, a positive correlation was observed between the two datasets (r = 0.9594). A strong positive correlation was evident between the ground and drone surveys in terms of both the average distance between shoots and the observed pattern (r = 0.933 and r = 0.9146). In light of these findings, it can be concluded that drone imaging represents an effective method for examining the size and pattern of populations. Consequently, it may prove to be a valuable tool for the accurate planning of invasive species management in conservation efforts and the monitoring of the effectiveness of treatments.