Distribution of Ligularia virgaurea in the source region of the Yellow River based on BIOMOD

The source region of the Yellow River (SRYR) lies in the northeastern Qinghai-Tibetan Plateau. The SRYR is a typical alpine region that is fragile and vulnerable. Ligularia virgaurea, one of the main toxic weeds, is widely distributed in the SRYR. There are few studies on the spatial-temporal distribution of L. virgaurea at a regional scale, and the most important limiting factor is the lack of broad scale, precise, and efficient monitoring methods. We proposed a practical method based on unmanned aerial vehicles (UAVs) and a widely used species distribution model, BIOdiversity MODelling (BIOMOD), and tested it to determine the distribution of L. virgaurea in the SRYR. During the growing season of 2018, we set 208 working points using the self-developed software-fragmentation monitoring and analysis with aerial photography (FragMAP) and obtained more than 5000 aerial photographs in the SRYR. Based on the data, we simulated the distribution of L. virgaurea using the 10 models in BIOMOD. The results showed that: 1) BIOMOD could reduce the uncertainty and improve the prediction performance of L. virgaurea distribution; 2) the generalized boosting model exhibited the best performance in predicting the potential distribution of L. virgaurea in SRYR, while the random forest model was the best at predicting its distribution in the future; the main factors affecting its distribution were the microhabitat (maximum value, average value, and ranges of normalized difference vegetation index), annual average radiation, radiation in cold and wet season, and precipitation in the wet season; and 3) climate warming may increase the distribution of L. virgaurea in SRYR, especially in the southeastern central area. This study described the spatial-temporal distribution of L. virgaurea, which provides basic data for estimating the damage rating and for implementing prevention measures in a rational and timely manner. Furthermore, it could provide a scientific basis for the sustainable development of grassland ecosystems and animal husbandry in the SRYR. Meanwhile, the UAVs-based monitoring featured with long-time, large scale and high precision, provided abundant data and a new method for biodiversity research and conservation in the alpine grassland ecosystem.