Species Monitoring Using Unmanned Aerial Vehicle to Reveal the Ecological Role of Plateau Pika in Maintaining Vegetation Diversity on the Northeastern Qinghai-Tibetan Plateau

Abstract

Plateau pika (Ochotona curzoniae, hereafter pika) is considered to exert a profound impact on vegetation species diversity of alpine grasslands. Great efforts have been made at mound or quadrat scales; nevertheless, there is still controversy about the effect of pika. It is vital to monitor vegetation species composition in natural heterogeneous ecosystems at a large scale to accurately evaluate the real role of pika. In this study, we performed field survey at 55 alpine grassland sites across the Shule River Basin using combined methods of aerial photographing using an unmanned aerial vehicle (UAV) and traditional ground measurement. Based on our UAV operation system, Fragmentation Monitoring and Analysis with aerial Photography (FragMAP), aerial images were acquired. Plot-scale vegetation species were visually identified, and total pika burrow exits were automatically retrieved using the self-developed image processing software. We found that there were significant linear relationships between the vegetation species diversity indexes obtained by these two methods. Additionally, the total number of identified species by the UAV method was 71, which was higher than the Quadrat method recognition, with the quantity of 63. Our results indicate that the UAV was suitable for long-term repeated monitoring vegetation species composition of multiple alpine grasslands at plot scale. With the merits of UAV, it confirmed that pika’s disturbance belonged to the medium level, with the density ranging from 30.17 to 65.53 ha−1. Under this density level, pika had a positive effect on vegetation species diversity, particularly for the species richness of sedge and forb. These findings conclude that the UAV was an efficient and economic tool for species monitoring to reveal the role of pika in the alpine grasslands.

Characterization of the spatial distribution of plateau pika burrows along an alpine grassland degradation gradient on the Qinghai–Tibet Plateau

“…The results of this study showed a density of 5500 pika burrows/ha in degraded alpine shrub meadow, whereas surveys conducted in the western part of the southern Qilian Mountains have shown that the average number of pika burrows in normal grassland is 300–800 burrows/ha (Qin, Sun, et al, 2020; Qin et al, 2019; Yi et al, 2016). In contrast, studies of degraded alpine grassland in the hinterland of QTP found the average number of pika burrows to be 2700–4775 burrows/ha (Liu et al, 2017; Tian et al, 2019; Wang et al, 2020; Wei et al, 2013), and in the degraded grasslands of the eastern QTP, the density of pika burrows can even reach 7066 burrows ha −1 (Zhang et al, 2021), which is close to our results.…”

Applications of UAVs in Cold Region Ecological and Environmental Studies

“…To verify the suitability and feasibility of UAVs in cold regions, we organized a Special Issue entitled "Applications of UAVs in Cold Region Ecological and Environmental Studies". Eight papers were published in this issue [1][2][3][4][5][6][7][8]. Among them, 1, 2 and 5 papers focused on studies conducted in the Arctic, Antarctic and Qinghai-Tibetan Plateau, respectively.…”

“…The common camera (with red, green and blue bands) was equipped with UAVs in all studies; only two studies used multispectral and thermal infrared cameras to retrieve surface temperature and soil moisture [7,8]. The flight height ranged from 2 m to observe grassland vegetation species [6] to 20-65 m to observe vegetation patches, surface type and animal [3,5,6], and 150-500 m to study the features of glacier [1,2]. Half studies used mosaic flight ways, which covered all areas of each study area, and the others used typical ecological sampling methods to take aerial photos at each point [4][5][6]8].…”

“…The flight height ranged from 2 m to observe grassland vegetation species [6] to 20-65 m to observe vegetation patches, surface type and animal [3,5,6], and 150-500 m to study the features of glacier [1,2]. Half studies used mosaic flight ways, which covered all areas of each study area, and the others used typical ecological sampling methods to take aerial photos at each point [4][5][6]8]. Some studies performed multiple aerial photographing over each study area at different times to investigate the dynamic changes [1,7,8].…”

“…The processing of aerial photos included: (1) visual interpretation to obtain plant species [6] and patchy distribution [4]; (2) retrieving vegetation cover using manual operation with self-developed software [6] and patch indices using Fragstats Landscape Analysis software [5,8]; (3) generating Orthomosaic and DEM using Pix4Dmapper (Pix4D S.A., Prilly, Switzerland) [1,3] or Agisoft Metashape Professional software (Agisoft LLC) [2]. With this information, the majority of the studies focused on the high-spatial-resolution feature itself; two studies related grassland patches with a remote sensing dataset to perform ecological risk assessment [4,5].…”