The application potential of unmanned aerial vehicle surveys in grassland plant diversity

doi:10.17520/biods.2023381

Abstract

Abstract:

Aims: The biodiversity of grassland is essential for maintenance of the ecosystems’ services. Unmanned aerial vehicle (UAV) remote sensing has attracted much attention in the survey and research of grassland species in recent years with its advantages of flexibility, high resolution, high efficiency, and low cost. However, current research on UAV surveys of grassland plant diversity are still insufficient. This study aims to explore the impacts of expanding survey area on the results of grassland plant diversity survey, and optimal aerial photography parameters and efficiency for UAV survey of grassland plant diversity, so as to analyze the application potential of UAV survey on grassland plant diversity.
Methods: UAV aerial photography and artificial ground survey were used to investigate plant diversity in the Hulunbuir meadow. By comparing the number of species observed and the survey time under different layout methods of quadrat and different shooting methods, the influence of expanding the survey area on the survey results was analyzed. The best aerial photography parameters and the time efficiency of using UAV to carry out grassland plant diversity survey were analyzed as well.
Results: (1) In the survey of grassland plant diversity, the number of species increased as the survey area increased within a certain range. Compared with the artificial ground survey of limited quadrats, more species could be observed using UAV in a large area survey. (2) In the survey of plant diversity in a semi-arid meadow grassland, the spatial resolution of UAV RGB image used for species identification should be better than 0.50 mm, and approximately 67.16% of species could be identified at a resolution of 0.45 mm. In terms of observation angle, it was better to shoot in two ways, which could increase 45° or 60° oblique shooting on the basis of 90° vertical shooting. (3) UAV survey could significantly shorten the time spent in species survey, but high-precision intelligent species identification model should be used to improve the survey efficiency.
Conclusion: By comparing the number of species observed by UAV and traditional artificial ground survey, this study further verifies the feasibility of UAV remote sensing for grassland plant diversity survey, and explores the key parameters of using UAV to obtain visible light images for grassland species survey. The results promote further implementation and prioritization of UAV in grassland monitoring, investigation, and protection.

Key words: grasslands, UAV, plant diversity, method of survey, species recognition

Fengming Wan, Huawei Wan, Zhiru Zhang, Jixi Gao, Chenxi Sun, Yongcai Wang. The application potential of unmanned aerial vehicle surveys in grassland plant diversity[J]. Biodiv Sci, 2024, 32(3): 23381.

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URL: https://www.biodiversity-science.net/EN/10.17520/biods.2023381

https://www.biodiversity-science.net/EN/Y2024/V32/I3/23381

Figures/Tables 8

References 38

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照片采集设备 Photo acquisition equipment	采集对象 Sampling objects	飞行高度 Flight height (m)	拍摄角度 Angle of photography	90°拍摄时空间分辨率 Vertical shooting spatial resolution (mm)	备注 Remarks
DJI Mini 3 Pro	30 m × 1 m样线 30 m × 1 m line transect	1	30°、45°、60°、75°、90°	0.43
DJI Mini 3 Pro	30 m × 1 m样线 30 m × 1 m line transect	2	30°、45°、60°、75°、90°	0.88
DJI Mavic 2 Pro	30 m × 1 m样线 30 m × 1 m line transect	1.5	30°、45°、60°、75°、90°	0.38
DJI Mavic 2 Pro	30 m × 1 m样线 30 m × 1 m line transect	3	30°、45°、60°、75°、90°	0.77
DJI Matrice 300 RTK + AQ600	1 m × 1 m样方 1 m × 1 m quadrat	2	90°	0.45
		3	90°	0.65
		4	90°	0.90
		5	90°	1.10
		6	90°	1.35
DJI Matrice 300 RTK + H20	30 m × 1 m样线 30 m × 1 m line transect	-	45°、60°、75°、90°	1.00	变焦相机, 固定分辨率拍摄 Zoom camera, fixed resolution shooting
		-	45°、60°、75°、90°	2.00
		5	90°	0.20

照片采集设备 Photo acquisition equipment	采集对象 Sampling objects	飞行高度 Flight height (m)	拍摄角度 Angle of photography	90°拍摄时空间分辨率 Vertical shooting spatial resolution (mm)	备注 Remarks
DJI Mini 3 Pro	30 m × 1 m样线 30 m × 1 m line transect	1	30°、45°、60°、75°、90°	0.43
DJI Mini 3 Pro	30 m × 1 m样线 30 m × 1 m line transect	2	30°、45°、60°、75°、90°	0.88
DJI Mavic 2 Pro	30 m × 1 m样线 30 m × 1 m line transect	1.5	30°、45°、60°、75°、90°	0.38
DJI Mavic 2 Pro	30 m × 1 m样线 30 m × 1 m line transect	3	30°、45°、60°、75°、90°	0.77
DJI Matrice 300 RTK + AQ600	1 m × 1 m样方 1 m × 1 m quadrat	2	90°	0.45
		3	90°	0.65
		4	90°	0.90
		5	90°	1.10
		6	90°	1.35
DJI Matrice 300 RTK + H20	30 m × 1 m样线 30 m × 1 m line transect	-	45°、60°、75°、90°	1.00	变焦相机, 固定分辨率拍摄 Zoom camera, fixed resolution shooting
		-	45°、60°、75°、90°	2.00
		5	90°	0.20

调查方式 Survey method	实际调查面积 Actual survey area (m²)	调查代表的区域面积 The area represented by the survey (m²)	物种数 No. of species
嵌套样方 Nested quadrats	1	-	19
	4	-	26
	9	-	33
	25	-	39
不同数量样方 Different number of quadrats	1	900	20.8
	3	900	33.6
	5	900	39.4
不同数量样地 Different number of plots	125	250,000	49.6
	250	250,000	62.7
	375	250,000	69.3
	500	250,000	74.0
	625	250,000	77
增加样线 Add line transects	120	900	10.2
增加样线 Add line transects	600	250,000	10

调查方式 Survey method	实际调查面积 Actual survey area (m²)	调查代表的区域面积 The area represented by the survey (m²)	物种数 No. of species
嵌套样方 Nested quadrats	1	-	19
	4	-	26
	9	-	33
	25	-	39
不同数量样方 Different number of quadrats	1	900	20.8
	3	900	33.6
	5	900	39.4
不同数量样地 Different number of plots	125	250,000	49.6
	250	250,000	62.7
	375	250,000	69.3
	500	250,000	74.0
	625	250,000	77
增加样线 Add line transects	120	900	10.2
增加样线 Add line transects	600	250,000	10

飞行高度 Flight height	拍摄角度 Angle of photography
飞行高度 Flight height	30°	45°	60°	75°	90°
1 m
2 m