Abstract
Biodiversity conservation, plant growth and spatial distribution of plant species are the central issues in contemporary community ecology. Ephemeral stream may influence soil properties, which in turn may determine biodiversity and function of an ecosystem in alluvial fan of arid desert region. Ephemeral stream is one of the most common natural disturbances, yet the effects of the ephemeral stream on plant communities in terms of species diversity and plant species distribution remain poorly studied. In this study, the information of species distribution, ephemeral stream beds (‘washes’), and the characteristics of plant growth, i.e. height, crown area, were interpreted at different heights using the images of low altitude unmanned aerial vehicle (UAV). After that, soil properties such as soil texture (sand, silt and clay), soil water content, pH, soil organic matter, soil electric conductivity, soil bulk density and the percentage of gravel content, and their relationships with UAV data were assessed in order to explore the influences of ephemeral stream on species diversity, plant growth characteristics and species distribution in an alluvial fan of arid desert region. The results showed that deep-rooted plants were only distributed in washes whereas shallow-rooted plants were distributed in both washes and the outside of washes (‘non-washes’). Species richness was significantly higher in washes than that in non-washes whereas the opposite pattern was true for abundance. Soil properties, plant height and crown area were higher in washes than that in non-washes. Plant height, crown area and the total number of individual plants increased with increasing wash width and per unit length of stream flow. This study highlights that the coupling factors of ephemeral stream, such as soil erosion, particle transport and sedimentation, can dramatically cause changes in soil properties and total number of individual plants, and hence, can influence species diversity, plant growth characteristics and spatial distribution of plant species in an alluvial fan of arid desert regions.
Highlights
An alluvial fan is a triangle-shaped deposit of gravel, sand, and smaller pieces of sediments such as silts, which are usually created as seasonal or intermittent flood interact with mountains, hills, or the steep walls of canyons in arid and semi-arid regions [1]
Based on the results of unmanned aerial vehicle (UAV) images and field investigation, our result showed that H. hispidus and P. harmala were distributed in washes only, whereas S. kaschgaricum and S. capillata were distributed in both washes and non-washes (Fig 1)
We show that the images of UAV at 20 m and 150 m above the ground can quickly and accurately interpret the field investigation data of herbaceous and shrubs in an alluvial fans of arid desert regions, respectively, suggesting that that UAV is a promising approach for exploring plant community ecology in arid desert regions
Summary
An alluvial fan is a triangle-shaped deposit of gravel, sand, and smaller pieces of sediments such as silts, which are usually created as seasonal or intermittent flood interact with mountains, hills, or the steep walls of canyons in arid and semi-arid regions [1]. As a common landscape type in the deserts of arid regions, alluvial fans are widely distributed in the foothills of mountains with elevation ranges from 1500~1900 m [1, 2]. Owing to the strong soil permeability in alluvial fans, water flow from rainfall and glacial melt-water in mountainous areas are usually converted into underground water in arid regions, and eventually can be used for industrial and agricultural ecosystem [2]. One of the most prominent surficial features of alluvial fans in arid desert regions is their system of drainage channels, which is recognizable in aerial images (Fig 1 and S1 Fig) [6]. Due to the remoteness of alluvial fans in arid desert regions, the occasional or accidental feature of the ephemeral stream, and both scarcities in quantities of species and plants, the relationships among ephemeral stream, plant species distribution and diversity remain unclear
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