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Biodiversity patterns are shaped by the interplay between geodiversity and organismal characteristics. Superimposing genetic structure onto landscape heterogeneity (i.e., landscape genetics) can help to disentangle their interactions and better understand population dynamics. Previous studies on the sub‐Antarctic Prince Edward Islands (located midway between Antarctica and Africa) have highlighted the importance of landscape and climatic barriers in shaping spatial genetic patterns and have drawn attention to the value of these islands as natural laboratories for studying fundamental concepts in biology. Here, we assessed the fine‐scale spatial genetic structure of the springtail, Cryptopygus antarcticus travei, which is endemic to Marion Island, in tandem with high‐resolution geological data. Using a species‐specific suite of microsatellite markers, a fine‐scale sampling design incorporating landscape complexity and generalised linear models (GLMs), we examined genetic patterns overlaid onto high‐resolution digital surface models and surface geology data across two 1‐km sampling transects. The GLMs revealed that genetic patterns across the landscape closely track landscape resistance data in concert with landscape discontinuities and barriers to gene flow identified at a scale of a few metres. These results show that the island's geodiversity plays an important role in shaping biodiversity patterns and intraspecific genetic diversity. This study illustrates that fine‐scale genetic patterns in soil arthropods are markedly more structured than anticipated, given that previous studies have reported high levels of genetic diversity and evidence of genetic structing linked to landscape changes for springtail species and considering the homogeneity of the vegetation complexes characteristic of the island at the scale of tens to hundreds of metres. By incorporating fine‐scale and high‐resolution landscape features into our study, we were able to explain much of the observed spatial genetic patterns. Our study highlights geodiversity as a driver of spatial complexity. More widely, it holds important implications for the conservation and management of the sub‐Antarctic islands. [ABSTRACT FROM AUTHOR]

This research explores intra-gully sediment volume changes of a massive gully network (42 ha) located in the Eastern Cape, RSA, in response to high rainfall events during a three-year study period (2017–2020). Unmanned aerial vehicles (UAVs) and photogrammetric processing were used to generate high resolution digital surface models (DSMs). Volumetric calculations were run to estimate the extent of gully expansion within the system to determine intra-gully changes and sediment erosion over the study period. The gully was categorised into four zones based on predominant structure and processes. These are the Extension Zone, Expansion Zone, Transport/Deposition Zone and the Side Branches. Rainfall data from a rainfall station (10 km away) was used to investigate the correlation between rainfall depth, rainfall intensity, and flow accumulation over two wetter years and one drier year with gully expansion experienced during these periods. The gully network encountered a total gully sediment volume erosion of 104,489 m3 (6.01%) over the study period. Nineteen high to extreme intensity (>20 mm per day) rainfall events produced the runoff necessary for gully expansion during the 2017 and 2018 hydrological years. Notably, lower gully growth was recorded in the Expansion and Transport/Deposition Zones during the subsequent below average hydrological year in 2019–2020. [ABSTRACT FROM AUTHOR]

Gully erosion can reach alarming dimensions, and in several cases contributes significantly to soil loss and sediment yield in catchments. The studied example is one of the largest known gully networks in the world (its surface area is approximately 0.5 million m2 and volume 5 million m3), more than twice as large compared to the largest gullies described in peer-reviewed literature. To improve gully management strategies, it is not only critical to understand the factors that lead to erosion, but also to identify the extent of in-channel erosional and depositional features. Few studies consider in-channel patterns of erosion and deposition within gully systems. This study utilises a fixed-wing Unmanned Aerial Vehicle (UAV) and Structure-from-Motion (SfM) photogrammetry to create a high resolution orthomosaic and Digital Surface Model (DSM) to determine the position and spatial extent of erosional and depositional features within a large gully network in South Africa. Formation of such a large gully in relation to a relatively small drainage area is unusual but can be explained by the presence of dispersive soils and regional landscape incision. Longitudinal and cross-sectional profiles indicate that the gully network consists of three channel types (i.e. V-shaped, U-shaped and trapezoidal), each with a unique combination of erosional and depositional features. This study demonstrates the value of identifying and mapping of intra-gully features to better understand sediment transfer within the gully network to implement appropriate restoration strategies, which in this instance should focus on depositional zones to enhance channel decoupling. [ABSTRACT FROM AUTHOR]