Mapping shrub cover in grasslands with an object-based approach and investigating the connection to topo-edaphic factors

Soubry, Irini; Robinov, Larissa; Chu, Thuan; Guo, Xulin

doi:10.1080/10106049.2022.2120549

Cited by 6 publications

(4 citation statements)

References 47 publications

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“…The establishment of new shrubs took place preferentially in those areas with shrubs in 1970, leading to a more marked contrast between areas with high and low shrub density. Other authors found similar results in other areas which were recently invaded by shrubs (Khazieva et al, 2022; Soubry et al, 2022). This spatial heterogeneity in shrub establishment was attributed to different reasons, biotic and abiotic (Turnbull et al, 2010).…”

Section: Discussionsupporting

confidence: 79%

“…Although reasonable, that cause seems unlikely in our case, since C. avellanedae achenes have a pappus that facilitate dispersal, strong winds are common during achenes dispersal, and the shrub‐steppe and herbaceous‐steppe stands are relatively small and intermingled in the landscape, so seeds could easily reach the stands of the herbaceous steppe. Another reason could be the existence of edaphic heterogeneity (Soubry et al, 2022). Soil characteristics can strongly affect seed germination and seedling emergence and establishment (Archer et al, 2017; Casalini & Bisigato, 2018; García‐Fayos et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

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Shrub encroachment occurs near previously invaded areas in Patagonia (southern South America)

Romero‐Ovalle,

Campanella,

Pascual

et al. 2023

Land Degrad Dev

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During the last century shrub encroachment has occurred in many arid and semiarid areas of the world. Patagonia is a large xeric territory located in the southern tip of South America, which has been grazed by sheep for more than a century. In many areas overgrazing led to vegetation change (shrub encroachment), which in turn reduced sheep carrying capacity and caused ranch abandonment. However, these changes in physiognomy did not occur everywhere, and even some authors did not find evidence that shrub encroachment is currently occurring. Our objectives were to determine if encroachment really happened in NE Patagonia and, in the case of confirming shrub encroachment, to evaluate if the increase in shrub density was spatially homogeneous. We used object‐based image analysis to evaluate shrub density and cover in aerial photographs taken in 1970 and 2018. In both dates, shrub density showed a clear contrast between two kinds of areas showing higher and lower density than was expected by chance. Shrub density and cover more than doubled between 1970 and 2018. This increase was concentrated in those areas with moderate or high densities of shrubs in 1970. Our results confirm the occurrence of shrub encroachment in NE Patagonia and demonstrate that it is currently concentrated near previously invaded areas. These findings have implications when defining protocols for monitoring shrub encroachment since monitors should focus on both areas that already have shrubs and areas that lack them.

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Section: Discussionsupporting

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Shrub encroachment occurs near previously invaded areas in Patagonia (southern South America)

Romero‐Ovalle,

Campanella,

Pascual

et al. 2023

Land Degrad Dev

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“…The impacts of slope aspect on woody plant encroachment through changes in density/cover are highly variable and suggest that cooler slopes result in higher shrub encroachment in the mountain rangelands [ 17 , 48 ]; Table 1 ). In their study on the topographic controls of Pteronia incana (Blue bush) in Great fish thicket rangelands in South Africa, Kakembo et al [ 49 ] reported higher shrub density on the cooler slopes.…”

Section: Effect Of Topographic Factors On Woody Plant Encroachmentmentioning

confidence: 99%

“…In mountainous rangelands, slope position regulates the microclimate and the physico-chemical characteristics of the soil, which in turn impacts the growth of woody plants [ 40 , 83 ]. Despite this, little is known about how slope position affects the encroachment of woody plants as some authors report that encroachment is higher on upslope position [ 48 , 52 , 57 , 58 , [84] , [85] , [86] , [87] ], while others report higher encroachment on the midslope position [ 88 ]5; [ 78 ] as well as downslope position [ 53 , [82] , [89] , [90] ] or no significant changes [ 76 , [91] , [92] , [93] ].…”

Section: Effect Of Topographic Factors On Woody Plant Encroachmentmentioning

confidence: 99%

The role of topographic and soil factors on woody plant encroachment in mountainous rangelands: A mini literature review

Gxasheka,

Gajana,

Dlamini

2023

Heliyon

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A bibliometric analysis for remote sensing applications in bush encroachment mapping of grassland and savanna ecosystems

Gcayi,

Adelabu,

Nduku

et al. 2024

Appl Geomat

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Grasslands and savannas are experiencing transformation and degradation due to bush encroachment (BE). BE has been monitored using restrictive traditional techniques that include field surveys and manual long-term observations. Owing to the limitations of traditional techniques, remote sensing (RS) is an attractive alternative to assess BE because of its generally high precision and return interval, cost-effectiveness, and availability of historical data archives. Furthermore, RS has an added advantage in its ability of acquiring global coherent data in near-real time compared to the snapshot acquisition mode with traditional surveying techniques. Despite its extensive application and vast possibilities, a critical synthesis for RS successes, shortcomings, and best practices in mapping BE in savannas and grasslands is lacking. Thus, broadly, the direction, which this type of investigation has taken over the years is largely unknown. This study sought to connect and measure the progress RS has made in mapping BE in grassland and savanna ecosystems through bibliometric analysis. One hundred and twenty-three peer-reviewed English written documents from the Web of Science and Scopus databases were evaluated. The study revealed 13.05% average annual publication growth, indicating that RS and BE mapping research in grasslands and savannas has been increasing over the survey period. Most published studies came from the USA, while the rest came from South Africa, China, and Australia. The results indicate that BE has been extensively mapped in grasslands and savannas using coarse to medium resolution data. As a result, there is a weak relationship (r² = 0.324) between the dependent variable (aerial images) and the independent variable (percentage of woody cover). This connotes the need to improve BE assessments in grasslands and savannas by integrating recent high-resolution data, machine learning algorithms and artificial intelligence.

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Mapping shrub cover in grasslands with an object-based approach and investigating the connection to topo-edaphic factors

Cited by 6 publications

References 47 publications

Shrub encroachment occurs near previously invaded areas in Patagonia (southern South America)

Shrub encroachment occurs near previously invaded areas in Patagonia (southern South America)

The role of topographic and soil factors on woody plant encroachment in mountainous rangelands: A mini literature review

A bibliometric analysis for remote sensing applications in bush encroachment mapping of grassland and savanna ecosystems

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