The soil microbiomics of intact, degraded and partially-restored semi-arid succulent thicket (Albany Subtropical Thicket)

Abstract

This study examines the soil bacterial diversity in the Portulacaria afra-dominated succulent thicket vegetation of the Albany Subtropical Thicket biome; this biome is endemic to South Africa. The aim of the study was to compare the soil microbiomes between intact and degraded zones in the succulent thicket and identify environmental factors which could explain the community compositions. Bacterial diversity, using 16S amplicon sequencing, and soil physicochemistry were compared across three zones: intact (undisturbed and vegetated), degraded (near complete removal of vegetation due to browsing) and restored (a previously degraded area which was replanted approximately 11 years before sampling). Amplicon Sequence Variant (ASV) richness was similar across the three zones, however, the bacterial community composition and soil physicochemistry differed across the intact and degraded zones. We identified, via correlation, the potential drivers of microbial community composition as soil density, pH and the ratio of Ca to Mg. The restored zone was intermediate between the intact and degraded zones. The differences in the microbial communities appeared to be driven by the presence of plants, with plant-associated taxa more common in the intact zone. The dominant taxa in the degraded zone were cosmopolitan organisms, that have been reported globally in a wide variety of habitats. This study provides baseline information on the changes of the soil bacterial community of a spatially restricted and threatened biome. It also provides a starting point for further studies on community composition and function concerning the restoration of degraded succulent thicket ecosystems.

Relationships of the very low birth weight infant microbiome with neurodevelopment at 2 and 4 years of age

“…In order to better understand the microbial ecology and interspecies interaction network of the gut microbiome of infants who were later classified as referrals and no referrals at 2 and 4 years of age, network The community networks suggest that children who required referral due to underachievement in the BDI 2 at 2 years of age had more complex interacting microbial networks in the NICU, but both at 2 and 4 years of age, microbes in the Clostridia class, mostly commensals, are abundant and are key taxa in the networks. It should also be noted that most of the interactions observed in this study were positive, which suggests that the interactions are stable and the interspecific competition is low (Schagen et al, 2021). Severe interspecific interactions might render the network unstable and lead to alteration over time.…”

Regeneration dynamics of Portulacaria afra in restored succulent thicket of South Africa

“…The loss of canopy cover, therefore, halts broad community assembly processes in degraded succulent thicket, evident in the general lack of seedlings reported in degraded thicket ( Sigwela et al, 2009 ). Restoring this canopy by planting P. afra appears to reverse this loss of ecological functioning by regenerating soil organic carbon ( Schagen et al, 2021 ; van der Vyver et al, 2013 ; Mills & Cowling, 2006 ) and providing a cool, shaded microclimate. This has facilitated the return of natural recruitment of woody canopy species within 35 years of P. afra reintroduction ( van der Vyver et al, 2013 ) and the regeneration of soil bacterial community compositions within 12 years of P. afra reintroduction ( Schagen et al, 2021 ).…”

“…Restoring this canopy by planting P. afra appears to reverse this loss of ecological functioning by regenerating soil organic carbon ( Schagen et al, 2021 ; van der Vyver et al, 2013 ; Mills & Cowling, 2006 ) and providing a cool, shaded microclimate. This has facilitated the return of natural recruitment of woody canopy species within 35 years of P. afra reintroduction ( van der Vyver et al, 2013 ) and the regeneration of soil bacterial community compositions within 12 years of P. afra reintroduction ( Schagen et al, 2021 ). In the ad hoc experiment presented here, significant returns of P. afra recruitment were detected 12–13 years after restoration intervention.…”

“…This species is capable of facilitating landscape-scaled processes by modifying soil properties ( van Luijk et al, 2013 ; Lechmere-Oertel et al, 2008 ; Mills & Fey, 2004 ) and providing the micro-climate required for recruitment of woody canopy species ( Wilman et al, 2014 ; Sigwela et al, 2009 ). Many of these properties are reported to return in restored ecosystems, including the accumulation of soil organic carbon ( Schagen et al, 2021 ; Mills & Cowling, 2014 ; van der Vyver et al, 2013 ) and the recovery of some recruitment dynamics ( van der Vyver et al, 2013 ). The remainder of thicket restoration success has largely been quantified in terms of living P. afra individuals present in restoration plots, measured to evaluate different planting treatments implemented in the TWPs ( van der Vyver, Mills & Cowling, 2021a ; Mills & Robson, 2017 ).…”

Restoring South African subtropical succulent thicket using Portulacaria afra: root growth of cuttings differs depending on the harvest site during a drought

“…This loss of plant cover, including P. afra , results in the disruption of various ecological processes. Exposed soils are especially prone to: erosion due to higher rates of water runoff ( Mills & de Wet, 2019 ; van Luijk et al, 2013 ; Cowling & Mills, 2011 ); loss of soil organic carbon ( Mills & de Wet, 2019 ; Lechmere-Oertel et al, 2008 ); and a disruption of soil microbial communities ( Schagen et al, 2021 ). Furthermore, the loss of the cool, damp understory microclimate required for germination ( Wilman et al, 2014 ; Sigwela et al, 2009 ) halts woody species recruitment in the degraded landscape ( Lechmere-Oertel, Cowling & Kerley, 2005 ).…”