Seed‐based ecosystem restoration has huge potential to restore degraded drylands. However, fewer than 10% of directly sown seeds transition to established seedlings. One of the potential factors ...restricting plant establishment in degraded soils is the low abundance and diversity of native soil micro‐organisms. In this study, we investigated whether returning indigenous bacteria and cyanobacteria consortia to degraded dryland soils improved seedling emergence, survival and growth of native plants.
We inoculated ‘culturable whole soil’ native heterotrophic bacteria and biocrust cyanobacteria individually and as a mixed inoculant into extruded pellets containing Acacia inaequilatera (Fabaceae) and Triodia epactia (Poaceae) seeds. The pellets were planted in an active minefield for 28 weeks and seedling emergence and total biomass of plants were determined.
Cyanobacteria and bacteria inoculants increased the emergence of A. inaequilatera by 55% and 48%, respectively. Seedling emergence in T. epactia was increased by 20% by cyanobacteria but was not increased by bacteria. The only effect of inoculation on seedling survival or mass per surviving seedling in either species was an 11% reduction of the growth of T. epactia seedlings that were inoculated with cyanobacteria.
Synthesis and applications: Our results suggest that the benefit of micro‐organisms on plant establishment is both species specific and life stage specific, with particularly strong benefits in the early stages of recruitment. Our experiment was conducted under shade and with additional water, so a worthwhile future direction would be to quantify the effect of inoculation under unmodified field conditions. It would also be worthwhile monitoring the outcomes for longer than 28 weeks. Since seedling emergence is one of the critical challenges in dryland restoration, our study provides direct evidence in the use of native micro‐organisms to potentially improve seedling emergence in seed‐based dryland restoration.
Our results suggest that the benefit of micro‐organisms on plant establishment is both species specific and life stage specific, with particularly strong benefits in the early stages of recruitment. Our experiment was conducted under shade and with additional water, so a worthwhile future direction would be to quantify the effect of inoculation under unmodified field conditions. It would also be worthwhile monitoring the outcomes for longer than 28 weeks. Since seedling emergence is one of the critical challenges in dryland restoration, our study provides direct evidence in the use of native micro‐organisms to potentially improve seedling emergence in seed‐based dryland restoration.
So‐called fairy circles (FCs) comprise a spatially periodic gap pattern in arid grasslands of Namibia and north‐west Western Australia. This pattern has been explained with scale‐dependent ...ecohydrological feedbacks and the reaction‐diffusion, or Turing mechanism, used in process‐based models that are rooted in physics and pattern‐formation theory. However, a detailed ecological test of the validity of the modelled processes is still lacking.
Here, we test in a spinifex‐grassland ecosystem of Western Australia the presence of spatial feedbacks at multiple scales. Drone‐based multispectral analysis and spatially explicit statistics were used to test if grass vitality within five 1‐ha plots depends on the pattern of FCs that are thought to be a critical extra source of water for the surrounding matrix vegetation. We then examined if high‐ and low‐vitality grasses show scale‐dependent feedbacks being indicative of facilitation or competition. Additionally, we assessed facilitation of grass plants for different successional stages after fire at fine scales in 1‐m2 quadrats. Finally, we placed soil moisture sensors under bare soil inside the FC gap and under plants at increasing distances from the FC to test if there is evidence for the ‘infiltration feedback’ as used in theoretical modelling.
We found that high‐vitality grasses were systematically more strongly associated with FCs than low‐vitality grasses. High‐vitality grasses also had highly aggregated patterns at short scales being evidence of positive feedbacks while negative feedbacks occurred at larger scales. Within 1‐m2 quadrats, grass cover and mutual facilitation of plants was greater near the FC edge than further away in the matrix. Soil moisture after rainfall was lowest inside the FC with its weathered surface crust but highest under grass at the gap edge, and then declined towards the matrix, which confirms the infiltration feedback.
Synthesis. The study shows that FCs are a critical extra source of water for the dryland vegetation, as predicted by theoretical modelling. The grasses act as ‘ecosystem engineers’ that modify their hostile, abiotic environment, leading to vegetation self‐organization. Overall, our ecological findings highlight the validity of the scale‐dependent feedbacks that are central to explain this emergent grassland pattern via the reaction‐diffusion or Turing‐instability mechanism.
Spatially periodic vegetation patterns of drylands have been extensively modelled by physicists based on ecohydrological feedbacks and the reaction‐diffusion or Turing mechanism. A detailed ecological test of the validity of such processes, however, is still pending. Based on the Australian fairy circles, we show that short‐range positive and long‐range negative feedbacks between plants are indeed explaining such emergent vegetation patterns.
A thorough knowledge of soil functionality is critical to successful restoration of disturbed ecosystems, and its evaluation involves the assessment of soil properties and processes as a component of ...a healthy ecosystem. Here, we propose a set of soil quality indicators to assess the soil status in restored soils (topsoil and waste material) and test new methods that are easy to apply, interpret, and cost‐effective for the analysis of soil biological indicators in restored ecosystems. We show that in addition to organic carbon and C:N ratio, biological indicators (microbial diversity and activity in particular) are the most sensitive indicators to detect differences among reconstructed soils and analogue undisturbed soils in semiarid areas. The use of the 1‐day CO2 test is proven to be an alternative cost‐ and time‐effective method to measure microbial activity and assess soil functionality of restored soils. Our results show a positive effect of vegetation on reconstructed soils and a recovery of soil functionality in waste material to levels similar to topsoil once vegetation is established. However, soil functionality in both restored waste materials and topsoils is still far from that in undisturbed native soils. We conclude that soil functionality is critical in the restoration process, particularly in semiarid areas, and the methods used here could be effectively applied in a broad range of restoration projects in arid and semiarid environments.
Cyanobacteria are photosynthetic bacteria that form a fundamental part of soil biocrusts, enhance soil function and structure, and can promote plant growth. We assessed the potential of cyanobacteria ...as a seed bio‐primer for mine‐site restoration in an arid region in Western Australia, examining its effects on native plant growth and the characteristics of mine soil substrates used in dryland restoration. Cyanobacteria strains indigenous to the study region (Leptolyngbya sp., Microcoleus sp., Nostoc sp., and Scytonema sp.) were used to create an inoculant. Seeds of seven native plant species were bio‐primed with the inoculant, and their germination and growth assessed in a laboratory experiment. Seedling growth after bio‐priming was assessed in a glasshouse experiment for a subset of three species, in two different substrates (topsoil and mine waste). Soil properties related to soil function, e.g. total organic carbon, total nitrogen, and microbial activity, were also measured. Minor effects on germination were recorded with only significantly higher germination rates reported in E. gamophylla. Soil parameters were generally higher in topsoil than in mine waste, regardless of bio‐priming treatment. However, bio‐priming resulted in seedlings of four species producing longer radicles and/or shoots. For example, seedling root lengths of bio‐primed G. wickhamii were 57% larger than the control treatment (30.1 ± 4.3 and 13.0 ± 1.6 mm, respectively); and shoots of T. wiseana were 54% longer in the bio‐primed treatment (18.6 ± 1.6 mm) compared to the control (8.53 ± 1.4 mm). Overall, our results highlight that bio‐priming with cyanobacteria may improve plant growth for some species commonly used in dryland restoration.
Forest are highly vulnerable to global change drivers, such as an increase in wildfire events. Learning more about how and why different post‐fire management strategies regulate the ability of forest ...ecosystem properties (e.g. plant diversity and function) to simultaneously recover after wildfire and provide multiple ecosystem functions is of critical importance.
This study aims to evaluate how unburned, burned managed and burned unmanaged plots regulate the responses of multiple forest ecosystem properties (e.g. plant diversity, nutrient cycling, soil carbon stocks, water regulation, decomposition and wood production) and overall multifunctionality to wildfires. In September 2017, we selected two post‐fire management strategies in a 3‐km2 watershed previously affected by a wildfire in July 2012: contour‐felled log debris (CFD), log erosion barriers area (LEB), and also unburned and unmanaged plots (BNA). We randomly distributed 12 plots among the three post‐fire management strategies (three plots per treatment) and unburned.
The results showed that multiple forest ecosystem properties were significantly affected by wildfire and that specific post‐fire management treatment (e.g. LEB and CFD) can be used to efficiently support plant diversity and ecosystem functioning. Our results revealed that the general indicators of ecosystem functions decreased in Mediterranean forests after wildfires and post‐fire management strategies (LEB and CFD) significantly helped to recover the ecosystems’ short‐term community‐level properties and ecosystem functions (5 years after a wildfire event) to pre‐fire levels.
Synthesis and applications. These findings demonstrate that multiple ecosystem functions are affected by wildfires in Mediterranean forests and show that post‐fire management treatments can promote multifunctionality and plant diversity. Our results unfold the potential of log erosion barriers (LEB) and contour‐felled log debris (CFD) as effective strategies for recovering community‐level properties and forest functions in the short term.
These findings demonstrate that multiple ecosystem functions are affected by wildfires in Mediterranean forests and show that post‐fire management treatments can promote multifunctionality and plant diversity. Our results unfold the potential of log erosion barriers (LEB) and contour‐felled log debris (CFD) as effective strategies for recovering community‐level properties and forest functions in the short term.
•We assessed short, medium, and long term changes in soil indicators after wildfire.•Soil pH, electrical conductivity and available P are higher immediately after fire.•Fungi to bacteria ratio and ...microbial quotient are sensitive indices of soil recovery.•Changes in the microbial composition are apparent one year after the fire.•Soil ecosystems partially recover in the medium term (five years following fire).
Natural disturbances such as wildfires cause significant alterations to the structure and functioning of semi-arid ecosystems. After such disturbances, the recovery of the soil ecosystem as a whole, and more specifically the belowground microbial communities, is poorly understood. In this study, we aimed to (a) assess the short, medium and long term changes in soil physicochemical and microbiological indicators and indices after a wildfire in a semi-arid environment, (b) analyse the key relationships of multiple soil parameters and indices, and (c) identify the most suitable indicators of post-fire recovery. The study was conducted across a wildfire chronosequence spanning sites recently burnt (three months) through to 14 years after fire in a semi-arid hummock grassland ecosystem of northern Western Australia. Immediate effects of the fire on the soil system were evident with increases in pH, electrical conductivity, and available nutrients. These chemical indicators showed a strong correlation with fire age and were consistent in the direction of change. Variations in the microbial composition were apparent one year after the fire, with a higher proportional abundance of bacterial communities. The fungi to bacteria ratio and the microbial quotient (proportion of microbial C to total organic C) proved to be significant indices to reflect the recovery of soils in these semi-arid environments. Overall, this study highlights the importance of understanding the post-fire response of belowground ecosystems, and particularly changes and recovery of soil microbial communities, at different time periods. The approach and methods followed in this research can be effectively extrapolated to other areas. This study can be used to inform better soil management of degraded systems in a rapidly changing climate.
•A native-plant based amendment increased C and N contents of reconstructed soils.•High microbial activity and C mineralisation were found in the amended mine waste.•Low N mineralisation in amended ...soils suggests N immobilisation by soil microbes.•The amendment did not increase emergence, survival or growth of native plants.•Adding topsoil to reconstructed soils increase native plants' survival and growth.
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One of the most critical challenges faced in restoration of disturbed arid lands is the limited availability of topsoil. In post-mining restoration, alternative soil substrates such as mine waste could be an adequate growth media to alleviate the topsoil deficit, but these materials often lack appropriate soil characteristics to support the development and survival of seedlings. Thus, addition of exogenous organic matter may be essential to enhance plant survival and soil function. Here, we present a case study in the arid Pilbara region (north-west Western Australia), a resource-rich area subject to intensive mining activities. The main objective of our study was to assess the effects of different restoration techniques such as soil reconstruction by blending available soil materials, sowing different compositions of plant species, and addition of a locally abundant native soil organic amendment (Triodia pungens biomass) on: (i) seedling recruitment and growth of Triodia wiseana, a dominant grass in Australian arid ecosystems, and (ii) soil chemical, physical, and biological characteristics of reconstructed soils, including microbial activity, total organic C, total N, and C and N mineralisation. The study was conducted in a 12-month multifactorial microcosms setting in a controlled environment. Our results showed that the amendment increased C and N contents of re-made soils, but these values were still lower than those obtained in the topsoil. High microbial activity and C mineralisation rates were found in the amended waste that contrasted the low N mineralisation but this did not translate into improved emergence or survival of T. wiseana. These results suggest a short- or medium-term soil N immobilisation caused by negative priming effect of fresh un-composted amendment on microbial communities. We found similar growth and survival rates of T. wiseana in topsoil and a blend of topsoil and waste (50:50) which highlights the importance of topsoil, even in a reduced amount, for plant establishment in arid land restoration.
Editorial: Fire in the environment Muñoz-Rojas, Miriam; Pereira, Paulo
Journal of environmental management,
2020-Jan-01, 2020-01-00, 20200101, Volume:
253
Journal Article
Restoring soil biodiversity Robinson, Jake M.; Liddicoat, Craig; Muñoz-Rojas, Miriam ...
Current biology,
05/2024, Volume:
34, Issue:
9
Journal Article
Peer reviewed
Soil health is crucial for all terrestrial life, supporting, among other processes, food production, water purification and carbon sequestration. Soil biodiversity — the variety of life within soils ...— is key to these processes and thus key to soil restoration. Human activities that degrade ecosystems threaten soil biodiversity and associated ecosystem processes. Indeed, 75% of the world’s soils are affected by degradation — a figure that could rise to 90% by 2050 if deforestation, overgrazing, urbanisation and other harmful practices persist. Restoring soil biodiversity is a prerequisite for planetary health, and it comes with many challenges and opportunities. Soil directly supports around 60% of all species on Earth, and land degradation poses a major problem for this biodiversity and the ecosystem services that sustain human populations. Indeed, 98% of human calories come from soil, and earthworms alone underpin 6.5% of the world’s grain production. Moreover, the total carbon in terrestrial ecosystems is around 3,170 gigatons (1 gigaton (Gt) = 1 billion metric tons), of which approximately 80% (2,500 Gt) is found in soil. Therefore, restoring soil biodiversity is not just a human need but an ecological and Earth-system imperative. It is pivotal for maintaining ecosystem resilience, sustaining agricultural productivity and mitigating climate change impacts.
Jake Robinson and colleagues discuss the challenges and opportunities to restore soil biodiversity — vital for life on Earth but under threat from ecosystem degradation.
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