Abstract
Prescribed fires are one of the most effective tools to reduce the risk of wildfires but this treatment may negatively affect the hydrological and erosive response of soil, with noticeable ...increases in surface runoff and soil erosion. Many studies have been published on this matter but there is no consensus in the literature on the magnitude and duration of these effects since the relevant hydrological conditions are site‐specific. Moreover, the relationship between post‐fire hydrology and its main environmental drivers has been little explored. This study has carried out a bibliographic review and a meta‐analysis of the changes resulting from prescribed fire applications (water infiltration, soil water repellency (SWR), surface runoff and soil erosion) using a database of 85 case studies from 41 academic papers that have been published over the last 23 years. The effects of annual precipitation, soil slope, burn severity, fire application season, post‐fire ground cover, and vegetation type on those changes have also been statistically explored. The bibliographic review has revealed that previous case studies have not been equally distributed across the globe but concentrated in only a few countries, mainly the United States and Spain. The meta‐analysis has revealed that (i) water infiltration generally decreases and SWR appears with noticeable increases in surface runoff and soil erosion immediately after the prescribed fire, while the pre‐fire values progressively recover over time; (ii) the window of disturbance in burned soils may last a few months (with some exceptions); (iii) annual precipitation and soil slope significantly influence water infiltration and surface runoff, but not soil erosion, in both the short‐term and medium‐term; (iv) moderate‐to‐high levels of soil burn severity severely enhance surface runoff and soil erosion, and noticeably reduce water infiltration in the short‐term; (v) the level of ground cover burning is important for reducing the runoff rates, but it plays a minor role in water infiltration and soil erosion rates;and (vi) the prescribed fire applied in spring results in lower increases in short‐term runoff and erosion, while fire applications in summer and in shrublands produce the highest increases in soil loss. The following practical recommendations arise from this study: (i) research should be better distributed across all environmental contexts on a global scale; (ii) post‐fire management actions should be immediately implemented after the prescribed fire application; (iii) prescribed fire should be carried out in spring and the soil burn severity should be kept low during burning; (iv) the monitoring studies should be prolonged at least for some years (more than two or three) after prescribed fire; (iv) the catchment‐scale investigations, although more difficult and expensive, should be encouraged (avoiding, however, areas to sparsely burnt in the context of the whole catchment); (v) the monitored variables should also include the most important physical, chemical and biological properties of soil, the cover and structure of regenerating vegetation, as well as the water quality parameters; (vi) the effects of repeated applications of prescribed fire should be experimentally assessed; and (vii) guidelines for standardized and appropriate measurements and analytical methods in experimental activities should be set up. These indications support the use of land managers in the monitoring of the hydrological impacts of the prescribed fire and in the choice of sites where post‐fire management actions must be implemented. The last recommendation of this study is the creation of an experimental database supporting the bibliographic review and the meta‐analysis, which is made available to other researchers and land managers, to create a public, easily‐accessible and comprehensive tool for future research needs and professional use.
Natural forest succession after disturbances is one of the most important restoration strategies. However, the responses of ecosystem multifunctionality during natural forest succession remains ...poorly understood in forest ecosystem.
Here we evaluated how the ecosystem multifunctionality including nutrient cycling, carbon stocks, water regulation, decomposition, wood production and symbiosis develops using a chronosequence, and identified the key factors contributing to the variations in the ecosystem multifunctionality during natural forest succession.
We provide evidence that the ecosystem multifunctionality gradually increased along with succession stages. The individual functions of carbon stocks and water regulation also exhibited increasing patterns with stand development. The microbial diversity were more principal factors than plant diversity and soil properties for the explanation of changes in the ecosystem multifunctionality. The regression analysis showed that the diversity of bacteria, general fungi, actinomycetes, nematodes, G+ bacteria and G− bacteria significantly and positively associated with ecosystem multifunctionality. Soil nematodes exhibited significantly positive correlation with most of the individual functions.
Synthesis and applications. Taken together, our results demonstrate that natural forest restoration plays a key role in promoting ecosystem multifunctionality, and emphasize the importance of soil microbial diversity for the maintenance of ecosystem functions and health.
Taken together, our results demonstrate that natural forest restoration plays a key role in promoting ecosystem multifunctionality, and emphasize the importance of soil microbial diversity for the maintenance of ecosystem functions and health.
Check dams are widespread and effective soil and water conservation structures throughout the world. This review paper presents an overview of the use of check dams for soil and water management and ...runoff control with examples from the literature based on field measurements from four continents. More than 150years of research has reported that check dams are civil engineering landmark structures used all over the world. Among all civil engineering structures, check dams are probably the most emblematic of torrent control works. They were used for centuries, and are located all around the world. Over the past several hundred years, people have increasingly realized the envisioned advantages of check dams such as land development, environmental improvement, agricultural production, enhancement of gully stabilities, and mitigation of intensive flood. The optimum size, location and type had great influences on the efficiency of check dams under watershed management. Moreover, in both the theoretical and practical realms, check dams have been proved to be a useful tool for controlling soil erosion and flooding at a catchment scale. This paper will be helpful for policy makers to extend check dam projects in the whole erosion-prone areas.
The extant development and research on check dams conducted in various parts of the world. Display omitted
•This paper reviews a large number of check dam studies all around the world.•Check dams are used for soil conservation, flood mitigation and land development.•Check dams also play eminent roles to provide number of ecological functions.
Soil protists play a key role in driving ecological functions through predation and parasitism. However, little is known about how nitrogen (N) deposition and seasonal variation influence soil ...protist functions in forest soils.
Here, we assessed first the impacts of N deposition (control, 50, 100 and 150 kg N ha−1 year−1) on the functional composition of the soil protist community in summer and winter, using amplicon sequencing of environmental DNA from a subtropical natural forest.
We found that soil protists were dominated by consumers (42.6%–51.6%), followed by parasites (32.9%–40.9%) and phototrophs (3.2%–13.1%), implying a predominant role of consumers and potential top‐down effects on the other trophic groups in subtropical forest soils. The functional composition of soil protists was greatly influenced by N deposition, but these responses were dependent on seasonal variation. The diversity of phototrophs was lower in summer than in winter. Instead, an opposite pattern was observed for consumers, resulting in a significantly higher protist diversity in summer than in winter. Furthermore, low and high N deposition simplified the structural complexity of soil protist communities, suggesting a nonlinear response of protist structural stability to N deposition.
Synthesis and applications. This study provides unprecedented evidence that seasonal variation plays an important role in regulating responses of soil protist functional composition to N deposition, and highlights the nonlinear effects of rising N deposition on the soil food web.
This study provides unprecedented evidence that seasonal variation plays an important role in regulating responses of soil protist functional composition to N deposition, and highlights the nonlinear effects of rising N deposition on the soil food web.
Over the last decades, the natural disturbance is increasingly putting pressure on European forests. Shifts in disturbance regimes may compromise forest functioning and the continuous provisioning of ...ecosystem services to society, including their climate change mitigation potential. Although forests are central to many European policies, we lack the long‐term empirical data needed for thoroughly understanding disturbance dynamics, modeling them, and developing adaptive management strategies. Here, we present a unique database of >170,000 records of ground‐based natural disturbance observations in European forests from 1950 to 2019. Reported data confirm a significant increase in forest disturbance in 34 European countries, causing on an average of 43.8 million m3 of disturbed timber volume per year over the 70‐year study period. This value is likely a conservative estimate due to under‐reporting, especially of small‐scale disturbances. We used machine learning techniques for assessing the magnitude of unreported disturbances, which are estimated to be between 8.6 and 18.3 million m3/year. In the last 20 years, disturbances on average accounted for 16% of the mean annual harvest in Europe. Wind was the most important disturbance agent over the study period (46% of total damage), followed by fire (24%) and bark beetles (17%). Bark beetle disturbance doubled its share of the total damage in the last 20 years. Forest disturbances can profoundly impact ecosystem services (e.g., climate change mitigation), affect regional forest resource provisioning and consequently disrupt long‐term management planning objectives and timber markets. We conclude that adaptation to changing disturbance regimes must be placed at the core of the European forest management and policy debate. Furthermore, a coherent and homogeneous monitoring system of natural disturbances is urgently needed in Europe, to better observe and respond to the ongoing changes in forest disturbance regimes.
Shifts in forest disturbance regimes may compromise the continuous provisioning of ecosystem services to society. Although forests in Europe are central to many policies, empirical data for understanding disturbance dynamics are lacking. We present a unique database of >170,000 ground‐based natural disturbance records in European forests from 1950 to 2019. Disturbances significantly increase over the study period, damaging on average 43.8 million m3 of timber volume per year. This is likely a conservative estimate due to under‐reporting. We estimated the magnitude of unreported damages to be between 8.6 and 18.3 million m3/year.
Display omitted
•Fire is a disruptive event for terrestrial ecosystems, especially for their living component.•Fire effects on soil-dwelling biota are chiefly related to fire severity and ...frequency.•Severe burning upsets the soil environment, and this can be more deleterious than direct killing.•Most organisms recolonize the burned soil if land use is not changed and erosion is limited.•Fire is a tremendous driver of ecosystem’s biodiversity.
Fire has always been a driving factor of life on Earth. Now that mankind has definitely joined the other environmental forces in shaping the planet, lots of species are threatened by human-induced variation in fire regimes. Soil-dwelling organisms, i.e., those organisms that primarily live in soil, suffer the numerous and different consequences of fire occurrence that are, however, often overlooked compared to those on vegetation and wildlife. Most of these organisms live in the uppermost soil layer, where fire-imposed temperatures on the ground are the highest insofar as they are lethal or dangerously upset natural habitats.
This contribution is a reasoned collation of findings from a number of works conducted worldwide that aims to gain insight into the immediate and longer-term impacts of single or repeated wild or prescribed fires on one group of soil-dwelling organisms or more.
In fire-prone ecosystems, fire is a controlling factor of soil biota biodiversity and activity, but also where it is infrequent its ecological footprint can be substantial and lasting. Generally, the immediate fire impact on soil biota is strictly related to the peak temperatures reached on the ground and their duration, and on a set of soil properties and water content. Vertebrates can escape overheating death by running away, searching for wet niches or burrowing deep into soil. Invertebrates and microorganisms, which have little or no mobility, succumb more easily to fire, but make up for this intrinsic vulnerability thanks to their greater fecundity at the population level.
Fire or burn severity, which can generally be defined as loss of organic matter aboveground and belowground, is the key factor of the indirect fire effects on soil-dwelling biota; whereas controlled burns do not often imply any substantial and lasting shift from the original situation, extreme and vast wildfires can have major consequences that may be severer than direct killing. In fact lairs are devastated, nutrient pools are heavily affected, food webs are upset, soil temperature and moisture regimes change, and toxic pyrogenic compounds remain in soil. All types of organisms can recolonise the burned area from their sanctuaries, provided that land use does not change, e.g., to pastures or arable fields, and prompt enough vegetation re-sprouting and/or encroachment prevent substantial soil erosion. Each major taxon has genera or species with useful traits and behaviours to resist fire or to recover from its unwelcome environmental legacy sooner than others. If burned soil does not undergo other fires that occur too closely together for the typical fire regime of that particular area, most of its living components are generally capable of returning to pre-fire levels in times that depend on a series of factors, such as fire severity and post-fire rainfall.
The response of soil biotas to climate change has the potential to regulate multiple ecosystem functions. However, it is still challenging to accurately predict how multiple climate change factors ...will affect multiple ecosystem functions. Here, we assessed the short‐term responses of agroecosystem multifunctionality to a factorial combination of elevated CO2 (+200 ppm) and O3 (+40 ppb) and identified the key soil biotas (i.e., bacteria, fungi, protists, and nematodes) concerning the changes in the multiple ecosystem functions for two rice varieties (Japonica, Nanjing 5055 vs. Wuyujing 3). We provided strong evidence that combined treatment rather than individual treatments of short‐term elevated CO2 and O3 significantly increased the agroecosystem multifunctionality index by 32.3% in the Wuyujing 3 variety, but not in the Nanjing 5055 variety. Soil biotas exhibited an important role in regulating multifunctionality under short‐term elevated CO2 and O3, with soil nematode abundances better explaining the changes in ecosystem multifunctionality than soil biota diversity. Furthermore, the higher trophic groups of nematodes, omnivores‐predators served as the principal predictor of agroecosystem multifunctionality. These results provide unprecedented new evidence that short‐term elevated CO2 and O3 can potentially affect agroecosystem multifunctionality through soil nematode abundances, especially omnivores‐predators. Our study demonstrates that high trophic groups were specifically beneficial for regulating multiple ecosystem functions and highlights the importance of soil nematode communities for the maintenance of agroecosystem functions and health under climate change in the future.
Changes in soil nematode abundance partially explain the effects of short‐term elevated CO2 and O3 on multiple ecosystem functions. Soil biotas exhibit an important role in regulating multifunctionality under short‐term elevated CO2 and O3. Soil nematode abundances better explain the changes in ecosystem multifunctionality than soil biota diversity. Soil omnivores‐predators serve as the principal predictor of agroecosystem multifunctionality.
The shift in ecosystem multifunctionality during ecosystem succession (years to decades) remains largely unexplored. In this study, we used a 120-year-old pine temperate forest chronosequence (1: ...1–19 years, stage 2: 20–39 years, stage 3: 40–59 years, stage 4: 60–79 years, stage 5: 80–99 years, stage 6: 100–120 years) to evaluate the role that time plays in shaping ecosystem multifunctionality (nutrient cycling, carbon stocks, water regulation, decomposition and wood production), and found that, over the first century, ecosystem functioning gradually increased every ~50 years. Such a result was maintained for individual groups of ecosystem functions and services including nutrient cycling, carbon stocks, decomposition and wood production. Plant diversity and soil stoichiometry (C:N ratio) were the major environmental predictors for the changes in ecosystem multifunctionality during forest secondary succession. Plant diversity increased during ecosystem succession and was positively related to ecosystem multifunctionality. The soil C:N ratio decreased during ecosystem succession and was negatively related to multifunctionality. Our results suggest that increases in aboveground resource heterogeneity (higher plant diversity) and organic matter quality (lower soil C:N ratios) could help explain the increases in multifunctionality over a century of forest development. Our work illustrates the importance of time in shaping multifunctionality during the first century of ecosystem succession, and further provide important insights for the management of temperate forest ecosystems.
Display omitted
•We used a 120-year-old forest chronosequence to evaluate forest multifunctionality.•Plant diversity was an environmental predictor of ecosystem multifunctionality.•The C:N ratio significantly affects the ecosystem multifunctionality.•Our work illustrates the importance of time in shaping multifunctionality.
Forest land affected by deforestation yields high soil and water losses. Suitable management practices need to be found that can reduce these losses and achieve ecological and hydrological ...sustainability of the deforested areas. Mulch has been found to be effective in reducing soil losses; straw mulch is easy to apply, contributes soil organic matter, and is efficient since the day of application. However, the complex effects of rice straw mulch with different application rates and lengths on surface runoff and soil loss have not been clarified in depth. The current paper evaluates the efficiency of rice straw mulch in reducing the hydrological response of a silty clay loam soil under high intensity and low frequency rainfall events (tap water with total depth of 49 mm and intensity of 98 mm/h) simulated in the laboratory. Surface runoff and soil loss at three lengths of the straw (10, 30, and 200 mm) and three application rates (1, 2, and 3 Mg/ha) were measured in 50 cm (width) × 100 cm (length) × 10 cm (depth) plots with disturbed soil samples (aggregate soil size < 4 mm) collected in a deforested area. Bare soil was used as control experiment. Runoff volume and erosion were significantly (at p < 0.05) lower in mulched soils compared to control plots. These reductions were ascribed to the water absorption capacity of the rice straw and the protection cover of the mulch layer. The minimum runoff was observed for a mulch layer of 3 Mg/ha of straw with a length of 200 mm. The lowest soil losses were found with straw length of 10 mm. The models developed predict runoff and erosion based on simple linear functions of mulch application rate and length, and can be used for a suitable hydrological management of soil. It is concluded that, thanks to rice straw mulch used as an organic soil conditioner, soil erosion and surface runoff are significantly (at p < 0.05) reduced, and the mulch protection contributes to reduce the risk of soil degradation. Further research is, however, needed to analyze the upscaling of the hydrological effects of mulching from the plot to the hillslope scale.
•Understanding the effects of rice straw mulch on surface runoff and soil loss is needed.•This study examines the effects of straw length and application rates on runoff and erosion rates.•Lowest and highest surface covers were measured in plots with 200-mm and 10-mm straw lengths, respectively.•200-mm straw length plots had the highest soil loss and the lowest runoff values.•10-mm straw mulch applied at 3 Mg/ha minimized soil loss.
Forest fires and post‐fire practices influence sediment connectivity (SC). In this study, we use the ‘aggregated index of connectivity’ (AIC) to assess SC in five Mediterranean catchments (198–1090 ...ha) affected by a wildfire in 2012 in south‐eastern Spain. Two temporal scenarios were considered, immediately after the fire and before post‐fire management, and 2 years after the fire including all practices (hillslope barriers, check‐dams, afforestation, salvage logging and skid trails). One LiDAR (light detection and ranging)‐derived digital elevation model (DEM, 2 m × 2 m resolution) was generated, per scenario. The five catchment outlets were established as the computation target (AICOUT), and structural and functional SC were calculated. Index outputs were normalized to make the results of the non‐nested catchments comparable (AICN‐OUT). The output analysis includes the SC distribution along the catchments and at local scale (929 sub‐catchments, 677 in the burned area), the hillslope and channel measures' effect on SC, and a sedimentological analysis using observed area‐specific sediment yield (SSY) at 10 new (built after post‐fire practices) concrete check‐dams located in the catchments (SSY = 1.94 Mg ha−1 yr−1; σ = 1.22). The catchments with more circular shapes and steeper slopes were those with higher AICN‐OUT. The structural SC maps – removing the rainfall erosivity influence – allowed evaluating the actual role played by the post‐fire practices that reduced SC (
x¯= − 1.19%; σ = 0.41); while functional SC was linked to the actual change of SC (
x¯= + 5.32%; σ = 0.62). Hillslope treatments resulted in significant changes on AICN‐OUT at sub‐catchment scale with certain disconnectivity. A good and positive correlation was found between the SSY and the changes of AICN‐OUT. However, the coarse DEM resolution explained the lack of effect of the rock check‐dams – located on the secondary channels – on AICN‐OUT. AICN‐OUT proved to be a useful tool for decision making in post‐fire restoration, but an optimal input data is still necessary to refine calculations.
Sediment connectivity has been studied in a burned area in two temporal scenarios, Pre‐management scenario (AIC 2012; just after wildfire) and post‐management (AIC 2014; after the application of post‐fire mitigation measures). The AIC index was calculated for 5 catchments with a structural and a functional approach. Differences between scenarios and approaches were observed and a positive relationship between the temporal AIC changes and the Specific sediment yield (SSY) measured in the catchments.
PDF
