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Forest fires increase variability of soil macrofauna communities along a macrogeographic gradient
Abstract
We assessed the impact of forest fires on macrofauna taxonomic richness, abundance and total biomass in 20 forests burnt five years ago and 20 respective control plots along a 3000-km-long north-south transect in European Russia that covered five major forest types (Mediterranean and broadleaved forests , southern, middle, and northern taiga). In parallel we assessed basic soil abiotic parameters in these stands. Within forest type, the spatial variance of macrofauna total biomass was 1.8 times higher in the burnt forests than in the controls. Due to this increase of variance in the burnt forests, the main effect of forest type on soil macrofauna parameters was generally weaker. Among different soil abiotic parameters , higher level of uniformity of macrofaunal community parameters between different forest types was explained by the labile P and N content in the soil, water-holding capacity and soil moisture. Presence of open areas within the burnt forests seems to be the leading driver of the increased similarity of soil macrofauna communities across different forest types. Forest fires thus act as a powerful force that raises within-forest-type soil macroinvertebrate beta-diversity and associated biomass fluctuations. At the same time burning reduces soil macrofauna gamma-diversity due to increased faunistic similarity between different forest types. This has potentially important implications for the functioning of soil macroinvertebate communities in the pyrogenic forests and its dependency on macroclimatic conditions.
... The use and management of soil are two of the factors that cause a drastic reduction in the number of fauna groups present in the soil, leading to degradation, reduction, or loss of agricultural production capacity (GORBUNOVA et al., 2017;SIQUEIRA;SILVA;PAZ-FERREIRO, 2014). The reduction or extinction of some soil invertebrate groups, and the subsequent loss of their beneficial activities, contribute to the high rates of land deterioration, fertility decline, nutrient reduction, and increase in arthropod pests (BEDANO et al., 2014). ...
... In the same way, a desiccant application in the soybean plantation explains the lower abundance in this area in conjunction with the constant use of the pesticide. The edaphic community is mainly influenced by the anthropic action (GORBUNOVA et al., 2017), with respect to the use and management of the soil (ASSIS et al., 2017), which directly interferes with the abundance and diversity (SANTOS et al., 2008). This is associated with the physical disturbances and the changes in the quantity and quality of the organic matter (FARIAS; HERNÁDEZ, 2017;PANT et al., 2017). ...
Soil is the habitat for a number of living organisms that perform essential functions within the ecosystem; their functions and interactions are modified according to different ways of land occupation. Thus, the objective of this study was to evaluate the diversity of edaphic fauna in different soil occupation systems. The study was carried out in different soil occupation systems: millet, maize, soybean, eucalyptus, preserved cerrado, disturbed cerrado, and pasture, with 130 pitfall traps installed per treatment. Soil fauna organisms were identified at the level of large groups (orders and family), and then examined under the following biological diversity indices: Shannon index, Pielou index, average and total richness, and abundance. The highest abundance was found under millet growing conditions (9,974 individuals), and the lowest abundance values were found in soybean soil (222 individuals) and maize (824 individuals). Uniform distribution of groups in the area with soybean crops, due to the homogeneous management of the area, provided the highest biological index (H'=2.69). Principal component analysis (PCA) explained 50.9% of the data along the main axis and 34.6% of the data along the secondary axis. The different systems of soil occupation showed different abundance and diversity, demonstrating how soil occupation interferes with the dynamics of the invertebrate soil fauna.
... Práticas inadequadas de produção, o uso e o manejo do solo são fatores que causam uma redução extrema na população da fauna presentes solo, causando a degradação, redução ou perda da capacidade produtiva agrícola (Gorbunova et al., 2017). A redução ou extinção de alguns grupos de invertebrados do solo seguido da perda de suas atividades benéficas contribuem para altas taxas de deterioração da terra, diminuição da fertilidade, redução de nutrientes e aumento das pragas (Bedano et al., 2016). ...
Os organismos edáficos que habitam no solo exercem diversos papeis fundamentais no ecossistema do planeta, alguns são encarregados pela decomposição da matéria orgânica, disponibilizam nutrientes para o crescimento das plantas, melhoram a produtividade do solo, e ajudam a controlar os organismos indesejáveis no mesmo. O objetivo deste trabalho foi comparar a diversidade da fauna do solo em propriedades agrícolas no município de Dom Pedrito que está localizado no estado do Rio Grande do Sul. O estudo foi conduzido em duas propriedades rurais do município, com campo natural e produção olerícola. A coleta dos organismos edáficos ocorreu em janeiro (verão) do ano de 2020. Para a captura dos invertebrados foi utilizado armadilhas do tipo PROVID com espaçamento de 10m, totalizando 20 armadilhas em cada área. Depois de sete dias as armadilhas foram retiradas, levadas ao laboratório e posteriormente, encaminhadas para identificação. A fauna edáfica foi avaliada quantitativamente por meio da abundância das ordens, e qualitativamente por meio do Índice de Dominância de Simpson (D). Os parâmetros avaliados para a população da fauna edáfica foram riqueza: abundância, índice de diversidade de Simpson e de Shannon. Os grupos taxonômicos encontrados foram: i) Aracnídea (ácaros, aranhas, opiliões e escorpiões); ii) Hymenoptera; iii) Hemíptera; iv) Homóptera, v) Collembola; vi) Crustaceae e; vii) Demáptera.Â
... Práticas inadequadas de produção, o uso e o manejo do solo são fatores que causam uma redução extrema na população da fauna presentes solo, causando a degradação, redução ou perda da capacidade produtiva agrícola (Gorbunova et al., 2017). A redução ou extinção de alguns grupos de invertebrados do solo seguido da perda de suas atividades benéficas contribuem para altas taxas de deterioração da terra, diminuição da fertilidade, redução de nutrientes e aumento das pragas (Bedano et al., 2016). ...
Diversidade de Organismos Edáficos em Campo Natural e Olericultura em Dom Pedrito, Município Situado no Bioma Pampa RESUMO-Os organismos edáficos que habitam no solo exercem diversos papeis fundamentais no ecossistema do planeta, alguns são encarregados pela decomposição da matéria orgânica, disponibilizam nutrientes para o crescimento das plantas, melhoram a produtividade do solo, e ajudam a controlar os organismos indesejáveis no mesmo. O objetivo deste trabalho foi comparar a diversidade da fauna do solo em propriedades agrícolas no município de Dom Pedrito que está localizado no estado do Rio Grande do Sul. O estudo foi conduzido em duas propriedades rurais do município, com campo natural e produção olerícola. A coleta dos organismos edáficos ocorreu em janeiro (verão) do ano de 2020. Para a captura dos invertebrados foi utilizado armadilhas do tipo PROVID com espaçamento de 10m, totalizando 20 armadilhas em cada área. Depois de sete dias as armadilhas foram retiradas, levadas ao laboratório e posteriormente, encaminhadas para identificação. A fauna edáfica foi avaliada quantitativamente por meio da abundância das ordens, e qualitativamente por meio do Índice de Dominância de Simpson (D). Os parâmetros avaliados para a população da fauna edáfica foram riqueza: abundância, índice de diversidade de Simpson e de Shannon. Os grupos taxonômicos encontrados foram: i) Aracnídea (ácaros, aranhas, opiliões e escorpiões); ii) Hymenoptera; iii) Hemíptera; iv) Homóptera, v) Collembola; vi) Crustaceae e; vii) Demáptera. Palavras-chave: Biodiversidade; fauna edáfica; manejo do solo. ABSTRACT-The edaphic organisms that live in the soil have several fundamental roles in the planet's ecosystem, some are responsible for the decomposition of organic matter, provide nutrients for plant growth, improve soil productivity, and help to control undesirable organisms in it. The objective of this work was to compare the diversity of soil fauna in agricultural properties in the municipality of Dom Pedrito, which is located in the state of Rio Grande do Sul. The study was conducted in two rural properties in the municipality, with rangelands and vegetable production. The collection of edaphic organisms took place in January (summer) of the year 2020. For the capture of invertebrates, PROVID-totaling 20 traps in each area. After seven days, the traps were removed, taken to the laboratory and later forwarded for identification. The edaphic fauna was evaluated quantitatively through the abundance of orders, and qualitatively through the Simpson Dominance Index (D). The parameters evaluated for the population of the edaphic fauna were wealth: abundance, Simpson and Shannon diversity index. The taxonomic groups found were: i) Arachnid (mites, spiders, harvestmen and scorpions); ii) Hymenoptera; iii) Hemiptera; iv) Homoptera, v) Collembola; vi) Crustaceae e; vii) Demáptera.
... Práticas inadequadas de produção, o uso e o manejo do solo são fatores que causam uma redução extrema na população da fauna presentes solo, causando a degradação, redução ou perda da capacidade produtiva agrícola (Gorbunova et al., 2017). A redução ou extinção de alguns grupos de invertebrados do solo seguido da perda de suas atividades benéficas contribuem para altas taxas de deterioração da terra, diminuição da fertilidade, redução de nutrientes e aumento das pragas (Bedano et al., 2016). ...
Os organismos edáficos que habitam no solo exercem diversos papeis fundamentais no ecossistema do planeta, alguns são encarregados pela decomposição da matéria orgânica, disponibilizam nutrientes para o crescimento das plantas, melhoram a produtividade do solo, e ajudam a controlar os organismos indesejáveis no mesmo. O objetivo deste trabalho foi comparar a diversidade da fauna do solo em propriedades agrícolas no município de Dom Pedrito que está localizado no estado do Rio Grande do Sul. O estudo foi conduzido em duas propriedades rurais do município, com campo natural e produção olerícola. A coleta dos organismos edáficos ocorreu em janeiro (verão) do ano de 2020. Para a captura dos invertebrados foi utilizado armadilhas do tipo PROVID com espaçamento de 10m, totalizando 20 armadilhas em cada área. Depois de sete dias as armadilhas foram retiradas, levadas ao laboratório e posteriormente, encaminhadas para identificação. A fauna edáfica foi avaliada quantitativamente por meio da abundância das ordens, e qualitativamente por meio do Índice de Dominância de Simpson (D). Os parâmetros avaliados para a população da fauna edáfica foram riqueza: abundância, índice de diversidade de Simpson e de Shannon. Os grupos taxonômicos encontrados foram: i) Aracnídea (ácaros, aranhas, opiliões e escorpiões); ii) Hymenoptera; iii) Hemíptera; iv) Homóptera, v) Collembola; vi) Crustaceae e; vii) Demáptera.
... On the one hand, wildfires affect numerous ecosystem processes such as water regulation and nutrient cycling mediated by changes in soil physical and chemical properties Fernández-García et al., 2019a;Francos et al., 2018), microbial communities (Pressler et al., 2019;Pérez-Valera et al., 2018), mesofauna (Butenko et al., 2017;Pressler et al., 2019) and macrofauna (Gorbunova et al., 2017). On the other hand, wildfires are the primary natural agent for generating and maintaining high habitat heterogeneity, increasing the diversity of light-loving species, and, thus, sustaining a myriad of ES (Pausas and Keeley, 2019). ...
Alterations generated by intensified wildfire regimes are leading to unprecedented impacts in the supply of ecosystem services (ES). We investigated how a large wildfire affected the components of ES delivery (capacity, flow, and demand) in a fire-prone landscape. We selected a set of socio-ecologically and economically important provisioning ES and analysed temporal trends in and mismatches between ES flow and demand indicators over three spatial scales. Serotinous pine forests were the principal service providing units (SPUs) contributing to ES supply before fire. Fire interrupted their ES capacity, correspondingly reducing the ES flow of wood production, hunting, livestock, and mushroom harvesting for several years. Actual fire-driven losses in wood production were masked by the immediate removal and selling of the burned trees. We detected two new opportunities of ES delivery emerge as a result of post-fire natural vegetation dynamics that last until today: honey and resin collection. Finally, there were no spatial mismatches between ES flow and demand over time due to wildfire occurrence. These findings highlighted the need to promote the post-fire recovery of key SPUs, and identify new unforeseen opportunities of ES supply created by fire and by the natural post-fire dynamics of the vegetation, to, at least partially, reverse the losses.
... Springtails may recover from low-intensity fires after a few years, but highintensity fires may lead to a long-term shift from fungal to bacterial feeding species (Malmström 2012). The patchiness of fire has also been shown to increase the diversity of forest macrofauna that include members of spiders (order Araneae), isopods, centipedes (class Chilopoda), milli-pedes (class Diplopoda), and click beetle (family Elateridae) larvae (Gorbunova et al. 2017). ...
Regardless of how soil is defined, soils are the most diverse of all ecosystems. It is estimated that 25–30% of all species on Earth live in soils for all or part of their lives (Decaëns et al. 2006). A single gram of soil is estimated to contain 1 × 109 microorganisms, roughly the same population size as the number of humans in Africa (Microbiology by Numbers 2011). That same gram of soil likely contains 4000 species. They are only one part of a larger food web, however, that includes roundworms (phylum Nematoda), springtails (order Collembola), and other fauna (Fig. 5.1). The soil fauna has equally astounding numbers (e.g., 40,000 springtails in 1 m2). Soil organisms, ranging from microbes to moles (family Talpidae), promote crop growth and livestock production (Barrios 2007; Kibblewhite et al. 2008), produce antibiotics (Wall et al. 2015), control nutrient loads in surface soils and groundwater (De Vries et al. 2011), and regulate greenhouse gas emissions (Singh et al. 2010).
Fires lead to dramatic shifts in ecosystems and have a large impact on the biota. Soil organisms, especially soil fauna, are often used as indicators of environmental change. At present, minimal attention has been paid to using soil fauna as an indicator of environmental change after a fire. Here, a field survey of burnt herbaceous vegetation in semi-arid areas was conducted to determine the response of soil arthropods to fire and their short–term recovery after fire. Overall, the abundance and biomass of soil arthropods was more sensitive to fire than the number of groups. The number of soil arthropod groups, especially the dominant groups (mites and springtails), was not significantly affected by wildfires. At the unburned site, soil arthropod abundance showed significant seasonal shifts that may be related to the vegetation properties, temperature, and precipitation caused by seasonal changes. In contrast, soil arthropods at the burnt sites showed a delayed recovery and had only reached 56%–82%, 17%–54%, and 91%–190% of the biomass in the unburnt forest at the 3, 6, and 9 months after the burning event. Our findings of soil arthropod abundance changes in the present study suggest that fire-induced changes in soil and vegetation properties (e.g., AN, LT, and VC) were crucial factors for the changes in soil arthropod abundance in this semi-arid grassland. We conclude that fire disturbance reduces the seasonal sensitivity of soil arthropods by altering their habitat. This study furthers our understanding of wildfire impact recovery by documenting the short-term temporal dynamics of soil arthropods.
We tested for fire-induced (5-6 years post-fire) changes in the structure and functioning of the soil food web along a 3000-km north-south transect across European Russia, spanning all major forest types in the northern hemisphere outside the tropics. The total biomass of the detrital food web, including microbes and invertebrates, was not affected by fire. However, fire reduced the bio-mass of microfauna and mites, but had no impact on mesofauna or macrofauna. Fire also reduced rates of carbon (C) mobilisation by soil biota. Our results demonstrate that fire-induced shifts in soil food webs have significant short-term effects on forest soil C cycling, but that these effects vary across forest types and geographic locations.
Fires change physical, chemical and biotic conditions of forest ecosystems. They also strongly affect soil macrofauna including key soil ecosystem engineers and regulators of soil-related processes in forest soils. However, due to a wide range of traits attributable to macroinvertebrates, the effect of forest burning on the macrofauna can be quite contrasting and still has not been quantified. We assessed the impact of forest fires on macrofauna taxonomic richness, abundance, total biomass and biomass of animals belonging to different functional traits in 20 forests burnt five years ago and 20 respective controls plots along a 3000-km-long north-south transect in European Russia which covered five major forest biomes (Mediterranean and broadleaved forests, southern, middle, and northern taiga).
The map of "The Biomes of Russia" is the result of many years of joint work of botanists and zoologists of the Department of Biogeography in various areas and cartographic support of the extensive problem of the "Geography of biodiversity".
The Biomes of Russia map illustrates the patterns of spatial differentiation of biotic cover of Russia, determined by indicators characterizing the flora and fauna of the country. The map is based on the biome concept (Walter, Bruce, 1980) and the idea of the geographical dimension of geosystems (Sochava, 1978). A biome is a large zonal ecosystem that combines a number of interconnected, smaller ecosystems, and which reflects the interaction of regional biota with climate and landscape structure. A biome’s biotic components evolve in relationship with, and dependent on, its abiotic components. Biomes reflect the ecological potential of a territory more fully than their separate components.
The map of zonal biomes (zonobiomes) and mountain biomes (first order orobiomes) is represented by the ecosystems of the regional dimension within the zones on the plains, and in accordance with the types of altitudinal zonation in the mountains, respectively. For most of the biomes, geographical variations were highlighted: for plain these were considered underzones, and for orobiomes they were considered in accordance with the variants of altitudinal belt spectra. Characteristics of regional biomes and geographic options include bioclimatic indicators shown on climate charts and the ecological structure of the biotic cover with a quantitative assessment of biological diversity for the main groups of terrestrial organisms.
Quantitative assessment of plant species aims to give a general (comparative) idea of the modern floristic richness of biomes. It is given for vascular plants (with regard to two indicators), mosses, lichens, as well as for terrestrial vertebrates: mammals, birds, reptiles and amphibians.
The influence of prescribed burning on ground beetles was studied in a single 12-ha stand that was partially clear-cut, selectively-cut and retained (= standing forest), and was compared to an unburned stand in 2002 in SE Norway. Thirty-two species were collected using Barber pitfall traps. Carabids were more numerous and more diverse in the burned area, compared to the unburned forest. Overall abundance was highest in the selectively-cut treatment, followed by the clear-cut and standing forest. Species diversity tended to increase in the sequence unburned forest - burned standing forest - burned selectively-cut - burned clear-cut. Species composition differed little between the burned treatments. Pterostichus adstrictus, a species associated with open habitats and which frequently colonizes burned areas, was the most abundant species collected. It was most common in the burned area, particularly in the selectively-cut treatment. Our results suggest that burning of a single stand may support some carabid species, even endangered ones, although larger forest fires are probably more effective for conservation purposes.
Trends in the diversity of structural organization of soil animal communities are analyzed using an example of the taxocenes of springtails, small soil arthropods. Different methods for describing the structure of communities are considered. On the basis of parameters characterizing specialization and stability of communities, several patterns of their organization in springtails are distinguished. It is shown that the new approach offers new opportunities in forecasting community dynamics under the effects of natural and anthropogenic factors.
The effect of surface fires of different intensity on soil invertebrates was evaluated in central taiga Scotch pine forests
in the Yenisey Region of Siberia. In the period of 4–5 years, the abundance and ecological and trophic structure of sandy
podzol population was almost completely restored after surface fires of medium and low intensity. The recovery process was
decelerated after high intensity fires.
Species invasions provide numerous unplanned and frequently, but imperfectly, replicated experiments that can be used to better understand the natural world. Classic studies by Darwin, Grinnell, Elton and others on these species-invasion experiments provided invaluable insights for ecology and evolutionary biology. Recent studies of invasions have resulted in additional insights, six of which we discuss here; these insights highlight the utility of using exotic species as ‘model organisms’. We also discuss a nascent hypothesis that might provide a more general, predictive understanding of invasions and community assembly. Finally, we emphasize how the study of invasions can help to inform our understanding of applied problems, such as extinction, ecosystem function and the response of species to climate change.
Fire and insects are natural disturbance agents in many forest ecosystems, often interacting to affect succession, nutrient cycling, and forest species composition. We review literature pertaining to effects of fire-insect interactions on ecological succession, use of prescribed fire for insect pest control, and effects of fire on insect diversity from northern and boreal forests in North America. Fire suppression policies implemented in the early 1900s have resulted in profound changes in forest species composition and structure. Associated with these changes was an increased vulnerability of forest stands to damage during outbreaks of defoliating insects. Information about the roles that both fire and insects play in many northern forests is needed to increase our understanding of the ecology of these systems and to develop sound management policies.
Changes in ecosystem functions following disturbances are of central concern in ecology and a challenge for ecologists is to understand the factors that affect the resilience of community structures and ecosystem functions. In many forest ecosystems, one such important natural disturbance is fire. The aim of this study was to understand the variation of resilience in six functional groups of invertebrates in response to different fire frequencies in southern Switzerland. We measured resilience by analysing arthropod species composition, abundance and diversity in plots where the elapsed time after single or repeated fires, as determined by dendrochronology, varied. We compared data from these plots with data from plots that had not burned recently and defined high resilience as the rapid recovery of the species composition to that prior to fire. Pooling all functional groups showed that they were more resilient to single fires than to repeated events, recovering 6-14 years after a single fire, but only 17-24 years after the last of several fires. Flying zoophagous and phytophagous arthropods were the most resilient groups. Pollinophagous and epigaeic zoophagous species showed intermediate resilience, while ground-litter saprophagous and saproxylophagous arthropods clearly displayed the lowest resilience to fire. Their species composition 17-24 years post-burn still differed markedly from that of the unburned control plots. Depending on the fire history of a forest plot, we found significant differences in the dominance hierarchy among invertebrate species. Any attempt to imitate natural disturbances, such as fire, through forest management must take into account the recovery times of biodiversity, including functional group composition, to ensure the conservation of multiple taxa and ecosystem functions in a sustainable manner.
Fires change physical, chemical and biotic conditions of forest ecosystems. They also strongly affect soil macrofauna including key soil ecosystem engineers and regulators of soil-related processes in forest soils. However, due to a wide range of traits attributable to macroinvertebrates, the effect of forest burning on the macrofauna can be quite contrasting and still has not been quantified. We assessed the impact of forest fires on macrofauna taxonomic richness, abundance, total biomass and biomass of animals belonging to different functional traits in 20 forests burnt five years ago and 20 respective controls plots along a 3000-km-long north-south transect in European Russia which covered five major forest biomes (Mediterranean and broadleaved forests, southern, middle, and northern taiga).
Relations between soil biota diversity and its contribution to the performance of some ecosystem functions were assessed based on the results obtained in undisturbed and burned spruce forests near the Central Forest Nature Biosphere Reserve (Tver oblast). In August 2014, in two 4-year-old burned areas, abiotic parameters of the soils, indicators of the state of the microbial communities, the number, taxonomic diversity, and the abundance of the main groups of soil invertebrates (testate amoebae, nematodes, enchytraeids, mites, collembolans, and the mesofauna as a whole) were determined. In the soils of the burned areas, higher CO2, CH4, and N2O emissions were observed. The number of bacterial cells remained similar, and the total length of active mycelium was not significantly different. All this implies a certain intensification of biogenic processes promoting the mobilization of carbon and nitrogen after fire. The number of most of the groups of soil animals was lower (not always significantly) in the burned area than that in the soils of the undisturbed forests. The changes in the taxonomic diversity were specific for each taxon studied. Overall, the diversity of invertebrates was related to the litter thickness. However, the high taxonomic diversity of soil fauna did not always correspond to the active functioning of the ecosystem. Thus, for some taxa, a quite close correlation was found, for instance, between the total number of species (of testate amoebae in particular) and the berry crop, as well as between the soil mesofauna population and the dead wood stock. The total diversity of the investigated taxa included in the detrital trophic web was the most reliable indicator of the carbon stock in the burned areas.
Abstract
Identifying factors that influence the survival of individuals during disturbance is critical to understanding patterns of species reassembly within ecological communities. Although most studies of recovery of populations post-burning acknowledge the potentially important contribution of animals surviving in situ, few have measured the effectiveness of refugia. This paper tests the hypothesis that some plants with tightly packed leaf-bases provide a refuge for invertebrates during fire (even when the plants themselves burn) by using the highly flammable grass tree (Xanthorrhoeaceae: Xanthorrhoea). Invertebrates were sampled from four unburnt and five experimentally burnt grass trees (Xanthorrhoea preissii Endl.). Also collected were invertebrates fleeing during burning. The dataset comprises 949 specimens, representing 81 species from 18 orders, of which 749 individuals were from unburned plants. Slaters (Isopoda), silverfish (Thysanura), spiders (Araneae) and bugs (Hemiptera) dominated assemblages of the unburnt grass trees. Despite grass trees burning at temperatures of up to 515°C, some invertebrates survived in situ. Species-specific microhabitat preferences within the plant appeared to influence survivorship. Species collected in the crown of unburned plants were found more often alive on burnt plants than species typically inhabiting the dead skirt of decaying leaves (thatch). We contend that the mechanism causing differential mortality is fire temperature. In the dead skirt, temperatures reached 225.33 ± 66.57°C. In contrast, a region of mild temperature (25.00 ± 3.54°C) persisted throughout burning near the apical meristem (within the crown). We conclude that grass trees are a potential reservoir from which invertebrates might re-colonize recently burnt areas. However, owing to species-specific microhabitat preferences and differential mortality across microhabitats, the invertebrate assemblage remaining in situ will be restricted taxonomically compared with the original grass tree fauna. Moreover, different fire regimes might mediate the effectiveness of grass trees as refugia. Finally, we argue that in situ survival of invertebrates within plants with tightly packed leaf-bases is an unrecognized global phenomenon applicable to a wide array of plant taxa.
In the northern Mediterranean Basin, agricultural land abandonment over the last century has resulted in increasing frequencies of very large, intense fires. In Catalonia (NE Spain) some fires have been locally associated with the expansion of the large, evergreen, resprouting tussock grass Ampelodesmos mauritanica. We tested the hypothesis of a positive feedback between the abundance of A. mauritanica and changing fire regimes.
We used permanent plots distributed across a natural gradient of density of A. mauritanica in the Garraf Natural Park near Barcelona. Total aboveground biomass nearly doubled from plots with low to high density through a combination of A. mauritanica replacing the biomass of other components of the community (predominantly native shrubs), and its absolute standing biomass increasing. The quantity of litter also increased. This increase in fuel load and changes in community functional composition resulted from the simultaneous decrease in shrub productivity and an increase in litter accumulation. Litter accumulation was the consequence of A. mauritanica litter decomposing 30% more slowly than that of shrubs. Under standardized conditions, A. mauritanica and its litter were considerably more flammable than any of the shrub species. This resulted in a more than 40-fold increase in calculated plot flammability from low-to-high-density plots.
Feedbacks, at the landscape scale, were then analysed using the landscape simulation platform LAMOS. Invasion success and contribution to community biomass of A. mauritanica increased with decreasing fire return intervals. Total area burnt in the landscape during each fire year was positively and exponentially related to the total biomass of A. mauritanica. Simulations showed that landscapes can abruptly switch from regimes of small localized to extensive fires as a result of the spread of A. mauritanica. Therefore, increases in fires under climate change represent threats not only through their direct impacts on ecosystems, but also by promoting invaders such as A. mauritanica, which have the potential to induce powerful feedforward processes and, thereby, fundamental changes to ecosystems.
The bait-lamina test was developed for estimating soil biotic activity in arable and contaminated soils. To investigate the utility of the test in unpolluted soils under various climatic and soil conditions, three plots along a north–south gradient in the European part of Russia were chosen. They are: (i) a pine forest at the White Sea coast on poorly developed podzolic soils (Karelia Region); (ii) a spruce forest near Borovsk (Kaluga Region) on podzolic soils; and (iii) oak-beech forest near Novorossiysk, on the Black Sea coast with brown soils (Krasnodar Region). Forty bait-laminas were used at each plot and checked at various times of exposure. Parallel sampling to investigate soil macrofaunal diversity was carried out. Litter and small stone mass, water-holding capacity (WHC), loss on ignition (LOI) and pH were determined in every soil sample in the laboratory.Differences in bait-lamina perforation over time were observed and it was concluded that a 10-day exposure is appropriate under most conditions. Great differences in bait-lamina perforation were found between soil types. An optimal combination of climatic factors (Borovsk plot) reflected by Budyko’s drought index corresponded with the highest feeding activity (65% of pierced apertures), although the abundance of soil macrofauna was only 287 individuals m−2. The Novorossiysk plot had higher densities of soil invertebrates (1380 individuals m−2), but they showed a lower trophic activity (27%), comparable to that of the White Sea cost plot (14%). The depth distribution of bait-lamina perforation varied from plot to plot, but maximal activity was always observed at a depth 0–4 cm from the soil surface, which was supported by a proposed index of average depth of tropic activity. Vertical distribution of bait-lamina perforation depended mostly on soil profile structure and climatic conditions.
Aim To review published evidence regarding the factors that influence the geographic variation in diversity of soil organisms at different spatial scales.
Location Global.
Methods A search of the relevant literature was conducted using the Web of Science and the author's personal scientific database as the major sources. Special attention was paid to include seminal studies, highly cited papers and/or studies highlighting novel results.
Results Despite their significant contribution to global biodiversity, our taxonomic knowledge of soil biota is still poor compared with that of most above-ground organisms. This is particularly evident for small-bodied taxa. Global patterns of soil biodiversity distribution have been poorly documented and are thought to differ significantly from what is reported above-ground. Based on existing data, it appears that microorganisms do not respond to large-scale environmental gradients in the same way as metazoans. Whereas soil microflora seem to be mainly represented by cosmopolitan species, soil animals respond to altitudinal, latitudinal or area gradients in the same way as described for above-ground organisms. At local scales, there is less evidence that local factors regulate above- and below-ground communities in the same way. Except for a few taxa, the humpbacked response to stress and disturbance gradients doesn't seem to apply underground. Soil communities thus appear weakly structured by competition, although competitive constraints may account for assembly rules within specific taxa. The main factor constraining local soil biodiversity is the compact and heterogeneous nature of soils, which provides unrivalled potential for niche partitioning, thus allowing high levels of local biodiversity. This heterogeneity is increased by the impact of ecosystem engineers that generate resource patchiness at a range of spatio-temporal scales.
Following the need for methods suitable for the assessment of the habitat function of soil (i.e. the ability of soil to act as an environment for organisms), particularly in Europe, the International Organization for Standardization (ISO) is harmonizing a standard called “soil quality—sampling of soil invertebrates” now include as many as four parts that are currently close to finalization: (1) ISO/DIS 23611-1: hand-sorting and formalin extraction of earthworms; (2) ISO/DIS 23611-2: extraction of microarthropods (Collembola and Acarina); (3) ISO/CD 23611-3: extraction of enchytraeids; (4) ISO/WD 23611-4: sampling, extraction and identification of free-living stages of terrestrial nematodes All drafts cover the technical details of the most appropriate methods, but also contain modifications of the methods required in special cases (e.g. when working in different climatic regions like the tropics). It is proposed to use these methods in all studies collecting data on soil organism communities for legal purposes such as long-term monitoring or soil quality assessment.