Mycorrhizal colonization of plants in set-aside agricultural land

Agricultural overproduction has led the European Union to encourage long-term abandonment of agricultural land and the adoption of management practices which enhance transition to semi-natural grassland or forest. This paper reports the results of a field study conducted in newly abandoned agricultural land where the development of the mycorrhizal community was investigated in response to manipulation of the above-ground vegetation. The field site consisted of plots where the plant diversity was managed by (1) sowing 15 plant species, (2) sowing four plant species, and (3) allowing plots to be naturally colonized by plants. The plant mixture contained grasses, legumes and forbs that were all expected to occur on the site following succession. Each of the low diversity replicates contained a different subset of the high diversity mixture, in order to avoid confounding diversity effects with sampling effects. A subset of these plots was inoculated with soil cores from a later successional stage and the experiment was arranged in a randomized block design. The catch plants, Fagus sylvatica, Picea abies and Plantago lanceolata, were planted in the experimental plots and the presence of ecto- or arbuscular mycorrhizal (AM) fungi on their roots was determined. The level of AM colonization of P. lanceolata and the ectomycorrhizal colonization of F. sylvatica was lower in the sown treatments with high and low plant diversity compared to areas that were naturally colonized by plants. The survival of catch plants of the tree species was also higher in the naturally colonized plots. Soil inoculations had no effect on either of the mycorrhizal types or the survival of catch plants. The establishment of non-introduced woody plant species was more successful in the naturally colonized treatments.     

Diversity of soil mite communities when managing plant communities on set-aside arable land

When restoring former agricultural land to more low-nutrient input ecosystems, the establishment of a plant community can be enhanced by sowing desirable species. In this study our aim was to determine whether management of the plant community influences the microarthropod community. We carried out a field experiment in three European countries on set-aside arable land and determined soil mites from the sites in Sweden, The Netherlands and Spain. Experimental plots on set-aside arable land were sown with high (15 species) or low (4 species) plant species seed mixtures; other plots were colonized naturally. A field with continued agricultural practices and a later successional site (target site) were used for comparison with the experimental plots. Soil from the later successional site was inoculated into half of the plots. Abandoning agricultural practices increased the density of mites at one site while the number of mite species was not affected. Sowing plant seeds had no effect on mite densities at any of the sites. The community composition of mites changed in response to management of the plant community, as shown by canonical correspondence analysis. Among the functional groups of mites, saprophytes generally dominated on all plots at all sites. Mites parasitic on insects were not present on fields with continued agricultural practice in Sweden and The Netherlands, and might thus be regarded as an indicator of an increase in trophic complexity in the sown and naturally colonized treatments. Predatory and plant parasitic mites showed no consistent pattern in relation to the treatments of the three sites. Soil inoculation treatment had only a minor impact on the soil mite communities.     

Assessment of fungal communities in soil and tomato roots subjected to diverse land and crop management systems

Effects of diverse agricultural land management practices on soil and on root colonizing fungal communities were determined through a PCR-based molecular method and a culture-dependent method, respectively, in a field location with uniform soil type. Initiated in July 2000, the management systems were: conventional tomato production, frequent tillage (disk fallow), undisturbed weed fallow, bahiagrass pasture (Paspalum notatum var. notatum ‘Argentine’), and an organically managed system including cover crops and annual applications of poultry manure and urban plant debris. Culture-dependent colony counting was used to identify and enumerate communities of root colonizing fungi and length heterogeneity polymerase chain reaction (LH-PCR) analysis of internal transcribed spacer-1 (ITS-1) profiles to characterize phylotypes in soil fungal communities. Three years after initiation of land management treatments and midway through tomato cultivation, both methods detected a high degree of similarity in fungal community composition between weed fallow and bahiagrass plots. Soil fungal communities in organically managed plots were similar to each other and distinct from communities in other land management systems while the composition of root colonizing fungal communities in organic plots was divergent. The results demonstrate that the soil fungal communities and root colonizing fungal communities were affected differently depending on land and crop management practices. Fusarium oxysporum was a dominant species in all soil and root colonizing fungal communities except those subjected to organic management practices.     

Effect of vegetation manipulation of abandoned arable land on soil microbial properties

 The effect of vegetation composition on various soil microbial properties in abandoned arable land was investigated 2 years after agricultural practice had terminated. Microbial numbers and processes were determined in five replicate plots of each of the following treatments: continued agricultural practice (monoculture of buckwheat in 1997), natural colonization by the pioneer community (arable weeds), and manipulated colonization from low (four species, three functional groups: grasses, forbs and legumes) or high diversity (15 species, three functional groups) seed mixtures from plant species that are characteristic of abandoned fields in later successional stages. The results indicated that differences in above-ground plant biomass, plant species composition and plant species diversity had no significant effect on soil microbial processes (net N mineralization, short-term nitrification, respiration and Arg ammonification), microbial biomass C and N (fumigation-incubation) or colony-forming units of the major microbial groups. Hence, there were no indications that soil microbial processes responded differently within 2 years of colonization of abandoned arable land by later successional plants as compared to that by plants from the natural pioneer weed community. Therefore, it seems that during the first few years after arable field abandonment, plants are more dependent on the prevailing soil microbiological conditions than vice versa. Received: 8 April 1999     

Differential effect of arbuscular mycorrhizal fungal communities from ecosystems along management gradient on the growth of forest understorey plant species

Arbuscular mycorrhizal fungi (AMF) are important functional components of ecosystems. Although there is accumulating knowledge about AMF diversity in different ecosystems, the effect of forest management on diversity and functional characteristics of AMF communities has not been addressed. Here, we used soil inoculum representing three different AM fungal communities (from a young forest stand, an old forest stand and an arable field) in a greenhouse experiment to investigate their effect on the growth of three plant species with contrasting local distributions - Geum rivale, Trifolium pratense and Hypericum maculatum. AM fungal communities in plant roots were analysed using the terminal restriction fragment length polymorphism (T-RFLP) method. The effect of natural AMF communities from the old and young forest on the growth of studied plant species was similar. However, the AMF community from the contrasting arable ecosystems increased H. maculatum root and shoot biomass compared with forest inocula and T. pratense root biomass compared to sterile control. According to ordination analysis AMF inocula from old and young forest resulted in similar root AMF communities whilst plants grown with AM fungi from arable field hosted a different AMF community from those grown with old forest inocula. AMF richness in plant roots was not related to the origin of AMF inoculum. G. rivale hosted a significantly different AM fungal community to that of T. pratense and H. maculatum. We conclude that although the composition of AM fungal communities in intensively managed stands differed from that of old stands, the ecosystem can still offer the ‘symbiotic service’ necessary for the restoration of a characteristic old growth understorey plant community.     

Land use influences soil fungal community composition across central Victoria,south-eastern Australia

Current theory expects that fungi, on the one hand, are spatially ubiquitous but, on the other, are more susceptible than bacteria to disturbance such as land use change due to dispersal limitations. This study examined the relative importance of location and land use effects in determining soil fungal community composition in south-eastern Australia. We use terminal restriction fragment length polymorphism (T-RFLP; primer pair ITS1-F–ITS4) and multivariate statistical methods (NMDS ordinations, ANOSIM tests) to compare relative similarities of soil fungal communities from nine sites encompassing three locations (ca 50–200 km apart) and four land uses (native eucalypt forest, Pinus radiata plantation, Eucalyptus globulus plantation, and unimproved pasture). Location effects were generally weak (e.g. ANOSIM test statistic R ≤ 0.49) and were, in part, attributed to minor differences in soil texture. By contrast, we found clear and consistent evidence of land use effects on soil fungal community composition (R ≤ 0.95). That is, soils from sites of the same land use grouped together in NMDS ordinations of fungal composition despite geographic separations of up to ca 175 km (native eucalypt forests) and 215 km (P. radiata plantations). In addition, different land uses from the same location were clearly separate in NMDS ordinations, despite, in one case, being just 180 m apart and having similar land use histories (i.e. P. radiata versus E. globulus plantation both established on pasture in the previous decade). Given negligible management of all sites beyond the early establishment phase, we attribute much of the land use effects to changes in dominant plant species based on consistent evidence elsewhere of strong specificity in pine and eucalypt mycorrhizal associations. In addition, weak to moderate correlations between soil fungal community composition and soil chemical variables (e.g. Spearman rank correlation coefficients for individual variables of 0.08–0.32), indicated a minor contributing role of vegetation-mediated changes in litter and soil chemistry. Our data provide evidence of considerable plasticity in soil fungal community composition over time spans as short as 6–11 years. This suggests that – at least within geographic zones characterised by more-or-less contiguous forest cover – soil fungal community composition depends most on availability of suitable habitat because dispersal propagules are readily available for colonisation after land use change.     

Grassland management influences spatial patterns of soil microbial communities

Soil micro-organisms play a vital role in grassland ecosystem functioning but little is known about the effects of grassland management on spatial patterns of soil microbial communities. We compared plant species composition with terminal restriction fragment length polymorphism (T-RFLP) fingerprints of soil bacterial and fungal communities in unimproved, restored and improved wet grasslands. We assessed community composition of soil micro-organisms at distances ranging from 0.01 m to 100 m and determined taxa–area relationships from field- to landscape level. We show that land management type influenced bacterial but not fungal community composition. However, extensive grassland management to restore aboveground diversity affected spatial patterns of soil fungi. We found distinct distance–decay and small-scale aggregation of fungal populations in extensively managed grasslands restored from former arable use. There were no clear spatial patterns in bacterial communities at the field-scale. However, at the landscape level there was a moderate increase in bacterial taxa and a strong increase in fungal taxa with the number of sites sampled. Our results suggest that grassland management affects soil microbial communities at multiple scales; the observed small-scale variation may facilitate plant species coexistence and should be taken into account in field studies of soil microbial communities.     

Soil community changes during secondary succession to naturalized grasslands

Succession to a naturalized grassland from former agricultural land and pastures is accompanied by changes in plant biodiversity and in the soil community. These changes are the result of a reduction or elimination of management, fertilizer applications and of grazing by large herbivores. We review soil biology studies on agricultural land that are in various successional stages towards naturalized grasslands, where interactions between plant species composition changes and the soil ecology affect each other. In many chronosequence studies, the soil microbial community tends to shift towards a less bacterial, and more fungal dominated food web energy channel following a reduction in fertilizer inputs and grazing intensity. Whereas changes in microarthropod communities are obscured, nematode trophic functional group (ecological guild) changes respond to both plant and soil community changes. There are opportunities to further study the feedback interactions between roots and soil organisms in grasslands. A better understanding of the molecular feedback mechanisms would be beneficial in long-term grassland management.     

RNA- and DNA-based profiling of soil fungal communities in a native Australian eucalypt forest and adjacent Pinus elliotti plantation

Total and active soil fungal communities in a native eucalypt forest and first rotation Pinus elliotti plantation were investigated by direct extraction of DNA and RNA from soil. Terminal restriction fragment length polymorphism (T-RFLP) analysis of internal transcribed spacer (ITS) and 18S rRNA profiles indicated that total and active fungal communities differed significantly in both forest types. This was supported by DGGE profile analysis on an individual plot basis for both forest types and when groups in the canonical analysis were redefined to allow comparison between forest types. Analyses of both ITS and 18S T-RFLP profiles indicated that conversion from native eucalypt forest to P. elliottii plantation may significantly alter total and active soil fungal communities. ITS DGGE (DNA) and 18S (RNA) profiles also suggested differences in fungal communities in the two forest types. No significant separation of the fungal communities in the two forest types was observed, however, when ITS DGGE (RNA) profiles were compared. Overall, the data suggest that conversion from native eucalypt forest to P. elliottii plantation at the Beerburrum State Forest in subtropical Australia has significantly altered soil fungal communities.     

Switch of tropical Amazon forest to pasture affects taxonomic composition but not species abundance and diversity of arbuscular mycorrhizal fungal community

Arbuscular mycorrhizal fungi (AMF) community composition and species richness are affected by several factors including soil attributes and plant host. In this paper we tested the hypothesis that conversion of tropical Amazon forest to pasture changes taxonomic composition of AMF community but not community species abundance and richness. Soil samples were obtained in 300 m × 300 m plots from forest (n = 11) and pasture (n = 13) and fungal spores extracted, counted and identified. A total of 36 species were recovered from both systems, with 83% of them pertaining to Acaulosporaceae and Glomeraceae. Only 12 species were shared between systems and spore abundance of the majority of fungal species did not differ between pasture and forest. Spore abundance was significantly higher in pasture compared to forest but both systems did not differ on mean species richness, Shannon diversity and Pielou equitability. Species abundance distribution depicted by species rank log abundance plots was not statistically different between both systems. We concluded that conversion of pristine tropical forest to pasture influences the taxonomic composition of AMF communities while not affecting species richness and abundance distribution.     

Discriminating the effects of agricultural land management practices on soil fungal communities

The structure of fungal communities was examined in soil subjected to 5 years of different agricultural land management and tomato production practices. Length heterogeneity polymerase chain reaction (LH-PCR) of fungal rDNA internal transcribed spacer-1 (ITS-1) regions was used to create genomic fingerprints of the soil fungal communities. Three years after initiation of land management practices, univariate analysis of genetic diversity failed to detect differences among soil fungal communities in plots managed organically, conventionally or maintained free of vegetation by continuous tillage (disk fallow). Genetic diversity was significantly higher in plots maintained as a perennial pasture grass (Paspalum notatum var Argentine bahiagrass) or as an undisturbed weed fallow. The composition of soil fungal communities within organic, pasture grass or disk fallow plots were separated into unique clusters by non-parametric multivariate analysis of their Bray-Curtis similarity matrices, computed from the relative abundance of ITS-1 amplicons, while the composition of communities within disk fallow and conventional plots could not be distinguished from each other. Diversity of soil fungal communities was significantly reduced following the cultivation of tomato in year four when compared to the diversity in plots where tomato was not cultivated. Divergence in the composition of soil fungal communities was observed following the cultivation of tomato under all land management regimes except organic, where communities continued to remained clustered based upon similarities among their ITS-1 amplicons. Divergence in the composition of fungal communities became more pronounced following two major hurricanes (Francis and Jeanne, September 2004) except for communities in the organic and pasture grass plots. Following the completion of a second tomato crop in year 5, genetic diversity and richness was similar under all land management regimes except the pasture grass, where it remained significantly higher. By contrast, following two consecutive years of tomato production, unique but mutually similar compositions of fungal communities were detected only in plots subjected to the organic land management regime. This was supported by observations that fungal communities were dominated by a 341 bp rDNA amplicon fragment in all land management regimes except the organic. Cloning and sequencing indicated that the 341 bp fragment generated by LH-PCR had a sequencing size of 343 bp, which was most closely related to Fusarium oxysporum. Thus, land management practices that disturb or disrupt soil fungal communities will significantly reduce their diversity. However, the composition of soil fungal communities is more strongly influenced by land management practices and communities within an organically management system were more resistant to anthropogenic and meteorological disturbances.     

Converting Australian tropical rainforest to native Araucariaceae plantations alters soil fungal communities

Native rainforest tree plantations are increasingly viewed as potentially important for high value timber production and provision of a range of ecological services in tropical and subtropical areas. In order to determine the extent to which conversion of rainforest to native Araucariaceae plantation influences soil fungi, we compared soil fungal communities under native rainforest and 73-74 year-old Araucaria bidwillii, Araucaria cunninghamii and Agathis robusta plantations at Gadgarra State Forest, Queensland, Australia. Following direct extraction of DNA from soil, terminal restriction fragment length polymorphism (T-RFLP) analysis of rDNA internal transcribed spacer (ITS) regions was conducted. Ordination analysis of the T-RFLP data revealed significant separation of the fungal communities according to forest type along the first canonical axis, with the native rainforest samples separating from the three Araucariaceae plantations along the second axis. Overall, the most abundant ITS sequences in clone assemblages from the four forest types were Ascomycota, followed by Basidiomycota, Zygomycota and Chitridomycota, however their relative importance varied in individual forest types. The results indicate that conversion of tropical rainforest to monoculture plantations of native trees can significantly alter soil fungal diversity.     

Functional diversity of microbial communities in the mixed boreal plain forest of central Canada

This study was designed to examine whether or not specific tree species (Picea glauca, Picea mariana, Pinus banksiana, Populus tremuloides), their post-fire stand age, or their position in a successional pathway had any significant effect on the functional diversity of associated soil microbial communities in a typical mixed boreal forest ecosystem (Duck Mountain Provincial Forest, Manitoba, Canada). Multivariate analyses designed to identify significant biotic and/or abiotic variables associated with patterns of organic substrate utilization (assessed using the BIOLOG™ System) revealed the overall similarity in substrate utilization by the soil microbial communities. The five clusters identified differed mainly by their substrate-utilization value rather than by specific substrate utilization. Variability in community functional diversity was not strongly associated to tree species or post-fire stand age; however, redundancy analysis indicated a stronger association between substrate utilization and successional pathway and soil pH. For example, microbial communities associated with the relatively high pH soils of the P. tremuloides-P. glauca successional pathway, exhibited a greater degree of substrate utilization than those associated with the P. banksiana-P. mariana successional pathway and more acidic soils. Differences in functional diversity specific to tree species were not observed and this may have reflected the mixed nature of the forest stands and of their heterogeneous forest floor. In a densely treed, mixed boreal forest ecosystem, great overlap in tree and understory species occur making it difficult to assign a definitive microbial community to any particular tree species. The presence of P. tremuloides in all stand types and post fire stand ages has probably contributed to the large amount of overlap in utilization profiles among soil samples.     

Recovery of woody plant diversity in tropical rain forests in southern China after logging and shifting cultivation

Logging and intense shifting cultivation have caused major degradation of tropical forests and loss of biodiversity. Understanding the direct and indirect effects of those land uses on plant biodiversity is essential to the restoration of tropical forests. We compared the species diversity, community composition and basal area of all stems ?1 cm dbh among 18 1-ha tropical lowland and montane rain forest plots with a well-recorded long-term history of shifting cultivation and logging on Hainan Island, south China. We also explored the relative importance of disturbance and environmental factors in determining forest recovery. We found that the species density and diversity in old growth forests were higher than in shifting cultivation fallows (55 years old) but lower than in logged forests (35–40 years since logging). The species composition of shifting cultivation fallows was distinct from other forest types but logged forests were similar to old growth forests, especially in lowland forests. Disturbance intensity was the most frequently important factor in determining species composition, species density, diversity, and basal area accumulation. Soil nutrient availability explained some of the variation in species composition and diversity. Stem density was related to multiple factors including disturbance history, soil nutrients, and distance to old-growth forest. In general, we found that disturbance intensity was a better predictor of forest structure and diversity than edaphic environmental variables, highlighting the importance of human impacts in shaping tropical forest successional pathways.     

Changes in plant diversity,biomass and soil C,in alpine meadows at different degradation stages in the headwater region of three rivers,China

Field surveys and experiment analyses were applied to detect the relationships between plant diversity, community biomass and soil resources at different degradation successional stages in the headwater region of three rivers in an alpine meadow. The chronosequence approach (space‐for‐time substitution) is a viable tool for obtaining integrated information within successional studies. The experimental plots were located in the Guoluo area, which is part of the source region for the Yangtze and Yellow Rivers. The results showed not only that the quantities of roots and soil that are ‘carriers’ for cultivating soil roots were altered not only by disturbance (including overgrazing) and environmental factors but also that the proportion of the rhizome to soil at the 0–10 cm soil layer was enhanced by disturbance in heavy degradation. The plant community composition changed, and the number of plant species and the proportions of fine forage decreased. Moreover, soil fertility levels decreased remarkably, and the soil was degenerated. Plant community biomass levels at different degradation successional stages affected the soil microbial biomass carbon, soil organic carbon and also affected soil fertility conditions. Soil organic carbon and soil total nitrogen declined with grassland degeneration, and the distribution of soil organic carbon was influenced greatly. The alpine species Kobresia pygmaea was at different degradation successional stages, and the plant community biomass was significantly related to soil nutrients. In the positive successional series, the composition of plant functional groups became complex gradually, plant species richness was gradually enhanced, and the change in the composition of each plant functional group also reflected the restoration degree plant community structure. Copyright © 2008 John Wiley & Sons, Ltd.     

亚马逊黑土及其黑碳颗粒中的真菌丰度和多样性互不相同

Amazonian Dark Earth (ADE) is a highly fertile soil of anthropogenic origin characterized by high levels of charred black carbon (BC).It is considered a model of fertility;however,knowledge on the fungal community structure and diversity inhabiting ADE and its BC particles is scarce.Fungal community structure and diversity of ADE and its BC from four sites under different land uses (three agricultural systems and a secondary pristine forest) in the Brazilian Central Amazon were evaluated by 18S rRNA gene pyrosequencing.Fungal communities in ADE and BC were dissimilar and showed differential abundances of fungal operational taxonomic units (OTUs).Estimated fungal species richness (abundance-based coverage estimate and Chao-1 index) and diversity estimators (Shannon and Simpson's reciprocal indices) were higher in ADE than in BC in all agricultural areas.No differences were observed in those parameters in ADE and BC samples from the secondary forest.Pezizomycotina fungi and OTUs assigned to Cordyceps confragosa,Acremonium vitellinum,Camarops microspora,and Hirsutella rhossiliensis were more abundant in BC particles than in ADE.These findings represent a breakthrough in our understanding of fungal communities in BC particles from ADE,and will be valuable in future studies considering biochar application in soil.     

Influence of agricultural practices on arthropod communities in a vertisol (Martinique)

The influence of human activities on soil arthropods of vertisols was assessed in several plots characterized by different land uses in the south-eastern part of Martinique (French West Indies). Abundance and diversity of soil invertebrate groups and collembolan species were measured in a 40-year-old secondary forest, a 15-year-old fallow, a 4-year-old fallow, a 4-year-old pasture, a 15-year-old pasture and a 20-year-old market-garden. Agricultural practices modified abundance and species distribution of soil arthropods, compared to forest. Arthropod richness (number of taxa present) decreased from forest to market-garden, according to a gradient of intensification of agricultural use (pesticides, tillage, weed control). In the old pasture, the arthropod diversity was lower in spite of a high carbon content. Species richness of Collembola decreased together with plant diversity and water availability.     

黄土高原油松根际土壤酶活性及真菌群落多样性研究——以黄龙山林场为例

为了解黄土高原油松林根际土壤酶活性和真菌群落多样性,本研究分析了陕西黄龙县不同样区油松根际土壤脲酶、碱性磷酸酶、多酚氧化酶和过氧化氢酶活性,并采用巢式PCR-变性梯度凝胶电泳(PCR-DGGE)技术研究了油松根际土壤中真菌群落多样性。结果表明,该地区油松根际真菌群落相似性较高,但受坡向、海拔、土壤水分及人类扰动等诸多因素的影响,不同样区的真菌群落多样性和土壤酶活性存在差异。油松根际各土壤酶活性均表现出坡顶样地高于坡底样地,阴面样地高于阳面样地,林区路旁样地由于采样环境不同于林中样地,酶活性介于其他样地之间;丰富度(S)、Shannon-Wiener指数(H)、Simpson指数(D)、均匀度指数(EH)分析表明,该区域油松根际土壤真菌群落多样性分布特征与酶活性分布特征相一致。相关性分析表明,除过氧化氢酶外,其余酶活性之间、以及与真菌多样性均呈显著正相关(p0.05);土壤含水量与真菌多样性和土壤酶活性除多酚氧化酶外均呈显著正相关(p0.05);而土壤p H与各种酶活性之间均未达显著相关水平(p0.05)。土壤含水量是影响该地区真菌群落多样性与土壤酶活性主要因素之一。     

Effects of the annual invasive plant Impatiens glandulifera on the Collembola and Acari communities in a deciduous forest

Invasive plants can disturb interactions between soil organisms and native plants and thereby alter ecosystem functions and/or reduce local biodiversity. Collembola and Acari are the most abundant microarthropods in the leaf litter and soil playing a key role in the decomposition of organic material and nutrient cycling. We designed a field experiment to examine the potential effects of the annual invasive plant Impatiens glandulifera on species diversity, abundance and community composition of Collembola and Acari in leaf litter and soil in a deciduous forest in Switzerland. Leaf litter and soil samples were obtained from plots invaded by I. glandulifera since 6 years, from plots in which the invasive plant had been removed for 4 years and from plots which were not yet colonized by the invasive plant. The 45 leaf litter and soil samples were equally distributed over three forest areas, which were differently affected by a wind throw 12 years prior to sampling representing a natural gradient of disturbance. Collembola species richness and abundance in the leaf litter and soil samples were not affected by the presence of the invasive plant. However, the species composition of Collembola was altered in plots with I. glandulifera. The abundance of leaf-litter dwelling Acari was increased in invaded plots compared to the two other plot types. Furthermore, the presence of the invasive plant shifted the composition of Acari individuals belonging to different groups. Our field experiment demonstrates that an annual invasive plant can affect microarthropods which are important for nutrient cycling in various ecosystems.     

Succession of plant and soil microbial communities with restoration of abandoned land in the Loess Plateau, China

Purpose

There have been a number of studies on the succession of vegetation; however, the succession of soil microbes and the collaborative relationships between microbes and vegetation during land restoration remain poorly understood. The objectives of this study were to characterize soil microbial succession and to explore the collaborative mechanisms between microbes and vegetation during the restoration of abandoned land through quantitative ecology methods.

Materials and methods

The present research was carried out in the succession of a 5-year abandoned land and its conversion to Hippophae rhamnoides shrubs, Larix principis-rupprechtii plantation, and a naturally regenerated forest (mixed forest). Soil bacterial, archaeal and fungal characteristics were tested by real-time quantitative PCR assays and terminal restriction fragment length polymorphism. The richness, diversity, and evenness indices were employed to analyze plant and microbial communities’ structure. The stability of plant and microbial communities was tested using Spearman’s rank correlation. The relationships between the regeneration scenarios and environmental factors were determined through canonical correspondence analysis.

Results and discussion

The aboveground biomass was significantly different among the sites. Soil bacterial, archaeal, and fungal rRNA gene abundances did not increase significantly with increasing soil organic carbon content. There were higher correlation coefficients between plant and total microbial communities on the richness, diversity, and evenness indices and ratios of positive to negative association compared to ones between plant and individual bacteria, archaea, and fungi. Soil bulk density, clay, pH, and litter were the primary significant environmental factors affecting the structure of plant and microbial communities. The positive relationships between plant and soil bacteria, fungi, and total microbe communities, as well as the negative relationships between plant and archaea, were demonstrated.

Conclusions

The results suggested that plants promote the growth of soil bacteria and fungi during the process of community succession on a small scale; however, plants inhibit the growth of soil archaea.