Impact of local forest composition on soil fungal communities in a mixed boreal forest

Plant and Soil - While fungi are key drivers of the carbon cycle and obligate symbionts of trees, the link between plant-fungal interactions and landscape vegetation changes has been largely...     

Stand- and plot-level changes in a boreal forest understory community following wildfire

Background: Boreal forest understory plant communities are known to be resilient to fire – the species composition of stands after a fire is quite similar to the pre-fire composition. However, we know little about recovery of individual plants within particular locations in forest stands (i.e. plot-level changes) since we usually do not have pre-fire data for plots.

Aims: We wanted to determine whether species recruited into the same or different locations in a Pinus banksiana stand that experienced a severe wildfire.

Methods: We used pre-existing permanent plots to evaluate the cover of understory after an unplanned wildfire.

Results: Across the entire stand nine of 47 species showed a significant change in cover. The largest change in a plant functional group was in the mosses, with all species present before fire being eliminated. There was no change in species diversity or total cover. At the plot level, species composition showed a much greater change. An average of 47% of the species present in a plot before the fire were absent in the same plot after the fire, and the total species turnover in plots was 88% of the species present before the fire. The plots showed a similar shift in species composition.

Conclusions: These results confirm that boreal forest communities show a high degree of resilience to fire, but within a forest stand species will be found in different locations following fire, potentially exposing them to a different set of biotic and abiotic conditions in these new locations.     

Ectomycorrhizal fungal communities in late-successional Swedish boreal forests, and their composition following wildfire

This study was conducted to evaluate the effects of wildfires on ectomycorrhizal (EM) fungal communities in Scots pine ( Pinus sylvestris ) stands. Below- and above-ground communities were analysed in terms of species richness and evenness by examining mycorrhizas and sporocarps in a chronosequence of burned stands in comparison with adjacent unburned late-successional stands. The internal transcribed spacer (ITS)-region (rDNA) of mycobionts from single mycorrhizas was digested with three restriction enzymes and compared with an ITS–restriction fragment length polymorphism (RFLP) reference database of EM sporocarps. Spatial variation seemed to be more prominent than the effects of fire on the EM fungal species composition. Most of the common species tended to be found in all sites, suggesting that EM fungal communities show a high degree of continuity following low-intensity wildfires. Species richness was not affected by fire, whereas the evenness of species distributions of mycorrhizas was lower in the burned stands. The diversity of EM fungi was relatively high considering that there were only three EM tree species present in the stands. In total, 135 EM taxa were identified on the basis of their RFLP patterns; 66 species were recorded as sporocarps, but only 11 of these were also recorded as mycorrhizas. The species composition of the below-ground community of EM fungi did not reflect that of the sporocarps produced. EM fungal species present in our ITS–RFLP reference database accounted for 54–99% of the total sporocarp production in the stands, but only 0–32% of the mycorrhizal abundance.     

Effects of a great cormorant colony on wood-inhabiting fungal communities in a coastal Scots pine forest

We studied the changes in the wood-inhabiting fungal communities on dead wood of Scots pine (Pinus sylvestris) under varying duration and intensity of cormorant nesting. The activities of the birds created large amounts of dead wood, changed wood chemistry and altered stand characteristics. Analyses based on records of fruiting structures of fungi showed that fungal communities in the cormorant colony differed from communities in unaffected forest. Ornithogenic factors impacted least on generalist species and promoted the occurrence of fungi uncharacteristic of coniferous wood or wood in general. The rate of ornithogenic change was rapid: a shift in fungal assemblages was evident by the third year of expansion of the bird colony into unaffected forest. It featured the disappearance of tremelloid fungi, a decline of corticioid fungi and an increase of hyphomycetoid fungi. The proportion of coniferous wood specialists decreased and that of generalists increased. It is expected that the changes in fungal communities will persist until the forest is fully regenerated.     

Successional trends in the energetics of forest bird communities

Thirty forest bird communities were studied with regard to the changes in structural indices (number of species, density, biomass, species diversity H') and in energetics (energy flow A, production P, ecological efficiency P/A) in temporal and spatial gradients. All these characteristics increase during temporal succession; in natural deciduous forest there is a two-peak pattern of the increase, with the maximum in 15–20 yr old forest ("time ecotone"; A = 692.9 Megajoules ha⁻¹ season⁻¹, H'= 4.2 bits), In artificially managed pine forest these indices rise monotonically, reaching a maximum in sub-climax (A = 426.2 MJ ha⁻¹ season⁻¹, H'= 4.2 bits). In a deciduous forest a tendency exists to decrease the ecological efficiency (from 8% to 2%), while in a coniferous stand this variable remains low (2%) and almost constant during succession. In a spatial gradient, the highest values of energy flow and species diversity occur in forest stands with moderate soil/water regime and of ecotonal character (A = 851.2 MJ ha⁻¹ season⁻¹, H'= 4.5 bits). All mature forest bird communities show similar values of diversity (4.2–4.5 bits) and ecological efficiency (appr. 2%), though they differ in the rate of energy flow. The relation of these findings to the current concepts of ecological succession are discussed.     

Changes in assembly processes in soil bacterial communities following a wildfire disturbance

Although recent work has shown that both deterministic and stochastic processes are important in structuring microbial communities, the factors that affect the relative contributions of niche and neutral processes are poorly understood. The macrobiological literature indicates that ecological disturbances can influence assembly processes. Thus, we sampled bacterial communities at 4 and 16 weeks following a wildfire and used null deviation analysis to examine the role that time since disturbance has in community assembly. Fire dramatically altered bacterial community structure and diversity as well as soil chemistry for both time-points. Community structure shifted between 4 and 16 weeks for both burned and unburned communities. Community assembly in burned sites 4 weeks after fire was significantly more stochastic than in unburned sites. After 16 weeks, however, burned communities were significantly less stochastic than unburned communities. Thus, we propose a three-phase model featuring shifts in the relative importance of niche and neutral processes as a function of time since disturbance. Because neutral processes are characterized by a decoupling between environmental parameters and community structure, we hypothesize that a better understanding of community assembly may be important in determining where and when detailed studies of community composition are valuable for predicting ecosystem function.     

Response of soil microbial communities to changes in a forest ecosystem brought about by pine wilt disease

Japan has suffered a lot from forestry losses due to pine wilt disease caused by pinewood nematode infestations. Studies were conducted regarding its causative agent and the effects of natural vegetation succession after pine wilt disease, but its effects on microorganisms were not given equal attention. This study determined the effects of pine wilt disease on light conditions, soil microbial biomass, litter decomposition, microbial abundance and the physical and chemical properties of the soil. Results showed that in a forest currently affected by pine wilt disease, there was higher light penetration, greater microbial biomass carbon, and a faster rate of litter decomposition. Microbial abundance was shown to be reduced in pine wilt affected areas. There were close correlations between the biological and physicochemical properties of the soil, but the reason for the decrease in microbial abundance is not yet well understood, and thus requires further study.     

Resistance to wildfire and early regeneration in natural broadleaved forest and pine plantation

The response of an ecosystem to disturbance reflects its stability, which is determined by two components: resistance and resilience. We addressed both components in a study of early post-fire response of natural broadleaved forest (Quercus robur, Ilex aquifolium) and pine plantation (Pinus pinaster, Pinus sylvestris) to a wildfire that burned over 6000 ha in NW Portugal. Fire resistance was assessed from fire severity, tree mortality and sapling persistence. Understory fire resistance was similar between forests: fire severity at the surface level was moderate to low, and sapling persistence was low. At the canopy level, fire severity was generally low in broadleaved forest but heterogeneous in pine forest, and mean tree mortality was significantly higher in pine forest. Forest resilience was assessed by the comparison of the understory composition, species diversity and seedling abundance in unburned and burned plots in each forest type. Unburned broadleaved communities were dominated by perennial herbs (e.g., Arrhenatherum elatius) and woody species (e.g., Hedera hibernica, Erica arborea), all able to regenerate vegetatively. Unburned pine communities presented a higher abundance of shrubs, and most dominant species relied on post-fire seeding, with some species also being able to regenerate vegetatively (e.g., Ulex minor, Daboecia cantabrica). There were no differences in diversity measures in broadleaved forest, but burned communities in pine forest shared less species and were less rich and diverse than unburned communities. Seedling abundance was similar in burned and unburned plots in both forests. The slower reestablishment of understory pine communities is probably explained by the slower recovery rate of dominant species. These findings are ecologically relevant: the higher resistance and resilience of native broadleaved forest implies a higher stability in the maintenance of forest processes and the delivery of ecosystem services.     

Characterization of fungal soil communities by F-RISA and arbuscular mycorrhizal fungi fromAraucaria angustifolia forest soils after replanting and wildfire disturbances

The Fungal Ribosomallntergenic Spacer Analysis (F-RlSA) was used to characterize soil fungal communities from three Cecosystems ofAraucaria angustifolia from Brazil: a native forest and two replanted forest ecosystems, one of them with a past history of wildfire. The arbuscular mycorrhizal fungi (AMF) infection was evaluated inAraucaria roots of 18-monthold axenic plants previously inoculated with soils collected from those areas in a greenhouse experiment. The principal componentanalysis of F-RISA profiles showed different soil fungal community betweenthe three studied areas. Sixty three percent of F-RISA fragments amplified in the soil and the substrate samples presented lengths between 500 and 700 bp. The number of Operational Taxonomic Units (OTUs) was 34 for soil and 38 for substrate, however, more fragments were detected in soil (214) than in substrate (163). Anin silico F-RISA analysis to compare our data with ITSI-5.8S-ITS2 sequences from NCBI database showed the presence of Ascomycota, Basidiomycota and Glomeromycota among the soil and substrate fungal communities. AMF infection was higher in plants inoculated with soil from the native forest and the replanted forest with wildfire, both presenting similar chemical characteristics but with different disturbance levels. These results indicate that soil chemical composition may influence the soil fungal community structures rather than the anthropogenicor fire disturbances.     

降水变化驱动下红松阔叶林土壤真菌多样性的分布格局

红松阔叶林生态系统是中国东北地区地带性顶极植被,具有重要的生态学意义,长白山是研究温带森林对大气降水变化正负反馈的理想地带.本文以长白山原始红松阔叶林为研究对象,基于末端限制性片段长度多态性分析技术,分析了降水控制样地(增、减30％)和对照样地的0 ～5 cm和5～ 10 cm表层土和红松根际土真菌多样性的空间异质性.结果表明:降水的增加和减少均能提高土壤真菌的多样性,但优势种群有所变化.表层土中,片段长度超过500 bp的T-RFs丰度随降水增加而提高,根际土中对降水变化响应的T-RFs分别为380、455和487 bp,且根际土的响应模式较表层土复杂.典范对应分析结果表明,土壤pH、有机碳含量、总氮和有效磷等对真菌群落组成影响显著.     

Insights into fungal communities colonizing the acarosphere in a forest soil habitat

Knowledge on the diversity and ecology of microfungi associated with soil-dwelling mites is rather limited. To get insights into associations between the two highly diverse groups, we studied composition and potential function of mite-associated fungal communities occurring in soil. Two different mite species living in temperate region pine forest soil were screened for associated fungi. The fungal community was assessed by restriction fragment length polymorphism (RFLP) analyses in a predatory (Leptogamasus obesus) and a predominantly saprobic (Oppiella subpectinata) mite species as well as in the organic soil layer. Key fungi were identified by sequencing, and community composition was exemplarily compared between the RFLP and a 454 metabarcoding approach. Composition of the fungal communities differed between mite species and between mites and organic soil layer. The mites were predominantly associated with Zygomycota, less frequently with Ascomycota, and rarely with Basidiomycota. The bulk soil was colonized by roughly equal proportions of the three phyla. Fungal taxa being known to exhibit chitinolytic activity were predominantly restricted to mites. Compositional and functional differences between the communities suggest that mites represent a particular microhabitat for fungi, the “acarosphere.” This mobile habitat may contribute to nutrient cycling by combining fungal and animal decomposition activities and serve as vector for soil-inhabiting fungi.     

Regeneration of different plant functional types in a Masson pine forest following pine wilt disease

Pine wilt disease is a severe threat to the native pine forests in East Asia. Understanding the natural regeneration of the forests disturbed by pine wilt disease is thus critical for the conservation of biodiversity in this realm. We studied the dynamics of composition and structure within different plant functional types (PFTs) in Masson pine forests affected by pine wilt disease (PWD). Based on plant traits, all species were assigned to four PFTs: evergreen woody species (PFT1), deciduous woody species (PFT2), herbs (PFT3), and ferns (PFT4). We analyzed the changes in these PFTs during the initial disturbance period and during post-disturbance regeneration. The species richness, abundance and basal area, as well as life-stage structure of the PFTs changed differently after pine wilt disease. The direction of plant community regeneration depended on the differential response of the PFTs. PFT1, which has a higher tolerance to disturbances, became dominant during the post-disturbance regeneration, and a young evergreen-broad-leaved forest developed quickly after PWD. Results also indicated that the impacts of PWD were dampened by the feedbacks between PFTs and the microclimate, in which PFT4 played an important ecological role. In conclusion, we propose management at the functional type level instead of at the population level as a promising approach in ecological restoration and biodiversity conservation.     

Local-scale spatial diversity patterns of ectomycorrhizal fungal communities in a subtropical pine-oak forest

This study aimed to analyze spatial patterns of soil ectomycorrhizal fungal (EMF) communities at the local scale in a subtropical pine-oak forest located in the Nearctic-Neotropical transition in central Mexico, to underpin biodiversity conservation strategies in forest fragments of this region. We used a spatially-explicit nested square sampling design with the same sampling representativeness at all scales and replicated three times. We detected 674 EMF OTUs within 19,200 m² and 65 OTUs on average per sample. Seventy percent of OTUs were detected in only 1–4 samples. Average community similarity was below 5%, showed minor change within 14 and 339 m distance and increased with the spatial grain used to compare the data. We found a high species-area relationship and beta diversity coefficients for soil fungi indicating that, at the local scale, increasing area by a constant factor of four represented an increase in OTU richness by a factor of two.     

地形对阔叶红松林物种多样性的影响

为了更好地了解阔叶红松林(Pinus koraiensis)物种多样性的维持机制,对不同地形下的阔叶红松林乔木和灌木种,进行了物种多样性指数比较、物种多度分布模型拟合及物种多样性指数与环境因子的排序分析。结果表明,乔木在阴坡、半阴坡的丰富度显著高于半阳坡;灌木在坡度25°处的均匀度显著高于坡度6°处,在谷地处的4个多样性指数显著低于其他坡位,在阴坡、半阴坡处的4个多样性指数显著高于平地。统计模型、生态位模型、中性模型在不同地形下均能够通过拟合优度检验,物种多度分布在不同地形间差异不明显;地形对乔木的多样性指数的影响:海拔凹凸度坡度坡向坡位,对灌木的多样性指数的影响:坡位海拔坡向坡度凹凸度,土壤对乔木的物种多样性指数的影响:土壤pH土壤容重土壤有效N含量土壤速效K含量,对灌木的物种多样性指数的影响:土壤pH土壤有机质含量土壤速效P含量土壤全N含量土壤全P含量。总体而言,物种多样性随着坡度的增加而增加,阴坡处最高,谷地处最低。     

Recruitment and growth dynamics of a temperate forest understorey species following wildfire in southeast Australia

In southeast Australia, fire regimes are changing. Conserving species into the future under these changing fire regimes will require understanding their recruitment and growth dynamics following historical fires. Where monitoring is absent, dendroecology provides a tool for reconstructing and quantifying these dynamics. The use of dendroecology in southeast Australia has been limited due to presumptions that many of the species do not produce annual growth rings. In this study, we determined the dendroecological potential of a fire-sensitive understorey tree species, Pomaderris aspera, as a case study species, to explore the potential to use of understorey species to provide insights into past fire history. We used growth patterns of this species to understand the role of resource limitation on growth and senescence. We found that P. aspera had distinct growth rings and high within tree correlation when cross-dated.Recruitment events of this species aligned with three known fire events. We found that the impacts of historical fire on tree canopy cover could be estimated. P. aspera grew rapidly post fire and then become suppressed within 9–15 years. Cycles of growth release and suppression were found with increasing incidence of suppression occurring over time. Increased suppression and reduced growth rates aligned with patterns of recorded senescence over time in the understories of a maturing.Eucalyptus canopy. Our results highlight the potential to use dendroecology to confirm past fire extents and amount of canopy disturbances and the impacts that these events have on the recruitment and growth dynamics of understorey species in southeast Australia.