Aboveground Structures Research Articles

Assessment of Excavated Tunnels Stability in the Maya Archeological Area of Copán, Honduras

ABSTRACT Archaeological buried structures have received less attention than aboveground historical structures, which seems evident given the visual impact of the latter. Archaeological structures present specific issues related to stability during excavation and after being exposed. This paper addresses a UNESCO world heritage site in Honduras (Copan), which has about 4 km of tunnels in a complex organization that were dug, in the last 100 years, for the purpose of investigation of buried structures under a temple complex. The objective of this work is to assess the safety of the tunnels, helping on the decision of back-filling the tunnels, adding new masonry linings and allowing access in current conditions (possibly with measures to avoid water infiltration). First, the long network of tunnels was categorized into different sections either in an earthen fill only or in presence of a masonry lining. Then, the stability of these sections was discussed as a function of the increase of soil saturation. It was found that unlined tunnels safety is likely to be compromised for a saturation higher than 70%, whereas lined tunnels do not fail when the soil becomes fully saturated, as far as drainage is ensured. Finally, this work allowed to issue recommendations on actions related to the site.

Application of the endurance time methodology on seismic analysis and performance assessment of hydraulic arched tunnels

The seismic nonlinear behavior and seismic stability of hydraulic arched tunnels remain critical issues with regard to evaluating seismic performance. Generally, evaluating the seismic performance of hydraulic arched tunnels under strong ground motions from low to high seismic intensities constitutes the basis for revealing their seismic resistance and is performed by either pushover analysis or incremental dynamic analysis (IDA). However, the abovementioned methods may have very high computational costs due to the high modeling complexity. Endurance time analysis (ETA) is a new time-history dynamic pushover methodology for assessing the seismic performance of aboveground structures. ETA gives acceptable numerical results for aboveground structures under a wide range of seismic intensities and significantly reduces the computational cost in comparison to conventional nonlinear dynamic analysis. Nevertheless, although the applicability of ETA to aboveground structures has been widely recognized, its suitability to underground structures, especially hydraulic arched tunnels, remains poorly understood. Hence, the focus of this paper is to evaluate the applicability of ETA to hydraulic arched tunnels and to perform an in-depth comparison between the results of IDA and ETA. A model of a hydraulic arched tunnel with two buried depths is first built in commercial ABAQUS software considering the nonlinear dynamic damage analysis model of fluid–structure–rock mass interaction systems. Then, IDA is employed to generate different seismic intensity results that are regarded as a benchmark for the hydraulic arched tunnel under 15 as-recorded ground motions. Subsequently, nonlinear dynamic analysis of the hydraulic arched tunnel is conducted under three ET ground motions. The findings highlight that the ETA methodology provides acceptable accuracy for engineering applications and can be implemented for the rapid nonlinear dynamic analysis and seismic performance evaluation of hydraulic arched tunnels.

Biomass allocation and seasonal non-structural carbohydrate dynamics do not explain the success of tall forbs in short alpine grassland

The majority of alpine plants are of small stature. Through their small size alpine plants are decoupled from the free atmospheric circulation and accumulate solar heat. However, a few alpine species do not follow that “rule” and protrude with their aboveground structures from the microclimatic shelter of the main canopy boundary layer. We aim at explaining the phenomenon of being tall by exploring the biomass production and carbon relations of four pairs of small and tall phylogenetically related taxa in alpine grassland. We compared species and stature-specific biomass allocation, shifts in non-structural carbohydrate (NSC) concentrations in different tissues throughout the season, and we used 13C labels to track carbon transfer from leaves to belowground structures. Small and tall herbs did not differ in their above- to belowground biomass allocation. The NSC composition (starch, fructan, simple sugars) and allocation did not show a stature-specific pattern, except for higher concentrations of simple sugars in tall species during their extended shoot growth. In relative terms, tall species had higher NSC pools in rhizomes, whereas small species had higher NSC pools in roots. Our findings do not place tall alpine forbs in an exceptional category in terms of biomass allocation and carbohydrate storage. The tall versus small stature of the examined herbs does not seem to be associated with specific adjustments in carbon relations. 13C pulse labelling revealed early C autonomy in young, unfolding leaves of the tall species, which are thus independent of the carbon reserves in the massive belowground organs.

Construction strategies for a NATM tunnel in São Paulo, Brazil, in residual soil

Due to the fast growth of urban areas worldwide, the demand for tunnels in developed areas is increasing. The design and construction of those tunnels are complex because of their shallow depths and their interaction with existing aboveground and buried structures, which results in rather limited allowable ground deformations induced by the tunnel excavation and support. In tropical regions, residual porous soils near the surface are common. Those soils are highly deformable; thus, tunneling may induce large ground deformations that may damage nearby structures. The new Austrian tunneling method (NATM) and the sprayed concrete lining (SCL) technique are being widely employed in several big cities in tropical regions, but little research has been conducted to assess the induced ground deformations in residual soils, common in tropical areas. This paper provides insight into this issue. A well-documented metro tunnel in São Paulo, Brazil, in a residual red porous clay, was analyzed using 3D finite element method (FEM). The behavior of the residual red porous clay was approximated by an advanced constitutive soil model calibrated with triaxial tests on intact samples extracted at the site. Predictions of the tunnel deformations during construction matched the field data. The calibrated model was then used to explore the tunnel performance under different construction strategies. The influence of partial face excavation, unsupported span length, support stiffness and pipe roof umbrella were assessed. The numerical results showed that partial face excavation was effective to reduce ground deformations ahead of the face of the tunnel and to improve face stability; however, the settlements behind the face increased because of the delay in closing the primary lining. The installation of a stiffer liner closer to the face reduced the ground deformations significantly. The pipe roof umbrella was the most effective technique to reduce the ground deformations around the tunnel; however, the numerical results did not consider deformations that could be induced by the drilling and grouting operations. The results shown in this paper provide both qualitative and quantitative information about the ground deformations induced by NATM tunneling in residual porous soils, that could help designers and contractors choose the optimum support and construction methods to minimize ground deformations.

Ryazanskaya Transit Oriented Development

The Ryazanskaya Transit Oriented Development (TOD) is a large intervention included in Moscow’s 2030 urban planning, realizing a transit hub, commercial / retail spaces, an office tower and two metro/rail terminal buildings, to be built around a public park where ground transportation is also located. Within this master plan, the Terminal 2 integrates an underground transit hall to provide access for three mass transportation lines merging at Ryazanskaya TOD. Such urban-scale complex required international best practice architectural solutions, particularly focused onto the relationship between underground spaces and above-ground structures. The Ryazanskaya project is a case study useful to understand and explain the typical TOD urban design methodology, as a part of a large city-making process originated by the design of underground infrastructures and concluded with the architectural design of a strategic asset for the contemporary metropolis.

Growth plasticity in response to shading as a potential key to the evolution of angiosperm herbs

In angiosperms, herbs evolved from ancestral woody growth form. A number of hypotheses on what was the driver of their evolution have been proposed, but none of them has received clear support so far. We are putting forward a new hypothesis that an important advantage of the herbaceous growth form lies in its greater capacity for plastic response to neighbour shading. Since most herbs form aboveground structures only for 1 year, they can respond to light heterogeneity more plastically than woody plants with long-living structures which need to pursue long-term goals such as stability and upward growth. To test the hypothesis, we carried out an experiment comparing plastic response to directional green shading of 21 species of young herbaceous and woody plants. We measured change of their tilt and length and compared it between herbs and woody plants using phylogenetic techniques. Both herbs and woody plants in our experiment responded to directed green shading by growing away from the shading plastic film. Overall response of herbs was, in agreement with the hypothesis, slightly stronger than response of woody plants, although there was high interspecific variation. The data indicate that herbs indeed have greater plasticity of stem growth in response to neighbour shading than woody plants, although the overall difference is not very strong. This capacity for plastic response might have played a role as one of the drivers of the evolution of the herbaceous growth form.

Implementation of two-phase flow models for recycled materials in embankments

Recycled materials like Bauxite Residue (Red Mud) and Fly Ash are prevalent in recent feasibility studies on reused materials in geotechnical engineering applications. Red Mud is a mining waste from aluminum manufacturing, and Fly Ash is a by-product of coal combustion in power plants. Nevertheless, to fully reveal the feasibility of using those materials for constructing above-ground earth structures, a better understanding of their unsaturated performance in geo-structure is essential. While some popular empirical models (e.g., van Genuchten 1980) in Soil Water Retention Curves (SWRC) are commonly used to describe soils' unsaturated conditions, those models may not apply to unique materials like Red Mud and Fly Ash. Recently, SWRC curves of both materials were acquired through the Steady-State Centrifuge (SSC) Unsaturated Flow Apparatus (UFA) procedure at Cal State LA. The experimental data were used to develop analytical models following the van Genuchten model. Using a finite-difference software (FLAC) and obtained SWRC curves, this study performed numerical simulations of embankments filled with Fly Ash and Red Mud, comparing it with an embankment filled with typical silty soil with the same dimensions and conditions. Results showed seepage flow rates for Fly Ash and Red Mud are higher when used as fill material as above-ground embankments.

Археологические раскопки на могильниках «Скальная» в 2021 году (Республика Хакасия)

In 2021, an excavation team from the Institute of Archaeology and Ethnography SB RAS carried out rescue archaeological works at the “Skalnaya” burial complex (Askiz district of the Republic of Khakassia) as a part of the Preservation project of the archaeological heritage objects during the construction of the second railway line at the Kamyshta - Uytag section of the Krasnoyarsk railway. According to the project requirements, 3 burial mounds were examined; 4296 sq. m. were excavated to terrestrial deposits; 7 burials (grave pits) yielded more than 100 individual finds (items made of bronze, iron, clay, gypsum and organic materials). All collective human burials in earthen grave pits with wooden log cabins were constructed inside stone fences under overhead stone and wooden coverings. Objects from the crypts and the diagnostic features of the funeral rite allow these burials to be dated to the Podgornovskiy (Skalnaya 7) Saragashenskiy (Skalnaya 6) and “Tesinskiy” stages (Skalnaya 5). Single kurgan Skalnaya 5 is an elite complex. This is evidenced by a massive aboveground and intra-grave structures, clay-plaster death masks, and preserved grave goods. Despite the serious robbery, the burial is very valuable because of all the details of two-levelled burial bed (boards, posts, support beams and traces of their attachment) preserved in the crypt. Burnt wood from the burial structures of the mound was analyzed in 2021. Comparison with the other materials obtained enabled us to establish clear chronological frame for mentioned in this article sites. Fence slabs of the Tagar kurgans with various embossed decorations (humanoidfigures, animals, hunting scenes, etc.) are very important objects of study.

Раскопки тагарских курганов в 2021 году на могильнике Уйтаг-3 (Республика Хакасия)

In 2021, an excavation team from the Institute of Archaeology and Ethnography SB RAS carried out rescue excavations at the Uytag-3 burial ground (Askiz district of the Republic of Khakassia). Three burial mounds were examined according to technical requirements of the Preservation project of the archaeological heritage objects during the construction of the second railway line at the Kamyshta — Uytag section of the Krasnoyarsk railway. Five burial vaults in a row were located at the center of kurgan No. 4 fence and three children’s graves in stone boxes were found to the east. The aboveground structures of the main burials are represented by stone and wood overhead covers. Collective burials of adults and children were found in wooden log constructions inside the grave pits. The overhead wooden covers of all examined vaults bear signs of the integrity violations. Known facts allow us to suggest that this was a part of a certain burial ritual, that is the vaults could be in use for a fairly long period of time. The bones position and the preservation of the grave goods do not allow us to suppose that mounds were robbed. The unearthed collection of artefacts reflects the original composition of the grave goods complex precisely: ceramic dishes, bronze weapons, jewelry. Based on the construction elements and finds a preliminarily date for mound No. 4 could fit within chronological diapason of the 6th—4th centuries BC. One robbed burial of the Podgornovo time and 8 structures (tiered graves) of the Tesinsky time were studied in mound No. 6. The fence form and the assemblage allow the central burial to be dated to the 7th - 6th centuries BC. The tiered burials with burial goods complexes go back to the Tesinsky time and were left by the population arrived to the territory of the Minusinsk depression from Tuva and Altai.

Курганы афанасьевской культуры на могильнике Казановка-13 в Аскизском районе Республики Хакасия

The preliminary results of rescue excavations at the Kazanovka-13 burial mound located in the southwest part of the Khakass-Minusinsk basin (the Askizskiy district, the Republic of Khakassia) are published. The burial mound stands at the foothill part of the Askiz river valley, on the border of the steppes and the mountain taiga area of the Abakan range. The examined burial mounds are part of the Afanasievo culture burial ground. Five kurgans with the preserved elements of stone constructions and 2 burial mounds with completely destroyed above-ground structures were discovered on the inspected area. 4 kurgans with seven burials and two separate graves were excavated. The preserved stone structures display uniformity of design, represented by a stone ring enclosing an embankment over the central burial. The kurgans differ in size and in specific construction of the stone structures, as well as in number and position of the graves. Two kurgans have adjacent to the ring extensions with burials or signs of the commemoration activities. Whole human skeletons, including those of children, have been found in the graves, both intact and damaged. The deceased were buried mostly with their heads facing southwest, on their right side. In two cases, whole large ceramic vessels were preserved in the graves; several small vessels were unearthed inside the ring and in the children’s burial annexes. A stone arrowhead was found in one of the graves. The studied mounds date back to the 3rd millennium BC and represent an important part of the history of the first pastoral population in the southern part of the Minusinsk Basin and the earliest kurgans of the burial steppe on its borders.

On typological characteristic of funerary architecture of uzbekistan in the ancient period

The funerary architecture of Uzbekistan of the ancient period, the development of which was directly related to the changes in religious beliefs of ancient peoples, went the evolutionary path - from simple underground crypts-nauses to monumental above-ground structures. In each historical and cultural region of Central Asia, the funerary architecture was characterized by its own distinctive features. In Bactria these were the single-, double- and multi-chamber above-ground tombs, in Chach - the buildings of round (with a rectangular chamber inside) and yurt-shaped forms, in Fergana - the mugkhonas and kurums, in Khorezm - the mausoleums of a cross-shaped configuration.

Experimental Study on the Mechanics Characteristics of CFRP Strengthening of Highway Tunnels at Different Damage States

Cracks and other diseases may occur in the long-term operation of highway tunnels and reduce the structural load-carrying capacity. Strengthening using carbon fiber reinforced polymer (CFRP) sheets and other materials could extend the service time of the tunnels. However, the process of strengthening tunnels is remarkably different from the process of strengthening aboveground structures because of the secondary load. In order to understand the development of stress and deformation of strengthened tunnels under secondary load, a 1 : 10 scaled model was tested to simulate the tunnel strengthened with CFRP under different damage states. The test results show that CFRP strengthening improved the stiffness of the structure and inhibited the propagation of the existing cracks. The peeling of the CFRP sheets made the strengthened structure quickly lose its load-carrying capacity, causing the instability of the structure. The failure loads of the structures strengthened at different damage states were essentially the same, with an average value of 184% of the original failure load. Nevertheless, the early strengthening helped control the structural deformation. The test results also demonstrate that the bonding strength between the CFRP and the lining is essential for strengthening effectiveness. This study provides a theoretical basis for similar engineering reinforcement designs.

Influence of the sequence of erection of build-ings on the formation of the stress-strain state of the system «base-foundation-overhead structures»

The influence of the order of construction of houses on the formation of the stress-strain state of the system "foundation-foundation-above-ground structures" is investigated
 For this purpose, several options for setting tasks for the phased construction of multi-section building sections are considered.
 With this in mind, it should be noted that the construction of each subsequent section has an impact on the built entirely or partially adjacent section. That is why this effect should be investigated to predict how serious this impact may be, and to draw appropriate constructive decisions.
 Thus, the main objectives of the study are:
 
 Creation of SEM without taking into account the stages of construction of the house;
 Calculation of a house with a phased loading of 5 floors. Taking into account changes in the order of construction of sections;
 Formation of SEM taking into account the sequence of erection of sections without including the sequence of erection of floors within the boundaries of the current section;
 Research of the impact of the calculation of sections of a multi-section building without and taking into account the summary of subsequent sections.
 
 The research of the impact of the sequence of construction and installation of the object will allow us to assess the stress-strain scheme at all stages of construction, so changes in the behavior of the scheme will be recorded at all stages of construction specified by the designers. To do this, the change in the stress-strain state (VAT) of the system "foundation - foundations - above-ground structures" must be modeled with different options for stages of construction, taking into account the real parameters of the soil base and so on.
 The interaction of piles in different zones of sections, the work of grids in the foundations of high-rise buildings are considered. The research was carried out with the help of numerical modeling of the system "foundation - foundations - aboveground constructions". The redistribution of forces in the piles depending on the formulation of problems on the stages of construction of sections and design parameters (location of piles in characteristic zones, the influence of the stiffness of the aboveground part on the redistribution of forces). Characteristic zones in the foundation are distinguished: they are central, lateral, angular and especially at the joints of adjacent sections. The redistribution of efforts between piles and a grid is revealed.

Stem and root assessment in mangrove forests using a low-cost, rapid-scan terrestrial laser scanner

Accurate assessment of forest structure and biomass is hampered by extensive field measurements that are time-consuming, costly, and inefficient. This is especially true in mangrove forests that have developed complex above-ground root structures for stability and survival in the harsh, anaerobic, and reducing conditions of water-logged sediments. These diverse structures can differ even among similar species, providing complex three dimensional structures and making them difficult to accurately assess using traditional allometric methods. Terrestrial laser scanners (TLS) have been used widely in collecting forest inventory information in recent years, mainly due to their fine-scale, detailed spatial measurements and rapid sampling. In this work we detected stems and roots in TLS data from three mangrove forests on Pohnpei Island in Micronesia using 3D classification techniques. After removing noise from the point cloud, the training set was acquired by filtering the facets of the point cloud based on angular orientation. However, many mangrove trees contain above-ground roots, which can incorrectly be classified as stems. We consequently trained a supporting classifier on the roots to detect omitted root returns (i.e., those classified as stems). Consistency was assessed by comparing TLS results to concurrent field measurements made in the same plots. The accuracy and precision for TLS stem classification was 82% and 77%, respectively. The same values for TLS root detection were 76% and 68%. Finally, we simulated the stems using alpha shapes for volume estimation. The average consistency of the TLS volume assessment was 85%. This was obtained by comparing the plot-level mean stem volume (m3/ha) between field and TLS data. Additionally, field-measured diameter-at-breast-heights (DBH) were compared to the lidar-derived DBH using the reconstructed stems, resulting in 74% average accuracy and an RMSE of 7.52 cm. This approach can be used for automatic structural evaluation, and could contribute to more accurate biomass assessment of complex mangrove forest environments as part of forest inventories or carbon stock assessments.

Divergent above- and below-ground responses of fungal functional groups to forest thinning

Forest disturbances have a strong effect on soil fungal communities and associated ecosystem processes. However, little is known about the response of mycelial biomass to disturbances, and how fungi reallocate carbon into different fungal structures under environmental stressors. We investigated above- and below-ground fungal biomass shifts in response to different intensities of forest management in Mediterranean Pinus pinaster forests. Soil fungal biomass was estimated by ergosterol quantification and production of sporocarps was estimated from repeated field samplings during 5 years in 26 experimental plots. Abundance of mycorrhizal and saprotrophic fungi belowground was determined using Pacific Biosciences sequencing of fungal ITS2 amplicons. Thinning had a prolonged negative effect belowground, inter- and intra-annually, on total fungal biomass and on the biomass of ectomycorrhizal fungi, but not on saprotrophic fungi. Total and ectomycorrhizal mushroom yields were negatively correlated with the total and the ectomycorrhizal mycelial biomass, respectively. Thinning also correlated positively with the aboveground/belowground ratio of both total and ectomycorrhizal fungal biomass. We show potential short-term shifts in resource allocation of fungi from below-to above-ground structures under disturbances such as forest thinning. Ectomycorrhizal fungi may respond to disturbances by increasing reproduction rather than colonizing the surrounding soil.

Spatial-temporal management of nitrogen and carbon on the peach tree (Prunus persicae L. Batsch.)

In perennial plants, the management of nitrogen (N) and carbon (C) is crucial to their durability, and studies encompassing an integrative viewpoint on the dynamics, location and form of the reserves are still missing. The carbon and nitrogen components were measured from September to May in peach trees which received two different levels of N fertilisation (control and limited). Significant differences were observed in the N and non-structural carbon concentrations regarding the organs, locations, time and fertilisation level. During the autumn, N and C accumulate at all levels of the tree and are sharply remobilised for the spring growth resumption. Amino acids (AA), especially arginine, appear to be the main form of storage of N. More present in roots, short branches and apices, the AA reach their maximum concentration in February and drop sharply with bud development. The remobilisation of the AA is initially induced in the branches close to the aboveground plant parts structures in formation, and before the contribution of the roots pool. The non-structural carbon (starch, soluble sugars, and organic acids) also accumulate during the autumn. No major differences are observed in the position and the size of the branches. The starch present in the root is the main form of carbon reserve of the peach tree. The starch stocks decline very early in November and are then gradually restored while the tree becomes autotrophic in the spring. The deprivation of N essentially caused a significant decrease in the stocks of AA and erased the differences in concentrations found in relation to the typology of branches. So the tree modified its N management strategy in response to the fertilisation level. The concentration of arginine, the main amino acid present in the bark or in the roots, appears as a relevant marker of its N status.

Mimicry of emergent traits amplifies coastal restoration success

Restoration is becoming a vital tool to counteract coastal ecosystem degradation. Modifying transplant designs of habitat-forming organisms from dispersed to clumped can amplify coastal restoration yields as it generates self-facilitation from emergent traits, i.e. traits not expressed by individuals or small clones, but that emerge in clumped individuals or large clones. Here, we advance restoration science by mimicking key emergent traits that locally suppress physical stress using biodegradable establishment structures. Experiments across (sub)tropical and temperate seagrass and salt marsh systems demonstrate greatly enhanced yields when individuals are transplanted within structures mimicking emergent traits that suppress waves or sediment mobility. Specifically, belowground mimics of dense root mats most facilitate seagrasses via sediment stabilization, while mimics of aboveground plant structures most facilitate marsh grasses by reducing stem movement. Mimicking key emergent traits may allow upscaling of restoration in many ecosystems that depend on self-facilitation for persistence, by constraining biological material requirements and implementation costs.

Interaction of load-bearing structures of the house with a pile basis

This paper presents the results of research of design solutions of multi-story building structures with the support of the extreme vertical load-bearing elements of the frame on the piles of the retaining wall. The research is performed on the basis of numerical modeling in three-dimensional formulation for the elements of the system «soil base - foundation - above-ground structures» at static loads. The analysis of the stress-strain state (SST) in the elements of the frame with such constructive solutions is carried out. Stresses of stress concentration in which irreversible deformations may occur at design loads have been identified.
 It is established that despite the fact that due to the change of the structural scheme of the foundation it was possible to achieve a relative difference of subsidence close to the normative value and a significant reduction of bending moments in the grille, there remained zones in the floor slabs manifestations of irreversible deformations were predicted. Recommendations are given and changes to the constructive scheme of the house are offered which allow to provide safe design decisions for all term of operation of the house.
 Another feature of the studied building is that the proposed design of foundations with piles of short length (6 m). With this solution, the zones of deformation under the height of the pile and the sole of the piles are closed and the deformations are determined by the size of the structure [1], and the piles only improve the soil properties in the upper part of the base due to its compaction. This solution allows you to achieve an economic effect by reducing the length of the piles, while ensuring the subsidence of the house within acceptable values.

Secret lifestyles of pyrophilous fungi in the genus Sphaerosporella.

PremisePyrophilous fungi form aboveground fruiting structures (ascocarps) following wildfires, but their ecology, natural history, and life cycles in the absence of wildfires are largely unknown. Sphaerosporella is considered to be pyrophilous. This study explores Sphaerosporella ascocarp appearance following a rare 2016 wildfire in the Great Smoky Mountains National Park (GSMNP), compares the timing of ascocarp formation with recovery of Sphaerosporella DNA sequences in soils, and explores the association of Sphaerosporella with post‐fire Table Mountain pine (Pinus pungens) seedlings.MethodsBurned sites in the GSMNP were surveyed for pyrophilous fungal ascocarps over 2 years. Ascocarps, mycorrhizae, and endophyte cultures were evaluated morphologically and by Sanger sequencing of the nuclear ribosomal ITS gene region (fungal barcode; Schoch et al., 2012). DNA from soil cores was subjected to Illumina sequencing.ResultsThe timing and location of post‐fire Sphaerosporella ascocarp formation was correlated with recovery of Sphaerosporella DNA sequences in soils. Genetic markers (fungal barcode) of Sphaerosporella were also recovered from mycorrhizal root tips and endophyte cultures from seedlings of Pinus pungens.ConclusionsThis study demonstrates that Sphaerosporella species, in the absence of fire, are biotrophic, forming both mycorrhizal and endophytic associations with developing Pinus pungens seedlings and may persist in nature in the absence of wildfire as a conifer symbiont. We speculate that Sphaerosporella may fruit only after the host plant is damaged or destroyed and that after wildfires, deep roots, needle endophytes, or heat‐resistant spores could serve as a source of soil mycelium.

Effects of Past and Present-Day Landscape Structure on Forest Soil Microorganisms

Theory surrounding landscape ecology have been built on the species distribution of birds and plants, but increasing evidence now exists for below-ground organisms, whose dispersal may also be affected by above-ground landscape structures. Uncertainties remain for how communities of microorganisms respond to landscape structure over time, and whether some groups of microorganisms react more than others. Here, we investigated if fungal or bacterial diversity is driven by the amount of forest cover in the current or the past landscape. We tested the Habitat Amount Hypothesis (HAH) on ancient forests of the Cevennes national park, that experienced increased fragmentation 150 years ago, and are today surrounded by recent forests. As ancient forests are often more diverse in plant species, we hypothesized that the higher quantity of ancient forests in the landscape, the richer local fungal and bacterial communities would be. More precisely, we expected that ectomycorrhizal fungi, and pathotrophic fungi, often indicators of mature forests, would be also more sensitive to forest history and therefore to the quantity of ancient forests than bacteria and saprotrophic fungi. We sampled 40 soil cores per 0.5 ha, pooled in 8 composite samples per plot in 27 landscapes and sequenced ITS and 16S markers by Illumina-Mi seq. To identify functional groups of fungi, we relied on their taxonomy and the use of public databases. Our results partly follow the HAH, as fungal richness was positively related with the quantity of ancient forests in the landscape and not by the focal patch size. Ectomycorrhizal and pathotrophic fungi were positively affected by the ancient forest cover, and so were saprotrophic ones, but not bacteria. Local factors also shaped the communities such as soil composition and elevation, confirming classical patterns in soil microbial ecology. Interestingly, past landscape structure was better at explaining fungal community richness than contemporary landscape, suggesting a time lag in the response of communities to landscape modification and a potential extinction debt. Our results reveal the importance of below-ground communities in studies of landscape and historical ecology, with their structure and functions likely to be intimately linked with soil and landscape history.