Differential Variation in Non-structural Carbohydrates in Root Branch Orders of Fraxinus mandshurica Rupr. Seedlings Across Different Drought Intensities and Soil Substrates

Non-structural carbohydrates (NSCs) facilitate plant adaptation to drought stress, characterize tree growth and survival ability, and buffer against external disturbances. Previous studies have focused on the distribution and dynamics of NSCs among different plant organs under drought conditions. However, discussion about the NSC levels of fine roots in different root branch orders is limited, especially the relationship between fine root trait variation and NSC content. The objective of the study was to shed light on the synergistic variation in fine root traits and NSC content in different root branch orders under different drought and soil substrate conditions. The 2-year-old Fraxinus mandshurica Rupr. potted seedlings were planted in three different soil substrates (humus, loam, and sandy–loam soil) and subjected to four drought intensities (CK, mild drought, moderate drought, and severe drought) for 2 months. With increasing drought intensity, the biomass of fine roots decreased significantly. Under the same drought intensity, seedlings in sandy–loam soil had higher root biomass, and the coefficient of variation of 5th-order roots (37.4, 44.5, and 53% in humus, loam, and sandy–loam soil, respectively) was higher than that of lower-order roots. All branch order roots of seedlings in humus soil had the largest specific root length (SRL) and specific root surface area (SRA), in addition to the lowest diameter. With increasing drought intensity, the SRL and average diameter (AD) of all root branch orders increased and decreased, respectively. The fine roots in humus soil had a higher soluble sugar (SS) content and lower starch (ST) content compared to the loam and sandy–loam soil. Additionally, the SS and ST contents of fine roots showed decreasing and increasing tendencies with increasing drought intensities, respectively. SS and ST explained the highest degree of the total variation in fine root traits, which were 32 and 32.1%, respectively. With increasing root order, the explanation of the variation in root traits by ST decreased (only 6.8% for 5th-order roots). The observed response in terms of morphological traits of different fine root branch orders of F. mandshurica seedlings to resource fluctuations ensures the maintenance of a low cost-benefit ratio in the root system development.

Water’s path from moss to soil: A multi-methodological study on water absorption and evaporation of soil-moss combinations

Mosses are often overlooked; however, they are important for soil-atmosphere interfaces with regard to water exchange. This study investigated the influence of moss structural traits on maximum water storage capacities (WSCmax) and evaporation rates, and species-specific effects on water absorption and evaporation patterns in moss layers, moss-soil-interfaces and soil substrates using biocrust wetness probes. Five moss species typical for Central European temperate forests were selected: field-collected Brachythecium rutabulum, Eurhynchium striatum, Oxyrrhynchium hians and Plagiomnium undulatum; and laboratory-cultivated Amblystegium serpens and Oxyrrhynchium hians. WSCmax ranged from 14.10 g g−1 for Amblystegium serpens (Lab) to 7.31 g g−1 for Plagiomnium undulatum when immersed in water, and 11.04 g g−1 for Oxyrrhynchium hians (Lab) to 7.90 g g−1 for Oxyrrhynchium hians when sprayed, due to different morphologies depending on the growing location. Structural traits such as high leaf frequencies and small leaf areas increased WSCmax. In terms of evaporation, leaf frequency displayed a positive correlation with evaporation, while leaf area index showed a negative correlation. Moisture alterations during watering and desiccation were largely controlled by species/substrate-specific patterns. Generally, moss cover prevented desiccation of soil surfaces and was not a barrier to infiltration. To understand water’s path from moss to soil, this study made a first contribution.

Beneficial cyanosphere heterotrophs accelerate establishment of cyanobacterial biocrust

Biological soil crusts (biocrusts) are communities of microbes that inhabit the surface of arid soils and provide essential services to dryland ecosystems. While resistant to extreme environmental conditions, biocrusts are susceptible to anthropogenic disturbances that can deprive ecosystems of these valuable services for decades. Until recently, culture-based efforts to produce inoculum for cyanobacterial biocrust restoration in the Southwestern US focused on producing and inoculating the most abundant primary producers and biocrust pioneers, Microcoleus vaginatus and members of the family Coleofasciculaceae (aka “ Microcoleus streenstrupii complex”). The discovery that a unique microbial community characterized by diazotrophs is intimately associated with M. vaginatus , known as the “cyanosphere”, suggests a symbiotic division of labor in which nutrients are traded between phototrophs and heterotrophs. To probe the potential use of such cyanosphere members in the restoration of biocrusts, we performed co-inoculations of soil substrates with cyanosphere constituents. This resulted in more rapid cyanobacterial growth over inoculations with the cyanobacterium alone. Additionally, we found that the mere addition of beneficial heterotrophs enhanced the formation of a cohesive biocrust without the need of additional phototrophic biomass within native soils that contain trace amounts of biocrust cyanobacteria. Our findings support the hitherto unknown role of beneficial heterotrophic bacteria in the establishment and growth of biocrusts and allow us to make recommendations concerning biocrust restoration efforts based on the presence of remnant biocrust communities in disturbed areas. Future biocrust restoration efforts should consider cyanobacteria and their beneficial heterotrophic community as inoculants. Importance The advancement of biocrust restoration methodologies for cyanobacterial biocrusts has been largely achieved through trial and error. Successes and failures could not always be traced back to particular factors. The investigation and application of foundational microbial interactions existing within biocrust communities is a crucial step toward informed and repeatable biocrust restoration methodologies.

Dependence of the Biological Activity of Brown Coal Humic Acids on the Concentrations of Macro and Trace Elements

The samples of humic preparations (HPs) containing macro and trace elements for plant nutrition were obtained based on humic acids isolated from brown coal of the Tisul deposit in the Kansk-Achinsk Coal Basin. The biological activity of the humic preparations was tested under laboratory and field conditions with the use of Iren and Novosibirskaya 89 varietal wheat seeds. A comparative assessment of the effects of the concentrations of various elements in the HPs on the growth parameters and productivity of cereals was carried out. The edaphic properties of soil substrates should be taken into account for a more effective use of humic preparations.

Spatiotemporal organization of bacteria/archaea in maize rhizosphere

<p>Plants interact with the rhizosphere microbiome via root exudates that consist of numerous metabolites serving as energy or carbon sources for microbial growth and as modulators of the uncountable rhizosphere interactions. The rhizosphere microbiome plays also an important role in plant health, growth, and productivity. Different drivers are known to shape the rhizosphere microbiome, but limited investigation exists whether there is a spatial variability in the microbiome along the root system (depth). The present study aimed to assess effects of potentially different drivers such as soil substrates, soil compartments (rhizosphere, and bulk soil), depths, and plant genotypes on bacterial/archaeal communities associated with two maize genotypes, root hair defective mutant (rth3), and the corresponding wild-type (WT). Experiments using maize genotypes rth3 and WT, grown on soil substrates loam, and sand under growth chamber, and field conditions were performed. Under growth camber conditions, the rhizosphere samples were harvested at twenty-two days after sowing the maize seeds from three different soil depths at 4.5 – 6.1 (GD1), 9.0 – 10.6 (GD2), and 13.5 – 15.1 (GD3) cm from soil surface. Under field conditions, analyses were carried out using both rhizosphere, and bulk soil samples taken at three developmental growth stages BBCH14, -19, and -59 of the maize plants; each from two depths at (0 – 20) FD1, and FD2 (20 - 40) cm from soil surface, except the BBCH14 (only samples from D1 were available). Bacterial/archaeal communities were analyzed by MiSeq Illumina sequencing of 16S rRNA gene fragments amplified from total community DNAs.</p><p>Under growth chamber conditions, we observed shifts in bacterial/archaeal diversity of maize rhizosphere at different depths as plant genotype- and soil substrate-dependent effects. Depth-dependent effects of maize rhizosphere (rth3/WT) on bacterial/archaeal compositions displayed high differences between GD1, and the GD3 on both soil substrates. The relative abundances of the bacterial phylum Proteobacteria were significantly higher at GD3 than GD1 for both plant genotypes on sand, but not on loam. Overall, the factor soil substrate was the strongest driver of bacterial/archaeal maize rhizosphere, followed by depth, and maize genotype.</p><p>Under field conditions, depths affected the rhizosphere bacterial/archaeal diversity only at the BBCH59 for WT grown on sand. Lower bacterial/archaeal diversity in soil substrates sand than loam was observed at both FD1 and FD2 in the rhizosphere, but not in bulk soil at all developmental growth stages of maize. The bacterial/archaeal diversity of both maize genotypes was not affected by developmental growth stages of maize on both soil substrates, and soil compartments. Depth gradients of bacterial/archaeal community composition in rhizosphere, and bulk soil displayed at BBCH59 on both soil substrates, and they were relatively higher on sand than loam (rhizosphere). Differences in relative abundances of the bacterial phyla Proteobacteria, and Actinobacteria between soil compartments, developmental growth stages of maize were observed mainly at FD1. Overall, factor soil compartment is the strongest driver of bacterial/archaeal communities followed by soil substrates, developmental growth stages and sampling depths for maize grown under field conditions.</p>

Comparative analysis of the bacterial community of the Patagonian lichen Peltigera frigida and its soil substrate

<p>The lichen microbiome includes a diverse community of organisms, spanning widely across the bacterial tree of life. Lichens have been proposed to form partially open symbiotic systems, in which some microorganisms may be transmitted along within lichen propagules, while others are acquired from the surrounding environmental community.</p><p>In this survey, we discuss the extent to which the lichen microbiome is connected to that of its immediate substrate. For this we sampled ten specimens of the Patagonian foliose cyanolichen <em>Peltigera frigida</em> and their underlying soil substrates in two forest sites of the Coyhaique National Reserve (Aysén Region, Chile). Using 16S metabarcoding with primers that exclude cyanobacteria, we identified a significant taxonomic divergence between the bacterial communities of lichens and substrates.</p><p>At the Phylum level, Proteobacteria (37% of relative abundance) are most abundant within lichens, while soil substrates are dominated by Acidobacteriota (39%). At the Genus level, some bacteria are significantly more abundant in lichens, such as <em>Sphingomonas</em> (8% in lichens vs 0.2% in substrates) or an unassigned genus of Chitinophagaceae (10% vs 2%). Conversely, genera like the unassigned acidobacterial genus SCN-69-37 (0.9% vs 12%) are more abundant in substrates.</p><p>Overall, our results are consistent with the idea that lichens shape their microbiome obtaining components from various sources, including reproductive propagules and the substrate on which they grow. Further experimental and ecological approaches are needed to assess the contribution of these microorganisms to the fitness of the symbiotic system.</p><p>Funding: FONDECYT 1181510.</p>

On the effect of different moss species on soil erosion, percolation and carbon relocation

<p>For decades, soil erosion has been a major environmental problem as it degrades the most productive soil layers, which threatens, among other things, food production worldwide. Although these effects have been known for a long time, there are still a variety of challenges to mitigating soil erosion in different ecosystems. As climate change progresses, the risk of soil loss increases, making the preparation of effective solutions very urgent. A current research focus is on the restoration of a protective soil cover following disturbances in the vegetation layer, e.g., through the reestablishment of biological soil crust communities. These are often dominated by bryophytes in humid climates. So far, several studies examined the general protective influence of bryophytes against soil erosion, however only few of them addressed how individual species affect specific erosion processes in detail.</p><p>To fill this research gap we investigated the impact of six moss species on soil erosion, percolation and carbon relocation by means of rainfall simulations. Therefore, we used topsoil substrate from four sites in the Schönbuch Nature Park in South Germany which covers different kinds of bedrock and varying soil texture and pH. Subsequently, they were sieved by 6.3 mm and filled into metal infiltration boxes (40 x 30 cm) up to a height of 6.5 cm. The moss species differ in origin (either collected in the field or cultivated in the lab) as well as growth form (pleurocarpous or acrocarpous). Rainfall simulations were performed for bare soil substrates, as well as for moss-covered soil substrates six months later and both in dry and wet conditions. Additionally, we conducted rainfall simulations with leaf and coniferous litter on bare soil substrates. During the simulations we monitored soil moisture in two position - 3 cm depth plus soil surface - with biocrust wetness probes (BWP) and quantified surface runoff, percolation and sediment discharge. Afterwards we determined carbon contents of the sediment and dissolved organic carbon in the liquid phase of runoff and percolated water.</p><p>While surface runoff was increased by 5% due to the litter cover compared to the bare soil substrate, sediment discharge decreased to 97%. Runoff rates could also be mitigated by 90 % as a result of the moss cover. Furthermore, due to the dense moss cover sediment rates were almost reduced to zero. Preliminary results show that there are differences between the moss species in terms of sediment discharge, but not in context with runoff. The analyses of carbon contents in surface runoff and the percolated water are still in progress, as is the evaluation of the BWP measurements. These outcomes will be presented at vEGU21.</p>

Soil-Moss-Relations: The path of water from dripping to infiltration

<p>Nonvascular plants like mosses are often overseen; however, they are important players in the soil-atmosphere interface in regard to water exchange. Mosses are especially known for their influence on surface runoff, infiltration, soil water content as well as soil evaporation. Moreover, they can enhance soil moisture by water uptake from dew, vapor or fog. Due to their ability to colonize a variety of different environments, such as temperate, boreal, alpine, arctic and dryland ecosystems, mosses are found all over the world. According to their wide distribution, the impact of mosses on soil hydrology is thus assumed to be of great relevance globally. In particular, the specific influence of different moss species and according soil substrates on water movement has been largely disregarded in this context.</p><p>In this study, we examined infiltration, percolation and evaporation patterns in moss-covered soil substrates typical for Central European forests during and after rainfall simulations. Soil substrates were sampled at four sites in the Schönbuch Nature Park in South Germany with different kinds of bedrock with varying soil texture and pH. Additionally, one acrocarpous and four pleurocarpous moss species common in central European forests were examined, either collected in Schönbuch Nature Park or cultivated in the lab. Substrates were filled into metal infiltration boxes (30 x 40 cm) to a height of 6.5 cm and mosses were placed on top of the substrates half a year prior to the experiment for acclimatization and rootage. The experimental setup consisted of duplicates of 6 differently combined soil substrate-moss cover samples. Using biocrust wetness probes (BWP), water content values were calculated from measurements of electrical conductivity during one hour of artificial irrigation and subsequent dehydration for 71 hours. BWPs were located in three positions per sample: a) in 3 cm soil depth, b) at the soil surface, and c) in the moss layer. Electrical conductivity and temperature at each BWP position, as well as air temperature and air humidity, were measured in 10 s intervals during the experiment.</p><p>Expecting a relation between infiltration, percolation, evaporation and maximum water content of moss species and soil substrates, we furthermore measured their maximum water storage capacities. As we assumed a high relevance of moss surface area on water storage capacities as well as evaporation rates, we also determined surface and leaf area indices of the studied moss species.</p><p>First results show relations between air humidity and moss as well as soil moisture. In addition, we observed different water content trends during percolation, infiltration and evaporation between the studied samples. Maximum water storage capacities differed significantly between the moss species with the loosest and the moss species with the densest structure. Preliminary results indicate that moss surface areas and maximum water storage capacities are not correlated. Since the data analysis is currently still in progress, further results will be presented at vEGU21.</p>