Pine Soil Research Articles

Input of high-quality litter reduces soil carbon losses due to priming in a subtropical pine forest

To date, it is unclear how differences in litter quality affect soil organic matter (SOM) decomposition through a phenomenon called 'priming effects' (PEs), especially for low-fertility forest soils under field conditions. Here, the effects of low- and high-quality leaf litter on PE and microbial metabolism of litter-derived carbon (C) were explored in a low-fertility pine (Pinus massoniana) plantation. A 185-day in situ incubation experiment was carried out by adding two 13C-labeled leaf litters to the pine soil—a low-quality (high lignin: nitrogen ratio) litter sourced from pine and a broadleaved species Schima superba produced high-quality (low lignin: nitrogen ratio) litter. To determine the key microbial groups contributing to PEs, the abundance of 13C-labeled litter enrichment in soil phospholipid fatty acids (13C-PLFAs) was quantified. We found that high-quality litter decomposed more rapidly than low-quality litter, with both litter-derived CO2 efflux reaching a plateaued level during the experimental period. Low-quality litter induced net positive PEs, while high-quality litter induced net negative PEs during the litter decomposition processes. The 13C-PLFAs results showed that bacterial groups governed the negative PEs induced by high-quality litter, whereas fungal communities targeted the positive PEs induced by low-quality litter. Random forest model and variation partitioning analysis demonstrated that the direction and magnitude of PEs were driven by litter-induced changes in key microbial groups rather than the structure of the microbial community. Our results demonstrate that microorganisms preferentially utilized litter-derived C in high-quality litter treatment and SOM in low-quality litter treatment, respectively. In contrast to low-quality litter, adding high-quality litter promoted the microbial metabolism of litter-derived C, reducing SOM decomposition (strong negative PEs). Taken together, this study provides isotope-based suggestions for the improvement of degraded pine forests—introducing tree species that produce high-quality litter may benefit soil C sequestration by reducing soil C losses due to PE in nutrient-poor pine forests.

Metal cation concentrations improve understanding of controls on soil organic carbon across a precipitation by vegetation gradient in the Patagonian Andes

Tephra-derived soils retain more organic carbon (C) than soils formed from any other parent material, but this C may be sensitive to changes in climate and land use. Here we evaluate the effects of precipitation, temperature, and afforestation on extractable metals and organic C storage in young tephra-derived soils in a temperate climate. We conducted our investigation across five sites in the Patagonian Andes that vary from 250 mm to 2200 mm mean annual precipitation, and 12 to 9.7 ℃ mean annual temperature from east to west. At each of the five sites are paired plots of natural vegetation, varying from grasses and shrubs at the dry sites to closed-canopy forest at the wet, and stands of Pinus ponderosa planted in monocultures 35 years prior to sampling. Previous research at these sites showed that aboveground net primary production and soil organic C increased with rainfall, but total soil organic C content was lower in pine plantations than natural vegetation. Here we assess whether variation in precipitation and vegetation type also affect soil mineral properties that promote soil C stabilization. Soils were collected to the depth of auger refusal and extracted with 0.5 M HCl for 24 h to target the combined exchangeable and adsorbed metals, including secondary short-range-ordered mineral phases and the plant available pools of Mg, Ca, and K. Pine afforestation lowered concentrations of HCl-extractable K (p < 0.1) and Ca (p < 0.01) within the top 0 – 30 cm. Other elements, while not affected by vegetation type, did respond to the rainfall gradient. Al, Si, P, and Mn all increased in the surface soils with increasing rainfall (p < 0.01), suggesting the development of short-range-order volcanic mineral phases that retain nutrients such as P and Mn. The addition of Al and Ca in the linear model to describe soil organic C explained more of the total variance than rainfall and vegetation type alone, indicating the importance of Al complexes and cation (Ca) bridging with secondary minerals to soil C retention. Importantly, the lower concentration of Ca in planted pine soils may signal a long-term decrease in the potential soil C stored in afforested soils due to a lower capacity for cation bridging. Our results show that the chemistry of these young tephra soils is dynamic, responding to both precipitation and afforestation in distinct ways with potential long-term impacts on nutrient cycling and C storage.

Hyperspectral Inversion of Soil Carbon and Nutrient Contents in the Yellow River Delta Wetland

Hyperspectral inversion techniques can facilitate soil quality monitoring and evaluation. In this study, the Yellow River Delta Wetland Nature Reserve was used as the study area. By measuring and analyzing soil samples under different vegetation types and collecting soil reflectance spectra, the relationships between vegetation types, soil depth, and the changes in soil total carbon (TC), total nitrogen (TN), and total phosphorus (TP) contents were assessed. The spectral data set was changed by spectral first derivative processing and division of the sample set according to vegetation type. The correlation between soil carbon, nitrogen, and phosphorus contents, and soil spectra was also analyzed, sensitive bands were selected, and the partial least-squares (PLS) method, support vector machine (SVM) method, and random forest (RF) model were used to establish the inversion model based on the characteristic bands. The optimal combination of spectral transformation, sample set partitioning, and inversion model was explored. The results showed significant differences (p &lt; 0.05) in soil TC, TN, and TP contents under reed and saline alkali poncho vegetation, but not between soil element contents under different stratifications of the same plant species. The first derivative reflectance had higher correlation coefficients with soil TC, TN, and TP contents compared with the original reflectance, while the sensitive bands and quantities of the three elements differed. The division of the sample sets according to vegetation type and the first derivative treatment can improve the prediction accuracy of the model. The best combination of sample set plus FD plus RF for TC, TN, and TP in reed soil and sample set plus FD plus SVM for TC, TN, and TP in saline alkali pine soil provides technical support to further improve the prediction accuracy of TC, TN, and TP in wetland soil.

Comparative analysis of planted and unplanted controls for assessment of rhizosphere priming effect

The rhizosphere priming effect (RPE) is increasingly being considered to be an important regulator of soil organic matter (SOM) decomposition and nutrient turnover, with potential importance for the global CO 2 budget. As a result, studies on the RPE have rapidly increased in number over the last few years. Most of these experiments have been performed using unplanted soil as the control, which could potentially lead to incorrect assessment of the RPE. Therefore, we performed a greenhouse experiment to investigate how the choice of control ( i.e. , unplanted control and planted control) influenced the quantification of RPE on SOM decomposition and gross nitrogen (N) mineralization, and to link this to differences in microbial and abiotic soil properties between the two controls. In the planted control, planted seedlings were cut at soil surface 5 d before measurement of the RPE. The RPE on SOM decomposition was positive in pine soil and almost 2-fold higher when calculated from the planted control than from the unplanted control. In spruce soil, a negative RPE on SOM decomposition was found when calculated from the planted control, while the RPE was positive when calculated from the unplanted control. No RPE on gross N mineralization was found when calculated from the planted control, while a positive RPE of more than 100% was found when calculated from the unplanted control. The microbial biomass and growth rate were lower, while the inorganic N content was higher in the unplanted control than in the planted control. The microbial community composition and potential enzyme activity were similar in the planted treatment and planted control, but they differed significantly in the unplanted control. The results showed that the RPE varied widely depending on the choice of control; thus, we suggest that a planted control, in which the aboveground plant parts are removed only a few days before the measurement of RPE, should be used as the control when elucidating the RPE on belowground C and N cycling responses to environmental change.

Response of bacterial community structure to different ecological niches and their functions in Korean pine forests.

A healthy plant microbiome is diverse, taxonomically-structured, and gives its plant host moderate advantages in growth, development, stress tolerance, and disease resistance. The plant microbiome varies with ecological niches and is influenced by variables that are complex and difficult to separate from each other, such as the plant species, soil, and environmental factors. To explore the composition, diversity, and functions of the bacterial community of Korean pine forests, we used high-throughput sequencing to study five areas with different forest ages from June to October 2017 in northeast China. We obtained 3,247 operational taxonomic units (OTUs) based on 16S rRNA gene sequencing via an Illumina Hi-seq platform. A total of 36 phyla and 159 known genera were classified. The Shannon index of the bacterial community from the rhizospheric soil was significantly higher (p < 0.01, n = 10) than that of the root tips. Beta-diversity analysis confirmed that the bacterial community of the rhizospheric soil was significantly different (p < 0.001) from the root tips. Nine bacterial phyla were dominant (relative richness > 1%) in the rhizospheric soil, but there were six dominant phyla in the root tips. Proteobacteria was the core flora in the root tips with a relative abundance of more than 50%. It is known that the formation of bacterial communities in the rhizospheric soil or the root is mainly caused by the processes of selection, and we found a relatively high abundance of a few dominant species. We further analyzed the correlations between the bacterial community from the rhizospheric soil with that of the root tips, as well as the correlations of the bacterial community with soil physicochemical properties and climate factors. We used Functional Annotation of the Prokaryotic Tax (FAPROTAX) to predict the functions of the bacterial community in the rhizospheric soil and root tips. Five related phototrophic functions, nine nitrogen cycle functions, two related chemoheterotrophic functions, and two others were predicted. The abundance of the bacteria phyla performing relevant functions was different in the rhizospheric soil than in the root tips. These functions were significantly influenced by the contents of nitrogen, phosphorus, and potassium in the soil habitat. The bacterial composition and functions in the rhizospheric soil and root tips of Korean pine were analyzed, and the results demonstrated the importance of soil and plant species on the bacterial community in the below ground plant microbiome.

Dark CO2 fixation in temperate beech and pine forest soils

Soils are the largest terrestrial organic carbon pool and the largest terrestrial source of atmospheric CO2. Non-phototrophic CO2 fixation by microbes re-fixes and recycles CO2 respired in soils. Our previous study showed that in temperate deciduous forest soil profiles, rates of dark CO2 fixation were proportional to microbial biomass, irrespective of soil depth. However, the amount and quality of organic matter entering different soil depths vary for different temperate forest types and these influence microbial communities with unknown consequences for CO2 fixation rates. To test whether differences in the amount and quality of SOC caused by tree species affect dark CO2 fixation rates with depth, we conducted a study using acidic soils from two forest plots from the Schorfheide-Chorin Exploratory, Germany. These soils, dominated by either beech (deciduous) or pine (coniferous) tree stands differ in their SOC content and quality. We traced the incorporation of 2% (v:v) 13C–CO2 label into microbial biomass and estimated the CO2 fixation rates relative to microbial biomass carbon content (in μg C g MBC−1 d−1) across the soil profiles. The rates of dark CO2 fixation per g MBC were similar across the beech soil profiles, but significantly lower in the pine soils at the B2 and BC horizons, suggesting that while dark CO2 fixation rates are linked to MBC in deciduous forest soils, other factors influence dark CO2 fixation rates in coniferous forest soils. The pine subsoils had low SOC content and quality, with a microbial community enriched with heterotrophic fermenters like Chloroflexi that are predicted to have a lower potential for heterotrophic CO2 fixation compared to the other dominant bacteria phyla. In contrast, the beech soil profiles, characterized by higher SOC inputs, featured higher fractions of copiotrophs like Proteobacteria, Acidobacteria, and Actinobacteria predicted to have high heterotrophic CO2 fixation potential. We thus speculate that in contrast to the beech soils, lower SOC inputs in the pine subsoils affected the community composition, leading to lower CO2 fixation rates. We further made comparisons to soils dominated by mixed deciduous trees and featuring a higher MBC and SOC content. Over this range of temperate forest soils, CO2 fixation rates were highest in the mixed deciduous forest soils, with MBC and Shannon index (used as a proxy parameter for community composition) showing the strongest correlations with the varying CO2 fixation rates. Our study suggests that predictions of dark CO2 fixation rates need to consider tree-species specific or site-specific conditions, as these may alter root carbon inputs and affect microbial community composition and their metabolic CO2 fixation potentials in soil.

Methodology for Assessing and Managing the Environmental Performance of Skidding and Feller Buncher Tractors

Systematic assessments on the effects of skidding systems on features of forest blueberry pine soil were conducted as part of this study. Assessing the ecological efficiency of forest skidding machines showed that the most significant impact (by 2.0–2.2 times) on soil compaction was observed at loading sites rather than during transportation. Lightweight loam density and sand density increased by 25% and 2%, respectively, after more than two passages of the skidding system. Pressure in 33L-32 tires of forestry machinery in operation on a solid surface varied from 46.5 kPa to 196 kPa at maximum load. Studying the impact of tires on soil compaction showed that the environmental efficiency of forestry equipment can be enhanced if the optimal tire pressure at average loads does not exceed 70 kPa for tracked vehicles and 150 kPa for wheeled vehicles in summer seasons. When ground grips were fully immersed, the pressure of forwarders on soil was reduced. These study results can be used to establish organizational and technological measures in order to manage the negative impact of skidding systems and to increase the environmental effects of their performance.

Substrate stoichiometric regulation of microbial respiration and community dynamics across four different ecosystems

Microbes decompose soil organic matter (SOM), yet it is unclear how substrate inputs (i.e., stoichiometry) directly mediate microbial activities and community dynamics. We hypothesized that C+N input has the largest effect on microbial respiration and community structure, followed by C input and N input. Soils were collected from four ecosystems (grassland, piñon-juniper, ponderosa pine, mixed conifer) and amended with NH4NO3 (N only; 100 μg g−1 wk−1), 13C-glucose (C only; 1000 μg g−1 wk−1), or C+N in a five-week laboratory incubation. We found that C+N input induced the greatest total respiration while C input induced the greatest SOM-derived respiration (i.e., priming effect) across ecosystems. Shifts in community composition were the largest with C+N input, followed by C input, and showed little response to N input. C only and C+N inputs increased both of the relative and absolute abundances of Actinobacteria and Proteobacteria (α, β, γ), but reduced the relative abundances of Verrucomicrobia and δ-Proteobacteria. C+N input increased the relative abundances of Bacillales, Rhizobiales, Burkholderiales and of 9 families, and reduced the relative abundances of Myxococcales and of 12 families, but showed little effect on the absolute abundances of these bacterial taxa. N input reduced the absolute abundances of Actinobacteria, Proteobacteria, and Verrucomicrobia but did not affect their relative abundances in the mixed conifer soil; by contrast, N input reduced relative abundances of δ-Proteobacteria and increased the relative abundances of γ-Proteobacteria but did not affect their absolute abundances in the ponderosa pine soil. We also found that substrate inputs were the main driver of SOM decomposition, microbial respiration and diversity, while soil ecosystem was the main driver of community composition and abundances of most bacterial phyla. Our work suggests that substrate stoichiometry has predictable effects on soil C cycling, microbial diversity and community composition, but has variable effects on microbial abundances, and that incorporating bacterial gene copies in abundance calculations can help more accurately estimate microbial responses across taxonomic levels and ecosystems.

Bioactive Compounds Involved in the Formation of the Sparse Understory Vegetation in Pine Forests

The spices of Pinus, the most widespread genus of the Pinaceae family in the northern hemisphere, often have sparse understory vegetation. However, sunlight intensity on the pine forest floor is sufficient for undergrowth. Allelopathy, therefore, is considered to be involved in the formation of sparse understory vegetation. The evidence for the allelopathy of several pine species has accumulated in the literature over the decades. Extracts of pine needle- like leaves, roots, litter, and soil under pine trees suppressed several plant species, including undergrowth plant species of pine forests. A substantial number of secondary metabolites such as terpenoids, phenolics, cinnamic acids, carboxylic acids, fatty acids, and flavonoids have been identified in pine needles and roots, litter and soil under pine trees. The evidence also suggests that some of these compounds are probably released into the soil through the decomposition of the plant litter, and into the surrounding environment as volatiles. The most active compounds found in the pine soil were methyl 15-hydroxy-7-oxodehydroabietate and 7-oxodehydroabietic acid; both compounds may also be formed through the degradation of resin acids, which were found abundantly in pine trees. Bioactive compounds released into the soil and surrounding environment possibly act as allelochemicals and suppress the invasion of undergrowth plants into the forests, resulting in the establishment of the sparse understory vegetation. The paper summarized the allelopathic activity of 16 Pinus species and 38 allelochamicals.

Covariation between plant biodiversity and soil systems in a European beech forest and a black pine plantation: the case of Mount Faito, (Campania, Southern Italy)

Both climate and land-use changes, including the introduction and spread of allochthonous species, are forecast to affect forest ecosystems. Accordingly, forests will be affected in terms of species composition as well as their soil chemical and biological characteristics. The possible changes in both tree cover and soil system might impact the amount of carbon that is stored in living plants and dead biomass and within the soil itself. Additionally, such alterations can have a strong impact on the detrital food web that is linked to litter decomposition. Although there are studies on the influence of plant diversity on soil physical and chemical characteristics, the effects on soil biological activity and carbon storage processes remain largely unknown. The aim of this study was to investigate and compare chemical and biological variables in covariation with plant communities in an autochthonous beech forest (Fagus sylvatica L.) and a black pine plantation (Pinus nigra J.F. Arnold subsp. nigra). Our results confirmed that the two communities were considerably different, with the old-growth beech community having a lower number of plant species and the pine community was in development as a consequence of anthropogenic activities. These aspects of the two communities were also reflected in the soil, with the beech soil having higher nitrogen levels and a more specialized microbial community compared to the pine soil, with most extracellular enzymes (such as peroxidase and chitinase) showing lower activity in the pine soil.

Аккумуляция кобальта и никеля в почве, подстилке и в органах сосны обыкновенной в условиях Елецкого промышленного центра

Information was obtained on the content of cobalt and nickel in soil, litter, and organs of Scots pine in the conditions of the Yelets industrial center. It was found that, under pollution conditions, the content of cobalt and nickel in vegetative organs, soil, litter is higher than the control values. Moreover, their content increases both during the growing season and with an increase in the age of the pine (needles and shoots). There is an uneven accumulation of metal in various organs of Scots pine. A high level of correlation was noted: between the content of cobalt in the soil and needles of the 1st year, shoots of the 1st year - PP No. 1 (r = 0.86; r = 0.78); between the content of cobalt in the soil and bark, litter - PP No. 2 (r = 0.99; r = 0.96); between the nickel content in the soil and needles of the 1st year, needles of the 2nd year, shoots of the 1st year - PP # 1 (r = 0.84; r = 0.78; r = 0.80); between the nickel content in soil and needles of the 1st year, shoots of the 1st year, bark, litter - PP No. 2 (r = 0.92; r = 0.89; r = 0.78; r = 0.87). Keywords: COBALT, NICKEL, SCOTS PINE, NEEDLES, SHOOTS, SOIL LITTER

Shifts in soil chemical and microbial properties across forest chronosequence on recent volcanic deposits

Afforestation of new unconsolidated volcanic deposits is a practice used to stabilize barren areas and enhance the accumulation of organic matter in the developing soil. Changes in soil carbon (C) and nitrogen (N) pools, including the soluble and microbial fractions, within the first decades since afforestation have been poorly investigated. Therefore the objective of the present study was to investigate how key C and N pools vary in litter and soil of four forests planted on barren volcanic deposits from recent Mount Vesuvius eruptions. We examined three forest stands (40, 70 and 100 years old) afforested with Stone pine (Pinus pinea L.) and a 40-year old forest of Black pine (Pinus nigra Arn.). As a baseline of C and N pools prior to afforestation, data from treeless sites were included in the study. Both the inputs with litter fall and soil C and N stocks increased with forest age in the Stone pine stands. In the mineral soil, C concentration per gram soil dry weight and C:N ratio increased with age from treeless sites to the oldest forest. Microbial biomass C and fungal biomass as a fraction of organic carbon (OC) and respiration per unit OC (an index of organic matter mineralization potential) decreased significantly with stand age. The results suggest that a main driver of C accumulation in the mineral soil is the decline with increasing stand age of the microbial fraction of organic matter and its activity. The comparison between the two pine species revealed that litter production was more abundant in the Black pine than in the even-aged, 40-year-old, Stone pine stand; moreover Black pine litter was more acidic and had a higher stable residue than Stone pine litter. Therefore a different pattern of C sequestration occurs with a higher C stock in the organic layers and a lower C stock in the mineral soil of Black pine compared to Stone pine.

Water repellency in eucalyptus and pine plantation forest soils and its relation to groundwater levels estimated with multi-temporal modeling

Abstract Water repellency makes soils capable of resisting to the penetration of water applied on the surface and inflict various influences on groundwater. The objectives of the present study were to identify the water repellency under pine and eucalyptus plantations, to determine social impacts of water level changes, to find possible changes in groundwater levels in the surrounding areas during the past four decades, and to relate water repellent characteristics of soils with the groundwater level changes. The study was conducted in eucalyptus (Eucalyptus grandis) and pine (Pinus caribaea) plantation forests located in Upcountry intermediate zone, Sri Lanka. Each land was separated into three blocks (B1, B2, B3) based on the slope. Water repellency was measured with water drop penetration time (WDPT) and contact angle. The water entry value was estimated with the pressure head method. Interconnected social impacts was examined using a questionnaire based survey. Groundwater levels from 1980 to present were modeled with remotely sensed information. Both eucalyptus and pine forest soils showed water repellency, which decreased with increasing soil depth. Eucalyptus soils showed highly hydrophobic conditions on the surface (WDPT&gt;7200 s). Ponding depths required for entry of water into the soil in eucalyptus soils was 4.6–5.3 cm, whereas that of pine soils was 1.5–4.0 cm, although achieving these levels would be difficult considering the steep slopes. Contact angle showed positive logarithmic correlation with water entry value. The people living in the surrounding areas expressed less water availability for their domestic purposes, decreased water level in household wells, and drying up of natural water resources at present compared with 1980s. Modelling with remotely sensed thematic maps confirmed that the groundwater levels in both areas has decreased over the time. It indicated that the eucalyptus and pine vegetation have created unfavorable conditions in regard with water entry and groundwater recharge. Proper attention from the responsible authorities will be essential to prevent the adverse impacts of on groundwater resources.

How does varying water supply affect oxygen isotope variations in needles and tree rings of Scots pine?

In many regions, drought is suspected to be a cause of Scots pine decline and mortality, but the underlying physiological mechanisms remain unclear. Because of their relationship to ecohydrological processes, δ18O values in tree rings are potentially useful for deciphering long-term physiological responses and tree adaptation to increasing drought. We therefore analyzed both needle- and stem-level isotope fractionations in mature trees exposed to varying water supply. In a first experiment, we investigated seasonal δ18O variations in soil and needle water of Scots pine in a dry inner Alpine valley in Switzerland, comparing drought-stressed trees with trees that were irrigated for more than 10years. In a second experiment, we analyzed twentieth-century δ18O variations in tree rings of the same forest, including a group of trees that had recently died. We observed less 18O enrichment in needle water of drought-stressed compared with irrigated trees. We applied different isotope fractionation models to explain these results, including the Péclet and the two-pool correction, which considers the ratio of unenriched xylem water in the needles to total needle water. Based on anatomical measurements, we found this ratio to be unchanged in drought-stressed needles, although they were shorter. The observed lower 18O enrichment in needles of stressed trees was therefore likely caused by increased effective path length for water movement within the leaf lamina. In the tree-ring study, we observed lower δ18O values in tree rings of dead trees compared with survivors during several decades prior to their death. These lower values in declining trees are consistent with the lower needle water 18O enrichment observed for drought-stressed compared with irrigated trees, suggesting that this needle-level signal is reflected in the tree rings, although changes in rooting depth could also play a role. Our study demonstrates that long-term effects of drought are reflected in the tree-ring δ18O values, which helps to provide a better understanding of past tree physiological changes of Scots pine.

Antifungal Effects of Volatile Organic Compounds Produced by Rahnella aquatilis JZ-GX1 Against Colletotrichum gloeosporioides in Liriodendron chinense × tulipifera.

The use of volatile organic compounds (VOCs) produced by microorganisms for the biological control of plant diseases has attracted much attention in recent years. In this study, the antifungal activity and identity of VOCs produced by Rahnella aquatilis JZ-GX1 isolated from the rhizosphere soil of pine were determined and analyzed. The effect of the VOCs on the mycelial growth of Colletotrichum gloeosporioides, the pathogen of Liriodendron chinense × tulipifera black spot, was determined by a joined-petri dish fumigation method. An in vitro leaf inoculation method was used to determine the fumigation effect of the VOCs on Liriodendron black spot. VOCs with antifungal activity were collected by headspace solid-phase microextraction (SPME), and their components were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that the VOCs secreted by JZ-GX1 inhibited the mycelial growth of the tested pathogen. The VOCs destroyed the morphology of the mycelium, significantly increased the permeability of the cell membrane and downregulated the expression of pathogenicity-related genes during mycelial infection, thus inhibiting the expansion of anthracnose disease spots in leaves. In the volatile compound profile, 3-methyl-1-butanol and 2-phenylethyl methyl ether significantly inhibited the mycelial growth and spore germination of C. gloeosporioides. This work provides a new strategy for the research and application of microorganisms and bioactive compounds to control plant anthracnose.

Bacterial Community Structure of Pinus Thunbergii Naturally Infected by the Nematode Bursaphelenchus Xylophilus.

Pine wilt disease (PWD) caused by the nematode Bursaphelenchus xylophilus is a devastating disease in conifer forests in Eurasia. However, information on the effect of PWD on the host microbial community is limited. In this study, the bacterial community structure and potential function in the needles, roots, and soil of diseased pine were studied under field conditions using Illumina MiSeq coupled with Phylogenetic Investigation of Communities by Reconstruction of Unobserved states (PICRUSt) software. The results showed that the community and functional structure of healthy and diseased trees differed only in the roots and needles, respectively (p < 0.05). The needles, roots, and soil formed unique bacterial community and functional structures. The abundant phyla across all samples were Proteobacteria (41.9% of total sequence), Actinobacteria (29.0%), Acidobacteria (12.2%), Bacteroidetes (4.8%), and Planctomycetes (2.1%). The bacterial community in the healthy roots was dominated by Acidobacteria, Planctomycetes, and Rhizobiales, whereas in the diseased roots, Proteobacteria, Firmicutes, and Burkholderiales were dominant. Functionally, groups involved in the cell process and genetic information processing had a higher abundance in the diseased needles, which contributed to the difference in functional structure. The results indicate that PWD can only affect the host bacteria community structure and function in certain anatomical regions of the host tree.

Heritable genetic variation but no local adaptation in a pine-ectomycorrhizal interaction

Local adaptation of plants to mycorrhizal fungi helps determine the outcome of mycorrhizal interactions. However, there is comparatively little work exploring the potential for evolution in interactions with ectomycorrhizal fungi, and fewer studies have explored the heritability of mycorrhizal responsiveness, which is required for local adaptation to occur. We set up a reciprocal inoculation experiment using seedlings and soil from four populations of Scots pine (Pinus sylvestris) from Scotland, measuring seedling response to mycorrhizal inoculation after 4 months. We estimated heritability for the response traits and tested for genotype × environment interactions. While we found that ectomycorrhizal responsiveness was highly heritable, we found no evidence that pine populations were locally adapted to fungal communities. Instead, we found a complex suite of interactions between pine population and soil inoculum. Our results suggest that, while Scots pine has the potential to evolve in response to mycorrhizal fungi, evolution in Scotland has not resulted in local adaptation. Long generation times and potential for rapid shifts in fungal communities in response to environmental change may preclude the opportunity for such adaptation in this species, and selection for other factors such as resistance to fungal pathogens may explain the pattern of interactions found.

Changes in carbon stocks of soil and forest floor in black pine plantations in Turkey

The objectives of this study were: (1) to determine carbon stock changes in the soil and forest floor of black pine (Pinus nigra subsp. pallasiana) plantations in Turkey; (2) to determine the effects of thinning on annual carbon accumulation in both; and, (3) to investigate relationships between annual carbon storage in soil and forest floor and stand characteristics of black pine. Samples were taken in 90 plots from stands at the pole (dbh = 11.0–19.9 cm) and sawlog (dbh = 20.0–35.9 cm) stages. Carbon analyses of soil and forest floor samples showed that in unthinned plantations significant organic carbon was sequestered an average of 1.47 Mg ha−1 a−1 in the soil and 0.20 Mg ha−1 a−1 in the forest floor. Organic carbon sequestered annually in the soil was significantly lower in thinned than in unthinned stands, while differences in the forest floor were insignificant. There were positive correlations between carbon sequestered in the soil and stand age, average DBH, mean stand height, basal area, and site index. Carbon sequestered the forest floor increased with basal area. As a result, carbon sequestered in the soil should not be ignored in greenhouse gas inventories because carbon stored belowground was approximately 70% of the aboveground pool.

Analysis of a New Strain of Pseudomuriella engadinensis (Sphaeropleales, Chlorophyta) for Possible Use in Biotechnology

The species diversity of green coccoid algae is often difficult to study using light microscopy due to their complex morphology. Algae, which have morphological and ecological similarities with the genera Bracteacoccus Tereg., Dictyococcus Gerneck, and Pseudomuriella Hanagata, are one of the most taxonomically complex examples. Often, only a comparison of nucleotide sequences allows one to carry out a reliable identification and find out the phylogenetic identity of the studied objects. Pseudomuriella belongs to the group of genetically diverse genera with a homogeneous Bracteacoccus-like morphology. The combined use of two genetic markers (18S rDNA nuclear gene and chloroplast rbcL gene), along with light microscopy and comparison of fatty acid profiles, allowed the identification of the green algae strain isolated from the soil of the artificial pine and robinia plantation in the steppe zone of Ukraine as Pseudomuriella engadinensis (Kol et Chodat) Fucikova, Rada et Lewis—the first find of the species in the flora of algae in Ukraine. Analysis of the fatty acid composition of the studied strain’s cells showed that the total lipid content in the stationary growth phase was at the level of 87.9 ± 2.1 mg/g dry cell mass, and the main fatty acids were palmitic, hexadecadienoic, ruganic, oleic, linoleic, and α-linolenic—their share accounted for 82.4% of the total amount of fatty acids.

Contribution of root-associated microbial communities on soil quality of Oak and Pine forests in the Himalayan ecosystem

Microorganisms, the fundamental components of all the ecosystems, play significant role in various biological processes such as biodegradation, mineralization and nutrient mobilization. The role of rhizosphere associated microbial interactions with reference to their contribution in enzymatic activities in two dominant forest tree species of Indian Himalaya, namely Oak (Quercus leucotrichophora) and Pine (Pinus roxburghii), is focused in the present study. Rhizosphere soil and root samples were collected in active and dormant seasons for two consecutive years from three selected sites. Root samples were studied for colonization by fungal associates as indicator of their ecological functions. Soil samples were analyzed for physico-chemical characteristics and enzymatic activities as a measure of soil health. Dark Septate Endophytes (DSE) and fungal colonization were observed in roots of both the tree species. Microscopic observations revealed high percentage of DSE and fungal hyphae (76–96 and 32–78%) in Oak while in Pine roots this percentage was 8–10 and 48–86%, respectively. Most of the soil physico-chemical parameters were found higher in Oak soil except total phosphorus content. Further, activity of acid phosphatase and dehydrogenase was recorded higher in Oak soil as compared to Pine soil. Pine soil samples showed high alkaline phosphatase and β-glucosidase activities. The study concludes that microbial associations and their activities in Oak and Pine soils appeared to define the specific properties of both forest types in terms of slow biodegradation in Pine and higher carbon sequestration in Oak.