Pine Stands Research Articles

Perbanyakan Mikoriza Indigenus Taman Nasional Gunung Ciremai dengan Berbagai Tanaman Inang

This study aimed to determine the effectiveness of the use of host plants in an effort to multiply mycorrhizal propagules indigenous to Gunung Ciremai National Park. The experimental method used a factorial complete randomized design with 2 factors. The first factor was the location of the source of inoculum by 3 levels: mixed forests, shrubs, and pine stands. The second factor was 4 types of host plant many as 4 levels: corn (Zea mays), sorghum (Sorghum bicolor. (L.) Moench), centro beans (Centrosema pubescens), and ruji beans (Pueraria javanica). Each treatment was repeated five times, so there were 60 experimental units. The spores were isolated by wet filtration and decantation methods adapted from Gerdemann and Nicolson (1963), followed by the modified sugar centrifugation method from Jenkins (1964). The observed parameter was the number of mycorrhizal spores. The data obtained were analyzed by a variance test (F test). To evaluate the treatment's effect and compare the selected treatments, Duncan's follow-up test was used at the level of 5%. The combination of the location of the shrub inoculum and the centro bean host plant showed the largest spore population, which was 222.60 per 50 g soil sample. Trapping techniques using host plants of corn, sorghum, centro beans, and ruji beans showed suboptimal results. The most common genera were Glomus (80%; 4 species), Gigaspora (10%, 1 species), and Acaulospora (10%, 1 species). Glomus was evenly found in all trapping results.
 
 Keywords: Acaulospora, Glomus, mycorrhiza, propagules, spores

The effect of shrubs admixture in pine forest stands on soil bacterial and fungal communities and accumulation of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent toxic pollutants. The species composition of the stand is important in shaping the quality of soil organic matter and, consequently, the PAH content. The main purpose of the research was to determine the role of shrubs in shaping PAH accumulation in forest soils. The study covered the soils of the pine stands of the Rybnik Forest District, which experiences some of the highest deposition of industrial emissions in Europe. Pine stands with admixture of shrubs (alder buckthorn Frangula alnus and European hazelnut Coryllus avellana) growing in the same soil conditions were selected for the study. Samples for analyses were collected from the organic horizon (O) (from a depth of 0–7 cm) and humus mineral horizon (A) (from a depth of 7–15 cm). The organic C and total N concentrations, pH, alkaline cation content, soil enzyme activity and PAH content were determined. Additionally, the taxonomic composition of soil bacterial and fungal communities was determined. The highest activity of enzymes was noted in soils under influence of shrubs. The enzymatic activity was positively correlated with the content of total N, organic C, pH H2O and KCl and negatively with the C/N ratio. The highest PAH content was recorded in the soils of pine stands without the admixture of shrubs. Our research indicates the importance of shrubs in shaping the properties of surface horizons of forest soil and, consequently on the accumulation of PAHs. Shrubs stimulate biochemical activity of soils which results in lower PAHs accumulation by providing more easily decomposable organic matter.

Conjugate Variability of Signs of the Female Generative System of Scots Pine (Pinus sylvestris L.) in the Conditions of Magnesite Pollution

In the conditions of environmental pollution by emissions of magnesite production (Combined Magnesite, Satka, Chelyabinsk region), a study of the conjugate variability of signs of the female generative system of the Scots pine (Pinus sylvestris L.) was carried out. Signs with a stable connection have been identified, as well as signs whose direction of interconnection changes under the influence of aerotechnogenic pollution. Thus, the relationship of the signs characterizing the size and mass of cones is rigidly genetically determined and is not violated in conditions of a strong level of pollution. The seed productivity of the pine stands, regardless of the growing conditions, is more closely related to the survival rates of ovules in the gametophytic period than in the period of embryonic development. However, in conditions of heavy pollution, the relationship between the survival of ovules in the 1st vegetative and embryonic periods is negative, which may indicate the effective elimination of abnormal gametophytes and the release of the stand from them in conditions of pollution. The strong weakening of trees and the low availability of mineral resources in conditions of high pH of the growing medium in the zone of heavy pollution cause an increase in the negative relationship between seed productivity and seed weight to a significant level. Also, the conditions of heavy pollution “contributed” to the development of a strategy of trees for the formation of small seeds with high quality and quality indicators, seedlings developed. Only in these growing conditions, with a decrease in seed weight, the indicators of germination energy, germination percentage, and morphometric indicators of seedlings significantly increased.

Формирование структурно-функциональной организации молодняков сосны обыкновенной (Pinus sylvestris L.) смешанного искусственно-естественного происхождения в условиях сосняков ягодникового и разнотравного Среднего Урала

Restoration of forests, the study of the processes of formation of their structure and productivity, is currently one of the most urgent tasks. The features of the formation of 12-year-old forest plantations and the concomitant natural regeneration of Scots pine (Pinus sylvestris L.) were studied under the conditions of berry pine forest and forb pine forest of the Middle Urals, on trial plots established in accordance with the existing requirements. For each Scotch pine (Pinus sylvestris L.) tree, the diameter at the middle height and height were measured, and the volume of the trunk in the bark was calculated. The rank distribution of trees was carried out by calculating their reduction numbers, determining the amplitude of the reduction numbers and subsequent distribution into 5 main classes. In the 12th year after planting, the survival rate in the berry pine forest was 47.0%, and in the forb pine forest - 35.3%. In the berry pine forest, taking into account the concomitant natural regeneration of Scots pine (Pinus sylvestris L.), a pine forest of artificial and natural origin is being formed, and in the forb pine forest, a pine forest of natural and artificial origin is being formed. The process of natural renewal of Scotch pine (Pinus sylvestris L.) took place over several years. Scots pine (Pinus sylvestris L.) trees of natural origin are 2-7 years younger in biological age than trees of artificial origin. Pine trees of artificial origin in the berry pine forest significantly exceed the average diameter at the middle of the height, height and trunk volume of the same trees in the forb pine forest. Pine trees of natural origin in the berry pine forest are significantly superior in average diameter at the middle of the height to trees in the forb pine forest, but they are significantly inferior to them in the average trunk height and practically do not differ in the average volume of the tree trunk. Trees of artificial origin in terms of diameter at the middle of the height, height and volume of the trunk significantly exceed trees of natural origin both in the berry pine forest and in the mixed grass pine forest. The distribution of trees by diameter and height in young forests of artificial and natural origin, both in the berry pine forest and in the forb pine forest, is characterized by a distribution close to normal. The distribution of trees of artificial and natural origin in the berry pine forest and the forb pine forest in terms of trunk volume is distinguished by left-sided asymmetry and sharpness. When distributed by rank height classes, a significant reduction in the level of variability of biometric indicators is provided. However, in natural young stands, a very high level of variability in stem volume in the bark remains. Both in artificial and natural young stands, the main (86.3-97.5%) stock of trunk wood in the bark falls on trees of I-III height classes. In the forb pine forest, artificial and natural young stands had almost the same reserve values, which confirms the formation of young pine stands of natural artificial origin. In the berry pine forest, birch renewal does not represent significant competition to pine. In the forb pine forest, birch creates serious competition for pine and, probably, the formation of deciduous-coniferous plantations and oppression of pine.

Динамика экосистем свежего бора центра Приволжской возвышенности

The results of a study of the dynamics of a rather rare type of forest ecosystem for the central part of the Volga Upland – fresh pinery (A2) – are presented. The research was carried out on the territory of the Upper Sura section of the Volga Forest-Steppe Nature Reserve. The progress of the process was studied in an age series, identified in homogeneous forest conditions based on the principles of dynamic classification of forest types. As a result of processing forest taxation data, average values of taxation indicators of forest stands were obtained for each age class. At the same time, an analysis of changes in all components of the plantings was carried out. On its basis, the age series was divided into separate periods and phases. Trends in the share of participation of each forest-forming species in the forest stand at different age stages are described by nonlinear equations. The study showed that the resulting age series represents a series of transformation of forest communities. Disruption of the forest formation process led to a large-scale replacement of indigenous plantings with derivatives. After the start of clear-cutting, the area occupied by deciduous trees (primarily birch) constantly grew. A consequence of the large-scale use of intermediate, sanitary and voluntary selective fellings was the formation of thinned pine stands. At the same time, a transformation of the lower tiers of communities also occurred. These factors caused a deterioration in the conditions for natural regeneration of pine (Pinus sylvestris L.). As a result, to date, the possibility of forming pine stands through natural regeneration is almost completely excluded.

The impact of stand composition and tree density on topsoil characteristics and soil microbial activities

The assessment of long-term effects of forest management practices, particularly species mixing and stand density, provides valuable information for the forestry sectors. This study evaluated and compared the effect of stand composition and density on organic horizon (i.e., OL, OF, OH) and organo-mineral horizon characteristics of nine stands in the Orleans State Forest (France), seven years after the first thinning treatments. To this end, three triplets of stands of pure Quercus petraea Matt., pure Pinus sylvestris L. and a mixture of both species were selected. Each stand consisted of two plots with different tree densities: low and normal. Physicochemical variables were measured on the organic humus horizon (OH), while microbial biomass carbon (MBC) and nitrogen (MBN), and soil microbial metabolic profile were evaluated on the organo-mineral horizon; the abundance of soil microbial populations (i.e., bacteria, fungi and archaea) in each plot was also assessed by qPCR. The OH thickness consistently increased under pure pine stands (25–35 mm), while other OH characteristics showed no variation based on stand composition and tree density. Low-density plots exhibited changes in microbial biomass, with a significant decrease in both MBC and MBN. Moreover, the highest MBC was recorded under pure pine stands (1241 mg C.kg−1 DW soil), and the highest MBN under pure oak stands (24–39 mg N.kg−1 DW soil). The highest C assimilation rates were recorded in the mixed stands, especially under low tree density. Bacteria and archea were similarly abundant across stand compositions and tree densities, while fungi tended to be more abundant in the mixed coniferous-broadleaf stands. Our findings should be considered by the forestry sectors of European countries where these two species are distributed, and suggest that EU forestry strategies should promote biodiversity in the context of tree plantations.

Diplodia sapinea as a contributing factor in the crown dieback of Scots pine (Pinus sylvestris) after a severe drought

The frequency and impact of drought on global ecosystems have increased within the last century, while drought has affected tree health in many regions. Diplodia sapinea is a widespread, opportunistic pathogen infecting most conifers, causing Diplodia tip blight, thriving on hosts impacted by stress such as drought, heat, or mechanical wounding. In summer of 2018, a large-scale drought was recorded all over Europe. In late summer, pine trees all over Gotland showed crown dieback, where necrotic twigs and needles were found, especially in the upper part of the crowns. Symptoms were consistent with a potential outbreak of D. sapinea. Effects of the combination of drought and Diplodia tip blight on mortality or recovery of Scots pine in Nordic conditions are unknown. This study confirmed the presence and potential contribution of D. sapinea in the observed damages of Scots pine. Shoot blight and drought led to crown defoliation which was observed one year post-drought, while trees showed a clear recovery of newly grown shoots within the second year. Severely affected pines (>70% of the upper third of the crown with shoot blight) showed increased mortality. Recovery of the surviving trees was independent of previous dieback levels. Diplodia sapinea was most abundant in twigs with shoot blight of the symptomatic trees compared to healthy-looking twigs from the same trees and asymptomatic trees in affected and healthy pine stands. Sampling on affected and healthy sites showed possible endophytic infections with low abundance within healthy-looking twigs. Spore deposition of D. sapinea was monitored on healthy and affected sites for two consecutive years after crown damages occurred to confirm the presence of the opportunistic pathogen in the affected region. Spore deposition was observed during all seasons and correlated with high precipitation during sampling. Our observations provide insights into the emergence of Diplodia tip blight in the Northern countries and underline the potential impact of D. sapinea on tree health in the course of a changing climate.

Scots pine stands in the Left-Bank Forest-Steppe of Ukraine

Abstract The article presents the results of the research on the features of Pinus sylvestris L. condition and productivity in forest stands of the Left-Bank Forest-Steppe of Ukraine (in Kharkiv and Sumy regions) for 2006–2021. The study was carried out using the ‘Forests of Ukraine’ Database as of 01.01.2017, and the results of field research at 30 temporary sample plots (TSP), 3 permanent sample plots (PSP) (in 2006–2018), and 13 monitoring plots (2009–2021). Generally accepted methods and new standards were used. The dynamics of forestry and evaluation indicators of Scots pine stands at sample plots were analyzed and compared with high-productive Scots pine stands. The characteristics of natural regeneration are given. It was revealed that the age structure of pine stands is not optimal: there is an excess of middle-aged stand areas. Changes in the structure and development of managed Scots pine stands with respect to changing environmental conditions were observed for 2009–2021. Studied forest stands showed a tendency for negative changes in stand structural characteristics related to regeneration and growth. Drought mainly in combination with even medium anthropogenic impact can further worsen the health status of Scots pine stands in lowland areas of the Left-Bank Forest-Steppe of Ukraine. Thus, the formulation of forest management measures to mitigate the impact of these stress factors is needed.

Higher site productivity and stand age enhance forest susceptibility to drought-induced mortality

Warmer and drier conditions increase forest mortality worldwide. At the same time, nitrogen deposition, longer growing seasons and higher atmospheric CO2 concentrations may increase site productivity accelerating forest growth. However, tree physiological studies suggest that increased site productivity can also have adverse effects, reducing adaptation to drought. Understanding such intricate interactions that might foster tree mortality is essential for designing activities and policies aimed at preserving forests and the ecosystem services they provide. This study shows how site factors and stand features affect the susceptibility of Scots pine to drought-induced stand-level mortality. We use extensive forest data covering 750,000 ha, including 47,450 managed Scots pine stands, of which 2,547 were affected by mortality during the drought in 2015–2019. We found that the oldest and most dense stands growing on the most productive sites showed the highest susceptibility to enhanced mortality during drought. Our findings suggest that increasing site productivity may accelerate the intensity and prevalence of drought-induced forest mortality. Therefore, climate change may increase mortality, particularly in old and high-productive forests. Such exacerbated susceptibility to mortality should be considered in forest carbon sink projections, forest management, and policies designed to increase resilience and protect forest ecosystems.

Carbon Stock of Australian pine (Casuarina equisetifolia) in Cemara Sewu Beach Jetis Cilacap

Global warming is the increase in temperature in the atmosphere, sea and land. The increase in carbon or greenhouse gases is one of the causes of global warming. One solution to reduce the presence of greenhouse gases is to increase carbon stock. Beach is home to the richest ecosystems in the world and many components of the vegetation that store large amounts of carbon stock. Carbon compounds in the atmosphere are absorbed and metabolized. The metabolic products are stored in tree biomass. One of the trees that can be relied on as a stock carbon is those located at Cemara Sewu Beach, Cilacap. Cemara Sewu Beach is one of the beach that has a relatively large amount of stored carbon potential. The purpose of this study was to determine the carbon stored in several types of trees at Cemara Sewu Beach. The method used in this study is a survey method with purposive sampling using without destroying. The sampling of Australian pine tree stands is grouped into certain diameter class. The coastal area was made into three research stations and each study was made into 5 replicated plots measuring 20 m x 20 m and placed on a transect line with a distance of 5 meters each. All of the Australian pine were plotted as samples. The independent variable in this study was the diameter class of Australian pine, while the dependent variable was carbon stock. The main parameters observed were tree density, trunk diameter and the number of individuals for each tree species were calculated. The data obtained were analyzed using Analysis of Variance (ANOVA) followed by the Least Significant Difference (LSD) test with an error rate of 5%. The results of the research on the diameter class of Australian pine greatly affect the presence of biomass and carbon stock. The results obtained that carbon stocks in diameter class 15-20 store 74,914 ton.ha-1, diameter class 21-25 as many as 164,599 ton.ha-1, diameter class 26-30 as many as 270,372 ton.ha-1, diameter class 31-35 store stocks carbon 462,478 ton.ha- 1 and in the diameter class 36-40 store as much as 462,478 ton.ha-1. The larger the class diameter, the greater the carbon stock produced. The diameter class of Australian pine stands has a relationship between biomass and carbon stock, and has an exponential relationship.

Nitrous oxide and methane emissions from a Ferralsol as affected by loblolly pine cultivation time in subtropical Brazil

We hypothesized that the age of loblolly pine stands influences soil methane (CH4) and nitrous oxide (N2O) emissions. This is a relevant topic to be studied in subtropical Brazil, where the pine plantation area is increasing considerably. We evaluated N2O and CH4 emissions for two years in a Ferralsol under loblolly pine (Pinus taeda L.) stands of 1, 9 and 18 year-olds and a native forest (NF). We calculated the net CO2eq emission by considering the N2O and CH4 emissions from soil and the carbon (C) accumulation as litter in the forest floor. The soil N2O emission reduced gradually over the loblolly pine cultivation years, whereas CH4 uptake rates showed no clear pattern. Soil N2O emission showed a positive relationship with soil temperature in NF, and with soil ammonium and nitrate intensities in the pine stands. Soil CH4 uptake was inversely related to water-filled pore space in the pine stands, but this relationship was not observed in NF. The soil CH4 uptake rate was 4.6 times higher (p < 0.10) in NF than the average uptake in loblolly pine stands. On the other hand, soil N2O emissions in 9 and 18-year-old stands were similar (p > 0.10) to those in NF (1.3 kg N ha−1 yr−1). Our results suggest that cultivation with loblolly pine for 18 years can reduce soil N2O emission, and the uptake of CH4 in this system offsets 17 % of N2O emissions. Furthermore, the C accumulation as litter in the forest floor of the mature pine stands (9- and 18-year-old) generated a net emission of −1.6 Mg CO2eq ha−1 yr−1, showing to be an expressive offsetting mechanism. Therefore, we conclude that aged loblolly forests can reach N2O emissions levels comparable to those of NF, and the C sequestration in these forests floor can significantly contribute to offset N2O emissions and act as sink for net atmospheric CO2eq.

Time series DNA barcoding provides insight into factors influencing wood-boring and bark-feeding insect communities in Scots pine, Sitka spruce, and Noble fir stands.

Bark-feeding and wood-boring insect pests can have significant negative impacts on conifers and wood production. The damage they cause is expected to increase in the future due to climate change and the growth of international trade. This study employed DNA barcoding of beetle juveniles (Coleoptera) sampled from standing trap trees and cut log piles at regular intervals over a 2-yr period to monitor the beetle community dynamics and associated environmental factors. Tree species was found to have a major influence on beetle communities, most strikingly at the start of early decay stages. Lower species diversity was reported from standing trap tree samples compared to log pile samples, likely due to higher residual defences in dying and recently dead trees. While the species identified from standing trap trees are more likely to be a threat to the forestry sector, the species found in the log piles are more likely to be beneficial due to their high abundance and their ability to compete with pests for breeding substrate. The analysis of beetles collected inside trees revealed additional information on ontogenetic niches and host preferences beyond that acquired solely from flight interception trap data. Our results offer insights on community composition and dynamics of bark-feeding and wood-boring insect species in Welsh conifer forests and provide resources for monitoring and management of potential pest species.

Dynamics of stand indicators of pine plantations according to the data of long-term observations

The purpose of the study is to study the dynamics of stand indicators (average height and diameter, the basal areas and stock) of pine forest plantations of different initial density over a 120-year period based on long-term observations on permanent sample plots. The object of the study was pine plantations on permanent trial plots of the Forest Experimental Station (Moscow). Course of Growth tables are among the simplest models that reflect the change in stand indicators of a collection of forest stands. A comparison of the growth and yield of forest stands on permanent test plots was carried out with tables of the growth course of full pine plantations in the European part of Russia and with tables of the growth course of modal pine stands of the European part of Russia (ecoregions of the southern taiga, zones of mixed, deciduous forests and forest-steppe). The actual curves of the dynamics of stand indicators are located in the entire range of the presented tabular values. It was revealed that the tables of the course of growth give a greatly simplified idea of the change in stand indicators, which in actual forest stands do not have a monotonous dynamic over time. Significant deviations of the series of dynamics of average heights and diameters, basal areas, wood stocks on trial plots from the data of tables of the growth rate of complete and modal pine forest stands were noted. An alternative to traditional tables can be predictive models of the dynamics of stand indicators with different initial state of forest stands, in which there is no strict link to the quality basis.

The Growing Dynamic of Pure Scots Pine Stands Using Different Thinning Regimes in Lithuania

The aim of this study is to relate initial stand density and thinning intensity to tree diameter, height, and volume increment based on continuous 30-year observations in thinning experimental stands of Scots pine (Pinus sylvestris L.). The thinning experiments on Scots pine were established in 1990 and 1992, and the experimental model in each trial comprised five density variants: control and four plots with tree densities up to 3.0–4.4, 2.0–2.4, 1.0–1.2, and 0.5–0.6 thousand trees per hectare after the initial thinning. Since the establishment, only the dead trees were removed in control plots, and other initial density plots were thinned according to predefined thinning treatment plans. Our study shows that the lowest increment in diameter was found in control plots and the highest in the most intensive thinning plots, in which the diameter increment was 1.5 times higher. However, the intensification of thinning and the signs of growth stabilization in the control stands cannot guarantee them the position of highest productivity and cumulative volume in the future.

Using Acoustic Tomography to Infer Stem Wood Quality of Pine Forests Affected by a Fungal Pathogen in Different Latitudinal Regions and Plantation Densities

Diplodia pinea is a fungal pathogen that causes Diplodia shoot blight in pines and is widely spread in red pine (Pinus resinosa) and jack pine (Pinus banksiana) forests in Michigan. The objective of this study was to examine whether infection with D. pinea compromises wood quality in pine stands. Acoustic data was collected using an acoustic tomographer from the stem region at breast height (1.3 m) of red pine and jack pine trees across two categories of forest health condition (control vs. Diplodia-affected), in two latitudinal regions (Lower Peninsula vs. Upper Peninsula), and two levels of initial stand density (low vs. high). The acoustic data was used to infer the wood quality (i.e., density) in these two tree species since material of higher density generally has higher sound velocity rates. Red pine had significantly higher wood quality (i.e., higher sound velocities) in the Upper Peninsula region compared to the Lower Peninsula region. Within each latitudinal region, red pine sound velocities did not show significant differences between forest health condition or initial stand density levels. Jack pine showed no significant differences in sound velocities across the treatment categories. The results indicate that latitudinal region appears to have more impact on red pine wood quality than the influence of forest health condition (presence of Diplodia shoot blight) or initial stand density. All analyzed factors (latitudinal region, forest health condition, and stand density) did not have a significant impact on the wood quality of jack pine.

Behavioral state‐specific resource selection of northern bobwhite chicks

AbstractDetermining resource selection rates across life stages of a species is important to enable a comprehensive management approach that focuses on bolstering populations. Moreover, tying these selection rates to specific life‐history needs (e.g., foraging, roosting, loafing) can provide information for management practices. We studied northern bobwhite (Colinus virginianus) chick resource selection on a private property in Brunswick County, North Carolina, USA, to better understand foraging and roosting habitat selection. We tested 2 hypotheses (resource selection is influenced by predator avoidance, resource selection is influenced by food availability) to understand what influences specific resource use. The site was managed intensively for bobwhites using prescribed fire, seasonal mowing and disking, meso‐mammal control, and supplemental feeding. We radio‐tagged 156 chicks between 11–15 days of age from 29 unique brood captures and collected location data of roost sites and daily movement tracks for individual chicks from 2018–2019. We modeled roosting and foraging habitat selection using mixed‐effects conditional logistic regression models under a Bayesian framework. Burned upland pine (Pinus spp.) stands were selected by chicks for foraging and roosting sites. Fallow fields, unburned uplands (1 yr post‐burn), and areas closer to supplemental feed were selected by chicks as foraging habitat. We observed a negative interaction between age and fallow field selection as roosting habitat and age and areas closer to supplemental feed as foraging habitat. Our study results shed light on how circadian habitat use can vary and illustrate that one specific land cover type may not provide ideal diurnal and nocturnal habitat for bobwhite chicks.

Dynamics of trace and rare earth elements during long-term (over 4 years) decomposition in Scots pine and Norway spruce forest stands, Southern Sweden

The temporal dynamics of 33 major, trace, and rare earth elements (REEs) were studied in the litter samples containing Swedish Norway spruce (Picea abies) (NSL) and Scots pine (Pinus sylvestris) (SPL), with the aim to assess their release and accumulation dynamics. Litter bags (8 × 8 cm) were incubated in paired monoculture stands with both the species for up to 5 years from 1979 to 1984 according to a randomized block design comprising 25 blocks (1 × 1 m) within an area of 625 m2. The decomposition rate was slightly higher for Scots pine litter (k = 0.315) than for Norway spruce litter (k = 0.217). During litter decomposition, at ∼70% accumulated mass loss (AML), the concentration of trace elements increased by &amp;gt;50% in both litter types compared to initial concentrations. The concentration change took place in a non-linear pattern, and polynomial quadratic regression between concentration change and accumulated mass loss resulted in significant relationships (adj R2 = 0.20–0.97; p = 0.15–&amp;lt;0.0001). The changes in concentration and amount of trace elements resulted in two main types of dynamics: 1) both concentration and amount increased for Fe, Al, Ti, Cu, Mo, V, Zr, Sb, As, Cs, Pb, Th, and U; 2) concentration increased but amount decreased for Ni, Zn, Li, and Sr. The amount of REEs increased from ∼3-fold to 99-fold from the beginning to the end of incubation, suggesting accumulation during litter decomposition. The dynamics of different REEs were similar in their change patterns in the two litters. Different REEs had generally identical change patterns during incubation, which is reflected in the high correlations among them (r2 = &amp;gt;0.95). A general upward convexity in the dynamics suggests that if further incubated in the field, decomposing litter could have accumulated more REEs in the organic matter. The results of this study can be useful for future studies in other ecosystems including metal-contaminated sites or element-depleted sites. Plant litter accumulation, its decomposition, and build-up of humic substances in the decomposing organic matter can act as a sink for elements and can be used as a management tool for ecological amelioration of metal-contaminated sites as well as natural systems that are impoverished, especially recuperating sites. The study’s findings have implications beyond such sites and can be useful in any research that seeks to understand the patterns of accumulation and release related to decomposition in different ecosystems.

Root trenching and stable isotope analysis uncover trophic links of euedaphic collembola species to mycorrhizal mycelium in pine forests

Ectomycorrhizal fungi are a prominent component of the soil biota of boreal forests, but the role of mycorrhizal mycelium as a food source for soil Collembola remains controversial. We addressed this question in a trenching experiment in young (70 years old) and old (180 years old) stands of Scotch pine, combined with stable isotope analysis. Trenching halved the biomass of ectomycorrhizal mycelium, estimated using in-growth mesh bags. In the young forest, the abundance of two euedaphic Collembola species, Mesaphorura yosiii and Willemia anophthalma, decreased after trenching by 99 and 97% respectively, while in the old forest the abundance of Collembola was not affected. In both forests, trenching reduced δ15N values of the dominant euedaphic species Isotomiella minor and W. anophthalma, indicating a shift in trophic niches. Thus, we obtained convincing evidence of species-specific trophic links of euedaphic Collembola species to the mycelium of mycorrhizal fungi.

Unraveling the Effect of Fire Seasonality on Fire-Preferred Fuel Types and Dynamics in Alto Minho, Portugal (2000–2018)

Socio-demographic changes in recent decades and fire policies centered on fire suppression have substantially diminished the ability to maintain low fuel loads at the landscape scale in marginal lands. Currently, shepherds face many barriers to the use of fire for restoring pastures in shrub-encroached communities. The restrictions imposed are based on the lack of knowledge of their impacts on the landscape. We aim to contribute to this clarification. Therefore, we used a dataset of burned areas in the Alto Minho region for seasonal and unseasonal (pastoral) fires. We conducted statistical and spatial analyses to characterize the fire regime (2001–2018), the distribution of fuel types and their dynamics, and the effects of fire on such changes. Unseasonal fires are smaller and spread in different spatial contexts. Fuel types characteristic of maritime pine and eucalypts are selected by seasonal fires and avoided by unseasonal fires which, in turn, showed high preference for heterogeneous mosaics of herbaceous and shrub vegetation. The area covered by fuel types of broadleaved and eucalypt forest stands increased between 2000 and 2018 at the expense of the fuel type corresponding to maritime pine stands. Results emphasize the role of seasonal fires and fire recurrence in these changes, and the weak effect of unseasonal fires. An increase in the maritime pine fuel type was observed only in areas burned by unseasonal fires, after excluding the areas overlapping with seasonal fires.

Soil microbiomes of hardwood‐ versus pine‐dominated stands: Linkage with overstory species

AbstractBiodiversity in forest ecosystems is paradoxical. Whereas their most apparent component—the woody overstory—is the least diverse with respect to numbers of species, the least apparent component is the biotic community of highest diversity—the soil microbiome. Numerous factors influence the composition and diversity of soil microbial communities, which in turn exert a profound impact on plant species occupying the soil and the biogeochemistry of essential plant nutrients. Of interest in forest ecosystems is how the soil microbiome interacts with the overstory, a phenomenon referred to as linkage. This study compared the soil microbiome of two adjacent stand types—hardwood‐ and longleaf pine (Pinus palustris)‐dominated—and addressed the following questions: (1) How does soil microbiome vary with stand type? (2) Do the forest overstory community and soil microbiome exhibit linkage? Twelve 0.04‐ha circular plots were established in each stand type to assess tree community composition and structure and to sample mineral soil for three separate analyses: assessment of soil fertility, measurement of total carbon and nitrogen (N), and extraction of genomic DNA for assessment of microbiome communities. All live stems ≥2.5 cm dbh in each plot were identified to species and measured for dbh to the nearest 0.1 cm. Mineral soil was taken from a depth of 5 cm and oven‐dried at 38°C prior to analyses. Hardwood stands were dominated by flowering magnolia (Magnolia grandiflora) and southern evergreen oaks, whereas pine stands were dominated by longleaf pine and live oak (Quercus virginiana). Although soils of both stand types were highly acidic, the hardwood stands were generally higher in fertility, especially for total and available N. The overstory and soil microbial communities exhibited evidence of linkage among all sample plots combined. When assessed separately by stand type, only hardwood‐dominated stands displayed evidence of overstory/microbial linkage. These results have broader implications for future scenarios given the sensitivity of soil microbes to climate change.