Mixed Pine Forest Research Articles

The Application of Percolation Theory in Modeling the Vertical Distribution of Soil Organic Carbon in the Changbai Mountains

A power-law formulation rooted in percolation theory has proven effective in depicting the vertical distribution of soil organic carbon (SOC) in temperate forest subsoils. While the model suggests the solute as the primary factor distributing SOC, this may not hold true in the surface soil in which roots contribute significantly to the SOC. This study in the Changbai Mountains Mixed Forests ecoregion (CMMF) evaluates the SOC profiles in three forests to assess the model’s efficacy throughout the soil column. Prediction of the SOC profile based on the regional average values was also assessed using field data. The observed scaling aligned well with predictions in mixed broadleaved and broadleaved Korean pine mixed forests, but disparities emerged in birch forest, possibly due to waterlogging. The predicted SOC levels correlate strongly with the field data and align well with the normalized average SOC levels. The findings suggest that the model remains applicable in the CMMF when considering root-derived carbon. However, the hindrance of solute transport may have a greater impact than roots do. The spatial heterogeneity of the SOC means that a single predicted SOC value at a specific depth may not fit all sites, but the overall agreement highlights the potential of the model for predicting the average or representative SOC profiles, which could further aid in regional-scale carbon stock estimation.

Mixing of pine and arbuscular mycorrhizal tree species changed soil organic carbon storage by affecting soil microbial characteristics

Pure and mixed pine forests are found all over the world. The mycorrhizal type affects soil microbial activity and carbon sequestration capacity in pure forests. However, the effects of mycorrhizal type on microbial characteristics and carbon sequestration capacity in pine mixed forests remain untested. Further, making it difficult to predict carbon storage of the conversion from pure pine forests to mixed forests at larger scales. Herein, a meta-analysis showed that the contents of soil microbial biomass, mineral-associated organic carbon, and soil organic carbon in pine mixed forests with introduced arbuscular mycorrhizal tree species (PMAM) increased by 26.41 %, 58.55 %, and 27.41 %, respectively, compared to pure pine forests, whereas those of pine mixed forests without arbuscular mycorrhizal tree species (PMEcM) remained unchanged. Furthermore, the effect size of microbial biomass, mineral-associated organic carbon and organic carbon contents in subsoil of PMAM are 56.48 %, 78.49 % and 43.05 %, respectively, which are higher than those in topsoil. The improvement of carbon sinks throughout the PMAM soil profile is positively correlated with increases in microbial biomass and mineral-associated organic carbon in subsoil, according to regression analysis and structural equation modelling. In summary, these results highlight that the positive effects of introducing arbuscular mycorrhizal tree species rather than ectomycorrhizal tree species into pure pine forests on soil microbial biomass and carbon sequestration. The positive link between microbial biomass, mineral-associated organic carbon, and soil organic carbon suggests an underlying mechanism for how soil microorganisms store carbon in pine mixed forests. Nevertheless, our findings also imply that the soil carbon pool of PMAM may be vulnerable under climate change. Based on the above findings, we propose that incorporating mycorrhizal type of tree species and soil thickness into mixed forests management and biodiversity conservation.

Microbiota associated with urban forests.

Urban forests are essential for maintaining urban ecological stability. As decomposers, soil microorganisms play an indispensable role in the stability of urban forest ecosystems, promoting the material cycle of the ecosystems. This study used high-throughput sequencing technology to explore the bacteria in six forest stands, including Phyllostachys edulis (ZL), Metasequoia glyptostroboides (SSL), Cornus officinalis (SZY), mixed broad-leaved shrub forest (ZKG), mixed pine and cypress forest (SBL), and mixed broad-leaved tree forest (ZKQ). Meanwhile, the differences in fungal communities were investigated. The results show that ZL has the highest alpha diversity of bacterial communities, while its fungal community is the lowest; Proteobacteria is the most abundant bacterial phylum in the six forest stands; ZKQ has the highest fungal diversity. In addition, soil microbial communities are affected by environmental factors. Soil pH, organic matter (SOM), and available phosphorus (AP) significantly influence the compositions of urban forest soil microbial communities. This study revealed the differences in bulk soil (BS) microbial community structures among six forest stands and the relationship between environmental factors and soil microbial communities, which has important guiding significance for creating healthy and stable urban forests with profound ecological benefits.

Seasonal Changes in the Soil Microbial Community Structure in Urban Forests.

Urban forests play a crucial role in the overall health and stability of urban ecosystems. Soil microorganisms are vital to the functioning of urban forest ecosystems as they facilitate material cycling and contribute to environmental stability. This study utilized high-throughput sequencing technology to examine the structural characteristics of bacterial and fungal communities in the bulk soil of six different forest stands: Phyllostachys pubescens (ZL), Metasequoia glyptostroboides (SSL), Cornus officinalis (SZY), mixed broad-leaved shrub forest (ZKG), mixed pine and cypress forest (SBL), and mixed broad-leaved tree forest (ZKQ). Soil samples were collected from each forest stand, including the corners, center, and edges of each plot, and a combined sample was created from the first five samples. The results revealed that among the bacterial communities, ZKG exhibited the highest alpha diversity in spring, while ZL demonstrated the highest alpha diversity in both summer and autumn. Proteobacteria was the most abundant bacterial phylum in all six forest stand soils. The dominant fungal phylum across the six forest stands was identified as Ascomycota. Notably, the microbial community diversity of SBL bulk soil exhibited significant seasonal changes. Although ZL exhibited lower bacterial community diversity in spring, its fungal community diversity was the highest. The bulk soil microbial diversity of ZL and SSL surpassed that of the other forest stands, suggesting their importance in maintaining the stability of the urban forest ecosystem in the Zhuyu Bay Scenic Area. Furthermore, the diversity of the bulk soil microbial communities was higher in all six stands during spring compared to summer and autumn. Overall, this study provides valuable insights into the seasonal variations of bulk soil microbial communities in urban forests and identifies dominant tree species, offering guidance for tree species' selection and preservation in urban forest management.

Microbial community and enzyme activity respond differently to seasonal and edaphic factors in forest and grassland ecosystems

Although microbial community and function patterns have been extensively studied, little is known about whether the patterns are consistent in different ecosystems and how they are influenced by seasonality or other environmental factors. To test the driving factors of microbial communities and potential functions, we collected soil samples from five forests (mixed broadleaved-Korean pine forest, mixed pine and oak forest, deciduous broadleaved mixed forest, subtropical evergreen broad-leaved forest and tropical rainforest) and three grassland ecosystems (meadow steppe, semi-arid grassland and arid grassland) across China in three seasons (spring, summer and autumn). Microbial diversity based on the sequencing of 16S rRNA gene for bacteria and internal transcribed spacer (ITS) genes for fungi were measured, and potential functions represented by soil extracellular enzyme activities (EEAs) were analyzed. The results found that soil EEAs were significantly higher in summer than in spring and autumn, and both bacterial and fungal richness indices showed greater seasonal fluctuations than the diversity. Fungal richness indices were highest in summer in both forest and grassland ecosystems, while the lowest were observed in spring for forest and in autumn for grassland, respectively. In addition, fungal communities were closely related to ecosystem types, while bacterial communities were not significantly different across ecosystems and exhibited a broader habitat niche breadth, but the relative abundance of dominant bacterial phyla showed stronger correlations with environmental variables (including climate, soil properties and nutrients) in grassland than in forest ecosystems. The decoupling of microbial community and EEAs was observed in both forest and grassland ecosystems, indicating the function redundancy of soil microorganisms. The present study provided crucial information about the effects of ecosystem types, seasonality and edaphic factors on soil microbial communities and EEAs, and could advance the understanding of soil potential function responses to environmental changes.

Dynamics of glomalin-related soil protein and soil aggregates during secondary succession in the temperate forest

Despite the key role of glomalin-related soil protein (GRSP) in soil organic C (SOC) and soil aggregate stability, the influence of secondary successional processes on GRSP and the interrelationship of GRSP on SOC and its soil aggregate stability is unclear. Based on this, four stages of the secondary succession (including 20-, 32–, 47-, and 61-year-old stands) and the primary broad-leaved Korean pine (Pinus koraiensis) mixed forest were selected. The results showed that total GRSP (T-GRSP), easily extractable GRSP (EE-GRSP), SOC, mean weight diameter (MWD), and geometric mean diameter (GMD) all tended to increase with the secondary succession at 0–30 cm soil layer. The secondary succession contributed to the accumulation of GRSP content, so much so that after 61 years, both EE-GRSP and T-GRSP reached the level of the primary forest. EE-GRSP, T-GRSP, SOC, MWD, GMD, and GRSP/SOC significantly decreased with the deepening of soil depth in all successional stages. In addition, during the 20- and 32 year-old stands of secondary succession, the proportion of GRSP in the SOC was relatively high. With the progress of secondary succession, the content of macroaggregates (>0.25 mm) in the soil increased significantly and was not significantly different from the primary forest. The correlation analysis showed that T-GRSP was more correlated with SOC than EE-GRSP, while EE-GRSP was more correlated with MWD than T-GRSP. Additionally, there was also a significant positive correlation between MWD and SOC at 0–20 cm soil layer. Our results elucidate that GRSP may stabilize SOC pools by direct contribution to SOC in the early secondary succession, and the stabilizing effect on SOC is more pronounced in the later stages by forming macroaggregates. This enables us to understand the ecological functions played by GRSP in soil C sequestration and the enhancement of soil stability during the secondary succession.

Spatial Distribution of Pinus koraiensis Trees and Community-Level Spatial Associations in Broad-Leaved Korean Pine Mixed Forests in Northeastern China.

Investigating the spatial distributions and associations of tree populations provides better insights into the dynamics and processes that shape the forest community. Korean pine (Pinus koraiensis) is one of the most important tree species in broad-leaved Korean pine mixed forests (BKMFs), and little is known about the spatial point patterns of and associations between Korean pine and community-level woody species groups such as coniferous and deciduous trees in different developmental stages. This study investigated the spatial patterns of Korean pine (KP) trees and then analyzed how the spatial associations between KP trees and other tree species at the community level vary in different BKMFs. Extensive data collected from five relatively large sample plots, covering a substantial area within the natural distribution range of KP in northeastern China, were utilized. Uni- and bivariate pair correlation functions and mark correlation functions were applied to analyze spatial distribution patterns and spatial associations. The DBH (diameter at breast height) histogram of KP trees in northeastern China revealed that the regeneration process was very poor in the Changbai Mountain (CBS) plot, while the other four plots exhibited moderate or expanding population structures. KP trees were significantly aggregated at scales up to 10 m under the HPP null model, and the aggregation scales decreased with the increase in size classes. Positive or negative spatial associations were observed among different life stages of KP trees in different plots. The life history stages of the coniferous tree group showed positive spatial associations with KP saplings and juvenile trees at small scales, and spatial independence or negative correlations with larger KP trees at greater scales. All broad-leaved tree groups (canopy, middle, and understory layers) exhibited only slightly positive associations with KP trees at small scales, and dominant negative associations were observed at most scales. Our results demonstrate that mature KP trees have strong importance in the spatial patterns of KP populations, and site heterogeneity, limited seed dispersal, and interspecific competition characterize the spatial patterns of KP trees and community-level spatial associations with respect to KP trees, which can serve as a theoretical basis for the management and restoration of BKMFs in northeastern China.

Stabilization of the pine increment during recent years of low precipitation and high temperatures by removal of the spruce lower storey

In stands dominated by Scots pine in Central European nutrient-poor sandy forest sites, deterioration of pine health due to recent development in climate change has been observed, whereas the vitality of the Norway spruce growing in the lower storey of such stands has remained stable. The study aims to analyse the impact of the spruce lower storey on pine increments and performance in relation to drought stress. Wood core samples were collected using an increment borer from mature pines growing in deep, sandy soils with ground water at a depth that was unreachable by the roots in three plot pairs (blocks) consisting of a pine-spruce plot and a plot with the lower-storey spruce removed. The increments of earlywood and latewood were measured separately. Health status and soil moisture were also evaluated. Spruce removal increased the radial growth (tree ring width – TRW) of the pines, and this manifested earlier in the latewood. Spruce removal significantly changed relationship of TRW and umbrothermic index of released pines. The treatment also increased pine foliation, while increases of topsoil moisture in the transects were insignificant. The study indirectly proves the existence of inter-species competition in the rooting zone for water in soils where the ground water is unreachable by the roots. The flat root system of spruce creates a barrier that reduces the amount of water available for pines with deeper growing roots. To reduce the risk of the negative impact of unfavourable climate change on pine as the target species in commercial mature mixed pine forests with similar site and stand conditions, lower-storey spruce reduction can be recommended, even though this might locally and temporarily lessen the biodiversity of the forest stand.

Effect of In Situ Large Soil Column Translocation on CO2 and CH4 Fluxes under Two Temperate Forests of Northeastern China

Global warming has a significant impact on soil carbon dioxide (CO2) and methane (CH4) fluxes in temperate forests. However, due to a lack of field observations, limited information is available about the responses of soil CO2 and CH4 fluxes to changes in temperature during the non-growing season and throughout the year in temperate forests. The broadleaf and Korean pine mixed mature forest (MF) and adjacent secondary white birch forest (BF) at different succession stages in the Changbai mountain region in northeastern China were selected, to study the effect of in situ soil column translocation on CO2 and CH4 fluxes in temperate forests. On average, the air temperature and soil temperature at 5 cm depth under BF stands from October 2018 to October 2022 increased by 0.64 and 0.42 °C during the non-growing season and by 0.49 and 0.43 °C throughout the year, respectively, compared with those under MF stands. Based on multi-year measurements in field experiments, it was shown that during the non-growing season, fluxes of CO2 and CH4 from soil columns under MF and BF stands ranged from 0.004 to 1.175 and from 0.015 to 1.401 (averages of 0.321 and 0.387) μmol CO2 m−2 s−1, and from −1.003 to 0.048 and from −1.037 to −0.013 (averages of −0.179 and −0.250) nmol CH4 m−2 s−1, respectively, accounting for approximately 20.8% and 25.3%, and 48.8% and 69.1% of the corresponding average fluxes during the growing season. When undisturbed soil columns of MF were transferred to a BF stand, to simulate warming, the cumulative soil CO2 emissions and CH4 uptake increased by 23.5% and 15.3% during the non-growing season, and by 9.5% and 16.3% across the year, respectively. However, when soil columns of BF were transferred to a MF stand, to simulate cooling, the cumulative soil CO2 emissions decreased by 16.9% and 0.1% during the non-growing season and across the year, respectively. Upon cooling, the cumulative soil CH4 uptake decreased by 21.8% during the non-growing season but increased by 15.4% across the year. The soil temperature and moisture at 5 cm depth in soil columns could explain 84–86% of the variability in CO2 fluxes and 16–51% of the variability in CH4 fluxes under the two forest stands throughout the field measurement period. The results of the in situ soil column translocation experiments highlight that a small climate warming in nature can increase soil CO2 emissions and CH4 uptake in the temperate forests of northeastern China, particularly during the non-growing season, which should be considered when predicting soil C fluxes in the temperate forests of northeastern China under global warming scenarios.

Cortinarius watsoneae, a new species of Agaricomycetes (Cortinariaceae) from the Gulf States

Cortinarius watsoneae, a new species in subgenus Myxacium, sect. Myxacium, is described from pine and mixed pine and hardwood forests from the Gulf States region of North America. It is characterized by the young lamellae that are grayish violet to pale violet, and relatively large basidiospores in comparison to C. mucosus. The ITS sequence is distinct from other members of sect. Myxacium, with 97% similarity to the closest known species, C. collinitus and C. mucosus. The new species is named in honor of the late Geraldine Watson.

Midstory removal of encroaching species has minimal impacts on fuels and fire behavior regardless of burn season in a degraded pine-oak mixture

Anthropogenic fire exclusion has contributed to forest structural and compositional shifts, resulting in the encroachment of shade-tolerant, often fire-sensitive and/or opportunistic species throughout forest ecosystems. In the central and eastern U.S., encroaching species often exhibit fire-suppressing leaf litter and crown traits, reducing prescribed fire efficacy to restore and maintain fire-dependent mixed pine (Pinus spp.) and oak (Quercus spp.) forests. Despite fire’s natural role in these forests, management using prescribed fire alone is unlikely to reverse encroachment impacts due to the degree of forest change since fire exclusion. Consequently, additional management techniques (e.g., chemical, mechanical) are often combined with fire to ensure persistence of pine-oak mixtures and their associated ecosystem services. In current-day degraded pine-oak mixtures in the southeastern U.S., where no one species represents > 75% dominance by stand basal area, encroaching species (e.g., Liquidambar styraciflua, Quercus nigra) commonly form a dense midstory and occupy overstory positions. To quantify how encroaching species in degraded mixed pine-oak forests impact fuels, canopy cover, and seasonal fire behavior, we thinned the midstory (<20 cm DBH) of all non-pyrophytic species in 12 0.10-ha blocks within a mixed pine-oak stand at the Mary Olive Thomas Demonstration Forest (Auburn, Alabama, USA) in July 2021. Midstory thinning reduced basal area by 6.7 m2 ha−1 and canopy cover by 9.1%. In general, midstory thinning reduced shrub and fine woody debris fuel loads while having no impact on herbaceous, leaf litter, and duff fuel loads. When compared to pre-treatment levels, midstory thinning increased the relative proportion of pine leaf litter contribution to the fuelbed by 10.9% while reducing that of encroaching species by 11.4%. Despite changes to residual basal area, canopy cover, and leaf litter contribution, midstory thinning had no statistical impact on fire behavior, regardless of burn season. Early (January) and late dormant season (April) experimental fires had higher fireline intensities, consumed more surface fuels, had faster rates of spread, and higher average maximum temperatures compared to growing season (September) fires. We also noted an increase in these fire parameters with increased pine litter contribution to the fuelbed. In degraded pine-oak mixtures where encroaching species now occupy overstory canopy positions, we recommend investigating the efficacy of more intense thinning treatments that remove overstory individuals with known fire-suppressing traits to have a larger impact on canopy openness, fuels, and fire behavior.

Changes in Bacterial Communities and Functions Associated with Litter Degradation During Forest Succession Caused by Forest Disease

Forest succession affects aboveground vegetation and belowground microbial community composition, in which litter degradation plays an important role in nutrient cycling. However, limited information is available on how microbial communities change during litter degradation in forests undergoing succession due to disease. In this study, the bacterial communities and functions in litter degradation during the forest succession from pure Pinus forest (PPF), mixed Pinus and Liquidambar forest (MPF and MLF), and pure Liquidambar forest (PLF) were investigated. The results showed that the bacterial community richness and diversity in both needles or leaves and branch litters increased progressively with forest succession. Proteobacteria, Actinobacteria, Bacteroidetes, and Acidobacteria were the most abundant bacterial phyla in the litter degradation during forest succession. The abundance of Bacteroidetes in branches increased significantly, while the abundance of genus Paraburkholderia decreased during forest succession. The different forests formed distinct bacterial community structures during litter decomposition. Functionally, chemoheterotrophy was the most abundant functional guild, followed by nitrogen fixation, intracellular parasitism, and urealysis. The abundance of nitrogen fixation decreased significantly during forest succession. Similarly, the different forests formed distinct bacterial functional structures in the needle or leaf during the succession. However, only two functional structures were formed in the branch. These results suggest that the bacterial community and its functions undergo significant changes during forest succession, particularly from the pure-pine to mixed-pine forest. These results provide a clear understanding of the changes in bacterial communities and functions during litter degradation in forests undergoing disease-induced succession.

Close-to-Nature Forestry Measures in East Polissia Region of Ukraine

The article discusses close-to-nature forestry measures for the natural regeneration of pure and mixed pine forests. It is shown that successful natural regeneration of high value tree species takes place after uniformly gradual logging and progressive strip felling as final cutting operations in pure pine forests in fresh or moist oak-pine forest stands on sandy soil, resulting in the development of natural young pine forests with mixed composition. The article analyzes the state of natural regeneration after the first cycle of transformation felling operations in pure even-aged pine stands aimed at converting them into mixed pine forests of natural origin. Systems of close-to-nature silvicultural measures for restoration, development, improvement and regeneration of forest stands in the process of continuous cover forestry have been elaborated.

An Individual Tree Segmentation Method That Combines LiDAR Data and Spectral Imagery

The dynamic monitoring of forest resources is an integral component of forest resource management and forest eco-system stability maintenance. In recent years, LiDAR (Light Detection and Ranging) has been increasingly utilized in precision forest surveys due to its great penetrating ability and capacity to detect forest vertical structure information. However, the present airborne LiDAR data individual tree segmentation algorithms are not highly adaptable to forest types, particularly in mixed coniferous and broad-leaved forest zones, where the accuracy of individual tree extraction is low, and trees are incorrectly recognized and missed. In order to address these issues, in this study, spectral images and LiDAR data of a red pine conifer–broadleaf mixed forest in the Changbai Mountain Nature Reserve in Jilin Province were chosen, and the normalized point cloud was segmented iteratively using the distance-threshold-based individual tree segmentation method to obtain the initial segmented individual tree vertices. For individual trees with deviations in the initial vertex identification position, and unidentified individual trees, identification anchor points of real tree vertices are added within the canopy of the trees. These identification anchor points have strong position directivity in LiDAR data, which can mark the individual trees whose vertices were misidentified or missed during the initial individual tree segmentation process and identify these two tuples. The tree vertices may be inserted precisely based on the 3D shape of the individual tree point cloud, and the seed-point-based individual tree segmentation method is used to segment the normalized point cloud and finish the extraction of individual trees in red pine mixed conifer forests. The results indicate that, compared to the previous individual tree segmentation approach based on the relative spacing between individual trees, this study enhances the accuracy of individual tree segmentation from 83% to 96%. The extremely high segmentation accuracy indicates that the proposed method can accurately identify individual trees based on remote sensing techniques to segment forest individual trees, can provide a data basis for subsequent individual tree information extraction, and has great potential in practical applications.

Climatic Variability Determines the Biological Diversity and Function of a Mixed Forest in Northeastern China at the Local-Scale

The adaptation to climatic variability and spatiotemporal distinctions in floristic and microbial assembly is important in forest ecology, especially in the context of biological diversity and functional traits. We investigated climatic variables, plant traits, edaphic properties, and microbial dimensions from various plots with an elevation gradient in a broad-leaved-Korean pine mixed forest. With increasing elevation, isothermality significantly increased; however, temperature and precipitation seasonality, as well as the mean temperature of the warmest quarter, significantly declined. Furthermore, high elevation sites were characterized by increased stand basal areas (Ba) and ectomycorrhizal (EM) tree abundance but featured decreases in the abundance of arbuscular mycorrhizal (AM) trees and the values of community-weighted mean (CWM) foliar traits (e.g., leaf area, leaf nitrogen content and leaf phosphorus content). Moreover, soil nutrient status, fungal and bacterial diversity indices, fungal saprotrophs, and bacterial function groups related to nitrite oxidation, ammonia oxidation, and nitrate denitrification were all negatively correlated to the elevation increment. In contrast, high elevation sites were characterized by enhanced EM growth and bacterial nitrogen fixation groups. Correlation analysis showed that the microbial diversity and relative abundances of microbial functional groups in soil were significantly influenced by climatic variability, CWM foliar traits and soil nutrient status. These findings demonstrate that the forces driving biological processes along climatic gradients are predictably in tandem with, but related to different extents, to the spatial compartmentalization of climatic variability in forest ecosystems at local scales.

State and productivity of mixed stands with silver birch and Scots pine in Ukrainian Polissya

The aim of the study was to assess the current state of silver birch (Betula pendula Roth.) stands in Ukrainian Polissya, as well as to identify optimal composition resulting in productive and resilient mixed birch forests. It was found that in forests managed by the State Forest Resources Agency of Ukraine, birch stands grow on an area of 352 800 ha, covering 5.6% of the total area of forests in Ukraine. Within the study region of Ukrainian Polissya, birch stands cover 294 900 ha making 12.3% of the total forest area. Naturally originated birch stands were found to dominate in the study region, with 65.4% of vegetative stands and 25.2% of those grown from seeds. However, planted stands significantly prevail in terms of growing stock as compared to natural ones. In Ukrainian Polissya, silver birch trees grow as a part of mixed pine and birch forests on 632 400 ha. Our study found that mixed pine and birch stands with 80–90% of Scots pine and 20–10% of silver birch in the composition are the most productive.

Labile carbon input and temperature effects on soil organic matter turnover in subtropical forests

The objective of this study was to assess the effects of labile organic carbon (LOC) input on the dynamic turnover of soil organic matter (SOM) with temperature in subtropical forests. Soil samples were collected from three subtropical forests: an evergreen broadleaf forest, a mixed pine and broadleaf forest, and a pine forest. To simulate LOC inputs, soil samples were supplemented with 13C-glucose at levels of 0, 0.2, 0.6, and 1.2 mg C g−1 soil. The soils with the LOC treatments were incubated for six weeks at temperatures of 15, 25, and 35 °C. Results showed that the increase in LOC inputs reduced the priming effects of SOM decomposition significantly, whereas native SOM mineralization increased with temperature. The preferential utilization of LOC by microorganisms reduced SOM decomposition, resulting in net SOC increases with LOC inputs. In the temperature range, the net increases in SOC with the LOC inputs were −0.19 to 0.56 mg C g−1 soil. Moreover, the LOC inputs aided microbial anabolism and promoted the formation of new mineral-associated organic matter and the aggregation of particulate organic matter, resulting in carbon sequestration. Among the forest soils, the soil with the highest organic carbon content, total nitrogen, and carbon to nitrogen ratio (i.e., the mixed forest soil) had the lowest priming effects and was the most conducive to net carbon increase. The priming and carbon sequestration caused by the LOC inputs were not sensitive to temperature changes. Our findings suggest that the increase in the supply of LOC has the potential to alleviate SOM decomposition and increase carbon storage in subtropical forest soils.

Functional ecosystem parameters: Soil respiration and diversity of mite (Acari, Mesostigmata) communities after disturbance in a Late Cambrian bedrock environment

AbstractWe analyzed the changes in ecosystem functions (soil respiration and Mesostigmata mite abundance, species richness and diversity) on various habitats after flooding by highly mineralized and acidic drainage water with fine As‐rich pyrite sediments, on a fragment of a natural ecosystem. In total, 177 plots that represented six types of habitats (undisturbed: pine mixed forests, Salix spp. thickets, Juncus effusus communities, wet meadows, and disturbed: bare ground and dead Salix spp. thickets) were sampled twice, in June 2019 and September 2020. Our study revealed that flooding affected essential ecosystem parameters, such as soil Mesostigmata mite abundance, species richness and diversity, and soil respiration, via an extreme decrease of soil pH. In total, 968 mites were collected from pooled data from the two samplings. Mite abundance, species richness and diversity were mainly shaped by habitat type and soil pH, and partially by soil respiration. These parameters were lower in disturbed habitats (bare ground and dead Salix spp. thickets) as compared with undisturbed ones. The highest mean mite density was recorded from mixed forests (4750 ± 600 ind. m−2) and wet meadows (2678 ± 361 ind. m−2), whereas the lowest in bare ground (449 ± 113 ind. m−2) and dead Salix spp. thickets (537 ± 146 ind. m−2). We noticed that mite diversity may be helpful to predict future changes in the physicochemical parameters of soils in disturbed areas. The vegetation patches built up by species adapted to grow in habitats characterized by relatively high metal and metalloid content (J. effusus and Salix spp.) represent an intermediate state of function of ecosystems in the study area.

Increasing the risk of severe wildfires in San Dimas, Durango, Mexico caused by fire suppression in the last 60 years

To sustainably manage forests, it is important to understand the historical fire regimes including the severity, frequency, seasonal timing of fires as well as the relationship between climate and fire in order to develop management plans that mimic and/or complements the natural disturbance pattern. The objectives of this study were to reconstruct the natural fire regime within a Pinus lumholtzii site in order to understand the fire regimes within this forest type as well as adjacent high timber value mixed-pine forests where historical fire regimes are not available due to past timber harvesting activities. Using 36 fire-scarred trees, we reconstructed the historical fire regimes in San Dimas, Durango, México for the last 238 years. We found a pattern of frequent fires but an absence of fire since 1962, with most fires (98%) being recorded in the spring season. The lack of fire for over six decades within these historically frequent fire forests could result in high fuel accumulation. Such conditions in combination with increasing temperatures and aridity in the region could increase the risk of high severity wildfires that could jeopardize the sustainability of these forests and the human communities that these forests support.

Evaluation of Multiple Forest Service Based on the Integration of Stand Structural Attributes in Mixed Oak Forests

In order to understand forest services at stand level through the integration of structural attributes, forest structures in three main stand types were analyzed based on various structural attributes relating to the services of habitat conservation, timber production and soil water conservation in Loess Plateau, China. Forty sample plots with similar site and environment conditions were established in three types of oak stands. Twenty-two indexes such as stand density, mean DBH, mean height, etc., were selected to analyze the relationship between structural attributes and forest service. With a core set of structural attributes selected by principal component analysis, the link between the service and structural attributes and the compatibility between each service was analyzed using correlation analysis. The results show that the oak–broadleaf mixed forest has the highest structural complexity index (SCI), indicating the best habitat conservation among others, while the oak–pine mixed forest and pure oak forest have the highest timber value in different scenarios of timber price, indicating the largest potential for timber production. Little differences were found between stand types regarding the indicators for soil water conservation. The structural attributes that had a positive correlation with habitat conservation (e.g., number of shrub species, species richness of canopy layer, the proportion of broadleaves and snag density) were identified to be negative for timber production; while the attributes that had a positive correlation with timber production (e.g., stand density and proportion of pine and oaks) were found to be negative for habitat conservation. The results of the trade-off analysis showed that timber production tends to be conflicting with the other two non-timber forest services. In order to enhance the provisioning of multiple services, it was suggested to implement the interventions that could balance these services, such as structural retention and single-tree selective logging. This study could contribute to the theoretical base for the decision making in the multi-purpose sustainable management of oak forests in China.