Fir Forests Research Articles

Forest vegetation of the national park “Koigorodsky” (Komi republic)

The Koygorodsky National Park was organized by the Resolution of the Government of the Russian Federation dated 07.12.2019. The area is 56.7 thousand hectares. Organizers of the Koygorodsky National Park hypostasized that in the Southern part of Komi Republic where the Park was located spruce and fir forests with nemoral occurred. They also hypostasized also that the forests of Koygorodsky National Park existed for a long period in the conditions of natural dynamics. The purpose of the article is to test these hypotheses. The National Park is located in the eastern part of the East European Plain near the border between meddle and southern subzones of taiga zone. The relief on the most part of the reserve is formed by the edges of the Northern Uvals The first data on the forest vegetation and flora of vascular plants of the Koigorodsky National Park, which has not been studied botanically before, have been obtained. 12 plant associations from five formations of dark coniferous (spruce, fir), light coniferous (pine) and small-leaved (aspen, birch) forests were identified in the classification of forest vegetation of the Koygorodsky National Park. Spruce forests occupy a fairly wide range of sites, were represented by three groups of associations: green-moss, herb-rich and bog moss, and occurred mainly to river valleys and wetlands of the watershed. Aspen forests were represented by green-moss and herbaceous communities and occupied most of the territory of the National Park. Birch, pine and fir forests occupied small areas. The predominance of secondary small-leaved aspen and birch forests in the territory of the National Park refutes the hypothesis that its forests existed for a long time without human influence. At the same time, the hypothesis about the presence of communities with a high proportion of nemoral species in the Koygorodsky National Park was confirmed.

The first occurrence of the genus Pristaulacus from the Late Miocene diatomitic maar of Sainte-Reine, Cantal, France (Hymenoptera, Aulacidae)

The first Miocene representative of the wasp genus Pristaulacus Kieffer, 1900, is described from the volcanic paleolake of Sainte-Reine in Cantal, France. Observable characters are identical to those of the extant Pristaulacus barbeyi (Ferrière, 1933), currently known from the southern and eastern Mediterranean regions and Iran and associated with mountainous fir forests where it is a parasitoid of buprestid beetles. Interestingly, the paleohabitat of the Sainte-Reine locality was a mountain paleolake surrounded by forests with firs (Abies Mill., Pinaceae) and with a rather cool climate, matching well with the occurrence of a species of Pristaulacus, phenetically at least, similar to P. barbeyi.

Preliminary study on dry and wet season changes of biomass on Chinese fir forest land based on UAV-Lidar

Preliminary study on dry and wet season changes of biomass on Chinese fir forest land based on UAV-Lidar

MAPPING BEE-KEEPING FOREST PLANTS FROM MEDIUM SPATIAL RESOLUTION MULTISPECTRAL SATELLITE DATA

Abstract. Apiculture is one of the main branches of agriculture and crucial to rural development since it provides farmers with unique products like honey, wax, pollen, royal jelly, propolis and bee venom. Due to pollination services provided by honeybees, environmental sustainability and diversity are also increased, as well as crop production. In Greece, approximately 2.000.000 bee colonies (second in the E.U.) are reported with a relatively high density per km2. There are more than 20.000 beekeeping operators that produce about 20.000 tons of honey every year, while more than 65% of Greek honey is produced from honey dew. To this end, this study aims to identify and map major honeybee flora in the Greek mainland and the Greek islands (Fir forests, Pine forests and Oak forests) for the year 2019, in order to examine best regions to deploy honeybee colonies. In particular, a classification framework for mapping the main honeybee flora is introduced that is exploiting annual moderate-resolution satellite multi-temporal data. Additionally, a methodology is presented to generate a coarser training dataset by utilizing a high-spatial resolution, detailed land cover map. This process specifically focuses on the integration of honeybee flora classes that are not present in the land cover map but are of significant great importance for honey flora mapping. The goal was to enable large-scale classification without the computational resource constraints typically associated with such national scale frameworks. Experimental results are quite promising with the quantitative validation indicating overall accuracy of more than 85%.

Impact of land use changes on the tsunami hazards in part of coastal Kebumen

This research was conducted to analyze land use change from 2016 to 2022 and their impact on the tsunami hazard zone on the coast of Kebumen Regency. For land use change analysis, remote sensing, geographic information systems (GIS), and statistical tests were applied to Sentinel-2A satellite imagery. The tsunami hazard was simulated using tsunami inundation modeling based on land use spatial data and DEMNAS processed using GIS. Land use changes occurred significantly in the study area, especially in Mirit District. The Southern Cross Road (JJLS) and coastal morphological conditions influence land use change patterns. Land use changes impact changes in the tsunami hazard zone, especially in the use of fir forests and shrimp ponds. The research findings can be used as input for developing a tsunami disaster mitigation plan and detailed spatial planning on the coast of Kebumen Regency.

Monastic silviculture legacies and current old-growthness of silver fir (Abies alba) forests in the northern Apennines (Italy)

Species-rich mixed silver fir (Abies alba Mill.) forests dominated in the northern Apennines, but climate and, mainly, anthropogenic land use provoked a sharp silver fir decline approximately 5000 years bp. The conservation of the silver fir in this region was mainly due to the establishment of monastic orders that preserved and even planted silver fir for its spiritual and economic value. In 1993, the best silver fir stands were included in the Parco Nazionale delle Foreste Casentinesi (FCNP), Monte Falterona e Campigna, and have been submitted to low-intensive management or strict protection regardless of past land use and cultural history. In this study, we have (1) analyzed the current structure of three silver fir forests that have had different ownership histories and (2) compared the structure of the three Italian forests among them and with two old-growth forests from the Dinaric Alps as a reference of naturalness. The results show that the current structures of the three Italian forests are very different among them and are strictly related to past land use and, mainly, to monastic legacies. Even if the Italian forests have experienced decades of low-intensity management or strict protection, they are currently structurally very different from Dinaric old-growth forests. Developing an old-growth structure in these forests can be very slow and, in some ways, unpredictable. The results also highlight the importance of recognizing protected areas as cultural landscapes that host an important biocultural diversity. The current risk is that by applying almost exclusive biodiversity-centered management and setting difficult or impossible-to-achieve biodiversity goals, total diversity will decrease, and biocultural diversity, the greatest richness of most European parks, will be lost.

Carbon balance of forest management and wood production in the boreal forest of Quebec (Canada)

Management of boreal forests can increase terrestrial carbon sinks and reduce greenhouse gas (GHG) emissions to the atmosphere. A case study was conducted in the boreal balsam fir forests of Quebec (Canada), a commercially important region for forestry, to identify optimal management and wood production solutions that contribute to reducing GHG emissions to the atmosphere. Scenarios were based on a steady level of harvest and silvicultural activities over time and a stable flow of wood products to markets. Scenarios included: increases and decreases in the volume of harvested timber; the transition of harvesting activities from clearcuts (the most common practice in the region) to partial cuts; and changes in the rate of natural regeneration (the usual mode of regeneration) vs. plantations. All scenarios provided a carbon sink regardless of the time frame. Compared with other scenarios, reducing harvest levels increased the forest carbon sink in the short (10 to 20 years) and medium (20 to 50 years) terms. Also, for a similar harvest level, the increased use of partial cutting and planting increased the forest carbon sink. In the long term (over 50 years), strategies with low harvesting levels resulted in lower ecosystem carbon sequestration, even though they still had the lowest cumulative emissions. Nevertheless, higher harvesting levels could not be justified because the long-term increase in the forest ecosystem carbon sink could not offset higher emissions from wood products, particularly from short-lived paper products. Sensitivity analyses showed that improving sawmill efficiency and thus increasing the proportion of long-lived products was an important factor that can greatly reduce emissions. On the other hand, transportation distances between forest stands and sawmills had a relatively marginal impact on the overall carbon balance of forest management and wood production scenarios.

Influence of Forest Type and Climate Factors on the Number of Caught Ips typographus (Coleoptera, Curculionidae) Bark Beetles in Pheromone Traps in Protected Areas of Bosnia and Herzegovina

As part of the research, the population of the eight-toothed spruce bark beetle in different types of forests in five protected areas in Bosnia and Herzegovina was analyzed. The study focused on the protected areas of Sarajevo Canton, specifically the secondary forests of fir and spruce, as well as the mixed forests of beech and fir (containing spruce). Pheromone traps were used as the research sample, and they were placed within PA Bijambara, PA Trebević, and PA Skakavac. The objective was to investigate the influence of forest type and climatological factors on the number of captured Ips typographus bark beetles from 2018 to 2021. The average number of captured I. typographus bark beetles during that period ranged from 491.39 to 901.68 individuals in secondary fir and spruce forests, and from 201.88 to 701.54 individuals in beech and fir forests (including spruce).

Predicting the Stand Growth and Yield of Mixed Chinese Fir Forests Based on Their Site Quality, Stand Density, and Species Composition

The Chinese fir (Cunninghamia lanceolata) is the largest tree species used for afforestation in China. The purpose of this study was to explore the effects of site quality, stand density, and tree species composition on the growth and yield of mixed Chinese fir forests and to build prediction models for their stand average DBH (diameter at breast height), average height, and volume. Using 430 plots of mixed Chinese fir forests in the Fujian Province of China, the optimal base models for predicting stand average DBH, average height, and volume were selected from the Schumacher, Korf, Logistic, Mitscherlich, and Richards equations. On this basis, the site class index (SCI), stand density index (SDI), and tree species composition coefficient (TSCC) were introduced to improve the model’s performance, and the applicability of the different models was evaluated. The optimal base models for the average DBH, average height, and stand volume of mixed Chinese fir forests all used the Richards equation. The best fitting effect was obtained when the SCI was introduced into parameter a in the average height model, while the inclusion of the TSCC did not improve the model significantly. The fitting effects of the average DBH and stand volume models were both best in the form of y=a1SCIa2[1−exp⁡(−b1SDIb2)t]c when the SCI and SDI were introduced. When the TSCC was further included, the fitting effects of the stand average DBH and volume models were significantly improved, with their R2 increased by 47.47% and 58.45%, respectively, compared to the base models. The optimal models developed in this study showed good applicability; the residuals were small and distributed uniformly. We found that the SCI had an impact on the maximum values of the stand average DBH, average height, and volume; the SDI was closely related to the growth rate of the diameter and volume, while the TSCC influenced the maximum values of the stand average DBH and volume. The model system established in this study can provide a reference for the harvest prediction and mixing ratio optimization of mixed Chinese fir forests.

Regeneration dynamics in mixed mountain forests at their natural geographical distribution range in the Western Rhodopes

Mixed mountain forests consisting of Norway spruce (Picea abies (L.) Karst.), European beech (Fagus sylvatica L.), and silver fir (Abies alba Mill.) are among the most productive and stable forest ecosystems in Europe. Their southeasternmost geographical distribution range is located in the Western Rhodopes, where they have high economic, recreational, and ecological value. In the past, shelterwood cuttings dominated forest management practices in these forests and were mainly aimed at maintaining and reproducing conifers. During the past two decades, single-tree and group-tree selection systems have been promoted as alternative management approaches to support the conversion of spruce-dominated stands to close-to-nature mixed forests of fir, beech, and spruce. However, the natural regeneration dynamics in these stands are barely known, and their dependence on microsite and management effects needs to be better understood.The objective of this study was to investigate ecological factors under management regimes of different intensity (“single-tree”-selection and “group-tree”-selection) that influence the regeneration processes in mixed mountain forests in the Bulgarian Rhodopes. Data on regeneration and microsite conditions were collected on 105 systematically distributed plots (25 m2/100 m2) in four 100–120 years old stands located in the regional forest district of Smoljan, Bulgaria (1580–1650 m a.s.l.). We relied on generalizeds linear mixed models to analyse for each species the (1) size-dependent regeneration density and (2) height increment in dependence on management practices, competing vegetation, as well as soil and light conditions.Our study revealed an overall high potential for recruitment in the Western Rhodopes. Regeneration density was highest in fir (median 12800 N ha-1), followed by spruce (median 1600 N ha-1) and beech (median 1200 N ha-1). Fir benefited most from “single-tree” selection cuttings, while “group-tree” selection cutting tended to promote beech and fir but also spruce. Competing ground vegetation was detrimental for seedling density of all species. Annual height increment increased with plant size, was lowest in spruce, and similar in fir and beech. Sapling increment was driven by light, whereas seedlings did not react to increased radiation. Browsing was species-specific and was highest in beech (15–30 %), followed by fir (5–10 %) and spruce (<1 %). It was not a crucial factor in impeding tree recruitment. We conclude that frequent harvest activities of low intensity which consider advanced regeneration are a promising approach to successfully convert the formerly spruce-fir-dominated forests to climate-adapted fir-beech-(spruce)-mixed stands.

Surface water balance at the Chapingo River basin: rainfall intercepted by vegetation and water infiltration into the soil

Objective: To estimate the surface water balance in the Chapingo River microbasin in the years 2014, 2016, 2017, and 2018, based on information collected on rainfall and runoff, the use of interception simulation models, and the estimation of the of infiltration as a remainder of the balance. Design/Methodology/Approach: During the 2014, 2016, 2017, and 2018 wet seasons, the water balance in unit sheet was estimated based on rainfall and runoff data, mathematical interception simulation models, and estimation of infiltration as a remainder of the balance. Results: The highest interception rate was recorded in 2014, with a shorter range and lower dispersion of rainfall, while the lowest interception occurred in 2018 with opposite rainfall characteristics. A linear relationship was found, in two years, between rainfall and surface runoff with R2 greater than 0.81. The interception rate was lower in the oyamel fir forest (7.7-9.3%), while the variation in interception between grasslands, pine forests, oak forests, and agricultural areas ranged from 20% to 23%. The remaining infiltration water represented between 85.5% and 88.2% of the rainfall. Study Limitations/Implications: Determining the temporal evolution of the interception and humidity in the soil is necessary to specify the potential recharge to the aquifer. Findings/Conclusions: Interception is the main vehicle by which water reaches the ground in areas covered by vegetation. Rainfall intensity has a negative impact on interception and infiltration. The basin under study offers a high recharge potential to the Texcoco aquifer.

Shedding light on dark taxa in sky‐island Appalachian leaf litter: Assessing patterns of endemicity using large‐scale, voucher‐based barcoding

Abstract Developing systematic conservation plans depends on a wealth of information on a region's biodiversity. For ‘dark taxa' such as arthropods, such data are usually very incomplete and in most cases left out from assessments. Sky islands are important and often fragile biodiversity hotspots. Southern Appalachian high‐elevation spruce–fir forests represent a particularly threatened sky‐island ecosystem, hosting numerous endemic and threatened species, but their arthropods remain understudied. Here we use voucher‐based megabarcoding to explore genetic differentiation among leaf‐litter arthropod communities of these highlands, and to examine the extent to which they represent dispersed communities of more or less coherent species, manageable as a distributed unit. We assembled a dataset comprising more than 6000 COI sequences representing diverse arthropod groups to assess species richness and sharing across peaks and ranges. Comparisons were standardised across taxa using automated species delimitation, measuring endemism levels by putative species. Species richness was high, with sites hosting from 86 to 199 litter arthropod species (not including mites or myriapods). Community profiles suggest that around one fourth of these species are unique to single sky islands and more than one third of all species are limited to a particular range. Across major taxa, endemicity was lowest in Araneae, and highest in neglected groups like Isopoda, Pseudoscorpionida, Protura and Diplura. Southern Appalachian sky islands of spruce–fir habitat host significantly distinct leaf‐litter arthropod communities, with high levels of local endemicity. This is the first work to provide such a clear picture of peak and range uniqueness for a taxonomically broad sample. Ensuring the protection of a sizeable fraction of high‐elevation litter species richness will therefore require attention at a relatively fine spatial scale.

Linkages of soil CO2 emission with plant functional traits in young subtropical plantations.

Soil respiration is a key process in forest biogeochemical cycling. Exploring the relationship between plant functional traits and soil respiration can help understand the effects of tree species conversion on soil carbon cycling. In this study, we selected 15 common subtropical tree species planted in the logging site of second-generation Chinese fir forest to measure soil CO2 emission fluxes, soil physicochemical properties, leaf and root functional traits of each species, and explored the effects of plant functional traits on soil respiration. The results showed that the annual flux of soil CO2 emissions varied from 7.93 to 22.52 Mg CO2·hm-2, with the highest value under Castanopsis carlesii (22.52 Mg CO2·hm-2) and the lowest value under Taxus wallichiana (7.93 Mg CO2·hm-2). Results of stepwise regression analysis showed that the annual flux of soil CO2 emission decreased with the increases of leaf nitrogen content and fine root diameter, and increased with increasing leaf non-structural carbohydrate. In the structural equation model, leaf non-structural carbohydrate had a direct and significant positive effect on soil CO2 emission fluxes, while leaf nitrogen content and fine root diameter had a direct negative effect by decreasing soil pH and soluble organic nitrogen content. Plantations of different tree species would affect soil CO2 emission directly by changing functional traits related to water and nutrient acquisition or indirectly through soil properties. When creating plantations, we should select tree species based on the relationship between plant functional traits and ecosystem functions, with a view to improving forest productivity and soil carbon sequestration potential.

Influence of Phoebe bournei (Hemsl.) Replanting on Soil Carbon Content and Microbial Processes in a Degraded Fir Forest

Replanting is a widely used method for improving the health and carbon sequestration capacity of degraded forests. However, its impact on soil carbon pools remains controversial. This study investigated the effects of replanting broadleaf Phoebe bournei (Hemsl.) Yang in a typical degraded fir forest. Soil carbon content, nutrient levels, and microbial community structure and function were measured at 0, 5, 8, and 12 years after replanting. The degraded fir forests were originally limited in nitrogen and phosphorus. Phoebe bournei replanting significantly increased soil total carbon but reduced total nitrogen and phosphorus levels, resulting in increased soil carbon:nitrogen, carbon:phosphorus, and nitrogen:phosphorus ratios. Microbial biomass carbon, nitrogen, and phosphorus were all significantly reduced, whereas microbial carbon:phosphorus and nitrogen:phosphorus ratios were enhanced. Enzyme activities related to nutrient cycling and carbon decomposition (acidic invertase, polyphenol oxidase, peroxidase, urase, nitrate reductase, and acidic phosphatase activities) were significantly lowered by replanting. Microbial richness and diversity significantly increased, and microbial community composition changed significantly due to replanting. Structural equation modeling revealed the significant role of total phosphorus in microbial biomass, microbial community composition, and enzyme activity, highlighting it as the main factor accelerating soil carbon accumulation. Network analysis identified Leifsonia, Bradyrhizobium, and Mycolicibacterium members as key microbial players in the soil carbon cycle. In summary, P. bournei replanting exacerbated soil phosphorus deficiency, leading to a decrease in soil microbial biomass and changes in community structure, reduced nutrient cycling and carbon-decomposition-related enzyme activities, less litter decomposition, and increased organic carbon accumulation. These findings demonstrate the importance of nutrient limitation in promoting soil carbon accumulation and offer new insights for soil carbon regulation strategies in forestry.

Effects of Mycorrhizal and Extraradical Hyphae of Subtropical Native Tree Species on Soil Enzyme Activities and Their Stoichiometric Ratios

We aimed to study the effects of mycorrhizal and extraradical hyphae on soil physical and chemical properties and enzyme activity characteristics in a subtropical plantation and to explore its indicative effect on the effectiveness of soil nutrients. In this study, three native afforestation tree species, Cunninghamia lanceolata, Schima superba, and Liquidambar formosana, with different biological characteristics, root functional traits, and nutrient acquisition strategies in subtropical regions were selected as the research objects. Based on the method of in-growth soil cores, the nylon mesh with different pore sizes was used to limited the root system and hypha into the soil column. The soil physical and chemical properties of five kinds of hydrolase related to the carbon (C), nitrogen (N), and phosphorus (P) cycles were determined in this study. The correlation of different tree species, roots, and mycelia with soil physicochemical properties, enzyme activity, and stoichiometric ratios was analyzed. The results revealed that mycorrhizal treatment significantly affected the soil total carbon (TC) and pH but had no significant effect on hydrolase activity and its stoichiometric ratio. Tree species significantly affected soil physical and chemical properties, soil β-1,4-N-acetylglucosaminidase (NAG), β-1,4-glucosidase (βG), and cellobiohydrolase (CB) activities and soil enzyme stoichiometric ratios. The soil enzyme activity and stoichiometric ratio of the Chinese fir forest had higher values than in monoculture broad-leaved stands of both Schima superba and Liquidambar formosana. There was no significant interaction effect of mycorrhizal treatments and tree species on all soil properties, enzyme activities, and stoichiometric ratios. In addition, the soil enzyme activity and stoichiometric characteristics were mainly affected by the pH. In this study, the soil enzyme activity ratios In(BG + CB):In(AP) and In(NAG + LAP):In(AP) were lower values than the global scale, while the ratios of In(βG + CB):In(NAG + LAP) were higher than the average, indicating that the soil microorganisms in this area were limited by C and P. Moreover, the soil enzyme activity and chemical metrology characteristics were mainly affected by the pH change. In conclusion, differences in litter quality and root functional traits of tree species affected the soil enzyme activity and its stoichiometric characteristics through the shaping of the forest environment by organic matter input, and the influence of pH was the main regulating factor.

Soil bacterial communities are more sensitive to short-term nitrogen deposition than fungal communities in subtropical Chinese fir forests

The increasing rate of atmospheric nitrogen (N) deposition seriously affects the structure and function of ecosystems. Although soil microorganisms play a crucial role in ecosystem carbon (C) and nutrient cycling, the impact of N deposition on soil microbial communities in subtropical forest ecosystems is unclear. Here, we selected the subtropical Chinese fir (Cunninghamia lanceolata) forest as the research object and conducted simulated N deposition experiments with different levels of N deposition (0 kg N ha−1 yr−1,50 kg N ha−1 yr−1, 100 kg N ha−1 yr−1, and 200 kg N ha−1 yr−1, respectively) to explore the response of soil nutrients, soil microbial community structure, and potential ecological functions to short-term N deposition. We found that the bacterial richness Chao1 index and phylogenetic diversity PD_whole_tree decreased with the N deposition level approximately 13 % −16 % under MN and HN treatment. N deposition significantly altered the composition of soil bacterial communities (P < 0.05), but the responses of different taxa to N deposition were inconsistent at different stages of growing season. N deposition treatment significantly increased the relative abundance of Actinobacteria at both beginning of growing season (BGS) and end of growing season (EGS), decreased the relative abundances of Planctomycetes at BGS, and decreased the relative abundances of Elusimicrobia and Cyanobacteria at both BGS and EGS. Non-metric multidimensional scaling (NMDS) and Anosim (Analysis of similarities) analyses showed that the bacterial communities were clearly distinguished among treatments at both BGS and EGS. However, N deposition had a relatively small impact on fungal communities, only altering the fungal community structure at BGS. The impact of N deposition on soil microbial communities was mainly induced by the alteration in soil water content (SWC), pH, NO3–-N, and available nitrogen (AN). Both bacterial and fungal communities exhibit seasonal community dynamics, while the interaction of N deposition and season was mainly reflected in the impact on bacterial communities. Our research not only provides research ideas for the potential impact of nitrogen deposition on subtropical forest ecosystems in the short term, but also provides a theoretical basis for future scientific management and regulation of forestry, microorganisms, and sustainable management of Chinese fir plantations.

A Quantitatively Divided Approach for the Vertical Belt of Vegetation Based on NDVI and DEM—An Analysis of Taibai Mountain

Vertical vegetation differentiation is the most important form of spatial pattern in mountainous areas. It is of great significance to accurately divide vegetation into vertical zones for the study of mountain ecosystems and ecological protection. In order to accurately divide the vertical zone of mountain vegetation and determine the spatial distribution of mountain vegetation, the relationship between the vegetation index of various vegetation types and altitude was examined using remote sensing and geographic information technology. Taking Taibai Mountain, the main peak of the Qinling Mountains in China, as the study area, based on the difference in NDVI between summer and autumn (DNSA), this work constructed a DEM-NDVI scatter plot and quantified the boundary of the vertical zone by the half-peak width calculation method. The findings showed that: (1) the vertical distribution pattern of mountain vegetation may very well be reflected in the scatterplot that NDSA and DEM created; (2) Six vertical belts could be accurately identified to the meter level on Taibai Mountain’s south slope. Up to the altitude, the oak forest zone from the bottom of the mountain to the elevation of 1919 m, the pine-oak mixed forest zone is distributed in 1919–2331 m, the birch forest is distributed in 2115–2585 m, the fir forest is distributed in 2516–3150 m, the redwood forest is distributed in 3109–3551 m, and the alpine scrub meadow is distributed in 3551 m to the peak. On the north slope, 1053–2087 m above sea level is oak forest, 2087–2693 is birch forest, 2562–3006 is fir forest, 2987–3513 m is redwood forest, and 3513 to the top of the mountain is alpine scrub meadow; and (3) the distribution pattern of the vegetation vertical belt on the DEM-NDVI scatter plot was essentially compatible with the vegetation classification results derived from remote sensing images. The DEM-NDVI scatter plot can reflect the average distribution of vegetation population and can more accurately express the characteristics of vegetation vertical zone changes with altitude.

Assessment of Soil Quality in the Transformation from Pure Chinese Fir Plantation to Mixed Broad-Leaved and Cunninghamia lanceolata Plantation in Subtropical China

To assess the alterations in soil properties resulting from the interplanting of broad-leaved tree species within coniferous forests, we conducted an investigation into soil quality in a mixed Chinese fir and broad-leaved forest, as well as in a Chinese fir pure forest (used as a control) in subtropical China. A total of 15 soil physicochemical properties were assessed across three soil depths—0–15 cm, 15–30 cm, and 30–45 cm—for the two forest types in the experimental study. Principal component analysis in conjunction with the Norm value was employed to create a minimal data set (MDS) for assessing six indicators, including bulk density (BD), total nitrogen (TN), total phosphate (TP), available potassium (AK), soil pH, and catalase (CAT). The soil quality index (SQI) was calculated for both forest types. The results demonstrated that following the interplanting of broad-leaved tree species in the Chinese fir forest, all soil physicochemical indicators were significantly improved compared to the control, and significant differences were also observed in the 0–15 cm and 15–30 cm soil layers (p &lt; 0.05). The overall average of the SQI of the mixed forest (0.8523, 0.6636) was significantly higher than that of the control (0.4477, 0.3823) (p &lt; 0.05) in the 0–15 cm and 15–30 cm soil layers, respectively. However, there was no significant difference in the SQI in the 30–45 cm soil layer (p &gt; 0.05) between the two forest types. The results indicated that the SQI based on the minimal dataset (MDS) can reflect the SQI of the total dataset (TDS) when assessing soil quality in forests. Our research provides valuable scientific insights into soil science and an understanding of the relationships between soil properties, forest structure, and species composition in sustainable forest management.

Excluding Roots or Mycorrhizal Hyphae Alters the Microbial Community and Function by Decreasing Available C and N in a Subtropical Chinese Fir Forest

Carbon (C) inputs, primarily from roots and associated mycorrhizal hyphae, serve as crucial energy sources for microbial-driven C and nitrogen (N) cycling in the soil. However, our understanding of how soil microbial diversity, function, and associated soil properties respond to the exclusion of roots and their associated mycorrhizal hyphae remains limited. In our study, we conducted an experiment with no exclusion of roots or mycorrhizal hyphae (Control), exclusion of roots and retention of mycorrhizal hyphae (NR), and exclusion of roots and mycorrhizal hyphae (NRH) in a Chinese fir (Cunninghamia lanceolata) forest, the most important plantation in China. The soil properties, microbial community diversity and composition, and microbial function were investigated after 2 years of experiment exclusion. We found that exclusion of roots and hyphae significantly decreased DOC, DON, NH4+-N, and NO3−-N, but not SOC, TN, and TP, indicating that the exclusion of roots and mycorrhizal hyphae mainly reduced available C and N concentrations. Meanwhile, the species richness and Chao1 of bacteria and fungi were significantly reduced, primarily due to the decrease in available C and N levels. These findings suggest that the removal of roots and mycorrhizal hyphae results in a decrease in C and N availability, subsequently leading to a loss of microbial diversity. Compared to after the CT treatment, the relative abundances of Proteobacteria and Actinobacteria phyla were reduced after exclusion of roots and hyphae. However, the relative abundances of the phyla Acidobacteria, WPS2, Rozellomycota, and Glomeromycota showed an increase in exclusion treatments. Furthermore, the relative abundances of genes for C degradation (e.g., malQ, malZ, chi, rfbB, bglX, and ablA), C fixation (e.g., accA, icd, korA, and korB), and N fixation (nifS) were increased; conversely, the N degradation genes (e.g., nasA, nirB, ureC, and gdh2) were decreased in treatments involving excluding roots and hyphae. These results, in conjunction with the strong relationships between functional genes and DOC, DON, NH4+-N, and NO3−-N, suggest that microorganisms regulate functional genes to enhance C and N fixation or organic matter decomposition in response to C or N limitation resulting from root and mycorrhizal hypha exclusion. Collectively, our study revealed that the changes in roots-derived C directly altered available C and N in soil, which influenced the microbial community and function, and, in turn, regulated microbial-driven nutrient cycling in forest soils.

Temporal changes in size inequality and stand growth partitioning between tree sizes under various thinning intensities in subtropical Cunninghamia lanceolata plantations

Stand structural complexity and growth partitioning between different tree sizes influence trees competition and resource use efficiency, and thus are closely linked to stand productivity. The main aim of this study was to examine how the stand structure complexity (Gini coefficient Gini) and size-related partitioning of stand growth (growth dominance coefficient GDC and size-growth relationship SGR) temporally changed after different thinning intensities in Chinese fir (Cunninghamia lanceolata) forests, Southeastern China. We analyzed the data of 6 repeated measurements over a nearly 10-year period from a forest thinning experiment with progressively increasing intensity (0, 20%, 25%, 33% and 50% reduction of stand density by selection logging of releasing target trees) and assessed the effects of different thinning intensities using generalized mixed effect model. The thinning intensity of 0 was taken as a control group to identify the stand changes in unthinned stands over time. Size heterogeneity and the relative contribution of larger trees to total stand growth tended to increase as forest grew without thinning management. While the increases in Gini and SGR (excluding between 0 and 0.5) overall negatively influenced the average annual basal area increment of the remaining trees (BAI). Gini in thinned stands decreased during the short term (two years or more) after thinning and the heavy thinning had lower Gini than other treatments several years (eight years or less) after thinning. GDC reduced greater with increasing thinning intensity, and thinning had a significant negative effect on Gini and SGR and a positive effect on BAI. The thinning impacts on BAI increased with the thinning intensity, while the effect magnitudes of different thinning intensities on Gini and SGR were: T50 < T20 < T25 < T33. Overall, thinning increased the stand growth partitioning of small trees, contributing to a uniform stand structure. However, the changes in stand structural complexity and the partitioning of stand growth were related to both thinning intensity and post-thinning time, particularly to thinning intensity. The results provided some implications for designing the intensity and timing of thinning, as well as for determining the size classes of removed trees for different management goals.