Forest Soil Fertility Research Articles

Fertility and ecotoxicological condition of light gray forest soils of the Ivanovo region

The results oflong-term monitoring of light gray forest soil for agricultural purposesin theIvanovo region are presented, which was carried outto establish the level of fertility according to the mainagrochemical indicators, the content of mobile forms of trace elementsand sulfur, the ecotoxicological state according to the content ofgross and mobile forms of heavy metals, arsenic, caesium-137 andstrontium-90.The average values of the indicators, their levels ofchange and trends in changes in the metabolic and hydrolyticacidity of the soil, availability of organic matter, mobile formsof nitrogen, phosphorus, potassium, exchangeable calcium, magnesium and other bases,mobile forms of boron, copper, zinc, molybdenum, cobalt, manganese andsulfur have been established.According to the content of traceelements in the soil, the needs for the use ofmicronutrients are determined.Changes, concentrations and trends in the mobileforms of cadmium, lead, copper, zinc, nickel, chromium, mercury andarsenic in the soil have been determined.The study establishedbackground values, changes and trends in the specific activities ofcaesium-137 and strontium-90, the density of their contamination of thesoil of the site and the power of the exposuredose of gamma radiation.According to thePearson–Spearman correlation coefficients,the peculiarities of the influence of the content of organicmatter, the level of acidity and the capacity of cationexchange on the content of mobile forms of trace elements,sulfur, gross and mobile forms of metals and radionuclides wereestablished.

Effects of LongTerm Application of Mineral Fertilizers and Manure on Agrochemical Properties of Gray Forest Soil, Crops Productivity and Carbon Sequestration

The effect of long-term application of increasing doses of mineral (from N90P75K100 to N360P300K400) and organic (cattle manure from 25 to 100 t/ha) fertilizers on the fertility of gray forest soil was studied in the micro-plot experiment. Over 9 years, 0.81–3.24 t/ha of nitrogen, 0.68–2.70 t/ha of P2O5 and 0.90–3.60 t/ha of K2O were applied with mineral fertilizers. Manure supplied 43–173 t/ha of dry matter, 16–65 t/ha of Corg, 0.85–3.41 t/ha of Ntot, 0.65–2.59 t/ha of P2O5 and 0.86–3.46 t/ha of K2O. In the yield the mineral fertilizer system exceeded the organic one by an average of 29%. At extreme doses (N360P300K400 and 100 t/ha of cattle manure) mineral fertilizers reduced crop productivity more strongly than organic fertilizers. A direct linear relationship was found between the doses of mineral and organic fertilizers and the increase in the content of available P2O5 and K2O in the soil. Application of extreme doses of fertilizers did not lead to saturation of the soil with available forms of phosphorus and potassium. Long-term application of organic fertilizers increased the soil pH(KCl) by 0.4–1.3 units and mineral fertilizers decreased it by 0.8–1.4 units. Annual application of mineral fertilizers increased soil Corg content by an average of 0.02–0.04% per year, and organic fertilizers – by 0.08–0.17% per year. Manure application at 100 t/ha over 9 years led to the saturation of the soil with organic carbon. The C : N ratio in the soil under a mineral fertilizer system was decreased, while it with the organic system was increased. An approach to calculate the carbon sequestration efficiency for the assessment of different agronomic practices is proposed. It is shown that the carbon sequestration efficiency of the organic fertilizers was 15% higher than that of the mineral fertilizers.

Climate regulates the effect of land‐use change on the diversity of soil microbial functional groups and soil multifunctionality

Abstract Although studies have explored how soil microbial diversity and soil multifunctionality respond to land‐use change at local scales, they have rarely been explored at larger scales and across different climatic and soil environmental conditions. By sampling 40 paired sites of land‐use change from natural forests to agricultural lands (including croplands and orchards) along the middle and lower Yangtze River, combined with a global meta‐analysis, we investigated the effects of land‐use change and climate on the alpha and beta diversity of soil bacterial and fungal functional groups (FGs) and their associated soil multifunctionality at a regional scale. Our results showed that land‐use change strongly changed the diversity of soil bacterial and fungal FGs and decreased multifunctionality, which was supported by our meta‐analysis at a global scale. Direct effects of land‐use change and climate and their interaction, together with changes in soil environmental variables, were the main determinants of the land‐use change‐induced changes in the diversity of soil bacterial or fungal FGs. The land‐use change‐induced decrease in multifunctionality was mainly associated with the direct effect of forest conversion, soil fertility and diversity of fungal FGs. Furthermore, climate also regulated the effects of land‐use change on multifunctionality by affecting soil fertility and fungal FGs diversity along the Yangtze River. Synthesis and applications. Taken together, our findings highlight the important effects of land‐use change, climate and their interactions on microbial diversity and multifunctionality and suggest that effective land‐use management and climate change mitigation strategies should be adopted to protect biodiversity and ecosystem function in the Yangtze River Basin.

Patterns and determinants of calcium concentrations in forest litter and different soil horizons in warm-temperate China

Calcium is an essential nutrition for the integrity and structure of plant cells, and is generally neglected because of its high abundance in temperate forest soil. To date, little is known about the changes in soil Ca and the main natural drivers in the conserved forests. Here, the concentrations of Ca in forest litter and different soil horizons (0–10, 10–20, 20–30, and 30–50 cm) from 234 forest plots were measured. Spatial variations in litter and soil Ca concentrations beneath different forest types were determined, and a structural equation model (SEM) was constructed to evaluate the causal pathways of the biotic and abiotic drivers. The results showed that litter Ca concentration beneath broadleaved forests and mixed broadleaf-conifer forests (22.62 and 19.76 mg/g, respectively) were significantly greater than that beneath the coniferous forest (15.35 mg/g). The Ca concentrations in the soil significantly increased with latitude (soil depth < 30 cm) and longitude. However, litter and soil Ca concentrations significantly declined with elevation. The basal area of the forest and soil C/N were the dominant factors regulating the concentration of Ca in litter and soil profiles, respectively. The SEM highlighted the important effects of Ca concentration in deep soil (soil depth > 20 cm) on litter Ca concentration. The basal area and soil C/N had negative and positive direct effects on Ca concentration in topsoil (soil depth < 20 cm), respectively. The precipitation and temperature in the growing season had indirect effects by affecting the soil C/N and basal area. These results collectively suggest that different forest types influence the redistribution of Ca belowground, and the process is mainly mediated by the basal area and soil C/N. The afforestation in the study area with admixture of conifers and broadleaved trees is a desirable management for the improvement of forest productivity and soil fertility.

Use of nitrogen-fixing plants to improve planted forest soil fertility and productivity in New Zealand: A review

Background: Planted forests with low fertility soils are likely to require increased inputs of nitrogen (N) to satisfy increasing productivity demands. The use of N fertilisers will become more challenging due to their increasing cost and the risk of unwanted environmental impacts. Nitrogen-fixing plants may provide an alternative option to chemical fertilisers that is not only cheaper but has a lower greenhouse gas footprint. Methods: Information on N-fixing plants was collated from available literature, focusing on species previously associated with planted forests as well as other exotic N-fixing trees and New Zealand native plants not used in commercial planted forests. Results: Benefits to planted forest growth in New Zealand by N-fixing plants have been proven in only a few cases. Lupinus arboreus Sims was used in the 1970s and 1980s to increase N inputs in a planted Pinus radiata D.Don coastal forest, and improved P. radiata productivity was demonstrated. Productivity gains ceased when a blight disease infected the lupin population. Many N-fixing plants have been shown to tolerate low fertility soils and establish in planted forests, but there is limited information on their N contribution to the soil, and whether this N contribution increases P. radiata productivity. Such N-fixing plants include Lotus species, clover (Trifolium species) and weeds such as gorse (Ulex europaeus L.) and broom (Cytisus scoparius (L.) Link), which are commonly found in association with P. radiata forests. New Zealand native N-fixing shrubs may be suitable but there is limited information available describing N-fixation or forestry management for native plant species. Conclusions: Nitrogen-fixing plants are a valuable resource, which when managed properly could be used for enhancing productivity. Issues with pests and disease, and limited knowledge regarding the management of N-fixing species, restricts adoption in planted forests. Well-designed research is needed to assess impacts on whole forest system N cycling as well as selection of appropriate plant species for use in planted forests without unintended consequences such as competition for soil moisture or light. This research needs to be integrated with forest management and delivered as practical options to ensure success.

Functional richness mediates landscape and management effects on tree biomass and soil fertility during secondary forest succession

Secondary forests can play a critical role in conserving plant biodiversity and sequestering carbon. However, intensive past management, fragmentation, and initial soil fertility can hinder forest recovery during secondary succession, especially in terms of tree species selection. In turn, tree species selection can negatively impact soil fertility recovery and may slow down the succession process, but the direct and indirect effects between these factors remain unclear. To assess the complex interactions among landscape, previous management, soil and vegetation, 27 secondary forests of varying ages, previously used for eucalyptus plantations, located in diverse landscape configurations within the Atlantic Forest biome, were examined. Key variables, such as planting frequency, cutting frequency, forest cover in the landscape, patch isolation between fragments, functional richness, tree aboveground biomass (AGB), soil sum of bases, soil organic matter, and soil phosphorus concentration were used to construct a structural equation model to evaluate the direct and indirect effects of landscape and previous management on forest development. Cutting frequency and patch isolation had a negative direct effect on functional richness. Additionally, a strong positive direct effect of functional diversity on aboveground biomass and soil sum of bases was found. Thus, cutting frequency and patch isolation had negative indirect effects on biomass and soil sum of bases (a proxy for soil fertility), mediated by functional richness. These findings underscore the significance of integrating plant functional diversity into restoration strategies to preserve ecosystem functioning and efficiently recover biodiversity, tree biomass, and soil fertility in secondary forests.

Reproduction of potential fertility of gray forest soil using elements of biological agriculture technologies

Reproduction of potential fertility of gray forest soil using elements of biological agriculture technologies

Response of L. Scoparium and K. Robusta to biosolids and dairy shed effluent application in a low fertility soil

Biosolids and Dairy Shed Effluent (DSE) can contain high concentrations of plant nutrients, making them potential resources for enhancing forest tree species growth and soil fertility. This study aimed to investigate the effects of biosolids and DSE application on the growth and nutrient uptake of Leptospermum scoparium and Kunzea robusta, while also considering the potential accumulation of contaminants. The results demonstrated that amending low-fertility soil with 2600 kg N ha-1 of biosolids and 200 kg N ha-1 of DSE positively influenced the growth of both L. scoparium and K. robusta. This improvement was evident through increased biomass production and enhanced uptake of essential elements such as calcium (Ca), potassium (K), and sulfur (S). Notably, L. scoparium exhibited superior growth when combined with DSE, while both species showed similar positive responses when combined with biosolids. However, it should be noted that the application of biosolids resulted in elevated concentrations of certain trace elements in the plants, whereas DSE did not. These trace elements included cadmium (Cd), copper (Cu), manganese (Mn), and zinc (Zn). Despite the increase, the levels of these elements did not exceed unacceptable thresholds. Considering the potential influence of biosolids on plant rhizodeposition, it is recommended that future studies investigate the interactions between plant roots and microbes, particularly in relation to plant element uptake. This line of research would further enhance our understanding of the underlying mechanisms involved. In conclusion, the findings suggest that the application of biosolids and DSE can effectively improve forest tree growth and nutrient uptake. However, careful management is necessary to mitigate the potential accumulation of trace elements. These results provide valuable insights for optimizing the use of biosolids and DSE in forestry practices, with potential economic and environmental benefits.

Tree canopy area-dependent changes in soil properties: a comparative study in the southern limit of boreal forest distribution

The forest distribution in relation to mountain slope position and the relationships between forest canopy area and soil physical and chemical properties in Mongolia attract the attention of scientists. In this study, we aimed to determine (1) how the slope aspect affects the forest soil physical and chemical properties, (2) how the soil variables correlate with projected canopy area. For comparative study, we established a total of 18 (20 × 25 m2 sized) sample plots in upper forest edge (UFE), upper slope of the forest (USF), lower slope of the forest (LSF), lower forest edge (LFE), sparse forest (SF), and degraded forest area (DFA) stand types with three replications. We measured the tree height, diameter and crown projection area of each growing tree in the sample plots, and collected soil samples for further soil physical and chemical analyses in the laboratory. Our results showed a high variation in growing stock (p < 0.0001), stand density and projected canopy area (p < 0.0001) in relation to mountain slope position and land-use management. We found that the slight changes in stand canopy area projection cause a high variation in soil physical and chemical properties. Among studied stand types higher means of soil temperature and bulk density and lower moisture content were observed on SF and DFA stand types. Contrary, relatively higher content of soil moisture and nutrient elements were recorded in USF, LSF, LFE. We conclude that tree canopy area becomes key determinant factor that positively influences forest soil moisture and fertility by increasing organic matter content in Mongolia.

The Role of Leaf Litter in Forest Soil Fertility and Microbial Diversity

The Role of Leaf Litter in Forest Soil Fertility and Microbial Diversity

Tree species identity affects nutrient accumulation and stoichiometric in soil aggregates in mixed plantations of subtropical China

The conversion of monocultural to mixed plantations is an increasing and widespread practice worldwide to improve forest productivity and soil fertility. Although tree species identity can affect soil ecological processes, there is still limited research on how it affects soil aggregate stability and nutrient variability. Here, we investigated the variation of 0–100 cm aggregate stability index (percent of aggregate destruction, PAD; fractal dimension, D; geometric mean diameter, GMD; mean weight diameter, MWD), associated carbon (C), nitrogen (N), phosphorus (P), and stoichiometry in mixed plantations from coniferous trees (Pinus massoniana Lamb.) and a variety of individual broadleaved trees (Camellia oleifera Abel, Manglietia chingii Dandy, Cercidiphyllum japonicum Sieb. et Zucc., Michelia maudiae Dunn, and Bretschneidera sinensis Hemsl.). We discovered that compared to coniferous plantations, most mixed plantations significantly improved the mechanical and water stability of topsoil aggregates. Deep-rooted tree species (e.g., Michelia maudiae Dunn) favored the development of subsoil macro-aggregates to improve aggregate water stability (e.g., PAD = 46.10, MWD = 1.23, GMD = 0.49, D = 2.81). Mixed planting led to the enrichment of soil C, N, and P in microaggregate, which increased by at least 37.14, 20.24, and 61.11 %, respectively. The reduced C:P and N:P in soil aggregates indicate that soil P limitation may be alleviated. Furthermore, tree species and soil depth indirectly affected aggregate stability to regulate the accumulation of C, N, and P. Overall, we emphasize the necessity of selecting tree species combinations with complementary ecological niches in mixed plantations to improve soil stability and support forest productivity.

A dataset of monthly and yearly litterfall production in different succession stages of evergreen broad-leaved forests in Tiantong (2008 – 2018)

Litter production is an important part of the matter cycle of forest ecosystems, which plays an important role in maintaining forest soil fertility and promoting ecosystem nutrient cycling. Additionally, it serves as an important indicator for the quantification of ecosystem function such as forest productivity and carbon balance. The data in the dataset are from two observation plots in Zhejiang Tiantong National Forest Ecosystem National Observation and Research Station. The community succession types in the above two pilots belong to the middle-late stage and mature stage of evergreen broad-leaved forest succession, respectively. The projected area of each plot is 50 m × 50 m. There are 27 litter traps of 0.5 m2 in each plot. We collected and counted the data in terms of litter components, i.e. branches, leaves, flowers (fruits), bark and debris). The dataset includes the monthly and annual production of each component and the total amount of litter in the two plots from 2008 to 2018. The data have been checked against the original paper records, as well as the dynamic trend of data in the same period, so as to ensure data quality control and accuracy assessment. This dataset can provide basic information for understanding the changes of ecosystem structure and function during the succession process of evergreen broad-leaved forests. Moreover, it can also provide data support for studying the impact of regional climate change on the forest ecosystem and the assessment of carbon balance in the zone of evergreen broad-leaved forests.

Collective forest tenure reform and forest conditions: evidence from the social-ecological system in Southwest China

China’s recent collective forest tenure reform (CFTR) aims to improve forest conditions by devolution of forest management rights from community collectives to individual households. Studies reveal substantial local variation in CFTR implementation, but the ecological effects and underlying mechanism have received little attention. Our study focused on community-managed forests and household-managed forests in four communities located in the mountains of Southwest China. The objective was to investigate the relationship between CFTR and forest conditions at the local scale. We employed a combination of remote sensing technology, field forest observations and socioeconomic surveys to gather data for analysis. The results showed that the forest cover change trends of collective forests and household forests in each community were consistent from 1994 to 2014. There was no significant relationship between CFTR implementation and local-level differences in species diversity and soil fertility in forests. The aboveground biomass of collective forests was significantly higher than that of household forests. Differentiated access and use, low compensation amounts, and loose payment terms jointly affected CFTR’s effectiveness to improve local-scale forest conditions in the study area. Attempts to formalize forest tenure rights must be flexible enough and adapted to the local environment so that changes induced by the CFTR can improve local access to forest resources and its benefits.

Improving spatial predictions of Eucalypt plantation growth by combining interpretable machine learning with the 3-PG model

Accurate predictions of forest plantation growth provide forest managers with improved forest inventory estimates, forest valuation, and timely harvest schedules. Forest process-based models are increasingly used for quantifying current and potential productivity, yield gaps, and factors limiting growth, such as climate variability, soil characteristics, and water deficit. Improvements in the availability and resolution of spatial and temporal data combined with advancements in machine learning algorithms provide new opportunities to improve model predictions. This study shows how interpretable machine learning (ML) can be used to independently predict site soil fertility rating (FR) and incorporate these results into the 3-PG forest process-based model to accurately predict plantation growth. Four ensemble decision tree machine learning models—random forest trees, extremely randomized trees, gradient boost, and XG boost—were trained and compared using spatial cross-validation across the study area. FR predictions were estimated in relation to the influencing soil type and terrain characteristics, and interpretable ML methods were used to show how input feature permutations may relate to the soil fertility predictions. The results show the explanatory variables are similar across the selected ML models, with the strongest influencing variables being water leaching index, site aspect, and the silt and sand soil texture properties. The extremely randomized tree models showed the overall best performance, with only a small variation in performance across the four ML models. The method was applied to Eucalyptus nitens plantations covering over 63,000 ha in north-west Tasmania, Australia. The results using the predicted FR spatial grid with 3-PG show a strong correlation with observed growth for tree diameter and stand volume (R2 tree diameter at breast height = 0.97, RMSE = 0.85 m; R2 stand volume = 0.96, RMSE = 23.1 m3 ha−1) obtained from 161 permanent sample inventory plots ranging from 3 to 31 years old. This method has practical utility for other study sites to calibrate forest plantation soil fertility rating, in both the spatial and point-scale 3-PG model, where spatial data of soil characteristics are available. The derived soil fertility grid can provide valuable insights into the spatial variability of soil fertility in unknown areas.

Production, Concentration and Flux of Major and Trace Elements in Juniperus przewalskii Litter of the Qilian Mountains, China

Forest litter is an important guarantee for maintaining forest soil fertility and circulating material in forest ecosystems. The input of litter plays an important role in soil organic matter formation and biogeochemical cycles in forest ecosystems. However, the production and elements concentrations of Juniperus przewalskii (JP) litter in the Qilian Mountains are still unknown. In this study, we investigated the production of needle, branch and bark, cone, and impurity litters. We determined the concentrations and fluxes of major (K, Mg, Al, and Fe) and trace (Na, Mn, Zn, Cr, Ni, Cu, Pb, Co, Cd, and Ag) elements in needle litter of JP from September 2020 to August 2021. The results showed that the annual litter production was 4040.74 ± 495.96 kg ha−1 a−1. Needle and cone litters were the main components of the total litter production. The major elements (MEs) and trace elements (TEs) fluxes of litter were consistent with the litter production trend. The concentrations and fluxes of MEs and TEs in needle litter decreased in the order: K &gt; Mg &gt; Al &gt; Fe &gt; Na &gt; Mn &gt; Zn &gt; Cr &gt; Ni &gt; Cu &gt; Pb &gt; Co &gt; Cd &gt; Ag. These results have important implications for understanding the migration processes of MEs and TEs in forest ecosystems of the Qilian Mountains.

Mixed-Species Acacia Plantation Decreases Soil Organic Carbon and Total Nitrogen Concentrations but Favors Species Regeneration and Tree Growth over Monoculture: A Thirty-Three-Year Field Experiment in Southern China

Mixed-species plantations of trees with N-fixing species have the potential of promoting forest productivity and soil fertility. However, few studies in the literature have addressed the advantages of mixed-species plantations of leguminous trees over monocultures of leguminous trees based on in situ inventories over a long time period. Here, we monitored the dynamics of tree community composition, vegetation biomass, soil nutrients, and soil microbial phospholipid fatty acids (PLFAs), in an Acacia mangium monoculture plantation during 33 years of development and compared it with a mixed-species plantation of A. mangium associated with 56 native species which were underplanted 14 years after the initial establishment. Leaf N and phosphorus (P) concentrations of three main species in the overstory and understory of the A. mangium monoculture were measured. Our results showed that the soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP) concentrations significantly increased over time during the approximately thirty years of A. mangium monoculture plantation, while the disadvantages were associated with new species regeneration and the increment of vegetation biomass. In the A. mangium monoculture plantation, leaf N concentration of A. mangium,Rhodomyrtus tomentosa, and Dicranopteris dichotoma continuously increased from 21 to 31 years, while the leaf P concentration of A. mangium and R. tomentosa decreased. The mixed-species plantations of A. mangium with native tree species had lower SOC and soil TN concentrations, more new tree species recruitment in the understory, and faster vegetation biomass increment than the A. mangium monoculture. However, the PLFAs of soil microbial groups were slightly different between the two types of plantations. We conclude that improved soil N nutrient condition by A. mangium monoculture benefits N absorption by A. mangium, R. tomentosa, and D. tomentosa, while low soil AP limits P absorption by A. mangium and R. tomentosa. Meanwhile, transforming the A. mangium monoculture into a mixed-species plantation via the introduction of multiple native species into the A. mangium monoculture decreases SOC and TN concentrations but the advantages include improving forest regeneration and maintaining forest growth in a long-term sequence. These findings provide useful and practical suggestions for managing forest monocultures of A. mangium in subtropical regions.

Regulation of the fertility of gray forest soil in a long-term stationary experiment under different fertilization and liming systems

Aim. To study the influence of the application of periodic liming, its effect and aftereffect under different systems of fertilization and saturation with agricultural crops in a 7-field crop rotation on the state of potential and effective fertility of gray forest soil. Methods. Field experiment, laboratory, analytical, mathematical-statistical, calculation-comparative. Results. The scientific substantiation of agrotechnological measures for reproduction and regulation of the fertility of gray forest soil for long-term (30 years) agriculture is presented. The types and forms of manifestation, reproduction factors, potential regulation, and effective fertility were highlighted in the article. The analysis of changes in physicochemical and agrochemical properties under the influence of periodic liming and the use of various fertilizer systems for completed four rotations of a 7-field crop rotation was carried out. During rotations, I and II, the balance of calcium and magnesium in the soil were calculated for various organomineral fertilizers against the background of the use of limestone and dolomite flour. For rotations, I, II, III, and IV, the dynamics of humus content are reflected, and the optimal parameters of its reserves and ways to achieve a consistently high level with different mineral fertilizers are determined when using 10 t/ha of manure in rotations I and II, and in rotations III and IV for lack of dung from the use of green manure (up to 5 t/ha) and by-products (up to 5 t/ha) of crops of a 7-field crop rotation against the background of repeated liming. Based on thirty years of research, the main issues of conducting periodic chemical reclamation in combination with organic and mineral fertilizers are considered and the effectiveness of its action and aftereffect is proved, as well as the effectiveness of the use of a one-and-a-half dose of the ameliorant with prolonged intensive mineral load in agrocenoses is substantiated. The productivity of agrocenoses was given for the completed four rotations of a 7-field crop rotation on gray forest soil. A set of agrotechnological measures aimed at preventing the manifestation of degradation processes in arable gray forest soils and the full reproduction of their fertility elements in agrocenoses with various technologies for growing crops is substantiated.

Legume-bacteria-soil interaction networks linked to improved plant productivity and soil fertility in intercropping systems

Intercropping with legumes is an effective strategy to increase plant productivity, reduce nitrogen (N) inputs, and maintain soil fertility in an industrial monoculture forest. However, the facilitation/complementarity mechanism of the interactions between legumes (keystone species in intercropping), bacteria and soil are still unknown, and the contribution of this triple interaction to plant growth and ecosystem function is still difficult to predict. Taking the introduction of Dalbergia odorifera (D. odorifera), into eucalyptus plantations as an example, we evaluated the changes in nutrient uptake, phytohormone contents, N metabolism-related enzyme activities, and root-associated bacteria of D. odorifera under different N applications (0, 3, 6 and 12 g pot−1) and different planting patterns (monoculture and intercropping), and investigated the regulatory mechanism of these cascaded changes on productivity and soil fertility in response to intercropping. The results showed that intercropping increased the total biomass by 5.90–56.29% compared to monoculture; in particular, intercropping in combination with 6 g N pot−1 had superiority in promoting the gibberellin content, glutamine synthetase activity, nitrogenase activity, soil fertility, and bacterial diversity, as well as the relative abundance of bacteria with the potential to undergo aerobic chemoheterotrophy, N fixation and N respiration. The differentially expressed genes identified via transcriptome analysis were mainly involved in metabolic pathways, signal transduction, and the tricarboxylic acid cycle. To integrate the associations between plant traits, bacterial communities, and soil properties, we built a multivariable network based on multiple plant traits, soil properties, differentially accumulated genera, and differentially expressed genes in monoculture and intercropping. These results led to the identification of candidates related to intercropping advantages, including two genes (acidic endo chitinase, Na+/K+ transporter) and four bacterial genera (Bacteroides, Coxiella, Pseudomonas, SJA-15). More specifically, moderate fertilization of eucalyptus/D. odorifera intercropping systems create a more stable interaction network with additional module hubs. These results highlight the importance of bacterial diversity and the plant-bacteria-soil interaction network in maintaining soil fertility and plant productivity, which may help fertilization practices in eucalyptus plantations and provide guidance for the ecological sustainability of introducing D. odorifera into industrial forests.

Novel Weighting Method for Evaluating Forest Soil Fertility Index: A Structural Equation Model.

Understanding nutrient quantity and quality in forest soils is important for sustainable management of forest resources and maintaining forest ecosystem services. In this study, six soil nutrient indicators, including soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) were measured in five different aged stands of Chinese fir forests in subtropical China. A structural equation model (SEM) was developed based on these soil nutrients indicators in order to better evaluate the soil fertility index (SFI) in these studied forests. The results show that soil nutrient contents changed with the soil depth in different age groups. The SOM decreased in a specific order: over mature > mature > near mature > middle > young stands. The TN content of the soil gradually decreased with increased soil depth throughout all age groups. The SEM indicated that the TN had the highest weight of 0.4154, while the TP had the lowest weight at 0.1991 for estimating the SFI. The weights of other indicators (AN, SOM, AP, and AK) ranged 0.2138−0.3855 in our study. The established SEM satisfied the fitness reference values and was able to accurately describe the forest soil nutrient status through the SFI. The overall SFI values were significantly higher in over mature stands than in young-aged stands and in topsoil than in deeper soil in all examined forests. Soil TN, AP, and AK were the most important nutrient indicators to the evaluation of the SFI in the study sites. The results confirmed that the SEM was suitable to estimate the weights of the SFI and better describe the soil nutrient status in forests. Our research provides an innovative approach to assess a soil nutrient status and soil fertility and provides a scientific basis for accurate implementation of soil nutrient assessment in forest ecosystems.

The effectiveness of the use of organic fertilizers in the link of crop rotation on light gray forest soil of the south of the Volga-Vyatka region

Relevance. The issues of reproduction of fertility of light gray forest soils of the forest-steppe zone and utilization of poultry industry waste as organic fertilizers are interrelated and are very relevant. Methods. The experiments studied the effect of one-time application of various doses (15, 30, 50 t/ha) of chicken manure, chicken manure compost and local organic fertilizers (sapropel and peat) on crop yields, and the aftereffect of fertilizers on the main indicators of soil fertility — amount of humus, nitrate nitrogen, phosphorus and potassium. The variants of the experiments were investigated sixfold. The Federal State Center of Agrochemical Service "Chuvashsky" was involved in laboratory analyses of soils and crop production. Mеthods of analysis of soil samples and crop production are generally accepted in agrochemical science.Results. Organic fertilizers for three years of research were introduced into the soil only once at the beginning of the experiment in doses of 15, 30 and 50 t/ha, and their effect on the yield and quality of crop production (potato tubers, spring wheat grains and peas) in 2020–2022 was positive. The agrochemical properties of the arable soil layer in the variants with the use of organic fertilizers have significantly improved. The nitrate content in the products in variants with doses of chicken manure and compost of 50 t/ha or more approached the critical level. Local fertilizers (sapropel and peat) at a dose of 30 t/ha, chicken manure and compost at a dose of 15 t/ha are good organic fertilizers with a long aftereffect.