Mixed Tree Research Articles

Shelterbelt Structure and Crop Protection from Increased Typhoon Activity in Northeast China

Global warming has led to increases in the frequency and intensity of typhoons. In recent years, super typhoons have had a greater impact on agriculture in the black soil farmland of Northeast China, posing serious threats to crop growth. Planting trees as windbreaks and to reduce erosion is common in this region, but their protective effects against crop damage from typhoons is still unknown. This paper studied the protective effect of different shelterbelt structures on crops that encountered a super typhoon. The results show that the distance between shelterbelt rows and shelterbelt porosity have significant influences on the starting lodging distance of crops behind the shelterbelt. Increasing the shelterbelt distance between shelterbelt rows or reducing shelterbelt porosity can enhance their protective effects on crops. Among the main crops, rice has the strongest lodging resistance, followed by soybeans, with maize being the least resistant. The protective effect of mixed tree and shrub shelterbelts is better than that of single tree species shelterbelts. Dead or missing trees reduce the shelterbelt protective effect. These results provide strategies for reducing the impact of more intense and frequent super typhoons.

Data set of long-term experiments in Forest Experimental Station of the Timiryazev Agricultural Academy since 1862

In the forest experimental station of the Russian State Agrarian University - Moscow Timiryazev Agricultural Academy, since 1862, experiments have been carried out to study the methods of planting, the geographical origin of seeds, methods of thinning for forest growth. The measurements available in the dataset are important for forestry. They are the basis for the development of models of growth and productivity of forest stands in the European part of Russia, for the development of methods for mixing tree species and thinning schemes.

Primed progressives? Predicting aspectual choice in World Englishes

AbstractThis corpus-based study focuses on the progressive:non-progressive alternation from a novel perspective, i.e. the effect of syntactic priming. We annotated a dataset of 5,000 progressive and non-progressive occurrences in ten different varieties of English from theInternational Corpus of Englishfor variables such as Aktionsart categories and elements related to priming and subjected the data to a generalized linear mixed methods tree analysis. The results indicate that the progressive is most likely to occur in situations that are durative in nature and when they are preceded by another progressive; overall, we find some evidence of probabilistic indigenization with regard to the use of progressives in different varieties. However, while syntactic priming seems to play a role overall in the choice of the progressive over the non-progressive, we do not find evidence supporting the idea that priming may explain the use of non-standard stative progressives.

Soil Fungal Communities and Enzyme Activities along Local Tree Species Diversity Gradient in Subtropical Evergreen Forest

The majority of studies have found that an increase in tree species diversity can increase the productivity of forest stands thanks to complimentary effects with enhanced resource use efficiency or selection effects; however, it is unclear how tree species diversity affects the soil fungal community and enzyme activities in subtropical evergreen forests. In this study, we used soil high-throughput sequencing to investigate the soil fungal community structure and diversity in the central area of tree clusters in the gradient of tree species richness formed by four possible dominant tree species (Pinus massoniana Lamb., Choerospondias axillaris Roxb., Cyclobalanopsis glauca Thunb. and Lithocarpus glaber Thunb.) in subtropical evergreen broad-leaved forest. The results showed that soil organic carbon content and total nitrogen content were significantly higher in mixed tree clusters, and that soil fungal richness and diversity increased with the increase in tree species diversity (1–3 species). Soil acid phosphatase and urease activity were also enhanced with tree species diversity (p < 0.05). The relative abundance of soil symbiotic fungi (ectomycorrhizal fungi) decreased, while the relative abundance of saprotrophic fungi increased. Redundancy analysis (RDA) revealed that soil acid phosphatase activity was the main factor affecting soil fungal communities and functional guilds, and that soil water content was the main driving force behind fungal trophic modes. In subtropical forests, changes in tree species diversity have altered the soil fungal community structure and trophic modes and functions, accelerating the decomposition of organic matter, increasing nutrient cycling, and perhaps also changing the nutrient absorption of trees.

Distribution of Soil Extracellular Enzymatic, Microbial, and Biological Functions in the C and N-Cycle Pathways Along a Forest Altitudinal Gradient.

The diverse chemical, biological, and microbial properties of litter and organic matter (OM) in forest soil along an altitudinal gradient are potentially important for nutrient cycling. In the present study, we sought to evaluate soil chemical, biological, microbial, and enzymatic characteristics at four altitude levels (0, 500, 1,000, and 1,500 m) in northern Iran to characterize nutrient cycling in forest soils. The results showed that carbon (C) and nitrogen (N) turnover changed with altitude along with microbial properties and enzyme activity. At the lowest altitude with mixed forest and no beech trees, the higher content of N in litter and soil, higher pH and microbial biomass nitrogen (MBN), and the greater activities of aminopeptidases affected soil N cycling. At elevations above 1,000 m, where beech is the dominant tree species, the higher activities of cellobiohydrolase, arylsulfatase, β-xylosidase, β-galactosidase, endoglucanase, endoxylanase, and manganese peroxidase (MnP) coincided with higher basal respiration (BR), substrate-induced respiration (SIR), and microbial biomass carbon (MBC) and thus favored conditions for microbial entropy and C turnover. The low N content and high C/N ratio at 500-m altitude were associated with the lowest microbial and enzyme activities. Our results support the view that the plain forest with mixed trees (without beech) had higher litter quality and soil fertility, while forest dominated by beech trees had the potential to store higher C and can potentially better mitigate global warming.

Compost-Based Growing Media Improved Yield of Leafy Lettuce in Pot Culture

Compost-based media were examined for effects on plant growth of leafy lettuce (Lactuca sativa L.) in pot culture. Four types of locally sourced composts were created using different proportions of wood chips from untreated pallets and mixed tropical tree debris, food waste from restaurants, and chicken manure. Compost-based media were prepared by mixing each compost with a commercial peatmoss to create 25, 50, and 100% compost-peatmoss mixtures (by volume). In Trial One, cv. Starfighter had the greatest shoot (leaves/stems) biomass when grown in 100% compost containing wood chips, food waste, and chicken manure. In Trial Two, cvs. Starfighter and New Red Fire were examined. Growing media affected all plant growth parameters including fresh and dry shoots and roots, shoot and root length, and number of leaves. Cultivar affected all except fresh root weight. Interaction effects of growing medium and cultivar type were found for fresh shoot weight, dry root weight, shoot, and root length. Regression analyses indicated increases in amount of compost in growing media increased dry shoot and root weights. Composts containing recyclable organic materials can be an alternative to commercial media in pot culture.

Transformative or Tokenistic?

Transformative or Tokenistic?

Integrative Survey of 68 Non-overlapping Upstate New York Watersheds Reveals Stream Features Associated With Aquatic Fecal Contamination

Aquatic fecal contamination poses human health risks by introducing pathogens in water that may be used for recreation, consumption, or agriculture. Identifying fecal contaminant sources, as well as the factors that affect their transport, storage, and decay, is essential for protecting human health. However, identifying these factors is often difficult when using fecal indicator bacteria (FIB) because FIB levels in surface water are often the product of multiple contaminant sources. In contrast, microbial source-tracking (MST) techniques allow not only the identification of predominant contaminant sources but also the quantification of factors affecting the transport, storage, and decay of fecal contaminants from specific hosts. We visited 68 streams in the Finger Lakes region of Upstate New York, United States, between April and October 2018 and collected water quality data (i.e., Escherichia coli, MST markers, and physical–chemical parameters) and weather and land-use data, as well as data on other stream features (e.g., stream bed composition), to identify factors that were associated with fecal contamination at a regional scale. We then applied both generalized linear mixed models and conditional inference trees to identify factors and combinations of factors that were significantly associated with human and ruminant fecal contamination. We found that human contaminants were more likely to be identified when the developed area within the 60 m stream buffer exceeded 3.4%, the total developed area in the watershed exceeded 41%, or if stormwater outfalls were present immediately upstream of the sampling site. When these features were not present, human MST markers were more likely to be found when rainfall during the preceding day exceeded 1.5 cm. The presence of upstream campgrounds was also significantly associated with human MST marker detection. In addition to rainfall and water quality parameters associated with rainfall (e.g., turbidity), the minimum distance to upstream cattle operations, the proportion of the 60 m buffer used for cropland, and the presence of submerged aquatic vegetation at the sampling site were all associated based on univariable regression with elevated levels of ruminant markers. The identification of specific features associated with host-specific fecal contaminants may support the development of broader recommendations or policies aimed at reducing levels of aquatic fecal contamination.

Periodicity of quantum walks defined by mixed paths and mixed cycles

In this paper, we determine periodicity of quantum walks defined by mixed paths and mixed cycles. By the spectral mapping theorem of quantum walks, consideration of periodicity is reduced to eigenvalue analysis of η-Hermitian adjacency matrices. First, we investigate coefficients of the characteristic polynomials of η-Hermitian adjacency matrices. We show that the characteristic polynomials of mixed trees and their underlying graphs are same. We also define n+1 types of mixed cycles and show that every mixed cycle is switching equivalent to one of them. We use these results to discuss periodicity. We show that the mixed paths are periodic for any η. In addition, we provide a necessary and sufficient condition for a mixed cycle to be periodic and determine their periods.

Effects of tree species interaction, stand density, and tree size on the productivity of Larix principis-rupprechtii

Pure and mixed larch (Larix pricipis-rupprechtii) and birch (Betula platyphylla) plantations in Saihanba area were selected as test objects, with two stand density (200-340 and 880-1100 trees·hm-2) of each stand type. Based on tree size-stratified sampling approach, a total of 668 tree core samples were collected. A linear mixed model was used to analyze the effects of tree species interaction, stand density, and tree size on larch productivity. Results showed that basal area increment of larch was affected by competition, diameter at breast height, tree age, and neighborhood density to different degrees. Overyielding of larch was mainly due to the positive effect of birch on larch growth in the mixed plantation with higher stand density. For mixed plantation with lower stand density, the productivity of those two species was lower than that pure plantation because of a lack of species interaction. Intraspecific competition was the main factor influencing larch productivity. Larch productivity was positively affected by tree size, with the magnitude of tree size effect varying with stand density and species composition. Suitable enhancement of stand density and selection of birch as the mixing tree species could improve productivity of larch.

Tree species mixing affects soil microbial functioning indirectly via root and litter traits and soil parameters in European forests

Abstract Plant community composition influences soil microbial communities through plant trait variations that lead to changes in nutrient and organic carbon inputs into the soil by root exudates and plant litter. Although plant litter and living roots are known to influence microbial functioning independently, their relative effects are rarely measured simultaneously in naturally occurring plant communities. Here, we sought to evaluate how forest floor litter and absorptive roots affect broad functions of soil microbial communities, and how this may be influenced by tree species mixing. To do so, forest floor litter, absorptive roots and soil were sampled from mono‐specific and three‐species mixed stands in four mature, natural forest ecosystems across Europe. The direct effects of tree species mixing, its indirect effects via litter and root traits, and the effects of soil parameters on microbial biomass, catabolic activity and diversity, and denitrification were analysed. Results did not show direct tree mixture effects on the soil microbial parameters we measured but did suggest indirect influences via tree mixture effects on traits of above‐ground litter and absorptive roots and soil parameters. Mixed forests composed of any three tree species modified soil microbial functioning by influencing nutrient availability in forest floor litter and root resource acquisition. Tree mixing also modified soil microbial functioning and catabolic diversity by influencing soil fertility and physicochemical properties. Our findings suggest an indirect but present influence of tree species mixing on the activity of heterotrophic soil microbial communities across four different forest ecosystems ranging from Mediterranean to boreal forests. Our study contributes to a better mechanistic understanding of mixed tree species effects on soil microbial functioning via the modification of forest floor litter properties and traits of absorptive roots represented by the tree community beyond simple species number consideration, and potentially via soil properties. A free Plain Language Summary can be found within the Supporting Information of this article.

EFFECTS OF HOT PRESSING PARAMETERS ON THE PROPERTIES OF HARDBOARDS PRODUCED FROM MIXED HARDWOOD TREE SPECIES

In this work, wet-process fibreboards (hardboards) were produced in the laboratory using industrial wood fibres of the species European beech (Fagus sylvatica L.) and Turkey oak (Quercus cerris L.) at the total volume of 40%, and white poplar (Populus alba L.) at 60% volume. The effects of hot pressing pressure (varied from 3.3 MPa to 5.3 MPa) and pressing time (from 255 s to 355 s) on the physical and mechanical properties of hardboards were investigated and optimal values of the parameters for fulfilling the European standard requirements were determined. It was concluded that hardboards with acceptable physical and mechanical properties may be produced from 60% poplar wood waste and residues, combined with 40% hardwood raw materials (beech and oak) by regulating the hot pressing regime only, i.e. pressure and pressing time. The following minimum parameters for producing hardboards from mixed hardwood tree species were determined: a pressure of 4.6 MPa and a pressing time of 280 s.

Modeling gas exchange and biomass production in West African Sahelian and Sudanian ecological zones

Abstract. West African Sahelian and Sudanian ecosystems provide essential services to people and also play a significant role within the global carbon cycle. However, climate and land use are dynamically changing, and uncertainty remains with respect to how these changes will affect the potential of these regions to provide food and fodder resources or how they will affect the biosphere–atmosphere exchange of CO2. In this study, we investigate the capacity of a process-based biogeochemical model, LandscapeDNDC, to simulate net ecosystem exchange (NEE) and aboveground biomass of typical managed and natural Sahelian and Sudanian savanna ecosystems. In order to improve the simulation of phenology, we introduced soil-water availability as a common driver of foliage development and productivity for all of these systems. The new approach was tested by using a sample of sites (calibration sites) that provided NEE from flux tower observations as well as leaf area index data from satellite images (MODIS, MODerate resolution Imaging Spectroradiometer). For assessing the simulation accuracy, we applied the calibrated model to 42 additional sites (validation sites) across West Africa for which measured aboveground biomass data were available. The model showed good performance regarding biomass of crops, grass, or trees, yielding correlation coefficients of 0.82, 0.94, and 0.77 and root-mean-square errors of 0.15, 0.22, and 0.12 kg m−2, respectively. The simulations indicate aboveground carbon stocks of up to 0.17, 0.33, and 0.54 kg C ha−1 m−2 for agricultural, savanna grasslands, and savanna mixed tree–grassland sites, respectively. Carbon stocks and exchange rates were particularly correlated with the abundance of trees, and grass biomass and crop yields were higher under more humid climatic conditions. Our study shows the capability of LandscapeDNDC to accurately simulate carbon balances in natural and agricultural ecosystems in semiarid West Africa under a wide range of conditions; thus, the model could be used to assess the impact of land-use and climate change on the regional biomass productivity.

Mixing tree species at different spatial scales: The effect of alpha, beta and gamma diversity on disturbance impacts under climate change

Abstract Single species forest systems often suffer from low resistance and resilience to perturbations. Consequently, fostering tree species diversity is discussed as an important management approach to address the impacts of changing climate and disturbance regimes. Yet, the effect of the spatial grain of tree species mixtures remains unknown. We asked whether increasing tree species diversity between stands (beta diversity) has the same effect as increasing tree species diversity within stands (alpha diversity) at similar overall levels of richness (gamma diversity). We conducted a multi‐model simulation experiment under climate change, applying two forest landscape models (iLand and LandClim) across two contrasting landscapes of Central Europe. We analysed the effect of different levels and configurations of diversity on the disturbance impact and the temporal stability of biomass stocks and forest structure. In general, increasing levels of diversity decreased disturbance impacts. Positive diversity effects increased with increasing severity of climate change. Beta diversity buffered disturbance impacts on landscape‐level biomass stocks more strongly than alpha diversity. The effects of the spatial configuration on forest structure were more variable. Diversity effects on temporal stability were less pronounced compared to disturbance impacts, and mixture within and between stands had comparable effects on temporal stability. Diversity effects were context‐dependent, with patterns varying between landscapes and indicators. Furthermore, we found a strong species identity effect, with increasing diversity being particularly beneficial in conifer‐dominated systems of the European Alps. The two models agreed on the effects of different levels and configurations of tree species diversity, underlining the robustness of our findings. Synthesis and application. Enhancing tree species diversity can buffer forest ecosystems against increasing levels of perturbation. Mixing tree species between stands is at least as effective as mixing tree species within stands. Given the managerial advantages of between‐stand mixtures (e.g. reduced need to control competition to maintain diversity, higher timber quality, lower logistic effort), we conclude that forest management should consider enhancing diversity at multiple spatial scales. ​

Effects of mixing tree species and water availability on soil organic carbon stocks are depth dependent in a temperate podzol

AbstractMixing tree species is a forest management strategy put forward to increase and stabilize primary productivity. Yet, little is known about soil organic carbon (SOC) storage in mixed species forests, particularly under water shortage. In this study, we used a tree diversity experiment in southwestern France to assess the interactive effects of water availability (via irrigation) and mixing tree species (monocultures of pine (Pinus pinaster) and birch (Betula pendula) versus mixed plots of pine‐birch and pine‐birch‐oak (Quercus robur)) on SOC stocks in the forest floor and across five mineral soil layers (0–5, 5–15, 15–30, 30–60 and 60–90 cm deep). We found that SOC stocks were negatively affected by irrigation in the forest floor due to an increase in decomposition rates. However, SOC stocks were positively influenced by both the mixing of tree species and irrigation in the mineral soil, particularly at the 15–30‐cm soil depth. This is because root niche partitioning in mixed plots and an increase in tree biomass in irrigated plots may have resulted in greater organic matter inputs through rhizodeposition and the incorporation of microbially‐derived compounds. These preliminary results indicate that SOC dynamics and its response to biotic and abiotic factors are strongly dependent on soil depth. Our data further highlight that the positive effect of mixing trees on SOC stocks was higher in irrigated plots, thereby contradicting the idea that tree mixture effects are expected to be greater when environmental conditions are harsher. We conclude that mixing tree species can increase SOC stocks in the short term in temperate forests, even if the exact mechanisms remain to be identified.Highlights Effects of mixing trees and increasing water availability on SOC are depth dependent. Increase in SOC stocks occurred mainly at the mid‐soil depth (15–30 cm). Effects of tree mixture on SOC were greater when soil water availability was high.

Including Mixed Tree Nut Snacks in a Weight Loss and Weight Maintenance Intervention Resulted in Weight Loss and Increased Satiety

Abstract Objectives Tree nuts are an excellent dietary source of protein and healthy fat leading to increased satiety. Tree nuts also provide polyphenols, vitamins and minerals supporting the immune response. However, there is a concern that tree nuts are not suitable to be included in a weight loss diet due to their fat content. Therefore, it was the objective of the study to test whether including mixed tree nuts in a weight loss and maintenance program will lead to weight loss by increasing satiety and decreasing inflammation. Methods We performed a randomized, controlled, two-arm study in 95 overweight individuals consuming 1.5 oz of mixed tree nuts daily (n = 56) or equal amount of calories in the form of a pretzel snack (n = 39) as part of a hypocaloric weight loss diet (−500 calories of resting metabolic rate) for 12 wks followed by an isocaloric weight maintenance program for an additional 12 wks. Results The dropout rate was significantly lower in the tree nut (16.4%) compared to the pretzel (35.9%) group. Participants experienced significant weight loss (12 wks: −1.6 and −1.9 and 24 wks: −1.5 kg and −1.4 kg) in the tree nut and pretzel group, respectively, without difference between groups at any time point. In addition, both groups showed a significant decrease in diastolic blood pressure at 12 wks and a significant increase in satiety at 24 wks, but only participants in the mixed tree nut group showed significant decrease in heart rate at 4, 12 and 24 wks. Plasma oleic acid concentration was significantly increased at 12 and 24 wks in the tree nut group, while in the pretzel group plasma oleic acid was significantly increased and stearic acid decreased at 12 wks and linolenic acid was increased at 24 wks. No change in fasting plasma triglyceride, total cholesterol and HDL-cholesterol was observed in both groups. No change in inflammatory markers except plasma MCP-1 was decreased significantly in the tree nut group at 4 wks. Conclusions In summary, including mixed tree nuts in a weight loss and maintenance diet can maintain compliance and promote weight loss similar to standard weight loss and maintenance diets. Although both, the mixed tree nut diet and pretzel diet resulted in decreased diastolic blood pressure, only consumption of the mixed tree nut diet led to significantly decreased heart rate and increased study retention. Funding Sources International Tree Nut Council.

Analysis of critical factors affecting the final decision-making for online grocery shopping

This study focuses on the importance of factors that both strongly impact logistics requirements and influence the final consumer decision for online grocery shopping. A stated preference survey was performed in Belo Horizonte, Brazil, using the following attributes: lead time, order fill rate and delivery-service price. Age and gender of interviewees were also considered in this decision-making process. The sample was composed of 222 interviewees. Mixed Logit models and Decision Trees were used to analyze the data and their interactions. Order Fill Rate was found to be the most important attribute. Failure to satisfactorily fulfill the order at the moment of shopping can significantly compromise e-groceries. Some interactions among the variables, such as between order fill rate and delivery-service price, have also led to interesting conclusions that should be taken into account by the grocer when planning special offers. Short lead times do not seem to be a very important priority for regular e-grocery purchasing. This research approach combines two statistical methods to better understand consumer behavior concerning e-grocery, in addition to providing insights for grocery retailers on the importance of some attributes for the effectiveness of e-grocery and their consequences on business logistics, which are particularly challenging during pandemics.

Mixed Tree Nut Snacks Compared to Refined Carbohydrate Snacks Resulted in Weight Loss and Increased Satiety during Both Weight Loss and Weight Maintenance: A 24-Week Randomized Controlled Trial.

Mixed tree nuts (MTNs) are an excellent source of protein and healthy fat contributing to satiety. However, their relatively high caloric content might not be beneficial in a weight loss diet. The present study was designed to test whether including MTNs in a weight loss and maintenance program interferes with weight management compared to a refined carbohydrate pretzel snack (PS). We performed a randomized, controlled, two-arm study in 95 overweight individuals consuming 1.5 oz of MTNs or PS daily as part of a hypocaloric weight loss diet (−500 kcal) over 12 weeks followed by an isocaloric weight maintenance program for 12 weeks. Participants in both groups experienced significant weight loss (12 weeks: −1.6 and −1.9 and 24 weeks: −1.5 and −1.4 kg) compared to baseline in the MTN and PS groups, respectively. However, there was no difference in weight loss and other outcome parameters between the MTN and PS groups. The MTN group showed a significant increase in satiety at 24 weeks. Both groups had a decrease in diastolic blood pressure at 12 weeks. Participants in the MTN group showed significant decreases in heart rate at 4, 12, and 24 weeks. Plasma oleic acid was significantly increased at 12 and 24 weeks in the MTN group but only at 12 weeks in the PS group. Plasma MCP-1 was decreased significantly in the MTN group at 4 weeks. In summary, participants in both groups lost weight, but only the MTN intervention increased satiety at 24 weeks, enhanced retention, decreased heart rate, and increased serum oleic acid at 24 weeks.

Impacts of Composition and Canopy Characteristics of Plant Communities on Microclimate and Airborne Particles in Beijing, China

As the basic component of urban green-spaces, plant communities regulate both the microclimate and air particle levels. Understanding the regulatory mechanism of plant communities represents the theoretical basis for using green spaces to improve the urban climate and mitigate air particle pollution. Based on field investigations, differences in the daily air temperatures (AT), relative humidity (RH), and PM10 and PM2.5 concentrations in eight compositional types of plant communities were quantitatively analyzed. In addition, the correlations between these variables and various canopy parameters were further established in order to detect critical thresholds. The results showed that, among the eight compositional types, significant differences existed in daily AT, RH, PM10 and PM2.5 levels. The mixed tree, shrub and grass (M-TSG) community had the strongest cooling and PM10 reduction effects; the broad-leafed tree, shrub and grass (B-TSG) community had the best humidifying effect; while the mixed tree and grass (M-TG) community most effectively reduced PM2.5 concentrations. The daily AT and PM10 concentrations were significantly negatively correlated with canopy density (CD) and leaf area index (LAI), but positively correlated with canopy porosity (CP) and sky view factor (SVF), while these correlations were opposite for daily RH. The response of daily PM2.5 concentrations to canopy characteristics was complex, featuring multiple non-linear relations. Critical thresholds were found in some cases. Overall, M-TSG or M-TG communities with about 75% CD, 55% CP, 2.5 LAI and 0.18 SVF perform most noticeable both microclimate and air particle regulation services.

Modelling Individual Tree Diameter Growth of Quercus mongolica Secondary Forest in the Northeast of China

Quercus mongolica secondary forest is widely distributed in the northeast of China, but it usually has low productivity, unstable structure, poor health, and low biodiversity. Diameter is a tree variable that is commonly used for forest growth measurement, to provide the basis for forest management decision. Two level generalized linear mixed effects individual tree diameter growth model were developed using data from two times surveys of 12 Q. mongolica secondary forest permanent plots that were distributed among Wangqing forest farms. Random effects of 14 tree species and 12 plots were introduced into the basic model consisting of three factors: tree size, competition of surrounding trees, and site quality. The results showed that initial diameter at breast height(DBH) was the most important variable affecting diameter growth, followed by competition, while the effect of site quality on diameter growth was not significant. Compared with the basic model, the prediction accuracy of the mixed effect model was improved by 17.69 %, where R2 reached to 0.6805, indicating that it is suitable for the individual-tree diameter growth prediction of the secondary forest of Q. mongolica.