A Geographic Information Systems approach for classifying and mapping forest management category in Baihe Forestry Bureau, Northeast China

This paper demonstrates a Geographic Information Systems （GIS） procedure of classifying and mapping forest management category in Baihe Forestry Burea, Jilin Province, China. Within the study area, Baihe Forestry Bureau land was classified into a two-hierarchy system. The top-level class included the non-forest and forest. Over 96% of land area is forest in the study area, which was further divided into key ecological service forest （KES）, general ecological service forest （GES）, and commodity forest （COM）. COM covered 45.0% of the total land area and was the major forest management type in Baihe Forest Bureau. KES and GES accounted for 21.2% and 29.9% of the total land area, respectively. The forest management zones designed with GIS in this study were then compared with the forest management zones established using the hand draw by the local agency. There were obvious differences between the two products. It suggested that the differences had some to do with the data sources, basic unit and mapping procedures. It also suggested that the GIS method was a useful tool in integrating forest inventory data and other data for classifying and mapping forest zones to meet the needs of the classified forest management system.

Spatiotemporal dynamics of vegetation response to permafrost degradation in Northeast China

Permafrost in Northeast China is undergoing extensive and rapid degradation,and it is of great importance to understand the dynamics of vegetation response to permafrost degradation during different periods in this region.Based on the meteorological station data and MODIS land surface temperature data,we mapped the distribution of permafrost using the surface frost number(SFN)model to analyze the permafrost degradation processes in Northeast China from 1981 to 2020.We investigated the spatiotemporal variation characteristics of vegetation and its response to permafrost degradation during different periods from 1982 to 2020 using the normalized difference vegetation index(NDVI).We further discussed the dominant factors influencing the vegetation dynamics in the permafrost degradation processes.Results indicated that the permafrost area in Northeast China decreased significantly by 1.01×10^(5) km^(2) in the past 40 a.The permafrost stability continued to weaken,with large areas of stable permafrost(SP)converted to semi-stable permafrost(SSP)and unstable permafrost(UP)after 2000.From 1982 to 2020,NDVI exhibited a significant decreasing trend in the seasonal frost(SF)region,while it exhibited an increasing trend in the permafrost region.NDVI in the UP and SSP regions changed from a significant increasing trend before 2000 to a nonsignificant decreasing trend after 2000.In 78.63%of the permafrost region,there was a negative correlation between the SFN and NDVI from 1982 to 2020.In the SP and SSP regions,the correlation between the SFN and NDVI was predominantly negative,while in the UP region,it was predominantly positive.Temperature was the dominant factor influencing the NDVI variations in the permafrost region from 1982 to 2020,and the impact of precipitation on NDVI variations increased after 2000.The findings elucidate the complex dynamics of vegetation in the permafrost region of Northeast China and provide deeper insights into the response mechanisms of vegetation in cold regions to permafrost degradation induced by climate change.

Long-term changes in radial growth of seven tree species in the mixed broadleaf-Korean pine forest in Northeast China:Are deciduous trees favored by climate change?

The role of the temperate mixed broadleaf-Korean pine forest(BKF)in global biogeochemical cycles will depend on how the tree species community responds to climate;however,species-specific responses and vulner-abilities of common trees in BKF to extreme climates are poorly understood.Here we used dendrochronological meth-ods to assess radial growth of seven main tree species(Pinus koraiensis,Picea jezoensis,Abies nephrolepis,Fraxinus mandshurica,Phellodendron amurense,Quercus mongolica,and Ulmus davidiana)in an old-growth BKF in response to climate changes in the Xiaoxing’an Mountains and to improve predictions of changes in the tree species compo-sition.Temperature in most months and winter precipita-tion significantly negatively affected growth of P.jezoensis and A.nephrolepis,but positively impacted growth of P.koraiensis and the broadleaf species,especially F.mandshu-rica and U.davidiana.Precipitation and relative humidity in June significantly positively impacted the growth of most tree species.The positive effect of the temperature during the previous non-growing season(PNG)on growth of F.mandshurica and Q.mongolica strengthened significantly with rapid warming around 1981,while the impact of PNG temperature on the growth of P.jezoensis and A.nephrolepis changed from significantly negative to weakly negative or positive at this time.The negative response of radial growth of P.jezoensis and A.nephrolepis to precipitation during the growing season gradually weakened,and the negative response to PNG precipitation was enhanced.Among the studied species,P.koraiensis was the most resistant to drought,and U.davidiana recovered the best after extreme drought.Ulmus davidiana,P.jezoensis and A.nephrolepis were more resistant to extreme cold than the other species.Climate warming generally exacerbated the opposite growth patterns of conifer(decline)and broadleaf(increase)spe-cies.Deciduous broadleaf tree species in the old-growth BKF probably will gradually become dominant as warming continues.Species-specific growth-climate relationships should be considered in future models of biogeochemical cycles and in forestry management practices.

Temporal changes in mixing effects on litter decay and nitrogen release in a boreal riparian forest in northeastern China

In riparian forests,litter decay provides essential energy and nutrients for both terrestrial and fluvial ecosystems.Litter mixing effects(LMEs)are crucial in regulating litter decay and nutrient dynamics,yet how LMEs change over time is unclear in riparian forests.In this study,leaf litter of three common species(Alnus sibirica Fisch.ex Turcz,Betula platyphylla Sukaczev,and Betula fruticosa Pall.)were mixed in an equal mass ratio and LMEs were measured for mass and nitrogen(N)remaining in whole litter mixtures over a 3-year period in a boreal riparian forest,northeastern China.LMEs were also assessed for component litter mass and N remaining by separating litter mixtures by species.During the decay of litter mixtures,antagonistic effects on mass and N remaining were dominant after one and two years of decay,whereas only additive effects were observed after three years.LMEs correlated negatively with functional diversity after the first and two years of decay but disappeared after three years.When sorting litter mixtures by species,non-additive LMEs on mass and N remaining decreased over incubation time.Moreover,non-additive LMEs were more frequent for litter of both B.platyphylla and B.fruticosa with lower N concentration than for A.sibirica litter with higher N concentration.These results indicate that incubation time is a key determinant of litter mixing effects during decay and highlight that late-stage litter mixture decay may be predicted from single litter decay dynamics in boreal riparian forests.

Segmented taper equations with crown ratio and stand density for Dahurian Larch (Larix gmelinii) in Northeastern China

Segmented taper equation was selected to model stem profile of Dahurian larch （Larix gmelinii Rupr.）. The data were based on stem analysis of 74 trees from Dailing Forest Bureau in Heilongjiang Province, Northeastern China. Two taper equations with crown ratio and stand basal area were derived from the Max and Burkhart’s （1976） taper equation. Three taper equations were evaluated： （1） the original equation, （2） the original equation with crown ratio, and （3） the original equation with basal area. SAS NLIN and SYSNLIN procedures were used to fit taper equations. Fit statistics and cross-validation were used to evaluate the accuracy and precision of these models. Parameter estimates showed that the original equation with inclusion of crown ratio and basal area variables provided significantly different parameter estimates with lower standard errors. Overall fit statistics indicated that the root mean square error （RMSE） for diameter outside and inside bark decreased respectively by 10% and 7% in the original model with crown ratio and by 12% and 7.2% in the original model with basal area. Cross-validation further confirmed that the original equation with inclusion of crown ratio and basal area variables provided more accurate predictions at the lower section （relative heights, 10%） and upper section （relative heights, 50%） for both outside and inside bark diameters.

Phytoplankton community structure in reservoirs of different trophic status, Northeast China

The aim of this study was to determine the phytoplankton community structures of reservoirs of different trophic status, located in a cold region. Physical and chemical variables and the phytoplankton communities were investigated in two reservoirs (Xiquanyan Reservoir and Taoshan Reservoir) in Northeast China in 2009. The two reservoirs showed strong seasonal fluctuations in their physical and chemical composition. Results of the trophic status index indicated that Xiaquanyan Reservoir was mesotrophic, whilst Taoshan Reservoir was eutrophic. Diatoms were the dominant phytoplankton group in Xiquanyan Reservoir throughout all seasons of the study, while in Taoshan Reservoir, diatoms dominated in spring, and cyanobacteria dominated in summer and autumn. This difference was resulted from differences in local environmental factors, including nutrients and hydrology. This study suggests that in mesotrophic reservoirs, nutrients played a key role in controlling seasonal phytoplankton successions, whereas in eutrophic reservoirs water temperature was the key factor in a cold region. Notably, the dominant species in summer in the Taoshan Reservoir was Microcystis, which may produce toxins depending on the ambient conditions, and presenting a risk of local toxin contamination.

Nest-site selection pattern of Grus japonensis in Zhalong Nature Reserve of northeast China

Nest-site selection patterns of Red-crowned cranes（Grus japonensis） and the effects of environmental variables were studied during the years of 2002-2008 in Zhalong Nature Reserve,Qiqihar city,northeast China.The nest-site selection pattern of Red-crowned cranes included two orders and three choices：the choice of nest-site habitat type within the macro-habitat order,nest zone selection and nest-site micro-habitat selection within the micro-habitat order.Various habitats（such as Carex swamps and reed fire districts） can be selected as the nest sites for Red-crowned cranes,of which reed swamps（93.15%） are given a preference.Factor Analysis reveals that the micro-habitat selection are affected by four main factors：fire,security（concealment /disturbance）,incubation（conditions,nest-material）,and food.Further analysis reveals that Red-crowned cranes have certain adaptability to the changes of nesting habitat quality in the Zhalong wetlands.In conclusion,fire,reeds,and water were the most important variables for nest-site habitat selection of Red-crowned Cranes in Zhalong Nature Reserve.

Optimal management of Korean pine plantations in multifunctional forestry

Korean pine is one of the most important plantation species in northeast China. Besides timber, it produces edible nuts and plantations sequester carbon dioxide from the atmosphere. This study optimized the management of Korean pine plantations for timber production, seed production, carbon sequestration and for the joint production of multiple benefits. As the first step, models were developed for stand dynamics and seed production. These models were used in a simulation-optimization system to find optimal timing and type of thinning treatments and optimal rotation lengths. It was found that three thinnings during the rotation period were optimal. When the amount or profitability of timber production is maximized, suitable rotation lengths are 65-70 years and wood production is 5.5-6.0 m(3) ha(-1) a(-1). The optimal thinning regime is thinning from above. In seed production, optimal rotation lengths are over 100 years. When carbon sequestration in living biomass is maximized, stands should not be clear-cut until trees start to die due to senescence. In the joint production of multiple benefits, the optimal rotation length is 86 years if all benefits (wood, economic profits, seed, carbon sequestration) are equally important. In this management schedule, mean annual wood production is 5.5 m(2) ha(-1) and mean annual seed yield 141 kg ha(-1). It was concluded that it is better to produce timber and seeds in the same stands rather than assign stands to either timber production or seed production.

Nonlinear mixed-effects height to crown base and crown length dynamic models using the branch mortality technique for a Korean larch( Larix olgensis ) plantations in northeast China

Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and shape.The majority of crown models are static models based on tree size and stand characteristics from temporary sample plots,but crown dynamic models has seldom been constructed.Therefore,this study aimed to develop height to crown base(HCB)and crown length(CL)dynamic models using the branch mortality technique for a Korean larch plantation.The nonlinear mixed-eff ects model with random eff ects,variance functions and correlation structures,was used to build HCB and CL dynamic models.The data were obtained from 95 sample trees of 19 plots in Meng JiaGang forest farm in Northeast China.The results showed that HCB progressively increases as tree age,tree height growth(HT growth)and diameter at breast height growth(DBH growth).The CL was increased with tree age in 20 years ago,and subsequently stabilized.HT growth,DBH growth stand basal area(BAS)and crown competition factor(CCF)signifi cantly infl uenced HCB and CL.The HCB was positively correlated with BAS,HT growth and DBH growth,but negatively correlated with CCF.The CL was positively correlated with BAS and CCF,but negatively correlated with DBH growth.Model fi tting and validation confi rmed that the mixed-eff ects model considering the stand and tree level random eff ects was accurate and reliable for predicting the HCB and CL dynamics.However,the models involving adding variance functions and time series correlation structure could not completely remove heterogeneity and autocorrelation,and the fi tting precision of the models was reduced.Therefore,from the point of view of application,we should take care to avoid setting up over-complex models.The HCB and CL dynamic models in our study may also be incorporated into stand growth and yield model systems in China.

Genetic variation and selection of introduced provenances of Siberian Pine(Pinus sibirica) in frigid regions of the Greater Xing'an Range,Northeast China

Siberian Pine （Pinus sibirica） is an ecologically and eco-nomically important species in pristine forests throughout northern Rus-sia. Four provenances of P. sibirica were introduced from Mongolia and Russia to the Greater Xing’an Range （the Daxing’anling）, northeast China in 1993. The aim of this research was to study genetic variation and selection of the introduced four Pinus sibirica provenances. Heights （H）, basal diameters （BD）, survival rates （SR） and crown lengths （CL） of different families were measured as primary outcomes in different growth years. Results of data analyses demonstrated high coefficients of phenotypic variation （PCV） and heritability （H2） for H, BD and CL at 18 years after introduction. PCV and H2 increased with age. Correlations of＆amp;nbsp;growth traits between any two growth years were all significantly positive, but the correlation coefficient was smaller when the growth year interval was larger. Correlations between H and the original environment factors decreased gradually, indicating that with long-term subsistence in the new environment, the influence of the source environment declined. Colligation of multiple traits to estimate provenances showed that Novosibirsk, Tomsk, and Altai Mountains had higher survival rates and biomass, and proved more suitable for introduction and plantation in the Greater Xing’an Range in China.

Variations in fine root dynamics and turnover rates in five forest types in northeastern China

Quantifying fi ne root(≤ 2.0 mm in diameter) distribution and turnover is essential for accurately estimating forest carbon budgets. However, fi ne root dynamics are poorly understood, possibly because of their inaccessibility. This study quantifi es fi ne root distribution and turnover rates for fi ve representative Chinese temperate forests types. Fine root number, diameter, biomass, necromass, production, mortality, and turnover rates were measured using a minirhizotron over a 12-month period. More than 90% of the fi ne roots were < 0.5 mm in diameter, with thin fi ne roots at shallow layers, and thicker ones in deeper soil layers. The fi ne root dynamics were signifi cantly diff erent among the forest types. Coniferous plantations had fewer fi ne roots, less biomass, necromass, production and mortality but greater average diameters than fi ne roots of broadleaved forests. All traits, except for diameter, decreased along the soil profi le. Fine root numbers and production exhibited a unimodal seasonal pattern with peaks occurring in summer, whereas biomass, necromass and mortality progressivelyincreased over the growing season. The turnover rates of roots < 0.5 mm varied from 0.4 to 1.0 a-1 for the fi ve forest types, 0.5–1.0 a-1 for the soil layers and 0.2–1.1 a-1 for the seasons, with the largest turnover rate at the 0–10 cm depth in summer. The patterns of fi ne root numbers, biomass, necromass, production, mortality, and turnover rates varied with forest types, soil depths, growing season and diameter classes. This study highlights the importance of forest types and diameters in quantifying fi ne root turnover rates.

Intra-and inter-species variations in carbon content of 14 major tree species in Northeast China

Reducing greenhouse gas emissions is one of the major challenges in combating global warming.Carbon,including in the form of carbon dioxide(CO_(2)),is considered an essential greenhouse gas under human control to demonstrate success in emission reductions.However,many carbon stock quantifications in forest ecosystems still rely on the estimated 50%carbon content instead of more precise species-,tissue-and site-specific values.Thus,this study aimed to thoroughly measure and analyze the carbon content and variability using the 14 major tree species in Northeast China.Over 600 trees were destructively sampled from three different major mountainous regions(i.e.,the Changbai,Daxing’an,and Xiaoxing’an mountains),and the carbon contents of each species were precisely measured to the sub-tissue level.Carbon contents varied significantly between species,with foliage carbon mostly found to be the highest,while root carbon contents were the lowest.Average carbon contents can be ranked as:Ulmus laciniata(43.4%)<Phellodendron amurense(43.5%)<Acer mono(43.8%)<Tilia amurensis(44.2%)<Populus davidiana(44.5%)<Fraxinus mandshurica(44.7%)<Juglans mandshurica(44.9%)<Quercus mongolica(45.3%)<Betulla davurica(45.8%)<Betulla platyphylla(46.7%)<Picea koreansis(46.9%)<Larix gmelinii(47.4%)<Pinus koreansis(48.3%)<Abies nephrolepis(48.3%).Carbon contents were higher in conifers(47.7%)compared to broadleaf species(44.9%).In addition,both tree tissues and growing sites also had a significant effect on carbon content.At the sub-tissue level,only stem’s sub-tissues(i.e.,bark,heartwood,and sapwood)carbon contents showed significant variations.The results suggest that bark should be separated from other stem sub-tissues and considered separately when determining carbon stocks.This research contributes to improving estimates of terrestrial carbon quantifications,and in particular,the values obtained can be used in China’s National Forest Inventory.

Ecosystem carbon storage and sink/source of temperate forested wetlands in Xiaoxing’anling, northeast China

Wetlands play an important role in the global carbon cycle, but there are still considerable uncertainties in the estimation of wetland carbon storage and a dispute on whether wetlands are carbon sources or carbon sinks. Xiaoxing’anling are one of several concentrated distribution areas of forested wetland in China, but the carbon storage and carbon sink/source of forested wetlands in this area is unclear. We measured the ecosystem carbon storage (vegetation and soil), annual net carbon sequestration of vegetation and annual carbon emissions of soil heterotrophic respiration of five typical forested wetland types (alder swamp, white birch swamp, larch swamp, larch fen, and larch bog) distributed along a moisture gradient in this area in order to reveal the spatial variations of their carbon storage and quantitatively evaluate their position as carbon sink or source according to the net carbon balance of the ecosystems. The results show that the larch fen had high carbon storage (448.8 t ha^(−1)) (6.8% higher than the larch bog and 10.5–30.1% significantly higher than other three wetlands (P < 0.05), the white birch swamp and larch bog were medium carbon storage ecosystems (406.3 and 420.1 t ha^(−1)) (12.4–21.8% significantly higher than the other two types (P < 0.0 5), while the alder swamp and larch swamp were low in carbon storage (345.0 and 361.5 t ha^(−1), respectively). The carbon pools of the five wetlands were dominated by their soil carbon pools (88.5–94.5%), and the vegetation carbon pool was secondary (5.5–11.5%). At the same time, their ecosystem net carbon balances were positive (0.1–0.6 t ha^(−1) a^(−1)) because the annual net carbon sequestration of vegetation (4.0–4.5 t ha^(−1) a^(−1)) were higher than the annual carbon emissions of soil heterotrophic respiration (CO_(2) and CH_(4)) (3.8–4.4 t ha^(−1) a^(−1)) in four wetlands, (the alder swamp being the exception), so all four were carbon sinks while only the alder swamp was a source of carbon emissions (− 2.1 t ha^(−1) a^(−1)) due to a degraded tree layer. Our results demonstrate that these forested wetlands were generally carbon sinks in the Xiaoxing’anling, and there was obvious spatial variation in carbon storage of ecosystems along the moisture gradient.

Variation of nutrient fluxes by rainfall redistribution processes in the forest canopy of an urban larch plantation in northeast China

Atmospheric deposition(dry and wet deposition)is one of the primary sources of chemical inputs to terrestrial ecosystems and replenishes the nutrient pool in forest ecosystems.Precipitation often acts as a primary transporting agent and solvent;thus,nutrient cycles in forests are closely linked to hydrological processes.We collected precipitation data during a growing season to explore variations in nutrient cycling and nutrient balances in the rainfall redistribution process(wet deposition)in a larch plantation in northeast China.We measured nutrient(NO_(3)^(-),PO_(4)^(3−),Cl^(−),K,Ca,Na,and Mg)inputs via bulk precipitation,throughfall and stemfl ow,and used a canopy budget model to estimate nutrient fl uxes via canopy exchange.Our results suggest that the average concentrations of the base cation(K,Ca,Na,and Mg)showed the following order:stemfl ow>throughfall>bulk precipitation.Throughfall and stemfl ow chemistry dramatically fl uctuated over the growing season when net fl uxes(throughfall+stemfl ow—bulk precipitation)of NO−3,PO3−4,SO2−4,Cl−,K,Ca,Na,and Mg were−6.676 kg·ha^(-1),−1.094 kg·ha^(-1),−2.371 kg·ha^(-1),1.975 kg·ha^(-1),0.470 kg·ha^(-1),−5.202 kg·ha^(-1),−0.336 kg·ha^(-1),and 1.397 kg·ha^(-1),respectively.These results suggest that NO−3,PO3−4,SO2−4,Ca,and Na were retained,while Cl−,K,and Mg were washed off by throughfall and stemfl ow.

Variation in glomalin in soil profiles and its association with climatic conditions,shelterbelt characteristics,and soil properties in poplar shelterbelts of Northeast China

Glomalin-related soil protein(GRSP)sequesters large amounts of carbon and plays important roles in maintaining terrestrial soil ecosystem functions and ecological restoration;however,little is known about GRSP variation in 1-m soil profiles and its association with stand characteristics,soil properties,and climatic conditions,hindering GRSP-related degraded soil improvement and GRSP evaluation.In this study,we sampled soils from 1-m profiles from poplar(Populus spp.)shelterbelts in Northeast China.GRSP contents were 1.8–2.0 times higher in the upper 40 cm soil layers than at 40–100 cm.GRSP-related soil organic carbon(SOC)sequestration in deeper soil layers was*1.2 times higher than in surface layers.The amounts of GRSP-related nutrients were similar throughout the soil profile.A redundancy analysis showed that in both surface and deeper layers,soil properties(pH,electrical conductivity,water,SOC,and soil nutrients)explained the majority of the GRSP variation(59.5–84.2%);the second-most-important factor in GRSP regulation was climatic conditions(temperature,precipitation,and altitude),while specific shelterbelt characteristics had negligible effects(<5%).Soil depth and climate indirectly affected GRSP features via soil properties,as manifested by structural equation model analysis.Our findings demonstrate that GRSP is important for carbon storage in deep soils,regardless of shelterbelt characteristics.Future glomalin assessments should consider these vertical patterns and possible regulating mechanisms that are related to soil properties and climatic changes.

Clonal variations in nutritional components of Pinus koreansis seeds collected from seed orchards in Northeastern China

From four Korean pine （Pinus koraiensis） orchards, 60 clones were selected and analyzed for the fatty acid and amino acid components of the seeds to reveal the variations and correlations of the seed characteristics among the clonal source orchards and clones. The nutri- tional components of the seeds of the P. koraiensis trees exhibited rich genetic variation; the variation coefficient of the fatty acids was 2.24-66.83 %, while the variation coefficient of the amino acids was 14.70-38.88 %. Rela- tively high genetic-improvement potential exists for the nutritional components of the seeds. The phenotypic dif- ferentiation of the fatty acid and amino acid components reveals that variation within the population （85.18 %） was the primary source for the variation of the fatty acid components; variation among the orchards （63.08 %） was the primary source of the variation of the amino acid components. Data drawn from various clonal source orchards all showed that the seed characteristics were highly controlled by heritability （h2 〉 80 %）, and the seed characteristics of the P. koraiensis trees exhibited a similar genetic gain trend. The principal components were ana- lyzed to obtain the comprehensive principal component value for each clonal seed orchard. Twelve clones were selected based on a clonal selection rate of 20 %. Corre- lation and multiple stepwise-regression analyses were conducted, considering different location conditions, to reveal the stable correlations between the seed character- istics to facilitate improvements of the seed yield of P. koraiensis trees and the clonal selection. Species of real characteristics in P. koraiensis were controlled by higher heritability. Genetic gain was obtained by selecting of superior clones.

The influence of selective cutting of mixed Korean pine(Pinus koraiensis Sieb.et Zucc.) and broad-leaf forest on rare species distribution patterns and spatial correlation in Northeast China

This study aimed to demonstrate change in spatial correlation between Korean pine （Pinus koraiensis Sieb. et Zucc.） and three rare species, and change in spatial distribution of four species in response to a range of selective cutting intensities. We sampled three plots of mixed Korean pine and broad-leaf forest in Lushuihe Forestry Bureau of Jilin province, China. Plot 1, a control, was unlogged Korean pine broad-leaf forest. In plots 2 and 3, Korean pine was selectively cut at 15 and 30 % intensity, respectively, in the 1970s. Other species were rarely cut. We used point-pattern analysis to research the spatial distributions of four tree species and quantify spatial correlations between Korean pine and the other three species, Amur linden （Tilia amurensis Rupr.）, Manchurian ash （Fraxinus mandshurica Rupr.）, and Mongolian oak （Quercus mongolica Fisch.） in all three plots. The results of the study show that selective cutting at 15 % intensity did not significantly change either the species spatial patterns or the spatial correlation between Korean pine and broadleaf species. Selective cutting at 30 % intensity slightly affected the growth of Korean pine and valuable species in forest communities, and the effect was considered nondestructive and recoverable.

Ectomycorrhizal communities associated with Tilia amurensis trees in natural versus urban forests of Heilongjiang in northeast China

The deciduous linden tree （Tilia amurensis Rupr.） is protected at National Level II in China as a species of ecological and economic importance. The objective of this study was to assess and compare the ectomycorrhizal communities associated with T. amurensis in natural versus urban forests of central Heilongjiang Province. The percentage of T. amurensis colonisation by ectomycorrhiza was more than 60 % in urban forests, compared to 34-49 % in natural forests. Use of a combi- nation of morphological and molecular methods docu- mented 18 ECM （ectomycorrhizal） types among three sites; 12-13 ECM species were identified in the natural sites versus 9 species in the urban site. Four ECM species （Boletus sp., Tuber sp., Inocybe sp.2, Leccinum sp.1） were the dominant mycorrhizal symbionts, and Cenococcum geophilum and Russula sp. were found only in the natural forests.

Forestry big data platform by Knowledge Graph

Using the advantages of web crawlers in data collection and distributed storage technologies,we accessed to a wealth of forestry-related data.Combined with the mature big data technology at its present stage,Hadoop's distributed system was selected to solve the storage problem of massive forestry big data and the memory-based Spark computing framework to realize real-time and fast processing of data.The forestry data contains a wealth of information,and mining this information is of great significance for guiding the development of forestry.We conducts co-word and cluster analyses on the keywords of forestry data,extracts the rules hidden in the data,analyzes the research hotspots more accurately,grasps the evolution trend of subject topics,and plays an important role in promoting the research and development of subject areas.The co-word analysis and clustering algorithm have important practical significance for the topic structure,research hotspot or development trend in the field of forestry research.Distributed storage framework and parallel computing have greatly improved the performance of data mining algorithms.Therefore,the forestry big data mining system by big data technology has important practical significance for promoting the development of intelligent forestry.

CDIO Based Optimization of Urban Planning Personnel Training Courses in Forestry Universities

On the basis of analyzing existing course system of urban planning discipline,this paper came up with a framework for optimization of urban planning personnel training mode and course system,oriented towards training practical engineering personnel and based on CDIO engineering education and teaching platform. Then it made empirical study on setting of the urban planning discipline in Northeast Forestry University. It proposed changing the original "3 + 2" course system,exploring and optimizing the course system,improving teaching effect of urban planning personnel training courses,and raising planning and design ability of students.