Assessing Biomass Expansion Factor of Birch Tree <i>Betula utilis</i>D. DON

Biomass is the component of living organism and mostly obtained from plants, animals, insects and the residue of all the mentioned organisms. Biomass is the key source of energy present in the form of organic matter. The study aimed to find out biomass and its variation in each component of Betula utilis D. Don (Birch Tree) with varying diameter at Kalam forest division Swat, Khyber Pakhtunkhwa (KPK) province, Pakistan. The biomass of different components was determined by non-destructive methods. Overall, 30 trees were selected from different diameter classes viz a viz up to 10, 11 - 20 and greater than 20 cm. Ten trees were selected from each class. The diameter of stem and large branches and their length were measured in the field. Later, the volumes of stem and branches were calculated and converted into biomass. The study revealed that stem contributes 42.65% biomass followed by large and sub branches as 39.22% and 13.54% respectively. Leaves contribute 4.59% only. The above tree biomass contribution by different components was arranged as stem was greater than large branches;these were greater than sub branches and the lowest was in leaves. The total above ground biomass of single tree was 20.59, 58.041 and 197.214 kg·tree-1 respectively for diameter up to 10, 11 - 20 and greater than 20 cm. The averaged biomass in all diameter classes was 91.95 ± 93.064 kg·tree-1. The total biomass of single tree of diameter class up to 10, 11 - 20 and greater than 20 cm was 24.71, 69.649 and 236 kg respectively. The below ground biomass of single tree of diameter class up to 10, 11 - 20 and greater than 20 cm was 4.11 ± 1.24 kg, 11.61 ± 3.56 kg and 39.44 ± 8.9 kg respectively. The biomass expansion factor was 1.34, 1.47, and 1.5 t·m-3 respectively for diameter classes up to 10 cm, 11 - 20 cm and greater than 20 cm respectively. The mean biomass expansion factor for all diameter classes was 1.44 t·m-3.

Factors Affecting Tree Husbandry and Woodlots Establishment in Kilimanjaro Region, Tanzania

The study on assessment of factors affecting tree husbandry and woodlots establishment was carried out between September and November 2014 in all seven districts of Kilimanjaro region, namely Hai, Siha Rombo, Mwanga, Same, Moshi Rural and Moshi Municipal Council (MMC). A purposive sampling design was employed whereby two wards per district were selected for the study. Household questionnaire survey was used in data collection. Results show that, factors affecting tree husbandry and woodlots establishment in Kilimanjaro region are gender, livelihood activities, access and ownership/land tenure, cultural factors, legal issues and by-laws insisting people to plant trees. About 32.4%, 32.4% and 30% of all respondents own land with size of 1.0 acre and below, 1.1 - 2.0 and 2.1 - 5.0 acres respectively. Respondents from Hai (55.3%), Same (26.3%), Rombo (11%) and MMC (8%) agreed that cultural issues affect tree husbandry. About 1%, 23%, 30% and 40.8% of respondents in Siha, Same, Hai and Rombo districts respectively agreed that some of by-laws insist people to plant trees on their environments. None of the respondents from any district reported labour availability to be one of the factors affecting tree husbandry. Other factors reported to affect tree husbandry in Kilimanjaro region were capacity building in tree planting and tending, insect pests, diseases and climate change. Formulation of by-laws which insist on tree planting and limit land degradation is recommended at village level. Every piece of land should be planned and used sustainably including area for tree planting. Custom and norms which inhibit women to plant trees should be prohibited through capacity building.

基于FP-tree的新能源汽车产业国际竞争力影响因素关联挖掘算法

为充分挖掘新能源汽车产业国际竞争力影响因素、探究价值增长点,提出了基于FP-tree的影响因素关联挖掘算法。通过构建国际竞争力各指标影响因素的关联规则,分析任意事务数据集中的关联数据,利用最小支持度参数minsup按照从上到下的方式搜索,确定最长的频繁项目集,采用FP-tree关联频繁项目集,设定分支关联性挖掘标准,实现了新能源汽车产业国际竞争力影响因素的挖掘。测试结果表明,设计算法的最小支持度和数据关联挖掘时间较短,置信度分析具有较高的稳定性。

Analysis of Short-Shoot Fuji Apple Tree Structure and Correlative Factors

In order to clarify the correlation between short-shoot Fuji apple tree structure and different factors under different trimming and pruning modes,we investigate the trunk taperingness of free-spindle short-shoot Fuji and slender-spindle short-shoot Fuji,respectively,as well as the total thickness,average thickness,total length and average length of small main branches in the standard demonstration apple garden in Xingtang County of Hebei Province. By SPSS analysis,we study the correlation between trunk taperingness of trees with different shapes and the growth indices of their small main branches. The results show that the trunk taperingness of free-spindle short-shoot Fuji apple is negatively correlated with the total thickness,average thickness,total length and average length of small main branches,but the correlation is not significant; the trunk taperingness of slender-spindle short-shoot Fuji apple is negatively correlated with the total thickness but positively correlated with other factors,and the correlation with average length reaches a significant level. The results of this study can provide a scientific basis for guiding the high-density dwarf rootstock short-shoot Fuji apple tree trimming technology.

老年COPD病人并发吞咽障碍风险预测模型的构建

目的:分析老年慢性阻塞性肺疾病(COPD)病人并发吞咽障碍的影响因素,分别构建Logistic回归模型和决策树风险预测模型。方法:选取2021年7月—2023年7月在我院住院治疗的250例老年COPD病人为研究对象,采用病人信息调查表进行调查,采用Logistic回归分析筛选老年COPD病人并发吞咽障碍的影响因素,构建老年COPD病人并发吞咽障碍的Logistic回归模型及决策树模型,并分析其对老年COPD病人并发吞咽障碍的预测效能。结果:250例老年COPD病人中有120例发生吞咽障碍,吞咽障碍发生率为48%。Logistic回归分析结果显示,牙齿缺失≥6颗及存在营养不良、认知障碍、口腔衰弱、中重度COPD为老年COPD病人并发吞咽障碍的危险因素(P<0.05)。构建的决策树模型合计6层、17个节点,选择牙齿缺失情况、营养状态、认知障碍、口腔衰弱以及COPD严重程度5个解释变量,其中营养状态为老年COPD病人并发吞咽障碍最重要的影响因素。老年COPD病人并发吞咽障碍的Logistic回归模型受试者工作特征曲线下面积(AUC)为0.682[95%CI(0.620,0.739)],决策树模型AUC为0.747[95%CI(0.689,0.800)],2种模型的Delong检验结果显示Z=3.118,P=0.001。结论:老年COPD病人吞咽障碍发生率较高,牙齿缺失≥6颗及存在营养不良、认知障碍、口腔衰弱、中重度COPD为老年COPD病人并发吞咽障碍的危险因素,构建的决策树模型预测效能高于国Logistic回归模型,可为老年COPD病人预防吞咽障碍的发生及制定针对性的预防性护理干预措施提供参考。

基于IEKF的快速三维激光惯导耦合SLAM算法

针对激光SLAM累计误差大、计算耗时长的问题,提出一种基于迭代扩展卡尔曼滤波器(IEKF)的快速三维激光惯导耦合SLAM算法。首先,在前端部分构建惯性测量单元(IMU)运动学模型,将点云与局部地图直接匹配得到观测模型,引入ikd-Tree结构存储点云以减少寻找邻近点的时间。然后,采用IEKF求解,快速估计机器人初步位姿,得到激光惯性里程计。同时加入回环检测模块,并在后端利用因子图优化方法融合IMU积分因子、激光里程计因子和回环因子来消除累计误差,进一步提升系统精度。在M2DGR数据集上进行了算法验证,结果表明,与A-LOAM、LIO-SAM、FAST-LIO2算法相比,本文算法应用于室外大场景时的精度分别提升了21.738%、9.112%和6.750%。在真实环境中进行的实验也表明所构建的地图能准确、完整地反映出周围建筑物的几何结构特征。而且,该算法构建地图的效率显著优于A-LOAM和LIO-SAM算法,建图模块平均单帧运行时间少于19 ms。

基于FP-tree增长算法的影响愤怒郁怒人群睡眠质量的强关联因素挖掘

目的:基于频繁模式树(Frequent Pattern-tree,FP-tree)增长算法挖掘影响愤怒郁怒人群睡眠质量的强关联因素。方法:设计了构造FP-tree的算法和挖掘频繁项集的算法,采用FP-Tree增长算法,通过状态树记录扫描的数据库信息,通过减少项目集的搜索空间,一次扫描数据库生成满足最小支持度要求的频繁项目集,实现了情志病证数据库对愤怒郁怒人群影响睡眠质量各种强关联因素的挖掘。结果:影响愤怒郁怒人群睡眠质量最频繁的关联因素是呼吸不畅、咳嗽或鼾声高、感觉冷、感觉热或做噩梦,程序分析总的时间是2 s。结论:基于FP-tree的频繁项集挖掘算法能有效实现对情志病证数据库海量数据中有用信息的针对性挖掘。

川崎病患儿冠状动脉病变的影响因素分析及预测模型构建

目的分析川崎病患儿冠状动脉病变(CAL)的影响因素,并构建预测模型。方法回顾性分析2020年1月至2024年1月神木市医院收治的306例川崎病患儿临床资料,根据患儿是否合并CAL将其分为CAL组(108例)和未合并CAL组(198例)。CAL组中男73例,女35例,年龄≤2岁69例,>2岁39例。未合并CAL组中男117例,女81例,年龄≤2岁105例,>2岁93例。采用多因素logistic回归分析法分析川崎病患儿CAL的影响因素。按照7∶3比例将306例川崎病患儿随机分为训练集(214例)和测试集(92例),基于训练集数据构建决策树模型,基于测试集数据验证决策树模型的预测效能。绘制受试者操作特征曲线(ROC)评价多因素logistic回归模型和决策树模型的预测效果。采用χ^(2)检验进行统计分析。结果CAL组持续发热时间>10 d、血小板计数(PLT)>300×10^(9)/L、C反应蛋白>50 mg/L、氨基末端脑钠肽前体(NT-proBNP)≥300 ng/L、肌酸激酶同工酶(CK-MB)>18 U/L、红细胞沉降率(ESR)>40 mm/h、静脉注射免疫球蛋白(IVIg)治疗2次占比分别为41.67%(45/108)、60.19%(65/108)、49.07%(53/108)、67.59%(73/108)、47.22%(51/108)、34.26%(37/108)、47.22%(51/108),未合并CAL组上述指标分别为14.65%(29/198)、45.96%(91/198)、35.86%(71/198)、36.87%(73/198)、32.83%(65/198)、16.67%(33/198)、26.77%(53/198),CAL组上述指标均高于未合并CAL组(均P<0.05)。多因素logistic回归分析结果显示,持续发热时间>10 d(比值比=3.449)、PLT>300×109/L(比值比=2.088)、C反应蛋白>50 mg/L(比值比=1.883)、NT-proBNP≥300 ng/L(比值比=3.267)、CK-MB>18 U/L(比值比=2.284)、ESR>40 mm/h(比值比=2.599)、IVIg治疗2次(比值比=2.930)均为川崎病患儿发生CAL的危险因素(均P<0.05)。基于训练集数据建立包括持续发热时间、NT-proBNP、IVIg治疗次数、ESR、CK-MB、PLT 6个变量的川崎病患儿CAL决策树模型,共提取7条分类规则,其中持续发热时间是该模型的首要影响因素。基于测试集数据对决策树模型和logistic回归模型进行验证,结果显示川崎病患儿CAL的决策树模型预测灵敏度、特异度、曲线下面积(AUC)分别为81.25%、86.67%、0.818,logistic回归模型预测灵敏度、特异度、AUC分别为62.50%、90.00%、0.662。结论川崎病患儿CAL的决策树模型包括6个变量,分别为持续发热时间、NT-proBNP、IVIg治疗次数、ESR、CK-MB、PLT,其中持续发热时间是该模型的首要影响因素;该模型具有良好的预测效能。

创伤病人术后多重耐药菌医院感染风险模型的构建

目的:应用Lasso-Logistic回归分析和分类树(CHAID)算法分析创伤病人术后多重耐药菌(MDRO)医院感染的危险因素,构建风险预测模型并比较结果的优劣性。方法:回顾性分析2019年1月—2022年1月郑州大学附属郑州中心医院创伤住院病人的临床资料,应用CHAID算法和Lasso-Logistic回归分别建立风险预测模型,采用拟合优度检验评价模型效果,使用受试者工作特征(ROC)曲线下面积(AUC)比较两种预测模型的优劣。结果:共纳入821例创伤病人,其中创伤合并多重耐药菌感染191例,感染率为23.26%,分类树模型和Logistic回归结果均显示,急性生理学及慢性健康状况评分系统(APACHEⅡ)评分≥20分、发热时间≥3 d、住院时间≥10 d、入院时降钙素原(PCT)≥0.5 ng/L是创伤病人术后多重耐药菌感染的独立危险因素。分类树模型的风险预测正确率为79.2%,模型拟合效果较好;Lasso-Logistic回归模型Hosmer-Lemeshow拟合优度检验显示模型拟合较好(P=0.146),Bootstrap内部验证模型预测能力较好。分类树模型的AUC为0.792[95%CI(0.763,0.819)],Lasso-Logistic回归模型的AUC为0.862[95%CI(0.836,0.885)],两种模型的预测价值中等,通过比较两种模型预测价值差异有统计学意义(P<0.001)。净重分类指数(net reclassification index,NRI)评价提示Lasso-Logistic回归模型优于分类树模型(NRI=0.1536)。结论:Lasso-Logistic回归分析与分类树模型均能提供较为直观的呈现形式,两种模型互补结合使用可以从不同角度早期识别创伤病人术后多重耐药菌感染的风险因素,应采取有效防控措施降低多重耐药菌医院感染发生率。

The role of climate factors in geographic variation in body mass and wing length in a passerine bird

Background: Geographic variation in body size is assumed to reflect adaptation to local environmental conditions. Although Bergmann's rule is usually sufficient to explain such variation in homeotherms, some exceptions have been documented. The relationship between altitude, latitude and body size, has been well documented for some vertebrate taxa during the past decades. However, relatively little information is available on the effects of climate variables on body size in birds.Methods: We collected the data of 267 adult Eurasian Tree Sparrow(Passer montanus) specimens sampled at 48 localities in China's mainland, and further investigated the relationships between two response variables, body mass and wing length, as well as a suit of explanatory variables, i.e. altitude, latitude, mean annual temperature(MAT), annual precipitation(PRC), annual sunshine hours(SUN), average annual wind speed(WS), air pressure(AP) and relative humidity(RH).Results: Our study showed that(1) although the sexes did not differ significantly in body mass, males had longer wings than females;(2) body mass and wing length were positively correlated with altitude but not with latitude;(3) body mass and wing length were negatively correlated with AP and RH, but not significantly correlated with WS. Body mass was positively correlated with SUN and inversely correlated with MAT. Wing length was not correlated with MAT in either sex, but was positively correlated with SUN and negatively correlated with PRC in male sparrows;(4) variation in body mass could be best explained by AP and SUN, whereas variation in wing length could be explained by RH and AP in both sexes. In addition, variation in male sparrows can be explained by SUN, WS and PRC but not in females.Conclusions: Two different proxies of body size, body mass and wing length, correlated with same geographic factors and different climate factors. These differences may reflect selection for heat conservation in the case of body mass, and for efficient flight in the case of wing length.

Fault-tree Models of Accident Scenarios of RoPax Vessels

Ro-Ro vessels for cargo and passengers （RoPax） are a relatively new concept that has proven to be popular in the Mediterranean region and is becoming more widespread in Northern Europe. Due to its design characteristics and amount of passengers, although less than a regular passenger liner, accidents with RoPax vessels have far reaching consequences both for economical and for human life. The objective of this paper is to identify hazards related to casualties of RoPax vessels. The terminal casualty events chosen are related to accident and incident statistics for this type of vessel. This paper focuses on the identification of the basic events that can lead to an accident and the performance requirements. The hazard identification is carried out as the first step of a Formal Safety Assessment （FSA） and the modelling of the relation between the relevant events is made using Fault Tree Analysis （FTA）. The conclusions of this study are recommendations to the later steps of FSA rather than for decision making （Step 5 of FSA）. These recommendations will be focused on the possible design shortcomings identified during the analysis by fault trees throughout cut sets. Also the role that human factors have is analysed through a sensitivity analysis where it is shown that their influence is higher for groundings and collisions where an increase of the initial probability leads to the change of almost 90% of the accident occurrence.

基于Extra-Trees算法的大气环境因素对聚酯涂层老化失光影响的研究

通过在4个试验站进行的自然曝晒试验和涂层的失光率测试,结合曝晒试验站的环境数据,使用ExtraTrees算法研究了环境因素对该聚酯涂层失光率的影响,并用袋外数据进行检验。最终结果的拟合优度为0.973 5,并表明:Extra Trees算法可以应用在环境因素对涂层老化失光影响的研究上,在一定的数据条件下,其计算结果符合有机涂层的老化过程,且显示水溶性污染物更易对老化失光产生影响;应用该算法研究环境因素对材料性能的影响时,可将试验周期与环境因素一同作为输入参数计算,提升数据量的同时增加数据间的差异性,满足模型的计算要求。

A Fast LDL-factorization Approach for Large Sparse Positive Definite System and Its Application to One-to-one Marketing Optimization Computation

LDL-factorization is an efficient way of solving Ax = b for a large symmetric positive definite sparse matrix A. This paper presents a new method that further improves the efficiency of LDL-factorization. It is based on the theory of elimination trees for the factorization factor. It breaks the computations involved in LDL-factorization down into two stages： 1） the pattern of nonzero entries of the factor is predicted, and 2） the numerical values of the nonzero entries of the factor are computed. The factor is stored using the form of an elimination tree so as to reduce memory usage and avoid unnecessary numerical operations. The calculation results for some typical numerical examples demonstrate that this method provides a significantly higher calculation efficiency for the one-to-one marketing optimization algorithm.

Family tree and population: Distinction and similarity of the analysis on example of hemophilia

On the basis of Hardy-Weinberg law the distinction in the philosophy of the description of a family tree and a population is considered. With the help of introduction of the equivalent constant mutagen factor both in a family tree and in a population, the analysis of hemophilia is led. Influence of selection at presence of hemophilia is considered. On the basis of idea of Danforth and Haldane about the balance mutagenesis and selection at presence of hemophilia, the inter-relation of selection parameter and the equivalent constant mutagen factor is found. It is shown, that dynamics of development of hemophilia in a family tree and in population are similar.

Intra-annual stem diameter growth of Tamarix ramosissima and association with hydroclimatic factors in the lower reaches of China's Heihe River

High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.

基于多模态超声建构胎儿先天性心脏病决策树模型及其应用价值

目的:分析基于多模态超声建构胎儿先天性心脏病决策树模型及其应用价值。方法:随机选取2021年4月-2023年7月在本院产前超声检查孕中期孕妇300例,常规产科超声检查确定胎儿生长程度,核实孕周,采用超声多断面模式方法对胎儿心脏进行多断面检测,包括四腔心断面、三血管断面、主动脉弓断面、左室流出道断面、右室流出道断面。对正常分娩的新生儿进行心脏多断面超声检测。对300例胎儿进行多断面模式超声检测,分析胎儿是否伴有先天性心脏畸形,对比超声检查与随访结果符合情况。结果:超声检出21例先天性心脏畸形胎儿,8例选择引产,余13例正常分娩。超声诊断与随访结果对比,卵圆孔直径增大、法洛四联症、完全型心内膜垫缺损、二尖瓣闭锁、右室发育不良综合征、左室发育不良综合征、大动脉转位、永存动脉干、单心室、三尖瓣下移符合率均为100%,超声诊断室间隔缺损7例,随访发现室间隔诊断5例,诊断符合率71.4%。279例超声诊断无先天性心脏畸形胎儿出生后经超声诊断发现有1例卵圆孔未闭、3例室间隔缺损,共4例漏诊患儿,漏诊率0.54%。四腔心断面、三血管断面、主动脉弓断面、左室流出道断面、右室流出道断面诊断胎儿畸形率分别为3.95%、0.63%、2.76%、3.27%、3.25%。由决策树模型可得,产前超声检查发现胎儿心脏可疑异常、高龄孕妇、孕妇接受药物治疗或射线暴露、孕妇有先天性心脏病家族史是胎儿存在先天性心脏病的独立危险因素,其中产前超声检查发现胎儿心脏可疑异常的影响最为显著。结论:孕中期胎儿产前超声多断面模式筛查胎儿先天性心脏病,能够对多数胎儿先天性心脏病进行诊断。

Generating Decision Trees Method Based on Improved ID3 Algorithm

The ID3 algorithm is a classical learning algorithm of decision tree in data mining.The algorithm trends to choosing the attribute with more values,affect the efficiency of classification and prediction for building a decision tree.This article proposes a new approach based on an improved ID3 algorithm.The new algorithm introduces the importance factor λ when calculating the information entropy.It can strengthen the label of important attributes of a tree and reduce the label of non-important attributes.The algorithm overcomes the flaw of the traditional ID3 algorithm which tends to choose the attributes with more values,and also improves the efficiency and flexibility in the process of generating decision trees.

Analysis on Free Spindle Pruning Mode and Related Factors in Fuji Apple

In order to clarify the correlations between the free spindle pruning mode and various factors in Fuji apple,the growth data of the free spindle-shaped short branch Fuji apple Tianhong No. 2 and the free spindle-shaped long branch Fuji apple Changfu No. 2 in the Apple Demonstration Park of Xingtang County,Hebei Province were investigated. Using SPSS statistical software,the correlations between the stem tapering grade and various growth traits were analyzed. The results showed that in Tianhong No. 2,the stem tapering grade was negatively correlated with various growth traits of the central shaft,and the correlation coefficients between the stem tapering grade and the central shaft total thickness,the central shaft average thickness,the central shaft total length and the central shaft average length were-0. 228,-0. 033,-0. 411 and-0. 430,respectively; and in Changfu No. 2,the stem tapering grade was positively correlated with various growth traits of the central shaft,and the correlation coefficients between the stem tapering grade and the central shaft total thickness,the central shaft average thickness,the central shaft total length and the central shaft average length were 0. 475,0. 181,0. 120 and 0. 258,respectively. This paper can provide a scientific basis for guiding the construction of free spindle pruning mode in densely planted dwarf apple trees.

羊源溶血性曼氏杆菌SYS-1株分离鉴定及其毒力与耐药性分析

绵羊上呼吸道疾病是兽医临床常见病,常见病因为溶血性曼氏杆菌感染。该菌具有多种血清型且呈区域性流行,造成当地绵羊养殖业严重经济损失。为探究陕西榆林羊场呼吸道疾病发病原因和危害,丰富该病防治措施,试验采集羊场有呼吸道病史的病死羊肺组织进行平板划线,对其分离的菌株进行形态学观察、生化试验及分子生物学鉴定及药敏性和小鼠致病性试验。结果表明,该菌株为A1型溶血性曼氏杆菌SYS-1株,含有毒力因子抗白细胞毒素,具有致死性风险。分离菌可发酵甘露醇和山梨醇,无法发酵甘露糖。吲哚试验结果阴性,过氧化氢试验呈阳性。该菌株生长缓慢,可对恩诺沙星、氟苯尼考等药物敏感,对庆大霉素和红霉素耐药。

Accumulation of heavy metals in stemwood of forest tree plantations fertilized with different sewage sludge doses

The levels of heavy metals that accumulated in stemwood of mature trees grown for 20 years in a plantation in an abandoned peat quarry in areas that were fertilized with different amounts of domestic sewage sludge(180,360,and720 Mg ha-1on a dry basis) were compared with trees grown in a reference nonfertilized area.Included in the study was a hybrid poplar(Populus tremula x Populus tremuloides) developed for use as an energy crop,three local tree species and one introduced tree species.The concentrations of Cd,Cr,Cu,Ni,Pb and Zn in the stemwood of the trees grown in the fertilized and nonfertilized fields were determined,and found to be significantly lower than their respective concentrations in the soil.Cd and Cr were found only in several wood samples at concentrations close to the limits of detection or qualification; therefore,they were not analyzed further.A correlation analysis suggested that 75%of the correlations between the concentrations of heavy metals in the stemwood and the concentrations in the soil were negative.The ability of trees to accumulate the metals from soil in most cases decreased for Cu and Ni; however,the correlations were not as clear for Pb and Zn.The followingsequence for the levels of heavy metals found in the stemwood of the analysed trees was Zn [ Pb [ Ni [ Cu [(Cr,Cd).The results of this study showed that the levels of heavy metals in the studied wood would not exceed the permitted limits of heavy metal pollution in the air and ash when used for energy production.