An Evaluation of Crown Structure and Site Index to Determine Crown Closure in Eucalyptus urophylla × E. grandis Stands in Guangxi,China

Eucalyptus forests are grown in many parts of the world for their commercial value and use in construction projects. Density management becomes im- portant as a means to attain the management goals in these forests. Changes in canopy and tree crown structure were quantified for Eucalyptus urophylla x E. grandis forests at different ages to determine when canopy closure occurs and the onset of competition begins. Site index was developed for these forests to determine whether site quality affects the canopy structure. Site index had little effect in the forests sampled, with the forest canopy on the better sites becoming slightly more elongated. Based upon crown projection ratio and crown diameter： dbh （diameter at breast height） ratio, it appears that crown closure occurs by age 4 years in these forests. The age at which this occurs was also checked and verified with the evaluation of relative spacing, RS （the ratio of the mean distance between trees to the average dominant height of the stand）. The RS value displayed a rapid decline until age 4 years, and then became relatively flat through age 21 years. The rapid height growth during the first 3 years with no change in density accounted for this rapid decrease. By age 4 years, reductions in the number of trees due to mortality began to have more of an influence on this value, resulting in a more gradual de- cline. The implications for management are discussed.

Site index for teak in Colombia

Determination of site quality is a basic tool for proper selection of locations and species, in management of forest plantations. Throughout the Caribbean studies of site quality are few and are hampered by statistical limitations, inappropriate growth models, and limited data. We fitted growth curves for dominant height to evaluate and clas- sify site quality ofteak （Tectona grandis） plantations by using data from 44 permanent sample plots established since 1990 in 3--22 years old teak plantations in the Colombian Caribbean region. We used Korf＇s and yon Bertalanffy＇s models to fit curves as non-linear effects models. Both models, with a single random parameter, were considered as adequate for dominant height growth modelling, but Korf＇s model was superior. The resulting curves were anamorphic and closely reflected high variability in site quality. Five site classes were clarified： at a base age of 12 years old, teak reached a mean dominant height of 24.8 m on the best sites, 9.8 m in the worst sites, and in the averages sites, 15.8-18.8 m. Using this model, we identified the best and the worst sites for teak plantations in the Caribbean region. This model proved a useful tool, not only for site quality evaluation, but also for improved teak plantation planning and management.

Site index for Chinese fir plantations varies with climatic and soil factors in southern China

Chinese fir[Cunninghamia lanceolata(Lamb.)Hook.]has a large native distribution range in southern China.Here,we tested differences in productivity of Chinese fir plantations in different climatic regions and screened the main environmental factors affecting site productivity in each region.Relationships of a Chinese fir site index with climatic factors and the soil physiochemical properties of five soil layers were examined in a long-term positioning observation trial comprising a total of 45 permanent plots in Fujian(eastern region in the middle subtropics),Guangxi(south subtropics)and Sichuan(central region in the middle subtropics)in southern China.Linear mixed effects models were developed to predict the site index for Chinese fir,which was found to vary significantly among different climatic regions.Available P,total N,bulk density and total K were dominant predictors of site index in three climatic regions.The regional linear mixed models built using these predictors in the three climatic regions fit well(R~2=0.86–0.97).For the whole study area,the available P in the 0–20-cm soil layer and total N in the 80–100-cm soil layer were the most indicative soil factors.MAP was the most important climatic variable influencing the site index.The model evaluation results showed that the fitting performance and prediction accuracy of the global site index model using the climatic region as the dummy variable and random parameters and the most important soil factors of the three climatic regions as predictors was higher than that of global site index model using the climatic variable and the most indicative soil variables of the whole study area.Our results will help with further evaluation of site quality of Chinese fir plantations and the selection of its appropriate sites in southern China as the climatic changes.

Model development to estimate site index values for six major tree species in North Korea

Due to considerable deforestation in North Korea,there is a need to plan forest restoration programs based on scientific forest management.In this study,a methodology was developed for estimating the site index values of six major tree species and the forest productivity potential.The site index values of these tree species were derived in South Korea using the Chapman-Richards equation.These values were used with data from the 6th National Forest Inventory,which included 20 types of edaphic,topographic,and climatic factors,and random forest analysis—a widely used machine learning technique for spatial prediction—to develop a new model for estimating the site index values of these species across South Korea.The prediction accuracy of this model was evaluated using the root mean square error.The results show that the prediction accuracy was high,with a root mean square error of~1m.Moreover,the importance of the variables related to climate and geography was generally high.The proposed site index estimation model for six tree species was applied across North Korea,and its effectiveness tested by comparing the estimated values with those reported in literature from North Korea.The differences between the model outputs and recorded data in the northern alpine regions were presumably due to the lack of data for high-altitude regions in South Korea.This model is based on the determination of the suitability of tree species in restoration efforts.Therefore,it can contribute to the evaluation of forest productivity in North Korea and may help plan efficient forest restoration programs.

Modelling the site index of Pinus pinaster plantations in Turkey using ecological variables

The determination of site productivity in forest ecosystems plays a crucial role in resource management.This study was carried out to identify relationships between site characteristics and height growth of Corsican maritime pine(Pinus pinaster Ait.)plantations in Turkey.Sixty-nine sample plots>20 years of age were selected from locations with different inclinations,aspects,elevations,slope positions and site class.Soil samples were taken at various depths.Height and age were measured on a dominant tree after felling in each plot.Physical and chemical properties of the soil were determined.Relationships between site index(SI 25)and physiographic factors,climatic attributes as well as soil properties were evaluated using correlation analysis and multiple regression analysis.Site index was significantly related with annual precipitation,mean spring rainfall,rainfall June to September,rainfall of the driest month,length of the dry period,mean maximum temperature,mean temperature of the warmest month,stoniness of the soil,sand,silt,clay,pH,electrical conductivity,and available water capacity.Multiple regression accounted for 57.9%of variations in height growth.The models obtained can be used to determine the site index of potential areas in Turkey for maritime pine.It can be said that the productivity of maritime pine may decline in the future due to global climate change.

Growth models and site index table of natural Korean pine forests

According to the growth characteristics of natural Korean pine (Pinus Koraiensis) forests, 6 equations such as Chapman-Richards equation, Logistic equation, Power equation, and so on were selected to ftt for the growth modeIs for Korean pine forest. The growth models were developed based on 208 random trees and 24o dominant trees. Results show that the Chapman-Richards equation is the best model for estimating tree height by age and DBH, while the Parabola equation is fittest for predicting DBH by age or estimating age from DBH. The site index table of Korean pine forest was compiled by using the proportional method with the Chapman-Richards equation as the guide curve and vaIidated by accuracy test.

Generalized Algebraic Difference Site Index Model for Ponderosa Pine in British Columbia,Canada

Based upon 3 widely used base models, a total of 8 ADA/GADA site index models were derived.The data for these models in this study were obtained from 79 pith-split stem analysis plots and the estimation method was "indicator variable approach".We used both fit statistics and visual analysis to select the best-fit model,and attached more importance to the visual analysis.A comprehensive application analysis was also given to the selected model.The results showed:1) GADA outperformed ADA with respect to predictions.2) A GADA model derived from HossfeldⅣpresented the best prediction ability.It was suggested that the model be used to predict dominant height and to estimate site index for ponderosa pine stands ranging 30 -200 years in British Columbia,Canada.3) The best site index age was age of 100 years,based upon relative errors of predictions.

Site quality evaluation of loblolly pine on the South Carolina Lower Coastal Plain,USA

Eleven soil types, which can be identified and delineated using conventional soil survey procedures, were characterized for loblolly pine （Pinus taeda L.） productivity. Four 4-hectare study sites, each containing four measurement plots, were established for every soil type studied. In a stepwise multiple regression, both soil parent material （i.e. a combination of subsoil texture and geology） （p〈0.001）, and drainage class （p=0.006） were significant predictors of site index （tree age 25）, and the overall linear regression model had an R2 value of 0.55. The extremes of soil parent material differed by 3.9 m site index （loamy subsoil on the Wicomico-Penholoway surfaces versus clayey subsoil on the Pamlico-Princess Anne surfaces）. Each increment of drainage class differed by 0.7 m site index. For example, a poorly drained soil had 0.7 m lower site index than a somewhat poorly drained soil. For seven of the eleven soil types studied, there is greater than 80% probability that estimated mean site index is within ±0.8 m of the actual soil type mean site index. The other four soil types （labeled G, I, C and K） need to be either redefined or sampled more intensively. Two of these need to be subdivided in order to adequately characterize site quality, one based on geology （Soil type G） and one based on soil drainage class （Soil type I）. Variation in soil drainage class and varying amounts of topsoil displaced into windrows were both factors influencing site quality variation of a third soil type （Soil type C）. The wide variation in site index data for a fourth soil type （Soil type K） appeared to be due, in part, to sampling study locations and individual measurement plots with less than optimum bedding and/or artificial drainage. Soil parent material （subsoil texture and geology） along with drainage class were found to be important factors influencing site quality on the South Carolina Lower Coastal Plain.

A site dependent top height growth model for hybrid aspen

In this study height growth models for hybrid aspen were developed using three growth equations. The mean age of the hybrid aspen was 21 years （range 15-51 years） with a mean stand density of 946 stems ha-~ （87-2374） and a mean diameter at breast height （over bark） of 19.6 cm （8.5-40.8 cm）. Site index was also examined in relation to soil type. Multiple samples were collected for three types of soil： light clay, medium clay and till. Site index curves were constructed using the col- lected data and compared with published reports. A number of dynamic equations were assessed for modeling top-height growth from total age.

Effects site conditions on industrial fiber plantations of Lar/x olgensis

Plot sampling was conducted in the second cultivation areas ofLarix olgensis in Heilongjiang Province, China. By analyzing plot investigation data, wood properties, and kraft pulps of 840 plots and 248 sample trees in industrial plantations of L. olgensis on different sites, we examined the growth process of L. olgensis industrial plantation with suitable structure, the wood fiber feature, chemical composition, physical performance and pulp characteristics. It is suggested that site conditions have major effects on plantation growth, fiber contains, fiber length, rate between fiber length and fiber width, pulping rate and pulp physics intensity. The best site for L. olgensis industrial plantation growth is site class Ⅰ and site class Ⅱ, which are on lower locations. Site condition has an obvious influence on the wood characteristics. Within the range of site conditions and stand densities studied, the worse the site condition, the less the fiber contains, the shorter the fiber length, and the more the 1% NaOH extraction. This kind of relationship becomes more obvious as stand age increases. However, the influence of site condition on pulping rate and pulp physics intensity is not obvious. The result provides theoretical base for cultivation of industrial fiber plantation of L. olgensis.

冷季不同饲养方式对牦牛生长性能及血液生理生化指标的影响

试验旨在研究冷季不同饲养方式对青海高原型牦牛生长及生理适应等特性的影响。选取320头18月龄自然放牧体重无显著差异的公牦牛[(142.45±2.65)kg]分为两组,一组在原群体自然放牧,另一组低海拔全舍饲育肥6个月。试验结束后随机屠宰育肥组和放牧组牦牛各3头,进行生长性能、屠宰性能以及血液生理生化等指标的测定。经过6个月冷季不同饲养方式饲养,育肥组牦牛体重、体斜长、胸围均极显著高于放牧组(P<0.01)。育肥组牦牛的宰前活重、肉重、骨重、蹄重、皮重、肉骨比、屠宰率、净肉率、心重、肺重和皮占体重极显著高于放牧组(P<0.01);育肥组牦牛的头重、胴体产肉率、肝重、脾重和肾重显著高于放牧组(P<0.05)。育肥组牦牛的红细胞数目(RBC)、血红蛋白浓度(HGB)显著高于放牧组(P<0.05);放牧组的平均血红蛋白含量(MCH)显著高于育肥组(P<0.05)。育肥组的总胆固醇(TC)含量显著高于放牧组(P<0.05);育肥组的钙(Ca)、磷(P)含量显著高于放牧组(P<0.05)。育肥组经济效益极显著高于放牧组(P<0.01)。冷季低海拔异地舍饲育肥能够提升牦牛的生长性能、营养代谢,优化血清生化指标,增加了牦牛的养殖效益。

Relationship between the productivity of Pinus brutia Ten. and site characters, the Taurus Mountains, Turkey

Turkish red pine is an important forest tree species because of its role in the ecosystem whose range includes many countries in the eastern Mediterranean basin.In addition,red pine is a preferred forest tree species due to rapid growth,usage in afforestation in arid areas and the production of non-wood forest products such as resin.The aim of the study was to examine the relationship between the productivity of red pine and ecosystem in the lower and middle belt of the Taurus Mountains,and to determine the interrelations between the productivity of red pine and ecosystem.Multivariate analyses(multiple regression analysis and artificial neural networks)were used to model the efficiency(biomass production)of red pine.From the multivariate analyses,a productivity model of the species was created with the slope,soil depth,and precipitation in the driest variables.A significant correlation was found between site index and site factors in the driest quarter.These variables had a statistically significant relationship with the site index in the multiple regression analysis.The forecast power of the model was 0.33.Of the methods used,the artificial neural network consisting of 2 L10 N(2 Layers 10 Neurons)had the highest margin of explanation(R^(2)=0.71)and the lowest margin of error.This model has the potential to open land aimed for afforestation studies with red pine in forestry areas.The results will shed light on afforestation studies to be carried out in the Western Mediterranean region and in similar ecosystems.

Site Quality Evaluation for Mixed, Uneven-aged, Natural Forest Dominatedby Korean Pine in Northeast China

Six site types of Korean pine(Pinus koraiensis) forest, Mongolian oak type, Yezo spruce type, Korean spruce type, Amur linden type, Ribbed birch type and Manchurian ash type, are easily found on the south slope of Xiaoxing’an Mountains. The analysis results of H-A and H-Dbh relationships by site type showed that height growth of Korean pine dominant or codominant stems in natural stands is not directly related to its age but is directly related to its diameter, which closely accords with the Chapman-Richards equation(Relativity coefficients more than 0:8668). A method for evaluating site quality using height and diameter of dominant or codominant tree independent of tree age is examined. There are signifi-cantly differences in site quality of Korcan pine among six site types above. The site index was highest on Manchurian ash type, and lowest on Mongolian oak type. Differences of site index with a reference dbh of 40 cm between highest and lowest sites can reach 11 m in maximum., 7 m in average, respectively. Other rationales of the H-D method were discussed.

THE STUDY ON SITE QUALITY EVALUATION FOR DAHURIAN LARCH(LARIX GMELINII RUPR.)

Site quality of larch(Larix gmelinii Rupr.)in Da Xingan Mountain in InnerMongolia was studied systematically with about 1000 temporary plots and computersoftware.The nature of site class and site index curve was discussed in view of generalmathematical model of height growth.The height growth of dominant tree of four divisionsof forest stands were studied and site index tables were constructed respectively.In orderto unify the comparing standard and convenience for management in this region,site indextable was constucted too.Based on discussing the action and accuracy of forest type,aseries of site quality evaluation(forest type-site index class-site index)was suggested.

EVALUATION OF SITE QUALITY FOR DAHURIAN LARCH FORESTS

The site index table, site class table and quantizing model ofdahurian larch forests were formed based on 418 temporary plots and 179 dominant stem analysis trees. By testing raw data which were not used to form the site index table, the site index table of plantations was validated. The site index table or site class table can be used in timber stands according to the intensive degrees of forest management. The quantizing model can be used in cutover, deforested and nonforested areas.

Site Productivity of Clone and Seed Raised Plantations of <i>Eucalyptus urophylla</i>and <i>Eucalyptus grandis</i>in Southeast Mexico

The relationship between soil variables and forest productivity of Eucalyptus urophylla (Eu) and E. grandis (Eg) was studied in commercial forest plantations (CFP) in Huimanguillo, Tabasco, Mexico. The group of Eu included seed and clone raised plantations and the Eg group included only seed raised plantations. Tree measurements and soil sampling were carried out at 56 500-m2 plots. Two soil depths (0 - 20 and 20 - 40 cm) were sampled and analyzed for physical and chemical properties. Site Index (SI), calculated at year 14 was used as indicator of forest productivity. Simple correlation, multiple and second order regressions were used to test the effect of soil variables on productivity. Results showed that mean annual increments (MAI) of Eu and Eg were comparable to other regions of the world reaching 49 m3·ha-1·y-1 across a range of low to high soil fertility gradient (15 to 80 m3·ha-1·y-1). For both species, regardless of the production method (seed or clone), soil texture was the most relevant variable to explain variation in productivity. Eu productivity was correlated to exchangeable Mg (0.3) and Al (0.3) in the 0 - 20 cm soil depth and CEC (0.4) and exchangeable Al (0.6) in the 20 - 40 cm soil depth. Compared to clone plantations, seed plantations showed higher correlations between soils properties and productivity. Aluminum saturation was negatively related to Eg productivity. The highest correlation between soil and productivity were found for Eg, with soil P-availability and aluminum saturation explaining 82 and 85% of the variation, respectively. This works shows that low fertility soils, previously used as pasturelands can be productive for forest plantation purposes and contribute to carbon sequestration.

恩施州乡村旅游地农户返贫风险评估及其影响因素研究

有效预防返贫风险是后脱贫时代脱贫攻坚和乡村振兴战略有效衔接的关键.该研究将风险的概率纳入返贫风险评估体系,从发生概率和破坏程度两方面综合评估其返贫风险,系统反映返贫风险的可能性和破坏性,进而探究其影响因素.研究发现:1)农户各维度的返贫风险水平从高到低依次为个体风险、家庭风险、社会风险和自然风险,农户受家庭风险和个体风险影响较大,存在明显的内生性、个体化特征.2)依据风险的发生概率和破坏程度,返贫风险可分为“高概率-高破坏”型、“高概率-低破坏”型和“低概率-低破坏”型3种类型,其中,“高概率-高破坏”型风险包括非农就业能力和教育负担,返贫风险指数最高,对农户返贫的威胁最大.3)抚养人数和户主的文化程度等家庭特征是影响返贫风险的主要因素,乡村旅游扶贫开发模式不同导致农户的返贫风险存在显著差异.在返贫防治实践中,应因户施策,重点防治内生性返贫,同时要根据返贫风险发生概率及破坏程度的差异,制定合理的返贫风险预警机制及防治措施.

Seismic Site Specific Study for Seismic Microzonation: A Way Forward for Risk Resiliency of Vital Infrastructure in Sikkim, India

Seismic Microzonation comprising study of site specific seismic Microtremor (H/V ratio) is deployed to generate seismological parameters (Peak Frequency, Peak Amplification, Site Vulnerability Index) that may help estimate requisite factors for sound building design codes that can be used to construct risk resilient infrastructures. In this paper the site of Pakyong, Sikkim, India has been investigated by dividing it into three differed zones (Zone 1, Zone II, Zone III). The study area is associated with site amplification factor varying from 1.47 to 11.49 with corresponding frequency variations from 0.5 Hz - 12.5 Hz in which site vulnerability index found varied from 0.2 to 220.6. The anomalous subsurface formation with its high amplification corresponds to the centre of the Pakyong sites having conspicuous trend in NW-SE direction suggesting the existence of geological formations of Chlorite, Phyllite with intercalations of Quartzite beneath the centre of Pakyong site. The risk associated with vulnerability index for different zones maintains its variability as Zone I > Zone II > Zone III, indicating the low vulnerability index values are attributed to compact parts of the sub-surface materials with less amplifications whilst high vulnerability index of the site corresponds to relatively lower strength of the sub-surface materials and soft sediments underlying the Pakyong site which can be used for constructing risk resilient structure by enhancing the stiffness coefficient of the sub-surface by providing plausible engineering solutions for the purpose.

Analysis on the noises from continuously monitoring GPS sites

In this paper, we analyze the time series of site coordinates of 27 continuously monitoring GPS sites covered by the Crustal Movement Observation Network of China over the whole country. The data are obtained in the period from the beginning of the observation to the November of 2005. On the basis of data processing, we analyze the power spectrum density of coordinate component noise at each site and calculate the spectral indexes manifesting the noise property of each component. The spectral indexes indicate that for most sites, the noise of time series of each coordinate component can be addressed by the model of white noise ＋ flicker noise; and for a small amount of sites, it can be described by the model of white noise ＋ flicker noise ＋ random walk noise. We also quantitatively estimate each noise component in the model by using the criterion of maximum likelihood estimation. The result shows that the white noise in the time series of GPS site coordinates does not constitute the main part of noise. Therefore, the error estimation of site movement parameters is usually too small, or too optimistic if we consider the white noise only. Correspondingly, if this factor is not fully considered in explaining these movement parameters, it might mislead the readers.

“双碳”愿景下CO_(2)驱强化采油封存技术工程选址指标评价

在国家能源安全和“双碳”战略愿景下,CO_(2)驱强化采油封存技术(CO_(2)-EOR)因能助力油气行业转型发展,成为“低碳化”乃至“负碳化”的首选技术和最现实的选择。无论是实验、数值模拟还是现场实践,目前国内外学者对CO_(2)-EOR研究侧重于CO_(2)作为高效的驱油“催化剂”本身及油藏CO_(2)-EOR适应性认识,对于工程选址评价缺乏统一标准和系统研究。在充分调研国内外文献的基础上,结合中国CO_(2)-EOR应用进展和工程实践,明确了CO_(2)-EOR工程选址可行性评价所需的通用依据,指出了CO_(2)-EOR工程选址遵循“CO_(2)封存与驱油双统一”、安全性、经济性的专属性原则,并从CO_(2)-EOR工程选址的地质、工程、安全、经济4个要素开展了较详尽系统的研究,定性-定量构建了“4+8+27”CO_(2)-EOR工程选址三级指标评价体系(GESE),以期为油藏开展CO_(2)-EOR工程选址提供借鉴,助力中国碳减排技术的应用与发展。