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51.
The aim of the study is to compare selected theoretical distributions (normal, lognormal, Weibull, gamma, logistic, and exponential)
in describing the tree diameter (DBH) distributions of mixed near-natural forests consisting of fir Abies alba Mill. and beech Fagus sylvatica L. growing in various vertical structures. Tree DBH data were collected between 1997 and 2008 from 51 sample plots established
in the Świętokrzyski National Park in Poland. The empirical data represent differentiated DBH distributions, ranging from
almost symmetric to extremely asymmetric ones. The chi-square test and the modified Kolmogorov–Smirnov test were chosen for
the goodness-of-fit testing. In addition to the test statistics, the bias (B), the root mean square error (RMSE) and the graphical method (quantile–quantile plots) were used. In one-storied stands,
the most suitable distributions were the normal and logistic distributions; in two-storied and multilayered stands, the Weibull
and gamma distribution were the most suitable; and in selection stands, the exponential distribution was the most appropriate
to describe the DBH distribution. The order of precision of the tested distributions (from the highest to the lowest) was
Weibull, gamma, logistic, normal, exponential, and lognormal. The normal and exponential distribution should be applied only
to one-storied and selection forests, respectively. The least suitable distribution for DBH distribution modelling was the
lognormal one. 相似文献
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Allometric equations for estimating the above-ground biomass in tropical lowland Dipterocarp forests
Allometric equations can be used to estimate the biomass and carbon stock of forests. However, so far the equations for Dipterocarp forests have not been developed in sufficient detail. In this research, allometric equations are presented based on the genera of commercial species and mixed species. Separate equations are developed for the Dipterocarpus, Hopea, Palaquium and Shorea genera, and an equation of a mix of these genera represents commercial species. The mixed species is constructed from commercial and non-commercial species. The data were collected in lowland mixed Dipterocarp forests in East Kalimantan, Indonesia. The number of trees sampled in this research was 122, with diameters (1.30 m or above buttresses) ranging from 6 to 200 cm. Destructive sampling was used to collect the samples where diameter at breast height (DBH), commercial bole height (CBH), and wood density were used as predictors for dry weight of total above-ground biomass (TAGB). Model comparison and selection were based on Akaike Information Criterion (AIC), slope coefficient of the regression, average deviation, confidence interval (CI) of the mean, paired t-test. Based on these statistical indicators, the most suitable model is ln(TAGB) = c + αln(DBH). This model uses only a single predictor of DBH and produces a range of prediction values closer to the upper and lower limits of the observed mean. Model 1 is reliable for forest managers to estimate above-ground biomass, so the research findings can be extrapolated for managing forests related to carbon balance. Additional explanatory variables such as CBH do not really increase the indicators’ goodness of fit for the equation. An alternative model to incorporate wood density must be considered for estimating the above-ground biomass for mixed species. Comparing the presented equations to previously published data shows that these local species-specific and generic equations differ substantially from previously published equations and that site specific equations must be considered to get a better estimation of biomass. Based on the average deviation and the range of CI, the generalized equations are not sufficient to estimate the biomass for a certain type of forests, such as lowland Dipterocarp forests. The research findings are new for Dipterocarp forests, so they complement the previous research as well as the methodology of the Good Practice Guidance for Land Use and Land Use Change and Forestry (GPG-LULUCF). 相似文献
55.
为了提高林地生产力,满足经济社会发展对杉木大径材的需求,采用不同抚育措施和测土配方平衡施肥技术,研究其对土壤养分变化和杉木胸径的影响。结果表明:间伐措施对土壤养分的影响不明显;测土施肥处理,与不施肥相比,有效促进了土壤碱解氮、有效磷、速效钾的积累,改善了土壤肥力水平。采取间伐施肥措施能显著增加杉木大径材胸径的生长,两年平均增加了3.43 cm,其中:平衡施肥带来的平均胸径增加量分别为1.03 cm;间伐带来的平均胸径增加量分别为2.4 cm。培育杉木大径材应实施间伐与测土施肥相结合的抚育措施。 相似文献
56.
A stemflow (SF) estimation model, based on the correlation between coefficients (a andb) of the regression equation (SF=aP
g −b, whereP
g is gross rainfall) obtained from sample tree and their diameter at breast height (DBH), is presented. Estimation by the model
forSF from two deciduous broad-leaved forests shows favorable agreement with the measurement. Once the equations for regression
coefficients are determined, the model has the potential to easily estimateSF from an entire stand through sampling of some representative trees. However, the model is site-specific. In order to mitigate
the weakness of this model, the combination of previous results provided generalized equations for the coefficients. The generalized
equation adequately estimatedSF of some forests while its estimation was biased for other forests, which indicates thatSF variation between forests is closely related to structural differences. Actually, theSF frequency distribution of two forest stands was significantly different. So, influence of structural factors onSF was also studied using funneling ratio (FR) that integrates the efficiency of trunk and canopy characteristics toSF. Comparison ofFR showed thatSF was significantly correlated to crown-projection area (CPA) and basal area at breast height (BA). Parameters (β
1 andβ
2) within the model were significantly correlated to respective stand density and leaf area index (LAI).
Part of this study was supported by Aichi Prefecture Collaboration of Regional Entities for the Advancement of Technological
Excellence, Japan Science and Technology Corporation. 相似文献
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对所营建的4个地理种源及其99个家系山桂花人工幼林(3年生)林木树高和胸径生长量的测定与分析结果表明:其山桂花人工幼林在种源及其家系间林木的树高和胸径生长差异显著,其中以普文种源生长为最好,3年生山桂花人工林林木的树高达2.3 m,胸径为1.8 cm。而3年生山桂花人工林林木的树高生长以19号家系表现最优,林木胸径生长以28号家系表现最优。综合表现最佳的家系有1、2、3、4、7、8、10、11、12、15、18、19、20、21、23、24、25、26、27、28、29、30、31、36、46、47、71,共27个。 相似文献
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