年龄对刨花楠胸径生长速率的影响

了解年龄对树木胸径生长的影响,对于研究森林群落结构、功能及碳循环等具有重要意义。代谢生态学认为植物的胸径生长速率正比于其胸径的1/3次幂。然而,最近的研究对该理论提出了质疑。通过分析刨花楠解析木数据,结果表明,胸径生长速率与胸径成异速生长关系,但不同年龄具有不同胸径异速生长指数,不支持代谢生态学的推论。随着年龄增加,刨花楠胸径生长呈现先减小后增加模式,这可能是由于植物对光资源的利用造成的。     

The Science of Forestry

ABSTRACT

Forestry is a large field with a long history and extensive contents consisting of practical recommendations arrived at by trial and error. In contrast, the science of forestry is a new development relying on reasoning to produce the optimal system of forest management aimed at satisfying human needs and preserving nature at the same time (though not at the same place). The presented overview of this science consists of two parts. The first one develops a theory of tree growth and stand dynamics. The second part applies this theory to optimize forest management and suggest practical recommendations.

What unites these two parts is a general method of inquiry. It starts with defining one problem, designs two opposing explanations, and then fuses them into a single solution. Hence, the name: the 1–2–1 method. Unlike material variables of process-based models, the explanations employed by the method are abstractions that outline the boundaries embracing all possible solutions. Each explanation in its turn may be subdivided into two opposites until a solution is reached by bringing the opposites together. The 1–2–1 method accounts for any number of variables by arranging them hierarchically into paired groups.

Why exactly two explanations? Because each complex problem has two opposite sides, waiting to be uncovered. We may never know how many factors determine tree growth, yet there is one thing as certain as any mathematical proposition: All these factors are of two kinds—those that facilitate growth and those that restrain it. A factor that does neither is not really a factor. The basic positive process of tree growth is uninhibited cell division. Negative processes include, among others, aging and impediments associated with increasing tree size. When these and several other processes are expressed analytically, we get a meaningful and accurate model of tree growth comprising three pairs of opposites arranged in two levels. The model generalizes empirical equations developed in forestry and exposes biological mechanisms that justify the structure of the equations and explain their success.

The resulting growth model describes density-independent growth. The complementary process of competition has inter- and intraspecific components. It is shown that to maximize forest productivity interspecific competition has to be minimized while the intraspecific kind optimized. Uniting the growth model with that describing the effect of intraspecific competition produces the growth-density model that solves many questions of forest management. In particular, the model helps to reconcile two main goals of management: (a) maximizing the financial returns from wood products, and (b) preserving forests with all their biodiversity and invaluable ecosystem services. Still, the thrust of this review is not another growth model or management system. The main point is an attempt to make forestry a science by consistent reasoning from first principles such as discreteness of plant biomass, the inverse relationship between average size and number of trees, and the conflict between the biotic potential and environmental resistance.     

Relationships between diameter and height of trees in natural tropical forest in Tanzania

The relationship between tree height (h) and tree diameter at breast height (dbh) is an important element describing forest stands. In addition, h often is a required variable in volume and biomass models. Measurements of h are, however, more time consuming compared to those of dbh, and visual obstructions, rounded crown forms, leaning trees and terrain slopes represent additional error sources for h measurements. The aim of this study was therefore to develop h–dbh relationship models for natural tropical forest in Tanzania. Both general forest type specific models and models for tree species groups were developed. A comprehensive data set with 2 623 trees from 410 different tree species collected from a total of 1 191 plots and 38 sites covering the four main forest types of miombo woodland, acacia savanna, montane forest and lowland forests was applied. Tree species groups were constructed by using a k-means clustering procedure based on the h–dbh allometry, and a number of different non-linear model forms were tested. When considering the complexity of natural tropical forests in general and in particular variations of h–dbh relationships due to high species diversity in such forests, the model fit and performance were considered to be appropriate. Results also indicate that tree species group models perform better than forest type models. Despite the fact that the residual errors level associated with the models were relatively high, the models are still considered to be applicable for large parts of Tanzanian forests with an appropriate level of reliability.     

Shoot allometry of Jatropha curcas

The South African government has banned planting of Jatropha curcas L. (Jatropha), potentially a multipurpose tree and biofuel source, owing to insufficient knowledge about the species. Use of allometry as a non-destructive method of monitoring growth and biomass attributes of Jatropha was investigated. The objectives were to examine: reliability of allometry between above-ground variables and basal diameter and crown depth of Jatropha; effects of below-ground interspecies competition and tree spacing on allometry; and validity of these relationships with independent data. The study site was Ukulinga Research Farm, South Africa. Destructive sampling was carried out in March 2008, and tree height and basal diameter were measured periodically during March 2005 to April 2007. Regression analysis and analyses of covariance were used to analyse the data. The height-diameter equation developed by destructive sampling was validated using independent data. Highly significant allometric regressions resulted from using basal diameter (r ≥ 0.89) and crown depth (r ≥ 0.94). Stem diameter had linear relationships with wood and foliage biomass percentages (r = 0.91). Height-diameter equations were equivalent across competition and tree spacing treatments. Predicted and measured tree heights were linearly related (r > 0.97). It could be concluded that above-ground allometry of Jatropha was very reliable and not significantly affected by either below-ground interspecies competition or tree spacing. The site-specific allometric equations are useful for accurate and non-destructive estimations of Jatropha growth under various growing and (non-pruning) tree management conditions. The equations presented here are, however, not universally applicable.     

Structure, allometry, and biomass of plantation Metasequoia glyptostroboides in Japan

We quantified structural features and the aboveground biomass of the deciduous conifer, Metasequoia glyptostroboides (Hu and Cheng) in six plantations in central Japan. In order to derive biomass estimates we dissected 14 M. glyptostroboides trees into three structural components (stem wood, branch wood and foliage) to develop allometric equations relating the mass of these components and of the whole tree to diameter at breast height (DBH). We found robust relationships at the branch and whole tree level that allow accurate prediction of component and whole tree biomass. Dominant tree height was similar within five older (>40 years) plantations (27–33 m) and shorter in a 20-year-old plantation (18 m). Average stem diameter varied from 12.8 cm in the youngest stand to greater than 35 cm in the oldest stand.

Metasequoia have relatively compact crowns distributed over the top 30% of the tree although the youngest stand had the deepest crown relative to tree height (up to 38%). At the individual tree level in older stands, 87% of the aboveground biomass was allocated to the stem, 9% to branch wood and 4% to foliage. We found little difference in the relative distribution of above ground biomass among the stands with the exception of lower foliage biomass in larger diameter trees. Total aboveground biomass of the older stands varied twofold, ranging from a maximum of 450 Mg ha⁻¹ in a 42-year-old stand to a minimum of 196 Mg ha⁻¹ in a 48-year-old stand. Total above ground biomass of the 20-year-old stand was 176 Mg ha⁻¹.     

Modeling the Trends of Nutrient Concentration Dynamics in S-Deprived Young Maize Plants

Sulfate deprivation altered nutrient concentrations in both shoot and root of young maize (Zea mays L.) plants. A model is presented to that simulates the trends of nutrient concentration dynamics relative to the dry mass accumulation in the roots and shoots of plants grown in sulfate-deprived nutrient solution against control. The relationship was found to adequately follow an allometric pattern, the exponent of which could be used to describe the trend of the course, whilst the differential fluctuation types for each nutrient were highlighted. Sulfate-deprivation altered the inclination of the trendline in a differential way for each nutrient, and in several cases reversed the fluctuation pattern. The exponents were ranked in decreasing order, ranking in this way the trends of the concentration dynamics for each nutrient. Observed low R²-values reflected significant scatter of the data set around the trendline.     

Importance of woody materials for seasonal variation in leaf area index from optical methods in a deciduous needleleaf forest

Woody materials (woody area index, WAI) is a key error source in estimating leaf area index (LAI) by optical methods, but how to correct the error caused by WAI during different seasons has not reached consensus. In this study, effective plant area index (PAI_e) was first estimated using two indirect optical methods (digital hemispherical photography, DHP, and LAI-2000) in a deciduous needleleaf forest, and then four different schemes for correcting the contribution of WAI to PAI_e were tested here. We also directly estimated the seasonality of LAI by a litter collection method and an allometric method. Directly subtracting WAI from PAI resulted in a greater degree of uncertainty in correcting seasonal changes of PAI_e from both DHP and LAI-2000. Therefore, we introduced a new correction factor, the stem-to-total area ratio, which was reasonable and useful for quantifying seasonal changes in the contribution of WAI to PAI_e. We finally recommend a practical scheme for correcting PAI_e from both DHP and LAI-2000, with accuracies as high as 88% and 87% during most growing seasons, respectively. Additionally, LAI values estimated from allometry were concordant with those estimated from litter collection, indicating that the allometry method is useful for tracking seasonal changes in LAI.     

Allometric equations for biomass estimations in Cameroon and pan moist tropical equations including biomass data from Africa

Moist tropical forests in Africa and elsewhere store large amounts of carbon and need accurate allometric regressions for their estimation. In Africa the absence of species-specific or mixed-species allometric equations has lead to broad use of pan moist tropical equations to estimate tree biomass. This lack of information has raised many discussions on the accuracy of these data, since equations were derived from biomass collected outside Africa.     

不同估算树冠生物量方法的比较——以长白落叶松林为例

以长白落叶松人工林为研究对象,应用平均标准木法及枝解析木法调查树冠生物量,并采用标准枝法与枝条模型估算法对估测的树冠生物量进行了比较研究。分析了枝长与枝基径,枝条生物量与枝基径、枝长等各因子的相关关系,建立一级枝长模型及枝条生物量模型。通过对枝条生物量估测模型的比较,结果表明:枝基径与枝条生物量、叶生物量有很高的相关性,幂函数拟合的精度较高,参数估计较稳定;虽然二次多项式模型拟合的相关系数较大,但因参数变动较大,预测不稳定。在树冠生物量模型研究中,基于胸径建立异速生物量模型,相关系数R2值达0.906以上;通过对估测树冠生物量模型的比较,枝条模型估测法优于标准枝法,同时对模型进行F检验,F值达极显著水平,所选枝条生物量模型对长白落叶松树冠生物量的估测具一定参考价值。