Prediction of stem profile of Picea abies using a process-based tree growth model

We built a simple tree growth model for Norway spruce (Picea abies (L.) Karst.) that describes the biomass and stem radial growth of one tree in a stand. Growth is controlled by an external height growth function that accounts for site quality. Crown recession is represented by an empirical function that accounts for the limitation to crown development caused by mechanical contacts with neighboring trees. The model describes biomass growth based on carbon budget (photosynthesis, respiration and senescence) and carbon partitioning between foliage, stem and root compartments. An internal regulation is introduced based on a functional balance between crown and root development. Stem annual growth is distributed along the stem by means of an empirical rule. Stem profile is the final output of the model and can be used to check the overall consistency of the model and as an aid in wood quality studies. The underlying assumptions of the model are described.     

DESPOT, a process-based tree growth model that allocates carbon to maximize carbon gain

We present a new model of tree growth, DESPOT (Deducing Emergent Structure and Physiology Of Trees), in which carbon (C) allocation is adjusted in each time step to maximize whole-tree net C gain in the next time step. Carbon gain, respiration and the acquisition and transport of substitutable photosynthetic resources (nitrogen, water and light) are modeled on a process basis. The current form of DESPOT simulates a uniform, monospecific, self-thinning stand. This paper describes DESPOT and its general behavior in comparison to published data, and presents an evaluation of the sensitivity of its qualitative predictions by Monte Carlo parameter sensitivity analysis. DESPOT predicts determinate height growth and steady stand-level net primary productivity (NPP), but slow declines in aboveground NPP and leaf area index. Monte Carlo analysis, wherein the model was run repeatedly with randomly different parameter sets, revealed that many parameter sets do not lead to sustainable NPP. Of those that do lead to sustainable growth, the ratios at maturity of net to gross primary productivity and of leaf area to sapwood area are highly conserved.     

Bridging process-based and empirical approaches to modeling tree growth

The gulf between process-based and empirical approaches to modeling tree growth may be bridged, in part, by the use of a common model. To this end, we have formulated a process-based model of tree growth that can be fitted and applied in an empirical mode. The growth model is grounded in pipe model theory and an optimal control model of crown development. Together, the pipe model and the optimal control model provide a framework for expressing the components of tree biomass in terms of three standard inventory variables: tree height, crown height and stem cross-sectional area. Growth rates of the inventory variables and the components of biomass are formulated from a carbon balance. Fundamentally, the parameters of the model comprise physiological rates and morphological ratios. In principle, the values of these parameters may be estimated by lower-level process models. Alternatively, the physiological and morphological parameters combine, under reasonable assumptions, into a set of aggregate parameters, whose values can be estimated from inventory data with a statistical fitting procedure.     

Calibration of the process-based model 3-PG for major central European tree species

European Journal of Forest Research - Process-based forest models are important tools for predicting forest growth and their vulnerability to factors such as climate change or responses to...     

阔叶树分段育苗技术探讨

通过对我州几个乡土珍贵阔叶树分段育苗的成活率，苗木合格率，合格苗产量以及育苗成本进行试，认为阔叶树分段育苗有较一般育苗不可比拟的优点。阔叶树分段育苗移栽平均成活率为97．46％，苗木移栽出辅平均合格率90．3％，提高亩木单产122．0％－163％，每亩节约育苗用工8个工日。     

林木免耕育苗技术研究

免耕育苗技术以前茬为水稻的稻田为苗圃地，免耕作床、插种育苗。较常规育苗而言，可提高单位面积的优质壮苗产量、产值，减少劳动量，降低育苗成本等。免耕育苗操作简单易行，在长江流域的砂质壤土地区均可推广。     

Rhizome growth of Calamagrostis canadensis into mounds created for tree seedling establishment

Mineral soil-capped, inverted mounds (a layer of organic matter topped by a mineral soil cap on an undisturbed in situ soil horizon) are often created as planting sites for tree seedlings in areas dominated by a very competitive grass, Calamagrostis canadensis. Mounding, however, has had variable success at slowing the spread of this grass into the planting sites. A series of three field experiments investigated the pattern of rhizome growth of C. canadensis into mounds. Experiment 1 tested the interaction of mound thickness and clonal connections of C. canadensis to plants outside the mounds; experiment 2 the removal of the organic layer containing most of the rhizomes (screefing) prior to mounding, and experiment 3 the effect of mulching and fertilising on penetration and distribution of rhizomes through the mound. The thickness of the mineral soil cap was the most important factor determining the success of C. canadensis colonisation, while clonal connections were only of importance for shallow mounds. Screefing before creating the mound resulted in a reduction of C. canadensis establishment. Rhizome penetration from plants outside of the mound was not strongly affected by fertilising and mulching. A fourth experiment, conducted in a controlled environment, tested the ability of rhizomes from buried C. canadensis sods to grow through mineral soil caps of different thickness. The grass sods had different growth potentials which were achieved by a pre-treatment of two levels of light and nutrients, resulting in high and low rhizome carbohydrate concentrations. Low reserves did not reduce the ability of rhizomes to penetrate any thickness of the mineral soil cap. Strategies of C. canadensis establishment on mounds are discussed.     

Extending a physiological forest growth model by an observation-based tree competition module improves spatial representation of diameter growth

One of the pivotal objectives in forestry research is to estimate the response of silvicultural target variables to climate change scenarios at high temporal resolution in order to consider within-year feedbacks between growth and environmental conditions. To meet this challenge, models are needed which support and complement the widely used observation-based decision systems in forest management and consulting. Physiological models in particular provide the fundamental prerequisites to reflect the impact of various simultaneously changing environmental conditions. However, a physiological representation at the individual tree level is computationally very expensive and sensitive to uncertain initializations. We thus propose an approach that combines a modern representative of the physiological cohort model type, MoBiLE-PSIM, with the individual tree competition concept of a distance-dependent empirical growth simulator (SILVA). The resulting hybrid provides a key feature for the consideration of forest management in long-term simulations at high computational efficiency. The extended model was evaluated with growth-diameter distributions obtained from core-boring at two beech (Fagus sylvatica L.) forest sites in south-west Germany that differ in exposure and soil conditions. The mean bias of annual stand-scale growth from 2001 to 2007 decreased from ?0.59 to ?0.41 mm at one evaluation plot and from ?0.55 to ?0.24 mm at the other when the competition module was coupled in. Inclusion of the SILVA-based individual tree module into MoBiLE-PSIM improved the size-dependent representation of competition and growth on five-year and even annual timescale. This was particularly the case where the spatial distribution of dominant trees was clustered.     

Relative importance of photosynthetic physiology and biomass allocation for tree seedling growth across a broad light gradient

Studies of tree seedling physiology and growth under field conditions provide information on the mechanisms underlying inter- and intraspecific differences in growth and survival at a critical period during forest regeneration. I compared photosynthetic physiology, growth and biomass allocation in seedlings of three shade-tolerant tree species, Virola koschynii Warb., Dipteryx panamensis (Pittier) Record & Mell and Brosimum alicastrum Swartz., growing across a light gradient created by a forest-pasture edge (0.5 to 67% diffuse transmittance (%T)). Most growth and physiological traits showed nonlinear responses to light availability, with the greatest changes occurring between 0.5 and 20 %T. Specific leaf area (SLA) and nitrogen per unit leaf mass (N mass) decreased, maximum assimilation per unit leaf area (A area) and area-based leaf N concentration (N area) increased, and maximum assimilation per unit leaf mass (A mass) did not change with increasing irradiance. Plastic responses in SLA were important determinants of leaf N and A area across the gradient. Species differed in magnitude and plasticity of growth; B. alicastrum had the lowest relative growth rates (RGR) and low plasticity. Its final biomass varied only 10-fold across the light gradient. In contrast, the final biomass of D. panamensis and V. koschynii varied by 100- and 50-fold, respectively, and both had higher RGR than B. alicastrum. As light availability increased, all species decreased biomass allocation to leaf tissue (mass and area) and showed a trade-off between allocation to leaf area at a given plant mass (LAR) and net gain in mass per unit leaf area (net assimilation rate, NAR). This trade-off largely reflected declines in SLA with increasing light. Finally, A area was correlated with NAR and both were major determinants of intraspecific variation in RGR. These data indicate the importance of plasticity in photosynthetic physiology and allocation for variation in tree seedling growth among habitats that vary in light availability.     

Truffle seedling production method has long-term consequences for tree growth and root colonization

Cultivation of Burgundy black truffles (Tuber aestivum syn. T. uncinatum) in Midwestern agroforestry has the potential to provide important income not only to landowners, but also to the hospitality industry. Economically viable harvest depends upon both successful seedling colonization by the truffle fungus and successful growth of the fungus along with the extending root system. We evaluated an established hybrid oak (Quercus bicolor × Q. robur) truffière 5 and 6 years after planting in May 2005, to evaluate the effects of three seedling production methods on tree growth and root colonization by T. aestivum. Oak seedlings produced using two variations on the RPM^© (Root Production Method) substrate grew significantly faster in height and diameter, but were significantly less well colonized by the truffle fungus compared with saplings from seedlings produced by the “Typical” method. We found that 0.7–19.8 % of root tips (mean 5.1 %) sampled from saplings grown from Typical seedlings were colonized by T. aestivum. By 2010, two distinct canopy forms had developed: ‘upright’ versus ‘spreading’. Although root colonization was not related to canopy form, future fruit body production may be influenced by the greater soil shading provided by the spreading canopy form. A comparison of autumn/winter air temperatures in Missouri, USA with European conditions suggests that fruit body production in Missouri will likely be greatest from mid-September through mid-December. Soil pH modification by application of crushed limestone prior to planting was effective in maintaining average pH at 7.16 through 2010, a level consistent with fruit body production.     

Adapting a growth equation to model tree regeneration in mountain forests

Management and risk analysis of protection forests depend on a reliable estimation of regeneration processes and tree growth under different site conditions. While the growth of forest stands and thus the average growth of larger trees is well studied and published in yield tables as well as embodied in numerous simulation models, there is still a lack of information about the crucial initial stages of tree growth. Thus, we evaluated juvenile tree growth for different site conditions in the Swiss Alps and developed an approach to model both the early and later stages of growth based on the Bertalanffy equation. This equation is physiologically well founded and requires only two parameter estimates: a maximum tree height and a growth parameter. Data for the parameter estimation were available from studies of tree regeneration at a range of sites in Switzerland: growth patterns of larch (Larix decidua) were available from a high-elevation afforestation experiment. For spruce (Picea abies), data were obtained from a blowdown area in the Alps. The growth equation was fitted to the observed data and we found a good correlation of the fitted curves with the observed data. The parameter estimates were validated with independent data sets. The extrapolated growth curves, calculated with the estimated growth rates, correspond well to the validation data. Thus, it is possible to use the Bertalanffy equation to model both the early and later stages of growth. With this approach, we provide a basis for modelling the growth of juvenile and mature trees of different tree species in mountain forests of the European Alps.     

Investigation of salinity impacts on germination and growth of two forest tree species at seedling stage

Soil salinity is becoming an increasingly serious constraint to plant growth in many parts of the world;this is particularly common in semi-arid and arid zones. This study was conducted to evaluate the...     

A non-linear hierarchical mixed model to describe tree height growth

A non-linear hierarchical mixed model approach is used to describe height growth of Norway spruce from longitudinal measurements. The parameter variation in the model was divided into unknown random effects, fixed effects and covariate-dependent effects in order to model tree height growth. The values for fixed effect parameters and the variance–covariance matrix of random effects were estimated. Covariates could only explain up to 10% of parameter variability. Height curves were calibrated by means of BLUPs for the unknown random effects using prior height measurements and evaluated using a separate dataset. The resulting curves had a small error variance and plausible shapes.     

An application of Neurogenetic Algorithm System to individual tree growth model

A neural network system with genetic algorithms (Neurogenetic Algorithm System, or NGAS) was employed to develop individual coniferous tree growth models. A multivariable regression model was applied to compare the performance of NGAS. An IBM personal computer with the BioComp System’s software program of NGO was used to execute this comparison. The results indicate that NGAS is more accurate and effective than the conventional regression method in modeling individual tree growth based on the criteria of Sum of Squared Error (SSE), Average Absolute Error (AAE), Mean Squared Error (MSE) and Final Predicted Error (FPE). This study also suggests that individual tree growth may indeed be a non-linear process. Using this flexible neural network system to model individual tree growth can yield satisfactory prediction results.     

植物生长调节剂对林木生长的控制

用植物生长调节剂处理樟子松。丁香幼苗。实验表明,经处理后的幼苗。高径生长提高１５％￣３０％。樟子松小苗造林成活率平均提高１９．８７％。     

河北省林木种苗生产现状分析及对策

河北省是造林大省，也是育苗大省。近几年来，全省的苗木生产突飞猛进，育苗面积一增再增，1998年只有1．9万hm^2，1999年达到2．7万hm^2，2001年发展到4万hm^2,2003年猛增到6万多公顷。目前，基本形成了国有、集体、个体等多层次，独资、合资、合作等多形式的苗木生产格局。     

Defoliation by processionary moth significantly reduces tree growth: a quantitative review

? Context

Forests are important carbon sinks, but increasing temperatures may favour increases in insect populations, resulting in greater damage to trees. This, in turn, would lead to lower levels of carbon sequestration, intensifying global warming.

? Aim

It is therefore important to predict the impact of insect defoliation on tree growth accurately. The main insect defoliators of conifers in Southern Europe and North Africa are pine and cedar processionary moths (Lepidoptera, Thaumetopoeidae).

? Method

We conducted a meta-analysis based on 45 study cases, to estimate the effect of processionary moth defoliation on tree growth.

? Result

Overall, processionary moth defoliation had a significant impact on tree growth, regardless of the tree and moth species considered. Mean relative tree growth loss increased with the rate of defoliation levelling out at ca. 50?%; it was significantly larger for young than for old trees.

? Conclusion

These results suggest that estimates of processionary moth defoliation could easily be incorporated into tree growth models, to predict the effect of processionary moth outbreaks on carbon sequestration in Mediterranean forests.     

Combining empirical models and the process-based model 3-PG to predict Eucalyptus nitens plantations growth in Spain

Empirical, statistically based models were used to describe the growth and development of Eucalyptus nitens plantations for a range of site productivities and the standard biomass and pulp silvicultural regime currently applied in Northern Spain. The results obtained, along with data gathered from a network of 68 plots, 48 trees felled for biomass estimations and 73 trees sampled for foliar area estimation were used to parameterize the 3-PG model for this species in Northern Spain. Most parameters associated with allometric relationships and partitioning (i.e. bark and branch fraction, basic density, age modifier and mortality) were derived from local data, and the remaining parameters were obtained from published studies on E. nitens or default values previously used for E. globulus. The parameterized model was validated with data from three trials measured from age 3 years until age 8-14 years, and performed better than the empirical model in terms of total stand under bark volume, mean diameter at breast height, basal area and foliar biomass. The process-based model was then used to forecast changes in plantations subjected to a clearwood regime, initializing the model at age 3 years, considering 3 prunings, 2 thinnings and lengthening the rotation to 18 years. This integrated regime was able to provide biomass for bioenergy, pulp or fibreboard wood and also solid wood, with thinning operations assisting the financial viability, and was a potentially good alternative for productive sites.