Applying GreenLab Model to Adult Chinese Pine Trees with Topology Simplification

International audienceThis paper applied the functional structural model GreenLab to adult Chinese pine trees (pinus tabulaeformis Carr.). Basic hypotheses of the model were validated such as constant allometry rules, relative sink relationships and topology simplification. To overcome the limitations raised by the complexity of tree structure for collecting experimental data, a simplified pattern of tree description was introduced and compared with the complete pattern for the computational time and the parameter accuracy. The results showed that this simplified pattern was well adapted to fit adult trees with GreenLab

Source-sink relationships vary with age in Chinese pine (Pinus tabulaeformis Carr.): analysis using the GreenLab model

International audienceTree growth and development rely on the underlying dynamics of their source-sink balance. Given the difficulty of collecting experimental data on adult trees, models can be used as tools to disentangle the complex processes that drive biomass production and allocation. This paper investigates the variations of parameters with age driving the source-sink balance of individual trees through the functional-structural plant model GreenLab. Six Chinese pine (Pinus tabulaeformis Carr.) trees were destructively sampled and were divided into three groups based on ages: 5-year old, 10-year old and 18-year old. Firstly, the effects of age on organ dimensions and on organ relative mass were analyzed based on direct experimental measurement. Secondly, the hidden parameters of the GreenLab model were estimated using the data of total tree biomass for needle and wood compartment independently and then for the six trees in parallel. The statistical tests showed that there were significant differences between the tip attributes on first-, second-, and third-order branches of the three age stages for internode diameter, internode sink and needle sink. Preliminary fitting results showed that the sink of layers and the parameter of biomass production efficiency 1/r decrease with age

Adaptation of the GreenLab model for analyzing sink-source relationships in Chinese Pine saplings

International audienceSince the 1990s, a new generation of models has emerged to simulate tree growth with consideration of both tree structure and functional processes. However, calibration of these functional-structural models (FSMs) often remains an open problem due to the topological complexity of trees and to the heavy measurements required. In this paper, we explore a possible way for dealing with the fitting problem, based on the GreenLab model approach. Detailed organ-level data including topological and geometrical measurements were collected on eight Chinese Pine saplings (Pinus tabulaeformis carr.) grown near Beijing. Adaptation of GreenLab to introduce a flexible modeling for biomass allocation to ring growth is presented. The main assumptions, such as allometry rules and sink relationships, were investigated. The problem of calibration of a complex branching structure was solved by defining an average tree. The results were interpreted with particular focus on the ones concerning the hidden mechanisms of secondary growth

Silvicultural alternatives to conventional even-aged forest management - what limits global adoption?

Background The development of forestry as a scientific and management discipline over the last two centuries has mainly emphasized intensive management operations focused on increased commodity production, mostly wood. This “conventional” forest management approach has typically favored production of even-aged, single-species stands. While alternative management regimes have generally received less attention, this has been changing over the last three decades, especially in countries with developed economies. Reasons for this change include a combination of new information and concerns about the ecological consequences of intensive forestry practices and a willingness on the part of many forest owners and society to embrace a wider set of management objectives. Alternative silvicultural approaches are characterized by a set of fundamental principles, including avoidance of clearcutting, an emphasis on structural diversity and small-scale variability, deployment of mixed species with natural regeneration, and avoidance of intensive site-preparation methods. Methods Our compilation of the authors’ experiences and perspectives from various parts of the world aims to initiate a larger discussion concerning the constraints to and the potential of adopting alternative silvicultural practices. Results The results suggest that a wider adoption of alternative silvicultural practices is currently hindered by a suite of ecological, economic, logistical, informational, cultural, and historical constraints. Individual contexts display their own unique combinations and relative significance of these constraints, and accordingly, targeted efforts, such as regulations and incentives, may help to overcome specific challenges. Conclusions In a broader context, we propose that less emphases on strict applications of principles and on stand structures might provide additional flexibility and facilitate the adoption of alternative silvicultural regimes in a broader set of circumstances. At the same time, the acceptance of alternative silvicultural systems as the “preferred or default mode of management” will necessitate and benefit from the continued development of the scientific basis and valuation of a variety of ecosystem goods and services. This publication is aimed to further the discussion in this context

Transformation of a Degraded Pinus massoniana Plantation into a Mixed-Species Irregular Forest: Impacts on Stand Structure and Growth in Southern China

We transformed a Pinus massoniana plantation, the most important conifer plantation in southern China, with four different transformation treatments, in which Pinus massoniana was thinned to a density of 70%, and then differing richness and compositions of enrichment plantings were added. In order to examine the effects of the transformation, we compared species composition, stand structure and growth pattern in transformed stands with those in control stands. The results suggested that in the transformed stands species composition was diverse with trees both from the enrichment plantings and from natural recruitment. The size structure was changed such that the diameter at breast height (DBH) distribution tended to shift from a nearly normal distribution to an irregular multi-modal distribution. Substantial new ingrowth was found in the small DBH classes. The residual trees in the transformed stands were significantly larger than in the control treatment. However, for all trees, the control stands had the largest mean size, even though the residual tree growth was significantly smaller in the control stands. Finally, transformation treatment A4, which had the smallest overall mortality rate and simultaneously the mortality rate of each tree species was smaller than the corresponding value in other transformation treatments, was identified as the optimal transformation

基于GreenLab原理构建油松成年树的结构-功能模型 (A functional-structural model for adults of Pinus tabulaeformis based on GreenLab)

National audienceAims : In functional-structural plant modeling, trees are composed of elements at the organ level and combined physiological processes and morphological structures. When it is applied to adult trees, we must deal with com- plexity of topology and consider ring growth. Our objective was to apply the functional structural model GreenLab to adult Pinus tabulaeformis trees and parameterize and validate the model. Methods : Destructive sampling was done to collect detailed data including structure and biomass measurements from one 18-year and one 41-year P. tabulaeformis. To extend its application in adult tree growth analysis, we used substructure model to simplify tree topology and introduce ring biomass allocation parameter λ to mix Pressler model and common pool model to analyze tree ring growth in different ages and different environments. Direct parameters were attained from the measurement data, and hidden parameters of the model were calibrated using the generalized least squares method. The model was validated by comparing simulation data with observed data and comparing simulation data to data calculated by empirical model. Important findings : Simulations of P. tabulaeformis growth based on the fitted parameters were reasonable. The coefficients of determination of linear regression equations between observations and predictions ranged from 0.84 to 0.98. The coefficient of determination of linear regression equations between GreenLab simulation data and empirical simulation data was 0.95. The results showed that the GreenLab model can be a new tool to simu- late tree biomass at different growth cycles

Development of a Compatible Taper Function and Stand-Level Merchantable Volume Model for Chinese Fir Plantations

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook) is one of the most important plantation tree species in China with good timber quality and fast growth. It covers an area of 8.54 million hectare, which corresponds to 21% of the total plantation area and 32% of total plantation volume in China. With the increasing market demand, an accurate estimation and prediction of merchantable volume at tree- and stand-level is becoming important for plantation owners. Although there are many studies on the total tree volume estimation from allometric models, these allometric models cannot predict tree- and stand-level merchantable volume at any merchantable height, and the stand-level merchantable volume model was not seen yet in Chinese fir plantations. This study aimed to develop (1) a compatible taper function for tree-level merchantable volume estimation, and (2) a stand-level merchantable volume model for Chinese fir plantations. This “taper function system” consisted in a taper function, a merchantable volume equation and a total tree volume equation. 46 Chinese fir trees were felled to develop the taper function in Shitai County, Anhui province, China. A second-order continuous autoregressive error structure corrected the inherent serial autocorrelation of different observations in one tree. The taper function and volume equations were fitted simultaneously after autocorrelation correction. The compatible taper function fitted well to our data and had very good performances in diameter and total tree volume prediction. The stand-level merchantable volume equation based on the ratio approach was developed using basal area, dominant height, quadratic mean diameter and top diameter (ranging from 0 to 30 cm) as independent variables. At last, a total stand-level volume table using stand basal area and dominant height as variables was proposed for local forest managers to simplify the stand volume estimationThis work was supported by Sino-German Cooperation on Innovative Technologies and Service Capacities of Multifunctional Forest Management (Lin2Value 033L049-CAFYBB2012013), funded by the Federal Ministry of Education and Research (BMBF) and the Chinese Academy of Forestry. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of manuscriptS

A Game Theoretic Approach for Balancing Energy Consumption in Clustered Wireless Sensor Networks

Clustering is an effective topology control method in wireless sensor networks (WSNs), since it can enhance the network lifetime and scalability. To prolong the network lifetime in clustered WSNs, an efficient cluster head (CH) optimization policy is essential to distribute the energy among sensor nodes. Recently, game theory has been introduced to model clustering. Each sensor node is considered as a rational and selfish player which will play a clustering game with an equilibrium strategy. Then it decides whether to act as the CH according to this strategy for a tradeoff between providing required services and energy conservation. However, how to get the equilibrium strategy while maximizing the payoff of sensor nodes has rarely been addressed to date. In this paper, we present a game theoretic approach for balancing energy consumption in clustered WSNs. With our novel payoff function, realistic sensor behaviors can be captured well. The energy heterogeneity of nodes is considered by incorporating a penalty mechanism in the payoff function, so the nodes with more energy will compete for CHs more actively. We have obtained the Nash equilibrium (NE) strategy of the clustering game through convex optimization. Specifically, each sensor node can achieve its own maximal payoff when it makes the decision according to this strategy. Through plenty of simulations, our proposed game theoretic clustering is proved to have a good energy balancing performance and consequently the network lifetime is greatly enhanced