森林动态模型概论

讨论了模拟森林林分动态变化的模型,并把模型分为森林生长模型和演替模型。森林生长模型包括：全林分模型、林分级模型和单木模型;演替模型包括马尔可夫类模型和林窗模型。文中给出了演替模型的基本原理和适用性,在比较早期和最新发展的林窗模型后,叙述了林窗模型的新进展。生长和演替模型的结构和数据要求不同决定了它们的在时间和空间上的适应性,最后指出模型将向综合总体方向发展     

中国东北森林生长演替模拟模型及其在全球变化研究中的应用

 NEWCOP模型是一个新的适于模拟东北森林的种类组成动态的林窗类计算机模拟模型,它通过模拟在每一个林分斑块上的每株树木的更新、生长和死亡的全过程来反映森林群落的中长期生长和演替动态。由于 NEWCOP模型是一个由气候变量驱动的生态系统模型,故可用于评价气候变化对东北森林生长和演替的影响。在东北大兴安岭、小兴安岭和长白山地区对NEWCOP模型进行了验证和校准。沿环境梯度对NEWCOP模型的数字模拟实验表明：它能准确地再现顶极森林中树种组成及其在东北地区的垂直分布规律和水平分布规律;能准确地再现大兴安岭、小兴安岭和长白山的主要类型森林的生长和演替规律;在一定的场合NEWCOP还可反映林分的径级结构;NEWCOP模型还具有对现有森林的跟踪模拟能力。应用NEWCOP模型评估了东北森林生态系统对可能气候变化的敏感性。在GFDL 2×CO2和GISS 2×CO2气候变化情景下,东北森林的种类组成将发生很大变化,落叶阔叶树将取代目前长白山、小兴安岭的红松(Pinus koraiensis)和大兴安岭的兴安落叶松(Larix gmelinii)成为东北森林主要树种,而针叶树将在地带性森林中占很小的比重,阔叶树中蒙古栎(Quercus mongolica)将是最重要的树种,它将成为小兴安岭和大兴安岭最主要树种;东北地区适于森林生长的区域将大幅度减少,这些变化主要发生在气候变化过渡期。东北森林对不同的气候变化情景有不同响应。但是,总的趋势是未来东北森林中落叶阔叶树的比重将大幅度增加。这些结论对在全球气候变化背景下,我国东北合理地选择造林树种和制定现有森林的保护经营策略具有一定参考价值。     

林窗干扰与森林群落演替

林窗干扰是影响森林群落演替的一个重要因素。该文从林窗干扰和森林群落演替理论及林窗对森林群落微环境、植物入侵和定居、群落结构、群落演替的影响等方面简要介绍了当前国内外有关林窗干扰与森林群落演替的研究现状和研究前景。     

蒙古栎红松林演替模型FOROAK的研究

以森林动态斑块理论为基础建立了蒙古栎（ＱｕｅｒｃｕｓｍｏｎｇｏｌｉｃａＦｉｓｃｈ．）红松（ＰｉｎｕｓｋｏｒａｉｅｎｓｉｓＳｉｅｂ．ｅｔＺｕｃｃ．）林动态变化的林窗模型ＦＯＲＯＡＫ,该模型包括对树木生长的生物学过程和影响树木生长的环境因子模拟两部分。用两种不同面积大小的样地分析森林动态,确定蒙古栎红松林林窗面积为０．０５ｈｍ２。以实际调查数据检验模型,证明所得模型能合理预测森林变化过程,在预测树种组成上精度很高,实际调查和预测的树种断面积组成比在６０、１００和２７０年非常接近,在森林发育后期观测样地的树种组成与预测结果吻合程度良好。对裸地上森林模拟,表明森林的动态过程规律是,蒙古栎和白桦（ＢｅｔｕｌａｐｌａｔｙｐｈｙｌａＳｕｋａｃｚ．）在林分发育开始占优势,中期形成阔叶树和针叶树混交,但以阔叶树为主的森林,后期渐被红松取代。对现实原始林预测显示,森林未来３００年变化稳定,红松株数和生物量变化很小。     

热带次生林森窗平均气温空间分布特征的初步分析

森林群落演替更新作为生态学研究的核心问题 ,一直是研究热点 ,而群落演替更新的重要生态动力乃是自然或人为的干扰。国内外关于大尺度干扰对不同森林类型演替更新已有较详细的研究 ;从 2 0世纪 80年代初开始 ,小尺度的林窗干扰开始受到广泛重视。由于林窗是群落演替的起始地 ,其大小和环境变化程度决定了林窗发展的方向和速度 ,并且林窗的更新状况直接影响到顶级森林的结构、种类组成和种群动态。对于世界范围内的各种森林类型的更新和演替均有重要作用 [17] ,而在热带雨林中的作用更加显著和重要[15] ,因此 ,国外学者十分重视林窗的研究。…     

山杨林林分密度效应动态模拟

 本文用林窗模型研究了小兴安岭南坡山杨林林分密度动态过程,在给定林分初始条件后,模拟了林分密度、断面积、生物量、叶面积指数和生产力150年的变化。用林分密度效应的3/2法则和产量恒定法则检验模拟林分,结果表明模拟林分密度发展与理论预测相符合。通过本文的研究既检验了林窗动态模型又印证了林分密度效应理论。     

气候变化对森林演替的影响

森林演替是森林生态动力源驱动下森林再生的生态学过程,自20世纪初建立群落演替理论以来,演替研究成为生态学研究中的热点．客观准确地认识森林演替规律,研究森林演替动力学机理及其模型,是科学管理森林生态系统的需要;对于天然林保护工程与森林植被的恢复重建,具有重要的理论与实际意义．干扰是森林循环的驱动力,导致森林生态系统时空异质性,是更新格局和生态学过程的主要影响因素．它可改变资源的有效性,干扰导致的林隙是森林循环的起点．回顾了目前演替研究的几种方法,即马尔科夫模型、林窗模型(GAP)、陆地生物圈模型(BIOME)和非线性演替模式．介绍了气候变化对森林演替的影响;并在已有成果的基础上,提出了目前研究存在的问题及未来的发展方向．     

红松单木高生长模型的研究

１引言生长模型是定量研究树木生长过程的有效手段。它既可对林木生长作出现实的评价,也可用来预估将来各测树因子的变化;既是编制修订各种数表的基础,也是森林经营中各种措施实施的依据。在林学上,生长模型主要包括单木生长模型和林分生长模型,其中单木生长模型是林...     

林窗模型及其在全球气候变化研究中的应用

林窗模型是基于个体的广泛应用于森林长期动态变化的模拟与预测的模型,是研究森林生态系统对气候变化响应的有效工具。本文把林窗模型的发展与演变过程概括为3个阶段:萌芽阶段、飞速发展阶段和提高阶段;展望了林窗模型的未来发展趋势;简要阐述了在全球气候变化背景下应用模型研究森林与气候间关系的可行性与必要性;对国际上相关的研究热点和前沿问题进行了探讨;综述了国内的研究现状,指出国内林窗模型的预测研究应以改进现有模型、构建新模型、耦合多模型作为未来的发展方向。     

林窗研究进展

本文从林窗的形成、林窗内微环境特点、林窗内树木更新、以及树轮分析与干扰重建,阐述了国内外在该领域的研究动态和取得的成果,以期推动和促进我国的林窗研究工作。根据欧美学者的研究报告,林窗的面积不仅与林冠和树径的大小成正比,而且与树木的倒伏方式有关;林窗的形成与特征主要受制造林窗树林的种类、树龄、海拔和气候带等因素的影响。林窗内微环境特点随林窗的大小、形状、纬度及所处位置的不同而变化。林窗是推动森林演替和更新的重要因素之一,林窗的形成、大小影响和控制着林内树种的组成和树木的更新。树轮分析可用于检测树木的生长释放,研究表明,在样本数量较大时,树木生长释放对重建过去的森林干扰是很有用的。     

当代森林动态的计算机模型述评

一、引言森林动态这一广义语,包括森林生态系统随时间的任何变化。要想经营好森林,使其为人类创造出最大的财富,必须深刻认识森林的动态规律。在过去的一个多世纪里,森林生态学家们对森林动态规律进行了广泛而深入的研究,现已形成各种动态学说。随着科学的发展以及森林经营水平的提高,人们逐渐用各种方     

A diffusion model of forest succession

Based on a tree by tree replacement mechanism, a diffusion model of forest stand canopy composition is formulated and analyzed. The model is used to explore composition dichotomies by estimating coefficients from forest stand data and interpreting the results in terms of mechanisms for succession. The model yields a concrete characterization of the succession phenomenon known as the climax state.     

Edge-mediated effects on stand dynamic processes in forest interiors: a coupled field and simulation approach

Researchers studying forest edge effects in fragmented landscapes have begun to move beyond merely documenting changes along the edge itself to examining the dynamic influences that edges may have on processes in adjacent areas. One such "edge-mediated effect" is the influence that edges may have on canopy gap replacement processes within the forest interior by acting as seed sources for shade-intolerant plant species. In this paper, we coupled analyses of woody species composition in gap and non-gap areas within the interior of an Ohio hardwood forest with a simple cellular automata model of forest dynamics. Non-gap composition was primarily correlated with disturbance history and site conditions (topographic position and slope) while a comparable analysis using a 24-year time series of composition in gaps showed that gap composition was related most strongly to the proximity of edge communities for the first 10–15 years. However, after 15–20 years of gap succession, composition was correlated with essentially the same variables and to the same degree as non-gap vegetation, suggesting that the influence of edge proximity on interior stand dynamic processes was transient. These results were used to develop a simple mathematical model of stand dynamics that showed that losses of interior forest area may be much greater than typically predicted by core-area models, which do not consider dynamic, edge-mediated effects. Further, our findings suggest the importance of considering disturbance interval in mediating edge-interior relationships, particularly as it may interact with forest size and shape.     

Carbon dynamics in the future forest: the importance of long‐term successional legacy and climate–fire interactions

Understanding how climate change may influence forest carbon (C) budgets requires knowledge of forest growth relationships with regional climate, long‐term forest succession, and past and future disturbances, such as wildfires and timber harvesting events. We used a landscape‐scale model of forest succession, wildfire, and C dynamics (LANDIS‐II) to evaluate the effects of a changing climate (A2 and B1 IPCC emissions; Geophysical Fluid Dynamics Laboratory General Circulation Models) on total forest C, tree species composition, and wildfire dynamics in the Lake Tahoe Basin, California, and Nevada. The independent effects of temperature and precipitation were assessed within and among climate models. Results highlight the importance of modeling forest succession and stand development processes at the landscape scale for understanding the C cycle. Due primarily to landscape legacy effects of historic logging of the Comstock Era in the late 1880s, C sequestration may continue throughout the current century, and the forest will remain a C sink (Net Ecosystem Carbon Balance > 0), regardless of climate regime. Climate change caused increases in temperatures limited simulated C sequestration potential because of augmented fire activity and reduced establishment ability of subalpine and upper montane trees. Higher temperatures influenced forest response more than reduced precipitation. As the forest reached its potential steady state, the forest could become C neutral or a C source, and climate change could accelerate this transition. The future of forest ecosystem C cycling in many forested systems worldwide may depend more on major disturbances and landscape legacies related to land use than on projected climate change alone.     

A spatial model of forest dynamics

Effects of spatial processes on temperate deciduous forest structure and dynamics were investigated with a spatial simulator derived from a forest gap model. The multi-species neighborhood model accounted for competitive interactions and endogenous disturbance in the form of small canopy gaps. Simulated and actual spatial pattern of old-growth stands were compared. The 400 yr simulations produced a pattern scale (0.07–0.2 ha patches) similar to that of an actual stand; simulated pattern intensity was greater than actual intensity, however. Distances to nearest neighbor were somewhat similar for trees in the simulated and actual stands; yet the frequency distributions of distance to nearest neighbor values differed substantially. The simulated stand patterns were generally less random than the actual patterns. Spatial pattern changed markedly during the course of simulated succession. Pattern approached a random dispersion in early succession. Intensity peaked at mid-succession (ca. 150 yr) with a hyperdispersed overstory and a strongly clumped understory. Pattern intensity diminished in late succession as a mixed size structure developed. Old-growth patch size was greater than the neighborhood (or gap) size, suggesting the gap-sized areas do not behave independently.     

Allometric constraints and competition enable the simulation of size structure and carbon fluxes in a dynamic vegetation model of tropical forests (LM3PPA‐TV)

Tropical forests are a key determinant of the functioning of the Earth system, but remain a major source of uncertainty in carbon cycle models and climate change projections. In this study, we present an updated land model (LM3PPA‐TV) to improve the representation of tropical forest structure and dynamics in Earth system models (ESMs). The development and parameterization of LM3PPA‐TV drew on extensive datasets on tropical tree traits and long‐term field censuses from Barro Colorado Island (BCI), Panama. The model defines a new plant functional type (PFT) based on the characteristics of shade‐tolerant, tropical tree species, implements a new growth allocation scheme based on realistic tree allometries, incorporates hydraulic constraints on biomass accumulation, and features a new compartment for tree branches and branch fall dynamics. Simulation experiments reproduced observed diurnal and seasonal patterns in stand‐level carbon and water fluxes, as well as mean canopy and understory tree growth rates, tree size distributions, and stand‐level biomass on BCI. Simulations at multiple sites captured considerable variation in biomass and size structure across the tropical forest biome, including observed responses to precipitation and temperature. Model experiments suggested a major role of water limitation in controlling geographic variation forest biomass and structure. However, the failure to simulate tropical forests under extreme conditions and the systematic underestimation of forest biomass in Paleotropical locations highlighted the need to incorporate variation in hydraulic traits and multiple PFTs that capture the distinct floristic composition across tropical domains. The continued pressure on tropical forests from global change demands models which are able to simulate alternative successional pathways and their pace to recovery. LM3PPA‐TV provides a tool to investigate geographic variation in tropical forests and a benchmark to continue improving the representation of tropical forests dynamics and their carbon storage potential in ESMs.     

Scale and resolution of forest structural pattern

An individual tree-based forest succession model was modified to simulate a forest stand as a grid of contiguous 0.01-ha cells. We simulated a 9 ha stand for 750 years and sampled the stand at 50 yr intervals, outputting structural variables for each grid cell. Principal components analysis was used to depict temporal patterns in forest structure as observed in 0.01 ha samples (individual grid cells). We then resampled the grid using square aggregates of 4 to 100 grid cells as quadrats. Principal component scores recalculated for the aggregates, using the original (0.01 ha scale) scoring matrix, depict the effects of obervational scale on perceived patterns in forest structure. Larger quadrats reduce the apparent variation in forest structure and decrease the apparent rate of structural dynamics. Results support a scale-dependent conceptualization of forest systems by illustrating the qualitative difference in forest dynamics as viewed at the scale of individual gap elements as compared to the larger scale steady state mosaic. The aggregation exercise emphasizes the relationship between these two observational scales and serves as a general framework for understanding scaling relationships in ecological phenomena.