首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 203 毫秒
1.
贡嘎山暗针叶林不同林型的优势木生长动态   总被引:10,自引:0,他引:10       下载免费PDF全文
 根据贡嘎山16块样地的调查资料,运用逻辑斯谛模型探讨了暗针叶林不同林型优势木生长动态。建立了峨眉冷杉(Abies fabri)、麦吊杉(Picea brachytyla)和鳞皮冷杉(Abies squamata)的高、径和材积生长的逻辑斯谛模型。研究结果表明,3种林分优势木的高、径和材积的速生期和速生点都不相同,林线附近的峨眉冷杉高、径和材积的速生期最短,麦吊杉高和材积的速生期最长,鳞皮冷杉基径的速生期最长;林分优势木的生长动态和森林更新关系密切,各优势木的生长指标表明各自立地生态条件差异很大。  相似文献   

2.
选取鹅掌楸(Liriodendron chinense)标准木进行树干解析,采用Logistic、Webull、二次曲线等13个有代表性的数学模型对鹅掌楸胸径、树高和材积生长进行方程拟合。经筛选和验证,得出鹅掌楸胸径生长的最佳模型为:D= 75.6887{1-e–[(T+2.3354)/19.5656]^3.1489};树高生长的最佳模型为:H=(55.5498+34.2298T1.9310)/(119.6386+T1.9310);材积生长的最佳模型为:V=2.5736{1-e–[(T–2.2455)/16.3381]^3.8741}。这三个模型的决定系数均为0.9999,拟合精度分别为99.7258%、99.8827%、99.7930%,且平均偏差、平均绝对偏差、平均相对偏差、平均相对偏差绝对值较小。各林龄段的生长预测值和实测值比较,数据吻合度高,残差总体偏小,趋势线表现一致。各模型可用于指导预测福建省闽北地区鹅掌楸人工林中幼林的生长情况。  相似文献   

3.
陕北白桦个体生长过程的谐波分析   总被引:1,自引:0,他引:1  
利用波谱分析方法中的谐波分析原理 ,对陕北白桦个体生长过程进行了不同层次的分析。结果表明 :白桦个体的树高、胸径和材积生长动态波动规律与Logistic模型不完全相同 ,树高在 2 0年后与Logistic模型吻合 ,胸径整个过程均不吻合 ,但材积生长与Logistic模型基本一致 ;应用波谱分析方法分析树木生长过程的动态规律 ,比Logistic模型更准确。  相似文献   

4.
长江干流季节性水淹滩地杨树生长规律研究   总被引:7,自引:0,他引:7  
研究了长江中下游干流滩地抑螺防病林的主要树种杨树的生长规律,建立了杨树的生 长动态数学模型.经过进一步的生长动态模型分析,研究结果表明:滩地高程是影响杨树胸径、 树高和材积生长量的关键因子.滩地淹水时间超过60天的地方,杨树生长受到明显的影响.  相似文献   

5.
利用波谱分析方法中的谐波分析原理,对陕北白桦个体生长过程进行了不同层次的分析。结果表明:白桦个体的树高、胸径和材积生长动态波动规律与Logistic模型不完全相同,树高在20年后与Logistic模型吻合,胸径整个过程均不吻合,但材积生长与Logistic模型基本一致,应用波谱分析方法分析树木生长过程的动态规律,比Logistic模型更准确。  相似文献   

6.
本文用灰色GM(1,1)模型对林分平均生长过程进行模拟,给出落叶松人工林林分在树高、胸径、材积3个指标上平均总生长量的灰色模型,经过检验,估测效果好.  相似文献   

7.
沙地樟子松林草木生长的研究   总被引:3,自引:3,他引:0  
樟子松由于适应性强而被广泛引种到我国主要沙区.通过采用ChampanRichards生长模型,模拟了红花尔基和章古台两地樟子松的胸径、树高和材积的生长过程.天然樟子松林速生期持续时间长,数量成熟年龄为100a,章古台人工林速生期持续时间短,数量成熟龄为46a  相似文献   

8.
水曲柳落叶松人工混交林中树木个体生长的竞争效应模型   总被引:36,自引:4,他引:32  
本研究从水曲柳落叶松混交林中树木的种内种间竞争机制出发,对与距离有关的竞争模型和邻体干扰模型进行了改进,提出了以竞争指数分量和竞争效应系数来量化树木间的空间竞争。根据野外的实测数据,以年材积生长量为因变量各竞争指数分量为自变量,通过多元回归分析建立了树木个体生长的竞争效应模型,回归结果有很好的拟合优度。本研究为空间竞争模型的进一步改进和生态学研究植物竞争生长关系提供了新的思路。  相似文献   

9.
林分生长量估测模型的研究   总被引:3,自引:1,他引:2  
本文用ARIMA(2,2,0)序列模拟了林分的平均生长过程,给出了落叶松(LarixolgensisHenry)人工林林分在树高、胸径、材积三个指标上平均总生长量的2阶求和自回归滑动平均模型,经模型残量的自相关检验及预测效果检验,估测效果良好.  相似文献   

10.
本文以Richards模型为基础,推导出了Richards衍生模型,刻服了时间因子获取比较困难的不足,又保留了Richards模型的优点.同时对北京市昌平区西部采用LIDAR技术获得的35株铅笔柏数据应用Richards衍生模型和其它常用的胸径一元材积公式进行了拟合,都通过了F检证,得到了Richards衍生模型的残差平方和最小为0.0315,可用;还可进一步推导出材积树高的Richards衍生模型.  相似文献   

11.
The Poisson regression model for the analysis of life table and follow-up data with covariates is presented. An example is presented to show how this technique can be used to construct a parsimonious model which describes a set of survival data. All parameters in the model, the hazard and survival functions are estimated by maximum likelihood.  相似文献   

12.
The paper develops a chi-square test with one degree of freedom for row-column interaction in a contingency table. Use is made of the JOHNSON-GRAYBILL [1972] model which is herein generalized to a twoway multiple response situation. Some of the merits of the new test over the better-known tests for the same hypothesis are discussed.  相似文献   

13.
This article discusses the application of statistical techniques in the analysis of the life table. Using a piece-wise continuous model for the mortality pattern, the maximum likelihood estimates of the probabilities of dying, qi in a life table are obtained. From the form of the covariance matrix it is deduced that the estimates are asymptotically independent. The distribution of qi and its large sample variance are also derived.  相似文献   

14.
Peatlands and forested wetlands can cover a large fraction of the land area and contain a majority of the regional carbon pool in wet northern temperate landscapes. We used the LANDIS-II forest landscape succession model coupled with a model of plant community and soil carbon responses to water table changes to explore the impacts of declining water table on regional carbon pools in a peatland- and wetland-rich landscape in northern Wisconsin, USA. Simulations indicated that both biomass accumulation and soil decomposition would increase as a consequence of drying. In peatlands, simulated water table declines of 100 cm led to large increases in biomass as well as short-term increases in soil carbon, whereas declines of 40 cm led to continuous declines in soil carbon and smaller increases in biomass, with the net result being a loss of total carbon. In non-peat wetlands, biomass accumulation outweighed soil carbon loss for both scenarios. Long-term carbon cycle responses were not significantly affected by the time scale of water table decline. In general, peatland carbon storage over the first 50–150 years following drainage was neutral or increasing due to increased plant growth, whereas carbon storage over longer time scales decreased due to soil carbon loss. Although the simplicity of the model limits quantitative interpretation, the results show that plant community responses are essential to understanding the full impact of hydrological change on carbon storage in peatland-rich landscapes, and that measurements over long time scales are necessary to adequately constrain landscape carbon pool responses to declining water table.  相似文献   

15.
Seedlings of two Nigerian varieties of cowpea (IT82D and IT84E716)were grown together from seeds on loamy soil for 8 weeks intwo identical sloping moisture gradient boxes established outdoorsduring the dry season. Gradients of 13 cm to 79 cm depth towater table were maintained. For all growth characters determined,differences between the two varieties did not differ statisticallythough variety IT84E716 showed marginal improvement over varietyIT82D. Depth to water table had significant effects on all growthcharacteristics determined except for number of lateral shoots.No significant depth to water table x variety interactions wererecorded for any characters examined. Nodules and nodulatedroots showed maximum development in the wettest soils wherethey were relatively thick and large. The main pattern of growththat emerged was limited growth in very wet soil, maximum growthin wet soil and increasingly limited growth as the soil becamedrier. The experiment supported the hypothesis that depth towater table may provide a major edaphic control of cowpea unlessthere is frequent rainfall or irrigation. Cowpea (Vigna unguiculata cylindrica (L.) Walp.), growth characteristics, moisture gradient boxes, phenotypic plasticity, water table  相似文献   

16.
The Early Stage (ES) intermediate represents the starting structure in protein folding simulations based on the Fuzzy Oil Drop (FOD) model. The accuracy of FOD predictions is greatly dependent on the accuracy of the chosen intermediate. A suitable intermediate can be constructed using the sequence-structure relationship information contained in the so-called contingency table − this table expresses the likelihood of encountering various structural motifs for each tetrapeptide fragment in the amino acid sequence. The limited accuracy with which such structures could previously be predicted provided the motivation for a more indepth study of the contingency table itself. The Contingency Table Browser is a tool which can visualize, search and analyze the table. Our work presents possible applications of Contingency Table Browser, among them − analysis of specific protein sequences from the point of view of their structural ambiguity.  相似文献   

17.
Plant organ growth changes under genetic and environmental influences can be observed as altered cell proliferation and volume growth. The two aspects are mutually dependent and intricately related. For comprehensive growth analysis, it is necessary to specify the relationship quantitatively. Here, we develop a simple mathematical model for this purpose. Our model assumes that the biological activity of a given organ is proportional to the cell number of the organ and is allocated into three aspects: cell proliferation, volume growth, and organ maintenance. We analyzed the growth of primary roots of Arabidopsis thaliana (L.) Heynh. in one tetraploid and four diploid strains using this model. The analysis determined various growth parameters, such as specific cost coefficients of cell proliferation and volume growth for each strain. The results provide insight into the basis of interstrain variations and ploidy effects in root growth.  相似文献   

18.
A large portion of the global carbon pool is stored in peatlands, which are sensitive to a changing environment conditions. The hydrological loss of dissolved organic carbon (DOC) is believed to play a key role in determining the carbon balance in peatlands. Zoige peatland, the largest peat store in China, is experiencing climatic warming and drying as well as experiencing severe artificial drainage. Using a fully crossed factorial design, we experimentally manipulated temperature and controlled the water tables in large mesocosms containing intact peat monoliths. Specifically, we determined the impact of warming and water table position on the hydrological loss of DOC, the exported amounts, concentrations and qualities of DOC, and the discharge volume in Zoige peatland. Our results revealed that of the water table position had a greater impact on DOC export than the warming treatment, which showed no interactive effects with the water table treatment. Both DOC concentration and discharge volume were significantly increased when water table drawdown, while only the DOC concentration was significantly promoted by warming treatment. Annual DOC export was increased by 69% and 102% when the water table, controlled at 0 cm, was experimentally lowered by −10 cm and −20 cm. Increases in colored and aromatic constituents of DOC (measured by Abs254 nm, SUVA254 nm, Abs400 nm, and SUVA400 nm) were observed under the lower water tables and at the higher peat temperature. Our results provide an indication of the potential impacts of climatic change and anthropogenic drainage on the carbon cycle and/or water storage in a peatland and simultaneously imply the likelihood of potential damage to downstream ecosystems. Furthermore, our results highlight the need for local protection and sustainable development, as well as suggest that more research is required to better understand the impacts of climatic change and artificial disturbances on peatland degradation.  相似文献   

19.
Abstract In this work we report on the seasonal trends of abundances in terms of temperature exposure for four coexisting cladoceran species (Daphnia ambigua (Daphniidae), Ceriodaphnia dubia (Daphniidae), Diaphanosoma chilense (Sididae) and Moina micrura (Moinidae)) from a Chilean temperate lake. In order to compare the demographic response to temperature, we used life table experiments to parameterize matrix models for the four species at four fixed temperatures. From these life table response experiments we assessed the effects of temperature, species and their interaction on the variation in growth rate, as well as the contribution of juvenile survival, adult survival, fertility and age at first reproduction to the changes in growth rate. Our results showed interspecific differences in the effect of temperature on the growth rate. Species that present higher field abundance at lower temperature also exhibited, under controlled experiments, higher growth rates at low temperature and lower growth rates at high temperature, relative to the additive model. Conversely, species with higher abundances during the warmer seasons exhibited higher growth rates at higher experimental temperatures and lower growth rates at lower temperatures, relative to the additive model. The vital rates that most contributed to the variation in growth rate were age at first reproduction and fertility. Our growth rate estimates matched predictions of the metabolic ecology model.  相似文献   

20.
1 Population growth of four arthropod pests on agricultural crops, the pea aphid, the bird‐cherry oat aphid, the Mediterranean fruit fly, and the two‐spotted spider mite, was modelled using stage matrix models. 2 Temperature was included as a variable in the model, affecting fecundity, mortality and growth rate. Linear temperature dependence was used to describe fecundity and individual growth rate in the matrix model. Life table data collected at various constant experimental temperatures were used to parameterize the model. 3 Sensitivity analysis identified the most influential demographic parameters determining the growth rate of the population at different temperature regimes. Mortality of young adults and immature stages were found to be the most important parameters in determining population growth for all species presented. However, high temperatures increased the relative impact of individual growth rates and fecundity on the growth of the population.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号