基于DEM的森林景观与自然度空间分异研究

该研究在Arc GIS支持下,建立乐东县数字高程模型(DEM)模型,提取海拔、坡度、坡位、坡向等各地形因子,将森林分为10种景观类型,并结合自然度与地形进行叠加分析,分析结果表明,森林资源景观分异频度与地形关系显著,各景观格局分异特征的形成,是自然选择的结果,也有人工干扰的因素。     

基于GIS的岷江上游植被特征研究

基于GIS技术,探索岷江上游植被空间格局与地形因子（高程、坡度、坡向等）之间的关系,得出不同地形地貌区的植被分布特征。研究表明,不同地形地貌区植被的分布状况不同,各种植被因受地形、水份等因素影响而具有一定的分布特征,GIS技术在植被空间分异研究中有很大的应用前景。     

基于FY3A的黑龙江省洪涝灾害风险评价研究

基于风云三号气象卫星A星的MERSI遥感影像数据,分别从自然因素角度和社会因素角度选取降雨量空间分布特征、地形特征、河网分布特征等影响因子和人口密度、地区生产总值、植被面积等影响因子做为洪涝灾害风险评价指标,综合影响因子对各水系流域洪涝灾害的影响度确定权重值,应用Arc GIS软件中空间分析模块的数据转换、分析、统计、分类和显示等功能进行处理和数据分析,建立洪涝灾害风险评价模型,得出风险分类区划图。研究结果表明:基于FY3A的MERSI数据,以GIS为技术平台能够得到更为直观表达的黑龙江省洪涝灾害风险评价图,在时间上和空间上具有一定的可信度。     

森林生态因子—地形

地形是指地球表面形态特征而言,通常所说的高山、河谷、平地、沙匠等都是地表形态特征的反映。地形对森林的影响不是直接的,但由于它对光、热、水等因子的再分配作用很大,因此也被看作是重要生态因子。在生产实践和科研活动中,通常按地形要素范围的大小将地形划分为巨地形、大地形、中地形、小地形和微地形等五个等级。巨地形一般指水平距离几十到几百公里,相对高差数百到数千米的广大范围内的地形。如大兴安岭山     

针阔混交林生物量稳定性驱动因子

【目的】阐明生物多样性、胸径结构和地形因子对针阔混交林生物量稳定性的相对影响,明确不同空间尺度下生物量稳定性的主要驱动因素。【方法】在吉林蛟河两个大型固定样地的基础上,通过随机抽取20 m×20 m、40 m×40 m和60 m×60 m样方的方式,定量分析不同空间尺度的影响。利用广义可加模型构建了三类嵌套模型：稳定性～生物多样性+胸径结构(模型1)、稳定性～生物多样性+地形因子(模型2)、稳定性～生物多样性+胸径结构+地形因子(模型3),并与稳定性～生物多样性(模型0)进行比较,通过赤池信息量准则变化量(ΔAIC)、贝叶斯信息量准则变化量(ΔBIC)、调整后的决定系数变化量(ΔR_adj²)和偏差解释率变化量(ΔDE)评价不同解释因子的相对贡献大小。【结果】广义可加模型分析显示,在20 m×20 m、40 m×40 m、60 m×60 m三个尺度上,生物多样性对生物量稳定性的相对贡献率分别为15.18%、12.66%和47.64%,胸径结构的相对贡献率分别为11.30%、72.38%和23.48%,地形因子的相对贡献率分别为73.52%、14...     

考虑地形效应的高山松地上生物量遥感估测模型构建

[目的]研究基于遥感因子与地形因子构建香格里拉市高山松地上生物量非线性混合效应估测模型,提高高山松地上生物量估测精度.[方法]以2015年和2018年Landsat 8 OLI与对应年份样地实测数据为基础,通过二元生物量模型计算出高山松地上生物量.提取植被指数、纹理等遥感因子.将地形因子按照一定等级进行划分后作为模型因...     

复杂地形约束下西昌市土地利用空间分布格局

以西昌市为研究区,基于DEM及遥感解译获取的土地利用数据,在GIS软件的支持下采用空间技术对提取的地形因子(高程、坡度、坡向、地形位)与土地利用现状图进行叠加处理,得到了4种地形因子影响下不同土地利用的分布特征,进一步分析土地利用空间分布与地形因子的耦合关系。结果表明:(1)西昌市土地利用类型以林地为主,占总面积的50.51%,草地、耕地、水田、建设用地面积接近,水体和其他用地类型所占比例较小;(2)各土地利用类型在不同高程、坡度、地形位分级上呈现出阶梯变化规律;阳坡、半阳坡土地利用程度高于阴坡、半阴坡,水体不受坡向影响;(3)西昌市土地利用类型受地形因素较严格限制,当前没有出现因强烈的人为扰动及地质灾害等导致的极端大规模分布情况。     

盐池县太阳直接辐射分布规律及对林业生态建设的影响

基于ViewGIS下的太阳直接辐射模拟计算模型,计算了宁夏回族自治区盐池县全境太阳直接辐射值,以定点实测数据为基准,对模型精度进行了检验,并分析了对林业生态建设的影响。结果表明:盐池县太阳直接辐射日总量在空间变化上呈现南少北多的特征;太阳直接辐射日总量随坡度的增加逐渐递减;太阳直接辐射日总量随坡向的递减规律是:阳坡、半阳坡、半阴坡、阴坡。盐池县林业生态建设应充分利用太阳辐射规律,中北部缓坡丘陵区结合封育禁牧恢复草场生产力和维持草场生物多样性;在南部黄土高原区,充分利用太阳直接辐射大、白昼温差大的特点,在阳坡、半阳坡发展节水型经济林,在阴坡、和半阴坡,培养生态林和薪炭林,逐步改善和优化区域生态环境。     

基于大比例尺航片的树种结构空间分布分析

以凉水自然保护区2008年拍摄的198张航空像片和2009年森林资源"二类清查"为数据源,根据光束法区域网平差原理,采用全数字摄影测量工作站VirtuoZo NT系统对航空像片提取生成比例尺为1∶10 000的数字高程模型(DEM)。同时,在GIS软件的支持下获取坡度、坡向等地形因子信息并根据小班的树种结构,分析树种结构与海拔、坡度和坡向之间的空间分布格局。     

基于ArcGIS10地形数据提取与分析

本文以森林资源调查工作实践为例,详细总结了如何利用Arc GIS10软件对纸质地形图,通过扫描、矢量化生成高程栅格数据;利用高程栅格数据进行等高线加密、高程统计、坡向和坡度分析,以及利用坡向、坡度等地形因子实现自动区划图斑的方法和过程。     

Multiscale computation of solar radiation for predictive vegetation modelling

The recent development of large environmental databases allow the analysis of the ecological behaviour of species or communities over large territories. Solar radiation is a fundamental component of ecological processes, but is poorly used at this scale due to the lack of available data. Here we present a GIS program allowing to calculate solar radiation as well locally as at large scale, taking into account both topographical (slope, aspect, altitude, shadowing) and global (cloudiness and latitude) parameters. This model was applied to the whole of France (540 000 km²) for each month of the year, using only a 50-m digital elevation model (DEM), latitude values and cloudiness data. Solar radiation measured from 88 meteorological stations used for validation indicated a R ² of 0.78 between measured and predicted annual radiation with better predictions for winter than for summer. Radiation values increase with altitude, and with slope for southern exposure, excepted in summer. They decrease with latitude, nebulosity, and slope for north, east, and west exposures. The effect of cloudiness is important, and reduces radiation by around 20% in winter and 10% in summer. Models of plant distribution were calculated for Abies alba, Acer pseudoplatanus, and Quercus pubescens, for France. The use of solar radiation improved modelling for the three species models directly or through the water balance variable. We conclude that models which incorporates both topographical and global variability of solar radiation can improve efficiency of large-scale models of plant distribution.     

油桐林内的太阳辐射分布

1986年4～8月,在油桐重点产区湖南、湖北5县12个地段65个测点,对油桐纯林内的太阳辐射分布进行观测研究,结果表明:油桐林内太阳辐射的垂直分布与树冠形状有关,塔形树冠内的太阳辐射分布均匀,到达量多;水平分布与树冠的方位和枝条的部位有关,南向方位或下坡方向所在方位的到达量多,枝条外端的到达量多;油桐叶片对太阳辐射的吸收率与品种有关,葡葡桐大于小米桐。     

A predictive model of burn severity based on 20-year satellite-inferred burn severity data in a large southwestern US wilderness area

We describe and then model satellite-inferred severe (stand-replacing) fire occurrence relative to topography (elevation, aspect, slope, solar radiation, Heat Load Index, wetness and measures of topographic ruggedness) using data from 114 fires > 40 ha in area that occurred between 1984 and 2004 in the Gila Wilderness and surrounding Gila National Forest. Severe fire occurred more frequently at higher elevations and on north-facing, steep slopes and at locally wet, cool sites, which suggests that moisture limitations on productivity in the southwestern US interact with topography to influence vegetation density and fuel production that in turn influence burn severity. We use the Random Forest algorithm and a stratified random sample of burn severity pixels with corresponding pixels from 15 topographic layers as predictor variables to build an empirical model predicting the probability of occurrence for severe burns across the entire 1.4 million ha study area. Our model correctly classified severity with a classification accuracy of 79.5% when burn severity pixels were classified as severe vs. not severe (two classes). Because our model was derived from data sampled across many fires over a 20-year period, it represents average probability of severe fire occurrence and is unlikely to predict burn severity for individual fire events. However, we believe it has potential as a tool for planning fuel treatment projects, in management of actively burning fires, and for better understanding of landscape-scale burn severity patterns.     

Seasonal growth of Eucalyptus species in New Zealand hill country

The seasonal growth (height and diameter) of 12 Eucalyptus species (E. agglomerata, E. baxteri, E. botryoides, E. cladocalyx, E. globoidea, E. microcorys, E. muelleriana, E. nitens, E. obliqua, E. pilularis, E. regnans, E. saligna) was measured on trees between 2 and 4 years of age on four hill country microsites; upper shady, lower shady, upper sunny and lower sunny slopes. Additionally, seasonal mean daily solar radiation and temperature were recorded on each aspect over the same time period. Height and diameter growth were both strongly seasonal; mean diameter growth was highest in the spring (0.91 cm) while height growth was greatest in the summer (0.57 m). Conversely, diameter and height growth were least in the winter (0.38 cm and 0.09 m respectively). There was a significant interaction between season and aspect for height (P = 0.01) and diameter (P = 0.02). Diameter and height growth on the shady face was similar to that on the sunny slopes during summer, but, in winter growth on the shady face was typically lower than the sunny. Slope position also influenced height growth (P = 0.001), particularly in the winter, growth on the lower slope being less than on the upper. There was a strong linear relationship between seasonal height growth and solar radiation but a curvilinear relationship between seasonal diameter growth and radiation. Consideration of the influence of topography on solar radiation and other environmental factors may allow more reliable assessment of potential forest production on a micro scale.     

Calculation method for sunshine duration in canopy gaps and its application in analyzing gap light regimes

Understory light is essential to the growth and survival of plants, yet the light varies temporally and spatially within forest gaps. Measurement of understory light levels using light sensors is both time and labor intensive. Sunshine duration (SD) has a strong correlation with solar radiation and has been the variable most widely used for estimating solar radiation. The power of SD-based methods for estimating solar radiation lies in its ability to quickly estimate light levels. Although several calculation methods for SD within canopy gaps are available, all the methods oversimplify canopy gaps by classifying them as cylindrical or ellipsoid and thus have a relatively low level of accuracy. In this study we developed a calculation method for SD at any given point within natural canopy gaps and we used SD to estimate solar radiation within 12 canopy gaps on Mt. Taibai in China based on the Angström-Prescott model. We then evaluated the SD-based solar radiation by the total and direct solar radiation derived from a gap light index based on hemispherical photographs (HP). Finally, we analyzed the spatial-temporal characteristics of light levels within these 12 gaps by using the solar radiation derived from SD at hundreds of simulated points in each gap. Our results showed that (1) SD-based solar radiation was not statistically different from HP-based direct solar radiation and had a strong linear correlation with HP-based total solar radiation; (2) growing-season daily mean solar radiation within the 12 gaps varied from 0.08 to 13.28 MJ m⁻² day⁻¹ with an average of 4.13 MJ m⁻² day⁻¹; (3) solar radiation had a positive correlation with the ratio of the square root of the canopy gap area to the mean canopy height. This relationship was significant but solar radiation had no correlation with the canopy gap area; (4) among most gaps solar radiation was greatest in May while potential SD was longest in June 2008. From these results we can conclude that the SD-based method for estimating solar radiation developed in this study can quickly and accurately estimate light levels at any specified point within canopy gaps. SD-based solar radiation appears to be a good choice for studies on the spatial-temporal characteristics of gap light levels.     

A weeding-duration model for Abies sachalinensis plantations in Hokkaido, northern Japan

I developed a weeding-duration model for Sakhalin fir (Abies sachalinensis (Fr. Schmidt) Masters) plantations that employs a generalized linear model. The number of years following planting that weeding is necessary is the response variable, and elevation, slope steepness, maximum snow depth, annual precipitation, geology, soil, site index, slope aspect, and vegetation type are explanatory variables. Among the explanatory variables, geology, soil, slope aspect, and vegetation type are categorical data. A Poisson distribution is assumed for the response variable, with a log-link function. Elevation, slope steepness, maximum snow depth, annual precipitation, site index, and vegetation type had a significant effect on weeding duration. Among the eight models with the smallest Akaike information criterion (AIC), I chose the model with no multicollinearity among the explanatory variables. The weeding-duration model includes site index, maximum snow depth, slope steepness (angle) and vegetation type as explanatory variables; elevation and annual precipitation were not included in the selected model because of multicol- linearity with maximum snow depth. This model is useful for cost-benefit analyses of afforestation or reforestation with Abies sachalinensis.     

Simulation of soil water dynamics in a Caragana intermedia woodland in Huangfuchuan watershed

As vegetation coverage increases, soil water content can decrease due to water uptake and evapotranspiration. At a very high level of plant density, poor growth and even mortality can occur due to the decrease of soil water content. Hence, a better understanding of the relationship between soil water content and the density of plants is important to design effective restoration projects. To study these relationships, we developed a soil water dynamic simulation model of a Caragana intermedia woodland under different slope gradient and slope aspect conditions in the Huangfuchuan watershed on the basis of the previous studies and field experiments. The model took into account the major processes that address the relationships of plants and the environment, including soil characteristics, precipitation, infiltration, vegetation transpiration, and soil evaporation. Daily changes in soil water content, transpiration, and evaporation of the Caragana intermedia woodland with different vegetation coverage, slope gradient, and slope aspect were simulated from 1971 to 2000. Based on the model simulations, we determined the functional relationships among soil water content, plant coverage and slope as well as the optimal plant density on flat slopes. We also determined the effects of slope gradient and slope aspect on soil water content. When slope gradient was less than 10°, the optimal plant density was sensitive to slope gradient. In the slope range from 10° to 30°, plant density was not sensitive to slope gradient. Therefore, it is important to consider planting densities on the hillsides with slope gradients less than 10° for reconstructing vegetation. __________ Translated from Acta Phytoecologica Sinica, 2005, 29(6): 910–917 [译自: 植物生态学报]     

Use of GIS-derived environmental factors in predicting site indices in Japanese larch plantations in Hokkaido

The objectives of this study were (1) to evaluate the effects of environmental factors derived from GIS on tree-height growth of Japanese larch (Larix kaempferi) and (2) to develop a best-fit regression model for its site index. Based on data from 40 sample plots situated in an even-aged (38 years), pure, and undamaged Japanese larch stand, multiple regression models for a site index of Japanese larch were constructed using environmental factors as independent variables. The average slope gradient, effective relief, distance from ridge, flow accumulation, degree of exposure, shading, solar radiation index, and gravitational water index were used as environmental factors and calculated on GIS using digital elevation model data. These factors were related to the Japanese larch site index through multiple-regression analysis. The result showed that the most effective factor for estimating site index was the degree of exposure. Through a backward stepwise procedure, the degree of exposure, shading, and average slope gradient were selected for a best-fit regression model. This model explained 72% of the variance in site index, with standard error estimates of 1.75 m. This strong relationship suggests that GIS-derived environmental factors can be used to predict site indices of Japanese larch. This study was supported by the experimental forest of Kyushu University.     

Spatial pattern of tree diversity and evenness across forest types in Majella National Park,Italy

Background:Estimation of tree diversity at broader scale is important for conservation planning.Tree diversity should be measured and understood in terms of diversity and evenness,two integral components to describe the structure of a biological community.Variation of the tree diversity and evenness with elevation,topographic relief,aspect,terrain shape,slope,soil nutrient,solar radiation etc.are well documented.Methods:Present study explores the variation of tree diversity(measured as Shannon diversity and evenness indices)of Majella National Park,Italy with five available forest types namely evergreen oak woods,deciduous oak woods,black/aleppo pine stands,hop-hornbeam forest and beech forest,using satellite,environmental and field data.Results:Hop-hornbeam forest was found to be most diverse and even while evergreen Oak woods was the lowest diverse and even.Diversity and evenness of forest types were concurrent to each other i.e.forest type which was more diverse was also more even.As a broad pattern,majority portion of the study area belonged to medium diversity and high evenness class.Conclusions:Satel ite images and other GIS data proved useful tools in monitoring variation of tree diversity and evenness across various forest types.Present study findings may have implications in prioritizing conservation zones of high tree diversity at Majel a.