基于无人机遥感影像的高精度森林资源调查系统设计与试验

为了实现林业的可持续发展,满足当今森林资源的精准化监测和信息化管理,该文以无人机航拍影像为数据基础,充分结合摄影测量技术、无人机影像后处理技术、地理信息系统技术和林业资源调查管理技术,构建了适用于林业调查和管理的专业森林资源调查系统。该系统以C#为编程语言,结合ArcGIS Engine10.2嵌入式组件技术开发而成,利用无人机影像实现高效快捷的林地空间区划、面积平差和高精度大比例尺的森林小班调查、信息提取等功能,可实现资源数据库的及时更新,极大地缩短了传统调查模式的调查周期,实现了森林资源的科学化管理。以辽宁老秃顶子林场作为试验区,利用1st Opt优化分析软件引入决定系数、估计值的标准差等评定因子,确定试验区冠径、树高、胸径之间的最优模型。同时基于试验区获取数据对系统进行了精度验证,结果表明,该系统获取坡度和高程的相对误差分别为5.17%和5.41%,株树密度、蓄积量的相对误差为2.68%和4.01%。     

Tree species-mediated spatial patchiness of the composition of microbial community and physicochemical properties in the topsoils of a tropical montane forest

To evaluate the importance of plant-soil feedbacks in forest ecosystems, it is fundamental to understand the spatial range within which plant species control soil physicochemical and microbial properties. We investigated the spatial pattern of soil properties associated with canopy trees in a tropical montane forest on Mt. Kianbalu, Borneo. We analyzed soil physicochemical properties and microbial communities (biomarker lipid abundance) as a function of soil depth and distance from the tree trunk of a conifer (Dacrydium gracilis) or a broadleaf tree (Lithocarpus clementianus). The concentration of condensed tannins and fungi-to-bacteria were higher beneath Dacrydium than beneath Lithocarpus. Furthermore, carbon-degrading enzyme activities were lower beneath Dacrydium. These effects of the tree species were more distinct on soil properties beneath the tree crown than on those outside the tree crown. These effects appeared to be largely due to differences in litter chemistry, and the distinct set of soil properties formed corresponding to the above canopy crown. In conclusion, the species-rich forest on the tropical mountain contains spatially distinct units of soil properties associated with canopy trees, and this spatial pattern can influence ecosystem dynamics in the forest through plant-soil feedback effects.     

Forest fragmentation and the distribution, abundance and conservation of the Tana river red colobus (Procolobus rufomitratus)

Evidence suggests that habitat heterogeneity, disturbance, disease, predation and food resources influence primate population abundance. However, few studies have focused on what habitat factors determine the probability that a primate species will occur in a habitat fragment. We analysed forest habitat and colobus population attributes to determine factors that influenced occurrence and abundance of the critically endangered Tana River red colobus. The probability of colobus inhabiting forests was positively related to the relative amount of habitat edge and canopy tree species composition. Most of the variance in the density of colobus monkeys was explained by basal area of food trees (per ha), basal area per food tree, density of food trees, and basal area per tree for all trees. We conclude that effective conservation of primates in fragmented habitats may require strategies that consider factors that influence both the occurrence of a species and its relative abundance.     

晋西黄土区刺槐林种植密度对植被生长状况的影响

通过对山西省方山县土桥沟流域刺槐人工林植被生长指标的比较研究,分析了不同密度刺槐人工林的生长状况,以期为该区刺槐人工林的经营管理提供理论依据和技术支持.研究结果表明,同是林龄为20 a的刺槐人工林,高密度林分内林木的树高、冠幅等生长指标值,均比低密度林分内的低,但郁闭度要比低密度林分高;密度大的林分胸径普遍较小,随着林分密度的降低,胸径逐渐增大.刺槐林下灌木层和草本层植被的平均高度、盖度、生物量、物种丰富度都随着林分密度的降低而升高;各林分林下植被层的含水量也存在着随林分密度的降低而升高的趋势.从人工林的生长状况来看,晋西半干旱黄土丘陵沟壑区刺槐人工林的适宜密度为1667株/hm2.     

黄前水库上游生态修复区典型植被林冠层水文效应

利用森林水文与水量平衡原理,采用固定标准地方法,对山东省泰安市黄前水库上游水土保持生态修复区典型植被类型的林冠层水文效应进行了研究。结果表明:①在P=18 mm的降雨条件下,生态修复区内不同树种林冠对降雨截留量的排序为油松>赤松>侧柏>麻栎>刺槐,树干径流量和林内穿透雨量没有发现有类似的规律,针叶林比阔叶林的林冠截留量大。②不同造林密度对林冠截留量的影响总体趋势为造林密度越大林冠截留量越多,反之林冠截留量就越少;林内穿透雨量与林冠截留量的变化规律相反。③不同郁闭度林分与不同造林密度的林分对降雨的再分配规律相同。④不同混交方式的林分对降雨的截留量排序为松刺栎混交>油松>松栎混交>松刺混交>麻栎>刺槐;树干径流量和林内穿透雨量的规律不明显。⑤生态修复区内典型植被林冠截留量在降雨量较小时(P=4.50 mm)截留作用很明显,林冠截留率较大;但随着雨量增加,树干径流量逐渐增大,林冠截留率呈减小趋势。     

基于苹果树冠层计盒维数的光照分布预测

果园精细管理中,苹果树冠层结构决定了叶幕期光照分布情况,而叶幕期光照分布又是关系到果实产量和质量的重要因素之一。该文以纺锤体苹果树为研究对象,提出了基于苹果树冠层计盒维数的光照分布预测方法。在冠层尺度内,按照网格法划分休眠期苹果树冠层三维点云数据,通过分析该数据构成的果树冠层空间结构,提出用计盒维数量化果树冠层结构的方法;通过分析休眠期冠层结构特征和叶幕期冠层相对光照分布特点,研究了休眠期苹果树三维冠层网格空间计盒维数与叶幕期冠层光照空间分布之间的关系,预测了叶幕成形期苹果树冠层光照分布。通过连续3 a的数据分析,叶幕期苹果树冠层阳面光照分布平均预测精度为76.11%,阴面平均光照分布预测精度为74.10%,该方法可为苹果树自动化修剪合理性评判提供技术支持。     

无人机机载激光雷达提取果树单木树冠信息

定株管理是未来果园精准生产管理的趋势,果树单木树冠信息的提取是定株管理的关键。该研究利用无人机采集的苹果园激光探测与测量数据（Light Detection and Ranging,LiDAR）检测和测量每棵果树的树冠面积和树冠直径,并评价空间分辨率对于果树单木树冠检测与提取的影响。该方法主要包括使用反距离权重插值法间接生成冠层高度模型（Canopy Height Model,CHM）;使用局部极大值滤波算法和标记控制分水岭分割算法（Marked-Controlled Watered Segmentation,MCWS）对果树进行单木树冠检测与提取,通过与参考数据的比较,评估了该方法的精度,并定量分析了空间分辨率对于单木树冠检测与信息提取结果的敏感性。结果表明,该方法有效地实现果树单木树冠检测与信息提取,代表果树检测精度的F1得分为94.86%,树冠轮廓提取准确率为86.39%,树冠面积的提取数据集和参考数据集的线性拟合结果决定系数和归一化均方根误差分别为0.81和20.56%,树冠直径的提取数据集和参考数据集的线性拟合结果决定系数和归一化均方根误差分别为0.85和14.79%,树冠面积和直径不同程度地被高估。此外,冠层高度模型的空间分辨率接近果树平均树冠直径的1/10时精度最高,可以有效检测果树单木树冠及提取树冠轮廓,从而准确提取果树单木树冠信息。     

华北山地6种天然次生林土壤氮素的空间异质性特征

 利用地统计学理论和方法研究华北山地次生林区6种天然次生林土壤氮素的空间异质性特征。结果表明:1)次生阔叶林土壤总氮质量分数相对较高（3 1004 500 mg/kg）,而针叶林相对较低（9001 300 mg/kg）,各森林类型土壤中有效NH4+-N质量分数均高于有效NO3--N,形成以NH4+-N占优势的氮营养生境;2)针阔混交林中,土壤全氮的变异强度最大,变异的空间相关性较差（随机性变异占总变异的42.7%）,针叶林中,全氮空间变异强度相对较弱,但以自相关变异为主（结构方差比为72.2%81.0%）,呈现弱的斑块分布特征;3)阔叶林中,NH4+-N具有很强的空间自相关变异,NO3--N异质性程度相对较弱,针叶林中,NH4+-N变异强度较小,而NO3--N空间变异却相对明显;4)不同森林类型对土壤全氮及各有效氮形态的空间异质性特征有影响;5)植被种类、植被组成、植被多样性等因素的差异及由此导致的树种空间分布格局是影响总氮量及氮矿化,进而导致氮素不同形态在林分间甚至林分内不同空间样点间异质性形成的重要原因。     

基于地表数码照相的林地总体植被覆盖度计算模型

Vegetation fractional coverage (VFC) is one of the key indicators of vegetation distribution. In the work a measurement-based model was developed to derive total forest VFC (TG) as well as the VFC of trees (T) and shrub-grasses (G) separately in a subtropical forest area in Nanjing, China. Both upward and downward photographs were taken with a digital camera in 72 quadrats (10 m × 10 m each). Fifteen models were established and validated. Models jointly using both T and G performed better than those using the T and G separately. The best model, TG = T + G- 1.134 × T × G- 0.025 (R2 = 0.9115, P 0.01, root mean squared error = 0.0789), is recommended for application. This model provides a good way to obtain total forest VFC values through taking tree and shrub-grass photos on ground below tree canopy rather than above tree canopy.     

Spatial variability of photosynthetically active radiation in European beech and Norway spruce

The vertical and horizontal variability of solar radiation within a mature European beech (Fagus sylvatica L.)-Norway spruce (Picea abies [L.] Karst) mixed stand in Southern Germany is investigated. A large dataset with more than one million spectral measurements of photon fluence rates at six vertical levels within the stand is analyzed with respect to tree species, meteorological sky conditions, and the influence of solar elevation angle on canopy penetration. Irradiance probability density functions of the photosynthetically active waveband are used to describe the three-dimensional radiation field. For a quantification of umbra, penumbra, and sunfleck frequencies, in-canopy fractions of photon fluence rates within the photosynthetically active waveband are investigated. Different phenological stages of beech and their effects on the in-canopy light climate are compared. The results show that during overcast conditions (OVC) fractions of photosynthetically active radiation (PAR) are higher at all canopy levels than during clear sky (CS) conditions due to their exclusively diffuse character. The lowest median PAR level of less than 1% of above-canopy PAR can be observed in the shade crown of beech and at ground level. More PAR can penetrate the canopy at a higher solar elevation under CS conditions. This effect is more pronounced for spruce than for beech due to the conical crown shape of the conifers that allows photons from higher angles to enter the gaps inbetween trees in contrast to the more homogeneously closed beech canopy. Solar elevation is not an important factor at uniformly overcast conditions. Differences in the vertical distribution of umbra and penumbra can be detected when comparing species or different sky conditions. The frequency of sunflecks differs more by species and by the vertical position within the canopy than by sky condition.     

采用水平集方法的无人机可见光DOM树冠分割

在天然林、混交林、复层林等复杂林分条件下,可见光森林影像受林分郁闭度、冠层结构、摄影季节等影响较大,对其进行树冠提取时,现有方法无法保证精度且缺乏有效的人工介入机制.该研究探索了一种能够在低郁闭度时自动分割,高郁闭度时可适当人工介入的树冠分割方法.先将无人机可见光森林影像处理成数字地表模型(Digital Surfac...     

Variabilität der Sulfatsorption in einem Gley-Podsol aus Sand unter Kiefernforst

Variability of sulfate sorption in a sandy Gleyic Podzol under a pine stand In acid forest soils sulfate can be stored by sorption processes. We studied the vertical heterogeneity and the horizontal variability of sulfate sorption in a sandy forest soil under a pine stand. Disturbed soil samples were taken from the horizons of a Gleyic Podzol (vertical heterogeneity). From a 120-m transect, 25 soil samples were taken from depth increment 35—50 cm and 65—80 cm at 5-m intervals by means of a hand auger (horizontal variability). In batch experiments, sulfate sorption isotherms were measured for all profile and transect samples. The Freundlich equation is suitable to describe the individual isotherms. The sulfate sorption isotherms show considerable differences in the horizons of the profile, systematic relations between the isotherm parameters and soil properties are not obvious. In order to quantify the spatial variability of the sulfate sorption isotherms, a scaling technique is used. The spatial distribution of scale factors for depth 35—50 cm along the transect reveals a periodicity of about 17 m length. The same recurrent pattern is also identified in the spatial distribution of the cumulative sulfate deposition by canopy throughfall along the transect, and in the spatial distribution of contents of iron and aluminium oxides soluble in oxalic acid at depth level 35—50 cm. This does, however, not refer to organic carbon content and pH at this depth. From these results it is concluded that in this soil at depth 35—50 cm oxide contents are related to the amount of sulfate deposition by throughfall. In spatial ranges with high sulfate and thus acid deposition, oxide contents of the soil are decreased by accelerated podzolization, and therefore, also the sulfate sorption of the soil is low in these ranges. The period length of this recurrent pattern of about 17 m is probably only an apparent period length that results from aliasing, because a very probably real periodicity of 3—4 m length, related to the canopy edge distribution of the pine trees along the transect, is sampled at an interval of 5 m. In the subsoil (65—80 cm depth) such relations could not be detected.     

利用轻小型飞机遥感数据建立人工林特征参数模型

目前获取森林特征参数的主要方法是外业测量,工作量大、效率低。该文以中国自主研发的轻小型航空遥感系统为数据获取工具,以油松人工林为研究对象,通过对获取森林的激光雷达（light detection and ranging,LIDAR）点云数据去噪,分类,提取等过程获得单木的树高数据,对获取的航空影像数据进行预处理,匹配,拼接,分割及冠幅提取获得单木的冠幅数据,再与外业抽样调查的单木的树高、胸径建立回归模型,同时验证模型精度。试验结果表明：通过LIDAR点云数据提取的树高与实测的树高具有极显著的相关性,所建立的模型预测精度达97.5%,通过影像提取的冠幅与实测的胸径也具有极显著的相关性,预测精度达91.6%,基本上能够满足林业生产的要求。     

Modeling Clustered Survival Times of Loblolly Pine with Time-dependent Covariates and Shared Frailties

Tree mortality is an important component of forest tree and stand growth models, which provide decision support for forest managers. Mortality patterns, however, are highly variable and difficult to describe. Despite numerous investigations aimed at developing tree survival models, there are still important gaps that need to be filled. This paper used a large-scale repeated measure dataset collected from permanent sample plots established in 1980/81 across the natural range of loblolly pine (Pinus taeda L.) in the Piedmont, Atlantic Coastal Plain and Gulf Coastal Plain physiographic regions of the US. The primary objective of this study was to explain the survival of loblolly pine trees using time-varying covariates such as diameter at breast height, total tree height, crown ratio, stand age, stand basal area, and dominant height. In this paper, individual-tree mortality was described using a semiparametric proportional hazards regression model. Shared frailty models were used to account for unobserved heterogeneity not explained by the observed covariates. Our investigation involved developing a modeling comparison procedure, predicting mortality based on a frailty model, and quantifying the predictive ability for tree mortality. The survival model developed using a large scale database provides further understanding of mortality trends in planted stands of loblolly pine. The survival model will enable forest managers to more accurately specify initial planting density, thinning schedules, and other management interventions.     

Seeing the forest for the deer: Do reductions in deer-disturbance lead to forest recovery?

High levels of deer browsing can prevent canopy tree regeneration, but little is known about changes to forest size-structure following long-term deer herd reductions. We monitored changes in forest stand structure and composition in southwestern Ontario, Canada, over 28-years using permanent plots. Our study site was the largest remaining tract of Carolinian (deciduous) forest in Canada (11 km²), a habitat type that contains up to a fifth of Canada’s species at risk and is under intense anthropogenic pressures. We recorded declines in all tree size classes between 1981 and 1996, during which densities of white-tailed deer (Odocoileus virginianus) reached a peak of 55 deer km⁻². Despite significant and sustained deer herd reductions between 1996 and 2009, which reduced deer densities to 7 deer km⁻², there was limited recruitment of small trees and declines in basal area of tree species that were sensitive to deer browsing. Our results suggest that recovery from herbivory is a protracted process during which canopy tree regeneration may continue to decline despite a reduction in browsing pressure due to deer culling. Large declines in canopy-tree densities in Carolinian forests may lead to forest size-structures and herbaceous plant communities that resemble rare oak savanna habitat, creating difficult decisions for conservation managers aiming to protect rare and endangered species within native ecosystems. We recommend that managers protect Carolinian forest stands and encourage canopy tree regeneration by increasing seed sources of native trees. While deer control is essential in reducing forest damage, our results highlight the need to explore other forms of active management to expedite otherwise slow increases in tree density.     

基于无人机平台的柑橘树冠信息提取

为了快速获取柑橘树冠信息,提升柑橘园精准管理,该研究基于无人机平台获取了柑橘数码和多光谱影像,分析了无人机影像反演柑橘树冠信息的效果。首先利用无人机数码影像及分水岭算法进行柑橘单木分割,然后构建柑橘树冠层高度模型,提取柑橘株数、株高、冠幅投影面积等结构参数信息,进而利用无人机多光谱影像获取柑橘的8种常用植被指数,采用全子集分析法筛选柑橘冠层氮素含量的敏感植被指数,构建基于多元线性回归的冠层氮素遥感反演模型,进行以冠幅为基本单元的柑橘树冠层氮素含量遥感制图。研究结果表明:柑橘的单木识别准确率在93%以上,召回率在95%以上,平均F值为96.52%;柑橘树的反演株高与实测株高具有较强的相关性,决定系数R2为0.87,均方根误差为31.9cm;单株冠幅投影面积与人工绘制的冠幅面积的决定系数,除果园A在12月的结果较低(R2为0.78)外,其余均在0.94及以上;采用全子集分析法筛选的柑橘冠层氮素敏感植被指数为归一化植被指数(NDVI)、绿色归一化植被指数和冠层结构不敏感指数,所建立的多元回归模型的决定系数R2达0.82,均方根误差为0.22%,相对误差为6.59%。综上,无人机影像在柑橘树冠参数信息提取方面具有较好的应用效果,能够快速有效地提取柑橘树冠参数信息。该研究可为使用无人机平台进行果园精准管理提供技术支撑。     

Influence of single trees on spatial and temporal patterns of belowground properties in native pine forest

Linkages between forest dynamics and ecosystem processes are poorly understood and this limits our ability to adequately estimate future changes in forest ecosystems due to human-induced global change. In particular at the single tree level, our understanding of temporal and spatial changes of belowground properties during forest succession is limited. Thus, our aim was to test whether we find a spatial and temporal gradient in nutrient availability and an associated shift in microbial community structure with increasing distance and age of single trees. We found that inorganic nitrogen was less available below the crown of single trees, while soluble organic carbon (DOC) was much more abundant, in particular in the inner zone of influence, i.e. close to the stem. The fungal:bacterial PLFA ratio was greater while microbial biomass carbon (MicC) was lower below the tree crown, indicating a strong influence of trees on spatial patterns of microbial biomass and community structure. Moreover, the positive correlation between MicC and total extractable N, and the negative correlation between fungal:bacterial biomass and δ¹⁵N, suggested that the microbial biomass was N limited below the tree crown and as a consequence nutrient cycling was presumably decelerated compared to open conditions. We also found a temporal pattern of increasing surface soil C and N content with increasing tree age (up to 250 years), underlining the significant role of single trees in creating spatial and temporal heterogeneity in forests.     

贵州省喀斯特阔叶林降雨截留分配特征

[目的]对贵州省喀斯特阔叶林降雨截留分配特征进行研究,为喀斯特地区水土保持和森林生态功能分析提供参考。[方法]以贵州喀斯特阔叶林的降雨分配特征为研究对象,利用2015年9月至2016年3月间野外实测的25场降水数据对森林林冠层、灌木层的降雨截留分配特征进行研究。[结果]观测期内降雨以小雨和中雨为主,降雨总量为208.25mm;树干流总量为21.83mm,占降雨总量的10.48%,变化范围为0~14.3%;林间穿透雨总量为186.89mm,占降雨总量的89.7%。灌木层截留总量为34.86mm,占降雨总量的16.74%;林冠截留的总量为22.58mm,占同期降雨的10.84%。当林外降雨量大于1.15mm时,研究区内开始产生树干流,且树干流与林外降雨量呈线性正相关关系;灌木截留量随着降雨量的增大而增大,但林冠层截留率与降雨量之间没有明显的相关关系。[结论]喀斯特阔叶林对降雨具有较强的截留和再分配作用,对区域水量平衡和水土保持具有重要影响。     

我国4种主要苹果树形冠层结构和辐射三维分布比较研究

树体结构和辐射分布是影响果树冠层光合生产力和果实产量品质的主要因素。本文以"富士"苹果(Malus domestica Borkh.cv.‘Fuji’)为试材,采用田间调查方法,系统研究了我国苹果生产中4种主要树形的树体结构参数以及叶面积密度(LAD)和光合有效辐射(PAR)的三维分布特征。结果表明,开心形树冠的枝量(894×103·hm-2)和叶面积指数(LAI,2.53)最小,其他3种树形中小冠疏层形分别为2 280×103·hm-2、4.14,疏散分层形分别为2 119×103·hm-2、3.98,纺锤形分别为2 190×103·hm-2、3.88。不同树形LAD三维分布各不相同,小冠疏层形苹果树的叶片主要分布在树冠的0.5~1.5 m之间,疏散分层形和纺锤形主要分布在0.5~2.0 m之间,开心形主要分布在1.0~2.0 m之间。通过对不同树形LAD和PAR三维分布比较发现,每种树形的PAR都随树冠深度的增加而降低,在树冠中部LAD最大部位辐射消减最快,PAR的三维分布主要与叶片分布有关。其中开心形树冠的平均PAR最高,分布最均匀。4种树冠内叶片得到的平均相对PAR小冠疏层形为24.85%,疏散分层形为28.84%,纺锤形为27.71%,开心形为37.28%。开心形树冠内低光区的叶片所占比例只有35%,其他树形都超过50%。研究表明,不同相对PAR范围内的叶片比例能够更好地反映果树冠层的辐射情况,开心形树冠在辐射分布上优于其他3种树形。     

长沙地区樟树林穿透水空间变异及稳定同位素特征

于2018年4月至2019年3月在长沙地区典型樟树林收集降水、穿透水和相应的冠层信息,分析穿透水量的空间变异及穿透水稳定同位素的特征,旨在揭示林冠层水文过程,为林地水文生态系统的科学管理提供参考。结果表明:樟树林下总穿透水量为340.1 mm,占林外总降水量的71.2%;受观测点距树干距离和冠层叶面积指数等因素的综合影响,穿透水量具有较大的空间变异,且在时间变化上相对稳定。分析表明,研究区穿透水量的空间变异系数随降水量增加而减小,体现了降水特征对穿透水空间变异的重要影响;相对穿透水量而言,穿透水稳定同位素组成受冠层结构和大气条件的影响较小,其空间变异较小,在时间变化上不稳定;大部分降水事件中穿透水稳定同位素较降水稳定同位素富集,但其平均值之间不具有显著性差异,说明穿透水在形成过程中经历了较弱的蒸发作用;穿透水与降水中稳定同位素和过量氘的偏离还暗示了冠层具有选择性穿透效应。