共查询到20条相似文献，搜索用时 15 毫秒
1.
The application of detailed models of canopy photosynthesis rely on the estimation of attenuation of light in the canopy. This attenuation is readily estimated with the Lambert-Beer law when the canopy is homogeneous. In reality, forest canopies are far from homogeneous, and this has led to the use of detailed light extinction models that account for grouping of foliage between and within trees. Because such models require detailed parameterization and fine resolution inputs, they are impractical in larger-scale applications. Thus, there is interest in simplified models that can be readily parameterized. We developed two equations that can be used to estimate mean annual light interception by single unshaded trees and by stands of Poisson distributed trees. Interception by single trees is a function of crown surface area, the ratio of leaf area to crown surface area, the extinction coefficient in a homogeneous canopy--which can be determined separately--and one empirical parameter that depends on the mean solar angle. The summary model was tested against a detailed model of interception, and showed good agreement, although with slight bias. The results showed that crown surface area is a good summary variable for crown size and shape, because errors are independent of crown shape (ellipsoids, cones and height:width ratios). We also tested whether canopy photosynthesis is proportional to light interception across canopies differing in structure and leaf area index, and found that light-use efficiency is influenced by canopy structure. The model is useful in larger-scale applications because it can be parameterized with available data without the need for additional empirical parameters. It can also be used to study the effect of stand structure on mean annual light interception and productivity. 相似文献
2.
[目的]基于华北石质山区侧柏人工林2014年(3—10月)降水数据进行量化分析,探究其降水的再分配规律。[方法]采用野外定位研究方法,对不同结构(郁闭度、枝下高)侧柏人工林林冠层降水再分配特征进行分析。[结果](1)1/2枝下高0.4、0.6、0.8郁闭度林内穿透雨总量分别为181.1、168.1、147.1 mm,穿透雨率分别为78.8%、73.1%、64.0%;树干径流总量分别为6.0、5.9、3.9 mm;总树干径流率分别为4.2%、2.6%、1.7%;林冠截留总量分别为39.5、56.1、79.1 mm;林冠截留率分别为17.2%、24.4%、34.4%。(2)1/3枝下高0.4、0.6、0.8郁闭度林内穿透雨总量分别为175.6、154.8、136.0 mm,穿透雨率分别为76.4%、67.3%和59.2%,树干径流总量分别为8.3、4.9、3.3 mm,总树干径流率分别为3.6%、2.1%和1.4%,林冠截留总量分别为46.3、70.4、90.7 mm,林冠截留率分别为20.1%、30.6%和39.5%。[结论](1)侧柏人工林同一枝下高不同郁闭度林分林内穿透雨量差异不显著。2种枝下高郁闭度为0.4和0.8之间的树干径流量均存在显著差异,郁闭度0.4和0.6以及0.6和0.8之间差异不显著。(2)郁闭度为0.4、0.6、0.8时,冠厚占树高2/3(即枝下高为1/3)的林分林冠截留量分别是1/2的1.17、1.25和1.14倍。(3)2种枝下高各自不同郁闭度间林冠截留量均存在显著差异。(4)同等降雨量情况下雨强越大,林冠截留量越小;2次降雨间隔时间越长,林冠层越干燥,林冠截留能力越强;枝下高越低(即冠层厚度越大),林冠截留量越大,且随着郁闭度的增加,林冠截留量逐渐增大。 相似文献
3.
Zebin Liu Yanhui Wang Ao Tian Yu Liu Ashley A. Webb Yarui Wang Haijun Zuo Pengtao Yu Wei Xiong Lihong Xu 《林业研究》2018,29(1):187-198
Canopy interception is a significant proportion of incident rainfall and evapotranspiration of forest ecosystems. Hence, identifying its magnitude is vital for studies of eco-hydrological processes and hydrological impact evaluation. In this study, throughfall, stemflow and interception were measured in a pure Larix principis-rupprechtii Mayr.(larch) plantation in the Liupan Mountains of northwestern China during the growing season(May–October) of 2015, and simulated using a revised Gash model. During the study period, the total precipitation was499.0 mm; corresponding total throughfall, stemflow and canopy interception were 410.3, 2.0 and 86.7 mm,accounting for 82.2, 0.4 and 17.4% of the total precipitation, respectively. With increasing rainfall, the canopy interception ratio of individual rainfall events decreased initially and then tended to stabilize. Within the study period, the simulated total canopy interception, throughfall and stemflow were 2.2 mm lower, 2.5 mm higher and0.3 mm lower than their measured values, with a relative error of 2.5, 0.6 and 15.0%, respectively. As quantified by the model, canopy interception loss(79%) mainly consisted of interception caused by canopy adsorption, while the proportions of additional interception and trunk interception were small. The revised Gash model was highly sensitive to the parameter of canopy storage capacity,followed by the parameters of canopy density and mean rainfall intensity, but less sensitive to the parameters of mean evaporation rate, trunk storage capacity, and stemflow ratio. The revised Gash model satisfactorily simulated the total canopy interception of the larch plantation within the growing season but was less accurate for some individual rainfall events, indicating that some flaws exist in the model structure. Further measures to improve the model's ability in simulating the interception of individual rainfall events were suggested. 相似文献
4.
应用ArcGIS判读2012年上海的遥感影像,分析上海浦西外环线内建成区(360 km2)树冠覆盖特征;判读样方218个、面积3 420 hm2,占研究区的9.5%。结果表明,现有树冠覆盖总面积为8 241.82 hm2、树冠覆盖率22.89%。浦西建成区内55所公园的平均覆盖率为53.72%;不同功能区的树冠覆盖率有显著差异,其中公园最高(53.72%),其次是外环林带(50.72%)、一般绿地(34.60%)、校园(24.13%),住宅最低(21.87%)。按树冠覆盖估算,研究区共有乔木810万余株,潜在的树冠覆盖率可达24.56%~25.67%,至少可增植乔木60万株。
相似文献
5.
6.
Yi-Chung Wang Jiunn-Cheng Lin Wan-Yu Liu Chi-Chwen Lin Shu-Hsin Ko 《Journal of Forest Research》2016,21(6):261-270
This study conducts a survey on the urban forest parks in Taiwan to assess the benefits and affecting factors. The results show that the larger the area of the park, the higher the degree of satisfaction with the landscape and the status of the plants, and the higher the density of trees, the lower the degree of satisfaction with the scenic view. The shading effect is positively correlated with the diameter of plants at breast height, canopy cover area, and proportion of green coverage. However, higher green coverage is associated with lower satisfaction regarding the scenic view and the uniqueness of the landscape. Most visitors are less satisfied with the area of plants and landscape attractiveness. The study results can be used to evaluate the impacts of setting up urban forest parks. The outcomes also provide guidance for the relevant authorities for sustainable management and future policy making. 相似文献
7.
上海植物园典型群落景观美景度评价 总被引：1，自引：0，他引：1
在全面调查上海植物园植物群落的基础上,采用美景度评判法(SBE)对33个典型群落进行美学价值评价,结果表明其美景度值为-1.38~1.37。得分值≥ 0的有16个群落,其建群树种几乎全为落叶阔叶树、且多为3层结构,得分较高的群落建群树种主要包括栾树、旱柳、乌桕、香樟、银杏、柿树、合欢等,下层以彩叶或观花树种如红花檵木、海棠、杜鹃、日本晚樱、八仙花等为主。影响群落景观美学特点的因素主要有树种组成、色彩、垂直结构、群落与周围环境的协调度、树木的健康状况及林冠线变化度等。植物园的植物群落美景度评价是构建城市绿地群落的重要参考。
相似文献
8.
9.
10.
在广州市天河区、越秀区、荔湾区、番禺区、海珠区等地选定46块面积为400 m2的标准地进行城市绿地调查,主要调查样地实际用途、样地地面覆盖信息,乔木树高、胸径、冠下高、冠幅、生长状况(包括主要病虫害)等信息,并对各样地及乔木调查数据进行分析。结果表明,46块样地共有乔木408株,涉及树种64种;应用频率较高的3个树种依次为小叶榕、垂叶榕、高山榕,其应用频率总和占总频率的67.5%;小叶榕、白兰、樟树、塞楝、红花羊蹄甲等乔木长势较好,其他树种长势一般;道路绿地树种长势较好,城市公园其次,街头绿地次之。 相似文献
11.
The process of rainfall interception by an inhomogeneous forest canopy composed of tree crowns with some gaps among them were
considered, and the previous theoretical models of rainfall interception were modified to model an inhomogeneous canopy instead
of a statistically homogeneous canopy. The paper deals with the following. First, the process of rainfall interception in
tree crowns and that of rainfall in the gaps among them are studied respectively to acquire the average rainfall interception
of a forest canopy. Based on the model derived by Liu (1987) and setting the canopy density value, both the relevant partial
equations and a formula to estimate rainfall interception were derived. Moreover, the new model was solved through a numerical
method and was illustrated with typical values of some ecological factors; three groups of curves were acquired by calculation
with the VisualBasic program. A model of rainfall interception by an inhomogeneous forest canopy is classified as a multi-layer
model, which is different from previous models (models where all the parameters represent the whole canopy). The results from
the model in this paper could be used to determine the relationship between interception and each ecological factor in detail.
__________
Translated from Scientia Silvae Sinicae, 2007, 43(3): 8–14 [译自: 林业科学] 相似文献
12.
To quantify the effects of crown thinning on the water balance and growth of the stand and to analyze the ecophysiological modifications induced by canopy opening on individual tree water relations, we conducted a thinning experiment in a 43-year-old Quercus petraea stand by removing trees from the upper canopy level. Soil water content, rainfall interception, sap flow, leaf water potential and stomatal conductance were monitored for two seasons following thinning. Seasonal time courses of leaf area index (LAI) and girth increment were also measured. Predawn leaf water potential was significantly higher in trees in the thinned stand than in the closed stand, as a consequence of higher relative extractable water in the soil. The improvement in water availability in the thinned stand resulted from decreases in both interception and transpiration. From Year 1 to Year 2, an increase in transpiration was observed in the thinned stand without any modification in LAI, whereas changes in transpiration in the closed stand were accompanied by variations in LAI. The different behaviors of the closed and open canopies were interpreted in terms of coupling to the atmosphere. Thinning increased inter-tree variability in sap flow density, which was closely related to a leaf area competition index. Stomatal conductance varied little inside the crown and differences in stomatal conductance between the treatments appeared only during a water shortage and affected mainly the closed stand. Thinning enhanced tree growth as a result of a longer growing period due to the absence of summer drought and higher rates of growth. Suppressed and dominant trees benefited more from thinning than trees in the codominant classes. 相似文献
13.
Several previous studies in Japan have examined differences in rainfall interception amounts induced by differences in forest properties by comparing the annual rainfall interception ratios (annual rainfall interception divided by annual rainfall) from various sites without considering variations in meteorological conditions between sites. Rainfall interception actually depends on meteorological conditions as well as forest properties. This study examined variations in the annual interception ratio relating to the variation in annual rainfall, which would be the primary factor relating to the interception ratio, across Japan with the use of a rainfall interception model assuming the same forest properties (i.e., the canopy storage capacity, canopy closure, leaf area index (LAI), and the bulk coefficient for sensible heat transfer). The ratio ranged between 0.12 and 0.24 across Japan and was highly correlated to annual rainfall. This indicates that considering the variation in annual rainfall is critical for assessing the difference in rainfall interception amounts induced by forest properties. We reconsidered the results of previous studies in Japan that compared annual interception ratios between sites with different forest properties: (i) there is no clear difference in interception amounts between broadleaf and coniferous forests and (ii) there is a positive correlation in stem density and interception amounts for coniferous forests. These results still held when considering differences in annual rainfall between sites. 相似文献
14.
森林乔木冠层雨水再分配特征及机制研究综述 总被引：3，自引：0，他引：3
森林乔木冠层对降雨的再分配具有重要的水文生态意义,有助于定量评价不同区域、尺度、类型的森林冠层雨水利用效率,可为深入研究森林冠层变化对区域水分循环的调节作用提供科学依据。文中从森林冠层雨水截留、林内穿透雨、树干茎流和林下凋落物截留4个方面评述了近20年来国内外对森林乔木冠层影响雨水再分配的研究最新进展。研究认为,由于森林冠层雨水再分配的生态机理仍未明晰,因此建立精确度高的截留模型仍将作为此类研究的重难点之一;引入激光雷达技术获得森林冠层三维结构,以及多角度、多通道的多种传感器观测垂直空间多层次的森林冠层雨水再利用规律将会成为未来的研究方向之一;目前林冠雨水截留研究缺乏其与区域水文变化之间的关联性研究,将林冠雨水再分配研究的成果转化为区域水文问题的解决方案也将会是未来研究的趋势之一。 相似文献
15.
The planting site, size, and health condition of street tree Ginkgo biloba in Beijing urban area were investigated and the influence factors were analyzed based on filed survey. The results showed that G. biloba were mainly planted in tree pit within strip planting median. The average height, diameter at breast height and canopy diameter were 8.11 m, 13.22 cm and 4.07 m, respectively, 82.9% trees were less than 10 m in height, and most G. biloba trees were still in the initial stage of height and diameter increment. The tree health status was described with three classes: class I (healthy), class II (fair) and class III (unhealthy). The percentage of class I, II and III for G. biloba trees in Beijing urban area accounted for 16.0%, 37.2% and 42.9% respectively. The results of analysis showed that the health status of G. biloba was associated with the site condition, tree size and management practices. The trees planted in urban forest patch grew better than the trees planted in green belts and tree pits; meanwhile, the bigger trees were healthier than the smaller ones. In addition, the effects of urban heterogeneous environment and human activities on the health of Ginkgo biloba were analyzed and the suggestions on management were launched. 相似文献
16.
Stand age is an important structural determinant of canopy transpiration (E(c)) and carbon gain. Another more functional parameter of forest structure is the leaf area/sapwood area relationship, A(L)/A(S), which changes with site conditions and has been used to estimate leaf area index of forest canopies. The interpretation of age-related changes in A(L)/A(S) and the question of how A(L)/A(S) is related to forest functions are of current interest because they may help to explain forest canopy fluxes and growth. We conducted studies in mature stands of Picea abies (L.) Karst. varying in age from 40 to 140 years, in tree density from 1680 to 320 trees ha(-1), and in tree height from 15 to 30 m. Structural parameters were measured by biomass harvests of individual trees and stand biometry. We estimated E(c) from scaled-up xylem sap flux of trees, and canopy-level fluxes were predicted by a three-dimensional microclimate and gas exchange model (STANDFLUX). In contrast to pine species, A(L)/A(S) of P. abies increased with stand age from 0.26 to 0.48 m(2) cm(-2). Agreement between E(c) derived from scaled-up sap flux and modeled canopy transpiration was obtained with the same parameterization of needle physiology independent of stand age. Reduced light interception per leaf area and, as a consequence, reductions in net canopy photosynthesis (A(c)), canopy conductance (g(c)) and E(c) were predicted by the model in the older stands. Seasonal water-use efficiency (WUE = A(c)/E(c)), derived from scaled-up sap flux and stem growth as well as from model simulation, declined with increasing A(L)/A(S) and stand age. Based on the different behavior of age-related A(L)/A(S) in Norway spruce stands compared with other tree species, we conclude that WUE rather than A(L)/A(S) could represent a common age-related property of all species. We also conclude that, in addition to hydraulic limitations reducing carbon gain in old stands, a functional change in A(L)/A(S) that is related to reduced light interception per leaf area provides another potential explanation for reduced carbon gain in old stands of P. abies, even when hydraulic constraints increase in response to changes in canopy architecture and aging. 相似文献
17.
彩叶树种以其丰富的色彩可较好地提高城镇绿地建设的品位,展现城镇园林绿地的景观多样性,因此,在园林绿化中的应用发展迅速.本文通过对景德镇市彩叶植物的种类及应用现状的调查,提出在今后的园林建设中应增加乡土彩叶植物的应用,扩大彩叶乔木树种的引种,并加强对彩叶树种的养护管理. 相似文献
18.
林冠截留模型 总被引：10，自引：0，他引：10
对林冠截留的研究已有近百年的历史。1971年,Rutter等人就推导出了一个具有清楚物理意义的林冠截留模型,结束了以往的林冠截留模型中只有统计模型的历史。1987年,刘家冈用数理方法,对林冠截留的时空演变过程作了很好的描述。但使用他们的模型对林冠截留进行估计时,需要同时对其它多个气象因子进行测定,而且人们普遍关心的不是林冠对次降雨截留的大小,而是林冠对降水的年截留量大小。 1979年,Gash用分析法代替了Rutter模型中的数值法,建立了截留模型,该模型能在只有降雨数据的情况下,对林冠的季节截留进行估计,结果与实测值接近。该模型将林冠截留分成两部分,即树冠截留和树干截留,因而引进了较多的参数。本文从林冠截留的过程出发,推导出一个有清楚物理意义,且含林冠和降雨参数较少的截留模型。 相似文献
19.
川西亚高山原始云杉林内降雨分配研究 总被引：17，自引：3，他引：17
穿透雨、茎流和林冠截留在森林生态系统水文循环和水量平衡中占有极其重要的地位 (VanDijketal .,2 0 0 1) ,因而从生理学、生态学和水文学的观点来看 ,研究一定区域内植被与降雨之间的相关性具有重要的意义 (Aboaletal .,1999)。川西亚高山针叶林处于我国东南半壁湿润地区与西北半壁干旱地区的过渡地带上 ,且多分布于江河上游 ,在涵养水源、保持水土、稳定河川流量、维护生态平衡等方面具有重要的地位 ,被誉为庇护四川及长江流域的“绿色万里长城”(杨玉坡 ,1990 )。马雪华 (1987)对米亚罗地区亚高山冷杉林的林冠截留做了一些初步的观测 … 相似文献
20.
东京城林业局森林水源涵养价值评估 总被引：1，自引：0，他引：1
徐衍武 《内蒙古林业调查设计》2014,(5):94-95
文章对东京城林业局森林从林冠截留降水量、枯枝落叶层的截留降水量和土壤蓄水量等3个方面,进行了森林水源涵养量的测算,同时,对森林水源涵养价值进行了测算。 相似文献