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1.
作物叶面积指数和倾角分布函数的一种推算方法   总被引:2,自引:1,他引:1  
设计了一种由作物冠层的辐射分布推算作物叶面积指数(LAI)和叶倾角分布函数的方法。根据作物冠层中太阳光斑密度与群体结构关系的数学表达式,LAI及其在各个叶倾角区间的分布可由不同太阳高度角时冠层内的光斑密度进行估计,而后者可通过观察冠层中的太阳总辐射和散射辐射的分布进行计算。因此,由容易测得的冠层总辐射的透过率,应用与多元回归分析类似的简单方法,就可以估算出难以趋势测量的LAI和叶倾角分布函数。用对  相似文献   

2.
日光温室黄瓜群体结构参数及群体内辐射分布分析   总被引:16,自引:3,他引:13       下载免费PDF全文
为研究作物群体结构与环境要素的关系,观测了日光温室内黄瓜不同生育时期的群体结构参数和群体内太阳总辐射的水平分布和垂直分布。发现叶面积指数、叶面积密度、叶倾角、叶方位角等结构要素在不同生育时期有明显的变化:随生育的进展,叶面积指数稳定增加,叶面积密度生育前期明显上升、后期有所下降,最大叶面积密度所在高度随黄瓜生长逐渐上移;叶倾角分布主要以水平叶为主;叶方位角以偏南居多,偏北叶所占比例较少;不同黄瓜品种间叶方位角和叶倾角也存在差异。这些变化与差异对黄瓜群体的辐射分布有重要影响,也直接影响群体叶的光合速率,此结果可为建立黄瓜群体辐射分布模型进一步优化日光温室结构,建立日光温室内作物生长模型、环境调节控制策略等提供理论依据,另外,对植株的调控技术(如整枝打杈技术等)也有一定的参考意义。  相似文献   

3.
农作物对紫外辐射(UV)的反射与吸收   总被引:6,自引:3,他引:3  
利用EPPLEY紫外辐射表(波长为295 ̄385nm)测量了4种作物对紫外辐射(UV)的反射与吸收。初步结果是:(1)作物对紫外辐射的反射率要比对太阳总辐射的反射率小得多。水稻、玉米、大豆和油菜对UV的反射率为1.8%、2.5%、2.8%和3.2%。(2)作物对UV的吸收随叶面积指数(LAI)增大而增大。(3)作物对UV反射率的日变程与对太阳总辐射反射率的日变程相似。  相似文献   

4.
日太阳总辐射推算模型   总被引:2,自引:0,他引:2  
为了推算广大无辐射观测地区的日太阳总辐射,需要根据有辐射观测地区的资料建立日太阳总辐射的推算模型。本文在深入了解国内太阳辐射观测与国内外太阳总辐射推算方法的基础上,设计了利用日照百分率、降水量与大气可降水量、温度日较差等因子推算日太阳总辐射的模型,选取武汉、宜昌、郑州2005年全年无加盖的、真实可信的太阳总辐射资料为样本序列,根据最小二乘法分别求出有日照和无日照两种情况下的模型参数,并对2005年进行了回代检验和2006年1-8月时段的独立样本检验。结果表明:模型推算序列与实际值序列的相关性均达到极显著程度,对2005-2006年8月推算的平均绝对误差和相对误差分别为1.31M J.m-2.d-1和9.5%,精度高,可以用于无辐射观测地区的日太阳总辐射的推算。  相似文献   

5.
基于夏玉米冠层内辐射分布的不同层叶面积指数模拟   总被引:2,自引:1,他引:1  
为了模拟夏玉米冠层内各层叶面积指数垂直分布,光合有效辐射(photosynthetically active radiation, PAR)是研究作物群体光合作用和长势的重要特征参数,阐明冠层内PAR的垂直分布规律与冠层结构等参数之间的相关关系,可为遥感定量反演冠层结构参数提供模型基础。该文基于PAR在冠层内的辐射传输规律结合冠层结构模拟不同太阳高度角的PAR透过率垂直分布模型,并用地面冠层分析仪测量值进行验证,结果表明模型对封垄前玉米抽雄期冠层内PAR透过率垂直分布模拟精度较高。通过不同太阳高度角PAR透过率的垂直分布模型结合消光系数运用不同算法分别反演层叶面积指数(leaf area index, LAI),并与不同高度层LAI实测值进行比较。结果显示:Bonhomme& Chartier算法反演不同高度层LAI精度较高,上层均方根误差(root mean square error,RMSE)为0.18,中层RMSE为0.55,下层RMSE为0.09。不同太阳高度角反演结果存在差异,30°和45°高度角均能较好地反演下层LAI,RMSE分别为0.11与0.09;30°高度角反演中层LAI精度较高,RMSE为0.30;45°高度角反演上层LAI精度较高,RMSE为0.18。结果表明基于不同太阳高度角构建的层LAI反演模型更适于实现夏玉米不同高度层LAI的遥感估算。该研究可为模拟垄行结构冠层内LAI垂直分布提供参考。  相似文献   

6.
根据光斑密度推算作物群体结构函数的一种方法   总被引:1,自引:0,他引:1  
叶面积指数LAI和叶倾角θ的概率密度函数g(θ)是难以直接测量而又十分重要的表征作物群体结构的参数.本文通过分析群体中光斑密度或直射光透过率T的数学表达式,从理论上导出了一种用容易测得的T值间接推算LAI和g(θ)的简单而实用的方法.  相似文献   

7.
基于机载激光雷达校正的ICESat/GLAS数据森林冠层高度估测   总被引:2,自引:1,他引:1  
针对星载激光雷达(geoscience laser altimeter system,GLAS)大光斑属性,该文提出了一种改进后的光斑尺度森林冠层高度估测方法,并分析了复杂地表对其估测精度的影响.首先,对机载lidar点云分类出地面点,并利用地面点对点云数据进行高度归一化处理,提取点云局部最大值得到光斑范围内机载lidar最大冠层高度;以机载lidar最大冠层高度作为模型参数拟合因变量,同时以坡度作为模型的输入变量,结合光斑大小和地表粗糙度,进行参数拟合,得到改进后光斑尺度森林冠层高度估测模型;最后,利用实测样地数据对冠层高度估测模型进行验证.结果表明:机载点云数据可以准确地反映光斑范围内森林冠层的分布,受到树种类型和点云密度的影响,不同森林类型的点云冠层分布存在明显差异.坡度等级直接影响GLAS光斑尺度森林冠层高度的估测精度,改进后的估测模型可以减小坡度对GLAS光斑森林冠层高度估测的影响,模型估测均方根误差(root mean square error,RMSE)稳定在3.26~3.88 m.样地Lorey's高与估测结果拟合度较好,相关系数r=0.66,不同森林类型光斑尺度冠层高度估测精度存在差异,混交林估测精度最高,r和RMSE分别为0.84和1.06 m.该方法可以有效减少地形条件对光斑尺度森林冠层高度估测的影响,并为更大尺度的冠层高度制图提供了有效的参考.  相似文献   

8.
Li-cor仪器太阳辐射测量单位定量变换的应用研究   总被引:2,自引:0,他引:2  
因研究的角度不同,辐射研究结果有能量、亮度、量子数等方面的量纲,实践中不同单位之间换算很有必要。该文研究了太阳辐射测定中几个单位的定量变换方法,得出了相应的变换系数;并实测了植物冠层上和冠层内太阳辐射,并对单位变换系数进行了检验,结果表明:在冠层上,单位变换差异晴天仅为7%,阴天为2%,处在仪器测定辐射的相对误差范围内;在植物冠层内,线状辐射仪和辐照度仪同时采样,以线状辐射仪测得结果为基准,相同时刻辐照度仪测得结果经换算成辐射量子流密度单位后,与线状辐射仪对比差异全天平均达25%,远大于冠层上;光斑作用使LI-200辐照度仪在群体内测光产生较大误差。除中午辐射最大值,光斑最多时段以外,线状传感器能消除光斑的影响。  相似文献   

9.
夏玉米冠层光合有效辐射垂直分布模型   总被引:5,自引:4,他引:1  
吸收光合有效辐射分量(FPAR)是研究植被群体光合作用和光能利用的重要参数,弄清冠层内FPAR的垂直分布规律及其与冠层结构等参数之间的定量关系,可以为遥感定量反演冠层FPAR提供模型基础。该文基于平均冠层的辐射传输过程,结合冠层结构建立玉米冠层内FPAR垂直分布计算模型,并就模型的参数如植被组分光学特性、株型、太阳高度角以及天空散射光比例等对FPAR垂直分布结果的影响进行了分析。利用实测结构参数模拟了玉米冠层内FPAR,并与SUNSCAN测量值进行了比较,结果表明模型对封垄后的玉米冠层内FPAR垂直分布的模拟精度较高,RMSE均小于0.18,并能较好地计算封垄前冠层内FPAR的垂直分布趋势。  相似文献   

10.
灰霾天气导致到达地面的太阳总辐射下降及散射辐射比例增加,从而影响作物生长和产量。为研究灰霾导致的太阳辐射变化对作物的影响,设计了田间开放式灰霾模拟装置。以空气质量等级做为灰霾严重程度的标准,根据不同程度灰霾条件下太阳辐射变化情况,确定了轻度、中度、重度霾下太阳总辐射和散射辐射比例。测定不同聚乙烯(PE)塑料薄膜的光学特性(透光率和散射特性及其覆盖下不同光质的光占总可见光比例的空间分布),选择光学特性满足模拟不同程度灰霾条件下太阳辐射状况的PE塑料薄膜作为覆盖材料。根据作物生长季节太阳高度角和方位角变化范围,确定了保证上午10:00到下午14:00遮荫面积达到4 m2的最小处理小区面积为20 m2,南北向边长为4 m,东西向边长为5 m。在2013-2014年水稻生长季利用所设计的试验装置进行田间模拟不同程度灰霾导致的太阳辐射变化处理试验,对太阳辐射和冠层微气候进行了持续观测。结果表明:该研究设计的灰霾模拟装置可以模拟中度及重度灰霾导致的太阳辐射变化情况。灰霾模拟装置在改变辐射状况的同时,保持了不同光质的光占总可见光比例的空间分布与自然灰霾条件相比没有显著变化。并且处理与对照小区的作物冠层温度及环境温湿度没有显著差异。该研究所设计装置可以较好地模拟不同程度灰霾条件下的太阳辐射变化,为研究灰霾对作物生长和产量的影响提供了有效的田间试验手段和技术支持。  相似文献   

11.
12.
《Journal of plant nutrition》2013,36(6):1203-1222
Abstract

Relative tillering rate (RTR) increases linearly as leaf nitrogen concentration (NLV) increases in rice (Oryza sativa L.) plants. Leaf area index (LAI) has a negative effect on the emergence and survival of tillers. The objectives of this paper were to quantify the interactive effect of NLV and LAI on tillering in irrigated rice. Field experiments were conducted at Philippine Rice Research Institute (PRRI) and International Rice Research Institute (IRRI), Philippines during the dry seasons of 1995 and 1998. Two indica cultivars, IR72 and IR68284H, were subjected to various nitrogen (N) treatments. Number of tillers (including main stems), leaf area, and tissue N concentration were measured. The NLV explained a large part of variation in number of tillers m?2 among treatments. However, the residual, defined as the difference between observed and estimated number of tillers m?2, was negatively correlated with LAI (P < 0.01). When LAI was considered in addition to NLV, the model explained the variation in number of tillers m?2 much better, and the correlation between the residual and LAI declined and became insignificant (P > 0.05). The critical NLV and critical LAI for tillering to stop were interrelated; higher NLV was needed to prevent tillers from dying when LAI was high, and vice versa. Use of stem or shoot N concentration instead of NLV gave similar results. Results suggest that LAI, in addition to NLV, should be considered in predicting tillers in rice crop.  相似文献   

13.
Abstract

A field study was conducted to study effects of four nitrogen (N) supplemental levels on biomass, protein‐N, non‐protein‐N, and starch of an upper and a lower leaf in rice (Oryza sativa L.). The ranges of leaf protein‐N, non‐protein‐N, total N, and starch concentrations were from 1.18% to 3.66%, from 0.13% to 0.67%, from 1.32% to 4.14%, and from 38.4 mg g?1 to 108.6 mg g?1, respectively. The upper leaf appeared to be more sensitive than the lower leaf in response to N levels on biomass, but larger differences of protein‐N, total N, and starch contents were observed among nitrogen level treatments in the lower leaf than in the upper leaf. Protein‐N may be the best indicative of N status in rice. The lower leaf had a considerably higher ratio of protein‐N to non‐protein‐N at panicle formation and heading growth stage. The lower leaf had higher starch contents, which decreased with increasing N level. The response differences between the upper leaf and the lower leaf with relation to light conditions, developmental extent and leaf function were discussed. The results suggested that the lower leaf could be more suitable as a test sample for N status diagnosis by leaf chemical analysis, especially during the reproductive growth stage.  相似文献   

14.
Abstract

The paclobutrazol (0, 50, 100, 200, and 500 mg L?1) and triapenthenol (175, 350, 700, and 1400 mg L?1) effects on specific leaf area (SLA) and leaf nitrogen (LN) concentration of Lantana camara L. (subsp. camara) under the shading levels 0%, 27%, and 66% were determined in glasshouse experiments. In most cases, increased concentrations of paclobutrazol and triapenthenol decreased SLA and increased LN of plants logarithmically at all shading levels. The SLA, at all concentrations examined, was generally increased with increased shading; LN showed an increase at 66% shading compared to 0% shading in the case of triapenthenol. The SLA reduction of paclobutrazol‐treated plants in relation to untreated plants of the same shading level was 18% to 37%; reduction was 49% to 73% for plants treated with triapenthenol at 0% shading, indicating a greater effect of triapenthenol on SLA reduction than paclobutrazol at previous shading.  相似文献   

15.
植物叶片截留特征分析   总被引:1,自引:0,他引:1  
植物最大截留量是分析植物截留量的重要参数,分别采用浸泡法和喷水法测定了13种植物叶片的最大截留量。结果表明:(1)不同植物叶片最大截留量相差较大,喷水法测定的植物叶片最大截留量从腊梅叶片的0.008g/cm2到小叶杨叶片的0.03g/cm2,差异性显著(p0.05),因此精确分析植物截留量时应考虑物种差异。(2)叶长、叶宽、叶周长、叶鲜重与叶片最大截留量的相关性不显著,而叶面积与叶片最大截留量遵循线性函数变化。(3)对于刺槐、杏树、石楠、柿子、柳树、小叶杨、石榴、白榆树、竹子、马铃薯、腊梅叶片而言,喷水法测得叶片最大截留量大于浸泡法,对于毛豆、樱桃而言,浸泡法测量的最大截留量值大于喷水法测量值。  相似文献   

16.
Abstract

The chemical diagnosis of nutritional status of Bael (Aegle marmelos Correa) tree by leaf analysis was done to study the effect of leaf age and leaf position on foliar nutrient composition of Bael. The results showed that leaf age has significant influence on leaf mineral content, whereas the position of leaf on shoot did not have any significant effect. Interactions between leaf age and position were found to be significant for nitrogen, boron and iron content. In general, stability in level of nitrogen (N), phosphorus (P), and potassium (K) contents was observed in November–December (6‐ to 7‐month‐old leaves) and calcium (Ca) and magnesium (Mg) showed their stability in 2‐to 3‐month‐old leaves (July–August). The contents of boron (B), manganese (Mn), copper (Cu), and zinc (Zn) were found stabilized in September–October (3‐ to 4‐month‐old leaves), indicating their suitability for sampling in Bael.  相似文献   

17.
缺素叶片彩色图像颜色特征提取的研究   总被引:40,自引:3,他引:37  
在提取无土栽培番茄营养元素亏缺叶片彩色图像的颜色特征时,为了使颜色特征有效性不受叶片大小、形状和叶片背景噪声影响,对由几种常用颜色系统表示的叶片图像进行了统计算法、相关系数算法提取叶片颜色特征的研究,以上的方法未能获得很有效的颜色特征。最后,提出了百分率直方图法提取缺素叶片图像颜色特征,进行了除去图像中白色背景影响的研究,用百分率直方图取代一般直方图以解决叶片大小对颜色特征提取影响的研究,以及如何确定提取颜色值区域的研究,此方法提取的颜色特征能理想地识别缺素番茄叶片,准确率在70%以上。  相似文献   

18.
ABSTRACT

Most of the sugarcane (interspecific hybrids of Saccharum sp.) production in Florida is on organic soils. Supplemental phosphorus (P) fertilizer is often applied for optimum yields, but producers are required to reduce P levels in farm drainage waters. The objectives of this study were to relate optimum leaf P tissue concentration with yield in organic soil, and to determine optimum leaf sampling dates during the summer. Eight genotypes were planted at two locations, eight additional genotypes were planted at a third location, and eight more genotypes were planted at a fourth location. Crops were grown for three years. Measurements of leaf P concentration were repeated during growth seasons and over crop years for a total of six sampling dates at each location. Three fertilizer P treatments (0, 24, and 48 kg ha?1 yr?1) were applied to all genotypes at each location. Leaf samples were partitioned into early-, mid-, and late-summer dates. Early-leaf samples had the widest range in leaf P concentrations compared with mid- and late-season leaf samples. Correlation analyses of yield vs. leaf P concentration across all treatments in early- and mid-summer were statistically significant (P < 0.05), but coefficients were low (r = 0.14 and 0.26, respectively). No consistent relationship across locations described the effect of leaf P tissue concentration on yield. Leaf P concentrations could not provide accurate P fertilization rates that will give maximum sugarcane yields and prevent over-fertilization of P. The highest potential for relating leaf P concentrations with yield appears to be from early leaf samples.  相似文献   

19.
Leaf area index measurements at Fluxnet-Canada forest sites   总被引:7,自引:2,他引:5  
Leaf area index (LAI) measurements made at 17 forest sites of the Fluxnet Canada Research Network are reported here. In addition to LAI, we also report other major structural parameters including the effective LAI, element clumping index, needle-to-shoot area ratio, and woody-to-total area ratio. Values of the fraction of photosynthetically active radiation (FPAR) absorbed by green leaves in these stands at noon of 15 August are also provided, and a procedure is suggested for using the effective LAI for estimating FPAR at various times of the day and year. Labour-intensive laboratory measurements of the needle-to-shoot area ratio were made for five conifer sites. For each site, 45 shoot samples were measured at three heights from three trees. LAI-2000, TRAC and digital hemispherical photography (DHP) were used in the field, and good agreements between these techniques were obtained. In particular, the low cost DHP technique agreed within 21% of LAI-2000 in terms of effective LAI measurements and 12% of TRAC in terms of element clumping index measurements, suggesting a possibility of using DHP alone for indirect LAI measurements. However, LAI-2000 and TRAC are still found to be more reliable than DHP because of some remaining technical issues with DHP. We confirm the correct method for determining the photographic exposure proposed in previous studies and suggest optimum zenith angle ranges in photograph processing to estimate the effective LAI and the clumping index.  相似文献   

20.
Sulfuric acid mist exposure of bush bean leaves at a low rate of precipitation suggested that acid on the leaf surface was neutralized by cations leached from leaf tissues and that Ca-S compounds were accumulated on the leaf surface (Kohno, 1994). This report summarizes visual observations of the neutralization process of acid on leaf surfaces as determined by a pH-imaging microscope. Small droplets of sulfuric acid were placed on the adaxial leaf surface and allowed to air dry under laboratory conditions. Droplets (0.1 µl) of sulfuric acid took about 7–8 minutes to dry. Leaf samples were cut at various times after the acid droplets dried. The adaxial leaf surface was placed on the pH-adjusted agar film layer on the pH-imaging sensor of the microscope. Hydrogen ions dispersed into the film layer and resulting pH distributions were visualized as pH distribution patterns. The size of the acidic area generated became smaller with time after the acid was added and allowed to dry. Results indicate that leaves could neutralize the surface acid probably by ion exchange with cations from their surface tissues and could recover from strong temporary acid stress imposed by acid rain or acid fog in a relatively short period of time. Our findings indicate that acidic precipitation at current acidity levels does not pose a direct threat to plants.  相似文献   

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