宽幅播种下带间距对冬小麦衰老进程及产量的影响

在大田试验条件下以多穗型品种‘百农矮抗58’和大穗型品种‘兰考矮早八’为供试材料,研究了宽幅播种(播幅8 cm)种植方式下不同带间距7 cm(KF7)、12 cm(KF12)和17 cm(KF17)对冬小麦(Triticum aestivum)衰老进程及产量的影响。结果表明:与常规条播(行距20 cm,播幅1—2 cm)相比,宽幅带播种植方式的花后旗叶叶绿素降解缓慢,丙二醛(MDA)含量降低,抗氧化酶活性增强,成穗数和产量提高。宽幅带播下不同带间距处理间差异因品种类型而异,矮抗58品种叶绿素相对含量(SPAD)、过氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性整体呈现为KF12KF17KF7,兰考矮早八品种表现为KF7KF12KF17,而MDA变化规律则相反。试验条件下,多穗型品种矮抗58以KF12处理、大穗型品种兰考矮早八以KF7处理花后叶绿素含量高,MDA含量低,抗氧化酶活性强,叶片衰老进程缓慢,产量结构协调,最终产量最高。     

窄行匀播对晚播冬小麦群体环境、个体性状和物质生产的影响

为了明确行距和行内种子分布形式对华北平原晚播冬小麦群体生长的影响,以济麦22为试验材料,在晚播条件下设置3种行距(10、15、20 cm)和2种行内种子分布形式[随机分布(R)和均匀分布(A)]处理,考察了不同处理冬小麦的冠层结构与环境特征、个体性状、生物量累积及产量性能。结果表明:在相同播种量下较小行距比较大行距、种子均匀分布比非均匀分布群体叶面积较大,冠层下部漏光较少,温度较低且相对湿度较高;缩小行距或增加行内种子分布均匀度使群体内个体间植株性状差异缩小,穗层分布趋向均匀,花后物质积累量增加,穗粒重增加,最终产量提高。10 cm行距的产量高于15 cm行距、显著高于20 cm行距;在15 cm和20 cm行距下植株均匀分布处理产量显著高于非均匀分布处理的产量。综合研究认为,窄行匀播是华北平原干旱缺水地区提高晚播小麦群体产量的有效措施。     

行距配置对‘兰考矮早八’小麦后期群体冠层结构及其微环境的影响

 在大田试验条件下,研究了在同一密度（375×104株&;#8226;hm^－2）下,行距配置对大穗型冬小麦(Triticum aestivum)品种‘兰考矮早八’后期群体 冠层结构、冠层微环境及产量构成的影响。结果表明,冠层叶面积指数随着行距的增大而减小;而冠层开度随着行距的增大而增加。行距配置 还可改变小麦冠层微环境,冠层不同层次的光截获及消光系数均随着行距的增大而减小;随着行距增加,冠层不同层次的温度升高,而湿度下 降; 随着行距缩小,冠层不同层次的CO₂分布更趋均匀,有利于群体光合作用。通过缩小行距,能够使植株分布均匀,竞争减弱,使产量构成 因素实现最佳配置,从而获得较高的产量。从该研究看,15 cm行距的产量最高,可作为该类品种的较佳行距配置。     

行距和播种量对冬小麦冠层光合有效辐射垂直分布、生物量和籽粒产量的影响

为明确行距和播种量对冬小麦冠层光合有效辐射(PAR)垂直分布、生物量和籽粒产量的影响,在不增加水肥等投入的基础上,设置等行距(R₁,20 cm+20 cm)、宽窄行(R₂,12 cm+12 cm+12 cm+24 cm)两种行距方式和低(D₁,120 kg·hm^-2)、中(D₂,157.5 kg·hm^-2)、高(D₃,195 kg·hm^-2)3个播种量水平,分析不同处理组合下冬小麦主要生育时期冠层PAR的截获率及利用率、群体光合能力、生物量和产量差异。结果表明: 冬小麦冠层总PAR截获率、上层PAR截获率均表现为R₁行距显著大于R₂,而中层和下层PAR截获率则表现为R₂大于R₁,且在中层差异显著;从小麦开花至成熟期,相同播种量下R₂行距光合势(LAD)、群体光合速率(CAP)、PAR转化率和利用率都显著高于R₁,并以R₂D₂处理最大;冬小麦的群体生物量(BA)和不同层次叶片生物量(BL)均表现为随播种量增加而增加,但单株生物量(BP)则相反。在同一播种量下,BA、BL和BP均在开花期之后表现为R₂行距高于R₁,其中,BA、BP在成熟期行距间差异显著,中层和下层BL在D₂、D₃播种量下行距间差异显著;不同处理组合间冬小麦的穗数、穗粒数、千粒重、籽粒产量分别以R₂D₃、R₂D₁、R₂D₁、R₂D₂最大,其中,R₂行距下千粒重、穗粒数和籽粒产量显著大于R₁。综上,改变行距可以改善小麦冠层中下层PAR的截获量,增强冬小麦单株和群体光合能力、光合有效辐射的利用及转化效率,提高生物量和籽粒产量。在冬小麦高产栽培中,应重视通过优化田间结构,塑造麦田理想的群体光合结构,以充分利用单位土地面积上光照资源,挖掘作物自身的光合生产潜力,达到高产高效的目的。在本试验条件下,以R₂D₂配置群体光合能力、光合有效辐射利用率和产量最佳。     

株行距配置对齐穗期粳稻冠层结构及产量的影响

以辽宁稻区3种穗型粳稻及杂交稻为试材,研究了不同株行距配置对齐穗期粳稻光截获能力、群体内部光分布特征和光转化效率以及产量构成的调控作用.结果表明：与光能截获密切相关的叶面积指数随着密度减小而先降低后升高.一天之内消光系数(K)的变化同样表现为先降低后升高,而不同株行距配置间K值随着种植密度的增加而增大.产量与各冠层消光系数、上部3叶叶倾角呈正相关.在光能利用率方面,产量与剑叶气孔导度、胞间CO₂浓度、蒸腾速率均呈正相关.在高密度(15 cm×25 cm)和低密度(20 cm×30 cm和20 cm×35 cm)株行距配置下,水稻分别可以提高光截获能力和光转化效率,却分别受到倒伏和单位面积穗数的限制而无法获得高产稳产.株行距为15 cm×30 cm和 20 cm×25 cm配置下,可以确保足够穗数,优化冠层结构并降低倒伏风险,为高产优质提供保障.     

Canopy Apparent Photosynthetic Characteristics and Yield of Two Spike-Type Wheat Cultivars in Response to Row Spacing under High Plant Density

In northern China, large-spike wheat (Triticum aestivum L) is considered to have significant potential for increasing yields due to its greater single-plant productivity despite its lower percentage of effective tillers, and increasing the plant density is an effective means of achieving a higher grain yield. However, with increases in plant density, the amount of solar radiation intercepted by lower strata leaves is decreased and the rate of leaf senescence is accelerated. Row spacing can be manipulated to optimize the plant spatial distribution under high plant density, therefore improving light conditions within the canopy. Consequently, field experiments were conducted from 2010 to 2012 to investigate whether changes in row spacing under high plant density led to differences in canopy apparent photosynthesis (CAP), individual leaf photosynthesis and grain yield. Two different spike-type winter wheat cultivars, Jimai22 (a small-spike cultivar as a control cultivar) and Wennong6 (a large-spike cultivar), were grown at a constant plant density of 3,600,000 plants ha^–1 (a relatively higher plant density) over a wide range of row spacing as follows: 5-cm row spacing (R₀), 15-cm row spacing (R₁), 25-cm conventional row spacing (R₂), and 35-cm row spacing (R₃). The two-year investigations revealed that increased row spacing exhibited a significantly higher light transmission ratio (LT), which improved light conditions within the canopy; however, excessive light leakage losses in R₂ and R₃ treatments were not favorable to improved irradiation energy utilization efficiency. Aboveground biomass accumulation was influenced by row spacing. Two spike-type wheat accumulated greater biomass under 15-cm row spacing compared to other row spacing treatments, although a markedly improved photosynthetic rate (P_N), effective quantum yield of photosystem II (Φ_PSII) and maximal efficiency of photosystem II photochemistry (F_v/F_m) in the penultimate and third leaves were observed in R₂ and R₃ treatments. At the same time, a longer duration of CAP and green leaf area was maintained in R₁ during grain filling. Compared with conventional row spacing, Wennong6 in R₁ treatment obtained 21.0% and 19.1% higher grain yield in 2011 and 2012, respectively, while for Jimai22 it increased by 11.3% and 11.4%, respectively. A close association of yield with CAP and LAI at mid-grain filling was observed. In conclusion, for the tested growing conditions, decreasing the row spacing to an optimal distance (15 cm) maintained a longer duration of LAI and CAP during grain filling, made a better coordination of group and individual leaf photosynthesis, and accumulated higher aboveground biomass, leading to a greater grain yield. In addition, Wennong6 had a more rational canopy architecture than Jimai22 (improved LT and higher LAI) and CAP under 15-cm row spacing, leading to a higher grain yield, which indicated that the large-spike type cultivar has the potential to obtain higher yields by increasing plant density through optimum row spacing allocation (15 cm).     

推迟拔节水灌溉对宽幅精播麦田冠层温度与叶片水分利用效率的影响

为了探讨冬小麦高效节水灌溉模式,于2012—2013年在山东农业大学试验站采用两种种植模式(宽幅精播种植和常规种植),每种种植模式设3种灌溉处理(全生育期不灌溉、拔节期灌溉60 mm和拔节后10 d灌溉60 mm),研究了推迟拔节水灌溉对宽幅精播麦田冠层温度、光合速率、蒸腾速率、叶片水分利用效率(WUEL)和籽粒产量等的影响。结果表明,推迟拔节水灌溉显著提高了宽幅精播麦田生育后期的冠层温度、旗叶光合速率和蒸腾速率,且在冬小麦生长后期推迟拔节水灌溉显著提高了宽幅精播麦田的WUEL,有利于实现宽幅精播麦田的节水高产;产量构成因素中,推迟拔节水灌溉对两种种植模式的千粒重均没有显著影响,但推迟拔节水灌溉显著提高了宽幅精播麦田的穗粒数和籽粒产量。统筹考虑冬小麦的WUEL和籽粒产量,推迟拔节水灌溉对宽幅精播麦田实现节水高产具有一定的现实意义。     

Improving the accuracy of indirect methods in estimating leaf area index using three correction schemes in a Larix gmelinii plantation

Aims Woody materials and clumping effects are key error sources in estimating leaf area index (LAI) by optical methods. However, how to correct the error caused by woody materials has not reached consensus. The aims of this study are (1) to evaluate the accuracy of optical methods for estimating effective LAI (L_e) in a deciduous needle leaf forest stand, and (2) to develop a practical correction scheme to improve the accuracy of optical methods in estimating LAI.Methods L_ewas estimated by two indirect methods (i.e., digital hemispherical photography (DHP) and LAI-2000 plant canopy analyzer method (LAI-2000 method) in an annual maximum leaf area period in a Larix gmelinii plantation. Then, we developed three correction schemes to improve the accuracy of indirect methods in estimating LAI. Meanwhile, two direct methods (i.e., litter collection and allometry methods) were used to estimate LAI. Taking LAI from litter collection as a reference, we evaluated the effectiveness of three correction schemes and tested the influence of zenith angle ranges on the correction results.Important findings With zenith angle ranges of 0-45° (rings 1-3), 0-60° (rings 1-4), 45°-60° (ring 4) and 0-75° (rings 1-5), L_eobtained from DHP underestimated LAI from both litter collection and allometry by 19%-32% and 18%-29%, respectively. L_efrom LAI-2000 method with four zenith angles also underestimated LAI from both litter collection and allometry by 9%-30% and 8%-28%, respectively. Although the contribution of woody materials to LAI was overestimated in correction scheme A, it was effective in correcting L_efrom DHP with zenith angles of 45º-60º (ring 4), and also effective for L_efrom LAI-2000 method with zenith angles of rings both 1-3 and 1-4. Correction scheme B was all effective in correcting L_efrom DHP with four zenith angle ranges. Generally, correction scheme C was more effective than other two schemes in correcting L_efrom both DHP and LAI-2000 method with four zenith angle ranges. These results indicate that the zenith angle range is a key factor for determining the accuracy of optical methods in estimating LAI besides woody materials and clumping effects.     

Spatiotemporal variation and scale effect of canopy leaf area index of larch plantation on a slope of the semi-humid Liupan Mountains,Ningxia, China

Aims Leaf area index (LAI) is an important canopy structure parameter characterizing ecological and hydrological processes, such as forest growth, canopy interception and transpiration. Forest LAI is limited by both light and soil water availability, thus may vary with slope position and seasonality. This study is aimed at the spatiotemporal variation of LAI and its relationship with environmental variables. Methods A 34-years-old Larix gmelinii var. principis-rupprechtii planted forest situated on a typical slope located in a small watershed of Xiangshuihe within Liupan Mountains was selected for LAI observations. Sixteen plots along a 30 m wide transect along the slope was surveyed from May to October of 2015 to measure the monthly canopy LAI. Important findings It showed there was a remarkable difference of LAI among slope positions. The LAI in May decreased toward downslope direction with a scale effect of -0.02/100 m. Whereas for the period from June to August, LAI showed a nonlinear variation along slope positions: increasing from to top slope downward, reaching its maximum at the middle slope, and then decreasing to the slope foot. The scale effect of LAI was +0.15/100, +0.16/100, and +0.18/100 m in the slope range (downward positive) of 0-244.2 m, but -0.09/100, -0.08/100, and -0.07/100 m in the slope range of 244.2-425.1 m for June, July and August, respectively. The LAI increased toward downslope in September and October, with a slope scale effect of +0.03/100 m and +0.09/100 m, respectively. The seasonal variation of LAI-slope relationship showed a shift from the light and temperature control in the early growing season, to the soil water resources control in the mid growing season, and then to an integrated control of many factors in the late growing season. In the early growing season when soil moisture and nutrients were abundant, terrain shading limited the leaf growth in middle and downslope. From early to the mid growing season, the soil moisture on the slope was quickly depleted due to fast evapotranspiration and poor moisture retention of the coarse soil. On the other hand, average solar height increased, and allowed direct light radiation to penetrate to the middle then downslope. The result is that the leaf growth in the middle slope was the strongest in the mid growing season. During the late growing season, the temperature decreased fast in the mountain top to incur earlier leaf fall than the mountain foot. Thus the LAI exhibited the increasing trend toward the downslope.     

Vertical variation and economic strategy of leaf trait of major tree species in a typical mixed broadleaved-Korean pine forest

分析不同树种叶片性状的变化有助于了解植物群落结构。该文通过对典型阔叶红松(Pinus koraiensis)林15种阔叶树种的比叶质量、叶片厚度、叶干物质含量、叶绿素含量指数、叶片碳、氮、磷含量的测定, 分析了冠层高度对叶性状及叶性状间相关关系的影响。结果表明, 水曲柳(Fraxinus mandshurica)和大青杨(Populus ussuriensis)上层的比叶质量显著大于下层, 而其他树种冠层间的比叶质量无显著变化; 叶绿素含量指数在白桦(Betula platyphylla)和春榆(Ulmus japonica)冠层间的分布分别为上层显著大于下层和上层显著大于中层; 单位质量氮含量在水曲柳的中层显著大于上层。叶片性状间存在着广泛的相关性, 比叶质量与叶片厚度、干物质含量在三层间均呈显著正相关关系, 而有些性状, 只在一或二个冠层中存在一定的相关性。山杨(Populus davidiana)和大青杨的叶片倾向于选择光合能力较低、营养浓度较低、呼吸速率较慢的一端, 而黄檗(Phellodendron amurense)和山槐(Maackia amurensis)叶片更倾向于光合能力强、营养物质浓度高的一端。不同树种对光照响应的差异可能会改变不同冠层中叶片的形态和化学性状, 从而有助于群落构建和物种共存。     

Canopy structure and radiation interception of Salix matsudana: Stand density dependent relationships

Aims Plants can enhance their photosynthetic efficiency and competitiveness by adjusting canopy structure and radiation interception. The objective of this paper was to quantify the relationship between canopy structure (crown depth and crown area) and light interception (LI) in a Salix matsudana stand under three different stand densities in a flood plain of Zhangye.Methods Our study site is located at the Heihe flood plain of Xichengyi in Ganzhou district, Zhangye City, Gansu Province in the middle Heihe River, where S. matsudana is the dominant species. Based on stand density (10 m × 10 m), the S. matsudana community is divided into three types: low density (I, 25-36 Ind.·plot^-1), medium density (II, 37-48 Ind.·plot^-1), and high density (III, 49-60 Ind.·plot^-1). Community characteristics, soil physical and chemical properties of each type were measured. At each plot, we measured photosynthetically active radiation (PAR), LI, net photosynthetic rate (P_n), transpiration rate (T_r), crown depth, crown area, leaf area index (LAI), twig numbers, twig length, and bifurcation angle. The standardized major axis (SMA) estimation method was used to determine the relationships between LI and canopy structure.Important findings With increasing in stand density, we found that soil moisture increased, and soil electric conductivity decreased, while twig length and crown depth increased, and PAR, twig numbers, bifurcation angle and crown area decreased. LAI and LI, P_n and T_r reached their maximum at the stand of medium density. There was a significant, positive correlation and negative correlation (p < 0.01), respectively, between the LI, crown depth and crown area at low density (I), whereas low significant (p < 0.05) at high density (III), and high significantly positive correlation (p < 0.01) at the medium density (II). S. matsudana has more horizontal branches that reduce LI. Canopy thickness and increased crown area at low density. More vertical distribution of branches at high density, and a more balanced spacial distribution were found at medium density.     

不同株行距配置对夏大豆群体结构及光截获的影响

以田间试验(2006—2007年)为基础,分析了地上部干物质、叶面积指数(LAI)、光合有效辐射(PAR)、光能利用率和植株形态指标变化特征,夏大豆‘鲁豆4号’(Glycine maxcv.Ludou 4)在同一密度(3.09×105株/hm2)下设5种株行距配置方式,即行距×株距分别为18 cm×18 cm(A)、27 cm×12 cm(B)、36 cm×9 cm(C)、45 cm×7.2 cm(D)、54 cm×6 cm(E)。结果表明,大豆在生育期间干物质变化因株行距不同而产生差异,2006和2007生长季的各处理干物质分别在播种后第70天和90天达到最高,播种后第80天和100天时,A处理比E处理分别高21.6%和34.0%;不同层次干物质积累重心随行距加大有上移趋势。各处理LAI随行距扩大、株距减少有下降趋势,其中,A和B处理LAI表现较稳定,LAI相对较高且时间较长。光能利用率随行距加大有降低趋势,A和B处理显著高于E处理(P0.05)。夏大豆在不同株行距配置下,株粒数、百粒重与产量相关系数分别为0.941*和0.926*(2006年),0.995*和0.892*(2007年),随行距变小PAR透射率降低、截获率和光能利用率上升而产量增加,A和B处理产量显著高于E处理(P0.05)。说明夏大豆在雨养农业条件下,植株相对均匀分布可改善群体结构和增强光截获,进而提高群体光能利用率和产量。     

小麦行距配置对套种花生生理特性和产量的影响

以大花生品种早熟型‘山花108’和晚熟型‘780-15’为试验材料,设置小麦3种行距配置(25 cm、30 cm、大小行40 cm+20 cm)和2种花生种植方式(麦套、夏直播),探讨不同种植模式对夏花生产量构成、光合特性、抗氧化活性和干物质积累与分配的调控作用.结果表明: 适当扩大小麦行距、相同平均行距下选用大小行种植,可提高套种花生荚果产量和籽仁产量,增大叶面积指数和干物质积累量,增强光合能力,同时提高超氧化物歧化酶、过氧化物酶和过氧化氢酶活性,降低丙二醛含量.麦套花生产量高于夏直播花生并且以大小行处理产量最高.与小麦行距30 cm相比,大小行处理山花108和780-15两品种花生荚果产量和籽仁产量分别提高6.3%、13.3%和7.7%、16.5%.表明大小行种植有助于扩大光合面积,提高净光合速率,增加干物质积累量,同时缓解花生植株个体与群体间的矛盾,延缓衰老,从而提高麦套花生产量.     

Root biomass distribution of triploid Populus tomentosa under wide- and narrow-row spacing planting schemes and its responses to soil nutrients

三倍体毛白杨(triploid Populus tomentosa)是我国华北地区主要纸浆林品种, 在该地区多采用宽窄行模式栽植。为基于根系结构特征制定该模式下毛白杨人工林高效水肥管理策略和明确影响其根系空间分布的主要因子, 在5年生林分中于8株样树周围挖取2106个土柱, 研究该栽植模式下毛白杨根系生物量的空间分布特征, 并分析了细根垂直分布对土壤有机质、速效磷和碱解氮等的响应。结果表明, 一维垂向上, 宽行内细根根重密度(FRBD)在0-30 cm土层中随深度增加而递减, 但在30 cm以下土层呈均匀分布(p = 0.079); 窄行内FRBD呈“双峰”分布, 即在0-20 cm (22%)和70-110 cm (31%)土层均有较多细根分布; 10-150 cm各土层中, 窄行FRBD较宽行高17%-148%。宽、窄行内, 随深度增加, 粗根根重密度(CRBD)均呈先增后减变化, 而细根粗根比(F/C)无显著变化(p > 0.05), 窄行平均F/C较宽行高60%。一维径向上, 宽、窄行内FRBD均呈近均匀分布, 而CRBD和F/C均随距离增加分别显著递减和增大。二维尺度上, FRBD在窄行内分布相对均匀, 但在宽行内主要集中在表土层且随距离增加细根浅层化程度增强; CRBD在树干两侧呈“不对称”分布; 垂向0-20 cm、径向160-300 cm范围是宽行内平均FRBD和F/C较高区域, 分别为宽行相应指标总平均的2.8和1.1倍。FRBD在0-30 cm土层中随土壤有机质、速效磷和碱解氮含量的增加而逐渐增大, 但在30 cm以下土层中无明显变化趋势。研究结果表明, 宽、窄行间毛白杨根系分布的差异性主要体现在细根一维垂直分布和细根、粗根二维分布上。土壤有机质、速效磷和碱解氮是0-30 cm土层中毛白杨细根垂直分布的重要影响因子, 但对下层土壤中根系分布无影响。对宽窄行栽植的毛白杨林分灌溉时, 灌溉水应供给到窄行区域; 施肥时, 缓释肥和速效肥应分别浅施在宽行中央附近和窄行内。     

间伐对杨桦次生林冠层结构及林下光照的影响

自然或人为干扰产生的森林冠层结构和林下光照差异是造成林下环境异质性、物种多样性的主要原因,对森林生态系统的结构、过程与格局具有重要作用.以桃山林场2块50 m×50 m的杨桦次生林固定样地为研究对象,分别作为间伐和对照样地,于2012—2016年、2018年获取样地冠层影像,通过方差分析、马尔科夫模型等方法分析其冠层结构、林下光照动态及间伐后林冠的恢复规律.结果表明: 间伐措施能显著调整冠层结构和林下光照,并能持续较长的作用时间,但调整效果随时间逐渐降低;间伐后冠层结构及林下光照的变化速度随时间推移而降低,间伐后前3年林冠恢复速度较快,3年后恢复速度降低并趋于平缓;林下光照与林冠开度呈显著正相关,与叶面积指数呈显著负相关,其中林下散射辐射与冠层结构参数的相关性最大,且间伐样地冠层结构与林下光照的相关性大于对照样地;间伐后冠层的恢复速度与林冠开度大小有关,林冠开度越大,林冠恢复越快,向更小林冠开度转移的时间越早.马尔科夫模型能够模拟冠层结构分布的变化,可用来预测冠层结构动态.     

行距配置对晚熟冬麦区群体结构与光合性能的影响

合理的行距配置可以调节群体冠层结构的光合作用。山西太谷冬小麦产量徘徊不前,为了研究晚熟冬麦区不同行距配置对不同穗型冬小麦光合性能与群体结构的影响,在大田条件下选用两种不同穗型品种,在播量一致的前提下,分别采用10 cm和20 cm两种行距配置,研究冬小麦群体结构、光能利用和产量结构的差异。研究结果表明:全生育期总LAI值表现为B2高于B1,10 cm行距配置改变了叶片的垂直分布,尤其对多穗型小麦品种冠层(60-80 cm)叶面积的提高最为明显。在小麦植株中、上部分45-90 cm处,两种行距配置LI%均表现为B2配置大于B1配置,在株高60-75 cm处,两种行距配置LI%差异最为明显,B2配置较B1配置LI%提高达30%以上。花后旗叶PN和孕穗期至蜡熟期群体NPR均表现为10 cm行距配置高于20 cm行距配置。四个处理的总干物质重、绿叶、茎和穗的干物质重均表现为B2B1行距配置。两个小麦品种的B2处理(10 cm行距配置)的产量和生物产量均极显著高于B1处理(20 cm行距配置);但经济系数则呈现B2处理(10 cm行距配置)均小于相应小麦品种的B1处理。行距配置对不同小麦品种的影响不大。表明10 cm行距配置适用于北方晚熟冬麦区。     

Exploring the influence of soil types underneath the canopy in winter wheat leaf area index remote estimating

Aims Remote sensing is an effective and nondestructive way to retrieve leaf area index (LAI) from plot, regional and global range. Soil background is one of the confounding factors limiting remotely estimating LAI. And soil type contains a large proportion of soil background information, which can influence the optical properties of vegetation canopy and soil. However, our knowledge on the effects stemmed from soil types underneath the canopy on LAI remote estimating have been in shortage. Thus, this study aims to explore the influences of soil types underneath the canopy on winter wheat LAI remote estimating. Methods We analyzed the sensitivity variation of eight spectral indices, named normalized difference vegetation index (NDVI), modified soil-adjusted vegetation index (MSAVI), modified chlorophyll absorption ratio index 2 (MCARI₂), red edge inflection point (REIP), red edge amplitude (Dr), red edge area (SDr), red edge symmetry (RES), normalized difference spectral index (NDSI), to LAI in different soil types, and then we identified some spectral intervals or parameters that were insensitive to soil type variations underneath the canopy. We also compared the accuracy of two commonly used regression models, partial least squares regression (PLSR) and random forest regression (RFR), in estimating LAI for different soil types. We also explored the problems arising from applying the regression model developed in single soil type area to complex soil types area in retrieving LAI. Important findings This paper demonstrates the effects of soil types underneath the canopy on LAI retrieving. 1) The sensitivity of spectral indices to LAI is significantly different due to the soil type variation, but REIP has the least effects from soil type variation among the eight spectral indices. Meanwhile, the band selection algorithm of lambda-by-lambda not only chooses the most sensitive spectral interval for LAI, but also provides a feasible way to construct the spectral index that exhibits strong resistances to the effects of soil types underneath the canopy. 2) The accuracy of LAI estimation by regression models differs under soil type considered or not. So we suggest that in small scale researches, especially in a field scale, the ability of regression models in explaining variables is the priority consideration, while the PLSR is superior to RFR in this respect. Under the premise of unknown priori knowledge of land surfaces, the RFR is more suitable for retrieving LAI than PLSR, but land surface priori knowledge is still necessary. These findings provide the theoretical basis and methods for developing remotely sensing estimating LAI models adapted to various land surfaces. Further analysis is needed in applying the findings in more crop types, cultivars and growth stages.     

Simulated insect defoliation on soybean: influence of row width

An ongoing change in soybean production gaining popularity in the United States is a reduction in row spacing. Plant canopy closure is quicker and leaf area index is greater, thus yield is usually higher. Because yield response to insect defoliation is primarily a function of how defoliation causes changes in light interception, the possibility exists that the insect-injury-yield-loss relationship might differ among row widths. Soybean was grown in four states using similar methodologies. Insect defoliation was simulated by picking leaflets based on an insect defoliation model. Plant growth measurements were taken immediately following the end of defoliation. Numerous independent variables were measured or calculated, including percentage light interception, leaf area index, percentage defoliation, and leaf area per plot. Analyses of covariance were conducted on the resultant data to determine whether insect-injury-yield-loss relationships interact with row width. A significant interaction would indicate that the impact of the variables on yield was dependent on the row width, whereas a nonsignificant interaction would suggest that the relationship between the variables and yield is similar at all row widths. Few significant interactions were obtained, indicating that the impact of the variables on yield is similar across row widths. Because of the lack of significant interactions, the insect-injury-yield-loss relationships previously developed should be usable across varying row widths. Thus, treatment decisions based on light interception and leaf area indices, both considered more appropriated measures of insect injury, should be applicable for all row spacings.     

旱地小麦理想株型研究进展

理想株型选择是旱地小麦节水栽培和高产育种的重要前提。围绕群体条件下旱地小麦产量形成、节水效率和干旱适应性等关键指标,从根型、茎型、叶型和穗型4个方面总结了旱地小麦株型演变规律和调控机理。旱地小麦从野生近缘种二倍体和四倍体向现代六倍体进化的漫长演变过程中,株型经历了从"高根冠比、低收获指数、高冠幅/株高比、小穗和种子扁长"等"杂草"型向"低根冠比、高收获指数和高粒叶比及小冠幅/株高、大穗多粒"的"作物"型的演变。从株型各组件演变规律看,根型以根系大小适中、根条数较多、根系生理活性较高为主;茎型以各茎节长度比例趋近"黄金分割"演变,株高控制在80-100 cm左右的适中高度;叶型以叶片直立、旗叶长宽比例适中为主,倒二叶长维持在20 cm左右;穗型以直立、大穗和小穗数多为主;单株分蘖数趋于减少,株型结构趋于紧凑。上述组件特征将促使旱地小麦向弱竞争能力的方向发展。总之,旱地小麦经历了自然选择和人工选择双重压力,其株型结构有利于群体产量和水分利用效率提高,从而获得较高的种群适合度。     

Effects of ozone and aerosol pollution on photosynthesis of poplar leaves

由于经济的快速发展, 中国大部分地区正面临着严峻的复合型大气污染, 其中臭氧和气溶胶是两种主要污染物。已有的研究表明臭氧对叶片的氧化性伤害能够抑制光合作用, 而气溶胶可通过增加散射辐射比例或缓解高温抑制促进光合作用。但复合污染下, 臭氧和气溶胶如何共同调控叶片光合作用, 仍缺乏研究。该研究利用北京及周边地区之间的污染梯度, 选择加杨(Populus × canadensis)作为实验对象, 于2012-2013年生长季期间对叶片光合速率进行连续观测, 并同时监测臭氧浓度(AOT40)、气溶胶光学厚度(AOD)、空气温度和冠层内外光合有效辐射(PAR)等环境因子, 以期探讨大气复合污染下臭氧和气溶胶变化对植物叶片光合作用的影响及相关机制。结果表明: (1)臭氧浓度与空气温度、气溶胶浓度之间均呈显著正相关关系, 但气溶胶浓度与空气温度没有显著相关关系; (2)臭氧浓度增加显著抑制了阳生叶片的光合作用, 但气溶胶浓度上升促进了阳生叶片的光合作用; 臭氧浓度升高对阴生叶片光合作用的影响较小, 但气溶胶浓度上升促进了阴生叶片的光合作用; (3)标准化后的结果显示, 臭氧对阳生叶片光合作用的影响最大, 此时气溶胶的促进作用一定程度上补偿了臭氧浓度上升所带来的抑制效应。对于阴生叶片光合作用而言, 气溶胶则是最重要的影响因素。该研究发现复合污染下阴生叶和阳生叶光合响应不同, 这表明冠层结构可能通过影响阴生叶和阳生叶的比例, 从而对植物生长产生不同影响。该研究对理解大气复合污染如何影响光合作用提供了的机理支持, 同时也表明, 为了维持生态系统生产力及功能, 需要同时控制气溶胶和臭氧污染。