光能竞争对农林复合生态系统生产力的影响

农林复合生态系统是改善渭北黄土区脆弱生态环境、促进该区域经济发展的重要举措.以该区具有代表性的核桃(Juglans regia L.)、李子(Prunus salicina),绿豆(秦豆6号)、辣椒(陕椒981)农林复合模式为对象, 研究不同农林复合系统对光能分布、农作物生长、生产的影响.研究结果表明,不同复合模式下,玉米、辣椒的光合有效辐射、光合速率、生物量及产量均有不同程度的下降,且距树行愈近,影响愈大.叶片水势与玉米、辣椒的光合速率、地上部分生物量以及产量不相关或负相关.而10～20cm土壤含水量与绿豆的生物量和产量以及辣椒的地上部分生物量正相关.但绿豆、辣椒的生产量与其光合有效辐射呈显著正相关性,这说明,农林复合系统中光能竞争是导致间作绿豆、辣椒产量下降的主要原因.     

渭北黄土区农林复合系统光能竞争与生产力

农林复合系统是改善渭北黄土区脆弱生态环境,促进该区域经济发展的重要举措.本文以该区具有代表性的核桃/李子与大豆(秦豆8号)/辣椒(陕椒981)农林复合模式为对象, 研究了复合系统内大豆、辣椒的光合作用、生长和产量等情况.结果表明:不同种植模式下,大豆、辣椒的光合有效辐射、光合速率、生物量及产量均有不同程度的下降,且距树行愈近,影响愈大.叶片水势与大豆、辣椒的光合速率、地上部分生物量以及产量呈不相关或负相关. 而10～20 cm土壤含水量与大豆的生物量和产量,以及辣椒的地上部分生物量呈正相关.大豆、辣椒产量与其光合有效辐射呈显著正相关.说明在农林复合系统中,光能竞争是导致间作大豆、辣椒产量下降的主要原因.     

商洛低山丘陵区农林复合生态系统中大豆与丹参的光合生理特性

农林复合系统作为一种传统而又新兴的土地利用和经营方式在改善商洛生态环境、增加该区农民收入、促进其生态和经济协调发展等方面发挥着非常重要的作用.为了研究林下作物的生理生态特性,对研究区农林复合系统中不同处理大豆、丹参的光合、叶绿素荧光参数进行了系统观测.结果表明,从单作到距核桃1m处,距核桃树越近,遮光愈多.各处理大豆的光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)表现出与光合有效辐射(PAR)基本一致的日变化趋势.不同处理丹参光合速率日变化趋势各不相同,且出现“午休”现象.与单作相比,各处理大豆、丹参的光合速率、气孔导度和蒸腾速率均有不同程度的降低.随着遮荫程度的提高,大豆、丹参叶绿素含量和表观量子效率(Φ)升高,光饱和点(LSP)和光补偿点(LCP)降低.二者叶绿素荧光参数最大光能转换效率(Fv/Fm)、PSⅡ电子传递量子效率(ΦPsⅡ)以及光化学猝灭系数(qP)均有不同程度的升高,而非光化学猝灭系数(qNP)却逐渐降低.说明大豆、丹参能适应弱光环境,在较低的光照条件下正常生长.     

渭北黄土区农林复合系统中大豆辣椒的光合生理特性

研究了农林复合系统不同处理对大豆、辣椒的光合特性和叶绿素荧光参数的影响.结果表明,从单作到距李子1m处,随着距李子树越近,遮光愈多.各处理大豆、辣椒的光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)表现出与光合有效辐射(PAR)基本一致的日变化模式,且与单作相比,各处理大豆、辣椒的光合速率、气孔导度和蒸腾速率均有不同程度的降低.相关性分析结果表明二者的光合速率、气孔导度及蒸腾速率均与光合有效辐射呈正相关关系.随着遮荫程度的提高,大豆、辣椒叶绿素含量和表观量子效率(Ф)升高,光饱和点(LSP)和光补偿点(LCP)降低.二者叶绿素荧光参数最大光能转换效率( Fv / Fm ) 、PSⅡ电子传递量子效率(ФPSⅡ ) 以及光化学猝灭系数( qP)均有不同程度的升高,而非光化学猝灭系数( qN P)却逐渐降低.说明大豆、辣椒能适应弱光环境,在较低的光照条件下正常生长.     

黄土区农林复合生态系统中大豆和绿豆的光合生理特性

用Li-6400光合测定系统和FMS-2.02荧光仪测定了单作及间作农林复合系统中大豆和绿豆的光合荧光参数日变化特征,进一步解析复合系统光能竞争机理.结果表明:(1)从单作到间距核桃1 m间作模式,距核桃树越近,遮光愈多,各处理大豆、绿豆的净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)表现出与光合有效辐射(PAR)基本一致的先升后降的日变化模式.(2)随着遮荫程度的提高,大豆、绿豆叶绿素含量和表观量子效率(Ф)升高,而光饱和点(LSP)和光补偿点(LCP)降低.(3)随着遮荫程度的提高,大豆、绿豆叶绿素荧光参数最大光能转换效率(Fv/Fm)、PSⅡ电子传递量子效率(ФPSⅡ)以及光化学猝灭系数(qP)均有不同程度的升高,而非光化学猝灭系数(qN)却逐渐降低.研究发现,大豆和绿豆能适应间作系统的弱光环境,在较低的光照条件下正常生长,植物的光合特性与其生境特点相符.     

玉米大豆对农林复合系统小气候的光合响应

对黄土区核桃(Juglans regia L.)-(玉米+大豆)、李子(Prunus salicina)-(玉米+大豆)农林复合系统小气候效应的研究表明,在玉米和大豆的花期,农林间作系统与对照地相比可以降低农田地面温度1.7-1.9℃,减低风速55%-67%,提高相对湿度6.9%-8.4%,降低光合有效辐射强度13.9%-24.5%和大气CO2浓度5.3-10.9μmol.mol-1。本研究中,单作大豆叶片光合速率午间变化主要受到非气孔的限制作用。逐步回归分析结果表明,光合有效辐射强度和大气CO2浓度是影响林下作物光合速率的主要环境因子。林下小气候可能是作物避免"午休"现象的主要原因。     

大豆幼苗对套作玉米遮荫环境的光合生理生态响应

以2个耐荫性不同的大豆品种为材料,田间试验设置大豆单作和玉米-大豆套作2个种植模式处理,研究不同耐荫性大豆品种的幼苗光合生理生态特性对套作玉米遮荫环境的响应。结果表明:1)玉米-大豆套作模式中,玉米遮荫显著降低大豆冠层的光合有效辐射,导致大豆幼苗光合速率、气孔导度、蒸腾速率显著下降(P0.05),分别达37.9%、54.2%和42.4%,但品种间无显著差异;而胞间二氧化碳浓度和Fv/Fm无显著变化,且光合速率的下降与气孔导度存在显著相关关系,光合速率下降主要是由气孔限制和CO2同化过程中能量不足所致;2)玉米遮荫显著降低大豆幼苗叶面积指数、叶片碳含量、叶片和根系干重及总生物量,且品种间差异显著,相关性分析显示,叶面积指数下降是导致生物量减少的主要原因;3)玉米遮荫环境中,大豆幼苗的叶片叶绿素和氮素含量提高以增强光捕获能力,但它们并不能补偿因光截获面积降低而引起的光截获量下降。     

Seasonal changes of photosynthetic characteristics of Alpinia oxyphylla growing under Hevea brasiliensis

利用农林复合模式发展生态农业可提高资源利用效率, 橡胶(Hevea brasiliensis)-益智(Alpinia oxyphylla)间作模式是橡胶园最主要的农林复合模式。该研究通过野外原位定位实验, 研究不同季节橡胶林下环境因子对益智光合作用的影响, 并进一步分析益智光合作用与主要环境因子的关系。结果表明: (1) 3月益智净光合速率日变化为“V”形曲线, 14:00降到最低值; 而6月、9月和12月益智净光合速率日变化趋势为10:00达到最大值, 随后缓慢降低; 在雨季(6月和9月)蒸腾速率的日平均值和日最高值均显著高于旱季(3月和12月)。表明林下益智在不同季节均能维持植株正常生长, 且表现出了较强的适应能力。3月土壤水分亏缺造成益智叶片气孔导度降低, 使其净光合速率维持在较低的水平。(2)通过光响应曲线修正模型计算出益智叶片各光合响应参数, 发现3月最大净光合效率和光饱和点显著低于6月、9月和12月; 而光补偿点和暗呼吸速率却显著高于6月、9月和12月, 表明3月土壤水分亏缺导致益智光合酶活性降低, 而表现出光抑制现象, 同时呼吸强度加剧, 光合能力显著下降。(3)采取相关分析发现, 3月气温与净光合速率显著负相关, 空气湿度与净光合速率显著正相关, 高温和低湿度共同限制了益智的光合作用; 而9月和12月, 林下光合有效辐射是益智光合作用的限制因子。     

橡胶林下益智光合特性的季节动态变化

利用农林复合模式发展生态农业可提高资源利用效率, 橡胶(Hevea brasiliensis)-益智(Alpinia oxyphylla)间作模式是橡胶园最主要的农林复合模式。该研究通过野外原位定位实验, 研究不同季节橡胶林下环境因子对益智光合作用的影响, 并进一步分析益智光合作用与主要环境因子的关系。结果表明: (1) 3月益智净光合速率日变化为“V”形曲线, 14:00降到最低值; 而6月、9月和12月益智净光合速率日变化趋势为10:00达到最大值, 随后缓慢降低; 在雨季(6月和9月)蒸腾速率的日平均值和日最高值均显著高于旱季(3月和12月)。表明林下益智在不同季节均能维持植株正常生长, 且表现出了较强的适应能力。3月土壤水分亏缺造成益智叶片气孔导度降低, 使其净光合速率维持在较低的水平。(2)通过光响应曲线修正模型计算出益智叶片各光合响应参数, 发现3月最大净光合效率和光饱和点显著低于6月、9月和12月; 而光补偿点和暗呼吸速率却显著高于6月、9月和12月, 表明3月土壤水分亏缺导致益智光合酶活性降低, 而表现出光抑制现象, 同时呼吸强度加剧, 光合能力显著下降。(3)采取相关分析发现, 3月气温与净光合速率显著负相关, 空气湿度与净光合速率显著正相关, 高温和低湿度共同限制了益智的光合作用; 而9月和12月, 林下光合有效辐射是益智光合作用的限制因子。     

修枝对复合农林系统内作物光合特性及生长的影响

以论证修枝作为复合农林系统优化措施的可行性为目的,对复合农林系统内的杨树进行4种不同强度的修枝处理,分别为P1(修掉树冠高度的1/6)、P2(修掉树冠高度的2/6)、P3 (修掉树冠高度的3/6) 、P4(修掉树冠高度的4/6),以CK(不修枝)为对照,研究了修枝对复合农林系统内冬小麦、夏玉米的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、细胞间隙CO2浓度(Ci)、气孔限制值(Ls)等光合生理特性以及农艺性状、产量构成因素的影响.结果表明:(1)修枝能有效增加作物光合速率、蒸腾速率,同一时刻修枝强度越大光合速率、蒸腾速率越大,下午时这种促进作用小于上午与中午.(2)修枝能显著促进小麦、玉米增高、增粗、增重,且越到后期修枝对作物生长的促进作用越明显.另外,修枝对玉米生长的促进作用大于小麦.(3)修枝能使林下作物大幅增产;修枝后玉米主要通过增加穗数,小麦主要通过增加粒重和穗粒数增产;修枝后玉米增产幅度大于小麦,小麦产量表现优于玉米,小麦比玉米更适合复合农林系统.     

Effects of tree competition on corn and soybean photosynthesis, growth, and yield in a temperate tree-based agroforestry intercropping system in southern Ontario, Canada

In 1987, the University of Guelph established a large tree-based intercropping system on 30 ha of prime agricultural land in southern Ontario, Canada. The purpose was to investigate various aspects of intercropping trees with prime agricultural crops. In this study, objectives were to investigate tree competitive effects (i.e., shading and competition for soil moisture) on under-story crop net assimilation (NA), growth, and yield. The effects of tree competition on corn (C4 plant) and soybean (C3 plant) photosynthesis and productivity in the intercropped system were studied during the 1997 and 1998 growing seasons. Corn and soybeans were intercropped with hybrid poplar (clone-DN-177) and silver maple (Acer sacharrinum) at a within-row spacing of 6 m and between-row spacing of 12.5 or 15 m. Trees were absent from control rows. Tree rows were oriented approximately north and south. Twelve crop locations were sampled around each tree. These were at 2 and 6 m east and west of the tree, located along a primary axis running through the tree trunk and perpendicular to the tree row, and at 2 m north and south of each location along the primary axis. Net assimilation and plant water deficit measurements were made three times daily (morning, noon, afternoon) on sampling days in July. Generally, tree competition significantly reduced photosynthetic radiation (PAR), net assimilation (NA), and growth and yield of individual soybean or corn plants growing nearer (2 m) to tree rows in both years and soil moisture in 1998. NA was highly correlated with growth and yield of both crops. These correlations were higher for corn than soybeans in both years, with corn, rather than soybeans being more adversely impacted by tree shading. In 1997, poplar, rather than maple, had the greatest competitive effect on NA. In 1997, the lowest plant water deficits, for soybeans and for corn, were observed for the maple treatment. Nonetheless, in both years, daily plant water deficits were non-significantly and poorly correlated with NA and growth and yield of both crops. However, soil moisture (5 and 15 cm depth) was significantly correlated with soybeans yield in 1998. Possible remediation strategies are discussed to reduce tree competitive interactions on agricultural crops.     

晋西黄土区果农间作的种间主要竞争关系及土地生产力

以晋西黄土区核桃×花生、核桃×大豆、苹果×花生和苹果×大豆4种典型果农间作模式为研究对象,分析果农间作模式中作物光合有效辐射（PAR）、净光合速率（P_n）、土壤水分和产量情况.结果表明：与农作物单作相比,间作模式中作物的PAR和P_n均出现不同程度的降低,并且离树体越近,PAR和P_n越小;P_n与作物产量呈显著正相关,说明光照是影响作物产量的重要因素之一;从整体趋势来看,核桃间作农作物0～100 cm土壤水分与相应单作模式间无明显差异,而苹果间作农作物0～100 cm土壤水分与相应单作模式间差异显著,说明苹果对作物土壤水分的竞争比核桃剧烈.研究区果农间作的土地利用效率平均提高70%,经济效益平均提高14%,且核桃间作模式优于苹果间作模式.为了提高间作作物产量,应加强水肥管理、增加树体与作物的间作距离或设置根障、定期适当修剪果树并种植耐荫作物.     

Main interspecific competition and land productivity of fruit-crop intercropping in Loess Region of West Shauxi

Taking the four typical fruit-crop intercropping models, i.e., walnut-peanut, walnut-soybean, apple-peanut, and apple-soybean, in the Loess Region of western Shanxi Province as the objects, this paper analyzed the crop (peanut and soybean) photosynthetic active radiation (PAR), net photosynthetic rate (P(n)), yield, and soil moisture content. Comparing with crop monoculture, fruit-crop intercropping decreased the crop PAR and P(n). The smaller the distance from tree rows, the smaller the crop PAR and P(n). There was a significantly positive correlation between the P(n) and crop yield, suggesting that illumination was one of the key factors affecting crop yield. From the whole trend, the 0-100 cm soil moisture content had no significant differences between walnut-crop intercropping systems and corresponding monoculture cropping systems, but had significant differences between apple-crop intercropping systems and corresponding monoculture cropping systems, indicating that the competition for soil moisture was more intense in apple-crop intercropping systems than in walnut-crop intercropping systems. Comparing with monoculture, fruit-crop intercropping increased the land use efficiency and economic benefit averagely by 70% and 14%, respectively, and walnut-crop intercropping was much better than apple-crop intercropping. To increase the crop yield in fruit-crop intercropping systems, the following strategies should be taken: strengthening the management of irrigation and fertilization, increasing the distances or setting root barriers between crop and tree rows, regularly and properly pruning, and planting shade-tolerant crops in intercropping.     

Intercropping Competition between Apple Trees and Crops in Agroforestry Systems on the Loess Plateau of China

Agroforestry has been widely practiced in the Loess Plateau region of China because of its prominent effects in reducing soil and water losses, improving land-use efficiency and increasing economic returns. However, the agroforestry practices may lead to competition between crops and trees for underground soil moisture and nutrients, and the trees on the canopy layer may also lead to shortage of light for crops. In order to minimize interspecific competition and maximize the benefits of tree-based intercropping systems, we studied photosynthesis, growth and yield of soybean (Glycine max L. Merr.) and peanut (Arachis hypogaea L.) by measuring photosynthetically active radiation, net photosynthetic rate, soil moisture and soil nutrients in a plantation of apple (Malus pumila M.) at a spacing of 4 m × 5 m on the Loess Plateau of China. The results showed that for both intercropping systems in the study region, soil moisture was the primary factor affecting the crop yields followed by light. Deficiency of the soil nutrients also had a significant impact on crop yields. Compared with soybean, peanut was more suitable for intercropping with apple trees to obtain economic benefits in the region. We concluded that apple-soybean and apple-peanut intercropping systems can be practical and beneficial in the region. However, the distance between crops and tree rows should be adjusted to minimize interspecies competition. Agronomic measures such as regular canopy pruning, root barriers, additional irrigation and fertilization also should be applied in the intercropping systems.     

Photosynthetic Response of Soybean to Microclimate in 26-Year-Old Tree-Based Intercropping Systems in Southern Ontario,Canada

In order to study the effect of light competition and microclimatic modifications on the net assimilation (NA), growth and yield of soybean (Glycine max L.) as an understory crop, three 26-year-old soybean-tree (Acer saccharinum Marsh., Populus deltoides X nigra, Juglans nigra L.) intercropping systems were examined. Tree competition reduced photosynthetically active radiation (PAR) incident on soybeans and reduced net assimilation, growth and yield of soybean. Soil moisture of 20 cm depth close (< 3 m) to the tree rows was also reduced. Correlation analysis showed that NA and soil water content were highly correlated with growth and yield of soybean. When compared with the monoculture soybean system, the relative humidity (RH) of the poplar-soybean, silver maple-soybean, and black walnut-soybean intercropped systems was increased by 7.1%, 8.0% and 5.9%, soil water content was reduced by 37.8%, 26.3% and 30.9%, ambient temperature was reduced by 1.3°C, 1.4°C and 1.0°C, PAR was reduced by 53.6%, 57.9% and 39.9%, and air CO₂ concentration was reduced by 3.7μmol·mol^-1, 4.2μmol·mol^-1 and 2.8μmol·mol^-1, respectively. Compared to the monoculture, the average NA of soybean in poplar, maple and walnut treatments was also reduced by 53.1%, 67.5% and 46.5%, respectively. Multivariate stepwise regression analysis showed that PAR, ambient temperature and CO₂ concentration were the dominant factors influencing net photosynthetic rate.     

不同土壤水分条件下紫藤叶片生理参数的光响应

测定了不同土壤湿度下2年生紫藤叶片光合速率（P_n）、蒸腾速率（T_r）及水分利用效率（WUE）等生理参数的光响应过程,探讨了紫藤正常生长发育所需的土壤水分和光照条件.结果表明:紫藤叶片的P_n、T_r及WUE对土壤湿度和光照强度的变化具有明显的阈值响应.维持紫藤正常生长（同时具有较高P_n和WUE）的土壤湿度范围为:体积含水量（W_v）15.3%～26.5%、相对含水量（W_r）46.4%～80.3%,最佳土壤湿度约为W_v 23.3%、W_r 70.6%.紫藤叶片对光照环境的适应性较强,在光合有效辐射强度（PAR）为600～1 600 μmol·m^-2·s^-1时,P_n和WUE具有较高水平,饱和光强在PAR为800～1 000 μmol·m^-2·s^-1.紫藤叶片光合作用非气孔限制的发生与土壤湿度与光照强度密切相关,W_v为18.4%～26.5%、W_r为55.8%～80.3%时,光合作用主要受气孔限制,光照强度的影响较小;超出此范围后,其受光照强度的影响较大,出现由气孔限制转变为非气孔限制的PAR临界值.紫藤正常生长允许的最低土壤湿度约为W_v 11.9%、W_r 36.1%,允许最高PAR约为1 000 μmol·m^-2·s^-1,是紫藤叶片光合机构受到破坏的临界点.     

农林复合系统中物种间水肥光竞争机理分析与评价

低丘红壤农林复合系统被认为能通过引入树木而利用土壤深层水分及防治水土流失,从而作为亚热带地区应对季节性干旱的有效利用方式。然而,复合也可引起光能、水分和养分的竞争,导致农作物减产。通过作物生长量的测定、利用多年监测的土壤水文数据、15N微区试验及光合有效辐射的测量,综合探讨了南酸枣-花生复合系统引起的物种间水肥光的变化;通过其交互作用形成的协同,竞争关系分析,较为全面地评价了农林复合系统水肥光竞争特征。研究表明：低丘红壤上南酸枣与花生复合,促进了南酸枣生长,却减小了20％～50％的花生产量和生物量。其原因不单是南酸枣遮荫引起复合花生光合有效辐射减弱,还与水、肥竞争有关。复合系统在旱季加大利用50～100cm土层土壤水分,从而缓冲了干旱造成的影响;但南酸枣与花生间作系统也存在着一定的水分竞争。复合使得南酸枣能够利用施于花生区及淋失到60cm深处的养分,提高了养分的利用率;但同时也导致养分的竞争并影响花生的生长。在花生产量、生物量受复合南酸枣竞争影响因子中,以光最大、养分其次、水分最小。农林复合系统水肥光交互作用因其组分类型与时空配置而异,需从生态、经济、社会效益方面对复合模式加以优化。     

灌溉量对苹果园内紫花苜蓿生物量与生理特征的影响

以苹果园内2年生紫花苜蓿为材料,设0.150、0.225(正常水平)和0.300m3/m2共3个灌溉量处理,研究不同灌溉量对紫花苜蓿生物量、光合生理指标、叶绿素含量、脯氨酸含量及电导率的影响。结果显示:(1)灌溉量对紫花苜蓿地上生物量有显著的影响,且随灌溉量的增加而增加;灌溉量大的处理苜蓿吸收根分布有浅层化趋势。(2)不同灌溉量处理的紫花苜蓿叶片净光合速率(Pn)与光合有效辐射(PAR)的变化趋势基本一致,均表现为在低PAR时Pn迅速增加,达到一定PAR后,Pn增幅渐趋平缓;净光合速率均随灌水量的增加而增加。(3)灌溉后土壤含水率和苜蓿叶片叶绿素含量随灌溉量的增加而升高,苜蓿叶片相对电导率随着灌水量的增加而呈现降低的趋势,低灌溉量可导致紫花苜蓿叶片中脯氨酸含量大量积累。研究表明,适当的灌溉可以有效改善苹果园土壤水分状况,提高紫花苜蓿光合生产力。