不同种植空间格局下本地作物对外来杂草的抑制作用及竞争机制的研究

Farmland is one of the major habitats invaded by non-native plant species, which damage crop production. There is a great need for new and environmentally-friendly methods to control invasive weeds. There is new evidence that the potential for many crop species to suppress weeds is much greater than previously thought, and this presents new possibilities for the management of agricultural weeds. Several studies have shown that a uniform crop planting spatial pattern can improve the suppression of weeds by crops, but there has no study specifically focusing on invasive weeds in a native crop. In addition, current research has considered only above-ground effects of competition among plants, not below-ground effects. This project will investigate the interaction between the important native crop soybean (Glycine max) and the invasive weed redroot pigweed (Amaranthus retroflexus) as a model system of crop-invasive weed competition. To improve our understanding of the mechanisms by which increased crop uniformity and density improve the suppression of invasive weeds, we will vary spatial uniformity (uniform grid planting pattern vs. the standard aggregated row pattern), crop density and crop variety, and evaluate the dynamics of photosynthesis, above and below-ground biomass accumulation, plant nutrient uptake, phenotypic plasticity, and soil nutrition content. The study will be performed on a typical farm in northeast China. Through this study, we hope to develop a new approach to management of invasive weeds, while reducing the use of chemical herbicides and decreasing environmental pollution. If successful, such a model system for increasing crop suppression of weeds will have great value for theory and practice of invasive weed management.

农田是外来入侵种入侵的主要生境类型，而外来杂草则是危害农业生产的重要因素。目前，主要采用化学除草剂控制外来杂草，危害生态环境和人类健康。因此，亟需探索新的环境友好型控制方法。已有研究表明，采用均匀型格局种植竞争力强的作物可有效抑制杂草生长，但研究多为本地杂草，未有研究针对外来杂草；且研究局限于地上部分的竞争，忽略了地下部分的竞争，不足以阐明相关的竞争过程。因此，本研究拟以本地作物大豆和外来杂草反枝苋为研究对象，比较研究均匀型格局（栅格化）和传统聚集型格局（行种）的大豆田中, 在不同密度的大豆和反枝苋条件下，两种表型不同的大豆和反枝苋的光合特性、地上/地下生物量积累、养分吸收、表型可塑性及土壤养分的动态变化，来探讨两者的竞争机制。通过本项研究，有助于更好地控制外来杂草，减少化学除草剂使用，减轻环境污染；有助于了解不同种植格局下本地作物与外来杂草的竞争机制；具有重要的理论和实践意义。

外来杂草是危害农业生产的重要因素。目前，主要采用化学除草剂来控制外来杂草，危害生态环境和人类健康。因而，亟需探索对环境友好的治理杂草方法。本研究以东北农田中常见外来杂草反枝苋和典型作物大豆为研究对象，通过研究两物种在不同大豆种植格局（匀播和行种）和密度下的竞争过程，来探索控制杂草的新方法。研究结果如下：.(1)均匀型种植格局降低了反枝苋的株高和比叶面积，减弱了其与大豆的竞争优势。当大豆与反枝苋混种时，无论在何种种植格局下，大豆比叶面积均显著大于反枝苋，即相同的叶生物量在大豆中形成的叶面积大，这很可能是其竞争光能的生态策略, 而反枝苋则在高度上占有优势，以高度来竞争光，两者竞争策略不同。.（2）当大豆和反枝苋混种时，在苗期，均匀型格局下大豆具有较高的净光合速率、光合水分利用效率和叶绿素含量，且以反枝苋密度为大豆田平均密度时（12万株·ha-1）差异较大；而反枝苋则相反，均匀型格局下反枝苋的净光合速率、光合水分利用效率、叶绿素含量均低于行种。.(3)当大豆和反枝苋混种时，匀播密植促进了大豆生物量积累而减弱了反枝苋生物量积累。在大豆盛荚期，高密度（49万株·ha-1）匀播下大豆总生物量较低密度（25万株·ha-1）行种（常见播种密度和方式）增加了96.52%-141.0%，反枝苋总生物量较低密度行种减少了30.05-55.00%；在大豆成熟期，高密度匀播下的大豆比低密度条播增产67.67-87.37%。.(4)当大豆和反枝苋混种时，均匀种植与行种相比，在均匀型格局下大豆的营养元素（氮、磷、钾）含量均大于行种，且以盛荚期较为显著；反枝苋茎和叶的氮、磷含量在两种格局之间差异不显著；就钾素而言，均匀格局下反枝苋茎钾含量高于行种，叶片差别不大，但反枝苋籽粒氮、磷含量显著小于行种。反枝苋入侵增加了大豆蛋白质含量，尤其增加了蛋氨酸含量。.

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