In agroforestry systems, the canopy of maturing trees progressively reduces the radiation available for the crop. Tree management practices such as pollarding can be used to restore the crop light availability. We monitored durum wheat, barley and pea yields during three consecutive years in an alley‐cropping agroforestry system with hybrid walnut trees in Southern France. Trees have been pruned regularly to 4 m since planting (in 1995), and a section of 50 trees was pollarded at 4 m height for the first time in 2013. We measured the yields and yields components in the two different tree management systems and in a sole crop control. The non‐pollarded trees reduced significantly the incident light (around 80% of the global radiation left in average) and both wheat (68% of the control) and pea (69% of the control), but not barley mean yields. In pollards inter‐row, the average incident light was 98% of the total radiation the first year and the wheat yield 89% of the control. But 3 years after pollarding, the incident light was 79% of the total radiation and the pea yield was only 67% of the control. Pollarding had a transient positive impact on crop yield; after 3 years, pollards were more competitive for light than control trees. Pollarding may also reduce the belowground trees competition, but slightly, as the crop vegetative growth occurs when the trees are leafless.

中文翻译：

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在成熟的小巷农林业系统中，结球果树能否提高作物产量？

在农林业系统中，成熟树木的树冠逐渐减少了可用于作物的辐射。树木管理（例如花粉剥落）可用于恢复作物光的可用性。在法国南部，采用杂种核桃树的小巷农作物种植系统，我们连续三年监测硬粒小麦，大麦和豌豆的产量。自种植（1995年）以来，树木被定期修剪至4 m，2013年首次在4 m高处对50棵树进行了修剪。我们测量了两种不同的树木管理系统中的产量和产量组成唯一的作物控制。非花粉树木可显着降低入射光（平均约占全球总辐射量的80％）以及小麦（占对照的68％）和豌豆（占对照的69％），但大麦平均单产不降低。在花poll行间，第一年的平均入射光占总辐射量的98％，小麦产量占对照的89％。但是在进行花粉授粉后3年，入射光占总辐射的79％，而豌豆的产量仅为对照的67％。授粉对作物产量产生了短暂的积极影响；3年后，与对照树相比，花果树在光照方面更具竞争力。授粉还可能减少地下树木的竞争，但会稍有减少，因为树木无叶时会发生作物营养生长。3年后，与对照树相比，花果树在光照方面更具竞争力。授粉还可能减少地下树木的竞争，但会稍有减少，因为树木无叶时会发生作物营养生长。3年后，与对照树相比，花果树在光照方面更具竞争力。授粉还可能减少地下树木的竞争，但会稍有减少，因为树木无叶时会发生作物营养生长。