光能竞争对商洛低山丘陵区农林复合系统林下作物生产力的影响

Impacts of Light Competition on Crop Productivity in Agroforestry Ecosystem in the Hilly Regions in Shangluo

农林复合系统是改善商洛低山丘陵区脆弱生态环境、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)-大豆(秦豆8号)和核桃-桔梗(Platycodon grandiflo-rum)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,大豆、桔梗的光合有效辐射、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、桔梗的光合速率、生物量以及产量不相关或负相关。而15～30cm土壤含水量与大豆的生物量和产量以及桔梗的生物量正相关。但大豆、桔梗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大豆、桔梗产量下降的主要原因。

Establishment of agroforestry is the most effective way to restore the disturbed lands in the hilly regions and to develop local economy. In order to study the potential benefits of tree-based intercropping systems, photo- synthesis, growth and yield of soybean （Qindou 8） and balloonflower （Platycodon grandiflorum） were studied by measuring photosynthetic active radiation （PAR）, plant water deficit and soil moisture in a 6-year-old plantation of walnut （Juglans regia） growing at a spacing of 5 m × 3 m in the hilly region in Shangluo, Shaanxi, China. Effects of tree competition significantly reduced the PAR, the Net photosynthetic rate （P,,）, growth and yield of individual soybean or balloonflower plants growing nearby （within 1 m） between tree rows. In 2010, daily plant water deficits were not significantly correlated with the Pn and growth and yield of the both crops. However, the soil moisture （15--30 cm depth） was significantly correlated with biomass and yield of the crops. The PAR was highly correlated with the growth and yield of both crops, which indicated that the competition for light was one of the key factors impacting crop yield. Possible remediation strategies were suggested to reduce competitive interac- tions between the tree and crop species.