基于稳定碳同位素技术的华北低丘山区核桃-小麦复合系统种间水分利用研究

农林复合系统的林木和作物会充分利用水肥光热等资源、而在资源亏缺时也可能产生竞争,在华北低丘山区等水资源紧缺地区,种间水分竞争尤为突出。在冬小麦返青期、拔节期、灌浆期和成熟期4个生育期,测算了该地区核桃-小麦间作系统和单作小麦不同组分的稳定碳同位素组成(Stable carbon isotope ratio,δ13C)和核桃树干液流,结合生物量和气象数据资料计算出水分利用效率(water use efficiency,WUE)和耗水量(Water use,WU)。结果表明,间作核桃树、间作小麦和单作小麦的WUE分别为10.771—21.233、9.946—19.149和9.878—18.431 mmol C/mol H2O。单作小麦WUE在拔节期显著小于间作小麦。间作系统总耗水量为1755.19 t/hm2,比单作系统的2538.13 t/hm2少30.85%。核桃-小麦间作系统中,核桃耗水量占系统总耗水量的36.34%,在小麦的生长前期所占比例最多、在小麦旺盛生长期所占比重较小,而小麦越往生长后期需水越多。核桃与间作小麦的需水期错开,在时间上避免水分竞争。距离核桃树越近浅层土土壤含水量越高、而深层土越低,表明核桃主要吸收深层水,而间作小麦主要吸收浅层水,从位置上避免水分竞争。单作小麦产量、总生物量和总耗水量分别比核桃间作小麦的高26.79%、27.12%、36.30%(P=0.001、P=0.033、P=0.050)。间作核桃和单作核桃的单株果实产量平均分别为0.88和0.94 kg(P=0.829)。然而,核桃-小麦间作系统的产量土地当量比(Land equivalent ratio,LER)和产值水分利用效率(WUE ofeconomics,WUEe)却分别达到1.67和25.92元.mm-.1hm-2,比单作系统明显提高、水资源获得高效利用,同时具备生产优势和经济优势。

Water use of walnut-wheat intercropping system based on stable carbon isotope technique in the low hilly area of North China

Trees and crops in agroforestry system can make the best use of water,nutrient,radiance and heat.However,competition may occur when resources are scarce,especially for the water competition in the warm temperate semi-arid region.Due to arid climate,less rainfall and poor irrigation condition,water is one of the major factors limiting the development of agriculture and forestry in the low hilly area of North China.Stable carbon isotope ratio(δ13C) of walnut(Juglans regia L.)-wheat(Triticum aestivum) intercropping system and monoculture wheat as well as sap flow of walnut tree at seedling establishment,jointing,filling and maturing growth period of winter wheat in the low hilly area of North China were researched.Water use efficiency(WUE) and water use(WU) were calculated by using the δ13C value,crop biomass,walnut sap flow and meteorological data.The results showed that the WUE of intercropping walnut,monoculture wheat and intercropping wheat were 10.771—21.233,9.946—19.149 and 9.878—18.431 mmol C/mol H2O,respectively.The WUE of intercropping wheat were significantly greater than that in monoculture wheat at wheat jointing growth period.The total water use of the walnut-wheat intercropping system was 1755.19 t/hm2,which was 30.85% less than that in the monoculture wheat system(2538.13 t/hm2).Water consumption of the intercropping walnut accounted for 36.34% in the walnut-wheat intercropping system,respectively 62.09%,30.80%,35.58% and 27.24% at sowing-seedling establishment,jointing,flowering-filling and filling-maturing growth period of winter wheat.The walnut tree consumed the greatest amount of water at earlier growth period of winter wheat,and the less at vigorous growth stages of winter wheat.Contrary to the walnut,the water use of wheat was greater at its later growth period.Intercropping walnut and wheat staggered water demand periods and avoided temporal competition for water.Soil volumetric water content in the intercropping system was the greater the closer to the walnut tree in the shallow soil layer,and the less the closer to the walnut tree in the deep soil,which suggested that the walnut tree mainly absorbed deep water,while the intercropping wheat mainly absorb shallow water,it avoided spatial competition for water.The grain yield,total biomass and water use of monoculture wheat were respectively 26.79%,27.12% and 36.30%(P=0.001、P=0.033、P=0.050) higher than that of the intercropping wheat.The average fruit yield of intercropping and monoculture walnut were respectively 0.88 kg and 0.94 kg per tree(P=0.829).However,yield LER(Land equivalent ratio) and WUEe(WUE of economics) of the walnut-wheat intercropping system respectively reached 1.67 and 25.92RMB · mm-1 · hm-2,improved obviously comparing with monoculture system.The walnut-wheat intercropping system utilized water with high efficiency and exhibited both production advantage and economic advantage at the same time.