The Ecological Mechanism Of Yield Advantage And Spatio-temporal Stability In Different Crop Combinations

Intercropping is widely used in agricultural practice,with numerous crop species mixtures.Little attetion was concentrated to the interspecific dynamic and temporal satbility of intercropping productivity,whereas most was concerned about the highly efficiency resources utilizations in previous.In the present study,a series of field experiments were conducted at three experimental sites including Wuwei,Zhangye,Jingyuan from 2012 to 2014 to investigate 19 intercropping systems and their corresponding monocultures.Our objectives were to investigat the influences of interspecific interactions on the advantages of crop productivity,nutrient acquisition and the spatio-temporal stabilities of the advantages.The dynamic process of biomass production and nutrient capture in different intercropping systems was investigated by using logistic models to improve the mechanism of interspecific interactions.The purpose of this study is to provide theoretical foundation to design species combinations for intercropping.The main results were as follows:(1)Intercropping increased the productivity and nutrient acquisition(based on yields on comparable areas)by 14.6%～46.0%for the most of the maize-based intercropping systems.Land equivalent ratios(LERs)were 1.18～1.54 based on productivity in the short-life-period crops(oilseed rape,flax and pea)/sunflower intercropping systems.There was significantly positive relationship(P<0.01)between LER and temporal niche differentiation(TND)in these intercropping systems,especially in the tall/short combinations.(2)Positive(or negative)of net biodiversity effect,positive(or negative)complementarity effect and positive(negative)selection effect occur when increases(or decreases)of productivity and nutrient acquisition in intercropping systems compared to the monoculture,were dominant by the high-yield component crops.Positive(or negative)net biodiversity effect,positive(or negative)complementarity effect and negative(or positive)selection effec occur when increases(or decreases)of productivity and nurient acquisition in intercropping systems compared to the monoculture,were dominant by the low-yield component crops.There was a significantly positive relationship(P<0.05)between complementarity effects and temporal niche differentiation,and a significantly negative relationship(P<0.05)between selection effects and temporal niche differentiation in the intercropping systems,especially in the tall/short combinations.(3)In the maize/faba bean,maize/pea and maize/wheat intercropping systems,the maximum above-ground dry weight and cumulative nutrient(Ymax)uptake of intercropped faba bean,pea and wheat increased by 34.5%～49.5%,8.6%～38.1%and 34.9%～62.4%,respectively,compared with that of the corresponding sole cropping.Maximum daily growth rates and nutrient uptake rates(Imax-Y)by intercropped faba bean,pea and wheat were significantly increased by 1.6～2.1 times,1.3～1.6 times and 1.7～2.4 times,relative to the corresponding sole cropped crops,respectively.There was no significant difference in Ymax and Imax-Y between sole maize and maize intercropped with faba bean or with wheat,while Ymax and Imax-Y of maize intercropped with pea increased by 25.5%～38.9%and 24.3%～60.7%,respectively,compared with that of sole maize.In addition,maize intercropped with faba bean,pea and whea significantly postponed the time to reach the maximum daily growth rates and nutrient uptake rates(TImax-Y)about 10～13d,11～20d and 3～12d compared with sole maize,respectively.Amplified niche differentiation between crop species in intercropping systems.(4)The spatio-temporal stabilities of productivity and nutrient acquisition of the most of the intercropping systems were comparable to the corresponding monoculture systems.The temporal stabilities of productivity and nutrient acquisition of intercropping systems,particularly short-life-period crops(oilseed rape,flax)/Iong-life-period and taller crops(maize,sunflower)combinations,increased by 35.2%～256.8%compared with that of sole crops.In contrast,the temporal stabilities of productivity and nutrient acquisition of legume cropps such as soybean or pea/maize intercropping was equal or greater than the corresponding sole crops.To sum up,the majority of intercropping systems had not only efficient resource utilization and yield advantage,but also sustain spatio-temporal stabilities of productivity and nutrient acquisition.