Research On Ecological Effects Of Agroforestry System Based On Meta-analysis

Agroforestry ecosystem is a land management method combining agriculture and forestry.It can make full use of various land resources,improve system productivity,and regulate climate,improve soil and maintain biodiversity,which is of great significance for sustainable agricultural development.Chinese agroforestry systems have a long history of development and are widely distributed.However,due to factors such as experiment cost and cycle,systematic studies on regional scale are lacking at present.For example,the change law of ecological effects of agroforestry systems under different climate and production conditions is not yet clear.Metaanalysis is a statistical method for the results of a single study of the same type,which can conduct a quantitative and scientific comprehensive analysis of the statistical results of several independent studies.Based on integration analysis,the ecological effects of typical agroforestry systems(farmland shelterbelt and tree-crop intercropping)were comprehensively analyzed in this study.Specific ecological effect indicators include farmland microclimate,soil physical and chemical properties and crop yield,and factors affecting ecological effects include altitude,average annual rainfall,average annual temperature and soil texture.The main research results are as follows:(1)Farmland shelterbelt and tree-crop intercropping system have obvious microclimate effects.Farmland shelterbelt forest significantly reduced wind speed(32.11%)and increased air humidity(20.37%);Both wind speed(38.10%)and air temperature(8.10%)were significantly reduced by tree-crop intercropping system.There is no significant difference between the two systems under different altitudes,average annual rainfall and average annual temperature.(2)Farmland shelterbelt and tree-crop intercropping system have obvious soil improvement effect.Farmland shelterbelt significantly increased soil water content(14.09%)and total nitrogen(33.70%),and significantly reduced soil total potassium(10.15%).Farmland shelter forest had no significant effect on the total soil porosity,but the effect was regulated by soil p H(QB=8.60,P=0.01),and the porosity increased significantly in acidic soil(17.28%).Soil water content(9.41%)and available P(33.43%)were significantly increased by tree-crop intercropping system.Soil bulk density(QB=6.08,P=0.04)and available nitrogen(QB=6.82,P=0.01)were significantly different among different soil textures.The bulk density decreased the most in clay(5.26%),and the available nitrogen increased the most in sand(18.66%).(3)Farmland shelterbelt has significant yield increasing effects on crops;tree-crop intercropping has a significant yield reduction effect on crops.Among them,shelterbelt could increase crop yield by 14.99% on average,and there was no significant difference among different crop species(QB=2.32,P=0.51),and corn(19.18%)had the largest effect.The effect of crop yield increase was significantly different among different annual mean temperature conditions(QB=9.33,P=0.03),and the yield reduction rate was the highest(30.24%)when the annual average temperature was 5-10℃.The crop yield had no significant change when the annual average temperature was higher than15℃ and lower than 5℃.Intercropping system significantly reduced crop yield(20.12%),and the yield variation trend of different crop species(QB=10.43,P=0.02)was significant.Peanut(38.49%)had the largest yield reduction,followed by wheat(20.40%),while corn and soybean yield had no significant change.The yield reduction effect of crops was significantly different under different annual average temperature(QB=6.36,P=0.04)and soil texture(QB=6.72,P=0.03).The maximum yield reduction(32.91%)was achieved under the condition of annual average temperature of 5-10℃,and the yield had no significant change under the condition of annual average temperature above 15℃.The grain yield decreased most significantly in sandy soil texture(27.65%),while there was no significant change in loam and clay texture.This study shows that agroforestry system can significantly regulate local microclimate,affect soil properties and crop yield,and has significant ecological effects.It is an effective path to realize sustainable management of agro-ecosystem.The types of agroforestry systems and different production conditions have different degrees of influence on the ecological effects of agroforestry systems.The differences of specific environmental factors should be taken into account in the promotion,application and future research.