| The land formation time of the Yellow River Delta is short,the groundwater salinity and water level are high,the soil salinization is serious,the afforestation difficulty of coastal saline-alkali land has become the focus of environmental protection and sustainable research.Based on this,this study took the heavy saline-alkali land in the Yellow River Delta as the research object,and studied the survival and growth effects of afforestation in the saline-alkali land under the orthogonal test condition by using three factors: platform height,laying salt barrier layer and tree species.The effects of ground cover on the survival and growth of robinia pseudoacacia,Broussonetia papyrifera and Tamarix chinensis Lour were discussed by mulching film and pine needle litter.The main results are as follows:(1)The effects of planting field and laying salt barrier layer on the survival rate,preservation rate and growth of afforestation varied with tree species.Orthogonal test showed that the order of importance factors affecting the survival rate and survival rate of tree species was tree species > isolation layer material > platform height.The best combination of survival rate was Tamarix chinensis Lour platform height 1.0m,straw isolation layer.The best combination of robinia pseudoacacia and Broussonetia papyrifera was platform height 1.0m,straw isolation layer.The best combination of retention rate is Tamarix chinensis Lour,platform height 0.5m,stone isolation layer,robinia pseudoacacia and Broussonetia papyrifera.The order of importance of influencing tree growth factors was tree species > material of isolation layer > platform height.The best combination of tree growth was robinia pseudoacacia,platform height 1.5m and straw isolation layer,and the best combination of Broussonetia papyrifera and Tamarix chinensis Lour was platform height 1.5m and straw isolation layer.It was found that plastic film and pine needle litter had positive effects on the survival and growth of trees.Pine needles had a significant effect on the growth of robinia pseudoacacia,and plastic film and pine needle litter had a very significant effect on the biomass of robinia pseudoacacia.Pine needle mulch had a significant effect on the survival rate and ground diameter growth,and had a significant effect on biomass,while plastic film and pine needle litter had a significant effect on the preservation rate.The two mulching methods had significant difference in height growth,ground diameter growth and biomass.(2)The physiological characteristics of different tree species were affected differently by tabbed and salt-separated layer.The results of orthogonal test showed that the order of importance of factors affecting photosynthetic characteristics was tree species > isolation layer material > platform height.The best combination of robinia pseudoacacia,platform height 1.0m,straw isolation layer,and the best combination of Tamarix chinensis Lour and Broussonetia papyrifera was platform height 1.0m,straw isolation layer.The order of importance of factors affecting tree species’ leaf nutrients was isolator layer material > tree species > platform height.The best combination of leaf nutrients was Tamarix chinensis Lour,platform height 1.0m,straw isolator layer,and the best combination of robinia pseudoacacia and Broussonetia papyrifera was platform height 1.0m,straw isolator layer.The order of importance of influencing factors on protective enzyme activity was tree species > platform height > isolation layer material.The best combination was Tamarix chinensis Lour,platform height 1.0m,straw isolation layer.The best combination of Robinia pseudoacacia and Broussonetia papyrifera was platform height 1.0m,straw isolation layer.The order of importance of influencing factors on plasma membrane permeability of trees was tree species > isolation layer material > platform height.The best combination was Tamarix chinensis Lour,platform height 1.5m and gravel isolation layer.The best scheme for plasma membrane permeability of robinia pseudoacacia and Broussonetia papyrifera was platform height 1.5m and gravel isolation layer.Forest coverage test showed that litter mulch,pine needles of acacia,Broussonetia papyrifera leaves significant influence of total phosphorus,for each tree transpiration rate has a significant impact,pine needle cover has a significant effect on Broussonetia papyrifera net photosynthetic rate,two kinds of different tree species protection enzyme activity,plasma membrane permeability have a significant impact,extremely significant difference effect on acacia POD,SOD activity,The effect on membrane permeability and MDA content was significant.(3)The soil condition was improved by the bed field and the salt separation layer.The results of orthogonal test showed that the order of importance of factors influencing soil physical properties was as follows: isolation layer material > platform height > tree species.The best combination for improving soil physical properties was Tamarix chinensis Lour,platform height 1.5m and gravel isolation layer.The order of importance of factors affecting soil chemical properties was isolation layer material > platform height > tree species,and the best combination for improving soil chemical properties was Tamarix chinensis Lour,platform height 1.5m and straw isolation layer.In woodland mulching experiment,pine needle mulching had positive effect on increasing soil total nitrogen,hydrolyzed nitrogen and organic matter,film mulching had significant effect on soil water holding capacity,and pine mulching had significant effect on soil p H and organic matter.In general,physical engineering measures(mulching)had some advantages in improving soil physical properties,while biological measures(mulching with pine needles)had better effects on improving soil chemical properties. |
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