Selection Of Mixed Tree Species Of Amygdalus Pedunculata Pall. Based On Allelopathy

Amygdalus pedunculata Pall.is an important eco-economic shrub species in Yulin area,which plays an important role in the ecological restoration process of local coal mine subsidence area.However,the pure forest of A.pedunculata has problems such as slow growth,easy to be buried by sand,difficulty in natural regeneration and low productivity per unit area.Compared with pure forests,mixed forests with reasonable interspecies collocation have the functions of maintaining stand stability,increasing the diversity of soil microbial communities,promoting stand growth and increasing productivity per unit area.Allelopathy plays an important role in interspecific allocation.Seed germination and seedling growth are closely related to allelopathy.Therefore,in this study,taking A.pedunculata as the research object,from the perspective of allelopathy,based on multi-disciplinary technical methods from plant physiology,soil science,forestry etc,through the experiment of indoor germination,pot planting and field cultivation,researched the allelopathic effects of leaf extracts of leaf extracts of local suitable shrub species(Amorpha fruticosa Linn.,Hedysarum mongolicum Turez.,Sabina vulgaris Ant.,Hippophae rhamnoides SSP.,Morus alba L.,Caragana korshinskii Kom.,Artemisia ordosica Krasch.and Salix psammophila Schneid.)and tree species(Pinus sylvestris var.mongolica Litv.,Broussonetia papyrifera(L.)Vent,Populus simonii Carr.and Pinus tabulaeformis Carr.)on the seed germination,seedling growth and physiology of A.pedunculata,and the effects of different mixed patterns on field young forest growth and soil physical and chemical properties of A.pedunculata under different environmental conditions.The aims to screened out the shrub and tree species suitable for mutual-benefit symbiosis with A.pedunculata,which provides a theoretical basis for the mixed afforestation of A.pedunculata in coal mine subsidence areas.Below are key research finding:(1)The treatment of A.fruticosa leaf extracts with a medium to low concentration(0.025-0.05 g·m L^-1)can promote seed germination and seedling growth of A.pedunculata to varying degrees,the inhibition effect was observed at the medium and high concentrations(0.15-0.20g·m L^-1),and medium concentration(0.10 g·m L^-1)varied with different cultivars of A.pedunculata.When the aqueous extract of A.fruticosa at the concentration of medium and low(0.025-0.05 g·m L^-1),the allelopathic comprehensive scores of seed germination,seedling growth and physiological of A.pedunculata decreased in the order of Yuyang No.1(YY₁),Shenmu No.6(SM₆),Shenmu No.8(SM₈),Shenmu No.7(SM₇),Yuyang No.6(YY₆),Yuyang No.3(YY₃),Yuyang No.5(YY₅)and Yuyang No.4(YY₄),cluster analysis showed that YY₁ and SM₆ had the strongest allelopathic effect.A.pedunculata of YY₁ and SM₆were selected as optimal seed sources for ecological restoration in coal mine subsidence areas.(2)The treatment of H.mongolicum,A.fruticosa,S.vulgaris,S.psammophila and C.korshinskii leaf extracts with a medium to low concentration can promote seed germination and seedling growth of A.pedunculata YY₁ and SM₆ to varying degrees,the inhibition effect on seed germination and seedling growth of A.pedunculata YY₁ and SM₆was significantly enhanced when the concentration was above medium and high.The comprehensive evaluation and cluster analysis of allelopathic effects of leaf extracts of eight shrubs on seed germination,seedling growth and physiological of A.pedunculata showed that the comprehensive scores of leaf extracts of H.mongolicum,A.fruticosa,S.vulgaris,S.psammophila and C.korshinskii on A.pedunculata YY₁ and SM₆were higher than those of the other three shrub species,the allelopathic comprehensive scores of four tree species on seed germination,seedling growth and physiological of YY1 and SM6 were as follows:P.sylvestris>B.papyrifera>P.tabulaeformis.H.mongolicum,A.fruticosa,S.vulgaris,S.psammophila and C.korshinskii can be used as primary selection mixed shrub species,and P.sylvestris,B.papyrifera,P.tabulaeformis are used as primary selection mixed tree species.(3)The comprehensive evaluation of allelopathic effects at medium and low concentrations showed that the allelopathic comprehensive scores of A.pedunculata aqueous leaf extracts on seed germination,seedling growth and physiological of two shrub species was A.fruticosa>C.korshinskii;The comprehensive evaluation of allelopathic effects showed that the allelopathic comprehensive scores of A.pedunculata aqueous leaf extracts on seed germination,seedling growth and physiological of four tree species were as follows:P.sylvestris>P.tabulaeformis>B.papyrifera>P.simonii.A.pedunculata leaf extraction at medium and low concentrations had the strongest promoting effect on A.fruticosa and P.sylvestris.(4)The leaf extracts of S.psammophila,A.fruticosa,S.vulgaris and C.korshinskii,P.sylvestris,B.papyrifera and P.tabulaeformis could significantly promote the potted seedling growth of A.pedunculata YY₁ at low and medium concentrations,while the above medium and high concentrations showed inhibitory effect,and the medium concentrations varied with different donor varieties.The allelopathic scores of primary shrub species leaf extracts on seedling growth and physiological of A.pedunculata YY₁were as follows:C.korshinskii>A.fruticosa>S.vulgaris>S.psammophila.The allelopathic scores of primary tree species leaf extracts on seedling growth and physiological of A.pedunculata YY₁were as follows:P.sylvestris>B.papyrifera>P.tabulaeformis.C.korshinskii,A.fruticosa and S.vulgaris can be used as multiple selection mixed shrub species,P.sylvestris can be used as multiple selection mixed tree species.(5)The overall physiological of seedling leaves with different receptors were as follows:With the increase of the concentration of donor leaf extract,CAT activity and root activity were firstly increased and then decreased,while the activities of POD and SOD,soluble protein and chlorophyll contents were decreased,while MDA,cell membrane permeability and soluble sugar contents had the opposite trend.(6)The mixed planting of C.korshinskii,A.fruticosa,S.vulgaris and P.sylvestris with A.pedunculata can significantly promote the growth of the seedlings and increase their biomass.The comprehensive score of soil characteristics of young forest land under four mixed patterns was as follows:A.pedunculata×A.fruticosa>A.pedunculata×C.korshinskii>A.pedunculata×P.sylvestris>A.pedunculata×S.vulgaris>A.pedunculata pure forest.(7)The suitable donor concentration range of A.pedunculata was 0.025-0.05 g·m L^-1,and the best concentration is 0.05 g·m L^-1.The priority order of selection of mixed tree species suitable for mutual benefit and symbiosis of A.pedunculata was A.fruticosa,C.korshinskii,P.sylvestris and S.vulgaris.In addition,the suggestions of mixed arrangement were put forward for the planting patterns of A.pedunculata in the area with annual precipitation of 300-400 mm.