| With the change of global climate,not only the functional characters of plants,but also the relationship between plant species will be affected by precipitation change,especially in desert areas.Therefore,it is important to reveal the response mechanism of eremophytes to adversity stress by studying the functional characters and interspecific relationship among eremophytes under different precipitation.In this study,monocultural and mixed Reaumuria soongarica and Salsola Passerina were taken as research objects,and different precipitation gradients(annual precipitation50mm~300mm,?=50)were set.The main functional character indexes of monocultural and mixed plants were measured,and the differences of plant functional traits and interspecific relationship indexes were compared.The adaptation mechanism of mixed R.soongarica and S.Passerina induced by precipitation change was revealed,which was of great significance for understanding and perfecting the negative/positive transformation of plant interaction driven by environmental stress.The results were as follows:(1)The root,stem and leaf biomass of mixed R.soongarica and S.Passerina decreased.The difference between monocultural and mixed R.soongarica was not significant.However,the indexes of mixed S.Passerina decreased sharply,in which the difference between monocultural and mixed S.Passerina was particularly significant under the treatment of 50 mm and 300 mm annual precipitation(P<0.01).It was indicated that R.soongarica benefited from the mixed relationship,while as the benefit,the biomass of S.Passerina was lost.The analysis of variance showed that the leaf biomass of R.soongarica root and S.Passerina were significantly influenced by precipitation(P<0.01).With the increase of precipitation,the biomass and its proportion of root,stem and leaf of R.soongarica and S.Passerina increased first and then decreased.When the annual precipitation was 150 mm to 200 mm,the biomass of each part reached the maximum.(2)Compared with monocultural ones,the leaf-root weight ratio,leaf weight ratio and source-sink weight ratio of mixed R.soongarica and S.Passerina increased,while the root-shoot ratio decreased,indicating that root growth of mixed R.soongarica and S.Passerina was inhibited due to the increased competition of underground root for water and nutrients.With the increase of precipitation(50mm~300mm,?=50),the leaf-root weight ratio of monocultural and mixed R.soongarica decreased first and then increased,while the root-shoot ratio was opposite;the two indexes of monocultural and mixed S.Passerina showed the opposite trend.The leaf weight ratio and source-sink weight ratio showed no much change.(3)The carbon sequestration capacity of mixed R.soongarica was significantly higher than that of monocultural ones(P<0.05),and interspecific relationship had a significant impact on the organic carbon content of R.soongarica in root,stem and leaf(P<0.01);while the carbon sequestration capacity of mixed S.Passerina was weakened,although the capacity of leaf was enhanced,the capacity of root and stem were greatly weakened.The interspecific relationship had a significant impact on the organic carbon content in root,stem and leaf of S.Passerina(P<0.05).Nitrogen fixation ability of R.soongarica and S.Passerina decreased after mixed condition.R.soongarica decreased mainly in leaf,up to 29.61% most and root nitrogen fixation ability increased.S.Passerina decreased sharply mainly in root,up to 53.03% most.The C/N ratio of root and stem had no much change in R.soongarica,but the C/N ratio of leaf increased significantly(P<0.05),with maximum increase of 153.14%.The C/N ratio of S.Passerina leaf did not change much,while the C/N ratio of stem decreased by 81.82% mostly.The C/N ratio of root increased by 106.92%.The total carbon content of R.soongarica increased gradually with the increase of precipitation,while S.Passerina showed the opposite rule.The total nitrogen content of the two plants fluctuated with the increase of precipitation.(4)The change of soil water content was significantly affected by precipitation,interspecific relationship and their interaction(P<0.01).The soil water content of R.soongarica was less in monocultural condition,but that of monocultural S.Passerina was higher.This indicated that the absorption capacity of R.soongarica root system was better than that of S.Passerina.The decrease of soil water content after mixing indicated that both plants in the mixed community need more water.The rootweight(RW),root length(RL)and root surface area(RSA)of mixed R.soongarica and S.Passerina decreased significantly compared with monocultural condition.R.soongarica decreased sharply in RL and RSA,while S.Passerina decreased mainly in RW.With the gradual increase of precipitation,RW,RL and RSA of R.soongarica and S.Passerina increased first and then decreased.The maximum value appeared under the treatment of 150 mm to 250 mm annual precipitation,which indicated that suitable precipitation significantly promoted plant growth and development.The specific root length(SRL)and specific surface area(SRA)of mixed R.soongarica decreased significantly after 50 mm and 100 mm annual precipitation treatment,while the S.Passerina remained basically unchanged.Under 250 mm and 300 mm annual precipitation treatment,SRL and SRA of mixed S.Passerina were much larger than those of monocultural ones,while the R.soongarica remained basically unchanged.Each index of fine root in mixed R.soongarica and S.Passerina was obviously smaller than that of monocultural ones,but the change of coarse root was not significant.This indicated that fine root of mixed R.soongarica and S.Passerina were more sensitive to interspecific interaction than coarse root.It also reflected that R.soongarica and S.Passerina could adapt to the new growth environment by adjusting the morphological development of fine root.(5)The relative root length(RRL)of fine root and relative yield total(RYT)under different precipitation were all greater than 1,which indicated that the root of R.soongarica and S.Passerina under different precipitation treatments utilized different resources and showed symbiotic and reciprocal relationship.With the increase of precipitation,RRL and RYT of the two plants showed a monocultural peak pattern.Under 150 mm and 200 mm annual precipitation treatment,RRL and RYT of R.soongarica and S.Passerina were the largest,suggesting the utilization efficiency of resources was the highest.The competition rate(CR)of R.soongarica under different precipitation was greater than 1,and that of S.Passerina was less than 1,which indicated that the competitiveness of R.soongarica was higher than that of S.Passerina when mixed.With the increase of precipitation,the CR of R.soongarica was U-shaped,while that of S.Passerinas was the opposite.It showed that the R.soongarica RCI was stronger than that of S.Passerinas except for 150 mm and 200 mm annual precipitation.The total RCI of R.soongarica and S.Passerina was greater than 0,and the distribution rule was similar to CR.It showed that the facilitation(mutual assistance)was produced after the mixing of R.soongarica and S.Passerina.RCI of R.soongarica was negative except in the treatment of 150 mm and 200 mm annual precipitation,and was all higher than that of S.Passerina under four precipitation treatment.It showed that S.Passerina could promote the growth of R.soongarica under the four kinds of annual precipitation treatments,while R.soongarica showed a negative effect on S.Passerina. |
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