| Schima superba,the main species of subtropical evergreen broad-leaved forest in China,widely distributed in southern provinces,with fast growing,high yield,high quality and strong adaptability,is an important valuable hardwood tree species and biological fire and ecological protection tree species.It is an ideal afforestation tree with pine and fir,and its growth competitive advantage and effect of mixed yield are remarkable,attributed to the strong ability to find the light plasticity in heterogeneous resource environment.However,little is known about the relationship between the behavior and the competitive advantage and the growth difference among the different genotypes of S.superba.For this reason,three representative S.superba species in different producing areas were selected as test materials,set in heterogeneous and homogeneous nutrient environment with factorial design for natural light level of 100%,50% and 25%,to carry out the pot experiment.Meanwhile,under each treatment,the interspecies and intraspecific competitions were simulated by mixed planting of S.superba and C.lanceolata,as well as the pure plantation of C.lanceolata.Taking the pure plantation of S.superba as the control,we studied the plasticity behavior of S.superba and its difference with C.lanceolata.under different light and environmental conditions,so as to reveal the plastic mechanism of the competitive advantage of S.superba and the possible reasons for the increase yield of mixed with C.lanceolata and the stability of pure forest.Compare the growth responses of different S.superba breeds in different photographic environment and adjacent plants to analyze the plastic behavior and relationship between the growth behavior and the genetic background of S.superba,to provide theoretical basis and technical guidance for the implementation of efficient plantation cultivation and management to new varieties of S.superba.The main findings are as follows:1.Differences in the plasticity of S.superba and its intercropping with C.lanceolataThe growth response of S.superba and C.lanceolata was significantly different in both homogeneous and heterogeneous nutrient environments.In the heterogeneous nutrient environment,the growth of S.superba seedlings was higher with more dry matter accumulation and developed root systems,on the contrary,C.lanceolata growth performance in the homogeneous nutrient environment was better.Under different light conditions,the growth of the two species was the highest in full explosure,indicating that the two species were very bright light.The results showed that the growth of S.superba and C.lanceolata mixed plantation was better in the full explosrue and heterogeneous nutrient environment,especially for the growth of S.superba.The reason was that the total root length and root surface area of S.superba were significantly increased compared with that of single variety planting,and the root system was well proliferated in the rich layer,which increased its effective absorption of nitrogen and phosphorus in soil.In contrast,the root system of C.lanceolata was mainly distributed in the deep and bottom layers of soil nutrient,with low nutrient content.The nitrogen and phosphorus absorption efficiency was also lower than that of S.superba,reducing its growth vigor.Compared with the mixed planting,the root growth of S.superba pure plant was significantly reduced and the distribution of root was uniform and dislocated in different media layers.According to the analysis,the niche separation of S.superba and C.lanceolata reduced the degree of underground competition of two tree species,which may be one of the main reasons for the increase of mixed forest;In the pure cultivation,it may be due to the root recognition ability with the performance of mutual avoidance growth to alleviate the competitive pressure on limited nutrient resources to improve the stability of S.superba forest.S.superba also had a certain shade tolerance,when the light was reduced,its satiated point and the maximum net photosynthetic rate were significantly reduced,but the ability of utilization low light was enhanced.In addition,the biomass distribution plasticity of S.superba was higher,when in shade or mixed with C.lanceolata,the root-shoot ratio of S.superba was significantly lower,and the input of dry matter was added to the ground,which promoted the acquisition of light resources,to get more carbon benefits,and higher dry matter accumulation quality.The study also found that the morphology and overall phenotypic plasticity of S.superba were significantly higher than that of C.lanceolata,while their nutrient physiologic plasticity was much the same.In conclusion,S.superba had occupied a clear advantage in terms of different soil nutrients and light to seek,which contributed to forming the growth advantage of S.superba.2.Perceptions of the growth of S.superba to adjacent plant competition in different light and nutrient environmentFocusing on the heterogeneity nutrient environment,the perception differences of the growth of the three representative producing areas of Fujian Jianou,Jiangxi Xinfeng and Zhejiang Longquan in different light environments to adjacent plant competition were compared,revealing it was significantly different in different provenances.Mixed cultivation significantly promoted the growth and dry matter accumulation of Fujian Jianou species in the central area of S.superba,but Jiangxi Xinfeng provenances were per contra,and the provenances of Zhejiang Longquan were changed a little,which was related to that of Fujian Jianou,where the root-shoot ratio was low,and more biomass was put into the ground part of the photosynthetic organ to get more carbon benefits,while the investment in the underground part in Zhejiang Longquan and Jiangxi Xinfeng provenances were increased.However,the neighbor competition of the same species resulted in a significant decrease in root dry matter quality and in nutrient availability,which showed that the growth of seedlings and the amount of dry matter accumulation were significantly reduced.Although the other two sources of growth indicators increased a certain,still far lower than Fujian Jianou provenance.According to the shading treatment,the dry matter quality of the three provenances decreased,among which Fujian Jianou provenances were the obvious,dropping by 46.4% and 76.3% respectively under the natural light of 50% and 25%,indicating that Fujian Jianou provenances were more sensitive to the light However,the leaf biomass was 1.3 to 3.5 times higher than that of the other two sources,and the leaf area was larger,which meant that the total leaf area of the whole plant was also huge,and the light capture ability was still stronger than that of Zhejiang Longquan and Jiangxi Xinfeng,making the dry matter quality to be the largest among the three sources.The above results meant that the growth advantage of the germplasm of Fujian Jianou may be due to high biomass distribution plasticity3.Perceptions of the root development and nutrient uptake of S.superba to adjacent plant competition in different light and nutrient environmentFurther studies on the root morphology,spatial configuration as well as nitrogen and phosphorus efficiency of S.superba in the above test showed that the differences in root development and nutrient uptake of different S.superba were markedly different.The root length,root surface area and nitrogen and phosphorus uptake efficiency of Fujian Jianou were higher than those of Zhejiang Longquan and Jiangxi Xinfeng provenances,especially when mixed planting.The reason showed that the root system of Fujian Jianou was not only increased the rich proportion of soil,but also compensated hyperplasia in the poor soil layer,due to its root forging precision and wideness,leading to a significant increase in total root length and root surface area,and hence increased the uptake efficiency of nitrogen and phosphorus in the soil;While the provenances of Zhejiang Longquan and Jiangxi Xinfeng were affected by the competition of C.lanceolata,bringing about that the root development was inhibited and the nitrogen and phosphorus uptake efficiency was also reduced.When pure planted,the root parameters of the three provenances were decreased,and the nitrogen and phosphorus efficiency varied,but they were the highest in Fujian Jianou,which was consistent with the highest dry matter accumulation.Under the shading treatment,the root parameters of the three S.superba superstages were significantly reduced,but the cultivars forging advantages were changed a little in Jianou,where the root length and root surface area were significantly higher than Zhejiang Longquan and Jiangxi Xinfeng provenance,meanwhile the nitrogen and phosphorus absorption efficiency was also the highest.The above results showed that the provenances of Jianou in Fujian could obtain obvious advantages in terms of root system morphology,spatial configuration,and their genetic characteristics in nutrient harvesting and absorption.4.Perceptions of provenance photosynthetic characteristics of S.superba to adjacent plant competition in different light environmentThe photosynthetic characteristics of Fujian Jianou,Zhejiang Longquan and Jiangxi Xinfeng were significantly affected by light conditions through the analysis.Under the condition of full explosure,the photosynthetic capacity and dry matter of Fujian Jianou were high,at the same time,with higher chlorophyll and leaf nitrogen and phosphorus,the maximum net photosynthetic rate and Fv / Fm than those of Zhejiang Longquan and Jiangxi Xinfeng provenances.Under the condition of shading,the saturation point,compensation point and dark respiration rate of Jianou species in Fujian were signally lower than those in Longquan and Jiangxi Xinfeng,which could further improve the use of low light or low light capacity,revealing that Fujian Jianou provenance could not only make good use of high light intensity to a greater extent to promote their own growth,but had a strong ability to adapt to the low light,with the wide ecological landscape,good light adaptation and plasticity,making the growth advantage remarkable.5.Perceptions of S.superba provenance to the photographic interactionThe effects of light,nutrient environment and their interactions on the main growth traits of S.superba were studied with three provenances,emphasizing the growth performance of S.superba in mixed stand.The results showed that the provenances of S.superba had significant effect,the growth and nutrient efficiency besides the root-shoot ratio were significantly affected by provenances and photosynthesis,and the dry matter and phosphorus uptake efficiency were distinctly affected by the interaction of provenances and nutrient environment,while the effect of provenance × nutrient environment and light interaction on all traits did not reach the significant level,which indicated that the light was the main external factor affecting the growth of S.superba instead of the relative performance difference of the source.Compared with Jiangxi Xinfeng and Zhejiang Longquan provenances,the provenances of Fujian Jianou were more sensitive to environmental factors,and all the indexes were significantly higher than those of the other two sources.The growth would be reduced with the decrease of light intensity.The quality of dry matter in Jianou,Fujian Province was the largest in heterogeneous nutrient environment,which was obviously reduced in homogeneous nutrient environment.According to the results,it is suggested that the mixed forest should be preliminarily selected from the provenances with high vigor and genetic stability,but when the forest is inter-planted or the soil is more barren,the higher genetic stability should be preferred,making full use of potential interactions between provenances and environmental factors to improve the production efficiency of S.superba. |
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