| Black pine（Pinus thunbergii）is one of the important tree species in coastal shelterbelts and mountainous forests in northern my country.It has strong adaptability,and has the characteristics of resistance to cold,drought,strong wind,and poor soil.It is widely popularized and planted in my country.However,in recent years,the coastal protection black pine forests in Jiaodong area of Shandong Province have brought devastating damage to the black pine due to the danger of pine wood nematode,Monochamus alternatus and Arhopalus rusticus.Monochamus alternatus and Arhopalus rusticus are two important borer pests on black pine.At present,two kinds of adult beetles can be detected in most black pine forests in Shandong,and two kinds of longhorn beetle larvae can be found on the same black pine.However,the phenomenon that two kinds of longhorn beetles can coexist in the same black pine and feed on harm together has not been clearly explained.According to classical niche theory,niche differentiation is the key to the coexistence of species.Therefore,this study carried out research from two aspects of time and space ecology,and provided an important theoretical basis for exploring the interspecific relationship,population monitoring and control measures of the two beetles.The main results are as follows:1.In Weihai City,Shandong Province,there is a peak period of occurrence of adults of Monochamus alternatus among black pine forests,which is from late June to early July;there are two peak occurrence periods for adults of Arhopalus rusticus,from mid to late June and early to mid-August.During the two consecutive years of investigation,the temporal niche overlap values of the two adult beetles were 0.53±0.21 and 0.47±0.21,respectively,indicating that the two adult beetles had niche differentiation in time.2.Through the dissection of the infected black pine,it was found that the larvae of Monochamus alternatus were mainly distributed in the range of 0-8m in the trunk of black pine,while the larvae of Arhopalus rusticus were mainly distributed in the black pine below3 m,and the number continued to decrease with the increase of height.The spatial niche width of Monochamus alternatus is 7.00±0.43,and the spatial niche width of Arhopalus rusticus is2.74±0.18,indicating that Monochamus alternatus has a wider distribution on the black pine than Arhopalus rusticus.The spatial niche overlap index of the two types of longhorn beetles was 0.29±0.05,indicating that the two types of longhorn beetle larvae had obvious niche differentiation in space.3.By measuring the nutrients in black pine roots and stems,combined with the data analysis of the digestive enzymes in the midgut of the two types of longhorn larvae,it was found that the contents of water,reducing sugar,total sugar and cellulose in the roots of black pine were higher than those in the trunk and the roots of black pine.and cadre fat content is lower and the difference is not significant;the amylase and cellulase activities of the larvae of Arhopalus rusticus fed on the roots were higher than those of the larvae of Monochamus alternatus fed on the stems,but the activity of trypsin was lower than that of the larvae of Monochamus alternatus.4.By measuring the secondary metabolites of black pine roots and cadres,combined with the data analysis of the detoxification enzymes in the midgut of the two types of beetle larvae,it was found that the content of flavonoids in black pine trees with different degrees of damage was the highest,followed by total phenols,tannins and alkaloids.In addition,the activities of glutathione S-transferase and carboxylesterase in the larvae of Monochamus alternatus were higher than those in the larvae of Arhopalus rusticus,but the activity of acetylcholinesterase was lower than that of the larvae of Arhopalus rusticus. |
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