| Tomicus yunnanensis Kirkendall&Faccoli and Tomicus minor Hartig are two species of wood borer pests that endanger pine species in the genus Pinus L.in southwest China.The two of them could usually be found together on Pinus yunnanensis Faranch.feeding on the shoot and boring the trunks at different stages,causing pine mortalities,ecological destruction,and economic losses.The article studied from 2015 to 2017 in the natural spruce forests in Mountain Tianfeng in town of Pupeng,through sampling survey at field sites,and stem dissection and analysis,author investigated on the temporal and spatial niche of the two Tomicus species during the "branch transferring to trunk" and "trunk transferring to branch" periods and annlyzing the photosynthetic physiological on healthy needles of Pinus yunnanensis after damaged by two Tomicus species,and making the progress of the periodic,which aimed at providing important insect pest occurrence ground-based data for remote sensing monitoring of the P.yunnanensis forest biological disasters.This paper mainly studies the following aspects:1.The feeding-length of the two Tomicus species in the boring period was defined:The tunnel length of two species range from 0 to 160 mm.The tunnel length of T.yunnanensis in P.yunnaneensis is mainly distributed in the interval of 60?100 mm,and T.minor is concentrated in the interval of 60?80 mm.2.The shoot selection preference of the two Tomicus species in the shoot-feeding period was clarified:The main food of the two species of Tomicus spp mainly feed on branches of 50-70 mm length branches;Mean distance of T.yunnanensis entrance hole to apical bud is 28.00±10.41mm and T.minor is 28.05±4.68 mm;T.yunnanensis mainly choose the tip that diameter is 6.91±0.102 mm,and T.minor mainly choose those of diameter at 6.65±0.1 14 mm;The length of gallery of T.yunnanensis which feeding in the tips is 13.02±4.78 mm,and T.minor is 13.55±6.41mm.The differences between the four indexes are not significant.3.The spatial distribution of two Tomicus species in P.yunnanensis was clarified:(1)Distribution in the trunk:T.minor was mainly distributed at the mid to bottom trunk,while T.yunnanensis were distributed in the upper trunk;(2)Distribution at the branches:T.minor just distributed at 1?2 m,2?3 m,3?4 m branch,T.yunnanensis mainly was found at the branches,and the number of T.yunnanensis at branches was big which distributed at branch higher than 1 m and concentrated in 4?5 and 5?6 m;Distribution at the treetops:Two Tomicus species were randomly distributed in the tips at branches which from top to bottom at 1st round branch to 7th round branch.4.The spatial niche of two Tomicus species damaged in P.yunnanensis was determined:The spatial niche breadth of two kinds of beetle value is large,and the range of their distribution in the trunk is wide,but the niche breadth of T.yunnanensis is greater than T.minor,which has a wide range;At branches,the niche breadth of T.yunnanensis(0.6099)is far greater than the value of T.minor(0.3408),that the niche breadth of T.yunnanensis in the collateral to be wider than the T.minor,In shoots,the width of niche of two Tomicus species(0.8882,0.8114)is very close and large,which showing that two kinds of beetles in the shoot is evenly distributed.From the perspective of niche overlap in the whole tree,the niche overlap index of T.yunnanensis and T.minor are small and similar approach that can also harm the whole tree.These two species of small bark beetles,and their distribution tends to be separated,sharing less of space resources.From the perspective of niche similarity proportion,two kinds of beetle have high value in the trunk and shoots(0.5017,0.5785),indicating the niche of T.yunnanensis and T.minor is closer.From the interspecific competition coefficient,T.yunnanensis and T.minor in the trunk and branches on the level of competition is moderate,but the interspecific competition coefficient of two kinds of small beetles in shoots reached 0.9334,which competition is fierce5.The "trunk transferring to branch" period and the "branch transferring to trunk" period of two Tomicus species were clarified:The "trunk transferring to branch" period of two Tomicus species began in mid—May,then the two Tomicus species entered into emergence period at the same time.T.yunnanensis reached the emergence peak around June 1st,and T.minor was about ten days later;The peak of T.yunnanensis in the "branch transferring to trunk"period was around 2nd half of February,and T.minor was around 1st half of March,which was about half a month later than T.yunnanensis.6.The temporal niche of two Tomicus species damaged in P.yunnanensis was determined Two kinds of beetles in the time niche breadth and niche overlap indices are basically equal,while the time niche similarity proportion is 0.7115,indicating that the two beetles can harm at the same time in the growing season of P.yunnanensis.The damage period is longer,and the damage location is very similar.The interspecific competition was up to 0.8958,indicating that at the different period of time two kinds of beetle exist competitions.Although the competition is strong,the two kinds of pests can still feed in the trunk to harm the tree together7.The changes of main physiological indexes of P.yunnanensis damaged by two Tomicus species was determined:(1)The chlorophyll content of healthy needles in different damage levels of P.yunnanensis did not change and the net photosynthetic rate(Pn)did not change significantly either,showing that after the part of shoots damaged,healthy needles on the other shoot can still photosynthesis normally;(2)After shoot-feeding by two Tomicus species,the color of needles that is on the injured shoot turns from green to withered yellow gradually,and the chlorophyll content of needles decreased significantly.The net photosynthetic rate(Pn)was significantly lower than that of healthy needles. |
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