Preliminary Studies On The Effects Of Stumping Treatment On The Photosynthesis And Growth Of Artermisia Ordosica

Artemisia ordosica,as a kind of sandy semi-shrub,owns the benefit of windbreak and sand fixation.However,with the increase of A.ordosica’s growing years,its adaptive capacity to sandy land has gradually weakened.In this paper,the stumping treatment was carried out on the decline A.ordosica community in Kubuqi Desert,and then physiological and ecological effects were clarified by comparative between stumping and un-stumping A.ordosica.The study was done mainly from the aspects on the photosynthetic physiological indexes,canopy characteristics,chlorophyll content and its growth.The main research results were as follows:1.From the changes of photosynthetic physiological indexes,the diurnal variation between the two treatments in various indexes had certain similarity.The diurnal variation of net photosynthetic rate(Pn)showed a double peak curve with a phenomenon of “midday depression” at noon in July,and at that moment water use efficiency(WUE)also showed a low.But in September and in May of the second year,it occurred to be a single peak curve,and there was no "midday depression" phenomenon.From the point the differences of photosynthetic physiological indexes,at the vigorous growth period(in July,2015),the late growth period(September 2015),and the initial growth period of the second year(May 2016),the net photosynthetic rate(Pn)and the water use efficiency(WUE)of stumping A.ordosica were mostly higher than those of un-stumping A.ordosica at each time point,and the difference at some time point is significantly.The results showed that the net photosynthetic rate and water use efficiency were improved to a certain extent by stumping treatment.2.From the canopy characteristics,the leaf area index(LAI)of stumping A.ordosica was significantly higher than that of un-stumping A.ordosica in July(P<0.01),the same in the early August(P<0.05).The canopy openness(DIFN)was also higher than the value of un-stumping A.ordosica in these two periods,and the difference was significant in July(P<0.05),extremely significant in the early August(P<0.01).There was no significant difference in leaf inclination angle(MTA)between two treatments.From the leaf area index and the canopy openness results,it could be found that the density of branches and leaves of stumping A.ordosica was higher than that of un-stumping A.ordosica,so that the leaf area index was increased to some extent as well as the ability of light interception was also improved.3.The difference of chlorophyll content between stumping and un-stumping A.ordosica at different stages showed that the value of stumping A.ordosica was significantly(P<0.01)higher than that of the un-stumping A.ordosica in August 2015.This has a certain relationship with the good growth condition and the strong photosynthetic ability of stumping A.ordosica.From the comparison of different periods,the value of two samples also were the highest in May 2016,which was mainly related to the local precipitation in May and the low water content of the plant.4.From the perspective of A.ordosica growth difference,the plant height,the crown width,the number of shoots and the length of the longest shoots were not significantly different in both sample plots after the second year of stumping.However,there was significant difference in biomass production(P<0.05),which was significantly higher in stumping A.ordosica,it indicated that stumping was beneficial to the improvement of productivity and the accumulation of organic matter.