| In order to explore the effect of global warming on the growth of Juglans mandshurica seedlings,the study used Juglans mandshurica seedlings in the mountainous area of Eastern Liaoning Province as material,using the open field warming system,and CK(+0 ℃),T1(+2 ℃)and T2(+4 ℃)treatment were set respectively.The changes of soil temperature,soil moisture and air temperature were monitored during the whole grow season.At the same time,the photosynthetic parameters,chlorophyll fluorescence parameter,seedling height,ground diameter and biomass of seedlings were measured monthly under different temperature warming treatments.The aim of the study was to reveal the response law of Juglans mandshurica seedlings to different warming treatments,and the result can provide scientific direction for Juglans mandshurica seedlings’ production and management under future climate change.The results are as follow:(1)The warming platform can increase the sample soil temperature well.The T1 treatment increase soil temperature by 1.7~2.3 ℃,and T2 treatment increase soil temperature by 3.2~4.5 ℃.While the effect of air temperature is relatively poor.The T1 and T2 treatment increase soil temperature by 1.5~2.1 ℃ and 2.3~3.7 ℃ respectively.At the same time,the warming effect of daily minimum temperature of soil and air were better than the daily mean temperature and the daily maximum temperature.There is no significant effect on soil moisture under different warming treatments.(2)In the early stage of the seedlings of Juglans mandshurica(June),warming treatments can promote photosynthesis of seedlings,and the promotion increased with the warming intensity.At the middle growth stage(July and August),the photosynthesis of seedlings were inhibited by warming treatments.In August,the inhibition of photosynthesis was more significant with the increase of warming intensity.At the late stage of seedling growth(September),the inhibition of the warming on seedling photosynthesis with the increase of the warming intensity was less than that at the middle stage.Although the photosynthetic intensity of Juglans mandshurica seedlings was inhibited by the warming treatment in the middle stage,the photosynthetic intensity was the strongest in the middle growth stage(July to August),followed by the early growth stage and the weakest photosynthetic intensity in the late growth stage.(3)In July,the Fo and NPQ values of Juglans mandshurica seedlings decreased under T1 treatment and turn to increase under T2 treatment.The value of Fv/Fm,ΦPSⅡ,q P and ETR showed a trend of increased first and decreased followed with the increase of warming intensity;In August and September,Fo and NPQ gradually increased with warming intensity,and Fv/Fm,ΦPSⅡ,q P and ETR showed a gradually decreased with warming intensity.The change trend of chlorophyll fluorescence parameters were consist with photosynthetic parameters during the growing season.(4)The survival rate and growth of Juglans mandshurica seedlings were affected by warming treatments.Comparing with CK treatment,the survival rate of seedlings increased from 1.6% to 18.4% under T1 treatment,while the survival rate of seedlings decreased from 6.6% to 11.7% under T2 treatment.In the early stage of seedling growth,the increment of plant height increased with the increase of warming intensity.Compared with CK treatment,the increment of plant height under T1 and T2 treatments increased by 26.0% and 77.6% respectively;In the middle and late stages of seedling growth,T1 treatment would promote the increase of plant height,the increament of plant height under T2 treatment turn to decrease.The change of ground diameter increment of seedlings was consistent with the change of plant height increment.The biomass of seedlings also changed with the warming intensity.During the middle growth period,the biomass of seedlings decreased with the increase of warming intensity.Compared with CK treatment,the biomass of T1 and T2 treatments decreased by 15.2% and 44.8% respectively,and the changes of biomass of roots,stems,and leaves were basically consistent with the change of total biomass.The effects of warming on biomass at the late stage of seedling growth and the biomass increase were consistent with the middle period of growth.At the same time,The effect of warming on above-ground biomass is larger than underground biomass. |
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