Effects Of Soil Warming And Nitrogen Desposition On Fine Root Anatomical And Morphological Traits And Arbuscular Mycorrhizal Colonization Of Chinese Fir Seedlings

There have been a large number of studies on branch order effectively distinguishes roots with absorptive capacity within root system,and the first two roots has been regarded as the absorptive roots,however,no study has determined how it responds to the interactive warming and nitrogen deposition.In this study,we attempted to examine the interactive effects of soil warming and nitrogen deposition on fine root of the 3-year-old Chinese fir(Cunninghamia lanceolata)seedlings in subtropical China.And in 2016 and 2017 the mesocosm experiment,with a factorial design of soil warming(ambient,+5 ?)and nitrogen desposition(ambient + 80 kg · hm-2 · a-1),was carried out in the Chenda State-owned Forest Farm in Sanmin,City,Fujian Province,China,and each had 5 replicate 2m×2m mini-plots.Four Chinese fir seedlings were planted in each mini-plot.We applied to measure fine root anatomy(Diameter,Cortex thickness,Cortical layer number,Stele diameter,Stele to diameter),morphology(Specific root length,Specific root surface area and Root tissue density),stoichiometry(C,N/P,C/N,N/P,C/P),and fine root tips arbuscular mycorrhizal colonization.The results showed that:(1)The W treatment had significantly decreased the first-two order roots diameter,the WHN treatment had significantly decreased the second-order root cortex thickness.The W and HN treatment had significantly increased the first-order root cortical layer number.The HN treatment had significantly increased the first-order root stele diameter;the WHN treatment had significantly decreased the second-order root stele diameter.The W and WHN treatment had significantly increased the first-order root stele to root diameter,but they had no effect on the second-order root stele to root diameter;(2)The W treatment had significantly increased the first two root specific root length,the HN treatment had only significantly increased the first-order root specific root length.The HN treatment had significantly decereased the first-order root tissue density;(3)The W,HN and WHN treatment had no effect on the first two root C concentration and C/N,and the WHN treatment had significantly decereased the first two P concentration,whereas the WHN treatment had significantly increased the first two N/P and C/P;(4)The W treatment had no effect on the first-order root arbuscular mycorrhizal infection,whereas both the HN and WHN treatmnet had significantly increased the first-order root arbuscular mycorrhizal infection.In conclusion,the Chinese fir seedlings had accommodated the situation that soil warming and N desposition led to the change of soil temperature and soil N availability by adjusting the fine root anatomical and morphological traits and arbuscular mycorrhizal colonization.Soil warming significantly reduced the concentration of fine root N,indicating that soil temperature increase has a weak effect on the effectiveness of soil N,which may be related to the dilution effect.Soil warming brought about fine root P concentration decreased and fine root N/P increased,which might indicate that soil warming decreased soil moisture and weakened the capacity of fine roots to absorb soil P.