The Effects Of Air And Soil Warming On The Production And Phenology Of Fine Roots Of Cunninghamia Lanceolata Seedlings

Fine root,as the most active and sensitive part in roots system,its phenology and production plays an important role in affecting the primary productivity of ecological system,plant competition and reflecting the effects of climate change on the ecosystem.Based on a rhizobox warming experiment,this study aimed to study the effects of different ways of warming on the dynamic of phenology and production of fine root on subtropical Chinese fir(Cunninghamia lanceolata)seedlings in individual level.Twelve non-warming(CT),twelve soil warming(W),twelve air warming(OTC)and twelve soil warmingxair warming(OTC-W)Chinese fir seedling rhizoboxes were established in Chenda State-Own Forest Farm,Sanming,Fujian.Soil warming was accomplished by buried heating cable technology,with soil temperature elevated to+4℃ above ambient,and that air warming was accomplished by Open-top chamber.Meanwhile,the effects of different ways of warming on the fine root respiration,morphology,nitrogen concentration and nitrogen uptake rate were measured by tracing and sampling the fine roots of different age from rhizoboxes.The results showed that:1)Fine root growth,during the past year,was mainly concentrated in spring and autumn,but there were significant differences in phonological characteristics of fine root of the different ways of warming.Soil warming advanced the phenology of fine root of Chinese fir seedlings,and reached the peak earlier;However,air warming delayed the phenology of fine root of Chinese fir seedlings,and reached the peak later.2)The time distribution of fine root production and the growth period of fine root,under the air warming(OTC,DOTCmean=2.07±0.81),was more uniform and prolonged than CT(DOTCmean=1.39±0.15);Soil warming(W,DWmean=1.14±0.23)reduced the uniformity of fine root production in time distribution and prolonged growth period of fine root significantly(P<0.05).Furthermore,interaction between soil warming and air warming(DOTC-Wmean=1.78±0.26)made the growth period of fine root was slightly longer than CT and OTC,and the time distribution of production is more uniform.3)During the whole period,there were significant differences in the total root length production of Chinese fir seedlings under different warming treatments.Soil warming had no significant effect on the total production of fine roots(P>0.05),but air warming significantly inhibited it(P<0.05),and there was no significant interaction between warming soil and air warming(P<0.05).4)There were no significant effect on vertical distribution of fine root production by different ways of warming,(P>0.05)and soil layer had no significant effect on fine root production(P>0.05).5)The nitrogen absorption rate of fine root of CT declined with root age significantly(P<0.05),but there had no significant variation in W,OTC and OTC-W treatment(P>0.05);Meanwhile,the respiration of fine root of CT treatment also declined with root age significantly(P<0.05),besides the W treatment(P<0.05),as well as OTC and OTC-W treatment.6)The interaction of soil warming and air warming,in 2 months age,resulted in a significant increase in physiological maintenance cost of fine root of Chinese fir seedlings(P<0.05),and significant decrease its RTD,increase the SRA(P<0.05).Meanwhile,air warming had increased SRA and decreased RTD significantly(P<0.05),and also reduce the consumption of physiological maintenance.Moreover,soil warming had increased SRA and decreased RTD significantly(P<0.05).However,the fine roots of Chinese fir seedlings on W and OTC treatment,as increasing age,had produced respiratory acclimation,and air warming also reduced the rate of fine root nitrogen uptake significantly(P<0.05).In summary,soil warming advanced the phenology of fine root of Chinese fir seedlings,prolonged the duration of the growing season and reduced the uniformity of fine root production in time distribution significantly,but had no significant effect on total fine root production;Air warming delayed the phenology of fine root of Chinese fir seedlings,prolonged the duration of the growing season significantly and made the time distribution of fine root production more uniform,but inhibited the production of fine roots;However,The interaction of soil warming and air warming delayed the phenology of fine root of Chinese fir seedlings and prolonged the duration of the growing season,but had no significant effect on the production and phenology of fine roots.