Responseof Rhizosphere Soil And Plant Nutrients To Acid Deposition In Tea Plantation

Acid deposition is one of the major ecological environment problems,which can acidfy soil, make nutrient loss and activate harmful ions, affect plant nutrient absorption and growth,threat to the health of the ecosystem.Tea tree as an important economic crops in southern hilly region of china,suffered the stress of acid rain for a long time. But so far the impact of acid rain to main element of plantations of biogeochemical cycle is unclear. To explore the impact of different intensity of acid deposition on rhizosphere soil nutrient supply,nutrient content tea tree body and their interconnectedness. A tea plantation in a typical hilly red soil region was selected for an in situ simulation experiment treated by pH 4.5,pH 3.5,pH 2.5,CK water and three reiterations in 2011. Rhizosphere and bulk soils were collected in the third and fourth year from the simulated acid deposition experiment.Soil nutrients analyzed using thechemical extraction and biochemical methods.Different parts of tee tree was collected by mixing method to measure the main nutrient content.Analysis the association betwwen soil nutrient supply and plant nutrient distribution Provide the basis for tea plantation in hilly red zone and adaptive management to deal with acid deposition.the mainresults were as follows:(1) Rhizosphere and bulk soil pH,NO3--N,available P content decreased with the elevate of acid deposition in both 2013 and 2014;The content of total N have different response in two years;The total P,NH4+-N and mineral N have no significant difference in differernt treatments。With the elevate of acid deposition,the ammonification rate,net N-mineralization rate and P mineralization rate of rhizosphere soil show the declining trends,But the N nitrification rate of rhizosphere and all N,P mineralization rate of bulk soil had no significant difference;Rhizosphere urease and acid phosphatase activities were enhanced with acid depositon aggravating,which shows control the highest,pH 4.5 and pH 2.5 second,pH 3.5 the lowest in bulk soil. Exchangeable Al of rhizosphere is increases with acid deposition is aggravating,the available Mg content in rhizosphere showed the opposite trends in 2014. The exchangeble Al and available Mg in rhizosphere and the available Ca in both soil has no significant difference between different treatment. In addition,N/P,mineral N/available P,exchangeable Al/available Ca,N nitrification rate/P mineralization rate has no significant difference between different treatments. Obviously,compared with bulk soil,rhizosphere soil nutrient supply and conversion more vulnerable to the effects of acid deposition. The balance of soil N and P,Al and Ca doesn’t change due to acid deposition aggravating,infer that the stability of soil is strong.(2) The rhizosphere effect of pH,total N,total P,NH4+-N,mineral N,available P,N nitrification rate,Net N-mineralization rate,P mineralization rate,available Mg, available Ca has no significant difference between different treatment.The rhizosphere effect of NO3--N showed pH 3.5 the highest,p H 4.5 and contral the second,pH 2.5 the lowest in 2014,but it`s not significant in 2013.With increasing the acid intensity,the rhizosphere effect of N ammonification rate was decrease,urease and acid phosphatease showed the oppsote trends. The rhizosphere effect of exchangeable Al in pH 2.5 is higer than other treaments. The rhizosphere effect of p H,NO3--N,N nitrification rate,exchangeable Al,available Mg shows positive effect,available P,P mineralization rate and available Ca shows negative effects。With increasing the acid intensity,other variables shows from positive to nagative or form negative to positive. Concluded that ecosystem of tea gardon is nitrogen surplus,phosphorus deficiency,Al surplus and Ca deficiency. Soil microbial activity activated by the elevate of acid deposition(3) The total N of buds,leaves,storage roots have no significant difference between different treatments. With increasing the acid intensity,total N of shoot,absorption roots increased, transitional root showed the oppsote trends.The elevated acid deposition has no significant effect with total P of leaves,shoots,absorption roots and transitional roots. Total P of buds showed pH 2.5,pH 4.5 the highest,pH 3.5 the second,control the lowest in 2014,but it`s not significant in 2013. Total P of storage roots in pH 2.5 significant lower than other treatments. The N/P of old branch and transitional roots has no significant betweent different treatments. The N/P of buds showed control higher than other treatments in 2014,but it`s not significant in 2013. N/P of leaves showed pH 3.5 the highest,pH 4.5 and pH 2.5 the second,control the lowest in 2014,not significant in 2013. N/P of shoots showed pH 4.5>pH 3.5>CK>pH 2.5 in 2014,not significant in 2013. With increasing the acid intensity,N/P of absorption roots decreased in two years. N/P of storage roots showed pH 2.5 the highest,control the second,pH 3.5 and pH 4.5 the lowest. Obviously,the effcet of acid treat to tea tree focused on the new parts(bud,shoot) and root.(4) The elevated acid deposition did not cause significant changes in total Al of buds,leaves and absorption roots;Shoot total Al shows pH 2.5 and pH 3.5 significant higher than pH 4.5 and control. The treatment of control is significant lower than other in old branch. Total Al of transitional roots and storage roots shows highest in pH 2.5,lowest in control.Among the 4 treatments,Mg in buds,leaves,old branch,transitional roots,storage roots was not significant different. With increasing the acid intensity,Mg in shoots,absorption roots decreased. Total Ca in Tea tree body parts which aboveground is not significantly affected by acid deposition; Total Ca content in absorption roots and transitional roots shows pH 4.5 higher than other treatment. The Al/Ca in shoots,old branch and all roots increased with acid deposition aggravating.Al/Ca in buds,leaves had no significant difference between different treatment. Obviously,The influence of acid treatment on tea tree mineral elements mainly characterized by acid treatment promote the accumulation of Al,and make Mg,Ca loss.(5) Soil pH have positive correlation with total Mg in absorption roots,N/P,total Mg,total Ca in transitional roots,P in storage roots.It also have negative correlation with transitional root Al/Ca and total storage root Al.Total N of soil has positive correlation with total Mg.total Ca in absorption roots.Soil total P have positive correlation with total Mg in transitional roots. Soil exchange Al has positive correlation with total N,N/P,exchange Al,Al/Ca in absorption roots,total Al in transitional roots and total Al,Al/Ca in storage roots.It also has negative correlation with total Mg in absorption roots,in transitional root total N and storage root total N.Soil available Mg has positive correlation with total Mg,total Ca in absorption roots,total Ca in transitional roots and total N in storage roots. It also have negative correlation with total Al in transitional roots. Soil N/P,available Ca and Al/Ca has no correlation with root nutrient. Obviously,the correlation between soil nitrogen,phosphorus and tea tree roots nutrient is weak. Changes in the soil of exchange Al,available Mg effectively can significantly influence the root nutrient,resulting elements loss or accumulation.(6) Soil pH has positive correlation with bud total Ca,shoot total Mg,and negatively correlated to leaf total Al.Soil total N positively correlated with bud N/P,total Mg,shoot total Ca,total Mg.It also has negative correlation with bud total P,leaf N/P,old branch N/P,total Ca. Soil total P is negatively related to the shoot total P,and postive correlation with N/P of buds. The correlation between soil N/P and leaf N/P,old branch N/P,total Ca is negative. Soil exchange Al has positive correlation with bud total P,Al/Ca,shoot total Al,Al/Ca.,and negatively correlated with bud N/P,total Ca,shoot total Ca.Soil available Mg have positive correlation with bud N/P,total Mg,total Ca,shoot total Ca,and negatively correlated with bud total P,leaf N/P,old branch total Al,Al/Ca. Soil available Ca has positive correlation with bud total Ca and leaf total Mg. Soil Al/Ca negatively correlated with bud total Mg,total Ca and leaf total Mg.