The Study Of Soil Respiration And Its Components In Chinesetea Gardens

Soil respiration(Rtotal), which mainly effected by biotic factor(vegetation types, biomass, and microbes) and abiotic factor(temperature, water content, and soil physicochemical properties), is consist of root respiration(Rroot) and soil microbes respiration(Rbasal). The contribution of each group needs to be understood to evaluate implications of environmental change on soil carbon cycling and sequestration. Rroot to total soil respiration is varying greatly due to differences among study area and research methods. Tea(Camellia sinensis) is a perennial evergreen plant and a major cash crop in many developing countries, mainly distributed over tropical and subtropical areas. The tea gardens were mostly transformed from woodland or uncultivated land. Chinese existing tea garden covers an area of 238.5 million hm-2, which accounting for 62% of the world’s tea garden area, and China is the biggest tea production country. Recently, In order to improve the tea production and economic benefit, a large number of chemical fertilizers to be used every year, which had led to the soil quality of tea garden declined to some extent. However, Domestic and foreign researches on soil respiration were mainly focus on forest, grassland and farmland ecosystem, and soil respiration on tea garden remains unclear. In this study, a series of tea soils and adjacent woodland derived from the same parent material were collected from tea research institute, Chinese academic of agriculture science, located in West Lake district of Hangzhou city, Zhejiang Province in Southeast of China. The methods of in situ measurement in the field and laboratory incubation in room were carried out to study the effect factors of soil respiration during 2013.9 to 2014.10. The main results are as follows:1. Seasonal variation of tea garden(HP: high production, MP: mediun production, LP: low production) and woodland(WL) soil respiration showed markedly single peak, and the trend was the same with variation of temperature. A markedly exponential relationship was found in each site between Rtotal, Rroot, and Rbasal with soil temperature measured in surface or in soil 5 cm depth. 5 cm depth temperature model could explain 83% ~ 91%, 64% ~ 81% and 32% ~ 94% of the variation of Rtotal, Rroot, and Rbasal, respectively. Temperature sensibility(Q10) in each site showed Rroot > Rbasal. Q10 value of Rtotal in tea gardens was higher than woodland; Q10 value of Rroot in HP and MP was higher than WL, but LP was not; Q10 value of Rbasal in HP, MP, LP was higher than WL. There was no significant relationship between soil respiration and soil water content in each site. Annual cumulate Rtotal fluxes of tea garden and woodland were 16.30, 15.35, 11.08 and 10.71 t C hm-2a-1, annual cumulate Rroot fluxes were 9.00, 9.25, 5.50 and 6.63 t C hm-2a-1, and account for 55.12%, 60.17%, 49.59% and 61.89% of annual cumulate Rtotal fluxes, Annual cumulate Rroot fluxes were 7.30, 6.10, 5.57 and 4.08 t C hm-2a-1, respectively.2. Seasonal variation of tea garden(10 a, 40 a, 100 a) soil respiration showed markedly single peak, and a markedly exponential relationship was found in each site between Rtotal, Rroot, and Rbasal with soil temperature measured in soil 5 cm depth. 5 cm depth temperature model could explain 81 ~ 87%, 64 ~ 79% and 53 ~ 75% of the variation of Rtotal, Rroot, and Rbasal, respectively. Temperature sensibility(Q10)in each site showed Rroot > Rbasal. Q10 value of Rtotal in 10 a tea garden was higher than 40 a and 100 atea garden, Q10 value of Rroot in 100 a tea garden was highest, and 40 a was lowest; Q10 value of Rbasal was decrease with increasing stand age. Annual cumulate Rtotal fluxes of tea garden were 11.03, 15.35 and 14.77 t C hm-2a-1, annual cumulate Rroot fluxes were 4.81, 9.25 and 7.83 t C hm-2a-1, and accounted for 43.59%, 60.17% and 52.55% of annual cumulate Rtotal fluxes, Annual cumulate Rroot fluxes were 6.22, 6.10 and 6.94 t C hm-2a-1, respectively.3. Addition of lime can significantly improve the tea garden soil pH, but soil water soluble organic carbon dropped significantly. Addition of aluminum can reduce the soil p H, decrease soil microbes, and it has inhibitory effect on Rbasal. Addition of glucose can increase the soil p H and enhance soil microorganism quantity, and it has a priming effect on the Rbasal.Addtion of ammonium sulphate reduced the soil p H, and rape seed cake significantly increased soil microbial biomass and soil basal respiration rate, ammonium sulfate increases microbial quantity but reduced soil basal respiration rate.4. SOC, WSOC, MBC and soil cumulative respiration flux in the tea garden and woodland decreased with the increasing depth of soil layers, and all of these parameters in the tea garden were greater than those in the woodland. The biological activity indicators(SWOC/SOC and q CO2) in the tea garden were also greater than those in the woodland. However, q MBC in the tea garden was less than that in the woodland. Soil respiration rate were significantly and positively related with SOC, WSOC and MBC, and multiple linear regression with “Backward” method showed that the soil respiration rate was affected by SOC>MBC>WSOC in the tea garden, and by WSOC>SOC>MBC in the woodland. All in all, soil metabolism in the tea garden was greater than that in the woodland, but the stability of soil carbon pool in the tea garden was less than that in the woodland, so it was not conducive to the accumulation of soil organic carbon pool in tea garden.5. Total nitrogen, N2 O emission and its cumulative flux in the tea garden and woodland soils were decreased with increase depth of the soil layers, and all of these in tea garden were greater than in woodland. Generally, p H, WSON, SMBN, NO3--N and NH4+-N had a downward trend with the deepening of soil layers. WSON, SMBN, NO3--N and NH4+-N in tea garden were greater than those in woodland, but the p H value in tea garden was lower than that in woodland. Correlation of N2 O emission rate with TN, SMBN and NH4+-N were significantly positive, but not significant with p H value. N2 O emission rate was significantly correlated with WSON in woodland, but not in tea garden. And N2 O emission rate was significantly correlated with NO3--N concentration in tea garden, but not in woodland. Ratios of WSON/TN and N2O-N/SMBN in tea garden were greater than these in woodland, and SMBN/TN of tea garden was lower than that in woodland. These results indicate that tea soil was not conducive to accumulate nitrogen pool, and to maintain soil quality and its sustainable use compared to the woodland soil.