施肥对油茶园土壤呼吸和异养呼吸及其温度敏感性的影响

油茶是中国南方重要的木本食用油料树种,研究施肥对油茶园土壤呼吸及其温度敏感性的影响,对于估算中国南方典型种植园林温室气体排放及其对气候变化的响应具有重要意义。设置对照(CK)、施肥(OF)、断根(CK-T)和断根施肥(OF-T)4个处理,采用静态箱-气相色谱法,通过多年观测,分析探讨施肥对油茶园土壤呼吸和异养呼吸及其温度敏感性的影响。结果表明:(1)施肥对油茶园土壤呼吸和异养呼吸无显著影响。研究期间,各处理(OF、CK、OF-T、CK-T)土壤CO_2通量依次为(77.91±2.59)、(73.71±0.97)、(66.82±1.02)mg C m~(-2)h~(-1)和(66.84±3.94)mg C m~(-2)h~(-1);(2)各处理土壤呼吸温度敏感性(Q_(10))表现为OF-T(1.96±0.01)CK-T(1.79±0.03)OF(1.77±0.01)CK(1.75±0.03),其中,OF-T处理下Q_(10)显著高于其他3个处理,即施肥显著增加了断根处理土壤呼吸Q_(10);(3)施肥显著增加了土壤表层NH_4~+-N和NO_3~--N含量,Q_(10)与土壤表层NH_4~+-N和NO_3~--N含量表现出显著的正相关关系。

Effects of fertilization on soil respiration, heterotrophic respiration, and temperature sensitivity in an oil tea plantation

As the largest carbon pool of terrestrial ecosystems, soils constitute important sources and sinks of global CO₂ balance. Soil respiration is an important pathway of carbon fluxes between the atmosphere and terrestrial ecosystems. Further, soil respiration can also influence terrestrial carbon cycling through climate feedbacks, specifically temperature sensitivity (Q₁₀). Oil tea (Camellia oleifera) is an important native woody oil crop, and has been widely developed in south China in recent years. High-level fertilization has been widely adopted to increase growth of oil tea trees and maintain soil fertility. In this study, the effects of fertilization on soil respiration, heterotrophic respiration and temperature sensitivity in an oil tea plantation were examined. Static chambers and gas chromatography were used to collect and analyze gas samples. To differentiate soil respiration and soil heterotrophic respiration, the trenching method was used. There were four treatments in this study:oil tea plots with fertilization (OF), oil tea plots without fertilization (CK), trenching plots with fertilization (OF-T), and trenching plots without fertilization (CK-T). The results showed that fertilization had no significant effects on either soil respiration or heterotrophic respiration. Soil CO₂ effluxes in different treatments (OF, CK, OF-T, CK-T) were 77.91±2.59, 73.71±0.97, 66.82±1.02, and 66.84±3.94 mg C m^-2 h^-1, respectively. The temperature sensitivity of soil CO₂ effluxes was 1.77±0.01, 1.75±0.03, 1.96±0.01, 1.79±0.03 in OF, CK, OF-T, and CK-T respectively. Fertilization significantly increased temperature sensitivity of soil heterotrophic respiration, with the Q₁₀ values in the OF-T plots significantly higher than those in the CK-T plots. In addition, fertilization significantly increased soil NH₄⁺-N and NO₃^--N contents in the surface layer (0-10cm). We also found significant linear relationships between the Q₁₀ of soil CO₂ effluxes and soil NH₄⁺-N, as well as NO₃^--N contents. Our findings may provide basic data for greenhouse gas inventories and understanding their responses to climate change in a typical cash crop plantation in south China.