凋落叶和磷添加对马尾松林土壤碳激发效应的影响

Effects of Litters and Phosphorus Addition on Soil Carbon Priming Effect in Pinus massoniana Forest

探究土壤有机碳(SOC)矿化的激发效应(Priming effect,PE)对了解森林土壤碳吸存具有重要意义。凋落叶输入是调节激发效应的重要因素,其对激发效应的影响可能受到关键养分(如磷)的制约。在亚热带低磷土壤中,凋落叶和磷添加如何影响森林土壤碳矿化和激发效应目前仍不清楚。以马尾松林土壤为研究对象,探究三种凋落叶(马尾松(Pinus massoniana)、火力楠(Michelia macclurei)和枫香(Liquidambar formosana))和磷(KH_(2)PO_(4))添加对土壤激发效应,土壤养分及微生物特性的影响。结果表明,三种凋落叶添加均显著增加了SOC矿化,产生了正激发效应,且马尾松凋落叶诱导的激发效应强度最大,火力楠凋落叶次之,枫香凋落叶诱导的激发效应强度最弱。此外,凋落叶添加整体上降低了土壤无机氮(铵态氮和硝态氮,IN)的含量,却增加了微生物生物量氮(MBN)和微生物生物量磷(MBP)的含量,提高了β-葡萄糖苷酶(β-glucosidase,βG)和酸性磷酸酶(Acid phosphatase,ACP)的活性。单独添加磷显著增加了SOC矿化,且提高了土壤有效磷(AP)、可溶性有机碳(DOC)和微生物生物量碳(MBC)、MBN和MBP的含量。而与单独添加凋落叶相比,火力楠和枫香凋落叶与磷共同添加显著降低了土壤激发效应的强度和ACP的活性。回归分析结果表明,累积激发效应与AP、MBN和MBP含量呈显著负相关,与ACP活性呈显著正相关。综上,凋落叶添加刺激了微生物生长,产生了正激发效应,且激发强度与凋落叶质量有关;而磷添加可能会降低低质量凋落叶产生的土壤激发效应。

【Objective】Priming effect(PE)plays a critical role in the storage and turnover of soil organic carbon(SOC)in forest ecosystems.The intensity and direction of the priming effect,induced by litters,usually depend on the availability of limited nutrient(e.g.,phosphorus,P),especially in subtropical highly weathered forest soils.However,how P and litters addition affect the soil priming effect in this region is not clear.This study aimed to investigate the effects of litter and phosphorus addition on SOC mineralization and priming effects in subtropical low-phosphorus soils and to provide a theoretical basis for the study of the carbon cycle in forest ecosystems in this region.【Method】Three kinds of 13C-labeled litters(Pinus massoniana,Michelia macclurei and Liquidambar formosana)and P(KH_(2)PO_(4))were added to P.massoniana forest soil.The incubation of treated and control soils was conducted for 35 days in the laboratory.The physical and chemical properties,microbial properties and priming effect of the soils were determined after incubation.【Result】The results showed that the addition of the three kinds of litters significantly increased the soil native SOC mineralization,and produced a positive priming effect.The intensity of priming effect performance for P.massoniana>M.macclurei>L.formosana.In addition,litters addition decreased the content of soil inorganic nitrogen(nitrate and ammonium nitrogen,IN),but increased microbial biomass nitrogen(MBN),microbial biomass phosphorus(MBP),andβ-glucosidase(βG)and acid phosphatase(ACP)activities.P addition alone significantly enhanced SOC mineralization,and the available phosphorus(AP),dissolved organic carbon(DOC),microbial biomass carbon(MBC),MBN,and MBP were also increased.Compared with the addition of litters alone treatment,the M.macclurei and L.formosana litters combined with P addition significantly reduced the priming effect and ACP activity.Linear regression analysis revealed that the cumulative priming effect was correlated negatively with soil AP,MBN and MBP content,whereas it was positively correlated with ACP activities.【Conclusion】The addition of litters stimulated microbial growth and as such promoted SOC mineralization and produced a positive priming effect.Also,the intensity of priming was mainly related to the quality of litters.Although P addition alone increased SOC mineralization,the influence of P added with litters on soil priming effect was dependent on the litter types;with low-quality litter having a lower soil priming effect.