不同林龄兴安落叶松林土壤总有机碳与理化性质的关系

Relationship between soil total organic carbon and physicochemical properties in Larix gmelinii forests at different ages

【目的】探讨不同林龄兴安落叶松林土壤总有机碳特征及其与理化指标的关系。【方法】在兴安落叶松林内,依据林龄不同(幼龄、中龄、近熟、成过熟)设置样地,分别采集0~10,10~20,20~40和40~60 cm土层的土样,测定不同林龄各土层土壤含水量、体积质量、pH及总有机碳、有机磷、总磷、无机磷、NH_(4)^(+)-N、速效钾、有效磷、Na_(2)O、MgO、Al_(2)O_(3)、K_(2)O、CaO、Fe_(2)O_(3)含量,分析其变化规律,并对土壤总有机碳含量与各理化指标的关系进行Pearson相关分析和通径分析。【结果】(1)兴安落叶松林0~60 cm土层土壤总有机碳含量为13.42~142.18 g/kg,随着林龄增加,土壤总有机碳含量呈现先减小后增加的“V”字型变化特征,不同林龄的土壤总有机碳含量大小表现为幼龄林(64.49 g/kg)>成过熟林(55.34 g/kg)>中龄林(53.22 g/kg)>近熟林(46.81 g/kg)。(2)随着林龄的增加,土壤含水量、体积质量和速效钾、Na_(2)O含量也呈“V”字型变化趋势,有机磷、MgO和Al_(2)O_(3)含量呈倒“V”字型变化趋势,pH及CaO、Fe_(2)O_(3)含量增加,NH_(4)^(+)-N、有效磷和K_(2)O含量减少。(3)土壤总有机碳含量与土壤含水量及NH_(4)^(+)-N、速效钾、有机磷、CaO含量均呈正相关,与土壤体积质量、pH及Na_(2)O、MgO、Al_(2)O_(3)、K_(2)O和Fe_(2)O_(3)含量呈负相关。(4)土壤含水量、pH、NH_(4)^(+)-N、有机磷、Na_(2)O、CaO、Fe_(2)O_(3)和Al_(2)O_(3)及其共同作用是影响兴安落叶松林整个生长周期土壤总有机碳含量变化的主导因素;随着林龄的增加,影响兴安落叶松林土壤总有机碳含量的主导因素由土壤养分转变为金属氧化物。【结论】不同林龄兴安落叶松林土壤的总有机碳含量存在差异,土壤理化指标对总有机碳含量具有显著影响。

【Objective】Characteristics of soil total organic carbon(TOC)and the relationship with physicochemical indexes in Larix gmelinii forests at different ages were studied.【Method】In L.gmelinii forests,soil samples were collected at the depths of 0-10,10-20,20-40 and 40-60 cm in plots with different ages(young,middle aged,near-mature,mature and over-mature).Soil water content,bulk density,pH and contents of TOC,organic phosphorus,total phosphorus,inorganic phosphorus,NH_(4)^(+)-N,available potassium,available phosphorus,Na_(2)O,MgO,Al_(2)O_(3),K_(2)O,CaO and Fe_(2)O_(3)were determined.The variation characteristics of TOC content and physicochemical indexes at different ages were analyzed,and relationships between TOC content and physicochemical indexes were analyzed by Pearson correlation analysis and path analysis.【Result】(1)The mean TOC content of L.gmelinii forest(0-60 cm)was 13.42-142.18 g/kg with a“V”shape during the growth process.TOC content was in the decreasing order of young forest(64.49 g/kg)>mature and over-mature forest(55.34 g/kg)>middle aged forest(53.22 g/kg)>near-mature forest(46.81 g/kg).(2)Soil water content,bulk density,contents of available potassium and Na_(2)O also showed a“V”shape with the increase of forest age.Contents of organic phosphorus,MgO and Al_(2)O_(3)showed an inverted“V”shape,while pH,contents of CaO and Fe_(2)O_(3)increased with the increase of age.Contents of NH_(4)^(+)-N,available phosphorus and K_(2)O decreased with the increase of forest age.(3)TOC content was positively correlated with soil water content,contents of NH_(4)^(+)-N,available potassium,organic phosphorus and CaO,while negatively correlated with soil bulk density,pH,contents of Na_(2)O,MgO,Al_(2)O_(3),K_(2)O and Fe_(2)O_(3).(4)Soil water content,pH,NH_(4)^(+)-N,organic phosphorus,Na_(2)O,CaO,Fe_(2)O_(3)and Al_(2)O_(3)and their combined effects were dominant factors affecting TOC variations in the whole growth cycle of L.gmelinii forest.With the increase of forest age,the dominant factors of TOC content in L.gmelinii forest changed from soil nutrients to metal oxides.【Conclusion】TOC contents of L.gmelinii forests at different ages were different,and soil physicochemical indexes had significant effects on TOC.