不同立地类型杉木人工林叶片的碳氮磷生态化学计量特征

Ecological stoichiometry of leaf carbon,nitrogen and phosphorus of Cunninghamia lanceolata plantations in different site types

【目的】分析立地类型与龄级对四川省杉木人工林叶片生态化学计量特征的影响,探讨杉木人工林叶片C、N、P化学计量随非生物环境的协同变化规律,并从养分管理角度筛选最佳立地类型。【方法】遵循综合多因子与主导因素相结合的立地分类原则,首先依据地貌将四川省杉木人工林54个标准样地划分为丘陵和山地2个立地类型区,再根据土壤类型各划分出黄壤和紫色土共计4个立地类型组,其中山地区的2个立地类型组还需根据坡向各划分出阴坡和阳坡共4个立地类型亚组,最后依据坡位、海拔与小地形等划分为19个立地类型;根据龄级判断标准,将54个杉木人工林样地林分划分为幼龄林、中龄林、近熟林和成熟林。采集各样地杉木叶片并测算C、N、P含量与C∶N、C∶P、N∶P,分析其对立地类型和龄级变化的响应,并对各样地杉木叶片生态化学计量与13个环境因子(地貌、土壤类型、坡位、坡向、海拔、小地形、土层厚度、pH值、土壤容重、土壤全C、土壤全N、土壤全P、土壤全K)和龄级的关系进行主成分分析。【结果】四川省杉木人工林叶片C、N、P含量及其比值均受立地类型与龄级的显著影响。杉木叶片C、N、P含量和C∶N、C∶P、N∶P平均值在丘陵区分别为527.61,9.86,1.06 g/kg和53.62,498.78,9.32,在山地区分别为544.78,9.51,1.03 g/kg和57.35,527.00,9.20。与N、P含量相反,杉木叶片C含量和C∶N、C∶P均为山地区显著高于丘陵区,2种立地类型区中均为黄壤组显著高于紫色土组,山地区各立地类型组中均为阴坡亚组高于阳坡亚组,且在丘陵坡下部和山地1000~1400 m海拔沟槽中较高。随龄级增加,杉木叶片C含量及C∶N、C∶P、N∶P均先降后升,在近熟林有拐点,N、P含量变化趋势反之。主成分分析结果显示,杉木叶片化学计量特征与13个环境因子间均有不同程度的相关关系,特别是与地貌、土壤类型、坡位、坡向、海拔、小地形等相关性较好。【结论】在山地黄壤阴坡1000~1400 m沟槽及丘陵黄壤坡下部杉木叶片有较高的C积累与N、P利用效率,宜施N肥或引入固氮植物以缓解四川省杉木人工林的N限制状况。

【Objective】This study aimed to analyze the effects of site types and age classes on leaf ecological stoichiometric characteristics of Cunninghamia lanceolata plantations in Sichuan,discuss regularity of leaf C,N and P stoichiometry to changing non-biological environment,and select optimal site type from the perspective of nutrient management.【Method】Following the principle of site classification combining multiple factors and dominant factors,the 54 standard plots of C.lanceolata plantations in Sichuan were firstly divided into two districts of hill and mountain based on landform,and then grouped to 4 groups based on soil types of yellow soil and purple soil.Among them,the 2 groups in mountain district were divided into shady slope and sunny slope subgroups.In total,the 54 plots were divided into 19 site types based on slope position,altitude,microtopography,and they were also divided into young,half mature,near mature and mature stands according to age classification criteria.The leaves of C.lanceolata plantations from each plot were collected,and contents of C,N and P and ratios of C∶N,C∶P and N∶P were determined.The responses of stoichiometry to site type and age class were analyzed and PCA was carried out to obtain relationships of leaf ecological stoichiometry with 13 environmental factors(landform,soil type,slope position,slope aspect,altitude,microtopography,soil thickness,pH value,bulk density,total C in soil,total N in soil,total P in soil and total K in soil)and age class in each plot.【Result】Leaf C,N and P contents and C∶N,C∶P and N∶P ratios of C.lanceolata plantations were all significantly affected by site type and age class.In hill district,the average leaf C,N and P contents were 527.61,9.86 and 1.06 g/kg and C∶N,C∶P and N∶P ratios were 53.62,498.78 and 9.32,respectively.In mountain district,contents were 544.78,9.51 and 1.03 g/kg and ratios were 57.35,527.00 and 9.20,respectively.Contrary to N and P contents,leaf C content,C∶N and C∶P ratios of C.lanceolata in mountain district were higher than in hill district,and those in yellow soil group were higher than in purple soil group in both districts.Those in shady slope subgroup were also higher than in sunny slope subgroup in mountain district,and they were higher in the lower slope of hill and high altitude(1000-1400 m)groove in mountain.With the increase of age class,leaf C content and C∶N,C∶P and N∶P ratios of C.lanceolata fell first and then rose,with the lowest value in the near mature stand,while the changing trends of N and P contents were opposite.PCA analysis showed that the leaf ecological stoichiometric characteristics of C.lanceolata plantations had different degrees of correlations with the 13 environmental factors.Especially,it had good correlation with landform,soil type,slope position,slope aspect,altitude and microtopography.【Conclusion】The leaves of C.lanceolata had higher C storage as well as N and P utilization efficiency in high altitude(1000-1400 m)groove on shady slope of yellow soil in mountain and lower slope of yellow soil in hill.It is suggested to apply N fertilizer or cultivate nitrogen-fixing plants to alleviate N limitation of C.lanceolata plantations in Sichuan.