雷州半岛不同林龄桉树人工林土壤碳氮磷和易氧化有机碳的特征

Characteristics of Soil Carbon,Nitrogen,Phosphorus and Easily Oxidized Organic Carbon in Eucalyptus Plantations with Different Ages in Leizhou Peninsula

为研究林龄对桉树人工林土壤碳(C)、氮(N)、磷(P)等养分含量和易氧化有机碳(ROC)的影响及其垂直变化规律,分析林龄对人工林土壤生态化学计量特征和碳稳定性的影响,以雷州半岛不同林龄(7 a生和12 a生)尾叶桉Eucalyptus urophylla人工林为研究对象,根据土层深度按0~10 cm、10~20 cm、20~40 cm、40~60 cm和60~100 cm共5个层次分别采集土壤样品并测定土壤养分与有机碳含量。结果显示:(1)12 a生尾叶桉人工林土壤ROC、总有机碳(TOC)、总氮(TN)和总磷(TP)比7 a生分别高72.64%、114.07%、225.69%和14.41%,说明尾叶桉人工林土壤TOC含量和养分水平随着林龄的增加而提高;(2)12 a生尾叶桉人工林表层土壤(0~10 cm)的ROC/TOC显著大于7 a生(P<0.05),说明前者表层土壤的碳稳定性较低;而12 a生尾叶桉底层土壤(20~60 cm)的ROC/TOC值对比7 a低36.85%,说明12 a生人工林底层土壤碳稳定性高于7 a;(3)相关性分析结果表明,两种林龄人工林土壤TOC与TN、速效磷(AP)和C/P呈显著正相关,且7 a生和12 a生人工林土壤TOC还分别受到TP和N/P的显著影响。土壤ROC与TN、C/P呈显著正相关,其中7 a生和12 a生土壤ROC还分别受到TP、AP和N/P的显著影响,表明7 a生尾叶桉人工林土壤有机碳含量和碳稳定性受到土壤P元素供应的影响更大。此外,12 a生人工林土壤ROC/TOC受到TN和N/P的显著影响,表明12 a生尾叶桉人工林则更容易受到土壤TN含量的调控。因此,在雷州半岛地区,适当延长桉树人工林的轮伐周期,并根据不同林龄改善土壤的氮磷养分供应水平,有利于提高雷州半岛桉树人工林土壤的碳封存潜力。

To investigate the impact of stand age on soil nutrient content carbon(C),nitrogen(N),phosphorus(P),etc.,and readily oxidizable carbon(ROC)in Eucalyptus plantations,we analyzed the ecological stoichiometry and C stability of soils at different depths in two Eucalyptus urophylla plantations(7 years and 12 years old)in the Leizhou Peninsula.Soil samples were collected at five layers,0-10 cm,10-20 cm,20-40 cm,40-60 cm,and 60-100 cm,for analyzing soil nutrient content and organic C.The results showed that:(1)ROC,total organic C(TOC),total N(TN),and total P(TP)of Eucalyptus urophylla plantation with 12 a were 72.64%,114.07%,225.69%,and 14.41%higher than those with 7 a,respectively,indicating that the soil TOC content and nutrient concentration of E.urophylla plantation increased with the increase of stand age.(2)The ROC/TOC of the surface soil(0-10 cm)of E.urophylla plantation with 12 a was significantly higher than that with 7 a(P<0.05),indicating that the soil C stability of 12 a plantation was lower,while the ROC/TOC of the bottom soil(20-60 cm)of E.urophylla with 12 a was 36.85%lower than that with 7 a,suggesting that the C stability of 12 a was higher than that of 7 a.(3)The correlation analysis showed that there was a significant positive correlation between soil TOC and TN,available P(AP),C/P in two plantations,and the soil TOC of 7 a and 12 a plantations was also significantly affected by TP and N/P;respectively.Soil ROC showed a significant positive correlation with TN and C/P,and 7 a and 12 a plantations were also significantly affected by TP,AP and N/P,respectively,indicating that the TOC content and C stability of 7 a were more affected by the supply of soil P elements.In addition,soil ROC/TOC of 12 a plantation was significantly affected by TN and N/P.The results show that the TOC content and C stability of 12 a were more easily regulated by soil TN content.Therefore,appropriately extending the rotation cycle of Eucalyptus plantations and improving the soil N and P supply levels according to different stand ages are conducive to improving the soil C sequestration potential of Eucalyptus plantations in the Leizhou Peninsula.