陈山红心杉土壤养分、酶活性的根际效应及肥力评价

【目的】 陈山红心杉是国家级林木良种，获国家地理标志保护。土壤肥力状况影响林木的生长，根际是植物与土壤物质直接交换的场所，研究不同林龄陈山红心杉根际和非根际土养分含量、酶活性及综合肥力状况，可进一步了解土壤养分状况随林龄的演变规律，为陈山红心杉的养分管理和合理经营提供理论依据。 【方法】 以江西省安福县陈山林场不同林龄陈山红心杉为试验对象，测定了根际和非根际土壤养分 (有机质、全氮、全磷、全钾、碱解氮、有效磷和速效钾) 含量和酶活性 (过氧化氢酶、蛋白酶、蔗糖酶、脲酶和磷酸酶)，分析了根际效应随林龄的变化规律，并进一步通过主成分分析对土壤肥力进行了综合评价。 【结果】 林龄对土壤养分、酶活性具有显著影响，仅碱解氮、全氮和全磷在根际和非根际间无显著差异。养分和酶活性在根际和非根际土中随林龄变化趋势一致，反映了根际受植物根系和林地土壤的共同影响。随着林龄的增加，有机质、氮素养分 (碱解氮和全氮)、钾素养分 (速效钾和全钾)、蛋白酶、脲酶和磷酸酶活性先下降后上升，总体以 10 年最低；有效磷变化趋势与之相反，全磷呈下降的趋势；蔗糖酶活性呈“下降 – 升高 – 下降”的趋势，过氧化氢酶活性变化趋势与蔗糖酶相反。有机质、碱解氮和酶活性的根际效应为正效应 (RE > 0)，其余均为负效应 (RE < 0，除 20 年全氮和 40 年有效磷外)，有机质和有效磷的根际效应在林龄间差异显著 (P < 0.05)。陈山红心杉根际和非根际土壤肥力综合指数 (IFI) 介于 –1.408～2.238，不同林龄土壤 (根际和非根际) IFI 变化趋势为 5 年 (2.238、2.413) > 40 年(– 0.313、0.065) > 20 a (– 0.773、–1.019) > 10 a (–1.203、–1.408)。5 年和 40 年土壤肥力综合指数表现为根际 < 非根际，主要由第二 (蔗糖酶)、第三 (速效磷和全磷) 主成分得分导致；而 10 年和 20 年土壤肥力综合指数表现为根际 > 非根际，主要是由第一主成分 (有机质、碱解氮、全氮、脲酶和蛋白酶等) 得分导致。 【结论】 随着林龄的增加，土壤肥力下降，尤其是 10 年前后最低，后虽有所恢复，但不能恢复到第 5 年水平。因此，在林木生长过程中，应在树龄 10 年左右适当补充林地土壤氮、磷养分。

Rhizosphere effects of nutrients and enzyme activities of Cunninghania lanceolata and soil fertility assessment

[Objectives] Cunninghania lanceolata (Chenshan-red-fir) is a national forest tree fine variety with national protected geographical indication.Soil fertility affects the growth of forest trees,study on soil nutrients content,enzyme activities and fertility status both in rhizosphere which is a place for exchange of plant and soil materials and in non-rhizosphere soil of different ages can further understand soil nutrients with evolution of the age,also can provide a theoretical basis for nutrient and scientific management of C.lanceolata.[Methods] Soil nutrient contents including soil organic matter (SOM),total N,P and K,alkali hydrolysable N and available P and K and enzyme activities (including calatase,protease,sucrase,urease and phosphatase) in rhizosphere and non-rhizosphere soil of C.lanceolata with different ages in the Chenshan Forest Farm of Anfu County,Jiangxi were determined and analyzed,and soil fertility was evaluated by using the principal component analysis (PCA).[Results] The stand age of the tree had a significant effect on soil nutrients and enzyme activities,while there were not significant differences of soil alkali hydrolysable N,total N and total P in rhizosphere and non-rhizosphere.The trends of soil nutrients and enzyme activities with changes of the age in rhizosphere and non-rhizosphere were in good agreements,which meant the rhizosphere was affected by both plant roots and soil.With the stand age increased,the SOM,total N and K,alkali hydrolysable N and available K,and the activities of protease,urease and phosphatase decreased first and then increased with the minima in 10 year,while the trend of available P was on the contrary,and the total P decreased.Contrary to the activity of sucrase,the activity of calatase showed a trend of decrease,increase and decrease.The rhizosohere effects of SOM,alkali hydrolysable N and enzyme activities were positive effects,while those of others were negative effects except for the total N and available P in 20 and 40 years,respectively.The rhizosphere effects of SOM and available P were different among the ages (P ＜ 0.05).The integrated fertility indices (IFI) of C.lanceolata (Chenshan-red-fir) were from-1.408 to 2.238,the trend of the IFIs (rhizosphere and non-rhizosphere) was in the order:5 a (2.238,2.413) ＞ 40 a (-0.313,0.065) ＞ 20 a (-0.773,-1.019) ＞ 10 a (-1.203,-1.408).The IFIs of rhizosphere were greater than those of non-rhizosphere in 5 and 40 years,mainly caused by PC2 (mainly include sucrase) and PC3 (mainly include available P and total P),while in 10 and 20 years,the change was just the opposite for the reason of PC1 (mainly include SOM,alkali hydrolysable N,total N,urease and protease).[Conclusions] Along with the stand age increasing,soil fertility will be declined,and reach the lowest at the tenth year.Although restored gradually afterwards,but will not reach the level in the 5th year.Therefore,nitrogen and phosphorous fertilizers should be applied appropriately for preventing soil degradation in the process of tree growth,particularly before and after the 10th year.