不同林龄杉木根际和非根际土壤矿质养分含量及根际效应

Mineral nutrient contents of rhizosphere and non-rhizosphere soils in Cunninghamia lanceolata plantations at different stand ages and rhizosphere effects

以中亚热带不同林龄(7、15、24和34 a)杉木林为研究对象,测定了根际和非根际土壤可浸提态矿质养分含量,并分析了不同林龄杉木林对各矿质养分的根际效应.结果表明:随林龄增大,根际和非根际土壤pH均呈下降趋势,而土壤含水率呈现先增后减的趋势;根际和非根际土壤P含量随林龄增大呈下降趋势,K、Ca和Mg含量呈先增后减的趋势,在中龄林到近熟林阶段均显著降低,在近熟林到成熟林阶段均没有显著变化;微量元素Fe和Zn含量在不同林龄间没有显著变化,Mn和Cu含量呈先增后减的趋势;非根际土壤pH与K、Ca、Mn和Cu含量呈显著正相关,而根际土壤pH与P和Ca含量呈显著正相关;根际土壤含水率与Mg和Al含量呈显著正相关,非根际土壤含水率与Na含量呈显著负相关.幼龄林和中龄林对土壤矿质养分的根际效应均为正效应,而近熟林和成熟林对K、Na、Cu和Fe的根际效应显著降低.综上,在杉木近熟林阶段土壤有效养分含量显著降低,应注意该阶段的养分供给;同时,为实现杉木人工林可持续性经营,应注意杉木生长期土壤pH的调节.

In order to investigate the dynamics of soil mineral nutrients during the development of Cunninghamia lanceolata(Chinese fir) plantation, mineral nutrient contents in the rhizosphere and non-rhizosphere soils of the plantation were determined at different stand ages(7, 15, 24 and 34 a), and the rhizosphere effects of various stand ages on soil mineral nutrients status were further interpreted. The results showed that soil pH value decreased with the increase of stand age, while soil moisture content increased and then decreased. The contents of available phosphorus(P) in the rhizosphere and non-rhizosphere soils declined with the stand development;the contents of potassium(K), calcium(Ca), magnesium(Mg), manganese(Mn) and copper(Cu) all rose and then decreased, while the contents of K and Mg experienced sharper decreases from the half-mature to near-mature period, and maintained at low levels towards the maturation of the plantation. The contents of iron(Fe) and zinc(Zn) were barely changed during the entire growth. Non-rhizosphere soil pH had significant and positive correlations with K, Ca, Mn and Cu contents while rhizosphere soil pH had significant and positive correlations with P and Ca contents;rhizosphere soil moisture content was significantly and positively correlated with Mg and aluminum(Al) contents while the moisture content of non-rhizosphere soil was significantly and negatively correlated with sodium(Na) content. The rhizosphere effect was positive on the mineral nutrients status of soils under both young and middle-aged C.lanceolata plantations, nevertheless, the rhizosphere effects on K, Na, Cu and Fe contents were diminished significantly from near-mature to mature period. Therefore, application of mineral nutrients is recommended when C.lanceolata plantation approaches near-maturation as soil mineral nutrients levels tend to decline at the period;routine monitor of soil pH is also advised for the sustainable management of Chinese fir plantation.