干热河谷4种固氮植物根瘤固氮潜力及其影响因素

Nitrogen-fixation Potential of Nodules in Four Types of Nitrogen-fixation Plants and Their Influencing Factors in Dry-hot Valley

氮是除水分之外影响干热河谷生物活性的关键因子,豆科植物生物固氮是该地区氮素的重要来源之一。采用乙炔还原法测定了干热河谷不同季节燥红土和变性土林地中大叶相思、新银合欢、木豆和山合欢根瘤固氮酶活性(NAs)。结果表明:新银合欢(16.25μmol.g-1.h-1)和大叶相思(15.85μmol.g-1.h-1)根瘤NAs显著(P<0.001)高于山合欢(9.60μmol.g-1.h-1)和木豆(9.42μmol.g-1.h-1)。雨季根瘤NAs显著高于旱季,约为旱季的2.3倍。燥红土样地上植物根瘤NAs是变性土样地的1.3 1.6倍。研究揭示:除植被类型外,干热河谷植物根瘤NAs主要受土壤类型、季节和土壤含水量的影响,而受土壤温度的影响较小。

In addition to water, Nitrogen （N） is often the key limiting factor for biological activity in Dry-hot Valleys. Biological N-fixation by nitrogen-fixation plants is of important source of N for vegetations in those areas. The nitrogenase activities （NAs） of nodules in Acacia auriliformis A. Cunn, Leucaena leucacephala （ Lam. ） de Wit, Cajanus cajan （L）. Millspangh and Albiza kalkora Prain plantations were determined at the Dry red soils and Vertisol spots at four different sampling times in a Dry-hot Valley with the acetylene reduction assay. The results showed that the NAs of nodules in L. leucacephala （ 16.25 μmol·g^-1·h^-1 ） and A. auriliformis （ 15.85 μmol·g^-1·h^-1） were significantly higher than those in A. kalkora （9.60 μmol·g^-1·h^-1 ） and C. cajan （9.42 μmol·g^-1·h^-1）. The NAs of nodules in rainy season were significantly higher than those in dry season, and approximated 2.3 times that in dry season. The NAs of nodules at the Dry red soils spots were 1.3 - 1.6 times higher than those at the Vertisol spots. The research revealed besides plant type, the NAs of nodules were primarily affected by soil type, season and soil water content, but less affected by soil temperature.