西南喀斯特石漠化环境适生植物构树细根、根际土壤化学计量特征

Stoichiometric characteristics of fine roots and rhizosphere soil of Broussonetia papyrifera adapted to the karst rocky desertification environment in southwest China

为了解西南喀斯特石漠化适生植物构树(Broussonetia papyrifera)对贫瘠土壤养分环境的适应策略,及其细根、根际土壤的化学计量特征对石漠化等级的响应,该研究以西南喀斯特石漠化环境适生植物构树为研究对象,运用生态化学计量学方法,开展不同等级石漠化环境构树细根、根际土壤有机碳(C)、全氮(N)、全磷(P)、全钾(K)、全钙(Ca)及全镁(Mg)养分含量特征及C、N、P化学计量特征研究。结果表明,除Ca含量外,喀斯特石漠化环境适生植物构树细根、根际土壤的养分含量均处于较低水平;细根N:P为12.59,表明构树生长受N和P共同限制;随着石漠化等级的增加,细根C、N含量和C:N、C:P呈先降后升的变化趋势,K、P含量是则表现为先升后降,Ca、Mg含量和N:P无明显变化规律;不同等级石漠化环境中的构树根际土壤N、P、K、Ca含量呈不同的变化趋势,而C、Mg含量及C、N、P化学计量特征的变化较不显著;细根与根际土壤的化学计量特征之间存在显著的相关性,二者的C、P、Ca、Mg含量、C:N、C:P分别对应呈显著正相关关系,而N含量呈极显著负相关关系;细根的K含量则较为稳定,几乎不受根际土壤养分的影响。

Aims The objectives of this study were to estimate the adaptation strategies of Broussonetia papyrifera to the poor soil nutrients in karst rocky desertification area in Southwest China,and to explore the response of stoichiometric characteristics of fine roots and rhizosphere soil to the degree of rocky desertification.Methods The contents of carbon(C),nitrogen(N),phosphorus(P),calcium(Ca),magnesium(Mg)and C:N:P ratios of fine roots and rhizosphere soil of B.papyrifera were studied.Important findings Results indicated that,except Ca content,the nutrient content of the fine roots and rhizosphere soil of B.papyrifera in karst rocky desertification environment remained at the low level.N:P ratio of fine roots was 12.59,which indicated that the growth of B.papyrifera was co-limited by N and P.With the increase of the degree of rocky desertification,the content of C and N as well as C:N and C:P ratios of fine roots decreased first and then increased;while the content of K and P increased first and then decreased;and neither the content of Ca,Mg nor N:P ratio changed significantly.The content of N,P,K,Ca in rhizosphere soil was different when the degree of rocky desertification was different,while none of C,Mg and C:N:P ratios in rhizosphere soil changed significantly.Additionally,the content of C,P,Ca,Mg as well as C:N and C:P ratios in the fine roots were positively correlated with their values in rhizosphere soil,while N content in fine roots was negatively correlated with its value in the rhizosphere soil.Moreover,the content of K in fine roots was relatively stable,and was hardly affected by the nutrients of rhizosphere soil.