持续干旱下沙地樟子松幼苗C、N、P化学计量变化规律

Variations in C,N and P stoichiometry of Pinus sylvestris var. mongolica seedlings under continuous drought

为明确沙地樟子松幼苗在干旱胁迫过程中C、N和P化学计量的变化规律及分配特征,通过盆栽试验,对2年生沙地樟子松幼苗进行自然干旱处理,当土壤含水量下降到田间持水量的60%、40%、30%和20%时,测定各器官(当年生叶、一年生叶、茎、粗根和细根)的C、N和P含量。结果表明:持续干旱过程中,沙地樟子松幼苗N、P含量及C∶P和N∶P变异系数在粗根中最大,C含量变异系数在细根中最大;C、P含量及C∶P变异系数在一年生叶中最小,N含量和C∶N变异系数在当年生叶中最小,N∶P变异系数在茎中最小。随着田间持水量下降,C含量在当年生叶中先下降再上升后下降,在一年生叶、茎和粗根中先升高后降低,在细根中先下降后上升;N含量在当年生叶中先下降后上升,在一年生叶、茎和粗根中下降,在细根中先降低再升高后降低;P含量在当年生叶中上升,在一年生叶、茎、粗根和细根中先下降后上升;C∶N在一年生叶、茎、粗根和细根中增加,C∶P在当年生叶中下降,各器官N∶P均降低。相同元素在不同器官间紧密相关,而不同元素间相关性较差。因此,随着干旱加剧,沙地樟子松幼苗生长受N限制逐渐增强,N利用效率提高,各元素在叶和茎中稳定性高于粗根和细根。

We examined the stoichiometric responses of Pinus sylvestris var.mongolica seedlings to drought stress by growing two-year-old P.sylvestris var.mongolica seedlings in pots and setting continuous natural drought treatment.We measured C,N and P contents in different organs(current-year needle,one-year-old needle,stem,coarse root and fine root)of the seedlings under the conditions of 60%,40%,30%and 20%of field water-holding capacity.Under drought stress,the variation coefficients of N and P content,C∶P and N∶P were the highest in coarse root,and the variation coefficient of C content was the highest in fine root.Meanwhile,the variation coefficients of C and P content and C∶P were the lowest in one-year-old needle,the minimum variation coefficients of N content and C∶N were found in current-year needle,and the minimum variation coefficient of N∶P was found in stem.With decreasing soil field capacity,C content in current-year needle showed a hump change,whereas it elevated and then reduced in one-year-old needle,stem and coarse root,and it decreased and then increased in fine root.Nitrogen content decreased and then increased in current-year needle,but it declined in one-year-old needle,stem and coarse root,whereas it showed a hump pattern in fine root.Phosphorus content was promoted in current-year needle,but it declined and then increased in one-year-old needle,stem,coarse root and fine root.In addition,C∶N increased in one-year-old needle,stem,coarse root and fine root,but C∶P declined in current-year needle,while N∶P decreased in all organs.There were close correlations among different organs for the same element but not for different elements.Therefore,with increasing drought stress,N limitation was gradually aggravated to the growth of P.sylvestris var.mongolica seedlings,and N use efficiency improved.Meanwhile,the contents of various elements were more stable in needle and stem than that in coarse root and fine root.