降水变化和氮添加对红砂幼苗根系形态特征的影响

Effects of precipitation change and nitrogen addition on root morphological characteristics of Reaumuria soongorica

水分和氮素是荒漠生态系统植物生长的主要限制因子,了解降水变化和氮沉降加剧如何影响典型荒漠植物根系形态特征,有助于揭示全球气候变化背景下的典型荒漠植物响应和适应机制,为有效进行荒漠植物恢复建设及管理提供理论依据。采用盆栽试验,研究了红砂(Reaumuria soongorica)幼苗根系形态特征对不同氮添加量(0g·m^-2·a^-1)、4.6 g·m^-2·a^-1、9.2 g·m^-2·a^-1和13.8 g·m^-2·a^-1和降水处理[(70%(W-)、100%(自然降水W)、130%(W+)]的响应。结果表明:(1)降水对红砂幼苗总根长、总表面积、总根体积、根系生物量、比根长和比表面积均有极显著影响(P<0.01);(2)氮添加对红砂幼苗总根体积有极显著影响(P<0.01),对根系生物量影响显著(P<0.05);(3)降水变化和氮添加交互作用对红砂根系形态指标无显著影响(P>0.05)。同一氮水平下,随降水量的增加红砂总根长、总表面积、总根体积、根生物量、比根长、比表面积均呈现增大的趋势,且在降水量130%处理下(W+)各相关指标达到最大值;在降水量70%(W-)和降水量不变(W)的条件下,红砂根系各形态指标随着氮添加量的增加呈现出先增大后减小的趋势,而在降水量130%条件下(W+),各指标随着氮含量的增加大致呈先减小后增大的趋势,且各个指标均在增水、高氮水平时最大。可见,红砂根系生长主要取决于降水,且红砂根系生长存在明显的水氮耦合效应,在高水、高氮条件下,红砂根系生长促进效应最明显。在我国西北干旱和半干旱区,可以在雨季降水量大时通过施入氮肥(N3)来促进红砂根系快速生长、下扎;在干旱少雨时,通过施入适量的氮肥(N1)来促进红砂根系的生长,缓解干旱对红砂根系的限制作用。

Water and nitrogen are the main limiting factors for plant growth in desert ecosystems.How precipitation change and nitrogen deposition aggravate affect the root morphological characteristics of typical desert plants helps reveal the response and adaptation mechanism of typical desert plants under the background of global change and provide a theoretical basis for effective restoration and management of desert plants.In this study,a pot experiment was conducted to study the root morphological characteristics of Reaumuria soongorica seedlings with different nitrogen additions(0,4.6,9.2,and 13.8 g?m^-2·a^-1)and precipitation[70%(W-),100%(natural precipitation W),and 130%(W+)]response.The results showed that varying precipitation had significant effects on total root length,total surface area,total root volume,root biomass,specific root length,and specific surface area of R.soongorica seedlings(P<0.01).Nitrogen addition significantly affectedthe total root volume of R.soongorica seedlings and root biomass(P<0.05).The interaction between precipitation change and nitrogen addition had no significant effect on the root morphological index of the R.soongorica(P>0.05).Under the same nitrogen level,the total root length,total surface area,total root volume,root biomass,specific root length,and specific surface area of the R.soongorica increased with the increase of precipitation.Under 130%precipitation(W+),the relevant indicators reached the maximum value;under 70%precipitation(W-)and constant precipitation(W),the morphological indexes of roots of R.soongorica increased first and then decreased with the increase of nitrogen addition.Under 130%precipitation(W+),each index decreases first and then increases with the increase of nitrogen content,and each index is the largest at the level of increasing water and high nitrogen.It was concluded that the root growth of R.soongorica was mainly determined by precipitation.Furthermore,it had an apparent water-nitrogen coupling effect.Under high water and high nitrogen conditions,the growth of R.soongorica root was mostly promoted.In the arid and semiarid areas of northwest China,nitrogen fertilizer(N3)can be applied to promote the rapid growth and rooting of R.soongorica in the rainy season when there is heavy rainfall.In the case of drought and lack of rain,proper nitrogen fertilizer(N1)was applied to promote the growth of R.soongorica roots and alleviate the limiting effect of drought on R.soongorica roots.