不同覆盖措施对盐碱地紫穗槐细根适应策略的影响

Effects of different mulching measures on the fine-root adaptation strategies of Amorpha fruticosa in saline soil

为分析不同覆盖措施对盐碱地以及紫穗槐(Amorpha fruticosa)细根垂直分布的影响,从而为宁夏引黄灌区盐碱荒地土壤改良与植被重建提供参考,本研究采用薄膜、沙子、稻草以及对照(无覆盖)4种覆盖措施,并测定0-60 cm土壤环境因子(水分、温度、盐分、有机碳和有效氮);利用全株挖掘法,测量粗放型策略指标(细根生物量、细根长)和密集型策略指标(比根长、比根表面积)。结果表明:2016和2017年,3种覆盖措施中稻草覆盖保水效果最好,0-60 cm土层土壤水分增加了13.59%~14.38%;与对照相比,薄膜、沙子覆盖下土壤温度分别增加了8.48%~20.17%和5.07%~18.20%,稻草覆盖则出现降温效应。薄膜覆盖降盐抑盐效果最佳,土壤盐分降低了12.05%~45.10%,其次为稻草覆盖,土壤盐分下降了10.34%~34.73%,而沙子覆盖的土壤盐分则下降了4.42%~19.61%。2016和2017年稻草覆盖下土壤有机碳增加了6.61%~9.22%;2016年薄膜、沙子覆盖下土壤有机碳分别降低了13.95%、7.80%,而在2017年却分别增加了7.07%和5.77%。2016-2017年,3种覆盖措施下土壤有效氮均有所增加,增加幅度表现为稻草(28.58%~48.20%)>薄膜(26.00%~39.39%)>沙子(10.18%~24.40%)。薄膜覆盖下细根在0-40 cm层采用粗放型策略最佳,而在40-60 cm层采用密集型策略表现最佳,这有利于其细根在空间异质性盐碱土中获取更多土壤资源;而对照在0-40 cm层密集型策略表现最佳。综上,薄膜覆盖在改良盐碱地土壤环境中效果较好,有助于细根在不同土层更好地发挥适应性策略。

In order to provide a reference for soil improvement and revegetation in the saline wastelands of the Ningxia Irrigation Area,we investigated the effects of different mulching materials on the soil microenvironment and vertical distribution of the fine roots of Amorpha fruticosa.In 2016 and 2017,we examined the effects of mulching using three different mulch materials,namely,plastic mulch(PM),sand mulch(SM),and rice straw mulch(RSM),and compared these with a non-mulch control(CK).To assess the effects of mulching,we measured the following soil microenvironmental factors at depths from 0 to 60 cm:soil water content(SWC),soil temperature(ST),electrical conductivity of a saturated paste extract(ECe),soil organic carbon(SOC),and available nitrogen(AN).Plants under different mulches were sampled to analyze extensive strategies(fine root biomass and fine root length)and intensive strategies(specific root length and specific root area).The results revealed that in both years of the study,RSM retained the highest SWC with increases of 13.59%~14.38%at depths of between 0 and 60 cm.Compared with CK,PM and SM increased ST by 8.48%~20.17%and 5.07%~18.20%,respectively,whereas the use of RSM reduced ST due to its greater heat capacity and lower thermal diffusivity.PM(12.05%~45.10%)showed the best performance with respect to a reduction in ECe at depths between 0 to 60 cm,followed by RSM(10.34%~34.73%)and SM(4.42%~19.61%).In both years,RSM promoted the largest increase in SOC,by 6.61%~9.22%.In 2016,PM and SM reduced SOC by 13.95%and 7.80%,respectively,whereas in 2017,respective increases of 7.07%and 5.77%were obtained using these mulches.In both years,all mulching treatments increased AN,in the order RSM(28.58%~48.20%)>PM(26.00%~39.39%)>SM(10.18%~24.40%).Fine roots in the 0-40 cm layer under PM showed the best performance with respect to extensive strategies,whereas those in the 40-60 cm layer performed best in terms of intensive strategies.These adaption would be beneficial with regards to acquiring larger amounts of resources in saline soils characterized by resource heterogeneity.Comparatively,we found that fine roots in the 0-40 cm showed the best intensive strategies under CK conditions.The findings of this study thus indicate that among the different mulches assessed,a plastic mulch would be the most effective in improving the saline soil environment,thereby enhancing performance of the fine roots of A.fruticosa in different soil layers with respect to two adaptive strategies.