不同秸秆填埋量对盐碱土水盐运移及垂柳反射光谱的影响

在宁夏西北盐化生态脆弱区的典型盐碱化土地,通过随机区组试验,探究在栽植穴填埋秸秆2000(T_1)、7000(T_2)、12000kg/hm~2(T_3)及17000 kg/hm~2(T_4)等作隔盐层对土壤水盐运移及垂柳(Salix babylonica)反射光谱的影响,将地下土壤水盐变化与地上植物生长及生理状况相结合,以期更准确的反映出各处理对盐碱土壤改良效果及地上植被恢复情况。研究结果表明:(1)填埋一定量的秸秆作隔盐垫层可以改变地下土壤水盐的剖面分布特征。T_2、T_3和T_4处理与对照组相比,20—80 cm土层土壤含水量都显著提高,填埋的秸秆层起到了蓄水保墒的作用;都明显降低了0—80 cm土层土壤盐分含量和盐溶质浓度;但这3种处理之间无显著差别。T_1由于填埋秸秆量过少,无显著蓄水控盐效果。(2)通过检测植物叶片反射光谱可以反映出地上植物生长及生理状况的变化。填埋一定量的秸秆作为隔盐垫层有助于改善垂柳的生理状况。T_2的垂柳叶片光合色素含量最高,光合特性及营养状况最好,其他光谱参数结果都显著提高。T_3显著提高叶绿素含量和光合特性,但效果均不如T_2,且营养状况差。T_4处理类胡萝卜素含量与叶片水分含量均处于最高水平,但叶绿素含量、营养状态以及光合特性都显著降低。T_1处理效果最差。(3)在地下填埋秸秆作隔盐层,会通过对地下土壤水盐运移及微域生态系统环境的调节,影响到地上植物生长及生理状况。综合地下水盐分布与地上植物叶片反射光谱的结果,T_2是宁夏引黄灌区盐碱地改良中最适宜的秸秆填埋量。

Effect of burying different amounts of straw on soil water, salt movement, and the spectral reflectance of Salix babylonico grown on saline-alkaline land

Salinization is the process by which water-soluble salts build up over the soil profile. Soil salinity is an escalating problem worldwide, especially in arid and semi-arid regions. Plants growing in salt-affected soils may suffer from physiological drought stress, ion toxicity, and mineral deficiency. These problems can lead to reduced growth and biomass. In previous studies on saline-alkali soil amelioration, evaluation of the amelioration measures has focused on the influence of soil salt ions and soil physical and chemical properties. However, this assessment is one-sided and does not consider simultaneously the effects on the growth and physiological conditions of the vegetation. Burying straw in soil as salt-isolation interlayers is a widely used and effective measure for soil salinity control. The effect of burying different amounts of straw on the amelioration of saline-alkali land and vegetation restoration was assessed by conducting field experiments on typical saline-alkaline land in the ecologically fragile area of Ningxia in northwest China. The experiment had four straw burial treatments. These were 2000 kg/hm² (T₁), 7000 kg/hm² (T₂), 12000 kg/hm² (T₃), and 17000 kg/hm² (T₄). The control treatment was no straw burial. All the treatments were arranged in a randomized complete block design with five blocks. Each block was then divided into three plots. The five treatments were randomly assigned to each block. The soil water and salt contents in the 0-100 cm soil layer and spectral reflectance were measured during the Salix babylonico growing season. The results indicated that (1) burying straw as a salt-isolation interlayer could significantly modify underground soil water and salt processes. The T₂, T₃, and T₄ treatments significantly increased the soil water content in the 20-80 cm soil layer compared to CK, and significantly reduced the soil salt content and salt solute concentration in the 0-80 cm soil layer. However, there were no significant differences between these three treatments. The amount of straw buried in T₁ was low. This meant that there was no significant difference between it and the distribution of soil water and salt in CK. Therefore, the salinity control effect was not obvious. (2) The results for the plant leaf spectral reflectance showed that plant growth and physiological condition could be estimated from the results. Straw interlayers significantly improved the physiological condition of Salix babylonico. The spectral reflectance results showed that the T₂ treatment produced the highest chlorophyll content, photosynthetic characteristics, and nutrition levels. Other spectral reflectance parameters also significantly improved compared to CK. The T₃ treatment significantly improved chlorophyll content and photosynthetic characteristics, but was less effective than T₂ and nutrition levels were poor. Carotenoids content and the leaf water content were highest in the T₄ treatment, but other parameters were significantly lower than CK. The T₁ treatment was the worst. (3) Burying straw in the ground as a salt-isolation interlayer could affect the growth and physiological state of the plant by regulating underground soil water and salt transport, and the micro-ecosystem environment. The results for the distribution of soil water and salt, and the spectral reflectance of the plant leaves suggested that the T₂ treatment was the most suitable straw burying amount for the amelioration of saline-alkaline land in the ecologically fragile area of Ningxia.