酸雨对三峡库区4种植物幼苗光合生理及根际土壤的影响

Effects of Acid Rain on Photosynthetic Physiology and Rhizosphere Soil of Four Plant Seedlings in the Three Gorges Reservoir Area

近年来酸雨的酸性和频率越来越高,酸雨类型逐渐由硫酸型向硫酸-硝酸混合型及硝酸型转变。该研究以两年生马尾松、杉木、青冈和毛竹幼苗为试验材料,通过4个月的盆栽实验对幼苗进行硫酸型(SAR)、硝酸型(NAR)和混合型(MAR)酸雨及其各自3个酸雨浓度(pH 2.5、pH 3.5、pH 4.5)的处理,并以pH 5.7的蒸馏水为对照组,对植物的净光合速率、叶绿素含量、树种株高变化量以及植物根际土壤pH值和交换性盐基离子含量进行测定,以探究植物幼苗对模拟酸雨的敏感性及抗性特征,为酸雨受灾区的植被建设和抗酸树种的培育提供参考数据。结果表明:(1)不同浓度及类型酸雨在一定程度上能够抑制植物的净光合速率、阻碍叶绿素的合成,即酸雨浓度越高,植物净光合速率越低,叶绿素含量越少。(2)低浓度酸雨能够促进植物株高的增长,但随着酸雨浓度的增大,植物株高增长量受到严重抑制,且马尾松和青冈的表现最为明显。(3)植物根际土壤在低浓度酸雨胁迫下能够有效释放出盐基离子中和酸根离子从而降低酸雨的毒害,但随着酸雨浓度的增大,盐基离子含量不断衰减,土壤pH值逐渐减小。(4)杉木、马尾松、毛竹、青冈的平均隶属度值在不同酸雨类型作用下的表现不尽相同,总体上杉木对硫酸型和混合型酸雨的抗性最强,而毛竹能耐受硝酸型及混合型酸雨,青冈相比其他3种树种对酸雨的抗性最弱。研究发现,马尾松对硝酸型酸雨最敏感,且受胁迫的pH阈值为2.5~3.5,但对硫酸型酸雨表现出明显的抗性;杉木对3种类型酸雨的抗性较其他3种树种要强,毛竹抵抗硝酸型酸雨能力强于其他2种酸雨,而青冈对硝酸型酸雨的抵抗力强于其他2种酸雨且是抗酸能力最弱的树种,毛竹、杉木及青冈受酸雨胁迫的pH阈值为3.5~4.5;4种植物对酸雨的综合抵抗能力表现为杉木>毛竹>马尾松>青冈。

In recent years,the acidity and frequency of acid rain are higher and higher,and the type of acid rain is gradually changing from sulfuric acid type to sulfuric acid nitric acid mixed type and nitric acid type.In this study,the seedlings of Cunninghamia lanceolata,Pinus massoniana,Phyllostachys edulis and Cyclobalanopsis glauca were treated with sulfuric acid rain(SAR),mixed acid rain(MAR)and nitric acid rain(NAR)and their three acid rain concentrations(pH 2.5,pH 3.5 and pH 4.5)in a pot experiment for 4 months.Along with pH value of 5.7 of distilled water as the control group,we investigated the net photosynthetic rate,chlorophyll content of plants,tree plant height variation and plant rhizosphere soil pH and exchangeable base for ion determination of plant seedlings on sensitivity and resistance characteristics of simulated acid rain,and acid for acid rain disaster area vegetation construction to provide the reference data in the cultivation of tree species.The results showed that:(1)acid rain of different concentrations and types could inhibit the net photosynthetic rate and chlorophyll synthesis of plants to a certain extent,that is,the higher the acid rain concentration,the lower the net photosynthetic rate and chlorophyll content of plants.(2)Low concentration of acid rain can promote the increase of plant height,but with the increase of concentration,the increase of plant height is severely inhibited,which is most obvious in P.massoniana and C.glauca.(3)Under low concentration acid rain stress,plant rhizosphere soil can effectively release base ions to neutralize acid ions,thus reducing acid rain toxicity.With the increase of acid rain concentration,the content of base ions decreases continuously,and the soil pH value decreases gradually.(4)The average membership values of C.lanceolata,P.massoniana,P.edulis and C.glauca showed different performances under different acid rain types.Comprehensively,C.lanceolata showed the strongest resistance to acid rain of sulfuric acid type and mixed acid type,while P.edulis could tolerate acid rain of nitric acid type and mixed acid type.C.glauca had the weakest resistance to acid rain compared with the other three species.The results showed that P.massoniana was the most sensitive to nitric acid rain,and the pH threshold was 2.5-3.5,but it showed significant resistance to sulfuric acid rain.C.lanceolata had stronger resistance to acid rain than the other three species.P.edulis had stronger resistance to nitric acid rain than the other two types,while C.glauca had stronger resistance to sulfuric acid rain than the other two types species,and the resistance was the weakest.The pH threshold of P.edulis,C.lanceolata and C.glauca under acid rain stress was 3.5-4.5.The comprehensive resistance of the four plants to acid rain was C.lanceolata>P.edulis>P.massoniana>C.glauca.