模拟林火与灭火剂联合对土壤化学特性的影响

Effect of Forest Fire and Fire Extinguishing Agent on Soil Chemical Properties

喷洒灭火剂可以有效防治林火发生,但其对林下土壤化学性质的影响尚不清楚,该文旨在通过试验研究林火与灭火剂联合对土壤化学特性的影响。文章通过野外模拟无火烧、中度和重度火烧3个林火梯度及无灭火剂、小剂量和大剂量灭火剂3个梯度灭火剂用量的正交试验,采集火烧灭火后即时(初期)和3个月后(后期)的表层土(0~10 cm)和深层土(10~20 cm)土样,测定土壤pH、电导率、磷酸酶活性、蔗糖酶活性、速效磷和速效钾等化学特性指标,分析不同强度火烧和不同剂量灭火剂处理对土壤化学特性影响。结果表明:(1)同一强度火烧干扰条件下,使用灭火剂对初期土壤p H的影响不显著;无灭火剂条件下,重度火烧显著提高了初期深层土的pH。火烧和灭火剂都会提高表层土的电导率,但影响不显著;重度火烧条件下,大剂量灭火剂的使用显著提高了后期深层土的电导率。(2)仅使用灭火剂对表层土磷酸酶活性有抑制作用,蔗糖酶活性有促进作用;但是灭火剂在火烧干扰时使用能缓解火烧对磷酸酶活性的抑制作用。火烧和灭火剂配合下破坏了初期土壤磷酸酶和蔗糖酶活性,影响随着土层深度增加而降低。(3)火烧对表层土速效磷含量的影响大于深层土;重度火烧条件下喷洒小剂量灭火剂的土壤速效磷含量与无灭火剂的差异不显著。火烧及火烧产物共同破坏了速效磷和磷酸酶活性,不同土层的影响一致。无灭火剂中度火烧在一定时期内显著提高了表层土速效钾含量;无火干扰喷洒灭火剂一定时期内对土壤速效钾含量影响不显著。整体来看,中度火烧干扰有利于促进森林生态系统内部的物质循环。通过喷洒小剂量灭火剂有利于林火防治,且不会造成土壤富营养化,有利于保护森林生态系统平衡,为高压输电线路下林火防治提供理论和实践指导。对土壤物理及生物性质的影响需做进一步深入探索。

Spraying extinguishing agent can effectively prevent forest fire, but its effect on soil chemical properties under forest is not clear. This study aimed to examine the influence of forest fire and fire extinguishing agent on soil chemical properties. Soil samples at depth of 0~10 cm and 10~20 cm were collected immediately(early) and 3 months later(later) after fire and fire extinguishing by simulating 3 bushfire gradients including without fire, moderate and severe fire in the field and 3 extinguishing agent quantities such as without extinguishing agent, small dose and high dose extinguishing agent. The indoor chemical properties of the collected soil were determined, including pH, conductivity, phosphatase activity, invertase activity,available phosphorus and available potassium, and the effects of different intensity fires and different doses extinguishing agent treatment on soil chemical properties under different spatial and temporal distributions were illustrated by comparative analysis of various chemical indexes and their changes. Results indicated that under the condition of the same intensity of fire disturbance, the use of fire extinguishing agent had no significant effect on the pH of the initial soil;without fire extinguishing agent, the use of heavy fire significantly increased the pH of the initial deep soil. Fire and extinguishing agent will improve the conductivity of surface soil, the effect is not significant;under the condition of severe fire, the use of high dose extinguishing agent significantly increases the conductivity of deep soil after 3 months of fire. The use of fire extinguishing agent alone inhibits the activity of the surface soil phosphatase, and the activity of sucrose enzyme promotes it, but the use of the extinguishing agent in burning disturbance can relieve the inhibition of the activity of phosphatase by fire. The law of immediate soil phosphatase and sucrose enzyme activity decreased with the increase of depth under the combination of fire and extinguishing agent. The effect of fire on the content of available phosphorus in surface soil is higher than that of deep soil, and there is no significant difference between the content of available phosphorus and the absence of fire extinguishing agent in soil sprayed with small dose extinguishing agent under severe burning conditions. The activities of available phosphorus and phosphatase were destroyed by fire and its products, and the effects of different soil layers were the same. The content of available potassium in surface soil was significantly improved in a certain period of time without fire extinguishing agent, and the effect of free interference spraying extinguishing agent on soil available potassium content was not significant in a certain period of time. On the whole, moderate fire disturbance is beneficial to promote the material circulation within the forest ecosystem. Spraying small dose fire extinguishing agent is beneficial to forest fire prevention and control, and does not cause soil eutrophication, is conducive to protecting forest ecosystem balance, and provides theoretical and practical guidance for fire prevention and control under high voltage transmission lines.The effects on soil physics and biological properties needs further exploration.