【作者】 张敏；

【导师】 胡海清； 崔晓阳；

【作者基本信息】 东北林业大学 ， 生态学， 2002， 博士

【摘要】 火对生态系统的影响是复杂的，范围也很广，从减少地上部分生物量到对地下部分物理性质、化学性质、微生物降解过程和细根系的生长。火烧对土壤的影响或有利或有害，这主要取决于火烧强度。高强度火烧往往能引起演替频率的改变，土壤物理性质退化，水文功能发生改变，改变C／N比，加剧侵蚀、淋溶和反硝化作用，导致养分流火，微生物数量及其相关过程发生变化。 本文重点研究了火对土壤物理性质、化学性质、微生物数量和细根系生物量的影响。 火烧后年限对土壤含水率、分散系数、孔隙度、持水量、有机质、有效氮、有效钙、真菌、细根系生物量的影响有显著差异；火烧强度对上壤分散系数、孔隙度、饱和持水量、有效镁、细根系生物量的影响有显著差异。 不同火烧强度对土壤含水率影响规律一致。低、中强度火烧对土壤容重和孔隙度的影响不是很人，而对土壤分散系数却有影响。高强度火烧对土壤容重、孔隙度和分散系数的影响均显著。低、中强度火烧迹地土壤持水能力的恢复较高强度火烧迹地快。连年火烧使土壤含水率、孔隙度、分散系数、毛管持水量和田间持水量升高，而使土壤饱和持水量、容重下降。高强度火烧对土壤结构的破坏严重，而低、中强度火烧对土壤结构破坏不大，但对土壤的保水保肥能力影响显著。火烧迹地在降第一场雨后土壤的物理性质有很大变化。 火烧使十壤pH值升高，但随着时间的推移，低、中强度火烧迹地土壤的pH值恢复得较快，高强度火烧迹地土壤的pH值恢复得较慢。大多数火烧迹地若干年后土壤有机质比邻近的未烧林地还高，但低、中强度火烧迹地土壤有机质恢复到未烧水平较高强度火烧迹地快。火烧后6年内，迹地土壤氮的含量较未烧前少。但6年以后，土壤氮的含量有增加的趋势。除少数迹地外，火烧后土壤全磷含量在若干年内呈增加的趋势，但中、高强度火烧迹地土壤全磷含量的恢复较低强度火烧迹地慢。火烧迹地土壤速效磷含量的变化与全磷有大致的趋势。火烧后土壤中的钾、镁含量变化较大，火烧后土壤中的钙易淋失，但随着火烧年限的增加，迹地土壤中的钙有逐渐恢复的趋势。 火烧迹地在降第一场雨后土壤pH值升高，有机质减少，全氮、全磷、钾、钙等含量减少，而有效氮、镁含量增加。 连年火烧迹地土壤pH值升高，有机质、全氮、全磷、速效磷、钙的含量均有所下降，而有效氮、有效钾的含量有所增加。 高强度火烧对土壤微生物有致死作用；中强度火烧后，土壤中细菌、真凶、放线菌数量有增加的趋势；而低强度火烧后，细凶、真菌、放线菌数量变化不明显。在连年火烧迹地上，细菌数量下降，真菌、放线菌数量有所增加。 火烧后，细根系的生物量均有所增加，且高强度火烧后增加最显著，其次是低强度火烧，中强度火烧最不明显；无论何种强度的火烧迹地，第一场雨过后，细根系生物量都有明显增加。更多还原

【Abstract】 The effects of fire on ecosystems are complex, ranging from the reduction or elimination of aboveground biomass to impacts on belowground physical, chemical and microbial mediated processes and fine root. The effect of fire on soil is either beneficial or deleterious, which mainly depends on fire intensity. Severe fires can often cause changes in successional rates and soil hydrologic functions, degradation of soil physical properties, alter C:N ratios, and result in subsequent nutrient loss through accelerated erosion, leaching or denitrification, and alterations in microbial populations and associated process can occur.The paper is mainly focused on the effects of fires on physical, chemical properties, microbial and fine root of soil.The effects of forest fires on soil moisture content, separate coefficient, porosity, water-retaining capacity, organic matter, available N, available Ca, fungi and fine root significantly varied between the years after burning. The effects of forest fires on soil separate coefficients, porosity, saturated water-retaining capacity, available Mg, fine root significantly varied between the fire intensity.The effects of different fire intensities on soil moisture content had similar laws. Low and moderate intensity fire had no or little effects on soil unit weight and porosity, which was different from that on separate coefficient. The effects of high intensity fires on soil unit weight, porosity and separate coefficient were significant. The soil water-retaining capacity at low and moderate intensity burnt site returned to the level before burning faster than at high intensity burnt site. After yearly burning, soil moisture content, porosity, separate coefficient, capillary and field moisture capacity increased, however, soil saturated water retaining capacity and unit weight decreased. High intensity fire can significantly destroyed the soil structure. After low and moderate intensity fire had little effect on degree of soil solidity and porosity, which was different from that on soil capability of preservation of water and fertilizer. The changes of soil physical properties at burnt site were very great following rainfall.Fire raised soil pH, but the soil pH after low and moderate intensity fires returned to the lever before burning faster than after high intensity fires.The changes of soil organic matter and pH were similar after fires. Soil N decreased within 6 years following burning and increase after 6 years after fires. Generally, soil total P increases after burning, but the soil total P after moderate and high intensity fires returned to level before burning slower than after low intensity fires, which is consistent with soil available N. The changes of soil K, Mg are great after burning. Soil Ca leaches easily after fire. Then soil Ca can returned to level before burning gradually.Soil pH, available N and Mg increase on burnt sites following the first rainfall, however, soil organic matter, total N, total P, K and Ca decrease.The yearly burning raised soil pll, available N and K and reduced soil organic mater, total N, total P, available P and Ca.High intensity fires can significantly kill soil microorganism. After moderate intensity fires, the amounts of bacteria, fungi and actinomycetes increased significantly. After low intensity fires , those changed insignificantly . At the yearly burnt si tes, the amounts of bacteria declined, the amounts of fungi and actinomycetes increased significantly.The fine root biomass increased after fires, which was the most significant after high intensity fires, and the least significant after moderate intensity fires. The fine root biomass increased following a rainfall after any fire.更多还原