火烧对喀斯特石漠灌丛林土壤关键要素的调控和植物响应机理

Karst rocky desertification, in which less soil coverage, small nutrient database and seasonal drought are main limiting factors to infuse the shrub forest restoration, is one of the important ecological problems in southwest China. Man-made causes of rocky desertification studied from home and abroad scholars were less fire factor and many other factors. We have studied the fire effects of artificial secondary tree forest and young tree forest in Guizhou karst mountainous area, and how effect is fire on desertification shrub forest? Based on field fire frequency randomized block experiment, surveying characteristics of vegetation and soil seed bank, monitoring plant growth and water potential change and carbon, nitrogen and phosphorus contents of leaf in located shrub species (group), and analyzing changes of soil water content and composition of carbon and nitrogen content and other physical and chemical indicators in observation quadrats, the application researches on key elements ecological process changes of vegetation-soil system before and after fire, and the recovery process in desertification shrub forest, and tests the hypothesis on the desertification shrub forest (1) fire is to change the shrub species (group) composition, community structure and organic carbon stocks and regeneration models, (2) fire is to improve the soil water content, components of carbon and nitrogen content and other physical and chemical indicators, (3) fire is a factor to maintain and succession of the vegetation. It reveals fire regulation on the soil key elements and mechanism of its plant response, and provides theoretical basis and technical support to further use fire to promote vegetation restoration in the desertification shrub forest. This research also has theoretical innovation and potential application value for karst rock desertification control.

喀斯特石漠化是我国西南地区的重要生态问题之一，石漠灌丛林植被恢复是生态治理的难点与重点。火是石漠灌丛林常见的灾害性因子之一，但国内外学者对石漠化人为成因的研究中缺少火因素。我们研究了黔中喀斯特人工乔木林及幼林的火烧效应，石漠灌丛林的火烧效应并不清楚。申请项目采用野外火频次随机区组试验，观测调查样方植物和土壤种子库、监测定位灌木种（组）生长及水势和叶片碳氮磷含量、分析观测样方土壤水、碳氮组分及其它理化指标，研究过火前后及恢复过程中石漠灌丛林植被-土壤系统关键要素的变化，检验假说①火烧改变了石漠灌丛林植物种（组）组成、群落结构及有机碳储量与更新方式，②火烧改善了石漠灌丛林土壤水、碳氮组分及其它理化指标和③火是石漠灌丛林的维持与演替因子。以揭示火烧对石漠灌丛林土壤关键要素的调控和植物响应机理，为进一步利用火烧促进石漠灌丛林植被恢复提供理论依据与技术支撑，对石漠化治理具有理论创新与潜在应用价值。

火是我国西南地区喀斯特石漠化重要的人为干扰因素之一，但国内外却缺少这方面的研究报道。课题以黔中喀斯特石漠灌丛林为研究对象，设置对照（CK）、年年烧（1a）、隔1年烧（2a）和隔2年烧（3a）4处理3重复野外试验，研究火烧对灌丛林和土壤主要理化指标的影响，以及火周期和灌丛林质量变化及演替的关系。研究发现①火烧前后灌木植物多样性和土壤主要理化指标的变化。火烧提高了土壤pH值和土壤过氧化氢酶活性，降低土壤有效磷含量、脲酶活性和碱性磷酸酶活性；火烧增加了表层土壤有机质和速效钾含量，降低了全磷含量。火烧处理前后年际间对比发现表层土壤有效磷和全氮含量升高，蔗糖酶和碱性磷酸酶活性增加；pH值、有机质、全磷、全钾、水解氮和速效钾含量降低，脲酶和过氧化氢酶活性减小，土壤微生物（细菌、真菌和放线菌）数量减少。对照和火烧处理灌木及草本植物多样性指数值在年际间差异显著，年内差异不显著。②火烧频次对灌木林和土壤主要理化指标的趋势性影响。火烧降低了表层土壤脲酶活性、非毛管孔隙度值，增加了碱性磷酸酶和过氧化氢酶活性、土壤密度、毛管孔隙度和总孔隙度值。火烧降低了灌木植物Margalef指数值，增加了Simpson指数、Shannon-Wiener指数和Pielou指数值。火烧降低了灌木林平均地径及高度、枝下高及冠幅、当年新茎的粗度、密度和生物量，提高了当年新茎长度及灌木林藤本化比率。③火烧对灌木林生态功能的影响。火前总肥量对灌木植物多样性、以及酶活性对灌木植物均匀度的贡献率较高，火后总肥量对灌木植物多样性、以及酶活性对灌木植物均匀度的贡献率降低，火烧对灌木林植物多样性-表层土壤系统产生了明显的综合影响。研究初步揭示了火烧对石漠灌丛林土壤关键要素的调控和植物响应机理，为进一步利用火烧促进石漠灌丛林植被恢复提供理论依据与技术支撑。