兴安落叶松林火烧迹地土壤速效钾时空动态分析

【目的】研究不同强度火干扰下兴安落叶松林土壤速效钾含量的时空变化,探讨其变化规律与空间格局的形成原因,分析火烧迹地恢复初期土壤速效钾营养水平,为林地土壤钾营养调控与管理提供参考。【方法】在大兴安岭北部兴安落叶松林地布设固定采样点,进行林火点烧试验,分别于火烧前、火烧后、融雪季后和生长季采用土钻法在固定点位30 cm半径内采集土壤样品,采用乙酸铵法测定土壤速效钾含量,分析轻、中、重度火烧区土壤速效钾时空变化特征。【结果】①轻度火烧区,土壤速效钾含量未因火烧立即发生明显变化,但在融雪季显著上升,生长季仍维持较高水平;中、重度火烧区,则在火烧后立即升高,融雪季进一步上升,而后相对稳定;②火烧强度空间格局与土壤速效钾含量空间格局在融雪季和生长季均极显著正相关,与土壤速效钾含量变化率在火烧后的各时期均极显著正相关;原生土壤速效钾含量与火烧后各时期土壤速效钾含量及其变化率均显著相关;火烧后,土壤速效钾空间格局是原生土壤速效钾含量空间格局与火烧强度空间格局综合作用的结果。【结论】经过融雪季与生长季,兴安落叶松林轻、中、重度火烧区土壤速效钾含量显著升高,有利于火烧迹地恢复初期森林植被更新与改造。

Temporal and spatial dynamics of soil available potassium in a post-fire Larix gmelinii forest

【Objective】 Both the temporal variation and spatial distribution of soil available potassium content were investigated in post-fire areas in a Larix gmelinii forest that experienced different intensity burns. The variation regularity and spatial pattern were also considered to better understand the characteristics of soil available potassium during the early restoration of burned plots and to provide insights into forest ecosystem restoration after fire disturbance.【Method】 In an L. gmelinii forest in the northern Great Xing’an Mountain region, fixed sampling points were established prior to conducting a fire experiment with three burn intensities (mild, moderate and severe). Using a soil core method, soil samples were collected within a 30 cm radius of each fixed sampling point before and after the burn, following the snowmelt season, and during the growing season. The soil available potassium content was determined using the ammo-nium acetate method. Temporal and spatial dynamics of soil available potassium in the post-fire areas were analyzed and compared.【Result】① In the mildly burned area, soil available potassium content was the same pre- and post-fire, but increased significantly following the snowmelt season, and remained at a high level during the growing season. In the moderately and severely burned areas, there was a post-fire increase in soil available potassium content which increased further following the snowmelt season, and remained unchanged during the growing season. ② The spatial pattern of burn intensity was positively correlated with the spatial pattern of soil available potassium content following the snowmelt season and during the growing season. The change rate of available potassium content after the fire was significantly positively correlated with burn intensity across all sampling times. The available potassium content or its change rate following the fire was significantly correlated with native soil available potassium content across all sampling times. The post-fire spatial pattern of soil available potassium was related to both the native soil available potassium content and burn intensity.【Conclusion】Following the snowmelt season, and during the growing season, soil available potassium content significantly increased in mildly, moderately and severely burned areas in an L. gmelinii forest. This may be beneficial for regeneration and reforestation during the initial post-fire recovery stage.