植被恢复对塞罕坝地区土壤养分质量的影响(2002-2022年)

Effects of Vegetation Restoration on Soil Nutrient Quality in the Saihanba Region(2002-2022)

以位于塞罕坝机械林场和乌兰布统自治区级自然保护区交界处(116°32′~118°14′E、41°35′~42°40′N,海拔1 010.0~1 939.9 m)的森林-草原、干旱-半干旱地区交错带为研究区域,于2022年8月下旬在冀蒙界河两岸以2 km×2 km为基本网格单元进行机械布点,选取63个网格交点为取样点,按2022年植被恢复类型进行分类(华北落叶松(Larix principis-rupprechtii)人工林、樟子松(Pinus sylvestris var.mongolica)人工林、天然林(自然恢复的次生阔叶森林,以白桦(Betula platyphylla)为主)、放牧草地、封育草地);在每个取样点使用土钻法采集0~20 cm土层的土壤样品,每次取样以网格交点为中心,按东西走向间隔10 m设置3次重复,所取同样点3份土样风干过筛后等量混合均匀,检测土壤的全氮质量分数、全磷质量分数、全钾质量分数、速效磷质量分数、速效钾质量分数、碱解氮质量分数、有机碳质量分数;以土壤质量指数为评价指标,以7项土壤养分指标为影响土壤质量指数的因素,构建评价指标体系;采用主成分分析法、单因素方差分析法、多重比较法,分析2002年与2022年不同植被类型的土壤化学性质差异、近20 a植被恢复对塞罕坝地区土壤养分的影响、植被恢复过程中土壤养分的变化趋势。结果表明:植被恢复显著影响土壤养分储量,不同恢复方式对土壤养分的影响存在差异,但均对土壤养分总量有所消耗。以樟子松人工林消耗量最大,其土壤有机碳质量分数、全氮质量分数、全磷质量分数、全钾质量分数,与2002年森林相比分别下降了68.07%、60.87%、81.38%、25.87%,但不同植被恢复类型均能提升土壤养分有效性(土壤的碳质量分数∶氮质量分数(w(C)∶w(N))、碳质量分数∶磷质量分数(w(C)∶w(P))明显下降)。土壤质量指数分析表明,不同植被恢复后土壤质量比2002年均有所下降,华北落叶松人工林在维持土壤养分质量方面效果最佳,其土壤质量指数为0.54,与2002年森林土壤养分质量无显著差异。研究结果说明,在植被恢复过程中应考虑乡土树种的重要性,建议制定针有对性的养分管理措施以优化植被恢复效果。

The study area encompasses the transitional zone between forest⁃grassland and arid⁃semiarid regions,located at the junction of the Saihanba Mechanized Forest Farm and the Ulan Butung Autonomous Region(116°32′to 118°14′E,41°35′to 42°40′N,with an altitude ranging from 1010.0 to 1939.9 m).In late August 2022,a grid⁃based sampling method was employed with 2 km×2 km grid cells along the borders of Hebei and Inner Mongolia,selecting 63 grid intersections as sam⁃pling points.These points were classified based on vegetation restoration types in 2022,including Larix principis⁃rupprechtii plantation,Pinus sylvestris var.mongolica plantation,natural forest(secondary broad⁃leaved forest that have naturally re⁃generated,dominated by Betula platyphylla),grazing grassland,and enclosed grassland.Soil samples from the 0-20 cm layer were collected using a soil auger at each sampling point,with three repetitions set 10 m apart in the east⁃west direc⁃tion from the grid intersection.The collected soil samples were air⁃dried,sieved,and mixed uniformly.Soil properties in⁃cluding total nitrogen,total phosphorus,total potassium,available phosphorus,available potassium,alkali⁃hydrolyzable nitrogen,and organic carbon were analyzed.A soil quality index was used as an evaluation indicator,with seven soil nutri⁃ent indicators as factors affecting the soil quality index to construct an evaluation index system.Principal component analy⁃sis,one⁃way ANOVA,and multiple comparison methods were employed to analyze the differences in soil chemical proper⁃ties among different vegetation types in 2002 and 2022,the impact of nearly 20 years of vegetation restoration on soil nutri⁃ents in the Saihanba area,and the trends in soil nutrient changes during the vegetation restoration process.The results showed that vegetation restoration significantly influences soil nutrient reserves,with varying impacts depending on the res⁃toration method,albeit all leading to a depletion in total soil nutrients.Among the restoration types,P.sylvestris plantation exhibited the greatest nutrient consumption,with significant decreases in soil organic carbon,total nitrogen,total phos⁃phorus,and total potassium by 68.07%,60.87%,81.38%,and 25.87%,respectively,compared to the forest in 2002.However,all vegetation restoration types improved soil nutrient availability(evidenced by decreased ratios of carbon to ni⁃trogen and carbon to phosphorus).Soil quality index analysis revealed a decrease in soil quality post⁃restoration compared to 2002,with L.principis⁃rupprechtii plantation demonstrating the best soil nutrient maintenance,with a soil quality index of 0.54,exhibiting no significant difference in SQI compared to the forest in 2002.These findings underscore the impor⁃tance of native tree species in vegetation restoration and suggest the development of targeted nutrient management measures to optimize restoration outcomes.