长汀红壤侵蚀区土壤砂砾化对土表温湿度及种子萌发的影响

Effects of soil gravelization on soil surface temperature and humidity and seed germination in red soil erosion area of Changting

土壤砂砾化、植被恢复困难是长汀红壤强度侵蚀区的突出生态问题.为探索土壤砂砾化对植被恢复的影响,本研究以长汀红壤侵蚀区植被恢复先锋植物马尾松、胡枝子和宽叶雀稗种子为试验材料,采集长汀红壤强度侵蚀区的土壤,按砾石(粒径>2 mm)含量(10%、20%、30%、40%和50%)模拟配制5种不同砂砾化程度的土壤作为发芽基质,在露天自然条件下进行盆栽发芽试验,研究不同砂砾化程度土壤环境对土表温湿度及植物种子萌发的影响.结果显示:(1)砂砾化使土表高温低湿,干热化加剧,试验期间土表日最高温度高于30℃的天数占86%,高于40℃的天数占35%,砾石含量40%的土表日最高温度甚至超过50℃;除少数降雨天外,土表湿度基本低于10%,日最低湿度仅为3.9%.(2)土表温度与土壤砂砾化程度间存在显著正相关关系,土表湿度与土壤砂砾化程度间存在显著负相关关系,土表温度与湿度间也存在显著负相关关系.随着砾石含量的增加,土表温度呈上升趋势,而湿度呈下降趋势,且砾石比例越高,其土表温湿度变化越明显.(3)砂砾化土壤环境中,乔灌草植物种子难以萌发,试验期间具有活力的马尾松、胡枝子和宽叶雀稗种子均无萌发.综上表明,长汀红壤侵蚀区土壤砂砾化导致土壤严重干热化,无法满足植物种子萌发需要,植被自然恢复困难,因此,土壤砂砾化是长汀红壤侵蚀区植被恢复的主要限制因子之一.

Soil gravelization and difficulty in vegetation recovery are distinguishing ecological problems in Changting red soil erosion area.In order to elucidate the influence of soil gravelization on vegetation restoration,germination of pioneer plants in vegetation restoration,Pinus massoniana Lamb.,Lespedeza bicolor Turcz.and Paspalum wettsteinii Hack seeds were tested on soils(gravel particle size>2 mm)sampled from the highly eroded red soil region in Changting County.Five grades of sand-gravel ratios(10%,20%,30%,40% and 50%)were set up and the germination tests were conducted in open air under natural condition.Soil surface temperature,soil humidity and seed germination were monitored.The results showed that:(1)gravelization led to high soil surface temperature and low humidity.During the test period,86%of the days with the maximum daily soil surface temperature was higher than 30℃,and 35% of the days with the maximum daily soil surface temperature was higher than 40℃.And the soil with 40% gravel content even experienced a maximum daily surface temperature over 50℃.Except for a few rainy days,soil surface humidity was generally less than 10%,with the lowest daily humidity being only 3.9%.(2)There was a significant positive correlation between soil surface temperature and the proportion of soil gravel,a significant negative correlation between soil surface humidity and the proportion of soil gravel,and a significant negative correlation between soil surface temperature and humidity.With the increase of gravel content,soil surface temperature increased while soil humidity decreased.The higher gravel proportion,the sharper change soil surface temperature and humidity experienced.(3)Germination in sandy soil environment was difficult for the seeds of trees,shrubs and grasses,neither did the vigorous seeds of P.massoniana,L.bicolor and P.wettsteinii during the experiment.In conclusion,soil gravelization in the eroded red soil area of Changting resulted in serious dry and hot soil,which failed to meet the requirements of seed germination,leading to difficulties in natural restoration of vegetation.Therefore,soil gravelization was one of the main limiting factors for vegetation restoration in the eroded red soil area of Changting.