沙地樟子松抗旱能力的分析

内蒙古呼伦贝尔盟红花尔基林场现有樟子松纯林82000ha,长势良好。但1986年6月至1987年5月,出现了大面积枯死现象,20年生以下的天然林枯死率100％。作者按林分年龄、坡向、坡位、坡度取样,分析了土壤含水量,调查枯死现象与林地环境因子和立地条件之间的相关性。结果证明,1986年的严重干旱使土壤含水量低于樟子松的含水量临界点,造成樟子松大面积枯死。1986降雨量为228.3mm,比年平均值334mm低105.77mm。在樟子松根系分布层中的含水量仅有2.288％～2.360％。郁闭度小或过大的林分因旱致死的多。天然林分因树木根系发育良好,其抗旱力强于人工林。混交林的抗旱力强于单纯林。20年生以下的林分旱死的多,10年生以下的林分旱死的更多。阴坡未发现受害的。

ANALYSES ON DRAUGHT RESISTANCE OF MONGOLIAN SCOTS PINE ON SANDY SOIL

There are 82000 hectares of well-growth pure mongolian scots pine(Pinus sylvestris var. mongolica) forest in Honghuaerji forest, farm of Hulunbeier Prefecture,, Inner Mongolian Autonomous Region. From June of 1986 to May of 1987,large area of the forest withered with mortality of 100% in the 20-year-stands. The author collected samples of soil from stands of different age according to different declivity, dircction and position of the slope, and analysed the soil moisture content and investigated the relationship between the forest withered and the environment factors as well as stand condition of the forest. The result shows that the soil moisture content fell below the threshold of the moisture content of mongolian scots pine due to the drought of 1986. This results in the death of large area of the forest. The rainfall of 1986 was 228.3 mm and 105.7 mm lower than the average of 334.0 mm. The moisture content of soil around rootsystem of mongolian scots pine is only 2.288% to 2.360%. There are more deaths of trees due to the drought in sparse and dense forests. Natural forests are more drought- resistant than plantations and the mixed stands are more drought-resistant than pure ones. Many stands below 20-year- olddied of drought and more dcath in the stands below 10-years-old. Damages were not found in thestands growing on the northword slopes.