中亚热带杉木人工林冰雪灾害引发的林木损害及林地养分分布

对中亚热带被冰雪灾害破坏的杉木林地的杉木损害程度及其林地养分分布变化进行了调查,冻雨在杉木枝叶上形成冰柱,造成大量的林木折冠,林木折断的树干部位随胸径的增加而显著升高。树木残体的干质量达25987.6kg·hm-2,树干、枝、叶和皮分别占44%、27%、22%和7%。树木残体中叶、干、枝和皮的N、P和K储量分别占其N、P和K总储量的62%、18%、13%和7%。杉木林地的N、P、K3种养分的积累量为63294.5kg·hm-2,杉木残体的养分仅占杉木林地的0.23%,凋落物层的养分占0.09%,而土壤养分所占比例高达99.68%。3种养分数量在各组分中均为N〉K〉P。雨雪冰冻灾害造成的杉木折干增加了土壤肥力。林冠残体分解引起的养分含量下降,林冠破坏后几乎没有凋落物归还土壤,华南地区频降大雨造成的速效养分流失将使土壤变得贫瘠。

Tree damage and woodland nutrient distribution caused by ice-snow damage in a Cunninghamia lanceolata plantation in mid-subtropical zone China

We statistically analyzed relationships between diameter at breast height（DBH） and tree height in a Cunninghamia lanceolata stand;investigated crown debris input induced by frozen rain and snows;and measured N,P and K contents in crown debris and soils using chemical analysis methods.Icicles were produced on branches and leaves of Cunninghamia lanceolata trees by sleets,resulting in that all live trees were damaged by crown breaking.The broken position of trees significantly ascended with increasing DBH.Woody debris input from broken crowns was 25 987.6 kg·hm-2;and stem,branches,leaves and bark accounted for 44%,27%,22% and 7%,respectively.Accumulation of N,P and K by the woodland was 63 294.5 kg·hm-2;and the nutrients of woody debris,litter and the plantation soil accounted for 0.23%,0.09% and 99.68%,respectively.The rank of nutrient accumulation in all of the components was NKP.Broken crowns caused by ice-snow damage improved fertility of the woodland,but it shall lead to soil depletion due to decreasing nutrient content of broken crowns by decomposition,little litterfall of the Cunninghamia lanceolata stand and available nutrients being washed away by heavy rains.