粉尘、SO_2和NO_x等的复合污染胁迫下马尾松林的退化特征研究

DEGRADED FEATURES OF PINUS MASSONIANA FOREST STRESSED BY COMPOUND POLLUTION DUE TO PARTICULATE,SO_2 AND NO_x

湖南省毛易林场马尾松林长期受粉尘、SO2 、NOx 等的混合污染物复合危害后 ,林相呈灰绿色 ,蒙尘量大 ,林冠不整 ,衰弱、死亡木增加 31 .4 %～ 4 7.8% ;针叶纤细 ,部分叶面有泛黄斑和坏死斑。林缘、林内松针长度分别缩短达 1 7.5 %和 1 0 .0 % ,百针重分别减少 74 .6%和 4 3.6% ;2年生松针内养分元素季节变化规律相似 ,但 N和 P含量下降 ,K和 S含量明显增高 ,显示养分循环失调。林分高和胸径生长明显受挫 ,受害最重的 A林分分别降低 2 .7m和 1 .6cm,林分胸径分布结构“左移”(小径级增多 ) ,高和胸径连年生长量退化了 1 1 .4 %和 8.1 % ;林分平均单株结球果数仅 5 .3～ 7.1个 ,成熟种子千粒重仅 6.8～8.1 g,其当年发芽率仅 31 %～ 5 2 % ,种子空粒、涩粒多。污染区 A、B林分乔木层地上部分生物量分别衰退了 1 1 9.4 %和 70 .7% ,其中最明显的是叶量 ,分别达 31 5 .1 %和 4 9.7% ;根量分别退化了 5 9.6%和38.5 % ,其中最明显的是吸收根量 ,分别降低 1 5 8.3%和 92 .2 %。草本层生物量分别衰退 75 .3%和1 5 7.8% ,但灌木层生物量未明显衰退 ;从林分物种及组织结构来看 ,长期污染胁迫未引起明显的种类组成变化 ,但种群结构发生变化 ,多样性指数 ( H′)和均匀度 ( EI)降低 ,生态优势度 ( SN)增加。

This study was conducted in Maoyi Forest Center, Lengshuijiang City of Hunan Province. Pinus massoniana Lamb. forests were injured by compound pollution due to particulate, SO 2,NO x for a long time. Three forests (A,B and CK) of differently injured degrees were investigated. The degraded features were mainly concerned with the forest appearance, needles and their seasonal changes in nutrient element contents, tree growth and propagation capability, biomass, and structure. The results show that the degraded forests had dark green appearance, abnormal canopy, much more declining and dying trees of 31 4%～47 8%. The needles were slender narrowly and distributed some light yellow or dead speckles. Length and weight of one hundred of the needles inside the forest and in forest edge reduced to 10 0% and 17 5%, and 43 6% and 74 6%,respectively. The seasonal changes in nutrient elements in two year needles were similar to those for normal masson pine stands. But generally speaking, K and S content increased apparently and P and N content dropped obviously. In the most serious injured forest, average height and diameter at breast height, mean annual increment of height and diameter decreased by 2 7m and 1 6cm,11 4% and 8 1%,respectively. Not only the average number of coniferophyte had 5 3～7 1 merely for a tree, but also the weight of one thousand of seeds and germination percentage had only 6 8～8 1g and 31%~52%,respectively. Aboveground biomass of the forest A and B decreased respectively by 119 4% and 70 7%. In addition, the most serious damage was found in the biomass of needles, decreasing by 315 1% and 49 7%,respectively. The root biomass of the forest A and B dropped by 119 4% and 70 7%,respectively; the most serious of those was absorbing root (diameter<0 5cm),by 158 3% and 92 2% respectively. Herbs' biomass of the forest A and B reduced by 75 3% and 157 8% respectively, but shrub layer did not decline. In the view of structure, species composition did not change, but population structure displayed big change, species diversity index H ' and community evenness EI lowered and ecological dominance SN raised. Degraded process and mechanism of masson pine forest and relationship among plant resistance, structure and degradation were also discussed.