蒲桃和人面子叶片单宁含量与凋落物分解速率及底栖动物定殖的关系

在广州龙洞水库一条天然2级溪流中,测定了蒲桃和人面子凋落物105 d分解过程中单宁含量的变化.结果表明：蒲桃叶片单宁的初始含量（0.191 g·g^-1DM）高于人面子（0.057 g·g^-1DM）.在最初一周内, 两种树木叶片的单宁含量分别下降了45 %和22 %,其中人面子叶片单宁含量降速比蒲桃快;21 d后，其下降速度减缓，而凋落物分解的速度加快，人面子叶片分解比蒲桃迅速（k值分别为0.038和0.013 d^-1）.定殖在人面子叶片上的底栖动物的平均密度显著高于蒲桃叶片（P<0.05），分别为每克叶片287.9头和26.2头；底栖动物的数量变化随叶片单宁含量的降低而呈逐渐增加趋势.富含单宁成分的蒲桃叶片分解速率缓慢，可能是凋落物中高浓度缩合单宁抑制了底栖动物，尤其是撕食者的定殖所致.

Relationships of Syzygium jambos and Dracontomelon duperreanum leaf tannin concentration and leaf litter breakdown with the colonization of benthonic invertebrates

An investigation was made on the dynamic changes of tannin concentration in Syzygium jambos and Dracontomelon duperreanum leaves over a 105-day period of leaf litter decomposition in a second-order stream in Longdong Reservoir,Guangzhou.The initial tannin concentration in S.jambos leaves(0.191 g·g~(-1) DM)was higher than that in D.duperreanum leaves(0.057 g·g~(-1) DM).In the first week of leaf litter decomposition,the tannin concentration in D.duperreanum and S.jambos leaves decreased by 45% and 22% respectively.21 days after,the decline in tannin concentration slowed down,but the decomposition rate increased,with the leaves of D.duperreanum decomposed faster than those of S.jambos(k value was 0.038 d~(-1) and 0.013 d~(-1),respectively).The average density of benthonic invertebrate colonized on D.duperreanum leaves(287.9 ind ·g~(-1) leaf mass) was significantly higher than that on S.jambos leaves(26.2 ind·g~(-1) leaf mass) (P ＜ 0.05).A continual increase of benthonic invertebrate' s abundance was observed during leaf litter decomposition,which could be attributed to the rapid decrease of leaf tannin concentration.The slower breakdown of S.jambos leaf litter was likely because of the high tannin concentration in S.jambos leaves,which inhibited benthonic invertebrate,especially the shredder's colonization.