| Popis: |
Acid rain is one of serious environmental problems in many cities due to the industrial pollution.In acid rain regions,it is important to understand the pattern of changes in element concentrations in leaves for selection of tree species planted and re-establishing mid-subtropical forests.In hilly secondary forests of acid rain regions,Acacia confuse and Leucaena glauca are the two dominant tree species in mid-subtropical zone.This study determined twelve element concentrations(N,P,S,K,Ca,Na,Mg,Fe,Mn,Cu,Zn and Al) in the leaves of the two species,and analyzed the potential harm of some toxic metal elements caused by the acid rain.The results showed that element concentrations were as following N K Ca S P Mg Na,and Fe Al Cu in leaves of the two species.Significant differences were found in the leaf element concentrations such as P,Ca,Mg,Na,Mn,Cu and Zn between the two species.Due to the frequent acid rains,mean leaf S concentrations of Acacia confuse(3.42 g/kg) and Leucaena glauca(2.70 g/kg) in our study region were higher than the average level of that of terrestrial angiosperm in China((1.66±3.06) g/kg).However,leaf Na concentrations((0.63±0.25) g/kg) were lower than leaf S concentrations for both of Acacia confuse and Leucaena glauca,respectively,and also lower than the average level of that of terrestrial angiosperm in China((2.48±5.45)g/kg).The characteristics of leaf Na concentration in study region could probably resulted from the soil acidification by acid rain which lowered soil Na content.On the one hand,according to the mol ratios of N/P and Ca/Al in leaves,Acacia confuse was one of the P-constrained species.Although leaf Al concentration of Acacia confuse was within the normal range,the mol ratio of Ca/Al in leaves was less than 12.5,which indicated that change in leaf Al concentration was potentially as a result of the harm caused by acid rain.On the other hand,Leucaena glauca was one of the N-constrained species and free of Al harm,suggesting that Leucaena glauca could be more adaptable to study region than Acacia confuse.Significant differences in leaf Al/P、Mn/Cu、Mn/Zn、Mn/Ca、Mn/Mg between the two species showed that the antagonism occured during the growth of Acacia confuse and Leucaena glauca by the joint actions of leaf Al and P concentrations,and those of Mn with Cu,Zn,Ca or Mg.According to the level of leaf element concentrations,Acacia confuse and Leucaena glauca in the study region could be harmed by Cu and Zn,and even more seriously harmed by Fe.The amounts of Zn and Cu accumulation in leaves of Leucaena glauca were larger than that in those of Acacia confuse,respectively,which indicated that Leucaena glauca was with higher resistance to the harm from heavy metal elements,and more acclimatized to the growth in the acid rain regions than Acacia confuse. |
