炼锌废渣-修复植物-凋落物体系的生态化学计量学研究

为揭示金属冶炼废渣堆场生态修复多年后,废渣-植物-凋落物系统中养分循环和系统维持机制。该研究以实现生态修复6 a的黔西北铅锌冶炼废渣堆场上土荆芥(Dysphania ambrosioides)、芦竹(Arundo donax)、刺槐(Robinia pseudoacacia)、构树(Broussonetia papyrifera)和柳杉(Cryptomeria fortunei)五种优势修复植物为对象,分析它们的主要营养器官(细根、粗根、茎/干、枝、叶片)、地表凋落物、植被下方表层废渣(0～10 cm)中碳(C)、氮(N)、磷(P)含量及化学计量特征,探讨它们之间的相互关系。结果表明:不同植物、不同营养器官间C、N、P的含量具有显著差异(P<0.05),C平均含量在两种草本植物中为茎>叶片>根>凋落物,在三种乔木中为干>枝>细根>粗根>叶片>凋落物; N和P的分布在草本植物中分别为叶片>凋落物>根>茎和叶片>根>凋落物>茎,在三种乔木中均为叶片>细根>凋落物>粗根>枝>干。五种植物中,柳杉各营养器官及凋落物中C含量均高于其他植物,N、P含量呈相反的规律; 刺槐中N含量最高。C:N和C:P在五种植物营养器官与凋落物中的变化规律跟N、P的分布相反,说明C:N和C:P分别主要受N和P含量影响。相关性分析指出,草本植物的N:P受N和P共同影响,三种乔木的N:P主要由N的分布决定,同时受到枝和叶片中P含量影响。五种植物中,仅豆科类刺槐的叶片N:P大于16,在系统中生长受P限制,其他植物生长均受N限制,说明刺槐更能适应贫瘠的废渣环境,建议在修复贫瘠的废渣堆场时优先选择豆科类植物作为先锋植物,改善基质养分条件。植被下方表层废渣中C、N、P含量基本都低于植物各营养器官及凋落物,不同修复植物下方对应的表层废渣中C、N、P含量间具有显著差异(P<0.05),草本植物修复下的废渣中C、N、P含量低于乔木修复下的含量。废渣-植物-凋落物体系中N、P、N:P之间的相关性分析显示,植物细根和凋落物中N、P含量与废渣中N、P含量及化学计量比关系更密切。

Ecological stoichiometry of lead-zinc smelting slags-remediation plant-litter

This study aimed to reveal the nutrient cycling and stability mechanisms in slag-plant-litter system on the metal smelting slags yard for many years of ecological restoration. Five dominant plants(Dysphania ambrosioides, Arundo donax, Robinia pseudoacacacia, Broussonetia papyrifera and Cryptomeria fortunei)planted on the lead-zinc smelting slag which had been ecologically restored for six years in Northwest Guizhou were selected as the objective in this study. The contents of carbon(C), nitrogen(N), phosphorus(P)and their stoichiometric characteristics in the organs of these dominant plants(fine root, coarse root, stem, branch and leaf), floor litter and surface waste slag beneath plants(0-10 cm)were studied, and their relationships were also determined. The results were as follows: There were significant differences in C, N and P contents between different plants and different vegetative organs(P<0.05). In the herbaceous plants,, the average content of C was stem > leaf > root > litter, and in the three trees, trunk > branch > fine root > coarse root > leaf > litter, The distributions of N and P in the herbaceous plants were leaf > litter > root > stem, leaf > root > litter > stem, while in the three trees, the distribution of N and P was leaf > fine root > litter > coarse root >branch > trunk. C content in litter of Cryptomeria fortunei was higher than that in all organs of others, but the contents of N and P showed an opposite rule. The highest concent of N was found in Robinia pseudoacacia. The change of C:N and C:P in organs and litter was contrary to the distributions of N and P, indicating that C:N and C:P were mainly affected by the content of N and P. Correlation analysis indicated that N:P of herbaceous plants was affected by N and P. N:P in the three arbor components was mainly controlled by N content, and also affected by P content in branches and leaves. Among the N:P leaves of the five plant leaves, only the N:P of leaves in Robinia pseudoacacia was greater than 16, and the growth in the system was restricted by P, while the growth of the other four plants were mainly restricted by N, indicating that Robinia pseudoacacia is more suitable for the waste residue environment, it was recommended to select legumes as pioneer plants in the restoration of barren waste residue yards to improve the substrate nutrient conditions. The contents of C, N and P in the waste slag were lower than those in organs and litter of the plant. The contents of C, N and P in the surface waste slag of different plants were significantly different(P <0.05). The contents of C, N and P in the residue under herbaceous restoration were lower than those under the three trees. Correlation analysis between N, P and N:P between waste residue and plant-litter showed that the N and P contents in fine roots and litter of plants were more closely related to the N and P contents and stoichiometric ratio in the waste residue.