铜尾矿生物结皮的生物固氮及其影响因素研究

在铜尾矿生态系统自然恢复过程中,生物结皮广泛存在并成为尾矿生态系统演替早期的重要阶段。本文采用乙炔原位还原法对藻类结皮、藻藓混合结皮和藓类结皮的生物固氮特征进行了系统研究。结果表明:(1)生物结皮显著提高了铜尾矿总氮含量,同时降低了铜的含量。(2)不同类型生物结皮的固氮能力差别较大,其中藻藓混合结皮的生物固氮量最高,在N 4.36～30.39 kg hm2 a–1之间;藻类结皮和藓类结皮的固氮量分别为N 1.32～8.78、0～16.34 kg hm2 a–1。(3)生物固氮能力随季节变化明显,夏季的生物固氮量最高,春季次之,秋冬季节相对较低。(4)铜尾矿基质pH、NH4+-N和水溶性有机碳(WSOC)等与生物固氮量呈显著正相关(p<0.05),而土壤容重、NO3--N和总铜等与生物固氮量呈显著负相关(p<0.05)。

Nitrogen fixation of biological soil crusts on copper mining tailings and its influence factors

The dumping site for copper mining tailings at Yangshanchong at Tongling city (Anhui Province) has been deserted for 20-years. The area is characterized by extremely high concentrations of heavy metals, poverty of nutrients, easy acidification and severe desertification. Biological soil crusts (BSCs), extensively existing on tailings is a major early stage of the ecological succession of the tailing ecosystem. The method of in situ acetylene reduction was applied to explore characteristics of biological nitrogen-fixation of algae, algae-moss and moss crusts on tailings. It was found that biological crusts significantly increased total nitrogen and lower Cu content in the tailings, and the nitrogen-fixing capability of the crusts varied sharply from type to type. Among the three types, the algae-moss type of crust was the highest in N₂ fixation rates, ranging between 1.32~8.78 kg hm^-2 a^-1, and followed by the algae type and the moss type, ranging between 4.36~30.39 kg hm^-2 a^-1 and between 0~16.34 kg hm^-2 a^-1, respectively, and followed a decreasing order of algae-moss, moss, and algae BSCs. N₂ fixation capacity of the BSCs varied with the season, too showing a decrease order of summer, spring, fall and winter. Besides, a negative line relationship was observed of the capacity with soil bulk density, NO₃^--N, and total Cu concentration and a positive one with pH, NH₄⁺-N, and water soluble organic carbon. On the whole, BSCs significantly enhanced total nitrogen content, and decrease total Cu concentration in tailings. The anomalous wet conditions experienced during the year of the study may have increased the temporal availability of soil mineral N and decreased N fixation rates. However, the presence of N fixation activity in all crusts analyzed their ability to survive at high Cu concentration, which may contribute to ecosystem resilience and recovery in areas under severe heavy metal stress.