2008年5—11月,对黄河口滨岸潮滩不同表现型碱蓬(Suaeda salsa)(中潮滩碱蓬,MMS,S.salsa in middle marsh;低潮滩碱蓬,LMS,S.salsa in low marsh)湿地植物-土壤系统V和Co含量的季节动态及其生物累积特征进行了研究。结果表明:MMS和LMS湿地表层土壤中V或Co含量的季节变化差异明显,但同一种湿地土壤中V和Co含量的变化模式相似。MMS(或LMS)湿地土壤的V含量均明显高于Co含量,二者在生长季的变异系数分别为12.01%、12.35%(MMS)和4.08%、4.94%(LMS)。MMS和LMS湿地表层土壤V的地累积指数(I_(geo))大多介于1—2,处于轻度污染状况;Co的I_(geo)大多介于0—1之间,处于无污染到轻度污染状态。V和Co含量在MMS不同部分中整体表现为枯落物>根>叶>茎(P<0.05),而在LMS中表现为枯落物>叶>茎>根(P<0.001)。MMS和LMS不同器官的V或Co转移能力存在较大差异,前者V和Co的R/S(根茎比)、R/L(根叶比)和S/L(茎叶比)大多大于1,后者中两种元素的相应比值则大多小于1。MMS和LMS不同部分的V和Co累积系数(AF)整体均表现为AFV
Episodic deposition has been recognized as a major factor affecting the decomposition rate of detrital material in salt marshes. In this paper, three one-off burial treatments, no burial treatment(0 cm, NBT), current burial treatment(10 cm, CBT) and strong burial treatment(20 cm, SBT), were designed in intertidal zone of the Yellow River Estuary to determine the potential influences of episodic deposition on nutrient(C, N) and heavy metal(Pb, Cr, Cu, Zn, Ni, Mn, Cd, V and Co) variations in decomposing litters of Suaeda glauca. Results showed that although various burial treatments showed no statistical difference in decomposition rate of S. glauca, the values generally followed the sequence of CBT(0.002 403/d) > SBT(0.002 195/d) > NBT(0.002 060/d). The nutrients and heavy metals in decomposing litters of the three burial treatments exhibited different variations except for N, Cu, Cr, Ni and Co. Except for Mn, no significant differences in C, N, Pb, Cr, Cu, Zn, Ni, V and Co concentrations occurred among the three treatments(P > 0.05). With increasing burial depth, Cr and Cd levels generally increased while Cu, Ni and Mn concentrations decreased. Although episodic deposition was generally favorable for C and N release from S. glauca, its influence on release was insignificant. In the three burial treatments, Pb, Cr, Zn, Ni, Mn, V and Co stocks in S. glauca generally evidenced the export of metals from litter to environment, and, with increasing burial depth, the export amounts increased greatly. The S. glauca were particular efficient in binding Cd and releasing Pb, Cr, Zn, Ni, Mn, V and Co, and, with increasing burial depth, stocks of Cu in decomposing litters generally shifted from release to accumulation. The experiment indicated that the potential eco-toxic risk of Pb, Cr, Zn, Ni, Mn, V and Co exposure would be serious as the strong burial episodes occurred in S. glauca marsh.
氮矿化是湿地生态系统养分循环的重要组成部分,氮输入及温度变化对土壤氮矿化的影响具有复杂性。为了探究湿地土壤氮矿化特征对温度及氮输入的响应,选择黄河入海口北部滨岸高潮滩的碱蓬湿地为研究对象,基于野外原位氮负荷增强模拟试验(N0:0 g N m^(-2) a^(-1);N1:9.0 g N m^(-2) a^(-1);N2:12.0 g N m^(-2) a^(-1);N3:18.0 g N m^(-2) a^(-1)),于生长季末获取不同氮处理下的土壤(S-N0、S-N1、S-N2和S-N3)开展室内培养实验。结果表明,不同氮处理土壤的氮累积矿化量均呈现出培养初期(0—14 d)增加迅速,培养中期(14—42 d)骤然降低,而培养后期(42—84 d)趋于稳定的变化特征,其值整体表现为S-N3>S-N0>S-N2>S-N1(P>0.05)。培养后期,不同氮处理土壤的累积矿化量在20℃和25℃下的差异均达到极显著或显著水平(P<0.01或P<0.05),且S-N2在此间的矿化能力最强。氮输入整体降低了土壤氮矿化对温度的敏感性(Q_(10)),其中S-N2土壤的温度敏感性最低,更利于持续供氮。不同氮处理土壤的氮矿化速率和累积矿化量与培养温度、土壤基质质量密切相关,且在一定范围内较高的温度和较低的C/N有利于氮矿化的进行。研究发现,未来黄河口氮负荷增强以及温度持续上升背景下,碱蓬湿地土壤氮养分及温度条件改变将会影响其供氮能力,适量氮输入(N2)将有利于土壤保持持续稳定的供氮能力。
