洪湖湿地生态系统土壤有机碳及养分含量特征

洪湖湿地是长江中游地区重要湿地生态区域,在维持区域生态安全中发挥着重要作用.通过对洪湖湿地5种类型土壤进行有机碳及养分含量进行研究,为湿地生态系统地球化学循环及碳储量估算提供重要基础.结果表明,(1)洪湖土壤有机碳含量随土壤容重增加递减.(2)洪湖湿地土壤有机碳平均含量为:湖中淤泥＞洪泛平原湿地＞草本沼泽＞林地＞农田,其中湖底淤泥的有机碳平均含量6.74％,农田的有机碳平均含量为1.241％.此外,有机碳含量随土层的加深而减少.(3)湖底淤泥N的平均含量(4.623±0.535) g/kg、Ca的平均含量(26.262±4.201) g/kg,与洪泛平原湿地、草本沼泽及林地有显著性差异.农田P的平均含量(2.876±1.253) g/kg-、K的平均含量(7.205±0.159) g/kg,与湖底淤泥、洪泛平原湿地、草本沼泽及林地有显著性差异.(4)湖底淤泥中Cu的平均含量(40.19±3.04) mg/kg,Fe的平均含量(8560.90±80.98) mg/kg,Co的平均含量((29.66±0.67) mg/kg),Cu、Fe和Co的平均含量都显著小于洪泛平原湿地、农田及林地,Pb的平均含量(35.13±2.40) mg/kg,Mn的平均含量(749.65±54.07) mg/kg,这两个元素的含量均与农田及林地有显著性的差异.湖底淤泥中重金属元素的平均含量小于其余4种湿地类型土壤.

Characteristics of organic carbon and nutrient content in five soil types in Honghu wetland ecosystems

Honghu Wetland, located on the northern bank of middle Yangtze River, provides significant valuable ecosystem services including flood control, storm protection, water purification, biodiversity conservation, shoreline stabilization, tourism development and maintaining wetland products in the Yangtze River region. Particularly, the wetland ecosystems play an important functional role in climate change mitigation and adaptation through their ability to sink carbon and regulate water. For better understanding of characteristics of carbon sequestration capacity and nutrient biogeochemical cycle in Honghu wetland ecosystems, organic carbon content and nutrient concentrations were determined from five soil types (a lake bottom silt (LBS), a floodplain wetland soil (FWS), a herbaceous swamp soil (HSS), a farmland soil (FLS), and a forested soil FDS)) in this wetland. The results showed that soil organic carbon concentration decreased with increasing soil bulk density in the five soil types. Soil organic carbon content ranged from 1.24% to 6.74% in the five soil types with the highest in LBS and the lowest in FLS, and was in the order LBS > FWS > HSS > FDS > FLS. The soil organic carbon content declined with the increase of the soil depth in the study region. The concentration of N and Ca was (4.623±0.535) g/kg (mean±s.e.) and (26.262±4.201) g/kg in LBS, which was significantly higher than that in other four studied soils (P < 0.05), except N concentration in FLS which did not significantly differ in LBS. The concentration of P was 0.533±0.026, 0.585±0.021, 0.651±0.016, 2.876±1.253, and (0.519±0.011) g/kg in LBS, FWS, HSS, FLS, and FDS, respectively. On average, P content was about 6 times higher in FLD than in other four soil types in the study sites. FLS had the highest concentration of nutrient K (7.205±0.159)g/kg, which was statistically significant higher than that in LBS (3.783±0.160)g/kg, FWS (4.815±0.662)g/kg, HSS (4.639±0.588)g/kg, and FDS (3.426±0.835)g/kg, respectively. All five wetland soils had the similar concentration of Mg (from (2.51 to 2.55))g/kg and no significant difference was found for Mg in the five soil types. For microelements, the concentrations of Cu, Fe and Co was 40.19±3.04, 8560.90±80.98, and 29.66±0.67 mg/kg in LBS, which were significantly lower than those in FWS, FLS, and FDS, but no significant difference was found for the three microelements in the study sites. No statistically significant difference was found for Zn and Cd in the five wetland soils (P > 0.05). The concentration of Pb was significant higher in LBS ((35.13±2.40) mg/kg) than in FLS and FDS, but the latters had significant higher concentration of Mn ((1049.47±71.07) mg/kg and (1117.91±192.52) mg/kg, respectively) than the former ((749.65±54.07) mg/kg). Our results suggest that plant types help to control organic carbon and other nutrient elements distributions in the wetland soils.