Floodplain ecosystems play a significant role in the global carbon (C) cycle, particularly due to their C sink potential in hardwood floodplain forests. However, in these forests, interactions between a heterogeneous micro-relief and anthropogenic landscape changes make estimating C loss through soil CO₂ efflux difficult. To determine the drivers of soil CO₂ efflux, we selected six hardwood floodplain forests at the lower middle Elbe River, which were distributed among different relief positions (low-lying or high-elevated) in the active and former flooding zone. We measured soil CO₂ effluxes over a full year using the closed-chamber method. Based on the response of soil CO₂ efflux to soil moisture and temperature, annual efflux rates were determined, which were then related to soil properties, such as pH, texture, soil organic carbon (SOC) and nitrogen (N) content. Soil CO₂ efflux ranged between 1006 (±99) and 2214 (±118) gC m⁻² year⁻¹. Maximum efflux occurred in a former floodplain forest that was disconnected from Elbe River water table fluctuations. SOC-specific soil CO₂ efflux (gC gSOC⁻¹ year⁻¹) was smallest in low-lying forests of the active flooding zone and reflected by the appearance of redoximorphic mottling close to the soil surface. Fine texture (<6.3 μm), SOC and N were related positively and electric conductivity, C/N and pH negatively to total soil CO₂ efflux. Soil pH and fine texture were the strongest univariate predictors for total soil CO₂ efflux (both R² = 0.59). Fine texture, pH and C/N ratio explained 66% of the variance in total soil CO₂ efflux according to multiple linear regression. We conclude that, in hardwood floodplain forests, soil CO₂ efflux is mainly controlled by fine texture and soil pH. Fine texture can be related to soil moisture and nutrient availability and may have a positive effect on the activity of microorganisms.

中文翻译：

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土壤质地和 pH 值影响易北河中下游硬木漫滩森林土壤 CO2 外排

漫滩生态系统在全球碳 (C) 循环中发挥着重要作用，特别是由于其在硬木漫滩森林中的碳汇潜力。然而，在这些森林中，异质微地形与人为景观变化之间的相互作用使得估计通过土壤 CO ₂外排造成的碳损失变得困难。为了确定土壤 CO ₂外排的驱动因素，我们选择了易北河中下游的六片硬木洪泛区森林，它们分布在活动和前洪水区的不同地形位置（低洼或高海拔）。我们使用密闭室方法测量了一整年的土壤 CO _{2排放量。}基于土壤CO _2的响应流出到土壤水分和温度，确定年流出率，然后将其与土壤特性相关，例如 pH 值、质地、土壤有机碳 (SOC) 和氮 (N) 含量。土壤 CO ₂流出量介于 1006 (±99) 和 2214 (±118) gC m ^-2 年^-1之间。最大流量发生在与易北河地下水位波动断开的前洪泛区森林中。SOC 特定土壤 CO ₂流出量 (gC gSOC ^-1 年^-1) 在活动洪水区的低洼森林中最小，并反映在靠近土壤表面的氧化还原斑点的出现上。_{精细结构（<6.3 μm）、SOC 和N 与土壤CO 2}总排放量呈正相关，而电导率、C/N 和pH 呈负相关。_{土壤 pH 值和精细质地是土壤 CO 2}总排放量的最强单变量预测因子（R ²  = 0.59）。根据多元线性回归，精细质地、pH 和 C/N 比解释了土壤 CO ₂总排放量中 66% 的变化。我们的结论是，在硬木漫滩森林中，土壤 CO ₂外排主要受细密质地和土壤 pH 值的控制。细腻的质地可能与土壤水分和养分有效性有关，可能对微生物的活动产生积极影响。