黄河三角洲高潮滩芦苇植被区天津厚蟹的食源食性

通过稳定同位素方法,研究植物在大型底栖动物的食源占比,可以为滨海湿地下行效应提供直接证据。本文研究了黄河三角洲高潮滩芦苇区天津厚蟹的食性和食源。结果表明: 该植被区蟹类密度为(5.5±1.5) ind·m^-2,存在夜间攀爬芦苇取食的行为。在室内试验条件下,天津厚蟹具有明显的食物偏好,偏好取食芦苇新鲜叶片。通过稳定同位素食源分析发现,在野外自然环境下,芦苇叶片是天津厚蟹的重要食源之一。鲜叶[5月:(6.4±4.9)%;7月:(5.8±4.9)%;9月:(12.5±8.8)%]和枯叶[5月:(12.4±7.8)%;7月:(15.5±9.9)%;9月:(15.1±9.4)%]的食源占比均具有时间异质性。天津厚蟹不仅可能通过取食抑制芦苇生长,还可能通过取食的扰动行为影响该植被区的枯落物分解。     

黄河三角洲河滩与潮滩芦苇对盐胁迫的生理生态响应

研究黄河三角洲两种生境芦苇对盐胁迫的生理生态响应差异,能为退化滨海湿地生态修复中芦苇植株来源的选择提供重要的理论支持。在盐胁迫(300 mmol/L NaCl)下,比较研究了黄河三角洲河滩芦苇(低盐生境)和潮滩芦苇(高盐生境)叶片中的Na~+含量、根部分生区Na~+流速、叶片的光合作用参数、H_2O_2的含量、抗氧化酶的活性、丙二醛和脯氨酸的含量。结果表明:盐胁迫显著提高了河滩芦苇叶片中Na~+含量,但对潮滩芦苇叶片Na~+影响不显著。进一步通过非损伤微测技术研究发现,盐胁迫后,潮滩芦苇比河滩芦苇的根部分生区的Na~+外排流速更高(潮滩芦苇:(1982.05±122.74) pmol cm~(-2) s~(-1)vs.(87.93±12.94) pmol cm~(-2) s~(-1),P0.01;河滩芦苇:(1574.16±458.90) pmol cm~(-2) s~(-1)vs.(-126.88±23.01) pmol cm~(-2) s~(-1),P0.01),能有效调节细胞内离子平衡。另外,盐处理7天后潮滩芦苇光合速率((16.36±1.09)μmol m~(-2) s~(-1)vs.(22.79±0.67)μmol m~(-2) s~(-1),P0.01)显著高于河滩芦苇((12.71±0.97)μmol m~(-2) s~(-1)vs.(23.81±0.55)μmol m~(-2) s~(-1),P0.01)。盐胁迫诱导了两种芦苇叶片中H_2O_2含量和丙二醛含量的显著升高,而脯氨酸及抗氧化酶的活性也随之显著升高,并且也显著升高了潮滩芦苇的谷胱甘肽还原酶(GR)活性((6.90±1.73) U/mg蛋白质vs.(3.54±0.54) U/mg蛋白质,P0.05)。综上,潮滩芦苇比河滩芦苇更适应盐胁迫,因其根系具有更高的排Na能力,且脯氨酸含量及抗氧化酶活性较高,提高了抗逆性。因此,在黄河三角洲退化滨海湿地生态修复中,可以优先选择潮滩芦苇作为植被修复的材料。     

潮汐作用下干湿交替对黄河三角洲盐沼湿地净生态系统CO2交换的影响

潮汐作用作为盐沼湿地独特的水文特征能在短时间内强烈影响盐沼湿地的碳平衡.利用涡度相关和微气象监测技术,对黄河三角洲盐沼湿地净生态系统CO₂交换(NEE)和环境因子进行监测,并同步监测潮汐变化,探究潮汐过程及潮汐作用下干湿交替对NEE的影响.结果表明: 潮汐过程促进了白天生态系统CO₂的吸收但未对夜晚CO₂的释放产生显著影响,潮汐淹水成为影响白天NEE的主要因子.干旱阶段和湿润阶段NEE的日平均动态均呈“U”型曲线,但干旱阶段NEE的变幅较小.干湿交替增强了白天生态系统CO₂的吸收,干旱阶段最大光合速率(A_max)、表观量子产量(α)和生态系统呼吸(R_eco)的均值均高于湿润阶段.此外,干湿交替减少了盐沼湿地夜晚NEE释放的同时增强了其温度敏感性.     

环境因子和生物因子对黄河三角洲滨海湿地土壤呼吸的影响

采用Li-8150多通道土壤呼吸自动测量系统对黄河三角洲滨海湿地土壤呼吸进行全年连续测定,同步测量了温度、土壤含水量、地上生物量以及叶面积指数等环境因子和生物因子.结果表明: 土壤呼吸日动态在全年尺度上多呈单峰型,但在受到土壤封冻和地表积水干扰时,土壤呼吸日动态呈多峰型.土壤呼吸具有明显的季节动态特征,总体呈单峰型,年平均土壤呼吸速率为0.85 μmol CO₂·m^-2·s^-1,生长季平均土壤呼吸速率为1.22 μmol CO₂·m^-2·s^-1.在全年尺度上,土壤温度是滨海湿地土壤呼吸的主要控制因子,可解释全年土壤呼吸87.5%的变化.在生长季尺度上,土壤含水量和叶面积指数对土壤呼吸的协同影响达到85%.     

降雨量改变对黄河三角洲滨海湿地土壤呼吸的影响

全球变化背景下,降雨模式变化造成土壤水分波动是引起土壤呼吸动态变化的重要驱动力。但滨海湿地如何响应降雨模式变化,进而引起生态系统蓝碳功能改变的机制尚不清楚。依托黄河三角洲滨海湿地增减雨野外控制试验平台,采用土壤碳通量观测系统(LI—8100)对湿地土壤呼吸速率进行监测,探究了2017年黄河三角洲滨海湿地土壤呼吸及环境、生物因子对减雨60%、减雨40%、对照60%、对照40%、增雨40%、增雨60%等变化的响应及机制。结果表明:1)随着降雨量增加,湿地土壤温度逐渐降低;同时增雨和减雨处理均显著提高了湿地土壤湿度(P0.05)。(2)降雨量变化显著影响湿地植被物种组成、地上和地下生物量分配以及植被根冠比(P0.05)。增雨40%和增雨60%均显著提高了湿地植物种类和植被根冠比,但同时显著降低了湿地植被地上生物量。此外,增雨40%和减雨60%处理均显著提高了湿地植被地下生物量。(3)降雨量变化对2017年湿地季节土壤呼吸无显著影响,但在湿地非淹水期,增雨60%和增雨40%均显著提高了湿地土壤呼吸速率(P0.05)。(4)2017年湿地不同降雨处理的土壤呼吸与土壤湿度均呈二次曲线关系(P0.05),相关系数随降雨量增加而降低;同时在非淹水期不同降雨处理的土壤呼吸与土壤温度均指数相关(P0.05),土壤呼吸温度敏感性(Q_(10))随降雨量增加而增大。在淹水期不同降雨处理土壤呼吸与土壤温度无显著相关关系。(5)淹水期土壤呼吸速率与地表水位呈指数负相关(P0.001)。     

模拟降雨量变化对黄河三角洲湿地植物群落特征的影响

气候变化背景下,降雨变化能够深刻影响河口湿地土壤水盐条件,而土壤水盐条件是影响植物群落特征的关键环境因子。本研究以黄河三角洲湿地植物群落为对象,依托野外降雨控制试验平台(减雨60%、减雨40%、自然对照、增雨40%、增雨60%),探讨了经过6年降雨处理后湿地植物群落特征对降雨量变化的响应及机制。结果表明: 随降雨量增加,土壤电导率显著降低,土壤湿度显著增大。降雨量变化影响了植物群落物种组成,增雨处理降低了碱蓬和盐地碱蓬的优势地位,提高了荻和白茅的优势地位。随降雨量增加,植物群落Shannon指数和Margalef丰富度指数显著提高。与对照相比,增减雨处理均降低了群落频度、多度和盖度,增雨60%处理群落频度显著降低54.9%,减雨60%、减雨40%、增雨40%、增雨60%处理群落多度分别显著降低38.9%、33.8%、35.8%和45.7%。随降雨量增加,植物群落地上生物量显著增加,但可能受淹水胁迫的影响,增雨60%处理地上生物量显著低于增雨40%。Margalef丰富度指数与地上生物量呈显著正相关;地上生物量、Shannon指数、Margalef丰富度指数、Simpson多样性指数均与土壤电导率呈显著负相关;地上生物量与土壤湿度呈显著正相关。降雨量变化通过改变黄河三角洲湿地土壤水盐条件显著影响了植物群落生长特征、物种组成和多样性。     

Effects of elevated temperature on soil respiration in a coastal wetland during the non- growing season in the Yellow River Delta,China

Aims Winter soil respiration plays a crucial role in terrestrial carbon cycle, which could lose carbon gained in the growing season. With global warming, the average near-surface air temperatures will rise by 0.3 to 4.8 °C. Winter is expected to be warmer obviously than other seasons. Thus, the elevated temperature can significantly affect soil respiration. The coastal wetland has shallow underground water level and is affected by the fresh water and salt water. Elevated temperature can cause the increase of soil salinity, and as a result high salinity can limit soil respiration. Our objectives were to determine the diurnal and seasonal dynamics of soil respiration in a coastal wetland during the non-growing season, and to explore the responses of soil respiration to environmental factors, especially soil temperature and salinity.
Methods A manipulative warming experiment was conducted in a costal wetland in the Yellow River Delta using the infrared heaters. A complete random block design with two treatments, including control and warming, and each treatment was replicated each treatment four times. Soil respiration was measured twice a month during the non-growing season by a LI-8100 soil CO₂ efflux system. The measurements were taken every 2 h for 24 h at clear days. During each soil respiration measurement, soil environmental parameters were determined simultaneously, including soil temperature, moisture and salinity.
Important findings The diurnal variation of soil respiration in the warming plots was closely coupled with that in the control plots, and both exhibited single-peak curves. The daily soil respiration in the warming was higher than that in the control from November 2014 to January 2015. Contrarily, from March to April 2015. During the non-growing seasons, there were no significant differences in the daily mean soil respiration between the two treatments. However, soil temperature and soil salt content in the warming plots were significantly higher than those in the control plots. The non-growing season was divided into the no salt restriction period (November 2014 to middle February 2015) and salt restriction period (middle February 2015 to April 2015). During non-growing season, soil respiration in the warming had no significant difference compared with that in control. During the no salt restriction period, soil respiration in the warming was 22.9% (p < 0.01) greater than the control when soil temperature at 10 cm depth in warming was elevated by 4.0 °C compared with that in control. However, experimental warming decreased temperature sensitivity of soil respiration (Q₁₀). During salt restriction period, soil warming decreased soil respiration by 20.7% compared with the control although with higher temperature (3.3 °C), which may be attributed to the increased soil salt content (Soil electric conductivity increased from 4.4 ds·m^-1 to 5.3 ds·m^-1). The high water content can limit soil respiration in some extent. In addition, the Q₁₀ value in the warming had no significant difference compared with that in control during this period. Therefore, soil warming can not only increase soil respiration by elevating soil temperature, but also decrease soil respiration by increasing soil salt content due to evaporation, which consequently regulating the soil carbon balance of coastal wetlands.     

潮汐作用下干湿交替对黄河三角洲盐沼湿地净生态系统CO2交换的影响

潮汐作用作为盐沼湿地独特的水文特征能在短时间内强烈影响盐沼湿地的碳平衡.利用涡度相关和微气象监测技术,对黄河三角洲盐沼湿地净生态系统CO₂交换(NEE)和环境因子进行监测,并同步监测潮汐变化,探究潮汐过程及潮汐作用下干湿交替对NEE的影响.结果表明: 潮汐过程促进了白天生态系统CO₂的吸收但未对夜晚CO₂的释放产生显著影响,潮汐淹水成为影响白天NEE的主要因子.干旱阶段和湿润阶段NEE的日平均动态均呈“U”型曲线,但干旱阶段NEE的变幅较小.干湿交替增强了白天生态系统CO₂的吸收,干旱阶段最大光合速率(A_max)、表观量子产量(α)和生态系统呼吸(R_eco)的均值均高于湿润阶段.此外,干湿交替减少了盐沼湿地夜晚NEE释放的同时增强了其温度敏感性.     

黄河三角洲刺槐人工林风害成因

在调查2010年6-7月大风对黄河三角洲地区人工刺槐林的影响基础上,测定了风倒木形态指标、根系特征及其所处林窗的大小和土壤紧实度,分析滨海盐碱地人工刺槐林风倒的成因.结果表明:风倒是刺槐林遭受风害的主要形式,以胸径15 ～20 cm的树木受害最严重.随着径级的增加,风倒木的树高、冠幅、冠高和尖削度显著增加,而枝下高、冠幅/冠高和枝下高/树高变化不显著;根系长度先迅速增加而后增加缓慢,根系质量逐渐增加.随林窗面积增加,倒木株数先增加后下降,100 ～ 150 m2林窗倒木株数最多.土壤紧实度随土壤深度增加而增加,而随样木径级增加变化不显著.随径级增加,树形因子增大、根系生长受抑是刺槐风倒的重要原因,而林窗起到了促进作用.