路南石林地区土壤呼吸及碳稳定同位素日动态特征

采用碱吸收法,于2002年4月13- 16日(晴)、8月21- 24日(晴)对路南石林地区次生草地及柏树林下的土壤呼吸进行了野外监测,同时收集其碳稳定同位素样品进行室内质谱仪分析。结果显示: 土壤呼吸速率日动态特征表现为夜间高于白天, 8月份土壤呼吸速率高于4月份; 4月份的草地系统土壤呼吸的碳稳定同位素日平均值偏轻,而柏树林系统土壤呼吸的碳稳定同位素日平均值则是8月份的偏轻;土壤呼吸与其碳稳定同位素值成负相关,草地系统的相关程度, 4月份的较8月份的高;柏树林系统的相关程度,则是8月份较4月份的高。这揭示了土壤呼吸及其碳稳定同位素交换对环境变化的敏感性,且不同的生物系统有不同的表现特征。      

Substrate influence and temporal changes on periphytic biomass accrual and metabolism in a tropical humic lagoon

We performed a field experiment in a tropical humic coastal lagoon to evaluate periphyton biomass accrual and metabolism on three different substrates (1) plastic ribbons, (2) green and (3) senescent leaves of the emergent macrophyte Typha domingensis) over 30 days. The contribution of autotrophic biomass decreased as total biomass increased over the time. Mean periphytic ash free dry weight ranged from 0.8 to 5.6 mg cm⁻², but periphyton chlorophyll a concentrations presented shorter amplitudes, which oscillated from 0.12 to 0.44 μg cm⁻² throughout the experiment. Periphyton metabolism was overall heterotrophic on all substrates, especially on senescent leaves. Our data show that substrate type influenced both biomass accrual and periphyton net productivity and respiration rates throughout periphyton development and highlighted the dominance of heterotrophic metabolism. The periphyton respiration may be subsidized by both water- and substrate-derived allochthonous energy pathways, shedding light on the role of periphytic assemblages to the carbon cycling, as a source of CO₂ to the system.     

科尔沁沙地土壤呼吸空间分布及其变化特征研究

利用LI-6400便携式光合作用测量系统和LI-6400-09土壤呼吸室,对不同地形和不同植被条件下土壤呼吸速率及其影响因子进行测定。结果表明：科尔沁沙地土壤呼吸速率日变化均表现出上午逐渐增大,下午逐渐减小、凌晨最小的趋势。沙地土壤呼吸变化具有明显的空间异质性,土壤呼吸由大到小变化依次为：背风坡（1.95±0.21 μmolCO2·m-2·s-1）>坡顶（1.05±0.14 μmolCO2·m-2·s-1）>迎风坡（0.74±0.08 μmolCO2·m-2·s-1）>丘间低地（0.62±0.09 μmolCO2·m-2·s-1）。沙地土壤呼吸与植物生长条件具有密切关系,狗尾草（0.86±0.11 μmolCO2·m-2·s-1）>小叶锦鸡儿（0.69±0.06 μmolCO2·m-2·s-1）。土壤呼吸日变化速率与空气温度呈正相关,与空气相对湿度呈负相关关系,并且与土壤温度呈指数相关。沙丘内部不同地形、植被的[WTBX]Q10[WTBZ]差异不大。     

干旱半干旱地区草地碳循环关键过程对降雨变化的响应

未来全球气候变化背景下,全球或局部地区的降雨量及降雨时间分布将发生一定的变化.草地生态系统在全球碳收支中作用显著,对气候变化的反馈起着重要的作用.但由于草地多处于干旱半干旱地区,受到水分条件的限制,对降雨变化响应敏感,其碳源汇功能表现出很大的不确定性.为了更好地预测未来全球气候变化背景下草地的碳源汇功能及其对气候变化的进一步反馈,有必要深入研究决定草地碳源汇功能的两大碳循环关键过程--净初级生产力和土壤呼吸对降雨变化的响应特征及机制.本文对国内外有关草地生产力和土壤呼吸如何对降雨量、降雨强度、降雨频率和间隔时间进行响应的相关研究成果进行了综述,在此基础上指出了目前研究存在的不足,并对未来相关的重点研究方向进行了探讨和展望.     

Overwintering of Vaccinium vitis-idaea in two sub-Arctic microhabitats: a reciprocal transplantation experiment

Northern plants have to cope with a wide range of overwintering conditions, as the depth and physical properties of snow show high spatial variation in the Arctic. The overwintering of lingonberry ( Vaccinium vitis-idaea ) was studied in a reciprocal transplantation experiment between two sub-Arctic microhabitats in northern Finland. The experiment was set up in the autumn, and physiological traits related to overwintering were measured at the time of snowmelt in the following spring. The origin of the plants was not a significant source of variation for most of the traits measured, whereas major differences were observed between the two sites. Plants that overwintered at an exposed site above the treeline showed high relative winter damage, assessed by the electrolyte leakage of the leaves. No severe winter damage was observed in the plants that overwintered under a moderate snowpack at a sheltered birch forest site. These plants were able to maintain their photosynthetic capacity through the winter. A low capacity of photosystem II and a very low capacity of CO₂ uptake were characteristic of the exposed site, where low temperatures and high irradiation predominate during late winter. However, photosynthetic capacity was recovered within a few days when the plants were kept under favourable conditions after the field experiment. The content of nonstructural carbohydrates was low, probably because of high respiratory losses under the snow. This short-term study suggests that lingonberry, which occupies a wide range of microhabitats in the present climate, may thrive even if the overwintering conditions change as a result of climatic warming.     

Variations in atmospheric CO2 at the Meteorological Research Institute, Tsukuba, Japan

Since April 1986, measurements of the CO₂ concentration in the surface air have been conducted at the Meteorological Research Institure (MRI, 36°04 N, 140°07 E, 25 m above sea level) in Tsukuba, located 50 km northeast of Tokyo, Japan. The CO₂ data measured over times between 11:00 Japan Standard Time (JST) and 16:00 JST (C _N ) were considered to be representative of the air (within a few ppmv) in the planetary boundary layer. To evaluate the representative CO₂ level on a spatial scale larger than that of the C _N record, the CO₂ data with hour-to-hour variation less than 1 ppmv were selected (C _P ). Comparison of these data with those of Ryori (39°02 N, 141°50 E), a continental station operated by the Japan Meteorological Agency, indicates that the C _P record provides a representative CO₂ level in the air on spatial scales of at least a few hundred kilometers.The C _N record allows an investigation of the internanual changes in photosynthesis/respiration against changes in climatological parameters. Within a small temperature anomaly (ca.±1 °C) respiration is sensitive to the temperature change, while photosynthesis is less sensitive. When the temperature anomaly is large, however, photosynthesis and respiration tend to be competitive.     

青藏高原冻土土壤呼吸温度敏感性和不同活性有机碳组分研究

对采自青藏高原的4个高海拔冻土样品在5、15、25和35℃4个温度下进行了为期90d的实验室培养。结果发现,随着温度升高,土壤呼吸强度和有机碳累积分解量呈现出不断增大的趋势;在时间变化上,培养初期土壤呼吸强度达到最高值随后不断下降,15d左右以后达到稳定。同样的温度下,土壤呼吸强度呈现如下顺序：沱沱河（草甸沼泽土）〉乌...     

中国陆地生态系统近 2 0年碳空间动态的初步研究(英文)

陆地生态系统的净生产力 (NEP)是生态系统净初级生产力 (NPP)和异氧呼吸 (Rh)之差。在全球尺度上 ,反映NPP和Rh之差的NEP直接揭示陆地生态系统与大气系统之间的二氧化碳交换 ,即碳平衡 ,因此 ,意义重大。文章简短回顾了关于中国陆地生态系统碳平衡的研究状况。由于植物根部呼吸很难从土壤表面总二氧化碳 (CO2 )通量中分开 ,因此直接从野外测量土壤异氧呼吸几乎是不可能的。虽然由于像诸如火灾、森林砍伐、土地利用变化及气候和大气变化等干扰因素 ,全球陆地生态系统很大程度上处于非平衡态 ,利用生态系统在平衡态时NPP等于Rh这一事实 ,我们估算了全球和中国森林生态系统的土壤异氧呼吸。利用遥感和地面的NPP观测数据 ,我们也估算了中国森林生态系统逐月的净生产力 (1982— 1998)。NPP的估算主要采用NOAA卫星AVHRR 8km的NDVI数据 ,结合地面气候数据完成。土壤呼吸是通过地面观测数据与温度和降水的关系得到的。在此基础上我们得到了中国陆地生态系统在过去近 2 0年中碳的动态变化 ,并给出了初步结果。     

土地利用变化对中国土壤碳储量变化的间接影响

中国土壤有机碳储量及其在全球变暖背景下的变化趋势是影响全球碳循环的一个重要因素。土地利用变化对土壤有机碳储量既有直接影响,也有间接影响。一方面,土地利用变化直接改变了生态系统的类型,从而改变了生态系统的净初级生产力（NPP）及相应的土壤有机碳的输入。另一方面,土地利用变化潜在地改变了土壤的理化属性,从而改变了土壤呼吸对温度变化的敏感性系数（常用Q10表示）。在全球变暖背景下,Q10值的改变显著影响着土壤有机碳释放的强度。利用生态系统碳循环过程模型（CASA模型）反演了不同土地利用类型下的Q10值,并评价了土地利用类型的改变对土壤有机碳储量变化的间接影响。研究结果表明,林地与草地转换成耕地后将增大土壤呼吸的Q10值,此外,人类通过灌溉、氮肥的施用也能增大土壤呼吸的Q10值,从而使得全球变暖背景下土壤呼吸的碳通量有所增强。     

Seasonal drought effects on carbon sequestration of a mid-subtropical planted forest of southeastern China

Continuous measurement of carbon dioxide exchange using the eddy covariance (EC) technique is made at the Qianyanzhou mid-subtropical planted forest as part of the ChinaFLUX network. Qianyanzhou planted forest is affected by typical subtropical continental monsoon climate. It has plentiful water and heat resource but is in inconsistency of its seasonal distribution in the mid-subtropical region, thus seasonal drought frequently occurs in this planted forest. In this study, seasonal drought effect on ecosystem carbon sequestration was analyzed based on net ecosystem productivity (NEP), ecosystem respiration (RE) and gross ecosystem productivity (GEP) at the month scale in 2003 and 2004. In this drought-stressed planted forest, ecosystem carbon sequestration showed a clear seasonality, with low rates during seasonal drought and in winter. The declining degree of ecosystem carbon sequestration under the seasonal drought condition was determined by the accumulation of soil moisture deficits and a co-occurrence of high temperatures. Different drought effects are expected for RE and GEP. The net effect of ecosystem carbon balance depends on how these two quantities are affected relatively to each other. Summer drought and heat wave are two aspects of weather that likely play an important part in the annual NEP of forest in this region.