石羊河下游白刺灌丛演替发育过程的土壤呼吸及其影响因素分析

对不同类型土壤呼吸及其影响因素的研究有助于了解区域生态过程和全球气候变化。在石羊河下游,根据白刺灌丛生长及其生境状况,选择了初期发育、稳定、衰退、严重衰退的白刺灌丛植被,采用Li-8100土壤碳通量监测系统,研究了白刺灌丛演替过程的土壤呼吸日变化。结果表明,各发育阶段的白刺灌丛土壤呼吸最大值均出现在12:00,呼吸速率均值大小顺序为:稳定阶段＞初期发育阶段＞衰退阶段＞严重衰退阶段。各发育阶段不同坡位土壤呼吸日变化动态存在差异,但平均值都表现为迎风坡＞背风坡＞丘间地。建立各因素与土壤呼吸之间的模型发现,白刺的生长状况与土壤呼吸之间的相关性达到极显著,表层土壤含水量对土壤呼吸的影响大于深层土壤,而二次函数较其他模型能更好地表达地下10 cm温度与土壤呼吸之间的关系,且两者之间相关性达到极显著。     

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.     

Spatial-temporal variation in soil respiration and its controlling factors in three steppes of Stipa L. in Inner Mongolia, China

Grassland is the largest terrestrial ecosystem in China. It is of great significance to measure accurately the soil respiration of different grassland types for the contribution evaluation of the Chinese terrestrial ecosystem’s carbon emission to the atmospheric CO2 concentration. A three-year (2005-2007) field experiment was carried out on three steppes of Stipa L. in the Xilin River Basin, Inner Mongolia, China, using a static opaque chamber technique. The seasonal and interannual variations of soil respiration rates were analyzed, and the annual total soil respiration of the three steppes was estimated. The numerical models between soil respiration and water-heat factors were established respectively. Similar seasonal dynamic and high annual and interannual variations of soil respiration were found in all of the three steppes. In the growing season, the fluctuation of soil respiration was particularly evident. The coefficients of variation (CVs) for soil respiration in different growing seasons ranged from 54% to 93%, and the annual CVs were all above 115%. The interannual CV of soil respiration progressively decreased in the order of Stipa grandis (S. grandis) steppe Stipa baicalensis (S. baicalensis) steppe Stipa krylovii (S. krylovii) steppe. The annual total soil respiration for the S. baicalensis steppe was 223.62?299.24 gC m-2 a-1, 150.62-226.99 gC m-2 a-1 for the S. grandis steppe, and 111.31–131.55 gC m-2 a-1 for the S. krylovii steppe, which were consistent with the precipitation gradient. The variation in the best fitting temperature factor explained the 63.5%, 73.0%, and 73.2% change in soil respiration in the three steppes at an annual time scale, and the corresponding Q10 values were 2.16, 2.98, and 2.40, respectively. Moreover, the Q10 values that were calculated by soil temperature at different depths all expressed a 10 cm 5 cm surface in the three sampling sites. In the growing season, the soil respiration rates were related mostly to the surface soil moisture, and the 95.2%, 97.4%, and 93.2% variations in soil respiration in the three steppes were explained by the change in soil moisture at a depth of 0-10 cm, respectively.     

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.     

江西大岗山杉木人工林生态系统土壤呼吸研究

以江西大岗山杉木人工林为研究对象,采用LI-6400便携式光合测定系统及土壤呼吸叶室6400-09,在2005年4—10月和2006年4—10月,连续测定了2个生长季的土壤CO2释放速率,并对土壤呼吸规律进行了分析研究。结果表明,土壤呼吸的日动态和季节动态都呈单峰型;土壤呼吸速率与地表空气温度和0～10 cm土壤温度的指数回归关系良好,但单独用土壤含水率的变化解释土壤呼吸速率变异是不合适的。选择0～10 cm土壤温度和0～10 cm土壤含水率解释土壤呼吸速率的变异,双因子模型比单因子模型好。根据土壤呼吸速率与0～10 cm土壤温度的指数模型,结合试验地2006年1—12月的气象资料,计算出大岗山杉木人工林土壤呼吸年释放碳量为9.80 t.hm-2。     

塔克拉玛干沙漠腹地流沙下垫面土壤呼吸特征及影响因素分析

通过LI-COR8100A土壤碳通量观测系统分别于2013年1月、5月、10月和11月进行了塔克拉玛干沙漠腹地塔中流沙下垫面土壤呼吸速率测定试验,并分析了相应的土壤水热因子对呼吸速率的影响。结果表明:塔克拉玛干沙漠腹地土壤呼吸速率整体偏低,但具有明显的昼夜波动性和季节变化特征。研究区流沙土壤中可能存在的无机碳过程是导致夜间及凌晨的土壤呼吸速率为负值,白天为正值的主要原因。不同时段的土壤呼吸速率(Rs)分别与土壤表层0~5 cm平均土壤温度(T)和湿度(W)间存在较为同步的昼夜变化趋势且具有良好的回归关系。相对于单因素影响的回归分析,土壤温、湿度的协同作用能够从整体角度更好地解释土壤呼吸速率的变化情况。回归方程Rs=a+bT+cW和Rs=a+bT+cW+dTW可解释不同时段土壤呼吸速率76.0%以上的变化情况。这说明土壤温、湿度是控制土壤呼吸速率的主要环境因子。沙漠腹地土壤极低的水分条件成为土壤呼吸的限制性因子,呼吸速率对于作为限制性因子的土壤湿度的变化响应则更加直接,而对于土壤温度变化的敏感性就有所下降,导致土壤呼吸速率与土壤温度回归关系出现明显的时滞环现象。     

南海北部及台湾海峡夏季自养与异养区域的分布

采用黑白瓶方法,在2012年夏季测定了台湾海峡及南海北部16个站位群落总的初级生产力(gross primary production,GPP)和群落呼吸(community respiration,CR),总的初级生产力GPP水柱积分平均值为106.6±7.51mmol O2 m–2·d–1(mean±SE,以下同),群落呼吸CR平均为131.1±5.95mmol O2 m–2·d–1,净群落生产力(net community production,NPP)变化范围为-179.0~377.6mmol O2 m–2·d–1(中值为-40.4mmol O2 m–2·d–1)。受上升流的影响,琼东海域呈现明显的自养状态。在珠江口,由于珠江冲淡水的流入,该区域也呈现自养状态。相反,台湾海峡近岸以及粤东近岸均为异养区域。由此可见,异养区域的群落呼吸并不是完全由本地初级生产力决定,有机碳在空间上的输送对海洋浮游生物群落新陈代谢的影响可能极为重要。     

Plankton carbon metabolism and air–water CO2 fluxes at a hypereutrophic tropical estuary

Multiple biotic and abiotic drivers regulate the balance between CO₂ assimilation and release in surface waters. In the present study, we compared in situ measurements of plankton carbon metabolism (primary production and respiration) to calculated air–water CO₂ fluxes (based on abiotic parameters) during 1 year (2008) in a hypereutrophic tropical estuary (Recife Harbor, NE Brazil – 08°03′S, 34°52′W) to test the hypothesis that high productivity leads to a net CO₂ flux from the atmosphere. The calculated CO₂ fluxes through the air–water interface (FCO₂) were negative throughout the year (FCO₂: –2 to –9 mmol C·m^?2·day^?1), indicating that Recife Harbor is an atmospheric CO₂ sink. Respiration rates of the plankton community ranged from 2 to 45 mmol C·m^?2·hr^?1. Gross primary production ranged from 0.2 to 281 mmol C·m^?2·hr^?1, exceeding respiration during most of the year (net autotrophy), except for the end of the wet season, when the water column was net heterotrophic. The present results highlight the importance of including eutrophic tropical shallow estuaries in global air–water CO₂ flux studies, in order to better understand their role as a sink of atmospheric CO₂.     

黑河中游不同土地覆被类型土壤呼吸及对水热因子的响应

以黑河中游6种典型土地覆被类型（百年灌溉农田、新垦灌溉农田、人工杨树林、人工樟子松林、人工梭梭灌木林和天然荒漠草地）为研究对象,对土壤呼吸及其对土壤含水量和土壤温度的响应进行测定。结果表明：灌溉农田的土壤呼吸速率显著大于人工樟子松林地和杨树林地,人工林地显著大于荒漠草地和梭梭灌木林地。6种土地覆被类型土壤呼吸速率与土壤温度显著正相关性,Q₁₀值1.14~1.31,表明该地区土壤呼吸速率对土壤温度的敏感性低于世界平均水平;土壤呼吸速率与土壤含水量呈显著的指数关系。这表明6种土地覆被类型的土壤呼吸特征存在显著差异,且不同土地覆被类型的土壤呼吸特征与水热因子关系密切,以人类活动为主导的土地覆被变化深刻影响着荒漠绿洲生态系统水土气生的相互作用。     

红海榄幼苗根系呼吸代谢对水淹胁迫的响应

本研究利用人工潮汐系统(每天淹水0、6、12和18h),研究了红海榄幼苗根系呼吸代谢对水淹胁迫的响应。结果表明,每天淹水6h对红海榄幼苗的生长影响不大,但随着水淹时间的延长,红海榄幼苗的生长显著受到抑制。水淹时间的延长同样明显抑制了红海榄幼苗根系的产能效率,且根系三羧酸循环的有氧呼吸速率、三磷酸腺苷含量以及琥珀酸脱氢酶和苹果酸脱氢酶活性最小值均出现在每天水淹18h处理组中。相反,水淹胁迫下红海榄幼苗根系乙醇脱氢酶、乳酸脱氢酶活性以及乙醇和乳酸含量都呈上升的趋势。综上,尽管无氧呼吸可一定程度上缓解三羧酸循环受阻所导致的产能匮乏,但是过度的水淹胁迫仍会扰乱红海榄幼苗正常的生长和代谢,导致三磷酸腺苷产能效率的降低以及无氧发酵代谢产物的积累。