The response of heterotrophic CO2 flux to soil warming

In a forest ecosystem at steady state, net carbon (C) assimilation by plants and C loss through soil and litter decomposition by heterotrophic organisms are balanced. However, a perturbation to the system, such as increased mean soil temperature, will lead to faster decay, enhancing CO₂ release from decomposers, and thus upsetting the balance. Recent in situ experiments have indicated that the stimulation of soil respiration following a step increase in annual average soil temperature declines over time. One possible explanation for this decline may be changes in substrate availability. This hypothesis is examined by using the ecosystem model G'DAY, which simulates C and nitrogen (N) dynamics in plants and soil. We applied the model to observations from a soil‐warming experiment in a Norway spruce (Picea abies (L.) Karst.) stand by simulating a step increase of soil temperature. The model provided a good qualitative reproduction of the observed reduction of heterotrophic respiration (R_h) under sustained warming. The simulations showed how the combined effects of faster turnover and reduced substrate availability lead to a transient increase of R_h. The simulated annual increase in R_h from soil was 60% in the first year after perturbation but decreased to 30% after a decade. One conclusion from the analysis of the simulations is that R_h can decrease even though the temperature response function for decomposition remains unchanged. G'DAY suggests that acclimation of R_h to soil warming is partly an effect of substrate depletion of labile C pools during the first decade of warming as a result of accelerated rates of mineralization. The response is attributed mainly to changing levels of C in pools with short time constants, reflecting the importance of high‐quality soil C fractions. Changes of the structure or physiology of the decomposer community were not invoked. Therefore, it becomes a question of definition whether the simulated dynamics of the declining response of CO₂ release to the warming should be named acclimation or seen as a natural part of the system dynamics.     

大气和土壤增温对杉木幼苗叶片功能性状的影响

为了探讨杉木幼苗叶片功能性状对全球气候变暖的响应与适应机制,在福建三明森林生态系统与全球变化研究站陈大观测点,设置大气增温(开顶箱被动增温,不增温)×土壤增温(电缆增温4℃,不增温)双因子试验,对杉木幼苗叶片生理代谢、形态属性、化学计量学特征等功能性状进行为期1年的研究。结果表明,虽然土壤增温和大气增温对4月和7月的叶片净光合作用速率和水分利用效率没有显著影响,但土壤增温对11月的叶片净光合作用速率有显著促进作用,而大气增温和土壤增温对11月的水分利用效率有显著促进作用。大气增温显著增加比叶面积和叶含水率,并降低叶厚度;而土壤增温则对其均没有显著影响。土壤增温、大气增温均显著增加杉木叶氮浓度,但只有同时大气增温和土壤增温处理才显著提高叶磷浓度。研究结论表明,从叶功能性状角度看,同时大气增温和土壤增温可能更有利于促进杉木幼苗生长。     

大气和土壤增温对杉木幼苗地上物候及生长的影响

为了探讨全球变暖对杉木幼苗地上物候和生长的影响,在福建三明森林生态系统与全球变化研究站陈大观测点开展大气温度控制(ambient, open-top chamber)和土壤温度控制(ambient, ambient+4℃)双因子试验,设置对照、单独大气增温、单独土壤增温、大气和土壤同时增温4种处理,大气增温采用开顶箱被动式增温,土壤增温采用电缆增温。建立48个单株水平的根箱,每个根箱内种植1棵1年生2代半短侧枝杉木幼苗,于2016年开始对杉木幼苗地上物候和生长动态进行为期1年的研究。结果表明:(1)大气温度控制对杉木幼苗物候和生长具有显著影响;与无大气增温相比,大气增温使杉木幼苗顶芽膨胀、顶芽展开和顶芽新稍生长时间显著提前,树高生长季长度显著延长,杉木幼苗树高生长得到显著促进。(2)土壤温度控制对杉木幼苗的物候和生长均没有显著影响。(3)大气温度控制和土壤温度控制的交互作用对杉木幼苗生长具有显著影响,大气和土壤同时增温处理的杉木幼苗树高和侧枝生长显著大于单独大气增温处理。表明全球气候变暖可能对杉木生产力具有一定的促进作用。     

凋落物和增温联合作用对峨眉冷杉幼苗抗氧化特征的影响

峨眉冷杉林是青藏高原东缘亚高山暗针叶林的重要组成部分,其自然更新对全球变化非常敏感,是研究气候变化对陆地生态系统影响的代表性森林类型.以峨眉冷杉幼苗为研究对象,以开顶式增温小室(Open top chambers,OTCs)和电热棒联合的方式增加环境温度,人为添加不同类型凋落物(A,75％峨眉冷杉针叶+25％杜鹃荚蒾灌木叶凋落物;B,55％峨眉冷杉针叶+45％杜鹃荚蒾灌木叶凋落物),共设置4个处理:(1)凋落物A+增温T(A-T);(2)凋落物B+增温T(B-T);(3)凋落物A+环境温度TO(A-T0);(4)凋落物B+环境温度TO(B-TO).研究增温和两种类型凋落物联合作用下峨眉冷杉幼苗的生理生态响应特征.得到以下结果:(1)在环境温度下,A型凋落物情景下的冷杉幼苗的电导率、丙二醛和脯氨酸含量、超氧阴离子自由基产生率比B型情景下高;而可溶性糖和淀粉含量、超氧化物歧化酶(SOD)、抗坏血酸过氧化物氢酶(APX)和过氧化氢酶(CAT)活性比B型凋落物情景下低.说明在当前环境温度下,B型凋落物比A型凋落物更加适合冷杉幼苗的生长.(2)在A型凋落物情景下,增温处理显著增加了冷杉幼苗叶片的自由脯氨酸含量和过氧化氢浓度;在B型凋落物情景下,增温处理显著降低了冷杉幼苗丙二醛、自由脯氨酸含量、可溶性糖和淀粉含量,增加了超氧阴离子自由基产生速率.可见,与A型凋落物相比,增温使得B型凋落物情景下的冷杉幼苗膜伤害程度减小.(3)不同类型凋落物与增温的联合作用均降低了冷杉幼苗的可溶性糖和淀粉含量.与A-T处理相比,B-T处理下冷杉幼苗叶片的电导率、丙二醛和脯氨酸含量更低,而POD、APX、GR、CAT抗氧化酶活性却更高.研究结果表明,针叶成分相对较少的B型凋落物更有利于峨眉冷杉幼苗适应未来气候变暖情景.     

三种增温情景对入侵植物空心莲子草形态可塑性的影响

虽然国内外已对克隆植物的表型可塑性开展了大量研究,但是气候变暖对克隆植物,尤其是入侵性克隆植物形态可塑性的影响及其可能的生态学意义研究仍然有限。通过设置白天增温、夜间增温和全天增温3种方式,通过切断或不切断匍匐茎处理,探讨入侵植物空心莲子草(Alternanthera philoxeroides)形态特征对不同气候变暖情景的响应。研究发现:夜间增温2℃条件下,切断匍匐茎连接显著降低空心莲子草匍匐茎总长度和平均分株长度;白天增温和全天增温2℃对匍匐茎切断和连接组的空心莲子草的匍匐茎总长和平均分株长影响不显著;3种增温方式对空心莲子草的分蘖数均无显著影响。这些结果表明:空心莲子草对增温具有较高的耐受性,并对不同增温方式采取不同的响应策略;夜间增温可能通过光合补偿效应增加其匍匐茎的长度和平均分株长从而促进其水平方向的扩展以占据更加有利的生境,增强其入侵能力;白天和全天增温对整个克隆片段匍匐茎形态几乎无影响。     

Resumption of metabolic activity of vitrified/warmed ovine embryos

To evaluate resumption of metabolic activity of vitrified ovine embryos during a short time immediately after warming, blastocysts collected from superovulated Sarda ewes were incubated with (35)S-methionine. In vitrified/warmed embryo groups the protein secretion significantly (P < 0.05) increased from 0 to 24 hr of culture, reaching significantly (P < 0.01) higher activity at 18-24 hr and dropping to values similar to the control nonvitrified embryo group at 29-35 hr. Within the control group at 29-35 hr there was a significantly (P < 0.01) higher level of protein secretion compared to the other interval times. The electrophoretic pattern showed a 48-50 kDa secreted protein identified as urokinase-type plasminogen activator (PA). The caseinolytic assay of PA activity showed a course similar to protein secretion in both vitrified and control groups. During 29-35 hr of culture, we did not observe any improvement in PA activity as seen for secreted proteins. At this time, we observed the secretion of a new 20 kDa protein that was not present in vitrified/warmed embryos. Analysis of BrDU incorporation in newly synthesised DNA showed a significant (P < 0.01) improvement in positive cell number from 3 to 9 hr after warming, reaching a value similar to that of the control group at 12 hr of culture. Our results suggest that vitrified/warmed embryos require 9-12 hr of culture to complete resumption of DNA synthesis and 29-35 hr to re-acquire the full capacity of protein secretion but not the qualitative secretion pattern.     

Benthic assemblages and temperature effects on Paracentrotus lividus and Arbacia lixula larvae and settlement

Recruitment is a principal controlling factor in population dynamics of marine species. In marine invertebrates with a planktonic larval stage, such as echinoids, recruitment is assured by larval supply, settlement and juvenile survival. Larval supply and juvenile survival are affected by a wide range of factors, including temperature, presence of predators, quality and quantity of food. Echinoid larval settlement is mainly conditioned by the finding of a suitable substrate to metamorphose. The sea urchins Arbacia lixula and Paracentrotus lividus are considered key species of the Mediterranean infralittoral rocky shores. At high densities, the grazing activity of both species can produce and maintain barren grounds, a particular habitat condition characterized by extremely low cover values of erect algae with high presence of naked substrates and encrusting corallinales, poor in biodiversity and ecosystem functions. We tested the role of different settlement substrates on the metamorphosis competent larvae of the two species. Furthermore, from our larval rearing trails we were able to identify strong temperature effects on larval development of the two species. P. lividus and A. lixula larvae have been reared at 18 °C but for the second species it was necessary to use higher temperatures (22 °C) to perform settlement experiments, as in the 18 °C set all larvae died in the first week. Both species larvae have been fed Cricosphaera elongata. Metamorphosis of competent larvae has been induced using different substrates: naked stones, Lithophyllum incrustans, Stypocaulon scoparium, Corallina elongata, turf forming algae and Posidonia oceanica. For each species, two larval batches were used for settlement experiments; for each larval batch two replicates/substrates were set up. No differences in the rate of metamorphosis on any of the tested substrates were observed for P. lividus, while A. lixula showed to prefer naked stones and encrusting coralline algae Considering that A. lixula population growth may trigger barren extension on rocky shores, this may lead to a positive feedback between barren extension and A. lixula population density. Furthermore, our results suggest that the predicted rise in seawater temperature may favor A. lixula larval survival and inhibit P. lividus. Combining information on temperature tolerance with other sources of information for these species in the Mediterranean, it is possible to develop a conceptual model of the interaction between the two species and the alternative state of their habitats.     

Warming prevents the elevated CO2-induced reduction in available soil nitrogen in a temperate, perennial grassland

Rising atmospheric carbon dioxide concentration ([CO₂]) has the potential to stimulate ecosystem productivity and sink strength, reducing the effects of carbon (C) emissions on climate. In terrestrial ecosystems, increasing [CO₂] can reduce soil nitrogen (N) availability to plants, preventing the stimulation of ecosystem C assimilation; a process known as progressive N limitation. Using ion exchange membranes to assess the availability of dissolved organic N, ammonium and nitrate, we found that CO₂ enrichment in an Australian, temperate, perennial grassland did not increase plant productivity, but did reduce soil N availability, mostly by reducing nitrate availability. Importantly, the addition of 2 °C warming prevented this effect while warming without CO₂ enrichment did not significantly affect N availability. These findings indicate that warming could play an important role in the impact of [CO₂] on ecosystem N cycling, potentially overturning CO₂‐induced effects in some ecosystems.     

Heat tolerance and physiological plasticity in the Antarctic collembolan, Cryptopygus antarcticus, and mite, Alaskozetes antarcticus

Polar amplification of global warming has led to an average 2 °C rise in air temperatures in parts of the polar regions in the last 50 years. Poikilothermic ectotherms that are found in these regions, such as Collembola and mites, may therefore be put under pressure by changing environmental conditions. However, it has also been suggested that the thermal sensitivity of invertebrates declines with higher latitudes and, therefore, that polar ectotherms may not be at risk. In the current study, the heat tolerance and physiological plasticity to heat stress of two well-studied Antarctic invertebrates, the collembolan, Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus, were investigated. Both species showed considerable heat tolerance, with each having an Upper Lethal Temperature (ULT) above 35 °C (1 h exposure). These species were also able to survive for over 43 d at 10 °C and for periods of 5–20 min at 40 °C. Across all experimental procedures, A. antarcticus possessed a somewhat greater level of heat tolerance than C. antarcticus. Water loss during short duration exposures did not differ between the two species at 30, 35 and 40 °C, suggesting that the greater tolerance of A. antarcticus over this timescale was not due to higher desiccation resistance. Physiological plasticity was investigated by testing for Rapid Heat Hardening (RHH) and long-term acclimation. RHH was observed to a small degree in both species at a warming rate of 0.5 °C min⁻¹, and also 0.2 °C min⁻¹ in A. antarcticus alone. Longer-term acclimation (1 week at 10 °C) did not enhance the heat tolerance of either species. Even with this limited physiological plasticity, the results of this study indicate that C. antarcticus and A. antarcticus have capacity in their heat tolerance to cope with current and future environmental extremes of high temperature.     

Experimental soil warming effects on CO2 and CH4 flux from a low elevation spruce–fir forest soil in Maine, USA

The effect of soil warming on CO₂ and CH₄ flux from a spruce–fir forest soil was evaluated at the Howland Integrated Forest Study site in Maine, USA from 1993 to 1995. Elevated soil temperatures (～5 °C) were maintained during the snow-free season (May – November) in replicated 15 × 15-m plots using electric cables buried 1–2 cm below the soil surface; replicated unheated plots served as the control. CO₂ evolution from the soil surface and soil air CO₂ concentrations both showed clear seasonal trends and significant (P < 0.0001) positive exponential relationships with soil temperature. Soil warming caused a 25–40% increase in CO₂ flux from the heated plots compared to the controls. No significant differences were observed between heated and control plot soil air CO₂ concentrations which we attribute to rapid equilibration with the atmosphere in the O horizon and minimal treatment effects in the B horizon. Methane fluxes were highly variable and showed no consistent trends with treatment.     

博斯腾湖人工和天然芦苇湿地土壤CO2、CH4和N2O排放通量

为研究干旱区淡水湖泊人工、天然芦苇湿地土壤温室气体源汇强度及其影响因素,采用静态箱-气相色谱法,于2015年1月—12月对博斯腾湖人工和天然芦苇湿地土壤CO_2、CH_4和N_2O通量进行全年观测。结果表明,人工芦苇湿地土壤CO_2、CH_4和N_2O排放通量变化范围分别为:10.1—588.4mg m~(-2)h~(-1)、2.9—82.4μg m~(-2)h~(-1)和1.32—29.7μg m~(-2)h~(-1),天然芦苇湿地土壤CO_2、CH_4和N_2O排放通量变化范围分别为10.3—469.6mg m~(-2)h~(-1)、3.1—64.8μg m~(-2)h~(-1)和1.9—14.3μg m~(-2)h~(-1)。人工和天然芦苇湿地夏季土壤CO_2排放通量均明显高于其他季节,而土壤CH_4和N_2O排放通量较大值多集中在春末夏初。全年观测期间,人工芦苇湿地土壤CO_2、CH_4和N_2O排放通量高于天然芦苇湿地(P0.05);温度是影响人工、天然芦苇湿地土壤CO_2和N_2O排放通量的关键因素,近地面温度和5cm土壤温度与CO_2和N_2O排放通量呈现极显著的正相关关系(P0.01)。土壤CH_4排放通量是温度和水分二者共同影响的,由近地表温度、5cm土壤温度和土壤含水量共同拟合的方程可以分别解释人工、天然芦苇湿地土壤CH_4排放通量的71%、74.5%;土壤有机碳、pH、盐分、NH_4~+-N、NO_3~--N也是人工、天然芦苇湿地土壤CO_2、CH_4和N_2O排放通量的影响因素;人工和天然芦苇湿地土壤均是CO_2、CH_4和N_2O的"源"。基于100年尺度,由3种温室气体计算全球增温潜势得出,人工芦苇湿地全球增温潜势大于天然芦苇湿地(15150.18kg/hm~212484.21kg/hm~2)。     

模拟增温和氮沉降对中亚热带杉木幼林土壤有效氮的影响

以中亚热带杉木(Cunninghamia lanceolata)幼苗为研究对象,设置埋设电缆以加热土壤增温(+5℃)结合模拟氮沉降的实验,施氮水平分别为对照(CT,0 kg hm~(-2)a~(-1))、施低氮(LN,40 kg hm~(-2)a~(-1))和施高氮(HN,80 kg hm~(-2)a~(-1)),用离子交换树脂袋法研究了土壤有效氮对模拟增温和施氮的短期响应。经过为期1a的研究,结果表明:土壤有效氮主要集中在夏冬季,而且硝态氮是土壤有效氮的主要存在形态;增温显著增加土壤有效氮含量(P0.05),各月间的有效氮含量与气温和降雨量有关;总体来看,氮沉降显著增加土壤有效氮含量(P0.05),而且随氮沉降水平的升高而增加。低氮处理下,大多数月份的土壤有效氮含量显著增加,高氮处理下,各月的有效氮含量均显著高于对照处理;增温×氮沉降在各月间均显著增加土壤有效氮含量(P0.05),并随氮沉降水平的升高而增加。而且,两者的交互作用对有效氮的增幅显著大于任一单一因子的作用。说明增温和氮沉降两者的交互作用对土壤有效氮的影响具有叠加效应。因此,增温和氮沉降及其交互作用短期内都会显著增加土壤有效氮含量,为植物生长提供充足的养分。     

土壤增温对亚热带杉木幼树不同深度土壤微生物胞外酶活性的影响

土壤微生物胞外酶可有效反映气候变暖对土壤微生物功能和土壤有机质分解的影响.目前关于气候变暖对土壤微生物胞外酶活性(EEAs)影响的相关研究主要关注有机碳含量较丰富的表层土壤(0～20 cm),而对深层土壤(>20 cm)EEAs的研究仍较缺乏.因此,本研究关注土壤增温对亚热带不同深度(0～10 cm、10～20 cm、20～40 cm和40～60 cm)EEAs的影响及主要调控因素,其中微生物胞外酶包括参与碳循环的β-葡萄糖苷酶(BG)、纤维二糖水解酶(CBH)、酚氧化酶(PHO)和过氧化物氧化酶(PEO).结果表明: 土壤增温提高了0～10 cm和10～20 cm土壤所有胞外酶的活性(18%～69%).在20 cm以下的深层土壤中,土壤增温仅显著提高了20～40 cm的PHO(10%),而对其余胞外酶的活性无显著影响或有一定的抑制作用(13%～31%).冗余分析(RDA)结果表明: 在微生物可利用有机碳较丰富的表层土壤中,铵态氮(NH₄⁺-N)和土壤含水率(M)是调控EEAs的主要因素,增温增强了微生物与植物之间的养分竞争,因而提高EEAs以获取微生物所需的养分NH₄⁺-N;而在微生物底物有效性较低的深层土壤中,EEAs主要受可溶性有机质(可溶性有机碳和可溶性有机氮)和微生物生物量(MBC)的影响,增温提高深层土壤可溶性有机质的含量,为微生物提供更多的底物,减少微生物对EEAs的需求,进而降低EEAs.本研究发现,不同深度EEAs对土壤增温具有不同响应,且土壤增温条件下表层和深层土壤的EEAs具有明显不同的调控因素.因此,加强不同深度土壤微生物的研究对于准确评估生态系统碳循环对全球变暖的响应具有重要意义.     

Induced climate change impairs photosynthetic performance in Echinocactus platyacanthus, an especially protected Mexican cactus species

The responses of desert plants to climate warming have been poorly assessed, perhaps due to the overall expectation that desert vegetation will expand as a consequence of this component of climate change. However, determining what plant species will tolerate the expected increase in temperature is a question that remains unanswered. The Chihuahuan Desert is the largest warm desert of North America, and predictive models of climate change indicate that summer temperatures in this desert will increase by 1–2 °C in the next decade. This study experimentally assessed the performance of an endangered cacti species from the Chihuahuan Desert under simulated warming conditions. Hexagonal open top-chambers (OTCs) were used to simulate the effects of global warming on five-years-old individuals of the specially protected species Echinocactus platyacanthus. Temperature was 1.9 °C higher in open top-chambers than in control plots. In contrast, relative humidity was 3.1% higher in control plots than in open top-chambers. E. platyacanthus showed 100% survival for 14 weeks in both OTC and control plots. However, induced warming negatively affected the photosynthetic performance of this species. Cacti located within OTCs displayed lower maximum quantum efficiency of photosystem II (F_v/F_m), effective quantum yield of photosystem II (Φ_PSII), and electron transport rate (ETR) values, but higher non-photochemical quenching (NPQ) values, than cacti from control plots. This is the first study focused on the potential impact of climate warming on survival and photosynthetic performance of young individuals of a succulent species from American deserts. Induced warming negatively affected the photosynthetic performance of young E. platyacanthus, but it also increased non-photochemical quenching, a mechanism for avoiding photoinhibition.     

Emission of N2O, N2, CH4, and CO2 from constructed wetlands for wastewater treatment and from riparian buffer zones

We measured nitrous oxide (N₂O), dinitrogen (N₂), methane (CH₄), and carbon dioxide (CO₂) fluxes in horizontal and vertical flow constructed wetlands (CW) and in a riparian alder stand in southern Estonia using the closed chamber method in the period from October 2001 to November 2003. The replicates’ average values of N₂O, N₂, CH₄ and CO₂ fluxes from the riparian gray alder stand varied from −0.4 to 58 μg N₂O-N m⁻² h⁻¹, 0.02–17.4 mg N₂-N m⁻² h⁻¹, 0.1–265 μg CH₄-C m⁻² h⁻¹ and 55–61 mg CO₂-C m⁻² h⁻¹, respectively. In horizontal subsurface flow (HSSF) beds of CWs, the average N₂ emission varied from 0.17 to 130 and from 0.33 to 119 mg N₂-N m⁻² h⁻¹ in the vertical subsurface flow (VSSF) beds. The average N₂O-N emission from the microsites above the inflow pipes of the HSSF CWs was 6.4–31 μg N₂O-N m⁻² h⁻¹, whereas the outflow microsites emitted 2.4–8 μg N₂O-N m⁻² h⁻¹. In VSSF beds, the same value was 35.6–44.7 μg N₂O-N m⁻² h⁻¹. The average CH₄ emission from the inflow and outflow microsites in the HSSF CWs differed significantly, ranging from 640 to 9715 and from 30 to 770 μg CH₄-C m⁻² h⁻¹, respectively. The average CO₂ emission was somewhat higher in VSSF beds (140–291 mg CO₂-C m⁻² h⁻¹) and at the inflow microsites of HSSF beds (61–140 mg CO₂-C m⁻² h⁻¹). The global warming potential (GWP) from N₂O and CH₄ was comparatively high in both types of CWs (4.8 ± 9.8 and 6.8 ± 16.2 t CO₂ eq ha⁻¹ a⁻¹ in the HSSF CW 6.5 ± 13.0 and 5.3 ± 24.7 t CO₂ eq ha⁻¹ a⁻¹ in the hybrid CW, respectively). The GWP of the riparian alder forest from both N₂O and CH₄ was relatively low (0.4 ± 1.0 and 0.1 ± 0.30 t CO₂ eq ha⁻¹ a⁻¹, respectively), whereas the CO₂-C flux was remarkable (3.5 ± 3.7 t ha⁻¹ a⁻¹). The global influence of CWs is not significant. Even if all global domestic wastewater were treated by wetlands, their share of the trace gas emission budget would be less than 1%.     

夜间增温品种混栽对稻田土壤CH4和N2O排放的影响

夜间增温幅度大于白天是气候变暖主要特征之一。夜间增温对水稻生产及CH₄和N₂O排放的影响备受关注。品种混栽可提高水稻产量,增强水稻植株抗性。增温或混栽单因子对稻田CH₄和N₂O排放影响已有报道,但二者耦合如何影响水稻生产及稻田CH₄和N₂O排放,尚不清楚。采用2因素随机区组设计,通过田间试验研究了夜间增温下品种混栽对水稻产量、CH₄和N₂O综合增温潜势和排放强度的影响。夜间增温设2水平,即对照（CK,control）和增温（NW,nighttime warming）;品种混栽设2水平,即混作（I,intercropping）,单作（M,monocropping）,混栽处理将主栽品种（超级稻南粳9108）与次栽品种（杂交稻深两优884）以3：1的比例种植。水稻生长期用铝箔反射膜覆盖水稻冠层进行被动式夜间增温试验（19：00-6：00）。结果表明,夜间增温或品种混栽均显著降低水稻植株分蘖数和生物量。品种混栽显著提高水稻产量,而夜间增温则显著降低产量。品种混栽可缓解夜间增温对水稻产量的抑制作用。夜间增温下品种混栽处理稻田CH₄累计排放量在分蘖期、拔节-孕穗期、抽穗-扬花期和灌浆-成熟期比单作对照分别高55.32%、45.89%、43.49和125.82%。夜间增温下品种混栽处理稻田N₂O累计排放量在分蘖期、拔节-孕穗期和抽穗-扬花期分别比单作对照高64.44%、46.26%和42.07%。研究认为,夜间增温下品种混栽显著提高稻田CH₄和N₂O排放通量和累积排放量,显著增加综合增温潜势（GWP）和排放强度（GHGI）。     

Simple carbon assimilation response functions from atmospheric CO2, and daily temperature and shortwave radiation

A global ‘CO₂ fertilizer effect’ multiplier is often used in crop or ecosystem models because of its simplicity. However, this approach does not take into account the interaction between CO₂, temperature and light on assimilation. This omission can lead to significant under- or overestimation of the magnitude of beneficial effects from elevated CO₂, depending on environmental conditions. We use a mechanistic model of the biochemistry of photosynthesis to represent the response of net assimilation to different levels of CO₂, temperature and radiation, on the daily time scale. Instantaneous assimilation rates for an idealized canopy model are integrated through diurnal cycles of environmental variables derived from historical climate data at three locations in North America. The calculated CO₂ fertilizer effect is greatest at high light and warm temperatures. The results are summarized by assimilation response surfaces specified by the CO₂ concentration, the canopy leaf area index, and by daily values of temperature and radiation available from climatic records. These summary functions are suitable for incorporation into crop or ecosystem models for predicting carbon assimilation or biomass production on a daily time step. An example application of the function reveals that for a relatively cool, high latitude location, the beneficial effects from a CO₂ doubling would be negligible during the early spring, even assuming a + 4°C global warming scenario. In contrast, the beneficial effects from increasing CO₂ at a relatively warm, lower latitude location are greatest in the spring, but decline in late summer because of excessively warm temperatures with a + 4°C global warming.     

Temperature and biomass influences on interannual changes in CO2 exchange in an alpine meadow on the Qinghai-Tibetan Plateau

Three years of eddy covariance measurements were used to characterize the seasonal and interannual variability of the CO₂ fluxes above an alpine meadow (3250 m a.s.l.) on the Qinghai‐Tibetan Plateau, China. This alpine meadow was a weak sink for atmospheric CO₂, with a net ecosystem production (NEP) of 78.5, 91.7, and 192.5 g C m^?2 yr^?1 in 2002, 2003, and 2004, respectively. The prominent, high NEP in 2004 resulted from the combination of high gross primary production (GPP) and low ecosystem respiration (R_e) during the growing season. The period of net absorption of CO₂ in 2004, 179 days, was 10 days longer than that in 2002 and 5 days longer than that in 2003. Moreover, the date on which the mean air temperature first exceeded 5.0°C was 10 days earlier in 2004 (DOY110) than in 2002 or 2003. This date agrees well with that on which the green aboveground biomass (Green AGB) started to increase. The relationship between light‐use efficiency and Green AGB was similar among the three years. In 2002, however, earlier senescence possibly caused low autumn GPP, and thus the annual NEP, to be lower. The low summertime R_e in 2004 was apparently caused by lower soil temperatures and the relatively lower temperature dependence of R_e in comparison with the other years. These results suggest that (1) the Qinghai‐Tibetan Plateau plays a potentially significant role in global carbon sequestration, because alpine meadow covers about one‐third of this vast plateau, and (2) the annual NEP in the alpine meadow was comprehensively controlled by the temperature environment, including its effect on biomass growth.     

增温和施氮对亚热带杉木人工林土壤溶液养分的影响

在增温和氮沉降等气候变化背景下,土壤溶液养分元素供应是否平衡对加速或减弱土壤养分循环起着至关重要的作用。为探究增温和施氮对亚热带杉木人工土壤溶液养分动态的影响,分别于各样地的0—15、15—30cm和30—60cm土层安装土壤溶液采集器。利用真空泵的负压原理采集土壤溶液,对其有机组分及无机组分进行了两年的动态监测。结果显示:增温及增温+施氮显著增加了各土层溶解性总氮(DTN)及硝态氮(NO-3)浓度,而施氮促进了植被对其的大量吸收而未呈现显著的促进作用。整体而言,短期增温和施氮处理显著降低了可溶性有机碳(DOC)浓度,对土壤溶液K~+、Ca~(2+)、Na~+、Mg~(2+)等离子含量影响较小。但相比于施氮,增温对土壤溶液中矿质元素的影响远大于施氮。增温导致的土壤孔径增大,通透性增强可极大地促进Fe~(3+)、Al~(3+)淋溶,同时导致表层Na~+、Mg~(2+)离子含量显著降低。增温+施氮交互作用对土壤溶液各养分的影响存在叠加效应,但并不是增温和施氮单因子的简单累加,要深入了解土壤养分对未来气候变迁的内部机制需进一步长期监测。