The ecology of Bactrocera tryoni (Froggatt) (Diptera: Tephritdae) : what do we know to assist pest management?

The distribution, systematics and ecology of Bactrocera tryoni, the Queensland fruit fly are reviewed. Bactrocera tryoni is a member of the B. tryoni complex of species, which currently includes four named species, viz. B. tryoni s.s., B. neohumeralis, B. melas and B. aquilonis. The species status of B. melas and B. aquilonis are unclear (they may be junior synonyms of B. tryoni) and their validity, or otherwise, needs to be confirmed as a matter of urgency. While Queensland fruit fly is regarded as a tropical species, it cannot be assumed that its distribution will spread further south under climate change scenarios. Increasing aridity and hot dry summers, as well as more complex, indirect interactions resulting from elevated CO2, make predicting the future distribution and abundance of B. tryoni difficult. The ecology of B. tryoni is reviewed with respect to current control approaches (with the exception of Sterile Insect Technique which is covered in a companion paper). We conclude that there are major gaps in the knowledge required to implement most non-insecticide based management approaches. Priority areas for future research include host plant interactions, protein and cue-lure foraging and use, spatial dynamics, development of new monitoring tools, investigating the use of natural enemies and better integration of fruit flies into general horticultural IPM systems.

Climate change effects on pasture systems in south-eastern Australia.

Climate change projections for Australia predict increasing temperatures, changes to rainfall patterns, and elevated atmospheric carbon dioxide (CO2) concentrations. The aims of this study were to predict plant production responses to elevated CO2 concentrations using the SGS Pasture Model and DairyMod, and then to quantify the effects of climate change scenarios for 2030 and 2070 on predicted pasture growth, species composition, and soil moisture conditions of 5 existing pasture systems in climates ranging from cool temperate to subtropical, relative to a historical baseline. Three future climate scenarios were created for each site by adjusting historical climate data according to temperature and rainfall change projections for 2030, 2070 mid-and 2070 high-emission scenarios, using output from the CSIRO Mark 3 global climate model. In the absence of other climate changes, mean annual pasture production at an elevated CO2 concentration of 550 ppm was predicted to be 24-29% higher than at 380 ppm CO2 in temperate (C-3) species-dominant pastures in southern Australia, with lower mean responses in a mixed C-3/C-4 pasture at Barraba in northern New South Wales (17%) and in a C-4 pasture at Mutdapilly in south-eastern Queensland (9%). In the future climate scenarios at the Barraba and Mutdapilly sites in subtropical and subhumid climates, respectively, where climate projections indicated warming of up to 4.4 degrees C, with little change in annual rainfall, modelling predicted increased pasture production and a shift towards C-4 species dominance. In Mediterranean, temperate, and cool temperate climates, climate change projections indicated warming of up to 3.3 degrees C, with annual rainfall reduced by up to 28%. Under future climate scenarios at Wagga Wagga, NSW, and Ellinbank, Victoria, our study predicted increased winter and early spring pasture growth rates, but this was counteracted by a predicted shorter spring growing season, with annual pasture production higher than the baseline under the 2030 climate scenario, but reduced by up to 19% under the 2070 high scenario. In a cool temperate environment at Elliott, Tasmania, annual production was higher than the baseline in all 3 future climate scenarios, but highest in the 2070 mid scenario. At the Wagga Wagga, Ellinbank, and Elliott sites the effect of rainfall declines on pasture production was moderated by a predicted reduction in drainage below the root zone and, at Ellinbank, the use of deeper rooted plant systems was shown to be an effective adaptation to mitigate some of the effect of lower rainfall.

The critical role of extreme heat for maize production in the United States

Statistical studies of rainfed maize yields in the United States(1) and elsewhere(2) have indicated two clear features: a strong negative yield response to accumulation of temperatures above 30 degrees C (or extreme degree days (EDD)), and a relatively weak response to seasonal rainfall. Here we show that the process-based Agricultural Production Systems Simulator (APSIM) is able to reproduce both of these relationships in the Midwestern United States and provide insight into underlying mechanisms. The predominant effects of EDD in APSIM are associated with increased vapour pressure deficit, which contributes to water stress in two ways: by increasing demand for soil water to sustain a given rate of carbon assimilation, and by reducing future supply of soil water by raising transpiration rates. APSIM computes daily water stress as the ratio of water supply to demand, and during the critical month of July this ratio is three times more responsive to 2 degrees C warming than to a 20% precipitation reduction. The results suggest a relatively minor role for direct heat stress on reproductive organs at present temperatures in this region. Effects of elevated CO2 on transpiration efficiency should reduce yield sensitivity to EDD in the coming decades, but at most by 25%.

The shifting influence of drought and heat stress for crops in Northeast Australia

Characterization of drought environment types (ETs) has proven useful for breeding crops for drought-prone regions. Here we consider how changes in climate and atmospheric carbon dioxide (CO2) concentrations will affect drought ET frequencies in sorghum and wheat systems of Northeast Australia. We also modify APSIM (the Agricultural Production Systems Simulator) to incorporate extreme heat effects on grain number and weight, and then evaluate changes in the occurrence of heat-induced yield losses of more than 10, as well as the co-occurrence of drought and heat. More than six million simulations spanning representative locations, soil types, management systems, and 33 climate projections led to three key findings. First, the projected frequency of drought decreased slightly for most climate projections for both sorghum and wheat, but for different reasons. In sorghum, warming exacerbated drought stresses by raising the atmospheric vapor pressure deficit and reducing transpiration efficiency (TE), but an increase in TE due to elevated CO2 more than offset these effects. In wheat, warming reduced drought stress during spring by hastening development through winter and reducing exposure to terminal drought. Elevated CO2 increased TE but also raised radiation use efficiency and overall growth rates and water use, thereby offsetting much of the drought reduction from warming. Second, adding explicit effects of heat on grain number and grain size often switched projected yield impacts from positive to negative. Finally, although average yield losses associated with drought will remain generally higher than for heat stress for the next half century, the relative importance of heat is steadily growing. This trend, as well as the likely high degree of genetic variability in heat tolerance, suggests that more emphasis on heat tolerance is warranted in breeding programs. At the same time, work on drought tolerance should continue with an emphasis on drought that co-occurs with extreme heat. This article is protected by copyright. All rights reserved.

The shifting influence of drought and heat stress for crops in Northeast Australia

Characterization of drought environment types (ETs) has proven useful for breeding crops for drought-prone regions. Here we consider how changes in climate and atmospheric carbon dioxide (CO2) concentrations will affect drought ET frequencies in sorghum and wheat systems of Northeast Australia. We also modify APSIM (the Agricultural Production Systems Simulator) to incorporate extreme heat effects on grain number and weight, and then evaluate changes in the occurrence of heat-induced yield losses of more than 10%, as well as the co-occurrence of drought and heat. More than six million simulations spanning representative locations, soil types, management systems, and 33 climate projections led to three key findings. First, the projected frequency of drought decreased slightly for most climate projections for both sorghum and wheat, but for different reasons. In sorghum, warming exacerbated drought stresses by raising the atmospheric vapor pressure deficit and reducing transpiration efficiency (TE), but an increase in TE due to elevated CO2 more than offset these effects. In wheat, warming reduced drought stress during spring by hastening development through winter and reducing exposure to terminal drought. Elevated CO2 increased TE but also raised radiation use efficiency and overall growth rates and water use, thereby offsetting much of the drought reduction from warming. Second, adding explicit effects of heat on grain number and grain size often switched projected yield impacts from positive to negative. Finally, although average yield losses associated with drought will remain generally higher than for heat stress for the next half century, the relative importance of heat is steadily growing. This trend, as well as the likely high degree of genetic variability in heat tolerance, suggests that more emphasis on heat tolerance is warranted in breeding programs. At the same time, work on drought tolerance should continue with an emphasis on drought that co-occurs with extreme heat. This article is protected by copyright. All rights reserved.

Modeling of solar radiation management: a comparison of simulations using reduced solar constant and stratospheric sulphate aerosols

The climatic effects of Solar Radiation Management (SRM) geoengineering have been often modeled by simply reducing the solar constant. This is most likely valid only for space sunshades and not for atmosphere and surface based SRM methods. In this study, a global climate model is used to evaluate the differences in the climate response to SRM by uniform solar constant reduction and stratospheric aerosols. Our analysis shows that when global mean warming from a doubling of CO2 is nearly cancelled by both these methods, they are similar when important surface and tropospheric climate variables are considered. However, a difference of 1 K in the global mean stratospheric (61-9.8 hPa) temperature is simulated between the two SRM methods. Further, while the global mean surface diffuse radiation increases by similar to 23 % and direct radiation decreases by about 9 % in the case of sulphate aerosol SRM method, both direct and diffuse radiation decrease by similar fractional amounts (similar to 1.0 %) when solar constant is reduced. When CO2 fertilization effects from elevated CO2 concentration levels are removed, the contribution from shaded leaves to gross primary productivity (GPP) increases by 1.8 % in aerosol SRM because of increased diffuse light. However, this increase is almost offset by a 15.2 % decline in sunlit contribution due to reduced direct light. Overall both the SRM simulations show similar decrease in GPP (similar to 8 %) and net primary productivity (similar to 3 %). Based on our results we conclude that the climate states produced by a reduction in solar constant and addition of aerosols into the stratosphere can be considered almost similar except for two important aspects: stratospheric temperature change and the consequent implications for the dynamics and the chemistry of the stratosphere and the partitioning of direct versus diffuse radiation reaching the surface. Further, the likely dependence of global hydrological cycle response on aerosol particle size and the latitudinal and height distribution of aerosols is discussed.

中国冬小麦品种对臭氧、二氧化碳和干旱的响应

臭氧属于二次污染物，它是由机动车、工厂等人为源以及天然源排放的氮氧化物(NOx)和挥发性有机物(VOCs)等一次污染物在大气中经过光化学反应形成的。O3 是光化学烟雾的主要成分，可对植物生长产生抑制。近几十年来，全球O3 污染的格局正在发生着巨大改变。由于北美及西欧等经济发达地区采取了有效控制臭氧形成前体物的措施，其空气中的O3 浓度在减少，而亚洲等经济发展中地区的O3 形成前体物的排放却在急剧攀升，导致大气中O3 浓度显著增加。中国经济的快速发展以及汽车保有量的迅猛增加导致O3 前体物的大量排放，许多经济较发达的地区空气中的O3 浓度超过了75ppb。由于O3 污染将导致农作物产量显著降低，因此，亚洲尤其是中国O3 污染对本地区农业生产的影响引起了国内外科学家的广泛关注。然而，在中国开展的关于O3 对植物生长及生产影响的研究相对较少，但已有的几篇研究报道确实指出目前中国部分地区的O3 浓度可导致冬小麦产量大幅下降，并预测到2020 年由O3 污染将引起小麦产量进一步降低。 植物对臭氧的反应或敏感性取决于诸如叶片导度、叶片结构及生化解毒等很多方面。首先，由于高叶片导度将吸收较多的臭氧量，因此，叶片导度通常被认为是决定抗性最为重要的因子。处于湿润条件下的植物，通常具有较高叶片导度，受到臭氧危害的程度一般也较大。其次，植物抗氧化胁迫能力的大小也决定着其对臭氧的敏感性。同一植株的老叶首先表现出伤害症状，这是由于老叶的抗氧化能力差于新叶，体现在抗坏血酸和谷胱甘肽含量及抗坏血酸氧化物酶和谷胱甘肽还原酶活性低于新叶。另外，叶片对臭氧的敏感程度与其叶片结构关系密切，拥有较大的细胞间隙对抗污染特性至关重要，由于叶片上表面的栅栏组织较海绵组织致密，因此通常较早表现出伤害症状。 影响植物对臭氧反应的环境因子很多，诸如光照、水气压亏、温度等。由于臭氧主要通过气孔进入植物体内，因此目前的研究主要集中在能显著调节气孔导度的环境因子，如土壤水分状况和在未来可能会与大气中臭氧浓度同步增加的CO2 浓度。CO2 浓度升高可降低植物的气孔导度，因此，CO2 浓度升高可减少叶片对O3 的吸收量。同时，大气CO2 浓度升高可提高净同化速率，可导致气孔的部分关闭而减少蒸腾，从而显著提高植株的水分利用效率，最终促进作物生长并提高产量。然而，二者对作物产量的交互影响尚不明确。水分胁迫被认为是影响O3 对植株伤害的一个重要环境因子。与正常供水相比，水分胁迫常常伴随着气孔导度的降低，导致进入到植株体内的O3 量相对较少而减轻植株受到的伤害程度。然而水分供应不足本身将导致小麦生长降低及产量下降。因此，水分亏缺可能会保护植株免受O3 伤害，同时也可能会加剧对植株的胁迫。 高浓度臭氧环境下，植物表现出较低的气孔导度。但研究表明，对臭氧敏感性不同的植物其气孔导度对臭氧的反应程度不同。臭氧对气孔的作用将影响植物生产力，同时也将影响植物对其它环境胁迫如干旱等的反应。短时间臭氧熏蒸小麦导致叶片细胞膜系统受损、光合产物输出受阻;而长期受臭氧污染后，小麦叶片的光合速率、光化学效率、叶绿素含量和蔗糖含量均显著降低，并与臭氧剂量的大小和峰值出现的早晚有关。O3 浓度升高将抑制光合作用，减少气孔导度，加强呼吸作用，改变C 同化物分配，加快叶片的衰老。众多研究表明，O3 导致的光合能力下降主要是由Rubisco 最大羧化效率降低导致;而O3 对光合器官捕获光的能力及光合电子传递速率的影响是光合作用下降的另一个原因。 尽管已有不少关于不同物种间对O3 敏感性的种间差异研究，然而育种方法或育种地点对中国不同冬小麦品种的O3 敏感性的影响尚不清楚。因此，我们假设育种年代、育种方法及地点将交互影响冬小麦品种对O3 的生长及生理响应。为进一步明确基因对冬小麦O3 敏感性的控制，研究了普通六倍体冬小麦的近缘体对O3 敏感性的差异。CO2 浓度升高及干旱胁迫对小麦臭氧敏感性的影响也进行了研究。论文主要从生理生化、生长及产量水平上来阐释O3 浓度升高、CO3加倍、干旱对冬小麦生长及生产影响的机理。 本研究主要是在温室中的上部开口的生长箱（open-top chamber, OTC）中进行。先后开展了四个盆栽实验研究，主要目的是确定中国不同基因型冬小麦种或品种对臭氧的敏感性及其反应机理;确定CO2 浓度升高及干旱在减轻O3 伤害方面的作用及其机理。实验材料为中国不同年代选育出的小麦品种，即1745年至2004 年间选育出的20 个品种和7 个小麦材料。主要评价指标包括相对生长速率、异速生长系数、叶绿素荧光、抗氧化活性、可溶性蛋白质含量、膜酯过氧化、气体交换、光合能力、叶绿素含量、暗呼吸、生物量及籽粒产量。实验研究得到的主要结果如下： 1) O3 升高显著降低整株及地上和地下部分的相对生长速率，显著降低异速生长系数、可变荧光、最大光化学效率、量子产额、光化学淬灭系数以及电子传递速率，但提高了非光化学淬灭系数。冬小麦不同品种对O3 的敏感性随育种年代的增加而增大，并与对照植株相对生长速率呈正相关。尽管近年来环境中的O3 浓度比过去显著增加，但新近育出的品种对臭氧的抗性却没有表现出协同进化效应。通过杂交选育的品种对臭氧的敏感性大于通过引进的和重选的品种。从生长和光合生理上来看，不同小麦品种对臭氧的敏感性与育种地点没有相关性，表明冬小麦品种对臭氧的适应能力与其生长环境下的臭氧浓度无关。因此，对臭氧相对敏感的冬小麦品种主要是由培育中较高相对生长速率或较高光合能力的杂交育种方式决定的，而与选育地点环境中的臭氧浓度无关。 2) 臭氧显著降低叶片中抗坏血酸（AsA）和可溶性蛋白的含量，但提高了过氧化物酶（POD）的活性和膜酯过氧化物（MDA）的含量。臭氧浓度升高抑制饱和光强下的净光合速率（Asat），降低气孔导度（gs）和总叶绿素含量，而显著提高暗呼吸速率（Rd）和胞间CO2 浓度（Ci）。臭氧导致总生物量降低，但地下部生物量受到的影响大于地上部。不同基因型小麦对臭氧的潜在敏感性与实际观察到的抗臭氧能力存在很大差异。冬小麦品种对臭氧的敏感性与臭氧环境下植株气孔导度和暗呼吸速率相关。臭氧导致Ci 浓度升高以及膜酯过氧化，由此得出臭氧导致的净光合速率主要是由于臭氧降低了叶肉细胞活性及细胞膜的完整性。新品种对臭氧相对敏感，主要是由于其具有较高的气孔导度抗氧化能力下降幅度较大以及较低的暗呼吸速率，从而对蛋白和细胞膜完整性造成较高的氧化伤害。 3) 臭氧对冬小麦光合和生长的影响存在着显著的种间差异。原初栽培种表现出最大的抗性，当代品种次之，而野生种对臭氧最为敏感。在普通冬小麦不同基因组供体中，钩刺山羊草（Aegilops tauschii，DD）对臭氧最敏感，其次为栽培一粒小麦（T. monococcum，AA），而圆锥小麦（Triticum turgidum ssp.Durum，AABB）对臭氧的抗性最大。因此，当代冬小麦品种对臭氧的敏感性可能是与其D 染色体供体-钩刺山羊草对臭氧敏感有关，而与其A、B 染色体供体-圆锥小麦的关系相对较小。 4) CO2 浓度升高提高了老品种和新品种的Asat，最大羧化速率（Vcmax），最大电子传递速率（Jmax）、光和CO2 饱和光合速率（Amax）。与之相反，臭氧显著降低了这些生理参数。虽然两品种对CO2 的响应没有显著性差异，但CO2浓度升高均有效保护了臭氧对它们的伤害。这种效应与CO2 浓度升高引起的气孔导度降低无关，而与代谢活性的提高有关。 5) 水分胁迫和臭氧分别都显著降低了 Asat 和gs。干旱显著降低Vcmax 和羧化效率（CE），而对Jmax 和暗呼吸（R）的影响不显著。臭氧显著降低冬小麦不同基因型的Vcmax，Jmax，R 和CE。二者均降低了生物量的积累及最终籽粒产量。与六倍体小麦相比，四倍体小麦对干旱相对敏感，但对臭氧却表现出较高抗性。干旱降低了气孔导度从而显著减少了植株对臭氧的吸收量，但两基因型的反应截然不同。干旱使臭氧对六倍体小麦产量和收获指数的伤害分别减少了约16%和50%，而干旱对该四倍体小麦的保护效应不大。

冬小麦对二氧化碳、臭氧和温度升高的生理生态响应

CO2浓度升高和气候变暖已成为不可逆转的现实，而具有强氧化性的臭氧浓度升高也被认为是全球变化的重要组成部分，已经或将对植被生长产生严重威胁。冬小麦（Triticum aestivum L.）生长发育期内受到环境变化的影响相对较大。小麦是对臭氧最为敏感的作物之一，华北地区冬小麦灌浆期容易发生臭氧污染。本研究以冬小麦为试材，研究了CO2浓度加倍和2oC增温对中国北方不同年代推出的冬小麦品种幼苗生长的效应；研究了不同小麦品种对花后短期臭氧胁迫的反应；分别研究了干旱、增温与臭氧污染对冬小麦旗叶光合和产量的交互影响。研究结果如下： 1) CO2浓度加倍和温度升高加快冬小麦幼苗的生长速率。CO2浓度加倍主要是促进了幼苗的分蘖(+1.54分蘖)，而增温加快了发育进程(主茎叶片数比对照多1叶)。不同品种对CO2浓度加倍和增温的响应存在着差异，但与育种年代没有显著相关关系。从20个品种的总体情况来看，CO2浓度加倍和2.0℃增温对冬小麦幼苗的生长具有叠加效应。生长较慢的冬小麦品种对CO2浓度加倍的反应越大。 2) CO2浓度加倍显著提高了小麦新展开叶的净光合速率（Psat），显著降低了气孔导度（gs）和蒸腾速率（E），从而显著提高了瞬时水分利用效率（ITE），但不同小麦品种对CO2浓度加倍的反应与其育种年代没有明显的相关性；增温对冬小麦叶片Psat的效应不显著，但显著降低了gs，而E显著增大，从而导致ITE显著降低，其中，Psat对增温的反应与品种育种年代呈显著正相关（R=0.525, p<0.05），并与叶片比叶面积（SLA）显著正相关（R=0.45, p<0.001）。CO2浓度加倍和增温同时处理时对Psat、gs和ITE的效应显著大于CO2浓度加倍处理。 3) 冬小麦灌浆初期，短时间的臭氧胁迫对旗叶的同化能力带来了显著的负效应，而且光合性能最大的叶片中部受到的抑制最为严重。同化能力的下降导致最终产量的降低。然而，不同品种对臭氧的敏感性存在着很大差异。臭氧对具有较高收获指数和产量的当代品种-烟农19的效应（-19%，p<0.01）明显大于产量较低的老品种-农大311（-8%，p<0.05），主要表现在叶片可见伤害程度较大，旗叶净光合速率受到的负效应较大，籽粒重量以及穗粒数均显著降低。 4) 短期高浓度臭氧胁迫对处于中度干旱胁迫下的小麦植株产生了可见伤害（<20%），但伤害程度明显低于处于土壤含水量较高的植株(>30%)。短期臭氧处理显著降低了处于较高土壤含水量下的小麦旗叶Psat（-36%），干旱胁迫也显著降低了旗叶Psat（-34%），但臭氧仅使处于中度干旱胁迫下的植株旗叶Psat进一步降低了7.8%。gs的变化趋势与Psat的变化基本一致。臭氧处理结束并复水后，干旱处理植株的Psat与对照基本相同，而臭氧处理过的植株均明显低于对照，其中臭氧处理期间处于良好土壤含水量条件下的植株旗叶Psat显著低于对照，并且随着植株的衰老，其下降的速度明显快于其它处理，表明衰老速度加快。而中度干旱胁迫可减轻臭氧对小麦产量的危害程度。 5) 正常供水条件下，短期臭氧处理结束2天后，小麦旗叶Psat与对照植株的值接近，然而随着时间的延长，Psat下降的速度明显快于对照。臭氧处理结束后，植株若遭受干旱胁迫，旗叶Psat显著低于对照。虽然gs的变化趋势与Psat基本一致，但臭氧处理后光合的降低主要是由非气孔限制因素引起的。旗叶光合能力下降、叶片提前衰老，是臭氧处理导致产量显著降低的主要原因。穗粒数没有显著变化，而千粒重却显著降低。而臭氧处理后若遇干旱胁迫，旗叶的光合能力以及光合有效期进一步减少，导致不育小花数增多，因此籽粒产量进一步减少。 6) 灌浆期臭氧浓度升高显著降低了小麦叶片的光合能力，导致产量显著降低；2oC升温加快了植株的衰老，然而并没有对产量性状产生显著效应；温度和臭氧两因子对旗叶的气体交换参数具有交互效应，但对各产量性状均没有交互效应发生。 综合以上研究结果，不同品种对环境变化的响应存在着显著差异，意味着可以通过育种途径来减轻未来环境变化对农业生产的负面影响；灌浆期臭氧胁迫显著降低冬小麦的产量，环境因子可影响臭氧胁迫效应，但之间的交互作用比较复杂，有待进一步深入研究，以保证未来全球变化环境下的粮食安全。

环境变化对内蒙古草原小叶锦鸡儿和羊草土壤氮素转化的影响

氮素是影响内蒙古温带典型草原植物生长和初级生产力的主要因素之一，土壤氮素的可利用性及其对全球环境变化的响应对于预测生态系统碳氮平衡显得尤为重要。空气中的游离氮和土壤中的有机氮必须通过固氮作用和矿化作用，转化为无机氮才能被绝大多数高等植物直接利用，氮素转化决定土壤氮素有效性。因此，研究环境变化对草原灌丛豆科固氮植物小叶锦鸡儿和草原优势植物种羊草土壤氮素转化重要生物过程的影响，对于进一步了解草原氮库变化及其对环境变化的可能响应有重要意义。 在中国科学院内蒙古草原生态系统定位站，利用开顶式生长室（Open-top chamber，OTC）控制实验模拟环境变化，经过三年的实验处理，研究氮素、水分和CO2浓度变化对小叶锦鸡儿根瘤生长和共生固氮、小叶锦鸡儿和羊草土壤净氮矿化速率的影响。观察小叶锦鸡儿根瘤形态和数量、测定根瘤长度和生物量以及固氮酶活性、测定土壤净氮矿化速率和土壤酶活性，探讨小叶锦鸡儿和羊草土壤氮素转化对环境变化响应机理。 结果表明，三年生桶培小叶锦鸡儿根瘤多着生于侧根，以浅黄色的小型球状根瘤为主，其次是棕褐色的棒状和纺锤状根瘤，较大型的褐色Y状根瘤相对较少。添加氮素极显著地抑制根瘤生长发育及其固氮酶活性，这种抑制效应随着水分增加和CO2浓度升高有所减缓。随着水分的增加，根瘤形态多样，根瘤着生部位由主根渐向侧根再向须根发展，根瘤数量和重量也显著增加。水分和CO2浓度升高，固氮酶活性增加但是未达到显著水平。小叶锦鸡儿根瘤生长及其固氮酶活性在加水条件下最好，水分可能是限制内蒙古半干旱草原小叶锦鸡儿固氮能力的关键因素。 环境变化影响小叶锦鸡儿土壤无机氮库。添加氮素处理，土壤无机氮库显著增加。添加氮素后，土壤脲酶活性显著降低，铵态氮和无机氮都出现明显的氮固持，但硝化速率增加，可能是由于添加氮素后土壤化学性质改变更利于硝化细菌进行硝化活动。随着水分和CO2浓度的升高，由于植物生长需求更多氮素的供应，土壤无机氮库显著降低。水分和CO2浓度处理对小叶锦鸡儿土壤脲酶活性和净氮矿化速率没有显著影响，但是能一定程度上减缓了氮素的负效应，促使无机氮的转化，使土壤微生物对铵态氮和无机氮的固持减少。但是蛋白酶活性和硝酸还原酶活性对三种环境因子响应均不敏感，脲酶对环境因子的变化最为敏感。小叶锦鸡儿土壤氮素转化与土壤理化性质密切相关，环境因子通过影响土壤脲酶活性以及土壤酸碱度等影响土壤矿化速率，进而影响土壤无机氮浓度和植物可利用氮。 羊草土壤无机氮库与小叶锦鸡儿土壤无机氮库对环境变化的响应较为一致，添加氮素羊草土壤无机氮含量显著增加，水分增加土壤无机氮含量显著降低。添加氮素使硝化速率显著增大，氨化速率和净氮矿化速率降低，但是未达到显著水平，铵态氮和无机氮出现固持现象。水分的增加降低土壤无机氮库，刺激脲酶活性，微生物对铵态氮的矿化作用增加，但是硝态氮的矿化作用受抑制，对净氮矿化没有影响。CO2浓度升高对羊草土壤无机氮库和土壤氮素矿化都没有显著地影响，但是CO2浓度升高在适宜水分下通过刺激土壤微生物活性，促进脲酶活性和无机氮的转化。羊草土壤酶活性对氮素和CO2浓度的响应与小叶锦鸡儿土壤酶活性的响应一致。 综上，不同环境因子对氮素转化过程影响不同，氮素添加抑制小叶锦鸡儿根瘤及其固氮酶活性，降低小叶锦鸡儿和羊草土壤净氮矿化速率。水分和CO2浓度升高一定程度上缓解了氮素对固氮酶活性以及土壤净氮素矿化速率的抑制作用，有利于土壤氮素转化。

Ocean acidification shows negligible impacts on high-latitude bacterial community structure in coastal pelagic mesocosms

The impact of ocean acidification and carbonation on microbial community structure was assessed during a large-scale in situ costal pelagic mesocosm study, included as part of the EPOCA 2010 Arctic campaign. The mesocosm experiment included ambient conditions (fjord) and nine mesocosms with pCO(2) levels ranging from similar to 145 to similar to 1420 mu atm. Samples for the present study were collected at ten time points (t-1, t1, t5, t7, t12, t14, t18, t22, t26 to t28) in seven treatments (ambient fjord (similar to 145), 2x similar to 185, similar to 270, similar to 685, similar to 820, similar to 1050 mu atm) and were analysed for "small" and "large" size fraction microbial community composition using 16S rRNA (ribosomal ribonucleic acid) amplicon sequencing. This high-throughput sequencing analysis produced similar to 20 000 000 16S rRNA V4 reads, which comprised 7000OTUs. The main variables structuring these communities were sample origins (fjord or mesocosms) and the community size fraction (small or large size fraction). The community was significantly different between the unenclosed fjord water and enclosed mesocosms (both control and elevated CO2 treatments) after nutrients were added to the mesocosms, suggesting that the addition of nutrients is the primary driver of the change in mesocosm community structure. The relative importance of each structuring variable depended greatly on the time at which the community was sampled in relation to the phytoplankton bloom. The sampling strategy of separating the small and large size fraction was the second most important factor for community structure. When the small and large size fraction bacteria were analysed separately at different time points, the only taxon pCO(2) was found to significantly affect were the Gammaproteobacteria after nutrient addition. Finally, pCO(2) treatment was found to be significantly correlated (non-linear) with 15 rare taxa, most of which increased in abundance with higher CO2.

Minor impact of ocean acidification to the composition of the active microbial community in an Arctic sediment

Effects of ocean acidification on the composition of the active bacterial and archaeal community within Arctic surface sediment was analysed in detail using 16S rRNA 454 pyrosequencing. Intact sediment cores were collected and exposed to one of five different pCO(2) concentrations [380 (present day), 540, 750, 1120 and 3000 atm] and RNA extracted after a period of 14 days exposure. Measurements of diversity and multivariate similarity indicated very little difference between pCO(2) treatments. Only when the highest and lowest pCO(2) treatments were compared were significant differences evident, namely increases in the abundance of operational taxonomic units most closely related to the Halobacteria and differences to the presence/absence structure of the Planctomycetes. The relative abundance of members of the classes Planctomycetacia and Nitrospira increased with increasing pCO(2) concentration, indicating that these groups may be able to take advantage of changing pH or pCO(2) conditions. The modest response of the active microbial communities associated with these sediments may be due to the low and fluctuating pore-water pH already experienced by sediment microbes, a result of the pH buffering capacity of marine sediments, or due to currently unknown factors. Further research is required to fully understand the impact of elevated CO2 on sediment physicochemical parameters, biogeochemistry and microbial community dynamics.

Organ damage in Atlantic herring larvae as a result of ocean acidification

The dissolution of anthropogenically emitted excess carbon dioxide lowers the pH of the world's ocean water. The larvae of mass spawning marine fishes may be particularly vulnerable to such ocean acidification (OA), yet the generality of earlier results is unclear. Here we show the detrimental effects of OA on the development of a commercially important fish species, the Atlantic herring (Clupea harengus). Larvae were reared at three levels of CO2: today (0.0385 kPa), end of next century (0.183 kPa), and a coastal upwelling scenario (0.426 kPa), under near-natural conditions in large outdoor tanks. Exposure to elevated CO2 levels resulted in stunted growth and development, decreased condition, and severe tissue damage in many organs, with the degree of damage increasing with CO2 concentration. This complements earlier studies of OA on Atlantic cod larvae that revealed similar organ damage but at increased growth rates and no effect on condition.

Living in warmer, more acidic oceans retards physiological recovery from tidal emersion in the velvet swimming crab, Necora puber

The distribution patterns of many species in the intertidal zone are partly determined by their ability to survive and recover from tidal emersion. During emersion, most crustaceans experience gill collapse, impairing gas exchange. Such collapse generates a state of hypoxemia and a hypercapnia-induced respiratory acidosis, leading to hyperlactaemia and metabolic acidosis. However, how such physiological responses to emersion are modified by prior exposure to elevated CO2 and temperature combinations, indicative of future climate change scenarios, is not known. We therefore investigated key physiological responses of velvet swimming crabs, Necora puber, kept for 14 days at one of four pCO(2)/temperature treatments (400 mu atm/10 degrees C, 1000 mu atm/10 degrees C, 400 mu atm/15 degrees C or 1000 mu atm/15 degrees C) to experimental emersion and recovery. Pre-exposure to elevated pCO(2) and temperature increased pre-emersion bicarbonate ion concentrations [HCO3-], increasing resistance to short periods of emersion (90 min). However, there was still a significant acidosis following 180 min emersion in all treatments. The recovery of extracellular acid-base via the removal of extracellular pCO(2) and lactate after emersion was significantly retarded by exposure to both elevated temperature and pCO(2). If elevated environmental pCO(2) and temperature lead to slower recovery after emersion, then some predominantly subtidal species that also inhabit the low to mid shore, such as N. puber, may have a reduced physiological capacity to retain their presence in the low intertidal zone, ultimately affecting their bathymetric range of distribution, as well as the structure and diversity of intertidal assemblages.

Sperm motility and fertilisation success in an acidified hypoxic environment

The distribution and function of many marine species is largely determined by the effect of abiotic drivers on their reproduction and early development, including those drivers associated with elevated CO2 and global climate change. A number of studies have therefore investigated the effects of elevated pCO2 on a range of reproductive parameters, including sperm motility and fertilisation success. To date, most of these studies have not examined the possible synergistic effects of other abiotic drivers, such as the increased frequency of hypoxic events that are also associated with climate change. The present study is therefore novel in assessing the impact that an hypoxic event could have on reproduction in a future high CO2 ocean. Specifically, this study assesses sperm motility and fertilisation success in the sea urchin Paracentrotus lividus exposed to elevated pCO2 for 6 months. Gametes extracted from these pre-acclimated individuals were subjected to hypoxic conditions simulating an hypoxic event in a future high CO2 ocean. Sperm swimming speed increased under elevated pCO2 and decreased under hypoxic conditions resulting in the elevated pCO2 and hypoxic treatment being approximately equivalent to the control. There was also a combined negative effect of increased pCO2 and hypoxia on the percentage of motile sperm. There was a significant negative effect of elevated pCO2 on fertilisation success, and when combined with a simulated hypoxic event there was an even greater effect. This could affect cohort recruitment and in turn reduce the density of this ecologically and economically important ecosystem engineer therefore potentially effecting biodiversity and ecosystem services.