华北地区油松林生态系统对气候变化和CO2浓度升高的响应——基于BIOME-BGC模型和树木年轮的模拟

应用BIOME-BGC模型和树木年轮数据模拟1952-2008年华北地区典型油松林生态系统净初级生产力(NPP)动态,探究了树木径向生长和NPP对区域气候变暖的响应以及未来气候情景下油松林生态系统NPP动态变化.结果表明:1952-2008年,研究区油松林生态系统NPP波动于244.12 ～645.31 g C·m-2·a-1,平均值为418.6 g C·m-2·a-1.5-6月的平均温度和上年8月至当年7月的降水是限制该地区油松径向生长和油松林生态系统NPP的主要因子.研究期间,随着区域暖干化趋势的加强,树木径向生长和生态系统NPP均呈下降趋势.未来气候情景下,NPP对温度和降水的单独和复合变化的响应为正向.CO2浓度升高有利于油松林生态系统NPP的增加,CO2的施肥效应使NPP增加16.1％.在生态系统和区域水平,树木年轮是一种理想的指示生态系统动态变化的代用资料,可以检验和校正包括BIOME-BGC模型在内的各种生态系统过程模型.     

华北地区油松林生态系统对气候变化和CO2浓度升高的响应——基于BIOME-BGC模型和树木年轮的模拟

应用BIOME-BGC模型和树木年轮数据模拟1952-2008年华北地区典型油松林生态系统净初级生产力（NPP）动态,探究了树木径向生长和NPP对区域气候变暖的响应以及未来气候情景下油松林生态系统NPP动态变化.结果表明：1952-2008年,研究区油松林生态系统NPP波动于244.12～645.31 g C·m^-2·a^-1,平均值为418.6 g C·m^-2·a^-1.5-6月的平均温度和上年8月至当年7月的降水是限制该地区油松径向生长和油松林生态系统NPP的主要因子.研究期间,随着区域暖干化趋势的加强,树木径向生长和生态系统NPP均呈下降趋势.未来气候情景下,NPP对温度和降水的单独和复合变化的响应为正向.CO₂浓度升高有利于油松林生态系统NPP的增加,CO₂的施肥效应使NPP增加16.1%.在生态系统和区域水平,树木年轮是一种理想的指示生态系统动态变化的代用资料,可以检验和校正包括BIOME-BGC模型在内的各种生态系统过程模型.     

盐胁迫对桑树幼苗生长、叶片水分状况和离子分布的影响

以黑龙江省两个桑树品种（秋雨桑和泰来桑）为试验材料,研究了不同盐浓度下桑树幼苗生长、叶片水分关系和不同器官中离子的分布.结果表明：盐胁迫明显降低了桑树幼苗的植株高度和每株干物质量,且对新生叶片干质量的影响大于老叶片.随着盐胁迫的加重,两个品种桑树的叶片水势、渗透势、压力势和相对含水量明显下降,根、茎中Na⁺浓度明显增加,当外界NaCl浓度达到或超过150 mmol·L^-1时,各器官中Na⁺浓度达到饱和.盐胁迫明显降低了两个品种桑树根、茎和叶片中K⁺ 和 Ca²⁺浓度,以及茎和叶片中Mg²⁺浓度,而对根中Mg²⁺浓度影响不大.Na⁺在根、茎和老叶中的区域化分布是两个品种桑树生长过程中表现出耐盐性的机理之一,而盐胁迫使叶片中的Ca²⁺、K⁺和Mg²⁺浓度降低,导致植株体内的离子亏缺,从而限制了植株的生长.     

1958-2008年太白山太白红杉林碳循环模拟

太白红杉(Larix chinensis林主要分布于我国秦岭太白山的林线位置,对气候变化的响应十分敏感.为了定量分析太白山太白红杉林在气候变化背景下的碳循环特征,基于模型(MTCLIM)模拟的温度和降水数据,应用植被动态过程模型(LPJ-GUESS)模拟了太白山南北坡1958-2008年太白红杉林的净初级生产力(NPP)、生物量和净生态系统碳交换量(NEE).结果表明:1)太白红杉和巴山冷杉(Abies fargesii)的NPP和生物量在太白红杉林占有优势,太白红杉的NPP和生物量均大于巴山冷杉.1958-2008年间太白红杉南北坡NPP的平均值为0.38 kgC·m-2·a-1,巴山冷杉为0.25 kgC·m-2,a-1,两者之和占整个太白红杉林NPP的86％;1958-2008年间太白红杉南北坡生物量的平均值为2.91 kgC/m2,巴山冷杉为2.02 kgC/m2,两者之和占太白红杉林生物量的94％.2)太白红杉和巴山冷杉的NPP均表现为北坡大于南坡,且南北坡均有逐年增加的趋势,北坡的增幅小于南坡,所以太白山南北坡太白红杉林的NPP差异有逐年减少的趋势.3)太白红杉生物量的年际波动较大,南北坡呈交替上升趋势,南坡的平均值(2.94 kgC/m2)大于北坡(2.89 kgC/m2).巴山冷杉生物量的年际波动相对较小,北坡生物量水平大于南坡.4)1958-2008年南北坡太白红杉林平均NEE均为-0.023 kgC·m-2·a-1,表现为碳汇.南北坡碳汇水平均呈逐年增加趋势,南坡的增加幅度(0.91 g·m-2·a-1)大于北坡(0.42 g·m-2·a-1).以气候和CO2为驱动因子对太白山太白红杉林的长期碳循环动态做了定量分析,从机理上揭示气候变化与生态系统碳循环的关系,还需要做进一步的野外观测和控制实验研究.     

秦岭山地植被净初级生产力及对气候变化的响应

基于1999~2009年的NDVI数据和气象数据,利用CASA模型对秦岭山地植被净初级生产力（Net primary productivity,NPP）进行模拟估算,并分析了秦岭NPP的时空变化特征及其对气候变化的响应。结果表明：1999~2009年11年间秦岭山地的平均年NPP为542.24 gC·m^-2·a^-1;研究期内秦岭NPP呈显著增长趋势（P<0.01）,2008年最高（718.77 gC·m^-2·a^-1）,2001年最低（471.78 gC·m^-2·a^-1）;四季对全年NPP的贡献率大小依次为夏季（49.90%）>春季（26.16%）>秋季（18.87%）>冬季（5.07%）;月NPP与温度和降水都显著相关,但与温度的相关性更高,月水平上温度对NPP的影响比降水大;生长季期间NPP与温度和降水的相关性在空间分布上都以正相关为主。     

1982—2015年气候变化和人类活动对内蒙古草地净初级生产力的影响

研究1982—2015年气候变化和人类活动对内蒙古草地净初级生产力(NPP)的影响。结果表明: 1982—1998年和1999—2015年2个时期,内蒙古草地实际NPP(ANPP)增长速率分别为1.08和1.36 g C·m^-2·a^-1,草地以恢复为主,2个时期草地恢复面积分别占研究区总面积的81.6%和76.3%;草地退化面积有增加趋势,且气候变化和人类活动对不同类型草地的影响不同。2个时期气候变化对草地恢复贡献率分别为79.3%和94.1%,气候变化是草地恢复的主要因素,其中,ANPP与降水呈显著正相关,而与温度的相关性不显著,表明降水是影响草地恢复的主要气候因子。2个时期人类活动对草地退化的贡献率分别为83.3%和87.8%,说明人类活动是导致草地退化的主要原因。气候变化对内蒙古草地恢复起主导作用,而人类活动诸如放牧数量、耕地面积和造林面积的增加,加速了草地退化。     

1981—2000年中国陆地生态系统碳通量的年际变化

应用一个生物地球化学模型(CEVSA)估算了中国陆地净初级生产力(NPP)、土壤异养呼吸(HR)和净生态系统生产力(NEP)在1981—1998年期间对气候和大气CO2浓度变化的动态响应。结果显示,全国NPP总量波动于2．89—3．37Gt／a之间,平均值为3．09Gt C／a,年平均增长趋势约为0．32％。HR总量变化范围为2．89—3．21Gt C／a,平均值为3．02Gt C／a,年均增长0．40％。NEP总量变动于-0．32和0．25Gt C／a之间,在统计上没有明显的年际变化趋势。在研究时段内,年平均NEP约为0．07Gt C／a,表明中国陆地生态系统在气候与大气CO2浓度变化的条件下吸收了碳,为碳汇,总的吸收量为1．22Gt C,约占全球碳吸收总量的10％,与同期内美国由大气CO2和气候变化所产生的碳吸收量大致相当。尽管由于较高的年际变率,NEP在统计上没有明显的变化趋势,但NPP的增长率低于HR的增长率,说明在研究时段内,中国陆地生态系统的吸碳能力由于气候变化降低了。全国大多数地区年平均NEP接近零,明显的NEP正值区(即碳汇)出现在东北平原、西藏东南部和黄淮平原等地区,而大小兴安岭、黄土高原和云贵高原等地区NEP为负值(即碳源)。研究认为,1981～1998年期间中国气候温暖、干旱,因此估算的NEP可能低于其他时段。如果气候进入一个比较湿润的时期,碳吸收量可显著增加,但若当前干旱和暖化趋势以此为继,中国的NEP可能会变成一个负值。     

Temporal and spatial variation characteristics of China shrubland net primary production and its response to climate change from 2001 to 2013

Aims Net primary production (NPP) is the input to terrestrial ecosystem carbon pool. Climate and land use change affect NPP significantly. Shrublands occupy more than 20% of the terrestrial area of China, and their NPP is comparable to those of the forests. Our objective was to estimate China shrubland NPP from 2001 to 2013, and to analyze its variation and response to climate change.Methods We used a Carnegie-Ames-Stanford Approach (CASA) model to estimate the NPP of six shrubland types in China from 2001 to 2013. Furthermore, we used Theil-Sen slope combined with Mann-kendall test to analyze its spatial variation and a linear regression of one-variable model to analyze its inter- and intra-annual variation. Finally, a multi-factor linear regression model was used to analyze its response to climate change.Important findings We found the annual mean NPP of China shrubland was 281.82 g•m^-2•a^-1. The subtropical evergreen shrubland has the maximum NPP of 420.47 g•m^-2•a^-1, while the high cold desert shrubland has the minimum NPP of 52.65 g•m^-2•a^-1. The countrywide shrublands NPP increased at the rate of 1.23 g•m^-2•a^-1, the relative change rate was 5.99%. The temperate deciduous shrubland NPP increased the fastest with a speed of 3.05 g•m^-2•a^-1 and subalpine evergreen shrubland had a decreasing trend with a speed of -0.73 g•m^-2•a^-1. Moreover, the other four shrublands NPP had a growing trend, only subalpine deciduous shrubland NPP did not change significantly. The response of NPP to climate change of different seasons varies to different shrubland types. In general, the NPP variation was mainly affected by precipitation, and the spring warming also contributed to it. The increase of countrywide shrubland NPP may promote its contribution to the regional ecosystem function.     

陕西省油松林生产力动态及对未来气候变化的响应

本研究利用LPJ-GUESS模型,分析了陕西省油松林在未来时期(2015-2100年)不同气候情景下净初级生产力(NPP)的变化趋势.结果表明: 在未来时期,研究区温度在RCP_2.6、RCP_4.5和RCP_8.5情景下将分别以0.12、0.23和0.54 ℃·10 a^-1的速率显著升高;降水在RCP_2.6和RCP_8.5情景下无显著变化,在RCP_4.5情景下将以14.36 mm·10 a^-1的速率显著增加.与历史时期(1961-1990年)相比,研究区油松林的NPP在未来时期将升高1.6%~29.6%;在RCP_8.5情景下21世纪末期(2071-2100年)油松林NPP将会升高45.4%;不同情景下油松林NPP表现为RCP_8.5＞RCP_4.5＞RCP_2.6.在未来时期,陕北地区油松林NPP在RCP_2.6和RCP_4.5情景下将分别以41.00和21.00 g C·m^-2·10 a^-1的速率下降,该区油松林有变为碳源的可能.     

吉林省落叶松林净初级生产力时空特征及其对气候变化的响应

为评估吉林省落叶松林的生产力现状并为我国森林生态系统生产力和植被监测研究提供基础数据,以吉林省落叶松林为研究对象,基于吉林省及其周边100 km范围内41个气象站点资料,采用LPJ-DGVM模型模拟了2000—2019年吉林省落叶松林近20年的净初级生产力,并采用线性回归趋势分析、变异系数、Hurst指数和相关性分析法对其时空变化、稳定性及其与气候因子的相关关系进行了分析。结果表明：(1)2000—2019年吉林省落叶松林年均净初级生产力(NPP)为592 g C m^-2 a^-1,年均增长率为2.81%,随时间推移呈现波动增长的趋势(β=14.55,R~2=0.784,P<0.01)。(2)NPP变异系数为0.07—2.33,均值为0.48,除幼龄林外,整体波动较小。Hurst指数介于0.441—0.849之间,均值为0.612,未来吉林省落叶松林NPP呈增加趋势。(3)吉林省落叶松林NPP存在明显的空间异质性,北部和南部区域NPP较高,是近20年NPP增长较快的区域。(4)2000—2019年吉林省落叶松林年均NPP与年总降水、生长季...     

Effect of nitrogen on thiocyanate content of Brassica oleracea var. acephala leaves

An experiment was carried out to study the effect of nitrogen fertilizer application levels (0, 47, 94 and 188 kg N/ha) on thiocyanate contents of petioles and lamina of two Brassica oleracea L. var. acephala varieties (Thousand-headed kale and Georgia collards).The results showed that N application significantly decreased thiocyanate contents of both laminae and petioles. Applying 47, 94, 188 kg N/ha reduced thiocyanate of laminae and petioles by 26, 41 and 52% and 2, 9 and 39%, respectively. The results also showed that thiocyanate of leaves from Thousand-headed kale was significantly higher than that of Georgia collards. Lamina and petiole thiocyanates of Georgia collards were 79% and 83% of those of Thousand-headed kale, respectively.     

Ultrastructural Study in Leaf Cell of Brassica oleracea var. capitata Under Heat Stress

Ultrastructural changes of the leaf cells in response to heat stress in thermo-resistant cultivar and thermo-sensitive cultivar of Brassica oleracea var. capitata L. were investigated. No ultrastructural change was shown in mesophyll cell of the thermo-resistant cultivar. All membrane-bound structure remained intact. However, the cell ultrastructure of thermosensitive cultivar showed significant changes. One of the major effects of heat stress was the disruption of membrane structure. Chloroplasts and nucleus were extremely sensitive to heat stress. Chloroplasts rounded off in different extents and their outer membranes disappeared. Structural alteration of the thylakoid membrane were visualized. Large amount of plastoglobulis appeared within the chloroplast. Mitochondria were far more resistant to heat stress than chloroplasts. There was no distinct changes of mitochondria structure. Nucleus suffered from serious damage as heat caused disruption of nuclear envelope and condensation of nucleoplasm, showing, eventually, numerous fibrillar granulous material and irregularly shaped hollow spaces presented within the nucleus.     

Control of isoperoxidases involved in chlorophyll degradation of stored broccoli (Brassica oleracea) florets by heat treatment

Changes in isoperoxidases involved in chlorophyll (Chl) degradation of stored broccoli (Brassica oleracea L.) florets and their control by heat treatment (HT) were determined. Chl a and b contents in non-heat-treated broccoli florets decreased greatly after 2 days at 15 degrees C, whereas the contents in heat-treated florets (50 degrees C for 2 h) showed almost no change. Three isoperoxidases involved in Chl degradation were detected by means of molecular exclusion chromatography and the molecular weights of those isoperoxidases were about 95 (Type I), 67 (Type II) and 56 (Type III) kDa, respectively. Only Type I was detected in broccoli florets immediately after harvest, and its activity in non-heat-treated broccoli increased greatly during storage. Both Type II and Type III were present in non-heat-treated broccoli with floret senescence. HT suppressed the enhancement of all of the isoperoxidase activities. Cycloheximide treatment also effectively retarded the increase in Types I, II and III isoperoxidase activities concomitant with the suppression of floret yellowing. The K(m) values corresponding to Chl a of Type II and Type III were lower than Type I, and the V(max)/K(m) values corresponding to Chl a of Type II and Type III were higher than Type I. This suggests that both Types II and III could be closely associated with Chl degradation in broccoli florets and that HT might inhibit floret senescence by suppression of isoperoxidase activities.     

Brief carbon dioxide exposure blocks heat hardening but not cold acclimation in Drosophila melanogaster

Carbon dioxide is a commonly used anaesthetic in Drosophila research. While any detrimental effects of CO2 exposure on behaviour or traits are largely unknown, a recent study observed significant effects of CO2 exposure on rapid cold hardening and chill-coma recovery in Drosophila melanogaster. In this study we investigated the effect of a brief CO2 exposure on heat hardening and cold acclimation in D. melanogaster, measuring heat knockdown and chill-coma recovery times of flies exposed to CO2 for 1 min after hardening or acclimation. CO2 anaesthesia had a significant negative effect on heat hardening, with heat knockdown rates in hardened flies completely reduced to those of controls after CO2 exposure. Chill-coma recovery rates also significantly increased in acclimated flies that were exposed to CO2, although not to the same extent seen in the heat populations. CO2 exposure had no impact on heat knockdown rates of control flies, while there was a significant negative effect of the anaesthetic on chill-coma recovery rates of control flies. In light of these results, we suggest that CO2 should not be used after hardening in heat resistance assays due to the complete reversal of the heat hardening process upon exposure to CO2.     

Quantitative genetic analysis of seed vigour and pre-emergence seedling growth traits in Brassica oleracea

The ability of seeds to germinate and establish seedlings in a predictable manner under a range of conditions has a direct contribution to the economic success of commercial crops, and should therefore be considered in crop improvement. We measured traits associated with seed vigour and pre-emergence seedling growth in a segregating population of 105 doubled haploid Brassica oleracea lines. The germination traits measured were: mean germination times for unstressed germination; germination under water stress or germination after a heat treatment; and conductivity of seed leachate. The seedling growth traits measured were: seed weight; seedling growth rate; and seedling size at the end of the exponential growth phase. There were some correlations, notably among germination traits, and between seed weight and pre-emergence seedling growth. Heritability of the various traits was typically in the 10–15% range, with heritability of conductivity and mean germination time under water stress 25 and 24% respectively. Collectively the results indicate that germination and pre-emergence seedling growth are under separate genetic control. Quantitative trait loci analyses were carried out on all measurements and revealed significant loci on linkage groups O1, O3, O6, O7 and O9. We suggest that genes at these loci are important in determining predictable seed germination and seedling establishment in practice.     

A two-photon excitation study on the role of carotenoid dark states in the regulation of plant photosynthesis

Plants are exposed to sun light intensities that vary rapidly over several orders of magnitude during a typical day. It is known that the regulation of photosynthetic activity under these circumstances is essential for the survival and fitness of natural and gene modified plants. A quick balancing between utilization and dissipation of absorbed light energy ensures optimized levels of CO₂ fixation and protection from photo damage by excessive light-irradiation. Despite intensive investigations the biophysical mechanisms of these regulation processes are still poorly understood. Potentially involved singlet states of carotenoids are optically “dark” and so far it was impossible to investigate their role directly in living plants by conventional absorption or fluorescence spectroscopy. Here, we show by selective two-photon excitation of the carotenoid dark states in planta that a dominant part of the regulation is correlated with a substantial change in the energy transfer between these states and the chlorophylls (Chl). The results support a considerable role of the molecular gear shift model in which a reversible and step-wise enzymatic modification of the electronic structure of xanthophyll carotenoids enables a switching between carotenoid-to-Chl light-harvesting and Chl-to-carotenoid quenching. The shifting can be observed in real time in any plant. Treatment with the xanthophyll cycle inhibitor dithiothreitol slowed down both the light adaptation and the carotenoid–Chl energy flow changes to the same extent. Based on these results, we propose a biophysical quenching model in which both carotenoid dark states and radical cations contribute to the dissipation of excessive excitation energy. An erratum to this article can be found at     

Effect of carbon dioxide and relative humidity on self incompatibility in cauliflower,Brassica oleracea

Summary The events of the progamic phase of fertilization have been monitored by in vitro experiments in self compatible (SC), partial self-incompatible (PSI) and self incompatible (SI) lines. The duration of the progamic phase is about 30 h. Treatment with low concentrations of CO₂ (3 to 5%) at high relative humidity (rH, 100%) had the following effects: pollen quality, which declines normally during flower ageing, was prematurely reduced; pollen adhesion and germination, both low in SI matings, were increased; the stigma callose response in SI matings was reduced to the low level of SC matings; and the number of pollen tubes in the style after SI matings significantly increased. CO₂ concentrations of 4 to 6% applied for 8, 16 or 24 h at 100% rH proved to be the most effective treatment for blocking the SI response in cauliflower.     

Effect of regeneration procedures on the genetic integrity of Brassica oleracea accessions

A Brassica oleracea collection of landraces collected in the northwest of Spain is kept at the Gene Bank placed at ‘Misión Biológica de Galicia’. Landraces of the collection are regenerated from time to time to restore the viability of the seed and to carry on field trials. The objective of this work is to study the effect of regeneration on the genetic integrity of three accessions of this collection, and to investigate the possible causes of the genetic changes observed. After characterizing the original populations and their following regenerated populations by 25 SSRs we concluded that there were significant changes in the population structure and the allelic frequency of individual loci due to the action of genetic drift, directional selection and probably assortative mating. Protocols to store and regenerate the accessions should be improved in order to avoid the effect of these forces in the genetic integrity of the collection. Research supported by the project PIE20064-01-089 and the Excma. Diputación Provincial de Pontevedra, Spain.     

辐照对青花菜生理生化指标及保鲜效果的影响

用0.08mm厚的聚乙烯薄膜袋包装青花菜,经0.5、1.5和2.5 kGy(千戈瑞)3个剂量⁶⁰Co-γ射线辐照,室温12~21℃贮藏。结果显示,2.5 kGy剂量辐照对青花菜的保鲜效果最佳,室温下放置7d,仍然保持鲜绿,而对照组3d已全部变黄,无商品价值。辐照后立即对2.5kGy处理组的青花菜进行生理生化分析,其蛋氨酸含量、乙烯释放率、呼吸强度等指标均比对照组显著降低;叶绿素、花青素、维生素C、还原糖及蛋白质含量等指标与对照组相比较变化不大。辐照保鲜7d后,乙烯释放量、呼吸强度及蛋氨酸含量都升至辐照前的水平;蛋白质、维生素C、还原糖、叶绿素和花青素含量比对照组高。由此表明,辐照造成的生理损伤已修复,不宜再继续贮藏。