橡胶林下益智光合特性的季节动态变化

利用农林复合模式发展生态农业可提高资源利用效率, 橡胶(Hevea brasiliensis)-益智(Alpinia oxyphylla)间作模式是橡胶园最主要的农林复合模式。该研究通过野外原位定位实验, 研究不同季节橡胶林下环境因子对益智光合作用的影响, 并进一步分析益智光合作用与主要环境因子的关系。结果表明: (1) 3月益智净光合速率日变化为“V”形曲线, 14:00降到最低值; 而6月、9月和12月益智净光合速率日变化趋势为10:00达到最大值, 随后缓慢降低; 在雨季(6月和9月)蒸腾速率的日平均值和日最高值均显著高于旱季(3月和12月)。表明林下益智在不同季节均能维持植株正常生长, 且表现出了较强的适应能力。3月土壤水分亏缺造成益智叶片气孔导度降低, 使其净光合速率维持在较低的水平。(2)通过光响应曲线修正模型计算出益智叶片各光合响应参数, 发现3月最大净光合效率和光饱和点显著低于6月、9月和12月; 而光补偿点和暗呼吸速率却显著高于6月、9月和12月, 表明3月土壤水分亏缺导致益智光合酶活性降低, 而表现出光抑制现象, 同时呼吸强度加剧, 光合能力显著下降。(3)采取相关分析发现, 3月气温与净光合速率显著负相关, 空气湿度与净光合速率显著正相关, 高温和低湿度共同限制了益智的光合作用; 而9月和12月, 林下光合有效辐射是益智光合作用的限制因子。     

运用SmartRoot测量橡胶树细根

SmartRoot是基于开放源ImageJ的免费根系分析软件, 通过软件分析根系照片可得到细根长度、表面积、体积和平均根直径等指标。该文以橡胶树(Hevea brasiliensis)细根为例, 探索利用SmartRoot分析细根不同形态特征的可能性。用不同拍照距离与分析方式的对比确定橡胶树细根适合的研究方法, 用WinRhizo软件分析结果验证结果的准确性。结果表明, 不同拍摄高度下对应的细根长度、表面积、体积和平均根直径等指标的标准均方根误差(NRMSE)分别为2.87%、15.73%、32.38%和16.88%; 手动分析与半自动分析相同照片细根长度、表面积、体积和平均根直径等指标的NRMSE分别为3.06%、21.00%、 40.96%和11.64%; 用WinRhizo软件验证SmartRoot分析细根长度、表面积、体积和平均根直径等指标结果NRMSE分别为5.31%、9.37%、9.61%和5.77%。本研究表明, 在适当方法下, 拍照法结合SmartRoot软件分析测量橡胶树细根细根长度、表面积、体积和平均根直径等指标有较高的准确度, 可用于橡胶树细根指标的分析。     

Impact of climate change on suitable distribution range and spatial pattern in Amygdalus mongolica

为模拟、预测气候变化对孑遗、濒危植物蒙古扁桃(Amygdalus mongolica)潜在分布的影响, 利用最大熵(MAXENT)模型模拟、预测、对比、分析、揭示蒙古扁桃在最大冰期(CCSM及MIROC模型)、历史气候(1961-1990年)及未来气候(2020年、2050年和2080年, 政府间气候变化专门委员会排放情景特别报告的A2A情景)条件下的适宜分布范围和空间格局的变化。结果表明: (1)蒙古扁桃在历史气候条件下的潜在分布区集中在蒙古的南戈壁省及东戈壁省, 我国内蒙古巴彦淖尔市、阿拉善左旗、鄂尔多斯市、锡林郭勒盟西部, 河西走廊中部及东部, 宁夏北部及陕西北部, 以及河北北部的部分地区; (2)与历史气候条件下的潜在分布相比, 蒙古扁桃在最大冰期CCSM气候情景下的分布经历了明显的、大范围的向南迁移和范围缩小; (3)未来A2A气候情景下, 其潜在分布范围表现出在2020年明显扩大, 在2050年减小, 到2080年又略有增大的趋势。分布格局表现出不断向我国河北及内蒙古东部, 蒙古东部、北部及西部大幅度扩散、迁移的趋势。     

Enzymatic formation and esterification of (S)-mandelonitrile

The (S)-selective hydroxynitrile lyase from Hevea brasiliensis (HbHNL) catalyzes the trans-cyanohydrin reaction (transcyanation). The equilibrium of this two-step reaction sequence is not favorable unless a large excess of acetone cyanohydrin (1) is used. Therefore, the coupling of this reaction with a follow-up reaction was investigated. It was established that the trans-cyanohydrin reaction could be performed in organic media, making it possible to couple it with a lipase-catalyzed acylation. Candida antarctica lipase B (CAL-B) shows a high selectivity (E=100) for (S)-mandelonitrile (4) and is, therefore, the ideal candidate for this type of multi-step one-pot reaction.     

Effects of climate change on net primary productivity in Larix olgensis plantations based on process modeling

Aims Climate change has significant effects on net primary productivity (NPP) in forests, but there is a large uncertainty in the direction and magnitude of the effects. Process-based models are important tools for understanding the responses of forests to climate change. The objective of the study is to simulate changes in NPP of Larix olgensis plantations under future climate scenarios using 3-PG model in order to guide the management of L. olgensis plantations in the context of global climate change.Methods Data were obtained for 30 permanent plots of L. olgensis plantations in Siping, Linjiang, Baishan, etc. of Jilin Province, and a process model, 3-PG model, was applied to simulate changes in NPP over a rotation period of 40 years under different climate scenarios. Parameter sensitivity was also determined. Important findings The locally parameterized 3-PG model well simulates the changes in NPP against the measured NPP data, with values between 272.79-844.80 g·m^-2·a^-1 and both mean relative error and relative root mean square error within 12%. The NPP in L. olgensis plantations would increase significantly with increases in atmospheric CO₂ concentration, temperature and precipitation collectively. However, an increase in temperature alone would lead to a decrease in NPP, but increases in precipitation and atmospheric CO₂ concentration would increase NPP; the positive effect of increasing precipitation appears to be weaker than the negative effect of increasing temperature. Sensitivity analysis shows that the model performance is sensitive to the optimum temperature, stand age at which specific leaf area equals to half of the sum of specific leaf area at age 0 (SLA₀) and that for mature leaves (SLA₁), and days of production loss due to frost.     

阿尔泰山西伯利亚落叶松径向生长对气候变化的分异响应

在全球气候变暖的背景下, 北半球中高纬度地区出现了树轮径向生长对气候变化的分异响应现象, 但是阿尔泰山优势针叶树种对气候因子响应的稳定性还存在不确定性。该研究选择阿尔泰山中段高海拔西伯利亚落叶松(Larix sibirica)样本建立了树轮宽度年表, 并对年表特征及树木径向生长-气候的动态关系进行了分析。结果表明: 生长季初期和中期的气温是研究区树木生长的主控气候因子; 树木径向生长与当年4月的气温显著负相关, 与当年6-7月的气温显著正相关; 研究区西伯利亚落叶松径向生长与当年4月和6-7月的气温发生了分异现象, 表现为随着气候变化, 树木径向生长对生长季初期由高温引起的干旱的响应敏感性越来越强, 而对生长季中期气温的敏感性表现出先减弱再增强的趋势。阿尔泰山西伯利亚落叶松径向生长对气候变化的响应比较敏感, 适合开展树木生长-气候变化的研究; 检验树木径向生长对气候变化分异响应为该区域基于树木年轮开展历史气候重建和提高未来森林生态系统发展趋势预测的准确性提供了科学依据。     

Responses of the distribution pattern of Quercus chenii to climate change following the Last Glacial Maximum

Aims Quercus chenii is a representative species of the flora in East China, with high ecological and economic values. Here, we aim to simulate the changes in the distribution pattern of this tree species following the Last Glacial Maximum (LGM) and to explore how climatic factors constrain the potential distribution, so as to provide scientific basis for protection and management of the germplasm resources in Q. chenii.
Methods Based on 55 presence point records and data on eight environmental variables, we simulated the potential distribution of Q. chenii during the Last Glacial Maximum, mid-Holocene, present and the year 2070 (the scenario of greenhouse gas emission is Representative Concentration Pathway 8.5) with MaxEnt model. The novel climate area and main factors influencing the changes in distribution pattern were evaluated by multivariate environmental similarity surface analysis and the most dissimilar variable analysis. The importance of environmental variables was evaluated by percent contribution, permutation importance and Jackknife test. Response curves were used to estimate the suitable value range of each variable.
Important findings The accuracy of MaxEnt model is very high, as indicated by the value of the area under the receiver operator characteristic curve of 0.9869 ± 0.0045. The highly suitable region for the present distribution covers southern Anhui, western Zhejiang, northeastern Jiangxi and eastern Hubei. The main factors affecting the potential distribution of Q. chenii are temperature and precipitation, with the former being more important. Mean temperature of the driest quarter is likely the main factor restricting Q. chenii growing in the north. During the LGM, the East China Sea Shelf occurs as the highly suitable region for the distribution of Q. chenii. In the mid-Holocene, the outline of the suitable area for the distribution of Q. chenii is similar to the present. The potential distribution region will likely move northward and experience an area expansion under the climate condition in 2070. At that time, climate anomaly will also be most severe compared to the LGM, mid-Holocene and present. Temperature seasonality and precipitation seasonality may be the main climatic factors promoting changes in the distribution pattern of Q. chenii.     

Carbon,nitrogen and phosphorus stoichiometry of Myrica nana in Yunnan,China

Aims Carbon (C), nitrogen (N) and phosphorus (P) play important roles in plant growth and physiological functions. We aimed at exploring the intrinsic relationships of C, N and P in Myrica nana—a common shrub in Yunnan Province—as well as their relationships with pant biomass and soil nutrients.
Methods We measured the concentration of C, N and P of M. nana from 29 sites for their magnitudes and correlations with soil nutrients.
Important findings 1) The arithmetic mean value of C, N and P concentration in the roots, stems and leaves of M. nana was 45.94%, 0.54%, 0.03%, and 46.32%, 0.58%, 0.03%, and 49.05%, 1.70%, 0.06%, respectively. C, N and P concentrations in the leaves were significantly higher than those in the roots and the stems. The C:N:P in roots, stems and leaves was 1531:18:1, 1544:19:1, and 818:10:1, respectively. 2) The C concentration and N:P in leaves of M. nana decreased with the increase of biomass of M. nana; the leaf C concentration was significantly correlated with biomass (p < 0.01), while the correlation between N:P and biomass was not significant (p > 0.05). The leaf N increased with the increase of plant biomass, the P was significantly correlated with biomass (p < 0.05), but the correlation between N concentration and biomass was not significant (p > 0.05). N:P in leaves was 34.2, suggesting that plant growth was limited by P. 3) C, N and P concentration in the roots were significantly correlated with soil P (p < 0.05), with N, P concentrations correlated with soil P positively (p < 0.01) and C negatively (p < 0.05). C concentration in the stems was significantly and negatively correlated with soil C, N, with significant correlation with C, N, and P concentration (p < 0.01). P concentration in the stems was significantly and positively correlated with soil P concentration (p < 0.01), while leaf P significantly and positively correlated with soil C, N and P (p < 0.01); leaf C concentration was significantly and negatively correlated with soil P (p < 0.01).     

Predicting phenology shifts of herbaceous plants on the Qinghai-Xizang Plateau under climate warming with the space-for-time method

气候变暖背景下的植物物候变化广受关注, 然而常用的植物物候变化预测模型未充分考虑植物对环境的适应性, 给预测结果带来了较大的不确定性。该文基于2002-2011年青藏高原10个站点的地面物候观测资料以及年平均气温数据, 对空间换时间模型预测车前(Plantago asiatica)和蒲公英(Taraxacum mongolicum)各主要物候事件(展叶始期、开花始期和黄枯普遍期)变化的可行性及其在升温背景下的变化规律进行了分析。首先利用不同海拔高度的气温和物候事件分别与地理因子(经度、纬度和海拔)建立多元线性回归模型, 然后在此基础上剔除经度和纬度的影响, 单独考察海拔变化所引起的气温与植物物候变化, 最后以海拔高度作为桥梁来考察物候变化与温度变化的关系。结果表明, 采用各站点对应的海拔高度来模拟年平均气温空间差异的R²均大于0.89, 表明海拔梯度可以用来反映时间尺度下的年际温度变化; 车前和蒲公英各物候事件发生日期拟合值均与海拔高度变化关系显著, R²均大于0.70, 表明海拔变化是影响它们各物候事件变化的主要地理因子; 在物候事件发生日期拟合值和年平均气温拟合值的回归方程中, R²均大于0.93, 说明基于不同海拔高度模拟得到的年平均气温变化可以对时间尺度上车前和蒲公英的物候事件变化进行预测。空间换时间预测表明, 温度每升高1 ℃, 车前展叶始期和开花始期分别提前5.1和5.4 d, 而黄枯普遍期推迟4.8 d; 蒲公英展叶始期和开花始期分别提前6.5和7.8 d, 而黄枯普遍期推迟6.7 d。     

Physiological responses and photo-protective mechanisms of two Rhododendron plants to natural sunlight after long term shading

AimsResponses of plants to increased irradiance are governed by two strategies: an increase in the utilization of absorbed light and photo-protective mechanisms. Varied physiological responses to increased irradiance were observed in plant species with differing adaptabilities to light regimes. This research aims to explore the physiological responses and photo-protective mechanisms of two Rhododendron plants to changes in light regimes. MethodsChlorophyll fluorescence parameters and rapid light curves were measured for leaves of R. hybrida (a shade-tolerant species) and R. simsii (a light-loving and shade-tolerant species) following exposure to sunlight for five days after growing in the shade for one year.Important findings Natural sunlight decreased the efficiency of photochemical reaction by reducing the fraction of incident light in photochemical energy utilization and decreased thermal dissipation through regulating energy dissipation in photosystem II (PSII) in the leaves of R. hybrida. As a result, natural sunlight induced the accumulation of excess excitation energy in PSII, and caused photo-inhibition and even photodamage in the leaves of R. hybrida, which was suddenly transferred from long-term shading to sun exposures. The acclimation capacity to changes of growth light regimes was stronger in R. simsii than in R. hybrida, due to a higher capability for photochemical reaction, thermal dissipation and cyclic electron flows around photosystem I in the leaves of R. simsii. Rhododendron simsii could utilize a high fraction of incident light in photochemistry and regulate energy dissipation in PSII to protect the photosynthetic apparatus under both shading and natural sunlight condition. Therefore, high light intensity under natural sunlight did not cause photo-inhibition in R. simsii.     

Gender-specific characteristics of tree-ring growth and differential responses to climate change in the dioecious tree Populus cathayana in Xiaowutai Mountains,China

近年来逆境导致植物雌雄幼苗的生长出现差异被许多控制实验所证实, 而有关气候变化对雌雄异株植物成树生长的潜在影响尚未引起人们广泛的关注。为进一步揭示气候变化对雌雄植株树木径向和密度生长的不同影响, 该文通过树轮生态学的研究方法, 选择小五台山天然青杨(Populus cathayana)种群为研究对象, 对青杨雌雄植株近30年(1982-2011)的树轮生长特性及其与气候的相关性进行了分析。结果显示: 1)在近30年当地气温不断升高的气候条件下, 雌株的年轮最大密度和晚材平均密度均高于雄株(p < 0.05), 但雌雄植株的径向生长无显著差异; 2)雌雄植株年轮最大密度和宽度差值年表的变化趋势具有一致性, 但在年轮最大密度差值年表的变化上雄株波动幅度大于雌株; 3)青杨雌雄植株年轮密度差值年表对温度响应的月份明显不同。雌株年轮最大密度与当年8月的月平均最高气温显著正相关, 而雄株年轮最大密度与当年1月和4月的气温负相关; 4)生长季前的气候变化对青杨雌雄植株的径向生长均有明显的限制作用。此外, 当年6月的高温对于早材生长的限制作用特别明显。上述结果表明, 雌雄异株植物在树木年轮生长方面对全球气候变暖可能具有不同的响应机制, 雌株比雄株更侧重于密度生长。     

不同林龄、树种落叶松人工林径向生长与气候变化的关系

研究人工林径向生长与气候变化的关系对全球气候变暖背景下人工林合理经营有着重要的意义。该文对在辽东山区广泛栽培的黄花落叶松(Larix olgensis)和日本落叶松(Larix kaempferi)人工林, 运用树木年轮气候学方法建立了辽宁草河口和湾甸子林场落叶松人工林年表, 分析了落叶松径向生长对气候变化的响应以及气候条件、树种、立地条件和林分因子(林龄、密度、蓄积量等)的相对影响程度。结果发现在影响年轮-气候关系的因素中, 气象因子的潜在蒸发散(PET)的影响力最大; 林龄、密度和蓄积量同时也具有重要的影响作用。中龄落叶松人工林径向生长主要与气温呈正相关关系, 成熟落叶松人工林径向生长主要与气温呈负相关关系; 而其他因素, 如树种、立地条件等的影响作用不大。这表明在气候变暖背景下随着林龄增加, 林分会逐渐受到气温升高导致的水分亏缺的限制, 导致明显的生长下降趋势, 因而气候变暖对成熟落叶松人工林威胁更为严重, 所以要注重对成熟林的优先保护, 同时可以预测, 随着东北地区今后气候进一步变暖, 可能将逐步影响到林龄更小的林分的生长, 因此需要进一步研究如何在落叶松人工林经营中采取科学的措施来更好地应对未来气候变化。     

末次盛冰期以来观光木的潜在地理分布变迁

观光木(Tsoongiodendron odorum)是木兰科的古老残遗物种, 目前正面临严峻的生存威胁, 属于极小种群濒危植物。通过生态位模型(ENM)能够重建观光木地理分布格局的历史变迁, 探究气候变化对该物种分布的影响, 并了解其地理分布与气候需求间的关系, 从而为全球变暖背景下观光木的保护提供理论基础。该文基于96条现代分布记录和8个环境变量, 采用最大熵(MaxEnt)模型模拟观光木在末次盛冰期、全新世中期、现代和未来(2061-2080年, RCP 8.5)的潜在分布区, 利用SDM toolbox分析观光木的地理空间变化, 并综合贡献率、置换重要值和Jackknife检验来评估气候因子的重要性。研究结果表明: (1)观光木的高度适生区在南岭地区, 末次盛冰期时没有大尺度向南退缩, 很可能在山区避难所原地存活; (2)在全新世中期和未来两个增温的气候情境下, 观光木的分布区均表现为缩减, 其中未来分布的减幅更大, 表明气候变暖对观光木的生长有一定的负面影响; (3)总体上看, 观光木各个时期的地理分布范围相对稳定, 说明观光木对气候变化有一定的适应能力, 人为活动或自身繁育问题可能是致濒的重要原因, 并建议对广东和广西群体进行优先保护。     

Simulation on the light-response curves of electron transport rate of Quercus variabilis and Robinia pseudoacacia leaves in the Xiaolangdi area,China

为了比较直角双曲线模型、非直角双曲线模型与叶子飘模型的优缺点, 研究阴生叶和阳生叶电子传递速率的差异, 探讨环境/生物因素对电子传递速率等参数的影响, 该文采用LI-6400XT荧光测定系统对黄河小浪底栓皮栎(Quercus variabilis)、刺槐(Robinia pseudoacacia)叶片电子传递速率-光响应(J-I)曲线进行了测定, 利用直角双曲线模型、非直角双曲线模型和叶子飘模型对J-I曲线进行了拟合。结果表明, 3种模型对叶片J-I曲线拟合的决定系数(R ²)在0.96以上, 叶子飘模型的R ²最高(> 0.99)。直角双曲线模型和非直角双曲线模型无法模拟植物叶片光系统II动力学下调现象, 且不能得出饱和光强(I_sat); 直角双曲线模型对最大电子传递速率(J_max)的模拟明显大于实测值; 叶子飘模型能很好地模拟光系统II动力学下调现象, 得出的J_max和I_sat均最接近实测值。对阴生叶和阳生叶J-I曲线研究发现, 栓皮栎、刺槐阴生叶的J_max分别低于阳生叶25.0%和18.0%, 阳生叶的I_sat分别高于阴生叶26.0%和10.1%。栓皮栎和刺槐J_max与气温显著正相关; 刺槐I_sat与气温、土壤水分含量和净光合速率具有显著的正相关关系; 栓皮栎和刺槐J-I曲线初始斜率α均与净光合速率呈显著负相关关系。     

内蒙古典型草原优势种冷蒿和克氏针茅对土壤低磷环境适应策略的比较

为探究典型草原植物长期共存的生理生态机制, 以典型草原的优势物种克氏针茅(Stipa krylovii)和冷蒿(Artemisia frigida)为材料, 采用基质培养方法, 通过比较不同供磷浓度对二者生物量、根系形态、质子分泌、酸性磷酸酶和有机酸分泌以及磷吸收利用效率的影响, 探讨克氏针茅和冷蒿对土壤磷缺乏的适应策略。研究结果表明: 冷蒿主要通过根系分泌酸性磷酸酶和酸化根际来适应低磷环境; 而克氏针茅主要是通过根系分泌有机酸(主要是苹果酸)来适应土壤磷缺乏。在低磷条件下, 克氏针茅和冷蒿的磷吸收效率没有显著差异, 但克氏针茅的磷利用效率显著高于冷蒿。随着供磷浓度增加, 二者的磷吸收速率增加, 磷利用效率降低。在生物量、地上部分性状以及根系生长方面, 克氏针茅和冷蒿对磷供给的响应都表现先增长后降低的趋势; 克氏针茅的生物量在外源供0.25 mmol·L^-1磷时达到最大, 而冷蒿的生物量在外源供0.50 mmol·L^-1磷时达到最大, 表明冷蒿对磷的生理需求高于克氏针茅。因此, 克氏针茅和冷蒿具备各自不同的适应土壤有效磷缺乏的生理策略, 这可能是它们在土壤贫瘠的温带典型草原长期共存的重要机制。     

Plastic responses of stem and leaf functional traits in Leymus chinensis to long-term grazing in a meadow steppe

植物对不同功能性状进行权衡, 通过表型可塑性达到对异质生境的适应是植物的一种生态对策。羊草(Leymus chinensis)是欧亚温带草原东缘的主要优势植物, 研究其对放牧的表型反应对揭示草原生态系统的放牧响应机制具有代表意义。该文以内蒙古呼伦贝尔草甸草原为例, 通过设置不同放牧压力与围封的长期试验, 研究了羊草茎叶功能性状对放牧的可塑性响应模式。结果表明: 1)与长期围封相比, 长期放牧导致羊草茎叶性状显著小型化, 其中, 株高和个体地上生物量分别降低76.82%和89.88%, 但3年短期围封对茎性状影响不显著, 说明羊草表型矮小化现象具有一定的保守性; 2)通过排序构建羊草性状可塑性变化谱, 发现茎质量、总质量、茎高、株高、叶面积等为对放牧响应的敏感性状, 而叶片数、茎粗、叶宽等较为稳定, 为惰性性状; 3)放牧干扰下, 羊草性状可塑性程度与其变异性之间符合y = y₀ + ae^bx拟合关系, 随着植物性状的响应强度增大, 其变异性增强; 4)偏最小二乘法分析发现茎长、株高、叶面积、叶长等性状的投影重要性指标大于1, 对地上生物量变化的解释率为68.6%, 是导致长期放牧下羊草个体生物量降低的主要因子。研究认为, 矮化型变是羊草的避牧适应对策, 在亚稳态下, 通过不同性状的权衡, 充分利用环境资源完成其生活史。     

Azimuthal variation in nighttime sap flow and its mainly influence factors of Populus tomentosa

为明确毛白杨(Populus tomentosa)不同方位夜间蒸腾量(Nt)及茎干充水量(Sr)等夜间液流活动的规律, 探究不同方位Nt和Sr的主要影响因子, 该研究使用热扩散的方法监测了宽窄行模式下栽植的毛白杨茎干不同方位夜间液流, 并用图像法区分Nt和Sr。使用自动气象站和机械式张力计监测太阳总辐射(R_s, kW·m^-2)、空气温度(T_a, ℃)、空气相对湿度(RH, %)、风速(v, m·s^-1)、土壤水势(ψ, kPa)等环境因子。通过比较各方位的Nt和Sr等液流活动的大小情况及其与环境因子之间的相关性得到方位间夜间液流的差异性以及各方位夜间液流的主要影响因子。结果显示: 宽行距位于东侧的样树西方位的Nt和Sr均最大, 其中西方位的Sr显著大于其他3个方位; 北方位的Nt显著小于其他3个方位; 其他方位间的Nt和Sr无显著差异; 各方位夜间茎干充水量占夜间液流量的比例(Sr/Q)无显著差异。宽行距位于西侧的样树西方位的Nt和Sr亦均最大, 其中西方位的Sr显著大于东方位和南方位; 南方位的Nt最小, 显著小于西方位和北方位, 其他方位间的Nt和Sr无显著差异; 南方位的Sr/Q显著大于其他3个方位。各方位的Nt和Sr均与水汽压亏缺(VPD)有显著的正相关关系, 部分方位Nt和Sr与T_a和RH有显著相关关系, 没有任何方位Nt和Sr与v和ψ有显著相关关系。Nt和Sr方位间的差异(Nt_CV、Sr_CV)与VPD、T_a、RH、v和ψ均无显著相关关系。此外, Sr受白天的液流活动的影响显著。综上所述, 毛白杨不同方位Nt和Sr等液流活动具有较大的差异, 且西方位是优势方位; VPD是影响各方位Nt和Sr的主要气象因子。     

泥炭地特征性环境因子促进泥炭藓持久孢子库的形成

研究泥炭地特征性环境因子——淹水、少氧和化感物质对泥炭藓孢子持久性的影响, 可深入理解泥炭地泥炭藓持久孢子库的形成机制, 为退化泥炭地泥炭藓地被恢复研究提供参考。该研究以藓丘种和丘间种两种泥炭藓的孢子为试验材料, 通过室内模拟控制实验的方法, 研究泥炭藓孢子在空气、超纯水、泥炭地地表水和泥炭藓沥出液中, 及3种速率充气下, 孢子萌发力持久性的变化。经充气处理后, 泥炭藓孢子持久性显著低于不充气处理。不充气时, 泥炭藓孢子在含有化感物质的泥炭地地表水和泥炭藓沥出液中保存, 持久性显著高于在超纯水中保存。通径分析结果显示, 溶解氧是影响泥炭地泥炭藓孢子持久性的主要因子和限制因子, 养分元素氮(TN)和磷(TP)的浓度为孢子持久性的负作用因子。研究结果表明, 泥炭藓孢子散布于苔藓地被基质或淹水的丘间生境中, 比暴露于空气或在无化感物质的水中, 能更好地维持萌发力。泥炭地中, 泥炭藓孢子和其他植物的繁殖体的超长寿命可能归因于少氧、养分贫乏和丰富的化感物质等泥炭地特征性环境因子。     

Kin recognition in Setaria italica under the condition of root segregation

Aims Kin recognition may play an important part in the performance and productivity of crop plants. However, so far, little is known about whether crop plants can recognize their kin neighbors. The aim of this study was to explore kin recognition in Setaria italica, and its responses to changes in environmental and biological conditions.Methods A field experiment was conducted in the suburb of Shanghai. Setaria italica grew with different neighbors (kin, non-kin and strangers), under the condition of root segregation and different plant densities (high and low) and soil nutrient levels (high and low), respectively. We investigated how neighbor identity and its interactions with plant density and soil nutrient level affected the morphology and biomass allocation of S. italica.Important findings Under the condition of root segregation, 1) Leaf biomass allocation and stem diameter of plants in the kin groups significantly decreased and increased, respectively, suggesting that plants of S. italica in the kin groups reduced inter-individual competition, and adapted to the local windy climate. 2) Compared with the non-kin groups, plants in the stranger groups significantly increased the biomass allocation to seeds, while plant height decreased significantly, suggesting that the plants of S. italica in the stranger groups may reduce the growth of their neighbors due to asymmetric competition (S. italica significantly increased height compared with the neighboring plants, Panicum miliaceum). Therefore, the S. italic plants in the stranger groups allocated more biomass to reproduction and increased fitness than those in non-kin groups. 3) Under the condition of high plant density, no significant differences were found in stem biomass and leaf biomass allocation of plants among different neighbor identity treatments. While under the condition of low plant density, compared with the non-kin groups, biomass allocation to stem and leaf in the kin groups significantly increased and decreased, respectively. As the plant density decreased, plants in the kin groups decreased leaf biomass allocation significantly, while plants in the non-kin and stranger groups did not show such a response. 4) Under the condition of low soil nutrient level, no significant difference was found in leaf biomass allocation between the kin and non-kin groups, while the ear length of plants in the kin groups decreased significantly. Under the condition of high soil nutrient level, the biomass allocated to leaves in the kin groups decreased significantly, while ear length increased significantly compared with the non-kin groups. Therefore, under the condition of root segregation, plants of S. italica showed the ability to recognize their kin neighbors, and the aboveground competitive cues may play important roles in the course of kin recognition in S. italica. Lower plant density and higher soil nutrient level may facilitate the ability of kin recognition in S. italica.     

Effects of wind erosion and sand burial on water relations and photosynthesis in Alhagi sparsifolia in the southern edge of the Taklimakan Desert

塔克拉玛干沙漠南缘风沙活动十分频繁, 风蚀和沙埋是该地区自然植被生长发育的重要影响因子。该文以塔克拉玛干沙漠南缘策勒绿洲-沙漠过渡带为研究区, 以该区域主要建群种植物骆驼刺(Alhagi sparsifolia)为研究对象, 对一次强沙尘天气过后沙丘表面5种不同风蚀沙埋状况的骆驼刺植物进行标定(包括10 cm风蚀、5 cm风蚀、不蚀不积、10 cm沙埋、30 cm沙埋), 天晴后测定其叶水势、叶片含水量、光合参数和叶绿素荧光等参数, 分析研究自然环境条件下风蚀和沙埋对骆驼刺水分和光合作用的影响。结果表明: (1)风蚀显著降低了骆驼刺叶水势和叶片含水量, 进而导致植物气孔导度降低, 并引起植物光合速率和蒸腾速率的下降。风蚀的植物水分利用效率低于沙埋, 特别是在10 cm风蚀深度明显降低。 (2)沙埋增加了骆驼刺的叶水势、叶片含水量和气孔导度, 并引起植物光合速率和蒸腾速率的上升, 水分利用效率也得到提升。(3)风蚀条件下骆驼刺所受胁迫增加, 但可以通过增加活性反应中心的数量和光化学效率来抵消胁迫造成的不利影响。沙埋条件下骆驼刺受胁迫减轻, 反应中心吸收的光能和用于光化学反应的能量随着沙埋程度增加而减小, 这是骆驼刺适应风沙环境的一种生存策略。(4)与5 cm风蚀以及10 cm沙埋相比, 10 cm风蚀显著抑制骆驼刺的生长, 30 cm沙埋则会显著促进骆驼刺的生长。