Spatial and interspecific variability in phenological responses to warming temperatures

A comprehensive understanding of species phenological responses to global warming will require observations that are both long-term and spatially extensive. Here we present an analysis of the spring phenological response to climate variation of twelve taxa: six plants, three birds, a frog, and two insects. Phenology was monitored using standardized protocols at 176 meteorological stations in Japan and South Korea from 1953 to 2005, and in some cases even longer. We developed a hierarchical Bayesian model to examine the complex interactions of temperature, site effects, and latitude on phenology. Results show species-specific variation in the magnitude and even in the direction of their responses to increasing temperature, which also differ from site-to-site. At most sites the differences in phenology among species are forecast to become greater with warmer temperatures. Our results challenge the assertion that trends in one geographic region can be extrapolated to others, and emphasize the idiosyncratic nature of the species response to global warming. Field studies are needed to determine how these patterns of variation in species response to climate change affect species interactions and the ability to persist in a changing climate.     

Spatio-temporal variation of environmental signals inducing seed germination in temperate conifer plantations and natural hardwood forests in northern Japan

To document the spatial and temporal variation of environmental signals inducing seed germination in temperate forests, we measured temporal patterns of environmental signals and seed germination of six pioneer tree species in unthinned and thinned stands of conifer forests (Cryptomeria japonica plantations) and in the understory and gaps of hardwood forests in Japan. We also conducted germination experiment in laboratory for the six pioneer species to test the effects of red:far-red (R:FR) light ratio and temperature fluctuations on the seed germination. In conifer forests, the photosynthetic photon flux density (PPFD), the R:FR ratio, and the amplitude of temperature fluctuations in thinned stands were 2, 1.5, and 3 times higher, respectively, than those of unthinned stands. The PPFD and R:FR ratios just above forest floor also increased after the removal of thick litter accumulation. As a result, higher seed germination was observed in thinned compared to unthinned stands for three photoblastic species, whereas little differences were observed for three non-photoblastic species. These findings suggest that thinning, which frequently reduces litter accumulation, can substantially affect the regeneration of pioneer species and the resultant species diversity in conifer plantations. None of the measured environmental signals changed seasonally in unthinned stands of conifer forests, but they all changed remarkably in the understory of the hardwood forests. In this system, all signals were high and nearly identical to those in the gaps in early spring prior to canopy closure. Thus, the percent germination of the three photoblastic species was enhanced by high R:FR ratios and/or large temperature fluctuations even beneath the canopy and was nearly equal to that in the thinned conifer stands where the environmental conditions were nearly identical to those in the gaps. However, all of the environmental signals decreased with the expansion of canopy leaves and reached minimums at canopy closure. Even in the thinned stands and the gaps, the PPFD and magnitude of temperature fluctuations decreased over time due to shading by growing herbs and/or emerging canopy leaves. In these temporally changing environments, the germination of all photoblastic species ceased simultaneously. This study clearly demonstrated that the environmental signals inducing seed germination of photoblastic pioneer species spatially and temporally change in temperate forests, particularly in deciduous hardwood forests. Furthermore, these signals, PPFD, R:FR ratio, and the amplitude of temperature fluctuations, appear to play a very important role in tree regeneration and subsequent species diversity.     

桂北地区蟋蟀物候对气候变暖的响应

对桂北地区蟋蟀始鸣和终鸣以及气候变化多年同步观测资料进行对比分析,结果表明:近10年来桂北地区蟋蟀始鸣期呈提前趋势,终鸣期稳定,始终鸣间隔日及生长繁殖季显著延长;桂林雁山近34年来平均气温呈显著上升趋势,特别是近10年来增温特别明显,在增温过程中又以春季增温为主,冬季和秋季增温次之,夏季呈弱降温趋势;2~4月平均气温(T2-4)是影响蟋蟀始鸣期和始终鸣间隔日的主要气候生态因子;蟋蟀物候期变化是对气候变暖响应的结果。     

鸡公山国家级自然保护区植物群落季相及其景观节奏

研究了鸡公山国家级自然保护区乔、灌植被的季相变化。结果表明,一年四季中,春花、夏绿、秋色、冬季枯黄,每个季节阶段都具有典型的植物物候形态组合与色彩组合,独特的季相特征为植物景观的持续开发利用提供了科学依据。     

长春市木本植物春季物候对气候变化的响应

根据中国物候观测网络长春观测站点的物候资料及国家气象中心提供的气象资料,采用相关分析、多元回归分析和数学模拟方法,分析了2003-2010年长春市木本植物春季物候与温度、日照、降水之间的相关关系,建立了模拟和预报4种木本植物开花始期的模型。结果表明：在各种气候因子中,温度对春季物候影响最大,日照、降水影响不显著;温度对春季物候影响集中在物候期前2个月,温度升高,春季物候期提前。春季物候期持续日数与1、2月份温度有关,分别与芽萌动期和展叶期成正相关和负相关。开花始期回归模型预测值与物候观测数值拟合较好,表明可以使用回归模型对长春几种木本开花期进行预测。     

Exploring Chenopodium album adaptive traits in response to light and temperature stresses

Weeds within canopies are depleted in photosynthetic photon flux density (PPFD) and red to far‐red light ratio (R/FR) throughout their lifespan. Growth cabinet studies isolated PPFD and R/FR effects and explored the adaptive traits of a model invasive weed, Chenopodium album, to light and temperature. Reproductive development progressed rapidly at high temperature, yet the rate of leaf appearance was insensitive to temperatures of 25:15 and 10:5°C (day:night). Low R/FR effects were detected early in the life cycle, but by seed set, growth was influenced by low PPFD. C. album adapted to the simulated canopy environments by delaying seed set, growing taller and producing more leaf area per mol of accumulated incident PPFD. Low PPFD reduced seed number per plant and the carbon/nitrogen ratio of those seeds, but not seed weight. PPFD was a primary cue for many shade avoidance traits and only under low PPFD did R/FR modify the expression of these traits. This study elucidates the adaptive strategies that make C. album a persistent weed.     

本溪山区旱柳物候变化特征及其对气候变化的响应

为了探讨本溪山区气候变化对木本植物物候的影响,利用1980—2012 年国家农业气象本溪县观测站旱柳物候期资料和气温、降水、日照等资料,运用线性倾向率和趋势系数等分析方法,研究了本溪山区旱柳物候期对气候变化的响应。结果表明：在近33 年本溪山区气温呈明显的升温趋势变化,升温速率为0.45℃/10 a,降水和日照呈波动性减小趋势变化,降水量波动幅度较大,最大降雨量与最小降雨量差异大。旱柳芽开放期呈明显的延后趋势变化,其线性倾向率为2.4 d/10 a;开花始期呈拖后趋势变化,线性倾向率为0.35 d/10 a;旱柳变色始期和落叶始期均呈显著的延后趋势,其线性倾向率分别为7.27 d/10 a和5.52 d/10 a。温度对旱柳物候影响最为显著,降水和日照对物候期的变化也有一定的影响。     

Biomass and Accumulation of Potassium,Calcium, and Magnesium in Gladiolus as Affected by Heat Units and Corm Size

In México, gladiolus is an important crop cultivated in the central part of the country. In ornamental geophytes, the size of bulbs is a critical factor, impacting plant growth and quality. The objective of the present study was to model the accumulation of potassium (K), calcium (Ca) and Magnesium (Mg) in gladiolus plants as affected by corm size (3.5, 3.0 and 2.5 cm). Regardless of corm size, total dry mass of plants accumulated in three different stages. The initial stage occurred during the corm sprouting phase and continued through the vegetative phase, ending either shortly before (plants from 3.5 cm corms), at (plants from 3.0 cm corms) or shortly after (plants from 2.5 cm corms) the heading phase. The second stage, on which the plants exhibited a rapid dry mass accumulation, occurred shortly before or shortly after the heading phase, finishing with the elongation of the flowering stem. The third stage showed the highest dry mass accumulation rate, coinciding with the elongation of the flowering stem and ending at the blooming of the spike. To complete all the phenological phases, gladiolus required 1818 heat units regardless of corm size. Not considering the nutrients provided by the corm, gladiolus required a total of 6.33, 5.59 and 5.01 mmol plant^?1 of K, 2.22, 1.69 and 1.38 mmol plant^?1 of Ca and 2.49, 2.00 and 1.68 mmol plant^?1 of Mg when grown from 3.5, 3.0, and 2.5 cm corms. At the beginning of the vegetative phase, plants tended to increase Ca content at the expense of K, whereas the proportion of Mg remained unaffected, however, between the vegetative and heading phases, the proportion of Ca declined while that of K and Mg increased. At the end of the study, the proportion of K was much higher than that of Ca and Mg, whereas the proportion of Ca and Mg was similar.     

作物模型中单叶最大光合作用速率的温度响应修订

作物的光合作用对温度变化敏感, 其温度依存性随品种、生长环境的变化而改变。基于光效率模型的作物生长模型, 在应用中很少对光合作用的温度影响参数值进行订正, 且在全生育期使用相同的参数值, 难免会增加干物质模拟的误差。为此, 本文以ORYZA2000模型为例, 提出了一种修订光合作用温度影响参数值的方法。为确定方法的有效性, 结合2012年和2013年水稻品种两优培九的温度梯度控制实验, 首先利用抽穗开花期光合作用观测曲线提取了不同温度水平的光合作用参数值, 然后结合Arrhenius方程和Peaked方程建立了温度敏感性参数的温度影响方程。将这些方程代入机理性光合作用模型, 模拟了单叶最大光合作用速率与温度的曲线关系。最后, 以归一化后的曲线关系修订作物模型参数值, 并利用两年地上部分生物量(WAGT)观测值对其验证。结果显示, 两优培九单叶最大总光合作用速率随温度的变化关系不同于ORYZA2000的默认设置, 修订后的最适温度为38~40°C, 高于默认值。在10~20°C的低温段, 修订后的温度影响系数低于默认值。从WAGT模拟值的相对误差看, 修订后较修订前平均降低约3.3%。本研究为改进干物质模拟精度和分析不同品种光合作用的温度依存性提供了重要参考。     

A long‐term study of burning effects on a plant pathogen in tallgrass prairie

Tallgrass prairie species have evolved with regular exposure to fire. However, burning has been used as a management tool for reducing plant disease in agricultural systems, posing the question of how plant pathogens of tallgrass prairie would be affected by burning. The rust fungus Puccinia dioicae, infecting Erigeron strigosus (Asteraceae), was studied for 8 years in long‐term experiments to evaluate the effects of burning in native tallgrass prairie. This experiment also allowed evaluation of the effects of nutrient additions, although E. strigosus was rare in the plots with added nutrients in most years. Burning reduced rust severity in most years, but effects from additions of nutrients were rarely observed. There was high interannual variation in rust severity within a location, suggesting that weather may be the most important of these three abiotic factors in determining infection. An analysis of weather variables associated with disease severity found that solar radiation in the month prior to sampling was associated with severity in unburned plots; temperature approximately 2 months prior to sampling was also associated with severity in burned plots. High interannual variation also suggests that the effects of this pathogen on its host would be sporadic and difficult to study in short‐term experiments.