植物物候研究进展

植物物候直接反映了气候变化的影响,是植被动态模拟的关键.在遥感和模型技术的推动下,植物物候与全球变化关系的研究日益受到人们的关注.文中从植物物候与环境因子的相互关系、植物物候对全球变化的响应以及植物物候的遥感监测方面,综合论述了植物物候的研究进展,找出植被物候研究的不足,进而提出未来植被物候的研究方向.     

Changes in autumn senescence in northern hemisphere deciduous trees: a meta-analysis of autumn phenology studies

Background and Aims Many individual studies have shown that the timing of leaf senescence in boreal and temperate deciduous forests in the northern hemisphere is influenced by rising temperatures, but there is limited consensus on the magnitude, direction and spatial extent of this relationship.Methods A meta-analysis was conducted of published studies from the peer-reviewed literature that reported autumn senescence dates for deciduous trees in the northern hemisphere, encompassing 64 publications with observations ranging from 1931 to 2010.Key Results Among the meteorological measurements examined, October temperatures were the strongest predictors of date of senescence, followed by cooling degree-days, latitude, photoperiod and, lastly, total monthly precipitation, although the strength of the relationships differed between high- and low-latitude sites. Autumn leaf senescence has been significantly more delayed at low (25° to 49°N) than high (50° to 70°N) latitudes across the northern hemisphere, with senescence across high-latitude sites more sensitive to the effects of photoperiod and low-latitude sites more sensitive to the effects of temperature. Delays in leaf senescence over time were stronger in North America compared with Europe and Asia.Conclusions The results indicate that leaf senescence has been delayed over time and in response to temperature, although low-latitude sites show significantly stronger delays in senescence over time than high-latitude sites. While temperature alone may be a reasonable predictor of the date of leaf senescence when examining a broad suite of sites, it is important to consider that temperature-induced changes in senescence at high-latitude sites are likely to be constrained by the influence of photoperiod. Ecosystem-level differences in the mechanisms that control the timing of leaf senescence may affect both plant community interactions and ecosystem carbon storage as global temperatures increase over the next century.     

植物物候与气候研究进展

植物物候及其变化是多个环境因子综合影响的结果,其中气候是最重要、最活跃的环境因子。主要从气候环境角度分析了植物物候与气候以及气候变化间的相互关系,概述了国内外有关植物物候及物候模拟等方面的研究进展。表明,温度是影响物候变化最重要的因子;同时,水分成为胁迫因子时对物候的影响也十分重要。近50a左右,世界范围内的植物物候呈现出了春季物候提前,秋季物候推迟或略有推迟的特征,从而导致了多数植物生长季节的延长,并成为全球物候变化的趋势。全球气候变暖改变了植物开始和结束生长的日期,其中冬季、春季气温的升高使植物的春季物候提前是植物生长季延长的主要原因。目前对物候学的研究方向主要集中在探讨物候与气候变化之间的关系,而模型模拟是定量研究气候变化与植物物候之间关系的重要方式,国内外已经开发出多种物候模型来分析气候驱动与物候响应之间的因果关系。另外遥感资料的应用也为物候模型研究提供了新的方向。物候机理研究、物候与气候关系以及物候模型研究将是研究的重点。     

Delayed autumn phenology in the Northern Hemisphere is related to change in both climate and spring phenology

The timing of the end of the vegetation growing season (EOS) plays a key role in terrestrial ecosystem carbon and nutrient cycles. Autumn phenology is, however, still poorly understood, and previous studies generally focused on few species or were very limited in scale. In this study, we applied four methods to extract EOS dates from NDVI records between 1982 and 2011 for the Northern Hemisphere, and determined the temporal correlations between EOS and environmental factors (i.e., temperature, precipitation and insolation), as well as the correlation between spring and autumn phenology, using partial correlation analyses. Overall, we observed a trend toward later EOS in ~70% of the pixels in Northern Hemisphere, with a mean rate of 0.18 ± 0.38 days yr^?1. Warming preseason temperature was positively associated with the rate of EOS in most of our study area, except for arid/semi‐arid regions, where the precipitation sum played a dominant positive role. Interestingly, increased preseason insolation sum might also lead to a later date of EOS. In addition to the climatic effects on EOS, we found an influence of spring vegetation green‐up dates on EOS, albeit biome dependent. Our study, therefore, suggests that both environmental factors and spring phenology should be included in the modeling of EOS to improve the predictions of autumn phenology as well as our understanding of the global carbon and nutrient balances.     

Nitrate uptake kinetics for rooted cuttings of Acer rubrum L.

Red maple (Acer rubrumL.) occurs in a broad spectrum of both woodland and managed landscapes in much of eastern North America. Earlier work has indicated considerable plasticity within the species in water use efficiency, as well as dry mass accumulation and tertiary root extension when grown in a solution in which all N was supplied as NO₃ ^-. Nitrogen uptake is largely a function of N supply, soil water availability and root surface area. Therefore, compensatory mechanisms could have evolved among cultivars to compensate for site differences. The objective of this study was to define NO₃ ^- uptake parameters for red maple in a hydroponic system through the use of two cultivars known to differ in root production and water use efficiency. Green wood stem cuttings of two red maple cultivars, `Autumn Flame' and `Franksred', were rooted and then transferred to solution culture. Using established techniques, three separate experiments were conducted to define ranges of I_max, K_m and C_min values and to determine root mass, length, mean radius and surface area. Estimates of I_max exhibited considerable variation between experiments with means ranging from 1.57E-5 to 5.91E-5 μmol cm^-2 s^-1. However, cultivar differences in I_max were statistically significant in only one of the three experiments. Means for K_m ranged from 2.04E-1 to 5.23E-1 μmol cm^-3, while C_min values were consistent at 0.001 μmol cm^-3 (the limit of analytical detection) across all experiments. While data on variation among red maple cultivars are not conclusive, some evidence exists for genotype differences that may relate to the broad range of site conditions under which red maple is successfully grown. This revised version was published online in June 2006 with corrections to the Cover Date.     

Frequency of inversions affects senescence phenology of Acer pseudoplatanus and Fagus sylvatica

In mountainous regions, inversion situations with cold-air pools in the valleys occur frequently, especially in fall and winter. With the accumulation of inversion days, trees in lower elevations experience lower temperature sums than those in middle elevations. In a two-year observational study, deciduous trees, such as Acer pseudoplatanus and Fagus sylvatica, on altitudinal transects responded in their fall leaf senescence phenology. Phenological phases were advanced and senescence duration was shortened by the cold temperatures in the valley. This effect was more distinct for late phases than for early phases since they experienced more inversion days. The higher the inversion frequency, the stronger the signal was. Acer pseudoplatanus proved to be more sensitive to cold temperatures compared to Fagus sylvatica. We conclude that cold-air pools have a considerable impact on the vegetation period of deciduous trees. Considering this effect, trees in the mid hillside slopes gain advantages compared to lower elevations. Our findings will help to improve knowledge about ecological drivers and responses in mountainous forest ecosystems.     

Simulated ungulate herbivory affects differently two herbivorous arthropod guilds in bilberry

Dense ungulate populations, both domestic and wild, accompanied by high grazing intensities, are known to have effects on the abundance and diversity of the community of arthropods hosted by plants. However, research combining ungulate herbivory with nutrient addition effects is scarce. By means of a nitrogen (N) addition and clipping experiment, we investigated the effects of both factors on the diversity, abundance and trophic structure of the arthropod community hosted by the bilberry, Vaccinium myrtillus, focusing on the response of herbivorous arthropods by considering leaf-chewers and sap-feeders separately. In addition, we assessed altitudinal variation on the arthropod community and also specifically on herbivores. Neither of the variables estimated for the arthropod community (total abundance, richness and biomass) were affected by simulated ungulate herbivory. However, clipping reduced the abundance of sap-feeders although had no significant effect on leaf-chewer insects. We therefore suggest that ungulates can compete with sap-feeders by reducing suitable food resources, or via changing plant nutritional state. Moreover, the lack of response on leaf-chewers could correspond with the absence of chemical defence in bilberry after repeated damage. Despite this effect on sap-feeder abundance, clipping did not cause a cascade effect on the trophic structure of the arthropod community associated with bilberry, at least in the short term. In turn, N fertilization at levels close to atmospheric N deposition did not cause any significant effect on the invertebrate community. Finally, the number of arthropod morphospecies and biomass decreased with altitude.     

Leaf flushing phenology and herbivory in a tropical dry deciduous forest,southern India

Patterns of leaf-flushing phenology of trees in relation to insect herbivore damage were studied at two sites in a seasonal tropical dry forest in Mudumalai, southern India, from April 1988 to August 1990. At both sites the trees began to flush leaves during the dry season, reaching a peak leaf-flushing phase before the onset of rains. Herbivorous insects emerged with the rains and attained a peak biomass during the wet months. Trees that flushed leaves later in the season suffered significantly higher damage by insects compared to those that flushed early or in synchrony during the peak flushing phase. Species whose leaves were endowed with physical defenses such as waxes suffered less damage than those not possessing such defenses. There was a positive association between the abundance of a species and leaf damage levels. These observations indicate that herbivory may have played a major role in moulding leaf flushing phenology in trees of the seasonal tropics.     

Spatial pattern of Quercus regeneration limitation and Acer rubrum invasion in a Piedmont forest

Abstract. Across eastern North America, there is a temporal trend from open Quercus forests to closed forests with increased Acer rubrum in the understory. We used a series of Ripley's K(d) analyses to examine changes in the spatial pattern of Quercus and Acer rubrum stems greater than 2.5 cm DBH over 45 yr in a 2‐ha mapped stand. Specifically, we asked whether changes over time were consistent with the hypothesis that Quercus is being competitively replaced by Acer rubrum. Both Acer rubrum and Quercus stems are spatially clumped, but have become less clumped over time. Stem mortality from Hurricane Fran (1996) was more clumped in all strata of the forest, at all spatial scales, than expected if damage had occurred to stems at random. Acer rubrum ingrowth occurred more often near established trees (all species) in the midstory, whereas Quercus ingrowth occurred less often near established trees in the midstory. The specific hypothesis that stems of Acer rubrum in the midstory of the forest are associated with a lack of Quercus regeneration was strongly supported. This effect occurred at all spatial scales tested, including scales larger than that at which direct competition for light can occur. Edaphic gradients in the plot are correlated with many of the observed trends at large spatial scales, and our results suggest that the presence of such gradients can generate complex spatial patterns over time.     

Latitudinal variation in resistance and tolerance to herbivory in the perennial herb Lythrum salicaria is related to intensity of herbivory and plant phenology

Both the length of the growing season and the intensity of herbivory often vary along climatic gradients, which may result in divergent selection on plant phenology, and on resistance and tolerance to herbivory. In Sweden, the length of the growing season and the number of insect herbivore species feeding on the perennial herb Lythrum salicaria decrease from south to north. Previous common‐garden experiments have shown that northern L. salicaria populations develop aboveground shoots earlier in the summer and finish growth before southern populations do. We tested the hypotheses that resistance and tolerance to damage vary with latitude in L. salicaria and are positively related to the intensity of herbivory in natural populations. We quantified resistance and tolerance of populations sampled along a latitudinal gradient by scoring damage from natural herbivores and fitness in a common‐garden experiment in the field and by documenting oviposition and feeding preference by specialist leaf beetles in a glasshouse experiment. Plant resistance decreased with latitude of origin, whereas plant tolerance increased. Oviposition and feeding preference in the glasshouse and leaf damage in the common‐garden experiment were negatively related to damage in the source populations. The latitudinal variation in resistance was thus consistent with reduced selection from herbivores towards the northern range margin of L. salicaria. Variation in tolerance may be related to differences in the timing of damage in relation to the seasonal pattern of plant growth, as northern genotypes have developed further than southern have when herbivores emerge in early summer.     

Simulated herbivory enhances leaky sex expression in the dioecious herb Mercurialis annua

Background and AimsPlant reproductive traits are widely understood to be responsive to the selective pressures exerted by pollinators, but there is also increasing evidence for an important role for antagonists such as herbivores in shaping these traits. Many dioecious species show leaky sex expression, with males and females occasionally producing flowers of the opposite sex. Here, we asked to what extent leakiness in sex expression in Mercurialis annua (Euphorbiaceae) might also be plastically responsive to simulated herbivory. This is important because enhanced leakiness in dioecious populations could lead to a shift in both the mating system and in the conditions for transitions between combined and separate sexes.MethodsWe examined the effect of simulated herbivory on the sexual expression of males and females of M. annua in two experiments in which different levels of simulated herbivory led to enhanced leakiness in both sexes.Key ResultsWe showed that leaky sex expression in both males and females of the wind-pollinated dioecious herb M. annua is enhanced in response to simulated herbivory, increasing the probability for and the degree of leakiness in both sexes. We also found that leakiness was greater in larger females but not in larger males.ConclusionsWe discuss hypotheses for a possible functional link between herbivory and leaky sex expression, and consider what simulated herbivory-induced leakiness might imply for the evolutionary ecology of plant reproductive systems, especially the breakdown of dioecy and the evolution of hermaphroditism.     

Temperature,precipitation, and insolation effects on autumn vegetation phenology in temperate China

Autumn phenology plays a critical role in regulating climate–biosphere interactions. However, the climatic drivers of autumn phenology remain unclear. In this study, we applied four methods to estimate the date of the end of the growing season (EOS) across China's temperate biomes based on a 30‐year normalized difference vegetation index (NDVI) dataset from Global Inventory Modeling and Mapping Studies (GIMMS). We investigated the relationships of EOS with temperature, precipitation sum, and insolation sum over the preseason periods by computing temporal partial correlation coefficients. The results showed that the EOS date was delayed in temperate China by an average rate at 0.12 ± 0.01 days per year over the time period of 1982–2011. EOS of dry grassland in Inner Mongolia was advanced. Temporal trends of EOS determined across the four methods were similar in sign, but different in magnitude. Consistent with previous studies, we observed positive correlations between temperature and EOS. Interestingly, the sum of precipitation and insolation during the preseason was also associated with EOS, but their effects were biome dependent. For the forest biomes, except for evergreen needle‐leaf forests, the EOS dates were positively associated with insolation sum over the preseason, whereas for dry grassland, the precipitation over the preseason was more dominant. Our results confirmed the importance of temperature on phenological processes in autumn, and further suggested that both precipitation and insolation should be considered to improve the performance of autumn phenology models.     

近十年的国际植被物候研究文献发展态势分析

基于Web of Science数据库的检索结果,利用Histcite、Bibexcel和Netdraw对国际植被物候研究文献进行计量分析。结果表明:1 060篇相关文献刊载于288种期刊,平均载文3.68篇; 共分33个研究方向; 3 380位作者(第一作者904位)、69个国家或地区、1 172个组织参与; 国际合作发文310篇,占比29.25%; 其中中美合作居第一(19次)。分析还表明:2002～2007年是该领域重要发展期; 国际植被物候研究热点主要集中在基于气候(climate)-物候的田间局地观测和基于遥感(remote sensing)的大尺度物候研究。     

Sensitivity of leaf size and shape to climate within Acer rubrum and Quercus kelloggii

* Variation in the size and shape (physiognomy) of leaves has long been correlated to climate, and paleobotanists have used these correlations to reconstruct paleo-climate. Most studies focus on site-level means of largely nonoverlapping species sets. The sensitivity of leaf shape to climate within species is poorly known, which limits our general understanding of leaf-climate relationships and the value of intraspecific patterns for paleoclimate reconstructions. * The leaf physiognomy of two species whose native North American ranges span large climatic gradients (Acer rubrum and Quercus kelloggii) was quantified and correlated to mean annual temperature (MAT). Quercus kelloggii was sampled across a wide elevation range, but A. rubrum was sampled in strictly lowland areas. * Within A. rubrum, leaf shape correlates with MAT in a manner that is largely consistent with previous site-level studies; leaves from cold climates are toothier and more highly dissected. By contrast, Q. kelloggii is largely insensitive to MAT; instead, windy conditions with ample plant-available water may explain the preponderance of small teeth at high elevation sites, independent of MAT. * This study highlights the strong correspondence between leaf form and climate within some species, and demonstrates that intraspecific patterns may contribute useful information towards reconstructing paleoclimate.     

Role of Simulated Acid Rain on Acer negundo and Plant Nitrition

The short-term effects of simulated acid rain on Acer negundo L. have been investigated using photoacoustic spectroscopy and modulated fluorescence measurements. Three seeding groups of Acer negundo L. were treated with simulated acid rain at pH 3.0, 4.5 and 5.6 levels for three months. The results indicated the photosynthetic activity, expressed in terms of normalized oxygen evolution signal, photochemical energy storage, normalized variable fluorescence (Fv/Fm), photochemical and non-photochemical chlorophyll fluorescence quenching, ranges in the order pH 4.5 > pH 3.0 > pH 5.6. This stimulation effect has been confirmed by increased growth rate observed in relation with increased acidity levels. The nutritional aspects of this favorable effect of the acid rain on plant growth were discussed.     

模拟酸雨对梣叶槭的作用和植物营养

应用光声光谱和调制荧光测量技术研究了模拟酸雨对叶槭（ＡｃｅｒＮｅｇｕｎｄｏＬ．）的短期作用。用ｐＨ值分别为５．６、４．５和３．０的模拟酸雨对相应的三个样本组的梣叶槭树苗进行了为期三个月的跟踪观察和研究。结果表明,用归一化氧信号、光化学能量贮备、归一化可变荧光（ＦＶ／Ｆｍ）、光化学和非光化学叶绿素荧光猝灭等所表示的光合作用活性对这三个样本组的顺序为ｐＨ４．５＞ｐＨ３．０＞ｐＨ５．６。实验证实由于酸度水平增加,酸雨促进了生长率增加。从植物营养角度对结果进行了讨论。