Phenological Sequences Research Articles

Back to the future for plant phenology research.

Back to the future for plant phenology research.

Timing and duration of phenological sequences of alpine plants along an elevation gradient on the Tibetan plateau

Previous studies have focused on the effects of increased temperatures on a single green-up and/or flowering event, but less is known about how acceleration of spring phenology may change subsequent phenological events. We present results of a field experiment to test the hypotheses that (1) the timing of phenological events does not necessarily delay as elevation increases; (2) changes in the timing of a sequence of phenological events will be consistent for all phenological events along the elevation gradient; and thus (3) change in the timing of phenological events does not affect the duration of the entire reproductive stage in the alpine region. The experiment was conducted along an elevation gradient from 3200 to 3800m using two early-spring flowering (ESF) sedges and four mid-summer flowering (MSF) plants (two forbs and two grasses). Generally, our results only supported the first hypothesis. Lower elevation delayed the starting dates of all phenological events for ESF plants at 3200m compared with other elevations, whereas the opposite trend was observed for MSF-grasses. MSF-forbs had the earliest leaf-out at 3200m and the earliest first flowering at 3600m, and onset of fruit-set advanced with increasing elevation. The entire reproductive duration was shortened with increasing elevation for MSF-forbs, whereas it was the shortest for ESF at 3600m and for MSF-grasses at 3200 and/or 3800m. Individual reproductive stages had independent responses to climate change. The duration of the entire growing season for ESF plants decreased as elevation increased. For MSF-forbs, it was longest at 3200m and shortest at 3400m, while for MSF-grasses it was shortest at 3200m and at 3800m. Reproduction was compressed into shorter time periods only for MSF-forbs at 3600 and 3800m. Therefore, reproduction is not tightly integrated across the life cycle, and earlier reproductive development induced by warmer spring temperatures did not consistently advance flowering and fruiting times and their durations for the alpine plants studied. The effects of climate change on the timing and duration of phenological events were species-specific. Selection for changes in the timing and duration of individual phenological stages in response to climate change due to evolutionary adaptation should be taken into account.

ANALYSIS OF SPATIO-TEMPORAL PATTERNS OF LEAF AREA INDEX IN DIFFERENT FOREST TYPES OF INDIA USING HIGH TEMPORAL REMOTE SENSING DATA

Abstract. Knowledge of temporal variations of Leaf Area Index (LAI) aids in understanding the climate-vegetation interaction of different vegetative systems. This information is amenable from high temporal remote sensing data. India has around 78.37 million hectare, accounting for 23.84% of the geographic area of the country under forest/tree cover. India has a diverse set of vegetation types ranging from tropical evergreen to dry deciduous. We present a detailed spatio-temporal and inter-seasonal analysis of LAI patterns in different forest types of India using MODIS 8-day composites global LAI/fPAR product for the year 2005 at 1-km spatial resolution. A forest cover mask was generated using SPOT 1-km landuse/landcover classification over the Indian region. The range of estimated LAI varied from 0.1–6.9 among the different forest types. Maximum LAI was observed in tropical evergreen forests in North-Eastern region and Western Ghats. Low LAI was observed in Central Indian region due to predominance of dry deciduous forests. The spatial patterns of seasonal variations detected that for most of the forest types, the peak LAI values were observed during September and October months of the autumn season in contrast to minimum LAI during summer season. The mean LAI and standard deviation for each 8-day LAI composite were also computed and mean monthly LAI profiles were derived for each forest type classified on the basis of their geographical locations. These results are useful indicators for detailed understanding of phenological sequence and may also serve as important inputs for deriving bioclimatic indices for different forest types of India.

Warming leads to divergent responses but similarly improved performance of two invasive thistles

AbstractPlants’ responses to climate change are complex. Even the same net performance changes may involve different responses of multiple life history traits. Here we show that two congeneric thistles, Carduus nutans and Carduus acanthoides, both grew taller under increased temperature, albeit following divergent response patterns. For C. nutans, warming advanced bolting more than flowering, leading to a longer growing period before flowering and ultimately taller plant height at the end of the growing season. Carduus acanthoides maintained the same length of growing period because of equally shifted events in the phenological sequence, however, post‐flowering growth rate was increased, which also led to enhanced final plant height. As seeds from taller plants disperse farther, their responses imply that future invasion spread rates of these two species will increase. Similar consequences due to divergent responses in life history traits, as demonstrated in this study, suggest that considering only ultimate performance outcomes, and not the underlying processes generating such outcomes, is not enough to understand the impacts of climate change.

Physiological performance and xylem water isotopic composition underlie gender-specific responses in the dioecious shrub Corema album

Gender-specific requirements of reproduction in dioecious species can lead to different physiological responses in male and female plants, made in relation to environmental constraints, and influencing growth, survival and population structure. Gender-related physiological differences and seasonal responses, indicating the existence of compensatory mechanisms of reproduction, were examined during a drought year in the dioecious shrub species Corema album. To integrate aboveground and belowground physiological responses, chlorophyll fluorescence, leaf gas exchange, water potential and xylem water isotopic composition were monitored throughout the diurnal cycle and annual phenological sequence of the species. Sampling was carried out in Doñana Natural Park (SW Spain) in Mediterranean-type climate conditions. The gender which bore greater reproductive effort showed higher physiological stress. Intersexual differences in leaf water potential were interpreted as arising from each gender's maximum reproductive allocation; lower values were found during flowering in males and during fruit production in females. Cold temperatures during winter fostered photoinhibitory responses that were most evident in male individuals, as a response to their relatively higher investment in reproduction during flowering. Net assimilation rate was not influenced by reproductive status; however, females tended to show higher values of this parameter at midday. The integrated analysis of photosynthetic variables and water relations indicated a gender effect in the physiological response at midday. The oxygen isotopic composition of xylem water showed a lack of dependence on the water table during the drought period, and indicated intersexual differences in water catchment. Females reached deeper soil layers, suggesting mechanisms compensating for their higher reproductive effort, and giving new evidence of physiological gender dimorphism in the belowground responses of a woody species.

Tracking the rhythm of the seasons in the face of global change: phenological research in the 21st century

Phenology is the study of recurring life‐cycle events, classic examples being the flowering of plants and animal migration. Phenological responses are increasingly relevant for addressing applied environmental issues. Yet, challenges remain with respect to spanning scales of observation, integrating observations across taxa, and modeling phenological sequences to enable ecological forecasts in light of future climate change. Recent advances that are helping to address these questions include refined landscape‐scale phenology estimates from satellite data, advanced, instrument‐based approaches for field measurements, and new cyberinfrastructure for archiving and distribution of products. These breakthroughs are improving our understanding in diverse areas, including modeling land‐surface exchange, evaluating climate–phenology relationships, and making land‐management decisions.

Ecological studies on the distribution and phenology of bush mango, <i>Irvingia wombolu</i> (vermoesen) in the humid forest of southeastern Nigeria.

Studies on the distribution, soil requirement for establishment and the phenology of Bushmango, Irvingia wombolu were undertaken in four selected geographic zones of Southeastern Nigeria. Enumeration and inventory of ten selected woody food tree crops were made in the homestead and outlying farms of each zone, with emphasis on Irvingia wombolu. Twenty soil samples comprising of ten samples from each of the farming zones were analysed for their physical and chemical properties. Phenological sequences of I. wombolu were made in the farming zones of the study areas. The plant species had generally very low densities. 0.3 – 2.7 trees/ha, and 1. wombolu had density 2.4 trees/ha. Irvingia wombolu occurred more in the outlying farms than in the homestead farms. Umuozu and Enugu-Ezike had higher densities of 1. wombolu in the two farming zones than the other towns. 1. wombolu had positive and significant relationship with P. macrophylla and Monodora. myristica, and positive but non-significant relationship with the other seven plant species. Soil samples obtained from different locations were heterogeneous. The species appear to thrive well in soils containing adequate amount of N, K, Ca, and C. The species' period of leaf flush appears an adaptive strategy for mobilizing nutrients for its reproductive phase, flowering and fruiting.Agro-Science Vol. 7 (1) 2008: pp. 1-8

PHENOLOGICAL SEQUENCES REVEAL AGGREGATE LIFE HISTORY RESPONSE TO CLIMATIC WARMING

Climatic warming is associated with organisms breeding earlier in the season than is typical for their species. In some species, however, response to warming is more complex than a simple advance in the timing of all life history events preceding reproduction. Disparities in the extent to which different components of the reproductive phenology of organisms vary with climatic warming indicate that not all life history events are equally responsive to environmental variation. Here, we propose that our understanding of phenological response to climate change can be improved by considering entire sequences of events comprising the aggregate life histories of organisms preceding reproduction. We present results of a two-year warming experiment conducted on 33 individuals of three plant species inhabiting a low-arctic site. Analysis of phenological sequences of three key events for each species revealed how the aggregate life histories preceding reproduction responded to warming, and which individual events exerted the greatest influence on aggregate life history variation. For alpine chickweed (Cerastium alpinum), warming elicited a shortening of the duration of the emergence stage by 2.5 days on average, but the aggregate life history did not differ between warmed and ambient plots. For gray willow (Salix glauca), however, all phenological events monitored occurred earlier on warmed than on ambient plots, and warming reduced the aggregate life history of this species by 22 days on average. Similarly, in dwarf birch (Betula nana), warming advanced flower bud set, blooming, and fruit set and reduced the aggregate life history by 27 days on average. Our approach provides important insight into life history responses of many organisms to climate change and other forms of environmental variation. Such insight may be compromised by considering changes in individual phenological events in isolation.

Phenological Correlations Between Flowering Plants and Activity of Urban Landscape Pests in Kentucky

Seasonal appearance of 33 insect pests of urban landscapes together with flowering phenology of 34 species of common woody ornamental plants were systematically monitored for 3 yr in central Kentucky. Base temperatures and degree-day requirements corresponding to these events also were determined. Phenological sequences of plant flowering and insect activity were highly consistent between years. For example, crawlers of the oystershell scale, Lepidosaphes ulmi (L.), hatched 1st in each year, followed by those of pine needle scale, Chionaspis pinifaliae (Fitch); euonymus scale, Unaspis euonymi (Comstock); juniper scale, Carulaspis juniperi (Bouche); calico scale, Eulecanium cerusorum (Cockerell); walnut scale, Quadraspidiotus juglansregiae (Comstock); a cottony maple leaf scale, Pulvillaria acericola (Walsh & Riley);) and obscure scale, Melanaspis obscura (Comstock). Similar consistency occurred with clearwing borers (Lepidoptera: Sesiidae), leafminers, and other pests. Plant phenology was generally a better predictor of insect activity than was calender date. Comparison of the temporal deviation between plant-insect correlations in Kentucky and Michigan suggests that some phenological predictors are consistent across geographic regions, whereas others are not. A phenology calender was developed that facilitates prediction of pest activity and timing of control actions by horticultural professionals and lay persons.

Phytomass and nutrient status of Kochia indica, a promising fodder plant in Egypt

The present study evaluated the above-ground phytomass and nutrient composition of the different organs of Kochia indica Wight, a summer annual weed, in relation to its phenological sequence in the Nile Delta region of Egypt. This plant attained its maximum phytomass, i.e. production, (1182 g dw/m2) and maximum contents of most the estimated nutrients during the vegetative stage. Its production is much higher than many of the vegetation types in the Mediterranean deserts which was partially related to differences in soil moisture and fertility. The nutrient content of this plant is as much or more than some of the forage species currently used for pasture, and many of the range species in the western Mediterranean desert of Egypt.

Rarity of figs (Ficus) on Madagascar and its relationship to a depauperate frugivore community

Several authors have recognized that Madagascar has a depauperate frugivore community, although few explanations have been offered to explain this observation. In comparison to other tropical Old World forests, Malagasy forest has a reduced diversity and density of Ficus (generally an important keystone group in tropical forests), relatively low fruit productivity, and an unusual phenological sequence. These factors, some of which are presumed to be related to Madagascar’s long isolation from other land masses, are considered important variables to explain the island’s reduced frugivore community.

Diversity and phenology of weed communities in the Nile Delta region

AbstractThis study evaluates the species diversity and phe‐nological behaviour of the weed communities associated with the common crops in the Nile Delta region (three winter crops: Egyptian clover, broad beans and wheat; and three summer crops: cotton, maize and rice). The weed communities of winter crops are of higher diversity than those of summer crops, presumably due to differences in sowing and weeding processes. The phenological sequences of the weed communities are, in most cases, closely related to those of the crops in which they occur. The correspondence between the crucial periods in the life cycle of the weed and the crop (seedling establishment and fruiting) often leads to severe competition.

Vertical profile and canopy organization in a mixed deciduous forest

A combination of optical measurements of leaf heights and observations on litterfall provided a vertical and temporal description of the leaf community structure in a tall, Liriodendron forest on the Maryland coastal plain. Leaf area, mass, and number were bimodally distributed with height. Median leaf number occurs far below (7–8 m) and median leaf mass far above (22–23 m) the median leaf area (18–19 m). Tree species exhibited leaf stratification into 3 height levels: understory (0–10 m), mid canopy (10–25 m), and overstory (25–37 m). Species leaf area in litterfall was related to the species basal area, although representation of leaf number in litterfall was not correlated with stem numbers for species in the stand. Species also showed a clear phenological sequence of leaf fall.

Phenology of Dent Corn and Popcorn. I. Analysis of Repeated Measurements from Phenology Experiments1

AbstractRepeated observations are commonly made on individual or multiple plant samples in order to generate data suitable for developing linear regression models with growth stage as the dependent variable. Most studies using regression, including those conducted at the University of Nebraska, Lincoln (UNL), have implicitly assumed that the data adhere to standard regression assumptions even though these assumptions may be tenuous. Misleading conclusions can be made if basic regression assumptions are not reasonably satisfied. Pilot studies may be used as a strategy for completing preliminary analyses of representative data from a larger phenology study to develop appropriate regression models and substantiate basic regression assumptions. The objectives of this research were to (i) validate regression models used in an interactive agrometeorology (AGNET) offered by UNL (ii) correctly specify thermal‐photoperiod regression models of corn phenology using hourly data generated by an automated weather station, (iii) investigate the validity of underlying assumptions of models developed, and (iv) investigate the application of growth curve analysis as a statistical procedure for comparing response profiles of different treatment effects in corn phenology experiments. A 2‐yr phenology study incorporating three planting dates, one dent corn cultivar (B73 ✕ Mo17), and three differently maturing popcorn cultivars (P410, P609, and Iopop 12) was conducted in eastern Nebraska during 1982‐1983. Climate records from an automated weather data network were used to develop daily and hourly heat sums. Corn growth was described using both current and modified staging procedures. Serious violations of standard regression assumptions were identified in the UNL‐AGNET corn phenology model and were commonly associated with one or more of the following conditions: (i) using incorrectly specified models, (ii) heterogeneity of error variance, and (iii) nonindependence of errors. Violations were considered serious since they were suspected of producing biased mean squares and regression estimates, indicating a need for further refinement of model definitions and growth staging procedures. Alternative regression models were developed and tested using a modified staging procedure combined with partitioning and modeling phenological sequences as pre‐ and post‐anthesis development. When applied to these data, growth curve analysis demonstrated a curvilinear response of corn phenology to planting date (daylength) within the range of 14.3 to 15.2 h, and provided a useful alternative to standard regression techniques for statistically analyzing data from corn phenology experiments.

THE POLLINATION DYNAMICS OF SYMPATRIC SPECIES OF PEDICULARIS (SCROPHULARIACEAE)

Sympatric populations ofPedicularis oederi, P. cystopteridifolia, andP. groenlandicaon the Beartooth Plateau (Montana) were obligately dependent onBombuspollinators. Their corolla colors were mutually distinct to insect vision, but their nectars had identical sugar components. Analysis of corbicular pollen loads of pollinating insects indicated a high degree of polylecty. Queen/worker ratios of pollinators on plant species corresponded to the parallel phenological sequences of plant blooming and insect caste development. The total number of individual pollinators of eachBombusspecies on all plants was directly related to the number of plant species it pollinated, but a comparable relationship between the number of pollinators on a plant species to the number ofBombusspecies pollinating it was not found. Morphological and behavioral correspondence of floral mechanisms and pollinators form an integral part of the general pattern of coadaptive evolution of the floral ecology ofPedicularisin North America known from previous studies. Reproductive isolation betweenPedicularisspecies in this study is attributed to internal barriers. Wide overlaps of blooming seasons, proboscis lengths of bumblebee species and castes, and pollinator species onPedicularisspecies suggest resource sharing, rather than resource partitioning or competition for resources among plant and insect species and individuals.

Flowering Phenology and Seed Set in Claytonia virginica (Portulacaceae)

SCHEMSKE, D. W. (Dept. Ecol., Ethol. and Evol., Vivarium Bldg., Univ. Ill., IL 61820). Flowering phenology and seed set in Claytonia virginica (Portulacaceae). Bull. Torrey Bot. Club 104: 254-263. 1977.-Data oll seed set anid floweriiig pheiiology were obtained for Claytonia virginica L. in Brownfield and Hart Woods in central Illinois. At both sites flowering time varied markedly between years with temperature as the proximate cue. Mean seed set per ovary at Brownfield and Hart was greatest in 1974, lowest in 1975 and intermediate in 1976. As determined from ceinsuses of flowers on marked inflorescences at Brownfield in 1975 and 1976, seed set was highest in flowers first-pistillate betweeln the 25 and 50% cumulative flowering poiints. In both years, flowers opening early and late in the phenological sequence had reduced seed production and seed set declined rapidly during the latter periods of heavy flowering. Maximum seed set coincided with the first of the two peaks in the bimodal 1975 flowering sequence but preceded peak flowering in 1976. Abortion rates were highest in flowers first-pistillate during the final periods of Claytonia flowering when reduction of light due to canopy development was most severe. The evolution of Claytonia flowering time has been influenced by 1) cold temperatures early in the season which milnimize pollination probabilities and 2) developmenit of the cainopy late in the season which reduces photosynthetic capabilities.