Variation In Plant Phenology Research Articles

Functional traits influence patterns in vegetative and reproductive plant phenology - a multi-botanical garden study.

Phenology has emerged as key indicator of the biological impacts of climate change, yet the role of functional traits constraining variation in herbaceous species' phenology has received little attention. Botanical gardens are ideal places in which to investigate large numbers of species growing under common climate conditions. We ask whether interspecific variation in plant phenology is influenced by differences in functional traits. We recorded onset, end, duration and intensity of initial growth, leafing out, leaf senescence, flowering and fruiting for 212 species across five botanical gardens in Germany. We measured functional traits, including plant height, absolute and specific leaf area, leaf dry matter content, leaf carbon and nitrogen content and seed mass and accounted for species' relatedness. Closely related species showed greater similarities in timing of phenological events than expected by chance, but species' traits had a high degree of explanatory power, pointing to paramount importance of species' life-history strategies. Taller plants showed later timing of initial growth, and flowered, fruited and underwent leaf senescence later. Large-leaved species had shorter flowering and fruiting durations. Taller, large-leaved species differ in their phenology and are more competitive than smaller, small-leaved species. We assume climate warming will change plant communities' competitive hierarchies with consequences for biodiversity.

Herbivory in a changing climate-Effects of plant genotype and experimentally induced variation in plant phenology on two summer-active lepidopteran herbivores and one fungal pathogen.

With climate change, spring warming tends to advance plant leaf‐out. While the timing of leaf‐out has been shown to affect the quality of leaves for herbivores in spring, it is unclear whether such effects extend to herbivores active in summer. In this study, we first examined how spring and autumn phenology of seven Quercus robur genotypes responded to elevated temperatures in spring. We then tested whether the performance of two summer‐active insect herbivores (Orthosia gothica and Polia nebulosa) and infection by a pathogen (Erysiphe alphitoides) were influenced by plant phenology, traits associated with genotype or the interaction between these two. Warm spring temperatures advanced both bud development and leaf senescence in Q. robur. Plants of different genotype differed in terms of both spring and autumn phenology. Plant phenology did not influence the performance of two insect herbivores and a pathogen, while traits associated with oak genotype had an effect on herbivore performance. Weight gain for O. gothica and ingestion for P. nebulosa differed by a factor of 4.38 and 2.23 among genotypes, respectively. Herbivore species active in summer were influenced by traits associated with plant genotype but not by phenology. This suggest that plant attackers active in summer may prove tolerant to shifts in host plant phenology—a pattern contrasting with previously documented effects on plant attackers active in spring and autumn.

Dynamic changes in the thermal growing season and their association with atmospheric circulation in China.

Vegetation phenology is one of the key agroclimatic indices that is sensitive to climate change. Analyzing the variation in plant phenology under a changing environment can provide reference information to assess the impact of climate change on ecosystems and agricultural management. In this study, we focused on the thermal growth season, an important phenology index. We defined four growing season indices based on the surface temperature to quantify the changes in thermal growth season and analyze their association with atmospheric circulation in China. The results showed that the start date of the growing season exhibited a significant advanced trend (P < 0.001), while the end date exhibited a significant delayed trend (P < 0.001). The length of growing season and the number of ≥ 10℃ days increased significantly in China (P < 0.001) from 1960 to 2018. The variation in thermal growth season differed in different regions. The Qinghai-Tibet Plateau and the Loess Plateau were the regions in which thermal growing season was the most sensitive to climate changes. Atmospheric circulation was one of the main factors affected the change in thermal growing season indices. The West Pacific Subtropical High Intensity Index and the Arctic Oscillation Index significantly negatively correlated with the start date of the growing season (P < 0.05), and significantly positively correlated with the length of growing season and the number of ≥ 10℃ days (P < 0.01). Atmospheric circulation affected the change in temperature and subsequently affected the thermal growth season. These findings will provide useful information to assess the risk assessment of climate change and take action to reduce in the impact of climate change on ecosystems and agricultural management.

The PhenObs initiative: A standardised protocol for monitoring phenological responses to climate change using herbaceous plant species in botanical gardens

Abstract Changes in phenology induced by climate change occur across the globe with important implications for ecosystem functioning and services, species performance and trophic interactions. Much of the work on phenology, especially leaf out and flowering, has been conducted on woody plant species. Less is known about the responses in phenology of herbaceous species induced by global change even though they represent a large and important part of biodiversity worldwide. A globally coordinated research effort is needed to understand the drivers and implications of such changes and to predict effects of global change on plant species phenology and related ecosystem processes. Here, we present the rationale of the PhenObs initiative—botanical gardens as a global phenological observation network. The initiative aims to collect data on plant phenology in botanical gardens which will be used alongside information on plant traits and site conditions to answer questions related to the consequences of global change: What is the variation in plant phenology in herbaceous species across the growing season and in response to changes in climate? How can plant phenology be predicted from species’ trait composition, provenance, position and extent of the distribution range and species’ phylogeny? What are the implications of this variation with respect to species performance and assembly, biotic interactions (e.g. plant–pollinator interactions) as well as ecosystem processes and services under changing land use and climate? Here, we lay out the development of a straightforward protocol that is appropriate for monitoring phenology across a vast diversity of growth forms of herbaceous species from various habitats and geographical regions. To focus on a key number of stages necessary to capture all aspects of plant species phenology, we analysed associations between 14 phenological stages. These data were derived from a 2‐year study on 199 species in four German botanical gardens. Based on the relationships of the phenological stages, we propose to monitor three vegetative stages (‘initial growth’, ‘leaves unfolding’ and ‘senescence’) and two reproductive stages (‘flowers open’ and ‘ripe fruits’) to fully capture herbaceous species phenology. A free Plain Language Summary can be found within the Supporting Information of this article.

Linkage between species traits and plant phenology in an alpine meadow.

Plant phenology differs largely among coexisting species within communities that share similar habitat conditions. However, the factors explaining such phenological diversity of plants have not been fully investigated. We hypothesize that species traits, including leaf mass per area (LMA), seed mass, stem tissue mass density (STD), maximum plant height (Hmax), and relative growth rate in height (RGRH), explain variation in plant phenology, and tested this hypothesis in an alpine meadow. Results showed that both LMA and STD were positively correlated with the onset (i.e., beginning) and offset (i.e., ending) times of the four life history events including two reproductive events (flowering and fruiting) and two vegetative events (leafing and senescing). In contrast, RGRH was negatively correlated with the four life phenological events. Moreover, Hmax was positively correlated with reproductive events but not with vegetative events. However, none of the eight phenological events was associated with seed size. In addition, the combination of LMA and STD accounted for 50% of the variation in plant phenologies. Phylogenetic generalized least squares analysis showed plant phylogeny weakened the relationships between species traits vs. phenologies. Phylogeny significantly regulated the variation in the ending but not the beginning of phenologies. Our results indicate that species traits are robust indicators for plant phenologies and can be used to explain the diversity of plant phenologies among co-occurring herbaceous species in grasslands. The findings highlight the important role of the combination of and trade-offs between functional traits in determing plant phenology diversity in the alpine meadow.

Seasonal dynamic variation of pollination network is associated with the number of species in flower in an oceanic island community

Abstract Aims Plant–pollinator interaction networks are dynamic entities, and seasonal variation in plant phenology can reshape their structure on both short and long timescales. However, such seasonal dynamics are rarely considered, especially for oceanic island pollination networks. Here, we assess changes in the temporal dynamics of plant–pollinator interactions in response to seasonal variation in floral resource richness in oceanic island communities. Methods We evaluated seasonal variations of pollination networks in the Yongxing Island community. Four temporal qualitative pollination networks were analyzed using plant–pollinator interaction data of the four seasons. We collected data on plant–pollinator interactions during two consecutive months in each of the four seasons. Four network-level indices were calculated to characterize the overall structure of the networks. Statistical analyses of community dissimilarity were used to compare this community across four seasons to explore the underlying factors driving these patterns. We also evaluated the temporal variation in two species-level indices of plant and pollinator functional groups. Important Findings Both network-level specialization and modularity showed a significantly opposite trend compared with plant species richness across four seasons. Increased numbers of plant species might promote greater competition among pollinators, leading to increased niche overlap and causing decreased specialization and modularity and vice versa. Further analyses suggested that the season-to-season turnover of interactions was dominated by interaction rewiring. Thus, the seasonal changes in niche overlap among pollinators lead to interaction rewiring, which drives interaction turnover in this community. Hawkmoths had higher values of specialization and Apidae had higher values of species strength compared with other pollinator functional groups. These findings should be considered when exploring plant–pollinator interactions in ecosystems of isolated oceanic islands and in other ecosystems.

Remote Detection of Large-Area Crop Types: The Role of Plant Phenology and Topography

Sustainable agricultural practices necessitate accurate baseline data of crop types and their detailed spatial distribution. Compared with field surveys, remote sensing has demonstrated superior performance, offering spatially explicit crop distribution in a timely manner. Recent studies have taken advantage of remote sensing time series to capture the variation in plant phenology, inferring major crop types. However, such an approach was rarely used to extract detailed, multiple crop types spanning a large area, and the impact of topography has yet to be well analyzed in mountainous regions. This study aims to answer two questions in crop type extraction: (i) Is it feasible to accurately map multiple crop types over a large mountainous area with phenology-based modeling? (ii) What are the effects of topography in such modeling? To answer the questions, phenological metrics were extracted from MODIS (Moderate Resolution Imaging Spectroradiometer) satellite time series, and the random forests classifier was used to map 12 crop types in South China (236,700 km2), featuring a subtropical monsoon climate and high topographic variation. Our study revealed promising results using MODIS EVI (Enhanced Vegetation Index) and NDVI (Normalized Difference Vegetation Index) time series, although EVI outperformed NDVI (overall accuracy: 85% versus 81%). The spectral and temporal metrics of plant phenology significantly contributed to crop identification, where the spectral information exhibited greater importance. The increase of slope led to a decrease in model accuracy in general. However, uniformly distributed tree plantations (e.g., tea-oil camellia, gum, and tea trees) being cultivated on large slopes (&gt;15 degrees) achieved accuracies greater than 80%.

Climate-driven reduction of genetic variation in plant phenology alters soil communities and nutrient pools.

We examined the hypothesis that climate-driven evolution of plant traits will influence associated soil microbiomes and ecosystem function across the landscape. Using a foundation tree species, Populus angustifolia, observational and common garden approaches, and a base population genetic collection that spans 17 river systems in the western United States, from AZ to MT, we show that (a) as mean annual temperature (MAT) increases, genetic and phenotypic variation for bud break phenology decline; (b) soil microbiomes, soil nitrogen (N), and soil carbon (C) vary in response to MAT and conditioning by trees; and (c) with losses of genetic variation due to warming, population-level regulation of community and ecosystem functions strengthen. These results demonstrate a relationship between the potential evolutionary response of populations and subsequent shifts in ecosystem function along a large temperature gradient.

Large herbivore migration plasticity along environmental gradients in Europe: life‐history traits modulate forage effects

The most common framework under which ungulate migration is studied predicts that it is driven by spatio–temporal variation in plant phenology, yet other hypotheses may explain differences within and between species. To disentangle more complex patterns than those based on single species/ single populations, we quantified migration variability using two sympatric ungulate species differing in their foraging strategy, mating system and physiological constraints due to body size. We related observed variation to a set of hypotheses. We used GPS‐collar data from 537 individuals in 10 roeCapreolus capreolusand 12 red deerCervus elaphuspopulations spanning environmental gradients across Europe to assess variation in migration propensity, distance and timing. Using time‐to‐event models, we explored how the probability of migration varied in relation to sex, landscape (e.g. topography, forest cover) and temporally‐varying environmental factors (e.g. plant green‐up, snow cover). Migration propensity varied across study areas. Red deer were, on average, three times more migratory than roe deer (56% versus 18%). This relationship was mainly driven by red deer males which were twice as migratory as females (82% versus 38%). The probability of roe deer migration was similar between sexes. Roe deer (both sexes) migrated earliest in spring. While territorial male roe deer migrated last in autumn, male and female red deer migrated around the same time in autumn, likely due to their polygynous mating system. Plant productivity determined the onset of spring migration in both species, but if plant productivity on winter ranges was sufficiently high, roe deer were less likely to leave. In autumn, migration coincided with reduced plant productivity for both species. This relationship was stronger for red deer. Our results confirm that ungulate migration is influenced by plant phenology, but in a novel way, that these effects appear to be modulated by species‐specific traits, especially mating strategies.

Maize carbon dynamics are driven by soil erosion state and plant phenology rather than nitrogen fertilization form

Carbon (C) stored in soils represents the largest C pool of terrestrial ecosystems and consequently plays a crucial role in the global C cycle. So far, it is widely unclear to what extent different land uses and land use change influence soil C storage. The hummocky ground moraine landscape of northeastern Germany is characterized by distinct small-scale soil heterogeneity on the one hand, and intensive energy crop cultivation on the other. Both factors are assumed to significantly influence gaseous C exchange; as such, they likely drive soil organic carbon (SOC) stock dynamics in terrestrial agricultural ecosystems. To date, it is not clear to what extent N fertilization forms, which are associated with energy crop cultivation (e.g., application of biogas fermentation residues) and soil type relative to soil erosion state, influence soil C dynamics, nor is it clear whether one of these factors is more important than the other. To investigate the influence of soil erosion state and N fertilization form on soil C dynamics, we present dynamic and seasonal net ecosystem carbon balances (NECB) as a proxy for changes in soil organic carbon stocks. Measurements were conducted for maize (Zea mays L.) at five sites in the “CarboZALF-D” experimental field during the 2011 growing season. Measurement sites represent different soil erosion states (non-eroded Albic Luvisols, extremely eroded Calcaric Regosols and depositional Endogleyic Colluvic Regosols) and N fertilization forms (100% mineral fertilizer, 50% mineral and 50% organic fertilizer, and 100% organic fertilizer). Fertilization treatments were established on the Albic Luvisol. Net ecosystem CO2 exchange (NEE) and ecosystem respiration (Reco) were measured every four weeks using a dynamic flow-through non-steady-state closed manual chamber system. Gap filling was performed based on empirical temperature and PAR dependency functions and was used to derive daily NEE values. In parallel, daily above-ground biomass production (NPPshoot) was estimated using a logistic growth equation, fitted on periodic biomass samples. Finally, C dynamics were calculated as the balance of daily NEE and NPPshoot based on the initial C input due to organic fertilization. Resulting NECB varied from pronounced soil C losses at the Endogleyic Colluvic Regosol (592g C m−2) to soil C gains at the Calcaric Regosol (−124g C m−2). Minor to modest C losses were observed for the Albic Luvisol. Compared to N fertilization forms, soil erosion states generally had a stronger impact on derived NECB. However, interannual variations in plant phenology and interactions between soil erosion states and fertilization forms might result in different NECB values over multiple years. Hence, long-term measurements of different fertilization treatments on characteristic soil landscape elements are needed.

气候变化背景下1964-2015年秦岭植物物候变化

PDF HTML阅读 XML下载 导出引用 引用提醒 气候变化背景下1964-2015年秦岭植物物候变化 DOI: 10.5846/stxb201702200277 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家林业公益性行业科研专项（201304309） Variation in plant phenology in the Qinling Mountains from 1964-2015 in the context of climate change Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以1964-2015年物候观测数据为基础，选取17种含乔木、灌木及藤本树种为研究对象，分析探讨了气候变化背景下秦岭地区植物物候变化规律及其差异性。结果表明：①52年来，秦岭地区物候始期普遍呈提前趋势，提前速率1.2d/10a，物候末期普遍呈推迟趋势，推迟速率3.5d/10a，物候生长期普遍延长；②秦岭地区物候突变发生于20世纪80年代，始期于1985年，末期于1984年。突变后，物候特征发生了显著变化，始期的提前速率较突变前显著加快，末期由突变前的提前趋势转变为极显著的推迟趋势，且变化速率和显著性均高于始期；始期与末期变化均表现出"趋同效应"；物候年代际变化趋势显示，始期自2001-2005年起提前速率减缓，植物对气候变化的响应表现出适应性及滞后性。③秦岭物候变化存在树种差异，3大类树种始期的提前速率呈藤本、乔木、灌木依次增大，而末期的推迟速率则呈藤本、灌木、乔木依次减小。④秦岭物候变化存在南北差异，北坡始期的提前速率均高于南坡，而南坡末期的推迟速率均高于北坡。 Abstract:In the context of global climate change, plant phenology has become the subject of intensive research. Mountains are considered indicators of global climate change. The Qinling mountain region, known as a unique geographical unit in China because of its ecological sensitivity and vulnerability, underwent a significant temperature increase in the last 50 years. Based on phenological data collected from 1964-2015, 17 plant species, including trees, shrubs, and vines, were selected as the subjects of the present study. This paper analyzes and discusses changing conditions and changes in plant phenology in the context of global climate change in the Qinling Mountains. Our analyses generated four primary results. First, over the past 52 years, the beginning of the plant phenophase has advanced at a rate of 1.2 days decade-1, and the end of the plant phenophase has delayed at a rate of 3.5 days decade-1, causing a significant prolongation of the growth period. The primary reason for this prolongation is the rising temperature in the region. There was a inconsistency on the response at the beginning and the end of the phenophase to temperature. Second, the abrupt change of phenophase occurred in the 1980s in Qinling area, the start of phenophase occurred in 1985 andthe end of phenophase did in 1984. After the abrupt change occurs, plant phenological characteristics changed significantly, compared with abrupt change before, showing that the advanced rate in the start of phenophase was faster, and the trend in the end of the phenophase turned into a very significant delay; the rate of change and the significance at the end of the plant phenophase were higher than that at the beginning of the period. These changes in the beginning and end points of plant phenophases manifest as a "convergence effect". Interdecadal variations in phenology indicate that the rate of advance in the beginning of plant phenophases slowed from 2001 to 2005, and that the response of plants to climate change showed qualities of adaptability and hysteresis. These results indicate that the dominant factor leading to changes in the beginning and end points of the plant phenophase was temperature, and that the response of plant phenology to changes in temperature is particularly sensitive, further demonstrating that there is a correlation between plant phenophase and climate change. Third, changes in phenophase varied by species. The advancement of the beginning of the phenophase promoted the prevalence of shrubs, trees, and vines, in this order, at the beginning of the phenophase, whereas the delay in the ending of the phenophase decreased the abundance of trees, shrubs, and vines, in this order, at the end. These differences in abundance are related to differences in physiological characteristics between the different species in response to climate change. Finally, plant responses to climate change in the Qinling Mountains differed along a north-south axis. The rate of advance in the beginning of the phenophase was higher in the northern slope than in the southern slope, whereas the rate of delay in ending of the phenophase was more severe in the southern slope than in the northern slope. 参考文献 相似文献 引证文献

Host plant phenology may determine the abundance of an ecosystem engineering herbivore in a tropical savanna

1. Variation in plant phenology allows plants to escape from herbivory. Insect herbivores manipulate their host plants by producing shelters, which they inhabit, and are protected against natural enemies and/or unfavourable environmental conditions. Environmental modifications induced by living organisms are characterised as ecosystem engineering.2. In the Brazilian savanna, the interaction between the Malpighiaceae shrub, Byrsonima intermedia, and its main herbivore, the caterpillar Cerconota achatina, a shelter‐building organism, was studied.3. It was focused on whether the phenological development of the host plant affects the caterpillars' infestation, and whether C. achatina acts as an ecosystem engineer by building shelters. All plant variables (number of leaves, flowers, buds, fruits and herbivores) were measured fortnightly. Phenological data were correlated with climatic information. The impact of the caterpillars acting as ecosystem engineers was measured experimentally.4. Infestation levels of C. achatina covaried with the phenology of their host plant B. intermedia. It suggests that plant phenology might be an important factor in determining the abundances of this ecosystem engineer species.

Time-invariant differences between plant individuals in interactions with arthropods correlate with intraspecific variation in plant phenology, morphology and floral scent.

The basic units of ecological and evolutionary processes are individuals. Network studies aiming to infer mechanisms from complex systems, however, usually focus on interactions between species, not individuals. Accordingly, the structure and underlying mechanisms of individual-based interaction networks remain largely unknown. In a common garden, we recorded all interactions on flowers and leaves of 97 Sinapis arvensis individuals from seedling stage to fruit set and related interindividual differences in interactions to the plant individuals' phenotypes. The plant individuals significantly differed in their quantitative and qualitative interactions with arthropods on flowers and leaves. These differences remained stable over the entire season and thus were time-invariant. Variation in interacting arthropod communities could be explained by a pronounced intraspecific variability in flowering phenology, morphology and flower scent, and translated into variation in reproductive success. Interestingly, plant individuals with a similar composition of flower visitors were also visited by a similar assemblage of interaction partners at leaves. Our results show that the nonuniformity of plant species has pronounced effects in community ecology, potentially with implications for the persistence of communities and populations, and their ability to withstand environmental fluctuations.

Geographic variations in spring and autumn phenology of white ash in a common garden

Geographic variations in plant phenology are known to be affected by climatic differences over space, but the role of adaptation variability of plant populations is less well understood. In this study, I examined the geographic variations in spring and autumn phenology of white ash (Fraxinus americana L.) in a common garden and related observations over a 2-year period (2013 and 2014) to climatic and geographic factors of their provenances. Spring leaf-out of trees with northern provenances occurred later in 2013, but slightly earlier in 2014, than those with southern provenances. This difference was potentially caused by the counterbalancing effect of chilling and forcing in response to interannual temperature fluctuations. In both years, leaf senescence of white ash occurred significantly earlier for trees with northern than southern provenances, reflecting strong adaptation to a photoperiod gradient. The growing season length for white ash, therefore, is constrained by spring and fall phenology through different environmental cues. Spring phenology exerted a greater influence on the interannual variability of growing season length. Identifying these detailed adaptive patterns facilitates a better understanding of phenological change over space and allows development of genotype-sensitive phenological models to predict the ecological impact of climate change.

Interannual variation in carbon sequestration depends mainly on the carbon uptake period in two croplands on the North China Plain.

Interannual variation in plant phenology can lead to major modifications in the interannual variation of net ecosystem production (NEP) and net biome production (NBP) as a result of recent climate change in croplands. Continuous measurements of carbon flux using the eddy covariance technique were conducted in two winter wheat and summer maize double-cropped croplands during 2003–2012 in Yucheng and during 2007–2012 in Luancheng on the North China Plain. Our results showed that the difference between the NEP and the NBP, i.e., the crop economic yield, was conservative even though the NEP and the NBP for both sites exhibited marked fluctuations during the years of observation. A significant and positive relationship was found between the annual carbon uptake period (CUP) and the NEP as well as the NBP. The NEP and the NBP would increase by 14.8±5.2 and 14.7±6.6 g C m−2 yr−1, respectively, if one CUP-day was extended. A positive relationship also existed between the CUP and the NEP as well as the NBP for winter wheat and summer maize, respectively. The annual air temperature, through its negative effect on the start date of the CUP, determined the length of the CUP. The spring temperature was the main indirect factor controlling the annual carbon sequestration when a one-season crop (winter wheat) was considered. Thus, global warming can be expected to extend the length of the CUP and thus increase carbon sequestration in croplands.

Back to the future for plant phenology research.

Back to the future for plant phenology research.

Effects of experimental warming on nitrogen concentration and biomass of forage plants for an arctic herbivore

Summary In many arctic herbivores, the growth of young depends upon a synchrony between hatching date and seasonal change in plant nutritive quality. If plants respond more quickly than herbivores to climate warming, this may cause a mismatch between the availability of high‐quality food and the hatching of young. This study examines the impact of experimental warming on the main food plants of an arctic herbivore, the greater snow goose (Chen caerulescens atlanticaL.) breeding on Bylot Island, Nunavut, Canada. During summers 2007–2009, we increased the temperature using small glasshouses (open‐top chambers, OTC) in two habitats, wetlands and mesic tundra. Every 10 days, we measured above‐ground plant biomass and a proxy of nutritive quality, nitrogen concentration, of graminoid plants in warmed and control plots from snowmelt in June until late July. Open‐top chambers increased mean maximum temperature by up to 2.0 °C in wetlands and 4.6 °C in mesic tundra. Annual warming significantly increased biomass of graminoids by up to 29% in wetlands and 20% in mesic tundra. There was no difference in nitrogen concentration of the four plant species sampled (Dupontia fisheri, Eriophorum scheuchzeri, Arctagrostis latifolia and Luzula spp.) early in the season, but the seasonal decline in nitrogen occurred more rapidly in warmed than in control plots (10% to 14% less nitrogen in warmed plots in July). This effect was consistent across the 3 years of the experiment and independent of annual variation in plant phenology. There was either a weak positive effect or no effect of the warming treatment on the nitrogen biomass of plants depending on species or period of the season. Synthesis. Our results show that warming speeds up plant phenology and the seasonal decline in nutritive quality for arctic herbivores. Because young herbivores like geese are highly sensitive to the nitrogen concentration of their food, a warmer climate will likely reduce their growth. Climate warming may therefore have a negative impact on the population dynamic of arctic herbivores by reducing the quality of their summer forage.

Population abundance and early spring conditions determine variation in body mass of juvenile chamois

For species living in seasonal environments the understanding of demographic processes requires identifying the environmental factors during spring and summer that shape phenotypic variation. We assessed the effects of plant phenology and population abundance during spring–summer on variation in autumn body mass among cohorts (1995–2006) of juvenile alpine chamois (Rupicapra rupicapra). We computed several metrics based on the normalized difference vegetation index (NDVI) to assess interannual variation in plant phenology and productivity. Body mass of both sexes decreased similarly during years with late springs (220%) and with increasing population abundance (215%), with no interactive effect. Our results also suggested that forage quality more than forage quantity influenced body mass of juveniles. Variation in body mass of juveniles thus can be used as an indicator of the relationship between chamois populations and their environment. This study also demonstrates the utility of satellite-based data in increasing our understanding of the consequences of spring–summer conditions on life-history traits.

Asynchrony, fragmentation, and scale determine benefits of landscape heterogeneity to mobile herbivores

Understanding the ways that resource heterogeneity shapes the performance of individuals and the dynamics of populations offers a central challenge in contemporary ecology. Emerging evidence shows that herbivores track heterogeneity in nutritional quality of vegetation by responding to phenological differences in plants, differences that result from spatial and temporal variation in conditions favoring plant growth. Theory predicts that when spatial variation in temperature, nutrients, or moisture results in spatially asynchronous pulses of plant growth, herbivores are able to prolong the period during which they have access to forage of peak nutritional value. Although this idea has substantial support from observational and modeling studies, it has not been examined experimentally. We hypothesized that access to asynchronous resources enhances nutritional status and growth of herbivores and that the magnitude of this effect depends on the scale of access relative to the grain of resources. We tested these hypotheses in mesocosm experiment using the migratory grasshopper, Melanoplus sanguinipes, feeding on young wheat and protein-rich bran as a model system. We demonstrated access to asynchronous pulses in resources enhanced the efficiency of use of high quality resource use and increased growth of individuals by 13%. Disruption of this mechanism when landscapes were fragmented lowered efficiency of resource use and caused growth of individuals to decline by 15%. However, the strength of the effects of fragmentation on herbivore performance depended on the spatial extent of fragmentation relative to the spatial and temporal grain of resource emergence. Our findings add experimental support to modeling and observational studies that have linked herbivore performance to spatial and temporal variation in plant phenology. We also offer evidence that fragmentation can impair herbivore performance, even when the total amount and quality of resources on landscapes remains unchanged.

Modeling temporal variations in multipolarized radar scattering from intertidal coastal wetlands

Coastal wetlands form critical ecosystems that are very sensitive to natural and anthropogenic environmental factors. These dynamic environments can exhibit both seasonal and year-to-year variability causing significant temporal variations in remotely sensed data. Understanding these variations is necessary if time series of remotely sensed data are to be used to monitor and manage coastal environments. Coastal areas can also experience persistent cloud cover, thereby making the use of microwave sensors, such as radar, potentially attractive for monitoring. Data acquired by polarimetric Synthetic Aperture Radar (SAR) and Laser Altimeter (LIDAR) sensors are analyzed to evaluate the response of a coastal marsh complex to climatic and tidal processes. The utility of L-band SAR data is investigated for detecting the presence of inundation and quantifying seasonal variations in plant phenology in several wetland environments. A coherent microwave scattering model is used to simulate radar backscatter from the marsh under different phenological and inundation conditions. Coastal marshes can exhibit scattering behavior that is different from other environments, such as forests and inland grasslands, for which scattering phenomena have been more thoroughly studied. Using a high-resolution Digital Elevation Model (DEM) derived from LIDAR data and ancillary measurements of climatic and tidal conditions, changes in the multi-polarization L-band SAR responses over a three-year period are related to specific scattering mechanisms in the marsh. Results indicate that variations in polarization preference of herbaceous marshes are often more pronounced than those observed over upland areas. Succulent halophytic plants in the high marsh respond strongly to inundation but only mildly to climatic factors, such as average daily temperature. Conversely, the response of non-succulent halophytic plants in the low marsh is strongly dependent on climate, which in turn affects their response to inundation. Results indicate that some knowledge of the vegetation phenology is required, along with scattering simulations, for meaningful interpretation of multi-temporal SAR data over coastal wetlands.