Early Season Temperature Research Articles

Overwintering Improves Ranunculus Cut Flower Production in the US Intermountain West

Ranunculus (Ranunculus asiaticus L.) cut flower production in the US Intermountain West is limited by a narrow window of optimal temperature ranges in the spring. With the increasing number of Intermountain West cut flower growers, regional management recommendations are needed to improve ranunculus harvest timing and yield. The objectives of this research were to evaluate planting dates, winter insulation, tuberous root (TR) preparation, and cultivar selection for flower timing, yield, quality, and profitability in high tunnel and field production systems. Trials were conducted in a North Logan, UT (41.7665° N, −111.811° W, 1405 m elevation, USDA hardiness zone 5) high tunnel and field from fall 2019 to spring 2022. TRs were either pre-sprouted or directly planted into a high tunnel (left bare or covered with low tunnels) or field (left bare or covered with mulch, a low tunnel, or mulch and a low tunnel) from November to April. High tunnels advanced production by four weeks, nearly doubled total yield, and increased the proportion of quality (longer than 25 cm) stems by 50% compared to the field. Planting pre-sprouted TRs in the high tunnel in November delivered the earliest harvest (6 Apr.), highest marketable yield (286 stems per m2 ± 36 SE), and highest net returns ($54 per m2), with 39% greater marketable yield for ‘LaBelle’ than ‘Amandine.’ Insulation nearly doubled emergence and improved marketable yield by 49 stems per m2 ± 8 SE for November field plantings. Ranunculus production was optimized as a fall-planted high tunnel crop in the Intermountain West but may be fall-planted in the field with insulation, allowing growers to maximize production during more optimal, early-season temperatures.

Impact of Early Season Temperatures in a Climate-Changed Atmosphere for Michigan: A Cool-Climate Viticultural Region

This study assesses the impacts of observed (2001–2012) and projected climate change on early season heat accumulation for grape production (viticulture) in a cool-climate region of the world (Michigan, USA). Observational data were generated from a weather station located in the center of one of the most important appellations located in the SW part of the state. Climate change projections retrieved from a high spatiotemporal weather model using atmospheric conditions simulated for the end of the 21st Century. All the temperature variables considered demonstrated significant warming trends especially during the months of March, April and May. Temperature differences, increases in heat accumulation, and changes to potential frost events would necessitate new approaches to vineyard management. In fact, it is likely that vine budburst will occur earlier and early season frost develop as a new challenge. However, our study results are comparable with other viticulture regions of the world, with a warming trend of at least 3 to 5 °C in the months leading up to the growing season by the end of the 21st Century. Therefore, effective climate change adaptations will be important to the grape and wine industry in this region. Management strategies are needed to minimize climate risks while taking advantage of new opportunities related to improved climatic conditions for growing more late-ripening European Vitis vinifera grape varieties, relevant for producing higher quality wines.

Dynamics of seasonal growth in a long-lived southern hemisphere conifer are linked to early season temperature

Standard correlation approaches in dendroclimatology provide limited scope to elucidate differences between years in timing of growth initiation and cessation. In the Southern Hemisphere (SH), with relatively few long-term climate reconstructions, a clearer understanding of signals contained in ring width variation is of particular importance. In this study, we monitored growth in detail at two sites (low and high altitude) in Lagarostrobos franklinii (Huon pine) for five growing seasons. In concert, local environmental data were recorded, and cambial samples taken on several occasions. Season duration in Huon pine at low altitude lasted about six months, generally starting in September/October and ending in April. At higher altitude, season duration did not exceed about four months and generally started during November, ending in March. The shortest season and smallest rings were linked to cooler conditions compared to other years. On the other hand, an earlier growth onset in the 2011 growing season was evidently brought on by unusually warm conditions in late winter. Growth onset was linked to a running mean temperature of about 8.5 °C and 6.5 °C at the lower and higher altitude sites, respectively. While effects of limiting water on growth cessation were not universally clear, our results suggest that limiting water (during hotter, drier summers) may reduce growth rates, and precipitate earlier growth cessation.

Modeling phenological reaction norms over an elevational gradient reveals contrasting strategies of Dusky Flycatchers and Mountain Chickadees in response to early-season temperatures

Abstract We developed an approach to distinguish among 3 alternative strategies that birds may employ relating the timing of egg laying across elevations to annual variation in spring temperature (phenological reaction norms), which we applied to analyze the breeding phenology of 2 species over an elevational gradient in the Sierra Nevada, California. In a “simple-offset” strategy, birds at different elevations initiate breeding relative to environmental temperature in a consistent manner, in that breeding onset is triggered by a critical temperature regardless of when it occurs in the spring. Elevation-specific reaction norms based on multiple years are offset (high-elevation birds start breeding later) but parallel. In a “delay” strategy, in cooler springs, populations at higher elevations that are sensitive to early-season weather-related risks delay laying onset relative to those at lower elevations, yielding a high-elevation reaction norm that diverges from a low-elevation one at cooler temperatures. Conversely, high-elevation populations in cooler springs that are sensitive to the risk of having insufficient time to complete a breeding cycle advance laying onset relative to lower populations (“advance” strategy), yielding a high-elevation reaction norm than converges with a low-elevation one. Both delay and advance strategies imply an elevation-dependent interaction between temperature and date (photoperiod) in influencing laying onset. Examined across 3 elevation groupings, phenological reaction norms of Mountain Chickadees (Poecile gambeli) were essentially parallel, consistent with simple offset, whereas Dusky Flycatchers (Empidonax oberholseri) relationships were more complex. In cooler springs, mid-elevation flycatchers bred comparatively late relative to lowest-elevation birds (delay), implying greater sensitivity to early-season risks, but still with sufficient time to complete a breeding cycle. However, high-elevation flycatchers bred comparatively early relative to mid-elevation populations (advance); delaying at these highest elevations may not be an option. Our approach revealed differences in risk sensitivity that were consistent with other ecological differences between the 2 species.

Detecting Recent Crop Phenology Dynamics in Corn and Soybean Cropping Systems of Kentucky

Accurate phenological information is essential for monitoring crop development, predicting crop yield, and enhancing resilience to cope with climate change. This study employed a curve-change-based dynamic threshold approach on NDVI (Normalized Differential Vegetation Index) time series to detect the planting and harvesting dates for corn and soybean in Kentucky, a typical climatic transition zone, from 2000 to 2018. We compared satellite-based estimates with ground observations and performed trend analyses of crop phenological stages over the study period to analyze their relationships with climate change and crop yields. Our results showed that corn and soybean planting dates were delayed by 0.01 and 0.07 days/year, respectively. Corn harvesting dates were also delayed at a rate of 0.67 days/year, while advanced soybean harvesting occurred at a rate of 0.05 days/year. The growing season length has increased considerably at a rate of 0.66 days/year for corn and was shortened by 0.12 days/year for soybean. Sensitivity analysis showed that planting dates were more sensitive to the early season temperature, while harvesting dates were significantly correlated with temperature over the entire growing season. In terms of the changing climatic factors, only the increased summer precipitation was statistically related to the delayed corn harvesting dates in Kentucky. Further analysis showed that the increased corn yield was significantly correlated with the delayed harvesting dates (1.37 Bu/acre per day) and extended growing season length (1.67 Bu/acre per day). Our results suggested that seasonal climate change (e.g., summer precipitation) was the main factor influencing crop phenological trends, particularly corn harvesting in Kentucky over the study period. We also highlighted the critical role of changing crop phenology in constraining crop production, which needs further efforts for optimizing crop management practices.

Widespread mortality of trembling aspen (Populus tremuloides) throughout interior Alaskan boreal forests resulting from a novel canker disease.

Over the past several decades, growth declines and mortality of trembling aspen throughout western Canada and the United States have been linked to drought, often interacting with outbreaks of insects and fungal pathogens, resulting in a “sudden aspen decline” throughout much of aspen’s range. In 2015, we noticed an aggressive fungal canker causing widespread mortality of aspen throughout interior Alaska and initiated a study to quantify potential drivers for the incidence, virulence, and distribution of the disease. Stand-level infection rates among 88 study sites distributed across 6 Alaska ecoregions ranged from <1 to 69%, with the proportion of trees with canker that were dead averaging 70% across all sites. The disease is most prevalent north of the Alaska Range within the Tanana Kuskokwim ecoregion. Modeling canker probability as a function of ecoregion, stand structure, landscape position, and climate revealed that smaller-diameter trees in older stands with greater aspen basal area have the highest canker incidence and mortality, while younger trees in younger stands appear virtually immune to the disease. Sites with higher summer vapor pressure deficits had significantly higher levels of canker infection and mortality. We believe the combined effects of this novel fungal canker pathogen, drought, and the persistent aspen leaf miner outbreak are triggering feedbacks between carbon starvation and hydraulic failure that are ultimately driving widespread mortality. Warmer early-season temperatures and prolonged late summer drought are leading to larger and more severe wildfires throughout interior Alaska that are favoring a shift from black spruce to forests dominated by Alaska paper birch and aspen. Widespread aspen mortality fostered by this rapidly spreading pathogen has significant implications for successional dynamics, ecosystem function, and feedbacks to disturbance regimes, particularly on sites too dry for Alaska paper birch.

Ring-widths of Abies at tree-line ecotone reveal three centuries of early winter season temperature changes in Yunnan, China

Variation in winter temperature is less well understood than in annual and summer temperatures over long timescales, particularly in low-latitude (0–30° N) montane regions with large spatial and topographic heterogeneity. Understanding these variations could be critical for forest manageemnt in these important tree growing regions. We collected tree-ring cores from Yunnan Province in montane southwest China, to determine how winter temperature has varied in the past and to explore its possible drivers in this region. Six highly correlated site chronologies were combined into a long and well-replicated regional composite (RC) chronology. The RC chronology correlated strongest with mean early winter season temperature (EWST) from November to January during 1959–2015. We applied RC chronology to reconstruct EWST from 1653 to 2015. The reconstruction shows five relatively warm historic intervals (1658–1718, 1743–1755, 1771–1791, 1929–1959, and 1995–2015) and cold intervals (1720–1742, 1792–1852, 1860–1883, 1905–1928, and 1960–1994). The 1950s with six anomalous warm seasons and 1980s with five anomalous cold seasons were the warmest and coldest decades, respectively. The EWST reconstruction generally agreed with other winter temperature reconstructions from nearby areas and with historical documents. Atlantic Multidecadal Oscillation (AMO) might be a key forcing of multidecadal winter temperature variations in montane southwest China over the past three and half centuries. Both warm and cold temperature periods coincide with respective positive and negative phases of AMO. Besides, the cold intervals during the nineteenth and twentieth centuries may also have been influenced by large volcano eruptions in low-latitude regions of south and east Asia. Our EWST reconstruction not only improves our understanding of the trends and variations of winter climate history, but also supports planning for resilience in conservation, agriculture, and forestry management in montane southwest China into the future.

Soybean yield, biological N2 fixation and seed composition responses to additional inoculation in the United States

It is unclear if additional inoculation with Bradyrhizobia at varying soybean [Glycine max (L.) Merr.] growth stages can impact biological nitrogen fixation (BNF), increase yield and improve seed composition [protein, oil, and amino acid (AA) concentrations]. The objectives of this study were to evaluate the effect of different soybean inoculation strategies (seed coating and additional soil inoculation at V4 or R1) on: (i) seed yield, (ii) seed composition, and (iii) BNF traits [nodule number and relative abundance of ureides (RAU)]. Soybean field trials were conducted in 11 environments (four states of the US) to evaluate four treatments: (i) control without inoculation, (ii) seed inoculation, (iii) seed inoculation + soil inoculation at V4, and (iv) seed inoculation + soil inoculation at R1. Results demonstrated no effect of seed or additional soil inoculation at V4 or R1 on either soybean seed yield or composition. Also, inoculation strategies produced similar values to the non-inoculated control in terms of nodule number and RAU, a reflection of BNF. Therefore, we conclude that in soils with previous history of soybean and under non-severe stress conditions (e.g. high early-season temperature and/or saturated soils), there is no benefit to implementing additional inoculation on soybean yield and seed composition.

Weed species and traits associated with organic grain crop rotations in the mid-Atlantic region

AbstractOrganic cropping systems are characterized by soil-disturbance events that can be diversified over years through crop rotations and within seasons by varying planting dates. The Farming Systems Project at Beltsville, MD, USA, is a long-term experiment that includes three organic rotations, corn (Zea mays L.)–soybean [Glycine max (L.) Merr.], corn–soybean–wheat (Triticum aestivum L.), and corn–soybean–wheat–alfalfa (Medicago sativa L.). Analysis of weed presence and cover over the first 18 yr of this experiment revealed that the tall, erect annual broadleaf weeds smooth pigweed (Amaranthus hybridus L.), common lambsquarters (Chenopodium album L.), horseweed (Erigeron canadensis L.), jimsonweed (Datura stramonium L.), and/or velvetleaf (Abutilon theophrasti Medik.) were most prominent in corn and soybean. Generally, these species exhibited traits adapted to the disturbance regimes, nutrient availability, crop environment and duration, and local meteorological conditions associated with the summer annual corn and soybean crops. Abundance of A. hybridus, D. stramonium, and A. theophrasti were controlled primarily by rotation diversity, whereby presence and cover of these species were highest in the short corn–soybean rotation and lowest in the longer rotations that had more diverse seasonal soil-disturbance regimes. Early-season temperature was the primary factor controlling C. album presence and cover, which were higher at lower temperatures associated with earlier planting dates. Higher early-season precipitation was the primary factor associated with higher presence of annual grass species. The relative abundance of species in organic corn and soybean was determined primarily by the diversity of crops and disturbance operations in rotation, the timing of spring tillage and planting, and annual meteorological conditions driving emergence periodicity.

Impact of First True Leaf Photosynthetic Efficiency on Peanut Plant Growth under Different Early-Season Temperature Conditions

ABSTRACT Selecting planting dates with optimal temperatures for plant growth and development is important for successful crop production. Photosynthetic rates of peanut leaves under adverse environmental conditions have been widely studied; however, characterization of photosynthetic efficiency of first true leaves as well as its contribution to plant growth is not well elucidated. The objectives of this research were to assess the influence of first true leaves of peanut cultivars on plant growth under different temperature conditions during early growth and at the onset of flowering and to identify the photosynthetic components more closely linked with photosynthetic efficiency of the first true leaves. Experiments were conducted with April (early), May (optimum), and June (late) planting dates in 2017 and 2018. Cultivars Georgia-06G, Georgia-14N, and TifNV-High O/L were evaluated. Measurements were taken at three and five wks after planting, early season and the onset of flowering, respectively. Rapid development of first true leaves of peanut plants contributed to whole-plant growth in the early season and at the onset of flowering across the temperature conditions. Net photosynthesis of first true leaves was not impacted by temperature conditions in the early season or at the onset of flowering primarily due to greater activity of non-stomatal components associated with the thylakoid reactions. Whole-plant growth was more considerably associated with first true leaf area development than photosynthetic efficiency of those leaves in peanut plants.

Early Spring and Early Vanishing Wetlands as Harbingers of the Future? The Climate Change Trap for Ephemeral Pond-Breeding Frogs

The decline of the northern red-legged frog, Rana aurora, in the Pacific Northwest has been attributed to invasive species, habitat loss, and climate change. Rana aurora lay eggs on emergent vegetation, and larval development occurs in shallow, often ephemeral wetlands. In 2015 and 2016 we investigated how habitat and water quality parameters influence breeding productivity and development of R. aurora. Early season temperatures in southwestern British Columbia during both years were warmer than in the previous two decades and egg-laying occurred much earlier than any previous records, allowing us to follow the development of R. aurora under unusual climatic conditions. We monitored 43 wetlands in the Little Campbell River Watershed and nearby areas in 2015 and selected six sites to monitor tadpole metamorphosis. Peak egg mass abundance was inversely proportional to concentrations of nitrates and orthophosphates, and colder water appeared to support greater egg mass abundance. Although warmer ambient temperatures facilitated earlier onset of R. aurora breeding, we observed some egg mortality due to subsequent frost. Sites with earlier peak egg mass abundance dates did not exhibit earlier peak metamorph dates, nor did warmer water appear to facilitate quicker larval development. In 2015, one wetland dried up before tadpoles completed metamorphosis. The frog's reproductive cycle may adapt to warmer temperatures to some degree, but erratic precipitation or frost events could reduce R. aurora survivorship beyond recovery. The disruption of larval development we observed under unusually warm spring conditions provides a useful vantage point for predicting future impacts of climate change.

Growth at the microscale: long term thinning effects on patterns and timing of intra-annual stem increment in radiata pine

BackgroundStem radial growth in forests is not uniform. Rather, it is characterized by periods of relatively fast or slow growth, or sometimes no growth at all. These fluctuations are generally a function of varying environmental conditions (e.g. water availability) and, importantly, will also be associated with adjustments in properties in the wood formed. Stand level conditions and forest management, particularly thinning and stand density will, however, also have a major influence on patterns of growth variation. We explore how different thinning histories and/or stand densities influence these dynamics of tree growth in the important commercial plantation species Pinus radiata D. Don.MethodsDaily stem size change was measured using electronic point dendrometers over two growing seasons on P. radiata trees at two sites, subjected to different thinning regimes. Timing, rates and periodicity of annual growth were calculated from these data.ResultsGreater overall cross-sectional growth in thinned plots was driven mainly by two dynamics. First, the cessation of seasonal growth occurred at least 3 weeks later in the stands in which thinning had taken place. There was no difference between thinned/unthinned stands, however, in the timing of growth onset. Second, within the longer season, trees in thinned plots had more growth days (as much as 20% more) than unthinned plots. The rates of growth on days when growth occurred were not different, however. In this context, it is notable that in trees in the unthinned plots experiencing the most severe competition there were strong “pulses” of growth following drought-breaking rainfall events. Unthinned plots at high stand densities also maintained a smaller (but consistent) zone of dividing cells throughout the season than thinned plots.ConclusionsIn Pinus radiata growing under conditions as in our study, conditions late in summer, particularly drought, have an important effect on the timing of cessation of growth. Early season temperature appears to have no effect in determining timing of annual growth. Limiting conditions during the season reduce growing duration, and thus total growth, more in unthinned stands than thinned stands. These findings are valuable in developing new generations of fine-scale growth and wood property models.

Long-term fertilisation strategies and form affect nutrient budgets and soil test values, soil carbon retention and crop yield resilience

The aim of this study was to evaluate the effects of long-term mineral and organic fertilisation on crop performance and soil fertility. The Long-Term Nutrient Depletion Trial (Denmark) was used to analyse changes in concentrations of Olsen-P, exchangeable potassium (K) and soil carbon (C). Yield responses (2010–2016) were evaluated making use of an early-season temperature model, fertilisation practices were evaluated by nutrient budgets, and nitrogen use efficiency by calculation of apparent recovery (ANR) in subplots receiving mineral N. Olsen-P (r2 = 0.68, P < 0.001) and exchangeable K (r2 = 0.86, P < 0.001) were correlated with the nutrient budgets. Soil C concentrations increased from 10.0 g kg−1 (1995) to between 11.1–14.6 g kg−1 (2016), with the greatest accumulation under slurry applications (P < 0.05, equalling 17–47% retention of slurry-C inputs). Relative yield responses of spring barley were associated with early season cold stress, but the model was not applicable to other crops. Increases of ANR in response to long-term phosphorus (P) applications were not significant. Balanced fertilisation is an effective way to maintain nutrient availability, and to ensure high and stable crop productivity and efficient use of nutrients. Direct C inputs from animal slurry are a major driver for increases of soil C concentrations.

Sub-optimal emergence temperature alters thermotolerance of thylakoid component processes in cotton seedlings

Cotton (Gossypium hirsutum) is often planted under sub-optimal early season temperatures, yet it is unknown whether this increases susceptibility to acute high temperature exposure. To address this, cotton seedlings were grown under optimal (30/20 °C) and sub-optimal (20/15 °C) growth temperature regimes, and comprehensive fluorescence analysis was conducted for cotyledons from both temperature regimes in response to incubation temperatures ranging from 30 to 50 °C. Results indicated that low growth temperature did not alter reaction center density (RC/CS0), but increased antenna size (ratio of antenna chlorophyll to reaction center chlorophyll; ABS/RC) and decreased the amplitude of the I to P phase of the fluorescence transient [ΔVIP; associated with the photosystem (PS) I content]. Photosynthetic performance indices (PItotal and PIABS), quantum yield of energy trapping (φPo), the contribution of the thylakoid reactions to PIABS (Fv/F0), electron transport to intersystem electron acceptors (φE0) and reduction of PSI end electron acceptors (φRo) were all substantially lower in plants grown under sub-optimal temperature than in plants grown at optimal temperature. Furthermore, thermotolerance of all the aforementioned parameters was significantly reduced by low early season growth temperatures. Among different OJIP-derived parameters, PIABS and PItotal were more heat sensitive than other fluorescence-based parameters, and φPo and φRo were the most heat tolerant. In addition, thermotolerance of PItotal (overall photosynthetic thermotolerance) was significantly correlated with thermotolerance of all other OJIP-derived parameters. Regression analysis indicated that heat tolerance trends for φE0 were more consistent with the changes in thermotolerance of PItotal. We conclude that 1) low growth temperature in the seedling phase of cotton results in decreased photosynthetic thermotolerance and 2) overall photosynthetic thermotolerance is primarily constrained by the ability of intersystem electron transport to acclimate to growth environment.

Factors associated with human West Nile virus infection in Ontario: a generalized linear mixed modelling approach

BackgroundWest Nile Virus (WNV) is a mosquito-borne pathogen that has become established in North America. Risk for human infection varies geographically in accordance with climate and population factors. Though often asymptomatic, human WNV infection can cause febrile illness or, rarely, neurologic disease. WNV has become a public health concern in Canada since its introduction in 2001.MethodsTo identify predictors of human WNV incidence at the public health unit (PHU) level in Ontario, Canada, we combined data on environmental and population characteristics of PHUs with historical mosquito and human surveillance records from 2002 to 2013. We examined the associations between annual WNV incidence and monthly climate indices (e.g. minimum and maximum temperature, average precipitation), land cover (e.g. deciduous forest, water), population structure (e.g. age and sex composition) and the annual percentage of WNV-positive mosquito pools from 2002 to 2013. We then developed a generalized linear mixed model with a Poisson distribution adjusting for spatial autocorrelation and repeat measures. Further to this, to examine potential ‘early season’ predictors of WNV incidence in a given year, we developed a model based on winter and spring monthly climate indices.ResultsSeveral climate indices, including mean minimum temperature (o C) in February (RR = 1.58, CI: [1.42, 1.75]), and the annual percentage of WNV-positive mosquito pools (RR = 1.07, CI: [1.04, 1.11]) were significantly associated with human WNV incidence at the PHU level. Higher winter minimum temperatures were also strongly associated with annual WNV incidence in the ‘early season’ model (e.g. February minimum temperature (RR = 1.91, CI: [1.73, 2.12]).ConclusionsOur study demonstrates that early season temperature and precipitation indices, in addition to the percentage of WNV-positive mosquito pools in a given area, may assist in predicting the likelihood of a more severe human WNV season in southern regions of Ontario, where WNV epidemics occur sporadically.

The interactive effects of early season temperatures, crop density and rootstock on average fruit weight of ‘Golden Delicious’ apple

The interactive effects of early season temperatures, crop density and rootstock on average fruit weight of ‘Golden Delicious’ apple

Summer solstice marks a seasonal shift in temperature sensitivity of stem growth and nitrogen-use efficiency in cold-limited forests

In boreal forests and alpine treelines, it is debatable how the temperature sensitivity of tree-ring growth should vary with changes in climate over time and the extent to which seasonal stem increments are controlled by leaf physiology. We aim to test the hypothesis that, in cold-limited forests, maximizing stem growth rate around summer solstice is closely related to foliage turnover, which generally results in high sensitivity of stem growth and less sensitivity of nitrogen-use efficiency (NUE) to early-season temperatures. Our analysis was based on repeat-census observations of stem radial increment (2008–2013; made with dendrometers) and monthly litterfall (2007–2015) as well as the measurements of tree-ring width series (1960–2015; made with tree-ring cores) in two Tibetan treeline forests. NUE was estimated as the inverse of leaf-litter nitrogen concentration. We further examined a global dataset of tree-ring chronologies (1931–1990) from 139 sites across temperate and boreal coniferous forests in the northern high-latitude region. Weekly stem increments across species and years synchronously peaked around summer solstice, with more than half of annual increment produced in the first 28–35days of the growing season when air and soil temperatures were still low. Monthly stem increments were positively related to previous-month litterfall, and higher litterfall generally resulted in higher NUE. NUE was insensitive or less sensitive to soil temperature in the early growing season. Among years, pre-peak increments were positively correlated with pre-solstice temperatures while post-peak increments varied little. The annual increment was dominated by and coherent with the pre-peak increment and well correlated with the ring-width measurements of monitored trees during 2008–2013. Variations in tree-ring width chronologies from the two Tibetan treelines and the global 139 forest sites mainly reflected the change of early summer temperatures. The findings suggest a day-length control on the linkage between seasonal stem growth and nitrogen cycling in a cold-limited forest ecosystem, and provide the basic for predicting responses of tree-ring growth and NUE to climatic warming.

Olive Cultivation in the Southern Hemisphere: Flowering, Water Requirements and Oil Quality Responses to New Crop Environments.

Olive (Olea europaea L.) is a crop well adapted to the environmental conditions prevailing in the Mediterranean Basin. Nevertheless, the increasing international demand for olive oil and table olives in the last two decades has led to expansion of olive cultivation in some countries of the southern hemisphere, notably in Argentina, Chile, Perú and Australia. While the percentage of world production represented by these countries is still low, many of the new production regions do not have typical Mediterranean climates, and some are located at subtropical latitudes where there is relatively little information about crop function. Thus, the primary objective of this review was to assess recently published scientific literature on olive cultivation in these new crop environments. The review focuses on three main aspects: (a) chilling requirements for flowering, (b) water requirements and irrigation management, and (c) environmental effects on fruit oil concentration and quality. In many arid and semiarid regions of South America, temperatures are high and rainfall is low in the winter and early spring months compared to conditions in much of the Mediterranean Basin. High temperatures have often been found to have detrimental effects on olive flowering in many olive cultivars that have been introduced to South America, and a better understanding of chilling requirements is needed. Lack of rainfall in the winter and spring also has resulted in an urgent need to evaluate water requirements from the flower differentiation period in the winter to early fruit bearing. Additionally, in some olive growing areas of South America and Australia, high early season temperatures affect the timing of phenological events such that the onset of oil synthesis occurs sooner than in the Mediterranean Basin with most oil accumulation taking place in the summer when temperatures are very high. Increasing mean daily temperatures have been demonstrated to decrease fruit oil concentration (%) and negatively affect some aspects of oil quality based on both correlative field studies and manipulative experiments. From a practical standpoint, current findings could be used as approximate tools to determine whether the temperature conditions in a proposed new growing region are appropriate for achieving sustainable oil productivity and quality.

Irrigated Sugarbeet Sucrose Content in Relation to Growing Season Climatic Conditions in the Northwest U.S.

The potential effects of changing climate on world food production have become a political and scientific focus. This study was conducted to investigate linkages between seasonal climatic conditions and sugarbeet sucrose content in southern Idaho and eastern Oregon. Sucrose content of irrigated sugarbeets delivered to 74 receiving stations in southern Idaho and eastern Oregon from 1997 through 2014, and daily climate data (growing degree days [GDD] and accumulated alfalfa reference crop evapotranspiration, maximum air temperature, minimum air temperature and mean air temperature, global solar radiation, accumulated growing degree days, and mean relative humidity) from regional weather stations were collected and analyzed using various regression techniques to investigate linkages between climate variables and sugarbeet sucrose content. Ninety-nine climatic parameters were analyzed with 34 having correlations with sugarbeet sucrose content > |0.3|. The most important climatic parameter related to mean sucrose content was early stage sugarbeet growth (late April to mid-May). In general, as temperature and GDD increased sucrose content decreased. Results indicate increases in both early season and mid-season temperatures will lead to decreases in sugarbeet sucrose concentrations. However, if sugarbeet root yields increase due to increasing temperatures and GDD accumulation, the sucrose yield changes would be buffered.

Integrating Environmental Monitoring and Mosquito Surveillance to Predict Vector-borne Disease: Prospective Forecasts of a West Nile Virus Outbreak.

Introduction:Predicting the timing and locations of future mosquito-borne disease outbreaks has the potential to improve the targeting of mosquito control and disease prevention efforts. Here, we present and evaluate prospective forecasts made prior to and during the 2016 West Nile virus (WNV) season in South Dakota, a hotspot for human WNV transmission in the United States.Methods:We used a county-level logistic regression model to predict the weekly probability of human WNV case occurrence as a function of temperature, precipitation, and an index of mosquito infection status. The model was specified and fitted using historical data from 2004-2015 and was applied in 2016 to make short-term forecasts of human WNV cases in the upcoming week as well as whole-year forecasts of WNV cases throughout the entire transmission season. These predictions were evaluated at the end of the 2016 WNV season by comparing them with spatial and temporal patterns of the human cases that occurred.Results:There was an outbreak of WNV in 2016, with a total of 167 human cases compared to only 40 in 2015. Model results were generally accurate, with an AUC of 0.856 for short-term predictions. Early-season temperature data were sufficient to predict an earlier-than-normal start to the WNV season and an above-average number of cases, but underestimated the overall case burden. Model predictions improved throughout the season as more mosquito infection data were obtained, and by the end of July the model provided a close estimate of the overall magnitude of the outbreak.Conclusions:An integrated model that included meteorological variables as well as a mosquito infection index as predictor variables accurately predicted the resurgence of WNV in South Dakota in 2016. Key areas for future research include refining the model to improve predictive skill and developing strategies to link forecasts with specific mosquito control and disease prevention activities.