A global analysis of the comparability of winter chill models for fruit and nut trees

Many fruit and nut trees must fulfill a chilling requirement to break their winter dormancy and resume normal growth in spring. Several models exist for quantifying winter chill, and growers and researchers often tacitly assume that the choice of model is not important and estimates of species chilling requirements are valid across growing regions. To test this assumption, Safe Winter Chill (the amount of winter chill that is exceeded in 90% of years) was calculated for 5,078 weather stations around the world, using the Dynamic Model [in Chill Portions (CP)], the Chilling Hours (CH) Model and the Utah Model [Utah Chill Units (UCU)]. Distributions of the ratios between different winter chill metrics were mapped on a global scale. These ratios should be constant if the models were strictly proportional. Ratios between winter chill metrics varied substantially, with the CH/CP ratio ranging between 0 and 34, the UCU/CP ratio between −155 and +20 and the UCU/CH ratio between −10 and +5. The models are thus not proportional, and chilling requirements determined in a given location may not be valid elsewhere. The Utah Model produced negative winter chill totals in many Subtropical regions, where it does not seem to be useful. Mean annual temperature and daily temperature range influenced all winter chill ratios, but explained only between 12 and 27% of the variation. Data on chilling requirements should always be amended with information on the location and experimental conditions of the study in which they were determined, ideally including site-specific conversion factors between winter chill models. This would greatly facilitate the transfer of such information across growing regions, and help prepare growers for the impact of climate change

The paleobiolinguistics of the common bean (Phaseolus vulgaris L.)

©2014 Society of Ethnobiology Paleobiolinguistics is used to determine when and where the common bean (Phaseolus vulgaris L.) developed significance for prehistoric groups of Native America. Dates and locations of proto-languages for which common bean terms reconstruct generally accord with crop-origin and dispersal information from plant genetics and archaeobotany. Paleobiolinguistic and other lines of evidence indicate that human interest in the common bean became significant primarily with the widespread development of a village-farming way of life in the New World rather than earlier when squash and maize and a few other crops became important

The paleobiolinguistics of the common bean (Phaseolus vulgaris L.)

<p>Paleobiolinguistics is used to determine when and where the common bean (<em>Phaseolus vulgaris</em> L.) developed significance for prehistoric groups of Native America. Dates and locations of proto-languages for which common bean terms reconstruct generally accord with crop-origin and dispersal information from plant genetics and archaeobotany. Paleobiolinguistic and other lines of evidence indicate that human interest in the common bean became significant primarily with the widespread development of a village‐farming way of life in the New World rather than earlier when squash and maize and a few other crops became important.</p

The Paleobiolinguistics of Maize (Zea mays L.)

Paleobiolinguistics is used to determine when and where maize (Zea mays L.) developed significance for different prehistoric groups of Native America. Dates and locations of proto-languages for which maize terms reconstruct generally accord with crop-origin and dispersal information from plant genetics and archaeobotany. Paleobiolinguistic and other lines of evidence indicate that human interest in maize was extensive millennia before the widespread development of a villagefarming way of life in the New World. © 2014 Society of Ethnobiology

Environmental flows in support of sustainable intensification of agriculture in the Letaba River Basin, South Africa

This study evaluates the socioecological consequences of the potential trade-offs between maintaining environmental flows (e-flows) and providing water for sustainable subsistence agriculture and livelihoods to the vulnerable human communities living along the lower Great Letaba River in South Africa. Implementation of e-flows is now generally recognized as an essential part of water resources management as they are designed to ensure that sufficient water is retained in a river to protect river ecosystems and all the beneficiaries of services that arise from those ecosystems. Understanding the relationship between e-flows and the use of water for small-scale agriculture is important for the management of trade-offs. The Letaba River Basin and it's tributary, the Great/Groot Letaba, are located in the eastern part of the Limpopo province in South Africa. This is one of the most important river basins in the region supporting both large-scale commercial and small-scale farmers. The river sustains many vulnerable human communities who depend on the ecosystem services provided by the river. Yet, the water resources of the Letaba River are heavily overutilized due to expanding developments, including upstream dams with associated offtakes mostly for irrigation. The findings of the study indicate that irrigation water demand from subsistence agriculture in the Great Letaba Basin amounted to around 2 million cubic meters annually with median demand not exceeding 300,000 cubic meters per month. This means that irrigation water demand from smallholder agriculture only amounts to about one-tenth of the estimated e-flow requirement. However, small-scale farmers contend with an increasing crop water gap which limits irrigated agriculture, especially during the dry season. Given the need to sustainably maintain e-flows for ecological purposes, crop water gaps are only likely to increase and compromise the sustainability of irrigated agriculture. With active upstream supplementation of river flows from dams to maintain both environmental and livelihoods-oriented river flows, the crop water gap can be fully eliminated. This supplementation is not assured due to competing uses

Stochastic simulation of restoration outcomes for a dry afromontane forest landscape in northern Ethiopia.

Forest and Landscape Restoration (FLR) is carried out with the objective of regaining ecological functions and enhancing human well-being through intervention in degrading ecosystems. However, uncertainties and risks related to FLR make it difficult to predict long-term outcomes and inform investment plans. We applied a Stochastic Impact Evaluation framework (SIE) to simulate returns on investment in the case of FLR interventions in a degraded dry Afromontane forest while accounting for uncertainties. We ran 10,000 iterations of a Monte Carlo simulation that projected FLR outcomes over a period of 25 years. Our simulations show that investments in assisted natural regeneration, enrichment planting, exclosure establishment and soil-water conservation structures all have a greater than 77% chance of positive returns. Sensitivity analysis of these outcomes indicated that the greatest threat to positive cashflows is the time required to achieve the targeted ecological outcomes. Value of Information (VOI) analysis indicated that the biggest priority for further measurement in this case is the maturity age of exclosures at which maximum biomass accumulation is achieved. The SIE framework was effective in providing forecasts of the distribution of outcomes and highlighting critical uncertainties where further measurements can help support decision-making. This approach can be useful for informing the management and planning of similar FLR interventions

Chilling requirements and dormancy evolution in grapevine buds.

Fluctuations in winter chilling availability impact bud dormancy and budburst. The objective of this work was to determine chilling requirements to induce and overcome endodormancy (dormancy controlled by chilling) of buds in different grape cultivars. "Chardonnay", "Merlot" and "Cabernet Sauvignon" shoots were collected in Veranópolis-RS vineyards in 2010, and submitted to a constant 3 °C temperature or daily cycles of 3/15 °C for 12/12h or 18/6h, until reaching 1120 chilling hours (CH, sum of hours with temperature &#8804; 7.2 °C). Periodically, part of the samples in each treatment was transferred to 25 °C for budburst evaluation (green tip). Chilling requirements to induce and overcome endodormancy vary among cultivars, reaching a total of 136 CH for "Chardonnay", 298 CH for "Merlot" and 392 CH for "Cabernet Sauvignon". Of these, approximately 39, 53 and 91 CH are required for induction of endodormancy in the three cultivars, respectively. The thermal regimes tested (constant or alternating) do not influence the response pattern of each cultivar to cold, with 15 °C being inert in the CH accumulation process. In addition, time required to start budburst reduces with the increase in CH, at a rate of one day per 62 CH, without significant impacts on budburst uniformity. Index terms: Chilling hours; endodormancy; budburst; Vitis vinifera

Climate change effects on winter chill for tree crops with chilling requirements on the Arabian Peninsula

Fruit production systems that rely on winter chill for breaking of dormancy might be vulnerable to climatic change. We investigated decreases in the number of winter chilling hours (0–7.2°C) in four mountain oases of Oman, a marginal area for the production of fruit trees with chilling requirements. Winter chill was calculated from long-term hourly temperature records. These were generated based on the correlation of hourly temperature measurements in the oases with daylength and daily minimum and maximum temperatures recorded at a nearby weather station. Winter chill was estimated for historic temperature records between 1983 and 2008, as well as for three sets of synthetic 100-year weather records, generated to represent historic conditions, and climatic changes likely to occur within the next 30 years (temperatures elevated by 1°C and 2°C). Our analysis detected a decrease in the numbers of chilling hours in high-elevation oases by an average of 1.2–9.5 h/year between 1983 and 2008, a period during which, according to the scenario analysis, winter chill was sufficient for most important species in most years in the highest oasis. In the two climate change scenarios, pomegranates, the most important tree crop, received insufficient chilling in 13% and 75% of years, respectively. While production of most traditional fruit trees is marginal today, with trees barely fulfilling their chilling requirements, such production might become impossible in the near future. Similar developments are likely to affect other fruit production regions around the world

Sensitivity of grapevine phenology to water availability, temperature and CO2 concentration

In recent decades, mean global temperatures have increased in parallel with a sharp rise in atmospheric carbon dioxide (CO2) levels, with apparent implications for precipitation patterns. The aim of the present work is to assess the sensitivity of different phenological stages of grapevine to temperature and to study the influence of other factors related to climate change (water availability and CO2 concentration) on this relationship. Grapevine phenological records from 9 plantings between 42.75°N and 46.03°N consisting of dates for budburst, flowering and fruit maturity were used. In addition, we used phenological data collected from 2 years of experiments with grapevine fruit-bearing cuttings with two grapevine varieties under two levels of water availability, two temperature regimes and two levels of CO2. Dormancy breaking and flowering were strongly dependent on spring temperature, while neither variation in temperature during the chilling period nor precipitation significantly affected budburst date. The time needed to reach fruit maturity diminished with increasing temperature and decreasing precipitation. Experiments under semi-controlled conditions revealed great sensitivity of berry development to both temperature and CO2. Water availability had significant interactions with both temperature and CO2; however, in general, water deficit delayed maturity when combined with other factors. Sensitivities to temperature and CO2 varied widely, but higher sensitivities appeared in the coolest year, particularly for the late ripening variety, ‘White Tempranillo’. The knowledge gained in whole plant physiology and multi stress approaches is crucial to predict the effects of climate change and to design mitigation and adaptation strategies allowing viticulture to cope with climate change