Showing papers on "Growing season published in 2008"
TL;DR: The findings point out the paradox of increased frost damage in the face of global warming, provide important insights into the adaptive significance of phenology, and have general implications for flowering plants throughout the region and anywhere climate change is having similar impacts.
Abstract: The timing of life history traits is central to lifetime fitness and nowhere is this more evident or well studied as in the phenology of flowering in governing plant reproductive success. Recent changes in the timing of environmental events attributable to climate change, such as the date of snowmelt at high altitudes, which initiates the growing season, have had important repercussions for some common perennial herbaceous wildflower species. The phenology of flowering at the Rocky Mountain Biological Laboratory (Colorado, USA) is strongly influenced by date of snowmelt, which makes this site ideal for examining phenological responses to climate change. Flower buds of Delphinium barbeyi, Erigeron speciosus, and Helianthella quinquenervis are sensitive to frost, and the earlier beginning of the growing season in recent years has exposed them to more frequent mid-June frost kills. From 1992 to 1998, on average 36.1% of Helianthella buds were frosted, but for 1999-2006 the mean is 73.9%; in only one year since 1998 have plants escaped all frost damage. For all three of these perennial species, there is a significant relationship between the date of snowmelt and the abundance of flowering that summer. Greater snowpack results in later snowmelt, later beginning of the growing season, and less frost mortality of buds. Microhabitat differences in snow accumulation, snowmelt patterns, and cold air drainage during frost events can be significant; an elevation difference of only 12 m between two plots resulted in a temperature difference of almost 28C in 2006 and a difference of 37% in frost damage to buds. The loss of flowers and therefore seeds can reduce recruitment in these plant populations, and affect pollinators, herbivores, and seed predators that previously relied on them. Other plant species in this environment are similarly susceptible to frost damage so the negative effects for recruitment and for consumers dependent on flowers and seeds could be widespread. These findings point out the paradox of increased frost damage in the face of global warming, provide important insights into the adaptive significance of phenology, and have general implications for flowering plants throughout the region and anywhere climate change is having similar impacts.
950 citations
TL;DR: This study provides comprehensive evidence that montane ungulate migration leads to greater access to higher-quality forage relative to nonmigratory congeners, as predicted by the forage maturation hypothesis, resulting primarily from large-scale selection patterns.
Abstract: The forage maturation hypothesis (FMH) proposes that ungulate migration is driven by selection for high forage quality. Because quality declines with plant maturation, but intake declines at low biomass, ungulates are predicted to select for intermediate forage biomass to maximize energy intake by following phenological gradients during the growing season. We tested the FMH in the Canadian Rocky Mountains by comparing forage availability and selection by both migrant and nonmigratory resident elk (Cervus elaphus) during three growing seasons from 2002-2004. First, we confirmed that the expected trade-off between forage quality and quantity occurred across vegetation communities. Next, we modeled forage biomass and phenology during the growing season by combining ground and remote-sensing approaches. The growing season started 2.2 days earlier every 1 km east of the continental divide, was delayed by 50 days for every 1000-m increase in elevation, and occurred 8 days earlier on south aspects. Migrant and resident selection for forage biomass was then compared across three spatial scales (across the study area, within summer home ranges, and along movement paths) using VHF and GPS telemetry locations from 119 female elk. Migrant home ranges occurred closer to the continental divide in areas of higher topographical diversity, resulting in migrants consistently selecting for intermediate biomass at the two largest scales, but not at the finest scale along movement paths. In contrast, residents selected maximum forage biomass across all spatial scales. To evaluate the consequences of selection, we compared exposure at telemetry locations of migrant and resident elk to expected forage biomass and digestibility. The expected digestibility for migrant elk in summer was 6.5% higher than for residents, which was corroborated with higher fecal nitrogen levels for migrants. The observed differences in digestibility should increase migrant elk body mass, pregnancy rates, and adult and calf survival rates. Whether bottom-up effects of improved forage quality are realized will ultimately depend on trade-offs between forage and predation. Nevertheless, this study provides comprehensive evidence that montane ungulate migration leads to greater access to higher-quality forage relative to nonmigratory congeners, as predicted by the forage maturation hypothesis, resulting primarily from large-scale selection patterns.
412 citations
TL;DR: In this paper, the authors investigated climate-crop relationships, recent trends in seasonal climate (maximum and minimum temperatures, diurnal temperature range and precipitation) and their impacts on the yields of major crops (i.e., rice, wheat, maize and soybean) at provincial scales throughout China over the last few decades.
Abstract: Understanding climate-yield relationships and the impacts of recent climate trends on crop productivity on a large scale is an important step in predicting regional agricultural production. In this study we investigated climate-crop relationships, recent trends in seasonal climate (maximum and minimum temperatures, diurnal temperature range and precipitation) and their impacts on the yields of major crops (i.e. rice, wheat, maize and soybean) at provincial scales throughout China over the last few decades. We found that major crop yields were significantly related to growing season climate in the main production regions of China, and that growing season temperature had a gener- ally significant warming trend. Due to the trends in growing season climate, total rice production in China was estimated to have increased by 3.2 × 10 5 t decade -1 during the period 1951-2002; total pro- duction of wheat, maize and soybean changed by -1.2 × 10 5 , -21.2 × 10 5 and 0.7 × 10 5 t decade -1 , respectively, during 1979-2002. The warming trend increased rice yield in northeast China and soy- bean in north and northeast China; however, it decreased maize yield in 7 provinces (autonomous region or municipality) and wheat yield in 3 provinces. Our analysis presents the general response patterns of regional agricultural productivity to seasonal climate variability and change over the last few decades. Crop response mechanisms to local seasonal climate change (and variability) need further investigation to better understand the patterns and predict future consequences of climate change and variability on regional agricultural production.
336 citations
TL;DR: The results support the essential role of the balance between light and moisture limitations for plant development during droughts and show that it is not appropriate to generalize about the way in which suppression affects climate-growth relationship in conifers.
Abstract: Tree-ring chronologies were examined to investigate the influence of climate on radial growth of Pinus nigra in southeastern Spain. We addressed whether drought differentially affected the ring-widths of dominant and suppressed trees and if our results supported the hypothesis that, in a Mediterranean climate, suppressed conifer trees suffer greater growth reductions than dominant trees. Climate-growth relationships were analyzed using response and correlation functions, whereas the effect of drought on trees growth was approached by superposed epoch analysis in 10 dry years. A cool, wet autumn and spring, and/or mild winter enhanced radial growth. Latewood was the most sensitive ring section in both kinds of trees and it was primarily influenced by current year precipitations. Earlywood was mostly influenced by climatic conditions previous to the growing season. In general, May was the most influential month. Pinus nigra was shown to be very drought sensitive tree in the study area. Tree-rings in suppressed trees showed lower growth reductions caused by drought than those of dominant trees. However, dominant trees recovered normal growth faster. Dominant trees showed a more plastic response, and suppression appeared to reduce the effect of climate on tree radial growth. Some possible causes for these effects are discussed. Our results support the essential role of the balance between light and moisture limitations for plant development during droughts and show that it is not appropriate to generalize about the way in which suppression affects climate-growth relationship in conifers.
228 citations
TL;DR: In this paper, the authors used a combination of biophysically informed sampling and dendroclimatology to identify growth-climate relationships along a climate gradient in northwestern United States mountain ecosystems from the western Olympic Peninsula, Washington to the eastern Rocky Mountain Front, Montana.
Abstract: The purpose of this work is to understand the nature of growth-climate relationships for Douglas-fir (Pseudotsuga menziesii) across the climatic dimensions of its niche. We used a combination of biophysically informed sampling (to identify sample sites) and dendroclimatology (to identify growth-climate relationships) along a climate gradient in northwestern United States mountain ecosystems from the western Olympic Peninsula, Washington to the eastern Rocky Mountain Front, Montana. We used a multi-scale sampling strategy that accounted for continentality, physiography, and topography as non-climatic factors that could influence climate and alter tree growth. We developed a network of 124 Douglas-fir tree-ring chronologies and explored growth-climate correlations across the sampled gradients. We considered two different spatial scales of monthly and seasonal climate variables as potential controlling factors on tree growth. Annual radial growth in 60-65% of the plots across the region is significantly correlated with precipitation, drought, or water balance during the late summer prior to growth and the early summer the year of growth. In a few plots, growth is positively correlated with cool-season temperature or negatively correlated with snowpack. Water availability is therefore more commonly limiting to Douglas-fir growth than energy limitations on growing season length. The first principal component derived from the chronologies is significantly correlated with independent drought reconstructions. The sensitivity of Douglas-fir to summer water balance deficit (potential evapotranspiration minus actual evapotranspiration) indicates that increases in April to September temperature without increases in summer precipitation or soil moisture reserves are likely to cause decreases in growth over much of the sampled area, especially east of the Cascade crest. In contrast, Douglas-fir may exhibit growth increases at some higher elevation sites where seasonal photosynthesis is currently limited by growing-season length or low growing-season temperature. Life-history processes such as establishment, growth, and mortality are precursors to changes in biogeography, and measurements of climate effects on those processes can provide early indications of climate-change effects on ecosystems.
216 citations
TL;DR: Differences in sources of water uptake among these species and their ecological implications on tree-grass dynamics and soil water in semiarid environments are discussed.
Abstract: We used the natural abundance of stable isotopic ratios of hydrogen and oxygen in soil (0.05–3 m depth), plant xylem and precipitation to determine the seasonal changes in sources of soil water uptake by two native encroaching woody species (Pinus ponderosa P. & C. Lawson, Juniperus virginiana L.), and two C 4 grasses (Schizachyrium scoparium (Michx.) Nash, Panicum virgatum L.), in the semiarid Sandhills grasslands of Nebraska. Grass species extracted most of their water from the upper soil profile (0.05–0.5 m). Soil water uptake from be low 0.5 m depth increased under drought, but appeared to be minimal in relation to the total water use of these species. The grasses senesced in late August in response to drought conditions. In contrast to grasses, P. ponderosa and J. virginiana trees exhibited significant plasticity in sources of water uptake. In winter, tree species extracted a large fraction of their soil water from below 0.9 m depth. In spring when shallow soil water was available, tree species used water from the upper soil profile (0.05–0.5 m) and relied little on water from below 0.5 m depth. During the growing season (May–August) significant differences between the patterns of tree species water uptake emerged. Pinus ponderosa acquired a large fraction of its water from the 0.05–0.5 and 0.5–0.9 m soil profiles. Compared with P. ponderosa, J. virginiana acquired water from the 0.05–0.5 m profile during the early growing season but the amount extracted from this profile progressively declined between May and August and was mirrored by a progressive increase in the fraction taken up from 0.5–0.9 m depth, showing plasticity in tracking the general increase in soil water content within the 0.5–0.9 m profile, and being less responsive to growing season precipitation events. In September, soil water content declined to its minimum, and both tree species shifted soil water uptake to below 0.9 m. Tree transpiration rates (E) and water potentials (Ψ) indicated that deep water sources did not maintain E which sharply declined in September, but played an important role in the recovery of tree Ψ. Differences in sources of water uptake among these species and their ecological implications on tree–grass dynamics and soil water in semiarid environments are discussed.
215 citations
TL;DR: In this paper, the authors examined the response of soil respiration to variation in pulses representative of climate change scenarios for the Sonoran Desert, and found that larger pulses resulted in higher respiration rates, particularly from vegetated fine-textured soil.
Abstract: Climate change predictions for the desert southwestern U.S. are for shifts in precipitation patterns. The impacts of climate change may be significant, because desert soil processes are strongly controlled by precipitation inputs (“pulses”) via their effect on soil water availability. This study examined the response of soil respiration—an important biological process that affects soil carbon (C) storage—to variation in pulses representative of climate change scenarios for the Sonoran Desert. Because deserts are mosaics of different plant cover types and soil textures—which create patchiness in soil respiration—we examined how these landscape characteristics interact to affect the response of soil respiration to pulses. Pulses were applied to experimental plots of bare and vegetated soil on contrasting soil textures typical of Sonoran Desert grasslands. The data were analyzed within a Bayesian framework to: (1) determine pulse size and antecedent moisture (soil moisture prior to the pulse) effects on soil respiration, (2) quantify soil texture (coarse vs. fine) and cover type (bare vs. vegetated) effects on the response of soil respiration and its components (plant vs. microbial) to pulses, and (3) explore the relationship between long-term variation in pulse regimes and seasonal soil respiration. Regarding objective (1), larger pulses resulted in higher respiration rates, particularly from vegetated fine-textured soil, and dry antecedent conditions amplified respiration responses to pulses (wet antecedent conditions dampened the pulse response). Regarding (2), autotrophic (plant) activity was a significant source (∼60%) of respiration and was more sensitive to pulses on coarse- versus fine-textured soils. The sensitivity of heterotrophic (microbial) respiration to pulses was highly dependent on antecedent soil water. Regarding (3), seasonal soil respiration was predicted to increase with both growing season precipitation and mean pulse size (but only for pulses between 7 and 25 mm). Thus, the heterogeneity of the desert landscape and the timing or the number of medium-sized pulses is expected to significantly impact desert soil C loss with climate change.
207 citations
University of Iowa1, Andrés Bello National University2, Massachusetts Institute of Technology3, University of California, Irvine4, Langley Research Center5, Goddard Space Flight Center6, Colorado State University7, Carnegie Institution for Science8, National Oceanic and Atmospheric Administration9, Cooperative Institute for Research in Environmental Sciences10
TL;DR: This work successfully modeled the persistent vertical drawdown of atmospheric COS using the quantitative relation between COS and photosynthesis that has been measured in plant chamber experiments, and provides quantitative evidence that COS gradients in the continental growing season may have broad use as a measurement-based photosynthesis tracer.
Abstract: Climate models incorporate photosynthesis-climate feedbacks, yet we lack robust tools for large-scale assessments of these processes. Recent work suggests that carbonyl sulfide (COS), a trace gas consumed by plants, could provide a valuable constraint on photosynthesis. Here we analyze airborne observations of COS and carbon dioxide concentrations during the growing season over North America with a three-dimensional atmospheric transport model. We successfully modeled the persistent vertical drawdown of atmospheric COS using the quantitative relation between COS and photosynthesis that has been measured in plant chamber experiments. Furthermore, this drawdown is driven by plant uptake rather than other continental and oceanic fluxes in the model. These results provide quantitative evidence that COS gradients in the continental growing season may have broad use as a measurement-based photosynthesis tracer.
198 citations
01 Jan 2008
TL;DR: In this article, the authors used four physiological and biochemical parameters including leaf relative water content (RWC), ascorbic acid (AA) content, total leaf chlorophyll (TCh), and leaf extract pH were used to develop an air pollution tolerance index.
Abstract: Air pollution tolerance index (APTI) is used by landscapers to select plant species tolerant to air pollution. Four physiological and biochemical parameters including leaf relative water content (RWC), ascorbic acid (AA) content, total leaf chlorophyll (TCh), and leaf extract pH were used to develop an APTI. Twenty-three plant species growing near a Beijing steel factory, an air pollution point source, were collected during five dates from July 1 to October 16, 2001. Our data suggested that combining a variety of physiological parameters could give a more reliable result than those air pollution tolerance classifications based on a single biochemical parameter. Through the growing season, some species exhibited APTI variation related to changes in air temperature and water status of the plant. The results highlighted the need for APTI measurements to be conducted throughout the growing season, when evaluating pollution tolerance of individual species. Plant species tolerant or moderately tolerant to air pollution under a variety of environmental conditions include non-trees (shrub, herb, vine) such as Metaplexis japonica, Ampelopsis aconitifolia var. glabra, Rhamnus parvifolia, Ziziphus jujuba var. spinosa, Pharbitis purpurea, Vitex negundo, and trees including Broussonetia papyrifera, Robinia pseudoacacia, and Ailanthus altissima. The APTI of species indicated as an ideal candidate for landscape planting in the vicinity of polluting industry.
195 citations
TL;DR: In this paper, a 1-week long extreme winter warming event was simulated in early March using infrared heating lamps run with or without soil warming cables, and the results demonstrate that a single, short, extreme winter heating event can have considerable impact on bud production, phenology and reproductive effort of dominant plant species within sub-Arctic dwarf shrub heathland.
Abstract: Climate change scenarios predict an increased frequency of extreme climatic events. In Arctic regions, one of the most profound of these are extreme and sudden winter warming events in which temperatures increase rapidly to above freezing, often causing snow melt across whole landscapes and exposure of ecosystems to warm temperatures. Following warming, vegetation and soils no longer insulated below snow are then exposed to rapidly returning extreme cold. Using a new experimental facility established in sub-Arctic dwarf shrub heathland in northern Sweden, we simulated an extreme winter warming event in the field and report findings on growth, phenology and reproduction during the subsequent growing season. A 1-week long extreme winter warming event was simulated in early March using infrared heating lamps run with or without soil warming cables. Both single short events delayed bud development of Vaccinium myrtillus by up to 3 weeks in the following spring (June) and reduced flower production by more than 80%: this also led to a near-complete elimination of berry production in mid-summer. Empetrum hermaphroditum also showed delayed bud development. In contrast, Vaccinium vitis-idaea showed no delay in bud development, but instead appeared to produce a greater number of actively growing vegetative buds within plots warmed by heating lamps only. Again, there was evidence of reduced flowering and berry production in this species. While bud break was delayed, growing season measurements of growth and photosynthesis did not reveal a differential response in the warmed plants for any of the species. These results demonstrate that a single, short, extreme winter warming event can have considerable impact on bud production, phenology and reproductive effort of dominant plant species within sub-Arctic dwarf shrub heathland. Furthermore, large interspecific differences in sensitivity are seen. These findings are of considerable concern, because they suggest that repeated events may potentially impact on the biodiversity and productivity of these systems should these extreme events increase in frequency as a result of global change. Although climate change may lengthen the growing season by earlier spring snow melt, there is a profound danger for these high-latitude ecosystems if extreme, short-lived warming in winter exposes plants to initial warm temperatures, but then extreme cold for the rest of the winter. Work is ongoing to determine the longer term and wider impacts of these events.
187 citations
TL;DR: In this article, the authors collected most relevant and up-to-date European literature on the response of dry biomass production to planting density and nitrogen (N) fertilizer and provided quantitative estimates of the effect of these practices.
TL;DR: In this article, a field experiment was conducted between April 2005 and October 2006 in a semiarid grassland in northern China to examine effects of topography, fire, nitrogen (N) fertilization, and their potential interactions on soil respiration.
Abstract: Soil respiration is one of the major carbon (C) fluxes between terrestrial ecosystems and the atmosphere and plays an important role in regulating the responses of ecosystem and global C cycling to natural and anthropogenic perturbations. A field experiment was conducted between April 2005 and October 2006 in a semiarid grassland in northern China to examine effects of topography, fire, nitrogen (N) fertilization, and their potential interactions on soil respiration. Mean soil respiration was 6.0% higher in the lower than upper slope over the 2 growing seasons. Annual burning in early spring caused constant increases in soil respiration (23.8%) over the two growing seasons. In addition, fire effects on soil respiration varied with both season and topographic position. Soil respiration in the fertilized plots was 11.4% greater than that in the unfertilized plots. Water- and plant-mediation could be primarily responsible for the changes in soil respiration with topography and after fire whereas the positive responses of soil respiration to N fertilization were attributable to stimulated plant growth, root activity and respiration. The different mechanisms by which topography, fire, and N fertilization influence soil respiration identified in this study will facilitate the simulation and projection of ecosystem C cycling in the semiarid grassland in northern China.
TL;DR: Differences between the early years and the final years of the experiment indicate the need for long-term monitoring of green roofs in addition to short-term experiments.
Abstract: Fifteen herbaceous perennial grass and herb species were planted into experimental green roofs in spring 2001. The species differed widely in their origins, heights, flowering times, life spans and growth forms but all were typical of dry and nutrient-stressed habitats. Three individuals of each species of a standardised size were randomly assigned to a planting grid at 20 cm apart in each experimental replicate plot at substrate depth of either 100 or 200 mm. Each treatment was replicated three times. During each growing season, the mean height and spread of each individual was recorded, together with flowering performance and % vegetation cover. In addition the numbers and % covers of all spontaneous colonised species were recorded. Greatest survival, diversity, size and flowering performance of planted species occurred at 200 mm depth. Bare ground and moss cover was greatest at 100 mm, as was diversity of colonising species. Differences between the early years and the final years of the experiment indicate the need for long-term monitoring of green roofs in addition to short-term experiments.
TL;DR: Results indicate that there exist organized progression of rainfall onset within the western Kenya region with the long rains showing a southerly progression while the short rains show a south-westerly progression.
TL;DR: In this paper, water and carbon fluxes, as measured by eddy covariance, climate, soil water content, leaf area index, tree biomass, biomass increment (BI), litter fall and mortality were monitored for 10 successive years in a young beech stand in Hesse forest (north-eastern France) under contrasting climatic and management conditions.
Abstract: • Water and carbon fluxes, as measured by eddy covariance, climate, soil water content, leaf area index, tree biomass, biomass increment (BI), litter fall and mortality were monitored for 10 successive years in a young beech stand in Hesse forest (north-eastern France) under contrasting climatic and management conditions. • Large year-to-year variability of net carbon fluxes (NEE) and to a lesser extent, of tree growth was observed. The variability in NEE (coefficient of variation, CV = 44%) was related to both gross primary production (GPP) and to variations in total ecosystem respiration (TER), each term showing similar and lower interannual variability (CV = 14%) than NEE. Variation in the annual GPP was related to: (i) the water deficit duration and intensity cumulated over the growing season, and (ii) the growing season length, i.e. the period of carbon uptake by the stand. Two thinnings occurring during the observation period did not provoke a reduction in either GPP, water fluxes, or in tree growth. Interannual variation of TER could not be explained by any annual climatic variables, or LAI, and only water deficit duration showed a poor correlation. Annual biomass increment was well correlated to water shortage duration and was significantly influenced by drought in the previous year. • The relationship between annual NEE and biomass increment (BI) was poor: in some years, the annual carbon uptake was much higher and in others much lower than tree growth. However this relationship was much stronger and linear (r 2 = 0.93) on a weekly to monthly time-scale from budburst to the date of radial growth cessation, indicating a strong link between net carbon uptake and tree growth, while carbon losses by respiration occurring after this date upset this relationship. • Despite the lack of correlation between annual data, the NEE and BI cumulated over the 10 years of observations were very close. • On the annual time-scale, net primary productivity calculated from eddy fluxes and from biological measurements showed a good correlation.
TL;DR: Results for these highest Eurasian tree lines suggest a common mechanism of alpine tree line formation for evergreen and deciduous species, and direct (meristematic) low temperature constraints of growth.
Abstract: 1. Whether the global high elevation tree line phenomenon is associated with a low-temperature-induced limitation of sink activities (i.e. direct impact on meristems and thus, growth) or by a limitation of the trees' carbon source activities (net photosynthesis) still awaits detailed tests across a range of taxa and regions, especially for deciduous species in a short growing season. 2. Here, we test the sink limitation hypothesis in the highest tree lines of Eurasia at altitudes up to 4700 m. We assessed growth and tissue concentrations of non-structural carbohydrates (NSC) as a measure of the carbon source-sink balance in needles and branchwood of Abies, Juniperus (evergreen), Betula and Larix (deciduous). 3. The mean soil temperature in deep shade (a proxy for mean air temperature) across the growing season at tree line in this region is around 6.6 degrees C, which is consistent with the threshold temperature found at the natural climatic limit of the tree life-form worldwide. Mean tree height and stem diameter decreased significantly towards the upper tree line in all species studied. 4. Air temperature measurements at an inverted tree line site (valley bottom) indicate strong and rapid oscillations between nighttime freezing and mild daytime temperatures during late winter, which apparently eradicate Abies and select for Juniperus, offering potential explanations for the inferiority of Abies also at the upper Tibetan tree line. 5. At none of the four altitudinal transects studied did we observe a significant depletion of NSC (carbon limitation) at tree line. Instead, NSC increased in the majority of cases, suggesting direct (meristematic) low temperature constraints of growth. These results for these highest Eurasian tree lines suggest a common mechanism of alpine tree line formation for evergreen and deciduous species.
TL;DR: In this paper, the authors examined the effectiveness of using multi-temporal satellite imagery, field spectral data, and LiDAR top of canopy data to classify and map the common plant communities of the Ragged Rock Creek marsh, located near the mouth of the Connecticut River.
TL;DR: For potato production in Mediterranean and Sahelian types of climate, during the heat-free period of the year, yields will go down as the suitable period becomes shorter as mentioned in this paper.
Abstract: Since the onset of the industrial revolution, in 1750, the concentration of carbon dioxide rose from 290 to 380 parts per million. Especially during the last decennia, the effects of increased greenhouse gases concentrations are being felt. The last 14 years worldwide contained the warmest 13 years since weather recording started. For southern Europe, the major effects reported by the International Panel on Climate Change are reduced water availability and a shorter suitable winter time slot for potato production. For northern Europe, climate change will bring a decreasing number of days with frost and a lengthening of the growing season. It will be associated with more rain in winter and less in summer, with more erratic but heavier rain storms. For potato production in Mediterranean and Sahelian types of climate, during the heat-free period of the year, yields will go down as the suitable period becomes shorter. With a higher evaporative demand, the resource water will be used less efficiently. Potato yields in temperate climates may increase—provided that water for irrigation is available—due to a longer growing season and higher carbon dioxide concentrations in the air. The quality may be affected as larger tubers with a higher dry matter concentration are expected. Problems with pests and diseases are expected to increase with a longer growing season at higher temperature which allows more cycles of multiplication and greater pressure. Late blight will also have a longer period to build up and erratic rains will make control more difficult. Seed production with increased vector pressure will become more costly because fewer field generations will follow the rapid multiplication stage and seed production may move further north. Present potato areas in Europe, however, are more affected by economic factors such as inadequate farm size, changing habits, and remoteness of markets than by climate determined suitability of growing conditions. To remain competitive, the industry will have to invest in strengthening existing production areas and assess the potential of new potato production areas (further north), in new varieties adapted to extremes in weather (heat, drought), in irrigation equipment, in equipment better adapted to wet soil conditions to assure accessibility, and in improved stores with more stores equipped with refrigeration as higher winter temperatures more frequently will make it impossible to keep ware potatoes cool with ambient air. Assessment of both climate change and market liberalization in Europe shows other roads ahead than when only climate effects are taken into consideration.
TL;DR: In this paper, the authors investigated the long-term ecohydrologic significance of hydraulic redistribution in mesquite roots and assessed how this affects tree water use and productivity in an upland savanna ecosystem over a two-year period.
Abstract: [1] Recent studies have illuminated the process of hydraulic redistribution, defined as the translocation of soil moisture via plant root systems, but the long-term ecohydrologic significance of this process is poorly understood. We investigated hydraulic redistribution (HR) by Prosopis velutina Woot. (velvet mesquite) in an upland savanna ecosystem over a two-year period. Our goal was to quantify patterns of HR by mesquite roots and assess how this affects tree water use and productivity. We used the heat ratio method to monitor bi-directional sap flow, an analog of HR, in both lateral and tap roots. Additionally, we monitored soil water content and used the eddy covariance technique to quantify ecosystem carbon dioxide and water exchange. Mesquite roots redistributed large amounts of water throughout the year, even during periods of canopy dormancy. Dormant season precipitation (November–March) was often taken up by shallow lateral roots and transferred downward in the soil profile by deeper lateral and tap roots. Such a transfer was also apparent when the trees were active and moisture from summer rainfall was plant available in the upper soil layers. As the upper soil layers dried, sap flow moving toward the canopy in the lateral roots diminished and water use from deeper soils increased via the taproots. The relationship between root sap flow and above-canopy fluxes suggested that deeper “stored” water from HR allowed the trees to transpire more in the spring that followed a winter with significant downward redistribution. Patterns of lateral and tap root sap flow also implied that redistribution may extend the growing season of the trees after summer rains have ended and surface soils are dry, thus allowing the trees to photosynthesize through periods of seasonal drought. The large hydrologic magnitude and the ecological effects of HR we studied, along with mounting evidence of this process occurring in many other ecosystems, indicates that HR should be accounted for in many ecohydrologic modeling efforts.
01 Jan 2008
TL;DR: In this article, Boyer et al. showed that low water availability limits the productivity of many natural ecosystems, particularly in dry climates (Fig. 3.1) and that losses in crop yield due to water stress exceed losses due to all other biotic and environmental factors combined.
Abstract: Although water is the most abundant molecule on the Earth’s surface, the availability of water is the factor that most strongly restricts terrestrial plant production on a global scale. Low water availability limits the productivity of many natural ecosystems, particularly in dry climates (Fig. 3.1). In addition, losses in crop yield due to water stress exceed losses due to all other biotic and environmental factors combined (Boyer 1985). Regions where rainfall is abundant and fairly evenly distributed over the growing season, such as in the wet tropics, have lush vegetation. Where summer droughts are frequent and severe, forests are replaced by grasslands, as in the Asian steppes and North American prairies. Further decrease in rainfall results in semidesert, with scattered shrubs, and finally deserts. Even the effects of temperature are partly exerted through water relations because rates of evaporation and transpiration are correlated with temperature. Thus, if we want to explain natural patterns of productivity or to increase productivity of agriculture or forestry, it is crucial that we understand the controls over plant water relations and the consequences for plant growth of an inadequate water supply.
TL;DR: Yield was lineally and positively associated with number of grains per m2, while average grain weight did not exhibit any clear trend with the year of release of the cultivars, and harvest index was the main attribute responsible for yield improvements.
TL;DR: The results of this study highlight the importance and significant effects of the long-term application of different fertilizers on edaphic factors and specific groups of fungi and bacteria playing a key role in arable soils.
TL;DR: Wang et al. as discussed by the authors analyzed wheat WUE not only on grain yield basis, but also on photosynthesis basis and biomass basis, and then discussed the effects of irrigation regimes on wheat water use efficiency.
TL;DR: In this article, the authors examined the structure and trends of climate parameters important to wine- grape production from 1952 to 2006 in the Alt Penedes, Priorat, and Segria regions of NE Spain.
Abstract: This study examined the structure and trends of climate parameters important to wine- grape production from 1952 to 2006 in the Alt Penedes, Priorat, and Segria regions of NE Spain. Aver- age and extreme temperature and precipitation characteristics from 3 stations in the regions were organized into annual, growing season, and phenological growth stage periods and used to assess potential impacts on vineyard and wine quality, and changes in varietal suitability. Results show an overall growing season warming of 1.0 to 2.2°C, with significant increases in heat accumulation indices that are driven mostly by increases in maximum temperature (average Tmax, number of days with Tmax > 90th percentile, and number of days with Tmax > 30°C). Changes in many temperature parameters show moderate to strong relationships with vine and wine parameters in the 3 regions, including earlier phenological events concomitant with warmer growing seasons, higher wine quality with higher ripening diurnal temperature ranges, and reduced production in the warmest vintages. While trends in annual and growing season precipitation were not evident, precipitation during the bloom to veraison period declined significantly for all 3 sites, indicating potential soil moisture stress during this critical growth stage. Shorter-term analysis of crop evapotranspiration (ETc) reveals that the current impact per 1°C of growing season (Apr to Oct) warming is an increase in water demands in the region by 6 to 14%. These observations, combined with climate projections, indicate potential disruption of climate-variety balance, increasing water stress, and challenges in producing quality wines without the adoption of appropriate adaptive measures.
TL;DR: In this article, the authors measured the tundra-atmosphere exchanges of carbon dioxide (CO2) and water vapour in the Canadian Low Arctic for three years, from late-winter until the end of the growing period.
Abstract: Tundra-atmosphere exchanges of carbon dioxide (CO2) and water vapour were measured near Daring Lake, Northwest Territories in the Canadian Low Arctic for 3 years, 2004–2006. The measurement period spanned late-winter until the end of the growing period. Mean temperatures during the measurement period varied from about 2 °C less than historical average in 2004 and 2005 to 2 °C greater in 2006. Much of the added warmth in 2006 occurred at the beginning of the study, when snow melt occurred 3 weeks earlier than in the other years. Total precipitation in 2006 (163 mm) was more than double that of the driest year, 2004 (71 mm). The tundra was a net sink for CO2 carbon in all years. Mid-summer net ecosystem exchange of CO2 (NEE) achieved maximum values of −1.3 g C m−2 day−1 (2004) to −1.8 g C m−2 day−1 (2006). Accumulated NEE values over the 109-day period were −32,−51 and −61 g C m−2 in 2004, 2005 and 2006, respectively. The larger CO2 uptake in 2006 was attributed to the early spring coupled with warmer air and soil conditions. In 2004, CO2 uptake was limited by the shorter growing season and mid-summer dryness, which likely reduced ecosystem productivity. Seasonal total evapotranspiration (ET) ranged from 130 mm (2004) to 181 mm (2006) and varied in accordance with the precipitation received and with the timing of snow melt. Maximum daily ET rates ranged from 2.3 to 2.7 mm day−1, occurring in mid July. Ecosystem water use efficiency (WUEeco) varied slightly between years, ranging from 2.2 in the driest year to 2.5 in the year with intermediate rainfall amounts. In the wettest year, increased soil evaporation may have contributed to a lower WUEeco (2.3). We speculate that most, if not all, of the modest growing season CO2 sink measured at this site could be lost due to fall and winter respiration leading to the tundra being a net CO2 source or CO2 neutral on an annual basis. However, this hypothesis is untested as yet.
TL;DR: In this article, the authors used a 0.5o latitude × 0. 5o longitude gridded dataset from the Finnish Meteorological Institute (EMI) to study the effect of greenhouse gas and aerosol emissions on Finnish field crop production.
Abstract: Climate change offers new opportunities for Finnish field crop production, which is currently limited by the short growing season. A warmer climate will extend the thermal growing season and the physiologically effective part of it. Winters will also become milder, enabling introduction of winter-sown crops to a greater extent than is possible today. With this study we aim to characterise the likely regional differences in capacity to grow different seed producing crops. Prolongation of the Finnish growing season was estimated using a 0.5o latitude × 0.5o longitude gridded dataset from the Finnish Meteorological Institute. The dataset comprised an average estimate from 19 global climate models of the response of Finnish climate to low (B1) and high (A2) scenarios of greenhouse gas and aerosol emissions for 30-year periods centred on 2025, 2055 and 2085 (Intergovernmental Panel on Climate Change). Growing season temperature sums that suit crop growth and are agronomically feasible in Finland are anticipated to increase by some 140 °Cd by 2025, 300 °Cd by 2055 and 470 °Cd by 2085 in scenario A2, when averaged over regions, and earlier sowing is expected to take place, but not later harvests. Accordingly, the extent of cultivable areas for the commonly grown major and minor crops will increase considerably. Due to the higher base temperature requirement for maize (Zea mays L.) growth than for temperate crops, we estimate that silage maize could become a Finnish field crop for the most favourable growing regions only at the end of this century. Winters are getting milder, but it will take almost the whole century until winters such as those that are typical for southern Sweden and Denmark are experienced on a wide scale in Finland. It is possible that introduction of winter-sown crops (cereals and rapeseed) will represent major risks due to fluctuating winter conditions, and this could delay their adaptation for many decades. Such risks need to be studied in more detail to estimate timing of introduction. Prolonged physiologically effective growing seasons would increase yielding capacities of major field crops. Of the current minor crops, oilseed rape (Brassica napus L.), winter wheat (Triticum aestivum L.), triticale (X Triticosecale Wittmack), pea (Pisum sativum L.) and faba bean (Vicia faba L.) are particularly strong candidates to become major crops. Moreover, they have good potential for industrial processing and are currently being bred. Realisation of increased yield potential requires adaptation to 1) elevated daily mean temperatures that interfere with development rate of seed crops under long days, 2) relative reductions in water availability at critical phases of yield determination, 3) greater pest and disease pressure, 4) other uncertainties caused by weather extremes and 5) generally greater need for inputs such as nitrogen fertilisers for non-nitrogen fixing crops.
TL;DR: In this article, three different methods were evaluated for analysing wood formation of Norway spruce [Picea abies (L.) Karst] and Scots pine (Pinus sylvestris L.) in Finland.
Abstract: Three different methods were evaluated for analysing wood formation of Norway spruce [Picea abies (L.) Karst.] and Scots pine (Pinus sylvestris L.) in Finland. During two growing seasons, wood formation dynamics were determined both by wounding the cambium with a needle followed by localisation of the wound-associated tissue modification after the growing season (pinning), and by extracting small increment cores during the growing season (microcoring). Stem radius was additionally monitored with band dendrometers. For Norway spruce, pinning and microcoring yielded similar dates for the onset of wood formation. The timing of wood production during the growing season was also similar for pinning and microcoring. For Scots pine, the onset of wood formation was recorded from microcores almost 2 weeks later than from pinning samples. In Scots pine, microcore measurements also produced somewhat later cessation dates for tracheid formation than the pinning samples. For both tree species, the total number of tracheids formed during the growing season was, however, about the same for pinning and microcoring. Dendrometer results clearly differed from those of pinning and microcoring. In particular, the dendrometers showed an increase of stem radius considerably earlier in spring, when the other methods did not detect wood formation. Thus, pinning and microcoring currently represent the most reliable techniques for detailed monitoring of wood formation.
TL;DR: In this paper, the authors present results from 4 years (May 2001-May 2005) of water and energy flux measurements made in a no-till, irrigated maize-soybean rotation system in eastern Nebraska, USA.
TL;DR: Comparing ancestors and descendants, it was found that the drought caused many changes in life‐history traits, including a shift to earlier flowering, longer duration of flowering, reduced peak flowering and greater skew of the flowering schedule.
Abstract: Climate change is likely to spur rapid evolution, potentially altering integrated suites of life-history traits. We examined evolutionary change in multiple life-history traits of the annual plant Brassica rapa collected before and after a recent 5-year drought in southern California. We used a direct approach to examining evolutionary change by comparing ancestors and descendants. Collections were made from two populations varying in average soil moisture levels, and lines propagated from the collected seeds were grown in a greenhouse and experimentally subjected to conditions simulating either drought (short growing season) or high precipitation (long growing season) years. Comparing ancestors and descendants, we found that the drought caused many changes in life-history traits, including a shift to earlier flowering, longer duration of flowering, reduced peak flowering and greater skew of the flowering schedule. Descendants had thinner stems and fewer leaf nodes at the time of flowering than ancestors, indicating that the drought selected for plants that flowered at a smaller size and earlier ontogenetic stage rather than selecting for plants to develop more rapidly. Thus, there was not evidence for absolute developmental constraints to flowering time evolution. Common principal component analyses showed substantial differences in the matrix of trait covariances both between short and long growing season treatments and between populations. Although the covariances matrices were generally similar between ancestors and descendants, there was evidence for complex evolutionary changes in the relationships among the traits, and these changes depended on the population and treatment. These results show that a full appreciation of the impacts of global change on phenotypic evolution will entail an understanding of how changes in climatic conditions affect trait values and the structure of relationships among traits.
TL;DR: Root colonization by arbuscular mycorrhizae and dark septate endophytic fungi in nitrogen amended and unamended mixed tallgrass prairie communities were analyzed monthly and hyperparasitism of AM hyphal coils by melanized sePTate fungi was frequently observed and increased with AM coil frequency.
Abstract: Root colonization by arbuscular mycorrhizae (AM) and dark septate endophytic (DSE) fungi in nitrogen amended and unamended mixed tallgrass prairie communities were analyzed monthly over two growing seasons. Roots were stained with Trypan blue and Sudan IV and fungal structures quantified using the modified magnified intersections method. Root length colonized (RLC) by DSE exceeded AM colonization during early part of the growing season. Fungal colonization varied among the years and was greater in 2003 than in 2002. Seasonal variation among the months within a growing season was observed in 2002 but not in 2003 for both AM and DSE. AM fungi were most abundant during the peak growing season of dominant C4 vegetation while DSE were most abundant during the early part of the growing season. Hyperparasitism of AM hyphal coils by melanized septate fungi was frequently observed and increased with AM coil frequency. Although nitrogen amendment had altered the plant community composition, it had no impact on the colonization by AM or DSE fungi.