Marginal Climatic Conditions Research Articles

Human pressures constrain Eurasian otter occurrence in semiarid Northern Africa

Populations inhabiting the periphery of species distribution ranges may experience suboptimal environmental conditions and higher vulnerability to anthropogenic pressures. Disentangling the role of natural and human-related factors and the relationships among them in these marginal areas is thus key to understand and prevent species declines and range reductions. We analysed Eurasian otter (Lutra lutra) occurrence patterns in relation to anthropogenic pressures and natural environmental gradients in Morocco, an area constituting the arid limit of the species’ global range. The probability of otter occurrence was higher as terrain ruggedness increased and at intermediate elevations, and lower in catchments exposed to higher anthropogenic pressures. Otters tended to be rare at higher elevations and in areas with less annual precipitation, probably as a result of trophic resource limitations and large water flow fluctuations, respectively. A combination of natural and anthropogenic factors, both at drainage area and local scales, was needed to understand the current occurrence of the species. Our study highlights a need for urgent action to conserve the Eurasian otter in northern Africa, where freshwater ecosystems and their associated biodiversity are threatened by rapid human development in areas of marginal climatic conditions.

Characterization of cocoa production, income diversification and shade tree management along a climate gradient in Ghana.

Reduced climatic suitability due to climate change in cocoa growing regions of Ghana is expected in the coming decades. This threatens farmers’ livelihood and the cocoa sector. Climate change adaptation requires an improved understanding of existing cocoa production systems and farmers’ coping strategies. This study characterized current cocoa production, income diversification and shade tree management along a climate gradient within the cocoa belt of Ghana. The objectives were to 1) compare existing production and income diversification between dry, mid and wet climatic regions, and 2) identify shade trees in cocoa agroforestry systems and their distribution along the climatic gradient. Our results showed that current mean cocoa yield level of 288kg ha-1yr-1 in the dry region was significantly lower than in the mid and wet regions with mean yields of 712 and 849 kg ha-1 yr-1, respectively. In the dry region, farmers diversified their income sources with non-cocoa crops and off-farm activities while farmers at the mid and wet regions mainly depended on cocoa (over 80% of annual income). Two shade systems classified as medium and low shade cocoa agroforestry systems were identified across the studied regions. The medium shade system was more abundant in the dry region and associated to adaptation to marginal climatic conditions. The low shade system showed significantly higher yield in the wet region but no difference was observed between the mid and dry regions. This study highlights the need for optimum shade level recommendation to be climatic region specific.

The importance of phenotypic differentiation and plasticity in the range expansion of the annual Atriplex tatarica (Amaranthaceae)

The ability of a species to adapt to sub-optimal conditions at the margin of its distribution range and to cope with environmental stress is considered to be important for its successful geographic expansion. To ascertain the roles of phenotypic differentiation and plasticity in the expansion of the annual Atriplex tatarica, we compared plants from populations found in Marginal and Central areas of the species’ range. We grew these plants under marginal climatic conditions in pots with different types of substrate. We assessed the population genetic structure at five putatively neutral allozyme loci to evaluate whether there was any evidence of reduced genetic diversity in Marginal populations compared to Central ones. We used the QST vs. FST approach (while FST gives a standardised measure of the genetic differentiation among populations for a genetic locus, QST measures the amount of genetic variance among populations relative to the total genetic variance) to ascertain the roles of adaptive vs. non-adaptive processes on phenotypic differentiation. Plants native to the Marginal area of the species’ range flowered earlier and had a lower shoot mass and a higher reproductive allocation than plants native to the Central part of the species’ range. The Marginal populations of Atriplex tatarica showed lower genetic diversity at allozyme loci and higher phenotypic differentiation than the Central populations. We recorded similar plastic responses to substrates in plants native to both regions. Our results indicate that Marginal populations of expanding A. tatarica maintain the ability to adapt locally and to elicit a plastic response to environmental stress, despite loss of genetic diversity.

Analysis of Induction and Establishment of Dwarf Bunt of Wheat Under Marginal Climatic Conditions.

Dwarf bunt caused by Tilletia contraversa is a disease of winter wheat that has a limited geographic distribution due to specific winter climate requirements. The pathogen is listed as a quarantine organism by several countries that may have wheat production areas with inadequate or marginal climate for the disease-in particular the People's Republic of China. Field experiments were conducted in the United States in an area of Kansas that is a climatic analog to the northern winter wheat areas of China to evaluate the risk of disease introduction into such areas. The soil surface of four replicate 2.8 × 9.75 m plots, planted with a highly susceptible cultivar, was inoculated with six teliospore concentrations ranging from 0.88 to 88,400 teliospores/cm2. A single initial inoculation was done in each of three nurseries planted during separate seasons followed by examination for disease for 4 to 6 years afterward. Any diseased spikes produced were crushed and returned to the plots where they were produced. One nursery had no disease during all six seasons. In two nurseries, the disease was induced at trace levels at the three highest inoculation rates. Disease carryover to the second year occurred during one year in one nursery in plots at the highest inoculation rate, but no disease occurred the following three seasons. A duplicate nursery planted in a disease conducive area in Utah demonstrated that the highest rate of inoculum used in the experiments was sufficient to cause almost 100% infection. This study demonstrated that in an area with marginal climatic conditions it was possible to induce transient trace levels of dwarf bunt, but the disease was not established even with a highly susceptible cultivar and high levels of inoculum. Our results support the conclusions of the 1999 Agreement on U.S.-China Agricultural Cooperation which set a tolerance for teliospores in grain, and supports the Risk Assessment Model for Importation of United States Milling Wheat Containing T. contraversa.

Yield and quality of forage maize grown under marginal climatic conditions in Northern Ireland

AbstractThe expansion of maize (Zea mays) into cooler areas has been facilitated by the availability of early maturing cultivars and by cultivation under plastic mulch. However, year‐to‐year variation in harvest quality remains a problem. The yield and quality of ‘Goldcob’, an early maturing forage maize, were assessed over 5 years from plots grown in the open and under plastic mulch. For both treatments, there was significant between‐year variation in yield and quality (starch content, metabolizable energy, organic matter and D‐value), and starch content was particularly variable. The use of plastic mulch to warm the soil advanced the establishment of the crop, with silking occurring on average 19 days earlier. This resulted in significantly higher yields under plastic mulch, with a mean increase of 3·9 t ha−1. The plastic mulch also resulted in significant increases in quality parameters, with starch content showing a mean increase of 36%. The Ontario heat unit model explained much of the variability in yield, both in the open and under plastic mulch. Plastic mulch had no consistent effect on Ontario heat units accumulated prior to silking, but Ontario heat units accumulated between silking and harvest (OHUpost‐silk) were found to be an adequate predictor of yield. The response of starch content was more complex, showing a clear plateau in the response to temperature at 1200 OHUpost‐silk, above which the accumulation of starch appears limited by other factors.

Growing maize in clumps as a strategy for marginal climatic conditions

Under dryland conditions of the Texas High Plains, maize ( Zea mays) production is limited by sparse and erratic precipitation that results in severe water stress particularly during grain formation. When plant populations are reduced to 2.0–3.0 plants m −2 to conserve soil water for use during grain filling, tillers often form during the vegetative growth and negate the expected economic benefit. We hypothesized that growing maize in clumps spaced 1.0 m apart would reduce tiller formation, increase mutual shading among the plants, and conserve soil water for grain filling that would result in higher grain yield. Studies were conducted during 2006 and 2007 at Bushland, TX. with two planting geometries (clump vs. equidistant), two irrigation methods (low-energy precision applicator, LEPA, and low-elevation spray applicator, LESA) at three irrigation levels (dryland, 75 mm and 125 mm in 2006; and dryland, 50 mm and 100 mm in 2007). For dryland plots in 2007, clump plants had only 0.17 tillers (0.66 tillers m −2) compared with 1.56 tillers per plant (6.08 tillers m −2) for equidistant spacing. Tillers accounted for 10% of the stover for the equidistant plants, but less than 3% of the grain. Clump planting produced significantly greater grain yields (321 g m −2 vs. 225 g m −2 and 454 g m −2 vs. 292 g m −2 during 2006 and 2007, respectively) and Harvest Indexes (0.54 vs. 0.49 and 0.52 vs. 0.39 during 2006 and 2007, respectively) compared with equidistant plants in dryland conditions. Water use efficiency (WUE) measurements in 2007 indicated that clumps had a lower evapotranspiration (ET) threshold for initiating grain production, but the production function slopes were 2.5 kg m −3 for equidistant treatments compared to 2.0 kg m −3 for clump treatments. There was no yield difference for method of irrigation on water use efficiency. Our results suggest that growing maize in clumps compared with equidistant spacing reduced the number of tillers, early vegetative growth, and Leaf Area Index (LAI) so that more soil water was available during the grain filling stage. This may be a useful strategy for growing maize with low plant populations in dryland areas where severe water stress is common.

Marginal Horticulturalists or Maize Agriculturalists? Archaeobotanical, Paleopathological, and Isotopic Evidence Relating to Langford Tradition Maize Consumption

AbstractLangford Tradition horticulture was long viewed as representing a marginalized form of Middle Mississippian agriculture resulting from an adaptation to the less fertile landscapes and marginal climatic conditions of northern Illinois. This adaptation was characterized as involving semi-sedentary maize horticulture combined with an intensive use of wild game and plants. Until recently direct evidence for reconstructing Langford diet and subsistence practices had been limited. In this first systematic study of the specific evidence of Langford maize consumption from archaeology, paleopathology, archaeobotany, and isotopic studies we suggest that these people are best characterized as maize dependent agriculturalists.If maize was universally available in the Midwest by at least A.D. 900 … why did the Oneota not practice agriculture with the same flourish as their nearby Middle Mississippian neighbors?—John P. Hart (1990)

Effects of plastic mulch, sowing date and cultivar on the yield and maturity of forage maize grown under marginal climatic conditions in Northern Ireland

The effects of growing forage maize (Zea mays) with or without plastic mulching treatments on the dry‐matter (DM) yield, cob yield, DM content and starch content was investigated in Northern Ireland in 1996 and 1997. Cultivars differing in maturity characteristics were sown in spring at a range of dates in three replicated plot experiments and were used to compare the effects of two plastic mulches and an untreated control: one plastic mulch completely covered the rows (floating); the other had holes punched in the plastic, through which the plants grew (punch). Between April and October in 1996 and 1997, the Ontario heat units (OU) received were above average at 2489 and 2660 respectively; in those years without plastic mulches, the earliest maturing cultivar, Melody, yielded 11·0 and 13·6 t DM ha–1, with dry‐matter contents of 214 and 215 g kg–1 respectively. Mean daily increases in soil and air temperature under plastic mulches of up to 6°C and 11°C, respectively, were closely related to solar radiation. Under plastic mulches, 15% fewer OU were required to reach silking, and 33% more OU were available between silking and harvest. Meaned over three experiments, two years and three cultivars, plastic mulches, when compared with the unmulched control, increased maize yield from 12·0 to 14·7 t DM ha–1, cob yield from 3·7 to 6·8 t DM ha–1, dry‐matter content from 230 to 270 g kg–1 and starch content from 198 to 272 g kg–1. The effect of plastic mulch on the maturation of the crop was greatest at earlier sowings. In 1997, plants from an early sowing date (10 April) that had recently emerged through the punch plastic mulch were damaged by frost, whereas those in the floating plastic mulch plots were unaffected. When the floating plastic mulch was left on after the six‐ to eight‐leaf stage of the first‐early maize cultivar Hudson, the plants were physically damaged and the yield reduced, but DM and starch contents continued to increase. The increases in yield and dry‐matter content under the plastic mulch were greater in Diamant (second‐early cultivar) than in Melody (first‐early cultivar). It was concluded that, under marginal climatic conditions, plastic mulches ought to be used to improve the reliability of early cultivars rather than growing later maturing cultivars.

The effect on milk production of replacing grass silage with maize silage in the diet of dairy cows

This experiment examined the effects of replacing high digestibility grass silage (GS) with maize silage (MS) grown under marginal climatic conditions on milk production and forage intake of Friesian cows. Fifty-six cows were fed 6 kg/d (fresh weight) of concentrates and one of four forages: (1) all GS, (2) 67:33 GS:MS, (3) 33:67 GS:MS, and (4) all MS. Concentrate crude protein (CP) level was varied to equalise total dietary CP. The analysis of the GS and MS were: DM (g/kg) 223 and 257, pH 3.91 and 3.98, and CP (g/kg DM) 155 and 91. The MS contained 219 g starch/kg DM. In vivo OM digestibilities were 0.782 and 0.674 (s.e.m.=0.0063, P<0.001) for the GS and MS respectively. Silage DM intakes were 8.8, 9.7, 10.4, and 10.7 (s.e.m.=0.35) kg DM/d for treatments 1 to 4, respectively. The intake on treatment 1 was significantly lower than on treatments 3 and 4 ( P<0.01 and P<0.001, respectively). Milk yields were 21.4, 23.0, 23.1, and 22.7 (s.e.m.=0.48) kg/d for treatment 1 to 4, respectively. The differences in milk yield between the GS only and the two GS:MS mixtures were significant ( P<0.05). Maximum milk protein concentration (31.6 g/kg) and yield of fat and protein (1.59 kg/d) were achieved on the mixed forage diet containing 67% maize silage. These results show that moderate quality maize silage can successfully replace a high proportion of high digestibility grass silage in dairy cow diets.

Cotton Pest Management: Part 5. A Commonwealth of Independent States Perspective

Cotton is the most important fiber and oil crop in the Commonwealth of Independent States (CIS, formerly USSR). The Cotton Belt in the CIS occupies a large area stretching along the border with Iran and Afghanistan from Azerbaijan in Transcaucasia in the west to Tadjikistan in Middle Asia in the east. Major areas of cotton production in the CIS are Uzbekistan (1,666,000 ha), Turkmenistan (620,000 ha), Azerbaijan (300,000 ha), and Tadjikistan (300,000 ha). The area is typically arid, particularly in Middle Asia, which encompasses two great deserts, the Karakum (Blacksand) and Kysilkum (Redsand). At present the southern segments of these deserts are intensively irrigated. The crop structure in the Murgab Oasis in Turkmenistan consists of cotton (50% and more), alfalfa (20%), wheat (up to 25%), and melons and vegetables (about 25%). Average yield of raw cotton throughout the Cotton Belt fluctuates around 2.6 tons per ha (=800-1000 kg lintlha). Marginal climatic conditions characterize cotton production in the CIS and determine both the production system and the spectrum of arthropod pests. Severe winters with temperatures reaching -20°C and below are common in the irrigated desert plains and valleys of Middle Asia. Spring frosts often destroy cotton seedlings, necessitating resowing. For example, cold weather and rains led to resowing of about 50% of the crop in the