Hot Dry Summers Research Articles

Farm Forestry in Agricultural Southern Ontario, ca. 1850-1940: Evolving Strategies in the Management and Conservation of Forests, Soils and Water on Private Lands

Early settlers in southern Ontario aspired to become prosperous land-owning farmers; they began by cutting trees. Within a few decades, wind and water, unimpeded by forest cover, devastated soil and crops. Farmers were encouraged by groups such as the Ontario Fruit Growers’ Association to reforest some of their land. Farm forestry, as part of scientific agriculture, had a strong beginning in the early 1900s with the Ontario Agricultural and Experimental Union, but that movement was poorly supported until the 1930s, when the relationship between deforestation and water supplies reached a crisis. The Ontario Conservation and Reforestation Association (OCRA) and the Ontario Crop Improvement Association (OCIA) were created in agricultural southern Ontario in 1937-8 after a disastrously hot dry summer. Each organization interpreted the conservation of natural resources in profoundly different ways: the OCRA as a movement to create forest resources on public property, and the OCIA as management of privately-owned farmlands to improve crop production.

Faunal diversity of Ajmer Aravalis with special reference to Reptiles

Reptiles are cold blooded vertebrates which breath by lungs throughout their existence and have the body covered by scales. The skull articulates with the vertebral column by a single median occipital condyle. This is the way reptiles can be distinguished by other vertebrates. Ajmer is located in the center of Rajasthan (INDIA) between 25 0 38 and 26 0 58 north Latitude and 73 0 54 and 75 0 22 east longitude covering a geographical area of about 8481sq km hemmed in all sides by Aravalli hills . About 7 miles from the city is Pushkar lake created by the touch of lord Brahma. The Dargah of khawaja Moinuddin chisti is holiest shrine next to Mecca in the world. Ajmer has hot dry summer and cold bracing winter. The winter extends from November to February and summer extends from March to June followed by rainy season till mid September. The temperature varies from 2 o c in winter and 49 0 c in summer. The normal annual rainfall is 527.3mm. The total population of the district is 2180526 persons. Around 5.56 % of total area available for land utilization is covered under forest. Ajmer is abode of certain flora and fauna that are particularly endemic to semi-arid and are specially adapted to survive in the dry waterless region of the state. Out of 19 orders of reptiles 4 survive today. Rhynchocephalia Single living species Tuatara , Sphellodoll pz 111 ctatlts, found only in Newzealand. .Testudines (Turtles, Tortoises, and Terrapins).Of these one species of Tortoise (Star Tortoise), Geochelone elegans is found in Ajmer. .Crocodylia (Gharial and Crocodole)..Squamata (Lizards and Snakes). Reptiles Lizards and Snakes are of immense ecological importance. Reptile diversity is highest in Deserts. But now these are declining at fast rate. 25 species of Reptiles are recorded from Ajmer out of which 16 species of Lizards and 8 species of snakes. Reptiles are specially adapted to survive dry waterless region of the state.

Canola integration into semi-arid wheat cropping systems of the inland Pacific Northwestern USA

The inland Pacific Northwestern USA (iPNW) wheat-producing region has a diversity of environments and soils, yet it lacks crop diversity and is one of the few semi-arid wheat-growing regions without significant integration of oilseeds. Four major agroecological zones, primarily characterised by water availability, feature distinctly different fallowed and annually cropped systems, each presenting different challenges and opportunities to integrate winter and spring canola. Although major interests in regional energy crops and rotational diversification spurred feasibility research on iPNW canola food, feed and fuel production in the 1970s, commercial canola adaptation has lagged behind other semi-arid wheat regions for various socioeconomic, ecophysiological and agronomic reasons. New federal crop insurance policies will reduce economic risks in new crop adaptation, and oilseed processing facilities are creating new local markets. Although canola management largely relies on wheat farm equipment, agronomic approaches require strategic adjustments to account for physiological differences between canola and cereals including seed size, seedling morphology and responses to temperature extremes. Climate change predictions for the region threaten to exacerbate current hot and dry summers and research aims to develop and adapt flexible winter and spring canola-based systems to regional water and temperature stressors in each zone. Adaptation will require novel planting, fertilisation and weed control strategies to successfully establish improved winter canola cultivars in hot dry summers that survive cold winters, and spring canola cultivars direct-seeded in cool wet springs. The adaptation of winter and spring canola will somewhat mirror the rotational placement of winter and spring cereals within each zone. Economic analysis of oilseed break crop benefits such as weed and disease control will help to demonstrate the medium-term economic benefits of crop diversification to support the growth of a regional canola industry in the iPNW.

Effect of seasonal variations on the haematochemical profile of Cholistani service bulls

ABSTRACTThis reported study is of Pakistan's indigenous Cholistani cattle breed, a native of the Cholistan desert where it has been reported as having high production potential for nomadic herders. The aim of the present study was to assess haematochemical profile of adult Cholistani service bulls (n = 16), being reared at the Semen Production Unit Karaniwala, Bahawalpur, Cholistan desert, Pakistan, during various seasons as an indicator of their health status. Keeping in view the prevailing climatic conditions of the study area, four seasons of three months duration each were defined as (i) cool dry winter (November, December, January) (ii) temperate spring (February, March, April) (iii) hot dry summer (May, June, July) and (iv) hot humid summer (August, September, October). Blood specimens were collected fortnightly during the study period for haematochemical analyses (automated). The present study revealed that Cholistani service bulls have a tendency to maintain most of their haematochemical parameters more or less at the same level during various seasons which is suggestive of their adaptability under stressful climates without showing any signs of stress.

Energy, comfort and environmental assessment of different building envelope techniques in a Mediterranean climate with a hot dry summer

The EU regulations on energy saving have been implemented in Italy with the adoption of the North-European super-insulated model that led to the construction of buildings not much related to their climatic context. The European Directives 2010/31/EU and 2012/27/EU highlighted the importance to consider the specific climate but the development of a technical culture suitable for a temperate climate still remains an open question.The aim of the paper is to quantify the effect on energy consumptions, comfort levels, environmental sustainability of the adoption of 3 energy efficient envelopes recently introduced in Mediterranean area and characterized by different thermal inertia (masonry, wood–cement, wood). In order to achieve this goal, a multidisciplinary approach was adopted involving: the study of the energy performance in winter and summer using analytical models both in semi-stationary and dynamic conditions (Termo and EnergyPlus programs) and the detailed analysis of thermal bridges (Therm software); the analysis of the annual comfort through dynamic analysis with Fanger’s PMV and adaptive comfort models; the quantification of environmental–economic impacts through LCA analysis (SimaPro software) with Eco-indicator 99, CED, EPS 2000 and IPCC 2001 GWP methods and LCC considering financial and environmental costs.The results made it possible to stress the differences between the various adopted methods and demonstrate that in such energy efficient envelopes the thermal mass has low influence on energy saving while it has a great effect on comfort levels and environmental burdens, with a conflicting incidence on these two aspects.

Different growth sensitivity to climate of the conifer Juniperus thurifera on both sides of the Mediterranean Sea

Mediterranean plants cope with cold wet winters and dry hot summers, with a drought gradient from northwest to southeast. Limiting climatic conditions have become more pronounced in the last decades due to the warming trend and rainfall decrease. Juniperus thurifera L., a long-lived conifer tree endemic to the western Mediterranean region, has a disjunct distribution in Europe and Africa, making it a suitable species to study sensitivity to climate in both sides of the Mediterranean Basin. Tree-ring width chronologies were built for three J. thurifera stands at Spain (Europe) and three in Morocco (Africa) and correlated with monthly temperature and precipitation. The temporal stability of climate-growth relationships was assessed using moving correlations; the drought effect on growth was calculated using the monthly standardized precipitation-evapotranspiration index (SPEI) at different temporal scales. In the wettest stands, increasing spring temperature and summer precipitation enhanced growth, while in the driest stands, growth was enhanced by higher spring precipitation and lower summer temperature. The climate-growth correlations shifted during the twentieth century, especially since the 1970s. Particularly noticeable is the recent negative correlation with previous autumn and winter precipitation in the wettest stands of J. thurifera, probably related with an effect of cloud cover or flooding on carbon storage depletion for next year growth. The driest stands were affected by drought at long time scales, while the wettest stands respond to drought at short time scales. This reveals a different strategy to cope with drought conditions, with populations from drier sites able to cope with short periods of water deficit.

Heat stress alleviation in lactating buffaloes: Effect on physiological response, metabolic hormone, milk production and composition

To find out the effect of heat stress alleviation on physiological response, metabolic hormone profiles, milk production and composition in lactating buffaloes during hot-dry (HD) and hot-humid (HH) seasons, 42 lactating Nili-Ravi buffaloes were uniformly divided into 2 groups of 21 each. The treatment (T1) group was supplemented with niacin, yeast, edible oil and provided with curtains, additional ceiling fans and mist fans in the shed. The feeding time, frequency and method for providing concentrate were altered. The control (T0) group buffaloes were kept in separate shed without any nutrient supplementation, modification in microclimate and management. The rectal temperatures, recorded at 10 AM and 3 PM, were significantly lower in treatment group buffaloes than control group under both seasons. Similar trends in pulse rate and respiration rate were recorded among treatment and control group buffaloes in both seasons. Plasma cortisol, T3 and T4 values were almost similar in both control and treatment groups. The average daily milk production was significantly higher in treatment group than control group from starting to the end of the experiment. The average total fat and SNF production in treatment group were significantly higher compared to control group. The overall fat per cent in milk of control group buffaloes was recorded to be 7.71% which was significantly higher than treatment group. It was concluded that nutrient supplementations, microclimate modifications and management alterations together in the form of one package help reducing heat stress.It has beneficial effect on physiological responses, total milk production and composition in lactating buffaloes during hot dry and hot humid summer without affecting cortisol, T3 and T4 profile.

Applicability of passive compost bioreactors for treatment of extremely acidic and saline waters in semi-arid climates

Extremely acidic and saline groundwater occurs naturally in south-western Australia. Discharge of this water to surface waters has increased following extensive clearing of native vegetation for agriculture and is likely to have negative environmental impacts. The use of passive treatment systems to manage the acidic discharge and its impacts is complicated by the region's semi-arid climate with hot dry summers and resulting periods of no flow. This study evaluates the performance of a pilot-scale compost bioreactor treating extremely acidic and saline drainage under semi-arid climatic conditions over a period of 2.5 years. The bioreactor's substrate consisted of municipal waste organics (MWO) mixed with 10 wt% recycled limestone. After the start-up phase the compost bioreactor raised the pH from ≤3.7 to ≥7 and produced net alkaline outflow for 126 days. The bioreactor removed up to 28 g/m2/d CaCO3 equivalent of acidity and acidity removal was found to be load dependent during the first and third year. Extended drying over summer combined with high salinity caused the formation of a salt-clay surface layer on top of the substrate, which was both beneficial and detrimental for bioreactor performance. The surface layer prevented the dehydration of the substrate and ensured it remained waterlogged when the water level in the bioreactor fell below the substrate surface in summer. However, when flow resumed the salt-clay layer acted as a barrier between the water and substrate decreasing performance efficiency. Performance increased again when the surface layer was broken up indicating that the negative climatic impacts can be managed. Based on substrate analysis after 1.5 years of operation, limestone dissolution was found to be the dominant acidity removal process contributing up to 78–91% of alkalinity generation, while bacterial sulfate reduction produced at least 9–22% of the total alkalinity. The substrate might last up to five years before the limestone is exhausted and would need to be replenished. The MWO substrate was found to release metals (Zn, Cu, Pb, Ni and Cr) and cannot be recommended for use in passive treatment systems unless the risk of metal release is addressed.

Seasonality and facilitation drive tree establishment in a semi-arid floodplain savanna

A popular hypothesis for tree and grass coexistence in savannas is that tree seedlings are limited by competition from grasses. However, competition may be important in favourable climatic conditions when abiotic stress is low, whereas facilitation may be more important under stressful conditions. Seasonal and inter-annual fluctuations in abiotic conditions may alter the outcome of tree-grass interactions in savanna systems and contribute to coexistence. We investigated interactions between coolibah (Eucalyptus coolabah) tree seedlings and perennial C4 grasses in semi-arid savannas in eastern Australia in contrasting seasonal conditions. In glasshouse and field experiments, we measured survival and growth of tree seedlings with different densities of C4 grasses across seasons. In warm glasshouse conditions, where water was not limiting, competition from grasses reduced tree seedling growth but did not affect tree survival. In the field, all tree seedlings died in hot dry summer conditions irrespective of grass or shade cover, whereas in winter, facilitation from grasses significantly increased tree seedling survival by ameliorating heat stress and protecting seedlings from herbivory. We demonstrated that interactions between tree seedlings and perennial grasses vary seasonally, and timing of tree germination may determine the importance of facilitation or competition in structuring savanna vegetation because of fluctuations in abiotic stress. Our finding that trees can grow and survive in a dense C4 grass sward contrasts with the common perception that grass competition limits woody plant recruitment in savannas.

Amelioration of soil chemical constraints for revegetation on gold oxide processing residues

Gold oxide processing residues are highly alkaline, sodic and saline and initially require amelioration for plant establishment. The aim of this study was to determine the efficacy of soil covers and residue ameliorants in alleviating chemical constraints for revegetation. The effects of residue covers (10cm topsoil plus 0, 15 or 30cm gravelly sub-soil referred to as gravel), combined with gypsum (30 and 60tha−1), and compost (0 and 50m3ha−1) on chemical properties (pH, electrical conductivity (EC), exchangeable Na percentage (ESP), cation exchange capacity (CEC), total N, extractable N, P, K, S, cations and micronutrients) of gold oxide processing residue were studied in a large-scale field trial at Boddington, Western Australia in a Mediterranean climate. After the first season's rainfall, the EC1:5 decreased substantially (from 4.5–5.0 to about 1.0dSm−1) across all treatments in the 0–10cm residue layer (RES1), while topsoil and gravel materials which had low initial salinity (0.04–0.07dSm−1) increased their EC1:5 to 0.40–0.45dSm−1 in the 10cm above the residue interface in the 2nd hot-dry summer season. pH of both RES1 and the 10–20cm layer of residue (RES2) dropped from 9.0 to 8.0 over the trial period but topsoil pH remained at 5.2–5.5, regardless of treatments. Exchangeable Na percentage in RES1 and RES2 decreased, but increased from 17 to 70% in topsoil placed directly on the residue surface, compared with no increase in topsoil where there was a gravel layer separating topsoil from residue. Fertiliser added to topsoil raised extractable nutrients to levels adequate for plant growth. Nutrient elements did not differ with gypsum rate and compost amendment except for S, on account of the gypsum applied, and extractable P and Mn, which were elevated by compost. These findings indicate the efficacy of gravel plus fertilised topsoil cover on residue treated with surface broadcast gypsum to alleviate the adverse properties of alkaline, saline, sodic gold oxide processing residue as a medium for plant establishment and early growth.

Performance analysis of the broiler chicks under different cooling devices during hot-dry summer

The efficacy of two cooling systems with a low-cost Fan-Fogger (FF) and the conventional Fan-Pad (FP) system was tested to reduce the effect of heat stress in broiler chicks. Four hundred eighty, day-old sexed commercial broiler chicks were randomly divided into twelve groups each having forty birds with similar body weight range and equal sex ratio. All the chicks were reared under similar brooding conditions for two weeks. The FF and FP systems were used for four groups of chicks each from third to six week of age. All chicks were reared under deep litter system of housing with similar managemental conditions except the cooling systems. The average body weight of chicks at the start of experiment was 280g. The temperature in control, FF & FP during the experimental period of 4 weeks was 32.18 ± 0.11, 30.22 ± 0.85 and 29.40 ± 0.09 ºC with relative humidity of 39.21 ± 0.09, 44.65 ± 0.14 and 48.91± 0.10%, respectively. The body temperatures of birds in FF and FP were recorded to be 107.2 ± 0.18 and 106.9 ± 0.04ºF respectively, as compared to 108.2 ± 0.13ºF, in birds of control. The weight gain was 1101± 1.00, 1241± 1.50 and 1320 ± 1.49 g; the FCR was 2.23 ± 0.01, 2.08 ± 0.01 and 2.03 ± 0.02 while the PER was 2.37 ± 0.01, 2.55 ± 0.02 and 2.61 ± 0.01 in control, FF & FP, respectively. The survivability rate was 95.04 ± 0.56% in control, 96.78 ± 0.62% in FF and 98.23± 0.42% in FP, respectively. It was concluded that both the cooling systems had significant (p < 0.05) effect on the comfort and production efficiency of broiler chicks during hot-dry season. The fan-pad system was found to be more efficient than fan-fogger system.

The distribution of four Caragana species is related to their differential responses to drought stress

Caragana species are widespread in northwest China. However, species in semiarid areas of Inner Mongolia experience summer and autumn rainfall, whereas morphologically similar close relatives in arid areas in Xinjiang Province experience wet springs, but hot dry summers. We hypothesize that the differences among species in response to soil drought help to explain their distributions. A comparison of the closely related species C. intermedia and C. microphylla from Inner Mongolia (semiarid species) and C. pruinosa and C. spinosa from Xinjiang (arid species) was conducted to examine whether responses to a water deficit in a pot experiment were associated with the environments of their habitat. In the two semiarid species, the stomatal conductance was relatively insensitive to the decrease in predawn leaf water potential (Ψleaf), and leaves did not abscise or die even when the Ψleaf decreased below −6.0 MPa, while in seedlings of the two arid species the stomata closed at a relatively high Ψleaf, and the leaves abscised gradually when Ψleaf fell below about −3.0 MPa. Furthermore, major vein density, minor vein density and the cubed ratio of the conduit wall thickness to the conduit lumen breadth [(t/b)3] of minor veins increased by an average of 60, 150 and 220 %, respectively, in the semiarid species compared with the arid species. The results indicated that semiarid species have typical anisohydric properties, while arid species have typical isohydric properties. We suggest that the divergence in water-use strategies in the genus may be associated with variation in vein architecture, and may possibly play an important role in determining the distribution of these species in the different environments of northwest China.

Differences in Temperature Responses of Achene Types in Centaurea melitensis

Southern California has a Mediterranean climate with wet winters and hot dry summers. This type of environment is associated with irregular temperature patterns and rainfall, which can be unpredictable. Unpredictable environments, can threaten the germination and survival of plants like Centaurea melitensis. To ensure germination and survival under unpredictable environmental conditions, some plants may develop characteristic structures like cleistogamous flower heads, and in some cases they will develop heteromorphic achenes. Morphological differences between peripheral and center achenes may indicate variable responses to temperature. Additionally, unpredictable environmental conditions may lead to differences in the number of peripheral to center achenes in each head type. This study was designed to investigate differences in germination of peripheral and center achene's of each head type CH (Chasmogamous), iCL (Initial cleistogamous) and fCL (Final cleistogamous) when subjected to constant temperatures 5C, 10C, 15C, 23.5C and 30C. Differences in achene ratios (central to peripheral) and persistence were also investigated. A total of 400 achenes per achene type was used. Twenty achenes were placed in a petri dish filled with 6 ml of distilled water; the plates were incubated at one of five temperatures for seven days. The number of achenes (central to peripheral) remaining in the flower head three months post dispersal was documented. The results indicate that Centaurea melitensis was significantly affected by temperature. A fraction of the achenes remain in the flower head until early fall. Ratio differences in peripheral and center achenes may be a reflection of unstable environmental conditions.

Sensitivity of typical Mediterranean crops to past and future evolution of seasonal temperature and precipitation in Apulia

The region of Apulia, which is located in the south-east tip of the Italian Peninsula, has a typical Mediterranean climate with mild winters and hot-dry summers. Agriculture, an important sector of its economy, is potentially threatened by future climate change. This study describes the evolution of seasonal temperature and precipitation from the recent past to the next decades and estimates future potential impacts of climate change on three main agricultural products: wine, wheat and olives. Analysis is based on instrumental data, on an ensemble of climate projections and on a linear regression model linking these three agricultural products to seasonal values of temperature and precipitation. In Apulia, precipitation and temperature time series show trends toward warmer and marginally drier conditions during the whole analyzed (1951–2005) period: 0.18 °C/decade in mean annual minimum temperature and −14.9 mm/decade in the annual total precipitation. Temperature trends have been progressively increasing and rates of change have become noticeably more intense during the last 25 years of the twentieth century. Model simulations are consistent with observed trends for the period 1951–2000 and show a large acceleration of the warming rate in the period 2001–2050 with respect to the period 1951–2000. Further, in the period 2001–2050, simulations show a decrease in precipitation, which was not present in the previous 50 years. Wine production, wheat and olive harvest records show large inter-annual variability with statistically significant links to seasonal temperature and precipitation, whose strength, however, strongly depends on the considered variables. Linear regression analysis shows that seasonal temperature and precipitation variability explains a small, but not negligible, fraction of the inter-annual variability of these crops (40, 18, 9 % for wine, olives and wheat, respectively). Results (which consider no adaptation of crops and no fertilization effect of CO2) suggest that evolution of these seasonal climate variables in the first half of the twenty-first century could decrease all considered variables. The most affected is wine production (−20 ÷ −26 %). The effect is relevant also on harvested olives (−8 ÷ −19 %) and negligible on harvested wheat (−4 ÷ −1 %).

Modeling complex systems in the geosciences

Many geophysical phenomena can be described as complex systems, involving phenomena such as extreme or “wild” events that often do not follow the Gaussian distribution that would be expected if the events were simply random and uncorrelated. For instance, some geophysical phenomena like earthquakes show a much higher occurrence of relatively large values than would a Gaussian distribution and so are examples of the “Noah effect” (named by Benoit Mandelbrot for the exceptionally heavy rain in the biblical flood). Other geophysical phenomena are examples of the “Joseph effect,” in which a state is especially persistent, such as a spell of multiple consecutive hot days (heat waves) or several dry summers in a row. The Joseph effect was named after the biblical story in which Joseph's dream of seven fat cows and seven thin ones predicted 7 years of plenty followed by 7 years of drought.

Physical weathering of slate gravestones in a Mediterranean climate

The physical weathering of vertically emplaced slate gravestones in two metropolitan cemeteries in Adelaide, South Australia, is documented and evaluated with respect to the prevailing Mediterranean climate. The gravestones bear inscriptions dating back to the 1860s, thus providing a time frame of about 150 years. It is proposed that a prime factor in the weathering regime is seasonal hydration during mild wet winters, followed by desiccation during the hot dry summers. This causes repeated expansion and contraction of the exposed constituent minerals, weakening the cohesive forces within the rock. Thermal expansion has promoted cleavage spalling of dislocated sheets of about 3 mm thickness from both the inscribed faces and the backs of the gravestones. Growth of moss and lichen along the weakened cleavages has further promoted opening of cracks parallel to the slate cleavage. Salt crystallisation has substantially damaged the lower parts of all the observed slate stones.

The influence of water level on macrophyte growth and trophic interactions in eutrophic Mediterranean shallow lakes: a mesocosm experiment with and without fish

Summary1. Water‐level fluctuations are typical of lakes located in the semi‐arid Mediterranean region, which is characterised by warm rainy winters and hot dry summers. Ongoing climate change may exacerbate fluctuations and lead to more severe episodes of drought, so information on the effects of water level on the functioning of lake ecosystems in such regions is crucial.2. In eutrophic Lake Eymir, Turkey, we conducted a 4‐month (summer) field experiment using cylindrical 0.8‐m‐ (low‐water‐level) and 1.6‐m‐deep (high‐water‐level) mesocosms (kept open to the sediment and atmosphere). Fish (tench, Tinca tinca, and bleak, Alburnus escherichii) were added to half of the mesocosms, while the rest were kept fishless. Ten shoots of Potamogeton pectinatus were transplanted to each mesocosm.3. Sampling for physicochemical variables, chlorophyll a (chl‐a), zooplankton and per cent plant volume inhabited (PVI%) by macrophytes was conducted weekly during the first 5 weeks, and subsequently biweekly. Macrophytes were harvested on the last sampling date. During the course of the experiment, the water level decreased by 0.41 ± 0.06 m.4. Throughout the experiment, fish affected zooplankton abundance (−), nutrient concentrations (+), chl‐a (+) and water clarity (−) most strongly in the low‐water‐level mesocosms and the zooplankton community shifted towards dominance of small‐sized forms. The fishless mesocosms had a higher zooplankton/phytoplankton ratio, suggesting higher grazing.5. Greatest macrophyte growth was observed in the low‐water‐level fishless mesocosms. However, despite high nutrient concentrations and low water clarity, macrophytes were also abundant in the fish mesocosms and particularly increased following a water‐level decrease from midsummer onwards. Macrophyte growth was poor in the high‐water‐level mesocosms, even in the fishless ones with high water clarity. This was ascribed to extensive periphyton development reducing light availability for the macrophytes.6. Our results indicate that a reduction in water level during summer may help maintain the growth of macrophytes in Mediterranean eutrophic shallow lakes, despite a strong negative effect of fish predation on water clarity. It is therefore probable that an expected negative effect of global climate change on water clarity because of eutrophication and enhanced top‐down control of fish may be, at least partly, counteracted by reduced water level, provided that physical disturbance is not severe.

Factors affecting yield and composition of camel milk kept under desert conditions of central Punjab, Pakistan

This study was planned to study the herd composition, farming system, and reproductive traits and to evaluate the effect of season, stage of lactation and parity on milk production, and composition of camels kept under pastoral environment of central Punjab, Pakistan. Based on purposive sampling method, 50 herds belonging to small, medium, and large-sized herds were selected. From these herds, 1,137 she-camels were entered in this study and their composite milk samples were collected and analyzed through standard procedures to determine the milk yield and percentages of milk contents. The results showed that the male camels constituted a lesser percentage (p < 0.05: 43.08; 380/882) in the total herd composition compared to that of she-camels (56.92; 502/882). The mean daily milk yield was 8.17 ± 0.09 L and mean percentage of fat was 3.79 ± 0.13%, protein was 3.66 ± 0.07%, lactose was 5.15 ± 0.09%, ash was 0.81 ± 0.02%, acidity was 0.20 ± 0.01%, solids not fat (SNF) was 9.63 ± 0.15%, total solids was 13.42 ± 0.21, and moisture was 86.58 ± 0.43. Mean daily milk yield was significantly higher (p < 0.01) during rainy season followed by winter season, warm dry summer, and hot summer season. Milk fat and protein contents were the highest in hot dry summer, while lactose contents were higher during rainy season. The stage of lactation and parity confirmed to impinge significantly (p < 0.01) on protein, lactose, and SNF. The present study will be helpful to design measures for the eradication of reproductive constraints and for the improvement of milk yield and composition in order to make camel rearing an economical proposition.

Mediterranean and Continental Tall Fescue: II. Effects of Cold, Nonfreezing Temperatures on Leaf Extension, Proline, Fructan, and Abscisic Acid

ABSTRACTContinental tall fescue [Festuca arundinacea Schreb. syn. Lolium arundinaceum (Schreb.) Darbysh.] is the predominant forage used by cattle producers throughout much of the Midwest. However, Mediterranean tall fescue is gaining popularity in warmer, drier climates. One major difference of Mediterranean tall fescue is that it enters a semidormant period during hot dry summers but resurges during the fall and winter months. During the autumn resurgence it has exceptional growth but does not survive prolonged freezing conditions typically found in the Midwest. To determine how both Continental and Mediterranean tall fescues respond to low temperatures that are typically encountered during the fall, the leaf extension rate (LER) was measured along with proline, simple sugars, fructan, and abscisic acid (ABA). Three Mediterranean and four Continental accessions were tested, including Kentucky‐31 and Flecha as “typical” Continental and Mediterranean accessions, respectively. The greatest difference observed between these types of tall fescue occurred at 4.5°C. The Mediterranean genotypes had greater LER and fructan concentrations while the Continental genotypes possessed greater proline, ABA, and simple sugar concentrations. Kentucky‐31 was typically found in the middle between the Mediterranean and the remaining Continental accessions. These data indicate that Mediterranean germplasm possesses superior cold growth, but the high proline levels produced by the Continental types may be critical for survival under cold conditions.

Soil water balance with cover crops and conservation agriculture in a Mediterranean climate

Modern conservation agriculture practices aim to maintain year-round ground cover in order to maximise soil protection from extremes of temperature and minimise erosion risk. However, in Mediterranean-style environments with hot dry summer periods, maintaining ground cover can be difficult, as these periods are generally too arid for plant growth. In this research, we investigated the use of cover crops, grown solely to increase ground cover and not harvested for grain or biomass, in a Mediterranean climate. Specifically, we examined the impact of cover crops and residue retention on evapotranspiration, both over the summer fallow period and during the winter and spring crop growth period, and on deep drainage from subsequent crops, on two contrasting soil types in south-western Australia. The impact of cover crops on weed populations and nitrogen dynamics is described in a companion paper. In contrast to previously published research, cover crops and residue retention were found to have limited impact on total evaporation during the summer and autumn period, although there were occasional short-term impacts on the rate of evaporation shortly after rainfall. There was also limited evidence of changes in evaporation during early crop growth. Drainage from crops grown after cover crops was not consistently different to drainage from crops grown after conventional crops. The inclusion of cover crops in farming systems in regions with a Mediterranean climate is unlikely to have major impacts on the water balance, but may still increase overall sustainability of the farming system.