Showing papers on "Growing season published in 1979"
TL;DR: In a field experiment on the effects of drought on spring barley the crop was protected from rain by automatic rain shelters as discussed by the authors, and a mathematical model has related the computed whole canopy photosynthesis to the measured total dry-matter yields at harvest.
Abstract: In a field experiment on the effects of drought on spring barley the crop was protected from rain by automatic rain shelters. Various plots received irrigation at different times to give a range of drought treatments from full irrigation to no irrigation between emergence and harvest. The foliage area, light interception, stomatal resistance and leaf photosynthesis rate of five treatments were measured throughout the growing season, and a mathematical model has related the computed whole canopy photosynthesis to the measured total dry-matter yields at harvest. Hence, it was possible to estimate tha independent influences of drought on radiation interception, efficiency of use of intercepted radiation, and respiration. The analysis shows that for all treatments the decrease of intercepted radiation was the major factor in reducing yield, and it accounted for a loss of 30–40% for treatments that were stressed from the beginning of the season, and of 10–20% for treatments that were stressed after mid-May. Stomatal closure caused a reduction of up to 11% in daily photosynthesis, and the maximum effect was on plants that acquired a large leaf area before being stressed. However, the effect of stomatal closure integrated over the whole season was only 6% or less. Our measurements of internal resistance to carbon dioxide transfer were not precise enough to show significant differences between treatments; but increases of internal resistance, caused by stress, may have contributed to loss of yield.
167 citations
TL;DR: The amount of mineral nitrogen in the root zone at the beginning of the growing season (Nmin content, kg N/ha) and the amount of nitrogen mineralized during growing season are the two main components of nitrogen supply in soil.
Abstract: Nitrogen supply in soil is divided into two components: the amount of mineral nitrogen in the root zone at the beginning of the growing season (Nmin content, kg N/ha) and the amount of nitrogen mineralized during the growing season.
158 citations
TL;DR: Comparison of depletion of the seed-bank in the soil and increase of plant density showed that seeds germinating in the first week of the growing season produced fewer established seedlings than seeds germination in the second or third weeks.
Abstract: (1) Data for plant density, germinable seed in the soil, and seed production in annual grassland were obtained at Hopland Field Station, California, U.S.A., in 1973 and 1974. The study combined indirect estimates of numbers of seed in the soil, germination in soil samples containing natural seed, and estimation of plant density. (2) Autumn patterns of establishment differed significantly between the two study years. Plant density increased through the autumn, reaching peaks of 261 8 and 345*3 plants per dM2 in the seventh week after germination began, in 1973 and 1974 respectively. (3) The numbers of germinable seed in the top 6.4 cm of the soil prior to the start of the growing season were 6705 per dM2 in 1973 and 6102 per dM2 in 1974, and thus showed little difference between years. (4) Comparison of depletion of the seed-bank in the soil and increase of plant density showed that seeds germinating in the first week of the growing season produced fewer established seedlings than seeds germinating in the second or third weeks. The few seeds remaining in the fifth and sixth weeks had a high probability for successful establishment. (5) Six species-groups exhibiting contrasting strategies for germination and establishment are discussed in detail.
143 citations
TL;DR: Investigating the nature of the distribution of plant species along a soil salinity gradient at Rittman, Ohio, indicates that there is a definite relationship between soilSalinity concentrations and the position of plantspecies along this environmental gradient.
Abstract: The nature of the distribution of plant species along a soil salinity gradient at Rittman, Ohio, indicates that there is a definite relationship between soil salinity concentrations and the position of plant species along this environmental gradient Only a single species of flowering plant, Salicornia europaea, was found growing at the most extreme portion of the salinity gradient Soil samples collected from sites dominated by S europaea had salinity levels which yielded in situ electrical conductivities ranging from 189 to 1428 mmhos/cm, Atriplex triangularis grew at sites with inter- mediate levels of soil salinity, 39 to 400 mmhos/cm, and Hordeum jubatum dominated the least saline sites, 11 to 140 mmhos/cm, which were directly adjacent to a nonsaline meadow Salicornia europaea had high levels of mortality during the spring and early summer months of the growing season, with the mean number of seedlings ranging from 58 plants per 100-cm2 quadrat in May to a mean value of 18 mature plants per quadrat at the end of the growing season in October At the most highly saline sites containing S europaea, seedling numbers ranged from a mean of 5 plants per 100- cm2 quadrat in May to 1 mature individual per quadrat by October Transplants of S europaea had the highest standing crop biomass levels in the Atriplex and Hordeum zones, with dry weight production decreasing in zones of both higher and lower soil salinity Laboratory investigations indicated that S europaea reached its optimal growth in nutrient solution treatments containing 170 meq/l and 340 meq/l NaCl Germination of seeds of S europaea under field conditions occurred over an extended period of time, from February through June, when soil salinity levels were lowest Seed germination was not stimulated by treatments with salt and maximum germination percentages occurred in distilled water controls
90 citations
TL;DR: In this paper, the authors analyzed rainfall and streamwater from the Bowl watershed in central New Hampshire during 1973 and 1974, and found that the biogeochemistry of the cations seemed to be regulated more by precipitation, soil-water movement, and chemical weathering reac- tions than by forest succession.
Abstract: Precipitation and streamwater from the Bowl, a watershed in central New Hampshire, were analyzed chemically during 1973 and 1974. The Bowl, covered by a northern hardwood forest with spruce and fir at higher elevations, has never been logged or otherwise disturbed by humans. Calcium, sulfate, and nitrogen ions dominated stream chemistry. The biogeochemistry of the cations seemed to be regulated more by precipitation, soil-water movement, and chemical weathering reac- tions than by forest succession. Nitrate concentrations remained nearly constant, at --2.5 mg/l throughout the study, with no apparent seasonal fluctuations; in contrast, nitrate concentrations in the stream draining a nearby 55-yr-old forest definitely declined during the growing season. Nitrate budgets indicated a net loss of this important plant nutrient from both watersheds. However, a net accumulation of ammonium was sufficient to give a net increase of total N in both watersheds. These data do not support the hypothesis of Vitousek and Reiners that old-growth forests may reach a point of no net growth and no net uptake of nutrients. Mixed deciduous-coniferous forests in New England, free from human disturbances, may reach an age where they become prone to natural disturbances that create a mosaic of similar-aged groups of trees, each group having differing abilities to accumulate nutrients.
61 citations
TL;DR: The growth of subtidal algae on calcareous cobbles is restricted to a short (2—4 mo) growing season, although biomass and diversity are closely related to short—term weather conditions, and available evidence suggests an annual floristic cycle.
Abstract: The growth of subtidal algae on calcareous cobbles is restricted to a short (2—4 mo) growing season. Most algae are destroyed during rainy season storms due to surge and cobble tumbling; algal density is low throughout the year. Significant interspecific competition does not occur on cobbles, and no species/area relationship could be demonstrated. The number of species per cobble is correlated with cobble moment of inertia (resistance to tumbling) during the rainy season. Species diversity on cobbles is significantly higher than on neighboring rocky reefs. Available evidence suggests an annual floristic cycle, although biomass and diversity are closely related to short—term weather conditions. Ephemerals, annuals, pseudoannuals, and prennials appear sequentially during the growing season. Species with greater potential size reach peak abundance late in the growing season, although many never reach maximum size or reproduce on cobbles. These longevity and size trends cannot be said to constitute adaptive strategies on cobbles. The high species diversity observed on cobbles is adequately explained by seasonal disturbance.
61 citations
TL;DR: Three species of aquatic macrophytes from an agricultural drainage ditch were analyzed for N, P, and organic C throughout the 1976 growing season and there were no differences among species or sites.
54 citations
TL;DR: In this article, time series of the length of differently defined growing seasons at four Wisconsin stations are compared and the results show that their lengths have fluctuated in a variety of patterns over the past 80 years.
Abstract: The growing season is considered by some to be a simple and yet significant indicator of the impact of hemispheric temperature variations at the local level. Yet, the effect of the use of different definitions of the growing season has never been determined. In the present paper, time series of the length of differently defined growing seasons at four Wisconsin stations are compared. The results show that their lengths have fluctuated in a variety of patterns over the past 80 years. Two growing seasons which showed a significant trend did not agree on its direction. The reason for this disparity is that trends in maximum and minimum temperatures are not necessarily of the same sign at different times of the year. These findings suggest that the length of the growing season is not the simple climatic indicator it has been assumed to be.
49 citations
49 citations
TL;DR: The maintenance of differences among the populations of E. schultzii even under uniform laboratory conditions indicates that they represent genetically based ecotypes, and Pubescence and thickness of the leaves may help to control leaf temperature by increasing albedo and heat capacity.
Abstract: Carbon dioxide exchanges, plant-water relations, and some morpho-anatomical char- acters were measured and compared between 3 elevational populations of Espeletia schultzii in the Venezuelan Andes. The paramo climate is characterized by large oscillations in temperature on a daily basis. Precipitation is strongly seasonal with rainy summers and dry winters. The elevational gradient chosen in the Sierra Nevada de Merida extends from 3450 to 4200 m and is characterized by an increase of solar radiation, wind velocity, evaporative forces, and a decrease of temperature and water availability from low to high elevation. Contrasting with temperate alpine areas, the growing season in the paramos extends throughout the entire year. Thus, the maintenance of adequate leaf temperatures on a daily basis and an adequate moisture balance on a seasonal basis are more critical than accumulating resources during a shortened growing season. Morpho-anatomical characters of E. schultzii such as thick leaves, dense pubescence, and water- storing parenchyma play important roles in regulating water loss by increasing water vapor diffusion resistance and buffering the periodic water stress during the dry season. The caulescent life form of the plant elevates the rosette of leaves above the soil surface avoiding extreme ground temperatures. Pubescence and thickness of the leaves may help to control leaf temperature by increasing albedo and heat capacity. The importance of such characteristics is evidenced by their increased prominence in plants of higher elevations. Photosynthetic rates, obtained in the field, using "4CO2 on mature leaves, were relatively low (2- 4 mg CO2 dm-2 h-') but correlate well with the slow growth rates and generation times reported. These low rates are not so disadvantageous in the paramos due to the extended growing season. Pubescence and density of the leaves probably have negative effects on photosynthesis by decreasing the photosynthetic active radiation (PhAR) reaching the chloroplasts and increasing resistance to CO2 diffusion. Controlled conditions in the laboratory produced different responses of the populations regarding photosynthesis. Under cold acclimation, high elevation populations showed highest rates. Under warm acclimation, low elevation populations showed highest rates. Also, different degrees of ho- meostasis were found among the populations which were correlated with their elevation of origin. The populations of E. schultzii are further differentiated by the degree of drought resistance; the higher elevation population being the most resistant. Among the populations, differences in density-thickness and leaf pubescence are maintained even under uniform laboratory conditions. The maintenance of differences among the populations of E. schultzii even under uniform con- ditions indicates that they represent genetically based ecotypes.
45 citations
TL;DR: In this paper, the CO2 concentration in broad-leaved Korean pine forest of Changbai Mountains was measured continuously with a CO2 infra-red analyzer in 2003.
Abstract: The CO2 concentration in broad-leaved Korean pine forest of Changbai Mountains was measured continuously with a CO2 infra-red analyzer in 2003. The results showed that the CO2 concentration in the forest had striking characteristics of temporal-spatial variations, which were mainly influenced by the physiological processes of plants, soil respiration, and intensity of turbulence exchange. In growing season, the daily maximum and minimum CO2 concentration appeared mostly on the surface floor at about 5:00 in the early morning and at canopy location at about 15:00 in the afternoon, respectively. There was an obviously process of forest CO2 emission when the inversion broke at dawn. The average CO2 concentration in forest was 377 micromol x mol(-1) in 2003, the maximum of monthly average appeared in January as 388 micromol x mol(-1), and the minimum of monthly average appeared in August as 352 micromol x mol(-1). The forest acted as CO2 source in night time and turned to sink in daytime, during growing season. In non-growing season, the forest acted as CO2 source in both daytime and night time, but still had a clear evidence of CO2 assimilation at noon, with canopy location during non-growing season.
TL;DR: Mn, Fe, Cu, and Zn in shoot tissue of Spartina alterniflora Loisel were analyzed for seasonal trends and relationships to dry matter standing crop in two brackish marshes in Virginia were sampled four times between April and September 1975.
TL;DR: The results of a grazing experiment in which Townsville stylo was oversown into native pasture in sub-coastal northern Queensland are reported and the responses to superphosphate fertilizer only in years of high rainfall suggests that its use is unlikely to be profitable on Townsville styling based pastures in this environment.
Abstract: The results of a grazing experiment in which Townsville stylo was oversown into native pasture in sub-coastal northern Queensland are reported. The region receives 650 mm average annual rainfall compared with >850 mm at other experimental sites where Townsville stylo has been tested under grazing. The experiment included three treatments in a factorial combination: timber clearing or not, application of 125 kg ha-1 superphosphate or not and stocking rates of 0.4 and 0.2 beasts ha-1. The yield of Townsville stylo depended on treatments and annual rainfall but was generally low in this environment. Over the ten year period of the experiment the pastures remained dominated by Heteropogon contortus and Bothriochloa bladhii, and there was no invasion of annual grasses. Clearing of the timber increased the pasture yield by 77%. There was no regrowth of trees after clearing. Within each year cattle gained weight in the wet season, when pasture quality was high, and lost weight in the dry season, when pasture quality declined. Mean liveweight gain over all treatments was correlated (r = 0.97) with the length of the growing season. A significant response in liveweight gain to fertilizer occurred only in years of average or above rainfall when there was also a response in Townsville stylo yield. The effect was due to increased gains during the wet season; there were no differences in liveweight gain during the dry season, when Townsville stylo became decomposed. Significantly greater liveweight losses occurred on the heavily stocked treatments during the dry season of drought years. The yield of Townsville stylo in the early years of the experiment was significantly higher on the cleared treatments and there was a corresponding response in liveweight gains in the wet season during this period. Liveweight losses in the dry season were also significantly higher on the timbered treatments in years of drought. The powerful influence of climatic variation on the treatments places reservations on their practical application. The increased pasture yield from tree clearing is likely to be a benefit to cattle only in years of drought. The responses to superphosphate fertilizer only in years of high rainfall suggests that its use is unlikely to be profitable on Townsville stylo based pastures in this environment.
TL;DR: In this article, the growth of Scots pine Pinus sylvestris, Lodgepole pine, Pinus contorta Douglas ex loud, Norway spruce Picea abies (L.) Karst.
TL;DR: In this paper, the authors measured, at various times during the growing season, the concentrations of soluble salts, ammonium, nitrates, and nitrites in the upper horizons of a common Piedmont soil which had received yearly up to 100 metric tons of poultry manure per ha for 5 years.
Abstract: The logistics of handling poultry manure often dictate that it be spread on land near to its source at rates far in excess of what would constitute its efficient use as fertilizer. This study measured, at various times during the growing season, the concentrations of soluble salts, ammonium, nitrates, and nitrites in the upper horizons of a common Piedmont soil which had received yearly up to 100 metric tons of poultry manure per ha for 5 years. During spring and summer, concentrations of soluble salts (up to 4,064 ppm) and nitrite-N (up to 60 ppm) were high enough to be toxic to corn (Zea mays, L. cultivar Pioneer 3369A). Ammonium-N was detected at up to 800 ppm in April, but decreased to less than 100 ppm by July. Both stand establishment and subsequent growth of corn were very poor on the heavily manured plots. As seedlings, corn plants on these plots exhibited burned leaf tips and margins and stunted root growth associated with high levels of ammonia, nitrites, and total soluble salts. Severe moisture stress was evident throughout the growing season due to the effects of salinity and stunted root systems. Rapid leaching of salts and nitrates did not take place until after September. Denitrification appeared to be responsible for some losses of nitrates. Despite the accumulation of nitrites, especially in May and July, most probable number determinations failed to show any consistent inhibition of the populations of Nitrosomonas and Nitrobacter.
TL;DR: The fate of photoassimilated 14C was followed by measuring 14C incorporation into leaf and branch tissues of two forest-grown white oak trees and Fate of 14C-labelled photosynthate was confirmed.
Abstract: The fate of photoassimilated 14C was followed by measuring 14C incorporation into leaf and branch tissues (≤ 5 years old) of two forest-grown white oak trees. Fate of 14C-labelled photosynthate was examined 7 days after 14CO2 uptake on live dates (April–October) during the growing season. Both upper and lower canopy positions were sampled. Incorporation of 14C into foliage was significant throughout the growing season. It ranged from 95% of the total 14C retained in April to 50% in October. Incorporation of 14C-labelled photosynthate into the canopy was highest in June and averaged 33% of gross photosynthetic production over the entire growing season. Higher retention of photosynthate in branches versus leaves was noted in the upper canopy than in the lower canopy during the middle and late growing season. Activity levels in tissues indicated that within-canopy sink strength was in the order acorns ≈ buds > leaves > branches. Translocation of initial 14C-labelled photosynthate from both leaves and branche...
TL;DR: Furrow irrigation studies comparing water applications to narrow and wide-spaced furrows were conducted on three crops at thee locations in Oklahoma over eight growing seasons as discussed by the authors. But no yield reductions were noted, the atmospheric evaporative demand was high.
Abstract: Furrow irrigation studies comparing water applications to narrow and wide-spaced furrows were conducted on three crops at thee locations in Oklahoma over eight growing seasons. Wide-spaced-furrow irrigation usually required about half the water of narrow spacing. In 9 of 11 studies, no yield reductions were noted. In the seasons where yield reductions were noted, the atmospheric evaporative demand was high. A simple test was devised to indicate if a season in progress shows high atmospheric demand. The evaporative demand test involves measurement of rainfall and daily wind movement. Using standard National Weather Service instruments, daily average of rain > 1.6 mm between 15 July and 31 Aug. combined with daily wind movement < 155 km in August caused no yield reduction in wide-spaced-furrow irrigation. Wind was measured at the standard height of a “Class A” evaporation pan (51 cm). Conservation of water from wide-spaced-furrow irrigation should be possible on medium to fine textured soils in many semiarid regions of the world.
TL;DR: In this paper, the authors combine the stress-degree-day concept of plant water stress assessment with the growing degree-day concepts of plant phenological development to predict grain crop yields.
01 Jan 1979
TL;DR: The growing season on the Hopi Reservation has been referred to in the literature since 1916 as between 130 and 145 days long as mentioned in this paper, with a growing season closer to 155 to 170 days in length.
Abstract: Growing season on the Hopi Reservation has been referred to in the literature since 1916 as between 130 and 145 days long. These figures were taken from canyon areas subject to the effects of cold air drainage. Recent work elsewhere on the reservation indicates a growing season closer to 155 to 170 days in length. On the mesa tops around which cold air subsides into topographically low areas, the growing season may approach 190 days. The implications of these revisions may be significant toward understanding the strategy of Hopi agriculture and its continuing success.
01 Apr 1979
TL;DR: In this paper, changes in standing crop, cover, and percent botanical composition of annual vegetation were investigated on an 86.2 hectare watershed at the Hopland Field Station, Mendocino County, California.
Abstract: Changes in standing crop, cover, and percent botanical composition of annual vegetation
as influenced by microsite and type conversion were investigated on an 86.2 hectare
watershed at the Hopland Field Station, Mendocino County, California.
Type conversion from woody vegetation to grassland tripled total standing crop of
herbaceous plants on the watershed, with much of this increase occurring on sites
formerly supporting a dense and semi-dense woodland overstory. However, the sites
that were originally woodland never produced as much forage as those that were originally
open grassland. The managerial problem of seasonally adjusting stocking rates in response
to changing forage availability was heightened by type conversion, since much of the
increased forage production occurred at the end of the growing season.
Short annual plants, such as nitgrass, silver hairgrass, rattlesnake weed, filaree,
bur-clover, and true clovers, attained their greatest percent botanical composition
on the historically open grassland sites. Type conversion produced increases in botanical
composition primarily for those taller annual and perennial plant species capable
of colonizing the formerly dense woodland sites mainly occurring on north-facing slopes.
These plant species included wild oats, ripgut, vetches, and Italian thistle.
In the sheep-grazing system employed, adding animal units to utilize increased spring
forage following brush conversion required alternative sources of feed during other
periods of the year.
TL;DR: In this paper, the average dry weight of leaves was affected by crown position and time of year, but not by the season, and the content of all elements tested and the concentrations of Ca and Mg increased with season while concentrations of N, P, K, Ca, and K decreased as the season progressed.
Abstract: Leaf samples were collected from upper and lower crown positions at three times during the 1971 and 1972 growing seasons for planted black walnut (Juglans nigra L.) trees on the Kaskaskia Experimental Forest in Hardin County, Illinois. The average dry weight of leaves was affected by crown position and time of year. Foliar concentrations of N, P, K, Ca, and Mg were affected by season, but not by crown position. The content of all elements tested and the concentrations of Ca and Mg increased with season while concentrations of N, P, and K decreased as the season progressed. Suggestions for sampling dates are given.
TL;DR: The variations undergone by chlorogenic acid, cynarine, cynazoside and scolymoside during the biological cycle of the artichoke plant were studied to derive the composition of the orthodiphenolic fraction between different organs of the plant.
Abstract: The variations undergone by chlorogenic acid, cynarine, cynazoside and scolymoside during the biological cycle of the artichoke plant were studied. Furthermore, the differences in the composition of the orthodiphenolic fraction between different organs of the plant were studied.
TL;DR: A simple model was constructed which predicted the rates of leaf photosynthesis (Fc) of the temperate C4 species Spartina townsendii, in the field, from the prevailing light and temperature, and the results show that high values of Fc are also a feature of plants of S. citiesendii growing on an intertidal marsh in Britain.
Abstract: SUMMARY (1) A simple model was constructed which predicted the rates of leaf photosynthesis (Fc) of the temperate C4 species Spartina townsendii, in the field, from the prevailing light and temperature. The parameters of the model were derived from laboratory studies. (2) The model was tested by measuring Fc with 14CO2 at regular intervals through one growing season at a field site on the Humber estuary. (3) Measured and predicted values of FC were similar, except during the early part of the growing season, when the model significantly over-estimated Fc. (4) The results show that high values of Fc, previously reported in laboratory studies, are also a feature of plants of S. townsendii growing on an intertidal marsh in Britain. In contrast to most other C4 species, exposure of S. townsendii to air temperature below 10 'C, and even to ground frosts, had little effect on subsequent Fc.
TL;DR: Wind-pollinated seed and ramets from lodgepole pine (Pinuscontorta Dougl.) plus tree selections in British Columbia were established and maintained under 24-h photoperiods for 6 months to establish and maintain tree selections.
Abstract: Wind-pollinated seed and ramets from lodgepole pine (Pinuscontorta Dougl.) plus tree selections in British Columbia were established and maintained under 24-h photoperiods for 6 months. Subsequently, these trees were outplanted in the nursery and periodically assessed for height, diameter, and dry weight. Seedlings and grafts developed considerably faster than normal nursery-grown controls during the treatment period, and they maintained an accelerated growth rate during the two growing seasons following outplanting. Root growth was particularly enhanced, as evidenced by the sharply reduced shoot:root ratio of treated seedlings relative to controls. Large differences in growth response existed among wind-pollinated families but family × environment (greenhouse vs. nursery) interaction confounded interpretation. Family performances for treated and control seedlings of the same families were not well correlated (r = 0.24) after two growing seasons. The rapid growth and development of seedlings and grafts un...
TL;DR: In this paper, a 52 plot experiment was performed during the growing season of 1977 in a Ste. Rosalie clay soil, using a randomized complete-block design with 13 treatments of machinery traffic within each of four blocks.
TL;DR: Crop production was lower in plots previously treated with DDT than in untreated plots, and although soil nutrients were depleted by the continuous cultivation there was no greater depletion in the plots with higher yields.
Abstract: (1) Seed yields of cowpea (Vigna unguiculata (L.) Walp) were assessed in each of two annual growing seasons over the 4-year period 1973 to 1976 from experimental plots under continuous cultivation on land newly cleared from bush regrowth in Ibadan, S. Nigeria. No fertilizer was applied throughout the experimental period. One set of plots was sprayed weekly with DDT during both growing seasons of each year and one received DDT treatment only in the first growing season of each year. The yield from untreated controls was also monitored. (2) Cowpea seed yields varied considerably from season to season and year to year in untreated plots due to differences in pest incidence and climatic conditions. The cowpea yield over the 4 years was considerably higher in the DDT treated plots but the decline of yield with time was faster than in untreated plots and by the seventh season of application DDT application did not significantly enhance cowpea yields. (3) Maize was cultivated without pesticide protection during the first season of 1977 in all plots as an additional indicator of soil fertility before the plots were allowed to return to bush fallow. Crop production was lower in plots previously treated with DDT than in untreated plots, and although soil nutrients were depleted by the continuous cultivation there was no greater depletion in the plots with higher yields. It is suggested that the more rapid decline in fertility of plots with a history of DDT treatment may be associated with pesticide effects on the soil biota.
TL;DR: In this article, a magnetic tape containing 50 years of daily weather records was modified to synthesize new records representing three different types of temperature change and used as input to a phenological response model for maize in a series of computer simulation studies.
TL;DR: It is reported that persistent heavy grazing significantly reduced the vigor of black grama (Bouteloua eriopodu (Torr.) Tot-t-.
Abstract: Production, total nonstructural carbohydrates, and crown diameters were measured to evaluate the effects of season of clipping on black grama and mesa dropseed. Vegetative reproduction was also monitored for black grama. Early defoliation of both black grama and mesa dropseed had less impact on plant vigor than ‘continuous defoliation or defoliation during the last half of the growing season. Black grama plants clipped during or after flowering, or continuously through the growing season, produced less herbage in the following year than those plants clipped during the vegetative stage. Removal of 65% of the current year’s growth any time during the growing season significantly reduced stolon numbers on black grama. Mesa dropseed clipped during maturity, during flowering, or clipped continuously throughout the growing season was negatively affected on one or more of the plant parameters measured. Clipping during the vegetative state had little apparent effect on plant vigor. Knowledge of plant responses to defoliation during various seasons, frequencies, and intensities is essential for proper management on rangelands. Limited data exist on season, frequency, and intensity of use on native plants occurring on Southwestern rangelands. Nelson ( 1934) and Canfield ( 1939) concluded that persistent heavy grazing significantly reduced the vigor of black grama (Bouteloua eriopodu (Torr.) Tot-t-.), an ecological dominant of much of the Southwest. Valentine (1970) found the number and length of stolons per black grama plant were closely correlated with intensity of winter grazing. Paulsen and Ares ( 1962) reported cyclic changes in black grama basal area were closely correlated with precipitation during the growing season. Paulsen and Ares ( 1962) reported that temperature requirements for mesa dropseed (Sporobofus flexuosus (Thurb.) Rybd.), another important Southwestern range plant, were less limiting than for black grama. Mesa dropseed seedlings establish well on open areas (Nelson 1934), especially during the first favorable growing season following drought (Dittberner 197 1). While ecological relationships and limited information on grazing tolerance are available, the impact of defoliation at different stages of phenological development on physiological and morphologcal characteristics have not been established for this area. Similarly, time necessary for recovery of vigor of
TL;DR: In this article, the degree of succession (DS) was calculated in the Miscanthus sinensis type grasslands of the Kirigamine Heights situated in a high altitude area (1,600 m) of Central Japan.
Abstract: In the Miscanthus sinensis type grasslands of the Kirigamine Heights situated in a high altitude area (1,600 m) of Central Japan, the biomass in various successional phases was measured and the degree of succession (DS) was calculated. The maximum biomass during the growing season was used to compare the productivity of different grassland communities.