Showing papers on "Growing season published in 1981"
TL;DR: Habitat partitioning appears to be a difference in morphology whereby T. latifolia was prevented from growing in deep water because of the higher cost of producing broader leaves but better able to compete for light in shallowWater because of its greater leaf surface area.
Abstract: The aquatic plants Typha latifolia and T. angustifolia are observed to be strongly segregated along a gradient of increasing water depth with T. latifolia restricted to depths of less than 80 cm and T. angustifolia to depths greater than 15 cm. Transplantation of both species along the gradient in the absence of competitors showed that T. latifolia was little affected by the presence of T. angustifolia but T. angustifolia was capable of growing over the entire gradient. The loss of precompetitive distribution was not statistically significant for T. latifolia compared to a 39.6% loss for T. angustifolia. It was further observed that overlap was reduced by 43.5% during the course of the growing season. Rhizomes transplanted into natural stands failed to survive, further demonstrating that competition was actively operating to maintain zonation between species. The basis for habitat partitioning appears to be a difference in morphology whereby T. latifolia was prevented from growing in deep water because of...
356 citations
TL;DR: In this article, the spectral data collected on 21 dates over the growing season with a hand-held radiometer were quantitatively correlated with total dry-matter accumulation in winter wheat.
356 citations
TL;DR: While there are -50 widespread sage scrub species, more than half of the 375 species encountered in the present study of the sage scrub flora are rare in occurrence within the habitat range.
Abstract: The facultatively drought-deciduous shrublands of coastal California and Baja Cali- fornia are lowest in species richness of the four Mediterranean-climate regions where this physiog- nomic type occurs Alpha richness in the North American coastal sage scrub varies primarily with the abundance of herbaceous annual species Herb levels in turn vary with differences in levels of precipitation, favorableness of temperature during the winter and spring growing season, shading by shrubs, soil nitrogen, and air pollution Levels of herbaceous annuals are highest in the growing season following fire, and show a second pulse of abundance in stands 15-25 yr old Mature stands of coastal sage scrub are typically low in species equitability, due at least in part to the shade- intolerance of the herbaceous understory and to reduced levels of soil nitrogen Symbiotic nitrogen- fixing organisms are virtually absent from stands which have not burned in 20 yr or more The pattern of postfire succession varies markedly with fire intensity; dominant shrubs sprout abundantly from root crowns only following less intense fires While there are -50 widespread sage scrub species, more than half of the 375 species encountered in the present study of the sage scrub flora are rare in occurrence within the habitat range In view of the reduction of the area of coastal sage scrub in California to 10-15% of its former extent and the limited extent of preserves, measures to conserve the diversity of the flora are needed
160 citations
TL;DR: It is suggested that in the low marsh, the plants can obtain sufficient nitrogen for osmoregulation and other metabolism, in the high marsh with higher soil salinity and lower nitrogen content, where the plants have to allocate a even greater proportion of the already limited nitrogen supply for os moregulation.
Abstract: The possible interaction of high soil salinity and low soil nitrogen content in affecting the growth of Spartina alterniflora Loisel in the high and low marshes of the Eastern U.S. was explored. Throughout the whole growing season, the short plants growing in the high marsh, where there was a higher soil salinity and lower available soil nitrogen, contained more proline and glycinebetaine and showed a lower leaf water potential than the tall plants growing in the low marsh. In both short and tall plants, the growing season, with the highest content occurring in spring and fall. In contrast, the glycinebetaine content in both short and tall plants remained fairly constant throughout the growing season, and was consistently at least 10 fold higher than the proline content. It is estimated that 19–30% of the total leaf nitrogen was in the form of proline and glycinebetaine in the short plants, and 14–27% in the tall plants. Ammonium nitrate fertilization in the field resulted in increased growth, higher proline and glycinebetaine contents, and lower water potentials in the short plants, but had little effect on these parameters in the tall plants. We suggest that in the low marsh, the plants can obtain sufficient nitrogen for osmoregulation and other metabolism. In the high marsh with higher soil salinity and lower nitrogen content, the plants have to allocate a even greater proportion of the already limited nitrogen supply for osmoregulation. Thus, nitrogen available for osmoregulation and other nitrogen-requiring metabolism is insufficient, resulting in reduced growth.
116 citations
TL;DR: Nine Colorado range species were studied for two consecutive years to relate the carbohydrate reserve status with phenological stage of development and current annual growth, including leaf, twig, or seedstalk length, or plant height, and growth was found to be related inversely to carbohydrate reserve storage.
Abstract: Nine Colorado range species were studied for two consecutive years to relate the carbohydrate reserve status with phenological stage of development and current annual growth, including leaf, twig, or seedstalk length, or plant height. The species were fourwing saltbush (A triplex canescens), antelope bitterbrush (Purshia tridentata), little rabbitbrush (Chrysothamnus vicidiflorus), fringed sagewort (A rtemisia frigida), scarlet globemallow (Sphaeralcea coccinea), blue grama (Bouteloua gracilis), western wheatgrass (Agropyron smithii), James’ cryptantha (Cryptantha jamesii), and pricklypear cactus (Opuntia polyacantha and rhodantha in a mixed stand). Seasonal total nonstructural carbohydrate (TNC) reserve cycles were related to phenological stages of development. Growth of all species appeared to be stimulated by late-summer or fall precipitation. Growth was found to be related inversely to carbohydrate reserve storage. Fourwing saltbush and antelope bitterbrush had typical V-shaped annual carbohydrate reserve cycles, and little rabbitbrush had a somewhat flat or extended V-shaped cycle. Fringed sagewort, scarlet globemallow, and western wheatgrass had flat or extended V-shaped cycles and maintained low reserves for more of the growing season than any of the species with typical reserve cycles. Blue grama was the only species that exhibited a narrow V-shaped cycle. The shape of the seasonal TNC cycle appeared to be a good screening tool for assessing the relative effects of defoliation on different plant species. Plants that replenished reserves rapidly after spring drawdown and regrowth periods, and minimized the part of the growing season with low reserve status, were least affected by defoliation and recovered rapidly from severe defoliation.
94 citations
TL;DR: The relationship between water stress and crop temperature in corn was investigated by Zea mays et al. as mentioned in this paper, who found that the average midday difference in canopy temperature between stressed and non-stressed areas was as large as 7.0°C and 4.6°C above air temperature.
86 citations
TL;DR: Spawning by young-of-the-year oysters is of minimal importance to population recruitment during the year they set, but widespread spawning of oysters older than one year occurs twice during the reproductive season.
Abstract: Oysters which set early in the spawning season reach sexual maturity and spawn before the end of their first year. The early sexual development in the southern latitudes is the result of both an extended growing season and an increased in stantaneous rate of growth. Widespread spawning of oysters older than one year occurs twice during the reproductive season, with a period of renewed development in between. Spawning by young-of-the-year oysters is of minimal importance to population recruitment during the year they set.
82 citations
TL;DR: In this paper, the SPAW model for estimating daily soil water and evapotranspiration using readily available climate, crop and soil data was expanded to include estimates of crop water stress and the effect of this stress on canopy development, plant phenology and crop grain yield.
Abstract: THE previously developed SPAW model for estimat-ing daily soil water and evapotranspiration using readily available climate, crop and soil data was expand-ed to include estimates of crop water stress and the effect of this stress on canopy development, plant phenology and crop grain yield. Crop yield susceptibility was represented by a bell-shaped weighting factor with peak at tasselling or flowering. A water stress index was com-puted for the growing season as an accumulative daily water stress multiplied by the daily yield susceptibility factor. Calibration of the water stress index for corn and soybeans was with data from research sites in western Iowa and central Missouri. The results showed that this daily soil water and crop water stress method is a prac-tical and accurate approach for assessing water stress ef-fects on crop yields.
80 citations
TL;DR: In this article, the authors studied the release of fixed NH4+ by clay minerals under field conditions on two representative arable sites, one on loess and the other on alluvial soil.
Abstract: We studied the release of fixed (nonexchangeable) NH4+ by clay minerals under field conditions on two representative arable sites, one on loess the other on alluvial soil. The nonexchangeable NH4+ content of soil from three depths was determined at five dates during the growing season in fields carrying winter barley (loess) or spring oats (alluvial soil). There were significant changes in the content of nonexchangeable NH4+ during the growing period. Early in crop growth particularly, the upper soil layers (0 to 60 cm) were depleted of nonexchangeable NH4+; later, nonexchangeable NH4+ declined at the depth of 60 to 90 cm. The nonexchangeable NH4+ content of alluvial soil recovered to approximately its original level at the end of the growing season. There was a substantial net loss on nonexchangeable NH4+ from the loess soil of about 40 ppm, equivalent to 500 kg N/ha assuming a soil depth of 90 cm. Soil samples labeled with nonexchangeable 15NH4+ and placed back into the field under sugar beet at the depths from which the samples had been taken, released, between May and October, significant quantities of labeled nonexchangeable NH4+, which, on the basis of a soil depth of 75 cm, were equivalent to about 350 kg N/ha in the loess and 150 kg N/ha in the alluvial soil. It is suggested that in these soil types, which are representative of many arable soils in central Europe, the so-called fixed NH4+ is involved in the general soil N cycle.
78 citations
TL;DR: The complex climatic control over phenology in Lotus scoparius constitutes an adaptation to the California mediterranean climate with water relations and photo- period having the greatest influence.
Abstract: In regions of Mediterranean climate drought deciduousness has been considered an important adaptation for many species. This investigation focuses on the influences of a Mediterranean climate on the phenology of a drought-deciduous shrub Lotus scoparius ssp. scoparius. Two research sites were chosen in the Santa Ynez mountains northwest of Santa Barbara, Cali- fornia for the field investigations. Phenological progressions of leaf production, leaf composition, shoot elongation, lateral branch production, and flowering in even-aged stands of Lotus scoparius were correlated with such factors as temperature, relative humidity, soil moisture, plant water rela- tions, and photoperiod. These correlations were determined during a characteristic and uncharacter- istic growing season for this mediterranean-climate region. Field correlations were the basis for the design of laboratory experiments in which the influences of photoperiod, temperature, water stress, and total daily photon flux on the phenological development of Lotus scoparius were studied. Climatic controls over Lotus scoparius phenology are complex with water relations and photo- period having the greatest influence. Photoperiodic control over leaf abscission during water stress, and leaf production following dormancy, were two important phenological phenomena related to the unpredictably fluctuating Mediterranean climate of southern California. The complex climatic control over phenology in Lotus scoparius constitutes an adaptation to the California mediterranean climate.
76 citations
TL;DR: In this paper, the authors investigated the relationship between crop temperature and the grain yields, phenological development, evapotranspiration rates and leaf water potential of two hybrids of grain sorghum (Sorghum bicolor L. Moench) subjected to varying levels of plant water stress.
Abstract: Recent studies have shown that the grain yields of corn (Zea mays L.) and wheat (Triticum aestivum L.) are related to the degree of water stress they undergo. The purpose of the study reported here was to establish relationships between crop temperature and the grain yields, phenological development, evapotranspiration rates (ET) and leaf water potential (ψl) of two hybrids of grain sorghum (Sorghum bicolor L. Moench) subjected to varying levels of plant water stress. The study was conducted at the University of Nebraska Sandhills Agricultural Laboratory in 1978 on a Typic Ustipsamment (Valentine fine sand) soil. The sorghum hybrids used were RS 626 and NB 505. Four irrigation treatments were applied in order to subject the crops to varying levels of water stress during each of three major growth stages. Soil moisture was monitored with a neutron probe. ET was estimated with the water balance technique. Crop temperature was measured with an IR thermometer and leaf water potential was measured with a Scholander pressure bomb. Grain yields were reduced by water stress occuring at anytime during the growing season. Yield reductions were largest when stress occurred during only the grainfill period and were least when stress occurred during the entire growing season. The percentage reduction in sorghum grain yield can be described by an index involving the seasonal accumulation of the daily mid-day temperature differences between well-watered and stressed crops (Σ TSD). As Σ TSD values increased, ET decreased. However, the correlation of ET with Σ TSD was relatively low (R2 = 0.60) probably due to the limited amount of data available for analysis and inaccuracies in the soil water balance method used to estimate ET. The mid-day temperature of well-watered rows ranged between 18.0 and 32.8 °C with a mid-day temperature range of about 0.5 °C between the well-watered rows in various plots for several days following an irrigation. However, in certain instances, the mid-day temperature range increased to 1–2 °C for a few days before irrigation. This suggests that certain of the rows experienced water stress and should have been irrigated earlier. Yield data support that conclusion. Range in crop temperature within a field appeared to be a sensitive indicator of crop water stress in sorghum. No significant difference in the phenological development of sorghum resulted from water stress except in one NB 505 plot in which plants were stressed throughout the entire season. In that plot, the stressed plants lagged in development behind non-stressed plants by approximately ten days. The differences in mid-day leaf water potentials (Δψl) and crop temperatures (ΔT) between stressed and non-stressed vegetation were examined. As ΔT increased up to about 4 °C, Δψl, also increased. Beyond that point, Δψl decreased while ΔT continued to increase. This behavior was attributed to stomatal closure which permitted an increase in ψl of the stressed plants (hence reducing Δψl) even as ΔT continued to increase.
TL;DR: Higher leaf area indices and better water relations after anthesis in biculm stands indicated more efficient water use when shoot population was controlled at near optimum level.
Abstract: The concept of the uniculm habit as an important feature of a wheat ideotype for a mediterranean environment was evaluated under field conditions. A uniculm plant produces a single shoot and when sown in a stand exemplifies a non-tillering crop with a fixed density of shoots throughout the growing season. Yield and harvest index of normal tillering spring wheat was compared with that of the same crop surgically detillered throughout the growing season to a constant density of 2 shoots per plant. The use of a biculm, whilst retaining the uniculm principle of a fixed density of shoots throughout the growing season, permitted comparison on a single crop sowing at normal field density.
TL;DR: The Chinese tallow tree (Sapium sebiferum Roxb) is a rapid growing species that has become naturalized along the Gulf and southern Atlantic coasts as discussed by the authors.
Abstract: The Chinese tallow tree (Sapium sebiferum Roxb.) is a rapid-growing species that has become naturalized along the Gulf and southern Atlantic coasts. The tree is particularly well adapted to poorly-drained and saline soils. Chinese tallow seedlings planted at 2’×2’ spacing produced over 5 dry tons of biomass/acre at the end of the second growing season while the biomass accumulation on coppiced plots was more than 7 dry tons /acre at the end of the second year. The Chinese tallow tree has considerable promise as a woody biomass species in the southern coastal regions of the United States.
TL;DR: Growth, reproduction and longevity of the fire weed Acacia pulchella var.
Abstract: Growth, reproduction and longevity of the fire weed Acacia pulchella var. glaberrima were examined in natural populations of known age in coastal sands in and around Perth, W.A. Dense populations (10000 plantsiha) were established after a summer burn; plant density was 30% of its initial value at 4 years. less than 8% at 13 years. Plants accumulated dry matter, nitrogen and phosphorus throughout a 13-year growth period. Seed production commenced at 2 years, reached a maximum (12000 seeds per plant per year) at 3 or 4 years declining to 2000 seedsiplant in the 13th year. Only a small fraction of the shed seed accumulated in soil under the stands. Changes in total plant N, nodule weightlplant, and C2H2 reduction capacity of detached nodules were followed in populations in their first, second and fourth growing seasons. A new set of nodules formed with the autumn rains, peak nodule mass and C2H2 reduction activity were recorded in July-October, and virtually no nodules survived the summer into a second growing season. A glasshouse study of N accumulation and C2H2 reduction by nodules in minus N sand culture gave acalibration value of 2.26 mol C2H2 : mol N2 fixed. Applying this value to data from nativepopulations, 8% of the N accumulated by first season plants, 45% of the N of second season plants and 68% of the N of fourth season plants were estimated to be derived from symbiosis. Average annual returns of N to the ecosystem were estimated at 3.9 kg/ha, probably more than half of this from N2 fixation. Progressive death of plants in the populations gave the greatest return ( 1.9 kg N per ha per yr), the remainder from litter (1 kg N per ha per yr) and shed seed ( 1 kg N per ha per yr).
TL;DR: In this paper, an investigation was made of the irrigation requirements of cotton grown in a sub-humid environment with significant but highly variable rainfall, and it was found that 70% of this amount could be depleted before irrigation without loss of yield.
Abstract: An investigation was made of the irrigation requirements of cotton grown in a sub-humid environment with significant but highly variable rainfall. In the first year of the study, no additional yield benefits accrued to subsequent irrigations following a pre-emergent irrigation due to above average rainfall (550 mm) throughout the growing season. In the second year a similar rainfall amount (502 mm) fell but significant yield increases to irrigation resulted due to the uneven distribution of the rainfall. The main effect was associated with later rains which influenced the number of bolls set. The maximum amount of water extracted by cotton from a deep grey cracking clay was 178 mm. It was found that 70% of this amount could be depleted before irrigation without loss of yield. Crop evapotranspiration varied from 607 mm with no irrigation after emergence to 775 mm following three irrigations. Irrigation was associated with significant losses from rainfall runoff. Too frequent irrigation creates a risk that soil will be too wet to permit utilisation of natural rainfall. Therefore, the use of soil water information to maximise the interval between irrigation is proposed as a necessary basis for efficient irrigation management.
TL;DR: The translocation of nutrients into and out of outer canopy leaves of ten eastern deciduous forest species was calculated from the temporal patterns of foliar nutrient pools sampled through a growing season.
Abstract: The translocation of nutrients into and out of outer canopy leaves of ten eastern deciduous forest species was calculated from the temporal patterns of foliar nutrient pools sampled through a growing season. The calculations accounted for average chemical leaching effects due to rainfall. There were no significant differences in translocation rate between species within the evergreen, understory, or overstory-deciduous tree groups. Evergreen species had lower translocation rates than deciduous trees. Translocation rates into leaves of deciduous species showed a very rapid increase during spring; however, by late May, foliar phosphorus was being translocated at a slow rate back to stems. A similar trend was established for nitrogen by mid-June. An internal storage pool is suggested as the major source of foliar nitrogen during the spring flush since a simulation of nitrogen uptake from soil could only account for one-fourth of the quantity of nitrogen transported to leaves by the end of May. Simulation further showed that trace levels of soluble nitrogen (0.01 ppm) in soil were sufficient to supply a deciduous forest with an estimated nitrogen uptake of 100 kg N ha/sup -1/ year/sup -1/.
TL;DR: Although defoliation increased seed yield in all growing seasons, the effect when measured on a relative scale was greater in T2 than in either T1 or T3, but on an absolute scale the size of the response was greaterin T2 and T3 than in T1.
Abstract: The effects of length of growing season and defoliation on seed yield and hard-seededness were examined in two strains of subterranean clover (Seaton Park, Midland B) grown in swards in the field. All plots were sown at the same time and the length of growing season was varied by altering the time of finish of the season (by withholding water). There were three length of growing season treatments: T1 (short), T2 (intermediate) and T3 (control). The defoliation treatments were D0, uncut (control), and D1, defoliated at weekly intervals until the commencement of flowering. Reducing the length of growing season drastically reduced seed yield. Thus when the growing season was only 3 weeks shorter than the control (i.e. T2 compared with T3), seed yields averaged over strains and defoliations were reduced by at least one half. With a further reduction of 2 weeks in the length of the season (T1) seed yields were only about one-third of those obtained in the control (T3). The reductions in seed yield were due to reductions in both the number of mature burrs produced and to a lesser extent in mean weight per seed. Although defoliation increased seed yield in all growing seasons, the effect when measured on a relative scale was greater in T2 than in either T1 or T3. But on an absolute scale the size of the response was greater in T2 and T3 than in T1. The rate of breakdown of hard-seededness was faster in Seaton Park than in Midland B, but it decreased in both strains with increasing length of growing season.
TL;DR: For example, the authors found that sorghum responded more to soil water content at planting than to mulch rate during the growing season when compared to the low water level at planting.
Abstract: Before sorghum was planted in 1977, 1978, and 1979, areas of Pullman clay loam (fine, mixed, thermic Torrertic Paleustolls) were irrigated twice, irrigated once, or not irrigated to simulate high, medium, and low levels of water storage in soil during fallow After sorghum emergence, wheat (Triticum aestivum L) straw was placed on the surface at rates of 0 (check), 2, 4, or 8 metric tons/ha Differences in sorghum response to the high and medium water levels were slight because the second irrigation resulted in relatively little additional water storage in the slowly permeable soil even though the soil was not filled to capacity Sorghum with the high and medium water levels grew taller, yielded more, and used water more efficiently than sorghum with the low water level at planting In general, sorghum responded more to soil water content at planting than to mulch rate during the growing season When significant responses to mulch rate were obtained, they resulted mainly from mulch on the low water level plots For the 3 years, the growing season mulch at 8 metric tons/ha increased water-use efficiency 19% over the no-mulch treatment, which was less than expected, based on earlier experiments and observations Apparently, shading from the plant canopy largely substituted for the beneficial effect of a mulch during the growing season When a mulch is present during both the fallow and the growing seasons, a major effect with respect to water conservation and crops production, therefore, is to enhance water storage in soil during fallow
TL;DR: The short-shoot leaves of Salivia mellifera have the same density thickness as those of the main stem, leaving open the question of whether the smaller summer leaves have physiological mechanisms for drought tolerance beyond a reduction in total transpiring surface.
Abstract: A pattern of seasonal variation in leaf size and position relative to the stem is reported for twelve mesophyllous shrubs in the coastal sage scrub of Mediterranean-climate areas of southern California. Leaves of reduced size, produced on axillary short shoots late in the growing season, persist through the dry season while many of the larger leaves on main stems are abscissed. The short-shoot leaves of Salivia mellifera have the same density thickness as those of the main stem, leaving open the question of whether the smaller summer leaves have physiological mechanisms for drought tolerance beyond a reduction in total transpiring surface. In Californian coastal shrublands seasonal dimorphism of leaves appears limited to mesophyllous shrubs. It is also found in analogues in comparable climatic regions of the Mediterranean, Chile and South Africa.
TL;DR: It can be surmised thus that resin is a feeding deterrent and that its distribution within the plant results in the greatest protection of the plant's carbon-gaining capacity.
Abstract: The phenology of the Californian shrub, Diplacus aurantiacus has been shown to be closely tied to habitat water availability, and the life cycle of the checkerspot butterfly, Euphydryas chalcedona, is in turn tied to the phenological development of Diplacus. Here this relationship is further documented by showing how the activity patterns of both the shrub and the butterfly vary from year to year, but in synchrony, dependent on the breaking of the annual drought. The end of the feeding period for the post-diapause larvae coincides with flowering of Diplacus. At this time the quality of leaves as a food source for the larvae declines as nitrogen evidently moves from the leaves into plant reproductive parts. The abundance of leaves available as food for the larvae varies greatly with season. The few leaves present during the drought period, when the larvae are inactive, are low in nitrogen and high in resin content. Even during this period, though, these leaves contribute to the carbon economy of the plant. Of the leaves produced during the principal growing season, it is the youngest leaves with the highest nitrogen contents, and hence greatest potential carbon-gaining capacity, that have the highest resin contents. Larvae feed preferentially on the older, lower-resin-content leaves. It can be surmised thus that resin is a feeding deterrent and that its distribution within the plant results in the greatest protection of the plant's carbon-gaining capacity.
TL;DR: A summary of literature data indicates that regrowth diminishes as harvests occur later in the growing season, perhaps because late harvards alter TNC storage more effectively.
TL;DR: Specific leaf weight appears to be a reliable index of the previous light environment of a leaf, but use to estimate Pnis is probably limited to the first half of the season, because of increased variation after mid-August.
Abstract: Specific leaf weight (SLW), net photosynthesis (Pn), and dark respiration (Rd) of apple leaves were monitored for an entire growing season. Leaves were sampled from the canopy interior and periphery to provide a range of SLW. Leaf Pnwas linearly correlated with SLW until mid-August, when Pnbegan to decline. During September the relationship between SLW and Pnwas a quadratic. Leaf Rdand SLW were linearly correlated throughout the season. Leaf Pnand Rdwere significantly correlated through most of the season, but the relationship was not always linear. Specific leaf weight appears to be a reliable index of the previous light environment of a leaf, but use to estimate Pnis probably limited to the first half of the season, because of increased variation after mid-August.
TL;DR: Impacts on the understory of a balsam fir – paper birch stand, caused by winter and spring full-tree logging and by winter tree-length logging, are revealed.
Abstract: Impacts on the understory of a balsam fir (Abiesbalsamea (L.) Mill.) – paper birch (Betuiapapyrifera Marsh.) stand, caused by winter and spring full-tree logging and by winter tree-length logging which was followed by summer burning, were monitored for two growing seasons after overstory harvest. New species invaded full-tree logging sites, while compositional changes on the burned area were due primarily to the disappearance of species. Prescribed burning on the tree-length logging area prevented the quick increase in density of woody species that occurred on full-tree harvested sites. However, understory production increased on all sites, and by the end of the second season aboveground biomass was 3847, 4516, and 2604 kg/ha on the winter full-tree, spring full-tree, and winter tree-length plus burning sites, respectively, compared with 942 kg/ha on the uncut control.The major factors causing differences were prescribed burning and snow cover during harvest operations. Since our results concur with previ...
TL;DR: To be able to deseribe the structure and functioning of Miscanthus sinensis grassland, its floristie composition, life-form spectra, stand productivity and dry matter allocation were studied.
Abstract: To be able to deseribe the structure and functioning of Miscanthus sinensis grassland, its floristie composition, life-form spectra, stand productivity and dry matter allocation were studied. 43 species were to be found during the growing season of 1976. 29 species, and 345 individuals per 1 m2, were observed in the sample areas in September. The values for standing crop of constituent species have been arranged in ascending order. The dominant Raunkiaer life-forms were the hemicryptophyte and geophyte. The stand was characterized by erect and tufted forms in Numata's system of growth form classification. The standing crop of the whole stand decreased from April to June, then increased from mid-July. The maximum standing crop of 3346 g m-2was observed in September. The net production of the stand was 959.4 g m-2year-1. Fifty one percent of this net production was allocated to the underground organs which consume it for respiration during winter and for initial growth in the next growing season.
TL;DR: During the 1976 and 1977 growing seasons the growth of wild rice was quantified at four sampling stations on the Mississippi River near the Clay Boswell Steam Electric Station at Cohasset, Minnesota.
Abstract: During the 1976 and 1977 growing seasons the growth of wild rice was quantified at four sampling stations on the Mississippi River near the Clay Boswell Steam Electric Station at Cohasset, Minnesot...
TL;DR: There was a pronounced seasonal pattern of live biomass production, the total biomass produced over the winter growing period representing only about 7% of the peak total summer biomass production of 1960 kg ha-1, and the yield production potential of the perennial grasses was severely depressed by low winter temperatures.
Abstract: SUMMARY (1) The seasonal pattern of above-ground live biomass production of a C4 Mitchell (Astrebla spp.) grassland community in subtropical, semi-arid Queensland, Australia, was studied over a 2.5 yr period. Actual evapotranspiration and the sequential uptake of nitrogen and phosphorus over continuous summer and winter growing periods were also measured. (2) There was a pronounced seasonal pattern of live biomass production, the total biomass produced over the winter growing period representing only about 7% of the peak total summer biomass production of 1960 kg ha-1. The yield production potential of the perennial grasses was severely depressed by low winter temperatures. (3) The maximum daily above-ground live biomass production rate for the perennial grass component during summer was 39 kg ha-1 day-1, compared with a maximum value of only 1 kg ha-1 day-' for the winter growing period. (4) The reduction in above-ground biomass production rate over the summer growing period was associated with a decline in the rate of nitrogen uptake. Phosphorus uptake was linear over almost the entire summer growing period. Nutrient uptake rate over the winter growing period was very low. (5) The ratio of actual evapotranspiration to precipitation for both the summer and winter growing seasons was around unity. (6) The results are compared with similar data for a major Australian C3 grassland in a climatic zone identical to that of the Mitchell grassland studied. The possible role of limiting soil nutrients and water as factors controlling the distribution and production of both grassland communities is discussed. (7) Some comments on animal management decision-making for Mitchell grasslands are also made.
TL;DR: In this article, a micrometeorological measurement program was conducted at Simcoe, Ontario, Canada to study atmospheric and surface control on hourly and daytime evaporation from soybeans.
Abstract: During the 1974 growing season, a micrometeorological measurement program was conducted at Simcoe, Ontario, Canada to study atmospheric and surface control on hourly and daytime evaporation from soybeans. For days when leaf area index exceeded unity, daytime evaporation varied linearly with volumetric soil moisture content when the latter was less than 0.12. At larger volumetric soil moisture contents, evaporation proceeded at a potential rate. The data confirm the usefulness of the Priestley and Taylor model with a proportionality constant of 1.26.
TL;DR: In this paper, the relation between slope properties, precipitation, movement of soil materials and are examined in western Nigeria during a single growing season, and it was shown that losses of soil material, five years after the land was cleared, are greatest not on the steepest slopes but on the 5 percent slopes.
TL;DR: It was concluded that resting the veld annually in the growing season and grazing only in the dry season is a simple and effective way of managing veld in the high rainfall areas of Zimbabwe.
Abstract: Brachystegia/Julbernardia veld was protected in the growing season and grazed by cows in the dry season for 60, 90 and 120 grazing days per ha per annum in combination with burning in the late dry season either annually, biennially or triennially. After 14 years of treatment there was evidence of a distinct improvement in grass species composition and in basal cover of grasses. While on veld cows were fed 800 g of cottonseed meal per head daily, and on average lost 4,38 kg in body mass per head per season. Burning at all frequencies reduced the number of trees and stunted their growth but the dominant species Brachystegia boehmii was reduced only by annual burning. It was concluded that resting the veld annually in the growing season and grazing only in the dry season is a simple and effective way of managing veld in the high rainfall areas of Zimbabwe where cultivated pastures are used for grazing during the growing season.
TL;DR: Primary production appeared to be related most to moisture during the growing season and temperature regimes and nutrient distribution in general reflected organic matter distribution.
Abstract: Biomass and nutrient distribution and aboveground net primary production were determined for two communities growing at 1600 m elevation and five communities growing at about 2000 m elevation in the alpine zone of the Kluane Ranges, Yukon Territory, Canada. Living biomass accumulations ranged from 183 to 1350 g/m2, whereas total organic matter accumulations ranged from 2126 to 51120 g/m2. Nutrient distribution in general reflected organic matter distribution. Highest nutrient concentrations were in leaves and fine roots. Aboveground net primary production ranged from 18.3 to 185.5 g/m2. Primary production appeared to be related most to moisture during the growing season and temperature regimes.