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1.
Above‐ground net primary production (ANPP) and precipitation‐use efficiency (PUE) are key factors that can clarify the response of grassland ecosystem carbon and water cycles to ongoing climate change. The variations of ANPP and PUE were analysed based on long‐term in situ observations of a species‐rich alpine meadow in the north‐eastern Qinghai‐Tibetan Plateau from 1981 to 2010. ANPP and PUE increased markedly over time. ANPP was significantly controlled by post‐growing season length (from 1 September to the end of growing season in the previous year, R2 = 0·31, P < 0·01). Regression trees showed that air temperature during October of the previous year played a predominant role in ANPP annual variations. Results indicated that a strong thermal‐lagging effect on ANPP variations was present in the alpine meadow ecosystem. ANPP variations were undetectable during wet, normal and dry years (P = 0·25). Our finding supported the hypothesis that temporal site‐specific ANPP variations were less regulated by a single factor. The temporal PUE declined linearly with increasing annual precipitation, and the slope was obviously steeper than that of spatial patterns. More ANPP variability in an alpine meadow under warming conditions might occur via community transition in the north‐eastern Qinghai‐Tibetan Plateau.  相似文献   

2.
Plant growth simulation models have a temperature response function driving development, with a base temperature and an optimum temperature defined. Such models function well when plant development rate shows a continuous change throughout the growing season. This approach becomes more complex as it is extended to cool‐season perennial grasses with a dormant period and bimodal growth curves. The objective of this study was to develop such a bimodal growth model for tall fescue (Schedonorus arundinaceus (Schreb.) Dumort) in the Midwest USA based on multiyear measurement trials. Functions for bimodal growth were incorporated into the ALMANAC model and applied to tall fescue using published tall fescue yields for a variety of sites and soils. Fields of cultivars “Kentucky 31” and “BarOptima Plus E34” were divided into paddocks and sampled weekly for dry‐matter accumulation. These biomass estimates were used to derive weekly growth values by differences between sequential weekly samplings. The measured values were compared to a single tall fescue simulation each year on one soil. Using these results, the ALMANAC model was modified and tested against mean reported tall fescue yields for 11 sites, with one to three soils per site. When we introduced midsummer dormancy into ALMANAC, we assumed dormancy began on the longest day of the year and lasted until the photoperiod was 0.68 hr shorter than the longest. ALMANAC simulated previously reported tall fescue yields well across the range of sites. Thus, ALMANAC shows great promise to simulate bimodal growth in this common cool‐season grass.  相似文献   

3.
Foam stability related to pasture bloat from alfalfa pastures might be reduced by introducing a gene that stimulates the accumulation of mono‐/polymeric‐anthocyanidin. The objective of this study was to determine the foam formation (at 0 min) and stability (at 150 min) from aqueous leaf extracts of three transgenic Lc‐alfalfa progeny (BeavLc1, RambLc3 and RangLc4), parental non‐transgenic (NT) alfalfa and AC Grazeland (bloat‐reduced cultivar) harvested at 07:00 or 18:00 h. Initial and final foam volumes at 07:00 h were lower for AC Grazeland compared with all other treatments and lower for RangLc4 compared with the other two Lc‐progeny at 0 min and NT‐alfalfa at 150 min. At 18:00 h, initial foam volume was larger for NT‐alfalfa and final foam volume was larger for RambLc3 compared with AC Grazeland, BeavLc1 and RangLc4. Spectroscopic vibration associated with carbohydrates increased initial foam volume and stability. More amide I relative to amide II, fewer α‐helices relative to β‐sheets and leaf extract ethanol‐film and protein content increased initial foam volume but did not stabilize it. Spectroscopic vibration associated with all carbohydrates other than structural carbohydrates was more important than vibration from protein structures for foam formation and stabilization. In conclusion, Lc‐alfalfa accumulated anthocyanidin and had reduced foaming properties compared with parental NT alfalfa but AC Grazeland and RangLc4 had the lowest foaming properties.  相似文献   

4.
Studying the seed production of herbaceous species can help to conserve grassland habitats and re‐create new high‐value grassland surfaces. Studies on grassland seed production have focused mainly on individual species and traits, without characterizing their relative importance at the plant community level. The aim of this study was to investigate the entire seed production process of the main species in a temperate grassland. Fertile shoots (FS) of twenty‐nine grasses and forbs were collected over 4 years and analysed for sixteen traits that determine inflorescence size, seed production and seed quality. The per cent viability played a predominant role in determining the total production of viable seeds. Forbs showed a range of reproductive strategies, including variable distribution of flowers among growth periods, number of inflorescences per FS and relationship between seed size and FS density in the grassland. The flower production for grasses was concentrated in the first growth period, but this limitation was mitigated by a higher seed dormancy. The number of viable seeds per FS and seed size were important components of the reproductive strategy of forbs, with heavy‐seeded species being characterised by high individual densities in the community, but producing few seeds per FS. Light‐seeded species showed an opposite pattern. The results suggest that when using seeds from semi‐natural grasslands for ecological restoration, special attention should be paid to the seed amount, germinability and viability of forbs, as they seem to depend more on seed reproduction and have a lower ovule to seed transformation efficiency.  相似文献   

5.
In a summer‐dominant high‐rainfall, yet seasonally dry environment, soil water dynamics and dry‐matter (DM) production were monitored during 2006–12, for three perennial pasture types: old man saltbush (Atriplex nummularia ssp. nummularia with native grass), native grass (Bothriochloa macra and Rytidosperma bipartita dominant) and lucerne (Medicago sativa cv. Venus). Plant root depth of the old man saltbush pasture (1·5 m) was greater than that of native grass (1·2 m), but equal to that of lucerne (1·5 m), resulting in equivalent levels of maximum extractable water (MEW; mm, 0–1·7 m) for saltbush and lucerne in five of the six seasons. Lucerne (MEW 242 mm) extracted more soil water than native grass (144 mm), but was similar to old man saltbush (205 mm). In the second year of growth, both the lucerne and old man saltbush pastures achieved their maximum yields of 16·8 and 7·9 t DM ha?1 respectively, but thereafter declined. The decline in yield of lucerne in later years was associated with a significantly lower plant frequency and increase in proportion of weeds. The decline in yield of old man saltbush appeared to be associated with an increasingly dry soil profile, despite receiving rainfall that was above average. The yield of the native grass pasture increased during the study as the proportion of weeds declined, and the presence of saltbush plants did not compromise the yield of perennial grasses in the inter‐row spaces. The implications of these findings for livestock production systems in this environment are discussed.  相似文献   

6.
The aim of this study was to evaluate the possible effect of pre‐fermented juice (PFJ) on the fermentation quality and nutritive value of first‐cut lucerne (Medicago sativa L.) silage. The PFJs were prepared using barley (B), wheat (W) and grass herbages (G). Both fresh (PFJ‐B, PFJ‐W and PFJ‐G) and frozen (PFJ‐BF, PFJ‐WF and PFJ‐GF) PFJs were examined. Frozen PFJs were prepared by freezing fresh PFJs at ?22°C with 20% glycerol (v/v). Treatments of lucerne silage included (1) control; (2) silage treated with PFJ‐B; (3) silage treated with PFJ‐W; (4) silage treated with PFJ‐G; (5) silage treated with PFJ‐BF; (6) silage treated with PFJ‐WF; and (7) silage treated with PFJ‐GF. All the treatments consisted of five replicate silos, and they were prepared in 1·0‐L glass jar silos. Results showed that silages treated with fresh and frozen PFJs, regardless of plant material, had better fermentation quality than the control silage in terms of lower pH, butyric acid (BA) and ammonia nitrogen (NH3‐N) concentrations, as well as higher lactic acid (LA) concentration (P < 0·05) and in vitro organic matter digestibility (IVOMD), metabolizable energy (ME) content, and gas production values (P < 0·05). Results indicated that PFJ treatments enhanced the nutritive value, fermentation quality and IVOMD, ME content and gas production values of first‐cut lucerne silages.  相似文献   

7.
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8.
Agronomic data on most broad‐leaved species of grasslands are scarce. The aim of this study was to obtain novel information on herbage DM yield and forage quality for several forb species, and on species differences and seasonal patterns across harvests and in successive years. Four non‐leguminous forbs [salad burnet (Sanguisorba minor), caraway (Carum carvi), chicory (Cichorium intybus) and ribwort plantain (Plantago lanceolata)] and three leguminous forbs [yellow sweet clover (Melilotus officinalis), lucerne (Medicago sativa) and birdsfoot trefoil (Lotus corniculatus)] and a perennial ryegrass–white clover mixture were investigated in a small‐plot cutting trial in Denmark during 2009 and 2010. Plots were harvested four times per year. On average, annual herbage yield was highest for lucerne (15·4 t DM) and grass–white clover (12·5 t DM ha?1), and lowest for salad burnet (4·6 t DM ha?1) and yellow sweet clover (3·9 t DM ha?1). Ribwort plantain and lucerne had the highest concentrations of acid detergent fibre (339 and 321 g kg?1 DM respectively) and lignin (78 and 67 g kg?1 DM respectively); contents in other species were similar to grass–white clover (275 and 49 g kg?1 DM respectively). No common feature was found within the functional groups of non‐leguminous forbs and leguminous forbs, other than higher crude protein contents (198–206 g kg?1 DM) in the legumes. DM yield and fibre content were lowest in October. Digestibility declined with higher temperature and increasing fibre content. Results are discussed in terms of the potential of forbs to contribute to forage resources in farming practice.  相似文献   

9.
In forage grasses, knowledge about the genetic basis of seed production and its association with related traits under water stress is very limited. Half‐sib families derived from the polycross of twenty five smooth bromegrass genotypes were evaluated in the field in well‐watered and water‐stressed environments during 2012 and 2013. Results showed that drought stress had a negative effect on seed yield and reduced phenotypic variation for seed yield and agro‐morphological traits. High genotypic variation was observed among families for seed yield and its components. Narrow‐sense heritabilities (h2) ranged from 0·22 (flag leaf weight) to 0·81 (days to anthesis). These moderate‐to‐high heritability estimates for seed yield and its components indicate that phenotypic selection can be successful to achieve genetic progress for these traits. Seed yield had a positive correlation with 1000‐seed weight, number of ears per plant, number of seeds per panicle, seed weight per panicle and panicle length.  相似文献   

10.
A nonlinear optimization model of a pasture‐based dairy farm, located in the Waikato region of New Zealand, is used to provide an integrated analysis of profitable stocking‐rate decisions for pasture‐based dairy production, across a range of alternative milk and nitrogen fertilizer prices. Previous research has identified that operating profit increases either in a linear or concave fashion as stocking rate is lifted. This study shows that both views are relevant, depending on the magnitude of milk and nitrogen fertilizer prices. A lower milk price and/or higher per‐unit cost for nitrogen fertilizer reduces profit at higher stocking rates, as the cost of maintaining a larger herd through pronounced feed deficits is magnified. In contrast to previous research, nitrogen fertilizer and imported supplement are shown to be highly complementary strategies under profitable farm management. Model output demonstrates that decreasing stocking rates to reduce leaching, in most cases, will impose a cost in terms of both production and profit. Overall, this work indicates the key importance of stocking‐rate decisions to profitable grazing strategies, relative to those concerning milk per cow. Nevertheless, it is the inherent linkages between stocking rate and the multiple elements of a grazing system that infers this importance, highlighting the need to carefully consider all management levers.  相似文献   

11.
Meadowfoam oil methyl ester was metathetically cleaved with ethylene catalyzed by Re2O7–B2O3/Al2O3–SiO2 + SnBu4 or bis(tricyclohexyl phosphine) benzylidene ruthenium dichloride yielding -olefins, ,ω-dienes and 5-hexenoic acid methyl ester as the main product. The corresponding ω-epoxy fatty acid ester was achieved by chemoenzymatic epoxidation with H2O2 in the presents of Novozym® 435. Glutaric acid mono methyl ester was synthesized by ruthenium-catalyzed oxidative cleavage with peracetic acid. Hydrocarboxylation with carbon monoxide/methanol yielded pimelic acid dimethyl ester. Metathetical dimerization of 5-hexenoic acid methyl ester yielded 5-decen-dioic acid dimethyl ester, which was subsequently polycondensed with ethylene glycole and 1,4-butanediol to high molecular weight polyesters. The ω-unsaturated ester was directly copolymerized with ethylene by an insertion-type palladium-catalyzed reaction to a high molecular weight functional polyolefin. The 5-epoxy hexanoic acid ester was polymerized to a comb like polyether.  相似文献   

12.
The outcomes of previous studies have resulted in differing recommendations on the rate and timing of fertilizer N applications for forage maize. In order to gain an improved understanding of the role of N fertilizer, a field experiment was carried out to investigate the effects of time and rate of N application on total and plant‐fraction yield, nutritive value and efficiency of nutrient utilization in early‐ and late‐sown forage maize. Treatments included two sowing dates (early, late), two rates of N (0, 135 kg ha?1) applied pre‐sowing (N1) and three rates of N (0, 79, 158 kg ha?1) applied post‐sowing (N2) at the six‐leaf stage (V6). Application of N at N1 (N0 vs. N135) increased dry‐matter (DM) stover yield by 11% and total yield by 7%. Application of fertilizer N at N2 (N0 vs. N158) increased grain yield by 44% and total yield by 34%. Application of N2 also increased irrigation and total water‐use efficiency (WUE) from 30 to 40 and 46 to 61 kg DM ml ?1 water respectively. Late sowing increased DM yield by 6%, but decreased WUE compared with early sowing. The results indicate that application of N at both N1 and N2 is essential to maximize total DM yield from forage maize, but application at V6 is recommended when N input is reduced.  相似文献   

13.
The effect of surface liming on herbage production in permanent grasslands is rather uncertain. To better understand the effect of liming on the grassland, a study was made with a field experiment and a pot experiment with soil from the same field. In the field, the effects of liming and NPK fertilization on the production and composition of the vegetation were studied. In pots, the effects of liming and phosphate fertilization on different grass species were analysed. The effect of NPK fertilization (+3·96 t ha?1) on the production of the original grassland was greater than that of liming (+0·68 t ha?1), which was only observed (P < 0·05) on the unfertilized plots. Liming increased the total number of species and the proportion of dicotyledons. After replacing the semi‐natural community with Dactylis glomerata L., the effects of liming (+2·37 t ha?1) and fertilization (+6·52 t ha?1) were increased. These results, together with those of the pot trial, show the important role of phosphorus in the fertilization effect, and are interpreted as a protective effect of P against aluminium toxicity.  相似文献   

14.
To address severe grassland degradation, the Chinese government implemented national restoration programmes, which in turn drove a research focus towards assessment of the environmental effectiveness of such initiatives. In this study, net primary productivity (NPP) was used as an indicator for assessing the impacts of land use and cover change (LUCC), improved land‐use management and climate change on the grassland ecosystem of the Shiyanghe River Basin. NPP was calculated on the basis of the Carnegie–Ames–Stanford Approach model, which is driven by a Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index and meteorological data. The LUCC data for 2001 and 2009 were derived from MODIS land‐cover data. During the study period, the net increase in grassland development was 5105·5 km2, with 80·4% of the newly developed grasslands attributed to desert‐to‐grassland conversion. The total NPP of grasslands in 2009 increased by 659·62 Gg C compared with that in 2001. The contributions of human activity and climate change to total NPP increase were 133 and ?33% respectively. Land conversion and improved management measures directly increased grassland NPP. These factors are dominant positive driving forces, whereas warm and dry climates impose adverse effects on grassland restoration in the study site.  相似文献   

15.
Temperate pasture‐based dairy farming systems with low input of supplementary feed are vulnerable to changes in climate through alterations in feed supply and nutritive value. Although current systems in New Zealand (NZ) and southeast Australia have been successful in adapting to variable weather conditions, they will need to undergo further changes to continue to profit in the future. This review describes predicted changes in climate in NZ and southeast Australia, likely effects on the feedbase used in the pasture‐based dairy industry and the flow‐on effect on milk‐solids production and profitability. Potential adaptation options that will allow farmers to take advantage of new opportunities and minimize any negative impacts of climate change are also identified. For example, in many regions, annual pasture production is predicted to increase due to carbon dioxide fertilization and warmer temperatures during winter/spring. Production may decline, however, in regions with either reduced rainfall or severe flooding. Should this occur, farmers could strategically use supplementary feed, reduce stocking rates, irrigate or sow alternative plant species with greater drought tolerance. Pasture‐based dairy systems have high levels of adaptive capacity, and there are opportunities to continue to improve production efficiencies particularly where rainfall change is small. Further investigation into possible adaptation options is required to determine their impact on milk‐solids production and profitability, as well as to identify additional options.  相似文献   

16.
Utilization of long‐chain alcohols (LCOH) as diet‐composition markers in sheep consuming six diets composed of improved pasture species (Lolium perenne and Trifolium repens) with heather–gorse components (Erica spp., Calluna vulgaris and Ulex gallii) was evaluated. Twenty‐four adult cross‐bred sheep were housed in individual stalls. Diet composition was estimated from LCOH concentrations, combined or not with alkanes and long‐chain fatty acid (LCFA) data using least‐squares procedures. Prior to calculations, faecal concentrations were corrected using mean treatment (faecal recovery 1, FR1) recoveries and mean recoveries across diets (FR2). Estimates were compared with those obtained without faecal correction (FR0) and known values. Large differences between plant species and plant parts were found in LCOH patterns and total LCOH concentrations. LCOH provided complementary information to that given by alkanes and LCFA. Even‐chain LCOH comprised the largest fraction, representing on average 0·894 of total concentrations. Faecal recovery was incomplete and tended to increase with carbon‐chain length (CCL) in a curvilinear manner (FR = ?7·872 + 0·580 × CCL ? 0·010 × CCL2; P < 0·001; r2 = 0·752). Diet composition influenced (P < 0·001) LCOH recovery, although variability within (CV of 9·0%) and between (CV of 13·3%) diets was low. Accuracy of estimates was influenced (P < 0·001) by faecal‐correction method and markers used, and the best estimate was obtained combining LCOH and alkanes. Improvement in estimate accuracy can be achieved if suitable correction of LCOH faecal concentrations is performed prior to calculations. Results indicated that LCOH showed lower dependence than alkanes and LCFA on the use of accurate faecal‐correction data.  相似文献   

17.
Livestock grazing can be a means to maintain biodiversity in grasslands, but the outcome for vegetation structure and species composition depends on livestock type and grazing regime. This study aims at disentangling the effects of plant functional‐group abundance and livestock type on the above‐ and below‐ground biomass and N allocation in temperate pastures. We investigated the effects of cattle, sheep and mixed stocking on above‐ground biomass (AGB) and belowground biomass (BGB) and plant N pools in a replicated grazing experiment in two pasture community types with different plant functional‐group abundance (diverse vs. grass‐dominated swards). In the six treatments, AGB was reduced up to 80% compared with an ungrazed control. Cattle reduced AGB to a larger extent than sheep in diverse pastures (80 vs 44% reduction) while sheep grazing tended to do so in grass‐dominated pastures (57 vs 46% reduction); mixed stocking led to intermediate values. Grazing reduced AGB more than the N pool in AGB, thus lowering the biomass C/N ratio relative to the ungrazed control. Neither BGB nor the N pool in BGB differed between the grazing treatments and the control plots. We conclude that livestock type and functional‐group abundance are interacting factors that influence plant biomass and N pools in swards of managed temperate pastures. The contrasting biomass removal rates of cattle and sheep could be used to increase the structural heterogeneity and total plant species pool of pastures by keeping different livestock species in neighbouring patches.  相似文献   

18.
Complementary forage rotation (CFR) systems based on non‐limiting inputs of fertilizer nitrogen (N) (～600 kg N ha?1) are perceived as uneconomic. An experiment was carried out in Australia to investigate the effects of rates and timing of N fertilizer and sowing date on yield, nutrient‐use efficiency and nutritive value of a triple‐crop (maize, forage rape, field peas) CFR system. Treatments were early‐ and late‐sown maize grown with 0 or 135 kg fertilizer N ha?1 pre‐sowing (N1) and 0, 79 or 158 kg N ha?1 post‐sowing (N2). Forage rape was sown with 0 or 230 kg N ha?1 (N3) and field peas without N. Application of fertilizer N at N1, N2 and N3 increased CFR yield from 28·5 to 48·8 t dry matter (DM) ha?1 and irrigation water‐use efficiency (IWUE) from 3·4 to 6·1 t DM per megalitre. Increase in yield and IWUE of CFR occurs at the expense of nitrogen‐use efficiency (NUE) as applications of N at N1, N2 and N3 decreased NUE of CFR from 524 to 91 kg DM kg?1 N. Nutritive value, particularly metabolizable energy content of all forages, was similar among N treatments, and interactions between treatments were minimal. Results indicate that increase in NUE of CFR may occur at the expense of reduced yield, but increased IWUE need not compromise the yield of this CFR system.  相似文献   

19.
In Europe, the decline in agriculture in traditional mountain farming areas has caused abandonment, or irregular grazing, of less accessible pastures. In the Italian Alps, we studied plant diversity, forage value and trophic traits in six large‐scale heterogeneously grazed Nardus pastures, in their central and peripheral parts, and across the montane, lower and upper subalpine zones. Seventy cover‐abundance floristic relevés were performed in randomly located permanent plots, half at the pasture edge (M‐plots) and half in their central part (C‐plots). Plant diversity varied significantly with respect to the distance from the edge, being higher in M‐plots because of shrub invasion as a consequence of reduced cattle pressure. Nardus cover was slightly higher in C‐plots and negatively related to plant diversity. Forage value was lower in M‐plots and negatively correlated with the cover of Nardus and woody species, implying that different grazing pressure was negatively influencing sward productivity. Differences in trophic traits of swards between C‐ and M‐plots existed mostly as trends. Forage value significantly decreased in the lower subalpine and montane pastures, which are further grazed in late summer. Heterogeneous grazing management was therefore exerting positive effects on plant diversity and negative effects on forage value. Results are discussed in the context of future management recommendations.  相似文献   

20.
Automatic milking systems (AMS) present an opportunity for dairy farmers to not only improve their lifestyle and conditions of work, but also save on labour costs and/or increase the time available to focus on overall farm management. However, the viability of AMS will rely on achieving high levels of pasture utilization. Well‐established pasture management principles are implemented on many conventional milking system (CMS) farms and high levels of pasture utilization are achieved; however, the ability to follow these same principles on AMS is unknown. This study compared levels of pasture utilization and pre‐ and post‐grazing pasture mass between AMS and CMS farms at the same site when managed by the same pasture management principles. From 1 March 2007 to 29 February 2008, pre‐ and post‐grazing compressed height, milk yield and milk composition data were collected for two CMS farms and one AMS farm at the Elizabeth Macarthur Agricultural Institute, Camden, Australia. Despite differences in pre‐ and post‐ grazing pasture mass between milking systems, pre‐grazing mass was predominantly maintained within the bounds of 2200 and 2500 kg DM ha?1 and post‐grazing mass between 1400 and 1500 kg DM ha?1 (5–6 cm height). Similar levels of pasture utilization (mean 13 500 kg DM ha?1 year?1) were recorded between AMS and CMS farms. These findings highlight the ability to follow established grazing management principles and achieve high levels of pasture utilization on pasture‐based AMS farms.  相似文献   

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