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1.
This work analysed the regulatory structural mechanisms involved in the competitive interactions between the annual grass Bromus willdenowii Kunth. (BW = prairie grass) and the perennial C3 grass Dactylis glomerata L. (DG = orchardgrass) during pasture establishment. Four combinations of species (pure BW, pure DG, DG flanked by BW and BW flanked by DG plants), with and without winter nitrogen fertilization, were factorially arranged in a randomized complete block design. Data were recorded at two organization levels: tillers (three tiller age cohorts) and target plants. Annual neighbours caused a decrease in the number of living leaves in tillers of intermediate age of both species. This structural regulatory mechanism led to a decrease in tiller number per plant and, therefore, restricted the development of horizontal space occupation. Annual neighbours did not cause an increase in tiller size, measured as lamina length or pseudostem height, but decreased root biomass. As a consequence, annual neighbours did not lead the hierarchy in light capture, but limited species radical colonization and competitive ability for soil resources. Winter nitrogen fertilization only affected tiller size in older tillers. These findings emphasize the importance of the cultural decisions, as sowing densities and nitrogen fertilization, to optimize pasture floristic composition.  相似文献   

2.
Management decisions should facilitate the dominance of C3 perennial grasses over annuals. This study examined the effects of defoliation frequencies and nitrogen fertilization on the productivity and potential for persistence of Dactylis glomerata L. (DG cocksfoot, perennial) in multispecies swards. Treatments were randomly applied to 24 mini‐swards of DG + Bromus willdenowii Kunth (BW prairie grass, annual/biennial) in a factorial design of four defoliation frequencies, based on number of leaves per tiller, by two nitrogen winter fertilization levels (N? or N+). Regardless of fertilization, very frequent and repeated defoliations were related to decreases of about 43% of aboveground biomass and frequent defoliations with decreases of about 44% of vegetative tillers associated with horizontal space occupation and potential for persistence. Nevertheless, differences in DG aerial productivity or reserves were not detected between frequent and optimal defoliation frequencies. Combined effects of N+ and optimal frequency were related to root biomass increment of about 200%, compared with frequent defoliation, associated with competitiveness and survival of DG. Optimal defoliation frequency would have ecological but not production advantages, compared with frequent defoliations. The results are discussed in terms of more objective decision‐making in the management of multispecies swards.  相似文献   

3.
Three cultivars (two diploid and one tetraploid) in each of three maturity groups (early, intermediate and late) of perennial ryegrass were sown in 10 m2 plots, replicated four times, in Northern Ireland in June 1997 in a study of the effect of heading date on tiller development (including initiation to flower) and turnover of tillers produced at specific times in spring in 1998 and 1999. The plots were harvested seven times in each year. Annual dry‐matter production was similar for all groups in each year. In spring and early summer of both years, tiller density of the diploid cultivars was 1·5 times greater than that of the tetraploid cultivars and the mean tiller density over all swards in June was about 0·40 times greater than that in April. Maximum proportions of reproductive tillers in the early, intermediate and late maturity groups, determined from apical dissections, were found in early April, mid‐May and early June, respectively. Although a high proportion of tillers, which were present when annual observations commenced in spring, was decapitated at the first harvest in the early group, the previous population density was maintained by rapid production of new tillers during May, including those from suppressed tiller buds during reproduction. It is concluded that the relationship between heading date and rate of tiller turnover (including flowering) at specified times in spring is important in sward management throughout the early part of the growing season and should be taken into account in tiller‐based grass growth models.  相似文献   

4.
Enhancing pasture persistence is crucial to achieve more sustainable grass‐based animal production systems. Although it is known that persistence of perennial ryegrass is based on a high turnover of tillers during late spring and summer, little is known about other forage species, particularly in subtropical climates. To address this question, this study evaluated survival of grazed tall fescue tillers growing in a subtropical climate. We hypothesized that hard tactical grazing during winter to remove reproductive stems (designated as ‘flowering control’), and nitrogen fertilization in spring, would both improve tiller survival over summer, and thus enhance tiller density. This was assessed in two experiments. In both experiments, few tillers appeared during late spring and summer and so tiller density depended on the dynamics of vegetative tillers present in the sward in spring. In Experiment 2, flowering control and nitrogen fertilization both enhanced the survival of that critical tiller cohort, but the effects were not additive. Responses were similar but not statistically significant in Experiment 1, which had a warmer, drier summer and lower overall survival rates. Unlike grasses in temperate environments, persistence of tall fescue in this subtropical site appeared to follow a ‘vegetative pathway’; i.e., new tillers were produced largely in autumn, from vegetative tillers that survived the summer.  相似文献   

5.
Nitrogen (N) inputs are recognised to maximise herbage mass (HM) in tropical perennial grasses, whereas less is clear on their impact on HM distribution and the effects on leaf mass (LM) and leaf area index (LAI) in the upper stratum. This 2 year study, carried out in Pirassununga, Brazil, assessed the HM distribution in the upper (>20 cm) and lower (<20 cm) strata in Urochloa hybrid ‘Mavuno’ grass maintained under similar pre- and post-cutting canopy heights with contrasting N fertilisation rates applied after each cutting (no-nitrogen, 15, 30, and 45 kg N ha−1). The relevance of specific leaf area (SLA), leaf N concentration (NLeaf), tiller weight (TW) and population density to the LM and LAI of the upper stratum were also examined. Mavuno grass expressed a stable HM < 20 cm (59%–71% during Year I and 66%–80% for Year II), and apparent N fertilisation impacts on HM > 20 cm were verified at specific regrowth cycles during Year II. Mavuno grass pastures expressed plasticity for adjustments on leaf, tiller and population attributes, which were modulated by both climatic conditions and N fertilisation. Under favourable growth conditions during Year I, fertilised pastures were able to sustain higher NLeaf and SLA but associated with lower TW, resulting in maximisation of LAI but not in LM in the upper stratum. During Year II, fertilised pastures expressed higher NLeaf, SLA, number of basal tillers, despite the lowest TW, which resulted in higher LAI and LM in the upper stratum compared with non-fertilised pastures. Our results highlighted that adjustments on leaf and population attributes within the canopy were driven to maximise the upper stratum LAI, being positively affected by N fertilisation.  相似文献   

6.
The morphogenetic responses of individual tillers and the composition of tiller populations throughout regrowth in response to all combinations of two post‐grazing heights (35 and 45 cm) and two pre‐grazing conditions (95% and maximum canopy light interception during regrowth – LI95% and LIMax) were studied in swards of elephant grass (Pennisetum purpureum Schum. cv. Napier) from November 2011 to April 2012. Swards were subjected to the same treatments from January 2011 until measurements began, to enable them to adapt to the defoliation regimes. Treatments were allocated to experimental units (850 m2 paddocks) according to a 2 × 2 factorial arrangement in a randomized complete block design, with four replications. The total number of tillers (basal + aerial) was similar for both LI pre‐grazing targets. However, there was a change in the preferential growth pathway used by plants characterized by modification in the proportion of tiller classes in plant population. Swards managed with the LIMax target had a smaller population density of basal tillers and used the recruitment of aerial tillers as the main growth pathway. Although effective for maintaining stable rates of leaf elongation and senescence, such a strategy resulted in greater tiller death. Additionally, stem elongation, a consequence of the competition for light under those circumstances, resulted in differences in sward herbage mass and morphological composition with potential implications for herbage feeding value.  相似文献   

7.
The relative contribution of tillers present in April and those appearing in consecutive periods in spring was assessed for perennial ryegrass cultivars in the three maturity groups (early, intermediate‐ and late‐heading). Each group was represented by two diploid and one tetraploid cultivar each in plots in their third (2000) and fourth (2001) harvest years in three replicated blocks receiving an average of 325 kg N ha?1 and cut seven (in 2001) or eight (in 2000) times annually. ‘Main’ tillers and their daughters were marked with colour‐coded PVC‐covered wire loops in early April as were daughters which appeared in consecutive periods between harvests, the loop colour identifying the period of origin of the tiller. Tillers were harvested at cutting height (5 cm) before the plots were harvested and the herbage from tillers with the same colour code bulked per plot. Tillers were identified retrospectively as ‘reproductive’ if they had been decapitated at the previous harvest. Dry‐matter yield was higher in the early than late‐heading cultivars in April and early May but this was reversed in harvests in late May and June. The early heading group had a lower lamina content than the late‐heading group during reproduction growth, both due to the reproductive tillers (mainly those which overwintered) having a lower leaf content and to their being fewer and smaller vegetative tillers during the reproductive phase than for the late‐heading group. Turnover of tillers was high in spring due to decapitation of reproductive tillers and rapid post‐flowering tillering. This was particularly pronounced in the early heading group which also had slightly more tillers marked in April which were subsequently decapitated than in the other maturity groups, i.e. 0·56 compared with 0·44 for the late‐maturing group. Mean ratios of rate of death: rate of tillering for 3 years (1999–2001) for the early and late‐heading groups were 0·8 and 0·4, respectively, for April–May and 1·1 and 2·4, respectively, for June indicating the different patterns in tiller turnover for the two extreme maturity groups. Information on tiller origin and contribution to yield can be used to refine tiller‐based grass growth models.  相似文献   

8.
The objectives of this study were to measure the variability in ‘realized’ tiller morphology and identify whether there are emergent generalizations about a tiller ideotype for productivity or survival. Morphological traits during the vegetative growth stage were measured for 2 years in the field for eight perennial ryegrass cultivars: six diploid and two tetraploid cultivars under low and high nitrogen fertilizer (50 and 225 kg N ha?1 year?1 respectively). Traits measured were lamina width, length and area; pseudo‐stem length and diameter; an index of tiller shape; tiller dry weight; tiller density; and herbage mass. Almost all the traits differed significantly between cultivars and significant correlations were found between the 2 years. Principal component analysis identified that tiller morphology and dry‐matter yield were independent. No trait associations indicating alternative cultivar‐specific tiller morphologies were detected but cultivars differed in tiller size. The patterns of change between the 2 years indicated a possible morphological trajectory as swards age. The genetic compensatory relationship between tiller size and density had a 1:1 slope, indicative of constant yield. This implies that larger tillers would be more leafy, and higher leafiness of tetraploid over diploid cultivars was confirmed by the leaf:non‐leaf ratio and tiller shape index.  相似文献   

9.
The aim of this study was to determine a temporary strategy for increasing the legume population in an established pasture of brachiaria grass (Brachiaria brizantha) and forage peanut (Arachis pintoi). The treatments comprised four previous long‐term canopy heights (10, 20, 30 and 40 cm) from the establishment (the first 32 months after treatment initiation). From September 2014, all of the experimental units were kept at 10 cm height. The pastures were evaluated for their forage harvest, forage mass, botanical composition and stolon and tiller density. The tiller density and brachiaria grass mass were maintained in all pastures since the first season of evaluation (p > 0.10). The stolon density and legume mass were initially lesser at 30 and 40 cm than those at 10 and 20 cm, early in the experiment, but progressively increased over time. After 1 year under 10 cm height, the population and mass of legume were similar in all treatments. Therefore, reducing the canopy height to 10 cm at the beginning of the rainy season is an efficient method to increase the botanical composition of forage peanut in mixed pastures with brachiaria grass.  相似文献   

10.
The objective of the study was to evaluate the grazing behaviour by sheep in hill country paddocks in New Zealand which had received two long‐term fertilization and stocking rate treatments [high fertility–high stocking rate (HH); low fertility–low stocking rate (LL)]. Herbage accumulation and selective grazing were evaluated within low slope (LS), medium slope (MS) and high slope (HS) categories. Transects lines were placed and tillers of Agrostis capillaris and Lolium perenne in the LS category; A. capillaris, Anthoxanthum odoratum and L. perenne in the MS category; and A. capillaris and A. odoratum in the HS category were marked. The leaf length of each marked tiller was measured and used to determine selective grazing over 3 weeks during each season. The highest herbage accumulation rates were during spring and the lowest in summer and winter. The LS category showed the highest herbage accumulation rates and HS the lowest. Except for autumn, the marked tillers were more frequently grazed in the HH than in the LL paddock. During summer, autumn and spring, grazing frequency in the slope categories was in the order LS > MS > HS. During winter sheep did not discriminate between slope category. During summer, autumn and spring, sheep did not selectively graze the species studied but this was not the case during winter. Overall, sheep selectively grazed L. perenne. In all the seasons L. perenne consistently had the longest leaves but within species there was no consistent relationship between leaf length and probability of being grazed. Selective grazing changed through the year according to herbage accumulation rate. Sheep concentrated grazing in the category LS when herbage accumulation rate was high, but they did not discriminate between slope categories in winter when herbage accumulation rate was low.  相似文献   

11.
The impact of deferred grazing (no defoliation of pastures for a period generally from spring to autumn) and fertilizer application on plant population density, ground cover and soil moisture in a hill pasture (annual grass dominated, with Australian native grasses being the major perennial species) were studied in a large‐scale field experiment from 2002 to 2006 in southern Australia. Three deferred grazing strategies were used: short‐term deferred grazing (no defoliation between October and January each year), long‐term deferred grazing (no defoliation from October to the autumn break, that is the first significant rainfall event of the winter growing season) and optimized deferred grazing (withholding time from grazing depends on morphological development of the plants). These treatments were applied with two fertilizer levels (nil fertilizer and 50 kg P ha?1 plus lime) and two additional treatments [continuous grazing (control) and no grazing for year 1]. Deferred grazing increased (P < 0·05) perennial grass tiller density compared with the control. On average, the tiller density of the three deferred grazing treatments was 27–88% higher than the control. There was a negative (P < 0·01) relationship between perennial and annual grass tiller density. Fertilizer application increased (P < 0·05) legume plant density. The densities of annual grasses, legumes, onion grass (Romulea rosea) and broadleaf weeds varied between years, but perennial grass density and moss cover did not. The ground cover of the deferred grazing treatments in autumn was on average 27% higher than the control. Soil moisture differed between treatments at 15–30 cm depth, but not at 0–15 depth over autumn and winter. The results imply that deferred grazing can be an effective tool for rejuvenating degraded native pastures through increases in native grass tiller density and population and through improving farm productivity and sustainability.  相似文献   

12.
Despite low net grass growth rates in Ireland between mid-November and February, tissue continuously turns over as new leaves are produced and older leaves senesce. The effects of closing swards from grazing on three dates in autumn (1 September, 20 September and 10 October) on tissue turnover in a perennial ryegrass sward during the winter were examined at two sites in the north-east and south of Ireland. Leaf extension and senescence rates were greater in the south than in the north-east, and were greatest on the earliest closing date at both sites. Leaf appearance and extension rates at both sites were closely correlated with accumulated daily air temperature above 6°C and mean soil temperature. Site-specific factors also influenced tissue flux, possibly including grazing intensity at closing and density of tillers of perennial ryegrass. Swards in the autumn with high herbage masses [>2000 kg dry matter (DM) ha−1 approximately] and high leaf area index (LAI; about 2·5 and above) had the greatest leaf senescence rates and the greatest declines in herbage mass during the winter. Leaf senescence rates per tiller in high LAI swards were correlated positively with amount of leaf per tiller and also the proportion of green leaf in the second youngest expanding leaf lost to senescence. As potentially a complex of interactive factors influences tissue flux in winter, it is proposed that the data from this study be used in conjunction with other data to construct a dynamic model to predict more reliably optimum closing date in autumn for herbage utilization in winter.  相似文献   

13.
Subtropical pastures are an important alternative to increase forage yields to fulfil cattle nutritional requirements. Despite the increasing expansion of these pastures in the semiarid subtropical region of Argentina, there is very little information about their responses to grazing management. The aim of this study was to evaluate the effect of different defoliation regimes on morphogenesis, sward structure and leaf area index of one of the most expanded forage species in this region, Chloris gayana Kunth. A combination of two defoliation frequencies (300 and 500 GDD) and two defoliation intensities (1 and 3 green stubble leaves) was compared by a controlled experiment that comprised 1,500 GDD. Defoliation frequency significantly affected leaf elongation rate (LER) and leaf area index (LAI). Under the high defoliation frequency, LER and LAI resulted almost half than under low defoliation frequency (0.34 ± 0.08 vs. 0.67 ± 0.08 mm·tiller?1·GDD?1; 8.31 ± 2.27 m2/m2 vs. 13.27 ± 1.59 m2/m2, at 300 or 500 GDD respectively), regardless of the intensity. Defoliation frequency or intensity did not affect leaf appearance rate, leaf lifespan, leaf size, number of green leaves per tiller nor tiller density at the end of the experiment. We conclude that to maintain high LER and LAI in Chloris gayana Kunth cv. Épica INTA‐Pemán pastures, defoliation frequency could be of 500 GDD. Since leaf lifespan was 415 ± 110 GDD, under this defoliation frequency, a maximum accumulation of green leaf tissues with very little dead tissues may be achieved.  相似文献   

14.
Varieties of Italian, perennial and Italian × perennial ryegrasses, tall fescue and cocksfoot were used to determine the effects of soil moisture on grass growth. Weather conditions were monitored and herbage accumulation, leaf extension rate, leaf appearance rate and tillering were recorded under natural (control), covered and irrigated treatments.
Water deficit reduced crop growth rate in the spring and drought was the major factor influencing crop growth rates in all varieties during the summer. The ryegrasses appeared most sensitive to drought, and particularly poor recovery growth was exhibited by the Italian ryegrass RvP and the hybrid ryegrass Snowdon.
Leaf extension rate and leaf appearance rate were both reduced by increasing soil water deficit. Herbage accumulation was increased by irrigation when potential soil water deficits were greater than 100 mm. When water deficits were large, irrigation increased leaf extension more than leaf appearance or tiller number. Increasing moisture deficit had a greater effect upon tiller number than on leaf extension.  相似文献   

15.
A field study was undertaken between April 2003 and May 2004 in southern Tasmania, Australia to quantify and compare changes in herbage productivity and water‐soluble carbohydrate (WSC) concentration of perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under a defoliation regime based on leaf regrowth stage. Defoliation interval was based on the time taken for two, three or four leaves per tiller to fully expand. Dry‐matter (DM) production and botanical composition were measured at every defoliation event; plant density, DM production per tiller, tiller numbers per plant and WSC concentration were measured bimonthly; and tiller initiation and death rates were monitored every 3 weeks. Species and defoliation interval had a significant effect (P < 0·05) on seasonal DM production. Prairie grass produced significantly more (P < 0·001) DM than cocksfoot and ryegrass (5·7 vs. 4·1 and 4·3 t DM ha?1 respectively). Plants defoliated at the two‐leaf stage of regrowth produced significantly less DM than plants defoliated at the three‐ and four‐leaf stages, irrespective of species. Defoliation interval had no effect on plant persistence of any species during the first year of establishment, as measured by plant density and tiller number. However, more frequent defoliation was detrimental to the productivity of all species, most likely because of decreased WSC reserves. Results from this study confirmed that to maximize rates of regrowth, the recommended defoliation interval for prairie grass and cocksfoot is the four‐leaf stage, and for perennial ryegrass between the two and three‐leaf stages.  相似文献   

16.
Oat and ryegrass intercropping in pastures is widely used in regions with subtropical climates. The aim of this study was to evaluate the tiller size/density compensation mechanisms in monoculture and intercropping swards of black oats (Avena strigosa Schreb cv. IAPAR 61) and annual ryegrass (Lolium multiflorum Lam. cv common) under intermittent grazing. Treatments (black oat, annual ryegrass and their mixture) were assigned according to a complete randomized block design with four replicates. Ryegrass, oat and intercropped pastures were grazed when the swards reached a height of 17, 25 and 23 cm, respectively, and with a level of defoliation of 40%. The aerial biomass was determined with a rising plate meter, and the tiller population density (TPD) was estimated by counting tillers in three 10 cm diameter PVC rings per paddock. The mass per tiller was estimated based on the aerial biomass and the TPD of each paddock. Total herbage production did not differ among treatments, with values around 7400 kg DM ha?1. TPD decreased and mass per tiller increased linearly in the monoculture treatments. Tiller size/density compensation was observed in the three plant communities (treatments) according to the self‐thinning rule. In addition, no relationships were found when each species was analysed individually in the intercrop treatment. The results suggest that species in grass mixed swards adjust their population to keep a relatively constant leaf area index (LAI) over the grazing seasons, and that would help pastures to stabilize herbage production.  相似文献   

17.
The field performance of the native Pappophorum vaginatum, the naturalized Eragrostis curvula and various cultivars of the introduced Achnatherum hymenoides and Leymus cinereus was evaluated as potential forage resources in rangelands of arid Argentina during the warm seasons of 2007/2008 and 2008/2009. Plants of these grass species, obtained from seeds, were transplanted to the field in 2006, when they were 1 year old. During the study years, there were two defoliation managements: plants of all study genotypes either remained undefoliated (controls) or were defoliated twice a year during spring at 5 cm stubble height. Despite tiller number being lower (P < 0·05) on defoliated than on undefoliated plants, and total leaf length per unit basal area being similar (P > 0·05) between defoliation managements by mid‐spring, there were no differences (P > 0·05) in dry weight production between defoliated and undefoliated plants in all genotypes at the end of the second growing season. Plants of one or more of the introduced genotypes showed a similar (P > 0·05) or greater (P < 0·05), but not lower, tiller number per plant and per square centimetre, daughter tiller production, total leaf length and dry weight production per unit basal area than the native species at the end of the first and/or second growing seasons. These morphological variables were similar (P > 0·05) or greater (P < 0·05) in the native than in the naturalized genotype. Plant survival, however, was lower (P < 0·05, overall mean = 20%) in the introduced than in the native (>70%) or naturalized (>39%) genotypes at the end of the first or second growing seasons.  相似文献   

18.
Rotational stocking theoretically enables regrazing of regrowth, but regrowth may be limited in xerophytic vegetation. We tested the hypothesis that regrowth would be slow and fixed in Hesperostipa comata (a caespitose, drought‐tolerant grass), while growth would be flexible in Pascopyrum smithii (a rhizomatous, less drought‐tolerant grass) under increasing defoliation and moisture, by assessing tiller growth rates, population dynamics and plant yield on marked plants in a Dry Mixed Grass prairie. Plots were clipped in late summer to simulate a deferred control, or intermittently during the growing season (May–August) at high intensity–low frequency (HILF), low intensity–high frequency (LIHF) or high intensity–high frequency and crossed with two water treatments (ambient and addition) in both a xeric upland and a mesic lowland. Growing season defoliation increased tiller growth rates of P. smithii in the upland, whereas HILF and LIHF reduced growth in the lowland. All defoliation regimes increased tiller growth for H. comata. Tiller populations of H. comata increased with frequent defoliation, while tiller populations of P. smithii decreased regardless of defoliation regime. Frequent defoliation, regardless of intensity, reduced yield relative to the deferred control for both grasses. While water addition consistently increased growth rates and reduced differences in tiller number among defoliation treatments, the regrowth of both grasses remained similar under varied defoliation with ambient moisture. High moisture conditions also promoted regrowth more in P. smithii compared to H. comata. In summary, neither grass species displayed an inherently fixed or flexible tiller or plant yield response in response to defoliation or moisture.  相似文献   

19.
Four‐species mixtures and pure stands of perennial ryegrass, tall fescue, white clover and red clover were grown in three‐cut and five‐cut systems at Ås, southern Norway, at a low fertilization rate (100 kg N ha?1 year?1). Over a three‐year experiment, we found strong positive effects of species diversity on annual dry‐matter yield and yield stability under both cutting frequencies. The overyielding in mixtures relative to pure stands was highest in the five‐cut system and in the second year. Among the possible pairwise species interaction effects contributing to the diversity effect, the grass–grass interaction was the strongest, being significant in both cutting systems and in all years. The grass–legume interactions were sometimes significant, but no significant legume–legume interaction could be detected. Competitive relationships between species varied from year to year and also between cutting systems. Estimations based on species identity effects and pair‐specific interactions suggested that the optimal proportions of red clover, white clover, perennial ryegrass and tall fescue in seed mixtures would have been around 0·1, 0·2, 0·4 and 0·3 in the three‐cut system, and 0·1, 0·3, 0·3 and 0·3 in the five‐cut system.  相似文献   

20.
Soil occupation capacity via lateral expansion of tussocks in elephant grass (Pennisetum purpureum Schum.) may be associated with basal tillering. As grazing management alters the proportion of basal and aerial tillers in a tiller population, the hypothesis of this work was that grazing management affects tussock size and distribution with implications for plant population stability. The objective of this study was to evaluate the tiller population stability index, the proportion of basal and aerial tillers, tussock size, and the frequency of tussocks and bare ground in rotationally managed elephant grass cv. Napier. Treatments resulted from the combination of two post‐grazing heights (35 and 45 cm) and two pre‐grazing conditions (95% and maximum canopy light interception during regrowth – LI0·95 and LIMax) and were allocated to experimental units (850 m2 paddocks) according to a 2 × 2 factorial arrangement in a randomized complete block design, with four replications. Measurements were taken from January 2011 to April 2012. The post‐grazing height treatments affected the tiller population stability index, but did not influence the pattern of tussock distribution. On the other hand, the different grazing frequencies (targets of LI pre‐grazing) altered the pattern of tussock distribution and the proportion of bare ground. In general, the tiller population stability index and frequency of tussocks were higher and the frequency of bare ground lower on swards managed with the LI0·95 target relative to those managed with the LIMax target, regardless of the post‐grazing height used, indicating a larger soil occupation capacity of plants under the more frequent defoliation regime. Such responses were associated with larger population of basal tillers and highlight the importance of tiller category and perennation pathway in defining patterns of plant growth and tussock distribution.  相似文献   

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