Dead Stem Research Articles

Effects of sward structure on the diet selected by guanacos (Lama guanicoe) and sheep (Ovis aries) grazing a perennial ryegrass‐dominated sward

The effect of three different vertical structures of a perennial ryegrass‐dominated sward, defined by pseudostem heights (cm) — 1·3 low (L), 2·5 medium (M) and 3·5 high (H) — on the bite depth and selection of plant parts within the grazed horizon of the sward by sheep and guanacos was studied. The bite depth (cm) was similar between sheep and guanacos across the different swards (L, 1·5; M, 3·6; H, 3·8) and was related to pre‐grazing sward surface height rather than to pseudostem height. There were differences in diet composition between species that were related to differences in selection for plant parts. Sheep had a higher proportion of green leaf in the diet than did guanacos in L (0·84 vs. 0·71, P < 0·05) and M (0·75 vs. 0·59, P < 0·05) swards, and possibly selected this plant part in H swards in which the proportion of green leaf in the grazed horizon was low (0·45–0·50). Guanacos had a higher proportion of dead leaf and sheath in the diet than did sheep in L (0·23 vs. 0·09, P < 0·05) and M (0·30 vs. 0·18, P < 0·05) swards, and possibly selected this plant part on these swards, in which the proportion of green leaf in the grazed horizon was high (0·70–0·95). The proportion of pseudostem in the diet of sheep and guanacos was similar across all swards (0·03) and was generally much lower than that in the grazed horizon (0·01–0·18). Guanacos had a higher proportion of dead stem in the diet than did sheep (0·06 vs. 0·02, P < 0·05) across all swards, but the proportion was similar to that in the grazed horizon of each sward.

Increasing Utilization Efficiency of Continuously Stocked Old World Bluestem Pasture

The objective of this 2 year study was to identify the optimal height to graze Old World bluestem pasture in the Southern Great Plains under continuous stocking during the growing season. We hypothesized that intensely grazing Old World bluestem pasture would increase utilization efficiency by increasing the proportion of live leaf in the pasture, enhance forage quality and animal performance, and animal performance and root biomass would decline if grazing intensity was beyond an optimal level. Pastures were maintained at 3 levels of standing crop using continuous variable stocking. Stock adjustments were made weekly. A disc meter was used to maintain pasture disc heights of short (35-40 mm), medium (41-45 mm), and tall (46-55 mm) levels. Average standing crops of short, medium, and tall pastures were 1,500, 1,900, and 2,400 kg ha-1, respectively. On the short pasture treatments the proportion of leaf and live stem was higher (P 0.05) in crude protein of forage between treatments during the vegetative growth phase in spring when forage nitrogen levels were fairly high (> 13%). When the grass began to produce reproductive organs and when forage nitrogen levels were lower (< 1.3%), forage crude protein was greater in the short pastures (P < 0.05). Individual animal performance was greater on the tall than on the short pastures (P < 0.10) over all dates. Individual animal performance was greatest when management maximized the proportion of leaf and live stem while minimizing dead stem. Animal performance per hectare was slightly higher on the short and medium height pastures. Both the short and medium height pastures had approximately 70% the root biomass of the tall pastures (P < 0.01) at the end of the trial. These results indicate that intense continuous variable stocking of Old World bluestem increases the utilization efficiency, but increases animal production per hectare only marginally, and reduces root biomass to an extent that production may not be sustained from year to year.

Formation and closure of canopy gaps in the rain forest at Nouragues, French Guiana

Formation and closure of canopy gaps was monitored for three years in 12 ha of primary rain forest at Nouragues, French Guiana. At the first inventory, in April 1991, 74 openings in the canopy > 4 m2 (sensu Brokaw 1982a) were located; 60 of these gaps were formed before January 1990. Between January 1990 and December 1993, 5 to 15 gaps were annually formed, opening 0.64–1.33% of the forest canopy each year. Of all gaps, 41% were created by a falling, snapped tree, 34% by a falling, uprooted tree, 22% by a falling branch, and 3% by a falling dead stem. A refined nearest neighbour analysis showed that gaps formed after January 1990 were clustered: uprooting of trees seemed to be related to shallow soils, and relatively many other trees fell when a tree uprooted, independent of the dbh of the uprooted tree. In 37 gaps, canopy openness in the gap centre (determined by hemispherical photographs) was monitored over three years. In 54% of the gaps, canopy openness increased in two successive years. It is reasoned that edges of especially large gaps may frequently be re-disturbed by falling trees or branches. Results suggest that gaps have closed after around 15 years. More data are needed to verify this.

Habitat Characteristics of American Woodcock Nest Sites on a Managed Area in Maine

We measured characteristics of habitat near 89 nests of American woodcock (Scolopax minor) and 100 randomly selected points on Moosehorn National Wildlife Refuge, Calais, Maine, an area managed for woodcock. At nest sites, basal area was lower (P 0.05) or between sites of successful nests and nests destroyed by predators, although the large variances of the variables reduced our power to detect differences. Habitat around sites of renests differed from sites of first nests. Sites around first nests had lower basal area of dead trees (P = 0.05) and higher stem densities of aspen (P = 0.03) and cherry saplings (Prunus spp.) (P = 0.001), and viburnum (Viburnum spp.) (P = 0.05), while renest sites had taller trees (P = 0.02). The change from nest sites in areas dominated by alders and tree-size gray birch used in 1977-80 to sites dominated by sapling trees, especially aspen, used during 1987-90 suggests that woodcock in the expanding population at the refuge are selecting nest sites created by habitat management since 1979.

Development of a Populus Balsamifera Clone in Subarctic Quebec Reconstructed from Spatial Analyses

1 The age, diameter and position of all living (n = 750) and dead (n = 286) stems of a northern clone of Populus balsamifera were recorded to study spatial dispersion patterns and to reconstruct clonal development. Position, age and diameter of all Picea spp. stems found within the study area were also recorded. Spatial autocorrelation analyses were performed on the data using age and diameter as variables. 2 Results from spatial analyses suggest that P. balsamifera stems could be classified into three age groups, each one with a distinct spatial pattern: younger stems ( 40 years old) also show significant anisotropy in a south-easterly direction, but only for the first distance class (i.e. 0-7.2 m); and middle-aged individuals (20-39 years old) have no significant isoor anisotropic pattern. Results from partial Mantel tests comparing the spatial occupation of the site by stems from the three age groups suggest that the clone developed in three phases 15-20 years apart: a first phase of postfire colonization, a second of consolidation, and a more recent one of directional expansion. The physical environment (e.g. elevation) and the presence of potentially competing shrubs are factors which probably have limited and may possibly still restrict clonal expansion. 3 There were numerous dead stems < 5 cm in diameter and these were contagiously dispersed; mortality was density-dependent for these individuals, as suggested by the positive correlation between live and dead stem numbers. The most likely densitydependent mechanism involved here is intracohort competition. The presence of Picea spp. does not appear to have significantly affected P. balsamifera mortality, but it may have limited clonal expansion (i.e. ramet birth). 4 The clone studied may still be in a phase of growth and of further expansion as evidenced by the large number of new suckers produced at the edge of the area already occupied. Invasion of the clone by the more shade-tolerant Picea spp. could occur in the future, if there is no disturbance (e.g. by fire), but the recent low recruitment of Picea spp. and the production of new Populus suckers where older stems have died in the central part of the clone suggest that this is unlikely.

The nutritive value of wheat and oat silages ensiled on three cutting dates

SUMMARYThe production of biomass and its partitioning into stem, leaf, ear and dead material were monitored weekly in crops of wheat and oats from 16 May 1990, which corresponded approximately to ear emergence in the wheat, until ensilage on 29 June, 7 July and 19 July 1990 using the Ag-Bag system. An enzyme/inoculant additive was used on both crops on each ensilage date, although a portion of oats was ensiled without additive on the first two cutting dates, giving a total of eight silages. Changes in rumen degradability of dry matter were assessed for both crops throughout the monitoring period using the synthetic fibre bag technique. The digestibilities of gross energy, modified acid detergent fibre, organic matter and crude protein were determined in vivo using sheep.Over the total period of monitoring, the daily rates of increase in dry matter (DM) yield were 15·1 (± 1·6) and 16·5 (±1·9) g DM/m2 for wheat and oats respectively. From 29 June to 19 July the rates of increase were 11·3 (± 3·1) and 23·1 (±6·0) g DM/m2. The increase in weight of the ears accounted for almost all of this increase and, by the end of the monitoring period, the ears contributed approximately half of the dry matter of each crop. In both crops the portion of dead material was small until 19 July, when there was a rapid increase in the amount of dead stem. The DM content of both crops remained &lt; 30% up to day 33 (18 June) but increased from c. 33% to c. 52% between days 53 and 65 (8–20 July). Rumen degradability of both crops decreased rapidly from c. 66% on 16 May until 16 June, when it was c. 56% for wheat and 55% for oats; it remained constant at these values thereafter.For silages made on the three successive ensilage dates, there was an increase in DM and starch contents but decreases in digestible energy, digestible fibre and digestible crude protein contents. Digestible organic matter was similar for the first two ensilage dates but lower in silage made on the third date.The use of an additive with the oat crop resulted in decreases in the digestible energy, digestible organic matter and digestible crude protein contents of the silages compared with untreated oats.Maximum yield of DM from wheat (18·6 t/ha) was obtained with the third cutting date, but optimum yield of energy (170 GJ/ha) and digestible crude protein (746 kg/ha) were found at the second cutting date. For oats, maximum yield of DM (17·3 t/ha) was again found with the third cut and maximum yield of energy (159 GJ/ha, untreated; 140 GJ/ha with additive) with the second cut. Digestible crude protein yield was greatest with the second cut of oats when no additive was used (708 kg/ha) but with additive it was greatest with the first cut (661 kg/ha).It was concluded that, under these conditions, the optimum date for ensilage of wheat or oats was 7 July and that the use of the additive was detrimental to the quality of the oat silage.

A forage dynamics model for use in range or pasture environments

AbstractA deterministic model that simulates forage dynamics is described and validation results presented. The model simulates different species of grasses and forbs for a production year and provides the necessary input for a diet selection model. The model does not simulate growth, but does simulate the accumulation of live leaf and stem, the senescence of live biomass, and its transfer to dead mass using growth rates for leaf and stem of each species, which are specified for the model. Using such an approach specific types of years can be simulated. Plant components in the model include live leaf and stem, dead leaf and stem, and old dead leaf and stem which were produced during the previous growing season. These plant components were chosen because of their importance in the diet selection process and their differences in forage quality. Plant species which the model was validated against were Cynodon dactylon, Avena sativa. Schizachyrium scoparium and Paspalum plicatulum. Validation results indicated that with adjustment to input growth rates, live biomass could be adequately simulated. Deviations between measured and simulated dead components were observed for S. scopariumand P. plicatulum.High values observed for dead stem early in the trial resulted from lack of separation of dead and old dead stem material in the field sampling. Variations in dead forage throughout the season were caused by unexplained sources of variation. This indicated a need for field research to better quantify the dynamics of dead biomass. The model meets its goal of simulating biomass dynamics and forage quality of plant parts and it provides a suitable forage base to interface with diet selection and animal simulation models.

Growth and turnover of microbial biomass during the decomposition of organic matter (Polygonum cuspidatum) in vitro

AbstractAir‐dried fresh and dead specimens of Polygonum cuspidatum were incubated for 250 days in the laboratory, and the growth and turnover of microbial biomass‐C in the organic matter were studied. The biomass‐C in the fresh leaf and fresh stem attained maximum levels on day 14 and day 7, respectively, and then settled down to stable levels. In the dead leaf and dead stem, increase in biomass‐C ceased by day 4 and the biomass‐C levels did not change thereafter. The turnover time of the biomass‐C was estimated from the amount of biomass‐C and the release rate of CO2‐C. The turnover was rapid in the early period of incubation. Then the turnover time became longer and after incubation for 70 days the values approached those in natural soils (longer than 16 days). During the incubation period, nitrogen was not mineralized in any organic matter. In the dead leaf and dead stem, asymbiotic nitrogen fixation activity increased after incubation for about 40 days and disappeared by the end of the incubation period, whereas nitrogen fixation was hardly detected in the fresh leaf and fresh stem.

Some consequences of imposing different continuous grazing pressures in the spring on sward morphology, herbage quality and the performance of young beef cattle

SUMMARYThe effects of different severities of continuous grazing imposed during the spring followed by a uniform continuous grazing management from midsummer onwards were examined in relation to sward morphology, herbage quality and the performance of young beef cattle in the years 1980 and 1981. The three grazing severities were based upon maintaining a constant sward height, namely 35 mm (severe), 50 mm (moderate) and 75 mm (lenient). From 1 June onwards a uniform grazing severity with a sward height of 60 mm was imposed. The grazing pressure on each paddock was adjusted by either adding or removing of cattle to maintain the target sward heights. When the grazing pressure was changed in June, the digestibility of both the herbage components on offer and the total herbage selected by the cattle was higher in the swards that had been severely grazed than that in the leniently grazed treatments. This appeared to be due to the combination of a higher proportion of younger, more digestible leaf laminae, less dead and less maturing true stem being present in the swards that had previously been severely grazed. Over the season as a whole, there was no significant difference between the grazing treatments in terms of individual animal performance or overall animal live-weight production per hectare.

Influence of season and weather factors on the occurrence of the sorghum stem borerChilo partellus(Swinhoe) in Tamil Nadu

Abstract Stem borer attack varied significantly on sorghum sown during different fortnights, ranging from 4.7 to 24.0% and 9.5 to 37.4% at 30 and 45 days after sowing (d.a.s.) respectively. The crop sown during the first fortnight of March was highest, followed by that sown in the second fortnight of February, in terms of stem borer damaged plants, damage rating, percentage dead hearts and percentage stem tunnelling. The least damage was in the crops shown during the second fortnight of June and of October. There was an indication that for every 1°C reduction in minimum temperature, there was a decrease of 1.69% stem borer damage at 30 d.a.s. At 45 d.a.s. none of the weather elements significantly contributed to the damage. During the summer the duration of egg to adult period of C. partellus on sorghum was significantly shorter at 39.48 days than in winter when it was 56.5 days. Double the rate of fecundity and higher fertility rate was also observed in summer.

Seasonal variations in the herbage mass, crude protein and in-vitro digestibility of native perennial grasses on the north-west slopes of New South Wales.

Seasonal variations in herbage mass, crude protein content and in-vitro organic matter digestibility of both the warm-season (summer-growing) native perennial grasses, Aristida mrnosa R.Br., Bothriochloa macra (Steud) S.T. Blake, Dichanthium sericeum R.Br. (Camus), Sporobolus elongatus RBI., Chloris truncata R.Br. and Eragrostis leptostachya Steud, and the year-long-green perennial grasses Stipa variabilis Hughes and Danthonia linkii Kunth were investigated at three sites on the North-West Slopes of New South Wales. These preliminary data were used to assess the relative grazing value of the dominant grasses in the region, although these initial rankings can only be confirmed by diet selection and animal production studies. The eight grasses tested were classified into three groups with respect to their green leaf mass per unit basal area throughout the year: (i) Aristida ramosa, Bothriochloa macra, Dichanthium sericeum and Sporobolus elongatus had low amounts of green leaf in winter and their green leaf mass in summer was related to rainfall. (ii) Chloris truncata and Eragrostis leptostachya showed considerably less seasonal variation in the amount of green leaf and had a higher percentage of green leaf than (i). (iii) Stipa variabilis and Danthonia linkii had the lowest variation in green leaf, and in winter and spring they generally had higher green leaf masses than the other groups. Among the warm-season and year-long-green grasses the green leaf crude protein content varied between 5 and 15% throughout summer and autumn and from 6 to 17% in winter and spring. In all seasons dead leaf crude protein contents were around 5% and dead stem crude protein contents were consistently less than 6%. Irrespective of species the digestibilities of the green leaf portions were higher in spring and summer (60 to 80%) than in autumn and winter (50 to 60%). At each of the ~ites the digestibility ofDanthonia linkii green leaf material was generally higher than 60% in all seasons, but that ofStipa variabilis green leaf was always less than 60%. Estimates of green stem digestibility ranged from as low as 25% for Avistida ramosa in autumn to around 60% for most other species in spring. Digestibilities of dead leaf ranged from 30 to 55%, those of dead stem ranged from 20 to 40%. These results indicate that Danthonia linkii is potentially valuable for grazing and that Aristida ramosa is an undesirable pasture species. Of the other grasses tested Chloris truncata and Eragrostis leptostachya may produce some green forage in autumn and winter but at these times the green forage production of Aristida ramosa, Bothriochloa macra, Dichanthium sericeum and Sporobolus elon- gatus is limited by low temperatures.

Growth Dynamics of Cordgrass, Spartina alterniflora Loisel., on Control and Sewage Sludge Fertilized Plots in a Georgia Salt Marsh

Seasonal plant growth dynamics were followed for a year in undisturbed plots of tall and short formSpartina alterniflora Loisel. and in plots of short formS. alterniflora which were enriched with sewage sludge at a rate of 100 g dry sludge m−2wk−1, corresponding to a nitrogen enrichment of 2 g N m−2wk−1. Monthly determinations of aboveground live and dead biomass, density of live stems, the ratio of number of young shoots to total number of shoots, and belowground mass of macro-organic matter to a depth of 30 cm were made for each area. Sludge fertilization increased the live biomass of the short formS. alterniflora by up to 150% of the control live biomass, but had little effect on the dead biomass, stem density, or proportion of young shoots. There was a trend of increased amount of belowground macro-organic matter in fertilized compared to control plots during the last 6 months of the study. In all areas, there was a marked decrease in the proportion of young shoots from winter to early summer, followed by a rapid increase in the percent of young shoots from late summer to fall. Sampling of plots 7 and 20 months after termination of sludge enrichment showed higher plant biomass and % N content in surface soils, but no difference in N content of live plant tissue, in fertilized compared to unfertilized marsh. After 20 months, about half of the sludge nitrogen remaining in the soils of the fertilized plots had disappeared.

日本産シャクナゲ&amp;lsquo;オオバシャクナゲ&amp;rsquo;の不定根形成に関する研究

Some methods of cutting in a propagation house equipped with intermittent mist and the effect of auxin treatments on rooting were investigated from 1973 to 1977, using as the mature stock plants R. metternichii var. hondoense growing in the mountains of Gifu prefecture.Stem cuttings were taken from 10 to 20 year old plants in the middle of July after the current shoot elongation had ceased. The period of cutting extended over four months.1. As a propagation bed soil for cuttings, a medium consisting of 7/10 Kanuma- tsuchi and 3/10 peatmoss or akadama-tsuchi were more suitable for rooting than Kanuma-tsuchi alone. Both a medium consisting of 7/10 Kanuma-tsuchi and 3/10 coarse sand, and a common field soil were inferior, and a medium consisting of 7/10 Kanuma-tsuchi and 3/10 chopped sphagnum was the most inferior for cuttings because a lot of dead stem cuttings occured. The physical conditions of the bed soils, investigated at the end of the experiment, had little difference among them, but it was judged that the medium of Kanuma-tsuchi and peatmoss was higher in water holding capacity than the Kanuma-tsuchi alone.2. Many more two year old branch cuttings rooted than current shoot cuttings, but current shoot cuttings rooted to the same degree in some cases; therefore, the influence of the stem cuttings′ age on rooting could not be made clear.No influence on rooting of different leaf areas among 3, 5 or 7 leaves per stem cutting was found. Within the limits of five leaves per stem cutting, restriction of leaf area due to cutting off half of each blade had no effect on increased rooting.3. In regard to the effect on rooting of auxin treatment at the base of stem cuttings, IBA had little or no effect, but NAAm was effective. Dipping stem cuttings into 35°C hot water or 2% ethanol as a pre-treatment was not injurious to their growth, and the former effectively increasing the rooting compared with non pretreated stem cuttings.4. First most of the stem cuttings began the callus formation at their cut surface 10 to 30 days after the beginning of cutting, and then they began the root differentiation 30 to 60 days after. Water content in the leaves of stem cuttings reduced continuously with the beginning of cutting, but it became constant after 60 days. Dry matter content in the leaves of stem cuttings reduced temporarily when they formed a callus and after that recovered slowly, and such stem cuttings survived although they still did not root.5. The highest percentage, of rooting, 65%, was obtained from only 2 year old branch cuttings from which the current shoot had been removed, and which were treated with NAAm and placed in bed soil consisting of Kanuma-tsuchi and peatmoss. This effectiveness may result from having removed the terminal bud, which contains the developing flower bud.The better cutting results in this experiment were obtained by rooting a current shoot cutting into bed soil consisting of Kanuma-tsuchi and peatmoss, and a two year old branch cutting into bed soil consisting of Kanuma-tsuchi and akadama- tsuchi. The ratio of rooted cuttings in these cases was 53% and 48%, respectively.Although these results may be unsatisfactory in view of practice, the callus formation was vigorous in the case of the cuttings which did not root. Therefore, an increase of rooting could be expected if physiological factors of stem cuttings in relation to rooting could be made clear, and a cutting method and its environmental condition could be improved.

Defect development in second-growth sugar maple in Ontario. I. Microfloral infection relationships associated with dead branches

From 293 second-growth sugar maple (Acer saccharum Marsh.) trees (maximum age 114 years) felled in Ontario, 966 branch stubs, 70 intact dead branches, and 58 stem stubs were dissected and studied. Microfloral associations, examined and related to many tree and wound characteristics with computer assistance, show a progressive pattern of invasion, spread, colonization, and replacement within dead branches, stubs, and adjacent stem wood tissue. A unique, limited fungal microflora colonizes dead branches and one of these fungi, Nodulisporium sp. 5, appears instrumental in the early self-pruning habit of sugar maple. All but 25 of the 80 organisms or organism groups isolated from stubs occurred rarely, and these were mainly near the exposed stub ends. Most organisms seem incapable of prolonged existence there, or of much penetration into the stub. Most stub fungi lose viability once the stubs are healed over, particularly those associated with decay pockets near the exposed ends. These include the two most frequently isolated fungi, Rhinocladiella sp. A and Stachybotrys atra Corda, whose occurrence in sugar maple trees is virtually limited to branch stubs. Only bacteria and four of the fungi that invade branch stubs appeared capable of appreciable spread and development after complete stub healing; these organisms generally dominate the resident microflora encountered in the stained core of living sugar maple trees. Evidence indicates that the stain present in many of the stubs, often extending into the main stem, is principally physiological in origin, but its development is enhanced by the presence of certain microorganisms. Decay was far less common, seldom reaching the main stem; evidence suggests most stub decay is caused by Corticium vellereum Ell. &amp; Cragin, a Basidiomycete isolated from, but reportedly incapable of causing, stem decay in mature maple.

On Robillarda phragmitis sp.nov.

Robillarda phragmitis sp.nov. isolated from a submerged dead stem of Phragmites communis Trin. is described and illustrated with particular reference to the development of the spore and its appendage. Behaviour of single spore isolates on agar media and on sterilized pieces of Phragmites stems and Carex leaves is briefly noted.

On the frost damage of wheat plants occured at Tokorozawa district, Saitama prefecture in 1955

In this paper, investigation on the frost damage of wheat plants which was found in Saitama Prefecture in April, 1955 is reported.The results of the investigation are as follows; -(1) This damage was found to be quite different from the frost damage which usually occurs in the North Kanto region. The latter causes death of young ears by frozen in wheat of high degree winter type. However, in the damage which we concern now, the death of young ears by frozen takes place in wheat of low degree winter type, and also the formation of ears on the lately developed tillers which usually are incapable of bearing, and the delaying of heading time were characteristic.(2) The death of young ears was caused by the low temperature (-2.4C) on the 5th of April. Ratio of dead (frozen) stem number to the all stems was estimated on the field and which was 68.3% in the severely damaged field, 48.1% in the intermediately damaged field, and 23.3% in the lightly damaged field.Such a difference in the damage was considered very likely as caused by the difference in the growth and developmental stage of the plants.(3) As the result of the damage, the growth of the suffered plants was changed. The change was apparently recognized with the number of lately formed stems, the stem length, the stem diameter and the heading time, etc. High correlation was found between the degree of damage and the changing of the above-mentioned morphological characters, as well as between each of these characters.(4) Effect of the damage of the yield of wheat was analyzed. The effect was apparently recognized in the decrease of complete grains, thus lowering the ratio of the complete grains to the whole, and also in the increase of quantity of incomplete grains and in the decrease of 1000 grains weight, etc. Actual decrease in yield was not found in the slightly damaged field, but decrease of about 30% and 70% in yield was found in the intermediately suffered and severely suffered field respectively. These defferences in the yield may be accounted for by the fact that the lately developed stems were capable of producing grains in compensation the decrease and this compensation differs with the defferent field.(5) Therefore it is likely possible to estimate the decreased amount of yield of wheat caused by the frost damage by the productivity of the lately developed stems action as a compensating factor.Significant correlations were found between the productivity and the number of days which the heading was delayed, length of stems, or diameter of stems, etc.