Rhizome Mass Research Articles

The ecology and conservation of the Killarney Fern Trichomanes speciosum willd. In Britain and Ireland

Trichomanes speciosum Willd. (Hymenophyllaceae) is one of the rarest and most celebrated species in the British and Irish vascular flora. The ecology and habitats of 43 colonies of the sporophyte (fern plant) generation are described. Two-way indicator species analysis suggests that T. speciosum occurs in four main floristic groups; in very deeply shaded habitats; in large dripping caves; in crevices in cliffs and small caves; and on dripping vertical cliffs and rocky banks in wooded ravines. Canonical correspondence analysis shows that altitude and habitat types are the major environmental variables influencing the floristic composition of the 43 colonies. Monitoring data suggest that frond number remains remarkably constant over 13–29 years. Possible reasons for the absence of T. speciosum in so many apparently suitable habitats in western Britain and Ireland are discussed. Sporophyte establishment appears to be most critical, especially under a climate that is marginal for its temperature requirements. The distribution pattern of T. speciosum and its ability to colonise man-made habitats in northern France but not in Britain or Ireland suggest that some factor associated with temperature may be limiting. As each colony may consist of one or two individual plants with many fronds arising from the rhizome mass, there are only about 50–100 plants of the sporophyte generation known in Britain and Ireland. There is thus a need to protect all remaining colonies in the British Isles from interference, especially collecting and habitat alteration. Extreme discretion with information about localities is essential. Translocation and re-stocking in the wild are only considered appropriate in special circumstances.

Rhizome Characteristics and Canopy Light Interception of Grazed Rhizoma Peanut Pastures

Abstract‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.) is a promising pasture legume for warm climates. In 1988 and 1989, the effect of grazing management on rhizoma peanut canopy light interception (LI) and the role of rhizome reserves in regrowth were studied on a Sparr fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudults). Treatments were replicated twice and included all combinations of three levels of residual dry matter (RDM; 500, 1500, and 2500 kg ha−1) and four grazing cycle lengths (GC; 7, 21, 42, and 63 d between grazings, including a 0.5 to 2‐d grazing period). Data were analyzed by fitting multiple regression equations starting with a second order polynomial model. Canopy LI before grazing ranged from 24 to more than 90% and was lowest for low RDM and short GC treatments, while canopy LI after grazing ranged from 9 to 79% and increased at a decreasing rate as RDM increased. When grazed to 500, 1500, and 2500 kg ha−1, RP required an average of 49, 24, and 12 d to reach 85% LI. At season‐end 1989, rhizome mass (range of 450‐4100 kg ha−1) and total nonstructural carbohydrate (TNC; range of 58‐210 g kg−) concentration were lowest at low RDM and short GC, increased with increasing GC when RDM was low, and changed only slightly with changes in GC at RDM above 1700 kg ha−1. Low postgraze light interception and depletion of rhizome mass and total nonstructural carbohydrate with close grazing suggest that reserves were mobilized for rhizoma peanut regrowth. In contrast, postgraze light interception and rhizome mass and reserve status remained high when residual dry matter was 1700 kg ha−1 or greater suggesting that residual leaf area was primarily responsible for regrowth under more lenient grazing.

Growth Analysis of ‘Florigraze’ Rhizoma Peanut: Shoot and Rhizome Dry Matter Production

Abstract‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.) is a perennial tropical forage legume grown in Florida and the southern Gulf Coast. It is vegetatively propagated with rhizomes and regrows from rhizomes in the spring following winter frost‐kill, but little is known about its growth and development. Two studies were conduced near Gainesville, FL, on Arredondo loamy sands (loamy, siliceous, hyperthermic Grossarenic Paleudults) in 1980 and 1981 to characterize aerial and underground growth of Florigraze. The establishment‐year study used spaced‐planted hills (three to five rhizomes per hill) in 1980 and 1981. The defoliation‐frequency study (undefoliated vs. defoliated every 2, 6, or 8 wk) was conducted in 1981 on plants (hills) that were undisturbed at the 1980 site. Entire hills were dug every 3 to 8 wk, and separated into shoots and primary and secondary rhizomes. In the establishment year, accumulated dry matter (DM) of shoots and rhizomes increased until September, when shoot growth plateaued or declined while rhizome growth continued. During cooler autumn months, photosynthate produced in shoots was partitioned into rhizome growth. Secondary rhizomes (smaller non‐branched rhizomes) constituted the bulk of rhizome mass. Shoot/rhizome ratios increased from zero at planting to about 1.5 to 2 by late summer, then declined to about 0.5 in autumn. Defoliation treatments decreased rhizome DM production by one‐half (8 wk) to two‐thirds (2 and 6 wk) that of the undefoliated control. Our results indicate that defoliation should be avoided for establishing plants and plants that will be used as a source of rhizomes for propagation.

Seed Size and Number in Rubus Chamaemorus: Between-Habitat Variation, and Effects of Defoliation and Supplemental Pollination

This study examines the within- and between-population variation in components of yield in R. chamaemorus. Specifically, it addresses the following questions: are there any consistent differences in seed size or total allocation to seeds between populations of open and shaded habitats? Is seed size negatively correlated with yield components like seed number, number of seeds per unit leaf mass, or number of seeds per unit rhizome mass? How do supplemental pollination and defoliation affect seed number and size?

Response of Solidago canadensis clones to competition

Transplants of ten Solidago canadensis clones were grown under high and low competition in the field to determine whether clones differed in survival, growth, and reproduction under natural conditions. Transplants had higher probability of survival and flowering and were larger in all measures of size when competition was experimentally reduced. Clones differed in almost all these measures of success, but only when variance among transplants within clones was reduced by excluding transplants that experienced heavy herbivore damage. Differences among clones were more apparent under low competition than under high competition, despite higher coefficients of variation within clones under low competition. Adjusting transplant size for initial size (parent ramet rhizome mass) did not change these results, although clones did differ in parent rhizome mass. All of these results suggest that there is little potential for selection to discriminate among these clones. Despite the strong differences in transplant performance between the competition treatments and among clones, the clones did not differ in competitive ability-almost none of the clone x competition interactions were significant. In addition, the measures of success of each clone were usually positively correlated between the high and low competition treatments, suggesting there were no tradeoffs between performance under high and low competition for these clones.

Effects of canopy light gap and early emergence on the growth and reproduction of Geranium maculatum

Biomass and reproduction of Geranium maculatum L. were measured in an artificial canopy light gap and under a closed canopy. The effects of emergence date were also compared. Increased light in the canopy gap resulted in increased biomass, rhizome mass, and percent of plants flowering in the second growing season after gap formation. The importance of proximate carbon in reducing fruit abortion was determined experimentally. The rate of fruit abortion increased and the number of days required for leaf expansion decreased when the plants were shaded by neutral screens. The reproductive effort of G. maculatum is thus primarily controlled by the previous year's carbon gain, while the proportion of flowers that matured to seeds was a function of proximate carbon gain. Shoots of G. maculatum emerged over a period of approximately 6 weeks in early spring, with canopy closure occurring midway through this interval. Early emergence of plants under the intact canopy permitted exploitation of the increased light levels in the period prior to canopy closure. This led to slightly increased aboveground growth and rhizome storage and a significant increase in the time spent in leaf expansion, though no differences in reproductive output existed between early and later emerging plants. Early emergence was less advantageous for gap plants. The role of gap-phase growth in G. maculatum is in increased genetic recombination and dispersal during this short period when the balance of sexual versus asexual reproduction is altered.

Root and rhizome distribution as an indicator of upper salt marsh wetland limits

Four wetland plant species, Deschampsia cespitosa, Distichlis spicata, Grindelia integrifolia, and Salicornia virginica, were tested to determine the effect of soil moisture on the vertical distribution of roots and rhizomes. In an 8-month greenhouse experiment involving plants grown from seeds and rhizomes the occurrence of more than 65% of the root and rhizome mass in the upper 10 cm of soil was indicative of saturated conditions. Roots and rhizomes were more evenly distributed under field capacity and low moisture conditions. The percent of total root and rhizome biomass in the upper 10 cm of a 35 cm core may be useful in determining whether or not a plant is experiencing saturated soil conditions, a criterion often used for defining wetlands. Limited field studies support the conclusion of the greenhouse study.