Belowground Root Research Articles

Defining competition vectors in a temperate alley cropping system in the midwestern USA; 3. Competition for nitrogen and litter decomposition dynamics.

An experiment was conducted in an 11-year-old black walnut (Juglans nigra L.), red oak (Quercus rubra L.), maize (Zea mays L.) alley cropping system in the midwestern USA to examine the extent of tree-crop competition for nitrogen and decomposition dynamics of tree leaves and fine roots. A below-ground polyethylene root barrier (1.2 m deep) isolated black walnut roots from maize alleys in half the number of plots providing two treatments viz. ‘barrier’ and ‘no barrier’. The percentage of N derived from fertilizer (%NDF) and fertilizer use efficiency (%UFN) were determined using 15N enriched fertilizer. Further, maize grain and stover biomass, tree leaf biomass, tissue N concentration, and N content were quantified in both treatments. The ‘barrier’ treatment resulted in a significantly greater grain (67.3% more) and stover (37.2% more) biomass than the ‘no barrier’ treatment. The %NDF in both grain and stover was higher in the ‘no barrier’ treatment as a result of competition from tree roots for water and mineralized N in soil. Maize plants growing in the ‘no barrier’ treatment had a lower %UFN than those in the ‘barrier’ treatment due to their smaller size and inability to take up fertilizer. Analysis of tree leaf and fine root decomposition patterns revealed faster release of N (39% over 15 days for black walnut and 17.7% for red oak) and P (30% over 15 days for both species) from roots compared to the leaves of both species. Following an early release of P (11.3% over 45 days), red oak leaves exhibited significant immobilization for the rest of the incubation period. The data indicate that competition for N from fertilizer is minimal since nutrient acquisition is not simultaneous among black walnut and maize. However, competition for mineralized N in soil can exist between black walnut and maize depending on water availability and competition. Tree leaves and fine roots can enhance soil nutrient pools through the addition of soil carbon and nutrients. Tree fine roots seem to play a more significant role in nutrient cycling within the alley cropping system because of their faster release of both N and P as compared to leaves. Selection of tree species and their phenology will impact the magnitude and rate of nutrient cycling.

Defining competition vectors in a temperate alley cropping system in the midwestern USA: 2. Competition for water

A study was carried out in an alley cropping system in the Eastern Maize Belt of the United States with the objective of quantifying the competition for water between trees (black walnut (Juglans nigra L.) and red oak (Quercus rubra L.) and maize (Zea mays L.). Spatial and temporal variation in soil moisture, tree and maize rooting patterns, tree and maize water uptake, and maize leaf area expansion were determined in three treatments; ‘barrier’ (polyethylene root barriers separating maize and tree roots), ‘trench’ (trenching without a polyethylene barrier), and ‘no barrier’ (control). Significant temporal variation in soil moisture was observed in both black walnut and red oak alley cropping systems. The ‘barrier’ and ‘trench’ treatments resulted in higher soil moisture in the ‘maize alley’ and lower soil moisture in the ‘tree row’ than the ‘no barrier’ treatment. Uptake of water by maize was higher in the ‘barrier’ than the ‘no barrier’ treatment. However, tree water uptake was higher in the ‘no barrier’ treatment than in the ‘barrier’ treatment because tree roots utilized water from the ‘maize alley’. Maize leaf area was negatively impacted by water stress in the ‘no barrier’ treatment. Quantification of rooting patterns revealed that maize and tree roots were concentrated in the top 30 cm soil layer where water fluctuations were greatest. The ‘barrier’ and ‘trench’ treatments successfully eliminated the belowground root competition between trees and maize and resulted in greater leaf area and higher grain yields than the ‘no barrier’ treatment. Thus, competition for water rather than competition for light seems to be critical in defining the productivity and sustainability of this alley cropping system.

Quantification of stability improvement of a dump through biological reclamation

An integrated study on biological stabilisation of a dump slope has indicated that biological reclamation with grass and tree species should be considered for long term stability of this coal mine dump in India. The grasses have greater soil binding capacity and help to control soil erosion and improve dump stability. Native grasses such as Bamboo (Dendrocalmus strictus) and Kashi (Saccharum spontaneum) are the important constituents of grass species which can stabilise the dump slopes. Field observation of growth performance of grasses have indicated that mean grass height, root depth and below-ground root biomass are 185 cm (±68), 45 cm (±5) and 467 g m−2 (±170), respectively after three years of grass growth on Mudidih overburden dump slope in India. The growth performance of tree species, namely Sisum (Dalbergia sisoo) and Subabool (Leucena lecocephala), in terms of height, diameter increment, below-ground biomass and root depth have shown mean values of 219 cm (±94), 48 mm (±6), 4.0 kg m−2 (±1.5) and 1 m (±0.1), respectively. This acts as biological fertility which helps in root proliferation and enhancement of dump stability. From the numerical modelling it is suggested that roots of these grass and tree species have significantly enhanced the factor of safety of dump from 1.4 to 1.8 and therefore have a positive role in maintaining long term stability.

Contrasting fine-root production, survival and soil CO 2 efflux in pine and poplar plantations

Tree root activity, including fine-root production, turnover and metabolic activity are significant components of forest productivity and nutrient cycling. Differences in root activity among forest types are not well known. A 3-year study was undertaken in red pine (Pinus resinosa Ait.) and hybrid poplar (Populus tristis X P. balsamifera cv `Tristis no. 1') plantations to compare belowground root dynamics. We measured fine-root production, mortality and standing crop, as well as soil CO2 efflux. Pine fine-root production was only 2.9% of that of poplar during three years; 85 pine roots were observed in minirhizotron tubes compared with 4088 poplar roots. Live-root density oscillated seasonally for both species with late winter minimum and autumn maximum. Poplar reached constant maximum live-root length within the first growing season, but pine continued to increase observed fine-root length for three growing seasons. Within the first 100 days following initial appearance, 22% of the pine roots disappeared and 38% of the poplar roots disappeared. Median fine-root longevity of pine was 291 days compared with 149 days for poplar roots. Fine-root longevity increased with depth in the soil, and was greater for roots with initial diameter >0.5 mm. The probability of poplar root death from late February to May was more than three times that in any other season, regardless of root age. Despite the greater poplar root production and live-root length, fine-root biomass and soil CO2 efflux was greater in pine. Greater metabolic activity in the pine stand may be due to greater fine-root biomass or greater heterotrophic respiration.

Root formation in ethylene-insensitive plants.

Experiments with ethylene-insensitive tomato (Lycopersicon esculentum) and petunia (Petunia x hybrida) plants were conducted to determine if normal or adventitious root formation is affected by ethylene insensitivity. Ethylene-insensitive Never ripe (NR) tomato plants produced more below-ground root mass but fewer above-ground adventitious roots than wild-type Pearson plants. Applied auxin (indole-3-butyric acid) increased adventitious root formation on vegetative stem cuttings of wild-type plants but had little or no effect on rooting of NR plants. Reduced adventitious root formation was also observed in ethylene-insensitive transgenic petunia plants. Applied 1-aminocyclopropane-1-carboxylic acid increased adventitious root formation on vegetative stem cuttings from NR and wild-type plants, but NR cuttings produced fewer adventitious roots than wild-type cuttings. These data suggest that the promotive effect of auxin on adventitious rooting is influenced by ethylene responsiveness. Seedling root growth of tomato in response to mechanical impedance was also influenced by ethylene sensitivity. Ninety-six percent of wild-type seedlings germinated and grown on sand for 7 d grew normal roots into the medium, whereas 47% of NR seedlings displayed elongated tap-roots, shortened hypocotyls, and did not penetrate the medium. These data indicate that ethylene has a critical role in various responses of roots to environmental stimuli.

Effects of mycorrhizal colonization and elevated atmospheric carbon dioxide on carbon fixation and below-ground carbon partitioning in Plantago lanceolata

Plantago lanceolata with or without the mycorrhizal fungus Glomus mosseae were grown over a 100 d period under ambient (380 ± 50 µmol mol-1) and elevated (600 ± 150 Émol mol-1) atmospheric CO2 conditions. To achieve similar growth, non-mycorrhizal plants received phosphorus in solution whereas mycorrhizal plants were supplied with bonemeal. Measures of plant growth, photosynthesis and carbon input to the soil were obtained. Elevated CO2 stimulated plant growth to the same extent in mycorrhizal and non-mycorrhizal plants, but had no effect on the partitioning of carbon between shoots and roots or on shoot tissue phosphorus concentration. Mycorrhizal colonization was low, but unaffected by CO2 treatment. Net photosynthesis was stimulated both by mycorrhizal colonization and elevated CO2, and there was a more than additive effect of the two treatments on net photosynthesis. Colonization by mycorrhizal fungi inhibited acclimation, in terms of net carbon assimilation, of plants to elevated CO2. 13C natural abundance techniques were used to measure carbon input into the soil, although the results were not conclusive. Direct measurements of below-ground root biomass showed that elevated CO2 did stimulate carbon flow below-ground and this was higher in mycorrhizal than non-mycorrhizal plants. For the four treatment combinations, the observed relative differences in amount of below-ground carbon were compared with those expected from the differences in net photosynthesis. A considerable amount of the extra carbon fixed both as a result of mycorrhizal colonization and growth in elevated CO2 did not reveal itself as increased plant biomass. As there was no evidence for a substantial increase in soil organic matter, most of this extra carbon must have been respired by the mycorrhizal fungus and the roots or by the the plants as dark-respiration. The need for detailed studies in this area is emphasized.

Effects of mycorrhizal colonization and elevated atmospheric carbon dioxide on carbon fixation and below-ground carbon partitioning in Plantago lanceolata

Plantago lanceolata with or without the mycorrhizal fungus Glomus mosseae were grown over a 100 d period under ambient (380±50 μmol mol -1 ) and elevated (600 ± 150 μmol mol -1 ) atmospheric CO 2 conditions. To achieve similar growth, non-mycorrhizal plants received phosphorus in solution whereas mycorrhizal plants were supplied with bonemeal. Measures of plant growth, photosynthesis and carbon input to the soil were obtained. Elevated CO 2 stimulated plant growth to the same extent in mycorrhizal and non-mycorrhizal plants, but had no effect on the partitioning of carbon between shoots and roots or on shoot tissue phosphorus concentration. Mycorrhizal colonization was low, but unaffected by CO 2 treatment. Net photosynthesis was stimulated both by mycorrhizal colonization and elevated CO 2 , and there was a more than additive effect of the two treatments on net photosynthesis. Colonization by mycorrhizal fungi inhibited acclimation, in terms of net carbon assimilation, of plants to elevated CO 2 . 13 C natural abundance techniques were used to measure carbon input into the soil, although the results were not conclusive. Direct measurements of below-ground root biomass showed that elevated CO 2 did stimulate carbon flow below-ground and this was higher in mycorrhizal than non-mycorrhizal plants. For the four treatment combinations, the observed relative differences in amount of below-ground carbon were compared with those expected from the differences in net photosynthesis. A considerable amount of the extra carbon fixed both as a result of mycorrhizal colonization and growth in elevated CO 2 did not reveal itself as increased plant biomass. As there was no evidence for a substantial increase in soil organic matter, most of this extra carbon must have been respired by the mycorrhizal fungus and the roots or by the the plants as dark-respiration. The need for detailed studies in this area is emphasized.

Insights into mycorrhizal colonisation at elevated CO2: a simple carbon partitioning model

A simulation model was used to investigate the effect of an increased rate of plant photosynthesis at enhanced atmospheric CO2 concentration on a non-leguminous plant-mycorrhizal fungus association. The model allowed the user to modify carbon allocation patterns at three levels: (1) within the plant (shoot–root), (2) between the plant and the mycorrhizal fungus and (3) within the mycorrhizal fungus (intraradical–extraradical structures). Belowground (root and fungus) carbon losses via respiration (and turnover) could also be manipulated. The specific objectives were to investigate the dynamic nature of the potential effects of elevated CO2 on mycorrhizal colonisation and to elucidate some of the various mechanisms by which these effects may be negated. Many of the simulations showed that time (i.e. plant age) had a more significant effect on the observed stimulation of mycorrhizal colonisation by elevated CO2 than changes in carbon allocation patterns or belowground carbon losses. There were two main mechanisms which negated a stimulatory effect of elevated CO2 on internal mycorrhizal colonisation: an increased mycorrhizal carbon allocation to the external hyphal network and an increased rate of mycorrhizal respiration. The results are discussed in relation to real experiments. The need for studies consisting of multiple harvests is emphasised, as is the use of allometric analysis. Implications at the ecosystem level are discussed and key areas for future research are presented.

Decomposition of emergent macrophyte roots and rhizomes in a northern prairie marsh

Dry mass, nitrogen and phosphorus content in belowground litter of four emergent macrophytes ( Typha glauca Godr., Phragmites australis (Cav.) Trin., Scolochloa festucacea (Willd.) Link and Scirpus lacustris L.) were followed for 1.2 years in a series of experimental marshes, Delta Marsh, Manitoba. Litter bags containing roots and rhizome materials of each species were buried in unflooded soil, or soil flooded at three water depths (1–30, 31–60, > 60 cm). There were few differences in dry mass loss in unflooded or flooded soils, and depth of flooding also had little effect on decomposition rates. In the flooded sites, Scolochloa and Phragmites roots lost more mass (48.9–63.8% and 59.2–85.5%, respectively) after 112 days than Typha and Scirpus (36.3–43.6 and 37.0–47.2%, respectively). These differences continued through to the end of the study, except in the shallow sites where Scirpus roots lost more mass and had comparable mass remaining as Scolochloa and Phragmites. In the unflooded sites, there was little difference between species. All litters lost nitrogen (22.9–90.0%) and phosphorus (46.3–92.7%) during the first 112 days, then levels tended to remain constant. Decay rates for our belowground root and rhizome litters were comparable to published literature values for aboveground shoot litter of the same species, except for Phragmites roots and rhizomes which decomposed at a faster rate (− k = 0.0014−0.0032) than shoots (− k = 0.0003−0.0007, [van der Valk, A.G., Rhymer, J.M., Murkin, H.R., 1991. Flooding and the decomposition of litter of four emergent plant species in a prairie wetland. Wetlands 11, 1–16]).

The dynamics of benthic nutrient pools and fluxes in tropical mangrove forests

Variations in benthic nutrient pools and rates of dissolved nutrient exchange between the forest floor and tidal waters were examined over a 5-yr period in mixed Rhizophora forests lining Coral Creek on Hinchinbrook Island in Queensland, Australia. Seasonal and spatial changes in redox status, porewater and solid-phase nutrients, and in exchange rates were not consistent and did not correlate with temperature. Below-ground roots, on average, accounted for ∼79%, 37% and 26% of bulk sediment TOC, total N and total P pools, respectively. Porewater nutrient concentrations were dominated by Si(OH) 4 + and DON with consistently low levels of NO 2 - + NO 3 - . At most sampling periods, porewater NH 4 + and PO 4 3- concentrations were higher in creek bank sediments than in mangrove sediments indicating uptake by trees. These sediments have low adsorption capacity (K = 0.17-0.47) for NH 4 + , but a moderate capacity (K = 0.8-4.8) for PO 4 3- adsorption. Most measured benthic fluxes of dissolved nitrogen and phosphorus showed uptake by sediments, prop roots and timber lying on the forest floor. Relative (per ha) estimates indicate that low-intertidal Rhizophora forests import ∼2220 mmol N ha -1 d -1 and ∼496 mmol P ha -1 d -1 , with sediments accounting for nearly all uptake while Si is exported (∼2475 mmol ha -1 d -1 . Mid-intertidal forests import ∼1385, 93 and 4720 mmol ha -1 d -1 of N, P and Si, respectively ; sediments, prop roots and timber respectively account for 36%, 62% and 2% of the N import. Mid-intertidal sediments account for all net P uptake, but prop roots and sediments account for 60% and 40% of total Si uptake. On an absolute basis, low-intertidal forests (78 ha total area) in Coral Creek import ∼881 kgN yr -1 , 436 kgP yr -1 and export 1963 kgSi yr -1 , and the mid-intertidal forests (338 ha total area) import ∼2392 kgN yr -1 , 356 kgP yr -1 and 16300 kgSi yr -1 . The sum of these estimates equates to ∼95% of the net annual import of total dissolved N and ∼66% of the net annual import of total dissolved P into the Coral Creek tidal basin from adjacent coastal waters. By difference, ∼14337 kgSi yr -1 is imported into the system. This indicates that mangrove forests are a very efficient sink of dissolved nitrogen, phosphorus and silicon in this tidally-driven coastal ecosystem. This import may be driven by the consistently high rates of microbial and plant growth and productivity within the forests.

Oxygen loss from Spartina alterniflora and its relationship to salt marsh oxygen balance.

Spartina alterniflora has been reported to lose significant amounts of oxygen to its rhizosphere with potentially important effects on salt-marsh biogeochemical cycling and plant productivity. The potential significance of this oxidative pathway was evaluated using laboratory split-chamber experiments to quantify oxygen loss from intact root systems under a wide variety of pre-treatment and incubation conditions including antibiotics to inhibit microbial respiration. The aerenchyma system of S. alterniflora was found to transport O2, N2, Ar, and CH4 from above-ground sources to its below-ground roots and rhizomes. While non-respiratory gases were observed to move from the lacunae to water bathing the root systems, net O2 loss did not occur; instead oxygen present outside of the roots/rhizomes was consumed. Net oxygen loss was found when resistance to gas transport was reduced in the lacunae-rhizosphere pathway by placing the root systems in a gas phase and when plant respiration was significantly reduced. Root system respiration appeared to be the major variable in the plant oxygen balance. When root and rhizome respiration was inhibited using poisons or lowered by cooling, the oxygen deficit was greatly reduced and oxygen loss was indicated. The effect of seasonal temperature changes on root system "oxygen deficit" presents a possible explanation as to why Spartina produces root systems with respiration rates that cannot be supported by gas transport. Overall, while oxygen loss from individual plant roots is likely, integrating measured root system oxygen loss with geochemical data indicates that the mass amount of oxygen lost from S. alterniflora root systems is small compared to the total oxygen balance of vegetated salt marsh sediments.

Relationships between CH4 emission, biomass, and CO2 exchange in a subtropical grassland

Methane flux was linearly correlated with plant biomass (r = 0.97, n = 6 and r = 0.95, n = 8) at two locations in a Florida Everglades Cladium marsh. One location, which had burned 4 months previously, exhibited a greater increase in methane flux as a function of biomass relative to sites at an unburned location. However, methane flux data from both sites fit a single regression (r = 0.94, n = 14) when plotted against net CO2 exchange suggesting that either methanogenesis in Everglades marl sediments is fueled by belowground root exudation or else factors which enhance photosynthetic production and plant growth are also correlated with methane production and flux in this oligotrophic environment. These data are the first to show a direct relationship between spatial variability in plant biomass, net ecosystem production, and methane emission in a natural wetland.

Above-Ground Emergence in the Desert Tulip Tulipa systola Stapf. in the Negev Desert of Israel

In populations of Tulipa systola Stapf. in the Negev Desert of Israel the number of plants appearing above ground during winter fluctuates from year to year. Between 10 and 70% of adult plants and between 40 and 80% of juveniles do not emerge in permanent quadrats in any year. Most of them reappear the following year. There is a significant positive correlation between the proportion of emergents in T. systola populations and the local amount of rainfall until 1 February. Rain after this does not affect emergence. Non-emergence during 1 year reduces the chance of emerging during the following year. In indoor experiments below-ground shoot and root development was initiated at the beginning of winter in response to the drop in soil temperature, regardless of soil moisture. However, further root growth depended on soil moisture. Early shoot development was independent of root development, but full root development was necessary for extension of the shoot to emerge above the soil. Key-words: Above-ground emergence, bulbs, desert, geophytes, rainfall, root development, runoff, shoot development

Production ecology of Ruppia maritima L. s.l. and Halodule wrightii Aschers, in two subtropical estuaries

Seasonal growth and production dynamics of Ruppia maritima L. s.l. were compared over a 3-year period in two south Texas estuaries characterized by different salinity and N regimes as a result of freshwater inputs. Measurements of shoot production in the Guadalupe Estuary (0–25‰ salinity) and the Nueces Estuary (32–38‰ salinity) revealed no major differences in the magnitude of growth, but the plant populations differed in the seasonality of growth, the time of flowering, and the persistence of an over-wintering population. During the period of rapid shoot development, from March to August, leaf elongation rates usually ranged from 2 to 4 mm·day −1 (0.04–0.08 mg dry wt·mg shoot −1·day −1), although peak growth rates of up to 8 mm·day −1 were also recorded. In both estuaries, R. maritima was a strict opportunist, yearly colonizing bare areas and completing its entire growth cycle in 4 months. Overwintering populations of R. maritima existed at the lower nutrient and higher salinity site in Nueces Estuary but not at the high nutrient, low salinity site in Guadalupe Estuary. Halodule wrightii Aschers, was absent from Guadalupe Estuary, but in the Nueces Estuary, H. wrightii maintained large and persistent overwintering populations characterized by sustained year-round growth and larger below-ground root and rhizome fractions of total biomass (50–85%) compared to R. maritima (20–70%). The high nutrient regimes associated with large inputs of freshwater in the Guadalupe Estuary appear to have little beneficial effect on the growth dynamics of R. maritima. Instead, significant reductions in underwater light may be most important for growth. Fouling by algal epiphytes, higher riverine inflow, and local physiographic differences in wave exposure appear to be the primary factors regulating light levels and thus the proliferation and year-round persistence of R. maritima.

A comparison of mineral uptake and translocation by above-ground and below-ground root systems ofSalix syringiana

Nutrient uptake and translocation by above-ground adventitious roots and below-ground roots of woodySalix syringiana saplings were studied with gamma spectrometry. Each of four radionuclides (75Se,138Cs,54Mn, and65Zn) administered to adventitious and belowground roots were detected in stems and leaves within one month. Nuclides tended to be immobilized in the leaves and branches closest to the adventitious roots that absorbed them, while nuclides absorbed from below-ground sources were distributed more evenly throughout the plant. The capacity of adventitious roots to acquire nutrients from above-ground sources suggests they function as a potential ‘auxiliary’ pathway of nutrient uptake and might enhance plant nutrient status where below-ground root uptake it hindered by adverse soil conditions.

Accretion rates in salt marshes in the Eastern Scheldt, South-west Netherlands

Vertical accretion and sediment accumulation rates were determined from the distribution of 137Cs in sediment cores, from historic documents, and from artificial white-coloured tracer layers in salt marshes in the Eastern Scheldt. Salt marsh accretion is related to the steady rise of the mean high tide in the Eastern Scheldt during the last few decades. Mean accretion rates vary from 0·4-0·9 cm year −1 in the St Annaland marsh to 1·0–1·5 cm year −1 in the Rattekaai marsh. Sediment accumulation in accreting marshes exceed the loss of sediment, by retreat of the marsh cliffs, by a factor of 10–20. Short-term spatial and temporal variations in accretion rates are large. Spatial variations are associated with levee and backmarsh sites and the density of marsh vegetation. Temporal variations are mainly related to fluctuations in hydrodynamic conditions. The net vertical accretion rate of organic carbon is 0·4±0·1 kg m −2 year −1; approximately half this rate is associated with the current deposit, and the other half with net additions from the belowground root biomass. A simple model for the root biomass distribution of Spartina anglica with depth and the depth-dependent fossilization of root biomass in sediments of the Rattekaai marsh is presented.

The pattern of winter respiratory response to temperature, moisture, and freeze–thaw exposure in Bouteloua gracilis dominated grassland soils of southwestern Alberta

Winter respiratory activity of soils from Bouteloua gracilis dominated grassland of southwestern Alberta was examined, both under in situ field conditions and over a matrix of defined laboratory conditions. The effect of winter thaw conditions was very pronounced on observed rates of soil surface CO2 evolution. Under conditions of diurnally fluctuating air temperatures, from ca. −18 to +8 °C, soil surface temperatures in early January ranged from ca. −12 to +4 °C, while concurrently measured respiratory activity ranged from less than 2 to over 16 mg CO2∙m−2∙h−1. By early spring, soil surface heating was even more extreme as a result of the greater magnitude of midday insolation exposure, with observed mean values of CO2 release ranging from less than 10 to over 60 mg CO2∙m−2∙h−1. Laboratory incubations showed continued, although low rates of respiratory activity in soils held at subzero temperatures, with a marked biphasic response pattern evident in Arrhenius plots of soil respiration. Predicted cumulative soil surface CO2 release was estimated at 34–48 g CO2∙m−2, depending on whether the effects of observed postthaw respiratory response were included. Some 55% of overall winter soil respiratory activity in the top 8 cm of the soil profile is predicted to occur at temperatures between −4 and +4 °C, with the remaining respiratory activity largely occurring at temperatures up to 15 °C. This magnitude of soil surface CO2 release represents between 3 and 30% of previously observed estimates of belowground root mass loss in the winter period, depending on whether this mass loss is presumed to occur over the entire winter period or mainly in early spring, coinciding with the peak period of root exudate production.

Life History and Production of Above-and Belowground Structures of Cladium mariscoides (Muhl.) Torr. in a Western New York Fen

BERNARD, J. M., F. K. SEISCHAB AND GAIL JACOBY (Dept. Biol., Ithaca College, Ithaca, NY 14850 and Dept. Biol. Rochester Inst. Tech., Rochester, NY 14623-0887). Life history and production of above and belowground structures of Cladium mariscoides (Muhl.) Torr. in a western New York fen. Bull. Torrey Bot. Club 112:288-294. 1985.-Seasonal changes in numbers and weights were determined for three categories of shoots aboveground and root and rhizome weights belowground. Total shoot numbers were over 1000/M2 in May, evenly divided between old and young categories. From late June to mid-September they averaged approximately 750-800/M2 with declining numbers of old and young but increasing numbers of newly emerged shoots. Shoot standing crop reached a maximum of 224 g/m2 in late August, most of the total contributed by young shoots. Aboveground production is estimated to be 227.6 g/m2/yr. Belowground root and rhizome standing crops reached a maximum of 68 and 51 g/m2 respectively and we estimate their annual production to be approximately 47 g/m2/ year (27.7 g/m2/year roots; 19.3 g/m2/year rhizomes). Live root/live shoot ratios ranged from 0.8-1.0.