Carex Diandra Research Articles

Wetland Plant Communities of the Eastern Himalayan Highlands in Northern Bhutan

The study was conducted to characterize previously unexplored wetland vegetation in lower montane areas of the Himalaya (1597–2538 m above sea level) of Jigme Dorji National Park, Gasa District, Northern Bhutan. A random quadrat sampling method was employed to assess percent plant cover and environmental data were collected following standard procedures. Cluster and indicator species analyses using plant cover data were used to define the species composition of plant communities. Differences in community composition along gradients of elevation, slope, soil pH, available phosphorus, and peat/soil depth were analyzed using Canonical Correspondence Analysis (CCA). The wetlands supported 120 vascular plant species from 84 genera and 51 families. Analyses identified four plant communities, I to IV, each named from the three most prominent species. The key indicator species of four plant communities, Acorus calamus, Carex diandra, Equisetum ramosissimum, and Carex capillacea, dominate shallow fresh marsh, seasonally flooded basin of flat, fresh water meadow, and poor fen, respectively. Elevation and soil phosphorus were the most important environmental variables in explaining the variation in wetland vegetation. The findings can be used to support the work of conservation agencies to identify and conserve these plant communities and their habitats in the Himalaya.

Simulating the germination response to diurnally alternating temperatures under climate change scenarios: comparative studies on Carex diandra seeds.

Environmental temperature regulates plant regeneration via seed in several superimposed ways, and this complex regulation will be disrupted by climate change. The role of diurnally alternating temperatures (ΔT) in terminating dormancy will be a major factor in this disruption, as its effects on seed germination are immediate. The effect of ΔT on seed germination was modelled using two populations of the wetland sedge Carex diandra, one from a montane site and one from a subalpine site. A cardinal-temperature model was fitted to germination results obtained from a thermal gradient plate, and the model was used to simulate changes in germination under two possible future climate scenarios (RCP2·6 and RCP8·5, for representative concentration pathways) as defined by the Intergovernmental Panel on Climate Change. Scenario RCP2·6 projected moderate increases in average temperatures and ΔT, whereas RCP8·5 projected greater warming and higher ΔT. Increasing ΔT decreased the base temperature for seed germination and the thermal time required for germination. The effect of higher ΔT together with the higher temperatures increased germination under both climate scenarios. Carex diandra germination is highly responsive to potential changes in ΔT, and thus this study highlights the role of ΔT in seed responses to climate change. Comprehensive cardinal-temperature models, encompassing the different effects of temperature on seed germination, are needed to understand how climate change will affect plant regeneration.

Decomposition of Carex and Sphagnum litter in two mesotrophic fens differing in dominant plant species

Peatlands can be classified into fens and bogs based on their hydrology. Development of fens to bogs is accompanied by the invasion of Sphagnum species. The purpose of this study was to determine how the decomposition process in fens is influenced by the transition from a vascular plant‐dominated system to a Sphagnum‐dominated system. We carried out a reciprocal litter bag experiment, using litter of Carex diandra, C. lasiocarpa, Sphagnum papillosum and S. squarrosum in a fen dominated by Sphagnum species and a fen without Sphagnum. Decomposition rate and nitrogen and phosphorus dynamics of the plant litter were measured in a field experiment for two years. Decomposition rate was highest for the Carex litter types and lowest for the Sphagnum litter types. Surprisingly, decomposition rates hardly differed between the two sites. Nutrient dynamics, however, showed a clear site‐effect: In the Sphagnum site net mineralization was observed for all litter types whereas in the Carex site net immobilization was observed. These results show that carbon and nutrient cycles were coupled in a different way in a Sphagnum‐dominated and a Carex‐dominated site, respectively. Nutrient availability and adaptation of the microbial community to nutritional and other environmental conditions may be the main regulators of carbon and nutrient cycles in these peatlands.

Root decomposition and soil nutrient and carbon cycling in two temperate fen ecosystems

Although root litter contributes to a large extent to soil organic matter accumulation in peatlands, decomposition of root litter is often neglected in studies on litter decomposition and carbon and nutrient cycling in these ecosystems. In this study, decomposition of root and rhizome litter of Carex diandra and Carex lasiocarpa was determined in two temperate fens, one dominated by Sphagnum species (Sphagnum fen; soil pH=4.4) and one without a Sphagnum cover (Carex fen; soil pH=5.7). One‐year mass loss increased in the order: roots Carex diandra<roots Carex lasiocarpa<rhizomes Carex lasiocarpa. This ranking was in agreement with the generally established relationships between decomposition rate and litter chemistry, since rhizome litter had the lowest concentration of lignin and the highest N and P concentrations. The decomposition constants (k‐values) varied from 0.10 to 0.30 yr−1, which is at the low end of the range found for above‐ground litter of Carex species in other studies. Decomposition rates of root litter were lower in the Sphagnum site than in the Carex site, probably as a result of a lower pH and a lower nutrient status in the Sphagnum site. At both sites, N and P content of the litter decreased rapidly in the first three months indicating fast nutrient leaching and mineralization. Nutrient release per unit initial litter mass in the Carex site did not differ from that in the Sphagnum site. Estimated first‐year losses of N and P from Carex diandra roots in the Carex site were 2.31 g N m−2 and 0.20 g P m−2. First‐year nutrient losses from leaf litter of this species, as determined in another study, were only 0.06 g N m−2 and 0.02 g P m−2. These results show that roots do indeed play a major role in the cycling of carbon and nutrients in temperate fen ecosystems.

NUTRITIONAL AND PLANT-MEDIATED CONTROLS ON LEAF LITTER DECOMPOSITION OFCAREXSPECIES

We studied the effects of experimentally induced variation in leaf litter chemistry on leaf litter decomposition and leaf litter nutrient release of Carex species from habitats that differ in nutrient availability. Carex diandra, C. rostrata, and C. lasiocarpa are dominant in less productive mesotrophic fens, whereas C. acutiformis is dominant in more productive eutrophic fens. For each species, three types of litter were used: litter collected in the field (FLD); and litter from experimental populations grown at low (LN: 3.3 g N·m−2·yr−1) and high N supply (HN: 20.0 g N·m−2·yr−1). For all the litter chemistry parameters studied there were highly significant interactions between species and litter type. This implies that, due to differential plant-mediated controls on leaf litter chemistry, it is not always possible to predict changes in litter chemistry in response to increased nutrient supply. Litter decay was determined in a long-term (3 yr) field experiment using litter bags. The litter types of each species were incubated at their native growing sites. Contrary to what is generally found, the leaf litter decomposition rate of the species growing at the nutrient-poorest site (C. diandra) was higher than that of the species growing at the nutrient-richest site (C. acutiformis). Only for C. diandra and C. lasiocarpa was the decomposition rate of the litter from the HN treatment higher than that of the field litter. Thus, increased nutrient supply does not necessarily lead to higher litter decomposition rates. Nutrient controls on litter decay changed with time: initial litter decay (≤3 mo) was strongly controlled (high r2 values) by all P-related litter quality parameters, whereas long-term litter decay (>1 yr) was most strongly related with the phenolics : N ratio, the phenolics : P ratio, the lignin : N ratio, and the C:N ratio. Our data suggest that high levels of atmospheric N deposition, such as in the study area (The Netherlands), may lead to a relative shortage of P in the plant-derived substrates for bacteria and fungi. As a result, P-related litter chemistry parameters exert a strong influence on litter decay. Our data did not support the hypothesis that high-nutrient species increase nutrient cycling due to the production of easily decomposable litter with high rates of nutrient release. The leaf litter from Carex acutiformis, the species from the high-productivity fens, decomposed more slowly than that of the other species, immobilized more N and P and had a longer period of net N and P immobilization. However, this species has a higher litter production than the other species and thereby increases the rate of nutrient cycling. At the intraspecific level, increased nutrient supply led to lower amounts of immobilized N and P and faster N and P release from litter in most species, and thereby to a higher rate of nutrient cycling. This positive feedback between nutrient supply rate and the rate of nutrient cycling is reinforced by the increase in litter production in response to increased nutrient supply.

Effects of soil P status on growth and P and N uptake ofCarexspecies from fens differing in P-availability

SUMMARY We studied the effects of different soil P status (P-deficient, P-poor and P-rich fen soils) on growth, root allocation and P and N-uptake of Carex species from fens differing in P-availability. We carried out a 3-month pot experiment where the three species were grown in each soil. Carex acutiformis, a species from eutrophic fens, showed the highest production under all soil conditions and changes in biomass allocation to belowground parts, but not in specific root length (SRL) or root length/leaf area ratio (RLLA) in response to changes in the P-soil status. Carex lasiocarpa Ehrh., a species from P-limited areas, showed intermediate biomass production and low inherent root weight ratio (RWR). Carex diandra Schrank., a species from areas where the growth of the vegetation is limited by nitrogen, showed low biomass production in all three fen soils studied, and no changes in its high specific root length (SRL) or root weight ratio (RWR) with soil phosphorus status. All three Carex species showed the best growth under P-poor conditions and a very reduced growth on the P-limited soil. Phosphorus uptake by Carex species was affected by P-soil status being lowest under P-deficient conditions for all three Carex species. P-soil status also affected N-uptake which was lower under P-deficient conditions than in the other two soils. It can be concluded that the success of both small Carex species in nutrient poor sites cannot be explained by higher relative growth rate, biomass production or nutrient uptake than the species from eutrophic areas. Other factors (water and soil chemistry other than N and P richness, presence of a bryophyte layer, establishment of seedlings, clonal reproduction, competition ability) must play a role in determining the distinct distribution pattern of these species.

Interspecific and intraspecific differences in shoot and leaf lifespan of four Carex species which differ in maximum dry matter production.

The effect of N supply on shoot and leaf lifespan was investigated in established stands of four herbaceous Carex species which differed in maximum dry matter production. These species were, in rank order of increasing maximum dry matter production (per unit ground area): Carex diandra≤C. rostrata<C. lasiocarpa≤C. acutiformis. The observed patterns of shoot and leaf turnover were compared with data on leaf characteristics and nitrogen use efficiency indices of these species. There was no consistent difference in shoot production (number of shoots produced per unit ground area) between species with low production and those with high production: Carex diandra (low production) and C. lasiocarpa (high production) had high shoot production, while shoot production in c. rostrata (low production) and C. acutiformis (high production) was much lower. The rank order of the mean lifespan of shoots was: C. diandra<C. rostrata≤C. lasiocarpa<C. acutiformis. Thus, the lifespan of shoots increased with increasing maximum dry matter production of these Carex species. In all species, increased N supply led to a significant reduction in shoot lifespan. The reduction of shoot lifespans in response to enhanced N supply will result in increased nutrient turnover rates in these species. There was no consistent difference in the number of leaves produced per shoot between low-production and high-production species. C. diandra and C. lasiocarpa had relatively low leaf production, while C. rostrata and C. acutiformis had relatively high leaf production per shoot. Thus, this pattern is opposite to the pattern in shoot production. The rank order of the mean lifespan of leaves was: C. diandra<C. rostrata<C. acutiformis≤C. lasiocarpa. This implies that the high-production species had longer mean leaf lifespans than the low-production species. Mean leaf lifespan was not significantly affected by enhanced N supply, except in C. diandra, where leaf lifespan decreased in response to enhanced N supply. Shoot lifespans did not show any significant relation with the specific leaf area (SLA, leaf area per unit leaf mass) or the leaf area ratio (LAR, leaf area per unit plant mass) of the species under study. There was, however, a negative relation (r 2=0.71) with the nitrogen concentration in the leaves. Shoot lifespans were positively related (r 2=0.79) with whole-plant nitrogen use efficiency (NUE, dry matter production per unit N-loss) and with the mean residence time of nitrogen (MRT, the average time-span during which a unit of nitrogen is present in the plant) (r 2=0.78), but not with the nitrogen productivity (A, annual dry matter production per unit N in the plant). Leaf lifespan was positively related with the mean residence time of nitrogen in the plants (r 2-0.70). For all the other parameters, there were no significant relations with leaf lifespan. From these results we conclude that: (1) at the stand level, shoot and leaf lifespans are positively related with maximum dry matter production; and (2) shoot and leaf lifespan are important determinants of whole-plant nitrogen economy.

Decomposition of Carex and Sphagnum litter in fens: Effect of litter quality and inhibition by living tissue homogenates

Decomposition of fresh litter of Carex diandra, originating from a base-rich fen, and Sphagnum fallax, originating from a base-poor fen, was investigated in field experiments with litter bags and laboratory experiments with aerobic incubators. The Carex litter decomposed significantly faster than the Sphagnum litter in all experiments. Further, both litter types decomposed faster in the base-rich than in the base-poor fen. The addition of a small amount of homogenized S. fallax capitulums to litter of both types in the laboratory experiments significantly slowed down the rate of weight loss. The addition of homogenized C. diandra leaves did not influence the decay rate. These results suggest that the slow litter decomposition in Sphagnum-dominated mires is due to the chemical composition of the litter itself and the antibiotic effect of a substance leaching from living Sphagnum cells. Literature on the biochemistry of Sphagnales suggests that ‘Sphagnum acid’, a phenolic compound found in all Sphagna tested, is responsible for these differences.

Nitrogen Use Efficiency of Carex Species in Relation to Nitrogen Supply

We studied the effect of nitrogen supply (3.3 and 20.0 g°m—2°yr—1) on the nitrogen use efficiency (NUE) of three Carex species that differ in maximum growth rate. The rank order of maximum growth rate of these species is: Carex diandra @&lt; Carex rostrata &lt; Carex acutiformis. We distinguished two components of NUE: the mean residence time of nitrogen (MRT) in the plant and the nitrogen productivity (A). In this concept, NUE equals the product of MRT and A, and thus equals total productivity divided by the total N loss in litter. The N productivity (A) of C. diandra was significantly higher than that of C. rostrata and C. acutiformis. In each species A decreased strongly at enhanced N supply. The MRT of N differed substantially between species, but was not significantly affected by N supply. Contrary to what is generally found, the species with the lowest maximum growth rate (C. diandra) had the highest N turnover rate (lowest MRT), while the species with the highest maximum growth rate (C. acutiformis) had the lowest N turnover rate (highest MRT). In all species, the NUE decreased with increasing N supply. As a result of the observed patterns in N productivity and mean residence time, the species with the lowest maximum growth rate (C. diandra) had the lowest nitrogen use efficiency, while the species with the highest maximum growth rate (C. acutiformis) had the highest NUE. These results are not in agreement with the generally observed patterns in NUE along gradients of primary productivity. Comparisons of the results of this study with those of other studies show that generalizations of patterns of NUE along gradients of primary productivity should explicitly take into account which growth forms are compared (evergreen species vs. deciduous species, or [congeneric] species with the same growth form). Moreover, this study shows that factoring NUE into its components is a useful tool in the analysis of the adaptive significance of the N economy of plants.

Effects of Nitrogen Supply on Canopy Structure and Leaf Nitrogen Distribution in Carex Species

Optimization theory of leaf nitrogen distribution in canopies with respect to photosynthetic carbon gain predicts that vertical leaf nitrogen gradients are steeper in dense canopies than in more open canopies. We tested this prediction at the intraspecific and the interspecific level by studying the effects of two levels of nitrogen supply on canopy structure and vertical leaf nitrogen distribution in experimental populations of three Carex species that dominate in low—productivity fens (Carex diandra and Carex rostrata) and in high—productivity fens (Carex acutiformis), respectively. The high—productivity species had a significantly higher amount of leaf area per unit ground area, a higher absolute amount of nitrogen in the canopy, proportionally more leaf area in upper canopy regions, and steeper gradients of leaf nitrogen in the canopy than the low—productivity species. Similarly, increased nitrogen supply resulted for each species in a higher amount of leaf area per unit ground area and a higher absolute amount of nitrogen in the canopy. However, only in C. acutiformis did an enhanced N supply led to proportionally more leaf area in upper canopy regions and to steeper gradients of leaf nitrogen in the canopy. It is suggested that the observed patterns in Carex acutiformis (a very high canopy with a large amount of leaf area) are not directed towards maximization of photosynthetic carbon gain, but are also directed towards suppression of other species in the competition for light. The interspecific differences in canopy structure and leaf nitrogen distribution are in agreement with the optimization theory. However, at the phenotypic level the low—productivity species did not show proportionally more leaf area in upper canopy regions and steeper gradients of leaf nitrogen in the canopy upon enhanced N supply, despite a strong increase in the total amount of leaf area. This suggests that low—productivity species have a lower phenotypic plasticity with regards to their vertical leaf distribution pattern and their vertical leaf nitrogen distribution than high—productivity species.

Seasonal Allocation of Biomass and Nitrogen in Four Carex Species From Mesotrophic and Eutrophic Fens as Affected by Nitrogen Supply

1. Allocation of biomass and nitrogen were studied for 1 year in experimental populations of Carex diandra, C. rostrata and C. lasiocarpa (species from mesotrophic fens) and C. acutiformis (a species from eutrophic fens). These species were grown at two levels of N supply (3.3 and 20.0 g N m −2 year −1 , respectively). 2. At low N supply, total biomass did not differ between the species. At high N supply, the total biomass of C. lasiocarpa and C. acutiformis («high-productive species») significantly exceeded that of C. diandra and C. rostrata («low-productive species»)

Growth characteristics and seasonal allocation patterns of biomass and nutrients in Carex species growing in floating fens

Carex acutiformis, C. rostrata and C. diandra occur as dominant species in different floating fens in the ‘Vechtplassen’ area in the Netherlands and have, in this order, a lower annual biomass production concurrent with the deceasing nutrient availability in the fens. The species allocated proportionally equal amounts of biomass to the leaf blades, but Carex diandra invested more in the leaf sheaths and in the roots than the other two species and also had the greatest root length proportional to leaf area. The leaf area ratio was greatest in Carex acutiformis, but C. diandra had the highest net assimilation rate and the highest relative growth rate. These characteristics are presumably connected with the vegetation structure of the fens which becomes, in the order mentioned, more open with increasing irradiance of the whole plant.

Carex litter decomposition and nutrient release in mires with different water chemistry

Losses of dry weight, nitrogen, phosphorus and potassium from shoot litter of Carex diandra Schrank and Carex acutiformis Ehrh. were studied in a 2-year litter bag experiment in two fens, each dominated by one of these species. Weight losses over time showed negative exponential curves during Year 1, with k values of 0.0018 and 0.0009 day −1 for Carex diandra and Carex acutiformis, respectively. Total weight loss during Year 1 equalled that during Year 2, and amounted to 45% and 27% of the initial weight for Carex diandra and Carex acutiformis, respectively. Total nitrogen in the litter bags remained approximately constant throughout the 2-year-period for Carex acutiformis, whereas it remained constant during Year 1 and then dropped to 23% of the initial value during Year 2 for Carex diandra. Total phosphorus showed a similar pattern: no changes for Carex acutiformis, and a substantial decrease to 15% of the initial value during Year 2 for Carex diandra. A study of cotton strip tensile strength loss showed that conditions for cellulose decay are much more suitable in the groundwater fed (base-rich) fen dominated by Carex diandra than in the rainwater fed (base-poor) fen with Carex acutiformis, which is in accordance with the results of the litter bag study. The slower nutrient release from Carex acutiformis litter does not lead to a lower mineralization rate of soil organic matter in the fen dominated by this species. The high release rates of inorganic nitrogen and phosphorus in this fen are probably because of the presence of Sphagnum-derived organic matter.

The relationships of vegetation to surface water chemistry and peat chemistry in fens of Alberta, Canada

The relationships between vegetation components, surface water chemistry and peat chemistry from 23 fens in boreal Alberta, Canada, substantiate important differences along the poor to rich fen gradient. Each of the three fen types have their own characteristic species. The extreme-rich fens are characterized by Calliergon trifarium, Drepanocladus revolvens, Scirpus hudsonianus, S. cespitosus, Scorpidium scorpioides, and Tofieldia glutinosa. Moderate-rich fens are characterized by Brachythecium mildeanum, Carex diandra, Drepanocladus vernicosus, D. aduncus, and D. polycarpus. Poor fens are characterized by Carex pauciflora, Drepanocladus exannulatus, Sphagnum angustifolium, S. jensenii, and S. majus. Moderate-rich fens have fewer species in common with poor fens than with extreme-rich fens, while species richness is highest in the moderate-rich fens and lowest in poor fens. Variation in vascular plant occurrence appears to be more associated with nutrient levels, while bryophytes are more affected by changes in acidity and mineral elements. Based on chemical criteria, the three fen types are clearly separated by surface water pH, calcium, magnesium, and conductivity, but are less clearly differentiated by the nitrogen and phosphorus components of the surface waters. Moderate-rich fens are chemically variable both temporally and spatially, whereas poor fens and extreme-rich fens are more stable ecosystems. Whereas components of alkalinity-acidity are the most important factors that distinguish the three fen types in western Canada, nutrient concentrations in the surface waters generally do not differ appreciably in the three fen types.

Untersuchungen zur kurzfristigen Sukzession von Torf- und Braunmoosgesellschaften in einem Übergangsmoor aus den Schweizer Alpen )

Summary The vegetation of an “intermediate fen” (natural preserve “Bedrina”, Leventina, Ct. Tessin, Switzerland) was mapped 1955/56 and 1985/86 (scale 1:1000). The 2 maps show a rapid plant succession. The fen became more acid (0.5-1 pH-unit) and more eutrophic. Especially the strong outspread of Molinia coerulea s.l. and the installation of hazel-bushes and raspberry-shrubs must be noticed. The following species disappeared: Carex diandra, Sphagnum centrale, Sphagnum warnstorfii and Sphagnum tenellum. Other species (like Rhynchospora alba or Sphagnum fuscum) immigrated on new places, after having lost most of their populations observed in the period of 1955/56. The causes of these processes are complex: increasing of litter, air pollution, further growth of peat

Variation in tissue element concentration in mire plants over a range of sites

Elements in surface peat and ground water were estimated on seven mire sites in central and north Sweden. The variation in tissue clement concentration was studied in eleven plants occurring on the studied sites. The elements estimated were: N, P, K. Ca, Mg, Fe, Mn, Zn, Al, Cu, Mo, Na, S, B, and Si. The species studied were; Carex diandra, Carex limosa, Carex rostrata, Epilobium palustre, Menyanthes trifoliate, Pedicularis palustris, Rumex acetosa, Saxifraga hirculus, Scirpus hudsonianus, Stellaria crassifolia and Tofteldia pusilla. In surface peat over the range of sites, the variation in total concentrations of nitrogen and phosphorus was six and tenfold, respectively. The variation in total concentration of potassium was four‐fold. Extractable concentrations of these three elements showed an even greater variation between sites. Over the range of sites, the variation in tissue element concentration was larger in roots than in above‐ground parls. In above‐ground parts, floral parts varied less in tissue element concentration than did stems and leaves. The largest variation in tissue element concentration was found in Carex rostrata and Menyanthes trifoliata. The smallest variation was found in Saxifraga hirculus. Tissues of the rich fen species Saxifraga hirculus and Stellaria crassifolia had the lowest concentrations of heavy metals. The correlation between substrate element concentration and tissue concentration differed both between tissues and species. Concentrations of N, P and K in tissues of the Carex species were highly correlated with the concentrations of these elements in the substrate, while N, P and K concentrations in tissues of the herbaceous species, especially Saxifraga hirculus. correlated less well.

Respiratory energy costs for the maintenance of biomass, for growth and for ion uptake in roots of Carex diandra and Carex acutiformis

van der Werf, A., Kooijman, A., Welschen, R. and Lambers, H. 1988. Respiratory energy costs for the maintenance of biomass, for growth and for ion uptake in roots of Carex diandra and Carex acutiformis. ‐ Physiol. Plant. 72: 483–491.The respiratory characteristics of the roots of Carex diandra Schrank and Carex acutiformis Ehrh. were investigated. The aims were, firstly to determine the respiratory energy costs for the maintenance of root biomass, for root growth and for ion uptake, and secondly to explain the higher rate of root respiration and ATP production in C. diandra.The three respiratory energy components were derived from a multiple regression analysis, using the relative growth rate and the net rate of nitrate uptake as independent variables and the rate of ATP production as a dependent variable. Although the rate of root respiration and ATP production was significantly higher in C. diandra than in C. acutiformis, the two species showed no significant difference in their rate of ATP production for the maintenance of biomass, in the respiratory energy coefficient for growth (the amount of ATP production per unit of biomass produced) and the respiratory energy coefficient for ion uptake (amount of ATP production per unit of ions absorbed). It is concluded that the higher rate of root respiration of C. diandra is caused by a higher rate of nitrate uptake. At relatively high rates of growth and nitrate uptake, the contribution of the rate of ATP production for ion uptake to the total rate of ATP production amounted to 38 and 25% for C. diandra and C. acutiformis, respectively. At this growth rate, the respiratory energy production for growth contributed 37 and 50%, respectively, to the total rate of ATP production. The relative contribution of the rate of ATP production for the maintenance of biomass increased from 25 to 70% with increasing plant age for both species. The results suggest that ion uptake is one of the major sinks for respiratory energy in roots.These experimentally derived values for the rate of ATP production for the maintenance of biomass, the respiratory energy coefficient for growth and the respiratory energy coefficient for ion uptake are discussed in relation to other experimentally and theoretically derived values.

Paleoecological aspects of the Red Lake Peatland, northern Minnesota

The Red Lake Peatland, situated on the eastern arm of the Lake Agassiz plain in north central Minnesota, is made up of large black spruce raised bogs separated by sedge-covered water tracks marked by string patterns and teardrop-shaped forested islands. About 3 m of peat overlie a prairie soil; the basal peat is 3170 ± 100 years old (14C date). Stratigraphic distribution of pollen, macrofossils, and peat components in a series of cores along a small forested island was used to study the development of the peatland.In pollen zone RLB-1 (lowest) the upland pollen types suggest an oak savanna with a developing mesic deciduous forest. The local pollen indicates a succession from a Typha marsh to a sedge meadow. Zone 2 shows a small rise in Pinus pollen; Ericaceae pollen and Sphagnum spores indicate the development of a bog–heath vegetation type at the coring site. An increase in pollen of spruce and larch reflects the establishment of the island forest. Zone 3 is marked by a rise in Ambrosia pollen, recording agricultural land clearance in northwestern Minnesota in about 1890.The Salix–herb macrofossil assemblage occurs at the base of some cores; it is succeeded stratigraphically by the Typha–Scirpus assemblage, which also makes up the base of the remaining cores. There follows the Carex diandra – Carex aquatilis assemblage, suggesting a sedge meadow. The overlying Menyanthes–Larix assemblage continues to the surface under the sedge fen; under the island, seeds of Chamaedaphne and needles of Picea occur in this assemblage. The incoming of the Menyanthes–Larix assemblage is believed to reflect the first development of the patterned wetland.Reed peat comprises the bottom 20–50 cm of all cores; it corresponds with the lower part of pollen zone 1 and contains the Typha–Scirpus macrofossil assemblage. Pure sedge peat or sedge peat with Bryales corresponds with zone 2 and upper zone 1 of the pollen diagram and contains the Carex diandra –C. aquatilis macrofossil assemblage. Ericaceous peat occurs only under the island, and it contains the Menyanthes–Larix macrofossil assemblage. Laterally under the present sedge fen it grades into sedge peat with ericaceous components.The general upward succession of communities observed in these peat cores can be duplicated along a west-to-east surface traverse across the present prairie–forest transition. The stratigraphic succession thus records the westward movement of the prairie–forest transition across Beltrami County about 4000–2000 years ago.The area was covered by prairie more than 3100 years ago. Development of a cooler, moister climate led to a Typha marsh in the poorly drained lowland; oak savanna occupied the surrounding upland. As the water level rose in the lowland, peat started to accumulate as sedge meadow developed, and aspen parkland and conifer–hardwood forest moved into the upland. About 2000 years ago the growth of Sphagnum moss increased, accompanied by the development of patterned wetland and bog forest, with conifer–hardwood forest on the upland.

The natural sterile hybridCarex Diandra X Secta

Abstract A natural hybrid between Carex diandra Schrank and C. secta Boott has been found growing in abundance in a swamp below the Grampian Range in the Mackenzie Country. This hybrid is morphologically intermediate between the two parents and is sterile. An examination of herbarium specimens shows that the hybrid occurs elsewhere in New Zealand.

邦産すげ屬植物ノ葉ノ解剖分類學的研究 XXIV

Remarks on the four species of Carices described in this paper:Carex diandra SCHRANK: Upper epidermal cells on the nerve and on the mesophyll are very similar in their structure and form. Protuberances and spine cells are numerous in the margins. Transfusion cells are prominent. Walls of the epidermal cells in the stomata-band protrude upwards.Carex disperma DEWEY: Protuberances occur in the margin and in the under epidermis on the midrib. Stomata are rhombic.Carex fallax var. Franchetiana OHWI: All epidermal cells are short. Stomata are found on the marginal portion of the upper epidermis. Upper epidermal cells on the nerve are indistinct.Carex gibba WAHLENBERG: Protuberances are distributed near the margins of the upper epidermis. Spine cells occur densely in the margins.