Maximum Aboveground Biomass Research Articles

Net primary production and decomposition of salt marshes of the Ebre delta (Catalonia, Spain)

Net primary production was measured in three characteristic salt marshes of the Ebre delta: anArthrocnemum macrostachyum salt marsh,A. macrostachyum-Sarcocornia fruticosa mixed salt marsh andS. fruticosa salt marsh. Above-ground and belowground biomass were harvested every 3 mo for 1 yr. Surface litter was also collected from each plot. Aboveground biomass was estimated from an indirect non-destructive method, based on the relationship between standing biomass and height of the vegetation. Decomposition of aboveground and belowground components was studied by the disappearance of plant material from litter bags in theS. fruticosa plot. Net primary production (aboveground and belowground) was calculated using the Smalley method. Standing biomass, litter, and primary production increased as soil salinity decreased. The annual average total aboveground plus belowground biomass was 872 g m−2 in theA. macrostachyum marsh, 1,198 g m−2 in theA. macrostachyum-S. fruticosa mixed marsh, and 3,766 g m−2 in theS. fruticosa biomass (aboveground plus belowground) was 226, 445, and 1,094 g m−2, respectively. Total aboveground plus below-ground net primary production was 240, 1,172, and 1,531 g m−2 yr−1. There was an exponential loss of weight during decomposition. Woody stems and roots, the most recalcitrant material, had 70% and 83% of the original material remaining after one year. Only 20–22% of leafy stem weight remained after one year. When results from the Mediterranean are compared to other salt marshes dominated by shrubbyChenopodiaceae in Mediterranean-type climates, a number of similarities emerge. There are similar zonation patterns, with elevation and maximum aboveground biomass and primary production occurring in the middle marsh. This is probably because of stress produced by waterlogging in the low marsh and by hypersalinity in the upper marsh.

Differential drought tolerance of five coexisting plant species in Mediterranean lowland grasslands

To investigate how soil water content affects plant productivity; phenology and changes in aboveground biomass of five species were recorded in a Mediterranean lowland grassland during a relatively wet year (1991) and a dry year (1992); soil-water potentials were related to changes in soil water content. Species examined were the early-season C3grasses Poa bulbosa and Anthoxanthum odoratum, the late-season C4grasses Chrysopogon gryllus and Cynodon dactylon, and the mid-season C3forb Rumex acetosella. Species were also grown as monocultures in pots under two watering treatments (irrigation, no irrigation). The soil-water potential at the times of maximum aboveground biomass for Poa and Anthoxanthum were similar in the un-irrigated pots and in the dry year (1992) in the field. Aboveground biomass of all species in the field, except Cynodon, was lower in 1992 than in 1991. The early-season species Poa and Anthoxanthum showed the greater decrease in biomass in response to drought, and tended to exhibit an earlier maximum aboveground biomass. Similarly, these species exhibited an earlier maximum shoot biomass in the un-irrigated pots than in the irrigated pots. The mid- and late-season species tolerated lower soil matric potential. In comparison with the early-season species, they had higher leaf water potentials and greater values of relative water content when leaf water potential was lower than −1·5 MPa. These results indicate that the early-season species are more drought-sensitive than late-season species and that their productivity and phenology is influenced greatly by variation in soil water content between years.

Carbon dioxide fluxes over a northern, semiarid, mixed-grass prairie

Temperate grassland ecosystems are an important component of the global carbon (C) cycle. The Bowen ratio/energy balance (BREB) technique was used to measure CO 2 fluxes over a mixed-grass prairie at Mandan, ND from 24 April to 26 October in 1996–1999. Above-ground biomass and leaf area index (LAI) were measured about every 21 days throughout the season. Root biomass and soil organic C and nitrogen (N) contents to 1.1 m depth were measured in mid-July each year. Peak above-ground biomass typically occurred between mid-July to early-August and ranged from 782 kg ha −1 in 1998 to 1692 kg ha −1 in 1996. Maximum LAI ranged from 0.3 in 1998 to 0.5 in 1999. Root biomass ranged from 12.7 mg ha −1 in 1996 to 16.2 mg ha −1 in 1997. Maximum daily CO 2 fluxes generally coincided with periods of maximum above-ground biomass. Total CO 2 flux for the 24 April to 26 October period ranged from 181 g CO 2 m −2 in 1998 to 474 g CO 2 m −2 in 1999 (positive flux is CO 2 movement from atmosphere to plants or soil). The 4-year average flux for this period was 345 g CO 2 m −2. Fluxes during the 1999–2000 dormant season were estimated from BREB (−349 g CO 2 m −2) and soil flux (−265 g CO 2 m −2) measurements and when combined with the growing season fluxes, resulted in estimated annual fluxes in 1999 of 125 and 209 g CO 2 m −2 for BREB and soil flux dormant season measurements, respectively. These results suggest that the C budget of Northern Great Plains mixed-grass prairie grasslands may be near equilibrium.

Clone specific differences in a Phragmites australis stand : II. Seasonal development of morphological and physiological characteristics at the natural site and after transplantation

Two Phragmites clones, growing adjacent to each other but differing conspicuously in stand structure, were investigated in 1996 regarding seasonal change in morphological and physiological parameters. Both clones showed significant differences in shoot morphology (length, diameter, dry weight, leaf area), maximum above-ground (420 versus 152 g DW m −2) and below-ground biomass (2.4 versus 1.5 kg DW m −2). Furthermore, physiological parameters (N concentration, N and P content per shoot and m 2, content of dissolved amino acids, N translocation rate) varied between clones in their time course. Clone-specific variations in these characteristics were significant even after transplantation to another field site. Overall, these results suggest that the distinct growth forms and levels of productivity of the two Phragmites clones are the result of genotypic variation. It is hypothesized that both clones follow distinct ecophysiological strategies causing their morphotypic differentiation. Implications of genotypic determination of growth forms are discussed in relation to nutrient supply, N limitation, population plasticity, eutrophication and reed regression.

Effects of elevated CO 2 on gas exchange characteristics of alpine grassland

The ecosystem-level gas exchange characteristics of an alpine grassland treated with a combination of elevated CO 2 and moderate additions of NPK fertilizer during the third season of experimental treatments are described. Mid-season maximum daytime net ecosystem CO 2 flux (NEC max) increased significantly under elevated CO 2 (+45%), whereas nighttime NEC was unaffected by the CO 2 treatment. Since daytimke NEC under elevated CO 2 underwent a seasonal decline, only moderate carbon surpluses accumulated under elevated CO 2. The observed seasonal decline in daytime NEC may be due to reduced sink strength once maximum aboveground biomass is attained and appears to be a regulatory mechanism of ecosystem carbon accumulation. Moderate additions of NPK fertilizer stimulated both day-(+39%) and nighttime NEC (+29%) due to increased plant biomass, independent of CO 2 treatment. Yet there is no indication that enhanced mineral nutrient status will increase ecosystem responsiveness to elevated CO 2.

Cultivation of Miscanthus under West European conditions: Seasonal changes in dry matter production, nutrient uptake and remobilization

There is increasing interest in cultivation of Miscanthus as a source of renewable energy in Europe, but there is little information on its nutrient requirements. Our aim was to determine the nutrient requirement of an established Miscanthus crop through a detailed study of nutrient uptake and nutrient remobilization between plant parts during growth and senescence. Therefore dry matter of rhizomes and shoots as well as N, P, K and Mg concentration under three N fertilizer rates (0, 90, and 180 kg N ha-1) were measured in field trials in 1992/93 and at one rate of 100 kg N h-1 in 1994/95. Maximum aboveground biomass in an established Miscanthus crop ranged between 25-30 t dry matter ha-1 in the September of both trial years. Due to senescence and leaf fall there was a 30% loss in dry matter between September and harvest in March. N fertilization had no effect on crop yield at harvest. Concentrations of N, P, K and Mg in shoots were at a maximum at the beginning of the growing period in May and decreased thereafter while concentrations in rhizomes stayed fairly constant throughout the year and were not affected by N fertilization. Nutrient mobilization from rhizomes to shoots - defined as the maximum change in nutrient content in rhizomes from the beginning of the growth period measured in 1992/93 was 55 kg N ha-1, 8 kg P ha-1, 39 kg K ha-1 and 11 kg Mg ha-1. This is equivalent to 21 N, 36 P, 14 K and 27 Mg of the maximum nutrient content of the shoots. Nutrient remobilization from shoots to rhizomes ‐ defined as the increase in nutrient content of rhizomes between September and March ‐ measured in 1994/95 was 101 kg N ha-1, 9 kg P ha-1, 81 kg K ha-1 and 8 kg Mg ha-1 equivalent to 46 N, 50 P, 30 K and 27 Mg of nutrient content of shoots in September. Results showed that nutrient remobilization within the plant needs to be considered when calculating nutrient balances and fertilizer recommendations.

Production and population ecology of Phyllospadix iwatensis Makino. II. Comparative studies on leaf characteristics, foliage structure and biomass change in an intertidal and subtidal zone

A seagrass in Japan, Phyllospadix iwatensis Makino, is distributed in the lower intertidal zone and upper subtidal zone making a dense population on the Choshi coast, Japan. Intertidal P. iwatensis is able to receive sufficient light for photosynthesis but experienced severe exposure to the air, which decreased a large amount of aboveground biomass in April to June (i.e. the daytime exposure season). Subtidal P. iwatensis was never exposed throughout the year and the aboveground biomass increased gradually over the daytime exposure season. However, the maximum aboveground biomass and shoot density of the subtidal plant never exceeded that of the intertidal plant. The dense foliage, large aboveground biomass and high shoot density of both intertidal and subtidal plants is likely to be an adaptation to heavy water movement, but the subtidal plants always received insufficient light for photosynthesis as a result of having dense foliage, particularly in turbid water. In choppy and swell sea, P. iwatensis did not seem to be adapted to growing in the subtidal zone where there was shortage of light.

Ecology and biomass ofPhragmites australis(Cav.) Trin. Ex. Steud. in the north-eastern region of the Nile Delta, Egypt

:Phragmites australis (Cav.) Trin Ex. Steud., the common reed is one of the most abundant species in the north-eastern region of the Nile Delta (Egypt). The phytosociological pattern of Phragmites australis was studied in relation to the most prevailing edaphic factors. The present results indicate that the maximum abundance of Phragmites was recorded in rich organic matter and alkaline habitats. In addition, field studies indicate that Phragmites is often associated with halophytes such as Arthrocnemum macrostachyum (Meikle) Moq., Halocnemum strobilaceum (Pallas) M. Beib and Aster squamatus (Spr.) Hieron ex Sod. Moreover, the reed tolerates soil conductivity up to 12 mS/cm and pH 7.0 to 9.3. The maximum above-ground biomass of the reed in 1992 occurred in September and was 5500 g/m2 (fresh) and 4400 g/m2 (dry). On the other hand, the maximum below-ground biomass occurred in October and was 2500 g/m2 (fresh) and 1100 g/m2 (dry). The succulence ratio varied seasonally, with the highest values for above-ground parts in April and March for below-ground parts.

The biomass of an Indian monsoonal wetland before and after being overgrown with Paspalum distichum L.

Paspalum distichum L. has been the dominant species in the monsoonal wetlands of the Keoladeo National Park in northcentral India since 1982 when grazing by water buffalo and domestic cattle was halted. Maximum water levels in these wetlands occur immediately after the end of the summer monsoon in late September of early October and then decline until the next summer monsoon the following June. After the normal 1985 monsoon, maximum water depths were around 140 cm. After the poor 1986 monsoon, maximum water depths were only around 60 cm. Paspalum distichum maximum aboveground biomass at four sites ranged from 850 g m-2 at the shallowest site to 3400 g m−2 at a deep water site. The maximum biomass of other vegetation types, which had dominated this wetland prior to 1982, ranged from 1400 g m-2 at a deep water site (Ipomoea aquatica Forsk.) to only 240 g m-2 to 400 g m-2 at a deep-water submersed site (Hydrilla verticillata (L. f.) Royle/Cyperus alopecuroides Rottb.) and at a shallow emergent site (Scirpus tuberosus Desf./Sporobolus helvolus (Trin.) Dur. et Schinz). For all vegetation types, biomass changed seasonally in response to changing water levels and temperatures. After the 1986 monsoon, above-ground biomass for all vegetation types was much lower than it had been after the 1985 monsoon. Mean below-ground biomass was very low in all vegetation types (1 to 47 g m-2). Paspalum distichum had a higher aboveground biomass at nearly all water depths in all seasons than that of the pre-1982 vegetation types. Paspalum distichum belowground biomass, however, is comparable to, or less than, that of the pre-1982 vegetation types. During years with an average monsoon, the overall primary production of these wetlands is estimated to have increased 2.5 to 3.5-fold since they were overgrown with Paspalum distichum.

Impact of light climate history on seasonal dynamics of a field population of Potamogeton pectinatus L. during a three year period (1986–1988)

The impact of light climate during the growing season and light climate history on the growth and survival of a Potamogeton pectinatus L. population was studied in a eutrophic shallow lake, Lake Veluwe (Netherlands), during the period 1986–1988. Four different light conditions were created in an experimental setup by manipulating the photon flux density using artificial shading (three levels of artificial shading and one control situation without artificial shading), during the growing season of 1986. During the growing season of 1987, part of the P. pectinatus vegetation in the experimental setup was artificially shaded in the same way as in 1986, while another part was not shaded. No artificial shading was applied at all during the growing season of 1988. Growth conditions for P. pectinatus were less favourable in 1987 than in 1986. On the whole, above- and below-ground biomass values were lower, the growing season was shorter, maximum above-ground biomass was lower and was reached earlier in the season, and net tuber production was lower in 1987 than in 1986 in the control situations. In both years, the above- and below-ground biomass values were lower, the growing season was shorter and maximum above-ground biomass was lower with higher levels of shading. The impact of shading on relative above-ground biomass development was similar in 1986 and 1987, whereas the impact of shading on relative tuber bank size at maximum above-ground biomass was more pronounced in 1987 than in 1986 in the experimental areas which were shaded both seasons. Mean individual tuber ash-free dry weight was lowest at the highest level of shading in both years. It is concluded that light climate is a dominant factor in controlling the biomass and tuber bank dynamics of a P. pectinatus population in Lake Veluwe. Additionally, water quality and meteorological characteristics are involved. At the highest level of shading, the photosynthetic tissue was able to sustain tuber growth and maintenance of the vegetation during a relatively short period only. As a consequence, the vegetation sloughed early in the growing season and the tuber bank size was smallest. The maximum above-ground biomass was positively correlated with the size of the hibernated tuber bank. Therefore, the biomass development in one season is at least partly determined by the light conditions of a previous growing season(s) through the size of the hibernated tuber bank. The Lake Veluwe vegetation has the potential to recuperate from negative shading effects on above-ground biomass and tuber bank size under field conditions. This may require more than one growing season, depending on actual growth conditions and size of the hibernated tuber bank.

Calamagrostis Canescens: Population Biology of a Clonal Grass Invading Wetlands

The preading ability of Calamagrostis canescens, a long-lived perennial grass of Central Europe, is exemplified by its behaviour in a sedge fen near Třeboň, Czechoslovakia. The process of invasion was observed within a stable community in the field. The hypothesis that the development of an invader is species-specific and does not depend on the original occupants was tested comparing natural invasion of communities by C. canescens with establishment of the species in experimental monocultures. The final stage of extensive spreading of the species was traced along a 510-m-long linear transect between 1982 and 1989. Closed stands with the maximum cover abundance (60 to 70%) and aboveground biomass (426 g m −2 ) were achieved within 5 to 6 years from a low initial occupation density of 1.5 seedlings m −2 (...)

Biomass and aboveground production of four angiosperms in Cantabrian (N. Spain) salt marshes

New data of aboveground biomass and production of four angiosperms over a 12 month period for the Cantabrian Sea salt marshes (Bay of Biscay, N. Spain) are presented. Based on harvest methods, maximum aboveground total biomass values for Spartina maritima (Curtis) Fernald, Spartina alterniflora Loisel, Salicornia ramosissima J. Woods and Halimione portulacoides (L.) Aellen were 628, 1109, 480 and 1267 gm-2, respectively. We conclude that although a slight latitudinal gradient in biomass is revealed in the data compiled with reference to some of the species studied, more work is neccesary in order to assess the potential productivity of these ecosystems on the coasts of Europe and/or to make comparisons with salt marshes of the American coasts. Annual net aerial primary production estimates using Smalley's method were: 296, 1160, 486 and 952 gm-2yr-1, for Spartina maritima, Spartina alterniflora, Salicornia ramosissima and Halimione portulacoides, respectively. These results together with turnover rate estimates point to the lack of vigour of the native S. maritima, while the exotic S. alterniflora, which seems to be spreading along the Cantabrian estuaries, behaves like a veritable pionner throughout the low marshes in this region.

Effects of nitrogen amendment on annual plants in the Chihuahuan Desert

Effects of nitrogen amendments on spring annual plant distribution, primary production, and species diversity in a semi-arid environment were studied. The ecological responses of spring annual plant species to nitrogen differed between species, and between sites. The distribution of each species in a control transect was wider than in a nitrogen-treated transect. Annual plant species diversity at each station in the control transect was higher than that of the nitrogen-treated transect. The lower site of the Lower Basin Slope areas had the highest species diversity (0.94 for the control and 0.84 for the nitrogen-treated), and the Upper Basin Slope area, shrub vegetation zone, had the lowest species diversity (0.27 for the control and 0.05 for the nitrogen-treated) in both transects. Inorganic nitrogen in the nitrogen-treated transect soils was consistently higher than that in the control transect soils; however, the former showed more fluctuation from station to station than the latter. Above-ground biomass of spring annual plants in the nitrogen-treated transect was consistently higher than that in the control at each station. The maximum above-ground biomass in the control and nitrogen-treated transect was 24.4±4.4 gm−2 and 61.2±10.6 gm−2, respectively. Variations in above-ground biomass along the transect did not parallel with the variation in inorganic nitrogen in soils and species diversity.

Above-ground biomass variation in Carex rostrata stokes in two contrasting habitats in central Sweden

Biomass development and seasonal maximum above-ground biomass of the perennial Carex rostrata Stokes were studied in two different habitats for three years in central Sweden. In a mire with a small water level amplitude, the shoot size, density and seasonal maximum above-ground biomass of the species fluctuated only little between years. In a reservoir with a water level changing much within and between years, the shoot size and density of C. rostrata fluctuated, but in opposite directions so that the maximum above-ground biomass remained at the same level. The regulation of the development of new shoots under oligotrophic conditions with total biomass controlled by scarcity of plant nutrients is discussed. The highest record of above-ground biomass was 220 g m −2 in the shallow water area of the reservoir.

Effects of irrigation and nitrogen on growth, light interception and efficiency of light conversion in wheat

Effects of three irrigation treatments (rainfed, and irrigation at 7-day and 14-day frequencies beginning in spring) and two rates of nitrogen (0 and 150 kg N ha −1) on growth, light absorption, and conversion efficiency in wheat were studied. Growth was considered in four phases extending from 95 days after sowing ( das 95) to the beginning of rapid stem growth ( das 120), the stem growth-phase lasting to the onset of rapid grain-filling ( das 148), the grain-filling phase between das 148 and das 170, and the final period to harvest. The first irrigation treatments were applied at das 120. Radiation interception was the major determinant of growth. Rainfed treatments captured ca. 1100 MJ m −2 between das 95 and das 148, by which time they had achieved maximum above-ground biomass. Irrigated treatments continued to grow until das 170. They captured ca. 1300 MJ m −2 to das 170 where no nitrogen was applied, and ca. 1500 MJ m −2 where N was applied. In addition to effects on leaf-area duration and radiation absorption, treatments also affected conversion efficiency, ϵ. In the first phase, ϵ increased from 0.85 g MJ −1 to 1.15 g MJ −1 where N was applied. After das 120, irrigation increased ϵ from a mean of 0.8 g MJ −1 in rainfed treatments to 1.2 g MJ −1. In the periods of rapid stem-growth and grain-filling, ϵ was a maximum of 1.45 g MJ −1 in the frequently irrigated treatment which received N, resulting in a maximum above-ground biomass of 2100 g m −2. Mean maximum biomass was 1670 g m −2 in the other irrigated treatments, as compared with a mean of 1100 g m −2 in rainfed treatments. Growth rates were compared with predicted potential rates. After accounting for differences in light absorption between treatments, rates of growth ranged between 0.4 and 0.65 of potential rates in treatments other than I wN 150, in which the growth rate between das 120 and das 170 was almost 0.8 of the potential rate. These proportions were strongly correlated with estimates of ϵ, although the relationship varied between phases as a result of differences in global radiation. Collectively, the data suggest that physiological constraints, associated with both N and water, contributed to differences in rates of growth in addition to those imposed by leaf-area duration and radiation absorption. The yield potential of the frequently irrigated treatment which received N was, however, not realised in the field. Lodging after das 162 was estimated to decrease yield from a potential of ca. 900 g m −2 to 650 g m −2.

Community structure and biomass distribution of seagrasses and macrofauna in the flores sea, Indonesia

In several locations in the Flores Sea region the community structure and the biomass distribution of seagrasses were studied along transects perpendicular to the shoreline. The share of each species within a sample plot was estimated, divided in above- and below-ground biomass. Statistics regarding substrate coverage, shoot density and leaf-area index were sampled. A standard relation was calculated between seagrass dry weight, ash-free dry weight and organic carbon content. The biotic data were related to environmental factors: DOC and nutrients in the water, salinity, tidal amplitude, sediment composition. A relation was estimated between bottom coverage of seagrasses and standing stock. Further calculations of biomass-production ratios allow a quick and rough estimate of seagrass productivity. Maximum above-ground biomass values (500–700 g AFDW·m −2) together with qualitative data indicate resource (= space) partitioning among the component seagrasses within a community, and suggest a carrying capacity of the reefflat habitat for seagrass density and biomass. A tentative model was constructed, starting from a constant, non-distributed multispecies vegetation in the lower intertidal and subtidal zone on sand and coral rubble, and moving into several suboptimal situations. The upper shore carries an impoverished, constrained vegetation (irregular tides, desiccation, harvesting). Sediment reworking by animals and physical displacement of sand disturbs the vegetation and favours pioneer species. Muddy habitats bordering mangroves carry monospecific stands showing extremely high biomass ( e.g. below-ground Enhalus acoroides 3500 g AFDW·m −2). Thalassia hemprichii and Enhalus acoroides are the most constant species in all habitats mentioned. Macrofauna biomass within the seagrass beds fluctuated widely (maximum values 50–70 g AFDW·m −2 in mixed seagrass vegetations) and only a weak relation between benthic macrofauna biomass and seagrass community structure and biomass was found.

Project STAG: an experimental study in agroforestry

An agroforestry study to identify problems in the development of stable silvopastoral systems in a subtropical environment was run over 4.6 years.Eucalyptusgrandis was planted in a Nelder fan design with tree stand densities ranging from 42 to 3580 stems ha-1 into a Seturia-dominated pasture. Growth of trees improved with increasing stand density until competition for water and light outweighed the benefits of mutual protection. For most parameters measured, there was a change in magnitude with time away from the centre of the wheel like ripples in a pond. At 1.5 years the maximum above-ground individual tree biomass was at a stocking of 3580 stems ha-1 . At 2,2.5,3,3.5 and 4.6 years the maxima were at 1140,595,305, 158 and 82 stems ha-1 respectively. Trees interacted with each other, even at low stand densities.Pasture production also showed a ripple effect, being little affected by the trees at age 0.5 years, but was substantially reduced after 1.5 years at stand densities over 1000 stems ha-1. By age 3.5 years, pasture production was reduced at stand densities over 300 stems ha-1. At this age and stocking, tree growth, taper, crown dimensions and health were also optimal.Trees and pasture can be successfully grown together to provide substantial production from each. A thinning regime would be required to maintain an optimum balance between the two components of this agroforestry system.

Biomass potentials of some firewood shrubs of North India

Seven firewood shrubs were evaluated with the maximum aboveground biomass being recorded for Sesbania aegyptica and Lagrastomia parviflora at 18·3 and 11·0 t/ha, respectively. Differences in proportion of woody biomass in relation to plant size led to variation in the energy content of the species studied.

Typha productivity in a Texas pond: Implications for energy and nutrient dynamics in freshwater wetlands

Above-and below-ground biomass of Typha angustifolia L. was sampled monthly for 18 months from a small Texas pond. Maximum above-ground biomass was 2559±284 g AFDW (ash-free dry weight) m −2 in 1983 and 2895±217 g AFDW m −2 in 1984. Peak below-ground biomass for these 2 years was 2506±278 g AFDW m −2 and 2314±226 g AFDW m t-2, respectively. Stepwise multiple linear regression analyses revealed that mean above-ground biomass accrual was related to duration of growing season, cumulative precipitation, cumulative degree days and/or cumulative pan evaporation. The same was not true for below-ground biomass increases. Analysis of covariance revealed that the rates of above-ground biomass production were not significantly different ( F test, p < 0.05) between the 1983 and 1984 growing seasons. Below-ground biomass turnover times for 1983 and 1984 were 2.47 and 1.21 years, respectively.

Plant Biomass, Primary Production and Litter Disappearance in a Filipendula Ulmaria Meadow Ecosystem, and the Effects of Cadmium

Cadmium was added at two concentration levels to the soil in 1973. Samplings were made in 1974. Filipendula ulmaria L. accounted for at least 80% of the total plant biomass. In untreated plots, maximum aboveground biomass of Filipendula (430 g m2) was obtained in early August. The main part of the total biomass, 60% or more, was below ground. About half of the belowground biomass was in rhizomes. A separation into current and previous year's roots revealed the yearly turnover of roots to be 75%. Primary production was estimated by four methods of calculation, which are compared and discussed. Depending on the method used, aboveground production was estimated at 409-544 g m2 and that below ground at 386-654 g m2. Within a year, 60% of aboveground litter might disappear, while disappearance of root litter seemed to be very rapid after root death. Aboveground biomass was only slightly affected at the lower Cd treatment. At the higher one, visual symptoms of Cd toxicity and reduced growth arose early in the season. Belowground organs was much more affected than aboveground ones. Especially the root biomass in the uppermost part of the soil was seriously decreased but in relation to untreated plots, growth was more vigorous deeper in the soil. Litter disappearance was retarded in Cd treated plots and root litter accumulated during the season.