Cultivation and carrageenan yield and quality ofKappaphycus alvarezii in the waters of Vietnam

The carrageenan-producing red algaKappaphycus alvarezii (Doty) Doty was brought to Vietnam from Japan in 1993. Branch fragments of this species were cultivated in a pond, lagoon, inlet and offshore in Vietnam for the first time. The best daily growth rate (DGR) of plants grown in the lagoon area attained 9–11 % day^–1 in May to June (cold season). The water temperature and salinity in this area ranged from 27.2–32.4 °C and 31.4–33.7 °C, respectively. DGR of plants grown in the inlet ranged from 7 to 9% day^–1 in June. Grazing by fish has been observed to occur in this area. The DGR of plants grown in the pond ranged from 5–6% in January–July, but decreased to less than 4% day^–1 in August (hot season). K. alvarezii in Vietnam showed a carrageenan yield of 18.8–24.6% and gel strength of 1566–1712 g cm^–2. These values are similar ones obtained fromK. alvarezii cultivated in the Philippines and Indonesia.     

Annual production by a stream brook charr population and by its principal invertebrate food

Synopsis Annual production by the brook charr (Salvelinus fontinalis) population in Valley Creek, Minnesota, over the five-year period 1968–1972, was closely correlated to production by its main invertebrate food, Gammarus pseudolimnaeus, which had been reduced by siltation. Annual production was 163–191 kg ha^–1 (wet weight) in 1968–1969, respectively, and then dropped to a mininum of 79 kg ha^–1 in 1971, the year most seriously affected by decreased invertebrate production and siltation; year-class strength, standing stock, and total year-class (cohort) production followed approximately the same pattern. Total year-class production was highest for the 1968–1969 year classes at 211–178 kg ha^–1, respectively, and lowest for the 1971 year class at 76 kg ha^–1. Annual P/B ratios ranged from 1.0 to 1.9; cohort P/B ratios, for the 1968–1972 year classes, ranged from 5.6 to 7.2.Paper No. 11,384, Scientific Journal Series, Minnesota Agricultural Experiment Station, St. Paul, Minnesota 55108, U.S.A.     

Biomass production by alders on four abandoned agricultural soils in Québec

The production of aboveground tissue of three alder species (Alnus crispa (Ait.) Pursh,A. rugosa (Du Roi) Spreng. andA. glutinosa (L) Gaertn.) on four sites ranged from 0.4 t ha^–1 yr^–1 to 4.0 t ha^–1 yr^–1 after four growing seasons. Large differences were observed among the four sites studied and among species. Soil nutrient levels affected the biomass production and foliar symptoms of P and Mg deficiency occurred withA. crispa andA. rugosa. Because of their poor aboveground biomass production (0.4–1.4 t ha^–1 yr^–1),A. crispa andA. rugosa should be used mainly as nurse trees. For its higher potential for biomass production (up to 4.0 t ha^–1 yr^–1), and its apparent higher ability to use P and Mg on deficient sites,A. glutinosa should be used preferably toA. crispa andA. rugosa for the production of biomass.     

Effect of soil-applied NPK fertilizers on severity of black spot disease (Alternaria brassicae) and yield of oilseed rape

Effect of soil application of eight combinations of NPK fertilizers on the severity of black spot disease (BSD), caused by Alternaria brassicae (Sacc.) Berk., and yield of short duration oilseed rape (Brassica campestris L) were investigated under both pot and field conditions in 1987–88, 1988–89 and 1990–91. The severity of BSD was significantly greater (36–48%) on plants grown in ground treated with NP (N 90 kg ha^–1+P 40 kg ha^–1) applied as urea and single superphosphate respectively than on plants from the unfertilized control (NoPoKo) (o). However, the severity of BSD was significantly smaller (25–33%) when K (40 kg ha^–1) was applied as muriate of potash than in plants from control and NP treatments. The effect of NK (N 90 kg ha^–1+K 40 kg ha^–1) in decreasing the severity of BSD was increasingly more pronounced than the effects of PK (P 40 kg ha^–1+K 40 kg ha^–1), NP and K (40 kg ha^–1) applications. The decrease in the severity of BSD due to K was due to increased production in plants of phenolics which inhibited conidial germination and decreased sporulation of A. brassicae.The decrease in the severity of BSD due to NK application gave consistently increased seed yield 68% more than those of control and other treatments. The K-fertilized plants also showed increased resistance to lodging, increased 1000-seed weight and decreased seed infection. Seeds obtained from K-fertilized plants showed good seed germinability and vigorous seeding growth.     

Production of a recombinant, immunogenic protein, P64k, of Neisseria meningitidis in Escherichia coli in fed-batch fermenters

P64k is a Neisseria meningitidis high molecular weight protein present in meningococcal vaccine preparations. The lpdA gene, codifying for this protein, was cloned in Escherichia coli and the P64k protein was expressed in Escherichia coli K12 W3110 under the control of the tryptophan promoter. The recombinant bacteria were grown in batch or fed-batch cultures. P64k was expressed as an intracellular soluble form at about 40% of the total cellular protein. A final productivity of 215 mg l^–1 h^–1 and 11 g cell dry wt l^–1 were obtained when the fed-batch culture conditions were optimised, compared to 30% of total protein, and a productivity of 76 mg l^–1 h^–1 and 5.1 g cell dry wt l^–1 in batch cultivation.     

Cage culture ofKappaphycus alvarezii var.tambalang (Gigartinales,Rhodophyceae)

Kappaphycus alvarezii var.tambalang was cultured in a 3 × 3 m bamboo raft installed inside a 4 × 4 m floating net cage ofLates calcarifer (sea bass) broodstock at SEAFDEC Sub-station Igang, Guimaras, Philippines, from December 1989 to May 1990. Growth and production ofK. alvarezii var.tambalang was influenced by the culture months. The highest growth rate and production were recorded in January and May, respectively, while the lowest growth rate and production were observed in March. Average growth rate (wet weight) ranged from 3.72 to 7.17% day^-1, while production ranged from 575.5 to 2377 g m^-1 line^-1. A total production of approximately 123 t (fresh) or 37 t (dried) ha^-1 in the 5-month harvest season was produced from this culture system. Cultivation ofK. alvarezii var.tambalang in cages is possible, which indicates that seaweeds can be grown with carnivorous finfish, a practice which is still untapped.     

Nitrogen concentration of cauliflower organs as determined by organ size,N supply,and radiation environment

Data from field experiments carried out in three consecutive years under contrasting N supply and radiation environment altered by artificial shading were used to identify (a) the relationship between N concentration and organ size under conditions of unrestricted N supply and (b) critical levels of soil nitrate (Nmin_crit), where nitrogen concentration of cauliflower organs begin to decline because of N limitations. The decline of N concentrations in cauliflower was analysed at different levels of morphological aggregation, i.e., the whole shoot level, the organ level (leaves, stem, and curd), and within different leaf groups within the canopy. Nmin_crit values (0–60 cm soil depth) for total nitrogen concentration of cauliflower organs leaves, stem and curd were estimated at 85, 93 and 28 kg N ha^–1, respectively. Within the canopy, Nmin_crit values for total N of leaves increased from the top to the bottom from 44 to 188 kg N ha^–1. Nmin_crit values for protein N in leaves from different layers of the canopy were much lower at around 30 kg N ha^–1, without a gradient within the canopy. It is discussed that these differences in Nmin_crit values are most likely a consequence of N redistribution associated with nitrogen deficiency. The decline of average shoot nitrogen concentrations, [Nm] (%N DM), with shoot dry matter, W _sh, (t ha^–1) under conditions of optimal N supply was [Nm]= 4.84 (±0.071) W _sh ^{–0.089(± 0.011)}, r ²=0.67 (±S.E.). The reduction of radiation intensity by artificial shading (60% of control) had no significant influence on total nitrogen concentrations of leaves and only a small influence on protein nitrogen concentrations in lower layers of the canopy. The leaf nitrate nitrogen fraction of nitrogen, f _nitr (–), within the canopy decreased linearly with increased average incident irradiance in different canopy layers (I _av, W PAR m^–2) (f _Nitr. = 0.2456(±0.0188) – 0.0023(±0.0004)I _av, r ² = 0.67.     

VA-mycorrhiza mediated P effect on growth and yield of sunflower (Helianthus annuus L.) at different P levels

A field trial was conducted to study the response of sunflower (Helianthus annuus L.) to different phosphorus levels (16, 24 or 32 kg P ha^–1) and inoculation with vesicular-arbuscular mycorrhizal fungus, Glomus fasciculatum on vertisol during summer 1993. At the vegetative stage of sunflower, percent mycorrhizal root colonization, spore count, dry biomass and P uptake did not differ significantly between inoculated and uninoculated control plants. However, at later stages (flowering and maturity) percent root colonization, spore count, total dry biomass and total P uptake were significantly higher in inoculated plants than in uninoculated control plants. The total dry biomass, P content and seed yield increased with increasing P level in uninoculated plants, whereas no significant difference was observed between 16 and 32 kg P ha^–1 in inoculated plants. The positive effect of mycorrhizal inoculation decreased with increasing P level above 16 kg P ha^–1, due to decreased percent root colonization and spore count at higher P levels.     

Biomass and production of a naturally regenerated oak forest in southern Korea

Biomass and production of two stands with Quercus variabilis Bl. as the dominant species (stands 1 and 3) and one with Q. mongolica Fisch. as the dominant species (stand 2) were investigated in southern Korea. Stands 1 and 3 naturally occurred on sites with southerly aspects while stand 2 naturally occurred on northerly aspects; stand ages were similar for the three stands (36–38 years old). Total above- and belowground biomass including understory vegetation (Mg ha^–1) was 108.4 for stand 1, 115.6 for stand 2, and 132.0 for stand 3, respectively. Understory vegetation constituted 17.4% of the total biomass in stand 1 but only 3.7–4.5% in stand 2 and stand 3. Roots constituted 20.1–24.6% of the biomass of the overstory vegetation. Although stand 3 showed the highest total biomass, net production was highest in stand 2 at 12.6 (Mg ha^–1 year^–1); net production levels for stands 1 and 3 were 11.7 and 11.1 (Mg ha^–1 year^–1), respectively. It appeared that the differences in site conditions related to aspect influenced the distribution of naturally regenerated oak species within a relatively small area and resulted in differences in biomass and production among the stands.     

Relationships between soil,fallow period,weeds and rice yield in slash-and-burn systems of Laos

Decline in soil fertility accelerated by shorter fallow periods was expected to be a major constraint in slash-and-burn rice production systems in northern Laos. In this paper we describe relationships between fallow period, soil fertility parameters, weeds and rice yield. Soil infertility is not perceived a major yield constraint by the farmers. Of the various soil parameters observed only soil organic matter showed consistent association with rice yield (r=0.42, p<0.01). Fallow period and rice yield showed no association and the relationship between fallow and organic matter was very weak (r=0.16, p<0.01). Rice yield was negatively related to densities of Ageratum conyzoides and Lygodium flexuosum. Soil loss during the cropping period ranged from 300–29.300 kg ha^–1. For the same period organic matter, total N, available P and available K content in the top 0–3 cm decreased by 11,12,17, and 17%, respectively, and loss of total N for the soil depth of 0–25 cm was estimated at 400 kg ha^–1. Soil physical properties, moisture stress and available N are the most likely detriments to rice yields. Further attempts to relate soil properties to rice yield should include repeated measurements during the cropping season and observations on soil physical properties.The research presented was supported by the Provincial Agriculture Service, Luang Prabang, Laos, and the Swiss Development Cooperation.     

Effect of crop residues on root growth and phosphorus acquisition of pearl millet in an acid sandy soil in Niger

The effect of long-term (1983–1988) applications of crop residues (millet straw, 2–4 t ha^-1 yr^–1) and/or mineral fertilizer (30 kg N, 13 kg P and 25 kg K ha^-1 yr^-1) on uptake of phosphorus (P) and other nutrients, root growth and mycorrhizal colonization of pearl millet (Pennisetum glaucum L.) was examined for two seasons (1987 and 1988) on an acid sandy soil in Niger. Treatments of the long-term field experiment were: control (–CR–F), mineral fertilizer only (–CR+F), crop residues only (+CR–F), and crop residues plus mineral fertilizer (+CR+F).In both years, total P uptake was similar for +CR–F and –CR+F treatments (1.6–3.5 kg P ha^-1), although available soil P concentration (Bray I P) was considerably lower in +CR–F (3.2 mg P kg^-1 soil) than in –CR+F (7.4) soil. In the treatments with mineral fertilizers (–CR+F; +CR+F), crop residues increased available soil P concentrations (Bray I P) from 7.4 to 8.9 mg kg^-1 soil, while total P uptake increased from 3.6 to 10.6 kg P ha^-1. In 1987 (with 450 mm of rainfall), leaf P concentrations of 30-day-old millet plants were in the deficiency range, but highest in the +CR+F treatment. In 1988 (699 mm), leaf P concentrations were distinctly higher, and again highest in the +CR+F treatment. In the treatments without crop residues (–CR–F; –CR+F), potassium (K) concentrations in the leaves indicated K deficiency, while application of crop residues (+CR–F; +CR+F) substantially raised leaf K concentrations and total K uptake. Leaf concentrations of calcium (Ca) and magnesium (Mg) were hardly affected by the different treatments.In the topsoil (0–30 cm), root length density of millet plants was greater for +CR+F (6.5 cm cm^-3) than for +CR–F (4.5 cm cm^-3) and –CR+F (4.2 cm cm^-3) treatments. Below 30 cm soil depth, root length density of all treatments declined rapidly from about 0.6 cm cm^-3 (30–60 cm soil depth) to 0.2 cm cm^-3 (120–180 cm soil depth). During the period of high uptake rates of P (42–80 DAP), root colonization with vesicular-arbuscular mycorrhizal (VAM) fungi was low in 1987 (15–20%), but distinctly higher in 1988 (55–60%). Higher P uptake of +CR+F plants was related to a greater total root length in 0–30 cm and also to a higher P uptake rate per unit root length (P influx). Beneficial effects of crop residues on P uptake were primarily attributed to higher P mobility in the soil due to decreased concentrations of exchangeable Al, and enhancement of root growth. In contrast, the beneficial effect of crop residues on K uptake was caused by direct K supply with the millet straw.     

Is a ferroxidase involved in the high-affinity iron uptake in Chlamydomonas reinhardtii?

In phosphorus deficient soils and under smallscale farming systems, the development of efficient management strategies for P fertilizers is crucial to sustain food production. A field experiment was conducted on a P-fixing Acrisol in western Kenya to study possibilities of replenishing soil P with seasonal additions of small rates of P fertilizers. Triple superphosphate was applied at 0, 10, 25, 50 and 150 kg P ha^–1 for 5 consecutive maize growing seasons followed by 4 seasons of residual crops. Maize yields and soil P fractions were determined. Although maize responded to additions of 10 kg P ha^–1 with a cumulative grain yield of 16.8 Mg ha^–1, at the end of the experiment, compared to 8.8 Mg ha^–1 in the non-P fertilized plots, soil labile P did not increase correspondingly. Seasonal additions of 150 kg P ha^–1 increased maize yields to a cumulative value of 39 Mg ha^–1 at the end of the experiment, and increased all soil inorganic P fractions. At the third season of residual phase, treatment with a cumulative addition of 750 kg P ha^–1 gave the highest yields compared to treatments in the same residual stage, but these yields were considered less than the maximum yield of the season. This indicates that the large build up of soil P was not available for crop uptake. The inorganic P fraction extracted by NaHCO₃ was the most affected by changes in management, increasing during the input phase and decreasing after interruption of P addition, for all P rates. The decrease in this pool during the residual phase could be explained by the maize uptake. This study showed that seasonal additions of 25 kg P ha^–1 can increase maize yield with gradual replenishment of soil P.     

Differences in biomass production and carrageenan yields among four strains of farmed carrageenophytes in Northern Bohol,Philippines

Comparative studies on the biomass and carrageenan production of two strains ofEucheuma denticulatum and two strains ofKappaphycus alvarezii were made to assess the seasonality in their production capacities.The high and similar refined carrageenan (RC) yields (43–53% of dry wt.) of the four strains in the first cropping season (June–October) coincided with their high biomass production with plants averaging from 1.1 to 1.8 kg each at harvest. The poor RC yields (21–33%) recorded in the second cropping (October–February) coincided with their season of low biomass (av. wt: 0.34 to 1.0 kg). The four strains, however, recorded contrasting performance in the third cropping season (February–July) with the twoE. denticulatum strains recording high RC yields (43 and 42.5%) together with high biomass (av. wt: 1.5 and 1.6 kg) in contrast to the low RC yields (30 and 39%) and low biomass (av. wt. 0.21 and 0.28 kg) of the twoK. alvarezii strains. Records for semi-refined carrageenan (SRC) yields in the second and third cropping seasons were quite consistent and similar for the four strains (42–55%), except in the second cropping where the twoK. alvarezii strains recorded low SRC. These differences in production potentials highlight the need for cropping management of the four strains to improve their cropping performance.     

Improvement of phenylethanoid glycosides production by a fungal elicitor in cell suspension culture of Cistanche deserticola

When, on the 15th day of growth, an elicitor from Fusarium solani was added at 40 mg l^–1 to Cistanche deserticola cell suspension cultures, the contents of echinacoside, acteoside and total phenylethanoid glycosides (PeGs) in cultured cells all increased over the next 27 d by over 100% to 15 mg g^–1 dry wt, 9 mg g^–1 dry wt and 57 mg g^–1 dry wt, respectively. The final biomass (1.3 mg dry wt ml^–1) was not affected.     

Growth,biomass, mortality,production and potential yield of the West African clam,Egeria radiata (Lamarck) (Lamellibranchia,Donacidae) in the Cross River system,Nigeria

An important fishery for the West African hemi-estuarine clam, Egeria radiata exists in the lower reaches of the Cross River (CR) system. The stock is heavily exploited but its productivity and potential yield have not been studied. This paper discusses the distribution and ecology of, and presents data on growth, abundance, mortality, biological production and potential yield of the CR stock of E. radiata based principally on length structured relative age. Growth was exponential and conformed to the von Bertalanffy's growth model (VBGM), with the parameters L = 9.3 cm, K = 0.36 and T _o = –0.10 year. The instantaneous total mortality coefficient (Z) by the catch curve method was 0.82 yr^–1; natural mortality coefficient (M) was estimated at 0.32 yr^–1. Total mean biomass computed from data obtained in two month's grab sample surveys in the area of occurrence of E. radiata was 1923 kg ha^–1 for total (i.e. flesh + shell) and 628 kg ha^–1 for flesh (i.e. shell-free) production units. The production-to-mean-biomass (or P/B ratio, R) were 0.31 and 0.52 for total and shell-free production units respectively. The maximum sustainable yield (Y _max) was estimated at 398.4 kg ha^–1 for total and 112.2 kg ha^–1 for shell-free production units. With an exploitation ratio (E) of 0.61 and an estimated present catch rate of 1970 tonnes(t) yr^–1 total weight (or about 82% of Y _max) the Egeria stock of the CR is currently being fished above the level of its optimum yield. Much of the fishing pressure is on the very young clams, thus lowering the age at first capture (T _c) to 1 year. This is an unhealthy situation for a species with limited area of distribution and low (< 1.0) P/B ratio; it can lead to rapid extinction of the stock if for some reason there is a substantial reduction in annual recruitment. It is recommended that in order to conserve this valuable resource and keep it at a level of sustained optimum yield, there should be a regulation prohibiting the landing of young clams (< 6.0 cm shell length). Furthermore the fishermen should learn to cultivate the animal by transplanting the young clams to new beds upstream to give them time to grow larger before harvesting. This type of management has been practised in Ghana for a long time and has helped to conserve the Egeria stock of the Volta River. The need for a continuous monitoring of the effluents from the Nigerian Newsprint Manufacturing Company's factory located at the bank of the CR in the centre of the clam industry is stressed; such monitoring would ensure that dangerous toxic chemicals are not discharged into the river to damage the Egeria industry.     

Production rate ofEichhornia crassipes (Mart.) Solms in river Ganga water

The production rate ofEichhornia crassipes was stimulated by water of the river Ganga and by prevailing environmental conditions. It was highest in October (4.76 g.m^–2.d^–1) and was positively correlated with ammonia nitrogen and total phosphorus in the water but negatively correlated with total alkalinity and transparency. The average annual production of 14.13 t.ha^–1.a^–1 is equivalent to the average production of 0.067 t.ha^–1.a^–1 phosphorus and 0.40 t.ha^–1.a^–1 nitrogen. The concentrations of total nitrogen and total phosphorus of the plant varied seasonally. They decreased with increasing production rate in summer and monsoon.     

Phosphorus budget in the Marne Watershed (France): urban vs. diffuse sources,dissolved vs. particulate forms

We evaluated the P sources (point, diffuse), through a nested watershed approach investigating the Blaise (607 km²), dominated by livestock farming, the Grand Morin (1202 km²), dominated by crop farming, and the Marne (12,762 km²), influenced by both agriculture and urbanization. Fertilizers account for the main P inputs (>60%) to the soils. An agricultural P surplus (0.5–8 kg P ha^–1 year^–1) contributes to P enrichment of the soil. The downstream urbanized zone is dominated by point sources (60%, mainly in dissolved forms), whereas in the upstream basin diffuse sources dominate (60%, mostly particulate). Among the diffuse sources (losses by forests, drainage and runoff), losses by runoff clearly dominate (>90%). P retention in the alluvial plain and the reservoir represents 15–30% of the total P inputs. Dissolved and particulate P fluxes at the outlet of the Marne are similar (340 and 319 tons of P year^–1, respectively). The Blaise sub-basin receives P from point and diffuse sources in equal proportions, and retention is negligible. The Grand-Morin sub-basin, influenced by the urbanized zone receives, as does to the whole Marne basin, 60% of P inputs as point sources. The total particulate phosphorus in suspended sediments averaged 1.28 g P kg^–1, of which about 60% are inorganic and 40% organic P. Particulate phosphorus exchangeable in 1 week and 1 year (³²P isotopic method) accounts for between almost 26% and 54% of the particulate inorganic phosphorus in the suspended sediment and might represent an important source of dissolved P, possibly directly assimilated by the vegetation.     

Optimization of growth and fatty acid composition of a unicellular marine picoplankton,Nannochloropsis sp., with enriched carbon sources

A unicellular marine picoplankton, Nannochloropsis sp., was grown under CO₂-enriched photoautotrophic or/and acetate-added mixotrophic conditions. Photoautotrophic conditions with enriched CO₂ of 2800 l CO₂ l^–1 and aeration gave the highest biomass yield (634 mg dry wt l^–1), the highest total lipid content (9% of dry wt), total fatty acids (64 mg g^–1 dry wt), polyunsaturated fatty acids (35% total fatty acids) and eicosapentaenoic acid (EPA, 20:53) (16 mg g^–1 dry wt or 25% of total fatty acids). Mixotrophic cultures gave a greater protein content but less carbohydrates. Adding sodium acetate (2 mM) decreased the amounts of the total fatty acids and EPA. Elevation of CO₂ in photoautotrophic culture thus enhances growth and raises the production of EPA in Nannochloropsis sp.     

Decomposition and nutrient release by green manures in a tropical hillside agroecosystem

The decomposition and nutrient release of 12 plant materials were assessed in a 20-week litterbag field study in hillsides from Cauca, Colombia. Leaves of Tithonia diversifolia (TTH) and Indigofera constricta (IND) decomposed quickly (k=0.035±0.002 d^–1), while those of Cratylia argentea (CRA) and the stems evaluated decomposed slowly (k=0.007±0.002 d^–1). Potassium presented the highest release rates (k>0.085 d^–1). Rates of N and P release were high for all leaf materials evaluated (k>0.028 d^–1) with the exception of CRA (N and P), TTH and IND (P). While Mg release rates ranged from 0.013 to 0.122 d^–1, Ca release was generally slower (k=0.008–0.041 d^–1). Initial quality parameters that best correlated with decomposition (P>0.001) were neutral detergent fibre, NDF (r=–0.96) and in vitro dry matter digestibility, IVDMD (r=0.87). It is argued that NDF or IVDMD could be useful lab-based tests during screening of plant materials as green manures. Significant correlations (P>0.05) were also found for initial quality parameters and nutrient release, being most important the lignin/N ratio (r=–0.71) and (lignin+polyphenol)/N ratios (r=–0.70) for N release, the C/N (r=0.70) and N/P ratios (r=–0.66) for P release, the hemicellulose content (r=–0.75) for K release, the Ca content (r=0.82) for Ca release, and the C/P ratio (r=0.65) for Mg release. After 20 weeks, the leaves of Mucuna deerengianum released the highest amounts of N and P (144.5 and 11.4 kg ha^–1, respectively), while TTH released the highest amounts of K, Ca and Mg (129.3, 112.6 and 25.9 kg ha^–1, respectively). These results show the potential of some plant materials studied as sources of nutrients in tropical hillside agroecosystems.     

Chaff piles of harvester ant (Messor spp.) nests in a desert ecosystem

Summary The plant species composition of the chaff piles of three species of harvester ant (Messor spp.) and the contribution of the chaff to the organic pool were studied from August 1985 to July 1987. There were distinct differences in the plant species composition of the chaff of the three species. We attribute this to the different diets of the three species, which reflect the relative sizes of their individuals and their foraging strategies. The amount of chaff accumulated varies greatly between the three species (Messor rugossus: 127–196 g · ha^–1 · y^–1;Messor ebeninus: 2823–4437 g · ha^–1 · y^–1;Messor arenarius: 2165–2535 g · ha^–1 · y^–1), although the number of nests per hectare is virtually the same. We found that the amount of chaff is related to the rate of activity and the size of the individuals of each of the three ant species. The total chaff accumulated during the study period was 19.2 kg · ha^–1, which is an important contribution to the organic matter in the soil in the Negev desert ecosystem.