Particulate organic matter in a mountain stream in the south-western Cape,South Africa

The quality and quantity of allochthonous inputs and of benthic organic matter were investigated in a second-order, perennial mountain stream in the south-west Cape, South Africa, between April 1983 and January 1986. Although the endemic, riparian vegetation is sclerophyllous, low and evergreen, inputs of allochthonous detritus to the stream (434 to 500 g m^–2y^–1) were similar to those recorded for riparian communities worldwide, as were calorific values of these inputs (9548 to 10 032 KJ m^–2y^–1). Leaf fall of the riparian vegetation is seasonal, occurring in spring (November) as discharge decreases, resulting in retention of benthic organic matter (BOM) on the stream bed during summer and early autumn (maximum 224 g m^–2). Early winter rains (May) scoured the stream almost clean of benthic detritus (winter minimum 8 g m^–2). Therefore, BOM was predictably plentiful for about half of each year and predictably scarce for the other half. Coarse BOM (CBOM) and fine BOM (FBOM) constituted 46–64% of BOM standing stock, ultra-fine BOM (UBOM) 16–33% and leaf packs 13–24%. The mean annual calorific value of total BOM standing stock was 1709 KJ m^–2. Both standing stocks and total calorific values of BOM were lower than those reported for streams in other biogeographical regions. Values of C:N ratios decreased with decrease in BOM particle size (CBOM 27–100; FBOM 25–27; UBOM 13–19) with no seasonal trends. The stream is erosive with a poor ability to retain organic detritus. Its character appears to be dictated by abiotic factors, the most important of which is winter spates.     

Lateral input of particulate organic matter from bank slopes surpasses direct litter fall in the uppermost reaches of a headwater stream in Hokkaido, Japan

In forested streams, surrounding riparian forests provide essential supplies of organic matter to aquatic ecosystems. We focused on two pathways of particulate organic matter inputs: direct input from upper riparian forests and indirect lateral input from bank slopes, for which there are limited quantitative data. We investigated the inputs of coarse particulate organic matter (CPOM) and carbon and nitrogen in the CPOM into the uppermost reaches of a headwater stream with steep bank slopes in Hokkaido, Japan. CPOM collected by litter traps was divided into categories (e.g., leaves, twigs) and weighed. Monthly nitrogen and carbon inputs were also estimated. The annual direct input of CPOM (ash-free dry mass) was 472 g m⁻², a common value for temperate riparian forests. The annual lateral CPOM input was 353 g m⁻¹ and 941 g m⁻² when they were converted to area base. This value surpassed the direct input. Organic matter that we could not separate from inorganic sediments contributed to the total lateral input from the bank slopes (124 g m⁻¹); this organic matter contained relatively high amounts of nitrogen and carbon. At uppermost stream reaches, the bank slope would be a key factor to understanding the carbon and nitrogen pathways from the surrounding terrestrial ecosystem to the aquatic ecosystem.     

Pattern of wood litter fall in five forests located along an altitudinal gradient in Central Himalaya

Wood and total litter fall were measured in five forests of the Kumaun Himalaya situated along an altitudinal gradient from 329 m to 1850 m. Total annual wood litter fall, which ranged from 93 to 197 g m², was inversely related with altitude and positively related with forest basal cover. Total litter fall ranged from 405 to 839 g m² yr¹ and was positively related with forest basal cover. Wood litter fall was highest in the rainy season and that of total litter in the summer season. Abscissed litter accounted for a maximum proportion of seasonal wood fall in summer. Monthly non-abscissed wood fall was positively related to the monthly rainfall on each site. The fractions in lower diameter classes (0–5 to 5–10 mm) dominated the annual wood fall in all forests and accounted for 59 to 78% of the total. Fractions in >10 mm size class fall maximally during the rainy months.Nomenclature follows Kanjilal & Gupta (1969) unless otherwise stated.The authors are thankful to Dr Uma Pandey for helpful suggestions and to the Department of Science and Technology, New Delhi for financial support.     

Litter input from riparian vegetation to streams: a case study of the Njoro River,Kenya

Allochthonous coarse particulate organic matter (CPOM) input into the Njoro River was measured between January and June 1998 at two contrasting sites: open-canopy and closed-canopy sites. Bank runoff and aerial drift traps were used for collecting CPOM inputs over periods of two weeks. Collected litter was sorted into four categories: leaves, fruits, wood and plant fragments. Monthly input ranged from 77 to 228 g ash free dry weight m^–1 for bank runoff input and from 64 to 129 g ash free dry weight m^–2 for aerial input. The highest input of 228 g ash free dry weight m^–1 was recorded in May at the closed-canopy site. Wood, fruits and plant fragments of particle size >100 m contributed a mean ± SE of 60±9% of the total inputs with the rest from leaf litter. The closed-canopy site had higher inputs (P<0.05) of bank and aerial input than the open canopy site. There was no relationship between total bank runoff input and rainfall (r _s = 0.08), however, total aerial input increased with decrease in rainfall (r _s = – 0.59). There were differences between inputs from different plant species (P<0.05) that ranked in the following order: Syzygium cordatum > Rhus natalensis > Pittosporum viridiflorum > Vangueria madagascariensis. Removal of riparian vegetation from the banks of the Njoro River would alter the quantity and quality of the litter and reduce CPOM inputs to the river and to a downstream lake with attendant consequences to the energy budget of biocoenoses in the two ecosystems.     

Dry matter and nutrient inputs through litter fall in a dry tropical forest of India

The present paper elucidates the pattern of leaf and non-leaf fall and quantifies of the total annual input of litter in a dry tropical forest of India. In addition, concentration of selected nutrients in various litter species and their annual return to the forest floor are examined. Total annual input of litter measured in litter traps ranged between 488.0–671.0 g m^-2 of which 65–72% was leaf litter fall and 28–35% wood litter fall. 73–81% leaves fall during the winter season. Herbaceous litter fall ranged between 80.0–110.0 g m^-2 yr^-1. The annual nutrient return through litter fall amounted (kg ha^-1): 51.6–69.6 N, 3.1–4.3 P, 31.0–40.0 Ca, 14.0–19.0 K and 3.7–5.0 Na, of which 71–77% and 23–29% were contributed by leaf and wood litter fall, respectively for different nutrients. Input of nutrients through herbaceous litter was: 13.0–16.6 for N, 1.0–1.4 for P, 4.0–5.0 for Ca, 7.9–10.5 for K and 0.8–1.0 kg ha^-1 yr^-1 for Na.     

Forest floor mass,litterfall and nutrient return in Central Himalayan high altitude forests

Dynamics of forest floor biomass, pattern of litter fall and nutrient return in three central Himalayan high elevation forests are described. Fresh and partially decomposed litter layer occur throughout the year. In maple and birch the highest leaf litter value was found in October and in low-rhododendron in August. The relative contribution of partially and more decomposed litter to the total forest floor remains greatest the year round. The total calculated input of litter was 627.7 g m^-2 yr^-1 for maple, 477.87 g m^-2 yr^-1 for birch and 345.9 g m^-2 yr^-1 for low-rhododendron forests. 49–61% of the forest floor was replaced per year with a subsequent turnover time of 1.6–2.0 yr. The annual nutrient return through litter fall amounted to (kg ha^-1 yr^-1) 25.5–56.1 N, 2.0–5.4 P and 9.9–23.3 K. The tree litter showed an annual replacement of 26–54% for different nutrients and it decreased towards higher elevation. The nutrient use efficiency in terms of litter produced per unit of nutrient was higher in present study compared to certain mid- and high-elevation forests of the central Himalaya.     

Forest floor biomass,litter fall and nutrient return in Central Himalayan oak forests

The seasonal dynamics of forest floor biomass, pattern of litter fall and nutrient return in Central Himalayan oak forests are described. Fresh and partially decomposed litter layers occur throughout the whole year in addition to herbaceous vegetation. The highest leaf litter value is found in April and May and the minimum in September. Partially and largely decomposed litter tended to increase from January to May with a slight decline in June. The wood litter peaked in March and April. The relative contribution of partially decomposed litter to the forest floor remains greatest the year round. The maximum herbaceous vegetation development was found in September with a total annual net production of 104.3 g m^-2yr^-1. The total calculated input of litter was 480.8 g m^-2yr^-1. About 68% of the forest floor was replaced each year with a subsequent turnover time of 1.47 yr. The total annual input of litter ranged from 664 (Quercus floribunda site) –952 g m^-2 (Q. lanuginosa site), of which tree, shrub and herbaceous litter accounted for respectively 72.0–86.3%, 6.4 – 19.4% and 5.2 – 8.6%. The annual nutrient return through litter fall amounted to (kg ha^-1) 178.0 – 291.0 N, 10.0 – 26.9 P, 176.8 – 301.6 Ca, 43.9 – 64.1 K and 3.98 – 6.45 Na. The tree litter showed an annual replacement of 66.0 – 70.0%, for different nutrients the range was 64 and 84%.     

Respiration and annual fungal production associated with decomposing leaf litter in two streams

1. We compared fungal biomass, production and microbial respiration associated with decomposing leaves in one softwater stream (Payne Creek) and one hardwater stream (Lindsey Spring Branch). 2. Both streams received similar annual leaf litter fall (478–492 g m^?2), but Lindsey Spring Branch had higher average monthly standing crop of leaf litter (69 ± 24 g m^?2; mean ± SE) than Payne Creek (39 ± 9 g m^?2). 3. Leaves sampled from Lindsey Spring Branch contained a higher mean concentration of fungal biomass (71 ± 11 mg g^?1) than those from Payne Creek (54 ± 8 mg g^?1). Maximum spore concentrations in the water of Lindsay Spring Branch were also higher than those in Payne Creek. These results agreed with litterbag studies of red maple (Acer rubrum) leaves, which decomposed faster (decay rate of 0.014 versus 0.004 day^?1), exhibited higher maximum fungal biomass and had higher rates of fungal sporulation in Lindsey Spring Branch than in Payne Creek. 4. Rates of fungal production and respiration per g leaf were similar in the two streams, although rates of fungal production and respiration per square metre were higher in Lindsey Spring Branch than in Payne Creek because of the differences in leaf litter standing crop. 5. Annual fungal production was 16 ± 6 g m^?2 (mean ± 95% CI) in Payne Creek and 46 ± 25 g m^?2 in Lindsey Spring Branch. Measurements were taken through the autumn of 2 years to obtain an indication of inter‐year variability. Fungal production during October to January of the 2 years varied between 3 and 6 g m^?2 in Payne Creek and 7–27 g m^?2 in Lindsey Spring Branch. 6. Partial organic matter budgets constructed for both streams indicated that 3 ± 1% of leaf litter fall went into fungal production and 7 ± 2% was lost as respiration in Payne Creek. In Lindsey Spring Branch, fungal production accounted for 10 ± 5% of leaf litter fall and microbial respiration for 13 ± 9%.     

The influence of crabs on litter processing in high intertidal mangrove forests in tropical Australia

Summary Measurements of litter fall and litter removal by crabs, in conjunction with estimates of litter decay by microbes and tidal export of litter from three high-intertidal mangrove forests were made during a year-long study in tropical northeastern Australia. In forests dominated by Ceriops tagal and Bruguiera exaristata, litter standing stocks remained low on the forest floor (mean 6 g·m^-2), although litter fall was high; 822 and 1022 g·m^-2·y^-1, respectively. Sesarmid crabs removed 580 (Ceriops) and 803 (Bruguiera) g·m^-2·y^-1, or 71 and 79%, of the total annual litter fall from the forest floor. Relative to the rate of litter removal by crabs, microbial turnover of whole, unshredded litter was insignificant, accounting for <1% of annual litter fall. Export of litter by tides was estimated to remove 194 (Ceriops) and 252 (Bruguiera) g·m^-2·y^-1 or 24 and 25% of annual litter fall. In a forest dominated by Avicenniamarina, in which an ocypodid crab was more abundant than sesarmids, litter standing stocks were higher (mean 84 g·m^-2) and crabs removed less litter; 173 g·m^-2·y^-1 or 33% of the annual litter fall of 519 g·m^-2·y^-1. Microbial turnover of intact litter was more important in the Avicennia forest (168 g·m^-2·y^-1 or 32% of annual litter fall), and tides exported 107 g·m^-2·y^-1 or 21% of litter production. In areas where sesarmid crabs were absent or rare in Ceriops forests, there were significantly higher standing stocks of litter and slower rates of leaf removal. Taking into account the probable assimilation efficiencies of sesarmid crabs feeding on mangrove leaves, we estimate that in Ceriops and Bruguiera forests leaf processing by crabs turns litter over at >75 times the rate of microbial decay alone, thus facilitating the high sediment bacterial productivity in these forests. The importance of litter processing by crabs increases with height in the intertidal in tropical Australia, in contrast to New World mangrove forests, where the reverse is true.Contribution No. 445 from the Australian Institute of Marine Science     

Leaf Litter Dynamics and Its Use by Invertebrates in a High‐Altitude Tropical Andean Stream

This study evaluates litter dynamics and its relation to macroinvertebrate communities (assemblages and feeding habits) at Piburja stream (3300 m, Ecuador). Annual litterfall (216 g AFDM/m²) was not related to rainfall, but differed significantly between months. Transport of Coarse Particulate Organic Matter (CPOM) did not differ between seasons, but retention was higher during the dry season. Thus, CPOM standing stock was higher in the dry (125.28 g AFDM/m²) compared to the wet season (12.27 g AFDM/m²). Macroinvertebrate richness and diversity were positively related to Coarse Benthic Organic Matter (CBOM) especially during the wet season. Gut content analysis revealed that, regardless of season, CPOM and Fine Particulate Organic Matter (FPOM) were the most important food items in the diet of most invertebrate taxa, including those that are not considered shredders or gathering collectors in the literature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Allochthonous litter inputs, organic matter standing stocks, and organic seston dynamics in upland Panamanian streams: potential effects of larval amphibians on organic matter dynamics

Allochthonous inputs of detritus represent an important energy source for streams in forested regions, but dynamics of these materials are not well studied in neotropical headwater streams. As part of the tropical amphibian declines in streams (TADS) project, we quantified benthic organic matter standing stocks and organic seston dynamics in four Panamanian headwater streams, two with (pre-amphibian decline) and two without (post-decline) healthy amphibian assemblages. We also measured direct litterfall and lateral litter inputs in two of these streams. Continuous litterfall and monthly benthic samples were collected for 1 year, and seston was collected 1–3 times/month for 1 year at or near baseflow. Direct litterfall was similar between the two streams examined, ranging from 934–1,137 g DM m⁻² y⁻¹. Lateral inputs were lower, ranging from 140–187 g DM m⁻¹ y⁻¹. Dead leaves (57–60%), wood (24–29%), and green leaves (8–9%) contributed most to inputs, and total inputs were generally higher during the rainy season. Annual habitat-weighted benthic organic matter standing stocks ranged from 101–171 g AFDM m⁻² across the four study reaches, with ∼4 × higher values in pools compared to erosional habitats. Total benthic organic matter (BOM) values did not change appreciably with season, but coarse particulate organic matter (CPOM, >1 mm) generally decreased and very fine particulate organic matter (VFPOM, 1.6–250 μm) generally increased during the dry season. Average annual seston concentrations ranged from 0.2–0.6 mg AFDM l⁻¹ (fine seston, <754 μm >250 μm) and 2.0–4.7 mg AFDM l⁻¹ (very fine, <250 μm >1.6 μm), with very fine particles composing 85–92% of total seston. Quality of fine seston particles in the two reaches where tadpoles were present was significantly higher (lower C/N) than the two where tadpoles had been severely reduced (P = 0.0028), suggesting that ongoing amphibian declines in this region are negatively influencing the quality of particles exported from headwaters. Compared to forested streams in other regions, these systems receive relatively high amounts of allochthonous litter inputs but have low in-stream storage. Handling editor: J. Padisak     

Seasonal changes in composition and biomass of epilithic algal floras of a chalk stream and a soft water stream with estimates of production

Microscopic epilithic algae in the River Itchen at Otterbourne near Southampton and in the Ober Water in the New Forest were studied during 1984 and 1985. The River Itchen rises from chalk springs and has a steady pH near 8.2 and a mean alkalinity of 236 mg HCO₃ 1^–1; at the study site the river is about 16 m wide and 20 cm deep, with a mean flow rate of 0.33 m s^–1 and a discharge ranging through the year between 0.34 and 2.46 m³ s^–1. The Ober Water, which drains sands and gravels, has a pH between 6.9 and 7.2 and a mean alkalinity of about 50 mg HCO₃ 1^–1; at the study site it is about 6 m wide, with a mean flow rate of 0.27 m s^–1 and a discharge ranging through the year between 0.08 and 1.0 m³ s^–1.Epilithic algae removed from the pebbles that form the major part of the beds of both streams show seasonal changes in abundance and composition. Diatoms peaked in April/May and dominate the epilithic flora in both streams, comprising 70–95% of all algal cells; highest numbers of chlorophytes occurred in summer and cyanophytes increased in autumn. The species composition of the epilithic flora in the two streams was different, as was the population density; algal cell numbers ranged between 500 and 7000 cells mm^–2 of stream floor in the River Itchen and between 8 and 320 cells mm^–2 of stream floor in the Ober Water. The chlorophyll a content of epilithic algae in the River Itchen ranged between 115 and 415 mg m^–2 of stream floor, representing an annual mean biomass of about 8 g m^–2, whereas in the Ober Water a chlorophyll a content of 2.2 to 44 mg m^–2 of stream floor was found, representing an annual mean biomass of about 1 g m^–2. Cautious estimates of the annual production of epilithic algae in these streams suggest a value of about 600 g organic dry weight m^–2 in the River Itchen and about 75 g m^–2 in the Ober Water.     

The response of Chironomidae (Diptera) to a long-term exclusion of terrestrial organic matter

We examined the effects of a seven-year detrital exclusion on chironomid assemblages in an Appalachian headwater stream. We hypothesized that litter exclusion would lead to a reduction in all chironomids at both the subfamily and generic levels because organic matter serves as both food and habitat in these headwater streams. Tanytarsini total abundance and biomass significantly declined after litter exclusion. Before litter exclusion, Tanytarsini average abundance was 4271 ± 1135 S.E. m⁻² and 625 ± 98 after litter exclusion. Biomass was 3.57 ± 0.96 mg AFDM m⁻² before litter exclusion and 1.03 ± 0.9 after exclusion. In contrast, Orthocladiinae abundance and biomass did not change because a psammanophilic chironomid, Lopescladius sp., and other Orthocladiinae genera did not decline significantly. Overall chironomid taxa richness and diversity did not change as a result of litter exclusion. However, Canonical Correspondence Analysis (CCA) of genus-level biomass did show a clear separation between the litter exclusion stream and a reference stream. Separation of taxa between the two streams was due to differences in fine (r ² = 0.39) and coarse (r ² = 0.36) organic matter standing stocks and the proportion of small inorganic substrates (r ² = 0.39) present within a sample. As organic matter declined in the litter exclusion stream, overall chironomid biomass declined and the chironomid community assemblage changed. Tanytarsini were replaced by Orthocladiinae in the litter exclusion stream because they were better able to live and feed on biofilm associated with inorganic substrates. Handling editor: K. Martens     

Trophic cascading effects of predatory fish on leaf litter processing in a Japanese stream

A manipulative field experiment to test for trophic cascading effects of predatory fish on detritus processing by benthic invertebrates was performed in stream channels running through a wetland forest in northern Japan. To control for fish effects on benthic invertebrates, two simple treatments (fish-present and fish-absent) were established for 4 weeks, with two common predatory fish, rainbow trout (Oncorhynchus mykiss) and freshwater sculpin (Cottus nozawae), being introduced into and excluded from stream cages. At the end of experiment, the biomass of the dominant detritivore, an amphipod (Jesogammarus jezoensis), was significantly less in the fish-present treatment (0.56 g m^–2 in dry mass on average) than that in the fish-absent treatment (1.32 g m^–2), there being no significant treatment effect evident for the second-dominant detritivore, coleopteran larvae (Optioservus kubotai). The loss of oak leaves (Quercus crispla) from litter bags in the fish-present treatment (0.31 g week^–1 in dry mass on average) was significantly less than in the fish-absent treatment (0.54 g week^–1). Predator-induced lower biomass and likely lowered foraging activities of the J. jezoensis were responsible for the suppression of litter processing efficiency. In contrast, the standing crop of fine particulate organic matter did not differ significantly between the treatments. The experimental results revealed that the predatory fish had an indirect but significant effect on leaf litter processing in the stream.     

Secondary production of Rhyacophila minora,Ameletus sp., and Isonychia bicolor from streams of low and circumneutral pH in the Appalachian Mountains of West Virginia

We estimated the secondary production of Rhyacophila minora, Ameletus sp., and Isonychia bicolor in three acidic streams and one circumneutral stream in Randolph County, West Virginia. Quantitative benthic samples were collected monthly from these second-order streams from November 1990 to October 1991. Mean pH values in the acidic streams were 4.5, 4.8, and 4.8, and mean pH in the circumneutral stream was 6.7. Production estimates for Rhyacophia minora in the acidic streams were 49.6, 19.2, and 15.8 mg m^–2 y^–1. Production of R. minora in the circumneutral stream was 1.0 mg m^–2 y^–1. Ameletus sp. production estimates for the acidic streams were 144.8, 176.8, and 208.3 mg m^–2 y^–1. Ameletus sp. production in the circumneutral stream was 7.4 mg m^–2 y^–1. Secondary production of I. bicolor in the circumneutral stream was 116.6 mg m^–2 y^–1. No Isonychia were collected from the acidic streams. The higher production of R. minora and Ameletus sp. in the acidic streams may be associated with differences in macroinvertebrate community structure.     

Comparison of Fungal Activities on Wood and Leaf Litter in Unaltered and Nutrient-Enriched Headwater Streams

Fungi are the dominant organisms decomposing leaf litter in streams and mediating energy transfer to other trophic levels. However, less is known about their role in decomposing submerged wood. This study provides the first estimates of fungal production on wood and compares the importance of fungi in the decomposition of submerged wood versus that of leaves at the ecosystem scale. We determined fungal biomass (ergosterol) and activity associated with randomly collected small wood (<40 mm diameter) and leaves in two southern Appalachian streams (reference and nutrient enriched) over an annual cycle. Fungal production (from rates of radiolabeled acetate incorporation into ergosterol) and microbial respiration on wood (per gram of detrital C) were about an order of magnitude lower than those on leaves. Microbial activity (per gram of C) was significantly higher in the nutrient-enriched stream. Despite a standing crop of wood two to three times higher than that of leaves in both streams, fungal production on an areal basis was lower on wood than on leaves (4.3 and 15.8 g C m⁻² year⁻¹ in the reference stream; 5.5 and 33.1 g C m⁻² year⁻¹ in the enriched stream). However, since the annual input of wood was five times lower than that of leaves, the proportion of organic matter input directly assimilated by fungi was comparable for these substrates (15.4 [wood] and 11.3% [leaves] in the reference stream; 20.0 [wood] and 20.2% [leaves] in the enriched stream). Despite a significantly lower fungal activity on wood than on leaves (per gram of detrital C), fungi can be equally important in processing both leaves and wood in streams.     

The influence of stream flow reduction on the energetics of endemic Hawaiian torrenticolous aquatic insects, <Emphasis Type="Italic">Telmatogeton</Emphasis> Schiner and <Emphasis Type="Italic">Procanace</Emphasis> Hendel

Tropical island stream ecosystems continue to be threatened by increasing anthropogenic demands for freshwater, with many streams dammed or diverted. Stream flow amendments can have substantial effects on aquatic insect populations of tropical archipelagoes. In Hawaiian streams, an endemic Diptera community of the following genera dominates cascades and other torrential habitats: Telmatogeton Schiner (Chironomidae), Procanace Hendel (Canacidae), Scatella Robineau-Desvoidy (Ephydridae). Larval densities, standing stock biomass (SSB, as ash-free dry mass [AFDM]), and monthly secondary production of Telmatogeton and Procanace were measured during two summers of significantly different stream discharge in Iao Valley, Maui, Hawaii. Very few Scatella larvae were collected (<20 larvae for both years combined), so they were omitted from subsequent analyses. Stream discharge decreased approximately 40% from 1994 to 1995, providing a ‘natural test’ of the effects of reduced stream flow on these torrenticolous populations between two years. Combined Telmatogeton and Procanace SSB (total torrential community SSB) was 3176 and 1683 mg AFDM m⁻² for 1994 and 1995, respectively, with Telmatogeton accounting for >95% in both years due to significantly larger body size and high density. The SSB of Telmatogeton significantly decreased from 3138 to 1622 mg AFDM m⁻² from 1994 to 1995 but increased for Procanace (37.6–60.9 mg AFDM m⁻², respectively). Total torrential community secondary production was 31% lower in 1994 (12,833 mg AFDM m⁻² mo⁻¹) compared to 1995 (8855 mg AFDM m⁻² mo⁻¹), reflecting the Telmatogeton proportion of total community production (99%); however, Procanace production increased by 40%. Monthly P/B ratios indicated that biomass turnover was generally high and increased for Telmatogeton from 1994 (3.8) to 1995 (5.1), whereas it remained lower and did not change between years for Procanace (1.7). A natural drought of the Iao Stream valley was associated with structural and functional changes in two endemic aquatic insects; these results are a conservative indication of permanent stream flow reductions from anthropogenic withdrawal (e.g., dams and diversions).     

Effect of riparian land use on contributions of terrestrial invertebrates to streams

Since terrestrial invertebrates are often consumed by stream fishes, land-use practices that influence the input of terrestrial invertebrates to streams are predicted to have consequences for fish production. We studied the effect of riparian land-use regime on terrestrial invertebrate inputs by estimating the biomass, abundance and taxonomic richness of terrestrial invertebrate drift from 15 streams draining catchments with three different riparian land-use regimes and vegetation types: intensive grazing — exotic pasture grasses (4 streams), extensive grazing — native tussock grasses (6 streams), reserve — native forest (5 streams). Terrestrial invertebrate drift was sampled from replicated stream reaches enclosed by two 1 mm mesh drift nets that spanned the entire channel. The mean biomass of terrestrial invertebrates that entered tussock grassland (12 mg ash-free dry mass m^–2 d^–1) and forest streams (6 mg AFDM m^–2 d^–1) was not significantly different (p > 0.05). However, biomass estimated for tussock grassland and forest streams was significantly higher than biomass that entered pasture streams (1 mg AFDM m^–2 d^–1). Mean abundance and richness of drifting terrestrial invertebrates was not significantly different among land-use types. Winged insects contributed more biomass than wingless invertebrates to both pasture and tussock grassland streams. Winged and wingless invertebrates contributed equally to biomass entering forest streams. Land use was a useful variable explaining landscape-level patterns of terrestrial invertebrate input for New Zealand streams. Evidence from this study suggests that riparian land-use regime will have important influences on the availability of terrestrial invertebrates to stream fishes.     

The soil fauna of a beech forest on limestone: trophic structure and energy budget

Summary The soil fauna of a mull beech forest on lime-stone in southern Lower Saxony (West Germany) was sampled quantitatively. Biomass estimates, trophic characteristics, and measurement and calculation of the energetic parameters of the constituent animal populations were used to construct an energy budget of the total heterotrophic subsystem of the forest. Mean annual zoomass amounted to about 15 g d wt m^–2; earthworms (about 10 g d wt m^–2) and other groups of the macrofauna were dominant. Protozoa constituted about 1.5 g d wt m^–2. Relative distribution of zoomass among the trophic categories was 50% macrosaprophages, 30% microsaprophages, 12% microphytophages, and 4% zoophages. Total annual consumption rate of the saprophagous and microphytophagous soil fauna (6328 and 4096 kJ m^–2 yr^–1, respectively) was of the same order of magnitude as annual litter fall (canopy leaves 6124 kJ m^–2 yr^–1, flowers and fruits 944 kJ m^–2 yr^–1, herbs 1839 kJ m^–2 yr^–1, fine woody material 870 kJ m^–2 yr^–1, tree roots 3404 kJ m^–2 yr^–1, without coarse woody litter). Primary decomposers (macrosaprophages) were the key group for litter comminution and translocation onto and into the soil, thus contributing to the high decomposition rate (k=0.8) for leaf litter. Consumption rates of the other trophic groups were (values as kJ m^–2 yr^–1): bacteriophages 2954, micromycophages 416, zoophages 153. Grazing pressure of macrophytophages (including rhizophages) was low. Faeces input from the canopy layer was not significant. Grazing pressure on soil microflora almost equalled microbial biomass; hence, a large fraction of microbial production is channelled into the animal component. Predator pressure on soil animals is high, as a comparison between consumption rates by zoophages and production by potential prey — mainly microsaprophages, microphytophages and zoophages — demonstrated. Soil animals contributed only about 11% to heterotrophic respiration. However, there is evidence that animals are important driving variables for matter and energy transfer: key processes are the transformation of dead organic material and grazing on the microflora. It is hypothesized that the soil macrosaprophages are donor-limited.     

Litter production in three mangrove forest zones in the malay peninsula

Total litter fall, over a period of more than 22 months, was 4.22, 3.84 and 4.32 g dry wt. m⁻² day⁻¹ in the Avicennia, Sonneratia and Rhizophora forests, respectively. Leaves comprised 40–67% of the total. The Avicennia alba Bl. forest, however, showed a distinct peak from August to October when fruits comprised 50–65% of the total litter. Correlations of total and leaf component litters with the four meterological parameters of wind run, mean temperature, evaporation and rainfall accounted for less than 50% of the variation in litter fall. Wind run had the greatest influence in the seaward Avicennia forest while mean temperature had the greatest influence on the landward Rhizophora forest.