Coarse Particulate Organic Matter Inputs Research Articles

Effect of plant richness on the dynamics of coarse particulate organic matter in a Brazilian Savannah stream

The high plant richness in riparian zones of tropical forest streams and the relationship with an input of organic matter in these streams are not well understood. In this study, we assessed (i) the annual dynamics of inputs of coarse particulate organic matter (CPOM) in a tropical stream; and (ii) the relationship of species richness on riparian vegetation biomass. The fluxes and stock of CPOM inputs (vertical-VI = 512, horizontal-HI = 1912, and terrestrial-TI = 383 g/m2/year) and the benthic stock (BS = 67 g/m2/month) were separated into reproductive parts, vegetative parts and unidentified material. Leaves that entered the stream were identified and found to constitute 64 morphospecies. A positive relationship between species richness and litterfall was detected. The dynamics of CPOM were strongly influenced by rainfall and seasonal events, such as strong winds at the end of the dry season. Leaves contributed most to CPOM dynamics; leaf input was more intense at the end of the dry season (hydric stress) and the start of the rainy season (mechanical removal). Our study show an increase of litter input of CPOM by plant diversity throughout the year. Each riparian plant species contributes uniquely to the availability of energy resources, thus highlighting the importance of plant conservation for maintaining tropical streams functioning.

Planting grass filter strips: Does it influence the structure and function of riparian habitats of agricultural headwater streams?

AbstractGrass filter strips are strips of cool or warm season grasses planted adjacent to agricultural streams to reduce nutrient, pesticide, and sediment input. This conservation practice is the most frequently planted riparian buffer type in the United States. Previous studies have not evaluated how grass filter strips alter the structure and function of riparian habitats of agricultural streams. Our objective was to examine the research hypothesis that planting grass filter strips will influence the structure and function of riparian habitats of channelized agricultural headwater streams. We sampled riparian vegetation, quantified coarse particulate organic matter input and nutrient input, and measured water temperature within two unplanted riparian habitat sites, two riparian habitat with grass filter strips sites, and two forested riparian habitat sites of agricultural headwater streams in central Ohio. Forested riparian habitats exhibited greater percent maximum frequency of woody vegetation and reduced water temperatures than unplanted riparian habitats and grass filter strips. Forested riparian habitats also exhibited greater canopy cover, woody vegetation taxa richness, and coarse particulate organic matter input than grass filter strips and greater riparian widths and woody vegetation abundance than unplanted riparian habitats. Grass filter strips did not differ in structure and function from unplanted riparian habitats. We conclude that planting grass filter strips does not influence the structure and function of riparian habitats of channelized agricultural headwater streams.

Organic-matter dynamics in the riparian zone of a tropical headwater stream in Southern Brasil

We assessed the dynamics of allochthonous coarse particulate organic matter (CPOM) in a tropical headwater stream in the foothills of the Ouro Branco Sierra (S. Brazil; at 1300m a.s.l.) over a yearly cycle, and the contribution of leaves, twigs, and other plant parts to the different types of input and stock. Additionally, we identified the key species that contribute to each type of input and to seasonal patterns in the input and storage of CPOM (particles>1.00mm). Our study tested (and rejected) the hypothesis that the majority of riparian plant species along tropical headwater streams are perennial, and therefore the input of CPOM tends to be continuous over the course of the year. Leaves contributed 74% of CPOM, with input increasing toward the end of the dry season (September to October). Of the total of 188 plant species identified in the riparian zone, 47 species together contributed over 28% of the detritus to the aquatic ecosystem. The species that contributed most were Protium spp., Cabralea canjerana (Vell.) Mart., and Casearia decandra Jacq. The CPOM dynamics of Garcia Stream showed a highly seasonal pattern due to the influence of precipitation. A number of species characteristic of the Amazon and Atlantic Rain forests were identified, together with species of the Cerrado, indicating that the riparian vegetation should not be considered part of a single forest domain, but rather a unique and integrated system that functions as an ecological corridor for species dispersal. The data obtained here confirmed the ecological complexity of the riparian tropical system, derived from the diversity of plant species and the seasonal dynamics of CPOM, related to the phenology of the plant community.

Environmental heterogeneity affects input, storage, and transformation of coarse particulate organic matter in a floodplain mosaic

Quantifying spatial and temporal dynamics of organic matter (OM) is critical both for understanding ecosystem functioning and for predicting impacts of landscape change. To determine the influence of different habitats and coarse particulate OM (CPOM) types upon floodplain OM dynamics, we quantified aerial input, lateral surface transfer, and surface storage of CPOM over an annual cycle on the near-natural floodplain of the River Tagliamento in NE-Italy. Using these data, we modelled floodplain leaf dynamics, taking account of the spatial distribution and hydrologic connectivity of habitats, and using leaf storage as a response variable. Mean aerial CPOM input to the floodplain was similar from riparian forest and islands, but surface transfer was greater from islands, supporting the suggestion that these habitats act as “islands of fertility” along braided rivers. Leaves were the lateral conveyor of energy to more open parts of the floodplain, whereas CPOM was mainly stored as small wood in vegetated islands and riparian forest. Simulating the loss of habitat diversity (islands, ponds) decreased leaf storage on the whole floodplain, on exposed gravel and in large wood accumulations. In contrast, damming (loss of islands, ponds and floods plus floodplain overgrowth) greatly increased storage on exposed gravel. A random shuffle of habitats led to a storage increase on exposed gravel, while that in large wood accumulations and ponds declined. These results disentangle some of the complexities of CPOM dynamics in floodplain ecosystems, illustrate the value of models in understanding ecosystem functioning at a landscape level, and directly inform river management practice.

Impact of timber harvesting on litterfall inputs and benthic coarse particulate organic matter (CPOM) storage in a small stream draining a eucalyptus plantation

Eucalyptus plantations have a short rotation cycle and harvesting occurs every 12–15 years, with the potential to modify the ecological integrity of the small streams draining the harvested areas through the reduction of litterfall inputs. We studied litterfall inputs and benthic coarse particulate organic matter (CPOM) storage in a small headwater stream draining a eucalyptus ( Eucalyptus globulus Labill.) plantation before and after clear felling of the plantation. We hypothesized that wood harvesting will result in a reduction of CPOM inputs and storage in the stream. Litterfall inputs ranged 530–700 g m −2 y −1 and were approximately halved (200–320 g m −2 y −1) after the harvesting of the eucalyptus trees. Bark and woody materials showed the largest reduction. Leaf inputs were initially reduced sharply, but, during the second year after the harvest, they recovered to about 90% of the values observed before the harvesting. Harvesting of the eucalyptus plantation caused an increase of benthic CPOM storage to 535 g m −2, but this was a temporary effect and these materials were washed downstream of the study reach. One year after the harvesting, benthic CPOM was reduced below 15 g m −2. Bark, twigs and other woody residues generated during the preparation of the logs for transportation were retained within the study site and represented the main component (>90%) of the benthic CPOM after timber harvesting. However, 2 years after the harvesting, low inputs of these materials caused an overall reduction of in-stream retention and residence time of benthic CPOM. Amount and composition of benthic CPOM changed quickly in response to alterations of the riparian forest, so we propose the use of CPOM as an indicator of the impact of forestry activities on the ecological functioning of small streams.

Urban catchment hydrology overwhelms reach scale effects of riparian vegetation on organic matter dynamics

1. Urbanisation severely affects stream hydrology, biotic integrity and water quality, but relatively little is known about effects on organic matter dynamics. Coarse particulate organic matter (CPOM) is a source of energy and nutrients in aquatic systems, and its availability has implications for ecosystem productivity and aquatic communities. In undisturbed environments, allochthonous inputs from riparian zones provide critical energy subsidies, but the extent to which this occurs in urbanised streams is poorly understood. 2. We investigated CPOM inputs, standing stocks, retention rates and retention mechanisms in urban and peri-urban streams in Melbourne, Australia. Six streams were chosen along a gradient of catchment urbanisation, with the presence of reach scale riparian canopy cover as a second factor. CPOM retention was assessed at baseflow via replicate releases of marked Eucalyptus leaves where the retention distance and mechanism were recorded. CPOM and small wood (>1 cm diameter) storage were measured via cores and direct counts, respectively, while lateral and horizontal CPOM inputs were assessed using riparian litter traps. Stream discharge, velocity, depth and width were also measured. 3. CPOM inputs were not correlated with urbanisation, but were significantly higher in ‘closed’ canopy reaches. Urbanisation and riparian cover altered CPOM retention mechanisms, but not retention distances. Urban streams showed greater retention by rocks; while in less urban streams, retention by small wood was considerably higher. CPOM and small wood storage were significantly lower in more urban streams, but we found only a weak effect of riparian cover. 4. These findings suggest that while riparian vegetation increases CPOM inputs and has modest/weak effects on storage, catchment scale urbanisation decreases organic matter availability. Using an organic matter budget approach, it appears likely that the increased frequency and magnitude of high flows associated with catchment urbanisation exerts an overriding influence on organic matter availability. 5. We conclude that to maintain both organic matter inputs and storage, the restoration and protection of streams in urban or rapidly urbanising environments relies on the management of both riparian vegetation and catchment hydrology.

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.

Fluxes of dissolved organic carbon, other nutrients and microbial communities in a water-filled treehole ecosystem

Water-filled treeholes are temporally and spatially variable habitats that consist of communities of a limited number of insect orders, namely dipterans and beetles. Since these systems are largely heterotrophic, treeholes are dependent on the surrounding terrestrial ecosystem for their basal energy input. In this study, we observed a cyclic succession of three system states in a water-filled Fagus grandifolia treehole: ‘connected’ during rainfall; ‘isolated’ during periods without rain; and ‘dry’ when no freestanding water was present. During the isolated phase, a rapid, microbially mediated turn-over of nitrogen and sulphate took place, coincident with an accumulation of orthophosphate. Ammonium was the dominant form of nitrogen in the treehole water, and a net decrease in its concentration was observed when the water volume decreased. Normally, nitrate concentration showed only minor fluctuations (0.3–1.3 mg l−1) and concentrations of nitrite were very low (3–18 μg l−1). Concentration of sulphate showed a net decrease, coincident with an increase in sulphide. During the connected phase, the effect of stemflow and throughfall on the nutrient concentrations in the treehole water proved to be variable. Over time, both dilution of, and increase in, treehole water nutrient concentrations were observed. Dissolved organic carbon (DOC) concentration showed a net decrease during the isolated phase. Spring coarse particulate organic matter input into the treehole was variable (0.20–1.74 mg cm−2 week−1). The observed variability in precipitation inputs as well as fall-in of organic matter underlines the pulsed character of basal energy entering the treehole food-web. DOC concentrations varied mainly with depth (15–57.4 mg l−1) as concentrations were almost three times greater within the detritus than within the water column. Bacterial abundances ranged from 7.3 × 105 to 9.3 × 106 cells ml−1 and did not appear to vary within the water column or in the detrital sediment. Rates of bacterial production increased 24 h after rain events, suggesting that the combined nutrient fluxes due to increased stemflow stimulate the microbial community.

Dynamics of allochthonous organic matter in a tropical Brazilian headstream

The species composition of the riparian vegetation and the seasonal contribution of input and storage of fine and coarse particulate organic matter were assessed in a 3rd order stretch. Fourteen tree species in the riparian zone were identified, with 3 species contributing with 68% of total litter input: Miconia chartacea Triana (43%), Miconia cyathanthera Triana (16%) and Erythroxylum pelletarianum St. Hil (9%). The allochthonous input of coarse particulate organic matter (CPOM) was composed mainly by leaves (over 50%). Species composition and the contribution of each plant species biomass for vertical, lateral and soil inputs and benthic stocks varied along the study period. The maximum values found in September, November and December coincided with the beginning of the rainy season. There were no differences between the allochthonous vertical and lateral inputs of CPOM to the stream. Differently to other studies, this result was probably due to the peculiar composition of stream’s riparian vegetation at Serra do Cipó.

Impact of a eucalyptus (Eucalyptus globulus Labill.) plantation on the nutrient content and dynamics of coarse particulate organic matter (CPOM) in a small stream

Litterfall inputs, benthic storage and the transport of coarse particulate organic matter (CPOM) were studied in two headwater streams, one flowing through a mixed deciduous forest and one through a plantation of Eucalyptus globulus. Vertical and lateral traps, transported CPOM and benthic CPOM were sampled monthly to biweekly and sorted into four categories: leaves, twigs and bark, fruits and flowers and debris. The litterfall inputs were about 20% lower at the eucalyptus site but this reduction was unevenly distributed among the litter categories. The reduction of the nitrogen and phosphorus inputs was larger (50%) than that of CPOM because of the low nutrient concentration of the CPOM at the eucalyptus site. Transported CPOM was also lower at the eucalyptus site. Although total CPOM inputs to the stream were reduced in the eucalyptus plantation, benthic storage of CPOM was 50% higher due to (1) high inputs of CPOM and low discharge during summer, (2) more twig and bark inputs, (3) eucalyptus leaves being retained more efficiently in the stream than deciduous leaves (4) a lower discharge, which may in part be attributable to eucalyptus-induced changes in the hydrological cycle. Increased retention balanced lower nitrogen and phosphorus content of CPOM, so benthic storage of nitrogen and phosphorus was similar at both sites. This work demonstrates that the timing, quality and quantity of inputs and benthic storage of CPOM in streams changes substantially because of the substitution of natural deciduous forest with eucalyptus plantation. Maintenance of buffer strips of natural vegetation may be the best way to protect ecological functioning of small, forested streams.

Seasonal dynamics of algal biomass and allochthonous input of coarse particulate organic matter in a low-order sandstone stream (Weidlingbach, Lower Austria)

From December 1997 to December 1998, benthic algal biomass and the input of allochthonous coarse particulate organic matter (CPOM) were investigated in bi-weekly intervals at two sampling stations (shaded and sunny) of the Weidlingbach, a fourth order sandstone stream in the Wienerwald. A total of 41 benthic algal taxa was collected, belonging to the groups Cyanobacteria (4 taxa), Bacillariophyceae (33), Rhodophyta (1), Chrysophyceae (1) and Chlorophyta (2). At the shaded site, periphyton dry mass ranged from 13 g m −2 in April to 440 g m −2 in August (annual mean = 93 g m −2), at the sunny site from 3 g m −2 in May to 512 g m −2 in late fall (annual mean = 70 g m −2). Based on the algal carotenoid pattern, Bacillariophyceae were most abundant in fall and winter while Chlorophyceae dominated during summer. Mean annual standing stock of chlorophyll-a was 8.65 μg cm −2 at the shaded station and 7.53 μg cm −2 at the sunny site. Annual allochthonous CPOM input rates ranged from 382 to 665 g dry mass m −2 for aerial input and from 1006 to 1062 g DM m −1 of stream length for lateral input. Lateral input rates were influenced by the bank inclination; the temporal distribution of aerial input showed an autumnal maximum (61–65% of the total). Direct CPOM input was significantly highest (P<0.05) during the period of defoliation from October to November. In the course of this period, 61.1% (shaded) to 64.9% (sunny) of the annual CPOM dropped into the brook, yielding daily input rates of 6.6 to 4.0 g DM m −2. From December to September, daily direct input rates decreased to 0.84 g DM m −2 (shaded) and 0.44 g DM m −2 (sunny). At both sites, retention capacity was high; 70% of marked leaves released along transects were retained by coarse sediment particles within 40 m from the starting point. The annual mean of periphyton dry mass made up 52% of CPOM standing stock at the shaded site and 39% at the sunny site.

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 μm 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 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.

Coarse particulate organic matter inputs to a headwater swamp stream

Inputs of allochthonous particulate organic matter were measured during 1992-94 in a headwater conifer swamp stream in southern Ontario, Canada. Litter transported to the stream by surface runoff from saturated areas of the swamp was compared to direct litterfall and lateral transfer from stream banks. Litterfall contributed 61-63 % of the annual litter input to the stream in comparison to 14-16 % and 20-25 % for lateral bank transfer and swamp surface runoff, respectively. Litterfall and bank inputs were seasonal with an autumn peak. In contrast, litter transport by surface runoff occurred mainly in May-September during episodes of rapid overland flow associated with thunderstorms. The annual composition of litterfall was approximately 48 % conifer needles, 32 % woody tissues and 17 % deciduous leaves. Lateral bank transfer contributed a smaller proportion of needles (37.5 %) and a higher proportion of leaves (22 %). Litter transported in runoff from the swamp was mainly woody tissues (70 %) and the needle and leaf fraction comprised <15 %, indicated that retention and decomposition occurred on the swamp surface. These results indicate that surface runoff from headwater swamps increases the amount and alters the composition and seasonality of litter inputs to streams.

Discharge-Export Relationships in Headwater Streams: The Influence of Invertebrate Manipulations and Drought

The role of physical (discharge) and biological (macroinvertebrate communities) factors in the control of coarse (>4 mm) and fine (≤4 mm > 0.5 μm) particulate organic matter (FPOM) transport was studied in three headwater streams of the southern Appalachian Mountains. The role of discharge was determined by relating two years of continuous measurements obtained over discrete (ca. 2-wk) time intervals. The role of macroinvertebrates was examined by treating one of the three streams, C 54, with an insecticide during Year 2 to reduce populations and alter community structure. Maximum discharge was the only discharge parameter which adequately predicted (linear regressions) FPOM export during a sampling interval (r² ≥ 0.70). These regressions were unique for each stream and were constant between years for the untreated streams, despite a record drought during the second year. Relationships between discharge and export of coarse particulate organic matter (CPOM) were not as strong nor as consistent as those for FPOM. CPOM export was very sensitive to timing of CPOM inputs and storms (e.g., 78 to 88% of CPOM export during Year 2 occurred during a single fall storm). Consequently, CPOM export-discharge relationships differed not only among streams but also between years and did not show treatment effects. Treating C 54 with methoxychlor during Year 2 resulted in massive invertebrate drift and drastically reduced populations of macroinvertebrates, practically eliminating shredders and collector-filterers. Maximum discharge continued to be a good predictor of FPOM export (r² = 0.83) for C 54 during the treatment year, but the yield of export per unit of maximum discharge (slope of the discharge-FPOM export regression) decreased by 65%. This contrasts with the untreated streams in which the slopes were constant between years despite the >50 year drought during Year 2. Most (75%) of the decrease in FPOM yield from C 54 is directly attributable to the reduction in macroin-vertebrates. Only 25% is attributable to the drought even though stream flows dropped by ca. 40% during Year 2. Relationships between export and discharge observed in this study are stronger than those reported elsewhere because measurements of export were made independent of discharge over long time intervals (ca. 2 wk). Collecting export over 2-wk intervals clearly shows the effects of storms while avoiding the problem of hysteresis commonly seen in relationships between discharge and export concentration made during single storms.

Spatial and temporal variation in the macroinvertebrate fauna of streams of the northern jarrah forest, Western Australia: functional organization

SUMMARY. 1. Spatial and temporal changes in functional organization of the invertebrate community of streams of the northern jarrah forest, Western Australia, were examined in the light of predictions of the river continuum concept (Vannote et al., 1980).2. The composition of the fauna was largely as predicted for forested headwater streams with detritivores, principally collectors, dominating the fauna. Although shredders are generally considered to be codominant in such streams, they were not abundant in the riffle areas sampled in this study.3. Some of the observed temporal changes in the composition of functional feeding groups were in agreement with those predicted by the generalized model. The abundance and richness of collectors were higher during the summer than winter, whereas the converse was true for filterers. This corresponded to the presumed availability of deposit and suspended fine‐particulate organic matter during summer and winter respectively. Scrapers and predators showed no consistent temporal pattern among sites. However, the density of the latter was highly correlated with the density of other invertebrates, particularly collectors.4. Temporal changes in the abundance and richness of shredders were not synchronized with the marked summer input of coarseparticulate organic matter. The possible reasons for this, and the role of shredders in Australian stream systems, are discussed.