Nutrient Trapping Research Articles

Movement of Nitrogen through an Agricultural Riparian Zone: 1. Field Studies

Forested riparian areas are believed to be important for reducing nonpoint source pollutants. These areas along streams, lakes, and wetlands have been reported to trap sediment and nutrients and enhance denitrification. Past research on the effectiveness of riparian areas has been based on existing forests rather than restored areas. An experiment using the paired-watershed design was established in northeastern Connecticut during 1992 to determine the water quality effects of reforestation on a riparian zone currently cropped in maize. Water quality fluxes in precipitation, overland flow, soil solution, groundwater, and streamflow were determined. Results indicate that this 35 m wide riparian zone had little attenuating influence on N concentrations in groundwater based on NO3−N concentrations and NO3−N:C1 ratios. The primary N flux to the stream was in the groundwater. Denitrification did not appear to be a major process operating in this system. Reforestation of this riparian buffer should result in improved surface and groundwater quality.

The generation of non-ruminant transgenic animals with cellulolytic capacity.

In non-ruminant livestock the energy which can be derived from dietary cellulose and xylan is limited by the inefficient microbial fermentation of these polymers in the hind-gut. Furthermore, in poultry, cereal-derived plant structural polysaccharides impair normal digestive function through the formation of gel-like structures that trap nutrients which are therefore unavailable to the animal. The nutrition of non-ruminant livestock could be significantly improved by the depolymerization of plant structural polysaccharides, through the introduction of cellulase activity in the small intestines of these animals. This report describes the generation of transgenic animals with the capacity to express and secrete a functional endoglucanase from the exocrine pancreas.The gene encoding endoglucanase E (celE) from Clostridium thermocellum was fused to the exocrine pancreas specific enhancer of the elastase I gene and the (β-globin polyadenylation signal, and used to create 14 lines of transgenic mice. A range of tissues were assayed for cellulase activity, using β-glucan and 4-methylumbelliferyl-β-D-cellobioside as substrates. The pancreas was also subjected to immunohistochemistry and in situ hybridization.

Manipulation of the Repertoire of Digestive Enzymes Secreted into the Gastrointestinal Tract of Transgenic Mice

In non-ruminant livestock the energy which can be derived from dietary cellulose and xylan is limited by the inefficient microbial fermentation of these polymers in the hind-gut. Furthermore, in poultry, cereal-derived plant structural polysaccharides impair normal digestive function through the formation of gel-like structures, which trap nutrients rendering them unavailable to the animal. The nutrition of non-ruminant livestock could be significantly improved by the depolymerization of plant structural polysaccharides, through the introduction of cellulase activity into the small intestines of these animals. Here we describe the expression of Clostridium thermocellum endoglucanase E in the exocrine pancreas of transgenic mice. A non-glycosylated active enzyme is secreted into the small intestines, and is resistant to proteolytic inactivation, demonstrating the feasibility of generating non-ruminant animals with the endogenous capacity to depolymerize plant structural polysaccharides in the small intestines.

Downward transport and fate of organic matter in the ocean: Simulations with a general circulation model

A phosphorus‐based model of nutrient cycling has been developed and used in conjunction with a general circulation model to evaluate the roles of the dissolved and sinking particulate phases in the downward transport of organic matter in the ocean. If sinking particles dominate the downward transport and remineralize in accord with observations made primarily with sediment traps, we find in equatorial upwelling regions that particle fluxes and thermocline nutrient concentrations are higher than observed. These enhanced fluxes and concentrations are a result of what we term “nutrient trapping,” a positive feedback whereby high upwelling produces high new production that results in remineralization and enhanced nutrient concentrations in the upwelling water, which further increases new production. Nutrient trapping in shallow upwelling zones can be eliminated by increasing the particle flux length scale, which suggests that if sinking particles dominate the downward transport of organic matter then the flux length scale is longer than observed. Even with a longer particle flux length scale, we find that nutrients are trapped in some deep convective regions of the southern ocean, where new production is predicted to be much higher than the observed primary production. In simulations where the downward transport of organic matter takes place primarily in a dissolved phase, nutrient trapping is completely eliminated, in both upwelling and convective regions. The models with dissolved organic matter also agree fairly well with nutrient transports in the north Atlantic Ocean calculated from observed nutrient and hydrographic data (Rintoul and Wunsch, 1991). Our results therefore support the dissolved organic nitrogen and carbon measurements made with the high‐temperature combustion technique of Suzuki et al. (1985) and Sugimura and Suzuki (1988) and suggest that there exists an as‐yet undiscovered pool of dissolved organic phosphorus in the ocean. We also use the various models to make an estimate of global new production of 2.9 to 3.6 mol C/m2/yr (12 to 15 Gt C/yr).

Regulations and policies relating to the use of wetlands for nonpoint source pollution control

The ability of wetlands to transform or trap nutrients and sediments has led to increasing attention to how wetlands can be used or their functions replicated to treat nonpoint sources of pollution. Protection, restoration, and creation of wetlands can be incorporated into nonpoint source pollution management strategies. There are, however, Federal regulations that prohibit the indiscriminate use of wetlands for water treatment. The Clean Water Act regulates all discharges into “waters of the United States” including wetlands. Restored wetlands are subject to the same protection and restrictions as natural wetlands. Created wetlands, on the other hand, are generally not considered “waters of the United States” if constructed solely for purposes of water treatment. Protection, restoration, and creation of wetlands provide opportunities to realize a number of functional benefits including water quality improvement.

Patterns of Fish Spawning in Hudson River Tributaries: Response to an Urban Gradient?

Large rivers, for all their importance to humans, are not well understood with respect to ecological patterns and processes. Although some generalizations have been made, e.g., the continuum concept (Vannote et al. 1980) and the nutrient trap created at saltfreshwater interfaces (Mansueti 1961), the geographic scope of large rivers presents considerable sampling difficulties for evaluation of many system-wide phenomena. Furthermore, studies of large rivers often fail to consider interactions between the lotic portion and surrounding watershed, whereas understanding largescale processes may require such attention. Two features of many large river watersheds, their large geographic extent and their occupation and use by humans, should render them good candidates for the manifestation of anthropogenic, ecological gradients. Many urban centers are located along major rivers, a fact that can be confirmed by examining any atlas. The impacts of urbanization, as a source of pollutants, upon rivers and streams have been studied by scientists and engineers for decades (cf. Hynes 1960, Nemerow 1985, Thomann and Mueller 1987); most situations involve point sources and their impacts upon individual waterways. Often, more subtle patterns of point and nonpoint source impacts on regional-scale ecological processes are not addressed. One approach is to examine properties of tributary watersheds within the overall drainage basin, as a function of urbanization. We demonstrate the approach with a study conducted to evaluate the contribution of nontidal tribu-

The metabolic environment of cancer.

The tumor cell has a very distinctive metabolism. It acts as a metabolic trap for host nutrients thus taking vital compounds for the metabolism of the host. Depending on the particular tumor growing pattern, cancer cells use preferentially glucose or amino acids for their energetic or biosynthetic needs. Lipids, fatty acids in particular, can also be taken up by the tumor cell. In addition, it can also release some compounds into the host circulation which are not normally produced by the original cell before neoplastic transformation. Some of these compounds affect the metabolism of the host in an unfavorable way since they can oppose the host's metabolic responses, which sustain homeostasis. The final product is that the metabolic machinery of these cells allows them to grow continuously in an uncontrolled manner. The consequences of tumor invasion on the host's metabolism are varied. They have, however, one thing in common: the reduction of the metabolic efficiency of the host. Muscular protein depletion, increased gluconeogenesis, uncoupling of oxidative phosphorylation constitute the main metabolic responses of the host as a result of tumor invasion. The net result of all these metabolic changes is profound energy imbalance which normally ends with cachexia and, eventually, death.

Crop growth across a toposequence controlled by depth of sand over clay

Sand soils containing, by definition, less than 5% clay, may give substantial variation in crop growth, even where they have apparently similar chemical and physical properties. This work tests the proposition that crop growth in a winter-rainfall environment is dependent upon the depth of a uniform sand profile, and that crop growth can be negatively correlated with depth to clay because of the low water and nutrient storage capacity of such soils. Spring wheat and barley, cereal rye, and narrow-leaf lupin were grown at three adjacent sites across a toposequence having a 3� slope with increasing sand depth (from 0.6 to >2.5 m) downslope. The experiments were conducted over two years, the first wetter than average, the second drier. In both years there was a significant decline in dry matter accumulation and crop yield with increasing sand depth in which the wheat biomass and lupin grain yield were most affected. Water uptake and nutrient distribution patterns within the profiles showed that available water was least and leaching most severe on the deepest sand, where no fine-textured materials at depth occurred to trap water and nutrients for later-season use within the rooting zone. Maximum rooting depths were estimated to average 2.0 m for wheat, and 2.4 m for lupin and cereal rye. However, on the deepest sand where roots grew to >2.5 m, yields were reduced to half, even under the high fertilizer conditions of the experiments. It is concluded that depth of sand provides the most reliable prognosis for crop growth and yield where there are no distinctive differences in clay content or chemical reaction.

Suspension settling effect on macrobenthos biomass distribution in the Hornsund fjord, Spitsbergen

Seasonal variations and spatial distribution of suspension composition and concentration were determined in the Hornsund fjord on south Spitsbergen along with bottom sediment mineralogy and glacial-marine mud accumulation rates. These data were related to macrobenthos biomass distribution, as well as geochemical and hydrognphic data. The axial distribution of sediment accumulation rates follows exponential decay. Slopes of the seaward decay are different for individual meltwater sources in Hornsund and, in general, they are higher than in river-fed fjords. Intensity of suspension settling is enhanced by strong retardation of meltwater flow and turbulence within the shear layer of meltwater jet sliding over strongly saline water. The most intensive settling, controlling the overall efficiency of mud deposition (up to 35 cm/a) occurs in the ice-proximal jet zone of meltwater plume. It results from turbulent diffusion of dense suspension (>1, 000 mg/1) to the underlying still-water layer. Within the more distal, slow-advection zone the sediment accumulation rate falls below 1 cm/a. Suspension is deposited here mostly due to slow settling of mature floes across the halocline. This bipartite lateral zonation results in (1) clay-mineral segregation observed in bottom mud in the ice-proximal jet zone (2M, large-flake muscovite is separated from lMd clay-grade illite), and (2) high accumulation rate and extremely rapid decay away from the source. High concentration of surface-active clays in the rapidly accumulating sediment renders the proximal mud a closed system and a physical trap for nutrients. The seasonal rhythm of changes in suspension composition reveals a time lag between maximum of organic suspension concentration and onset of clastic sedimentation. This lag along with the absolute dominance of clastic flux during summer-autumn, result in sulphidic (dark-light) lamination of ice-proximal mud. High clastic input and high surface water turbidity result in formation of a benthos-poor zone in the ice-proximal settings. There, formation and preservation of original monosulphidic lamination and scarcity of benthic life are mutually dependent. Control over these follows by damping of primary production in the photic zone and trapping of nutrients in the bottom sediment by clastic dilution and fast burial of organic material.

Persistence and movement of atrazine in a salt marsh sediment microecosystem.

Pesticides enter salt marshes in runoff from agricultural lands or through direct or near-by application. Concern has been raised that the tidal action in the salt marsh that functions to trap sediment and nutrients may also function to concentrate pesticides to harmful levels. Studies have been conducted to evaluate the effect of pesticides on representative species of salt marsh ecosystems. This paper describes the use of a modified salt marsh microecosystem to evaluate persistence and movement of atrazine in salt marsh sediment under simulated tidal flux and continuous flooding conditions. Atrazine persistence was also compared under normal field conditions.

Suspension settling effect on macrobenthos biomass distribution in the Hornsund fjord, Spitsbergen

Seasonal variations and spatial distribution of suspension composition and concentration were determined in the Hornsund fjord on south Spitsbergen along with bottom sediment mineralogy and glacial-marine mud accumulation rates. These data were related to macrobenthos biomass distribution, as well as geochemical and hydrognphic data. The axial distribution of sediment accumulation rates follows exponential decay. Slopes of the seaward decay are different for individual meltwater sources in Hornsund and, in general, they are higher than in river-fed fjords. Intensity of suspension settling is enhanced by strong retardation of meltwater flow and turbulence within the shear layer of meltwater jet sliding over strongly saline water. The most intensive settling, controlling the overall efficiency of mud deposition (up to 35 cm/a) occurs in the ice-proximal jet zone of meltwater plume. It results from turbulent diffusion of dense suspension (>1, 000 mg/1) to the underlying still-water layer. Within the more distal, slow-advection zone the sediment accumulation rate falls below 1 cm/a. Suspension is deposited here mostly due to slow settling of mature floes across the halocline. This bipartite lateral zonation results in (1) clay-mineral segregation observed in bottom mud in the ice-proximal jet zone (2M, large-flake muscovite is separated from lMd clay-grade illite), and (2) high accumulation rate and extremely rapid decay away from the source. High concentration of surface-active clays in the rapidly accumulating sediment renders the proximal mud a closed system and a physical trap for nutrients. The seasonal rhythm of changes in suspension composition reveals a time lag between maximum of organic suspension concentration and onset of clastic sedimentation. This lag along with the absolute dominance of clastic flux during summer-autumn, result in sulphidic (dark-light) lamination of ice-proximal mud. High clastic input and high surface water turbidity result in formation of a benthos-poor zone in the ice-proximal settings. There, formation and preservation of original monosulphidic lamination and scarcity of benthic life are mutually dependent. Control over these follows by damping of primary production in the photic zone and trapping of nutrients in the bottom sediment by clastic dilution and fast burial of organic material.

Nutrient Acquisition Facilitated by Litter Collection and Ant Colonies on Two Malaysian Palms

Daemonorops verticillaris (Griff.) Mart. and D. macrophylla Becc. are two rattan palms of peninsular Malaysia which are characteristically associated with a resident ant colony. The ants construct a nest utilizing plant hairs alone, or hair and spines, which is capable of absorbing approximately 185 percent water by weight. Use of a 14C tracer shows that wateror nutrient-enhanced throughfall is absorbed by the nest, subsequently taken into the plant, and translocated to developing tissues. D. verticillaris and, to a lesser extent, D. macrophylla trap falling debris (leaves, twigs, and fruits) around the plant apex. Precipitation, or throughfall, percolates through this material, is directed toward the stem, and is absorbed by the ant nest material. Taken together, debris collection and water absorption constitute a unique and effective mechanism of nutrient enhancement and recycling for these particular plants. NUTRIENT ACQUISITION IS A PRIME REQUISITE for any organism's continued existence. In addition to maximizing purely physiological functions, tissue nutrient level can also affect the production and growth of anatomical characteristics. Most plants seem to exist at a level somewhat below maximal growth in that added nutrients increase growth over wild populations. Methods for nutrient acquisition should have been under intense selection pressure throughout a species' evolutionary history, and to this end, we find that a variety of characteristics, both physiological and morphological, aid in nutrient trapping, uptake, and incorporation. Lamont (1982) has reviewed nutrient uptake in plants, and his list of modifications includes: mycorrhizal associations; nitrogen fixation; carnivorous habit; proteoid, capillaroid, and dauciform root systems; persistent, detritis trapping leaf bases which include aerial roots; and a parasitic habit. To this list we would add direct nutrient uptake by leaves (Benzing et al. 1976, Bentley & Carpenter 1984) and certain ant-plant relationships in which there is an uptake of nutrients by the plant from various ant residues. We know of such uptake in Hydnophytum (Rubiaceae) (Huxley 1978, Rickson 1979), several Bromeliaceae (Benzing 1970), and Cecropia (Moraceae), Macaranga (Euphorbiaceae), and Piper (Piperaceae) (F. R. Rickson, pers. comm.). No long term exclusion studies have explored any actual benefit of this uptake to the plant; however, over the past four years a trend toward lower flower production and seed set in a set of greenhouse Hydnophytum plants from which fertilizer has been withheld is beginning to be discernable (F. R. Rickson, pers. comm.). In addition, a number of studies have shown increased plant fecundity associated with insect trapping (Darwin 1878, Kellermann & Von Raumer 1878, Harder & Zemlin 1967). Twelve genera and 600 species of rattans grow in South East Asia. Ants are consistently associated with 5 species in 2 genera. Daemonorops macrophylla and D. verticillaris are two rattan palms of the lowland dipterocarp forests of western peninsular Malaysia. Rattans are climbers, and Daemonorops uses a modified leaf rachis tip possessing recurved spines to anchor the leaves as the stem ascends into the forest canopy. These two species are constantly associated with an ant colony living on the leaf sheaths; D. verticillaris especially, by virtue of leaf placement and spine orientation, accumulates dead leaves and other debris in the region of the shoot apex. Rattans possess a leaf sheath that bears spines (Fig. 1A). The spines may be small but most often are large, stiff, and formidable to the collector. Spines in herbarium material are oriented horizontally or downward in most species; however, in the two species considered here, particularly D. verticillaris, many of the spines point decidedly upward, and a few inserted at the junction of the petiole and sheath reach 10 cm in length. It is the upward orientation of spines and new leaves which allows for the collection of debris. Field observation indicated that the ant colony nest material was very absorbent of rainwater and throughfall. This fact, coupled with the cluster of debris around the shoot apex, suggested that the total system might function in nutrient acquisition and transfer to the main plant stem. I Received 28 January 1986, revision accepted 23 August 1986. BIOTROPICA 18(4): 337-343 1986 337 This content downloaded from 157.55.39.58 on Tue, 15 Nov 2016 03:54:50 UTC All use subject to http://about.jstor.org/terms FIGURE 1. Morphology of D. verticillaris and D. macrophylla. (A) General morphology of D. verticillaris. (B) Section through the center of a stem as in Figure IA. Note the overlapping spines and the indumentum material placed within the resulting cavity. 338 Rickson and Rickson This content downloaded from 157.55.39.58 on Tue, 15 Nov 2016 03:54:50 UTC All use subject to http://about.jstor.org/terms STUDY SITE AND METHODS The study was conducted at Pasoh Forest Reserve, Negri Sembilan, Malaysia, between October 1981 and March 1982. Pasoh is an IBP study area located approximately 2?59'N latitude and 102?17.5'E longitude. The area is classified as a lowland dipterocarp forest and receives an annual rainfall of approximately 200 cm (Manokaran

NONPOINT POLLUTION CONTROL STRATEGIES FOR MOSES LAKE, WASHINGTON

ABSTRACT Nutrient sources influencing eutrophication of Moses Lake, Wash., have been evaluated in a multistage investigation of urban and agricultural land uses in the watershed. Nutrient loadings from surface and groundwater contributions were quantified in a year-long monitoring program. Subsequent studies have assessed effectiveness of various control techniques to reduce nutrient input to the lake. These recent (1984) investigations include full-scale field demonstrations of agricultural irrigation practices involving cablegation, wheel line, and center pivot systems monitoring nutrient and water movement through coarse native soils. Over 75 percent of local farmers are trying control measures under a unique agricultural cost-sharing program. Other nutrient sources and controls evaluated and ranked for nutrient removal effectiveness include shallow detention ponds to enhance nutrient trapping, local septic tank management policies, animal waste and fish hatchery controls, and miscellaneous in-lake imp...

Microparticulate feeds for marine suspension-feeders.

The development of microparticulate food particles for marine suspension-feeders is discussed with respect to the difficulties of nutrient delivery in the aquatic environment and to feeding and digestion in crustacea and bivalve molluscs. Loss of nutrients from particles suspended in seawater must be minimized by either trapping nutrients in gel particles or by encapsulation of the nutrients within impermeable walls. The gel matrix or capsule wall must be readily broken down by the animal so as to release the trapped dietary components.

Nutrient Trapping by Sediment Deposition in a Seasonally Flooded Lakeside Wetland

AbstractSediment and nutrient retention was studied in a seasonally flooded lakeside wetland as a natural mechanism for preventing water quality deterioration. Both wetland and upland soils in the watershed had comparable concentrations of inorganic P on a per‐volume basis, while NH4+‐N and organic forms of N and P were much higher in the wetland soils. Nitrate concentrations expressed in a per‐volume basis were lower in the wetland soils than in the upland soils.The distribution of sediment and nutrients in the wetland was correlated with distance from a small stream flowing through the wetland. Deposition patterns were affected by recent stream channel migrations.The accumulation of nutrients and sediment delivered from the upland to wetland soils was estimated in two ways: (i) by calculating the volume of alluvium deposited in low natural levees adjacent to the stream; and (ii) by estimating nutrient and ash enrichment of histic surface soils farther away from the stream. Although the levees constituted only about 20% of the wetland surface area, they accounted for 81% of the sediment, 84% of the N, and 67% of the P retained by the wetland.The depth of Cs‐137 in the soil was used to estimate net sedimentation rates. Average annual accumulations over the wetland as a whole were: 2.0 kg sediment m−2 yr−1, 2.6 g P m−2 yr−1, and 12.8 N g m−2 yr−1. Since these values exceed those published for average annual storage by wetland plants, soil mechanisms are more important than vegetative uptake for long‐term nutrient and sediment retention in the White Clay Lake wetland.

Waterborne Nutrient Flow Through an Upland‐Peatland Watershed in Minnesota

Water and nutrient flow were measured on a complex upland—peatland watershed in north central Minnesota. Annual water budgets for upland and peatland components and for the total watershed were developed. Nutrient input and output budgets were developed for each component on a seasonal basis, using net precipitation inputs, and an annual nutrient budget was developed for the entire watershed, using gross precipitation and total outputs. Both components evapotranspire water near potential rates. The upland converts 34% of the water input to water yield, while the peatland (a bog in a lower topographic position) converts 55% of its water input to water yield. The upland annually retains some N, P, K, and Ca from net precipitation, but passes through Mg and supplies Na in excess of inputs. The peatland is a nutrient trap retaining 36—60% of all nutrient inputs annually. There are striking differences in the seasonal retention of nutrient forms between the upland and bog. The total watershed accumulates P and (apparently) N but loses more K, Ca, Mg, and Na than it receives in gross precipitation. Nutrient flow is interpreted for the design of nutrient—added technologies (fertilization and sewage treatment) and as a bench mark for nutrient—depleted technology (whole—tree harvesting).

Ectogenic Meromixis at Layton's Lake, Nova Scotia, Canada

Abstract Prior to 1960, Layton's Lake, N.S., received periodic intrusion of seawater from the Bay of Fundy and now exhibits ectogenic meromixis. The chemocline is situated at a depth of 8.0 to 8.5 meters and is approximately 1 meter thick. This region has a strong specific conductance gradient with values increasing by a factor of 20 over a distance of 1 meter. Tracing conductance isopleths over time suggests that the chemocline is being eroded at a rate of less than 1 cm per annum. Meromictic stabilities are low (⋍ 100 g-cm/cm2), however factors such as morphometric protection, summer thermal stratification and winter ice cover are probably important in maintaining meromixis. The monimolimnion has high specific conductance (26,000 umho/cm) and appears to be acting as a nutrient trap. Monimolimnetic phosphorus concentrations are as high as 26,000 mg P/m3 with more than 85% in the soluble reactive form.

On the distribution of copper, nickel, and cadmium in the surface waters of the North Atlantic and North Pacific Ocean

Concentrations of copper, nickel, and cadmium have been determined for about 250 surface water samples. Nonupwelling open‐ocean concentrations of these metals are Cu, 0.5–1.4 nmol/kg; Ni, 1–2 nmol/kg; and Cd, less than 10 pmol/kg. In the equatorial Pacific upwelling zone, concentrations of Ni (3 nmol/kg) and Cd (80 pmol/kg) are higher than in the open ocean, but Cu (0.9 nmol/kg) is not significantly enriched. Metal concentrations are higher in cool, nutrient‐rich eastern boundary currents: Cu, 1.5 nmol/kg; Ni, 3.5 nmol/kg, and Cd, 30–50 pmol/kg. Copper is distinctly higher in the coastal waters of the Gulf of Panama (3–4 nmol/kg) and also higher in the shelf waters north of the Gulf Stream (2.5 nmol/kg); these copper enrichments may be caused by copper remobilized from mildly reducing shelf sediments and maintained by a coastal nutrient trap. In the open ocean, events of high‐Cu water (1.5–3.5 nmol/kg) are seen on scales up to 60 km; presumably, these are due to the advection of coastal water into the oceanic interior. The lowest copper concentrations in the North Pacific central gyre (0.5 nmol/kg; (Bruland, 1980)) are lower than in the Sargasso Sea (1.3 nmol/kg), while for nickel the lowest concentrations are 2 nmol/kg in both the North Pacific and the North Atlantic. Nickel and cadmium, while generally correlated with the nutrients in surface waters, show distinct regional changes in their element‐nutrient correlations. The residual concentrations of trace metals in the surface waters of the ocean can be explained if biological discrimination against trace metals relative to phosphorus increases as productivity decreases.

Sediment and Nutrient Trap Efficiency of a Small Flood‐Detention Reservoir

AbstractSignificant amounts of sediment and nutrients are removed from storm runoff by small flood‐detention reservoirs such as Callahan Reservoir in central Missouri, which stores 1 cm of runoff from its 1,460‐ha drainage area. The purpose of this study was to compare the trap efficiencies of sediment and nutrients and determine which factors affect them. During a 3‐year study, this reservoir trapped an average of 85% of the incoming sediment, 77% of the total sediment phosphorus (P), and 37% of the inorganic nitrogen (N). Sediment leaving the reservoir was clay and contained about 23% of the inflowing total sediment P. Sediment and P trap efficiencies (TE) for individual storms were related to concentrations of sediment and P (solution and sediment) in runoff, respectively.Average TE of total solution P (35%) was slightly lower than the TE of NO3‐N (40%). Annual TE of ortho‐P ranged from 8 to 64% and averaged 43%.Dissolved organic and hydrolyzable P yields were greater in outflow than in inflow. These increases, which were <1% of the total P budget, may have been due to biological activity in the reservoir.

Root Productivity in an Amazonian Rain Forest

Average rate of root biomass accumulation in the surface root mat of an Amazonian rain forest near San Carlos de Rio Negro, Venezuela was 117 g°m—2°yr—1, and total root biomass increment was 201 g°m—2°yr—1. Root growth was higher in the surface root mat when fresh litter was present. Root growth rates relative to shoot growth rates at San Carlos were similar to ratios for a temperate forest near Oak Ridge, Tennessee, USA. However, turnover rates of roots were higher at the San Carlos site. High turnover rates result in a relatively large proportion of the roots in smaller size classes, which have a large surface area in relation to their volume and thus area efficient nutrient traps. High efficiency of nutrient trapping is important in the nutrient—poor San Carlos forest.