Mycoecology of willow and cottonwood lowland communities in Southern Wisconsin I. Soil microfungi in the willow-cottonwood forests

Summary A survey of the soil microfungi in 5Salix nigra-Populus deltoides forests in southern Wisconsin was conducted. The dilution plate method was employed to obtain 500 isolates per stand. The species present and their frequencies of occurrence were determined. The dominant forms,Trichoderma viride, Cladosporium cladosporioides, Gliocladium roseum, Mucor hiemalis, Coniothyrium sp. 5154,Mortierella minutissima, andPenicillium thomii, accounted for 41 % of the 2,500 isolates but only 4.5 % of the 154 species. They were followed at a second level of prevalence byPenicillium janthinellum P. multicolor, Mortierella alpina, andPhoma sp. 5157. The distribution of these taxa and others in the willow-cottonwood community was found to be correlated with an organic matter gradient. The Dematiaceae and the Sphaerioidaceae characterized populations obtained from the dry pioneer sites; the Mucorales and Moniliaceae became increasingly abundant as the percentage of organic matter increased. The number of fungal propagules ranged from 3,000 to 234,000 per gram of dry soil, the highest numbers occurring in soils with greater organic matter. The willow-cottonwood microfungal population was most similar to one obtained from soils of the closely related southern Wisconsin wet-mesic forests and least similar to ones isolated from the northern Wisconsin bogs and spruce-tamarack swamps.     

Food availability and gut contents in the ascidian Cnemidocarpa verrucosa at Potter Cove, Antarctica

A high seasonality characterizes Antarctic environments, and generates marked differences in availability and composition of food for benthic filter feeders. During a year-round period at Potter Cove, Antarctica, algal pigment concentration (chlorophyll a) and organic matter were measured in water column and sediment samples. Chemical composition of gut contents of the ascidian Cnemidocarpa verrucosa was also analyzed. Despite the low standing stock, capture and absorption of organic matter were detected year-round, suggesting intake of other particles besides microalgae. The mechanism that provides food to the ascidians and epibenthic communities may be related to the supply of allochtonous particles, bottom resuspension events, and microbial community dynamics. Sea-ice cycles may affect food availability in terms of water-column mixing and benthic resuspension. The scarce primary production and the high amount of sedimented material are not limiting conditions in Potter Cove, which presents a rich ascidian community.     

Inter-regional predictability of cation-exchange capacity by multiple regression

Summary Based on 125 surface soil samples, a multiple-regression prediction equation of the form, CEC=b₀+b₁ (% clay) +b₂ (% organic matter) was developed for Mississippi soils. These data plus data from comparable studies in Ohio, Wisconsin, North Carolina, and Florida were utilized to develop a relationship between the percentage contribution of organic matter to CEC and the clay content of the horizon. Multiple-regression equations from Mississippi, Florida, and Wisconsin studies were employed with data from Mississippi soils to determine the amount of variation between predicted and reported values of CEC. Although statistical differences were found between the three populations, the majority of these differences are within the realm of laboratory error, and it appears feasible to develop inter-regional CEC prediction equations.     

Benthic-Pelagic Coupling: Effects on Nematode Communities along Southern European Continental Margins

Along a west-to-east axis spanning the Galicia Bank region (Iberian margin) and the Mediterranean basin, a reduction in surface primary productivity and in seafloor flux of particulate organic carbon was mirrored in the in situ organic matter quantity and quality within the underlying deep-sea sediments at different water depths (1200, 1900 and 3000 m). Nematode standing stock (abundance and biomass) and genus and trophic composition were investigated to evaluate downward benthic-pelagic coupling. The longitudinal decline in seafloor particulate organic carbon flux was reflected by a reduction in benthic phytopigment concentrations and nematode standing stock. An exception was the station sampled at the Galicia Bank seamount, where despite the maximal particulate organic carbon flux estimate, we observed reduced pigment levels and nematode standing stock. The strong hydrodynamic forcing at this station was believed to be the main cause of the local decoupling between pelagic and benthic processes. Besides a longitudinal cline in nematode standing stock, we noticed a west-to-east gradient in nematode genus and feeding type composition (owing to an increasing importance of predatory/scavenging nematodes with longitude) governed by potential proxies for food availability (percentage of nitrogen, organic carbon, and total organic matter). Within-station variability in generic composition was elevated in sediments with lower phytopigment concentrations. Standing stock appeared to be regulated by sedimentation rates and benthic environmental variables, whereas genus composition covaried only with benthic environmental variables. The coupling between deep-sea nematode assemblages and surface water processes evidenced in the present study suggests that it is likely that climate change will affect the composition and function of deep-sea nematodes.     

The responses of lake waters to organic matter additions

The increase of inorganic nitrogen subsequent to the addition of organic matter was investigated in replicate lake-water aliquots. Two experiments used freshly killed bacteria as the organic addition. In both, inorganic nitrogen in the water column increased only after a lag period following the organic addition, and only if the amount of organic matter added exceeded a threshold value. Two other experiments used freshly killed algae as the organic addition; in these, neither the lag period nor the threshold value were seen. A qualitative explanation for these observations is offered.     

Can we produce carbon and climate neutral forest bioenergy?

Harvesting branches, stumps and unmercantable tops, in addition to stem wood, decreases the carbon input to the soil and consequently reduces the forest carbon stock. We examine the changes in the forest carbon cycle that would compensate for this carbon loss over a rotation period and lead to carbon neutral forest residue bioenergy systems. In addition, we analyse the potential climate impact of these carbon neutral systems. In a boreal forest, the carbon loss was compensated for with a 10% increase in tree growth or a postponing of final felling for 20 years from 90 to 110 years in one forest rotation period. However, these changes in carbon sequestration did not prevent soil carbon loss. To recover soil carbon stock, a 38% increase in tree growth or a 21% decrease in the decomposition rate of the remaining organic matter was needed. All the forest residue bioenergy scenarios studied had a warming impact on climate for at least 62 years. Nevertheless, the increases in the carbon sequestration from forest growth or reduction in the decomposition rate of the remaining organic matter resulted in a 50% smaller warming impact of forest bioenergy use or even a cooling climate impact in the long term. The study shows that carbon neutral forest residue bioenergy systems have warming climate impacts. Minimization of the forest carbon loss improves the climate impact of forest bioenergy.     

Seston dynamics and tripton sedimentation in the pelagic zone of a shallow eutrophic lake

The transport of organic matter from the water column to the sediment and the relationship between the dynamics of the settleable fraction and that of the total suspended particulate matter were studied in shallow eutrophic Lake Wingra, Wisconsin. Tripton sedimentation was closely related to the dynamics of seston with a lag of 2 to 4 weeks. Sedimentation rate of tripton ranged from 0 to 8 g m^–2 day^–1 (in May and August respectively). Relative t0 the standing crop 0f seston the maximum sedimentation rate was 8% seston per day (in September). The annual tripton sedimentation was estimated at 632 g dry weight or 215 g C per m² which was equivalent t0 55% of the annual phytoplankton production and 42% of the phytoplankton and macrophytes annual production. It was estimated that 70% of the settling organic matter is decomposed annually, consequently only a small fraction 0f tripton is involved in the long term accumulation of bottom deposits. Factors influencing tripton sedimentation are discussed.Research supported by the Eastern Deciduous Forest Biome US-IBP, funded by the National Science Foundation under Interagency Agreement AG-199 BMS69-01147 A09 with the Energy Research and Development Administration-Oak Ridge National Laboratory. Contribution N0. 233 from the Eastern Deciduous Forest Biome US-IBP.Research supported by the Eastern Deciduous Forest Biome US-IBP, funded by the National Science Foundation under Interagency Agreement AG-199 BMS69-01147 A09 with the Energy Research and Development Administration-Oak Ridge National Laboratory. Contribution N0. 233 from the Eastern Deciduous Forest Biome US-IBP.     

Changes in soil carbon stock after deforestation and subsequent establishment of “Imperata” grassland in the Asian humid tropics

Globally, tropical deforestation is often followed by the establishment of fire-prone grassland. In Southeast Asia, Imperata cylindrica grassland is the dominant land cover after deforestation. No quantitative data are available on the changes in soil carbon (C) stock upon such land conversion. We aimed to elucidate changes in soil C stock after deforestation followed by the occurrence and persistence of I. cylindrica grassland in the Asian humid tropics. We compared soil C stock between primary forests (n?=?20) and grasslands (n?=?14) with a wide range of soil textures in East Kalimantan (Indonesian Borneo). We also assessed the temporal change in soil C stock in the grassland sites between 1992 and 2004 by comparing identical soil pits (n?=?7). Soil C stock (0–100 cm deep) increased by 23% following transition from primary forest to grassland during about 10 years. Over 12 years at the grassland sites, however, soil C stock did not change in the 0–100 cm depth, but we observed increased blackness of soil, especially coarse-textured soils. The increase in C stock following the transition was largely attributed to the organic matter supply by grass roots, rhizomes, and charred materials from wildfires to the subsurface soils and subsoils (5–100 cm). The unchanged soil C stock (0–100 cm) over 12 years at the grassland sites suggests that the soil C stock level there has nearly reached a new equilibrium state. However, the increased blackness of the soil suggests changes in the quality of soil organic matter by higher subsoil root input and deeper bioturbation by earthworms.     

Dynamics of amino acids in the conditioning film developed on glass panels immersed in the surface seawaters of Dona Paula Bay

The conditioning film developed on glass panels immersed in surface seawater over a period of 24 h was analysed for total organic carbon (OC), total organic nitrogen (ON), and total hydrolyzable amino acid (THAA) concentrations and composition. The concentrations of C and N and THAA increased, whereas the C/N ratio decreased over the period of immersion. The amino acid-C and N accounted for 3.7-6.7% and 10.3-65.3% of OC and ON, respectively. The relative contribution of glycine plus threonine and serine to the total amino acids decreased while that of valine, phenylalanine, isoleucine and leucine increased over the period of immersion. Principal component analysis (PCA) based on mole% amino acid composition showed that the degradation indices (DI) for the conditioning film organic matter increased over the period of immersion. A high C/N ratio, a low %THAA-C, % THAA-N and DI values and the abundance of glycine plus threonine and serine in the conditioning film organic matter during the first few hours following immersion imply that the adsorbed organic matter was mostly derived from degraded organic matter.     

Dynamics of amino acids in the conditioning film developed on glass panels immersed in the surface seawaters of Dona Paula Bay

The conditioning film developed on glass panels immersed in surface seawater over a period of 24?h was analysed for total organic carbon (OC), total organic nitrogen (ON), and total hydrolyzable amino acid (THAA) concentrations and composition. The concentrations of C and N and THAA increased, whereas the C/N ratio decreased over the period of immersion. The amino acid-C and N accounted for 3.7?–?6.7% and 10.3?–?65.3% of OC and ON, respectively. The relative contribution of glycine plus threonine and serine to the total amino acids decreased while that of valine, phenylalanine, isoleucine and leucine increased over the period of immersion. Principal component analysis (PCA) based on mole% amino acid composition showed that the degradation indices (DI) for the conditioning film organic matter increased over the period of immersion. A high C/N ratio, a low %THAA-C, % THAA-N and DI values and the abundance of glycine plus threonine and serine in the conditioning film organic matter during the first few hours following immersion imply that the adsorbed organic matter was mostly derived from degraded organic matter.     

Temporal niches of shredders in lake littorals with possible implications on ecosystem functioning

Temporal growth separation of shredders is known in streams but has not been reported from lakes. In the present study, temporal niche/trait differentiations among shredders in lakes were investigated. We sampled quantitatively three lakes in SE Sweden over a period of 18 months. Dry weight and number of individuals of the collected shredders were measured monthly. Standing stock of detritus types was also monitored. The same 10 species of lentic shredders were found in each lake, one isopod and larvae of nine trichopterans. Functionally, the shredders could be categorized into two main groups; winter and summer growing species. However, also within these groups, temporal differences in growth pattern existed. The main input of detritus occurred during the autumnal leaf fall and a majority of winter shredders had the start of their lives tied to this period. A succession in loss of detritus types was evident with easily degraded matter disappearing first followed by more resistant matter. Shredder species richness, shredder biomass per m² and the ratio coarse/fine detritus all reached its annual low in late summer. We propose a temporal link between the shredder groups and the organic matter subject to decomposition; the successive palatability of coarse detritus is likely to make a temporally separated community of shredders efficient in terms of decomposition. We believe that a temporal differentiation per se is sufficient to conclude that different impact on ecosystem function exists among shredders. Additionally we discuss impacts of differences in abundance and shredding capacity among the species.     

土壤有机质对农田管理措施的动态响应

土壤有机质在农田肥力、环境保护、农业可持续发展等方面具有重要意义。它不仅决定农作物产量,而且在全球碳素循环中起着重要作用。由于大气CO2浓度升高与全球气候变暖等一系列环境问题的加剧,全球碳素循环受到越来越多的关注。农田具有大气CO2源和库的双重潜力。历史上由于人类对农田的过度开垦和耕种,造成土壤有机质含量大幅度下降,降低了农田的作物产量潜力;同时导致大量的碳以CO2形式由陆地生态系统排放到大气圈,加剧了全球温室效应。大量研究结果表明,诸如耕作、种植制度、施肥等农田管理措施能够显著地影响土壤有机质动态,而免耕、提高复种指数、合理的轮作换茬、有机肥料和化肥的施用以及弃耕农田还林还草等保护性管理措施则能够提高农田土壤有机质含量,使农田起到大气CO2汇的作用。综述了近年来农田管理对土壤有机质动态影响研究方面的进展。     

Distribution and movement of toxaphene in anaerobic saline marsh soils

The biological oxygen demand (BOD) of filtered water from Lake Wingra, Wisconsin is significantly higher in the littoral zone than in the pelagial zone. Laboratory experiments indicate that BOD is not influenced by water temperature at the time of sampling or by enrichment with nitrate or ammonia. Rather, enrichment with macrophyte leachate sharply increases BOD, and enrichment with phosphate produces a small but significant increase in BOD. We conclude that high BOD in littoral waters of the lake is an indication of production of labile organic matter in the water by dense beds of the macrophyte Myriophyllum spicatum.     

Dynamics of structure and biological productivity of post-fire larch forests in the Northern Mongolia

Peculiarities of forming and growth of post-fire larch (Larix sibirica Ledeb.) forests at the southern range of their distribution in the Northern Mongolia were studied. Regularities of the stand structure and dynamics of biological productivity are analyzed and discussed in the paper. It has been proved that the structure of the organic mass of the post-fire herb-carex type larch tree stands at the southern border of forest vegetation distribution is closely related to their biometric indices as-age, density, and productivity. In comparison with tree stands from the other areas of forest vegetation, the total phytomass stock of larch phytocenoses appropriately increases by zonal gradient from forest-tundra border to the Transbaikalian southern taiga and northern regions of Mongolia. Regeneration of forest cover by edificator and formation of the original larch coenopopulation is a positive trend from an environmental point of view, because the Siberian larch in young and middle-age period in the area has a sufficiently high growth energy and rate of phytomass production, with more than twice exceeding mature forests in fixed carbon of the atmosphere and has positive values of carbon balance and total destruction of organic matter by the “input-output” parameters.     

A Cross-System Comparison of Bacterial and Fungal Biomass in Detritus Pools of Headwater Streams

The absolute amount of microbial biomass and relative contribution of fungi and bacteria are expected to vary among types of organic matter (OM) within a stream and will vary among streams because of differences in organic matter quality and quantity. Common types of benthic detritus [leaves, small wood, and fine benthic organic matter (FBOM)] were sampled in 9 small (1st-3rd order) streams selected to represent a range of important controlling factors such as surrounding vegetation, detritus standing stocks, and water chemistry. Direct counts of bacteria and measurements of ergosterol (a fungal sterol) were used to describe variation in bacterial and fungal biomass. There were significant differences in bacterial abundance among types of organic matter with higher densities per unit mass of organic matter on fine particles relative to either leaves or wood surfaces. In contrast, ergosterol concentrations were significantly greater on leaves and wood, confirming the predominance of fungal biomass in these larger size classes. In general, bacterial abundance per unit organic matter was less variable than fungal biomass, suggesting bacteria will be a more predictable component of stream microbial communities. For 7 of the 9 streams, the standing stock of fine benthic organic matter was large enough that habitat-weighted reach-scale bacterial biomass was equal to or greater than fungal biomass. The quantities of leaves and small wood varied among streams such that the relative contribution of reach-scale fungal biomass ranged from 10% to as much as 90% of microbial biomass. Ergosterol concentrations were positively associated with substrate C:N ratio while bacterial abundance was negatively correlated with C:N. Both these relationships are confounded by particle size, i.e., leaves and wood had higher C:N than fine benthic organic matter. There was a weak positive relationship between bacterial abundance and streamwater soluble reactive phosphorus concentration, but no apparent pattern between either bacteria or fungi and streamwater dissolved inorganic nitrogen. The variation in microbial biomass per unit organic matter and the relative abundance of different types of organic matter contributed equally to driving differences in total microbial biomass at the reach scale.     

Phytoplankton and nutrients in the Helgoland region

During recent decades, phytoplankton stock on the one hand and inorganic nutrients (P and bound N) on the other have increased considerably in the southern North Sea, as demonstrated at a permanent station (since 1962) near the island Helgoland. This correlation between phytoplankton and inorganic P and N need not have anything to do with causality; exceptional algal blooms have been observed and reported in the literature since in the 19^th century. Furthermore, these increases (four-fold for phytoplankton and two-fold for nutrients) are in the same range as the fluctuations from year to year under different hydrographical conditions. A detailed investigation carried out in 1981 demonstrated the presence of a slowly growing phytoplankton population. Starting with a considerable stock of flagellates in spring, it reached a peak in cell numbers over a long reproduction period which contrasted with the normal duration of a spring bloom of diatoms. These processes were not related to a limited production by P or N. A considerable concentration of these nutrients was permanently available in the form of inorganic compounds. The total amount of nutrients surpassed by far the portion incorporated in the phytoplankton. This is a consequence of the fact that small organisms have a high metabolic rate. Therefore, the relation between stock and production (daily production ≈stock) is completely different from that known e.g. in agriculture. The nutrients exist during the vegetation period mainly in the form of dissolved organic matter that is accessible to plankton. The great dynamics of this system, including a phase shifting during the year between inorganic P, N, Si, and production, indicates the significance of permanent and fast remineralization. Calculations demonstrate that the natural nutrient content of seawater normally satisfies the demands of phytoplankton present in the North Sea area under study. Only in the more productive coastal region (salinity<30 associated with fresh water run-offs of low nutrient content — an unrealistic assumption in the German Bight) might some limitation be observed. For diatoms, silicate may represent a critical component, but a high dynamic force exists in the presence of small Si concentrations. Therefore, a lack of silicon must not represent any limitation; however, knowledge on the silicon system is insufficient up to now. Dedicated to Dr. Dr. h. c. Peter Kornmann on the occasion of his eightieth birthday.     

Mesoscale Dynamics of Ephemeral Wetlands in the Antarctic Dry Valleys: Implications to Production and Distribution of Organic Matter

ABSTRACT Ephemeral wetlands in the Antarctic dry valleys alternate as sites of in situ net primary production when inundated and sources of organic matter for eolian export when desiccated. Evidence of this switch was obtained from observations made in two field seasons (2001 and 2003), coincidentally separated by a season of exceptionally high water yield from nearby glaciers (2002). In 2001, organic matter on soil surfaces adjacent to several ponds in Taylor Valley often exceeded 500 g C/m². One pond had a total stock of approximately 1,388 kg organic C on soils within 20 m of the shoreline. These materials formed concentric rings around the pond, suggesting historically higher water levels, consistent with aerial photographs taken a decade earlier (1993). In 2003, these materials were submerged by water apparently received during the intervening year. Also in 2003, pitfall traps were placed along the edges of exposed organic matter adjacent to another pond to evaluate organic material erosion by wind. Over 4.5 days, traps collected 0.22 ± 0.12 to 2.91 ± 1.68 g C/m², both confirming and quantifying wind transport. These results indicate that organic matter production and movement, driven by seasonal and decadal patterns of inundation/desiccation of small, ephemeral wetlands, overlay longer term (centuries and millennia) and larger scale (landscape) patterns of production and distribution driven by regional fluctuations in hydrological balance between glaciers and large freshwater lakes.     

Influence of organic matter and climatic factors on the harpacticoid copepod (Crustacea) population from the well sorted fine sands of Banyuls Bay

The authors investigated the development of the harpacticoid copepod population in relation to the variations in organic matter and meteorology. Sediment sampling was performed over a 2-year period in the shallow waters (3 m deep) of Banyuls Bay (Western Mediterranean). Each year presents two distinct periods: winter to early spring, and from late spring until fall. During the first period of the annual cycle, the organic carbon and nitrogen cycles are fairly dissociated; the quantity of copepods appears to be dependent upon the climatic and physical conditions. During the second period, the climatic conditions are very similar from year to year, without heavy rains or strong storms, and the values observed both for the organic matter and the copepod population are also similar. The hypothesis is proposed that organic matter can be considered a limiting factor to population increase.     

High-resolution spectroscopic study of pore-water dissolved organic matter in Holocene sediments of Lake Peipsi (Estonia/Russia)

Ultraviolet–visible absorption and fluorescence spectroscopies allow simultaneous detection of several organic substances. These spectra also contain information on whether the organic matter is produced in the water body or in its catchment. In this work various spectral indices, which are widely used in aquatic studies to determine humic substances, proteinaceous matter, chlorophyllous pigments and the origin (autochthonous versus allochthonous) of organic matter, were applied to track changes in a Holocene record from the large and shallow northern temperate Lake Peipsi (Estonia/Russia) at a high-resolution scale. Absorption and three-dimensional fluorescence spectra of the organic matter fraction dissolved in sediment pore water (pDOM) were analysed. In addition to the spectral measurements of pDOM, the sediment samples were analysed for main constituents (water and organic and mineral matter) and magnetic properties. The core chronology was established by nine radiocarbon datings. Temporal changes in pDOM in the record were quite variable; however, three periods in the development of the lake can be distinguished: a 2500 yr period in the early Holocene and a 2500 yr period in the late Holocene, when drastic changes in the accumulated matter occurred, and a rather stable 5000 yr period in between. We postulate that the changes over the period in the early Holocene reflect a rise of water level in the lake; the oscillations over the relatively steady period were probably caused by climatic factors, and alterations over the period in the late Holocene were due to the expansion of agricultural activity in the lake catchment. Our findings indicate that the use of spectral indices in palaeoinvestigations offers valuable information for reconstructing natural and human-induced developments of lakes.     

Some Aspects of Energy Flow in Plantations of Pinus sylvestris L.

Calorific values are given for the different types of plantmaterial in an age series of plantations of Pinus sylvestrisand the amounts of energy in the organic matter present perhectare of woodland are calculated. Following afforestationwith Scots pine a progressive accumulation of energy occursup to 35 years of age when the organic matter present per hectarecontains about 10, 000x10⁸ calories. Values are given for theenergy content of the primary production by the trees and groundvegetation, of energy accumulation in the tree stock, understoryvegetation, and litter, of energy removed in the harvested treesand of energy released by decomposition. The photosyntheticefficiency of the forest community is calculated and shown tobe comparable to that of high producing agricultural crops sothat it is suggested that the forest community makes very fulluse of site conditions.