Litter Components Research Articles

Litter-fall and litter decomposition in a low Mediterranean shrubland

Annual production of litter by Cistus incanus (L.) and Myrtus communis (L.) and decomposition dynamics of leaf litter of these species was studied in a Mediterranean shrubland. Myrtus and Cistus produced 472 and 429 g dry weight litter m-2 year-1, respectively. Leaves were the predominant litter component for both species. The average decay constant of Myrtus and Cistus litters enclosed in litter bags, calculated over the whole study period (38 months), was 0.71 year-1 and 0.31 year-1 respectively. In green leaves the N content differed during growth seasons for both species, whereas the content of Ca, Mg, P, K, and Na did not show significant changes. Abscised leaves had lower N, P and K contents than green leaves, evidencing that a nutrient translocation before abscission occurred from senescent leaves. The nutrient contents of the leaves at abscission time, generally higher in Cistus than in Myrtus, allowed us to estimate the annual nutrient input to the soil. Phosphorus and K more than N were rapidly released by the decomposing litters after exposure. Nutrient limitation, in particular P, might be considered the main growth limiting factor for Myrtus and Cistus. Both species were adapted to recovery and rapidly recycle P more than N and K in the living biomass through retranslocation from green leaves before abscission and/or a high release rate from the decomposing litter. The former strategy was better used by Cistus, the latter by Myrtus.

Litter decomposition, ectomycorrhizal roots and the ‘Gadgil’ effect

○Ectomycorrhizas may interact with saprotrophic microorganisms to influence decomposition. These interactions are poorly understood. ○We buried mesh envelopes filled with either litter or F-layer material in the forest floor of a Pinus resinosa plantation. After 16 months we characterized decomposition, C: N ratio, water content, and the density of four ectomycorrhiza morphotypes. ○For both substrates there were negative correlations between ectomycorrhiza density and decomposition, and between ectomycorrhiza density and water content. The relative proportion of morphotypes was significantly different in litter and F-layer material buried at the same depth in the forest floor. ○We conclude that the negative effect of ectomycorrhizas on decomposition could be mediated by extraction of water, particularly in relatively dry years. The 'Gadgil effect' may be explained by this phenomenon. In wetter years, water extraction may be less consequential. Also, variation in substrate quality may influence the structure of ectomycorrhizal fungal communities.

Orchid species succession in rehabilitated bauxite mines in Western Australia

Twenty-three orchid species were recorded in Alcoa's permanent vegetation-monitoring plots in unmined and rehabilitated jarrah forest. Of these, 22 were identified in the unmined jarrah forest and 20 were recorded in rehabilitated areas of between 1 and 31 years old. Three species (Cyrtostylis ovata, Lyperanthus serratus and Prasophyllum elatum) were only recorded in the unmined forest and one species was only recorded in rehabilitated areas (Diuris carinata). The overall density of native orchids in the forest was 13 755 plants ha–1, 10 times greater than the density in rehabilitated areas (1381 plants ha–1). The most abundant species in the forest were Cyrtostylis robusta, Caladenia flava, Pterostylis nana and Thelymitra crinita, all with densities greater than 1000 plants ha–1. The most abundant species in the rehabilitated areas were Microtis media, Disa bracteata (an introduced species), Caladenia flava, Pterostylis nana, Diuris longifolia and Pterostylis vittata, all with densities greater than 60 plants ha–1. In rehabilitation older than 10 years, the density of orchids increased to 2685 plants ha–1. Burning in rehabilitated areas resulted in large increases in orchid densities. It is believed that orchid colonisation of rehabilitated bauxite mines is dependent on symbiotic mycorrhiza, which are in turn dependent on development of an organic litter component in the soil.

Biomass and nutrient dynamics in a littoral savanna subjected to annual fires in Congo

Abstract The dynamics of nutrient accumulation were studied between two annual fires in a herbaceous savanna of the Congolese littoral region. Trees and shrubs were not studied because of their very low density. After fire the aboveground biomass increased for 10 months up to a maximum of 520 g m–2. The underground biomass amounted to roughly 630 g m–2 during the dry season and increased after the fire up to a maximum of 870 g m–2 during the rainy season. In the aerial parts, the accumulation dynamics differed according to the type of nutrient: Ca accumulation was steady until the following dry season in proportion to the total biomass, while the pattern of K accumulation was similar to the living biomass dynamic and reached a maximum four months after the fire. N, P and Mg followed a middle course. For the underground biomass, N accumulation reached a maximum value at the end of the rainy season (10 g m–2) and decreased at the beginning of the dry season. Most of this element was incorporated into the root system. During the rainy season, accumulation in the root system was of the same order of magnitude as in the aerial parts for P and Ca, whereas it was much lower for K and Mg. Transfers of nutrients to the atmosphere during the annual burning amounted, respectively, to 85, 25, 39, 21 and 28% of the amounts of N, P, K, Ca and Mg accumulated in the aerial biomass and litter components. Losses during fire were small for P, K, Ca and Mg compared to the available soil reserves, but not for N. The legume Eriosema erici-rosenii ought to play an important role in N input in this ecosystem.

Litterfall from trees in semiarid woodlands of north‐east Queensland

AbstractThe amount and chemical composition (nitrogen, phosphorus and sulfur concentrations) of the components of tree litter were measured in eucalypt woodlands at two sites (Cardigan and Hillgrove) near Charters Towers, Queensland, Australia. Annual litterfall averaged 720 kg ha–1 (Cardigan) and 1270 kg ha–1 (Hillgrove) over 3 years with leaves the major component at both sites. Rate of litterfall was greatest during September–December and lowest during May–July. Nutrient concentrations varied widely but no seasonal patterns were detected. Phosphorus concentrations in the leaf litter at Hillgrove (mean = 0.112%) were much higher than in other studies of eucalypt litter, probably reflecting the high soil phosphorus levels at the study site. Tree litter represents an important proportion of the organic material and nutrients being cycled through these woodlands.

Release and bioavailability of dissolved organic matter from floodplain litter: influence of origin and oxygen levels

1. We determined the rate of release and microbial uptake of dissolved organic carbon (DOC) leached from three components (leaves, bark and twigs) of river red gum (Eucalyptus camaldulensis) forest litter originating from different parts of a floodplain and under different oxygen levels. 2. Preliminary experiments showed that substantially more DOC was released from leaves than from bark or twigs; there was relatively little DOC release from coarse particulate matter or soil. 3. Both the amount of DOC released from each litter component and the amount metabolized by the microbial community were independent of position on the flood‐plain or amount of oxygen available to microbes. 4. Although the bioavailability of DOC was independent of oxygen concentration, the microbial utilization of DOC under aerobic and anaerobic conditions differed. Under aerobic conditions, leaves were colonized by fungi, while bacteria were dominant under anoxic conditions. 5. Phospholipid fatty acid profiles of the microbial communities growing on leaf extracts showed that different microbial communities developed in each oxygen concentration treatment suggesting that, irrespective of flood conditions, a microbial community will develop to utilize a significant proportion of the DOC leached from litter.

Estimation of genetic and environmental risk factors associated with pre-weaning mortality in piglets using generalized linear mixed models

AbstractRisk factors and variance components of pre-weaning mortality were estimated using generalized linear mixed models. Data were from 12 727 piglets born alive from 1338 litters recorded at the pig breeding farm of the University of Kiel from 1989 to 1994. Deviances due to risk factors were estimated by generalized linear model and their odds-ratios by generalized linear mixed model both with binomial errors and a logistic link. Variance components of sire, dam and litter were estimated using a logit or probit link function as well as a linear model for which estimates were transformed to the underlying continuous scale. Highest increase in deviance, indicating the risk factor, which accounts for the greatest amount of unexplained variation of pre-weaning mortality was obtained after exclusion of individual birth weight (1206) from the model, followed by year-season (217), parity-farrowing age or interval (58), genotype of piglets (56), sex (39), total number of piglets born (18) and gestation length (16). Substitution of individual birth weight successively by average piglet birth weight per litter, litter birth weight and standard deviation of birth weight within litter resulted in models with substantially lower explained variation of pre-weaning mortality. Odds of pre-weaning mortality was 1·5 times higher for males than for females and 2·0 times higher in piglets from German Landrace dams than from Large White dams. Odds increased to the fifth parity by 2·2 times the odds of the first parity or increased for the age group of dams between 850 and 949 days by 2·3 times the odds of the age group with less than 350 days. When the continuous risk factors of individual birth weight, average piglet birth weight and litter birth weight decreased or standard deviation of birth weight within litter increased by one standard deviation from the mean, the odds ratios increased by 6·0, 1·6, 0·8 and 0·4, respectively. Piglets with individual birth weights of 1·8, 1·5, 1·2 and 1·0 kg showed a rapid increase in odds ratios of pre-weaning mortality of 1·4, 2·7, 7·0 and 16·1, respectively, relative to piglets with 2·1 kg. Estimates of direct heritability for pre-weaning mortality on the linear observed, transformed underlying, logit and probit scale were 0·02, 0·06, 0·07 and 0·07, respectively. Low estimates of heritability for pre-weaning mortality, even on the underlying continuous scale, suggested low potential for improvement by selection. Therefore, selection for individual birth weight phenotypically closely associated with pre-weaning mortality was recommended to improve survival of piglets during the nursing period.

Genetic and environmental influences on size of first litter in sheep, estimated by the REML method

Fixed effects of age at first litter and of season of lambing as well as variance components for additive genetic, flock × year and sire of litter effects on size of first litter were estimated for an animal model by a derivative‐free REML procedure. Data of the four Swiss sheep breeds White Alpine (WAS), Brown‐headed Meat (BFS), Black‐Brown Mountain (SBS) and Valais Black Nose (SN) were available. Number of first litters used were 21 384, 21 607, 15 013, 12 394 and 18 110 the WAS (two data sets, WAS1, WAS2), BFS, SBS and SN, respectively. Litter size of ewes lambing the first time at 2 years of age was 0.27, 0.31, 0.41, 0.46 and 0.26 lambs larger than of ewes lambing the first time at 1 year of age. The largest increase occurred for the two breeds (BFS, SBS) with the lowest average age at first litter. The largest difference between any two lambing seasons within breed were 0.16, 0.16, 0.29, 0.22 and 0.07 lambs. Estimates of additive genetic variance of size of first litter were between 0.0269 (SN) and 0.0765 (SBS). Heritability estimates for this trait were 0.171, 0.156, 0.114, 0.225 and 0.122 for WAS1, WAS2, BFS, SBS and SN, respectively. A large flock × year component (relative to phenotypic variance) of 0.148 was found for SN, compared with estimates between 0.042 and 0.067 for the other breeds. A sire of litter component (relative to phenotypic variance) of 0.066 was found for SN, compared with estimates between 0.016 and 0.039 for the other breeds. It can be concluded that all nongenetic effects investigated should be taken into account for the estimation of additive genetic variance and breeding values for size of first litter, and that considerable variation in size of genetic and nongenetic effects exists in the sheep breeds under consideration.

Responses of plant rhizosphere to atmospheric CO2 enrichment

Plant root growth is generally stimulated under elevated CO2. This will bring more carbon to the below-ground through root death and exudate. This potential increase in below-ground carbon sink may lead to changes in long-term soil sequestration and relationship between host plants and symbions. On the other hand, changes in litter components due to the changes in plant chemical composition may also affect soil processes, such as litter decomposition, soil organic matter sequestration and hetero-nutritional bacteria activities. These issues are discussed.

The effect of flooding and flood timing on leaf litter breakdown rates and nutrient dynamics in a river red gum (Eucalyptus camaldulensis) forest

AbstractComparisons of litter standing‐stocks in low‐lying and higher areas of the floodplain and the effects of controlled flooding events on leaf litter decomposition and leaf litter nutrients were examined during autumn and winter in a southeastern Australian river red gum (Eucalyptus camaldulensis) floodplain forest. The mean mass of total litter and some litter components was significantly greater in autumn than in winter but there were few differences in litter mass between low‐lying flood runners and higher sites (1.5 m) on the floodplain, regardless of season. Leaf decomposition was more rapid in flooded areas than in non‐flooded areas and was significantly faster in autumn than in winter. In flooded leaves, concentrations of phosphorus and nitrogen dropped rapidly during the first 3 days of each experiment, increased to near original after 7–10 weeks and then decreased again. After 112 days of decomposition the C:N:P ratios of leaf litter increased, but this effect was most marked for flooded leaves. Simple models of leaf litter dynamics indicated that leaf litter standing‐stocks in low‐lying flood runners would be reduced by flooding, particularly during autumn. In contrast, models predicted a net gain in standing‐stocks of leaf litter to be higher on the floodplain, particularly in autumn. Alteration to the seasonal timing of floods by river regulation has probably decreased litter standing‐stocks and nutrients available in low‐lying areas of the floodplain to support the production of macrophytes and biofilms during winter and spring floods.

Environmental Heterogeneity, Animal Disturbances, Microsite Characteristics, and Seedling Establishment in a Quercus havardii Community

AbstractIn restoration experiments it is imperative to consider the study of mechanisms of how species are maintained and preserved in a system. This paper reports on the results of a field experiment examining the growth and survival of seedlings of Schizachyrium scoparium, a dominant perennial bunchgrass member of the Quercus havardii (sand shinnery oak) communities of semiarid western Texas, on mounds of displaced soil produced by Sylvilagus auduboni (rabbit). The central question posed is: does environmental heterogeneity created by small mammals influence seedling survival and growth? The specific questions addressed are: (1) Does seedling survival, growth, and nutrient uptake vary when grown on mounds, off‐mound soils, and artificially created mounds?; (2) What is the influence of the microbial and litter components of mound soils on seedling survival?; and (3) In communities where animal disturbances create environmental heterogeneity and may impact seedling establishment, is it possible to artificially create mounds that could serve a similar function? Results show that characteristics of mound soils increase seedling survival, shoot and root biomass, root length, number of tillers, mycorrhizal infection, and nutrient uptake more in plants grown on mounds than off mounds. Both the microbial and litter components of mound soils are essential components of this effect. Artificial mounds generated from soils associated with the herbaceous community were more similar to intact rabbit mounds than artificial mounds generated from soils associated with the oaks. The results indicate that rabbits produce rich patches (both nutrient and microbial) favorable to the growth of seedlings of the dominant bunchgrass, and point to the potential importance of rabbit disturbances in shaping the dynamics of this plant community. Thus, rabbit‐generated disturbances produce environmental heterogeneity in the sand shinnery oak community, similar to that produced by harvester ants in this community as shown by an earlier study. Small animal activity that results in soil displacement, and influences soil characteristics, may indirectly contribute to the persistence of certain plant species within a community. Thus, disturbances may well operate in semiarid communities to produce nutrient and microbe rich microsites which may function to maintain diversity.

Spatial variation in litter production by the mangrove Avicennia marina var. australasica in Rangaunu harbour, Northland, New Zealand

Litter fall was measured at two intertidal levels within two stands of the mangrove Avicennia marina (Forsk.) Vierh. var. australasica (Walp.) Moldenke in Rangaunu Harbour, New Zealand (34° 57'S, 173° 15'E). The seasonal pattern of litter fall was typical of A. marina at high latitudes. Flowering occurred in March‐April and fruit fell 9 months later during December‐January. Leaf fall was highest from November to February and was positively correlated with temperature and negatively correlated with sediment water availability (total rainfall minus total evaporation). Total annual litter fall ranged from 1.81 ha‐1 yr‐1 to 6.21 ha‐1 yH and was proportional to mean tree height at each site. Leaves constituted on average 73% of the total litter fall and were the only litter component to show significantly lower magnitude at both elevated sites. The largest litter collections were made during the summer months coincident with peak falls of leaves and fruit. The possible contribution of mangrove litter to es‐tuarine food chains in northern New Zealand estuaries is discussed.

Saprotrophic cord-forming fungi: meeting the challenge of heterogeneous environments

Many saprotrophic fungi, especially basidiomycetes, which are able to grow out of the substratum that they are colonizing in search of new resources (i.e., nonresource-unit-restricted fungi) form mycelial cords, which are aggregations of predominantly parallel, longitudinally aligned hyphae. These cords often form extensive, long-lived systems which interconnect discrete nutrient resources, e.g. woody litter components, on the floor of boreal, temperate and tropical forests, and some can form networks in tropical canopies. They exhibit foraging strategies which vary among species, and which alter depending on resource quantity and quality, the presence of other organisms, and microclimatic environment. The morphological patterns they form are well described by fractal geometry. Their mycelia show remarkable patterns of reallocation of biomass and mineral nutrients when new resources are encountered during mycelial foraging or when new resources are added to mature systems. Mycelial-cord systems encountering heterogeneously distributed organic substrata coordinate use of available resources so that demands are met by ‘spreading the load’ through the system. The persistent networks, ability to forage for new resources, and ability to reallocate mycelial biomass and nutrients exhibited by saprotrophic cord-forming fungi provide a solution to the problems of life in a spatially and temporally heterogenous environment. Response to the heterogenous environment in which these fungi exist generates heterogeneity in themselves, and they in turn generate heterogeneity in their environment, both in space and time.

Alum Sludge and Zeolite as Components of Broiler Litter

This study investigated whether alum sludge, a coproduct of drinking water purification, and natural zeolites could be used as components of broiler litter. The two alternatives were used singly and in combination to constitute a portion of the litter. Alum sludge at 20% and natural zeolite at 10% replaced wood shavings. Commercial broiler chickens were grown on the different litter combinations from day-old to market age. The response criteria examined included growth, feed conversion, livability, leg score, tibial dyschondroplasia score, and litter characteristics. Mortality and morbidity were negligible and 16 beetle traps yielded two beetles from the pen. A statistically significant effect due to litter was not detected in body weight, feed conversion, or leg scores at 3 and 6 wk of age. Litter treatments did not influence litter characteristics such as ammonia, pH, nitrogen, phosphorus, and copper. The results showed that there were no detrimental effects associated with using alum sludge and/or natural zeolites as components to reduce the amount of wood shavings needed for litter.

Some nutrient dynamics associated with litterfall and litter decomposition in hoop pine plantations of southeast Queensland, Australia

Litterfall was collected over a 12-month period with littertraps in hoop pine ( Araucaria cunninghamii) plantations aged 10, 14 and 62 years in southeast Queensland, Australia. The bulk of litterfall occurred during spring, mainly as hoop pine foliage with the annual litterfall ranging between 6.0 and 10.9 t ha −1, respectively, for the younger stands (10 and 14 years) and the mature 62-year old stand. The amount of nitrogen (N) and phosphorous (P) recycled annually through litterfall was lower in the younger stands (28–37 kg N ha −1 and 4.4–5.3 kg P ha −1) compared with that of the mature stand (85 N ha −1 and 6.2 kg P ha −1). The N and P retranslocated during senescence varied across the three stands studied with a trend for N and P retranslocation to increase as availability of soil mineral-N decreased. Decomposition of the hoop pine foliage component of litter was also studied in the same stands using a litterbag technique and mass-balance analysis. The estimated half-life of hoop pine foliage mass ranged between 1.5 and 1.8 years. Litter-mass loss was strongly correlated with litter substrate quality indicators of N, C, P, C/N ratio, lignin, lignin/N ratio and polyphenols. During the course of the study, there was no difference in litter-mass loss between the stands of different ages. During the 15-month period, the order of element release from the hoop pine litter was K>Na>C>Mg>P, with N, Ca and Mn generally demonstrating varying degrees of net accumulation. During the course of the study, the lignin/C ratio of the hoop pine litter increased from 0.61 to 0.96. This suggested that the litter-C was predominantly in a recalcitrant form and, therefore, the associated N was unlikely to be rapidly released in the hoop pine litter layer.

Soil phosphorus extractability and uptake in a Cirsio-Molinietum fen-meadow and an adjacent Holcus lanatus pasture on the culm measures, north Devon, UK

The seasonal pattern of extractable soil P and soil solution P was determined for topsoil samples taken from a Cirsio-Molinietum fen-meadow community, and also for an adjacent agriculturally improved pasture in Devon, UK. Phosphorus concentration was investigated using three methods during 1993; Olsen's reagent (sodium bicarbonate) for soil P, centrifuging and polymeric suction cups for soil solution P. Solutions were extracted at two-weekly intervals during the spring and at monthly intervals during the summer. Phosphorus removed from both sites by centrifuging was in the range 5–30 μg dm −3 soil, in comparison with 1–6 mg kg −1 for Olsen P. Olsen P on the Cirsio-Molinietum was significantly lower than on the improved pasture in mid-March and mid-June. The concentration of P in soil solution removed by suction cups was below the level of detection (<2 μg dm −3) on the Cirsio-Molinietum. Suction cup P on the improved pasture peaked in April and May at 16–19 μg dm −3 soil. Herbage yield and P concentration were measured throughout the growing season. Above-ground standing crop was greater on the Cirsio-Molinietum than the improved pasture at the beginning of the grazing season, because of the large litter component on the former. Total P content of this material was only 1.81 kg P ha −1 on the Cirsio-Molinietum, in comparison with 5.58 kg P ha −1 on the improved pasture. Phosphorus concentration of plant material obtained by repeated defoliation was approximately 1.0 mg P g −1 DM on the Cirsio-Molinietum, whereas a clear seasonal trend, peaking at 3.5 mg P g −1 DM, was observed on the improved pasture. Phosphorus concentration of litter, grass and sedge from ungrazed plots on the Cirsio-Molinietum indicated distinct seasonal variations for the grass, with no seasonal pattern for the sedge component.

Fire in the Brazilian Amazon 2. Biomass, nutrient pools and losses in cattle pastures.

Conversion to cattle pasture is the most common fate of the ≈426,000 km2 of tropical forest that has been deforested in the Brazilian Amazon. Yet little is known about the biomass, C, nutrient pools, or their responses to the frequent fires occurring in these pastures. We sampled biomass, nutrient pools and their losses or transformation during fire in three Amazonian cattle pastures with typical, but different, land-use histories. Total aboveground biomass (TAGB) ranged from to 53 to 119 Mg ha-1. Residual wood debris from the forests that formally occupied the sites composed the majority of TAGB (47-87%). Biomass of fine fuels, principally pasture grasses, was ≈16-29 Mg ha-1. Grasses contained as much as 52% of the aboveground K pool and the grass and litter components combined composed as much as 88% of the aboveground P pool. Fires consumed 21-84% of the TAGB. Losses of C to the atmosphere ranged from 11 to 21 Mg ha-1 and N losses ranged from 205 to 261 kg ha-1. Losses of S, P, Ca, and K were <33 kg ha-1. There were no changes in surface soil (0-10 cm) nutrient concentration in pastures compared to adjacent primary forests. Fires occur frequently in cattle pastures (i.e., about every 2 years) and pastures are now likely the most common type of land burned in Amazonia. The first 6 years of a pastures existence would likely include the primary forest slash fire and three pasture fires. Based upon our results, the cumulative losses of N from these fires would be 1935 kg ha-1 (equivalent to 94% of the aboveground pool of primary forest). Postfire aboveground C pools in old pastures are as low as 3% of those in adjacent primary forest. The initial primary forest slash fire and the repeated fires occurring in the pastures result in the majority of aboveground C and nutrient pools being released via combustion processes rather than decomposition processes.

Nutrient cycling in deciduous forest ecosystems of the Sierra de Gata mountains: aboveground litter production and potential nutrient return

The potential nutrient return in a chestnut coppice (Castanea sativa Miller) over a period of 3 years (1991-1994) has been established and compared with the returns found in four deciduous oak (Quercus pyrenaica Wild.) forests (1990-1993) located in the Sierra de Gata mountains (central Spanish system). A convergence of abscission phenology patterns was observed among the different ecosystems studied, together with a delay in leaf fall at the warmest plot. This similarity is logical since the plots harbour the same deciduous species which are, however, subjected to climatological vari- ations. The chestnut coppice was found to be more productive than the oak forests, the amounts of leaves, branches, flowers and total litterfall being significantly greater. Statistical analysis showed a highly significant correlation between the chestnut coppice and the oak forest aboveground produc- tion, ranging between 0.82 and 0.96 for the leaves and between 0.72 and 0.89 for the total litter. In general, the leaf organs of the chestnut trees showed a higher concentration of bioelements than the oaks, with N and Ca predominant in the buds, Ca and Zn in the branches, K in the fruits, and above all Fe and Cu in the other plant remains. In all the forests studied, the potential nutrient supply fluc- tuated over the years and depended strongly on phenological factors; above all it was found to be gov- erned by the leaves, which contributed most to the return of mineral nutrients to the soil. The most marked potential nutrient return through the oak aerial organs occurred on the plot with the lowest rain- fall, particularly with respect to P and Ca. Considering all the forest plots, the general sequence of the amount of bioelements returning with the litterfall to the soil was as follows: with the exception of one oak plot (with an acid soil reaction and poor soil drainage), where the Mn return was higher than that of P owing to the high concentration of Mn in all the litter components. (© Inra /Elsevier, Paris.)

Litter in a first–order stream of a temperate deciduous forest (Margaraça Forest, central Portugal)

To evaluate the importance and fate of organic matter inputs in forested streams, we determined the litterfall inputs and the benthic coarse particulate organic matter (CPOM) in one headwater stream flowing through a mixed deciduous forest, during one year. Both vertical traps and the stream bottom were sampled monthly. The material collected was sorted into four main categories: leaves, fruits and flowers, twigs and debris. Litter production was 715 g m−2 y−1 and seasonal, with 73% of the annual total during October–December (autumn). Leaves comprised the largest litter component. Benthic organic matter was 1880 g m−2 y−1, and was also seasonal. Highest accumulation was attained in spring, and twigs and branches comprised the major component.

13C nuclear magnetic resonance spectroscopy with cross-polarization and magic-angle spinning investigation of the proximate-analysis fractions used to assess litter quality in decomposition studies

Proximate analysis is often used in decomposition studies to characterize the organic components of foliar litter. The percent weight residue remaining after extraction by nonpolar and polar solvents and H3SO4 hydrolysis (Klason lignin, KL) is commonly used as a measure of litter quality and a modelling parameter. While KL is associated with resistance to decay, its nature is not well understood and it has long been suspected that it incorporates nonlignin components. We used solid-state 13C nuclear magnetic resonance (NMR) spectroscopy to characterize litter, extracted residue, and the KL fraction of five species. NMR shows that cutin and condensed tannin are both significant components of litter and its extraction residues, in addition to lignin and carbohydrate. Hydrolysis with H2SO4 removes carbohydrates and amino acids, leaving the KL fraction derived from cutin, tannin, and lignin. Tannin retention in KL was also demonstrated by a hydrolysis study of purified tannins and a brown-rot lignin, using both NMR and the proanthocyanidin assay for condensed tannins. Although the NMR results are qualitative at this stage, it is clear that KL has limited use as a parameter controlling litter decomposition, and that other biopolymers should not be ignored in conceptual models, chemical analysis, and experimental design. Key words: Klason lignin, 13C CPMAS NMR, proximate analysis, litter quality, decomposition, tannin.