Higher Litter Production Research Articles

Primary Succession Following Deglaciation at Koryto Glacier Valley, Kamchatka

ABSTRACTWe studied the course of primary succession following deglaciation and the convergence/divergence of plant community development with respect to topographic factors at Koryto Glacier Valley on Kamchatka’s Pacific coast. Vegetation changes over an ∼270-yr-old chronosequence were related to concurrent changes in substrate and soil properties. Ordination analyses showed that substrate texture and topography are the most important environmental factors influencing the course of succession. About 25 yrs after surface deglaciation, belowground stagnant ice melts, and moraine consolidation causes the successional communities to diverge. Species-poor communities, dominated by alder and grasses (Alnus fruticosa, Calamagrostis purpurea), occurred on the fine-grained substrate of moraine crests, while species-rich communities, dominated by legumes and forbs (Oxytropis kamtschatica, Saxifraga species), developed on the coarse-grained substrate of moraine flanks, and in depressions communities dominated by willows and sedges (Salix arctica, Juncus beringensis) developed. In depressions and plains adjacent to the ridges, succession toward Alnus stands is hindered by late-melting snow and flooding. Plant-species richness peaked at the 80-yr-old moraine, but thereafter decreased as the rapid growth of Alnus led to dense stands that dominated resources and inhibited colonization and growth of earlier, as well as later, successional species. Mat-forming capacity, high litter production, an extensive root system, and snow-pressure tolerance enable A. fruticosa to maintain dominance without replacement by Betula ermanii. This potential climax species remains scattered on rock terraces and elevated locations above the valley basin where it escapes snow avalanches and accumulation, a factor responsible for the inversion of vegetation zones in this maritime region.

Produção de serapilheira em floresta Atlântica secundária numa paisagem fragmentada (Ibiúna, SP): importância da borda e tamanho dos fragmentos

Litter is an important compartment in tropical forests, responsible for most of nutrient cycling. Several environmental factors may affect litter production, and the ones mostly investigated are climate and vegetation structure. The influence of landscape structure on patterns of litter production is poorly studied. This study investigated edge and size effects on patterns of litter production in three Atlantic forest fragments (Ibiuna, SP: 23°35' S - 23°50' S; 46°45' W - 47°15' W), one large (ca. 175 ha) and two small (ca. 5 ha) with different degrees of isolation. The litter collected was fractioned following the predominant plant material, and grouped into two periods, of high and low production. We used analysis of variance and a posteriori tests to detect differences in litter production between edge and center of each fragment, and among the centers of the three fragments. Most biomass consisted of leaves+flowers, followed by twigs < 0.5 cm (62.9% and 24.7% of the total), a common pattern in tropical forests. It was possible to perceive an edge effect related to litter production in the three fragments, especially in the large one, and higher litter production in their centers. The observed patterns showed to be strongly related to the vegetation structure, as the size of trees and canopy density. A higher production of fruits+seeds in the large fragment or in the small and connected one indicate a relationship between forest connectivity and the activity of disperser animals.

Determinants of fine‐scale plant species richness in a deciduous forest of northeastern North America

AbstractQuestion: What are the determinants of fine‐scale plant species richness (SR)?Location: Île‐aux‐Grues, Québec, Canada.Methods: Elevation, soil organic matter, soil pH, irradiance, tree basal area (BA) and plant SR (herbs, shrubs, and trees) were determined in 100 contiguous 25 m2 quadrats in a deciduous forest. Each variable was analysed for spatial autocorrelation using Moran's I. Path analysis was used to determine the effects of different variables on tree, shrub and herb SR in a hierarchical modelling approach.Results: Most of the variables, except tree BA, PPFD (photo‐synthetic photon flux density) and shrub SR, were positively autocorrelated at a scale of ca. 20 m or less. The path analyses explained ca. ll%‐40% of the variance in plant SR; however, the model for shrub SR was not significant. Tree SR was positively associated, but herb SR was negatively associated with tree BA. Tree SR had a positive influence on shrub SR, but herb SR remained unaffected by tree or shrub SR.Conclusion: The positive association of tree BA and tree SR suggests that the data from the study site correspond to the left (ascending) portion of the SR‐biomass relationship (un‐dersaturated SR). The negative effect of tree BA on herb SR is direct and not mediated through reduced PPFD. High tree BA might cause high resource use, induce high litter production and affect soil properties, all of which might significantly affect herb SR. Several factors not considered here might influence fine‐scale SR, such as interspecific interactions, fine‐scale disturbances and heterogeneity (both spatial and temporal) in resources and abiotic conditions. Within‐site variations of SR might be difficult to model with precision because of the relative importance of stochastic vs deterministic processes at this spatial scale.

Determinants of fine-scale plant species richness in a deciduous forest of northeastern North America

Question: What are the determinants of fine-scale plant species richness (SR)? Location: Île-aux-Grues, Québec, Canada. Methods: Elevation, soil organic matter, soil pH, irradiance, tree basal area (BA) and plant SR (herbs, shrubs, and trees) were determined in 100 contiguous 25 m2 quadrats in a deciduous forest. Each variable was analysed for spatial autocorrelation using Moran's I. Path analysis was used to determine the effects of different variables on tree, shrub and herb SR in a hierarchical modelling approach. Results: Most of the variables, except tree BA, PPFD (photo-synthetic photon flux density) and shrub SR, were positively autocorrelated at a scale of ca. 20 m or less. The path analyses explained ca. ll%-40% of the variance in plant SR; however, the model for shrub SR was not significant. Tree SR was positively associated, but herb SR was negatively associated with tree BA. Tree SR had a positive influence on shrub SR, but herb SR remained unaffected by tree or shrub SR. Conclusion: The positive association of tree BA and tree SR suggests that the data from the study site correspond to the left (ascending) portion of the SR-biomass relationship (un-dersaturated SR). The negative effect of tree BA on herb SR is direct and not mediated through reduced PPFD. High tree BA might cause high resource use, induce high litter production and affect soil properties, all of which might significantly affect herb SR. Several factors not considered here might influence fine-scale SR, such as interspecific interactions, fine-scale disturbances and heterogeneity (both spatial and temporal) in resources and abiotic conditions. Within-site variations of SR might be difficult to model with precision because of the relative importance of stochastic vs deterministic processes at this spatial scale.

Litterfall and Decomposition of Rhizophora mangle L. in a Coastal Lagoon in the Southern Gulf of Mexico

The dynamics of Rhizophora mangle litter production and decomposition were studied in a tropical coastal lagoon on the Gulf of Mexico in Veracruz, Mexico over a year (October 2002–October 2003). This region is characterized by three seasons: northerly winds (called ‘nortes’), dry, and rainy. Annual litter production (1116 g m−2) followed a seasonal pattern with leaf litter as the main fraction (70%) with two peaks in the dry and one in the rainy season. Leaf decomposition was evaluated with two types of litter bag in each season: fine mesh (1×1 mm) and coarse mesh (3×7 mm). Decomposition data were adjusted to a single negative exponential model. The results indicated faster decomposition rates in the coarse litter bag and significant differences among seasons. However these differences occurred after the 60th day of decomposition, indicating that leaching and microbial action were responsible for more than 50% of mass loss. After this period, the effects of aquatic invertebrates were evident but depended on climatic conditions. In the rainy season, the gastropod Neritina reclivata was associated with increasing leaf decomposition rate. In the ‘nortes’ season, the effect of aquatic invertebrates was smaller, and there were no differences in the decay constants calculated for the two litter bag types. High litter production represents an important input of organic matter which, through decomposition, may represent an important source of C, N, and P in this aquatic system.

Aboveground litter production, accumulation, decomposition, and tidal transportation of coral reef-type mangrove forest on Pohnpei Island, Federated States of Micronesia

Litter production, accumulation, and decomposition were examined on the seaward and landward sides of a long-term mangrove research site on Pohnpei Island, the Federated States of Micronesia, to estimate the contribution of litter deposited on the mangrove forest floor to carbon accumulation in mangrove forests. The annual litter production in the forest site was relatively high, 15 Mg ha-1 yr-1. The litterfall was composed of leaves (55%), reproductive organs such as flowers and seeds (34%), and bark and small branches (11%). The seasonal fluctuation of the litter was small. The amounts of litter deposited on the floor were 0.51 Mg ha-1 on the seaward side and 0.76 Mg ha-1 on the landward side. Compared with the mangrove substratum, the litter deposited on the forest floor has an extremely low capacity to act as a carbon sink. During the first year of the leaf decomposition, the mangrove leaves decomposed markedly (k = 7.0 - 18.2) faster than the leaves of the terrestrial mahogany forest (k = 0.3). The mangrove leaves decomposed rapidly, losing more than 60% of their initial weight in the first month. This high rate might result from leaching of labile fraction from the leaves by the high frequency of immersion as well as by the high levels of activity of decomposers on the forest floor at high temperatures and humidity. Moreover, the effect of crab’s feeding on the litter disappearance could not be disregarded. Tidal litter transportation rate was examined by collection of marked leaves along a tide level gradient. The transportation rate was greater as the highest tide level was higher. This study clarified that the disappearance of litter on the mangrove forest floor was strongly influenced by the tide, especially on the seaward side, as well as by the active microbial and faunal decomposability. We concluded that, despite the mangrove forest’s high litter production, litter on the forest floor did not contribute much to carbon accumulation, especially on the seaward side, since litter was disappeared rapidly from forest floor by tidal exportation and strong microbial activity.

Assessment of biological soil quality in wooded reclaimed mine sites

Species numbers and biomass of earthworms increased nearly continuously from the 3rd to the 46th year after recultivation, reaching 100 g m −2 at the oldest sites. This development is characterised by a decreasing proportion of epigeic life forms. In contrast to data from coniferous afforestations in Berzdorf mine sites and other mine sites studied in Lower Lusatia as well as from the literature, the earthworm development on Berzdorf mine sites with deciduous afforestation appear as an ideal and regionally typical development series (ITDS). Earthworm populations at 13 Lower Lusatian mine sites 35–50 years after afforestation were found to have a biomass between 0.1 and 21 g m −2, dependent on humidity and kind of litter (pine, beech, oak, alder, poplar, lime). An increase of earthworm biomass above 20 g m −2 was accompanied by a change of humus type from mor via moder to a mull humus. At the same point the biomass share of the humiphagous macrofauna other than earthworms (Diplopods, Isopods, Diptera larvae) decreased, i.e. the biomass of earthworms became more and more dominant. Further information comes from the comparison of the yearly input of dead soil organic matter (SOM), measured as the energy content of the yearly litter fall out and field layer production, and as the potential ability of the soil humiphagous fauna to decompose the yearly supply of SOM, expressed as the potential zootic decomposition level (DLZpot; kJ m −2 a −1). A very high litter production 3–5 years after afforestation is combined with a low DLZpot, caused by the absence of earthworms, thus leading to a high ectohumus layer. As soon as earthworm biomass rises (after 10 years), the DLZpot becomes very high, later levelling out depending on primary production, and causing a mull humus type. Microarthropods (Collembola, Actinedida, Oribatida, Gamasida) colonised young mine sites with deep deciduous litter layer very quickly and in high densities (>100.000 ind. m −2). Later on, the rising competition with earthworms caused a decline of microarthropods, followed by a second maximum after about 30 years. At the oldest studied sites, the density reached a level near to that of a neighbouring native woodland. On pine afforestations, the colonisation needs more time but reaches the highest observed density (>250.000 ind. m −2) after 30 years. In parallel to the earthworms, the quantitative development of microarthropods on deciduous mine sites can be taken as an ideal and regionally typical developmental series (ITDS). At the species level, 8 colonising groups of Collembola could be distinguished according to the centre of their temporal occurrence. Besides fugitive initial species at the start and stenoecious woodland species at the temporary finish, 6 groups were found to be typical for certain periods of the mine site development. In contrast to the Collembola with 99 species found at the mine sites, only 14 species of predatory centipedes were observed, but as within the Collembola, the centipedes showed a species-specific colonisation behaviour, also marking certain periods of ecosystem succession on the mine sites.

Litter production and nutrient concentration by the growing Albizia amara (Roxb.) Boiv. trees in a Silvopastoral system

Litter fall and nutrients return by eight year old trees of Albizia amara in a silvopastoral system on degraded shallow soils of Jhansi was assessed. The average litter production was 6.08 t/ha/yr of which major proportion was leaf (84.2 %) followed by branch (12.8 %), miscellaneous (1.8 %) and pod (1.2 %). The litter fall was recorded throughout the year; highest litter production was recorded in the month of February (1.5 t/ha), followed by January (0.87 t/ha) and April (0.72 t/ha). The total litter production was significantly correlated with leaf litter (r = 0.96) and branch litter (r = 0.89). No significant correlation was found between climatic parameters and leaf litter. However, branch litter production was negatively correlated with the average minimum temperature (r = 0.55). Among different litter parts, highest concentration of nitrogen, phosphorus and potassium was found in pod followed by leaf, miscellaneous and branch. Potential nutrient return to the system on account of tree litter produced by this species, computed on an annual basis, was 77.8 kg/ha nitrogen, 49.6 kg/ha potassium and 3.9 kg/ha phosphorus.

Nutrient retention and nutrient-use efficiency in Phragmites australis stands after wasterwater application

The capacity of Phragmites australis to extract nutrients from its environment and to store them in plant tissue was studied in an infiltration wetland used for wastewater treatment. The aims of the study were to estimate the contribution of plant uptake to the overall nutrient removal efficiency of the wastewater treatment system and to determine measures to enhance the nutrient removal efficiency. The functional response of Phragmites australis to nutrient addition was studied at two levels of nutrient availability by comparing a wetland used for wastewater treatment with a natural, undisturbed wetland. In the nutrient-rich wastewater wetland, biomass production, nutrient content of plant tissue, shoot/root ratios, and translocation rates were much greater than in the natural wetland. In contrast, plant nutrient-use efficiencies of both nitrogen and phosphorus were much lower in the wastewater wetland. The lower nutrient-use efficiencies were probably due to (1) lower nutrient productivity, which was probably due to self-shading resulting in a lower photosynthetic activity, and (2) lower mean nutrient residence time, which can be explained by a higher litter production (higher shoot and leaf turnover). In the wastewater wetland, harvesting during winter removed only 9% of the total nitrogen input and 6% of the total phosphorus input associated with the loading of wastewater. The low nutrient removal efficiency by aboveground plant harvesting is caused by translocation of nutrients from shoots and leaves to rhizomes and roots in autumn. Nutrient removal efficiency of the wastewater wetland could be enhanced by 40–50% by harvesting at peak nutrient storage levels in the aboveground plant parts in August or September.

Litter production and decomposition in a subtropical mangrove swamp receiving wastewater

Litter production in a mangrove swamp was estimated by litter trapping for 2 years in 2 sites, one receiving wastewater and the other was the control. Mean annual litter production was about 11.7 t·ha −1 with leaf and reproductive materials contributing more than 70% of total litter production. A distinct seasonal pattern was found in both years with peak litter fall occurring in the summer rainy season, in particular, August. In terms of total litter production, variations between years and sites were statistically not significant: (at P≤0.05 level). Total litter biomass in 1991–92 and 1995–96 were 1149 and 1187 g·m −2, respectively. Sites receiving wastewater did not show any significant changes in litter production. Leaf litter decomposition rates in different locations within the mangrove swamp were similar. Neither wastewater discharge nor distance from land had any effect on the decay process. When the two plant species were compared, leaves of Kandelia candel (L.) Blanco degraded more rapidly with more nutrient released and exported to the foreshore environment than those of Aegiceras corniculatum (L.). The decay constant ( k) of K. candel and A. corniculatum was 0.052 and 0.015 day −1, respectively. The high litter production and rapid turnover of leaf litter indicated the importance of this mangrove swamp in supplying nutrients and organic matter to the estuarine ecosystems.

NUTRITIONAL AND PLANT-MEDIATED CONTROLS ON LEAF LITTER DECOMPOSITION OFCAREXSPECIES

We studied the effects of experimentally induced variation in leaf litter chemistry on leaf litter decomposition and leaf litter nutrient release of Carex species from habitats that differ in nutrient availability. Carex diandra, C. rostrata, and C. lasiocarpa are dominant in less productive mesotrophic fens, whereas C. acutiformis is dominant in more productive eutrophic fens. For each species, three types of litter were used: litter collected in the field (FLD); and litter from experimental populations grown at low (LN: 3.3 g N·m−2·yr−1) and high N supply (HN: 20.0 g N·m−2·yr−1). For all the litter chemistry parameters studied there were highly significant interactions between species and litter type. This implies that, due to differential plant-mediated controls on leaf litter chemistry, it is not always possible to predict changes in litter chemistry in response to increased nutrient supply. Litter decay was determined in a long-term (3 yr) field experiment using litter bags. The litter types of each species were incubated at their native growing sites. Contrary to what is generally found, the leaf litter decomposition rate of the species growing at the nutrient-poorest site (C. diandra) was higher than that of the species growing at the nutrient-richest site (C. acutiformis). Only for C. diandra and C. lasiocarpa was the decomposition rate of the litter from the HN treatment higher than that of the field litter. Thus, increased nutrient supply does not necessarily lead to higher litter decomposition rates. Nutrient controls on litter decay changed with time: initial litter decay (≤3 mo) was strongly controlled (high r2 values) by all P-related litter quality parameters, whereas long-term litter decay (>1 yr) was most strongly related with the phenolics : N ratio, the phenolics : P ratio, the lignin : N ratio, and the C:N ratio. Our data suggest that high levels of atmospheric N deposition, such as in the study area (The Netherlands), may lead to a relative shortage of P in the plant-derived substrates for bacteria and fungi. As a result, P-related litter chemistry parameters exert a strong influence on litter decay. Our data did not support the hypothesis that high-nutrient species increase nutrient cycling due to the production of easily decomposable litter with high rates of nutrient release. The leaf litter from Carex acutiformis, the species from the high-productivity fens, decomposed more slowly than that of the other species, immobilized more N and P and had a longer period of net N and P immobilization. However, this species has a higher litter production than the other species and thereby increases the rate of nutrient cycling. At the intraspecific level, increased nutrient supply led to lower amounts of immobilized N and P and faster N and P release from litter in most species, and thereby to a higher rate of nutrient cycling. This positive feedback between nutrient supply rate and the rate of nutrient cycling is reinforced by the increase in litter production in response to increased nutrient supply.

Litter production in an Avicennia Gerrninans (L.) stearn forest in Guyana, South America

Litter production of A. germinans was determined during a twelve month period (July, 1994 to June, 1995). Litter traps of 25 cm by 25 cm, with a 1.0 mm mesh size, were suspended above high tide level. Collection of litter was done every two weeks. The litter was dried at 103°C to constant weight and separated into leaves, flowers, fruits and woody parts. Total litter biomass was 1771 (SD 66.7) g m−2y−1, with leaf litter constituting 61.41% of the total. Fruits contributed 24.84%, flowers (8.88%) and woody parts (4.87%). Leaf litter production showed two peaks (a major one in August, 1994 and a minor one in February, 1995). High flower litter production was observed in October and November, 1994, while peak fruit litter was produced in January, 1995. The production of woody parts was spread between November, 1994 and March, 1995 with a slight peak in February, 1995. Great variation was observed in the production of the plant organs within and between sampling stations. It seems litter production is influenced by the inflowing rivers which drain the Amazon Basin, rather than by rainfall in the area.

PRIMARY PRODUCTION AND NUTRIENTS IN A HONG KONG SHRUBLAND

Secondary shrubland is widespread in southern China. This study is a pioneer one of this plant community's distribution and seasonal dynamics of phytomass and nutrients, production of dry matter and nutrients, cycling and use of nutrients. These were studied for a period of two years in the shrubland at sites in Hong Kong's New Territories. Above-ground phytomass, including standing dead matter and litter, averaged 2 239 g/m2 and below-ground phytomass averaged 1 408 g/m2. Foliage production of the evergreen shrub Rhodomyrtus tomentosa, the dominant species, was continuous and gradual. The foliage phytomass depended upon a balance of production of new foliage and senescence and abscission. The phytomass of reproductive structures of R. tomentosa tended to increase regularly from April to July and exhibited a sudden decline after September. A study of the nutrient distribution showed that the distribution patterns of phytomass and nutrient resources are significantly different. For foliage and reproductive structures, the distribution ratios of nutrients were larger than those of phytomass. It is inverse for standing dead matter and stems and branches. The seasonal pattern of N, P and K contents in the foliage and reproductive structures of R. tomentosa paralleled that of the phytomass. R. tomentosa contained a relatively large amount of nutrients in the leaves throughout the year. Mean net primary production (NPP) of the shrubland was 972 g/m2/yr. The mean above-ground dry matter production was 757g/m2/yr which made up 77.9 per cent of the total NPP. The mean production of N, P and K in the shrubland were, respectively, 6 726, 464 and 4 282 mg/m2/yr. Litterfall occurred throughout year, but there was a marked seasonal pattern in the rates of litter production. Climatic factors have an important influence on litter fall seasonality. High litter production is associated with a period of dry weather or a typhoon. The mean return of dry matter by litter fall for two years was 477 g/m2/yr; the N, P and K returns were respectively 2 815,164 and 892 mg/m2/yr. This study showed that 45.1 per cent of the N requirement in NAPP and 51.3 per cent of the P requirement in NAPP came from internal cycling of the plants. Four definitions of nutrient-use efficiency are discussed and compared. An assessment of nutrient-use efficiency through the litter fall mass and concentration data indicated that efficiency for the use of nutrients in the shrubland was greater than the value for an efficient nutrient economy in tropical forest. A conservative utilization of phytomass resources based on reduced nutrient losses is stressed. It is suggested that the foliage, branchlets, bark and reproductive structures from shrubs and trees are not removed.

Litterfall and litter accumulation in red alder stands in western Oregon

Litter production in red alder communities 2 to 33 years old was higher than that reported for any plant community of the temperate regions. Litter production is also atypically high in communities of other nitrogen fixers, which suggests that nitrogen fixation may be an important contribution to the high litter production. Litter accumulates rapidly on the ground during the first 5 years after red alder establishment, but equilibrium is reached at the age of 6 years and maintained for several decades. During this time, the decomposition of litter equals the annual litterfall. In 50 years, cumulative litterfall reaches over 300 metric tons per ha, most of which is decomposed and incorporated into mineral soil. Favorable physical, chemical, and nutritional conditions of soil are created by alder for development of the climax vegetation.