Effects Of Litter Removal Research Articles

Effect of repeated burning on plant and soil carbon and nitrogen in cheatgrass (Bromus tectorum) dominated ecosystems

Fire has profound effects on ecosystem properties, but few studies have addressed the effect of repeated burns on soil nutrients, and none have been conducted in cold desert ecosystems where invasion by exotic annual grasses is resulting in greater fire frequency. In a 5 year study, we examined effects of repeated burning, litter removal, and post-fire seeding on carbon (C) and nitrogen (N) contents in soils, litter, and vegetation in a cheatgrass-dominated Wyoming big sagebrush ecological type. We developed a multivariate model to identify potential mechanisms influencing treatment effects and examine the influence of environmental factors such as precipitation and temperature. We found that repeated burning had strong negative effects on litter C and N contents, but did not reduce soil nutrients or vegetation C and N contents, likely due to cool fire temperatures. There were few effects of litter removal or post-fire seeding. Instead, precipitation and temperature interacted with burning and had the strongest influences on soil N and vegetation C and N contents over time. Management strategies aimed at decreasing litter and seed banks and increasing competitive interactions may be more effective at reducing cheatgrass success than approaches for reducing soil nutrients.

Assessing the impact of land abandonment, nitrogen enrichment and fairy-ring fungi on plant diversity of Mediterranean grasslands

Semi-natural calcareous grasslands are of great conservation interest because of their high species richness, but they are threatened by land abandonment and nitrogen eutrophication. These plant communities evolved as a result of a long history of human activity, which generated and maintained these habitats by extensive grazing and mowing. Calcareous grasslands are listed as a priority for conservation in the EC Habitats Directive. However, the effects of different management regimes, nitrogen enrichment, and soil-borne pathogens on plant species diversity are less clear for grasslands of the Mediterranean Basin, compared to meadows in Northern and Central Europe. In this study, we assessed the impact of land abandonment, nitrogen enrichment, and fairy-ring fungi on species diversity in semi-natural grasslands found in the Mediterranean Basin by comparing the available literature with findings from recent studies carried out in Central Italy. In a series of field experiments, the cutting of abandoned grassland consistently reduced the living biomass of the dominant perennial grasses, such as Brachypodium rupestre and Bromus erectus, and promoted a rapid increase in species richness and diversity by allowing the establishment of rare species. There was a similar, but less effective, restoration of species diversity and composition in mowed grassland after litter removal. We also show that nitrogen enrichment at levels comparable to atmospheric deposition depresses species diversity, which also hampers the positive effects of litter removal. Our findings are consistent with previous results achieved in Northern and Central Europe, which however, mainly focused on grasslands with intermediate to high primary productivity levels. The limited availability of data from low-productivity, drought-prone Mediterranean grasslands requires further studies to assess the impact of land abandonment and nitrogen eutrophication in such ecosystems. Finally, we discuss the role of fairy-ring fungi in the maintenance of plant diversity in species-rich grassland. We show that fairy-ring fungi (e.g. Agaricus campestris) critically affect the spatial distribution and diversity of coexisting plant species. By killing the dominant perennial herbs, these radially growing plant pathogens produce empty niches for rare, short-lived species, thus affecting the vegetation pattern. Overall, our results are of interest for environmental managers, as they provide guidelines for the restoration of abandoned areas and the conservation of these species-rich habitats.

The Effects of Removal of Juniperus virginiana L. Trees and Litter from a Central Oklahoma Grassland

We studied species composition after Juniperus virginiana tree and litter removal in a central Oklahoma grassland. Tree removal had the most significant effect on stems per quadrat and vegetation cover. Litter removal effects were not as strong. However, stems per quadrat and vegetation cover in litter removal treatments were higher than in litter intact treatments. Species richness increased for all treatments in the first year post-treatment, after which species richness declined at every sampling period and in every treatment for the duration of the study. Absolute cover of typical prairie species increased in the cut with no litter treatment hereas cover of woody forest species increased in the no cut with no litter treatment. We suggest that even without prescribed fire, redcedar tree removal may result in a return of prairie vegetation. However, additional efforts besides tree removal may be required to restore some invaded grasslands.

Effects of Yeast Extract Addition in Diet on Performances and Feather Pecking of Pullets When Raising under Feed Restriction and Litter Removal

3 Abstract: This study was performed with pullets to evaluate the effects of dietary yeast extract on bir d performances and feather pecking. A total of 2400, 10-weeks-old pullets were divided into 8 groups: C, R, L and LR are control, feed restriction (from 09h00 to 15h00), litter removal (from 12 to 17 weeks of age) and both feed restriction and litter removal groups, respectively. CA, RA, LA and LRA groups received the diet supplemented with yeast extracts. The dietary yeast extract additive was used at the dose of 50 mg per kg live weight. The experiment lasted 8 weeks. Body weight, feed intake and feather pecking were recorded. Litter removal and/or feed restriction affected the growth rate of pullets and increased the frequency of feather pecking. The yeast extract dietary addition did not have any influence when animals were fed ad libitum, but significantly alleviated the feed restriction and litter removal effects. The results of the pecking observations showed that RA, LA and LRA groups had less frequency of gentle pecks and severe pecks compared to R, L and LR groups. In addition, pullets fed C and CA diets had the lowest frequency of gentle pecks (12.65 and 19.45%, respectively) and severe pecks (0.23 and 0.17%, respectively) compared to R, L and LR groups. In conclusion, the dietary addition of yeast extract could reduce significantly the feather pecking as well as the depressive effects of feed restriction and/or litter removal on body weight gain.

Effects of litter removal on arthropod communities in pine plantations

Natural and anthropogenic disturbances can cause abrupt changes in trophic interactions by altering the rate, timing, or composition of organic inputs to ecological systems which in turn can shift patterns of species dominance. We examined the short-term effects of litter removal on soil fauna in pine plantations of three different species (longleaf, Pinus palustris; loblolly, P. taeda; and slash, P. elliottii) using a manipulative experiment, with the goal of examining differences among dominant orders of arthropods and differences among timber types. We sampled arthropods once per month for 6 months immediately following raking, and found that removal of the litter caused significant changes to abundance or presence of five of the nine dominant orders. Reductions in abundances of arthropod orders were most apparent in loblolly pine stands, while increases in abundance were more common in longleaf and slash pine stands. The differential impact among orders suggests that removal of the litter layer is likely to alter trophic interactions by changing the relative abundance of functional groups. Repeated litter removal via raking could have negative repercussions on ecosystem stability. Finally, nutrient additions through fertilization seem unlikely to mitigate the changes imposed on the arthropod community through litter removal.

Recovery of plant diversity following N cessation: effects of recruitment, litter, and elevated N cycling

Plant species richness has declined and composition shifted in response to elevated atmospheric deposition of biologically active nitrogen over much of the industrialized world. Litter thickness, litter nitrogen (N) content, and soil N mineralization rates often remain elevated long after inputs cease, clouding the prospects that plant community diversity and composition would recover should N inputs be reduced. Here we determined how N cycling, litter accumulation, and recruitment limitation influenced community recovery following cessation of long-term N inputs to prairie-like grasslands. We alleviated each of these potential inhibitors through a two-year full-factorial experiment involving organic carbon addition, litter removal, and seed addition. Seed addition had the largest effect on increasing seedling and species numbers and may be necessary to overcome long-term burial of seeds of target perennial grassland species. Litter removal increased light availability and bare sites for colonization, though it had little effect on reducing the biomass of competing neighbors or altering extractable soil N. Nonetheless, these positive influences were enough to lead to small increases in species richness within one year. We found that, although C addition quickly altered many factors assumed favorable for the target community (decreased N availability and biomass of nearby competitors, increased light and site availability), these changes were insufficient to positively impact species richness or seedling numbers over the experimental duration. However, only carbon addition had species-specific effects on the existing plant community, suggesting that its apparent limited utility may be more a result of slow recovery under ambient recruitment rather than from a lack of a restorative effect. There were dramatic interactions among treatments, with the positive effects of litter removal largely negated by carbon addition, and the positive effects of seed addition generally amplified by litter removal. It remains unclear whether each mechanism explored here will induce community recovery, but over different temporal scales. Long-term monitoring will help resolve these remaining questions. Regardless, our results suggest that reversal of species loss and compositional shifts from N deposition in prairies may be more inhibited by habitat fragmentation, recruitment limitation, and long-term suppression of fire than from continued effects of elevated N.

Effects of litter removal and mowing on germination and establishment of two fen-grassland species along a productivity gradient

To study the factors that limit the occurrence of species in fen grasslands, the effects of mowing and litter removal on germination, growth and establishment of two common species (Silene flos-cuculi andLotus pedunculatus) were analyzed along a productivity gradient at seven sites in Northern Germany. The sites differed in nutrient availability, vegetation composition and standing crop. In autumn 2002 a field experiment was set up at each site, including factorial combinations of two treatments (litter removal, mowing). Seeds and juvenile individuals of both species were transferred within the treatment combinations. The number of germinated and transplanted individuals was recorded during the 2003 and 2004 seasons and biomass of survived plants weighed in late summer 2004.

Effect of litter, leaf cover and cover of basal internodes of the dominant species Molinia caerulea on seedling recruitment and established vegetation

The effects of litter removal, leaf cover of established plants and cover of basal internodes of a dominant species Molinia caerulea on seedling germination and the dynamics of established plants were studied in a field experiment in an oligotrophic wet meadow. Although the negative influence of litter on total seedling number and seedling species composition was non-significant, litter significantly affected the dynamics of the established vegetation and caused inhibition of total leaf cover development. The effects of total leaf cover of established plants on seedling establishment changed during the vegetation season. Whereas the effect of total leaf cover was positive at the start and in the middle of the vegetation season, at the end the total leaf cover negatively affected seedling establishment. Both total leaf cover and cover of basal internodes affected seedling composition. Effects of these two variables were statistically separable suggesting that they are based on different mechanisms. The response of seedling establishment to these factors was species specific and, consequently, our data support the hypothesis that that biotically generated spatial heterogeneity can promote species co-existence through the differentiation of species regeneration niches.

Frequent nest relocation in the antAphaenogaster araneoides: resources, competition, and natural enemies

Sessile and vagile organisms differ from one another in some fundamental ways, including methods of resource acquisition and competition. Ant colonies are typically studied as sessile entities, even though a large fraction of ant species frequently relocate their nests in the course of their life history. Little is known about the causes and consequences of nest relocation, but it is likely that the costs and benefits of relocation are driven by nest quality, neighborhood competition, or resource availability. In this paper, we document several cycles of nest relocation in a population of the Central American antAphaenogaster araneoides. In our first experiment, we tracked the pattern of relocation, testing whether environmental characteristics and colony demography were associated with relocation behavior. In our second experiment, we manipulated resource availability by adding or subtracting leaf litter, which is known to predict colony growth. We found that colonies relocated their nests once per week on average and colonies often reoccupied nests from which they had once emigrated. Larger colonies relocated more frequently than smaller colonies, and quickly growing colonies utilized a greater number of nests within their home range compared to slowly growing colonies. Relocation events were most likely to occur in periods when vapor pressure deficits were greatest. Nearest neighbor distance and other measures of environmental conditions were not associated with relocation behavior and there was no significant effect of litter removal or supplementation. We found evidence that multiple natural enemies attackedA. araneoidescolonies. Based on the demographic correlates of relocation and our rejection of other plausible hypotheses, we propose that nest relocation is driven by the escape from natural enemies.

Dispersal limits natural recruitment of African mahoganies

The abundance of forest tree species may be locally limited by the inability of species to disperse to all sites suitable for germination and establishment. This phenomenon of “dispersal limitation” has been suggested to promote the maintenance of high species diversity in tropical forests by slowing down competitive exclusion. We present the first direct experimental evaluation of dispersal limitation in tropical forests, and of its importance relative to other factors affecting recruitment. Seed addition, litter removal and light availability effects on seedling establishment were evaluated in a full factorial experiment on two African mahogany species, Entandrophragma utile and Khaya anthotheca. Seedling recruitment after 18 months, was ∼22 times greater in seed addition treatments (with addition rates corresponding to the tail of seed shadows of large reproductive trees) compared to controls. This seed addition effect was an order of magnitude greater than either gap or litter removal effects, with similar results observed in both logged and primary forest locations. We conclude that dispersal limitation strongly limits seedling establishment for the two species studied. An important “applied corollary” of this result is that seed supplementation may substantially increase local abundance of valuable or rare species in disturbed or managed tropical forests.

The importance of former land use in determining successful re-creation of lowland heath in southern England

In order to reverse losses of lowland heathland substantial areas of former agricultural and forestry land are currently being targeted for restoration. In this study we assessed the success of heathland re-creation on 37 former arable, improved grassland and conifer plantation sites in southern England, UK. The similarity between the vegetation and seed banks of the re-creation sites and undisturbed heathland controls were examined in relation to former land use, soil properties and re-creation management. Former land use was found to be the most important determinant of re-creation success. On former arable, and to a lesser extent improved grassland, antecedent management had caused significant changes to seed bank and soil properties. As a result, regeneration of Calluna heath had been minimal, even on sites where appropriate management (e.g. cropping, addition of pH amendments) had been undertaken and heathland species introduced. In contrast, former plantation seed banks and soils were similar to heathland controls, and, as a result, rapid regeneration of Calluna heath had taken place. It was concluded that conifer removal provides the most practical and cost-effective means of re-creating Calluna heath on former heathland, although further research is required to assess the effect of litter removal and the rate at which heather seed banks decline following conversion to forestry. In contrast, re-creation on former agricultural sites will require effective management to reduce soil pH, fertility and the abundance of competitive species as well as the introduction of heathland propagules. Given limited resources a more realistic objective for these sites is likely to be reversion to an acid grassland or grass-heath.

Effect of litter removal on species richness and acidification of a mixed oak-pine woodland

Eutrophication of woodland ecosystems and disappearance of acidophilous species have often been observed in central and western Europe over recent decades. Considerable increase in air-borne nitrogen and sulphur has been invoked as responsible for these processes in most studies. Historic data indicate that for hundreds of years man removed litter and fodder from many woodlands in these areas. As a result, woodland soils became poorer and more acid than they were originally. Cessation of the removal of materials may resulted in soil enrichment and eutrophication of many woods. This hypothesis was tested in a 16-year litter removal experiment in an acidophilous mixed oak–pine wood in southern Poland. It was found that litter removal resulted in substantial impoverishment of soil. After 16 years soil of the litter removal plots contained significantly less P, Mg and Ca, and had a lower cation exchange capacity (CEC) in the epihumus subhorizon, and less Ca and a lower CEC in the humus and lessivage horizons than soil in the control plots. Vascular plant species and bryophytes colonized the litter removal plots much more frequently. Within 16 years species richness increased in the field layer of these plots, but abundance of dominant species and character of vegetation remained unchanged, while vegetation of the control plots changed from acidophilous to neutrophilous. Disappearance in the control plots of vascular plants species and mosses common in mixed woodlands was caused by thick litter layer which impeded seed germination and seedling development, and by competition of dominant species. The results obtained suggest that acidophilous vegetation in the field layer of the study wood was associated with material removal by man over a long time, and its eutrophication largely resulted from the cessation of traditional methods of management.

Effects of litter removal on the germination of Anemone nemorosa L.

In a recent article, Eriksson (1995) showed high germination rates in Anemone nemorosa . To check whether ERIKSSON'S results are also valid in Central Europe, a litter removal experiment was carried out in Northeastern Switzerland. In both experimental series, litter removal plots and control plots, high germination of A. nemorosa occured. Nevertheless, litter removal greatly enhanced germination of A. nemorosa . A significant correlation between seedling number and ramet density within the plots pointed to a dominance of very local dispersal. These facts lead to the hypothesis that reproduction by seeds in A. nemorosa as well as vegetative reproduction by clonal growth are of great importance for the maintenance of populations of this species. Surprisingly, no successful germination of A. nemorosa was detected in seed bank investigations.

Expression of PK-A catalytic and regulatory subunits in lactating rat mammary tissue: effects of litter removal

Expression of PK-A catalytic and regulatory subunits in lactating rat mammary tissue: effects of litter removal

Effects of litter removal on the lipolytic response and the regulatory components of the adenylate cyclase in adipocytes isolated from lactating rats

The effects of litter removal on the status of different components of the hormone-sensitive adenylate cyclase system were analysed in plasma membranes of rat adipocytes. These effects were correlated with the decreased lipolytic response of adipose tissue. No changes in total number of A1 adenosine receptors or their affinity were detected in response to litter removal. In contrast, beta-adrenergic receptors showed a decrease (35%) in total number of receptors, without any significant change in their affinity. The status of alpha-GS and alpha-Gi, the alpha-subunits of G proteins which mediate stimulation and inhibition respectively of adenylate cyclase, were probed by cholera- and pertussis-toxin-catalysed ADP-ribosylation respectively and by immunoblot. Associated with litter removal, decreases of 63% and 62% in the incorporation of [alpha 32P]ADP-ribose catalysed by cholera toxin and pertussis toxin into alpha-Gs and alpha-Gi respectively were detected. Immunoblotting using RM/1 (anti-alpha-Gs) and AS/7 (anti-alpha-Gi) antisera also showed decreases in the levels of alpha-Gs (52%) and alpha-Gi (55%) in adipocyte membranes from litter-removed rats compared with lactating rats. Alterations in the status of hormone-sensitive adenylate cyclase components, such as those described herein, may be biochemical mechanism(s) by which adipose tissue shows a decreased lipolytic response during recovery from lactation.

Nature management experiments in a derelict reedmarsh. I: Effects of winter cutting

Lowering of the summer water table, eutrophication and dereliction have caused severe ruderalisation of the reedmarsh in the important Belgian wetland site of the Blankaart. The reed vegetation has become totally overgrown by competitive species such as Urtica dioica, Calystegia sepium and Calamagrostis canescens. Management experiments conducted from 1978 to 1986 have shown that a regime of annual winter cutting can substantially reduce the ruderal and nitrophilous character of the vegetation and increase species diversity. The process is mostly linked to the correlated effects of litter removal. The changes in the vegetation are influenced by the position in the zonation/succession. It is argued that, for complete restoration of the vegetation, efforts should be made to raise the summer water table and to stop eutrophication and silting of the pond.

Intraspecific fighting during late pregnancy and lactation in rats and effects of litter removal

Female rats (Experiment 1A) were tested for aggression against an adult male intruder in a home-cage test situation at several-day intervals from Day 18 of gestation through Day 21 of lactation. The peak frequencies of attacks and bites and the lowest latency to the first attack occurred on Day 9 of lactation, with concomitant increases in subordinate behaviors by the intruders occurring at that time. Virgin females (Experiment 1B) isolated for comparable periods of time in the test cage showed no differences in fighting levels as a function of length of residence in the home cage. Removal of the litter 4 hr prior to aggression testing on either Day 9 or 10 of lactation (Experiment 2) resulted in significant decreases in fighting levels by lactating females and in significant decreases in subordinate behaviors by intruders. These studies demonstrate that high levels of intraspecific aggression are exhibited during lactation in the rat and that the aggression is dependent upon stimuli from the litter for its expression.

Effects of Snow Removal, Litter Removal and Soil Compaction on Soil Freezing and Thawing in a Minnesota Oak Stand

AbstractThe depths of soil freezing and thawing were measured periodically with a Veihmeyer tube in snow removed, litter removed, compacted, compacted‐snow removed, and undisturbed plots during the 1962–63 season near St. Paul, Minn. The soil was a sandy loam to a loamy sand with a high water content when the study began. Cold conditions and minimal snowfall resulted in deeply frozen soil throughout Minnesota this season. At a station near the study site, the mean monthly snowfall and mean daily air temperature were, respectively, 4 to 6 cm and 2 to 5C below normal during January and February.The removal of a snow layer 13 cm or less in depth caused deeper and more persistent soil freezing than did either litter removal or soil compaction. For several weeks, frozen soil averaged 38 cm deeper in snowless plots than in snow‐covered control plots. For about the same period, frozen soil averaged 20 cm deeper in plots without litter than in litter‐covered control plots, and 13 cm deeper in snowless compacted plots than in snowless control plots. The presence of even a shallow snowpack (13 cm) seemed to reduce the individual effects of litter removal and soil compaction on the depth of soil freezing. “Concrete” and “porous concrete” were the types of frozen soil observed in all treatments. The most significant hydrologic effect of deep freezing in snowless plots may have been the 10 additional days required for complete thawing in comparison to snow‐covered plots. However, late in the thawing period, the top of the frozen layer was 60‐cm beneath the soil surface, and it was discontinuous as indicated by complete thawing at some sample points. A discontinuous frozen layer was observed in all treatments 1 to 2 weeks before the complete disappearance of frozen soil. Thawing began earliest in plots without litter.