Influence Decomposition Rates Research Articles

Species and tissue type regulate long-term decomposition of brackish marsh plants grown under elevated CO2 conditions

Organic matter accumulation, the net effect of plant production and decomposition, contributes to vertical soil accretion in coastal wetlands, thereby playing a key role in whether they keep pace with sea-level rise. Any factor that affects decomposition may affect wetland accretion, including atmospheric CO2 concentrations. Higher CO2 can influence decomposition rates by altering plant tissue chemistry or by causing shifts in plant species composition or biomass partitioning. A combined greenhouse-field experiment examined how elevated CO2 affected plant tissue chemistry and subsequent decomposition of above- and belowground tissues of two common brackish marsh species, Schoenoplectus americanus (C3) and Spartina patens (C4). Both species were grown in monoculture and in mixture under ambient (350–385 μL L−1) or elevated (ambient + 300 μL L−1) atmospheric CO2 conditions, with all other growth conditions held constant, for one growing season. Above- and belowground tissues produced under these treatments were decomposed under ambient field conditions in a brackish marsh in the Mississippi River Delta, USA. Elevated CO2 significantly reduced nitrogen content of S. americanus, but not sufficiently to affect subsequent decomposition. Instead, long-term decomposition (percent mass remaining after 280 d) was controlled by species composition and tissue type. Shoots of S. patens had more mass remaining (41 ± 2%) than those of S. americanus (12 ± 2%). Belowground material decomposed more slowly than that placed aboveground (62 ± 1% vs. 23 ± 3% mass remaining), but rates belowground did not differ between species. Increases in atmospheric CO2 concentration will likely have a greater effect on overall decomposition in this brackish marsh community through shifts in species dominance or biomass allocation than through effects on tissue chemistry. Consequent changes in organic matter accumulation may alter marsh capacity to accommodate sea-level rise through vertical accretion.

Relationships between estuarine modification and leaf litter decomposition vary with latitude

Decomposition of leaf litter plays a major role in carbon and nutrient cycling and in fuelling food webs. Environmental conditions may influence decomposition rates directly by influencing rates of biological reactions, and indirectly by influencing consumer communities. This study assessed how climate influences the relationship between estuarine nutrient enrichment and decomposition. Eelgrass (Zostera muelleri) and mangrove (Avicennia marina) leaves from a common source were deployed within two estuaries with anthropogenically enhanced and two with largely unmodified nutrient loadings, at each of two temperate latitudes of New South Wales, Australia. The latitudes were separated by ∼1000 km and differed in mean water temperature by ∼2 °C. Mass loss of litter was assessed after 13, 27 and 65 days, and the invertebrate communities colonizing the bags were censused at 13 and 65 days. At the end of the experiment, mass loss of seagrass blades was greater in nutrient enriched estuaries of the lower latitude than in higher latitude estuaries or those that were relatively unmodified. Mass loss of mangrove leaves was greater in the low latitude or nutrient enriched estuaries than in the largely unmodified estuaries of the higher latitude. Aspects of the abiotic environment, in particular temperature and phosphorous loading, were key correlates of litter mass loss, with only weak relationships between mass loss and macroinvertebrate communities. These results suggest that the sensitivity of decomposition processes to estuarine modification may be dependent on climatic setting, and the dominant litter resources present. Manipulative experiments are now needed to confirm the environmental conditions under which nutrient impacts on decomposition are exacerbated.

Control of climate and litter quality on leaf litter decomposition in different climatic zones.

Climate and initial litter quality are the major factors influencing decomposition rates on large scales. We established a comprehensive database of terrestrial leaf litter decomposition, including 785 datasets, to examine the relationship between climate and litter quality and evaluate the factors controlling decomposition on a global scale, the arid and semi-arid (AS) zone, the humid middle and humid low (HL) latitude zones. Initial litter nitrogen (N) and phosphorus (P) concentration only increased with mean annual temperature (MAT) in the AS zone and decreased with mean annual precipitation (MAP) in the HL zone. Compared with nutrient content, MAT imposed less effect on initial litter lignin content than MAP. MAT were the most important decomposition driving factors on a global scale as well as in different climatic zones. MAP only significantly affected decomposition constants in AS zone. Although litter quality parameters also showed significant influence on decomposition, their importance was less than the climatic factors. Besides, different litter quality parameters exerted significant influence on decomposition in different climatic zones. Our results emphasized that climate consistently exerted important effects on decomposition constants across different climatic zones.

Effects of elevation and nitrogen and phosphorus fertilization on plant defence compounds in subarctic tundra heath vegetation

Summary Plant chemical and structural defence compounds are well known to impact upon herbivory of fresh leaves and influence decomposition rates after leaf senescence. A number of theories predict that alleviating nutrient limitation and reducing other environmental stressors will result in decreased production of plant chemical defences. In this study, we measured plant defence properties [total polyphenols (TP), condensed tannins (CT) and lignin concentrations, and protein complexation capacity (PCC)] in both fresh and senesced plant leaves in a fully factorial N and P fertilization experiment set‐up at each of three elevations along an elevational gradient in Swedish subarctic tundra heath vegetation. Further, we performed a decomposition of variance analysis on community‐weighted averages (CWAs) of plant defence properties to determine the relative contributions of interspecific and intraspecific variation to the total variation observed in response to elevation and nutrient addition. We hypothesized that N fertilization would reduce plant defence properties and that this reduction would be greater at higher elevations, while the effects of P fertilization would have no effect at any elevation. At the community level, N addition reduced CT and PCC in both fresh and senesced leaves and TP in senesced leaves, while P addition had few effects, broadly in line with our hypothesis. The effects of N addition frequently varied with elevation, but in contrast to our hypothesis, the said effects were strongest at the lowest elevations. The effects of N addition and the interactive effect of N with elevation were primarily driven by intraspecific, rather than interspecific, variation. Our findings suggest that as temperatures warm and N availability increases due to global climate change, secondary metabolites in subarctic heath vegetation will decline particularly within species. Our results highlight the need to consider the effects of both nutrient availability and temperature, and their interaction, in driving subarctic plant defence.

Soil respiration, microbial biomass and nutrient availability after the second amendment are influenced by legacy effects of prior residue addition

It is well-known that plant residue composition (e.g. C/nutrient ratio, organic C composition) and environmental factors influence decomposition rate. Nevertheless, the magnitude and timing of nutrient availability after residue addition often differ from predictions indicating other factors may also play a role. One such factor could be the legacy effect which we define as the influence of previous plant residue C/nutrient ratio on the microbial activity, biomass and nutrient availability after addition of a second residue with the same or different C/nutrient ratio. To a loam soil, a high (C/N 60) or a low (C/N 20) C/N ratio residue were added at 10 g kg−1. After 20 days, either high or low C/N residue was added at the same rate, resulting in four residue treatments: high–high (HH), high-low (HL), low–low (LL) or low–high (LH). Unamended soil served as control. Soil respiration was measured continuously over 42 days. Soils were destructively sampled on day 0 (after first residue addition), 7, 20 (before second addition), 28 and 42 (after second addition) and analysed for microbial biomass C, N and P as well as available N and P. After the first residue addition, soil respiration, available N and P and microbial biomass C, N and P were higher with low C/N than high C/N residue. The previously added low C/N residue (treatment LH) stimulated soil respiration, microbial growth and nutrient availability compared to high C/N residue following high C/N residue (HH). Compared to LL, the previously added high C/N residue delayed the peak of respiration rate after the addition of low C/N residue and reduced MBC, MBN and MBP concentrations by about 25% on day 28. There were only small and mainly transient differences in the measured parameters between HL and LH. This study showed that the C/N ratio of the previously added residue influences microbial activity and nutrient availability. In this short term study, a large proportion of the residue added initially remained in the soil at the time of the second addition (70–90% of added) which would be decomposed together with the residue added on day 21. The observed legacy effect is likely due to nutrient availability and amount of previously added residue still present in soil at the time when the second residue is added.

Isolating the effects of precipitation, soil conditions, and litter quality on leaf litter decomposition in lowland tropical forests

Global change drivers such as climate change influence decomposition by altering extrinsic site conditions and intrinsic litter traits. This study aimed to quantify the relative importance of these two pathways for litter decomposition in tropical forests. The effects of soil nutrient availability, mean annual precipitation (MAP), and leaf litter chemistry on decomposition were isolated by measuring mass loss of leaf litter from 10 tropical tree species transplanted to 19 sites along independent gradients of soil fertility and precipitation in Panama. Across species, litter nitrogen (N) content ranged from 7.1 to 13 mg N g−1 and phosphorus (P) from 0.077 to 0.56 mg P g−1. Across sites, soil N content ranged from 1.7 to 5.5 g N kg−1, soil P from 77 to 1500 mg P kg−1, and MAP from 1900 to 2700 mm. Variation in leaf litter mass loss was explained largely by litter species identity (55 %). Site only explained a small, but significant, amount of variance (6.5 %); soil C:N ratio explained this response. Notably, neither litter nutrient content nor MAP were significant predictors of litter decomposition. Changes in tree species composition may influence decomposition rates more than changes to site conditions.

Seasonal patterns in decomposition and nutrient release from East African savanna grasses grown under contrasting nutrient conditions

Litter decomposition and nutrient release is one of the key biogeochemical processes that regulate plant productivity and nutrient cycling in African savanna ecosystems. We examined the influence of nitrogen and phosphorus additions on grass decomposition and nutrient release rates in an Acacia savanna ecosystem in central Kenya. Grass was clipped from a factorial nitrogen×phosphorus experiment and decomposed in a common plot that had not received fertilizer. After 20 weeks, including one dry season and one wet season, 50–65% of carbon, 68–75% of nitrogen and 73–83% of phosphorus had been released from the litter. Decomposition was slow in the dry season (mass loss 1–2% wk−1) compared to the wet season (7–11% wk−1). Wet season decomposition was more rapid for grasses that had been fertilized with nitrogen, even though tissue nitrogen was not significantly different from the control grass, indicating that factors other than litter nitrogen concentration influenced decomposition rates under nitrogen enrichment. Surprisingly, nutrient loss from decomposing litter was relatively high during the dry season, suggesting a role for dew in leaching nutrients from dry litter. We conclude that seasonal rain and nitrogen addition (but not phosphorus addition) accelerate decomposition of grass litter, but that nutrient leaching during the dry season can be considerable.

Interactions between leaf litter and soil organic matter on carbon and nitrogen mineralization in six forest litter-soil systems

Background and aims Leaf litter decomposes on the surface of soil in natural systems and element transfers between litter and soil are commonly found. However, how litter and soil organic matter (SOM) interact to influence decomposition rate and nitrogen (N) release remains unclear.

Water Table Regime Regulates Litter Decomposition in Restiad Peatlands, New Zealand

A 5-year litterbag study examined decomposition rates at four sites representing restiad peatland succession in Waikato, New Zealand. Early successional sites were dominated by Baumea rubiginosa, or Leptospermum scoparium, mid-successional by Empodisma robustum, and late successional by Sporadanthus ferrugineus. Leaf/culm materials from these species were placed on the surface, and roots of Empodisma and Sporadanthus buried at depths of 5, 25, and 55 cm to test the influence of succession on species and site decomposition rates. Typha latifolia leaves from a Canadian bog were placed at the surface and three depths to allow comparisons with northern peatlands. Litterbags were retrieved after 0.5, 1, 2, 3, 4, and 5 years, and mass remaining characterized by an exponential model k value. Surface litter k values (0.12–0.80 y−1) decreased from early to late successional species; however, decomposition was slower at more waterlogged early successional sites. Buried litter k values (0.04–0.24 y−1) decreased with depth and increased from early to late successional sites, with Empodisma roots having the slowest rates. Few strong relationships existed between litter quality and decomposition rates. In contrast, water table regime strongly influenced decomposition rates; k values for the “standard” Typha litter decreased exponentially as period of saturation increased, irrespective of site successional status, nutrients, or other factors. Lower water tables in the more aerated later successional sites have led to faster decomposition rates. Ongoing drainage combined with the potential impacts of climate change may increase organic matter decomposition and accelerate carbon release into the atmosphere.

The influence of litter quality and micro-habitat on litter decomposition and soil properties in a silvopasture system

Studies to understand litter processes and soil properties are useful for maintaining pastureland productivity as animal husbandry is the dominant occupation in the hot arid region. We aimed to quantify how micro-habitats and combinations of litters of the introduced leguminous tree Colophospermum mopane with the grasses Cenchrus ciliaris or Lasiurus sindicus influence decomposition rate and soil nutrient changes in a hot desert silvopasture system. Litter bags with tree litter alone (T), tree + C. ciliaris in 1:1 ratio (TCC) and tree + L. sindicus 1:1 ratio (TLS) litter were placed inside and outside of the C. mopane canopy and at the surface, 3–7 cm and 8–12 cm soil depths. We examined litter loss, soil fauna abundance, organic carbon (SOC), total (TN), ammonium (NH4–N) and nitrate (NO3–N) nitrogen, phosphorus (PO4–P), soil respiration (SR) and dehydrogenase activity (DHA) in soil adjacent to each litter bag. After 12 months exposure, the mean residual litter was 40.2% of the initial value and annual decomposition rate constant (k) was 0.98 (0.49–1.80). Highest (p < 0.01) litter loss was in the first four months, when faunal abundance, SR, DHA and humidity were highest but it decreased with time. These variables and k were highest under the tree canopies. The litter loss and k were highest (p < 0.01) in TLS under the tree canopy, but the reverse trend was found for litter outside the canopy. Faunal abundance, litter loss, k, nutrient release and biochemical activities were highest (p < 0.01) in the 3–7 cm soil layer. Positive correlations of litter loss and soil fauna abundance with soil nutrients, SR and DHA demonstrated the interactions of litter quality and micro-habitats together with soil fauna on increased soil fertility. These results suggest that a Colophospermum mopane and L. sindicus silvopasture system best promotes faunal abundance, litter decomposition and soil fertility. The properties of these species and the associated faunal resources may be utilised as an ecosystem-restoration strategy in designing a silvopasture system. This may help to control land degradation and increase productivity sustainably in this environment.

Invertebrate footprints on detritus processing, bacterial community structure, and spatiotemporal redox profiles

Detritus processing is driven by a complex interplay between macroinvertebrate and microbial activities. Bioturbation/feeding activities of invertebrates in sediments are known to influence decomposition rates. However, direct effects of invertebrates on bacterial communities and detritus processing remain ill-defined, mainly because identifying interactions between invertebrates and sediments is methodologically challenging. We incubated 5 macroinvertebrate species with various bioturbation/feeding traits separately in sediment-filled microcosms inoculated with bacterial communities for 5 d. At the end of the experiment, we assessed: 1) detritus processing (mass loss on ignition [LOI] and dissolved organic C accumulation in the overlying water [absorbance at 280 nm]), 2) bacterial community structure (intergenic spacer analysis [RISA]) and bacterial activity (electron transport system activity [ETSA]), and 3) development of redox potential (Eh) over time (with permanently installed microelectrodes). Invertebrates enhanced bacterial activity and detritus processing, and the magnitude depended on bioturbation/feeding traits. Bacterial community structure differed significantly between microcosms with burrowing invertebrates and microcosms with sediment-dwelling invertebrates. Eh profiles were similar among microcosms with invertebrates with similar bioturbation/feeding traits, but differed among microcosms with invertebrates with dissimilar bioturbation/feeding traits. Our results suggest that bioturbation by aquatic invertebrates mediates detritus processing, Eh dynamics, and structure of the microbial community. These findings highlight the significance of bioturbation and show the utility of spatiotemporal Eh dynamics as footprints reflecting functioning of benthic detrital food webs.

The resilience and functional role of moss in boreal and arctic ecosystems

Mosses in northern ecosystems are ubiquitous components of plant communities, and strongly influence nutrient, carbon and water cycling. We use literature review, synthesis and model simulations to explore the role of mosses in ecological stability and resilience. Moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories. Simulations from two process-based models suggest that northern ecosystems would need to experience extreme perturbation before mosses were eliminated. But simulations with two other models suggest that loss of moss will reduce soil carbon accumulation primarily by influencing decomposition rates and soil nitrogen availability. It seems clear that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species. We highlight several issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, and parameter vs conceptual uncertainty in models. Mosses play an important role in several ecosystem processes that play out over centuries - permafrost formation and thaw, peat accumulation, development of microtopography - and there is a need for studies that increase our understanding of slow, long-term dynamical processes.

Do canopy herbivores mechanically facilitate subsequent litter decomposition in soil? A pilot study from a Neotropical cloud forest

AbstractThere is increasing evidence that the above‐ and belowground components of ecosystems influence one another, thereby controlling key processes such as organic matter decomposition. The aim of this study was to test the hypothesis that leaf herbivory in forest canopies could facilitate subsequent leaf litter decomposition in soils, through changes in leaf quality (i.e., litter palatability) or geometric form (i.e., increased availability of leaf edges made by herbivore damages). In a 9‐month field experiment in an Ecuadorian tropical cloud forest, we compared the decomposition rates of entire leaves (EL) and 15 %‐damaged leaves (DL) of Ficuscuatrecasana showing similar initial leaf chemistry. We found that DL decomposed significantly faster than EL in early stages of decomposition (i.e., between 0 and 38 days). A parallel experiment using cellulose discs on which we simulated different degrees of damages revealed, however, that geometry per se (i.e., increased edge availability) did not influence decomposition rates. We discuss these contrasting results and propose that higher edge availability in damaged leaves may promote the access of microbes and/or macro‐detritivores to leaf tissues thereby enhancing the initial stages of leaf decomposition.

Interacting effects of leaf litter species and macrofauna on decomposition in different litter environments

The leaf litter environment (single species versus mixed species), and interactions between litter diversity and macrofauna are thought to be important in influencing decomposition rates. However, the role of soil macrofauna in the breakdown of different species of leaf litter is poorly understood. In this study we examine the multiple biotic controls of decomposition – litter quality, soil macrofauna and litter environment and their interactions. The influence of soil macrofauna and litter environment on the decomposition of six deciduous tree species (Fraxinus excelsior L., Acer pseudoplatanus L., Acer campestre L., Corylus avellana L., Quercus robur L., Fagus sylvatica L.) was investigated in a temperate forest, Wytham Woods, Southern England. We used litterbags that selectively excluded macrofauna to assess the relative importance of macrofauna versus microbial, micro and mesofauna decomposition, and placed single species bags in either conspecific single species or mixed species litter environments. The study was designed to separate plant species composition effects on litter decomposition rates, allowing us to evaluate whether mixed species litter environments affect decomposition rates compared to single species litter environments, and if so whether the effects vary among litter species, over time, and with regard to the presence of soil macrofauna. All species had faster rates of decomposition when macrofauna were present, with 22–41% of the total mass loss attributed to macrofauna. Macrofauna were most important for easily decomposable species as soon as the leaves were placed on the ground, but were most important for recalcitrant species after nine months in the field. The mass loss rates did not differ between mixed and single species litter environments, indicating that observed differences between single species and mixed species litterbags in previous field studies are due to the direct contact of neighbouring species inside the litterbag rather than the litter environment in which they are placed.

A petiole-galling insect herbivore decelerates leaf lamina litter decomposition rates

Summary 1. Herbivore-mediated changes in leaf-litter chemistry are often considered responsible for altering litter decomposition rates, but such chemical changes often co-occur with other factors such as physical alteration of leaf material that also influence decomposition rates. We attempted to disentangle these effects using the poplar petiole gall moth (Ectoedemia populella Brusk), which forms galls on petioles at the base of the leaf lamina but does not alter leaf morphology. Thus, differences in leaf decomposition rates between galled and ungalled leaves should be explained by gall-mediated changes in leaf chemistry. 2. Petiole galling decelerated leaf lamina litter decomposition in two Populus host species, but in temporally distinct ways. In Populus granidentata, galling decelerated decomposition by 7% after 4 months. After 12 and 18 months, Populus tremuloides litter decomposition rates were 12% and 17% lower, respectively, in lamina tissue whose petiole had been galled relative to ungalled. On average, the petiole galler increased leaf lamina nitrogen concentrations by 17%, decreased tannin concentrations from 37% to 53% and decreased tannin-binding capacity by 11% and 37% in P. grandidentata and P. tremuloides, respectively. These changes would be expected to increase, rather than decrease, decomposition rates. 3. Unlike other insect herbivores guilds that have variable effects on litter decomposition in direction and magnitude, all gall insects studied to date have decelerated leaf-litter decomposition. This consistent effect of galling on decomposition provides a framework for deciphering a fundamental aspect of insect herbivory on a critical ecosystem process. 4. We used a gall-inducing moth with a distinctive natural history to confirm the role of herbivore-mediated litter chemistry in leaf-litter decomposition dynamics. Moreover, we advance the hypothesis that gall-induced defensive manipulations that protect a host plant from injury by other herbivores lead to decelerated litter decomposition.

Evaluation of Roth C model using four Long Term Fertilizer Experiments in black soils, India

Carbon content in soils changes depending on the land use system, type of management practice and time. There is an increasing concern about the soil quality vis-à-vis organic carbon content in soils due to global warming and enhanced CO 2 concentration in the atmosphere. This has led to estimate carbon stock in soils at global and regional levels. The objective of the present study was to evaluate Roth C model to estimate total organic carbon (TOC) changes under four long term fertilizer experimental sites representing sub-humid moist (Sarol and Nabibagh), sub-humid dry (Panjri) and semi-arid (Teligi) climate in India. The plant carbon input rate was calibrated using organic carbon and other soil parameters using Roth C. The results showed that Roth C could simulate changes in TOC in two contrasting eco-sites for surface soil layers. The root mean square error (RMSE) considered as modelling error ranged from 11.50 to 15.01, 4.70 to 11.60, 2.14 to 6.52 and 1.45 to 13.74 in the surface layers of Sarol, Nabibagh, Panjri, and Teligi sites, respectively. The simulation biases expressed by M (relative error) by Student‘ t’ value for all the treatments at these sites were non-significant with two exceptions. Observed trends in TOC consist of an increase for all the four treatments in the sub-humid site of Sarol and Nabibagh; while manures alone or in combination increase TOC appreciably in Teligi and Panjri. TOC remained, however, almost similar over years for the control (no fertilizer or manure) and NPK treatments in all the four sites. Analysis of Roth C output data showed that this model could be used as a tool to arrive at different threshold values of rainfall to influence decomposition rate modifier and thus to find out rate of organic carbon sequestration in various bioclimatic systems.

Leaf litter breakdown in Mediterranean streams: effect of dissolved inorganic nutrients

Agricultural runoff and urban activities can increase the inputs of nitrogen (N) and phosphorus (P), into headwater streams, leading to eutrophication and thus substantially affecting the structure and functions of benthic communities. A high P concentration in water stimulates the activity of heterotrophic microorganisms associated with leaf litter and, hence, influences decomposition rates and the availability of detrital resources for macroinvertebrates. Litter breakdown of alder (Alnus glutinosa) leaves enclosed in coarse mesh bags was studied in five low-order Mediterranean streams with different trophic status defined by their soluble reactive phosphorus (SRP) concentrations. Decomposition rates differed significantly between these streams and increased with the eutrophication gradient, but these differences were not always related to the availability of P in water. Leaf mass loss was directly correlated with shredder density, but macroinvertebrate density and diversity were not related to P availability in water, and ammonium concentration had a negative effect on macroinvertebrate diversity and shredder relative abundance. A significantly positive effect of nitrate concentration in water on aquatic hyphomycete sporulation rates was observed, but there also was a negative effect of % ammonium on dissolved inorganic nitrogen (DIN). The predominantly available ionic form of DIN could thus affect the structure of the aquatic hyphomycete community. These results suggest that the response of litter decomposition to eutrophication in forested headwater streams is strongly influenced by local stream characteristics and by the nature of nutrient pollution.

Epigeic earthworms increase soil arthropod populations during first steps of decomposition of organic matter

Earthworms and soil arthropods are major groups involved in soil decomposition processes. Although the interaction between these organisms can influence decomposition rates, little is known about their population dynamics during the decomposition of organic matter. In this study, we used the pig manure decomposition process to evaluate the effects of the presence of the epigeic earthworm Eisenia fetida on seven groups of soil arthropods: springtails, astigmatid, prostigmatid, mesostigmatid and oribatid mites, psocids and spiders. We carried out an experiment in which low and high doses (1.5 and 3 kg, respectively) of pig manure were applied in consecutive layers to small-scale mesocosms with and without earthworms. The presence of E. fetida increased the overall number of soil arthropods regardless of the dose of manure applied. This result was mainly due to the presence of large populations of springtails and mesostigmatid mites. Springtails were more abundant in the new layers of the mesocosms, which indicated a preference for substrates with fresh organic matter and higher microbial biomass. The other arthropod groups were consistently favored by the presence of earthworms, but remained at low densities throughout the decomposition process. Only the psocids were negatively affected by the presence of E. fetida. These results suggest that the development of large populations of soil arthropods, mainly springtails, in the mesocosms with earthworms is a characteristic feature of the initial stages of the earthworm-driven decomposition process.

The impact of two arable field margin management schemes on litter decomposition

A primary objective of agri-environment schemes is the conservation of biodiversity; in addition to increasing the value of farmland for wildlife, these schemes also aim to restore natural ecosystem functioning. The management of scheme options can influence their value for delivering ecosystem services by modifying the composition of floral and faunal communities. This study examines the impact of an agri-environment scheme prescription on ecosystem functioning by testing the hypothesis that vegetation management influences decomposition rates in grassy arable field margins. The effects of two vegetation management practices in arable field margins – cutting and soil disturbance (scarification) – on litter decomposition were compared using a litterbag experimental approach in early April 2006. Bags had either small mesh designed to restrict access to soil macrofauna, or large mesh that would allow macrofauna to enter. Bags were positioned on the soil surface or inserted into the soil in cut and scarified margins, retrieved after 44, 103 and 250 days and the amount of litter mass remaining was calculated. Litter loss from the litterbags with large mesh was greater than from the small mesh bags, providing evidence that soil macrofauna accelerate rates of litter decomposition. In the large mesh bags, the proportion of litter remaining in bags above and belowground in the cut plots was similar, while in the scarified plots, there was significantly more litter left in the aboveground bags than in the belowground bags. This loss of balance between decomposition rates above and belowground in scarified margins may have implications for the development and maintenance of grassy arable field margins by influencing nutrient availability for plant communities.

Effects of Ips typographus (L.) damage on litter quality and decomposition rates of Oriental Spruce [Picea Orientalis (L.) Link.] in Hatila Valley National Park, Turkey

This study investigated the effects of Ips typographus (L.) damage on initial litter quality parameters and subsequent decomposition rates of oriental spruce tree species [Picea orientalis (L.) Link]. The needle litter was collected from highly damaged, moderately damaged and control stands on two aspects (north and south) and two slope position (top and bottom) on each aspect. The litter was analyzed for initial total carbon, lignin and nutrient (nitrogen, phosphorus, potassium, calcium, magnesium and manganese) concentrations. The variability in nitrogen and calcium concentrations and ratios of C:N, lignin:N and lignin:Ca was significantly affected by the insect damaged levels. While nitrogen concentrations in needle litter increased with increasing insect damage (and consequently the ratios of C:N and lignin:N decreased), calcium concentrations decreased (and consequently the ratio of lignin:Ca increased). Aspect and slope positions explained most of the variability in carbon, lignin, phosphorus, potassium, magnesium and manganese concentrations and lignin:P ratio between all studied stands. Litter decomposition was studied in the field using the litterbag technique. The litter from highly damaged stands showed highest decomposition rates followed by moderately damaged and control stands. The mass loss rates were significantly positively correlated with initial nitrogen concentration and negatively with C:N and lignin:N ratios. The effects of microclimate resulting from canopy damage on litter decomposition was also examined at the same time using standard litter with the same litter quality parameters, but they showed no significant differences among the insect damage levels indicating that alteration of the litter quality parameters produced by I. typographus damage played a more important role than altered microclimate in controlling needle litter decomposition rates. However, changes in microclimate factors due to topography influenced decomposition rates.