Litter Loss Research Articles

Commentary on the Role of Maternal Toxicity on Developmental Toxicity

Maternal mammalian toxicity impacts prenatal development, with general systemic maternal toxicity, from reduced weight gain to morbidity, causative for reduced fetal weights/litter and increased fetal variations (especially skeletal)/litter, but not, in the author's opinion, for increased fetal malformations, reduced litter sizes or full litter losses. Increased fetal malformations are likely due to exposure to specific chemicals which alter specific maternal functions at critical point(s) in pregnancy, typically exaggerated effects from higher doses by drugs under development with known, desired pharmacological effects. Malformations can also be from genetic/epigenetic alterations, specific altered proteins, molecular pathways, etc. Full litter losses are triggered by the mother and are rare in rats. Information to inform maternal (and developmental) toxicity includes ovarian corpora lutea counts, uterine implantation profile, degree of litter reduction (if present), timing and extent of maternal toxicity relative to those of adverse embryofetal effects, etc. The view of maternal toxicity as confounding results in in vivo developmental toxicity studies, worldwide concerns about increased research animal usage, increasing time, labor, costs, and new software and hardware sophistication all drive the interest in development, validation, and performance of in vitro/in silico assays. These assays are fast, inexpensive, responsive to animal use concerns and amenable to mechanistic questions. The strength of these in vitro/in silico assays is considered by many to be the absence of the maternal organism/placenta. These assays inform mechanism and hazard, but NOT risk. The Environmental Protection Agency currently estimates that these new assays are approximately 70% accurate versus the whole animal tests.

Greater accumulation of litter in spruce (Picea abies) compared to beech (Fagus sylvatica) stands is not a consequence of the inherent recalcitrance of needles.

Background and aimsReplacement of beech by spruce is associated with changes in soil acidity, soil structure and humus form, which are commonly ascribed to the recalcitrance of spruce needles. It is of practical relevance to know how much beech must be admixed to pure spruce stands in order to increase litter decomposition and associated nutrient cycling. We addressed the impact of tree species mixture within forest stands and within litter on mass loss and nutritional release from litter.MethodsLitter decomposition was measured in three adjacent stands of pure spruce (Picea abies), mixed beech-spruce and pure beech (Fagus sylvatica) on three nutrient-rich sites and three nutrient-poor sites over a three-year period using the litterbag method (single species and mixed species bags).ResultsMass loss of beech litter was not higher than mass loss of spruce litter. Mass loss and nutrient release were not affected by litter mixing. Litter decay indicated non-additive patterns, since similar remaining masses under pure beech (47%) and mixed beech-spruce (48%) were significantly lower than under pure spruce stands (67%). Release of the main components of the organic substance (Corg, Ntot, P, S, lignin) and associated K were related to mass loss, while release of other nutrients was not related to mass loss.ConclusionsIn contradiction to the widely held assumption of slow decomposition of spruce needles, we conclude that accumulation of litter in spruce stands is not caused by recalcitrance of spruce needles to decay; rather adverse environmental conditions in spruce stands retard decomposition. Mixed beech-spruce stands appear to be as effective as pure beech stands in counteracting these adverse conditions.

Colonization and decomposition of leaf litter by ligninolytic fungi in Acacia mangium plantations and adjacent secondary forests

Colonization of leaf litter by ligninolytic fungi and relationships between mass loss and chemical qualities of surface leaf litter were examined in Acacia mangium plantations and adjacent secondary forests in southern Sumatra Island, Indonesia. Leaves were collected from eight A. mangium plantations of different ages and three secondary forests. Partly decomposed leaves beneath the surface leaf litter were used to measure the bleached area which indicated colonization by ligninolytic fungi. Surface leaf litter was used to measure initial chemical content and subjected to the pure culture decomposition test. The bleached area was greater in secondary forests than in A. mangium plantations. Nitrogen content was higher in all the A. mangium plantations than in the secondary forests, and acid unhydrolyzable residue (AUR) content was generally higher in the A. mangium plantations than in the secondary forests. The bleached area of leaf litter was negatively correlated with nitrogen content of surface leaf litter at all sites, indicating an inhibition of the colonization by ligninolytic fungi of leaves with higher nitrogen content. In a pure culture decomposition test inoculating a ligninolytic fungus to surface leaf litter, mass loss of leaves was negatively correlated with AUR content of surface leaf litter. Mass loss of leaves and AUR was not significantly related to nitrogen content. These results suggested that higher nitrogen content in A. mangium leaf litter had a negative effect by colonization of ligninolytic fungi, but the effect of high N in A. mangium leaf litter on the decomposition of leaf litter and AUR remained unsolved.

Effects of climate change on leaf litter decomposition across post-fire plant regenerative groups

Decomposition is a determining factor for the functioning of ecosystems because litter dynamics (litter fall and litter decomposition) constitute a key process in the regulation of the recycling of carbon and nutrients. We studied the litter decomposition properties of a set of 19 Mediterranean-basin woody species with different post-fire regenerative strategies (resprouters and non-resprouters), under experimental climate manipulation (simulating warming and drought) over a 2-year period. We show that climate change modifies litter decomposition of these Mediterranean woody species as litter contributions to the soil (g/year) were lower under drought experimental conditions. Species with different post-fire regeneration performance showed different leaf decomposition patterns, though these patterns were influenced by the taxonomical affiliation of the species. As expected, the mass loss of the non-resprouter litter, after 2 years, was higher than in resprouters. Non-resprouters showed higher nutrient concentration per mass of leaf litter after 2 years of experiment than resprouters, possibly because they have lost more C-rich biomass, allowing high nutrients concentration in the remaining litter. That would apply particularly to P as litter N:P ratio was lower in non-resprouters than in resprouters. This study suggests that, in Mediterranean ecosystems, nutrients’ return from leaf litter to the soil will be slower under the projected future drier conditions. Furthermore, changes in fire regimes that lead to modifications in the abundance of post-fire regenerative groups are likely to affect ecosystem's functional properties. Thus, if new fire regimes enhance non-resprouters’ abundance, we can expect a greater return of organic matter contributions to the soil and a lower litter N:P.

Post-fire succession of collembolan communities in a northern hardwood forest

Forest fire intensity can impact the survival and recovery of soil fauna at local scales. We compared three contiguous sites differing in fire history to explore post-fire succession of collembolan (Hexapoda: Apterygota) communities in a maple-oak forest in southern Québec, Canada. We found a total of 22 collembolan species from 8 families and 17 genera at sites burned 0, ∼50, and ∼100 years in the past; samples from the most recent fire were collected in both lightly and intensely burned patches. Shifts in community composition were significantly related to time since a fire disturbance, burn intensity, and consumption of litter and organic soil horizons during recent fire events. Using a trait-based approach we demonstrate that species that remain following high-intensity fire are smaller-bodied than species in unburned areas. Additional character states (eyeless, unpigmented) suggest these species are endogeaic versus epigeaic, and that litter loss associated with high-intensity fire is the main driver of collembolan community compositional changes. We suggest that understanding Collembola community dynamics in response to a fire disturbance will require a better understanding of the spatial configuration of remnant habitat patches within heterogeneous burn sites, and patterns of collembolan dispersal and recolonization in three dimensional space.

Enzyme activities and metabolic profiles of soil microorganisms at KILN sites in Quercus spp. temperate forests of central Mexico

Temperate forest dominated by Quercus L. spp. cover large parts of central Mexico and rural communities depend on these forests for wood and charcoal. The impact of charcoal production on enzymatic and metabolic profiles of soil microorganisms in the 0–15 cm layer were investigated during the dry and rainy season. A KILN site, used for charcoal production, is prepared by clearing all vegetation, removing litter and soil from the surrounding area. The wood is piled up in the centre of the KILN site and covered with litter and soil. Incomplete combustion with a minimum of flame production is maintained for 12 days. The charcoal production had a negative effect on the functional diversity and enzymatic microbial activity in soil. Community level physiological profiles (CLPP) analyses showed a lower average well color development, substrate richness, and functional diversity in soil at the KILN sites compared to the undisturbed soil. Cluster analysis dendrograms and canonical discriminant analysis of CLPP indicated that substrate utilization at the KILN sites was different from undisturbed forest soil. The activity of six enzymes, i.e. CM-cellulase, β-glucosidase, N-acetyl-β- d-glucosaminidase, nitrate reductase, urease and proteinase, decreased from 44% to 90% at the KILN sites compared to the undisturbed forest soil. It was found that charcoal production at a KILN site showed lower functional diversity and enzymatic microbial activity than in the surrounding forest soil as a result of loss of litter and organic matter and changes in microclimatic conditions.

Soil properties and nitrogen utilization of hinoki cypress as affected by strong thinning under different climatic conditions in the Shikoku and Kinki districts in Japan

The effect of climate conditions and strong thinning on the soil organic layer, surface soil, and nitrogen and water utilization by plants was evaluated for hinoki cypress forests in Shikoku and Kinki districts in Japan. Thirty-five forests were selected in Kochi, Ehime, Kagawa and Kyoto prefectures. The mean annual temperate of the studied forests ranged from 9.6 to 16.3°C, and the mean annual precipitation ranged from 1,350 to 3,960 mm. Carbon and nitrogen content in the organic layer decreased with increasing mean annual precipitation. In high precipitation areas, carbon and nitrogen content in the organic layer would be lower due to rapid decomposition with low soil acidity and due to loss of litter because of heavy rainfall. Carbon and nitrogen content in the surface soil at 0–5 cm depth decreased with increasing mean annual temperature, but was not related to mean annual precipitation. The results indicate that loss of organic layer by raindrops in a high precipitation area causes lower nitrogen availability for plants. Strong thinning significantly reduced carbon and nitrogen content in the organic layer but did not affect nitrogen concentration and δ13C in leaves. These results suggest that climate conditions and strong thinning can affect carbon and nitrogen content in the organic layer and subsequent nitrogen availability in soil, but strong thinning does not appreciably affect nitrogen and water utilization by hinoki cypress.

Effects of temperature and litter type on fungal growth and decomposition of leaf litter

The dependence of fungal decomposition of leaf litter on incubation temperature and litter types used as substrata was assessed under pure culture conditions. Isolates of Xylaria sp., a major ligninolytic fungus in cool temperate forests in Japan, were used as the fungal material. Xylaria sp. is mesophilic; maximum growth and decomposition occurred at 25°C. In the temperature test, the decomposition pattern of beech leaf litter by three isolates of Xylaria sp. changed at a threshold at 25°C. Cellulolytic activity increased with temperature from 5 to 25°C, whereas above 25°C ligninolytic activity increased at the expense of cellulolytic activity, leading to suppressed overall decomposition as a result of the higher temperature. The mass loss of leaf litter caused at 20°C by an isolate of Xylaria sp. was variable among 15 litter types and was correlated negatively with acid-unhydrolyzable residue (AUR) content and positively with total carbohydrate content for the 15 litter types. The effects of temperature and litter type on the growth and decomposition of leaf litter by Xylaria sp. may have implications for changes in fungal decomposition of leaf litter that would be predicted in response to future environmental changes

Assimilation of multiple data sets with the ensemble Kalman filter to improve forecasts of forest carbon dynamics

The ensemble Kalman filter (EnKF) has been used in weather forecasting to assimilate observations into weather models. In this study, we examine how effectively forecasts of a forest carbon cycle can be improved by assimilating observations with the EnKF. We used the EnKF to assimilate into the terrestrial ecosystem (TECO) model eight data sets collected at the Duke Forest between 1996 and 2004 (foliage biomass, fine root biomass, woody biomass, litterfall, microbial biomass, forest floor carbon, soil carbon, and soil respiration). We then used the trained model to forecast changes in carbon pools from 2004 to 2012. Our daily analysis of parameters indicated that all the exit rates were well constrained by the EnKF, with the exception of the exit rates controlling the loss of metabolic litter and passive soil organic matter. The poor constraint of these two parameters resulted from the low sensitivity of TECO predictions to their values and the poor correlation between these parameters and the observed variables. Using the estimated parameters, the model predictions and observations were in agreement. Model forecasts indicate 15 380-15 660 g C/ m2 stored in Duke Forest by 2012 (a 27% increase since 2004). Parameter uncertainties decreased as data were sequentially assimilated into the model using the EnKF. Uncertainties in forecast carbon sinks increased over time for the long-term carbon pools (woody biomass, structure litter, slow and passive SOM) but remained constant over time for the short-term carbon pools (foliage, fine root, metabolic litter, and microbial carbon). Overall, EnKF can effectively assimilate multiple data sets into an ecosystem model to constrain parameters, forecast dynamics of state variables, and evaluate uncertainty.

Chemical composition of litter affects the growth and enzyme production by the saprotrophic basidiomycete Hypholoma fasciculare

Abstract Chemical composition of litter has previously been reported to affect in situ decomposition. To identify its effects on a single species level, the saprotrophic basidiomycete Hypholoma fasciculare was grown on 11 types of litter with variable chemical composition (N content of 3.4–28.9 mg g−1), and the mass loss of litter and lignin, production of extracellular enzymes and fungal biomass were followed. After 12 weeks, mass loss ranged from 16 % to 34 %. During early decomposition stages, litter mass loss, fungal biomass production (estimated by ergosterol content) as well as fungal substrate use efficiency all increased with increasing initial N content of the litter. The initial litter decomposition rate was significantly positively correlated with the activities of arylsulfatase, cellobiohydrolase, endoxylanase and phosphatase. Contrary to expectations, the lignin content did not affect litter mass loss, when covariation with N content was accounted for. The ratio of lignin loss to total mass loss depended on the litter type and did not reflect the activities of ligninolytic enzymes.

Artesunate and artelinic acid: association of embryotoxicity, reticulocytopenia, and delayed stimulation of hematopoiesis in pregnant rats

The artemisinin antimalarials cause embryo death and malformations in animals by killing embryonic erythroblasts. Groups of pregnant rats (N = 4) were administered 35 and 48 µmol/kg artesunate and 17.2, 28.7, 48, 96, and 191 µmol/kg artelinic acid as a single oral dose on gestational day (GD) 12. Litters were examined on GD21. The ED(50) for embryo death with artelinic acid (23.4 µmol/kg) was just slightly lower than that for decreased reticulocyte count at 24 hr postdose (33.5 µmol/kg) and both had similarly steep dose responses (maximal effects of total litter loss and ∼60% decreases in reticulocyte count at 48 µmol/kg). Results with artesunate were similar. The correlation coefficient between embryo death and decreased reticulocyte count was 0.82 (p<0.01). The close relationship between embryotoxicity and reticulocytopenia is suggestive of a common mechanism-artemisinin-induced mitochondrial damage leading to cell death. At 9 days postdose, treatment with artesunate and artelinic acid also caused increases in counts of reticulocytes, lymphocytes, basophils, and monocytes (up to 3.7 ×, 1.7 ×, 4.7 ×, and 1.7 × control, respectively). This stimulation of hematopoiesis may have been mediated by the direct oxidative conversion of artesunate or artelinic acid to the artemisininyl hydroperoxide within the bone marrow cells or by an indirect increase in reactive oxygen species. The high correlation between embryotoxicity and reticulocytopenia further supports the assertion that therapeutic dosage regimens of artemisinins that cause decreases in reticulocyte count in pregnant women during the putative critical period (approximately postconception wk 3 to 9) are at risk of also causing adverse effects on the embryo.

CADANGAN, KEHILANGAN, DAN AKUMULASI KARBON PADA PERKEBUNAN KELAPA SAWIT DI LAHAN GAMBUT TROPIKA

Peat land conversion to oil palm plantation affects carbon stocks and can change a net sink of atmospheric carbon (C) into a net source. The influence of location, type of peat, drainage practices and fertilization is insufficiently known. A study was conducted in West Aceh from May 2008 until October 2009 in oil palm plantations of various age. Carbon stocks and C loss were calculated from data of bulk density (BD), ash content, carbon content, and peat depth. A new method for C loss estimates using ash as internal tracer was developed and tested. Peat land characteristics after drainage and conversion to oil palm plantation were investigated by field observation and laboratory analysis of peat soil samples in the laboratory. Results showed that: 1) Distance from the drain influences the rates of: a) water table depth, b) subsidence, with rates of 1,1 to 9,2 cm/year and 22.67 – 57.23% influence of C loss, and c) soil carbon loss. 2) Ash content and bulk density of the peat are related, indicating the partial loss of soil C during compaction. 3) An “internal tracer” estimate of peat C loss yields estimates of CO2 flux up to 48 t CO2-eq ha-1 y-1 for young oil palm, highly correlated with measured rates of subsidence of the surface and water table depth. 4) Patterns of weight loss of surface litter, measured in litter bags, respond to inherent quality (C/N). Some data for oil palm on shallow peat suggest that a net sink for C can be maintained under such conditions.Key words: Carbon stock, carbon loss, carbon accumulation, oil palm, tropical peat

Effects of temperature and litter type on fungal growth and decomposition of leaf litter

The dependence of fungal decomposition of leaf litter on incubation temperature and litter types used as substrata was assessed under pure culture conditions. Isolates of Xylaria sp., a major ligninolytic fungus in cool temperate forests in Japan, were used as the fungal material. Xylaria sp. is mesophilic; maximum growth and decomposition occurred at 25°C. In the temperature test, the decomposition pattern of beech leaf litter by three isolates of Xylaria sp. changed at a threshold at 25°C. Cellulolytic activity increased with temperature from 5 to 25°C, whereas above 25°C ligninolytic activity increased at the expense of cellulolytic activity, leading to suppressed overall decomposition as a result of the higher temperature. The mass loss of leaf litter caused at 20°C by an isolate of Xylaria sp. was variable among 15 litter types and was correlated negatively with acid-unhydrolyzable residue (AUR) content and positively with total carbohydrate content for the 15 litter types. The effects of temperature and litter type on the growth and decomposition of leaf litter by Xylaria sp. may have implications for changes in fungal decomposition of leaf litter that would be predicted in response to future environmental changes

Assessing the functional importance of large‐bodied invertebrates in experimental headwater streams

Recent theoretical advances in food web ecology emphasize the importance of body size disparities among species for the structure, stability and functions of ecosystems. Experimental confirmations of the functional importance of large species, independent of their trophic position, are scarce. We specifically examine the multiple ecological roles of large invertebrates from two distinct trophic levels in headwater streams. We experimentally manipulated the presence of large predatory invertebrates (two Perlid stoneflies) or detritivores (a limnephilid caddisfly and aPteronarcysstonefly) in a two‐by‐two design in stream channels open to immigration/emigration of smaller biota. We assessed treatment effects on the trophic structure of the benthic invertebrate community, dynamics of basal resources (benthic algae and leaf litter of cedar and alder), and stability of litter decomposition rates against an experimental pulse perturbation (fine sediment input). The presence of the large invertebrates was associated with a ten‐fold decrease in the biomass of invertebrate filterers whereas other trophic groups were unaffected by the large species. The biomass of benthic algae was lower and the rate of mass loss of alder litter was higher in channels lacking the large predators, thus revealing trophic cascades operating along both algal‐based and detritus‐based food chains. The large predators had no detectable effect on the decomposition of cedar whereas both cedar and alder disappeared faster in the presence of the large detritivores. Furthermore, the large predators and large detritivores interactively influenced the decomposition of the cedar–alder mixture through a litter diversity effect and the variability of the rate of alder decomposition after a pulse of fine sediment. Because the large invertebrates affected multiple ecosystem properties, and as their absence was not rapidly compensated for by small immigrant species, our findings support the notion that large species could be critically important in controlling ecosystem structure and functioning.

Role of fungi in litter decomposition associated with Casuarina equisetifolia L. plantations in coastal sand dunes, Orissa, India

Seasonal dynamics of soil microfungal populations, their metabolic activity and decomposition of leaf litter were studied in a monoculture plantation of Casuarina equisetifolia L. in coastal sandy belt of Orissa for a period of 2 years (June 2002–May 2004). Fungal succession of litter was also studied. Microbial isolation and soil analysis was performed using standard procedures and decomposition of leaf litter was studied using litter bag technique. Maximum population density was observed in the rainy season followed by winter and lastly summer. Larger microbial populations were encountered in plantation soil compared to barren sand, corresponding with the fluctuation of prevailing temperature, moisture and total organic carbon content. Rates of litter loss and carbon dioxide output followed the same trends as the population density. The annual K value was 0.41. The diversity index varied from 2.87 to 3.71 (Shannon) and 0.356 to 0.885 (Simpson). The similarity index showed that highly decomposed litter (HDL) is more similar to Soil A (barren sand dune) than Soil B (sand dune with monoculture plantation of Casuarina). The introduction of predominantly decomposing microorganisms isolated from samples from the present study could help to increase the nutrient status of these soils. This research will hopefully improve the monitoring and management of decomposing fungi in the study area and highlights their importance in maintaining ecosystem services which could be a valuable tool for better understanding the long-term effects of changes in soil condition of the forest floors in coastal sand dunes of Orissa, India.

Wood decomposition model for boreal forests

Abstract The decomposition of woody litter is a biochemical process, controlled by physical, chemical and biological environmental conditions. To develop a practicable model of this complex process, it is necessary to identify the major controlling factors and quantify their effects. We used four data sets (total N = 2102) on mass loss of decomposing woody litter in Northern Europe to extend an earlier decomposition model of non-woody litter and make it suitable for describing also decomposition of woody litter. We compared alternative ways to model the effects of size and chemical composition of woody litter on decomposition using the Bayesian model selection theory. The best model fitted to the diverse data sets (woody litter of four tree species, diameter 0.5–60 cm, time series up to 70 years) with little systematic error. Based on this result, we concluded that the extended model is suitable for describing decomposition of woody litter of the common tree species in the boreal forests studied. According to the model developed, frequently observed sigmoidal patterns in mass loss of woody litter are related to high concentrations of slowly decomposing lignin compounds and these patterns become stronger with an increasing size of decomposing woody litter.

Effect of prenatal peroxisome proliferator-activated receptor α (PPARα) agonism on postnatal development

Recent work indicates that PPARα is required for perfluorooctanoic acid (PFOA)-induced postnatal lethality resulting from prenatal exposure. The present study tested the hypothesis that relatively modest activation of PPARα during prenatal development will cause postnatal lethality, similar to that observed with PFOA, a relatively low affinity PPARα agonist. Female wild-type and Pparα-null mice were mated overnight with males of the same genotype. The presence of a copulatory plug on the morning after mating was indicative of pregnancy and considered gestation day (GD) 0. Plugged female mice were fed either a control diet or one containing clofibrate (0.5%) or Wy-14,643 (0.005%) until GD18 or until parturition. Mice were examined on GD18 or on postnatal day (PND) 20 following the prenatal exposure period. Dietary administration of clofibrate or Wy-14,643 did not affect maternal weight or weight gain, the average number of implantations, the percentage of litter loss, the average number of live/dead fetuses, average crown-rump length, or the average fetal weight on GD18 in either genotype. An increase in relative maternal liver weight and elevated expression of PPARα target genes in maternal and fetal livers on GD18 were observed, indicative of PPARα-dependent changes in both the maternal and fetal compartments. However, no defects in postnatal development were observed by either clofibrate or Wy-14,643 in either genotype by PND20. These results demonstrate that relatively low level activation of PPARα by clofibrate or Wy-14,643 during prenatal development does not cause postnatal lethality.

Reestablishment of ecological functioning by mulching and termite invasion in a degraded soil in an Australian savanna

Abstract Soil degradation is a major source of ecological dysfunction in both natural and agricultural landscapes. Termites are key mediators of tropical soil structure and function, but there has been little experimental evaluation of their potential in soil rehabilitation. This study investigated if termite activity can be used as a tool to improve the properties and function of degraded soil in tropical Australia, through mulch addition. A 2 × 2 randomised block design was used, with mulch (bare [B] or mulched [M] plots) and termiticide (termite [T] or non-termite [NT] plots) as factors. Over 4.5 years I tested the hypothesis that the MT plots would show greatest increase in (i) soil macroporosity, (ii) total soil surface carbon and nitrogen, (iii) litter decomposition, (iv) soil water storage and (v) plant cover, and (vi) greatest reduction in soil strength. MT treatment plots showed a 46% and 45% increase in soil macroporosity and plant cover, respectively, and a 25% reduction in soil strength compared with MNT plots. Compared with B treatments (BT, BNT), macroporosity and plant cover were 98% and 60% higher, respectively and soil water storage increased by up to 15%. Termites contributed to 58% of litter loss in MT plots over the transitional/dry season period. Mulching doubled soil carbon and nitrogen levels. This research demonstrates termite-mediated processes can be initiated and maintained in degraded soil, thereby improving soil structure and key ecosystem functions. Termites may represent a valuable biological resource for promoting tropical soil restoration, through incorporating techniques that promote their activity into tropical soil rehabilitation management.

EFFECT OF BIRTH WEIGHT AND LITTER SIZE AT SUCKLING AGE ON REPRODUCTIVE PERFORMANCE IN DOES AS ADULTS

A total of 121 Pannon White female rabbits born with low (39-43 g) or high (63-70 g) weight were raised in litters of 6 or 10 kits. Their reproductive performance (Al practiced 9-11 days after kindling) was controlled for 6 consecutive litters for a total of 300 kindlings. The does' birth weight had a significant effect on the number of inseminations necessary for the first kindling: the higher the birth weight of does, the lower their kindling rate. Later on, however, birth weight no longer affected the conception rate. With higher birth weight, significantly improved doe performance could be expected. Litter size at birth was 12.4% higher (9.52 vs 8.34; P:50.01), litter size at 21 days was 9.4% higher (7.64 vs 6.92; P:50.01) and litter weight at 21 days was 5.9 % greater (2.73 vs 2.57 kg; P:50.05) when the doe was born with greater weight. Total litter loss was 21.0% and 8.2% (P:50.01) for the high and low birth weight does, respectively. The size of the litters in which the does had been reared (6 or 10) did not influence their performance.

Drought impact on stream detritivores: experimental effects on leaf litter breakdown and life cycles

Predictions of effects of global climate change include decreased runoff for many parts of the world, which will result in drying of streams. Information of the effects of drought on aquatic ecosystems is limited and little is known of the effects on ecosystem functions. Our main objective was to measure the direct effects of drought on leaf litter breakdown by invertebrate shredders in a controlled laboratory experiment. We hypothesized a decreased breakdown at high drought level. Single-species and multi-species treatments with three shredder species (Asellus aquaticus, Limnephilus bipunctatus, and L. flavicornis) were set up in an experiment with three drought level treatments, control, medium, and high drought (6 cm water level, 1 cm water level, and water level below sediment surface, respectively). Breakdown measured as leaf litter loss was significantly lower in both medium and high drought treatments compared to the control. Previously, decreased breakdown due to drying has been reported, but attributed to low densities of invertebrate shredders. We show that even when shredders are present, drought decreases the breakdown. Drought treatments also induced earlier pupation for the caddisfly L. flavicornis. Shifts in species phenology due to drought, e.g., earlier emergence, may affect species ability to adult survival and reproduction. Shifts in timing of emergence may also affect terrestrial food webs, where emerging aquatic insects may constitute an important food subsidy. Our knowledge of the complex effects of droughts in aquatic systems is limited with an urgent need of extended knowledge of the ecological effects of droughts on freshwater ecosystem functioning.