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The abundance and community structure of soil arthropods in reclaimed coastal saline soil of managed poplar plantations

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The abundance and community structure of soil arthropods in reclaimed coastal saline soil of managed poplar plantations

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Abstract

Establishing poplar plantations is a common practice for improving the quality of reclaimed coastal saline soils in Eastern China. The abundance and diversity of arthropods can reflect changes in soil quality. However, the extent to which intensive forest management serves to alter soil arthropod communities remains elusive. In this study, we examined the effects of applying organic fertilizers (OF) and removing understory plants (UP) (two common practices to promote poplar growth) on the abundance and diversity of soil arthropods of poplar plantations in a reclaimed coastal area of Northern Jiangsu Province, China. We found that the OF addition significantly increased the total abundance of soil arthropods, and the abundance of Macrophytophages, Microphytophages and Omnivorous Acari, but decreased the total evenness. The removal of UP did not sig- nificantly influence the abundance and diversity of soil arthropods in the 0–20 cm soil layer. Our results sug- gested that the OF addition is a preferable management practice to UP removal in order to elevate the abundance of soil arthropods while promoting poplar plantation productivity

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... The soil samples were immediately shipped back to our laboratory. The soil fauna was then collected from each soil sample using Tullgren extractors (Tullgren Funnel Unit, BURKARD, BURKARD SCIENTIFIC Ltd., Uxbridge, UK) [50][51][52][53]. All collected fauna samples were preserved in 75% ethanol and then sorted under a dissecting microscope (Nikon Eclipse E200, Nikon Instech Co., Ltd., Tokyo, Japan). ...
... The density and the number of groups of soil fauna usually decrease along soil profile [48,74], and this holds true under N addition in our study. Surface soil is more hospitable to soil fauna, as it always has a higher substrate content and air circulation rate [53,75]. Higher N addition thresholds for soil fauna may be attributed to the fact that topsoil could be more sensitive to environmental stress (e.g., N addition) than deeper soil layers [75]. ...
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Soil fauna is critical for maintaining ecosystem functioning, and its community could be significantly impacted by nitrogen (N) deposition. However, our knowledge of how soil-faunal community composition responds to N addition is still limited. In this study, we simulated N deposition (0, 50, 100, 150, and 300 kg N ha−1 year−1) to explore the effects of N addition on the total and the phytophagous soil fauna along the soil profile (0–10, 10–25, and 25–40 cm) in poplar plantations (Populus deltoids) on the east coast of China. Ammonium nitrate (NH4NO3) was dissolved in water and sprayed evenly under the canopy with a backpack sprayer to simulate N deposition. Our results showed that N addition either significantly increased or decreased the density (D) of both the total and the phytophagous soil fauna (Dtotal and Dp) at low or high N addition rates, respectively, indicating the existence of threshold effects over the range of N addition. However, N addition had no significant impacts on the number of groups (G) and diversity (H) of either the total or the phytophagous soil fauna (Gtotal, Gp and Htotal, Hp). With increasing soil depth, Dtotal, Dp, Gtotal, and Gp largely decreased, showing that the soil fauna have a propensity to aggregate at the soil surface. Htotal and Hp did not significantly vary along the soil profile. Importantly, the threshold effects of N addition on Dtotal and Dp increased from 50 and 100 to 150 kg N ha−1 year−1 along the soil profile. Fine root biomass was the dominant factor mediating variations in Dtotal and Dp. Our results suggested that N addition may drive changes in soil-faunal community composition by altering belowground food resources in poplar plantations.
... Poplar stands dominate artificial afforestation forests throughout this area. The dominant understory plants in this forest include vines (Cayratiatrifolia, Humulusscandens, and Dioscorea opposite), herbs (Erigeron annuus and Corchoropsis psilocarpa), and graminoids (Lophatherum gracile, Misanthus sinensis, and Oplisments undulatifolius) (Li et al., 2018). ...
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Drought has been observed to decrease the accumulation of carbon (C) and nitrogen (N) in forest ecosystems. The microbial C use efficiency (CUE) and N use efficiency (NUE) are critical to elemental cycling in terrestrial ecosystems, which can be calculated by the C:N stoichiometry of soils, microbial biomass, and extracellular enzyme activities. However, little is known about how drought affects microbial CUE and NUE. We extracted soil samples at different depths (0-15 cm, 15-30 cm, and 30-45 cm) in forest stands that were subjected to 30% and 50% throughfall reduction manipulation experiments, in contrast to those obtained from stands that were left undisturbed from July 2019 to April 2020 in a poplar plantation of Eastern China. Under drought conditions, we found that the soil moisture, soil C:N ratio, and C-and N-acquiring enzyme activities decreased; however, the soil pH, microbial biomass C:N ratio, ecoenzymatic activity C:N ratio, and fungi:bacteria ratio increased. Microbial CUE and NUE, which were calculated based on these C:N stoichiometric ratios, also increased. These responses were similar at different soil depths across sampling dates. Our structural equation models indicated that drought-induced increases in CUE and NUE were driven by changes in the soil moisture, fungi:bacteria ratio, and ecoenzymatic activity C:N ratio. Our results suggested that decreases in soil moisture and increases in the ecoenzymatic activity C:N and fungi:bacteria ratios could stimulate microbial CUE and NUE.
... Throughout this region, poplar communities dominate artificial afforestation forests. Graminoids (Lophatherum gracile, Misanthus sinensis and Oplisments undulatifolius), herbs (Erigeron annuus and Corchoropsis psilocarpa), and vines (Cayratiatrifolia, Humulusscandens and Dioscorea opposite) comprise the dominant understory plants (Li et al., 2018b). ...
... On the other hand, poplars are also acknowledged as significant contributor to carbon sequestration. It has been anticipated that due to climate change poplar plantations would experience intensified drought spells that could significantly cutback the overall productivity [23,24]. Moreover, Jamun (Syzygium cumini) is a large fruit tree which is native to South Asia and is also cultivated in Hawaii since 1871. ...
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Drought is one of the most devastating climate factors in terms of its spatial extent and intensity. Therefore, a study was conducted to evaluate the water stress tolerance in young saplings of Syzygium cumini (L.) Skeels and Populus deltoides Marchall that are cultivated in the rain fed areas of Pakistan. Plants were subjected to three levels of moisture regimes: well-watered (WW, 90% of field capacity), mild stress (MS, 60% field capacity), and severe stress (SS, 30% of field capacity). Results showed that dry biomass production (leaf, stem, and root), chlorophyll a, b and carotenoid contents decreased significantly while osmolyte accumulation increased in both species, with the highest increase was evidenced in Populus deltoides saplings. A significant decrease was evidenced in CO2 assimilation rate and stomatal conductance that resulted in a significant increase in intrinsic water use efficiency in both species under MS and SS. In both the species, along with a significant increase in the production of hydrogen peroxide and superoxide radical, the antioxidants enzyme activities of superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase also increased significantly in both species under MS and SS with highest activity evidenced in Syzygium cumini. The results suggest that Syzygium cumini saplings showed better a tolerance mechanism to water stress.
... decompose litter faster than that in understory absent stands without the help of soil mesofauna. Soil mesofauna more evidently stimulated litter mass loss when understory species was present than when it was absent (Table 2 and Fig. 3), mainly because that understory vegetation could provide shelter, food, and shadow for soil mesofauna, thus its loss would suppress the activity of soil mesofauna (Taki et al., 2010;Li et al., 2018). Taken together, our results partially supported the second hypothesis. ...
Article
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... Throughout this region, poplar communities dominate artificial afforestation forests. Graminoids (Lophatherum gracile, Misanthus sinensis and Oplisments undulatifolius), herbs (Erigeron annuus and Corchoropsis psilocarpa), and vines (Cayratiatrifolia, Humulusscandens and Dioscorea opposite) comprise the dominant understory plants (Li et al., 2018b). ...
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Abstract: Canopy closure (CC), a useful biophysical parameter for forest structure, is an important indicator of forest resource and biodiversity. Light Detection and Ranging (LiDAR) data has been widely studied recently for forest ecosystems to obtain the three-dimensional (3D) structure of the forests. The components of the Unmanned Aerial Vehicle LiDAR (UAV-LiDAR) are similar to those of the airborne LiDAR, but with higher pulse density, which reveals more detailed vertical structures. Hemispherical photography (HP) had proven to be an effective method for estimating CC, but it was still time-consuming and limited in large forests. Thus, we used UAV-LiDAR data with a canopy-height-model-based (CHM-based) method and a synthetic-hemispherical-photography- based (SHP-based) method to extract CC from a pure poplar plantation in this study. The performance of the CC extraction methods based on an angular viewpoint was validated by the results of HP. The results showed that the CHM-based method had a high accuracy in a 45 ◦ zenith angle range with a 0.5 m pixel size and a larger radius (i.e., k = 2; R 2 = 0.751, RMSE = 0.053), and the accuracy declined rapidly in zenith angles of 60 ◦ and 75 ◦ ( R 2 = 0.707, 0.490; RMSE = 0.053, 0.066). In addition, the CHM-based method showed an underestimate for leaf-off deciduous trees with low CC. The SHP-based method also had a high accuracy in a 45 ◦ zenith angle range, and its accuracy was stable in three zenith angle ranges ( R 2 : 0.688, 0.674, 0.601 and RMSE = 0.059, 0.056, 0.058 for a 45 ◦ , 60 ◦ and 75 ◦ zenith angle range, respectively). There was a similar trend of CC change in HP and SHP results with the zenith angle range increase, but there was no significant change with the zenith angle range increase in the CHM-based method, which revealed that it was insensitive to the changes of angular CC compared to the SHP-based method. However, the accuracy of both methods showed differences in plantations with different ages, which had a slight underestimate for 8-year-old plantations and an overestimate for plantations with 17 and 20 years. Our research provided a reference for CC estimation from a point-based angular viewpoint and for monitoring the understory light conditions of plantations. Keywords: canopy closure; UAV; LiDAR; HP; CHM; SHP; poplar plantation
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Although there has been much recent interest in the effect of litter mixing on decomposition processes, much remains unknown about how litter mixing and diversity affects the abundance and diversity of decomposer organisms. We conducted a litter mixing experiment using litterbags in a New Zealand rainforest, in which treatments consisted of litter monocultures of each of 8 forest canopy and understory plant species, as well as mixtures of 2, 4 and 8 species. We found litter mixing to have little effect on net decomposition rates after either 279 or 658 days, and for each species decomposition rates in mixture treatments were the same as in monoculture. Litter species identity had important effects on litter microfauna, mesofauna and macrofauna, with different litter types promoting different subsets of the fauna. Litter mixing had few effects on densities of mesofauna and macrofauna, but did have some important effects on components of the microfauna, notably microbe-feeding and predatory nematodes. At day 279, litter mixing also consistently reduced the ratio of bacterial-feeding to microbe-feeding (bacterial-feeding+fungal-feeding) nematodes, pointing to mixing causing a significant switch from the bacterial-based to the fungal-based energy channel. Litter mixing sometimes influenced the community composition and diversity of nematodes and macrofauna, but effects of litter mixing on diversity were not necessarily positive, and were much weaker than effects of litter species identity on diversity. We conclude that litter mixing effects on the abundance and diversity of decomposer biota, when they occur, are likely to be of secondary and generally minor significance when compared to the effects of litter species identity and composition.
Article
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The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.
Article
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Ecosystems of northern North America existed without earthworm fauna until European settlers arrived and introduced European species. The current extent of invasion by some of these species, Lumbricus terrestris L., Octolasion tyrtaeum Savigny and Dendrobaena octaedra Savigny, into an aspen forest in the Canadian Rocky Mountains and the effects of the invasion on soil chemistry, microflora, soil microarthropods and vegetation were investigated. Densities of earthworm species, soil structure, plant coverage and abundance were determined along three transects starting at the edge of the forest. At locations with L. terrestris, litter was incorporated into the soil, and where O. tyrtaeum was present, organic layers were mixed with mineral soil layers. Organic layers disappeared almost entirely when both species occurred together. Carbon and nitrogen concentrations were reduced in organic layers in the presence of L. terrestris and O. tyrtaeum. Microbial biomass and basal respiration were reduced when L. terrestris and O. tyrtaeum were present, presumably due to resource competition and habitat destruction. Microarthropod densities and the number of microarthropod species were strongly reduced in the presence of O. tyrtaeum (−75% and −22%, respectively), probably through mechanical disturbances, increasing compactness of the soil and resource competition. The coverage of some plant species was correlated with earthworm abundance, but the coverage of others was not. Despite harsh climatic conditions, the invasion of boreal forest ecosystems by mineral soil dwelling earthworm species is proceeding and strongly impacts soil structure, soil chemistry, microorganisms, soil microarthropods and vegetation.
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Cette revue place au centre des interactions entre les plantes, les animaux et les microorganismes du sol, les invertébrés abondants et de grande taille qui ingèrent des particules organiques et minérales produisant ainsi des structures durables. Ces invertébrés sont appelés organismes ingénieurs du sol et les données disponibles sur leur abondance, leur distribution géographique et leurs rôles fonctionnels montrent que les vers de terre et les termites en sont les principaux représentants. Ils influencent la diversité et l'activité des organismes appartenant à des groupes fonctionnels subordonnés, les transformateurs de litière, les microprédateurs et les microorganismes, régulant ainsi les transformations de nutriments. Les liens entre l'activité et la diversité des ingénieurs et les propriétés physiques du sol sont détaillés ; une mention particulière est faite de leurs effets sur l'hétérogénéité du sol, sa stabilité structurale, la distribution de la matière organique dans le profil, l'infiltration et la rétention de l'eau. Il est probable que les changements globaux attendus affecteront l'abondance et la diversité des organismes ingénieurs par le biais de la quantité et de la qualité de la litière et d'autres effets liés aux modifications des plantes et de leurs peuplements. Les changements de température attendus pourraient élargir la distribution latitudinale des termites et favoriser les termites humivores et les vers de terre endogés à régime géophage. Dans certaines régions, cependant, ces changements ne pourront s'observer car la faune locale ne comprend pas de représentants de ces groupes. Dans l'immédiat, c'est surtout l'intensification de l'usage des terres et en particulier, la perturbation des milieux forestiers qui est préoccupante car des modifications de l'équilibre des groupes fonctionnels d'organismes ingénieurs s'observent déjà... (D'après résumé d'auteur)
Article
Fire has largely been excluded from many mountain big sagebrush communities. Managers are reluctant to reintroduce fire, especially in communities without significant conifer encroachment, because of the decline in sagebrush-associated wildlife. Given this management direction, a better understanding of fire exclusion and burning effects is needed. We compared burned to unburned plots at six sites in Oregon. Soil nutrient availability generally increased with burning. Plant diversity increased with burning in the first post-burn year, but decreased by the third post-burn year. Burning altered the arthropod community, which included doubling the density of arthropods in the first post-burn year. Some arthropod Orders increased and others decreased with burning. For example, Araneae were 1.7- and 1.8-fold less and Hemiptera were 6.6- and 2.1-fold greater in the burn compared with the control in 2008 and 2009. Our results provide evidence that burning can create spatial and temporal heterogeneity in sagebrush communities and thus, it is an important component of the ecosystem. We suggest that management plans for many mountain big sagebrush communities may need to include infrequent burning. At the very least managers should be aware that fire exclusion has some potentially negative effects other than the encroachment of conifers in these communities.
Article
Information content may be used as a measure of the diversity of a many-species biological collection. The diversity of small collections, all of whose members can be identified and counted, is defined by Brillouin's measure of information. With larger collections it becomes necessary to estimate diversity; what is estimated is Shannon's measure of information which is a function of the population proportions of the several species. Different methods of estimation are appropriate for different types of collections. If the collection can be randomly sampled and the total number of species is known, Basharin's formula may be used. With a random sample from a population containing an unknown number of species, Good's method is sometimes applicable. With a patchy population of sessile organisms, such as a plant community, random samples are unobtainable since the contents of a randomly placed quadrat are not a random sample of the parent population. To estimate the diversity of such a community a method is proposed whereby the sample size is progressively increased by addition of new quadrats; as this is done the diversity of the pooled sample increases and then levels off. The mean increment in total diversity that results from enlarging the sample still more then provides an estimate of the diversity per individual in the whole population.
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We give a canonical form to the double cosets of Γ = SL(r + s, Z) with respect to the congruence subgroup Γ0(n; r, s), and determine the number of the double cosets.
Article
A study was conducted in an 11-year field experiment in a winter wheat–summer maize rotation agroecosystem in the North China Plain. We aimed to evaluate the changes in soil physico-chemical parameters and the abundance, diversity and community structure of soil mites, under organic fertilizer (OF) and chemical fertilizer (CF) treatments, compared to unfertilized soil as the control (U). Soil organic matter content, available potassium (K), total nitrogen (N) and hydrolyzable N were significantly higher in the plots under the OF treatment than under the other treatments. Available phosphorus (P) content was similar in OF and CF plots and higher than in the control. After continuous 11-year application, both the organic and chemical fertilizer treatments reduced the abundance and diversity of soil mites. Both types of fertilizer significantly reduced the abundance of Oribatida such as Epilohmannia sp., Xylobates sp., Scheloribates sp., and Cultroribula sp. This result was positively related to the high level of phosphorus in the two treatments, which probably suppressed fungi, thus reducing the food resources for mycophagous mites. However, the organic fertilizer remarkably increased the abundance of r-strategic, predatory Mesostigmata, such as Ascidae, possibly due to abundant prey under the nutrient-rich conditions. However, the number of predatory mites did not increase in the chemical fertilizer treatment. While organic fertilizer application did not increase the overall abundance and diversity of soil mites, especially Oribatida, parallel studies (unpublished) show that the increase in predatory Mesostigmata reflected enhanced biological activity and functioning of the bacterial decomposition pathway especially in the food web of this treatment.
Article
Plant chemical composition and the soil community are known to influence litter and soil organic matter decomposition. Although these two factors are likely to interact, their mechanisms and outcomes of interaction are not well understood. Studies of their interactive effects are rare and usually focus on carbon dynamics of litter, while nutrient dynamics in the underlying soil have been ignored. A potential mechanism of interaction stems from the role fauna plays in regulating availability of litter-derived materials in the mineral soil. We investigated the role of soil fauna (meso, macro) in determining the effect of surface-litter chemical composition on nitrogen mineralization and on the micro-food web in mineral soils. In a field setting we exposed mineral soil to six types of surface-applied litter spanning wide ranges of multiple quality parameters and restricted the access of larger soil animals to the soils underlying these litters. Over six months we assessed litter mass and nitrogen loss, nitrogen mineralization rates in the mineral soils, and soil microbes and microfauna. We found evidence that the structure of the soil community can alter the effect of surface-litter chemical composition on nitrogen dynamics in the mineral soil. In particular, we found that the presence of members of the meso- and macrofauna can magnify the control of nitrogen mineralization by litter quality and that this effect is time dependent. While fauna were able to affect the size of the micro-food web they did not impact the effect of litter composition on the abundance of the members of the micro-food web. By enhancing the strength of the impact of litter quality on nitrogen dynamics, the larger fauna can alter nitrogen availability and its temporal dynamics which, in turn, can have important implications for ecosystem productivity. These findings contribute to evidence demonstrating that soil fauna shape plant litter effects on ecosystem function.
Article
To compare the effects of a drought disturbance on species of Oribatida and Collembola, and subsequent recovery of their populations after the drought, we examined a Norway spruce, Picea abies, stand in south-western Sweden, where 6 years of experimentally induced summer droughts had resulted in major changes in the soil faunal communities. We followed the population densities during a 4-year period and sought correlations between the species’ drought responses and their ecological characteristics. Data on depth preference, habitat choice and reproductive mode were collected from the literature. Surface-living species, which tended to have narrow habitat width, were less negatively affected by the drought. However, among species showing negative population responses to drought, species with large habitat widths tended to recover faster after the drought. Furthermore, parthenogenesis was more common among the oribatid species that showed a population recovery than among those that did not. Overall, collembolan species recovered faster than oribatids, and among the species that did not recover, Oribatida were over-represented. No general differences in characteristics between oribatids and collembolans were observed that could explain their different responses. Possibly, traits other than those examined were more important, such as differences in dispersal rates between the two groups.
Article
The soil macrofaunal communities (Lumbricidae, Formicidae, Coleoptera, Chilopoda, Diplopoda, Isopoda, Arachnida, Gastropoda) were studied in six plots representing different stages in a theoretical post-pastoral succession on chalk grassland. Macrofaunal biomass was high in all the plots (70.2±140.3 g m ÿ2). The macroinvertebrate communities along successional gradients respond to two major environmental factors: the structure of the vegetation, which determines the diversity of microhabitats and life conditions for macroinvertebrates; and the quality of above-ground litter production, which depends on the nature of vegetation and the presence of domestic herbivores.
Article
Abstract 1. Temperate woodland Collembola feed predominantly on plant detritus and fungi. They exhibit preferences for different fungi reflecting resource value in terms of Collembola growth and reproduction. 2. Studies of fungal grazing by Collembola have focused on non-interacting fungi and have used one genetic isolate as representative of an entire fungal species. This study examines the effects of fungal interactions on Collembola behaviour, and elucidates differences arising from the use of genetically distinct fungal isolates. 3. Folsomia candida were added to microcosms in which paired combinations of the fungi, Hypholoma fasciculare (four isolates), Phallus impudicus, Phanerochetae velutina and Resinicium bicolor (two isolates), were interacting. Collembola movement and mortality was recorded for 26 days. A constant preference for one fungal mycelium over the other was shown by Collembola in 12 of the 36 interactions studied. Lowest Collembola mortality was normally recorded on the preferred mycelium. 4. In 11 of the remaining 24 interactions, Collembola preference switched from one mycelium to the other; the greatest number of dead Collembola was recorded on the final preference. 5. Collembola behaviour on different fungal isolates was broadly similar, although in one species’ combination a change in fungal isolate resulted in a total reversal of Collembola preference. The implications of these results for decomposer food webs are considered.
Article
1. A microcosm experiment was performed to test the impacts of Cognettia sphagnetorum on carbon leaching in a cambic stagnohumic gley soil.2. Leaching of dissolved organic carbon (DOC) was significantly enhanced by C.sphagnetorum, with the greatest effect being found in the upper, 0–6 cm, soil layers. The ratio of DOC to dissolved organic nitrogen (DON) in the leachate decreased in faunated systems, indicating that the enchytraeids were mobilizing carbon from organic matter with a low C to N ratio.3. The vertical distribution of the enchytraeids had an effect on the production of DOC, and this vertical distribution is affected strongly by climate. It is proposed that increases in DOC found in a field soil-warming experiment with the same soil are largely a result of changes in the vertical distribution of these organisms.
Article
Although soil-dwelling Collembola can influence plant growth and nutrient cycling, their specific role in soil food webs is poorly understood. Soil-free microcosm studies suggest that Collembola are primarily fungivores where they feed preferentially on saprophytic fungi (SF) over other fungal types. We directly assessed collembolan consumption of arbuscular mycorrhizal fungi (AMF) and SF using plant–soil mesocosms and natural abundance stable carbon isotope techniques. Mycorrhizal Andropogon gerardii (C4 grass) seedlings were placed in pots containing Collembola and soil from a C3 plant dominated site, while mycorrhizal Pascopyrum smithii (C3 grass) seedlings were placed in pots with Collembola and soil collected at a C4 plant dominated site. After 6 weeks, collembolans assimilated carbon derived from C3 and C4 sources in both A. gerardii and P. smithii treatments. Comparing Collembola isotope values in AMF vs. AMF-suppressed treatments, our data show that both AMF and SF were consumed in these experimental soil environments.
Article
Plant diversity is predicted to be positively linked to the diversity of herbivores and predators in a foodweb. Yet, the relationship between plant and animal diversity is explained by a variety of competing hypotheses, with mixed empirical results for each hypothesis. We sampled arthropods for over a decade in an experiment that manipulated the number of grassland plant species. We found that herbivore and predator species richness were strongly, positively related to plant species richness, and that these relationships were caused by different mechanisms at herbivore and predator trophic levels. Even more dramatic was the threefold increase, from low- to high-plant species richness, in abundances of predatory and parasitoid arthropods relative to their herbivorous prey. Our results demonstrate that, over the long term, the loss of plant species propagates through food webs, greatly decreasing arthropod species richness, shifting a predator-dominated trophic structure to being herbivore dominated, and likely impacting ecosystem functioning and services.
Article
1. Although direct contributions of soil invertebrates to carbon turnover are modest, they have a disproportionally large indirect impact through their control over the activity of microbial decomposers. Shifts in soil invertebrate species distribution might have a substantial effect on the decomposition process because their functional role depends on the species’ vertical position in soils. Gradients in microclimate and substrate quality and structure largely determine the vertical position of soil invertebrates. Because of the possible impact of climate change on soil invertebrate distribution, and consequently on decomposition, it is important to know the relative contributions of microclimate and substrate quality to the vertical distribution patterns of soil invertebrates. 2. We studied this for springtails (Collembola) as a keystone group in cool and cold biomes, by turning peat cores in a subarctic blanket bog upside down, thereby reversing the substrate quality gradient and leaving temperature and moisture gradients intact. 3. Two opposing groups of springtail species could be distinguished with respect to their abundance responses along the vertical gradient: (i) species that remain associated with the stratum they were originally found in (‘stayers’) and (ii) species that re-establish the original stratification pattern, by remigration either to the top or deeper layers, irrespective of any substrate quality change (‘movers’). Within the ‘mover’ response pattern, the direction of their migration in response to microclimate changes seemed to coincide with their ecomorphological traits. 4. Our results not only demonstrate that springtail species differ in their responses to changes in climate or substrate quality; they also suggest that interspecific faunal trait variation may provide a useful tool to predict animal responses to climatic changes.
Article
Loss-on-ignition (LOI) and the organic C content have been used to estimate soil organic matter. Organic matter is often estimated from organic C by applying a factor of 1.724. Several authors have examined the relationship between LOI, used as an estimate of organic matter, and C by simple linear regressions. In the present study, this approach was examined in relation to two sets of data. LOI overestimates organic matter in soils with significant proportions of clay minerals because of bound water, and correcting for bound water gives some LOI: C ratios of less than 1. It is concluded that differences in the nature of the organic matter in different soils and horizons make the simple regression approach unsuitable. More attention needs to be paid to studies of the nature of the organic matter.
Article
The pH of weak-acid solutions is controlled by acid concentration (HA + A–), the degree of acid dissociation (A–/HA), and the strength of the acids present (pKa). We developed an empirical approach that allows the relative importance of each of these factors to be estimated for soils. This empirical model was applied to soils collected from an old-field plantation of loblolly pine (Pinus taeda L.) at 5 and 25 years of age. During this period, soil pH dropped by 0.3 to 0.8 units, and extractable calcium, magnesium and potassium declined by 20 to 80%. The empirical model indicates that the decline in pH resulted largely from the reduction in base saturation of the exchange complex. However, the average acid strength of the exchange complex decreased during the 20 years, preventing a greater decline of perhaps 0.1 to 0.2 units in the observed pH. The rate of decrease in the acid neutralizing capacity to pH 3.5 was about 1.3 kmolc/ha annually, while the increase in base neutralizing capacity was about 2.7 and 1.6 kmolc/ha annually to pH 5.5 and 8.2, respectively. Extractable alkali and alkaline earth cations declined by about 2.2 kmolc/ha annually, matched by the rate of increase in aluminium. These changes demonstrated the dynamic nature of poorly buffered soils, and indicated that changes in soil acidity may be expected over a period of decades (especially following changes in land-use).
Article
Organic farming may contribute substantially to future agricultural production worldwide by improving soil quality and pest control, thereby reducing environmental impacts of conventional farming. We investigated in a comprehensive way soil chemical, as well as below and aboveground biological parameters of two organic and two conventional wheat farming systems that primarily differed in fertilization and weed management strategies. Contrast analyses identified management related differences between "herbicide-free" bioorganic (BIOORG) and biodynamic (BIODYN) systems and conventional systems with (CONFYM) or without manure (CONMIN) and herbicide application within a long-term agricultural experiment (DOK trial, Switzerland). Soil carbon content was significantly higher in systems receiving farmyard manure and concomitantly microbial biomass (fungi and bacteria) was increased. Microbial activity parameters, such as microbial basal respiration and nitrogen mineralization, showed an opposite pattern, suggesting that soil carbon in the conventional system (CONFYM) was more easily accessible to microorganisms than in organic systems. Bacterivorous nematodes and earthworms were most abundant in systems that received farmyard manure, which is in line with the responses of their potential food sources (microbes and organic matter). Mineral fertilizer application detrimentally affected enchytraeids and Diptera larvae, whereas aphids benefited. Spider abundance was favoured by organic management, most likely a response to increased prey availability from the belowground subsystem or increased weed coverage. In contrast to most soil-based, bottom-up controlled interactions, the twofold higher abundance of this generalist predator group in organic systems likely contributed to the significantly lower abundance of aboveground herbivore pests (aphids) in these systems. Long-term organic farming and the application of farmyard manure promoted soil quality, microbial biomass and fostered natural enemies and ecosystem engineers, suggesting enhanced nutrient cycling and pest control. Mineral fertilizers and herbicide application, in contrast, affected the potential for top-down control of aboveground pests negatively and reduced the organic carbon levels. Our study indicates that the use of synthetic fertilizers and herbicide application changes interactions within and between below and aboveground components, ultimately promoting negative environmental impacts of agriculture by reducing internal biological cycles and pest control. On the contrary, organic farming fosters microbial and faunal decomposers and this propagates into the aboveground system via generalist predators thereby increasing conservation biological control. However, grain and straw yields were 23% higher in systems receiving mineral fertilizers and herbicides reflecting the trade-off between productivity and environmental responsibility. © 2008 Elsevier Ltd. All rights reserved.
Article
In forest ecosystems, the effects of litter or understory on soil properties are far from being fully understood. We conducted a study in a pure Acacia mangium Willd. plantation in southern China, by removing litter or understory or both components and then comparing these treatments with a control (undisturbed), to evaluate their respective effects on soil physical, chemical and biological properties. In addition, a litter decomposition experiment was conducted to understand the effects of understory on litter decomposition. Our data showed that the presence of understory favored litter decomposition to a large extent. In 1year, 75.2 and 37.2% of litter were decomposed in the control and understory removal treatment (UR), respectively. Litter had a profound significance in retaining soil water and contributing to soil fertility, including organic matter (OM), available phosphorus (P) and alkali-hydrolyzable nitrogen (N), but understory exerted less influence than litter on soil physical and chemical properties. Both litter and understory played an important role in soil biological activity as indicated by microbial biomass carbon (MBC), while there were no significant impacts on soil exchangeable potassium (K) after either or both were removed. Contrary to our hypothesis, the effects of understory or litter removal were not always negative. A significant soil pH increase with litter removal was a positive factor for acid soil in the studied site. Except for soil moisture, significant effects, caused by removal of litter or/and understory, on measured soil chemical characteristics were only observed in the top 10cm soil layer, but not in the 10–20cm layer. Soil available P and exchangeable K contents were significantly higher in the rainy season than in the dry season, however, for the other soil properties, not substantially affected by season.
Article
We studied the effect of salal (Gaultheria shallon Pursh.) competition on height, diameter and biomass growth and biomass partitioning in coniferous trees planted to a recent clearcut site of old growth western red cedar-western hemlock (CH) forest on northern Vancouver Island, British Columbia. Tree species used were western red cedar (Thuja plicata Donn ex D. Don), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and Sitka spruce (Picea sitchensis (Bong.) Carr). Salal removal treatment was initiated at the time of planting in spring 1987. Plots were fertilized with 200 kg N ha−1 in spring 1991 and destructively sampled in fall 1992. Height growth from planted to 1989, in 1992 and total height growth were significantly greater in treated plots (salal removed) than in the control plots (salal remaining). Salal removal had a rather uniform impact on height growth for the three species tested. Total root collar diameter was 38% (P < 0.1), 88% (P < 0.05), and 65% (P < 0.05) greater in the treated plots than in the control plots, for red cedar, hemlock and spruce, respectively. Exclusion of understory vegetation had resulted in biomass increases of all the components (namely in the 1-year and 2-year foliage and branches and the older than 3-year components and various sized roots) we studied. Improved tree growth in the treated plots was attributed to the reduced uptake and immobilization of N and other nutrients by the competing understory. Below-ground understory was found to be quite persistent to surviving even after a prolonged period (6 years) of above-ground understory vegetation removal
Article
There has been recent interest in the characterization of soil biodiversity and its function in agricultural grasslands. Much of the interest has come from the need to develop grassland management strategies directed at manipulating the soil biota to encourage a greater reliance on ecosystem self-regulation. This review summarises information on selected groups of soil animals in grasslands, the factors influencing their abundance, diversity and community structure and their relationships to the functioning and stability of grassland ecosystems. Observations on the impacts of agricultural managements on populations and communities of soil fauna and their interactions confirm that high input, intensively managed systems tend to promote low diversity while lower input systems conserve diversity. It is also evident that high input systems favour bacterial-pathways of decomposition, dominated by labile substrates and opportunistic, bacterial-feeding fauna. In contrast, low-input systems favour fungal-pathways with a more heterogeneous habitat and resource leading to domination by more persistent fungal-feeding fauna. In view of this, we suggest that low input grassland farming systems are optimal for increasing soil biotic diversity and hence self-regulation of ecosystem function. Research is needed to test the hypothesis that soil biodiversity is positively associated with stability, and to elucidate relationships between productivity, community integrity and functioning of soil biotic communities.
Article
We investigated the within-site distribution of Enchytraeidae, Collembola, Oribatida, Mesostigmata and Prostigmata relative to varying water level and substrate quality on pine mire sites forming a drainage succession continuum. Collembolans were most intolerant of wetness, favoring drier locations at all stages of the drainage succession. In general, the effect of water level variation on the within-site distribution of the soil fauna was strongest when the site was at an early stage of either progressive or regressive water level change. When the average water level was below 20 cm, it no longer had a significant effect on the distribution of mites, but still affected that of Enchytraeidae and Collembola. Boron was positively correlated with faunal density in several cases, and thus may be the growth limiting nutrient affecting substrate quality for decomposers in these sites. The overall changes in the soil mesofauna in drained peatlands depicted here show that these peatland forests are converging ecologically on upland forests where decomposition in general is much faster than in pristine peatlands. The change caused by restoration shows how labile these ecosystems are also with respect to the mesofaunal community.
Article
Litterbags have been utilized in soil ecology for about 50 years. They are useful because they confine organic material and thus enable the study of decomposition dynamics (mass loss and/or nutrient loss through time, colonization by soil biota) in situ, i.e. under field conditions. Researchers can easily restrict or permit access to certain size classes of soil fauna to determine their contribution to litter mass loss by choosing adequate mesh size or applying specific biocides. In particular, the mesofauna has received much attention since it comprises two very abundant and diverse microarthropod groups, the Collembola (springtails) and Acari (mites). We comprehensively searched the literature from the mid-1960s to the end of 2005 for reports on litterbag experiments investigating the role of microarthropods in terrestrial decomposition. Thirty papers reporting 101 experiments satisfied our selection criteria and were included in the database. Our meta-analysis revealed that microarthropods have a moderate but significant effect on mass loss. We discuss in detail the interactions of the microarthropod effect with study characteristics such as experimental design (e.g. number of bags, duration of experiment), type of exposed organic matter, climatic zone and land use of the study site. No publication bias was detected; however, we noticed a significant decrease in the microarthropod effect with publication year, indicating that, in the first decades of litterbag use, soil zoologists may have studied “promising” sites with a higher a priori probability of positive microarthropod effects on litter mass loss.
lme4: Linear Mixed-effects Models Using Eigen and S4. R Package Version 1
  • D Bates
  • Maechler
  • Martin
  • Bolker
  • Ben
  • Walker
  • Steven
  • Rune Christensen
  • Haubo Bojesen
  • Singmann
  • Henrik
  • Dai
  • Bin
  • Grothendieck
  • Gabor
  • P Green
Bates, D., Maechler, Martin, Bolker, Ben, Walker, Steven, Christensen, Rune Haubo Bojesen, Singmann, Henrik, Dai, Bin, Grothendieck, Gabor, Green, P., 2017. lme4: Linear Mixed-effects Models Using Eigen and S4. R Package Version 1. pp. 1-13.
  • D Borcard
  • F Gillet
  • P Legendre
Borcard, D., Gillet, F., Legendre, P., 2011. Numerical Ecology with R. Springer, New York, NY, New York.
Soil invertebrate controls and microbial interactions in nutrient and organic matter dynamics in natural and agroecosystems
  • C A Edwards
Edwards, C.A., 2000. Soil invertebrate controls and microbial interactions in nutrient and organic matter dynamics in natural and agroecosystems. In: Coleman, D., Hendrix, P. (Eds.), Invertebrates as Webmasters in Ecosystems. CAB International, Wallingford, UK, pp. 141-159.
Managing Soil pH in Utah
  • J Gale
  • R Koenig
  • J Barnhill
Gale, J., Koenig, R., Barnhill, J., 2001. Managing Soil pH in Utah. Utah State University Extension.
A Manual of Acarology, Third Edition
  • G W Krantz
  • D E Walter
Krantz, G.W., Walter, D.E., 2009. A Manual of Acarology, Third Edition. Texas Tech University Press, Lubbock, Texas.