Leaf Litter Samples Research Articles

Two new species of Cavernocepheus (Acari, Oribatida, Otocepheidae) from Mexico

Two new species of Cavernocepheus (Cavernocepheus): C. (C.) icpallitelleriani n. sp. and C. (C.) xipetoteci n. sp. are described. These species were obtained from soil and leaf litter samples of conifers, collected in the states of Michoacan and Veracruz, Mexico, respectively. Cavernocepheus (Cavernocepheus) icpallitelleriani n. sp. is distinguished from existing species by the presence of a long, pointed projection of the internal zone of the lateral notogastral condyles. Cavernocepheus (Cavernocepheus) xipetoteci n. sp. differs from Cavernocepheus (Cavernocepheus) longicristatus Ermilov, 2024 by the shape of the bothridial setae, size of the notogastral setae and shape of u setae.

Design and partial validation of novel eDNA qPCR assays for three common North American tick (Arachnida: Ixodida) species

AbstractThe range expansion of ticks to higher latitudes poses a severe threat to human health exposing human populations who had no prior contact with ticks to several harmful tick‐borne diseases. Early detection of ticks in new areas is critical to help inform the public and medical professionals of the dangers associated with tick encounters. Environmental DNA represents a novel survey method that could provide reliable records of tick occurrences and timely warnings of their range expansions. In this study, we designed novel eDNA qPCR assays for three common North American tick species (Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis) and tested them on 51 samples of grasses and leaf litter collected from 12 grassland and forest sites in central and southern Illinois. We provide in silico and in vitro validation of all three assays; however, we were unable to generate any positive detections from field samples. Our lack of eDNA detections likely stems from low eDNA deposition rates coupled with rapid degradation in grasslands and forests, a problem exacerbated by terrestrial eDNA sampling methods limited by volume of substrate. We provide recommendations for improving sample collection methods to increase detection probability in future efforts. Continued research should focus on the viability of eDNA to detect small terrestrial invertebrates, like ticks, and it potential as early warning indicator of the spread of vector‐borne diseases.

Ant communities respond to a large‐scale disturbance along an elevational gradient in Puerto Rico, U.S.A.

AbstractLarge scale disturbances are known to significantly alter aspects of both species diversity and ecosystem function. In the Caribbean, hurricane events are a significant form of disturbance, the effects of which have been shown to alter food web function, especially in the terrestrial environment. Although hurricanes have been studied from a variety of their effects on ecosystems, there is little research on how these storms affect species along elevational gradients. Within terrestrial habitats, ants form the basis of many food webs, being both numerically dominant and functioning in a variety of roles within the food web. On September 20th, 2017 Hurricane Maria, a category 4 storm, crossed over the island of Puerto Rico, causing significant damage to both human and natural systems. We collected data on ant abundance and composition from 150 samples of leaf litter along a 700 m elevational gradient during June the year of and after the storm event. Ant abundance increased by 400% after the storm with many common ant species seeming to benefit, especially at lower elevations. There were subtle changes in ant richness, with declines generally after the storm, but yet again this response was dependent on elevation. This is one of the first studies to consider how terrestrial insect communities are affected by large hurricane events across elevations, and our results are in contrast to past work showing declines in ant abundance after such storms.Abstract in Spanish is available with online material.

Litter-dwelling terrestrial molluscs of Nepisiguit Protected Natural Area and Mount Carleton Provincial Park, north-central New Brunswick

No comprehensive study of the terrestrial gastropod fauna of northern New Brunswick has previously been undertaken. Most terrestrial gastropod molluscs are tiny and generally live unnoticed under debris, in leaf litter, and among other dead and living vegetation. Sifting and sorting collected samples of leaf litter are effective in sampling snails. In June–July 2015 and August 2016, 43 samples of forest leaf litter were collected in Nepisiguit Protected Natural Area and Mount Carleton Provincial Park. These samples yielded 22 species of terrestrial gastropods. Seven species are reported from New Brunswick for the first time.

Occurrence of myxomycetes in selected elevated urban residential gardens in Metro Manila, Philippines

Roof-top gardens in low- and high-rise urban residential buildings are common in many urban cities for their aesthetic value and perceived health benefits for the building occupants. Leaf litter from plant communities in these gardens offer suitable microclimate conditions and substrates that can support growth and development of myxomycetes. Myxomycetes, also called slime molds, play a role in maintaining the soil microbiome, and can influence the microbial communities in these residential gardens. In this study, 204 ground leaf litter samples of ornamental woody shrubs and herbaceous flowering plants were collected from elevated gardens in eight low-to-high rise buildings for the preparation of moist chambers (MC). A total of 14 species of myxomycetes belonging to nine genera were recorded and identified in this study: Arcyria cinerea, Collaria arcyrionema, Diachea leucopodia, Diderma effusum, Diderma hemisphaericum, Didymium nigripes, Didymium sp., Didymium squamulosum, Ophiotheca chrysosperma, Perichaena cf. corticalis, Perichaena depressa, Physarum album, Physarum cinereum, and Stemonitis cf. pallida. Overall MC productivity ranged from 43 to 45%. In terms of species abundance, Arcyria cinerea and Perichaena depressa were among the most recorded myxomycetes. The study provided evidence of rooftop gardens as suitable habitats for myxomycetes.

Invasion of farmland hedgerows by non-native small mammals is associated with lower soil surface invertebrate diversity, abundance, body size and biomass

Small mammals in farmland hedgerows feed on soil surface invertebrates with non-native invasive species potentially affecting prey species and populations. We investigated terrestrial invertebrates using pitfall traps and leaf litter samples across four zones of invasion in Ireland: (1) native species only (wood mouse Apodemus sylvaticus and pygmy shrew Sorex minutus), (2) natives plus the non-native bank vole (Myodes glareolus), (3) natives plus the non-native greater white-toothed shrew (Crocidura russula) and (4) natives plus both. After accounting for regional and local environmental variation, small mammal invasion was associated with lower invertebrate species richness (9–39% lower than uninvaded zones), reduced abundance (18–56% lower), shorter arthropod body length (24–52% shorter) and lower arthropod biomass (63–89% lower). Negative effects were observed on a wide range of disparate functional groups spanning phytophagous, detritivorus, zoophagous and omnivorous taxa including: the Staphylinidae, Carabidae and Coleoptera larvae, Isopoda, Diplopoda, Diptera, Hymenoptera, Pulmonata and Acari. The greater white-toothed shrew had greater negative effects than the bank vole with presence of both having greater effects than either alone though the majority of their combined effects were largely attributable to the former. The bank vole may mitigate some of the negative effects of the greater white-toothed shrew on invertebrate abundance perhaps indicating of some form of trophic interaction. Predation of detritivores and large invertebrate predators may impact farmland ecosystem service delivery i.e. nutrient cycling and pest biocontrol. Hedgerow biodiversity loss may induce indirect trophic cascades negatively impacting other taxa including farmland birds.

New species of Miradiscops (Gastropoda: Scolodontidae) from Martinique

Only 17 endemic land snail species are known so far on the Lesser Antillean island of Martinique, most of which are macrogastropods that are easily visible, and thus, easily collectable. On the other hand, species of microgastropods remain undersampled and overlooked. Based on recently collected shells from Mount Vauclin, we describe a new species of Scolodontidae, Miradiscops madinina sp. nov. from Martinique. This is the first recorded incidence of Miradiscops stricto sensu from the volcanic arc of the Lesser Antilles, as well as the second species of Scolodontidae recorded from Martinique. This emphasises the importance of Mount Vauclin as a home to endemic invertebrates on the island and the need for collection efforts that includes soil and leaf litter sampling.

Sampling local ant diversities and the importance of trait analyses

AbstractAnts are an incredibly diverse and ubiquitous group of invertebrates in most terrestrial ecosystems. Although extensively sampled, the majority of ant inventories do not evaluate the effect of different sampling techniques in capturing nontraditional metrics of diversity. We aimed to quantify TD (taxonomic) and FD (functional) diversities for a local ant assemblage by integrating metrics and evaluating complementarity of pitfall traps and Winkler extractors for the leaf litter versus epigeic ant faunas and to determine the effect of sampling techniques on functional composition (community‐weighted means of 11 morphological traits) and functional diversity (multi‐trait morphospace measured with three different metrics). We sampled the local community in an Atlantic Forest fragment using week‐long pitfall traps and 1m2 leaf litter samples submitted to Winkler extractors and quantified the contribution on the technique to uniquely capture the ant morphospace by applying a new index (PWindex). Although ant TD overlapped, FD was significantly affected by the sampling technique. By controlling for TD effects, the community collected by each technique was differentially structured. Higher TD did not translate into wider morphospace for Winklers. Pitfalls recovered more functionally overdispersed assemblages. Pitfalls and Winklers overlapped in the sampling of the overall community, but each sampling method contributed with a unique spectrum to the ant morphospace. Our results suggest the importance of incorporating FD metrics in local ant inventories and the importance of sampling techniques when measuring the magnitude of FD and community structure. Our PWindex further illuminates sampling effects for ant assemblages.Abstract in Portuguese & Spanish is available with online material.

Effects of Forest Management Approach on Carbon Stock and Plant Diversity: A Case Study from Karnali Province, Nepal

The mitigation of global warming and conservation of biodiversity are two significant environmental challenges today. Estimating and comparing forest carbon stock and plant diversity under different management approaches provide insight into the choice of management approaches for carbon and plant diversity management. We investigated the variation in carbon stock and diversity of plant species in two forest managements under different approaches: the Kakrebihar protection forest (PF) and Sano Surkhet community forest (CF) in Karnali Province, Surkhet, Nepal. In total, 63 sample plots (30 plots in PF and 33 plots in CF) were laid out systematically across the forests. Dendrometric measurements were carried out for trees, poles, and saplings, and representative leaf litter and herb samples were collected. Soil samples were taken at 10 cm, 20 cm, and 30 cm depths using a soil auger. The existing tree volume equations of tree species of interest were used to estimate tree volume, and species-specific wood density and conversion factors were used to obtain total biomass and carbon content. Soil samples were analyzed using the Walkley-Black method to determine soil organic carbon. PF had higher carbon stock, plant species richness, and abundance at the landscape level than CF; however, the scenario differed at the plot level. At the plot level, PF had significantly higher total carbon stock and biomass carbon stock than CF. However, PF and CF were statistically indistinguishable in term of soil carbon stock. At the plot level, PF and CF were statistically indistinguishable regarding richness, Simpson diversity, and Shannon diversity, but PF had significantly higher plant abundance than CF. In conclusion, the value of PF for carbon stock and plant diversity surpassed those of CF. This study suggests that PF might be a better strategy to enhance carbon stock in forests and maintain habitat for various plant species.

Appendage-Bearing Sordariomycetes from Dipterocarpus alatus Leaf Litter in Thailand.

Leaf litter is an essential functional aspect of forest ecosystems, acting as a source of organic matter, a protective layer in forest soils, and a nurturing habitat for micro- and macro-organisms. Through their successional occurrence, litter-inhabiting microfungi play a key role in litter decomposition and nutrient recycling. Despite their importance in terrestrial ecosystems and their abundance and diversity, information on the taxonomy, diversity, and host preference of these decomposer taxa is scarce. This study aims to clarify the taxonomy and phylogeny of four saprobic fungal taxa inhabiting Dipterocarpus alatus leaf litter. Leaf litter samples were collected from Doi Inthanon National Park in Chiang Mai, northern Thailand. Fungal isolates were characterized based on morphology and molecular phylogeny of the nuclear ribosomal DNA (ITS, LSU) and protein-coding genes (tub2, tef1-α, rpb2). One novel saprobic species, Ciliochorella dipterocarpi, and two new host records, Pestalotiopsis dracontomelon and Robillarda australiana, are introduced. The newly described taxa are compared with similar species, and comprehensive descriptions, micrographs, and phylogenetic trees are provided.

Leaf litter combustion properties of Central European tree species

AbstractTemperate forests of Central Europe are exposed to increasing fire risk. However, little is known about combustion properties of leaf litter, which plays an important role in the spread of surface fires. We used cone calorimetry to compare combustion properties of leaf litter samples from seven common tree species of Central European forests by reconstructing a litter layer of original depth in sample holders with a size of 10 cm × 10 cm. In addition to mono-specific leaf litter beds, combustion experiments included mixtures of different litter types, mixtures of litter and bryophytes and one mixture of litter and fine woody debris, totalling to 13 different setups (i.e. litter types). Recorded combustion properties included ignitability, flaming duration and heat release. Differences in combustion properties were analysed using analyses of variance followed by pairwise post-hoc tests. Combustion properties mainly differed between different litter types (broadleaf, pine needle, short needle). Highest total and peak heat release were observed for Scots pine (Pinus sylvestris), while peak heat release rates showed only minor differences for litter of the remaining species. Broadleaf litter was characterized by highest ignitability. For short-needle litter, we observed long flaming duration and incomplete combustion, resulting in the lowest total heat release on a sample mass basis. For litter mixtures of pine and broadleaf litter, we observed lower peak heat release rates in comparison to mono-specific pine litter. Mosses reduced peak heat release rates and increased the proportion of unburned biomass. However, the magnitude of this effect differed between bryophyte species included in the mixtures. The addition of fine woody debris strongly increased total heat release, highlighting the importance of fine woody fuels for fire behaviour. The results of this study provide valuable baseline information on combustion behaviour of leaf litter from Central European forests. Due to the limitations of laboratory combustion experiments to reproduce conditions of real forest fires, there is a need for future field studies investigating fire behaviour under natural conditions.

青海云杉林凋落物分解早期微生物生物量时空动态变化

PDF HTML阅读 XML下载 导出引用 引用提醒 青海云杉林凋落物分解早期微生物生物量时空动态变化 DOI: 10.5846/stxb202203220711 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31901130）；中国地质调查局地质调查项目（DD20208065） Temporal and spatial changes of microbial biomass in litter decomposition early process in Qinghai spruce (Picea crassifolia) forests Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:凋落物分解过程中的微生物生物量动态对于深入了解森林生态系统凋落物分解机理具有重要意义。为了解高寒山地森林典型树种凋落物分解过程中的微生物生物量动态特征，采用凋落物袋野外原位分解法，研究了海拔2850 m、2950 m、3050 m、3150 m和3250 m树冠中心（CC）与树冠边缘（CE）青海云杉（Picea crassifolia）叶凋落物分解过程中凋落物和土壤中的微生物生物量碳（MBC）、微生物生物量氮（MBN）和微生物生物量磷（MBP）时空动态变化。时间尺度上，不同海拔CC与CE凋落物中的MBC、MBN和MBP在生长季节初期上升，生长季节后期下降；但土壤中的MBC、MBN和MBP却在生长季节初期下降，生长季节后期上升。然而，3050 m海拔CE和3250 m海拔土壤中的MBP含量呈"先下降-后上升-再下降"的倒"N"型变化格局。空间尺度上，凋落物中的MBC和MBN含量高于土壤中的，但MBP出现相反情况；CE处的MBC、MBN和MBP含量均显著（P<0.05）高于CC；总体而言，MBC、MBN和MBP含量以中海拔显著最高（P<0.05），其次为低海拔，高海拔显著最低（P<0.05）。这些结果为清晰地认识高寒山地森林凋落物分解过程及机理，以及进一步理解陆地生态系统结构和功能奠定了基础。 Abstract:Microorganism plays an important role in litter decomposition, and the change of microbial biomass is of ecological significance in understanding the mechanism of litter decomposition in the forest ecosystem. In order to understand the dynamic characteristics of microbial biomass during litter decomposition process in the Qinghai spruce forest, Qilian Mountains, we collected leaf litter samples at the crown center (CC) and crown edge (CE) by decomposition litterbags in different times (the early growing season and the late growing season) and altitudes (i.e., 2850 m, 2950 m, 3050 m, 3150 m and 3250 m). The temporal and spatial changes of microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and microbial biomass phosphorus (MBP) in litter and soil were analyzed. Temporally, the MBC, MBN and MBP increased in the early growing season and decreased in the late growing season. On the contrary, the MBC, MBN and MBP in soil decreased in early growing season and increased in late growing season. However, the content of MBP in soil at CE of 3050 m altitude and 3250 m altitude showed an inverted "N" shaped pattern, that is, "decrease-rise-decrease". Spatially, the contents of MBC and MBN in litter were higher than those in soil at all plots, but MBP was the opposite. The contents of MBC, MBN and MBP at the CE were significantly (P<0.05) higher than those at the CC. In general, the contents of MBC, MBN and MBP were the highest at medium altitude (P<0.05), followed by low altitude, and then the lowest at high altitude (P<0.05). The results would lay foundation to understand the process and mechanism of litter decomposition in the alpine mountain forest ecosystem, and further understand the structure and function of the ecosystem. 参考文献 相似文献 引证文献

Effects of resource size on invertebrate assemblages in water-filled treeholes

Water-filled treeholes are important habitat patches for aquatic invertebrates in forest ecosystems. A detailed understanding of the interspecies relationships that occur within them will help in understanding how invertebrate diversity is maintained in forests, particularly with respect to resource utilization. The sequential use of the same food resource among several different species is called a processing chain. In this study, we focused on the aspects of leaf litter in the treeholes as a food and habitat resource, and tested the following hypotheses using artificial containers as treeholes with three different leaf litter samples categorized as “untreated”, “fragmented”, and “pulverized”: (1) inorganic ions would leach out as leaf fragmentation progresses, resulting in water acidification, which consequently affects invertebrates. (2) filter-feeder species that consume microorganisms and fine particle organic matter increase as leaf fragmentation progresses. (3) differences in the size of leaf litter fragments affect the inhabitant species and cause differences in the assemblage structure of invertebrates. We observed an increase in pH and dissolved oxygen (DO) with increasing the fragmentation of leaf litter; however, the results were marginally non-significant. The assemblage composition of aquatic invertebrates did not show clear patterns in relation to the leaf litter treatments. Invertebrate assemblages from treeholes with pulverized leaf litter appeared to be associated with increasing DO. We found that the filter-feeder Tripteroides bambusa (Diptera: Culicidae) was dominant under conditions where treeholes contained fine particles of leaf litter, while the benthic inhabitant Ceratopogonidae sp. (Diptera) dominated under conditions with coarse leaf litter fragments. Our results suggest that fragmentation of leaf litter may have different effects on the different dominant species. We conclude that resource processing does not necessarily have positive effects on the species.

Leaf litter decomposition and its drivers differ between an invasive and a native plant: Management implications.

Litter decomposition is a key process of the carbon cycle in terrestrial and aquatic ecosystems. The dominant conceptual model of litter decomposition assumes that environmental conditions, litter traits, and decomposer composition control litter decomposition in a decreasing order, yet whether this hierarchical model applies to both invasive and native plant species is unknown. Here, by comparing a widespread invasive plant and its native counterpart in Chinese coastal saltmarshes, we aimed to examine whether the hierarchy of factors controlling litter decomposition varies with plant species in the face of plant invasions. Leaf litter of invasive Spartina alterniflora and native Phragmites australis was collected across an 18° latitudinal range to capture wide variation in litter traits. These leaf litter samples were transported to three saltmarsh sites of different latitudes and were incubated in litterbags varying in mesh size (0.1, 2, and 5mm) to manipulate decomposer composition. After 90-day incubation, we found a parallel latitudinal pattern in leaf litter decomposition rate (k) between S. alterniflora and P. australis regardless of saltmarsh site and mesh size. Nonetheless, the k value of S. alterniflora was 2.2-fold higher than that of P. australis. Moreover, there was a shift in the hierarchy of factors controlling k values between S. alterniflora and P. australis: environmental conditions (climate and soil) dominated other factors in P. australis, whereas litter traits contributed more than environmental conditions in S. alterniflora. Overall, our findings show that leaf litter decomposition and its dominant controlling factors across broad geographical ranges can vary with plant invasions, having important implications for managing invasive plants in the context of conserving coastal blue carbon.

Leaf-litter-dwelling microsnails of Prince Edward Island, Canada (Mollusca, Gastropoda, Eupulmonata)

Samples of leaf litter were collected from 22 woodland sites throughout Prince Edward Island, Canada. Eighty-two specimens belonging to 15 species of litter-dwelling land snails were recovered from 20 of the 22 samples. One-third of the species—Carychium exile H.C. Lea, 1842, Helicodiscus shimeki Hubricht, 1982, Strobilops labyrinthicus (Say, 1817), Perpolita binneyana (Morse, 1864), and Striatura ferrea Morse, 1864—were previously undocumented in the literature as occurring in PEI. Leaf-litter sampling, even in smaller quantities, is an effective method for finding the often-neglected terrestrial mollusc fauna, which is composed largely of minute species.

Assessing the immediate impacts of the 2019/2020 bushfires on land snails in north-eastern New South Wales

ABSTRACT This study aimed to improve our understanding of the immediate response of 26 priority species of land snail that may have been severely impacted by the 2019/2020 megafire event in north-eastern New South Wales. Our study covered a range of ecosystem types over an area of approximately 20,400 km2. We searched 70 survey sites that differed in burn severity for all species of land snail visually on-site and by sifting leaf litter samples under a microscope in the laboratory. These survey sites were selected for representing pre-existing occurrence records of priority species at sites that differed in mapped fire severity classes as based on Fire Extent and Severity data available from public sources. We also surveyed unburnt sites for comparative purposes. We found that nearly all survey sites encompassed a patchwork of areas with different burn extent and severity and that more humid forest types were overall affected by lower fire extent and severity than surrounding more xeric forest types. Only one site with extreme fire extent and severity was surveyed. The survey covered 165 historical occurrence records, 96 of which (58%) were re-confirmed. We also found 55 new occurrence records, 11 of which were in burnt and 44 in unburnt sites. Burnt and unburnt sites showed slight, yet insignificant differences in the redetection rate of species, which was generally low (on average 50–65%). Our data does not reveal an association between the number of specimens found at sites and burn severity and extent (from unburnt to extreme burnt). While we infer that populations have declined in areas affected by more severe fires, we found proportions of the survey area to be affected by fires of lower severity, which likely did not substantially affect the size of local land snail populations. Based on this, we conclude that initial concerns that the bushfires had led to a substantial deterioration of the conservation status of land snails are not generally corroborated. Instead, we have assessed just 3 species (10% of all studied species) as of conservation concern and 7 species (23%) as near threatened due to direct impacts of the 2019/2020 megafires. However, the paucity of occurrence records for many species and our limited knowledge of their ecology hampers a more detailed assessment of the potential fire impacts on many species, including possible on-going threats. Long-term monitoring and research are critical to ensure effective management especially of narrow range endemics.

Distributions and impacts of plutonium in the environment originating from the Fukushima Daiichi Nuclear Power Plant accident: An overview of a decade of studies

This paper reviews the current knowledge on plutonium (Pu) isotopic composition (the atom or activity ratios) and activity concentrations of 238Pu, 239Pu, 240Pu, and 241Pu resulting from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011. In this critical review, we document the characteristic values of Pu atom or activity ratios (fingerprints) and present their spatial distributions around the FDNPP site. Based on multiple Pu fingerprints (238Pu/239+240Pu activity ratio, 240Pu/239Pu atom ratio, and 241Pu/239Pu atom ratio), we clarify that Pu contamination from the FDNPP accident occurred in a restricted terrestrial area, while Pu in the Northwest Pacific Ocean is still predominately sourced from the Pacific Proving Grounds (PPG) and global fallout. Using a simple two end–member mixing model, we calculate average contributions of Pu from the FDNPP accident of 13 ± 20% (n = 180) in soil samples, 55 ± 32% (n = 38) in leaf litter samples, and 67 ± 26% (n = 129) in air dust/black substances. In the marine environment, the PPG source average contributions are 45 ± 15% (n = 76) in seawater and 42 ± 12% (n = 48) in sediments. The spatial distributions of Pu atom or activity ratios based on existing studies suggest that: 1) in the terrestrial region investigated 80 km northwest of the FDNPP site, the Pu contamination is mainly observed in an area within a 50 km distance, and 2) in the terrestrial region investigated 60 km southwest of the FDNPP site, the Pu contamination is mainly observed in an area within a 30 km distance. Studies of Cs-bearing radioactive particles indicate that Pu occurs as Pu oxide, and the fuel fragments containing Pu that were released from the reactors to the surrounding environment are associated with micron-scale Cs-bearing radioactive particles. We note that the fractionation between Pu and other radionuclides occurred after release. These new findings about the Pu fingerprints around the FDNPP site will help researchers to establish a reference background database for future environmental risk assessment and geochemical study there.

Soil phosphorus fractions and their relation to leaf litterfall in a central Amazonian terra firme rainforest

ABSTRACT Phosphorus (P) cycling is an important yet poorly studied aspect of the macronutrient balance in tropical rainforest ecosystems. As soil P occurs in different organic and inorganic forms (fractions) with varying degrees of lability, we hypothesized that these fractions will vary between soil types, and temporally within soil types. Additionally, we hypothesized a direct influence of leaf litterfall P input on soil total P and soil P fractions. We collected soil and leaf litter samples from three soil types in a central Amazonian lowland rainforest in Brazil over five months, and used a modified Hedleys fractionation method to determine six organic and inorganic soil P fractions, and also total, labile and residual P. Leaf litterfall P concentrations were determined colorimetrically. Soil inorganic and organic P fractions varied between soil types and across months, but soil type and month interactions were mostly non-significant. Some inorganic P fractions (Pi-NaOH) peaked while the organic fractions (Po-NaOH) fell and vice versa. Leaf litterfall production and leaf litterfall P input peaked around two months following the wettest month. Leaf litterfall P input was a significant predictor of Po-NaHCO3, a bioavailable P fraction. Future studies on P cycling in terrestrial ecosystems should examine the roles played by individual soil P fractions as they cycle asynchronistically and differently across soil types.

Pseudomonas syringae on Plants in Iceland Has Likely Evolved for Several Million Years Outside the Reach of Processes That Mix This Bacterial Complex across Earth's Temperate Zones.

Here we report, for the first time, the occurrence of the bacteria from the species complex Pseudomonas syringae in Iceland. We isolated this bacterium from 35 of the 38 samples of angiosperms, moss, ferns and leaf litter collected across the island from five habitat categories (boreal heath, forest, subalpine and glacial scrub, grazed pasture, lava field). The culturable populations of P. syringae on these plants varied in size across 6 orders of magnitude, were as dense as 107 cfu g−1 and were composed of strains in phylogroups 1, 2, 4, 6, 7, 10 and 13. P. syringae densities were significantly greatest on monocots compared to those on dicots and mosses and were about two orders of magnitude greater in grazed pastures compared to all other habitats. The phylogenetic diversity of 609 strains of P. syringae from Iceland was compared to that of 933 reference strains of P. syringae from crops and environmental reservoirs collected from 27 other countries based on a 343 bp sequence of the citrate synthase (cts) housekeeping gene. Whereas there were examples of identical cts sequences across multiple countries and continents among the reference strains indicating mixing among these countries and continents, the Icelandic strains grouped into monophyletic lineages that were unique compared to all of the reference strains. Based on estimates of the time of divergence of the Icelandic genetic lineages of P. syringae, the geological, botanical and land use history of Iceland, and atmospheric circulation patterns, we propose scenarios whereby it would be feasible for P. syringae to have evolved outside the reach of processes that tend to mix this bacterial complex across the planet elsewhere.

Soil Fauna of Ranibari Community Forest, Kathmandu, Nepal

Abstract Ranibari Community Forest (RCF) is the important forest patch present within the highly urbanized Kathmandu Valley with information gaps on soil fauna. This study aimed to explore the soil meso and macrofauna of the forest. Fourteen random quadrats (1 × 1 m2) were laid within seven blocks. Leaf litter samples and soil cores were collected, screened, sieved, and searched under a white sheet, once a fortnight from May to November 2019. The results showed that the diversity, abundance, and richness of soil fauna were the highest in the summer season (H´ = 2.897, abundance = 1,973, S = 84) dominated by Collembola. The Soil Biological Quality Index (QBS-ar) value was also found to be the highest in summer (QBS-ar = 417) and successively decreased in succeeding seasons. Soil fauna was diverse and evenly distributed in soil layers throughout the seasons, but the abundance was greater in leaf litters, particularly in summer. Fauna like Chilopoda, Diplopoda, Haplotaxida, and Isopoda were seen to be affected negatively by soil temperature in summer and autumn seasons. Soil moisture content was found to be positively correlated with immature insects, earthworms, and millipedes in the rainy and autumn seasons. Besides, the pH of the soil was seen to affect Diplura only in the autumn season. The relation of fauna with the physicochemical parameters (temperature, moisture, and pH) and also with other taxa showed their ecological roles and adaptation to a specific microclimate.