Frankia inoculation,soil biota,and host tissue amendment influence Casuarina nodulation capacity of a tropical soil

The effects of soil biota, Frankia inoculation and tissue amendment on nodulation capacity of a soil was investigated in a factorial study using bulked soil from beneath a Casuarina cunninghamiana tree and bioassays with C. cunninghamiana seedlings as capture plants. Nodulation capacities were determined from soils incubated in sterile jars at 21 °C for 1, 7, and 28 days, after receiving all combinations of the following treatments: ± steam pasteurization, ± inoculation with Frankia isolate CjI82001, and ± amendment with different concentrations of Casuarina cladode extracts. Soil respiration within sealed containers was determined periodically during the incubation period as a measure of overall microbial activity. Soil respiration, and thus overall microbial activity, was positively correlated with increasing concentrations of Casuarina cladode extracts. The nodulation capacity of soils inoculated with Frankia strain Cj82001 decreased over time, while those of unpasteurized soils without inoculation either increased or remained unaffected. The mean nodulation capacity of unpasteurized soil inoculated with Frankia CjI82001 was two to three times greater than the sum of values for unpasteurized and inoculated pasteurized soils. Our results suggest a positive synergism between soil biota as a whole and Frankia inoculum with respect to host infection.     

叶凋落物数量和类型对森林土壤动物及其生物学质量的影响

评估森林凋落物的管理效应是一项重要的工作,本文在亚热带湖南会同林区,通过2011年5月布置的野外控制实验,采用区组设计和巢式设计,通过添加凋落物与否来检查凋落物的数量效应,添加阔或针叶凋落物来检查凋落物的质量效应,研究了叶凋落物对土壤动物群落的影响.在2012年7月对土壤动物多度、多样性、群落组成等指标进行测量,检测到跳虫多度对添加凋落物处理以及双翅目幼虫多度对凋落物类型处理有显著响应,其他指标包括土壤动物的群落组成和多样性则未能检测出显著效应.添加凋落物显著提高了土壤的生物学质量值,幅度达32.45％,且巢式方差分析显示这种增加与凋落物类型无关,表明在土壤质量演变的较早阶段,凋落物数量在该地区起到了更加重要的作用.由于土壤生物学质量比多度、多样性等指标要灵敏得多,因此基于土壤动物的土壤生物学质量指数可以作为评估森林凋落物管理效果的指标.     

蚯蚓和秸秆对铜污染土壤微生物类群和活性的影响

试验设置4个Cu浓度水平：0、100、200和400 mg·kg^-1 Cu²⁺,每个Cu浓度水平设置4个处理：对照(CK)、表施秸秆(M)、接种蚯蚓(E)、同时加入蚯蚓和秸秆(ME),研究了在Cu污染土壤中加入蚯蚓和秸秆对土壤微生物数量及活性的影响.结果表明：Cu污染、秸秆和蚯蚓均明显影响土壤微生物类群; Cu污染对细菌、放线菌具有抑制作用,而对真菌没有影响;秸秆显著提高了真菌数量;蚯蚓使土壤细菌、放线菌数量显著增加,而对真菌数量影响不大.Cu污染浓度＞200 mg·kg^-1处理对微生物量碳具有抑制作用;加入秸秆或蚯蚓,可显著提高土壤微生物量碳,而且同时加蚯蚓和秸秆处理土壤微生物量碳增加最显著.加入蚯蚓和秸秆后,土壤呼吸值显著增高.Cu<200 mg·kg^-1时,蚯蚓处理土壤呼吸值最大,平均比对照高3.06～5.58倍;Cu≥200mg·kg^-1时,蚯蚓、秸秆同时加入处理土壤呼吸值最高.4个处理土壤代谢商大小顺序为：ME>E>M>CK.蚯蚓和秸秆处理对土壤NH₄⁺-N没有影响,而对土壤NO₃^--N影响各异.接种蚯蚓,可显著提高土壤NO₃^--N含量;加入秸秆,可显著降低土壤NO₃^--N含量;同时加入蚯蚓和秸秆处理NO₃^--N含量最低.相关分析表明,土壤有效态Cu(DTPA-Cu)与土壤放线菌、细菌呈显著负相关,而与土壤呼吸、土壤NO₃^--N、NH₄⁺-N含量呈显著正相关.引入秸秆和蚯蚓,可在一定程度上减缓Cu污染对微生物数量和活性的影响.     

Effect of seed inoculation,mycorrhizal infection and organic amendment on wheat growth

Summary The effect of seed inoculation withAzotobacter spp. orAzospirillum spp., and garbage amendment (0.5%), on the growth of wheat was studied in a field experiment under sub-tropical conditions. Two levels of N fertilizer were applied, the usual field rate (150 kg N ha^–1) and half this amount. Tillering of plants, dry matter contents and nitrogenase activity were determined 30, 60 and 90 days after sowing. At the end of the experimental period, spore numbers and percentage of mycorrhizal infection were observed in the rhizosphere and root systems of plants. Straw and grain yields were also determined. The results of this study showed that seed inoculation and/or organic amendment stimulated plant growth, nitrogenase activity and mycorrhizal infection. This was more noticeable withAzotobacter than withAzospirillum. Inoculation withAzotobacter together with 1/2 N dose and organic amendment was the most effective application (19.75 and 10.70 t ha^–1 were recorded for straw and grain yield, respectively).     

Effect of leaf litter characteristics on leaf conditioning and on consumption by Gammarus pulex

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Differential responses of ammonia/ammonium-oxidizing microorganisms in mangrove sediment to amendment of acetate and leaf litter

The effects of acetate and leaf litter powder on ammonia/ammonium-oxidizing microorganisms (AOMs) in mangrove sediment were investigated in a laboratory incubation study for a period of 60 days. The results showed that different AOMs responded differently to the addition of acetate and leaf litter. A higher diversity of anaerobic ammonium-oxidizing (anammox) bacteria was observed when acetate or leaf litter was added than the control. However, acetate and leaf litter generally inhibited the growth of anammox bacteria despite that leaf litter promoted their growth in the first 5 days. The inhibitory effects on anammox bacteria were more pronounced by acetate than by leaf litter. Neither acetate nor leaf litter affected ammonia-oxidizing archaea (AOA) community structures, but promoted their growth. For ammonia-oxidizing bacteria (AOB), the addition of acetate or leaf litter resulted in changes of community structures and promoted their growth in the early phase of the incubation. In addition, the promoting effects by leaf litter on AOB growth were more obvious than acetate. These results indicated that organic substances affect AOM community structures and abundances. The study suggests that leaf litter has an important influence on the community structures and abundances of AOMs in mangrove sediment and affects the nitrogen cycle in such ecosystem.     

Growth of Frankia strains in leaf litter-amended soil and the rhizosphere of a nonactinorhizal plant

Verticillium leptobactrum , a rare fungal species, has repeatedly been isolated from serpentinic rocks in the Western Alps, thus suggesting that it adapts easily to this selective mineral substrate. The rRNA internal transcribed spacer region of several isolates has been sequenced to confirm their identity and taxonomic position within Verticillium , a recently revised polyphyletic entity. Isolates of V. leptobactrum have also been investigated to establish their ability to weather asbestos chrysotile, the most common mineral in the isolation sites. The results of solubilization assays on magnesium and silicon, as well as measurement of the Mg/Si ratio in the asbestos fibres after exposure to fungal mycelia, indicate a high bioweathering activity of V. leptobactrum towards chrysotile. Comparison with data on Fusarium oxysporum shows differences among species, with V. leptobactrum being more active than F. oxysporum in removing structural ions from chrysotile. Asbestos weathering by fungi could be envisaged as a bioremediation strategy for hazardous asbestos-rich soils (e.g. abandoned mines). Fungi that have adapted to live in serpentine sites could be good candidates for this purpose.     

Effects of water stress, organic amendment and mycorrhizal inoculation on soil microbial community structure and activity during the establishment of two heavy metal-tolerant native plant species

Our aim was to examine the effect of water stress on plant growth and development of two native plant species (Tetraclinis articulata and Crithmum maritimum) and on microbial community composition and activity in the rhizosphere soil, following the addition of an organic amendment, namely sugar beet residue (SBR), and/or the inoculation with an arbuscular mycorrhizal (AM) fungus, namely Glomus mosseae, in a non-sterile heavy metal-polluted soil. The AM inoculation did not have any significant effect on plant growth of both species. In T. articulata, SBR increased shoot growth, foliar P, total phospholipid fatty acids (PLFA), fungi-related PLFA, AM fungi-related neutral lipid fatty acid, bacterial gram-positive/gram-negative PLFA ratio and the β-glucosidase and dehydrogenase activities. SBR and AM inoculation increased phosphatase activity in T. articulata plants grown under drought conditions. In both plants, there was a synergistic effect between AM inoculation and SBR on mycorrhizal colonisation under drought conditions. In C. maritimum, the increase produced by the SBR on total amounts of PLFA, bacterial gram-positive-related PLFA and bacterial gram-negative-related PLFA was considerably higher under drought conditions. Our results suggest that the effectiveness of the amendment with regard to stimulating microbial communities and plant growth was largely limited by drought, particularly for plant species with a low degree of mycorrhizal colonisation.     

Effects of mycorrhizal fungi inoculation and soil amendment with hydrogel on leaf anatomy,growth and physiology performance of olive plantlets under two contrasting water regimes

Abiotic stresses present a real environmental problem in agriculture field. In our paper, we examine the significance of arbuscular mycorrhizal fungi (AMF) and soil amendment with water retaining superpolymers (hydrogel) on growth and physiology performance of olive plantlets. Our experiment was carried out in nursery conditions, to test the impact of hydrogel (TH) and mycorrhizal fungi (TM), used individually or combined (THM), and compare them with non inoculated plants (TC), to understand and reduce the water stress damage in olive plantlets (cv. Chemlali). We also evaluate interactions between hydrogel, mycorrhizal treatments and water regimes. Results of mycorrhization (M%) show that roots colonized by Rhizophagus irregularis of well-watered plants were about 40.87%. In combined treatment (THM), M% was about 32.14%. Compared to TC treatment, TM treatment enhances significantly the dry weights of the whole plant under the two water regimes. The TM treatment had the highest relative water content (66.50%) and Chl (a?+?b) (0.83 mg g^??1) in stressed conditions. We found also that under water stress, the maximal quantum efficiency of the photosystem II measurements in leaves were significantly improved by 50.70% in TH treatment compared to control. For phenolic contents, TH treatment decreased significantly total phenols by 50.10% compared to TC. Our study gives evidence that the use of AMF and the hydrogel separately or in combination may enhance the capacity to avoid drought damages of olive plantlets and improve olive performances.     

亚热带溪流中树叶凋落物多酚含量对树叶分解过程的影响

利用邻二氮菲-铁(Ⅲ)分光光度法测定了蒲桃与人面子树叶在二级溪流中分解时植物多酚含量的变化,并研究了多酚含量对树叶分解速率、底栖动物定殖以及微生物呼吸量的影响。结果表明,蒲桃叶片中初始多酚含量(19%)比人面子树叶的含量高(6%),其分解速率(分解系数k=0.01d^-1)比人面子树叶慢(k=0.04d^-1)。研究还发现,蒲桃叶片上的微生物呼吸量比人面子的低(每克叶片单位时间的耗氧量分别为0.2和0.4毫克),而且底栖动物中撕食者的种类和数量也比人面子树叶少。说明蒲桃叶片中较高的多酚含量抑制了微生物的活性和底栖动物的取食,从而减缓了蒲桃树叶的分解进程,表明叶片中多酚含量与树叶凋落物分解速率呈负相关关系。     

Preferential use of root litter compared to leaf litter by beech seedlings and soil microorganisms

Background and aims

Litter decomposition is regulated by e.g. substrate quality and environmental factors, particularly water availability. The partitioning of nutrients released from litter between vegetation and soil microorganisms may, therefore, be affected by changing climate. This study aimed to elucidate the impact of litter type and drought on the fate of litter-derived N in beech seedlings and soil microbes.

Methods

We quantified ¹⁵N recovery rates in plant and soil N pools by adding ¹⁵N-labelled leaf and/or root litter under controlled conditions.

Results

Root litter was favoured over leaf litter for N acquisition by beech seedlings and soil microorganisms. Drought reduced ¹⁵N recovery from litter in seedlings thereby affecting root N nutrition. ¹⁵N accumulated in seedlings in different sinks depending on litter type.

Conclusions

Root turnover appears to influence (a) N availability in the soil for plants and soil microbes and (b) N acquisition and retention despite a presumably extremely dynamic turnover of microbial biomass. Compared to soil microorganisms, beech seedlings represent a very minor short-term N sink, despite a potentially high N residence time. Furthermore, soil microbes constitute a significant N pool that can be released in the long term and, thus, may become available for N nutrition of plants.     

Decoupling litter barrier and soil moisture influences on the establishment of an invasive grass

Background and aims

Through recruitment, plants establish in novel environments. Recruitment also is the stage where plants undergo the highest mortality. We investigate the recruitment niche for Microstegium vimineum, an annual grass from East Asia spreading throughout eastern North American forests.

Methods

Current observational and greenhouse research indicates that M. vimineum recruitment may be inhibited by leaf litter and promoted by soil moisture; we use field studies to experimentally test how these factors influence M. vimineum germination, seedling survival and reproduction. Specifically, we introduce M. vimineum seeds into forest microhabitats with experimentally varied levels of soil moisture and leaf litter.

Results

Soil moisture increases M. vimineum germination regardless of leaf litter thickness and ameliorates seedling mortality in deep leaf litter. Seed production per m² increases with watering, reflecting higher germination and survival, whereas per capita seed production increases with leaf litter thickness, reflecting density-dependent limits on seed production.

Conclusions

The interactive effects of varied levels of soil moisture and leaf litter thickness on key M. vimineum life history stages highlight the need to consider multiple drivers, such as rainfall and local forest disturbance, when assessing how soil properties influence the establishment of invasive plants.     

The effects of a pesticide program on microbial populations from apple leaf litter

The leaf litter microbial community was quantitatively and qualitatively changed when a standard pesticide schedule that comprised an insecticide, a bactericide, and a fungicide was applied to McIntosh apple trees in the summer. Effects were observed for two winters by four indirect assays and three direct methods. Populations were altered qualitatively both years, but the most striking difference was the quantitative impact from year to year. Bacteria, filamentous fungi, and yeasts from treated leaves were reduced 10- to 10 000-fold between November 1976 and April 1977 and did not recover until snow cover had melted in March. Reductions in 1977-1978 were negligible. The marked seasonal difference is attributed to meteorological influences. Fluorescent pseudomonads were among the bacteria depressed by chemicals. Of the 49 genera of fungi and yeasts isolated, Coniothyrium sp., Penicillium spp., Arthrobotrys spp., and Nodulisporium sp. were appreciably reduced, whereas Typhula spp., Pleurophomella sp., Sporobolomyces spp., and Rhodotorula spp. were substantially enhanced by the spray program.     

Elevated UV-B radiation incident on Quercus robur leaf canopies enhances decomposition of resulting leaf litter in soil

We examined whether the exposure of Quercus robur L. to elevated UV-B radiation (280–315 nm) during growth would influence leaf decomposition rate through effects on litter quality. Saplings were exposed for eight months at an outdoor facility in the UK to a 30% elevation above the ambient level of erythemally weighted UV-B radiation under UV-B treatment arrays of fluorescent lamps filtered with cellulose diacetate, which transmitted both UV-B and UV-A (315–400 nm) radiation. Saplings were exposed to elevated UV-A alone under control arrays of lamps filtered with polyester and to ambient radiation under unenergised arrays of lamps. Abscised leaves from saplings were enclosed in 1 mm² mesh nylon bags, placed in a Quercus–Fraxinus woodland and were sampled at 0.11, 0.53, 1.10 and 1.33 years for dry weight loss, chemical composition and saprotrophic fungal colonization. At abscission, litters from UV-A control arrays had ≈ 7.5% higher lignin/nitrogen ratios than those from UV-B treatment and ambient arrays (P < 0.06). Dry weight loss of leaves treated with elevated UV-B radiation during growth was 2.5% and 5% greater than that of leaves from UV-A control arrays at 0.53 and 1.33 years, respectively. Litter samples from UV-B treatment arrays lost more nitrogen and phosphorus than samples from ambient arrays and more carbon than samples from UV-A control arrays. The annual fractional weight loss of litter from UV-B treatment arrays was 8% and 6% greater than that of litter from UV-A control and ambient arrays, respectively. Regression analyses indicated that the increased decomposition rate of UV-B treated litters was associated with enhanced colonization of leaves by basidiomycete fungi, the most active members of the soil fungal community, and that the frequency of these fungi was negatively associated with the initial lignin/nitrogen ratio of leaves.     

Decomposition and element concentrations of silver birch leaf litter as affected by boron status of litter and soil

Inadequate boron (B) nutrition can affect the structural integrity and chemical composition of plant tissues. The changes in mass and element concentrations were studied using silver birch (Betula pendula Roth) leaf litter from seedlings grown with or without added B (B_litter+ or B_litter?). The litter was produced in a growth room, and it was incubated in either B fertilised or control forest plots (B_soil+ or B_soil?) between the moss and humus layers in two Norway spruce stands for 13 months. Additionally, the field decomposition experiment included long-term N and P application treatments (N_soil and P_soil). B_litter+ somewhat reduced the remaining litter mass. In contrast, B_soil+ increased it, possibly because of lower soil pH. The +N_soil treatment reduced the remaining mass. B_litter+ increased the remaining P, S, Cu, Cd, Ni and Zn but reduced Pb. Remaining B was high in the B_litter– which also accumulated B from soil. B_soil increased remaining Ca, Cd, Mg, Na, Pb, and slightly reduced N (in N fertilised plots). These changes in decomposition and element release have a potential to affect nutrient, carbon, and heavy-metal cycles in areas where B deficiencies are common, and where B fertilisation is practised.     

Effect of small reservoirs on leaf litter decomposition in Mediterranean headwater streams

Leaf litter decomposition is a crucial process providing matter and energy to communities inhabiting headwater streams. This process could be affected by many man-made landscape transformations and its response can vary depending on the climate setting. In this study, we test the hypothesis that the presence of small headwater reservoirs decreases litter decomposition downstream, as reported for temperate Oceanic climatic regions, and that this effect is more accentuated in the Mediterranean. The effect of small dams on the decomposition of alder (Alnus glutinosa) leaves was studied in four headwater streams in Catalonia (NE Spain). The presence of a dam affected litter decomposition rates in three of the four streams studied, and this depended on reservoir typology. In those with seasonal surface release, decomposition rates were slower downstream from the dams, but in the case of a continuous hypolimnetic release, it was faster, with higher DIN and temperature and abundance of shredders. Alder litter decomposition rates were twice those reported for Oceanic climatic conditions. In Mediterranean headwaters, the effect of small dams will even be more evident at an annual scale due to the diminished flow rates in summer and this effect will be more pronounced than in the more Oceanic.     

Effect of litter substrate quality and soil nutrients on forest litter decomposition: A review

Forest litter plays an important role in determining nutrient cycling, balance and maintaining ecosystem function of forest ecosystems. Studies have shown that litter substrate quality is one of the most important factors affecting litter decomposition in a given area. It is, hence, important to understand the factors controlling litter decomposition in the late decomposition stage and determining organic matter changes over the duration of litter decomposition. Decomposition rate of mixed litter may differ with that of a single specie litter. Supply of soil nutrients is an important factor controlling litter decomposition rate, because the essential nutrients in soil or litter material influence community and activity of decomposers (soil organisms). There were clear relationships among soil nutrient, litter substrate quality, and decomposition. Soil nutrient contents were positively correlated with litter substrate quality, showing that higher contents of soil nutrient were accompanied with good quality of litter substrate, and lower soil nutrients with poor litter quality. The effects of soil fertility on litter decomposition rate varied with environmental conditions. It was reported that litter quality regulates the early stage of carbon decomposition and its accumulation in soil, however, it could not predict the long-term dynamics of soil organic carbon. Hence, the formation and stabilization of soil organic carbon are controlled by the quantity of litter input and its interaction with the soil circumstances rather than by the litter quality. The present paper reviewed the research findings about litter decomposition related to litter substrate quality and soil nutrients, including short-term and long-term litter decomposition, decomposition of single-species vs. mixed-litter decomposition and litter nutrients release. The present paper aimed to clarify the relationship between soil nutrients and litter decomposition, which will help to understand forest succession, forest water conservation and soil re-production capacity.     

Effects of soil disturbance,fire and litter accumulation on the establishment of Cistus clusii seedlings

Cistus clusii is an early successional shrub, the most drought-resistant species of Cistus which colonises perturbed areas in the southern Iberian Peninsula and regenerates entirely from seeds after a fire. Some of the factors controlling germination and seedling establishment were examined in a field experiment in which we tested the effect of soil disturbance, fire, and litter accumulation on seedling emergence. In a first experiment, soil disturbance and fire were applied to plots in the field with a factorial design in April 1992. In a second experiment, we measured the effect of adding C. clusii litter. The number of seedlings, annual plants and grasses, and the coverage of mosses were recorded in 1993 and 1994.Soil disturbance increased the number of C. clusii seedlings almost seven-fold but did not change the number of grasses, annual plants nor moss cover. Fire significantly increased the number of C. clusii seedlings only in combination with soil disturbance, and it did not affect the presence of annuals, grasses nor moss cover. Litter increased the number of C. clusii seedlings in the following two years.Overall, soil disturbance as a single factor had the most significant effect on seedling emergence, though plots disturbed and treated with fire had the highest number of seedlings, implying that germination of C. clusii seeds was enhanced by processes that alter the hard seed coat and break the physical dormancy imposed by the testa. In addition, recruitment of C. clusii was dependent on rainfall, as drought significantly reduced the number of seedlings appearing in winter.     

The effect of microhabitats on the leaf litter decomposition and on the distribution of soil animals

Earthworm burrows as microhabitats for other soil fauna were studied in a hornbeam-oak mixed forest in Hungary. Comparative chemical analysis and feeding experiments were carried out to find out whether the leaves in the burrows of large-bodied earthworms are more decomposed than those from the surrounding areas. The total organic matter content, the C/N ratio, the stability coefficient and the percentage of tannins and lipids indicate that the chemical breakdown of the litter material is more advanced in the burrows than on the other parts of the forest floor especially in autumn. No consistent differences were observed in the amounts of other organic components. Feeding experiments showed that three species of the fauna preferred the leaves pulled into the burrows to those from the surrounding areas and the preference was greater in autumn than in spring.
It is suggested that the high density of some soil animals in the burrows in autumn is due to the more palatable food there; in summer the microclimate of the burrows is favoured, whereas spring can be considered as a transition period.