Azadirachta indica A. Juss, Dalbergia, sissoo Roxb., and Melia azedarach L. are little studied species in nutrient return capabilities from leaf litter decomposition to maintenance of the soil fertility despite their ...Azadirachta indica A. Juss, Dalbergia, sissoo Roxb., and Melia azedarach L. are little studied species in nutrient return capabilities from leaf litter decomposition to maintenance of the soil fertility despite their importance in agroforestry practices of Bangladesh. A leaf litter decomposition experiment was conducted using a litterbag teeh7 nique to assess the nutrient reaun efficiency of these species. The de- composition rate of leaf litter was highest for M. azedarach and lowest for D. sissoo. Rainfall and temperature of study sites showed a significant (p〈0.05) positive relationship with the rate of leaf litter decomposition. The highest decay constant was observed for M. azedarach (6.67). Nitrogen and Phosphorus concentration in leaf litter showed a decreased trend sharply at the end of the first month, whereas rapid decrease of Potassium concentration was reported within 10 days. Conversely, higher concentration of nutrient was observed at the later stages of decomposition. All three species showed a similar pattern of nutrient release (K 〉 N 〉 P) during the decomposition process of leaf litter. Among the studied species, D. sissoo was best in terms of N and P return and A. indica was best in terms of K return.展开更多
Dissolved organic matter(DOM) represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM ...Dissolved organic matter(DOM) represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM from seagrass leaves contributed to the coastal biogeochemical cycles. To address this gap, we carried out a 30-day laboratory chamber experiment on tropical seagrasses Thalassia hemprichii and Enhalus acoroides. After 30 days of incubation, on average 22% carbon(C), 70% nitrogen(N) and 38% phosphorus(P) of these two species of seagrass leaf litter was released. The average leached dissolved organic carbon(DOC), dissolved organic nitrogen(DON) and dissolved organic phosphorus(DOP) of these two species of seagrass leaf litter accounted for 55%, 95% and 65% of the total C, N and P lost, respectively. In the absence of microbes, about 75% of the total amount of DOC, monosaccharides(MCHO), DON and DOP were quickly released via leaching from both seagrass species in the first 9 days. Subsequently, little DOM was released during the remainder of the experiment. The leaching rates of DOC, DON and DOP were approximately 110, 40 and 0.70 μmol/(g·d). Leaching rates of DOM were attributed to the nonstructural carbohydrates and other labile organic matter within the seagrass leaf. Thalassia hemprichii leached more DOC, DOP and MCHO than E. acoroides. In contrast, E. acoroides leached higher concentrations of DON than T. hemprichii, with the overall leachate also having a higher DON: DOP ratio. These results indicate that there is an overall higher amount of DOM leachate from T. hemprichii than that of E. acoroides that is available to the seagrass ecosystem. According to the logarithmic model for DOM release and the in situ leaf litter production(the Xincun Bay, South China Sea), the seagrass leaf litter of these two seagrass species could release approximately 4×10~3 mol/d DOC, 1.4×10~3 mol/d DON and 25 mol/d DOP into the seawater. In addition to providing readily available nutrients for the microbial food web, the remaining particulate organic matter(POM)from the litter would also enter microbial remineralization processes. What is not remineralized from either DOM or POM fractions has potential to contribute to the permanent carbon stocks.展开更多
The effects of extraction fluids from the leaf litter from different dominant tree species on the functional characteristics of the soil microbial community were studied to understand how changes in soil quality and s...The effects of extraction fluids from the leaf litter from different dominant tree species on the functional characteristics of the soil microbial community were studied to understand how changes in soil quality and synergism between plants and soil contribute to the process of forest succession. Leaf litter from dominant tree species at different stages of succession were collected and extracted with sterile deionized water. After treating the soil of abandoned land with the different extraction fluids, we analyzed changes in carbon utilization of the soil microbial community in Biolog EcoPlates, then considered these results with those of our previous study on forest vegetation succession in the Malan forest. The leaf litter enhanced the metabolic capacity and functional diversity of the soil microbes, especially in the following combinations: the leaf litter of Quercus liaotungensis-Pinus tabulae- formis, P. tabulaeformis-Betula platyphylla, Q. liaotun- gensis and P. tabulaeformiss. Second, when litter from onespecies evaluated, the species enhanced metabolism and diversity in the order of their successional relationship: B. Platyphylla 〈 P. tabulaeformis 〈 Q. liaotungensis. After soils were treated with different leaf litters at 25 ℃ for 7 days, the sorting pattern of the PCA values, based on the similarity of carbon source utilization by the soil microbes, corresponded to the successional pattern on the basis of the similarity of community composition of forest plants. Thus, changes in soil properties caused by leaf litter from different dominant trees probably play a unique role in the successional pattern of a forest community. We thus pro- pose a successional mechanism that underlies the natural succession process within the Malan forest region. When the dominant forest species of the climax successional stage develops during the early successional stages, its forest litter probably alters soil properties such that the soil becomes unsuitable for the gradual growth and regenera- tion of the original dominant tree species but promotes the growth and establishment of later-invasive plants. In this way, the originally dominant species is replaced by the newly dominant tree species during forest succession.展开更多
Two dominant species of Willow( Salix triandra )and Reed (Phragmites australis) along the Schelde Estuary(in Belgium)were selected in this research. The pigments of higher plant was used as biomarkers, the deco...Two dominant species of Willow( Salix triandra )and Reed (Phragmites australis) along the Schelde Estuary(in Belgium)were selected in this research. The pigments of higher plant was used as biomarkers, the decomposition process of the two species were studied after they fall into the Schelde Estuary. After statistical analysis(Spearman rank order correlation, P <0 05), the results has shown the decomposition dynamics pattern of the pigments, and the willow showed different pattern in comparing with the reed, e.g. Chlorophyll a decomposition dynamics for willow is: y 1=12196 x 2 - 175895 x +1E+06+ k , R 2=0 5706 while for reed is: y 2=-37878 x 2+229782 x +734282+ k , R 2=0 9065 The precise time of the leaf litter spent in the water was also calculated as were less than 24 days, 24-37 days, longer than 37 days(willow)and less than 24 days, longer than 24 days(reed), the leaf litter fate of the two dominant species in the Schelde Estuary was also compared.展开更多
Soil fauna decompose litter, whereas land use changes may significantly alter the composition and structure of soil fauna assemblages. However, little is known of the effects of land-use on the contribution of soil fa...Soil fauna decompose litter, whereas land use changes may significantly alter the composition and structure of soil fauna assemblages. However, little is known of the effects of land-use on the contribution of soil fauna to litter decomposition. We studied the impacts of soil fauna on the decomposition of litter from poplar trees under three different land uses (i.e. poplar-crop integrated system, poplar plantation, and cropland), from December 2013 to December 2014, in a coastal area of Northern Jiangsu Province. We collected litter samples in litterbags with three mesh sizes (5, 1 and 0. 01 mm, respectively) to quantify the contribution of various soil fauna to the decomposition of poplar leaf litter. Litter decomposition rates differed significantly by land use and were highest in the cropland, intermediate in the poplar-crop integrated system, and lowest in the poplar plantation. Soil fauna in the poplar-crop integrated system was characterized by the highest numbers of taxa and individuals, and highest Margalef's diversity, which suggested that agro-forestry ecosystems may support a greater quantity, distribution, and biodiversity of soil fauna than can single-species agriculture or plantation forestry. The individuals and groups of soil fauna in the macro-mesh litterbags were higher than in the meso-mesh litterbags underthe same land use types. The average contribution rate of meso- and micro-fauna to litter decomposition was 18.46%, which was higher than the contribution rate of macro-fauna (3.31%). The percentage of remaining litter mass was inversely related to the density of the soil fauna (P 〈 0.05) in poplar plantations; however, was unrelated in the poplar-crop integrated system and cropland. This may have been the result of anthropogenic interference in poplar-crop integrated systems and croplands. Our study suggested that when land-use change alters vegetation types, it can affect species composition and the structure of soil fauna assemblages, which, in turn, affects litter decomposition.展开更多
Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia Sta...Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia State, Nigeria in 2016 and 2017. Three 1<span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 1</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m trays were randomly positioned for collection of leaf litter production from 4/5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">years old <i>Diospyros crassiflora</i> species in each block (10</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 25</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m) within the plantation totaling 1.5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">ha. A Randomised Complete Block Design (RCBD) with three replicates was used to study the mean monthly leaf litterfall of <i>Diospyros crassiflora</i>. Leaf litter was collected from each of the three litter trays per block and placed in paper bags every 28<sup>th</sup> day of each month from January-December in 2016 and in 2017. Fifteen grammes (15</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g) of properly mixed and oven-dried samples of <i>D. crassiflora</i> leaf litter were milled and sieved in 1</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">mm sieve;0.3</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g was used to determine nutrient elements and their concentrations. The data obtained from mineral nutrient contents of <i>D. crassiflora</i> leaf litter was analysed using analysis of variance. Result reveals the mean concentrations of nitrogen</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.41 and 1.41 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), phosphorus (0.18 and 0.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), potassium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.68 and 0.68 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), sodium (0.35 and 0.30 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), calcium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.57 and 1.56 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), magnesium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.32 and 0.31 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), chlorine (0.25 and 0.24 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), Organic carbon (0.03</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">and 0.03 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) and Organic matter</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.17 and 1.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) etc. in <i>D. crassiflora</i> leaf litter in January-December (2016 and 2017). The study shows almost uniform distribution of mineral elements concentrations in 2016 and 2017.</span></span></span>展开更多
Microorganisms are nutritious resources for various soil fauna.Although soil fauna grazing affects microorganism composition and decomposition rate,the responses of soil fauna and leaf litter decomposition to added mi...Microorganisms are nutritious resources for various soil fauna.Although soil fauna grazing affects microorganism composition and decomposition rate,the responses of soil fauna and leaf litter decomposition to added microorganism is little understood.In this study,in the coniferous and broad-leaved mixed forest of Tahe County in the northern Da Hinggan Mountains,China,three sampling sites(each has an area of 10 m2) were selected.The first two sites were sprinkled with 250 times(EM1) and 1000 times(EM2) diluted effective microorganism(EM) preparations evenly,and the third site was sprinkled with the same volume of water as a control site.The responses of soil fauna structure and leaf litter decomposition to EM treatment were conducted during three years.The results revealed that EM treatment resulted in significant increase of soil organic matter.The number of soil fauna in the EM1 and EM2 sites increased by 12.88% and 2.23% compared to the control site,and among them springtails and mites showed the highest increase.However,the groups of soil fauna in the EM1 and EM2 sites decreased by 6 and 9,respectively.And the changes in the diversity and evenness index were relatively complicated.EM treatment slowed the decomposition of broad-leaved litter,but accelerated the decomposition of coniferous litter.However,the decomposition rate of broad-leaved litter was still higher than that of coniferous litter.The results of this study suggested that the added microorganisms could help individual growth of soil fauna,and this method led to a change in the process of leaf litter decomposition.This paper did not analyze the activity of soil microorganisms,thus it is difficult to clearly explain the complex relationships among litter type,soil fauna and soil microorganisms.Further research on this subject is needed.展开更多
Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in t...Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in the decomposition of litters and fast release of available nutrients. Leaf litters of leguminous and non-leguminous species in alone and mixed form were applied as treatments in the soil to observe the changes in the magnitude of soil microbial biomass. Soil microbial biomass C and N were determined by chloroform fumigation extraction method. Increment in the concentration of microbial biomass C and N was higher in the treatments with leguminous leaf litter (497 - 571 μgCg?1, 48 - 55 μgNg?1) than the non-leguminous one (256 - 414 μgCg?1;22 - 36 μgNg?1). However, when non-leguminous litters were mixed with leguminous litters then the values increased distinctly (350 - 465 μgCg?1, 28 - 48 μgNg?1). On the basis of increment in soil microbial biomass, leaf litters of the species considered potential to improve soil nutrients are—Cassia siamea and Dalbergia sissoo from leguminous trees, Anthocephalus + Cassia and Shorea + Dalbergia from mixed form of non-leguminous and leguminous one and Eichhornia crassipes, an alien aquatic macrophyte. The leaf litters of these species can be used as source of organic matter to improve the crop yield.展开更多
Litter microorganisms play a crucial role in the biological decomposition in forest ecosystems;however,the coupling effect of meteorological and substrate changes on it during the different stages of leaf decompositio...Litter microorganisms play a crucial role in the biological decomposition in forest ecosystems;however,the coupling effect of meteorological and substrate changes on it during the different stages of leaf decomposition in situ remains unclear.Hence,according to meteorological factors dynamics,a one-year field litter of Quercus wutaishanica in situ decomposition experiment was designed for four decay stages in a warm temperate forest.Microbial community composition was characterized using Illumina sequencing of fungal ITS and bacterial 16S genes.Bacterial(6.6)and fungal(3.6)Shannon indexes were the largest after 125 days’litter decomposition(October).The relative abundance of Acidobacteria after 342 days and Bacteroidetes after 125 days were 3 and 24 times higher than after 31 days,respectively.Some non-dominant species(bacteria:Firmicutes,Planctomycotes,and Verrucomicrobia;fungi:Chytridiomycota and Glomeromomycota)may be absent or present at different decomposition stages due to litter properties or meteorological factors.Chemoheterotrophy and aerobic-chemoheterotrophy were the dominant bacterial functional groups,and the dominant fungal functional groups were saprotrophs,pathotrophs,and symbiotrophs.Precipitation and relative humidity significantly affected bacteria.Temperature,sunlight intensity,and net radiation significantly affected fungi.Besides,among the relative contributions of changes in bacterial and fungal community structure,leaf litter properties alone explained the variation of 5.51%and 10.63%.Microbial diversity and decay stage directly affected the litter mass-loss rate,with meteorological factors(precipitation,relative humidity,air temperature,and sunlight intensity)being indirect.Our findings highlight the importance of microbial diversity for leaf litter decomposition and the influence of meteorological factors.展开更多
To study the role of leaf litter in the mercury (Hg) cycle in suburban broadleaf forests and the distribution of Hg in urban forests, we collected leaf litter and soil from suburban evergreen and deciduous broadleaf...To study the role of leaf litter in the mercury (Hg) cycle in suburban broadleaf forests and the distribution of Hg in urban forests, we collected leaf litter and soil from suburban evergreen and deciduous broadleaf forests and from urban forests in Beijing. The Hg concentrations in leaf litter from the suburban forests varied from 8.3 to 205.0 ng/g, with an average (avg) of (49.7 ± 36.9) ng/g. The average Hg concentration in evergreen broadleaf forest leaf litter (50.8 ± 39.4) ng/g was higher than that in deciduous broadleaf forest leaf litter (25.8 ± 10.1) ng/g. The estimated Hg fluxes of leaf litter in suburban evergreen and deciduous broadleaf forests were 179.0 and 83.7 mg/(ha·yr), respectively. The Hg concentration in organic horizons (O horizons) ((263.1 ± 237.2) ng/g) was higher than that in eluvial horizons (A horizons) ((83.9 ± 52.0) ng/g). These results indicated that leaf litterfall plays an important role in transporting atmospheric mercury to soil in suburban forests. For urban forests in Beijing, the Hg concentrations in leaf litter ranged from 8.8–119.0 (avg 28.1 ± 16.6) ng/g, with higher concentrations at urban sites than at suburban sites for each tree. The Hg concentrations in surface soil in Beijing were 32.0–25300.0 ng/g and increased from suburban sites to urban sites, with the highest value from Jingshan (JS) Park at the centre of Beijing. Therefore, the distribution of Hg in Beijing urban forests appeared to be strongly influenced by anthropogenic activities.展开更多
Fungi are an essential component of the ecosystem.They play an integral role in the decomposition of leaf litter and return nutrients to the ecosystem through nutrient cycling.They are considered as the“key players”...Fungi are an essential component of the ecosystem.They play an integral role in the decomposition of leaf litter and return nutrients to the ecosystem through nutrient cycling.They are considered as the“key players”in leaf litter decomposition,because of their ability to produce a wide range of extracellular enzymes.Time-related changes of fungal communities during leaf litter decomposition have been relatively well-investigated.However,it has not been established how the tree species,tree phylogeny,and leaf litter chemistry influence fungal communities during decomposition.Using direct observations and a culturing approach,this study compiles fungi found in freshly collected leaf litter from five phylogenetically related,native tree species in Taiwan:Celtis formosana(CF),Ficus ampelas(FA),Ficus septica(FS),Macaranga tanarius(MT),and Morus australis(MA).We investigated(i)the effects of tree species(including tree phylogeny)and leaf litter chemistry on fungal community succession,and(ii)specific patterns of fungal succession(including diversity and taxonomic community assembly)on decomposing leaf litter across the selected tree species.We hypothesized that host species and leaf litter chemistry significantly affect fungal community succession.A total of 1325 leaves(CF:275,FA:275,FS:275,MT:275 and MA:225)were collected and 236 fungal taxa were recorded(CF:48,FA:46,FS:64,MT:42 and MA:36).Tree species relationships had variable associations on the fungal communities,as even closely related tree species had strongly differing communities during decomposition.A high number of species were unique to a single tree species and may indicate‘host-specificity’to a particular leaf litter.The overlap of microfungal species in pair wise comparisons of tree species was low(7–16%),and only 1–2%of microfungal species were observed in leaves of all tree species.The percentage of occurrences of fungal communities using Hierarchical Cluster Analyses(HCA)showed that there were at least four succession stages in each tree species during decomposition.Fungal diversity increased at the beginning of each tree species leaf decay,reached peaks,and declined at the final stages.Overall,our findings demonstrate that tree species and leaf litter chemistry are important variables in determining fungal diversity and community composition in leaf litter.Referring to the establishment of fungal discoveries from this experimental design,two new families,two new genera,40 new species and 56 new host records were reported.This study provides a host-fungus database for future studies on these hosts and increases the knowledge of fungal diversity in leaf litter.展开更多
In the first tier risk assessment(RA) of pesticides, risk for aquatic communities is estimated by using results from standard laboratory tests with algae, daphnids and fish for single pesticides such as herbicides, ...In the first tier risk assessment(RA) of pesticides, risk for aquatic communities is estimated by using results from standard laboratory tests with algae, daphnids and fish for single pesticides such as herbicides, fungicides, and insecticides. However, fungi as key organisms for nutrient cycling in ecosystems as well as multiple pesticide applications are not considered in the RA. In this study, the effects of multiple low pesticide pulses using regulatory acceptable concentrations(RACs) on the dynamics of non-target aquatic fungi were investigated in a study using pond mesocosm. For that, fungi colonizing black alder(Alnus glutinosa) leaves were exposed to multiple, low pulses of 11 different pesticides over a period of 60 days using a real farmer's pesticide application protocol for apple cropping.Four pond mesocosms served as treatments and 4 as controls. The composition of fungal communities colonizing the litter material was analyzed using a molecular fingerprinting approach based on the terminal Restriction Fragment Length Polymorphism(t-RFLP) of the fungal Internal Transcribed Spacer(ITS) region of the ribonucleic acid(RNA) gene(s). Our data indicated a clear fluctuation of fungal communities based on the degree of leaf litter degradation. However significant effects of the applied spraying sequence were not observed. Consequently also degradation rates of the litter material were not affected by the treatments. Our results indicate that the nutrient rich environment of the leaf litter material gave fungal communities the possibility to express genes that induce tolerance against the applied pesticides. Thus our data may not be transferred to other fresh water habitats with lower nutrient availability.展开更多
Seagrass leaf litters are an important source of sediment organic carbon(SOC). However, the mechanisms of seagrass leaf litter decomposition influencing SOC composition and the key transformation processes remain unkn...Seagrass leaf litters are an important source of sediment organic carbon(SOC). However, the mechanisms of seagrass leaf litter decomposition influencing SOC composition and the key transformation processes remain unknown. We performed a laboratory chamber experiment to compare the labile organic carbon(OC) composition and the enzyme activities governing SOC transformation between the seagrass group(seagrass leaf litter addition) and the control group. The results showed that the seagrass leaf litter decomposition significantly elevated the salt-extractable carbon(SEC) content and the SEC/SOC. Additionally,the levels of invertase, polyphenol oxidase, and cellulase in the seagrass leaf litters addition group were generally higher than in the control group, which could elevate recalcitrant OC decomposition. Following 24 days incubation, addition of seagrass leaf litter increased the amount of CO_2 released, but decreased the SOC content. Therefore, seagrass leaf litter decomposition leached abundant dissolved OC, which enhanced the activity and transformation of SOC.展开更多
The productivity of Robinia pseudoacacia(R.p.) pure forest usually declines at the late growth stage,and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tre...The productivity of Robinia pseudoacacia(R.p.) pure forest usually declines at the late growth stage,and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tree species that can be mixed with R.p., the interspecific relationship is an important issue. Therefore, we gathered the autumn litter fall from R.p. and 10 other species from the Loess Plateau of China were mixed in dual species litterbags(R.p.+each other species) and buried them in soil for a 345 days lab decay incubation. We measured the litter mass loss and nutrient contents to determine whether the nutrient release was affected by mixed species litter decomposition. The impacts of mixed litter decomposition on macro-elements release were more obvious than on micro-elements. The litters with similar substrate quality might show variable impacts on nutrients release in mixed decomposition. The C loss and release of nutrient was improved by descending order when R.p. litter was mixed with Hippophae rhamnoides, Ulmus pumila, Populus simonii, Larix principis-rupprechtii and Quercus liaotungensis(Q.l.). But, except for Q.l., only the other species were recommended as suitable mix-plants for R.p. since promoting a high turnover of the nutrient in the litter compartment and a rapid availability for tree.展开更多
基金supported by Bangladesh Academy of Science and University Grants Commissions of Bangladesh
文摘Azadirachta indica A. Juss, Dalbergia, sissoo Roxb., and Melia azedarach L. are little studied species in nutrient return capabilities from leaf litter decomposition to maintenance of the soil fertility despite their importance in agroforestry practices of Bangladesh. A leaf litter decomposition experiment was conducted using a litterbag teeh7 nique to assess the nutrient reaun efficiency of these species. The de- composition rate of leaf litter was highest for M. azedarach and lowest for D. sissoo. Rainfall and temperature of study sites showed a significant (p〈0.05) positive relationship with the rate of leaf litter decomposition. The highest decay constant was observed for M. azedarach (6.67). Nitrogen and Phosphorus concentration in leaf litter showed a decreased trend sharply at the end of the first month, whereas rapid decrease of Potassium concentration was reported within 10 days. Conversely, higher concentration of nutrient was observed at the later stages of decomposition. All three species showed a similar pattern of nutrient release (K 〉 N 〉 P) during the decomposition process of leaf litter. Among the studied species, D. sissoo was best in terms of N and P return and A. indica was best in terms of K return.
基金The National Basic Research Program of China under contract Nos 2015CB452905 and 2015CB452902the National Natural Science Foundation of China under contract No.41730529the National Specialized Project of Science and Technology under contract No.2015FY110600
文摘Dissolved organic matter(DOM) represents a significant source of nutrients that supports the microbial-based food web in seagrass ecosystems. However, there is little information on how the various fractions of DOM from seagrass leaves contributed to the coastal biogeochemical cycles. To address this gap, we carried out a 30-day laboratory chamber experiment on tropical seagrasses Thalassia hemprichii and Enhalus acoroides. After 30 days of incubation, on average 22% carbon(C), 70% nitrogen(N) and 38% phosphorus(P) of these two species of seagrass leaf litter was released. The average leached dissolved organic carbon(DOC), dissolved organic nitrogen(DON) and dissolved organic phosphorus(DOP) of these two species of seagrass leaf litter accounted for 55%, 95% and 65% of the total C, N and P lost, respectively. In the absence of microbes, about 75% of the total amount of DOC, monosaccharides(MCHO), DON and DOP were quickly released via leaching from both seagrass species in the first 9 days. Subsequently, little DOM was released during the remainder of the experiment. The leaching rates of DOC, DON and DOP were approximately 110, 40 and 0.70 μmol/(g·d). Leaching rates of DOM were attributed to the nonstructural carbohydrates and other labile organic matter within the seagrass leaf. Thalassia hemprichii leached more DOC, DOP and MCHO than E. acoroides. In contrast, E. acoroides leached higher concentrations of DON than T. hemprichii, with the overall leachate also having a higher DON: DOP ratio. These results indicate that there is an overall higher amount of DOM leachate from T. hemprichii than that of E. acoroides that is available to the seagrass ecosystem. According to the logarithmic model for DOM release and the in situ leaf litter production(the Xincun Bay, South China Sea), the seagrass leaf litter of these two seagrass species could release approximately 4×10~3 mol/d DOC, 1.4×10~3 mol/d DON and 25 mol/d DOP into the seawater. In addition to providing readily available nutrients for the microbial food web, the remaining particulate organic matter(POM)from the litter would also enter microbial remineralization processes. What is not remineralized from either DOM or POM fractions has potential to contribute to the permanent carbon stocks.
基金supported by the National Key Basic Research Program of China(2002 CB111505)Natural Science Basic Research Project in Shaanxi Province(2011 JM3003)Project PCSIRT(No.IRT1035)
文摘The effects of extraction fluids from the leaf litter from different dominant tree species on the functional characteristics of the soil microbial community were studied to understand how changes in soil quality and synergism between plants and soil contribute to the process of forest succession. Leaf litter from dominant tree species at different stages of succession were collected and extracted with sterile deionized water. After treating the soil of abandoned land with the different extraction fluids, we analyzed changes in carbon utilization of the soil microbial community in Biolog EcoPlates, then considered these results with those of our previous study on forest vegetation succession in the Malan forest. The leaf litter enhanced the metabolic capacity and functional diversity of the soil microbes, especially in the following combinations: the leaf litter of Quercus liaotungensis-Pinus tabulae- formis, P. tabulaeformis-Betula platyphylla, Q. liaotun- gensis and P. tabulaeformiss. Second, when litter from onespecies evaluated, the species enhanced metabolism and diversity in the order of their successional relationship: B. Platyphylla 〈 P. tabulaeformis 〈 Q. liaotungensis. After soils were treated with different leaf litters at 25 ℃ for 7 days, the sorting pattern of the PCA values, based on the similarity of carbon source utilization by the soil microbes, corresponded to the successional pattern on the basis of the similarity of community composition of forest plants. Thus, changes in soil properties caused by leaf litter from different dominant trees probably play a unique role in the successional pattern of a forest community. We thus pro- pose a successional mechanism that underlies the natural succession process within the Malan forest region. When the dominant forest species of the climax successional stage develops during the early successional stages, its forest litter probably alters soil properties such that the soil becomes unsuitable for the gradual growth and regenera- tion of the original dominant tree species but promotes the growth and establishment of later-invasive plants. In this way, the originally dominant species is replaced by the newly dominant tree species during forest succession.
文摘Two dominant species of Willow( Salix triandra )and Reed (Phragmites australis) along the Schelde Estuary(in Belgium)were selected in this research. The pigments of higher plant was used as biomarkers, the decomposition process of the two species were studied after they fall into the Schelde Estuary. After statistical analysis(Spearman rank order correlation, P <0 05), the results has shown the decomposition dynamics pattern of the pigments, and the willow showed different pattern in comparing with the reed, e.g. Chlorophyll a decomposition dynamics for willow is: y 1=12196 x 2 - 175895 x +1E+06+ k , R 2=0 5706 while for reed is: y 2=-37878 x 2+229782 x +734282+ k , R 2=0 9065 The precise time of the leaf litter spent in the water was also calculated as were less than 24 days, 24-37 days, longer than 37 days(willow)and less than 24 days, longer than 24 days(reed), the leaf litter fate of the two dominant species in the Schelde Estuary was also compared.
基金supported by the National Basic Research Program of China(973 Program,2012CB416904)partially supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Soil fauna decompose litter, whereas land use changes may significantly alter the composition and structure of soil fauna assemblages. However, little is known of the effects of land-use on the contribution of soil fauna to litter decomposition. We studied the impacts of soil fauna on the decomposition of litter from poplar trees under three different land uses (i.e. poplar-crop integrated system, poplar plantation, and cropland), from December 2013 to December 2014, in a coastal area of Northern Jiangsu Province. We collected litter samples in litterbags with three mesh sizes (5, 1 and 0. 01 mm, respectively) to quantify the contribution of various soil fauna to the decomposition of poplar leaf litter. Litter decomposition rates differed significantly by land use and were highest in the cropland, intermediate in the poplar-crop integrated system, and lowest in the poplar plantation. Soil fauna in the poplar-crop integrated system was characterized by the highest numbers of taxa and individuals, and highest Margalef's diversity, which suggested that agro-forestry ecosystems may support a greater quantity, distribution, and biodiversity of soil fauna than can single-species agriculture or plantation forestry. The individuals and groups of soil fauna in the macro-mesh litterbags were higher than in the meso-mesh litterbags underthe same land use types. The average contribution rate of meso- and micro-fauna to litter decomposition was 18.46%, which was higher than the contribution rate of macro-fauna (3.31%). The percentage of remaining litter mass was inversely related to the density of the soil fauna (P 〈 0.05) in poplar plantations; however, was unrelated in the poplar-crop integrated system and cropland. This may have been the result of anthropogenic interference in poplar-crop integrated systems and croplands. Our study suggested that when land-use change alters vegetation types, it can affect species composition and the structure of soil fauna assemblages, which, in turn, affects litter decomposition.
文摘Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia State, Nigeria in 2016 and 2017. Three 1<span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 1</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m trays were randomly positioned for collection of leaf litter production from 4/5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">years old <i>Diospyros crassiflora</i> species in each block (10</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 25</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m) within the plantation totaling 1.5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">ha. A Randomised Complete Block Design (RCBD) with three replicates was used to study the mean monthly leaf litterfall of <i>Diospyros crassiflora</i>. Leaf litter was collected from each of the three litter trays per block and placed in paper bags every 28<sup>th</sup> day of each month from January-December in 2016 and in 2017. Fifteen grammes (15</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g) of properly mixed and oven-dried samples of <i>D. crassiflora</i> leaf litter were milled and sieved in 1</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">mm sieve;0.3</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g was used to determine nutrient elements and their concentrations. The data obtained from mineral nutrient contents of <i>D. crassiflora</i> leaf litter was analysed using analysis of variance. Result reveals the mean concentrations of nitrogen</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.41 and 1.41 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), phosphorus (0.18 and 0.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), potassium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.68 and 0.68 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), sodium (0.35 and 0.30 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), calcium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.57 and 1.56 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), magnesium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.32 and 0.31 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), chlorine (0.25 and 0.24 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), Organic carbon (0.03</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">and 0.03 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) and Organic matter</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.17 and 1.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) etc. in <i>D. crassiflora</i> leaf litter in January-December (2016 and 2017). The study shows almost uniform distribution of mineral elements concentrations in 2016 and 2017.</span></span></span>
基金Under the auspices of National Natural Science Foundation of China(No.41071033,41101049)China Postdoctoral Science Foundation(No.2012M511361)
文摘Microorganisms are nutritious resources for various soil fauna.Although soil fauna grazing affects microorganism composition and decomposition rate,the responses of soil fauna and leaf litter decomposition to added microorganism is little understood.In this study,in the coniferous and broad-leaved mixed forest of Tahe County in the northern Da Hinggan Mountains,China,three sampling sites(each has an area of 10 m2) were selected.The first two sites were sprinkled with 250 times(EM1) and 1000 times(EM2) diluted effective microorganism(EM) preparations evenly,and the third site was sprinkled with the same volume of water as a control site.The responses of soil fauna structure and leaf litter decomposition to EM treatment were conducted during three years.The results revealed that EM treatment resulted in significant increase of soil organic matter.The number of soil fauna in the EM1 and EM2 sites increased by 12.88% and 2.23% compared to the control site,and among them springtails and mites showed the highest increase.However,the groups of soil fauna in the EM1 and EM2 sites decreased by 6 and 9,respectively.And the changes in the diversity and evenness index were relatively complicated.EM treatment slowed the decomposition of broad-leaved litter,but accelerated the decomposition of coniferous litter.However,the decomposition rate of broad-leaved litter was still higher than that of coniferous litter.The results of this study suggested that the added microorganisms could help individual growth of soil fauna,and this method led to a change in the process of leaf litter decomposition.This paper did not analyze the activity of soil microorganisms,thus it is difficult to clearly explain the complex relationships among litter type,soil fauna and soil microorganisms.Further research on this subject is needed.
文摘Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in the decomposition of litters and fast release of available nutrients. Leaf litters of leguminous and non-leguminous species in alone and mixed form were applied as treatments in the soil to observe the changes in the magnitude of soil microbial biomass. Soil microbial biomass C and N were determined by chloroform fumigation extraction method. Increment in the concentration of microbial biomass C and N was higher in the treatments with leguminous leaf litter (497 - 571 μgCg?1, 48 - 55 μgNg?1) than the non-leguminous one (256 - 414 μgCg?1;22 - 36 μgNg?1). However, when non-leguminous litters were mixed with leguminous litters then the values increased distinctly (350 - 465 μgCg?1, 28 - 48 μgNg?1). On the basis of increment in soil microbial biomass, leaf litters of the species considered potential to improve soil nutrients are—Cassia siamea and Dalbergia sissoo from leguminous trees, Anthocephalus + Cassia and Shorea + Dalbergia from mixed form of non-leguminous and leguminous one and Eichhornia crassipes, an alien aquatic macrophyte. The leaf litters of these species can be used as source of organic matter to improve the crop yield.
基金This research was supported by the National Natural Science Foundation of China(Grant Nos.41877074 and 42077072).
文摘Litter microorganisms play a crucial role in the biological decomposition in forest ecosystems;however,the coupling effect of meteorological and substrate changes on it during the different stages of leaf decomposition in situ remains unclear.Hence,according to meteorological factors dynamics,a one-year field litter of Quercus wutaishanica in situ decomposition experiment was designed for four decay stages in a warm temperate forest.Microbial community composition was characterized using Illumina sequencing of fungal ITS and bacterial 16S genes.Bacterial(6.6)and fungal(3.6)Shannon indexes were the largest after 125 days’litter decomposition(October).The relative abundance of Acidobacteria after 342 days and Bacteroidetes after 125 days were 3 and 24 times higher than after 31 days,respectively.Some non-dominant species(bacteria:Firmicutes,Planctomycotes,and Verrucomicrobia;fungi:Chytridiomycota and Glomeromomycota)may be absent or present at different decomposition stages due to litter properties or meteorological factors.Chemoheterotrophy and aerobic-chemoheterotrophy were the dominant bacterial functional groups,and the dominant fungal functional groups were saprotrophs,pathotrophs,and symbiotrophs.Precipitation and relative humidity significantly affected bacteria.Temperature,sunlight intensity,and net radiation significantly affected fungi.Besides,among the relative contributions of changes in bacterial and fungal community structure,leaf litter properties alone explained the variation of 5.51%and 10.63%.Microbial diversity and decay stage directly affected the litter mass-loss rate,with meteorological factors(precipitation,relative humidity,air temperature,and sunlight intensity)being indirect.Our findings highlight the importance of microbial diversity for leaf litter decomposition and the influence of meteorological factors.
基金supported by the National Natural Science Foundation of China (No. 40803033, 41073092)
文摘To study the role of leaf litter in the mercury (Hg) cycle in suburban broadleaf forests and the distribution of Hg in urban forests, we collected leaf litter and soil from suburban evergreen and deciduous broadleaf forests and from urban forests in Beijing. The Hg concentrations in leaf litter from the suburban forests varied from 8.3 to 205.0 ng/g, with an average (avg) of (49.7 ± 36.9) ng/g. The average Hg concentration in evergreen broadleaf forest leaf litter (50.8 ± 39.4) ng/g was higher than that in deciduous broadleaf forest leaf litter (25.8 ± 10.1) ng/g. The estimated Hg fluxes of leaf litter in suburban evergreen and deciduous broadleaf forests were 179.0 and 83.7 mg/(ha·yr), respectively. The Hg concentration in organic horizons (O horizons) ((263.1 ± 237.2) ng/g) was higher than that in eluvial horizons (A horizons) ((83.9 ± 52.0) ng/g). These results indicated that leaf litterfall plays an important role in transporting atmospheric mercury to soil in suburban forests. For urban forests in Beijing, the Hg concentrations in leaf litter ranged from 8.8–119.0 (avg 28.1 ± 16.6) ng/g, with higher concentrations at urban sites than at suburban sites for each tree. The Hg concentrations in surface soil in Beijing were 32.0–25300.0 ng/g and increased from suburban sites to urban sites, with the highest value from Jingshan (JS) Park at the centre of Beijing. Therefore, the distribution of Hg in Beijing urban forests appeared to be strongly influenced by anthropogenic activities.
文摘Fungi are an essential component of the ecosystem.They play an integral role in the decomposition of leaf litter and return nutrients to the ecosystem through nutrient cycling.They are considered as the“key players”in leaf litter decomposition,because of their ability to produce a wide range of extracellular enzymes.Time-related changes of fungal communities during leaf litter decomposition have been relatively well-investigated.However,it has not been established how the tree species,tree phylogeny,and leaf litter chemistry influence fungal communities during decomposition.Using direct observations and a culturing approach,this study compiles fungi found in freshly collected leaf litter from five phylogenetically related,native tree species in Taiwan:Celtis formosana(CF),Ficus ampelas(FA),Ficus septica(FS),Macaranga tanarius(MT),and Morus australis(MA).We investigated(i)the effects of tree species(including tree phylogeny)and leaf litter chemistry on fungal community succession,and(ii)specific patterns of fungal succession(including diversity and taxonomic community assembly)on decomposing leaf litter across the selected tree species.We hypothesized that host species and leaf litter chemistry significantly affect fungal community succession.A total of 1325 leaves(CF:275,FA:275,FS:275,MT:275 and MA:225)were collected and 236 fungal taxa were recorded(CF:48,FA:46,FS:64,MT:42 and MA:36).Tree species relationships had variable associations on the fungal communities,as even closely related tree species had strongly differing communities during decomposition.A high number of species were unique to a single tree species and may indicate‘host-specificity’to a particular leaf litter.The overlap of microfungal species in pair wise comparisons of tree species was low(7–16%),and only 1–2%of microfungal species were observed in leaves of all tree species.The percentage of occurrences of fungal communities using Hierarchical Cluster Analyses(HCA)showed that there were at least four succession stages in each tree species during decomposition.Fungal diversity increased at the beginning of each tree species leaf decay,reached peaks,and declined at the final stages.Overall,our findings demonstrate that tree species and leaf litter chemistry are important variables in determining fungal diversity and community composition in leaf litter.Referring to the establishment of fungal discoveries from this experimental design,two new families,two new genera,40 new species and 56 new host records were reported.This study provides a host-fungus database for future studies on these hosts and increases the knowledge of fungal diversity in leaf litter.
文摘In the first tier risk assessment(RA) of pesticides, risk for aquatic communities is estimated by using results from standard laboratory tests with algae, daphnids and fish for single pesticides such as herbicides, fungicides, and insecticides. However, fungi as key organisms for nutrient cycling in ecosystems as well as multiple pesticide applications are not considered in the RA. In this study, the effects of multiple low pesticide pulses using regulatory acceptable concentrations(RACs) on the dynamics of non-target aquatic fungi were investigated in a study using pond mesocosm. For that, fungi colonizing black alder(Alnus glutinosa) leaves were exposed to multiple, low pulses of 11 different pesticides over a period of 60 days using a real farmer's pesticide application protocol for apple cropping.Four pond mesocosms served as treatments and 4 as controls. The composition of fungal communities colonizing the litter material was analyzed using a molecular fingerprinting approach based on the terminal Restriction Fragment Length Polymorphism(t-RFLP) of the fungal Internal Transcribed Spacer(ITS) region of the ribonucleic acid(RNA) gene(s). Our data indicated a clear fluctuation of fungal communities based on the degree of leaf litter degradation. However significant effects of the applied spraying sequence were not observed. Consequently also degradation rates of the litter material were not affected by the treatments. Our results indicate that the nutrient rich environment of the leaf litter material gave fungal communities the possibility to express genes that induce tolerance against the applied pesticides. Thus our data may not be transferred to other fresh water habitats with lower nutrient availability.
基金supported by the National Basic Research Program of China(Grant Nos.2015CB452905,2015CB452902)the National Natural Science Foundation of China(Grant Nos.41730529,41306108,41406128)the National Specialized Project of Science and Technology(Grant No.2015FY110600)
文摘Seagrass leaf litters are an important source of sediment organic carbon(SOC). However, the mechanisms of seagrass leaf litter decomposition influencing SOC composition and the key transformation processes remain unknown. We performed a laboratory chamber experiment to compare the labile organic carbon(OC) composition and the enzyme activities governing SOC transformation between the seagrass group(seagrass leaf litter addition) and the control group. The results showed that the seagrass leaf litter decomposition significantly elevated the salt-extractable carbon(SEC) content and the SEC/SOC. Additionally,the levels of invertase, polyphenol oxidase, and cellulase in the seagrass leaf litters addition group were generally higher than in the control group, which could elevate recalcitrant OC decomposition. Following 24 days incubation, addition of seagrass leaf litter increased the amount of CO_2 released, but decreased the SOC content. Therefore, seagrass leaf litter decomposition leached abundant dissolved OC, which enhanced the activity and transformation of SOC.
基金supported by the National Science Foundation of China (No. 31070630)
文摘The productivity of Robinia pseudoacacia(R.p.) pure forest usually declines at the late growth stage,and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tree species that can be mixed with R.p., the interspecific relationship is an important issue. Therefore, we gathered the autumn litter fall from R.p. and 10 other species from the Loess Plateau of China were mixed in dual species litterbags(R.p.+each other species) and buried them in soil for a 345 days lab decay incubation. We measured the litter mass loss and nutrient contents to determine whether the nutrient release was affected by mixed species litter decomposition. The impacts of mixed litter decomposition on macro-elements release were more obvious than on micro-elements. The litters with similar substrate quality might show variable impacts on nutrients release in mixed decomposition. The C loss and release of nutrient was improved by descending order when R.p. litter was mixed with Hippophae rhamnoides, Ulmus pumila, Populus simonii, Larix principis-rupprechtii and Quercus liaotungensis(Q.l.). But, except for Q.l., only the other species were recommended as suitable mix-plants for R.p. since promoting a high turnover of the nutrient in the litter compartment and a rapid availability for tree.