Vegetation C–N–P accumulation and allocation patterns at the community level in early restored plantations in the loess hilly-gully region

Accumulation of vegetation biomass is a crucial process for carbon fixation in the early stage of afforestation and a primary driving force for subsequent ecological functions.Accurately assessing the storage and allocation of elements in plantations is essential for their management and estimating carbon sink capacity.However,current knowledge of the storage and allocation patterns of elements within plant organs at the community level is limited.To clarify the distribution patterns of elements in plant organs at the community level,we measured the biomass within plant organs of five typical plantations in the early stage of afforestation in the loess hilly-gully region.We assessed the main drivers of element accumulation and distribution by employing redundancy analysis and random forest.Results revealed significant differences in biomass storages among plantations and a significant effect of plantation type on the storages of elements within plant organs.Furthermore,the dominant factors influencing C–N–P storage and allocation at the community level were found to be inconsistent.While the storage of elements was mainly influenced by stand openness,total soil nitrogen,and plant diversity,the allocation of elements in organs was mainly influenced by stand openness and soil water content.Overall,the spatial structure of the community had an important influence on both element storage and allocation,but soil conditions played a more important role in element allocation than in storage.Random forest results showed that at the community level,factors influencing element storage and allocation within plant organs often differed.The regulation of elemental storage could be regulated by the major growth demand resources,while the allocation was regulated by other limiting class factors,which often differed from those that had a significant effect on element storage.The differences in plant organ elemental storage and allocation drivers at the community level reflect community adaptation strategies and the regulation of resources by ecosystems in combination with plants.Our study provides valuable insights for enhancing plantation C sink estimates and serves as a reference for regulating element storage and allocation at the local scale.

Beyond hypoxia: Occurrence and characteristics of black blooms due to the decomposition of the submerged plant Potamogeton crispus in a shallow lake

Organic matter-induced black blooms （hypoxia and an offensive odor） are a serious ecosystem disasters that have occurred in some large eutrophic shallow lakes in China. In this study, we investigated two separate black blooms that were induced by Potamogeton crispus in Lake Taihu, China. The main physical and chemical characteristics, including color- and odor-related substances, of the black blooms were analyzed. The black blooms were characterized by low dissolved oxygen concentration （close to 0 mg/L）, low oxidation-reduction potential, and relatively low pH of overlying water. Notably higher Fe^2＋ and ∑S2- were found in the black-bloom waters than in waters not affected by black blooms. The black color of the water may be attributable to the high concentration of these elements, as black FeS was considered to be the main substance causing the black color of blooms in freshwater lakes. Volatile organic sulfur compounds, including dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide, were very abundant in the black-bloom waters. The massive anoxic degradation of dead Potamogeton crispus plants released dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide, which were the main odor-causing compounds in the black blooms. The black blooms also induced an increase in ammonium nitrogen and soluble reactive phosphorus levels in the overlying waters. This extreme phenomenon not only heavily influenced the original lake ecosystem but also greatly changed the cycling of Fe, S, and nutrients in the water column.

Performance test of organic planting bags for woody plant seedlings

Organic planting bag has been developed to overcome both weaknesses of plastic polybags,contaminating the soil and damaging the plant’s root when transplanting.The improvement in this stage was achieved by inserting coconut fiber to strengthen a bag.The main purpose of this study was to investigate the effectiveness of seedling and transplanting by using organic planting bags,employed,three woody plants,i.e.,Albizia(Albizia julibrissin),Cadam(Neolamarckia cadamba)and Gmelina(Gmelina arborea).Performance testing of organic plant bags was conducted on three compositions of coconut fiber and water hyacinth.Two stages of experiments were conducted to know bag performance.First,the testing of organic plant bags during the nursery was conducted for 50 d from day 0 to day 50.Second,the testing of organic plant bags after transplanting and observed on days 60,70,and 80,after transplanted on the field.The parameters in this study were plant height,a total of roots that penetrate the organic plant bags and a total of leaves and stem diameters of plant grown in the organic bag and transplanting on land.The results showed that organic planting bag with the composition 155 g of coconut fiber and 505 g of water hyacinth(A3B3)has 0.020 kg/cm^(2) compressive strength and provides the best plant growth rates.Compressive strength affects the number of roots which penetrate the organic bag.Generally,the growth of seed in organic bags is faster than that in polybags.Albizia shows a higher growth rate(0.379 cm/d)compared to Cadam and Gmelina.

Variation of carbon and nitrogen stoichiometry along a chronosequence of natural temperate forest in northeastern China

Aims Carbon(C)and nitrogen(N)stoichiometry contributes to under-standing elemental compositions and coupled biogeochemical cycles in ecosystems.However,we know little about the temporal patterns of C:N stoichiometry during forest development.The goal of this study is to explore the temporal patterns of intraspecific and ecosystem components’variations in C:N stoichiometry and the scaling relationships between C and N at different successional stages.Methods Along forest development in a natural temperate forest,northeastern China,four age gradients were categorized into ca.10-,30-,70-and 200-year old,respectively,and three 20 m×20 m plots were set up for each age class.Leaves,branches,fine roots and fresh litter of seven dominant species as well as mineral soil at depth of 0-10 cm were sampled.A Universal CHN Elemental Analyzer was used to determine the C and N concentrations in all samples.Important Findings Intraspecific leaf C,N and C:N ratios remained stable along forest development regardless of tree species;while C,N concentrations and C:N ratios changed significantly either in branches or in fine roots,and they varied with tree species except Populus davidiana(P<0.05).For ecosystem components,we discovered that leaf C:N ratios remained stable when stand age was below ca.70 years and dominant tree species were light-demanding pioneers such as Betula platyphylla and Populus davidiana,while increased signifi-cantly at the age of ca.200 years with Pinus koraiensis as the dom-inant species.C:N ratios in branches and fresh litter did not changed significantly along forest development stages.C concentrations scaled isometrically with respect to N concentrations in mineral soil but not in other ecosystem components.Our results indicate that,leaf has a higher intraspecific C:N stoichiometric stability compared to branch and fine root,whereas for ecosystem components,shifts in species composition mainly affect C:N ratios in leaves rather than other components.This study also demonstrated that C and N remain coupled in mineral soils but not in plant organs or fresh litter during forest development.

Olive fruits infested with olive fly larvae respond with an ethylene burst and the emission of specific volatiles

Olive fly（Bactrocera oleae R.） is the most harmful insect pest of olive（Olea europaea L.） which strongly affects fruits and oil production. Despite the expanding economic importance of olive cultivation, up to now, only limited information on plant responses to B. oleae is available. Here,we demonstrate that olive fruits respond to B. oleae attack by producing changes in an array of different defensive compounds including phytohormones, volatile organic compounds（VOCs）, and defense proteins. Bactrocera oleaeinfested fruits induced a strong ethylene burst and transcript levels of several putative ethylene-responsive transcription factors became significantly upregulated. Moreover, infested fruits induced significant changes in the levels of 12-oxophytodienoic acid and C12 derivatives of the hydroperoxide lyase. The emission of VOCs was also changed quantitatively and qualitatively in insect-damaged fruits, indicating that B.oleae larval feeding can specifically affect the volatile blend offruits. Finally, we show that larval infestation maintained high levels of trypsin protease inhibitors in ripe fruits, probably by affecting post-transcriptional mechanisms. Our results provide novel and important information to understand the response of the olive fruit to B. oleae attack; information that can shed light onto potential new strategies to combat this pest.