Long-term organic phosphorus mineralization in Spodosols under forests and its relation to carbon and nitrogen mineralization

In forest soils where a large fraction of total phosphorus (P) is in organic forms, soil micro-organisms play a major role in the P cycle and plant availability since they mediate organic P transformations. However, the correct assessment of organic P mineralization is usually a challenging task because mineralized P is rapidly sorbed and most mineralization fluxes are very weak. The objectives of the present work were to quantify in five forest Spodosols at soil depths of 0-15 cm net mineralization of total organic P and the resulting increase in plant available inorganic P and to verify whether net or gross P mineralization could be estimated using the C or N mineralization rates. Net mineralization of total organic P was derived from the net changes in microbial P and gross mineralization of P in dead soil organic matter. We studied very low P-sorbing soils enabling us to use lower extractants to assess the change in total inorganic P as a result of gross mineralization of P in dead soil organic matter. In addition, to enable detection of gross mineralization of P in dead soil organic matter, a long-term incubation (517 days) experiment was carried out. At the beginning of the experiment, total P contents of the soils were very low (19-51 μg g⁻¹) and were essentially present as organic P (17-44 μg g⁻¹, 85-91%) or microbial P (6-14 μg g⁻¹; 24-39%). Conversely, the initial contents of inorganic P were low (2-7 μg g⁻¹; 9-15%). The net changes in the pool size of microbial P during the 517 days of incubation (4-8 μg g⁻¹) and the amounts of P resulting from gross mineralization of dead soil organic matter (0.001-0.018 μg g⁻¹ day⁻¹; 0.4-9.5 μg g⁻¹ for the entire incubation period) were considerable compared to the initial amounts of organic P and also when compared to the initial diffusive iP fraction (<0.3 μg g⁻¹). Diffusive iP corresponds to the phosphate ions that can be transferred from the solid constituents to the soil solution under a gradient of concentration. Net mineralization of organic P induced an important increase in iP in soil solution (0.6-10 μg g⁻¹; 600-5000% increase) and lower increases in diffusive iP fractions (0.3-5 μg g⁻¹; 300-2000% increase), soil solid constituents having an extremely low reactivity relative to iP. Therefore, soil micro-organisms and organic P transformations play a major role in the bioavailability of P in these forest soils. In our study, the dead soil organic matter was defined as a recalcitrant organic fraction. Probably because gross mineralization of P from this recalcitrant organic fraction was mainly driven by the micro-organisms’ needs for energy, the rates of gross mineralization of C, N and P in the recalcitrant organic fraction were similar. Indirect estimation of gross mineralization of P in dead soil organic matter using the gross C mineralization rate seems thus an alternative method for the studied soils. However, additional studies are needed to verify this alternative method in other soils. No relationships were found between microbial P release and microbial C and N releases.     

Priming effects: Interactions between living and dead organic matter

In this re-evaluation of our 10-year old paper on priming effects, I have considered the latest studies and tried to identify the most important needs for future research. Recent publications have shown that the increase or decrease in soil organic matter mineralization (measured as changes of CO₂ efflux and N mineralization) actually results from interactions between living (microbial biomass) and dead organic matter. The priming effect (PE) is not an artifact of incubation studies, as sometimes supposed, but is a natural process sequence in the rhizosphere and detritusphere that is induced by pulses or continuous inputs of fresh organics. The intensity of turnover processes in such hotspots is at least one order of magnitude higher than in the bulk soil. Various prerequisites for high-quality, informative PE studies are outlined: calculating the budget of labeled and total C; investigating the dynamics of released CO₂ and its sources; linking C and N dynamics with microbial biomass changes and enzyme activities; evaluating apparent and real PEs; and assessing PE sources as related to soil organic matter stabilization mechanisms. Different approaches for identifying priming, based on the assessment of more than two C sources in CO₂ and microbial biomass, are proposed and methodological and statistical uncertainties in PE estimation and approaches to eliminating them are discussed. Future studies should evaluate directions and magnitude of PEs according to expected climate and land-use changes and the increased rhizodeposition under elevated CO₂ as well as clarifying the ecological significance of PEs in natural and agricultural ecosystems. The conclusion is that PEs - the interactions between living and dead organic matter - should be incorporated in models of C and N dynamics, and that microbial biomass should regarded not only as a C pool but also as an active driver of C and N turnover.     

Effects of live prey availability on growth and survival in the early stages of cuttlefish Sepia officinalis (Linnaeus, 1758) life cycle

This investigation examined the effects of live prey availability on growth and survival of Sepia officinalis. Two independent experiments, comprising two feed rations each, were performed, using adequate prey size. In the first experiment, cuttlefish hatchlings were fed live mysids, Paramysis nouvelli [(feed ratio I (fr I)], at 15% body weight per day (bw day^?1) (fr I₁₅) and 30% bw day^?1 (fr I₃₀). In the second experiment, juvenile cuttlefish were fed live Atlantic ditch shrimp, Paleomonetes varians (fr II), under the same experimental design. In both experiments, the final mean weight, feeding rate and instantaneous growth rate were higher when animals were fed feed ratio fr II₁₅ and fr II₃₀ (30% bw day^?1). The results indicate that prey availability influenced weight gain, irrespective of the prey used, during the first 2 months of cuttlefish life cycle. This effect seems to be more noticeable when a certain limit of prey is achieved. For cuttlefish fed fr II, the optimal prey density is thought to be under 2.5 g prey L^?1 (i.e. 14 shrimp L^?1). Results indicate that cuttlefish can withstand prey densities up to 120 mysids L^?1 for cuttlefish up to 3 weeks old and 19 shrimps L^?1 for cuttlefish up to 6 weeks old.     

不同基质配比对黄瓜幼苗生长的影响

为提高农业废弃物利用率,减少环境污染,以黄瓜品种津绿3号为试验材料,研究牛粪、花生壳、草炭、蛭石、珍珠岩等不同基质成分配比对黄瓜幼苗生长及光合作用的影响。结果表明:不同基质配比对黄瓜的生长有显著影响。其中C处理(花生壳︰蛭石︰珍珠岩体积比7︰3︰3)效果最好,育苗40 d后,黄瓜幼苗叶片大而肥厚,叶色浓绿,株高、茎粗、地上和地下部分鲜质量均达到了最大值,分别为17.21 cm、5.4 mm、6.82 g和2.26 g,分别是对照的2.1倍、1.5倍、2.7倍和1.1倍;光合速率为13.95μmol/(m2·s),比A处理稍低,但无显著差异,且显著高于其他处理。综合各项指标,C处理成本低,原料来源方便,建议在黄瓜育苗中应用。     

Review on the roles and effects of growing media on plant performance in green roofs in world climates

Growing media (substrate) is a fundamental part of a green roof, providing water, nutrients and support to plants. However, little research has reviewed how it affects plant performances in different climatic regions. This study aims to analyse published research on green roof growing medium across world’s climate zones. Findings are structured according to Köppen–Geiger climate classification, aiming to investigate the prevalence of research conducted in different climate zones. Results from full-scale studies and laboratory or greenhouse experiments were reviewed. The later were included as they provide systematic knowledge on the effect of individual factors on system performances although cannot provide climate specific information. Studies discussed effects of major substrate components and depths on plant survival and establishment using standard test procedures. Results showed that most research in the subject were in temperate (group C climate classification), continental (group D) and dry climates (group B), respectively. Considerable number of investigations was conducted in controlled laboratory or greenhouse environments. Based on the results, future green roof research and guidelines should consider climate specifications of the region in designing growing medium, depths and attribute of green roof substrates in order to ensure enhanced plant performance. Especially, for more fragile but less investigated dry climate, considerations should be made to tackle heat fluctuations and drought stress by enhancing water holding capacity and thermal isolation of the substrate. To move forward, sustainable building solutions as a part of future urban forms, climate-adaptive green roof systems should be included into future research, practice and guidelines.     

The effect of various nitrogen fertilizers on zinc (zn) availability in non calcic brown forest soils

In this article the effect of different nitrogen fertilizer application on the availability of zinc (Zn) content in non calcic brown forest soil was investigated. For this purpose increasing rates of NH₄Cl, (NH₄)₂S0₄; NH₄N0₃ and Ca(N0₃)₂.4H₂0 fertilizers were applied for having different physical and chemical properties in two soil samples. An incubation experiment was carried out over 4 months. The available Zn content of the soils was determined each month. According to the results the highest available Zn content of the soils was obtained from NH₄Cl applied to the soils followed by (NH₄)₂S0₄; NH₄N0₃ and Ca(N0₃)₂.4H₂0 application to soil. At the end of the experiment the average available Zn content of non calcic brown forest soils for NH₄Cl, (NH₄)₂S0₄; NH₄N0₃ and Ca(N0₃)₂.4H₂0 fertilizers are 0.93, 0.91, 0.88 and 0.77 mg kg^?1, respectively.     

竹柳扦插育苗技术研究

对影响竹柳扦插的插穗直径、插穗长度和扦插基质3个因素分别进行了研究.结果表明,直径为0.5 cm≤Φ＜1.5 cm的穗条、长度5 cm的穗条、穗条在河沙基质中扦插使得各试验中插穗的生根数量、成活率和苗高等指标均较高,且竹柳的繁殖系数较高,生产成本较低,适合苗圃生产.     

Feeding of Atlantic salmon, Salmo salar L., parr in the subarctic River Teno and three tributaries in northernmost Finland

Abstract— Available food and feeding of Atlantic salmon parr were studied in different parts of a subarctic river in northernmost Finland, the River Teno: in the large main stem, in a major tributary influenced by lakes, and in two minor tributaries. The highest density of benthic organisms was found in an outlet of a lake, but drifting organisms were the most abundant in the small tributaries. Migrant parr that move to the small tributaries from the main stem have better food resources in their new habitat. Plecoptera nymphs were the most important prey for salmon parr early in the spring. Later in the summer dipterans were usually the dominant prey group. In September the importance of Plecoptera was emphasized in the small tributaries and the lake outlet, and that of Trichoptera in other sites. Drifting prey was used more by large than by small parr. The utilization of drifting food appeared to be related to the water temperature rather than to the availability of the drift.     

不同无土栽培方式对上海青生长量的影响

研究了气雾培、水培和基质栽培3种无土栽培方式对上海青生长量的影响。试验结果表明,生长初期,3种栽培方式下,上海青生长量差异不大;而在生长中后期,水培的上海青叶面积、单株质量等指标明显较优,且水培运转成本相对较低,适宜于大面积推广。     

种子发芽纸测试报告

发芽纸是种子发芽试验必需的材料。国内首次研制成的专用种子发芽纸具有吸水快、持水性好、韧度大、厚度适中等特点。该纸无毒性、幼根不易穿透,且成本低。它既可衬垫于发芽容器中,更宜作发芽纸卷。试用结果表明,它能广泛适用于农作物、蔬菜、牧草、瓜、豆类等各种种子的发芽试验。在植物种子科学研究和生产实际中,经常需要进行种子发芽试验,一般的种子发芽试验常采用纸张作为发芽床。为使种子正常发芽和便于检查发芽结果,要求发芽纸有良好的理化特性。对此,国际种子检验协会对种子发芽纸的质地、灰分、韧度和吸水性能等有明确的规定指标,如要求纸张有足够强度,在发芽试验操作中不致撕破;质地要通透多孔,但幼根不能穿入纸中。国外已有不少国家都生产有专用的种子发芽纸,而国内至今还没有一种专门供种子发芽用的纸张,长期以来使用的是普通滤纸、卫生纸、乃至黄草纸等代用品。这些纸张在协调种子发芽所需的水气条件方面存有不少缺陷,其质地、强度或吸水性等都达不到要求。为了填补国内这一空白,浙江农业大学种子科学中心和浙江民丰造纸厂造纸研究所自1987年开始进行种子发芽纸的研制。经过多次反复研制和测试,已研制成功一种种子发芽纸。它厚度适中,既可平垫于玻皿之中,又可用作发芽纸卷,且成本低于目前代用的普通滤纸。经数家种子部门试用,反应良好。此将发芽纸研制过程中生物学适用性测试的部分内容报告如下。