Vegetation Succession After Bauxite Mining in Western Australia

Alcoa World Alumina Australia has been rehabilitating bauxite mines in the jarrah forest of Western Australia for more than 35 years. An experiment was established in 1988 using three different seed treatments (legume and small understorey mix, small understorey mix only, and no seed) and two fertilizer treatments (N and P, and P only). The objectives of this study were to (1) document vegetation changes in the first 14 years after bauxite mining; (2) assess whether the vegetation is becoming more similar to the unmined forest; and (3) gain a better understanding of successional processes. Seed treatments significantly affected 13 of the 14 measured vegetation characteristics. Native species richness was higher in seeded than in unseeded sites at 1, 2, and 5 years of age, whereas diversity and evenness were generally higher at all assessment ages. Exotic species density was higher in unseeded than in seeded sites from 5 years onward, whereas richness was higher from 8 years onward. Nitrogen fertilizer significantly increased exotic species richness, density, and cover. Ephemerals dominated plant density in all rehabilitation treatments over time, whereas seeder species dominated cover. In contrast, resprouting species dominated density and cover in the unmined forest. Orchids were the only species that were not present in the first year in rehabilitated sites but increased in abundance over time. Vegetation composition in rehabilitated areas did not become more similar to the unmined forest during the 14 years since seeding, instead strongly reflected the initial species mix. Rehabilitated bauxite mines appear to follow the initial floristic composition model of succession.     

The influence of compound fertilizer and cupric sulfate on the growth and the bioelement content of cembra pine seedlings (Pinus cembra)

Summary It was the purpose of this study to investigate the effect of compound fertilization and compound fertilization with cupric sulfate on the growth and the bioelement content of cembra pine seedlings. At the same time microbiological investigations of the soil were carried out under the same conditions.Five months after fertilization the seedlings of the plot treated with compound fertilizer showed lower total weights and lower bioelement contents in their organs than the seedlings in the untreated control plot and in the plot treated with copper.In addition to these results it was found that in the plot treated with compound fertilizer there was an increase in the activity of those microorganisms which are probably nutrient competitors to the cembra pine seedlings whereas the plot treated with cupric sulfate showed a decrease in the activity of these microorganisms. The addition of cupric sulfate caused a partial elimination of this competition because of the toxic properties of the heavy metal and enabled the young cembra pine plants to increase their uptake of nitrogen, phosphorus and other bioelements.In the control plot and in the plot treated with copper beginnings of mycorrhiza were observed. It could not be proved that the results were influenced by weed competition.These observations have contributed to explaining the results of previous experiments which have always shown that fertilizers containing cupric sulfate favour the growth of cembra pine seedlings.     

A model to describe the pattern of availability of broadcast phosphorus fertilizer during the growth of a crop

A model is described which compares the rate of phosphorus demand of a field grown lettuce crop with the rate at which the crop can obtain phosphorus from broadcast fertilizer. Early root growth of lettuce is so slow that on average it takes about 21 days for the first granule of fertilizer to be exploited by a plant, whereas seed reserves of phosphorus are depleted within about 8 days of sowing. This is likely to result in a reduction in yield which cannot be overcome by simply applying more broadcast fertilizer. Some placement of fertilizer near to each plant is required if phosphorus deficiency is to be avoided. The model can also be applied to other crops, and the delay before the first fertilizer granule is exploited is shown to be slightly shorter in cabbage and very short in wheat.     

Greenhouse gas fluxes over managed grasslands in Central Europe

Central European grasslands are characterized by a wide range of different management practices in close geographical proximity. Site‐specific management strategies strongly affect the biosphere–atmosphere exchange of the three greenhouse gases (GHG) carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄). The evaluation of environmental impacts at site level is challenging, because most in situ measurements focus on the quantification of CO₂ exchange, while long‐term N₂O and CH₄ flux measurements at ecosystem scale remain scarce. Here, we synthesized ecosystem CO₂, N₂O, and CH₄ fluxes from 14 managed grassland sites, quantified by eddy covariance or chamber techniques. We found that grasslands were on average a CO₂ sink (−1,783 to −91 g CO₂ m⁻² year⁻¹), but a N₂O source (18–638 g CO₂‐eq. m⁻² year⁻¹), and either a CH₄ sink or source (−9 to 488 g CO₂‐eq. m⁻² year⁻¹). The net GHG balance (NGB) of nine sites where measurements of all three GHGs were available was found between −2,761 and −58 g CO₂‐eq. m⁻² year⁻¹, with N₂O and CH₄ emissions offsetting concurrent CO₂ uptake by on average 21 ± 6% across sites. The only positive NGB was found for one site during a restoration year with ploughing. The predictive power of soil parameters for N₂O and CH₄ fluxes was generally low and varied considerably within years. However, after site‐specific data normalization, we identified environmental conditions that indicated enhanced GHG source/sink activity (“sweet spots”) and gave a good prediction of normalized overall fluxes across sites. The application of animal slurry to grasslands increased N₂O and CH₄ emissions. The N₂O‐N emission factor across sites was 1.8 ± 0.5%, but varied considerably at site level among the years (0.1%–8.6%). Although grassland management led to increased N₂O and CH₄ emissions, the CO₂ sink strength was generally the most dominant component of the annual GHG budget.     

Comparison of selenium treatments of crops in the field

Field experiments with spring and winter barley and ryegrass were carried out to compare the effect of fertilizers enriched with selenate or selenite with foliar application on the selenium (Se) concentrations in the crops. Application of about 20 g Se/ha given as selenate or about 100 g as selenite in a PK fertilizer and about 5 g Se/ha sprayed on the plants increased the Se-concentrations from insufficient levels to levels that met the animal nutritional requirement. Ryegrass obtained sufficient Se concentrations at lower levels of added Se than did the barley. Toxic concentrations did not occur. The choice of method thus depends on the farming practice in the individual cases.     

解磷微生物研究及应用进展

磷是植物生长所必需的重要营养元素之一,以难溶性磷酸盐形式存在于土壤中,磷肥在施入土壤后,极易被土壤固定,难以被作物吸收利用,从而降低了磷肥的利用率.解磷菌通过酸解、酶解、降低土壤环境pH及其他方式溶解土壤中难溶性磷酸盐,供作物吸收利用.解磷菌种类繁多,其存在方式和数量受土壤环境、植物种类、人为扰动等因素影响.详细论述了...     

Microbial community and network differently reshaped by crushed straw or biochar incorporation and associated with nitrogen fertilizer level

Straw returning has been demonstrated as a beneficial approach for the utilization of renewable biomass source, which contributes to reducing environmental pollution and strengthening the sustainability of agriculture. However, information on how microorganisms respond to different straw return modes (SRMs) at varying nitrogen fertilizer levels (NFLs) in the black soil is still limited. The community composition, network pattern, and modular function of bacteria and fungi are investigated under three SRMs, including straw removal (CK), crushed straw incorporation (SD), and biochar incorporation (BC) at three NFLs (0, 144, and 240 kg N ha⁻¹, respectively) mainly using Illumina MiSeq technique based on a long-term maize field experiment. Results showed that bacterial richness, diversity, and fungal richness decreased with NFL reduction. However, these decreases can be compensated by SD and BC, demonstrating superiority for BC at reduced NFLs. SD and BC differed in their effects on the bacterial and fungal abundances (showing increments only in SD) and fungal Shannon diversity (remaining stable only in BC irrespective of NFLs). Microbial communities were substantially affected by SRMs and interacted with NFLs, which were driven by soil NH₄⁺-N, available potassium, total nitrogen, and pH. In addition, SD induced a network characterized by its highly complex (average degree 10.259 vs. 3.364) and stable structure (average clustering coefficient 0.503 vs. 0.239), Ascomycota as predominating keystone taxa, and abundant N-cycling related bacteria, while BC formed a network comprising a superior modular structure (modularity 2.599 vs. 0.912), dominant symbiotic fungi, and soil bulk density as specific shaping factor, indicating that network pattern, keystone taxa, modular function, and determining factors shifted between SD and BC co-occurrence networks. These results deepen insights into the response divergence of bacteria and fungi to SRMs and NFLs, providing a scientific basis for selecting the suitable strategy for sustainable straw utilization in the black soil area.