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Introduction: The relief acts as a soil formation factor and interferes, even indirectly, in the physical-chemical composition of soils, so that important variations in fertility can occur along a toposequence. In agricultural crops, variations in fertility have a major impact on productivity and production costs, which makes mapping soil fertility important. The aim of this study was to evaluate the fertility of soils under different agricultural crops and different points of relief in a mountainous area located in the municipality of Aratuba-CE.   Theoretical reference: Various studies that relate soil types to the landscape show that deeper and more developed soils generally occupy flatter, or top, relief positions, where conditions for water percolation are favored. (ARTUR et al., 2014; SOUZA JUNIOR and DEMATTÊ, 2008). Braga et al. (2015) verified the existence of a correlation between soil fertility and distribution of tree species.   Methodology: The design was in a randomized block in a split-plot scheme, with the plots formed by four cultivation areas, namely: banana trees (A1), banana trees and cashew trees (A2); grass (A3); pigeon pea (A4); and a control area (A5), maintained with natural vegetation. The subplots were formed by three relief positions: top, middle and slope. The physical-chemical variables of the soil were analyzed: pH, potassium, magnesium, calcium, phosphorus, aluminum, potential acidity, base sum, base saturation, total CEC, effective CTC, PST and soil density.   Results: It was observed that the top areas have greater amounts of nutrients. Studies of this nature can provide indications about the evolution of pedogeomorphological systems in landscapes and enable the planning of the most appropriate and sustainable agricultural exploration.   Conclusion: The top area presents nutrients in greater quantities, compared to the middle and slope, which may indicate that, although this region is more susceptible to leaching, this still occurs initially, to the point of not affecting soil fertility in the area. local.

Soils are increasingly recognized as major contributors to ecosystem services such as food production and climate regulation (1, 2), and demand for up-to-date and relevant soil information is soaring. But communicating such information among diverse audiences remains challenging because of inconsistent use of technical jargon, and outdated, imprecise methods. Also, spatial resolutions of soil maps for most parts of the world are too low to help with practical land management. While other earth sciences (e.g., climatology, geology) have become more quantitative and have taken advantage of the digital revolution, conventional soil mapping delineates space mostly according to qualitative criteria and renders maps using a series of polygons, which limits resolution. These maps do not adequately express the complexity of soils across a landscape in an easily understandable way

Nutrient limitation to primary productivity and other biological processes is widespread in terrestrial ecosystems, and nitrogen (N) and phosphorus (P) are the most common limiting elements, both individually and in combination. Mechanisms that drive P limitation, and their interactions with the N cycle, have received less attention than mechanisms causing N limitation. We identify and discuss six mechanisms that could drive P limitation in terrestrial ecosystems. The best known of these is depletion-driven limitation, in which accumulated P losses during long-term soil and ecosystem development contribute to what Walker and Syers termed a \"terminal steady state\" of profound P depletion and limitation. The other mechanisms are soil barriers that prevent access to P; transactional limitation, in which weathering of P-containing minerals does not keep pace with the supply of other resources; low-P parent materials; P sinks; and anthropogenic changes that increase the supply of other resources (often N) relative to P. We distinguish proximate nutrient limitation (which occurs where additions of a nutrient stimulate biological processes, especially productivity) from ultimate nutrient limitation (where additions of a nutrient can transform ecosystems). Of the mechanisms that drive P limitation, we suggest that depletion, soil barriers, and low-P parent material often cause ultimate limitation because they control the ecosystem mass balance of P. Similarly, demand-independent losses and constraints to N fixation can control the ecosystem-level mass balance of N and cause it to be an ultimate limiting nutrient.

Background and aims Biochar has attracted research interest due to its ability to increase the soil carbon pool and improve crop productivity. The objective of this study was to evaluate the metal immobilizing impact of chicken manure- and green waste-derived biochars, and their effectiveness in promoting plant growth. Methods The immobilization and phytoavailability of Cd, Cu and Pb was examined using naturally contaminated shooting range and spiked soils. Biochar samples prepared from chicken manure and green waste were used as soil amendments. Results Application of biochar significantly reduced NH4NO3 extractable Cd, Cu and Pb concentrations of soils, indicating the immobilization of these metals. Chicken manure-derived biochar increased plant dry biomass by 353 and 572% for shoot and root, respectively with 1% of biochar addition. This might be attributed to reduced toxicity of metals and increased availability of nutrients such as P and K. Both biochars significantly reduced Cd, Cu and Pb accumulation by Indian mustard (Brassica juncea), and the reduction increased with increasing amount of biochar application except Cu concentration. Metal sequential fractionation data indicated that biochar treatments substantially modified the partitioning of Cd, Cu and Pb from the easily exchangeable phase to less bioavailable organic bound fraction. Conclusions The results clearly showed that biochar application was effective in metal immobilization, thereby reducing the bioavailability and phytotoxicity of heavy metals.

Summary Soil is the primary source of plant silicon (Si) and therefore a key reservoir of the Si biological cycling. Soil processes control the stock of Si‐bearing minerals and the release of dissolved Si (DSi), hence the Si fluxes at the Earth's surface. Here, we review the interdependent relationship between soil processes and the return of plant Si in soils, and their controls on the biological Si feedback loop. Dissolution and precipitation of soil silicate minerals govern the bioavailability of Si. Plants affect Si biocycling through mineral weathering, root uptake, phytolith formation, return and dissolution in soil. Thus, soil processes and Si biocycling readily interact in soil–plant systems. Rock mineral weathering and soil formation are driven by the five soil‐forming factors: parent rock, climate, topography, age and biota. These factors govern Si fluxes in soil–plant systems since they impact both the mineral weathering rate and fate of DSi. The variability of soil‐forming factors at a global scale explains both the soil diversity and high variability of the rates of Si cycling in terrestrial ecosystems. Plants play a crucial role in soil evolution by promoting weathering and forming phytoliths (plant silica bodies). They thus act as Si sinks and sources. With increasing depletion of lithogenic (LSi) and pedogenic (PSi) silicates, the biological Si feedback loop progressively takes over the Si plant uptake from weatherable LSi and PSi minerals. With rising weathering, the soil becomes increasingly concentrated in phytoliths, phytogenic amorphous silicates (PhSi), which are constantly formed in plant and dissolved in soil. Paradoxically, the Si biocycling is thus more intense in soils depleted in primary LSi source. By converting soil LSi and PSi into PhSi, plants increase the mobility of Si in soil and alleviate desilication in the topsoil. Non‐essential plant Si is therefore an essential link between mineral and living worlds. The dynamics of Si in terrestrial ecosystems is thus largely governed by pedogenesis and its relationship with plant community and diversity. Consequently, the appraisal of soil constituents and processes is central to further understand their interaction with the biological Si feedback loop. Lay Summary

1. Chronosequences and associated space-for-time substitutions are an important and often necessary tool for studying temporal dynamics of plant communities and soil development across multiple time-scales. However, they are often used inappropriately, leading to false conclusions about ecological patterns and processes, which has prompted recent strong criticism of the approach. Here, we evaluate when chronosequences may or may not be appropriate for studying community and ecosystem development. 2. Chronosequences are appropriate to study plant succession at decadal to millennial time-scales when there is evidence that sites of different ages are following the same trajectory. They can also be reliably used to study aspects of soil development that occur between temporally linked sites over time-scales of centuries to millennia, sometimes independently of their application to shorter-term plant and soil biological communities. 3. Some characteristics of changing plant and soil biological communities (e. g. species richness, plant cover, vegetation structure, soil organic matter accumulation) are more likely to be related in a predictable and temporally linear manner than are other characteristics (e. g. species composition and abundance) and are therefore more reliably studied using a chronosequence approach. 4. Chronosequences are most appropriate for studying communities that are following convergent successional trajectories and have low biodiversity, rapid species turnover and low frequency and severity of disturbance. Chronosequences are least suitable for studying successional trajectories that are divergent, species-rich, highly disturbed or arrested in time because then there are often major difficulties in determining temporal linkages between stages. 5. Synthesis. We conclude that, when successional trajectories exceed the life span of investigators and the experimental and observational studies that they perform, temporal change can be successfully explored through the judicious use of chronosequences.

Little is known about the response of arbuscular mycorrhizal fungal communities to ecosystem development. We use a long‐term soil chronosequence that includes ecosystem progression and retrogression to quantify the importance of host plant identity as a factor driving fungal community composition during ecosystem development. We identified arbuscular mycorrhizal fungi and plant species from 50 individual roots from each of 10 sites spanning 5–120 000 yr of ecosystem age using terminal restriction fragment length polymorphism (T‐RFLP), Sanger sequencing and pyrosequencing. Arbuscular mycorrhizal fungal communities were highly structured by ecosystem age. There was strong niche differentiation, with different groups of operational taxonomic units (OTUs) being characteristic of early succession, ecosystem progression and ecosystem retrogression. Fungal alpha diversity decreased with ecosystem age, whereas beta diversity was high at early stages and lower in subsequent stages. A total of 39% of the variance in fungal communities was explained by host plant and site age, 29% of which was attributed to host and the interaction between host and site (24% and 5%, respectively). The strong response of arbuscular mycorrhizal fungi to ecosystem development appears to be largely driven by plant host identity, supporting the concept that plant and fungal communities are tightly coupled rather than independently responding to habitat.

Long‐term pedogenesis leads to important changes in the availability of soil nutrients, especially nitrogen (N) and phosphorus (P). Changes in the availability of micronutrients can also occur, but are less well understood. We explored whether changes in leaf nutrient concentrations and resorption were consistent with a shift from N to P limitation of plant productivity with soil age along a > 2‐million‐year dune chronosequence in south‐western Australia. We also compared these traits among plants of contrasting nutrient‐acquisition strategies, focusing on N, P and micronutrients. The range in leaf [P] for individual species along the chronosequence was exceptionally large for both green (103–3000 μg P g⁻¹) and senesced (19–5600 μg P g⁻¹) leaves, almost equalling that found globally. From the youngest to the oldest soil, cover‐weighted mean leaf [P] declined from 1840 to 228 μg P g⁻¹, while P‐resorption efficiency increased from 0% to 79%. All species converged towards a highly conservative P‐use strategy on the oldest soils. Declines in cover‐weighted mean leaf [N] with soil age were less strong than for leaf [P], ranging from 13.4 mg N g⁻¹ on the youngest soil to 9.5 mg N g⁻¹ on the oldest soil. However, mean leaf N‐resorption efficiency was greatest (45%) on the youngest, N‐poor soils. Leaf N:P ratio increased from 8 on the youngest soil to 42 on the oldest soil. Leaf zinc (Zn) concentrations were low across all chronosequence stages, but mean Zn‐resorption efficiency was greatest (55–74%) on the youngest calcareous dunes, reflecting low Zn availability at high pH. N₂‐fixing species had high leaf [N] compared with other species. Non‐mycorrhizal species had very low leaf [P] and accumulated Mn across all soils. We surmise that this reflects Mn solubilization by organic acids released for P acquisition. Synthesis. Our results show community‐wide variation in leaf nutrient concentrations and resorption that is consistent with a shift from N to P limitation during long‐term ecosystem development. High Zn resorption on young calcareous dunes supports the possibility of micronutrient co‐limitation. High leaf [Mn] on older dunes suggests the importance of carboxylate release for P acquisition. Our results show a strong effect of soil nutrient availability on nutrient‐use efficiency and reveal considerable differences among plants of contrasting nutrient‐acquisition strategies.

Background Soil phosphorus availability declines during long-term ecosystem development on stable land surfaces due to a gradual loss of phosphorus in runoff and transformation of primary mineral phosphate into secondary minerals and organic compounds. These changes have been linked to a reduction in plant biomass as ecosystems age, but the implications for belowground organisms remain unknown. Methods We constructed a phosphorus budget for the well-studied 120,000 year temperate rainforest chronosequence at Franz Josef, New Zealand. The budget included the amounts of phosphorus in plant biomass, soil microbial biomass, and other soil pools. Results Soil microbes contained 68-78 % of the total biomass phosphorus (i.e. plant plus microbial) for the majority of the 120,000 year chronosequence. In contrast, plant phosphorus was a relatively small pool that occurred predominantly in wood. This points to the central role of the microbial biomass in determining phosphorus availability as ecosystems mature, yet also indicates the likelihood of strong competition between plants and saprotrophic microbes for soil phosphorus. Conclusions This novel perspective on terrestrial biogeochemistry challenges our understanding of phosphorus cycling by identifying soil microbes as the major biological phosphorus pool during long-term ecosystem development.