Elemental sulfur recommendation for pH reduction in soils from Southern Brazil

ABSTRACT The elemental sulfur (S0) application may reduce soil pH, benefiting plants adapted to acid conditions and lessening problems of overliming. Nevertheless, there is no official recommendation for its application. The objective of the study was to quantify the S0 doses required to reduce the pH of soils from Southern Brazil. The experiment was carried out in the laboratory in a factorial scheme (5 × 5), with a completely randomized design and three replicates. The treatments consisted of five soils, and five doses of S0, corresponding to 0, 50, 100, 150, and 200% of the estimated dose need to reach pH 4.0. The applied doses of S0 resulted in reduction of pH and base saturation (V%) and increase of potential acidity (H + Al). These effects, however, were reduced due to the low rate of oxidation of the S0 applied (0.76-3.36%). The soil variables correlated with S0 oxidation were Mg2+ (0.86***), Al3+ (-0.82***), H + Al (-0.89***), V% (0.68***) and aluminum saturation (m%) (-0.87***). In the evaluated soils the oxidation of 50 kg ha-1 of S0 was required to reduce one unit of pH in H2O.

Trait variation between and within Andes and coastal mountain ranges in the iconic South American tree Araucaria araucana in Chile

As global commitments to restoration are underway, science is needed to support capacity to achieve meaningful gains for ecosystems and human communities. In Chile, identification and generation of appropriate plant material is a barrier to achieving major restoration goals under the Paris Climate Agreement. Understanding genetic differentiation among plant populations is needed to maximize restoration success. For Araucaria araucana, a highly threatened iconic South American tree, this information is greatly needed to guide restoration and conservation efforts because this species occurs across a strong climate gradient. We grew seedlings from 12 populations of A. araucana across its range in Chile in a common garden to assess regional (coastal versus Andes mountain ranges) and population variation in key plant traits and relate this variation to environmental variables. We demonstrate that A. araucana is differentiated within regions and populations across its range in Chile by a suite of traits, particularly branch number and length (showing plant architectural differences) and needle width (showing leaf investment differences). We show that this variation is at least partly explained by climate and soil variables, with the most variation explained by differences between regions in temperature annual range. Thus, we recommend that restoration efforts focus on conserving genetic variation among and within regions and their populations and preventing the translocations of genotypes between coastal and Andes populations.

Soil Quality Restoration during the Natural Succession of Abandoned Cattle Pastures in Deforested Landscapes in the Colombian Amazon

Successional processes in abandoned pastures in the Amazon region have been well-documented for the floristic component; however, soil succession has been poorly studied. This study assessed the physical, chemical and biological responses of soils in the Amazon region during the natural succession process in two main landscapes of the Colombian Amazon. Soil data on soil physico–chemical (bulk density, macroaggregates, pH and minerals) and biological (soil macrofauna) composition were evaluated along chronosequence with four successional stages: (i) degraded pastures, (ii) young (10–20-year-old), (iii) middle-age (25–40-year-old) and (iv) mature forests, in two different landscapes (hill and mountain). Individual soil variables and a synthetic indicator of soil quality (GISQ) were evaluated as tools for natural succession monitoring. The results corroborated the negative impact that cattle ranching has on Amazon soils. After 10 years of natural succession, the physico–chemical and biological soil components were widely restored. Less soil compaction and organic carbon occurred in older successional stages. Soil macrofauna richness and density increased along the chronosequence, with an evident association between the macrofauna composition and the macroaggregates in the soil. None of the individual soil properties or the GISQ indicator discriminated among natural succession stages; therefore, new soil quality indicators should be developed to monitor soil quality restoration in natural successions.

Biodiversity and ecosystem functions depend on environmental conditions and resources rather than the geodiversity of a tropical biodiversity hotspot

Biodiversity and ecosystem functions are highly threatened by global change. It has been proposed that geodiversity can be used as an easy-to-measure surrogate of biodiversity to guide conservation management. However, so far, there is mixed evidence to what extent geodiversity can predict biodiversity and ecosystem functions at the regional scale relevant for conservation planning. Here, we analyse how geodiversity computed as a compound index is suited to predict the diversity of four taxa and associated ecosystem functions in a tropical mountain hotspot of biodiversity and compare the results with the predictive power of environmental conditions and resources (climate, habitat, soil). We show that combinations of these environmental variables better explain species diversity and ecosystem functions than a geodiversity index and identified climate variables as more important predictors than habitat and soil variables, although the best predictors differ between taxa and functions. We conclude that a compound geodiversity index cannot be used as a single surrogate predictor for species diversity and ecosystem functions in tropical mountain rain forest ecosystems and is thus little suited to facilitate conservation management at the regional scale. Instead, both the selection and the combination of environmental variables are essential to guide conservation efforts to safeguard biodiversity and ecosystem functions.

Shrub richness is primarily driven by climate conditions in Southwestern European woodlands

• Key message The shrub species richness in Spanish forests is mainly linked to climatic variables and the importance of the groups of variables scarcely differs among forest types. Forest surrounding the Mediterranean Basin exhibit the highest levels of shrub richness. • Context Shrub species account for a high proportion of the plant diversity in Spanish forests and are a determinant factor in forest dynamics and ecosystem functionality. • Aims To investigate the relative importance of climatic, forest stand features, soil and topographic variables in explaining shrub richness in Spanish forests and if the relative importance of these four groups of variables reflects variations among forest types. • Methods We used the Spanish National Forest Inventory and a boosted regression trees approach to identify which climatic, soil, stand and topographic variables (N = 19 variables) are related to the richness of shrub species in Spanish woodlands. • Results The shrub species richness is mainly related to climatic variables followed by soil variables whereas stand and topographic variables play a minor role. The importance of the groups of variables scarcely differs among forest types although forests located around the Mediterranean Sea display the highest levels of shrub richness. • Conclusion Shrub richness in Spain is primarily driven by climatic and soil variables, both at country and forest-type scales. Forests surrounding the Mediterranean Basin account for the highest richness of shrub species but are also those most threatened by global change. Therefore, special attention must be paid to the monitoring and assessment of these forest ecosystems.

Water Availability Controls the Biomass Increment of Melia dubia in South India

Farmland tree cultivation is considered an important option for enhancing wood production. In South India, the native leaf-deciduous tree species Melia dubia is popular for short-rotation plantations. Across a rainfall gradient from 420 to 2170 mm year–1, we studied 186 farmland woodlots between one and nine years in age. The objectives were to identify the main factors controlling aboveground biomass (AGB) and growth rates. A power-law growth model predicts an average stand-level AGB of 93.8 Mg ha–1 for nine-year-old woodlots. The resulting average annual AGB increment over the length of the rotation cycle is 10.4 Mg ha–1 year–1, which falls within the range reported for other tropical tree plantations. When expressing the parameters of the growth model as functions of management, climate and soil variables, it explains 65% of the variance in AGB. The results indicate that water availability is the main driver of the growth of M. dubia. Compared to the effects of water availability, the effects of soil nutrients are 26% to 60% smaller. We conclude that because of its high biomass accumulation rates in farm forestry, M. dubia is a promising candidate for short-rotation plantations in South India and beyond.

Assessment of soil quality in agroecosystems based on soil fauna

Soil arthropods respond sensitively to land management practices and correlate with beneficial soil functions. The aim of this research was to determine soil quality using the QBS index in different types of crops and influence of soil variables (pH soil, soil moisture, potassium, phosphorus and nitrogen) on soil arthropods. Between the years 2018 and 2020, we studied different types of crops (Brassica napus, Pisum sativum, Triticum aestivum, T. spelta, Zea mays, Grass mixture and Hordeum vulgare) and recorded 14 taxa. Our results suggest a higher QBS index value in crops grass mixture, Pisum sativum, Triticum aestivum, T. spelta. The EMI value grew with increasing values of soil moisture, soil pH, phosphorus, potassium and nitrogen; indicating the presence of soil arthropods occurring in higher quality soil. Our results suggest that agricultural intensification affects soil arthropods, which are important for the production of biomass, which also affects crop yields.

How Can Geomorphology Inform Ecological Restoration? A Synthesis of Geophysical and Biological Assessment to Determine Restoration Priorities

<p>The central concern that this study addresses is how an understanding of geomorphological processes and forms may inform ecological restoration; particularly practical restoration prioritisation. The setting is that of a hill country gully system covered in grazing pasture which historically would have been cloaked in indigenous forest. The study examines theory in conjunction with an application using a case study centred on Whareroa Farm (the restoration site) and Paraparaumu Scenic Reserve (the reference site) on the southern Kapiti Coast, north of Wellington. The impact that the change of land use has had on the soil and geomorphic condition of Whareroa and the influence the changes may have on the sites restoration is investigated. The thesis demonstrates a method of choosing reference sites to be used as templates for rehabilitating the restoration site. Geographical Information Systems and national databases are used and supplemented with site inspection. The reference site chosen, Paraparaumu Scenic Reserve, proved to be a good template for the restoration site particularly given that it is located in the midst of a heavily modified area. On-site inspection considering dendritic pattern and floristic composition confirms the database analysis results. Soil variables (bulk density, porosity, soil texture, pH, Olsen P, Anaerobic Mineralisable N, Total N (AMN), Total C and C:N ratio) are investigated and statistical comparisons made between the sites to quantify changes due to land-use change, i.e. deforestation and subsequent pastoral grazing. Factors investigated that may explain the variation in the soil variables were site (land use), hillslope location, slope aspect, and slope angle. Permutation tests were conducted to investigate the relationships between the independent factors and the SQI (dependent soil variables). Land use and slope angle were most frequent significant explanatory factors of variation, followed by hillslope location whilst slope aspect only influenced soil texture. A number of soil variables at Whareroa were found to be outside the expected range of values for an indigenous forest soil including AMN, Total N, Olsen P, and pH ...</p>

How Can Geomorphology Inform Ecological Restoration? A Synthesis of Geophysical and Biological Assessment to Determine Restoration Priorities

<p>The central concern that this study addresses is how an understanding of geomorphological processes and forms may inform ecological restoration; particularly practical restoration prioritisation. The setting is that of a hill country gully system covered in grazing pasture which historically would have been cloaked in indigenous forest. The study examines theory in conjunction with an application using a case study centred on Whareroa Farm (the restoration site) and Paraparaumu Scenic Reserve (the reference site) on the southern Kapiti Coast, north of Wellington. The impact that the change of land use has had on the soil and geomorphic condition of Whareroa and the influence the changes may have on the sites restoration is investigated. The thesis demonstrates a method of choosing reference sites to be used as templates for rehabilitating the restoration site. Geographical Information Systems and national databases are used and supplemented with site inspection. The reference site chosen, Paraparaumu Scenic Reserve, proved to be a good template for the restoration site particularly given that it is located in the midst of a heavily modified area. On-site inspection considering dendritic pattern and floristic composition confirms the database analysis results. Soil variables (bulk density, porosity, soil texture, pH, Olsen P, Anaerobic Mineralisable N, Total N (AMN), Total C and C:N ratio) are investigated and statistical comparisons made between the sites to quantify changes due to land-use change, i.e. deforestation and subsequent pastoral grazing. Factors investigated that may explain the variation in the soil variables were site (land use), hillslope location, slope aspect, and slope angle. Permutation tests were conducted to investigate the relationships between the independent factors and the SQI (dependent soil variables). Land use and slope angle were most frequent significant explanatory factors of variation, followed by hillslope location whilst slope aspect only influenced soil texture. A number of soil variables at Whareroa were found to be outside the expected range of values for an indigenous forest soil including AMN, Total N, Olsen P, and pH ...</p>

Earthworm Community In Relation To Soil Properties And Metals In Hebei Province, North China

In this study, we examined the influence of soil properties (pH, total potassium (TK), available potassium (AK), total nitrogen (TN), total phosphorus (TP), available potassium (AP), cation exchange capacity (CEC), and soil organic carbon (SOC)), and metals (Cd, Pb, Cu, and Zn) on the density, diversity, and species composition of earthworms in the Hebei Province, North China. In total, 535 earthworms were collected from 20 sites in the study area, and belonged to three families, six genera, and ten species. Amynthas hupeiensis (39.4%) and Drawida gisti (37.8%) were the dominant species. The correlations between soil variables and earthworm composition determined using redundancy analysis indicated that SOC, TK, and AK enhanced earthworm density (total, adult, and juvenile) and species (A. hupeiensis and D. gisti) abundances. Earthworm composition remained unaffected by the metals (Cd and Pb) in the uncontaminated sites; in contrast, species were absent in areas with high metal concentrations (S19 and S20). Soil TN content was negatively and positively related to Shannon and Peilou indexes (p<0.05), respectively, indicating that TN may be pivotal in influencing earthworm diversity and species evenness. Overall, the soil properties such as K, SOC, and TN were the key variables affecting earthworm density, diversity, and species dominance.