Salinity and sodicity effects on respiration and microbial biomass of soil

An understanding of the effects of salinity and sodicity on soil carbon (C) stocks and fluxes is critical in environmental management, as the areal extents of salinity and sodicity are predicted to increase. The effects of salinity and sodicity on the soil microbial biomass (SMB) and soil respiration were assessed over 12weeks under controlled conditions by subjecting disturbed soil samples from a vegetated soil profile to leaching with one of six salt solutions; a combination of low-salinity (0.5dSm⁻¹), mid-salinity (10dSm⁻¹), or high-salinity (30dSm⁻¹), with either low-sodicity (sodium adsorption ratio, SAR, 1), or high-sodicity (SAR 30) to give six treatments: control (low-salinity low-sodicity); low-salinity high-sodicity; mid-salinity low-sodicity; mid-salinity high-sodicity; high-salinity low-sodicity; and high-salinity high-sodicity. Soil respiration rate was highest (56–80mg CO₂-C kg⁻¹ soil) in the low-salinity treatments and lowest (1–5mg CO₂-C kg⁻¹ soil) in the mid-salinity treatments, while the SMB was highest in the high-salinity treatments (459–565mg kg⁻¹ soil) and lowest in the low-salinity treatments (158–172mg kg⁻¹ soil). This was attributed to increased substrate availability with high salt concentrations through either increased dispersion of soil aggregates or dissolution or hydrolysis of soil organic matter, which may offset some of the stresses placed on the microbial population from high salt concentrations. The apparent disparity in trends in respiration and the SMB may be due to an induced shift in the microbial population, from one dominated by more active microorganisms to one dominated by less active microorganisms.     

A comparison of the properties of manufactured soils produced from composting municipal green waste alone or with poultry manure or grease trap/septage waste

Manufactured soil for landscaping purposes was produced by composting for 6 weeks (1) municipal green waste alone, (2) green waste amended with 25% v/v poultry manure, or (3) green waste immersed in, and then removed from, a mixture of liquid grease trap waste/septage. Composting temperatures increased most rapidly and reached highest values (78oC) in the grease trap/septage-amended green waste. In comparison with green waste alone, addition of poultry manure prolonged the period of elevated temperatures and increased the maximum temperature attained from 52oC to 61oC. Following composting, each of the materials was split into (1) 100% compost, (2) 80% compost plus 20% v/v soil, and (3) 70% compost plus 20% soil plus 10% coal fly ash. Addition of poultry manure or grease trap/septage to green waste prior to composting increased bulk density and reduced total porosity of the composted product. Addition of soil, or soil and ash, to composts increased bulk density, reduced total porosity, decreased percentage macropores, and increased percentage mesopores and available water-holding capacity. Bicarbonate-extractable P, exchangeable NH₄⁺ and NO₃⁻, electrical conductivity (EC), soluble C, soluble C as a percentage of organic C, basal respiration, and metabolic quotient were all markedly greater in the grease trap/septage-amended than poultry manure-amended or green waste alone treatments. Values for extractable P and EC were considered large enough to be damaging to plant growth and germination index (GI) of watercress was less than 60% for all grease trap/septage composts. Extractable P and EC were also high, and GI was <100%, in the green waste alone and poultry manure-amended green waste alone treatments. Addition of soil or soil and ash to these composts resulted in GI values >100%.     

Resettling,disconnecting or displacing? Attending to local sociality,culture and history in disaster settings

In many disaster settings, top‐down responses emphasise ‘expert‐led’ solutions that often involve relocating disaster‐affected communities. While the intention might be to move people from harm's way and facilitate recovery, failure to attend to local pre‐disaster circumstances as well as the interplay between power, resilience and vulnerability within and around affected communities often sees resettlement reconfigure as displacement or disconnection. This oversight may even usher in a new phase of dispossession and disadvantage for marginalised groups (particularly in colonial settings). This paper explores experiences in Australia, Japan and Taiwan to reflect on what issues of local sociality, local culture and local resilience need to be attended to in framing ‘better’ disaster responses.     

A new framework of spatial targeting for single-species conservation planning

Context

Organisations acting to conserve and protect species across large spatial scales prioritise to optimise use of resources. Spatial conservation prioritization tools typically focus on identifying areas containing species groups of interest, with few tools used to identify the best areas for single-species conservation, in particular, to conserve currently widespread but declining species.

Objective

A single-species prioritization framework, based on temporal and spatial patterns of occupancy and abundance, was developed to spatially prioritize conservation action for widespread species by identifying smaller areas to work within to achieve predefined conservation objectives.

Methods

We demonstrate our approach for 29 widespread bird species in the UK, using breeding bird atlas data from two periods to define distribution, relative abundance and change in relative abundance. We selected occupied 10-km squares with abundance trends that matched species conservation objectives relating to maintaining or increasing population size or range, and then identified spatial clusters of squares for each objective using a Getis-Ord-Gi* or near neighbour analysis.

Results

For each species, the framework identified clusters of 20-km squares that enabled us to identify small areas in which species recovery action could be prioritized.

Conclusions

Our approach identified a proportion of species’ ranges to prioritize for species recovery. This approach is a relatively quick process that can be used to inform single-species conservation for any taxa if sufficiently fine-scale occupancy and abundance information is available for two or more time periods. This is a relatively simple first step for planning single-species focussed conservation to help optimise resource use.

     

Spatial relationship between biodiversity and geodiversity across a gradient of land-use intensity in high-latitude landscapes

Context

‘Conserving Nature’s stage’ has been advanced as an important conservation principle because of known links between biodiversity and abiotic environmental diversity, especially in sensitive high-latitude environments and at the landscape scale. However these links have not been examined across gradients of human impact on the landscape.

Objectives

To (1) analyze the relationships between land-use intensity and both landscape-scale biodiversity and geodiversity, and (2) assess the contributions of geodiversity, climate and spatial variables to explaining vascular plant species richness in landscapes of low, moderate and high human impact.

Methods

We used generalized additive models (GAMs) to analyze relationships between land-use intensity and both geodiversity (geological, geomorphological and hydrological richness) and plant species richness in 6191 1-km² grid squares across Finland. We used linear regression-based variation partitioning (VP) to assess contributions of climate, geodiversity and spatial variable groups to accounting for spatial variation in species richness.

Results

In GAMs, geodiversity correlated negatively, and plant species richness positively, with land-use intensity. Both relationships were non-linear. In VP, geodiversity best accounted for species richness in areas of moderate to high human impact. These overall contributions were mainly due to variation explained jointly with climate, which dominated the models. Independent geodiversity contributions were highest in pristine environments, but low throughout.

Conclusions

Human action increases biodiversity but may reduce geodiversity, at landscape scale in high-latitude environments. Better understanding of the connections between biodiversity and abiotic environment along changing land-use gradients is essential in developing sustainable measures to conserve biodiversity under global change.

     

Genetic analysis of early-maturing maize (Zea Mays L.) inbred lines under stress and nonstress conditions

Early-maturing maize (Zea Mays L.) germplasm developed from diverse sources has the potential for use in developing maize hybrids suitable for increasing maize production in the dry ecologies of eastern Africa. A diallel study was conducted to estimate general combining ability (GCA) of 12 early-maturing maize inbred lines, identify potential single-cross hybrids for use as parents, assess genetic diversity among the inbred lines, and relate genetic distance to specific combining ability (SCA) and hybrid performance. Sixty-six F₁ diallel hybrids were evaluated under optimal and drought stress conditions at four locations in Kenya and Uganda. The parental inbred lines were genotyped using 94 single nucleotide polymorphism (SNP) markers. Additive gene action was more important than nonadditive gene action for inheritance of grain yield (GY) under optimal conditions. However, nonadditive gene effects were more important in the inheritance of GY under drought and across all environments. Inbred lines CKL0722, VL058014, and CZL0724 were among the best with positive GCA effects for GY across both optimal and drought stress conditions. The correlation between SCA and both genetic distance and F₁ GY was significant under both drought stress and across all environments. Inbred lines with desirable GCA effects for GY and other agronomic traits and hybrids with good performance under both optimal and drought stress conditions are potential parents for development of various types of high-yielding, stress-tolerant, and early-maturing hybrids.     

Short-term effects of aglime on inorganic- and organic-derived CO2 emissions from two acid soils amended with an ammonium-based fertiliser

Purpose

Aglime application can promote carbon dioxide (CO₂) emissions from acid soils. However, the controlling mechanisms are still poorly understood, particularly the role of fertiliser-ammonium oxidation. This study therefore assessed the effects of aglime on soil inorganic C (SIC)– and soil organic C (SOC)–derived CO₂ emissions from acid soils amended with ammonium.

Materials and methods

Ammonium at three N rates [0% (A0), 0.005% (A1), and 0.2% (A2) w/w] and labelled aglime (Ca¹³CO_3,¹³C 5.94% aa) at three rates [0% (L1), 0.067% (L1), and 0.392% (L2) w/w] were applied to two contrasting acid soils (Nariva series, Mollic Fluvaquents; and Piarco series, Typic Kanhaplaquults) and incubated in 1-l media bottles for 23 days. A calcareous soil (Princes Town series, Aquentic Eutrudepts, carbonate δ¹³C of ??4.79‰) was included as a control that only received ammonium at the three rates.

Results and discussion

The application of ammonium at the A2 rate significantly (p?<?0.05) increased cumulative SIC-CO₂ emissions by 15.8 and 27.1% in comparison to the A0 rate for the Nariva and Piarco soils, respectively, when they were limed at the L2 rate. The lower rate of ammonium (A1), however, had no effect on these emissions, which suggests that enough acidity may not have been generated at this rate to significantly enhance the release of SIC-CO₂. Furthermore, no effect of ammonium rates was observed on SIC-CO₂ emissions from the calcareous soil, which refutes the hypothesis that this amendment plays a greater role in regulating these emissions from calcareous soils compared with acid soils. Also, in contradiction to another hypothesis, the aglime-induced priming effect on SOC decomposition was more apparent in the low-C Piarco soil. This effect was also significantly (p?<?0.05) greater at the L2 rate (above the lime requirement for Piarco), which demonstrates the negative impact that over-liming could have on the sequestration of C in this soil. Our results also showed that ammonium addition may also help to reduce the magnitude of the aglime-induced priming effect in the Piarco soil when it is not over-limed.

Conclusions

Overall, the findings of this study suggest that ammonium fertiliser broadcast at conventional rates may not serve as a significant regulator of SIC-CO₂ emissions from highly to moderately acidic soils amended with aglime. Our findings also indicate a need to consider nitrogen management as an important factor regulating the effects of aglime on SOC-CO₂ emissions.

     

Sand colic in a mule: A case report

A 25-year-old mule was showing signs of colic. Clinical examination revealed acute pain, bilateral abdominal distention, stretching out and standing in this position. Rectal palpation revealed a hardened mass in the ventral region of the pelvic inlet. Surgical intervention was accomplished and faecaliths removed by colotomy. The mule died unexpectedly and postmortem examination revealed sand masses within the right ventral and right dorsal colon which caused obstruction of the intestinal tract in sternal and diaphragmatic flexures, respectively. This appears to be the first report of sand colic in a mule in Iran.     

Using an unmanned aerial vehicle to evaluate nitrogen variability and height effect with an active crop canopy sensor

Ground-based active sensors have been used in the past with success in detecting nitrogen (N) variability within maize production systems. The use of unmanned aerial vehicles (UAVs) presents an opportunity to evaluate N variability with unique advantages compared to ground-based systems. The objectives of this study were to: determine if a UAV was a suitable platform for use with an active crop canopy sensor to monitor in-season N status of maize, if UAV’s were a suitable platform, is the UAV and active sensor platform a suitable substitute for current handheld methods, and is there a height effect that may be confounding measurements of N status over crop canopies? In a 2013 study comparing aerial and ground-based sensor platforms, there was no difference in the ability of aerial and ground-based active sensors to detect N rate effects on a maize crop canopy. In a 2014 study, an active sensor mounted on a UAV was able to detect differences in crop canopy N status similarly to a handheld active sensor. The UAV/active sensor system (AerialActive) platform used in this study detected N rate differences in crop canopy N status within a range of 0.5–1.5 m above a relatively uniform turfgrass canopy. The height effect for an active sensor above a crop canopy is sensor- and crop-specific, which needs to be taken into account when implementing such a system. Unmanned aerial vehicles equipped with active crop canopy sensors provide potential for automated data collection to quantify crop stress in addition to passive sensors currently in use.