Louis A. Schipper

Incorporating plantain into grazed pasture swards is proposed as an approach to reduce nitrate leaching and nitrous oxide emissions. However, consideration must be given to potential emission-swapping, such as a reduction in soil carbon (C), which can contribute to increases in atmospheric CO ₂ . We compared the net ecosystem C balance (NECB) of two adjacent newly-sown paddocks (~ 3 ha each) of (i) traditional ryegrass and white clover pasture (RyWC) and (ii) a pure plantain sward, to assess whether plantain was beneficial or detrimental for the carbon balance. The NECB was calculated by combining eddy covariance (EC) measurements of CO ₂ with measurements and estimates of lateral C transfers. Concurrently, regular measurements of sward composition and properties were taken. During the approximately 2.5-year experiment, the RyWC sward had an NECB of −199 g C m ⁻² period ⁻¹ compared with −273 g C m ⁻² period ⁻¹ for the plantain sward. The slightly larger loss from the plantain sward was attributed to lower excretal C returns due to differences in grazing duration (13.9 days for the RyWC paddock, and 5.9 days for the plantain paddock) during the first year of grazing. In the second year, the grazing management of the two paddocks was the same, and the NECBs were comparable. Both pasture dry matter production and CO ₂ uptake were similar between the swards, although the lower C content of the plantain resulted in smaller C exports by either harvest or grazing. We conclude that small differences in NECB (and assumed soil C) between a pure plantain sward and a traditional ryegrass and white clover sward are associated with management rather than pasture species.

Urban expansion depletes soil organic carbon (SOC) stocks through topsoil disturbance, removal, and sealing, contributing to carbon emissions and climate change. However, SOC considerations are largely absent from urban sustainability practice. This study integrates SOC loss into two distinct assessment domains—urban planning and building life cycle assessment (LCA)—to evaluate its magnitude at both the urban and building levels and investigate potential pathways to mitigate it. At the urban level, a business-as-usual urban expansion scenario for Auckland, New Zealand, is modelled and compared with a SOC-aware alternative that prioritizes development on low-SOC soils. The SOC-aware scenario was found to conserve 14.6% of SOC (0.092 MtCO₂-eq), equivalent to 46% of the national embodied impact reduction target for the construction sector, demonstrating the significance of SOC-aware planning. At the building level, SOC loss is introduced as a potential LCA module, examining four residential typologies—apartment, townhouse, double-storey detached, and single-storey detached—to evaluate its magnitude relative to conventional embodied impacts. The results indicate that SOC loss can account for up to 70.9% of conventionally assessed embodied impacts (for single-storey detached house built on Organic Soils), while remaining a substantial contributor in all other cases—on average representing 0.9%, 4.6%, 9.3%, and 21.5% of conventional embodied impacts for apartment, townhouse, double-storey detached, and single-storey detached houses, respectively. Overall, integrating SOC loss into decision-relevant assessments reveals its substantial magnitude and offers an opportunity to reduce it, while underscoring the need for improved soil characterization in areas zoned for urban expansion.

Soil is the Earth's largest carbon (C) reservoir, holding nearly twice as much C as the atmosphere. Climate change-induced temperature increases could enhance soil organic matter (SOM) decomposition, potentially releasing carbon dioxide (CO2) into the atmosphere, thus resulting in a positive feedback to climate change. This presents the question: how can we define the response of SOM decomposition rates to short-term changes in temperature? Can we utilize this data to fit mechanistically defined equations in Earth system models for climate predictions? Most research to date has focused on laboratory soil incubations at different discrete temperatures. This, however, does not result in a detailed temperature response curve, which is required to test novel hypotheses imposed by the latest developments in the field, such as the macromolecular rate theory (MMRT). In this paper, we introduce a temperature gradient block, modified and improved from earlier work, detail its construction process, and provide a detailed explanation for its utilization. The temperature gradient block is an aluminum block with four rows of 22 discrete holes, allowing the simultaneous incubation of 88 microcosms (60 mL vials). The block is cooled at one end and heated at the other, creating a linear temperature distribution. It provides 22 discrete temperature points along a user-defined range within limits of 0 to 90 °C. After 3.5 h of incubation, CO2 production is measured from each of the 88 microcosms. Results demonstrate that the block produces the user-defined temperature gradient and facilitates the construction of temperature response curves of SOM decomposition. Additionally, the data collected from this setup can be used to test and develop new hypotheses and theories regarding the impact of temperature changes on SOM decomposition rates, an area of increasing importance in the context of climate change.

Soil is the Earth's largest carbon (C) reservoir, holding nearly twice as much C as the atmosphere. Climate change-induced temperature increases could enhance soil organic matter (SOM) decomposition, potentially releasing carbon dioxide (CO2) into the atmosphere, thus resulting in a positive feedback to climate change. This presents the question: how can we define the response of SOM decomposition rates to short-term changes in temperature? Can we utilize this data to fit mechanistically defined equations in Earth system models for climate predictions? Most research to date has focused on laboratory soil incubations at different discrete temperatures. This, however, does not result in a detailed temperature response curve, which is required to test novel hypotheses imposed by the latest developments in the field, such as the macromolecular rate theory (MMRT). In this paper, we introduce a temperature gradient block, modified and improved from earlier work, detail its construction process, and provide a detailed explanation for its utilization. The temperature gradient block is an aluminum block with four rows of 22 discrete holes, allowing the simultaneous incubation of 88 microcosms (60 mL vials). The block is cooled at one end and heated at the other, creating a linear temperature distribution. It provides 22 discrete temperature points along a user-defined range within limits of 0 to 90 °C. After 3.5 h of incubation, CO2 production is measured from each of the 88 microcosms. Results demonstrate that the block produces the user-defined temperature gradient and facilitates the construction of temperature response curves of SOM decomposition. Additionally, the data collected from this setup can be used to test and develop new hypotheses and theories regarding the impact of temperature changes on SOM decomposition rates, an area of increasing importance in the context of climate change.

Global warming is altering the structure and dynamics of ecological communities, with significant consequences for soil food webs. Rising temperatures are expected to accelerate metabolic rates in organisms, potentially altering species interactions, and the structure and energetics of food webs. However, most studies assessing warming impacts on soil invertebrates have been short‐term, taxonomically narrow, or confounded by large‐scale variability. We investigated how long‐term warming affects soil invertebrate community structure across trophic levels. We sampled soil invertebrate along natural temperature gradients (17–40°C) of geothermal surface features of New Zealand, and we analysed community composition and population densities in relation to soil temperature, pH, water content, and microbial biomass. We found that the invertebrate community composition was significantly influenced by temperature and associated environmental variables. Total invertebrate density increased with warming, primarily driven by decomposers, while diversity metrics generally declined (except for omnivores). Decomposer diversity declined due to reductions in both dominant and rare species (Hill q = 1 and q = 2), whereas predator richness decreased mainly due to the loss of rare species (Hill q = 1) that resulted in higher evenness. In contrast, omnivores exhibited increased species richness. Our results highlight that warming effects are trophic‐level specific and environmentally context‐dependent. This suggests that long‐term warming may disrupt key ecosystem functions – such as decomposition, predator–prey interactions, and top‐down control by reshaping community composition and inducing the loss of decomposer taxa and rare predatory taxa. Such alterations could compromise soil food web stability and the resilience of those communities to disturbance events in a changing climate.

Drained peatlands are a substantial contributor to global anthropogenic greenhouse gases despite the relatively small areas they occupy. In New Zealand, drained Organic Soils (former peatlands) under cropland and grazed grasslands disproportionately contribute to emissions, but outdated mapping and limited measurements result in large uncertainties. To progress our understanding of the magnitude of these emissions and potential for mitigation, we compiled existing measurements from New Zealand and default emission factors from the IPCC along with updated soil mapping to develop a comprehensive national assessment. Using the IPCC 2013 Wetland Supplement (WS), Tier 1 default emission factors, total CO ₂ equivalent (CO ₂ e) drained Organic Soil emissions were 3.86 Mt yr⁻¹, equivalent to 6.5 % of the country’s net emissions. This was similar to the estimate derived from the mean of New Zealand-specific annual CO ₂ e emissions (3.61 Mt yr⁻¹). However, there are insufficient measurements from which to develop robust Tier 2 emission factors, and the range of CO ₂ e estimates based on existing data (3.06–4.69 Mt yr⁻¹) reinforces the need for more distributed measurements. The estimated CO ₂ e contribution to national emissions increased to 6.34 Mt yr⁻¹ (or 11 % of net emissions) when peaty-mineral soils were included in the calculations. Carbon-rich soils with a peaty surface horizon that do not meet the technical definition of Organic Soils are increasingly recognised as a potential source, but we have even less data quantifying their emissions to determine appropriate emission factors. We evaluated the potential for emissions mitigation through rewetting Organic Soils by running scenarios representing different areal rates of annual rewetting over the next ten years using WS default emission factors. Cumulative emissions avoided by rewetting 500–3000 hectares per year from 2026 until 2035 ranged from 0.53 to 1.25 Mt of CO ₂ e. Despite the barriers to practical implementation of peatland rewetting in New Zealand, the opportunity for emissions reductions is substantial. Further work is needed to refine emission factors, improve spatial activity data, and develop operational water table management capability to realise the potential in climate mitigation.