Soil organic carbon (SOC) in the subsoil below 0.3 m accounts for the majority of total SOC and may be as sensitive to climate change as topsoil SOC. Here we map global SOC turnover times (τ) in the ...subsoil layer at 1 km resolution using observational databases. Global mean τ is estimated to be Formula: see text yr (mean with 95% confidence interval), and deserts and tundra show the shortest (Formula: see text yr) and longest (Formula: see text yr) τ respectively. Across the globe, mean τ ranges from 9 (the 5% quantile) to 6332 years (the 95% quantile). Temperature is the most important factor negatively affecting τ, but the overall effect of climate (including temperature and precipitation) is secondary compared with the overall effect of assessed soil properties (e.g., soil texture and pH). The high-resolution mapping of τ and the quantification of its controls provide a benchmark for diagnosing subsoil SOC dynamics under climate change.
Soil organic carbon (SOC) dynamics are regulated by the complex interplay of climatic, edaphic and biotic conditions. However, the interrelation of SOC and these drivers and their potential ...connection networks are rarely assessed quantitatively. Using observations of SOC dynamics with detailed soil properties from 90 field trials at 28 sites under different agroecosystems across the Australian cropping regions, we investigated the direct and indirect effects of climate, soil properties, carbon (C) inputs and soil C pools (a total of 17 variables) on SOC change rate (rC, Mg C ha−1 yr−1). Among these variables, we found that the most influential variables on rC were the average C input amount and annual precipitation, and the total SOC stock at the beginning of the trials. Overall, C inputs (including C input amount and pasture frequency in the crop rotation system) accounted for 27% of the relative influence on rC, followed by climate 25% (including precipitation and temperature), soil C pools 24% (including pool size and composition) and soil properties (such as cation exchange capacity, clay content, bulk density) 24%. Path analysis identified a network of intercorrelations of climate, soil properties, C inputs and soil C pools in determining rC. The direct correlation of rC with climate was significantly weakened if removing the effects of soil properties and C pools, and vice versa. These results reveal the relative importance of climate, soil properties, C inputs and C pools and their complex interconnections in regulating SOC dynamics. Ignorance of the impact of changes in soil properties, C pool composition and C input (quantity and quality) on SOC dynamics is likely one of the main sources of uncertainty in SOC predictions from the process‐based SOC models.
We quantitatively assessed the interconnections of a series of climatic, edaphic and biotic factors in controlling soil organic carbon (SOC) dynamics. We found that, overall, soil properties, soil C pools, climate and C inputs were almost equally important in terms of overall effect on SOC dynamics. However, if the effect of soil was controlled, the effect of climate was significantly weakened, and vice versa, while the effects of carbon input and soil carbon pool composition were significantly strengthened if climate and/or soil were controlled. These results force us to revise SOC predictions based on modelling and empirical approaches mainly considering climatic factors, and provide new insights into mechanistic understanding of SOC dynamics under different soil and climate conditions across ecosystems.
Our meta-analysis based on data from 69 paired-experiments indicated that: ▶ Cultivation with conventional tillage (CT) and no-tillage (NT) resulted in comparable soil C loss comparing with adjacent ...natural soils. ▶ In most cases, adopting NT did not increase the total C in the soil profile. ▶ Climatic conditions and fertilization did not significantly regulate the response of soil C to the adoption of NT. ▶ However, the type of crops and cropping systems caused variations in soil C change after adopting NT. Compared with CT, NT in double cropping systems significantly increased soil total C, while NT in single cropping systems with more diverse crop types could lead to net reduction in total soil C.
Adopting no-tillage in agro-ecosystems has been widely recommended as a means of enhancing carbon (C) sequestration in soils. However, study results are inconsistent and varying from significant increase to significant decrease. It is unclear whether this variability is caused by environmental, or management factors or by sampling errors and analysis methodology. Using meta-analysis, we assessed the response of soil organic carbon (SOC) to conversion of management practice from conventional tillage (CT) to no-tillage (NT) based on global data from 69 paired-experiments, where soil sampling extended deeper than 40
cm. We found that cultivation of natural soils for more than 5 years, on average, resulted in soil C loss of more than 20
t
ha
−1, with no significant difference between CT and NT. Conversion from CT to NT changed distribution of C in the soil profile significantly, but did not increase the total SOC except in double cropping systems. After adopting NT, soil C increased by 3.15
±
2.42
t
ha
−1 (mean
±
95% confidence interval) in the surface 10
cm of soil, but declined by 3.30
±
1.61
t
ha
−1 in the 20–40
cm soil layer. Overall, adopting NT did not enhance soil total C stock down to 40
cm. Increased number of crop species in rotation resulted in less C accumulation in the surface soil and greater C loss in deeper layer. Increased crop frequency seemed to have the opposite effect and significantly increased soil C by 11% in the 0–60
cm soil. Neither mean annual temperature and mean annual rainfall nor nitrogen fertilization and duration of adopting NT affected the response of soil C stock to the adoption of NT. Our results highlight that the role of adopting NT in sequestrating C is greatly regulated by cropping systems. Increasing cropping frequency might be a more efficient strategy to sequester C in agro-ecosystems. More information on the effects of increasing crop species and frequency on soil C input and decomposition processes is needed to further our understanding on the potential ability of C sequestration in agricultural soils.
Priming of soil organic matter decomposition by fresh carbon inputs is a key ecological process determining soil carbon (C) and nutrient cycling in terrestrial ecosystems. Although this priming ...effect (PE) has been studied under various environmental conditions, the conclusions are inconsistent across space and time and the underlying mechanisms unclear. We used a meta-analysis with extensive datasets of CO2 effluxes from soils with 13C or 14C labelled fresh C inputs and without fresh C inputs under various soil conditions to synthesize and assess the temporal dynamics of the PE. The results indicated that the PE declined in 20 days on average from 67−21+26% (95% confidence interval) immediately following the fresh C inputs to less than 7.6−1.8+2.0% and remained relatively stable thereafter. We also assessed the variability of the temporal dynamics of the PE in the collected datasets and the underlying drivers. The results showed that the magnitude of PE at a specific time (i.e., the instantaneous PE after the fresh C inputs) was significantly and positively correlated with the instantaneous quantity of remaining fresh C. Under the same quantity of remaining fresh C, the PE varied significantly across ecosystems (in the order of grasslands < farmlands < forests < other ecosystems such as lake beds and volcanic soils), but, contrary to our expectation, the PE was independent of the quality of the added fresh C. We found that the PE experienced a faster decrease in soils with higher clay and moisture contents. These results describe the temporal dynamics of PE and the underlying drivers, underpinning the robust predictions of PE dynamics and their impact on soil C and nutrient balances.
•The datasets from 171 experiments were used to assess the temporal PE dynamics.•The average PE declines from 67% to <10% in 20 days after fresh C inputs.•The quantity not the quality of fresh C significantly affects the PE temporal dynamics.•The PE varies significantly across ecosystems under certain fresh C inputs.•The PE decreases faster with time in soils with higher clay and moisture content.
The North China Plain (NCP) is the most important agricultural production area in China. Crop production in the NCP is sensitive to changes in both climate and management practices. While previous ...studies showed a negative impact of climatic change on crop yield since 1980s, the confounding effects of climatic and agronomic factors have not been separately investigated. This paper used 25 years of crop data from three locations (Nanyang, Zhengzhou and Luancheng) across the NCP, together with daily weather data and crop modeling, to analyse the contribution of changes in climatic and agronomic factors to changes in grain yields of wheat and maize. The results showed that the changes in climate were not uniform across the NCP and during different crop growth stages. Warming mainly occurred during the vegetative (preflowering) growth stage of wheat and maize, while there was a cooling trend or no significant change in temperatures during the postflowering stage of wheat (spring) or maize (autumn). If varietal effects were excluded, warming during vegetative stages would lead to a reduction in the length of the growing period for both crops, generally leading to a negative impact on crop production. However, autonomous adoption of new crop varieties in the NCP was able to compensate the negative impact of climatic change. For both wheat and maize, the varietal changes helped stabilize the length of preflowering period against the shortening effect of warming and, together with the slightly reduced temperature in the postflowering period, extend the length of the grain-filling period. The combined effect led to increased wheat yield at Zhengzhou and Luancheng; increased maize yield at Nanyang and Luancheng; stabilized wheat yield at Nanyang, and a slight reduction in maize yield at Zhengzhou, compared with the yield change caused entirely by climatic change.
In the North China Plain, the grain yield of irrigated wheat-maize cropping system has been steadily increasing in the past decades under a significant warming climate. This paper combined regional ...and field data with modeling to analyze the changes in the climate in the last 40 years, and to investigate the influence of changes in crop varieties and management options to crop yield. In particular, we examined the impact of a planned adaptation strategy to climate change -“Double-Delay” technology, i.e., delay both the sowing time of wheat and the harvesting time of maize, on both wheat and maize yield. The results show that improved crop varieties and management options not only compensated some negative impact of reduced crop growth period on crop yield due to the increase in temperature, they have contributed significantly to crop yield increase. The increase in temperature before over-wintering stage enabled late sowing of winter wheat and late harvesting of maize, leading to overall 4–6% increase in total grain yield of the wheat-maize system. Increased use of farming machines and minimum tillage technology also shortened the time for field preparation from harvest time of summer maize to sowing time of winter wheat, which facilitated the later harvest of summer maize.
Aims
Quantification of variations in plant available water holding capacity (PAWC) of soils helps to improve yield forecast and inform spatially variable management practices in dryland agriculture ...systems. We developed and tested a general inverse approach to estimate PAWC from crop yield.
Methods
The APSIM model was used to simulate wheat yield on synthetic soils with contrasting PAWC and climates. The simulated results were used to develop an empirical model to relate simulated yield to PAWC. The empirical model was inversely used to predict PAWC from observed crop yield. Potential prediction ability was quantified using independently simulated wheat yield on actual soils. The actual ability was assessed with measured wheat yields and PAWC.
Results
The approach had higher accuracy for sites with high rainfall or dominant summer rainfall. It could potentially provide acceptable PAWC predictions across contrasting climate regions (prediction error < 37 mm, 33.5%). The prediction error using crop yield against measured PAWC was <25 mm (26.5%).
Conclusions
Our results demonstrate that soil PAWC can be reliably predicted from crop yield. This approach provides an alternative way to predict PAWC rather than directly measuring it via soil sampling, with profound implications for reducing labour and costs.
Soil is the largest reservoir of carbon (C) in the terrestrial biosphere and a slight variation in this pool could lead to substantial changes in the atmospheric CO
2 concentration, thus impact ...significantly on the global climate. Cultivation of natural ecosystems has led to marked decline in soil C storage, such that conservation agricultural practices (CAPs) are widely recommended as options to increase soil C storage, thereby mitigating climate change. In this review, we summarise soil C change as a result of cultivation worldwide and in Australia. We then combine the available data to examine the effects of adopting CAPs on soil C dynamics in Australian agro-ecosystems. Finally, we discuss the future research priorities related to soil C dynamics. The available data show that in Australian agro-ecosystems, cultivation has led to C loss for more than 40
years, with a total C loss of approximately 51% in the surface 0.1
m of soil. Adoption of CAPs generally increased soil C. Introducing perennial plants into rotation had the greatest potential to increase soil C by 18% compared with other CAPs. However, the same CAPs could result in different outcomes on soil C under different climate and soil combinations. No consistent trend of increase in soil C was found with the duration of CAP applications, implying that questions remain regarding long-term impact of CAPs. Most of the available data in Australia are limited to the surface 0.1 to 0.3
m of soil. Efforts are needed to investigate soil C change in deeper soil layers in order to understand the impact of crop root growth and various agricultural practices on C distribution in soil profile. Elevated atmospheric CO
2 concentration, global warming and rainfall change could all alter the C balance of agricultural soils. Because of the complexity of soil C response to management and environmental factors, a system modelling approach supported by sound experimental data would provide the most effective means to analyse the impact of different management practices and future climate change on soil C dynamics.
Extreme weather events threaten food security, yet global assessments of impacts caused by crop waterlogging are rare. Here we first develop a paradigm that distils common stress patterns across ...environments, genotypes and climate horizons. Second, we embed improved process-based understanding into a farming systems model to discern changes in global crop waterlogging under future climates. Third, we develop avenues for adapting cropping systems to waterlogging contextualised by environment. We find that yield penalties caused by waterlogging increase from 3-11% historically to 10-20% by 2080, with penalties reflecting a trade-off between the duration of waterlogging and the timing of waterlogging relative to crop stage. We document greater potential for waterlogging-tolerant genotypes in environments with longer temperate growing seasons (e.g., UK, France, Russia, China), compared with environments with higher annualised ratios of evapotranspiration to precipitation (e.g., Australia). Under future climates, altering sowing time and adoption of waterlogging-tolerant genotypes reduces yield penalties by 18%, while earlier sowing of winter genotypes alleviates waterlogging by 8%. We highlight the serendipitous outcome wherein waterlogging stress patterns under present conditions are likely to be similar to those in the future, suggesting that adaptations for future climates could be designed using stress patterns realised today.
Northeast China (NEC) is one of the major agricultural production areas in China and also an obvious region of climate warming. We were motivated to investigate the impacts of climate warming on the ...northern limits of maize planting. Additionally, we wanted to assess how spatial shifts in the cropping system impact the maize yields in NEC. To understand these impacts, we used the daily average air temperature data in 72 weather stations and regional experiment yield data from Jilin Province. Averaged across NEC, the annual air temperature increased by 0.38 °C per decade. The annual accumulated temperature above 10 °C (AAT10) followed a similar trend, increased 66 °C d per decade from 1961 to 2007, which caused a northward expansion of the northern limits of maize. The warming enabled early-maturing maize hybrids to be sown in the northern areas of Heilongjiang Province where it was not suitable for growing maize before the warming. In the southern areas of Heilongjiang Province and the eastern areas of Jilin Province, the early-maturing maize hybrids could be replaced by the middle-maturing hybrids with a longer growing season. The maize in the northern areas of Liaoning Province was expected to change from middle-maturing to late-maturing hybrids. Changing the hybrids led to increase the maize yield. When the early-maturing hybrids were replaced by middle-maturing hybrids in Jilin Province, the maize yields would increase by 9.8 %. Similarly, maize yields would increase by 7.1 % when the middle-maturing hybrids were replaced by late-maturing hybrids.
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