No abstract

Patterns and elevational controls on the response of soil organic matter (SOM) decomposition to temperature in alpine forest soils are critical to efforts to quantify the regional carbon cycle-climate feedback, but are not well known.Here, we report rates of SOM decomposition (R S ) and temperature sensitivity (Q 10 ) determined in a short-term laboratory incubation with gradual warming from 5 to 29 C of soils from different elevations in the Qilian Mountains, China (2600, 2800, 3000, and 3200 m). The results showed the R S significantly increased with increasing elevation (p < 0.001), in which R S was significantly greater at 3200 m than that at the other elevations but had no significant difference in R S among elevations below 3200 m. Across all elevations, R S first showed an increasing trend at temperatures <20 C and then declined substantially (>20 C), most likely in response to the content of labile C (greater at the start of incubation and declining over time). Q 10 of SOM decomposition increased significantly with increasing elevation and decreasing incubation temperature (p < 0.001). Meanwhile, soil organic carbon (SOC), total nitrogen, and 1-to 2-mm aggregate-associated organic carbon (OC) were the main control factors affecting R S and Q 10 along an elevational gradient. These results indicate that high-altitude soils in alpine forests of the Qilian Mountains are relatively more sensitive to warming and have greater potential to release CO 2 due to higher SOC contents and 1-to 2-mm aggregate-associated OC than lowaltitude soils. The findings could serve as a reference for how regional C pools may respond to future warming in alpine forests of the Qilian Mountains.

The desert oasis is one of the major grain production areas in arid land, and many intensive farming practices have been adopted to improve the land utilization in the agriculture system. However, there remains little consensus on how to improve such farming practices for increasing both productivity and environment benefits in this system. A 4-year experiment was conducted in a typical desert oasis farmland to determine the effects of the farming practices on crop yield, soil carbon (C) and nitrogen (N) accumulation, and carbon footprint (CF). The farming practices included two tillage patterns: conventional (CT) and reduced tillage (RT), two cropping patterns: continuous (Con) and rotation cropping (Rot), and two mulching pattern: film (F) and straw mulching (S) with eight combined treatments. The RT did not significant decrease crop yield but increase soil C and N accumulation rate by 59% and 130%, and thus decrease CF for crop production compared with the CT. S can also improve soil C and N accumulation, and cause low CF for crop production, but leading to 14-41% decrease in maize yield compared with F. Rot result in a 14% increase on maize yield also has extra benefit to decrease CF for crop production, but no significant effect on soil C and N accumulation compared with Con. Our study adds a reasonable perspective on how to improve the conventional farming systems in desert oasis, the information about RT, straw mulching, and maize-soybean rotation have positive effect on improving soil quality and decreasing CF for crop production in this desert soil area is critical to develop the sustainable agriculture system in this desert oasis farmland, which both maintaining crop productivity and minimizing negative environmental impacts.

Distribution and elevational controls on soil aggregate‐associated organic carbon (OC) and nitrogen (N) in alpine soils are not well known, but may be critical to the stabilization of soil C and N pools in alpine areas. In this study, we determined the variability in aggregate associated OC and N concentration and aggregate‐stability in 0 to 20 cm layers along the elevation gradient in an alpine forest (2,600–3,200 m) of the Qilian Mountains. The results showed that 1–2 mm macroaggregate accounted for the largest proportion (33.9%) of all aggregate fractions, and also contributed greater proportions (33.2 and 32.6%) to OC and N in bulk soils. Concentrations of OC and N, and C to N ratio increased with increasing aggregate size across all elevations. With increasing elevation, the proportion of >1 mm macroaggregates, mean weight diameter (MWD) and geometric mean diameter (GMD) increased significantly (p < .01). Aggregate OC and N concentration and C to N ratios, and the contribution of > 1 mm aggregate OC and N to OC and N in bulk soils also increased significantly (p < .01), while the contribution of 0.25–1 mm and 0.053–0.25 mm aggregates decreased with increasing elevation. In addition, MWD, GMD, OC and N concentration in aggregate decreased with mean annual temperature (MAT) and increased with mean annual precipitation (MAP). Our results demonstrated that the stability of soil structure improved, and accumulation of OC was mainly due to increases in the contribution of OC in the >1 mm macroaggregate with increasing elevation. Given that higher elevations in this alpine forest support large concentrations of SOC and macroaggregate OC, which may be vulnerable to climate warming.

This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

No abstract

Plant secondary metabolites (PSMs) contained in plant litter will be released into soil with the decomposition process, which will affect the diversity and function of soil microbiomes. The response of soil microbiomes to PSMs in terms of diversity and function can provide an important theoretical basis for plantations to put forward rational soil ecological management measures.

Understanding how soil nitrogen (N) mineralization (Nmin) responds to environmental changes is critical for improving ecosystem management, especially in a resource‐constrained region. Intensive land exploitation in arid land has profound influences on soil ecosystems and thus on soil Nmin. A local‐scale field investigation was conducted to reveal the temporal dynamics of Nmin under land‐use change from desert to farmland, and to verify the mechanisms controlling Nmin change during this process in a typical desert oasis region. The results showed that Nmin ranged from −0.14 to 2.69 mg N kg−1 day−1, with an average value of 0.74 mg N kg−1 day−1. Nmin in old oasis farmland (OOF) was significantly higher than that in GCF (Gobi desert conversion farmland) and SCF (sandy desert conversion farmland), and the average change rates of Nmin were 0.036 and 0.032 mg N kg−1 day−1 year−1 in GCF and SCF, respectively. Structural equation modelling (SEM) was used to test whether the measured variables affected Nmin, and the results showed that soil organic matter (SOM), bulk density (BD) and sand content were the main soil factors affecting Nmin. These soil factors, together with farmland type and cropping time, can explain 31% of the variation in Nmin. Our observations revealed that Nmin changed substantially under the land conversion process from desert to farmland, and our findings will help with assessments and predictions of future N cycles in desert oasis regions in response to land‐use change.Highlights We used Nmin as an observed variable to evaluate the dynamics of the soil evolution process under a land‐use change from desert to farmland. Cropping year was identified by using map image data to reveal temporal trend of Nmin. Nmin was primarily affected by soil organic matter, bulk density and sandy content. Intensive land exploitation in arid land profoundly influences soil Nmin.