Abstract Soil net nitrogen mineralization rate (N min ), which is critical for soil nitrogen availability and plant growth, is thought to be primarily controlled by climate and soil physical and/or chemical properties. However, the role of microbes on regulating soil N min has not been evaluated on the global scale. By compiling 1565 observational data points of potential net N min from 198 published studies across terrestrial ecosystems, we found that N min significantly increased with soil microbial biomass, total nitrogen, and mean annual precipitation, but decreased with soil pH. The variation of N min was ascribed predominantly to soil microbial biomass on global and biome scales. Mean annual precipitation, soil pH, and total soil nitrogen significantly influenced N min through soil microbes. The structural equation models ( SEM ) showed that soil substrates were the main factors controlling N min when microbial biomass was excluded. Microbe became the primary driver when it was included in SEM analysis. SEM with soil microbial biomass improved the N min prediction by 19% in comparison with that devoid of soil microbial biomass. The changes in N min contributed the most to global soil NH 4 + ‐N variations in contrast to climate and soil properties. This study reveals the complex interactions of climate, soil properties, and microbes on N min and highlights the importance of soil microbial biomass in determining N min and nitrogen availability across the globe. The findings necessitate accurate representation of microbes in Earth system models to better predict nitrogen cycle under global change.
This dataset contains python code and datasets generated from the study: Increasing sensitivity of terrestrial nitrous oxide emissions to precipitation variations
Many studies have found that plant invasion can enhance soil organic carbon (SOC) pools, by increasing net primary production (NPP) and/or decreased soil respiration. While most studies have focused on C input, little attention has been paid to plant invasion effects on soil respiration, especially in wetland ecosystems. Our study examined the effects of Spartina alterniflora invasion on soil respiration and C dynamics in the Yangtze River estuary. The estuary was originally occupied by two native plant species: Phragmites australis in the high tide zone and Scirpus mariqueter in the low tide zone. Mean soil respiration rates were 185.8 and 142.3 mg CO2 m−2 h−1 in S. alterniflora and P. australis stands in the high tide zone, and 159.7 and 112.0 mg CO2 m−2 h−1 in S. alterniflora and S. mariqueter stands in the low tide zone, respectively. Aboveground NPP (ANPP), SOC, and microbial biomass were also significantly higher in the S. alterniflora stands than in the two native plant stands. S. alterniflora invasion did not significantly change soil inorganic carbon or pH. Our results indicated that enhanced ANPP by S. alterniflora exceeded invasion-induced C loss through soil respiration. This suggests that S. alterniflora invasion into the Yangtze River estuary could strengthen the net C sink of wetlands in the context of global climate change.
Abstract Nitrogen immobilization usually leads to nitrogen retention in soil and, thus, influences soil nitrogen supply for plant growth. Understanding soil nitrogen immobilization is important for predicting soil nitrogen cycling under anthropogenic activities and climate changes. However, the global patterns and drivers of soil nitrogen immobilization remain unclear. We synthesized 1350 observations of gross soil nitrogen immobilization rate (NIR) from 97 articles to identify patterns and drivers of NIR. The global mean NIR was 8.77 ± 1.01 mg N kg −1 soil day −1 . It was 5.55 ± 0.41 mg N kg −1 soil day −1 in croplands, 15.74 ± 3.02 mg N kg −1 soil day −1 in wetlands, and 15.26 ± 2.98 mg N kg −1 soil day −1 in forests. The NIR increased with mean annual temperature, precipitation, soil moisture, soil organic carbon, total nitrogen, dissolved organic nitrogen, ammonium, nitrate, phosphorus, and microbial biomass carbon. But it decreased with soil pH. The results of structural equation models showed that soil microbial biomass carbon was a pivotal driver of NIR, because temperature, total soil nitrogen, and soil pH mostly indirectly influenced NIR via changing soil microbial biomass. Moreover, microbial biomass carbon accounted for most of the variations in NIR among all direct relationships. Furthermore, the efficiency of transforming the immobilized nitrogen to microbial biomass nitrogen was lower in croplands than in natural ecosystems (i.e., forests, grasslands, and wetlands). These findings suggested that soil nitrogen retention may decrease under the land use change from forests or wetlands to croplands, but NIR was expected to increase due to increased microbial biomass under global warming. The identified patterns and drivers of soil nitrogen immobilization in this study are crucial to project the changes in soil nitrogen retention.
The logistics industry has developed rapidly and has a significant role in promoting economic growth is also obvious. Due to the complexity of regional economic growth, how logistics contributes to economic development and the extent to which its role is related has not yet been answered. The purpose of this paper is to find out the main factors on the coordinated development between regional logistics and economy. Through an exploratory study, a set of new indicators system of regional logistics and economy was determined, and the coupling coordination model was established. Shaanxi Province is used as an example to analyze the coupling coordination degree. The result shows the development environment of logistics in Shaanxi Province can be improved by increasing investment in logistics infrastructure. Scientific value of this research is that the coupling coordination model can be used more widely.
Given the immense quantities of plastics in the environments worldwide, it is inevitable that soil animals are exposed to microplastics. However, a comprehensive elucidation of the cascading responses of different levels of functional traits in soil animals to microplastics remains unclear. A meta-analysis based on 80 published studies was conducted to quantify the hierarchical changes in soil animal traits from genes to survival under microplastics. Under microplastics, soil animals substantially increased (by 62.1%) reactive oxygen species (ROS), copies of antioxidant genes increased by 35.7%, and antioxidant enzyme activities increased by 11.5%. Unfortunately, the antioxidant responses did not completely eradicate the increased ROS. Animal traits at behavioral and survival levels were consequently significantly decreased (e.g., movement capacities, reproduction rate, growth rate, and survival rate decreased by 22.7%, 12.8%, 7.5%, and 3.1%, respectively). Compared with macrofauna, microfauna endured more severe damage by microplastics due to higher ROS (63.7%) than in macrofauna (33.5%). Additionally, round microplastics typically caused severe damage to soil animal survival rate, which was inhibited by 16.6%. This study aimed to quantify the cascading responses of soil animal functional traits at multiple levels to microplastics, which will provide a comprehensive perspective for assessing the toxicities of microplastics in soil environments.
Drought disasters jeopardize the production of vegetation and are expected to exert impacts on human well-being in the context of global climate change. However, spatiotemporal variations in drought characteristics (including the drought duration, intensity, and frequency), specifically for vegetation areas within a growing season, remain largely unknown. Here, we first constructed a normalized difference vegetation index to estimate the length of the growing season for each pixel (8 km) by four widely used phenology estimation methods; second, we analyzed the temporal and spatial patterns of climate factors and drought characteristics (in terms of the Standardized Precipitation Evapotranspiration Index (SPEI)), within a growing season over vegetation areas of the northern hemisphere before and after the critical time point of 1998, which was marked by the onset of a global warming hiatus. Finally, we extracted the highly drought-vulnerable areas of vegetation by examining the sensitivity of the gross primary production to the SPEI to explore the underlying effects of drought variation on vegetation. The results revealed, first, that significant (p < 0.05) increases in precipitation, temperature, and the SPEI (a wetting trend) occurred from 1982 to 2015. The growing season temperature increased even more statistically significant after 1998 than before. Second, the duration and frequency of droughts changed abruptly and decreased considerably from 1998 to 2015; and this wetting trend was located mainly in high-latitude areas. Third, at the biome level, the wetting areas occurred mainly in the tundra, boreal forest or taiga, and temperate coniferous forest biomes, whereas the highly drought-vulnerable areas were mainly located in the desert and xeric shrubland (43.5%) biomes. Our results highlight the fact that although the drought events within a growing season decreased significantly in the northern hemisphere from 1998 to 2015, the very existence of a mismatch between a reduction in drought areas and an increase in highly drought-vulnerable areas makes the impact of drought on vegetation nonnegligible. This work provides valuable information for designing coping measures to reduce the vegetative drought risk in the Northern Hemisphere.
Abstract Nitrous oxide (N 2 O), a major greenhouse gas and ozone-depleting agent, is generated over land mostly from two key biochemical processes—nitrification and denitrification. Nitrifying and denitrifying N 2 O production occurs preferably under alternative oxic and anoxic conditions, which are closely linked with variations in water filled soil pores, and thus indirectly with precipitation. We show here that the interannual anomalies in the annual growth rate of the global land N 2 O emissions are significantly ( P < 0.001) correlated with precipitation anomalies, with an overall sensitivity ( αPRE , changes of land N 2 O emission variations per precipitation anomalies) of 2.50 ± 0.98 Tg N 2 O–N per 100 mm of precipitation across the global land (1998–2016). The sensitivity ( αPRE ) and precipitation-driven N 2 O anomalies increased during 1998–2016, partly due to increased nitrogen inputs to agricultural lands and enhanced precipitation anomalies. Spatially, we find that the αPRE increases with aridity. We predict a larger αPRE under future climate conditions (with radiative forcing levels of 4.5, 7.0 and 8.5 Wm −2 ) by the year 2100 if nitrogen fertilization follows the present practice.
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