Molecular Weight Distribution of Humic Acids Isolated from Calcic Cryosol in Central Yakutia, Russia.

The transition of soils into fallow state has a significant impact on the accumulation and transformation of soil organic matter (SOM). However, the issue of SOM transformation as a result of soil transition to fallow state in cryolithozone conditions is insufficiently studied. The aim of this study is to investigate the molecular weight (MW) distribution of humic acids (HAs) isolated from soils of central Yakutia. Native, fallow and agricultural soils in the vicinity of Yakutsk city were studied. MW distributions of HA preparations were obtained on an AKTAbasic 10 UPS chromatographic system (Amersam Biosciences, Uppsala, Sweden) using a SuperdexTM 200 10/300 GL column (with cross-linked dextran gel, fractionation range for globular proteins 10-600 kDa). The data on the molecular-mass distribution of HAs of fallow and agricultural soils of Central Yakutia were obtained for the first time. According to the obtained data, it was found that the highest carbon content in the structure of HAs was observed in agricultural soils (52.56%), and is associated with soil cultivation and fertilizer application. Among the HAs of fallow soils, we note that those soils that are in the process of self-vegetation have a relatively high carbon content in the HAs (45.84%), but the highest content was observed in fallow soils used as hayfields (49.98%), indicating that the reinvolvement of agriculture in fallow soils leads to an increase in the carbon content of HAs. According to the data of the MW distribution of HAs, it was found that the highest content of a high MW fraction of HAs was recorded in native soil (18.8%); this is due to the early stages of humification and the low maturity of organic matter. The highest content of a low MW fraction of HAs was recorded in agricultural soil (73.3%); this is due to the formation of molecular complexes of a "secondary" nature, which are more stable in the environment than the primary transformation products of humification precursors. The molecular composition of the HAs of fallow soils in the process of self-overgrowing is characterized by values closer to the HAs of native soils, which indicates their transformation towards HAs of native soils. The obtained results indicate that the reinvolvement of fallow soils leads to the transformation of the molecular composition of HAs towards HAs of agricultural soils, and to an increase in the resistance of SOM to biodegradation.

Mapping China's reserved arable lands and its sustainable cropping layout.

BACKGROUND: Reserved arable lands in China is of great significance for rationally allocating crop planting structures, alleviating the pressure of grain imports, and protecting food security. Owing to data acquisition limitations, obtaining the spatial distribution of reserved arable lands at large spatial scales is relatively rare, and there is little information on predicting the suitability, production capacity, and ecological effects of crop cultivation in reserved arable lands. This study obtained the distribution of reserved arable lands in China by applying restrictive factors, and used the Food and Agriculture Organisation of the United Nations (FAO) suitability index for eight crops to obtain a spatial distribution map of suitable crops, proposed a cropland ecological efficiency index (CEEI) to analyse the ecological impact of crop cultivation in reserved arable lands. RESULTS: China possesses approximately 3.93 million hectares of viable reserved arable lands comprising primarily grasslands (67.68%), sandy land (8.11%), saline-alkali land (20.68%), and bare land (3.53%). The average CEEI for the eight crops under irrigation conditions ranges from 0.844 to 0.865, and that under rain-fed conditions (excluding rice) ranges from 0.609 to 0.779. CONCLUSION: We proposed the development of rain-fed agriculture with sorghum as the primary crop in the central part of Shanxi and Inner Mongolia, while promoting the cultivation of rapeseed and soybeans in the eastern parts of Heilongjiang, Jilin, and Inner Mongolia. Overall, the development of irrigation agriculture focusing on wheat and barley should be pursued only when water resources are guaranteed, particularly in north-western regions such as Gansu, Ningxia, Xinjiang, Qinghai, and Shaanxi. © 2024 Society of Chemical Industry.

Fungal necromass contribution to carbon sequestration in global croplands: A meta-analysis of driving factors and conservation practices.

Fungal necromass carbon (FNC) contributes significantly to the build-up of soil organic carbon (SOC) by supplying abundant recalcitrant polymeric melanin present in the fungal cell wall. However, the influence of a wide range of conservation practices and associated factors on FNC accumulation and contribution to SOC in global croplands remains unexplored. Here, a meta-analysis was performed using 873 observations across three continents, together with structural equation modeling, to evaluate conservation practices and factors responsible for the enhancement of FNC and SOC. FNC content (8.39 g kg-1) of North American soils was highest compared to FNC content of Asian and European soils. The structural equation models showed a significant (p < 0.05) positive influence of microbial biomass carbon (MBC), soil pH, and clay contents on the accumulation of FNC. Soil C/N ratio and climate factors, however, had only minor influences on FNC accumulation. Notably, the main driver of FNC was MBC, which is mainly influenced by the soil total N and geographic factors in the study areas. Typical 5 cropland practices had significant effect size (p < 0.05) on FNC, leading to an increase of 12 % to 26 %, and the FNC content was greatest under straw amendment (26 %). Fungal necromass accumulation efficiency ranged from 23 % to 45 % depending on cropland practices: non- and reduced tillage was the most efficient (45 %), followed by crop coverage (32 %), straw amendment (30 %), and manure application (27 %), while N fertilization had the lowest efficiency (23 %). We conclude that FNC contributes to over a quarter of SOC, highlighting its major role in enhancing C sequestration worldwide. Conservation practices, particularly non-tillage or reduced tillage, are important to enhance C sequestration from FNC in croplands.

Arable lands under the pressure of multiple land degradation processes. A global perspective.

While agricultural systems are a major pillar in global food security, their productivity is currently threatened by many environmental issues triggered by anthropogenic climate change and human activities, such as land degradation. However, the planetary spatial footprint of land degradation processes on arable lands, which can be considered a major component of global agricultural systems, is still insufficiently well understood. This study analyzes the land degradation footprint on global arable lands, using complex geospatial data on certain major degradation processes, i.e. aridity, soil erosion, vegetation decline, soil salinization and soil organic carbon decline. By applying geostatistical techniques that are representative for identifying the incidence of the five land degradation processes in global arable lands, results showed that aridity is by far the largest singular pressure for these agricultural systems, affecting ~40% of the arable lands' area, which cover approximately 14 million km2 globally. It was found that soil erosion is another major degradation process, the unilateral impact of which affects ~20% of global arable systems. The results also showed that the two degradation processes simultaneously affect an additional ~7% of global arable lands, which makes this synergy the most common form of multiple pressure of land degradative conditions across the world's arable areas. The absolute statistical data showed that India, the United States, China, Brazil, Argentina, Russia and Australia are the most vulnerable countries in the world to the various pathways of arable land degradation. Also, in terms of percentages, statistical observations showed that African countries are the most heavily affected by arable system degradation. This study's findings can be useful for prioritizing agricultural management actions that can mitigate the negative effects of the two degradation processes or of others that currently affect many arable systems across the planet.

Gastrointestinal nematodes of European wild boar from distinct agricultural and forest habitats in Poland.

The study aimed to compare the gastrointestinal helminthofauna of free-ranging wild boars from arable lands and forests, which are the natural habitats for wild boar in Poland and further to investigate if wild boars living in agricultural environments could acquire helminths commonly detected in domestic pigs. In 2011-2014, a total of 57 wild boars were examined post-mortem for the presence of gastrointestinal nematodes. Altogether, all but two of the animals were infected, and seven nematode species were found. The mean infection burden was 68.9 parasites, ranging from 1 to 381 worms. In forest areas, Ascarops strongylina, Physocephalus sexalatus, and Globocephalus urosubulatus were common, whereas on arable lands, the animals were more frequently infected (P < 0.05) by Ascaris suum and Trichuris suis, which are parasites that commonly occur in domestic pigs. Oesophagostomum dentatum was observed only in wild boars on arable lands, and Bourgelatia diducta, which is alien to European suids, appeared irrespective of habitat type. These results show significant differences in parasite spectra among wild boars living in forests or arable lands in Poland and indicates the risks of parasite transfer from domestic pigs to free-ranging wild boars. Furthermore, in farmed game, organic farming, or in the case of agritourism farms, one should be aware of the risk of related animals acquiring new and alien parasite infections by being kept outdoors.

Wind erosion on arable lands, associated with extreme blizzard conditions within the hilly area of Eastern Romania.

The removal of wind-blown soils from cultivated fields is often expensive. It physically removes the most fertile portion of the soil that can lead to yield reduction in areas where wind erosion is a recurring problem. Soil nutrients and surface-applied chemicals can also be carried along with soil particles, contributing to off-site impacts. An extreme blizzard event has been investigated as case study within the Moldavian Plateau of eastern Romania. The results obtained, based on 45 snow core samples, show that the deposited sediment widely varied depending on land-use. The highest mean value of 5967 g m-2 occurred on fallow land and it sharply decreased under winter wheat (445 g m-2) and pasture (345 g m-2). Regarding the major subunits of the Moldavian Plateau, the Jijia Rolling Plain (JRP) was the most affected, with mean value of 7547 g m-2. The Barlad Plateau (BP) and the Falciu Rolling Plain (FRP) are depicted by smaller values, namely: 395 g m-2 and 386 g m-2. By using remote sensing it was estimated that 208,990 ha under fallow from JRP (34% of the total) were heavily subjected to wind erosion with a mean soil loss of 2.04 t ha-1, while the depositional area comprised 175,440 ha (29% of the total). The deposited soil is loamy compared with the general clayey-loamy texture of local soils. The main source of the wind-blown material is represented by the close proximity fields under fallow of the depositional areas.

Elevational gradient and human effects on butterfly species richness in the French Alps.

We examined how butterfly species richness is affected by human impact and elevation, and how species ranges are distributed along the elevational gradient (200-2700 m) in the Isère Department (French Alps). A total of 35,724 butterfly observations gathered in summer (May-September) between 1995 and 2015 were analyzed. The number of estimated species per 100-m elevational band was fitted to the elevational gradient using a generalized additive model. Estimations were also performed on a 500 m × 500 m grid at low altitude (200-500 m) to test for the human impact on species richness using generalized least squares regression models. Each species elevational range was plotted against the elevational gradient. Butterfly richness along the elevational gradient first increased (200-500 m) to reach a maximum of 150 species at 700 m and then remained nearly constant till a sharp decrease after 1900 m, suggesting that after some temperature threshold, only few specialized species can survive. At low elevation, urbanization and arable lands had a strongly negative impact on butterfly diversity, which was buffered by a positive effect of permanent crops. Butterfly diversity is exceptionally high (185 species) in this alpine department that represents less than 5% of the French territory and yet holds more than 70% of all the Rhopalocera species recorded in France. Both climate and habitat shape the distribution of species, with a negative effect of anthropization at low altitude and strong climatic constraints at high altitude.