Short-term effects of wildfire on soil arthropods in a semi-arid grassland on the Loess Plateau.

Fires lead to dramatic shifts in ecosystems and have a large impact on the biota. Soil organisms, especially soil fauna, are often used as indicators of environmental change. At present, minimal attention has been paid to using soil fauna as an indicator of environmental change after a fire. Here, a field survey of burnt herbaceous vegetation in semi-arid areas was conducted to determine the response of soil arthropods to fire and their short-term recovery after fire. Overall, the abundance and biomass of soil arthropods was more sensitive to fire than the number of groups. The number of soil arthropod groups, especially the dominant groups (mites and springtails), was not significantly affected by wildfires. At the unburned site, soil arthropod abundance showed significant seasonal shifts that may be related to the vegetation properties, temperature, and precipitation caused by seasonal changes. In contrast, soil arthropods at the burnt sites showed a delayed recovery and had only reached 56%-82%, 17%-54%, and 91%-190% of the biomass in the unburnt forest at the 3, 6, and 9 months after the burning event. Our findings of soil arthropod abundance changes in the present study suggest that fire-induced changes in soil and vegetation properties (e.g., AN, LT, and VC) were crucial factors for the changes in soil arthropod abundance in this semi-arid grassland. We conclude that fire disturbance reduces the seasonal sensitivity of soil arthropods by altering their habitat. This study furthers our understanding of wildfire impact recovery by documenting the short-term temporal dynamics of soil arthropods.

[Responses of ground-active arthropod community in Caragana shrub plantations to grazing management in desertified region.] / 干旱风沙区灌丛林地地面节肢动物群落对放牧管理的响应.

We investigated the community structure of ground-active arthropods as well as vegetation and soil properties in Caragana shrub plantations under grazing and exclosure management across spring, summer and autumn in Yanchi County of Ningxia in northern China. The aim of this study was to uncover the responses of ground-active arthropods in shrub plantations to grazing management in desertified regions. The results showed that: 1) plant height, soil fine sand content, and soil electrical conductivity were significantly lower, whereas soil bulk density and coarse sand were significantly higher in shrub plantations under grazing than exclosure. 2) There were 40 families from 13 orders captured. The dominant groups included Formicidae and Tenebrionidae families, which comprised 68.75% of the total individuals. There were four common groups occupying 20.82% of the total individuals. The remaining 34 groups were relatively rare, only accounting for 10.44% of the total. Across the three seasons, the composition of ground-active arthropod community was significantly different between grazing and exclosure, which indicates the sensitivity and adaptability of ground-active arthropods to environmental changes including grazing management and seasonal changes. 3) There was a significant effect of grazing on total abundance of ground-active arthropods in shrub plantations, with significantly higher values under grazing than under exclosure. There was no significant effect of grazing management on group richness and diversity of ground-active arthropods in shrub plantations. 4) There was a correlation of total abundance, evenness index and the Simpson index with plant abundance, vegetation height, soil moisture, soil pH and electrical conductivity. There was a significant correlation of the Shannon index with vegetation height, soil moisture and soil fine sand. Plant density, and soil pH, soil moisture and soil temperature were the key factors driving the structure of ground-active arthropod communities in shrub plantations under gra-zing management across seasons based on the partial RDA results. It was concluded that the variations of plant height, soil pH, soil moisture and soil temperature under grazing management could result in different ground-active arthropod taxon to changing habitats. The conservation effect of shrub on ground-active arthropod could reduce the negative impacts of grazing. Spring grazing could enhance ground-active arthropod abundances in shrub plantations. It was necessary to pay attention to prevention of insects which are caused by spring grazing in shrub plantations.

[Response of soil microbial biomass and microbial entropy to desertification in desert grassland]. / è’æ¼ è‰åœ°åœŸå£¤å¾®ç”Ÿç‰©ç”Ÿç‰©é‡å’Œå¾®ç”Ÿç‰©ç†µå¯¹æ²™æ¼ åŒ–çš„å“åº”.

Using an approach of spatial sequence instead of temporal succession, we investigated the variation and driving factors of soil microbial biomass and microbial entropy in desert grasslands across four different desertification stages (grassland, fixed dune, semi-fixed dune and mobile dune) in Yanchi County, Ningxia, China. The results showed that soil microbial biomass carbon, nitrogen and phosphorus reduced by 46.1%, 80.8% and 30.0% from grassland to mobile dunes, respectively. The soil microbial entropy (qMBC, qMBN, and qMBP) decreased but soil-microbial stoichiometry imbalance (C:Nimb, C:Pimb and N:Pimb) generally increased with the development of desertification. There were significantly positive relationship between soil microbial biomass nitrogen and C:Nimb, soil microbial biomass phosphorus and C:Pimb, while negative relationship between soil microbial biomass nitrogen and N:Pimb. The RDA result showed that soil ecological stoichiometry (C:N, C:P) had the strongest negative effect on soil microbial entropy carbon (qMBC). Soil microbial biomass and microbial entropy were significantly affected by desertification in desert grassland.

[Soil particle composition, fractal dimension and their effects on soil properties following sand-binding revegetation within straw checkerboard in Tengger Desert, China]. / è ¾æ ¼é‡Œæ²™æ¼ è‰æ–¹æ ¼å›ºæ²™æž—åœŸå£¤é¢—ç²’ç»„æˆã€åˆ†å½¢ç»´æ•°åŠå ¶å¯¹åœŸå£¤æ€§è´¨çš„å½±å“.

This study aims to elucidate the effects of soil particle composition and fractal dimension on soil physical and chemical properties following sand-binding revegetation within straw checkerboard in south-eastern Tengger Desert. Three afforested plantations in the year of 2016 (i.e., 1 year), 2013 (i.e., 4 years) and 1987 (i.e., 30 years) were selected as study sites, with the adjacent mobile sand land as control (CK). We measured soil particle composition, soil fractal dimension, and the changes of soil physical and chemical properties. The relationship between soil particle composition, soil fractal dimension, and soil properties was analyzed. The results showed that contents of soil particle with the size of both 100-250 µm and 250-500 µm were greater than that of 50-100 µm, ranging from 42.5% to 80.1% and from 12.5% to 42.2% relative to that ranging from 0.2% to 20.8%. Contents of soil particle with the size of <2 µm and 2-50 µm were remarka-bly lower than that of 100-250 µm, 250-500 µm and 50-100 µm, ranging from 0 to 1.3% and from 0 to 22.7%, respectively. However, contents of soil particle at the size of 500-1000 µm was the lowest occupying <0.3% of soil particle composition. Soil particle with the size of <2 µm and 2-50 µm were found in the 30-year sites only. Soil particle distribution at the size of 50-100 µm, 100-250 µm, and 250-500 µm followed the order of 30 a>1 a>4 a＞CK, 4 a>1 a>CK>30 a, and CK>1 a>4 a> 30a, respectively. Soil particle with the size of 500-1000 µm occupied little of soil particle composition, with no significant difference between each site. The fractal dimension of soil particles ranged from 0.54 to 2.59. There was significantly greater soil fractal dimension in 30 a in comparison to 4 a, 1 a and CK, with the intermediate values in 4 a and 1 a, and the lowest values in CK. There was a significantly positive correlation of fractal dimension of soil particles with soil particle content of clay, silt, very fine sand, and a significantly negative correlation of fractal dimension of soil particles with soil particle content of medium sand. Fractal dimension of soil particles was positively correlated with soil electrical conductivity, organic carbon, total nitrogen, and carbon-nitrogen ratio, but with no correlation with soil pH and soil water content. Soil particle content at the size of <2 µm, 2-50 µm, and 50-100 µm had a significant positive correlation with soil electrical conductivity, organic carbon, total nitrogen, and carbon-nitrogen ratio, whereas soil particle content at the size of 250-500 µm had a negative correlation with the former four soil indices and soil water content. In addition, there was a significant negative correlation of soil particle content at the size of 500-1000 µm with soil water content. It was concluded that the sand-binding reve-getation within straw checkerboard in Tengger Desert could facilitate the fine soil particles by ameli-orating stressful soil conditions. Long-term succession of revegetation on mobile sand land could enhance soil clay and silt content as well as soil fractal dimension, thus be beneficial for the improvement of soil physical and chemical properties and desertification control.

[Assemblage effect of ground arthropod community in desert steppe shrubs with different ages].

Taking the 6-, 15-, 24- and 36-year-old Caragana intermedia shrubs in desert steppe as a subject, an investigation on soil properties and ground arthropod community was carried out under the shrub and in the open to probe into the assemblage effect of ground arthropod community in desert steppe shrubs with different ages. The results were as follows: 1) In the 6-year-old shrubland, significant differences were only found in soil physical properties (soil texture, soil moisture and electrical conductivity) between the microhabitats under shrub and in the open. Beginning from the 15-year-old shrubland, however, soil organic matter and nutrition (N, P) increased significantly. 2) A total of 27 groups were captured in the studied sites which dominated by Carabidae, Tenebrionidae and Formicidae. From 6- to 15-year-old shrubland, the number of dominant groups decreased while that of common groups increased for the ground arthropod community under the shrub. From 15- to 24- and 36-year-old shrubland, the difference between the microhabitats under the shrub and in the open decreased firstly, and then increased. Some special groups appeared under the shrub in the 36-year-old shrubland, and dung beetles became dominant. 3) In the 6- and 24-year-old shrublands, there were no significant differences in group richness, abundance, and diversity index between the microhabitats under the shrub and in the open. As for the 15- and 36-year-old shrublands, however, significant differences were observed. 4) The shrub age had a stronger effect on the distribution of ground arthropods living under the shrubs compared to that in the open. The changes in soil texture, pH and electrical conductivity could significantly influence on the distribution of ground arthropods under the shrub, also in the open to some degree. It was suggested that the development of shrubland had strong impact on assemblage effect of ground arthropods, which was closely correlated with the stand age and would affect the recovery of sandy grassland ecosystems.

[Effects of cutting and reseeding on the ground-dwelling arthropod community in Caragana intermedia forest in desert steppe].

Taking a 25-year-old Caragana intermedia forest in desert steppe as test object, an investigation was conducted on the ground-dwelling arthropod community in cutting and no-cutting stands with and without reseeding, aimed to understand the effects of cutting, reseeding and their interaction on the individual number and group richness of ground-dwelling arthropod in C. intermedia forest. There were significantly lower number and richness of ground-dwelling arthropod in the open spaces than under the shrubs in the no-cutting and no-reseeding stands. Cutting, reseeding and both of them could significantly increase the number and richness of ground-dwelling arthropod in the open spaces, but not under the shrubs, compared with no cutting or reseeding. Consequently, there were no significant differences in the distribution of ground-dwelling arthropod in the open spaces and under the shrubs in the cutting, reseeding, or cutting and reseeding stands. Further, there was a similar buffer effect between cutting and reseeding on the ground-dwelling arthropod. No significant differences were observed in the ground-dwelling arthropod distribution, between cutting stand and reseeding stand, between cutting stand and cutting and reseeding stand, and between reseeding stand and cutting and reseeding stand. It was suggested that cutting, reseeding, or both of them could significantly improve the ground-dwelling arthropod diversity especially in the open spaces, being beneficial for the restoration of degraded grassland ecosystem and the rational management on artificial C. intermedia forest in desert steppe.

[Effects of different afforestation types on soil faunal diversity in Horqin Sand Land].

In order to deeply understand the effects of afforestation on the soil faunal diversity in mobile sand land, an investigation was conducted on the community structure of soil animals in the mobile sand land and its adjacent about 30 years old forest land and shrub land in Hrqin Sand Land. Afforestation on the mobile sand land had remarkable effects on the soil properties, especially the soil environment in shrub land, in which, the soil water content, pH, and nutrient contents were improved. In the three lands investigated, a total of 485 individuals belonging to 11 soil animal groups were collected, among which, Acarina and Collembola were the dominant groups, Corrodentia was the common group, and the others were of rare groups. From the mobile sand land to shrub land to forest land, the soil faunal density decreased, group richness and Shannon index increased, and evenness declined, but no significant differences were observed in these indices among these three lands. It was suggested that afforestation on mobile sand land could improve the soil environment and enhance soil faunal diversity, but there was a limitation to take 30 years old plantations as test objects to investigate the effects of afforestation on soil faunal diversity in mobile sand land.

[Variations of ground vegetation and soil properties during the growth process of artificial sand-fixing Caragana intermedia plantations in desert steppe].

To study the variation characteristics of ground vegetation and soil properties during the growth process of Caragana intermedia plantations in desert steppe is of scientific significance in revealing the ecological effect of the plantations on the restoration of desertified grassland ecosystem. In this paper, an investigation was conducted on the ground vegetation and soil properties in 6-, 15-, 24-, and 36-yr artificial sand-fixing C. intermedia plantations in desert steppe of Ningxia, Northwest China, with the variation characteristics of the ground vegetation and soil properties during the growth process of the C. intermedia plantations analyzed. With the growth and development of the plantations, the shrub crown width, height, sprout number, and basal diameter all increased significantly, the contents of soil coarse sand and fine sand had significant decrease while those of very fine sand and clay silt were in adverse, the soil organic carbon, total N, and total P contents increased linearly, and the soil pH decreased significantly. During the growth process of the plantations, the species number and individual number of ground vegetation increased significantly, and the vegetation coverage and height presented the order of 24- > 15- > 6- > 36-yr plantation. The soil texture, bulk density, nutrient contents, and pH value were the main factors affecting the species and individual number as well as the coverage of ground vegetation in C. intermedia plantations. It was suggested that in desert steppe, the growth process of artificial sand-fixing C. intermedia plantation benefited the improvement of soil conditions and the recovery of ground vegetation, and promoted the restoration of degraded grassland ecosystem in desert steppe.

[Responses of ground arthropod functional groups to the enclosure of grazing grassland in desert steppe].

With the support of the National Resources Monitoring Station in Yanchi County of Ningxia, an investigation was conducted on the ground arthropods, vegetations, and soil properties in the enclosed and un-enclosed grazing grassland in desert steppe. In the meantime, the functional groups of ground arthropods were classified according to their feeding habits. The ground arthropods in the desert steppe could be classified into four functional groups, i.e., predatory, phytophagous, saprophagous, and omnivorous, among which, predatory and phytophagous groups were dominant in quantity, and phytophagous and saprophagous groups were predominant in biomass, implying that the ground arthropod in desert steppe was mainly characterized by phytophagous arthropods. Enclosure increased the individual and group number of predatory, phytophagous, and omnivorous arthropods as well as the biomass of predatory and omnivorous arthropods, and enhanced the biodiversity of predatory and phytophagous arthropods, which was closely correlated with the vegetation recovery and soil environment improvement, and demonstrated that the enclosure of grazing grassland increased the diversity and complexity of ground arthropod functional groups in desert steppe. Nevertheless, the individual number and biomass of saprophagous arthropods decreased after the enclosure, reflecting the dependence of these arthropods on grazing grassland.

[Community structure and diversity of soil arthropods in naturally restored sandy grasslands after grazing].

Taking the Naiman Desertification Research Station under Chinese Academy of Sciences as a base, an investigation was conducted on the community structure of soil arthropods in the naturally restored sandy grasslands after different intensity grazing disturbance, with the effects of vegetation and soil on this community structure approached. In the non-grazing grassland, soil arthropods were rich in species and more in individuals, and had the highest diversity. In the restored grassland after light grazing, soil arthropods had the lowest evenness and diversity. In the restored grassland after moderate grazing, the individuals of soil arthropods were lesser but the major groups were more, and the evenness and diversity were higher. In the restored grassland after heavy grazing, the individuals of soil arthropods were more but the major groups were lesser, and the diversity was higher. Plant individuals' number, vegetation height and coverage, and soil alkalinity were the main factors affecting the soil arthropod community in naturally restored grasslands after different intensity grazing disturbance. It was implied that after 12-year exclosure of grassland, soil arthropod community could be recovered to some degree, while grazing disturbance had long-term negative effects on the arthropod community.

[Distribution of Formica cunicularia mound and related affecting factors on mobile dune in Horqin sandy land].

Taking the typical mobile dune in Horqin sandy land as test object, the density, diameter, and coverage of Formica cunicularia mounds on different land forms were investigated by quadrate method, with the spatial distribution of F. cunicularia mounds and the effects of topography and soil property on F. cunicularia nest-building activities discussed. The results showed that the density of F. cunicularia mounds decreased in the order of ridge > leeward slope > windward slope, while the diameter and coverage of the mounds were in the order of ridge > windward slope > leeward slope and conditioned by mound density. The spatial distribution of F. cunicularia mounds was in random pattern. Topography and soil property co-affected the nest-building activities of F. cunicularia.