Shrub Caragana Research Articles

Predicting the potential risk of Caragana shrub encroachment in the Eurasian steppe under anthropogenic climate change

Climate change and human activities drive widespread shrub encroachment in global grassland ecosystems, particularly in the Eurasian steppe. Caragana shrubs, the primary contributors to shrub encroachment in this region, play a crucial role in shaping the ecosystem's structure and function. Future changes in the suitable distribution range of Caragana species will directly affect the ecological security and sustainable socio-economic development of the Eurasian steppe ecosystem. We used an ensemble modeling approach to predict Caragana shrub-dominated plant communities' current and future distribution in three major steppe subregions: the Black Sea-Kazakhstan steppe, the Tibetan Plateau steppe, and the Central Asian steppe. We assessed the potential risk of Caragana shrub encroachment by predicting changes in the suitable distribution area of 19 Caragana shrub species under future climate changes. Our research findings suggest that the expansion of Caragana species in different subregions of the Eurasian steppe is influenced by the effects of climate change in various ways. The distribution of Caragana species is primarily influenced by precipitation and temperature, and the global human modification (ghm) has a significant impact on the Central Asian and Tibetan Plateau subregions. Minimal changes are expected in the Black Sea-Kazakhstan subregion, a slight increase on the Tibetan Plateau, and a substantial rise in the Central Asian subregion, which suggests a higher potential risk of Caragana species shrub encroachment in that area. Our research provides valuable insights into the response of Caragana shrub encroachment to changing climates and human activities. It also has implications for the sustainable management of different areas of the vast Eurasian steppe ecosystem.

Asymmetric pre-growing season warming may jeopardize seed reproduction of the sand-stabilizing shrub Caragana microphylla

Our current understanding of the processes and mechanisms by which seasonal asymmetric warming affects seed reproduction in semiarid regions, which are essential in preserving the stability of both vegetation ecosystem structure and function, remains poorly understood. Here, we conducted a field warming experiment, including pre-growing season warming (W1), in-growing season warming (W2), and combined pre- and in-growing season warming (W3) treatments, to investigate the seed reproductive strategy of Caragana microphylla, an important sand-stabilizing shrub, from the perspective of reproductive phenology, reproductive effort, and reproductive success. Results show that the warming treatments advanced the initial stages of reproductive phenology, prolonged its duration, and decreased its synchrony (magnitude = W3 > W2 > W1). Additionally, flowering phenology was more sensitive to warming than podding phenology. The W1 treatment inclined seed reproduction towards the conservative strategy with low reproductive effort and success. The W3 treatment tended to increase seed reproductive effort and success. While the W2 treatment did not affect reproductive success, it did increase reproductive effort. Changes in reproductive phenology explained 20 % of the variation in reproductive effort and 38 % of the variation in reproductive success. However, these changes also directly hindered reproductive success (direct effect = −0.57) while indirectly promoting reproductive success (indirect effect = 0.27) by increasing reproductive efforts. Our results reveal that the seasonal asymmetry of warming altered the seed reproduction strategy of sand-stabilizing shrubs, with warmer winters and springs before the growing season decreasing seed fecundity.

Sexual Reproduction Is Not Responsible for Caragana Shrub Encroachment in Grasslands

Shrubs tended to increase their abundance as climatic aridity and grazing intensity increased in the Inner Mongolian grassland. Increasing shrub abundance was believed to be due to enhanced reproduction. However, the effects of climatic aridity and grazing on the sexual reproduction of shrubs in grassland remain largely unclear. In this study, we conducted field experiments with Caragana microphylla to examine the variation of sexual reproduction aspects (seed production, seed vigor, and sapling establishment) along a climatic aridity gradient (subhumid, semiarid, arid, and dry arid zones) and a grazing intensity gradient (fenced, mildly grazed, and severely grazed). We then quantified the population growth rate based on seed production and sapling establishment rates. Our objective was to evaluate whether sexual reproduction is the main mechanism for Caragana encroachment into grasslands. We found that climatic aridity decreased seed quantity and seed vigor but increased the sapling establishment rate of Caragana shrubs. Under ungrazed conditions, climatic aridity did not affect population growth rates, while under grazing conditions, increased aridity stresses reduced population growth rates. Grazing reduced seed production, sapling establishment, and population growth rates. Climatic aridity enhanced the negative effects of grazing on sexual reproduction, while grazing intensified the negative effects of aridity on the population growth of Caragana shrubs. In conclusion, climatic aridity, grazing, and their combined effects had negative effects on the sexual reproduction of Caragana shrubs. Therefore, sexual reproduction could not fully explain the increased abundance of shrubs with increasing aridity and grazing. Clonal reproduction might be of considerable importance for understanding the mechanism of shrub encroachment in grasslands.

Phytopathogenic fungi of Caragana arborescens Lam., growing in the city Karaganda

The article presents the results of the determination of powdery-mildews fungi and rust fungi of shrub plantings growing on the streets, squares and parks of the city of Karaganda. The article presents data on the species composition of phytopathogenic fungi, where the host-plant is the Caragana arborescens Lam., growing in the city of Karaganda. Theoretical and practical information on methods for determining phytopathogenic fungi by fruit bodies, appendages, asci and ascospores has been collected by us. Phytopathogenic fungi are directly dependent on their host-plant, the conditions of development and the duration of the period of vegetation. Timely study of the condition of the plants used for greening the city, identification of diseases, level of their development, distribution, biology in accordance with the climatic conditions of the region is the basis for preventing the spread of these harmful organisms, carrying out effective control measures against them. For the first time in this region, the shrub Caragana arborescens Lam. is a host-plant for such species of phytopathogenic fungi as: powdery-mildews fungi Microsphaera caraganae L., rust fungi Uromyces cytisi J. Schröt.

Shrub-mediated effects on soil nitrogen determines shrub-herbaceous interactions in drylands of the Tibetan Plateau.

Shrub promotes the survival, growth and reproduction of understory species by buffering the environmental extremes and improving limited resources (i.e., facilitation effect) in arid and semiarid regions. However, the importance of soil water and nutrient availability on shrub facilitation, and its trend along a drought gradient have been relatively less addressed in water-limited systems. We investigated species richness, plant size, soil total nitrogen and dominant grass leaf δ13C within and outside the dominant leguminous cushion-like shrub Caragana versicolor along a water deficit gradient in drylands of Tibetan Plateau. We found that C. versicolor increased grass species richness but had a negative effect on annual and perennial forbs. Along the water deficit gradient, plant interaction assessed by species richness (RIIspecies) showed a unimodal pattern with shift from increase to decrease, while plant interaction assessed by plant size (RIIsize) did not vary significantly. The effect of C. versicolor on soil nitrogen, rather than water availability, determined its overall effect on understory species richness. Neither the effect of C. versicolor on soil nitrogen nor water availability affected plant size. Our study suggests that the drying tendency in association with the recent warming trends observed in drylands of Tibetan Plateau, will likely hinder the facilitation effect of nurse leguminous shrub on understories if moisture availability crosses a critical minimum threshold.

Seasonal community stability increased with water addition and shrub removal but reduced with nitrogen addition in semi‐arid grassland

Abstract Stability is a useful indicator of the functioning and sustainability of an ecosystem, and much studies have explored the effects of anthropogenic disturbance on the inter‐annual stability of plant community. However, the effects of multiple anthropogenic stressors on seasonal community stability have not been clearly elucidated, especially for vulnerable semi‐arid grasslands. During the growing season in the 5th year of the experiment, we determined how nitrogen (N) addition, water addition and shrub removal altered seasonal community stability in a semi‐arid grassland dominated by the shrub Caragana microphylla on the Mongolian Plateau. We found that shrub removal, N addition and water addition had different effects on the stability of community and plant functional groups (PFGs). Shrub removal increased seasonal community stability mostly via increases in the stability of perennial forbs and C4 plants, and shrub removal did not alter the effects of N addition or water addition on seasonal community stability or PFG stability. N addition decreased seasonal community stability mostly via decreases in the stability of perennial rhizome grasses and C4 plants. Water addition increased seasonal community stability mostly via increases in the stability of annuals and biennials, perennial forbs, perennial rhizome grasses, dominant species and C4 plants. Species asynchrony and PFG stability but not species richness or soil abiotic or biotic variables helped to maintain seasonal community stability under N addition or water addition. Our findings indicate that future scenarios of increases in N deposition and shrub encroachment will strongly reduce community stability in drylands, and that future scenarios of increases in precipitation together with shrub removal might help to maintain the stability of this and other dryland ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

Sandy Habitats Play an Important Role in Shrub Encroachment in Grasslands

Shrub species have increased in density and cover in desertification areas, however, the role of sandy habitats in contributing to the expansion of shrubs is poorly understood. Although the effect of sandy habitats on plant growth and reproduction have been demonstrated, most existing studies lack either experimental demonstration or an integrated study during the whole shrub life cycle. We performed field and laboratory experiments to examine the responses of four stages in the life cycle of shrubs (seed germination, plant growth, seed reproduction, clonal reproduction) to sandy habitats (including sand substrate, sand burial and wind erosion) for Caragana shrubs. Results showed that both sand substrate and sand burial facilitated seed germination, seedling biomass, sapling establishment, plant growth, and root-shoot ratio of Caragana. Meanwhile, they both strongly increased seed number and seed preservation, and thus enhanced sexual reproduction. Sand burial favored clonal reproduction of Caragana by promoting the formation of branch-derived ramets, while wind erosion benefited clonal reproduction by facilitating the formation of root-derived ramets. These results suggested that sandy habitats facilitated seed germination, plant growth, sexual reproduction, and clonal reproduction of Caragana, which could explain why shrub abundance, shrub area and shrub height of Caragana in sandy areas was higher than in grasslands. Our study provided an experimental demonstration that sandy habitats promoted the population growth of Caragana shrubs during the whole life cycle and highlighted the significant role of sandy habitats in facilitating shrub encroachment in grasslands.

Carbon–water coupling and its relationship with environmental and biological factors in a planted Caragana liouana shrub community in desert steppe, northwest China

Abstract The carbon and water cycle, an important biophysical process of terrestrial ecosystems, is changed by anthropogenic revegetation in arid and semiarid areas. However, there is still a lack of understanding of the mechanisms of carbon and water coupling in intrinsic ecosystems in the context of human activities. Based on the CO2 and H2O flux measurements of the desert steppe with the planted shrub Caragana liouana, this study explored the carbon and water flux coupling of the ecosystem by analyzing the variations in gross primary productivity (GPP), evapotranspiration (ET) and water use efficiency (WUE) and discussing the driving mechanisms of biological factors. The seasonal variation in climate factors induced a periodic variation pattern of biophysical traits and carbon and water fluxes. The GPP and ET fluctuated in seasons, but the WUE was relatively stable in the growing season. The GPP, ET and WUE were significantly driven by global radiation (Rg), temperature (Ta and Ts), water vapor pressure deficit, leaf area index and plant water stress index (PWSI). However, Rg, temperature and PWSI were the most important factors regulating WUE. Rg and temperature directly affected WUE with a positive effect but indirectly inhibited WUE by rising PWSI. Plant water stress inhibited photosynthesis and transpiration of the planted shrub community in the desert steppe. When the plant water stress exceeded a threshold (PWSI >0.54), the WUE would decrease since the GPP responded more quickly to the plant water stress than ET. Our findings suggest that policies related to large-scale carbon sequestration initiatives under afforestation must first fully consider the status of water consumption and WUE.

The Characteristics of Radial Growth and Ecological Response of Caragana korshinskii Kom. Under Different Precipitation Gradient in the Western Loess Plateau, China.

Understanding the temporal-spatial variability of tree radial growth and ecological response is the basis for assessing forest vulnerability in sight of climate change. We studied stands of the shrub Caragana korshinskii Kom. at four sampling sites (natural forest CL and plantation forests XZJ, CK and TPX) that spanned the different precipitation gradient (180–415 mm) across China’s western Loess Plateau, and demonstrated its radial growth dynamics and ecological response. We found that the growth of natural C. korshinskii in arid regions have adapted and cope with regional environmental changes and radial growth was less affected by drought stress. However, the growth of planted C. korshinskii was significantly affected by drought stress in arid and semi-arid regions, especially during the growing season (from June to September). Variations in radial growth rates and growth indicators such as shrub height, canopy area are consistent with the climate-growth relationship. With increase of precipitation, the limiting of drought on the growth of planted C. korshinskii gradually decreased and the amount of radial growth variation explained by drought decreased from 53.8 to 34.2% and 22.3% from 270 to 399 and 415 mm of precipitation, respectively. The age-related radial growth trend shows that radial growth increased until 4 years of age, then decreased rapidly until 12–14 years of age, and then eventually tend to stabilized. In the context of climate warming and humidification, increased precipitation and regular branch coppicing management at around 12 years old will help to mitigate the limitation of drought on the growth of C. korshinskii. Moreover, the initial planting density should be tailored to local precipitation conditions (below 5,000 shrubs per hectare). The above results have important practical significance for the maintenance of the stability and sustainable management of plantation forests in the western Loess Plateau.

Improvement of xylo-oligosaccharides dissolution from Caragana korshinskii through liquid hot water pretreatment with tiny choline chloride

Xylo-oligosaccharides (XOS) is a kind of high-value substance with bioactivity, extracted from plants with liquid hot water (LHW) treatment that is usually applied for biorefinery. Herein, we reported a system of LHW with tiny choline chloride (ChCl) to treat a shrub Caragana korshinskii to improve XOS extraction. It is found that the ChCl acted as a buffer in LHW pretreatment promotes the XOS extraction with a yield of 36.59% at 160 °C for 120 min. Compared with LHW/NaOH pretreatment, it also showed that the content of xylan in the residue was decreased by about 14% after LHW/ChCl pretreatment. The concentrations of furfural and 5-HMF in the hydrolysate were decreased after LHW/ChCl pretreatment. Moreover, the cellulose conversion rate of the residue treated with ChCl was 41.30% when using 25 FPU/g-substrate cellulase and 25 CBU/g-substrate β-glucosidase, an increase of 38% compared with the untreated one. The LHW/ChCl pretreatment provided a strategy to utilize the sandy growth biomass for high value products.

Survival of forest strips in ash and slag dump territory of Chita combined heat and power plant

This article is a continuation of research on creation of forest protective strips on the territory of sanitary protection zone with intensive influence of ash and slag dump of the Chita CHPP-1 (TGC-14). Earlier (2017-2019), plantings were made focused on reducing atmospheric pollution, improving soil properties, regulating surface runoff that prevents erosion, fixing ground cover, reducing wind speed and retaining small solid particles. The aim of the research was to analyze survival rate and health of woody and shrubby plant species in protective forest strips; to obtain linear indicators of plant growth and development in experimental plots. In the course of the research, it was found that the overall survival of plants in the experimental plots differed by year. Survival rate of woody and shrubby plant species also differed. Larix gmelinii, Betula pendula, Hippophae rhamnoides, Crataegus sanguinea, Caragana spinosa and Elaeagnus commutata had the highest survival rate in the experiment. The survival of shrubs was generally better than that of trees. Among shrub species, Caragana spinosa (92 and 81 %) and Elaeagnus commutata (95 and 86 %) were characterized by good survival in plantings in 2017 and 2018, respectively. Rosa acicularis (20 %), Spiraea media and Sorbaria sorbifolia (28 %) showed low survival in 2019. The plant survival varies significantly depending on the planting season, types of seedlings and planting technology. The use of planting material (wildfowl) with a large earthen lump increases plant survival in forest protection strips. Unfavorable factors that have a negative impact on the transplanted plants are man-made landscapes, harmful atmospheric impurities from the ash and slag dump. Moreover, competitive relations with herbaceous plants, intensive grazing of animals, insect and disease damage have an additional impact. For healthy growth of plants, it is necessary to perform care for plantings, and organizational measures (fencing of experimental plots with signal tapes). It is important to continue observations and repeat plantings to clarify the adaptive ability of plant species grown in protective plantings, improve planting technology.

Soil moisture and species richness interactively affect multiple ecosystem functions in a microcosm experiment of simulated shrub encroached grasslands

Understanding relationships between biodiversity and ecosystem functions (BEF) and the way in which ecosystem functions respond to changing climatic conditions or community composition is useful for predicting ecological consequences of global changes. However, how soil moisture condition, plant species richness interactively affect ecosystem functions in shrub-encroached grasslands is poorly understood. We conducted a soil moisture × species richness microcosm experiment using semi-arid grassland species with a N-fixing shrub Caragana microphylla Lam. as the dominant species to evaluate how soil moisture and plant species richness affected ecosystem functions directly or indirectly via regulating community functional structure, such as community-weighted mean values (CWM) and functional dispersion (FDis). Soil moisture and species richness interactively affected soil functions (soil C-, N-, P cycles and soil multifunctionality), with greater species richness buffering the adverse effects of soil drought. Soil moisture and species richness showed opposite effects on FDis but similar effects on CWM. FDis mediated the indirect effect of soil moisture and species richness on ecosystem functions, while CWM only mediated the indirect effect of soil moisture. More specifically, both soil moisture and plant species richness were negatively associated with soil P cycle, and the CWMPC1 contributed by traits related to resource-conservative strategy was positively associated with soil N cycle. Species richness showed a positive direct effect on total shoot biomass, which was mainly contributed by the complementarity effect of neighbor species richness. This study provides strong empirical support of how biomass and soil nutrient cycles respond to the changes of soil moisture and plant species richness in C. microphylla shrub-encroached grasslands, and insights on the mechanisms underlying the interactive effects of soil condition and community species composition on multiple ecosystem functions in N-fixing shrub encroached grasslands in semi-arid grassland regions.

Changes in the composition of soil bacterial and fungal communities after revegetation with Caragana microphylla in a desertified semiarid grassland

Revegetation with native leguminous shrub Caragana microphylla in the Horqin Sandy Land, China, has been reported to increase plant coverage and diversity, and ameliorate abiotic soil property. However, comprehensive investigation of soil microbial-community composition after revegetation in this area has been rarely conducted. In this study, DNA of sand dunes restored for a period of 12 and 30 years, and an unrestored sand dune (control), was extracted and sequenced using Illumina Miseq. The results indicated that revegetation of C. microphylla significantly altered soil microbial communities as reflected by the significantly different bacterial and fungal composition and fungal diversity between the restored dunes and the control; however, there was no significant difference in soil microbial composition between the dunes restored for different years. Specifically, microbial consortia that involved in a wide range of ecological function, including recalcitrant organic carbon decomposition, plant-microbe symbiosis and nitrogen fixation, were enriched on restored dunes particularly on the 30-year restored dune. The changes in soil microbial communities were significantly correlated with the content of soil organic carbon (SOC) and the proportions of labile and recalcitrant organic carbon in SOC, which may indicate a mutual-regulated ecological improvement between soil abiotic and biotic processes along sand dune restoration.

Determination of ureid content in shoots of russian pea shrub and siberian pea tree

Among natural ureides, allantoin (5-ureidohydantoin or 2,5-dioxoimidazolidin-4-yl urea) is the most famous compound which have been found in various organisms: bacteria, plants, and animals. Allantoin is a product of purine catabolism in mammals (except for primates and humans) and insect larvae. It is found in many plants: comfrey (Symphytum officinale L.), soybean (Glycine hispida (Moench) Maxim), alfalfa (Medicago sativa L.), purslane (Portulaca oleracea L.).
 Allantoin has a reparative, antimicrobial, and anti-inflammatory effect, that substantiate it use in the composition of numerous cosmetic and therapeutic dermatological agents. It can be used also used for the treatment of gastroduodenal ulcers and chronic gastritis. In most species of the legume family allantoin is a transport form of nitrogen, besides, its role in the adaptation of plants to stress factors is known.
 The plants of the genus Caragana (Caragana) of the legume family (Fabaceae), due to nitrogen-fixing bacteria, receive nitrogen from the soil and convert it into transport forms, namely allantoin and allantoic acid. These substances were previously isolated from the shoots of russian pea shrub (Caragana frutex (L.) C. Koch) and siberian pea tree (Caragana arborescens Lam.) and identified, but the quantitative content of ureids in these raw materials has not been studied.
 The aim of the work was to determine the content of ureides in the shoots of russian pea shrub tree and siberian pea tree.
 The objects of study were shoots of russian pea shrub tree and siberian pea tree harvested in Kharkov in May 2019 (during flowering period). The total ureide content was determined by spectrophotometric method based on the reaction of chemical decomposition of allantoin to glyoxylic acid with subsequent formation of coloured phenylhydrazone, which had absorption maximum at 530 nm.
 The study results have shown that the content of ureides (expressed as allantoin) is slightly lower in the shoots of russian pea shrub than in the shoots of siberian pea tree and equals 0.34 ± 0.03% and 0.41 ± 0.02% respectively.
 The content of total ureids in the shoots of russian pea shrub and siberian pea tree was determined. The flowering shoots of these plants can be used as herbal raw material for the development of therapeutic and prophylactic dermatological and antiulcer drugs possessing reparative, anti-inflammatory, and astringent effects.

Leaf wax <i>n</i>-alkane patterns and compound-specific <i>δ</i><sup>13</sup>C of plants and topsoils from semi-arid and arid Mongolia

Abstract. Leaf wax n-alkane patterns and their compound-specific δ13C signatures are valuable proxies for paleoenvironmental reconstructions. So far, their potential has not been investigated in semi-arid to arid Mongolia. We have therefore analysed the leaf wax n-alkanes and their compound-specific δ13C signature of five plant species (Poaceae, Cyperaceae, Artemisia spp., Caragana spp. and Larix sp.) and topsoils (0–5 cm) along two transects in central and southern Mongolia. Grasses show a distinct dominance of the n-C31 homologue, whereas the shrubs Caragana spp. and Artemisia spp. are dominated by n-C29. Larix sp. is characterised by the mid-chain n-alkanes n-C23 and n-C25. From plant to topsoil, n-alkane patterns show the potential to differentiate between grass-covered sites from those covered by Caragana spp. n-Alkane concentrations and odd-over-even predominance (OEP) of the topsoils are distinctly influenced by mean annual temperature, mean annual precipitation and aridity, likely reflecting the degree of n-alkane degradation and biomass production. In contrast, the average chain length (ACL) and the n-alkane ratio (n-C31∕n-C29+n-C31) are not affected by climatic parameters and, thus, are not biased by climate. The compound-specific δ13C signatures are strongly correlated to climate, showing a significant enrichment with increasing aridity, indicating the effect of water use efficiency. Our calibration results suggest that long-chain n-alkanes and their compound-specific δ13C signatures have great potential to reconstruct paleoenvironmental and paleoclimatic conditions when used in sediment archives from Mongolia.

The fertile island effect collapses under extreme overgrazing: evidence from a shrub-encroached grassland

Woody plant encroachment is a phenomenon of global concern in drylands due to demonstrated reductions in livestock carrying capacity. However, shrubs are known to contribute to the development of patches of enhanced fertility that might offset any negative effects of increasing grazing. We measured soil physical and chemical characteristics within shrub and open patches across a gradient in livestock grazing to explore how the relative effect of shrubs might change with increasing grazing-induced disturbance. Soil carbon, nitrogen phosphorus and bulk density were measured within 92 shrub patches and their paired interspaces at five sites ranging from long-grazed to long-ungrazed in a semiarid grassland encroached by the N-fixing shrub Caragana microphylla. We used a combination of linear and structural equation modelling to test whether shrubs might buffer any negative effects of overgrazing on soils. Shrub soils were more porous, and had more organic carbon, nitrogen and phosphorus than interspace soils. Within both microsites, however, soil bulk density increased, and soil organic carbon and nutrients declined, with increasing grazing intensity. Grazing reduced interspace plant cover and height and exacerbated the negative effects of bulk density on soil carbon, whereas shrubs had the opposite effect. The relative importance of shrubs for soil carbon and nutrients increased with increasing grazing intensity but collapsed under extreme overgrazing. These findings highlight the effect of grazing in promoting shrub dominance, which can also prevent grassland degradation. However, any positive effects of grazing collapsed when sites were severely overgrazed.

Герпетобионтные членистоногие в урбанистическом градиенте г. Иркутска

Four biotops with arboreal vegetation situated in the Irkutsk town territory were studied by pitfall traps method: artifitially forrestated park zone, coastal band of willow shrubs, Caragana arborescens shrubs on steep slope of southern exposition, group of bird-cherry trees. Biodiversity of high taxonomical groups, and the same on species level for carabid beetles, were estimated. Carabid’s communities were compared on dominant species, biodiversity and dynamic density of populations. Sörensen – Chekanovsky coefficient for comparison of different biotopes in number of species and specimens was used. In the willow shrubs minimal number of high groups of arthropods were collected, but maximal biodiversity and dynamic density of carabids populations was postulated. It depends first of all the high number of small species Trechus secalis. Biodiversity is increased in the row: park zone (14) – bird-cherry trees (21) – caragana shrubs (24 groups). Set of the high taxonomical groups in the different biotopes has a specific features. Such taxa like carabids, staphylinids, silphids, ants and spiders were recorded in all biotopes, but could differ each other in the set of species and dynamic density very sufficiently. Sörensen coefficient estimated for carabids communities demonstrates very low similarity between biotopes as in set of species, as in number of specimens. Caragana shrubs has a maximal level of isolation. The simplest structure of community with very low number of species in park zone was postulated. In this biotopes silphid beetles was dominated group due to maximal level of anthropogenic influence. Refugial zones, like Kaya river basin in the town landscape surroundings, could be preserved for recreation and biodiversity maintenance.

Changes in soil properties following shrub encroachment in the semiarid Inner Mongolian grasslands of China

ABSTRACT Shrub encroachment is very common in the semiarid regions of China. However, surprisingly little research has been conducted to evaluate the effects of shrubs on soil properties in these regions compared with other regions in the world. Three sites, one without shrub (state 1), one with 13% shrub coverage (state 2), and the third one with 40% shrub coverage (state 3) in the semiarid Inner Mongolian grasslands were selected to investigate the effects of the shrub Caragana microphylla Lam on soil properties. Soil samples were collected from three sites to evaluate the changes of bulk density (BD), grain size distribution, aggregate stability, soil organic carbon (SOC), total nitrogen (TN), and soil water content (SWC) with the development of shrub encroachment. The results showed that BD and soil sand declined, and silt, aggregate >2 mm and the mean weight diameter (MWD) rose from state 1 to state 3, especially in 20–60 cm depths. With the shrub encroachment, the content of SOC and TN increased, and especially, the increase trends were more obvious in the deeper soil than in the surface soil. SWC increased with the development of shrub encroachment at 20–60 cm depths. Greater and deeper water infiltration existed after heavy rainfall in states 2 and 3, suggesting that macropore flow appeared in shrub encroachment sites. All these results indicated that shrub encroachment improved soil physicochemical properties, particularly in deep soil.

Comparison of water-use patterns for non-native and native woody species in a semiarid sandy region of Northeast China based on stable isotopes

In the semiarid sandy region of Northeast China, non-native woody species such as Pinus sylvestris var. mongolica L. and Populus x xiaozhuanica W.Y. Hsu & Liang frequently suffer dieback during years of extreme drought events due to water deficiency. In contrast, dieback does not usually occur in native woody species, e.g., Pinus tabuliformis Carr., Ulmus pumila L., and shrub Caragana microphylla Lam. However, the mechanism of water-use patterns between the non-native and native woody species remain unclear, which limits our understanding of the mechanisms underlying dieback of non-native woody species. During two consecutive growing seasons in 2014 and 2015, sources of water uptake by two non-native (P. mongolica and P. xiaozhuanica) and three native (P. tabuliformis, U. pumila and C. microphylla) woody species were determined using the stable isotopes of δ2H and δ18O in the twig xylem water, soil water at various depths (0–200 cm), groundwater (water from capillary fringe or beneath the water table) and precipitation, coupled with soil moisture and groundwater level measurements. Results showed that both P. mongolica and P. tabuliformis trees used the 0–100 cm soil water in the spring and the 0–40 cm and 0–100 cm soil water in summer of 2014 and autumn of 2015, respectively, when soil moisture was high. In contrast, in summer of 2015 and autumn of 2014, when soil moisture was low, P. mongolica trees used both the 0–100 cm soil water and groundwater, whereas P. tabuliformis trees used the 0–200 cm soil water and both the 40–200 cm soil water and relatively limited groundwater, respectively. The P. xiaozhuanica trees used the 40–200 cm or the 100–200 cm soil water and groundwater, whereas U. pumila trees mainly used the 0–100 cm or 0–200 cm soil water, except in autumn when soil moisture was high. P. xiaozhuanica trees used the 0–200 cm soil water, while U. pumila trees used the 0–40 cm soil water. The shrub C. microphylla mainly used the 0–200 cm soil water during the measurement period irrespective of soil moisture conditions. Compared with the native woody species, which mainly used soil water, the non-native tree species relied on groundwater besides soil water, especially under low soil moisture conditions. Therefore, a sharp decline in groundwater level during extreme drought years might have a strong negative impact on the growth and survival of non-native woody species.

Effects of planting Caragana shrubs on soil nutrients and stoichiometries in desert steppe of Northwest China

Caragana korshinskii shrubs are widely planted in desert steppe of Northwest China to mitigate desert encroachment. Soil nutrients and stoichiometries reflect the cycling of soil organic matter in ecosystems. Thus, there is a dynamic balance between soil nutrients and stoichiometries due to the establishment of Caragana shrubs in this region. Here, soil nutrients and stoichiometries were characterized with different planting densities of Caragana shrubs (HD, high density, 4530 bundle/hm2; MD, mid density, 3670 bundle/hm2; LD, low density, 2560 bundle/hm2) to explore how the planting of Caragana shrubs affects soil nutrients and stoichiometries in desert steppe of Northwest China. The results showed that soil available phosphorus (AP) and soil total phosphorus (TP) had no significant differences between LD and control (CK) (p > 0.05). Further, soil organic carbon (SOC), soil total nitrogen (TN), and soil alkali-hydrolyzable nitrogen (AN) followed the order of HD > MD > LD > CK, indicating that the planting of Caragana shrubs had an increasing effect to soil nutrients, with the exception of AP and TP (p < 0.05), and the increasing effect gradually died down along soil profile. In addition, the planting of Caragana shrubs significantly affected soil stoichiometries. Specifically, soil N/P and C/P gradually increased with soil depth with fluctuation, while soil C/N decreased with soil depth. Besides, soil water content (SW), AP, AN, and SOC had strong positive effects on soil C/N, while they had strong negative effects on soil C/P and N/P, highlighting the importance of soil properties in determining soil stoichiometries. Overall, our results indicated that planting Caragana shrubs can improve levels of soil nutrients, and HD can be considered the optimal planting density for vegetation restoration in desert steppe. Nevertheless, the threshold of the planting density most favorable for the special climates must be identified through further study in this region.