Shrub Plant Research Articles

Fabrication of Calotropis Gigantea fibre reinforced compression spring for light weight applications

A new attempt has been made in the manufacturing of helical springs, using Calotropis Gigantea fibre as the raw material. Calotropis Gigantea (CG) is a tropical shrub plant with high seasonality and naturally high yield; its fibre is extracted from the stem of the plant and rendered in a twisted form. Twisted fibre is treated with NaOH to address the major drawback associated with this natural fibre; its hydrophilicity. The treated fibre is then dipped in to a matrix, and turned into a spring in the lathe, using a shock absorber spring as a die. The spring is tested and the basic properties are analysed; the performance as a function of NaOH treatment is duly evaluated. The stiffness and shear modulus value increases slowly and reaches 1 N/mm and 1.28 GPa, with 4 wt% NaOH based alkali treatment. The results obtained are rationalized Finite Element Analysis as well; it is shown that the material may be considered to isotropic in the transverse direction, when under axial loading (as on the surface of the fabricated coil).

Putative local adaptations modulate the interactions of the carnivorous plant Drosera uniflora Willd (1809) (Droseraceae) with cushion and shrub nurse plants

AbstractCushion and shrub plants are typical high mountain nurse plants. In Magellanic tundras of the Cordillera del Sarao on the coast of Chile, the carnivorous plant Drosera uniflora grows in association with cushions of Donatia fascicularis and the shrubs Chusquea montana var. nigricans and Lepidothamnus fonkii. The different microhabitats for recruitment, in addition to the limited gene flow of D. uniflora, enable us to hypothesise that this plant manifests putative local adaptations, expressed in seed germination and population abundance. Our aim was to evaluate the local adaptation of D. uniflora to cushion and shrub microhabitats by estimating germination and abundance. Local adaptation of seed germination was determined by means of reciprocal transplant experiments. Abundance was determined in small plots located inside, on the edge and outside the nurse plants. Seed origin and growth substrate play a decisive role in D. uniflora germination. Seeds that originate from cushions plant habitat and germinate in the same substrate do so in greater numbers than when those which originate from shrubby habitats. Conversely, seeds that originate from shrubby habitat and germinate in the same substrate do not exhibit significant differences. Abundance was always greater inside than outside of the nurse plants. We concluded that availability and quality of different microhabitats for seed germination and recruitment, together with a limited gene flow, would trigger putative local adaptations in D. uniflora, modulating a long history of interactions with the plants that act as nurse plants.

A Canadian range extension for Wormslug (<i>Boettgerilla pallens</i>; Gastropoda: Stylommatophora: Boettgerillidae)

The introduced Wormslug (Boettgerilla pallens Simroth, 1912) is reported from Quebec, Canada, for the first time, from two closely situated localities in Gatineau Park. It was previously reported from the Vancouver area of British Columbia and, very recently, from Newfoundland. Within the Americas, the species has been reported from northern California, Mexico, and Colombia, and, because it is easily overlooked, likely occurs elsewhere in North America, especially in the eastern United States. In Quebec, it was found in a natural Sugar Maple (Acer saccharum Marshall) woodland and an ornamental garden. Wormslug likely reached both sites with shrub plantings from commercial nurseries, probably quite recently, because the invasive spread of the species, worldwide, has occurred mostly during the last few decades. Although the woodland where it occurred is dominated by native plants, the gastropod fauna there is mainly introduced. Identification, characteristics, and ecology of Wormslug are discussed. The potential for impact on native soil and soil surface organisms, including native terrestrial slugs and snails, is noted.

The assessment of cadmium, chromium, copper, and nickel tolerance and bioaccumulation by shrub plant Tetraena qataranse

Heavy metals constitute some of the most significant environmental contaminants today. The abundance of naturally growing Tetraena qataranse around Ras Laffan oil and gas facilities in the state of Qatar reflects its toxitolerant character. This study examined the desert plant’s tolerance to Ba, Cd, Cr, Cu, Ni and Pb relative to soil concentration. Analysis by inductively coupled plasma – optical emission spectroscopy (ICP-OES) showed that the plant biomass accumulates higher Cd, Cr, Cu and Ni concentration than the soil, particularly in the root. The bioconcentration factor (BCF) of all metals in the root and shoot indicates the plant’s capacity to accumulate these metals. Cd had a translocation factor (TF) greater than one; however, it is less than one for all other metals, suggesting that the plant remediate Cd by phytoextraction, where it accumulates in the shoot and Cr, Cu and Ni through phytostabilization, concentrating the metals in the root. Metals phytostabilization restrict transport, shield animals from toxic species ingestion, and consequently prevent transmission across the food chain. Fourier Transform Infrared Spectroscopy (FTIR) analysis further corroborates ICP-OES quantitative data. Our results suggest that T. qataranse is tolerant of Cd, Cr, Cu, and Ni. Potentially, these metals can accumulate at higher concentration than shown here; hence, T. qataranse is a suitable candidate for toxic metals phytostabilization.

Diversity and abundance of Lepidoptera and Coleoptera in multiple-species reforestation plantings to offset emissions of carbon dioxide

ABSTRACT Multiple-species (floristically diverse) plantings of trees and shrubs in former agricultural landscapes to offset (sequester) emissions of carbon dioxide are a recent component of Australian landscapes. Although their potential to mitigate biodiversity loss is recognised, this ecological function has not been investigated, in particular with respect to insect diversity. Over two summers, we used light trapping to sample Lepidoptera (moths) and Coleoptera (beetles) in multiple-species plantings in two distinct locations in Victoria (plantings of four ages per location) as well as in nearby remnant forest and in pasture. At both locations, we found that plantings had a greater abundance of Lepidoptera than remnants but that the abundance in plantings was comparable to the abundance in pasture. The species richness of Lepidoptera in plantings did not differ significantly from that in remnants but was significantly greater than that in pasture. The abundance and species richness of Coleoptera in plantings was lower than in remnant forests but higher than in pasture. The community composition of Lepidoptera and Coleoptera in plantings was intermediate between that of remnant forest and pasture, i.e. possibly transitional between the two vegetation types. Dissimilarity between all vegetation types was nevertheless high, reflecting that the abundance of individual taxa reflects the influence of temporally and spatially dependent factors, e.g. host plant size and suitability. Greater abundances of grass-feeding Lepidoptera in plantings explained much of the dissimilarity between plantings and remnant forests. Proximity to remnant forest was an important determinant of the community composition of Lepidoptera but not of Coleoptera. Moth forewing length (relevant to vagility which is an indicator of dispersal capacity) appeared less important to proximity relationships than larval host plant specificity, i.e. whether grass or dicot-feeding. The location of sequestration plantings relative to remnant forest as well as their composition (including the persistence of pasture grasses) will determine the attractiveness of the resources provided to insect herbivores and hence the rate at which they are colonised. Plantings near remnant native forest benefit insect diversity but adoption of novel silvicultural practices could hasten the rate at which they become functional mimics of native forests and support more comparable communities of insect. Potential trade-offs between increased establishment costs and more complex carbon accounting might need to be investigated to cost biodiversity credits associated with dual accreditation schemes.

Phytochemical and antiemetic studies on aqueous ethanol extract of the root of <i>Senna occidentalis</i> (L.) link

Senna occidentalis (Caesalpiniaceae) is a pan tropical shrub plant widely distributed in warm regions of the world. The root infusion of the plant has been used for the treatment of gastro-intestinal disorders including emesis. The current research is aimed at evaluating the antiemetic property of the aqueous ethanol extract and solvent fractions of the root and also verifying the classes of phytochemicals in the extract and fractions. The LD 50 of the extract and its solvent fractions was determined. The antiemetic property was evaluated using copper sulphate induced emesis in chicks while phytochemical screening was carried out using standard methods. The three doses of the extract (300, 150 and 75mg/kg) conferred dose-independent protection and inhibition against retching compared to the control group. At a dose of 150mg/kg, the extract completely (100%) prevented copper sulphate-induced emesis comparable to promethazine at 150mg/kg, the standard antiemetic used. Other doses of the extract 300 and 75mg/kg showed lower effect relatively. Two of the three fractions of the ethanol extract; Hexane and n-butanol fractions at 150mg/kg dose protected against retching in a similar degree (100%) demonstrated by the crude ethanol extract and the standard antiemetic promethazine at 150mg/kg, while ethyl acetate fraction exhibited its maximum protection (100%) at the lowest dose used (75mg/kg).The extract and all of its solvent fractions were found to be non-lethal at up a dose of 5000mg/kg via the oral route. Identified phytochemicals in the ethanol extract include; unsaturated steroids, cardiac glycosides, saponins and tannins. These phytochemicals were found to be distributed across different fractions of the extract in order of their polarity; Steroids and resins in the n-hexane fraction, Cardiac glycosides, unsaturated sterols, saponins and tannins in the Ethylacetate and N-butanol fractions. In addition to the ones mentioned, ethyl acetate fraction contains flavonoids. The observed antiemetic activity of the extract and fractions could be due to one or some of these phytochemicals present. Keywords: Antiemetic, Copper sulphate, Phytochemicals, Senna occidentalis

The facilitative effects of shrub on induced biological soil crust development and soil properties

Both planting sand-fixation vegetation and inoculation of cyanobacteria are effective pathways to form induced biological soil crusts (IBSCs) and achieve desertification reversal. Nonetheless, available information on the combination of vegetation plantation and cyanobacteria inoculation is insufficient. In the sand-fixation experimental area of Hobq Desert, IBSCs and underlying soil along two shrub canopies gradient were investigated to reveal the effects of shrub on IBSCs development and soil properties. Results showed that shrub canopy accelerated the development level of IBSC as indicated by higher crust thickness, DNA content and moss abundance under plant canopy than the surroundings. Soil under plant cover contained finer particles, higher carbon and nitrogen content, and more bioavailable dissolved organic matter (DOM). Interspaces between two plants which accounted for about 12% of the variation in soil characteristics and crust developmental indicators, might be more conducive to the growth of IBSCs and soil accumulation than other exposed microsites. Both Salix psammophila and Artemisia ordosica have a positive effect on IBSC development and soil quality. Our study indicates cyanobacteria inoculation combined with optimized sand-fixing shrub plantation might be promising in soil formation and desertification control.

Does biocrust successional stage determine the degradation of vascular vegetation via alterations in its hydrological roles in semi‐arid ecosystem?

AbstractBiocrusts may influence soil moisture by changing soil hydrological properties and thus affect the growth of vascular vegetation. However, their effects on soil moisture and vascular vegetation have not been sufficiently evaluated. In this study, five treatments, including bare land with sporadic cyanobacterial biocrusts (BL), lichen‐dominated biocrusts, Artemisia ordosica (AO), A. ordosica with moss biocrusts, and old‐aged A. ordosica with moss biocrusts (OAMB), were established to evaluate the effects of biocrusts on soil hydrological properties and shrub growth. Our results showed that the field capacity (θf) and saturated soil moisture (θs) for the OAMB treatment was higher than that for the BL treatment, although the difference between the five treatments was insignificant. The OAMB treatment deceased soil moisture 8.7% on average due to their significant lower saturated hydraulic conductivity (Ks) (82.9%), compared with the BL treatment. The OAMB treatment protected against soil water loss during the beginning stages of evaporation and facilitated soil evaporation during the late stages. Interestingly, the soil water condition underneath the OAMB treatment was not improved after the degradation of AO. The A. ordosica with moss biocrusts treatment had 12.7% lower aboveground biomass and 46.0% lower twig biomass than that for the AO treatment, suggesting the negative effects of biocrusts on the growth of artificially planted shrubs. The findings have important implications for the competitive relationships between biocrusts and vascular vegetation and managing artificial planted shrubs.

Exotic earthworms maintain soil biodiversity by altering bottom-up effects of plants on the composition of soil microbial groups and nematode communities.

Bottom-up effects of plants on soil communities can be modified by the activity of exotic earthworms, by altering resource availability for soil food webs through feeding, burrowing, and casting activities. The present study explored effects of plants (planting of shrubs) on soil micro-food webs (composition of soil microbial and nematode communities), and whether these effects were altered by the activity of exotic earthworms (exotic earthworms addition). Planted shrubs resulted in a non-significant increase of bacterial biomass and significantly increased the abundance of different nematode trophic groups and total nematode biomass, indicating that planted shrubs had significant bottom-up effects on soil bacteria and nematodes. Planted shrubs decreased nematode diversity, evenness, and richness, but increased nematode dominance in the plots where the abundance of exotic earthworms was not amended. By contrast, these effects of shrub presence on soil biodiversity were not found in the plots that received exotic earthworms. In addition, planted shrubs increased the total energy flux to the nematode community. By contrast, the elevated activity of exotic earthworms mitigated the increase in total energy flux to nematodes in the presence of shrubs, and increased the ratio of fungal to bacterial PLFAs. Both of these changes indicate reduced energy flux in the plots with added exotic earthworms. Nematode diversity decreased, while nematode dominance increased with increasing total energy flux to nematodes, probably because few species benefited from high energy flux. Our study indicates that exotic earthworms can maintain soil biodiversity by reducing the energy flux through soil food webs.

Nanocellulose-Graphene Oxide Hybrid Aerogel to Water Purification

The depletion of non-renewable resources and pollution of industrial wastewater are major challenges to the human security. Using green renewable resources to address the above problems coincides with the sustainable development of human society. In this study, we attend to design hybrid aerogel, derived from nanocellulose and graphene oxide (GO), to realize wastewater purification via adsorption behavior, benefitting from its high specific surface area and high porosity. Nanocellulose, isolated from Amorpha fruticosa Linn. as a shrub plant, and graphene oxide were combinely employed to prepare the hybird aerogel via freeze-drying process; and its purification ability to remove methylene blue(MB), congo red (CR) and waste oil in waste water was tested. The results indicate that the isolated nanocellulose bears abundant hydroxyl groups and high aspect ratio of ~500 with average diameter of ~30 nm, which is well distributed on the surface of graphene oxide sheet with side length of about 1~3 μm, both of which form the hybrid aerogel with porosity larger than 99%. The nanomaterials physically assemble its orignial aggregation state. When the mass ratio of nanocellulose and graphene oxide is 8 : 2, the hybrid aerogel reaches the highest adsorption capacity of 265.6mg/g and 21.5mg/g for MB and CR, respectively. The hybrid aerogel after hydrophobic treatment shows excellent oil adsorption capacity up to 25.6 g/g, which is beneficial to oil/water separation. This strategy provides potential great-application of the nanocellulose in water purification.

Environmental monitoring and urban phytodesign in ensuring the radioecological safety of urban buildings

The purpose of this paper is to study the migration and accumulation of 90Sr in vegetative and generative organs of plants: golden currant (Ribes aureum) and cherry plum (Prunus cerasifera Ehrh). Research objectives: 1) 90SrCl2 is artificially deposited on the soil, precipitation imitation (field experiments); 2) planting plants: Prunus cerasifera Ehrh and Ribes aureum to the soil artificially contaminated with 90SrCl2; 3) cultivation and monitoring of the studied plants in the soil artificially contaminated with 90SrCl2. The contamination level of the experimental area was 500 MBq/m2. The possibilities of tree and shrub plant forms (Prunus cerasifera Ehrh; Ribes aureum) to accumulate 90Sr in their vegetative and generative organs were studied. The activity of the beta-emitting radionuclide in the counting samples was measured using the “Progress” software on the Multi-purpose spectrometric complex “Gamma Plus” device (beta path). As a result of research, the accumulation of radionuclides in both studied plants was found. In 2016, the difference in the content of 90Sr between cherry plum and golden currant in bark, wood, leaves, and fruits was 1.6, 1.5, 1.8, and 2.0 times, respectively. Experimental data can be used in the environmental monitoring of the radiation situation in urban areas of the territories allocated for the construction of public, residential buildings and structures, to be the basis for further advanced research in the designated area.

Promising bay laurel (Laurus nobilis L.) genotypes for fruit production

Bay laurel (Laurus nobilis L.) is an evergreen and dioecious tree or shrub plant with a small black fruit. This study was conducted to determine bay laurel genotypes with high-quality characteristics which grown intensively in Hatay. 149 female trees were preselected and then 49 laurel genotypes were used as material according to Turkish Standards (TS-5205) for fatty acid compositions. In the study, berry weights (0.77-1.76 g), kernel weights (0.49-1.12 g), kernel ratios (51.73-77.44%), dry matter ratios (44.89-69.44%), berry oil ratios (18.92-37.85%), berry flesh oil ratios (20.76-53.98%) and kernel oil ratios (11.75-27.49%) of genotypes were determined. The content of fatty acid compositions ranged between 12.74-31.19% for lauric acid, 12.35-19.91% for palmitic acid, 30.35-44.43% for oleic acid and 15.93-26.75% for linoleic acid. Genotype K9 has attracted attention with high lauric acid and low palmitic acid ratio. On the other hand, genotype ER6 for berry weight, B30 for kernel weight and ER14 for kernel oil ratio were found to be promising genotypes.

Structure Analysis of Arbuscular Mycorrhizal in Roots from Different Shrubs in Karst Regions

To explore if there are species-preferential characteristics of arbuscular mycorrhizal (AM) and host plants in karst regions, 13 shrub plants (including leguminosae and non-leguminosae) were selected to study the AM community structure of root samples. The soil nutrients in rhizosphere soils significantly differ among shrubs; they are higher in leguminosae than in non-leguminosae. Cluster analysis shows that all 13 shrubs can be infected by AM. Significant differences of the AM community structure were observed among root samples from different shrubs, especially leguminosae and non-leguminosae. Redundancy analysis shows that soil Olsen-P, pH, and total nitrogen significantly influence the AM community structure of plant roots, although the factors affecting this fungus in leguminosae and non-leguminosae differ. These results indicate species-preferential characteristics of AM and host plants in karst regions, especially of the plant function group compared with plant species, suggesting that these characteristics should be taken into account when AM fungi are used for vegetation restoration in karst regions.

Methodical aspects of various biomorphs ornamental plants regeneration study

The paper raises the problem of conservation, maintenance, rejuvenation and accelerated reproduction of plant objects in bioresource collections using green cutting propagation. The authors describe experimental methods of herbaceous and woody plants regeneration study in agricultural, physiological-biochemical and morphological directions. In agricultural direction the main factors are the timing and methods of green cutting, as well as the microecological conditions in which regeneration takes place (humidity, temperature of the air and substrate). The physiological and biochemical aspect concerns the use of various growth stimulants, including concentrations and timing for the treatment of unruly cuttings. The reliable positive effect of the growth stimulants in comparison with control natural regeneration can be proved by the t-criteria. The morphological aspect shows features of callusogenesis and rhizogenesis. The most profound analysis is possible when representatives of generic complexes, species and varieties of various ecological, geographical and genetic origin are involved in the experiment. A highly informative classification of callusogenesis and rhizogenesis proposed by N.F. Dovbysh, N.A. Oleinik and G.A. Kudina (1993) is described in detail; in this classification three types of callus implantation are described: circular, focal and continuous, as well as five types of localization and development of roots. Root formation can occur 1) in the zone of the node, 2) from the callus tissue, 3) from the side of the bud and leaf trail, 4) over the entire surface of the internode, as well as 5) mixed (from the tissues in the node zone and from callus tissue). Based on the long-term study of the regeneration of shrub and herbaceous ornamental plants, the authors of the paper propose one more type in the entire surface of the lower cut.

Озеленення забудованих територій малих міст у контексті дотримання державних будівельних норм

Стале міське землекористування передбачає дотримання чинних національних стандартів. Відстежено дотримання вимог державних будівельних норм (ДБН 360-92. Планування і забудова міських і сільських поселень) щодо планування міст у частині формування системи зелених насаджень на прикладі території малого історичного міста Вишгород Київської області. Виявлено слабкі місця у нормативному документі та рекомендовано заходи з озеленення забудованих територій з метою подальшої оптимізації містобудівного планування в Україні. Дослідження виконано у чіткій послідовності відповідно до вимог, викладених у ДБН-360-92 з порівнянням реальної ситуації на території міста, визначеної способом натурних обстежень. Методи дослідження – експертно-аналітичні. Встановлено, що на території дослідного міста зазначені нормативні рекомендації порушують або взагалі ігнорують. Не дотримано мінімальні відстані насаджень дерев і кущів від будівель і споруд, вуличні насадження мають обмежений асортимент кущових рослин. Ущільнене будівництво зазвичай здійснюють за рахунок територій зелених насаджень, зокрема центрального парку міста. Не дотримано рекомендації щодо максимального збереження ділянок із існуючими насадженнями. Нормативи з влаштування майданчиків різного функціонального призначення на прибудинкових територіях житлових масивів давно забуто, що, можливо, потребує перегляду самих нормативів, викладених у ДБН.

Pemberdayaan Ekonomi Kelompok Tani Desa Nyogan Kabupaten Muaro Jambi Melalui Pemanfaatan Lahan Tidak Produktif dengan Penanaman Tanaman Lada Perdu (Piper Nigrum)

Pepper Plant (Piper nigrum L), better known as pepper, is one of the most economically valuable plantation commodity crops that has the opportunity to be developed in order to increase economic income for the State and for the farming community. This plant starts to bear fruit at the age of 2-3 years. Historically, the Nyogan villagers used to plant climbing pepper as their livelihood. So far, farmers have planted climbing pepper which requires a sturdy climbing pole. Climbing poles for pepper plants besides being expensive are also increasingly rare nowadays, for the Nyogan villagers to do socialization and planting of pepper shrubs. In theory, shrub pepper plants will grow and develop well if cultivated properly and grow without climbing poles so as to reduce the cost of purchasing climbing poles and do not require large areas. On this basis it is very possible if applied to sleeping land that is not used anymore or (on land that already has unproductive commodities). Pepper plants are very likely to be developed on people's lands around residential areas or empty plantation areas that have not been utilized in the Nyogan Village, Mestong Subdistrict, Muaro Jambi Regency. By utilizing this pattern, people can use their land to be productive and have economic and ecological added value

Feeding red osier dogwood (Cornus sericea) to beef heifers fed a high-grain diet affected feed intake and total tract digestibility

Red osier dogwood (ROD; Cornus sericea) is an abundant native shrub plant across North America and it is rich in bioactive compounds with total phenolic concentration up to 220 g/kg dry matter (DM) depending on the season. The phenolics include anthocyanins, gallic acid, ellagic acid, quercetin, and cyanin, which have both antioxidant and antimicrobial properties. The objective of this study was to determine the effect of increasing substitution of ROD for barley silage in a high-grain diet on DM intake, ruminal pH and fermentation, digestibility in the total digestive tract, blood metabolites and acute phase response in beef heifers. Five ruminally cannulated Angus heifers (averaged body weight of 660 ± 40.8 kg; initial age of 18 months) were used in a 5 × 5 Latin square design with 21-d periods including 14 d for adaptation to new diets and 7 d for data collection. Treatments were a control diet containing 150 g/kg barley silage and 850 g/kg barley concentrate mix (DM basis), the control diet substituted with 30, 70 or 100 g/kg of ROD for equal proportions of barley silage, respectively, and the control diet supplemented with antibiotics (330 mg monensin + 110 mg tylosin/heifer/d). Apparent digestibility was determined using Cr2O3 as external marker by sampling feces from the rectum. Intake of DM quadratically (P < 0.02) increased with increasing the substitution of silage for ROD. Mean ruminal pH were not affected by diets, and no effects of diets on total volatile fatty acid (VFA) concentration were observed. However, ruminal NH3-N concentration linearly (P < 0.01) decreased with increasing ROD feeding. Digestibility of DM linearly (P < 0.04) increased with increasing dietary ROD. Increasing ROD feeding also linearly increased plasma concentration of haptoglobin (P < 0.01) and concentration of serum amyloid A (P < 0.06). Compared with antibiotic group, feeding ROD resulted in greater (P < 0.01) intake and digestibility of DM, and greater (P < 0.05) VFA concentration. These results indicate greater feed value of ROD versus barley silage in high-grain diets. Feeding ROD potentially improves immune status and antioxidant activity in finishing beef heifers. Beef cattle fed ROD performed better or at least equal to antibiotics currently used in beef cattle rations and it could be used as a natural alternative for beef cattle production.

Assessment of the Role of Forest Land in Samara Region as Environmental Protection and Land Degradation Prevention Factor

The article discusses the current state of forest land, the history of formation of large tracts of forest in the Samara region and analyses some of the results of implementation of target programs to improve the forest cover in the region under the Kyoto Protocol. This program was designed for the period from 2006 to 2015, but in 2009 was discontinued. However, large segment of assets was allocated and a number of works was carried out. Currently the objectives of the programme to increase the forest cover in the territory of Samara region through the creation of tracts of forest are not achieved. Tree and shrub plantations play an important role in reducing the activity of processes of erosion, prevent degradation and desertification. Therefore, the problem of increasing forest cover, especially in the steppe zone of the region, to the level of the preindustrial era remains relevant and requires science-based measures for their solution.

Restoring dryland old fields with native shrubs and grasses: Does facilitation and seed source matter?

Restoration of agricultural fields is challenging, especially in arid and semi-arid ecosystems. We conducted experiments in two fields in the Great Basin, USA, which differed in cultivation history and fertility. We tested the effects of different levels of functional diversity (planting grasses and shrubs together, vs. planting shrubs alone), seed source (cultivars, local or distant wild-collections), and irrigation regime (spring or fall and spring) on restoration outcomes. We sowed either: 1) grasses and shrubs in year one, 2) shrubs only, in year one, 3) grasses in year one with herbicide, shrubs in year two, or 4) shrubs alone in year two, after a year of herbicide. We irrigated for two years and monitored for three years. Shrub emergence was highest in the lower fertility field, where increasing functional diversity by seeding grasses had a neutral or facilitative effect on shrub emergence. In the higher fertility field, increasing functional diversity appeared to have a neutral to competitive effect. After declines in shrub densities after irrigation ceased, these effects did not persist. Grasses initially suppressed or had a neutral effect on weeds relative to an unseeded control, but had neutral or facilitative effects on weeds relative to shrub-only seeding. Initially, commercial grasses were either equivalent to or outperformed wild-collected grasses, but after irrigation ceased, commercial grasses were outperformed by wild-collected grasses in the higher fertility field. Local shrubs initially outperformed distant shrubs, but this effect did not persist. Fall and spring irrigation combined with local shrubs and wild-collected grasses was the most successful strategy in the higher fertility field, while in the lower fertility field, irrigation timing had fewer effects. Superior shrub emergence and higher grass persistence indicated that the use of wild and local seed sources is generally warranted, whereas the effects of functional diversity and irrigation regime were context-dependent. A bet-hedging approach that uses a variety of strategies may maximize the chances of restoration success.

Plants mitigate detrimental nitrogen deposition effects on soil biodiversity

Anthropogenic nitrogen (N) deposition is an important component of global change and threatens terrestrial biodiversity. Most previous studies of the consequences of N deposition have focused on plant community responses and found that N deposition decreases plant diversity. However, the effects of N deposition on soil biodiversity and belowground biotic interactions remain poorly understood. We explored the changes in main soil food web components (microbes, nematodes, springtails, and mites) in response to elevated N deposition (60 kg N ha−1yr−1, starting from 2012 to 2014), and whether these changes are altered by the presence of plants (planting of shrubs in 2008) in a two-factorial field mesocosm experiment with 16 equally-sized plots (1 × 2 m). Our results showed that elevated N deposition negatively affected soil bacteria, while fungi showed rather neutral responses. Specifically, N deposition decreased bacteria Shannon's diversity index H′, richness, observed species abundance, bacterial activity, and resulted in a non-significant decrease of the relative abundance of rare bacterial taxa. By contrast, for fungi, only a non-significant decrease of richness was observed with N deposition. Importantly, those N deposition effects mostly occurred in the absence of planted shrubs. Moreover, shrub presence and N deposition also interactively affected the diversity of soil invertebrates, i.e., N deposition had little effect on them in the absence of planted shrubs, but resulted in an increase or a non-significant increase of soil invertebrate diversity in the presence of planted shrubs. Furthermore, N deposition did not affect the biomass/density of any soil food web component and biomass/density ratios related to soil food web structure regardless of absence or presence of planted shrubs; these indices were only affected by the presence of shrubs. Overall, these dissimilar responses of the diversity of soil microorganisms and animals to elevated N deposition indicate that plants are important mediators of N deposition effects on soil biodiversity. Thus, the present results may imply that an intact plant cover may mitigate detrimental N deposition effects on soil biodiversity.