Plant species diversity of buffer zones in agricultural landscapes : in search of determinants from the local to regional scale

Buffer zones are vegetated strip-edges of agricultural fields along watercourses. As linear habitats in agricultural ecosystems, buffer strips dominate and play a leading ecological role in many areas. This thesis focuses on the plant species diversity of the buffer zones in a Finnish agricultural landscape. The main objective of the present study is to identify the determinants of floral species diversity in arable buffer zones from local to regional levels. This study was conducted in a watershed area of a farmland landscape of southern Finland. The study area, Lepsämänjoki, is situated in the Nurmijärvi commune 30 km to the north of Helsinki, Finland. The biotope mosaics were mapped in GIS. A total of 59 buffer zones were surveyed, of which 29 buffer strips surveyed were also sampled by plot. Firstly, two diversity components (species richness and evenness) were investigated to determine whether the relationship between the two is equal and predictable. I found no correlation between species richness and evenness. The relationship between richness and evenness is unpredictable in a small-scale human-shaped ecosystem. Ordination and correlation analyses show that richness and evenness may result from different ecological processes, and thus should be considered separately. Species richness correlated negatively with phosphorus content, and species evenness correlated negatively with the ratio of organic carbon to total nitrogen in soil. The lack of a consistent pattern in the relationship between these two components may be due to site-specific variation in resource utilization by plant species. Within-habitat configuration (width, length, and area) were investigated to determine which is more effective for predicting species richness. More species per unit area increment could be obtained from widening the buffer strip than from lengthening it. The width of the strips is an effective determinant of plant species richness. The increase in species diversity with an increase in the width of buffer strips may be due to cross-sectional habitat gradients within the linear patches. This result can serve as a reference for policy makers, and has application value in agricultural management. In the framework of metacommunity theory, I found that both mass effect(connectivity) and species sorting (resource heterogeneity) were likely to explain species composition and diversity on a local and regional scale. The local and regional processes were interactively dominated by the degree to which dispersal perturbs local communities. In the lowly and intermediately connected regions, species sorting was of primary importance to explain species diversity, while the mass effect surpassed species sorting in the highly connected region. Increasing connectivity in communities containing high habitat heterogeneity can lead to the homogenization of local communities, and consequently, to lower regional diversity, while local species richness was unrelated to the habitat connectivity. Of all species found, Anthriscus sylvestris, Phalaris arundinacea, and Phleum pretense significantly responded to connectivity, and showed high abundance in the highly connected region. We suggest that these species may play a role in switching the force from local resources to regional connectivity shaping the community structure. On the landscape context level, the different responses of local species richness and evenness to landscape context were investigated. Seven landscape structural parameters served to indicate landscape context on five scales. On all scales but the smallest scales, the Shannon-Wiener diversity of land covers (H') correlated positively with the local richness. The factor (H') showed the highest correlation coefficients in species richness on the second largest scale. The edge density of arable field was the only predictor that correlated with species evenness on all scales, which showed the highest predictive power on the second smallest scale. The different predictive power of the factors on different scales showed a scaledependent relationship between the landscape context and local plant species diversity, and indicated that different ecological processes determine species richness and evenness. The local richness of species depends on a regional process on large scales, which may relate to the regional species pool, while species evenness depends on a fine- or coarse-grained farming system, which may relate to the patch quality of the habitats of field edges near the buffer strips. My results suggested some guidelines of species diversity conservation in the agricultural ecosystem. To maintain a high level of species diversity in the strips, a high level of phosphorus in strip soil should be avoided. Widening the strips is the most effective mean to improve species richness. Habitat connectivity is not always favorable to species diversity because increasing connectivity in communities containing high habitat heterogeneity can lead to the homogenization of local communities (beta diversity) and, consequently, to lower regional diversity. Overall, a synthesis of local and regional factors emerged as the model that best explain variations in plant species diversity. The studies also suggest that the effects of determinants on species diversity have a complex relationship with scale.This study conducted on plant species diversity of field boundary habitat in agricultural landscapes. Along waterways, the vegetation boundaries, called buffer zones here, served to protect water in agricultural ecosystems. In recent decades, plant species diversity in these linear landscape structures has declined severely. Recently, emphasis has been laid on the importance of buffer zones for maintaining and enhancing the biodiversity of agricultural environments. The linear habitats have a leading ecological role on many aspects. Animal and plant species can use the linear habitats as corridors or refuges in agricultural ecosystem. The diversity of vegetation (for example, species richness, vertical structure, and species composition) in the buffer zones is important for its function to protect from agrochemicals and from eroded soil. With their year-round vegetation cover, buffer zones significantly decrease (by about 20%) the amount of solid particles and their bound nutrients reaching waterways. Buffer zones also efficiently prevent pesticides from spreading from one field to another and into the surrounding environment, and provide habitats for animal species. In Finland, a typical field margin includes a grassy ditch bank. Maintaining plant species diversity in the linear habitats is a major aim of sustainable agricultural land-use. However, since the 1950s, with extension and intensification of agriculture Finnish rural landscape has become simplified and the semi-natural linear habitats have been declined rapidly, particularly in southern Finland. It has resulted mainly from a shift to subsurface drainage, and associated to enlargement of parcel size and homogenization of parcel shape. This change is believed to have a subsequent adverse impact on farmland wildlife. To restore and maintain species diversity in the landscapes, This study served to understand the relationships between plant species diversity and factors from local to regional scale

Spatio-Temporal Patterns and Impacts of Sediment Variations in Downstream of the Three Gorges Dam on the Yangtze River, China

Spanning the Yangtze River of China, the Three Gorges Dam (TGD) has received considerable concern worldwide with its potential impacts on the downstream side of the dam. This work investigated the spatio-temporal variations of suspended sediment concentration (SSC) at the downstream section of Yichang-to-Chenglingji from 2002 to 2015. A random forest model was developed to estimate SSC using MODIS ground reflectance products, and the spatio-temporal distributions of SSC were retrieved with this model to investigate the characteristics of water-silt variation. Our results revealed that, relatively, SSC before 2003 was evenly distributed in the downstream Yangtze River, while this spatial distribution pattern changed ce 2003 when the dam started storing water. Temporally, the SSC demonstrated a W-shaped curve of seasonal variation as one peak occurred in September and two troughs in March and November, and showed a significantly decreasing trend after three-stage impoundment. After official operation of the TGD in 2009, the SSC was reduced by over 40% than before 2003. Spatially, the most significant changes occurred in the upper Jingjiang section, where the SSC dropped by 45%. During all stages of impoundment, the water impoundment to 135 m in 2003 had the most significant impact on suspended sediment. The decreased SSC has led to emerging risks of bank failure, aggravated erosion of water front and aggressive down-cutting erosion along the downstream of the dam, as well as other ecological and environmental issues that require urgent attention by the government

PCR-Based Seamless Genome Editing with High Efficiency and Fidelity in <i>Escherichia coli</i>

Efficiency and fidelity are the key obstacles for genome editing toolboxes. In the present study, a PCR-based tandem repeat assisted genome editing (TRAGE) method with high efficiency and fidelity was developed. The design of TRAGE is based on the mechanism of repair of spontaneous double-strand breakage (DSB) via replication fork reactivation. First, cat-sacB cassette flanked by tandem repeat sequence was integrated into target site in chromosome assisted by Red enzymes. Then, for the excision of the cat-sacB cassette, only subculturing is needed. The developed method was successfully applied for seamlessly deleting, substituting and inserting targeted genes using PCR products. The effects of different manipulations including sucrose addition time, subculture times in LB with sucrose and stages of inoculation on the efficiency were investigated. With our recommended procedure, seamless excision of cat-sacB cassette can be realized in 48 h efficiently. We believe that the developed method has great potential for seamless genome editing in E. coli

Estimating seasonal aboveground biomass of a riparian pioneer plant community:An exploratory analysis by canopy structural data

The aboveground biomass (AGB) of vegetation is of central importance for ecosystem services by providing a measure of productivity. Models have been developed for estimating AGB via canopy structural variables in both fundamental and applied ecological studies. However, the potential of canopy structural variables for describing AGB dynamics throughout a growing season are still unclear. This study focuses on the AGB seasonal dynamics of a pioneer community, Cynodon dactylon (L.) Pers. (Bermuda grass), in a newly-formed riparian habitat at China’s Three Gorges Reservoir. The objectives are (1) to determine the most important structural variable for estimating AGB at different growing stages during the season, and (2) to develop a model that can estimate AGB at the different growing stages and using multiple structural variables. We sampled the C. dactylon community six times during the growing season from May to September 2016. Six variables were engaged in the analysis, including five canopy structural variables, i.e., canopy height (H), canopy cover (CC), leaf area index (LAI), the volume related variables VLAI (H × LAI) and VCC (H × CC), and one seasonal growth effect variable (SV). We conducted univariate linear regression analysis to determine the most important estimator of AGB and the best subset regression analysis were used to develop the AGB estimation model. The detected most important AGB estimator changed with different growing stages throughout a season. Canopy structural characteristics of the community are key factors for determining such changes. Cover was the most important variable for AGB estimation during the early growing season and VLAI was the most important variable in the mid and end of the growing season. The developed best multivariate models explained an additional 11% in AGB variance on average for the different growing stages compared with the univariate models using the most important estimators. SV was found to be useful in developing an acceptance general AGB estimation model appropriate for the entire growing season. The findings of this study are expected to provide knowledge for guiding sampling work and to assist with modeling AGB and understanding the AGB seasonal dynamics in the future

Plant–plant interactions vary greatly along a flooding gradient in a dam-induced riparian habitat

Plant–plant interactions under extreme environmental stress are still controversial. The stress gradient hypothesis (SGH) proposes that facilitation prevails under extreme environmental stresses, while an alternative view states that facilitation collapses or even switches back to competition at the extreme end of stress gradients. However, how the relationship between plant–plant interaction and periodic extreme flooding stress varies and its underlying mechanism are still unclear in a dam-regulated riparian ecosystem. We established a controlled experiment using two dominant species pairs (Cynodon dactylon–Cyperus rotundus and C. dactylon–Xanthium sibiricum) in the water level fluctuating zone of the Three Gorges Dam to examine their growth responses to the periodic extreme flooding stress. The results showed that as flooding stress increased, the competitive effect of C. dactylon on X. sibiricum shifted to facilitation, whereas the effect of X. sibiricum on C. dactylon maintained a strong inhibition. The plant height of X. sibiricum was the most important driver of the interaction between X. sibiricum and C. dactylon along the flooding gradient. The net effect of C. dactylon on C. rotundus shifted from neutral to negative, and the inhibitory effect of C. rotundus on C. dactylon became stronger at the extreme end of flooding stress. The root biomass of the two species was the key trait regulating their interaction with increasing flooding stress. Overall, the SGH was partially supported along our periodic extreme flooding stress gradient. Aboveground resource (light) might be the dominant factor driving the response of the interaction between annual plants and perennial clonal plants to periodic flooding stress, whereas belowground resource (water and nutrients) was probably the dominant factor for perennial clonal plants. Our study will help to further understand the environmental responses of plant–plant relationships and their regulatory mechanism, and the succession of riparian plant communities under extreme environmental changes, providing a basic theoretical basis and data support for the ecological restoration and management of riparian wetland vegetation

Lepsämänjoki LTSER: pitkäaikaisen sosioekologisen maatalousekosysteemitutkimuksen verkosto

Lepsämänjoki LTSER (long term social ecological research platform) kuuluu kahdeksan muun erilaisiaekosysteemityyppejä edustavan verkoston kanssa vuonna 2007 perustettuun Suomen LTSER- konsortioon(FinLTSER:http://www.ymparisto.fi/default.asp?contentid=257172&amp;lan=FI). FinLTSERpuolestaan onsamana vuonna hyväksytty kv. ILTER -verkostoonjäseneksi (http://www.ilternet.edu/). LTSER toiminnanperusajatus on luoda ja ylläpitää ekosysteemitutkimuksen infrastruktuureja, joissa pitkäaikainen ja seuranta-aineistoihinperustuva tutkimus kohdistuu ns. ydinalueelle. Tällainen ydinalue on maantieteellisesti määriteltyekosysteemialue, jossa verkoston tutkimusryhmät tuottavat pitkäaikaista, julkista ja hyvin dokumentoituaseurantajatutkimustietoa sosioekologisistaekosysteemin tilaan ja muutokseen sekä muutosta ohjaaviinvoimiin liittyvistä muuttujista. LTSER- verkoston tulisi mahdollistaa monitieteinen ja tieteidenvälinen sosioekologinentutkimus, ja sen tulisi tuottaa laadukasta tutkimusdataa kv. tutkimusyhteisön käyttöön.Lepsämänjoki LTSER on keskeisten maatalousekosysteemien tilasta ja muutoksesta kiinnostuneidentutkimuslaitosten ja –ryhmien verkosto. Se on avoin yhteenliittymä, joka pyrkii kehittämään julkista jayleishyödyllistä yhteistyötä ja infrastruktuuria maatalousympäristön monitieteiseen tutkimukseen. Verkostonydinalue on Lepsämänjoen maataloudellinen valuma-alue,joka suurimmaksi osaksi kuuluu UusimaalaisenNurmijärven kunnan alueeseen noin 30 km Helsingistä luoteeseen (60° 23' 60°28' N, 24° 31' 24°43' E).Se on topografialtaan laakea 213 km² suuruinen alue, jossa harjoitetaan Etelä-Suomensavikoille ominaistapeltoviljelyvaltaista maataloutta. Alueen pohjoisosassa on useita vihannesviljelyyn keskittyneitä tiloja. Alueon kaupungin läheistä maaseutua, jolle muualla työskentelevien haja-asutusleviää, ja jonka eteläosassasijaitseva Klaukkalan taajama on kasvussa.Lepsämänjoen valuma-alueeltaon parhaimmillaan jo vuosikymmenten ajalta biofysikaalisiinympäristömuuttujiin liittyviä tutkimusaineistoja: jokiveden laatu, maatalouden ravinne- jakiintoaineskuormitus, maataloudellinen maankäyttö, maatalouden ravinnetaseet, maalajit ja topografia, alue-ekologinenmonimuotoisuus, putkilokasvien, perhosten ja peltolintujen lajimonimuotoisuus. Verkoston eritutkimusryhmät ovat toisistaan riippumatta koonneet em. aineistoja eri seurannoissa ja tutkimus- jakehityshankkeissa.Lepsämänjoki LTSER-verkostontavoite on LTSER-konseptinmukaisesti verkostoitumisen avullakehittää tutkimuksen infrastruktuuria, parantaa seuranta-aineistojensaatavuutta ja laatua sekä edistääekologisen, ympäristöjayhteiskunnallisen tutkimuksen integraatiota. Tiedustelut voi osoittaa verkostonkoordinaattorille ([email protected])

Anti-HIV-1 Activity of a New Scorpion Venom Peptide Derivative Kn2-7

For over 30 years, HIV/AIDS has wreaked havoc in the world. In the absence of an effective vaccine for HIV, development of new anti-HIV agents is urgently needed. We previously identified the antiviral activities of the scorpion-venom-peptide-derived mucroporin-M1 for three RNA viruses (measles viruses, SARS-CoV, and H5N1). In this investigation, a panel of scorpion venom peptides and their derivatives were designed and chosen for assessment of their anti-HIV activities. A new scorpion venom peptide derivative Kn2-7 was identified as the most potent anti-HIV-1 peptide by screening assays with an EC50 value of 2.76 µg/ml (1.65 µM) and showed low cytotoxicity to host cells with a selective index (SI) of 13.93. Kn2-7 could inhibit all members of a standard reference panel of HIV-1 subtype B pseudotyped virus (PV) with CCR5-tropic and CXCR4-tropic NL4-3 PV strain. Furthermore, it also inhibited a CXCR4-tropic replication-competent strain of HIV-1 subtype B virus. Binding assay of Kn2-7 to HIV-1 PV by Octet Red system suggested the anti-HIV-1 activity was correlated with a direct interaction between Kn2-7 and HIV-1 envelope. These results demonstrated that peptide Kn2-7 could inhibit HIV-1 by direct interaction with viral particle and may become a promising candidate compound for further development of microbicide against HIV-1

Empirical models for estimating monthly global solar radiation: a most comprehensive review and comparative case study in China

Global solar radiation is a core component of scientific research and engineering application across a broad spectrum. However, its measurement is limited by a small number of stations due to the technical and financial restricts. Estimating solar radiation with the meteorological variables using empirical models is of benefit to obtain solar radiation data at global scale. Yet, there are various options of available empirical models to select the most suitable one. This study conducted a most comprehensive collection and review of empirical models employing the commonly measured meteorological variables and geographic factors. A total of 294 different types of empirical models were collected and classified into 37 groups according to input attributes. Such collection built an empirical model library providing an overall overview of the developed empirical models in literatures. Furthermore, the collected models were calibrated and evaluated at three meteorological stations in the Three Gorges Reservoir Area in China. This study suggests that these model-comparing processes can assist the governments, scientists and engineers in tailoring the most fitted model for specific applications and in particular areas