Functional Group Level Research Articles

Ecological equivalence of species within phytoplankton functional groups

Summary There are tens of thousands of species of phytoplankton found throughout the tree of life. Despite this diversity, phytoplankton are often aggregated into a few functional groups according to metabolic traits or biogeochemical role. We investigate the extent to which phytoplankton species dynamics are neutral within functional groups. Seasonal dynamics in many regions of the ocean are known to affect phytoplankton at the functional group level leading to largely predictable patterns of seasonal succession. It is much more difficult to make general statements about the dynamics of individual species. We use a 7‐year time series at station L4 in the Western English Channel with 57 diatom and 17 dinoflagellate species enumerated weekly to test whether the abundance of diatom and dinoflagellate species varies randomly within their functional group envelope or whether each species is driven uniquely by external factors. We show that the total biomass of the diatom and dinoflagellate functional groups is well predicted by irradiance and temperature and quantify trait values governing the growth rate of both functional groups. The biomass dynamics of the functional groups are not neutral and each has their own distinct responses to environmental forcing. Compared to dinoflagellates, diatoms have faster growth rates and grow faster under lower irradiance, cooler temperatures, and higher nutrient conditions. The biomass of most species varies randomly within their functional group biomass envelope, most of the time. As a consequence, modellers will find it difficult to predict the biomass of most individual species. Our analysis supports the approach of using a single set of traits for a functional group and suggests that it should be possible to determine these traits from natural communities.

Infrared Spectroscopic and Electrochemical Approaches for the Study of the Reaction Mechanism of Immobilized Membrane Proteins from the Respiratory Chain

Although the architectures of several membrane proteins in respiration as well as the basic chemical reactions have been described, the interactions on molecular level, the high diversity and the high efficiency of mechanisms, are under discussion. Experiments have been developed which reveal how protons and other ions are drawn through proteins and how they are coupled to electron transfer.An electrochemical approach on proteins immobilized on gold nano particles was used to get insight into the redox properties in the presence and absence of substrate and inhibitors to the proton channels (Zn2+).1 Two approaches are presented to functionally probe the enzymes against substrates and inhibitors: i) The redox reaction was IR spectroscopically studied in solution and ii) the proteins are immobilized via their His-Tag on a gold layer, deposited on an ATR-crystal and studied by surface enhanced IR spectroscopy (SEIRAS). 2 The combination of the electrochemical and IR spectroscopic approach allowed the observation of protein action at the level of single functional groups within the large protein studied and thus provides essential knowledge's for the understanding of the mechanism of the studied enzymes.

青藏高原高寒草甸门源草原毛虫取食偏好及其与植物C、N含量的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 青藏高原高寒草甸门源草原毛虫取食偏好及其与植物C、N含量的关系 DOI: 10.5846/stxb201410081973 作者: 作者单位: 北京林业大学自然保护区学院,中国科学院地理科学与资源研究所生态网络观测与模拟重点实验室,中国科学院地理科学与资源研究所生态网络观测与模拟重点实验室,北京林业大学自然保护区学院 作者简介: 通讯作者: 中图分类号: 基金项目: 中央高校基本科研业务费专项资金(TD-JC-2013-1); 国家自然科学基金面上项目(31270503) Feeding preference of Gynaephora menyuanensis and its relationships with plant carbon and nitrogen contents in an alpine meadow on the Tibetan plateau Author: Affiliation: School of Nature Conservation, Beijing Forestry University,Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences,Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences,School of Nature Conservation, Beijing Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:草食性昆虫对不同植物物种的取食存在偏好,这种取食偏好可能受其自身对蛋白质和碳水化合物的需求及二者平衡的调节。以青藏高原高寒矮嵩草草甸31种常见植物及门源草原毛虫为对象,通过饲喂实验,研究了草食性昆虫对不同物种和不同功能群植物的取食偏好,及其与植物叶片C、N含量和C:N之间的关系。在31种植物中,门源草原毛虫对19种植物进行了取食,尤其对矮嵩草、红棕薹草、藏异燕麦和垂穗披碱草四种植物表现出强烈的取食偏好,而对另外12种植物未进行任何取食。在物种水平上,门源草原毛虫取食量与植物叶片N含量呈显著负相关,与叶片C:N呈正相关。从功能群水平上看,门源草原毛虫对莎草类的取食偏好最大,而对豆科植物取食偏好最低;相应地,莎草类植物叶片N含量最低、C:N最高,而豆科植物叶片N含量最高、C:N最低。因此,即使在土壤有效氮匮乏、植物生长受氮素限制的高寒草甸生态系统,植物体内N含量的增加也可能不利于草食性昆虫的取食。门源草原毛虫对优势植物矮嵩草和垂穗披碱草的取食对高寒矮嵩草草甸物种共存和生物多样性维持可能具有重要的作用。 Abstract:Phytophagous insects show feeding preference for different plant species, and such preference may be regulated by their demands for proteins and carbohydrates and the balance between them. Therefore, feeding preference of phytophagous insects may be closely related to carbon (C) content, nitrogen (N) content, and the C:N ratio of plants. Although many studies have investigated feeding preference of phytophagous insects for different plant species, relatively few have examined how plant functional groups affect feeding preference of phytophagous insects and whether their leaf C and N content, and C:N ratio matter. To examine feeding preference of phytophagous insects for different plant species and for different functional groups and its relationships with leaf C, N, and the C:N ratio of plants and functional groups, we conducted a feeding experiment in which we fed the larvae of a phytophagous insect, Gynaephora menyuanensis (Lymantriidae), with leaves of 31 common herbaceous plant species of four functional groups (sedges, grasses, legumes and forbs) collected in an alpine meadow dominated by Kobresia humilis on the Tibetan plateau. Fresh leaves of the 31 plant species were cut into pieces of the similar area (about 0.5 cm2) and fixed randomly on the arenas made of foam boards installed at the inner bottoms of six glass boxes (each measuring 1 m long × 1 m wide × 0.25 m high). Each box was treated as a block, containing ten leaf pieces of each of the 31 plant species collected on the same day. We put on the arena of each box 20 larvae of G. menyuanensis that were collected in the same meadow and had been starved for 24 hours, and measured consumption of each leaf piece (i.e., the percentage of leaf area loss) after 72 hours. Leaf area consumed by the larvae was further transformed into dry mass based on the relationship between leaf area and dry mass of each plant species. Of the 31 plant species, 19 were consumed by the larvae to different degrees, but the other 12 were not. The larvae showed strong feeding preference only for four species, i.e., K. humilis, Carex przewalskii, Helictotrichon tibeticum and Elymus nutans. At the species level, leaf consumption by the larvae was significantly negatively related with plant leaf N content and significantly positively related with the leaf C:N ratio. At the functional-group level, the sedges had the highest leaf consumption by the larvae, the lowest leaf N content and the highest leaf C:N ratio, whereas the legumes had the lowest leaf consumption, the highest leaf N, and the lowest leaf C:N ratio. We conclude that increasing N content of plants may not increase the feeding preference of phytophagous insects even in alpine meadow ecosystems where plant growth is highly limited due to the lack of soil available N. Our results also suggest that the strong feeding preference of G. menyuanensis larvae for the dominant species K. humilis and E. nutans may help in maintaining species coexistence and biodiversity in the alpine meadow dominated by K. humilis. 参考文献 相似文献 引证文献

Surface activation of CNT Webs towards layer by layer assembly of biosensors

Several surface activation methods such as chemical, electrochemical and plasma have been used for enhancing the electrochemical performance of carbon based electrodes for various applications. However, some of these surface activation methods may not be useful depending on the chemical and physical properties of the activated surface. Herein we investigate the surface activation of carbon nanotube (CNT) webs by electrochemical and plasma techniques to enhance their electrochemical performance and enable the fabrication of a biosensor using the layer-by-layer (LBL) approach. The pretreated CNT webs were characterized by SEM, TEM, Raman, XPS and electrochemical methods. TEM images and Raman analysis showed an increase in the level of surface defects upon pretreatment with higher number of defects after electrochemical pretreatment. XPS analysis showed an increase in the level of oxygen functional groups after pretreatment (4 to 5 times increase) which resulted in enhanced water wettability especially for plasma pretreated CNT webs. The pretreated CNT web electrodes also showed an enhanced electrochemical activity towards the oxidation and reduction of different redox probes with higher sensitivity for the electrochemically pretreated CNT web electrode that was accompanied by a higher level of noise in amperometric measurements. A highly linear response was obtained for the untreated and the electrochemically pretreated CNT web electrodes towards the amperometric detection of NADH (R(2) of 0.9996 and 0.9986 respectively) while a non-linear response was observed for the plasma pretreated CNT web electrode (R(2) of 0.8538). The pretreated CNT web electrodes enabled the fabrication of a LBL biosensor for alcohol detection with highest operational stability obtained for the plasma pretreated CNT web surface.

Can digital image classification be used as a standardised method for surveying peatland vegetation cover?

The ability to carry out systematic, accurate and repeatable vegetation surveys is an essential part of long-term scientific studies into ecosystem biodiversity and functioning. However, current widely used traditional survey techniques such as destructive harvests, pin frame quadrats and visual cover estimates can be very time consuming and are prone to subjective variations. We investigated the use of digital image techniques as an alternative way of recording vegetation cover to plant functional type level on a peatland ecosystem. Using an established plant manipulation experimental site at Moor House NNR (an Environmental Change Network site), we compared visual cover estimates of peatland vegetation with cover estimates using digital image classification methods, from 0.5m×0.5m field plots. Our results show that digital image classification of photographs taken with a standard digital camera can be used successfully to estimate dwarf-shrub and graminoid vegetation cover at a comparable level to field visual cover estimates, although the methods were less effective for lower plants such as mosses and lichens. Our study illustrates the novel application of digital image techniques to provide a new way of measuring and monitoring peatland vegetation to the plant functional group level, which is less vulnerable to surveyor bias than are visual field surveys. Furthermore, as such digital techniques are highly repeatable, we suggest that they have potential for use in long-term monitoring studies, at both plot and landscape scales.

Leaf non-structural carbohydrates regulated by plant functional groups and climate: Evidences from a tropical to cold-temperate forest transect

Non-structural carbohydrates (NSCs), e.g., glucose and starch, play important roles in metabolic processes of plants and represent important functional traits in plant's adaptation to external environment. To explore the variations in leaf NSCs among species and communities at a large scale and their influencing factors, we investigated the contents of leaf NSCs among 890 plant species in nine typical forests along the north–south transect of eastern China. The results showed that the contents of leaf soluble sugars, starch, and NSCs (sugars+starch) were highly variable among different plant species on the site scale, and their mean values for the 890 plant species were 45.7mgg−1, 47.5mgg−1, and 93.2mgg−1, respectively. All three metrics varied markedly across plant functional groups in the order of trees<shrubs<herbs. Weak latitudinal patterns of leaf soluble sugars, starch, and NSCs were observed from tropical to cold-temperate forests at the levels of species and plant functional groups. The contents of leaf soluble sugars, starch, and NSCs decreased with increasing temperature and precipitation which supports the growth limitation hypothesis at a large scale. In trees, leaf soluble sugars, starch, and NSCs increased with increasing photosynthetic active radiation (PAR); and were positively correlated with specific leaf area (SLA). The spatial patterns of leaf NSCs in forests along the north–south transect of eastern China and their relationships with temperature, precipitation, PAR, and SLA illustrate an important adaptation of plant communities to environmental changes at the continental scale.

Cellulose as a Source of Water Dispersible Renewable Film-Forming Materials

Cellulose is found to be a good source of waterborne film-forming materials when modified with the correct type and level of functional groups. The modification of cellulose to incorporate high levels of levulinic functionality and other C2–C6 alkyl esters is reported for the first time. The levulinyl-functionalized cellulose is readily modified to produce oxime or acylhydrazone derivatives, which is particularly useful to fine-tune the physical characteristics of the cellulose ester. This includes the glass transition temperature of the cellulose esters, their ability to produce fine uniform colloidal particles in aqueous media and ultimately provide the principle film-forming component of an architectural coating. The process has been demonstrated at the 500 g level suggesting ready scalability. Lewis acids and Lewis acid-assisted Bronsted acids are employed for the first time in such chemistry, and together with sulfur-based Bronsted acids are all found to be effective catalysts for the esterification ...

Bird fruit consumption results from the interaction between fruit-handling behaviour and fruit crop size

Bird foraging behaviour is a major factor involved in mutualistic interactions of fleshy-fruited plants. Despite much research, we still lack quantified demonstrations of how fruit display traits affect fruit removal behaviour. Although the fruit crop size hypothesis proposes a general mechanism for fruit trait selection, it overlooks the fact that distinctive bird behaviours in a bird assemblage would have different effects on fruit crop size. Here, we show that the relevance of fruit crop size for bird fruit consumption is driven by two basic components of fruit foraging behaviour: fruit handling and residence time. We assessed bird fruit-eating behaviour (fruit consumption, fruit handling and residence time) and its relationship with fruit crop size, taking into account body size and spatial focal context (conspecific neighbour density and distance to the forest edge from individual plants) in a population of Vassobia breviflora (Solanaceae) in Tucumán, Argentina. At the assemblage level, fruit consumption was positively related to fruit crop size and residence time, and the interaction between fruit crop size and residence time depended on fruit-handling behaviour. At the functional group level, both gulpers and pulp consumers showed a positive relationship between fruit consumption and residence time. However, gulpers showed a negative interaction between fruit crop size and residence time, while pulp consumers showed no interaction. At the species level, fruit consumption by Turdus rufiventris (gulper) was positively related to fruit crop size, whereas fruit consumption by Thraupis sayaca and Zonotrichia capensis (pulp consumers) depended positively on residence time. Essentially, gulpers spent short residence times in plants with larger fruit crops, whereas pulp consumers spent long residence times in plants regardless of fruit crop size. The segregation between fruit-eating behaviours and their relationship with fruit crop size suggests that bird functional groups (i.e. gulpers and pulp consumers) would shape fruit display traits with different intensities.

Differential responses of grasses and forbs led to marked reduction in below‐ground productivity in temperate steppe following chronic N deposition

Summary Enhanced deposition of atmospheric nitrogen (N) has profound impacts on ecosystem processes such as above‐ground productivity and community structure in grasslands across the globe. But how N deposition affects below‐ground processes of grasslands is less well known. Here, we evaluated the effects of chronic N amendment at a relatively low rate (20 kg ha−1 year−1) on root traits (root productivity, root biomass, root/shoot ratio) in Inner Mongolia steppes by rhizotron and ingrowth core and soil monolith techniques at levels of individual species, functional groups and ecosystem. For 8 years, N amendment suppressed above‐ground net primary production (ANPP), photosynthetic rates and root biomass of forbs, but enhanced ANPP and root biomass of grasses. This led to an overall reduction in below‐ground productivity of the grassland by 24–33%, while ANPP remained unchanged. Nitrogen amendment acidified soil and subsequently increased extractable soil manganese (Mn) concentration. Nitrogen amendment increased foliar Mn concentrations in forb, but not grass species, leading to a significant inhibition of photosynthetic rates in forb species. Synthesis. These findings highlight the importance of the differentiating responses of plant functional groups to long‐term N deposition and the important consequences of these responses for below‐ground productivity and long‐term soil C sequestration.

Precipitation modifies the effects of warming and nitrogen addition on soil microbial communities in northern Chinese grasslands

Terrestrial ecosystems experience simultaneous shifts in multiple drivers of global change, which can interactively affect various resources. The concept that different resources co-limit plant productivity has been well studied. However, co-limitation of soil microbial communities by multiple resources has not been as thoroughly investigated. Specifically, it is not clearly understood how microbial communities respond to shifts in multiple interacting resources such as water, temperature, and nitrogen (N), in the context of global change. To test the effects of these various resources on soil microorganisms, we established a field experiment with temperature and N manipulation in three grasslands of northern China, where there is a decrease in precipitation from east to west across the region. We found that microbial responses to temperature depended upon seasonal water regimes in these temperate steppes. When there was sufficient water present, warming had positive effects on soil microorganisms, suggesting an interaction between water and increases in temperature enhanced local microbial communities. When drought or alternating wet–dry stress occurred, warming had detrimental effects on soil microbial communities. Our results also provide clear evidence for serial co-limitation of microorganisms by water and N at the functional group and community levels, where water is a primary limiting factor and N addition positively affects soil microorganisms only when water is sufficient. We predict that future microbial responses to changes in temperature and N availability could be seasonal or exist only in non-drought years, and will strongly rely on future precipitation regimes.

Studies on the preferred uracil–adenine base pair at the cleavage site of 10–23 DNAzyme by functional group modifications on adenine

10–23 DNAzyme is capable of catalytically cleaving RNA substrates with the preferred cleavage sites rAU and rGU, in which the common base pair U-dA0 forms between the substrate and the DNAzyme in the cleavage reaction. Here its conservation was studied with base modifications on dA and extra functional groups introduced. The nitrogen atom at 7- or 8-position of adenine was demonstrated to be equally important for the cleavage reaction, although it is not related to the thermal stability of the base pair. Deletion of 6-amino group led to decreased stability of the base pair and a slight slower reaction rate. Extra functional groups through 6-amino group were not favorably accommodated in the cleavage site. From these modifications at the level of functional groups, it demonstrated that the base pair U-dA0 not only contributes to the recognition and binding stability, but also it is involved in the active catalytic center by its functional groups and base stacking. This kind of chemical modifications with 7-substituted 8-aza-7-deaza-2′-deoxyadenosine at dA0 is favorable for the introduction of signal molecules for mechanistic studies and biological applications, without significant loss of the catalytic function and structural destruction.

Comparing trophic structure of a subtropical bay as estimated from mass-balance food web model and stable isotope analysis

The trophic structure of a subtropical bay in Taiwan Strait was analyzed by using two methods: mass balance modeling (Ecopath) and stable isotopic analysis (SIA). Trophic levels (TLs) of main functional groups estimated from the two methods were compared. The Ecopath model was built based on the fishery resource survey in Xiamen Bay in 2009. Specifically, data on species composition, biomass, mortality rates, diet composition and fisheries catches were obtained from the survey in and around the bay. The model consisted of 26 functional groups, including plankton, benthos, fish, cephalopods, shrimps, crabs and marine mammals. TLs of the main functional groups were estimated to be between 2.89 (cephalopods) and 3.94 (congers), with an average of 3.11. Trophic transfer efficiencies from levels II to V were 12.8%, 19.2%, 19.7% and 12.1%, respectively. Catfish (Tachysurus sinensis and Netuma thalassina) and the fisheries have major trophic impacts on most functional groups in the Xiamen Bay ecosystem. Total system throughput was estimated to be 411tkm−2year−1. TLs derived from isotopic analysis were highly correlated with those estimated from Ecopath (Linear regression: R2=0.696, n=23, p<0.001). On an average, Ecopath underestimated TLs of the functional groups by about 12.2% compared to those estimated from SIA, with TLs from Ecopath being slightly higher at low TLs and lower at high TLs. This studies support value of using both stable isotopes and Ecopath methods to analyze this food web.

Helical and Dendritic Unzipping of Carbon Nanotubes: A Route to Nitrogen-Doped Graphene Nanoribbons.

Bamboo structured nitrogen-doped multiwalled carbon nanotubes (CN(x)-MWCNTs) have been successfully unzipped by a chemical oxidation route, resulting in nitrogen-doped graphene nanoribbons (CN(x)-GNRs) with a multifaceted microstructure. The oxidation of CN(x)-MWCNTs was carried out using potassium permanganate in the presence of trifluoroacetic acid or phosphoric acid. On the basis of the high resolution transmission electron microscopy studies, the bamboo compartments were unzipped via helical or dendritic mechanisms, which are different from the longitudinal unzipping of open channel MWCNTs. The product graphene oxide nanoribbons were simultaneously reduced and doped with nitrogen by thermal annealing in an ammonia atmosphere. The effects of the annealing temperature, time, and atmosphere on the doping level and types of the nitrogen functional groups have been investigated. X-ray photoelectron spectroscopy results indicate that a wide range of doping levels can be achieved (4-9 at %) simply by changing the annealing conditions. Pyridinic and pyrrolic nitrogen functional groups were the dominant species that were attached to the edges of the CN(x)-GNRs. The GNRs, with a faceted structure and pyridinic and pyrrolic groups on their edges, have abundant nitrogen sites. These active sites could play a vital role in enhancing the electrocatalytic performance of GNRs.

Changes in fungal communities along a boreal forest soil fertility gradient.

Boreal forests harbour diverse fungal communities with decisive roles in decomposition and plant nutrition. Although changes in boreal plant communities along gradients in soil acidity and nitrogen (N) availability are well described, less is known about how fungal taxonomic and functional groups respond to soil fertility factors. We analysed fungal communities in humus and litter from 25 Swedish old-growth forests, ranging from N-rich Picea abies stands to acidic and N-poor Pinus sylvestris stands. 454-pyrosequencing of ITS2 amplicons was used to analyse community composition, and biomass was estimated by ergosterol analysis. Fungal community composition was significantly related to soil fertility at the levels of species, genera/orders and functional groups. Ascomycetes dominated in less fertile forests, whereas basidiomycetes increased in abundance in more fertile forests, both in litter and humus. The relative abundance of mycorrhizal fungi in the humus layer remained high even in the most fertile soils. Tolerance to acidity and nitrogen deficiency seems to be of greater importance than plant carbon (C) allocation patterns in determining responses of fungal communities to soil fertility, in old-growth boreal forests.

Response of diatom and dinoflagellate lifeforms to reduced phosphorus loading: A case study in the Thau lagoon, France

The basin of Thau in southern France is a shallow, weakly flushed lagoon which is an important location for oyster cultivation. Phytoplankton analyses were carried out in 1975–1976 and then (almost) continuously since 1987. We report an investigation of ‘the balance of organisms’ in phytoplankton in relation to reductions in phosphorus loading, using two new tools based on phytoplankton lifeforms: the Plankton Index for Phytoplankton (PIp); Euclidean distance in state-space. Our results show the utility of the tools for analysing changes in the ‘balance of organisms’ at the level of functional groups (in our study diatoms and dinoflagellates), but also illustrate the difficulties in demonstrating the reversal of human impacts resulting from eutrophication.The comparison between 1987–89 and 1976 showed the expected ‘de-eutrophication’ due to the reduction in dissolved inorganic phosphate (DIP), with a decrease in dinoflagellate abundance. Since 1989, year-to-year variation in annual mean concentrations of DIP may have contributed to inter-annual variability in the balance of the two lifeforms, but the data suggest that the system has remained in a dynamically stable regime because: (1) there was no long-term trend in Euclidean distance from the reference; and (2) there was no increase in inter-annual variability about the time-series mean Euclidean distance suggesting there has been no decrease in resilience which might signal a regime change.Integrated management of human activities will be required to manage (and reduce) total P in the system. Monitoring phytoplankton and nutrients concentrations to determine how primary production and the balance of species respond to further changes in the nutrient status of the lagoon should be an integral part of any management programme.

Integral structural-functional method for characterizing microbial populations

An original integral structural-functional method has been proposed for characterizing microbial communities. The novelty of the approach is the in situ study of microorganisms based on the growth kinetics of microbial associations in liquid nutrient broth media under selective conditions rather than on the level of taxa or large functional groups. The method involves the analysis of the integral growth model of a periodic culture. The kinetic parameters of such associations reflect their capacity of growing on different media, i.e., their physiological diversity, and the metabolic capacity of the microorganisms for growth on a nutrient medium. Therefore, the obtained parameters are determined by the features of the microbial ecological strategies. The inoculation of a dense medium from the original inoculate allows characterizing the taxonomic composition of the dominants in the soil community. The inoculation from the associations developed on selective media characterizes the composition of syntrophic groups, which fulfill a specific function in nature. This method is of greater information value than the classical methods of inoculation on selective media.

Disentangling direct and indirect effects of a legume shrub on its understorey community

Direct and indirect interactions among plants contribute to shape community composition through above‐ and belowground processes. However, we have not disentangled yet the direct and indirect soil and canopy effects of dominants on understorey species. We addressed this issue in a semi‐arid system from southeast Spain dominated by the legume shrub Retama sphaerocarpa. During a year with an exceptionally dry spring, we removed the shrub canopy to quantify aboveground effects and compared removed‐canopy plots to open plots between shrubs to quantify soil effects, both with and without watering. We added a grass removal treatment in order to separate direct from indirect shrub effects and quantified biomass, abundance, richness and composition of the forb functional group. With watering, changes in forb biomass were primarily driven by indirect shrub effects, with contrasting negative soil and positive aboveground indirect effects; changes in forb abundance and composition were more influenced by direct shrub soil effects with contrasting species composition between open and Retama patches. As community composition was different between open and Retama patches the indirect effects of Retama on forb species did not concern forbs from the open community but forbs from Retama patches. Indirect effects are, thus, important at the functional group level rather than at the species level. Without watering, there were no significant interactions. Changes in species richness between treatments were weak and seldom significant. We conclude that shrub effects on understorey forbs are primarily due to their influence on soil properties, directly affecting forb species composition but indirectly affecting the biomass of the forbs of the Retama patches, and only with sufficient water.

Latitudinal concordance between biogeographic regionalization, community structure, and richness patterns: a study on the reptiles of China.

Latitudinal patterns in species richness may be affected by both continuous variations in macroecological factors as well as discrete change between biogeographic regions. We examined whether latitudinal reptilian richness and community structure in China were best explained by three macroecological patterns (mid-domain effects, Rapoport's rule effects, or environmental correlates) within or across the ranges of biogeographic realms. The results showed that (1) there was a weak mid-domain effect within the Oriental Realm. However, the mid-domain effect was detected neither at the overall regional scale nor in the Palaearctic Realm. (2) Rapoport's rule was only weakly supported for reptilian fauna in China at lower latitudinal areas. (3) Environmental variables were more strongly correlated with species' latitudinal community structure and richness patterns at the scale of biogeographic realms. Based on the faunal similarity of reptilian community across latitudinal bands, we proposed a latitudinal delineation scheme at 34° N for dividing East Asia into Oriental and Palaearctic biogeographic realms. At last, at the functional group level, we also evaluated the relevant ecological patterns for lizard and snake species across different latitudinal bins, showing that the distributions of lizards presented strong mid-domain effects at the latitudinal ranges within the Oriental Realm and over the whole range but did not support Rapoport's rule. In comparison, snake species supported Rapoport's rule at low latitudinal zones but did not present any remarkable mid-domain effects at any spatial extents. In conclusion, biogeographic realms are an appropriate scale for studying macroecological patterns. Reptilian latitudinal richness patterns of China were explained by a combination of environmental factors and geometric constraints, while the latitudinal community structure patterns were greatly affected by environmental gradients. Functional guilds present differentiated macroecological patterns along the latitudinal gradients.

Plant species diversity is correlated with climatic factors differently at the community and the functional group levels: A case study of desert steppe in Inner Mongolia, China

In the desert steppe of Inner Mongolia, mean annual precipitation was found to be the dominant factor that correlated positively with species richness at the community level and for the perennial forb functional group. Shrub and semi-shrub functional group exhibited positive correlation with mean temperature of the coldest month.

Early-season movement dynamics of phytophagous pest and natural enemies across a native vegetation-crop ecotone

There is limited understanding about how insect movement patterns are influenced by landscape features, and how landscapes can be managed to suppress pest phytophage populations in crops. Theory suggests that the relative timing of pest and natural enemy arrival in crops may influence pest suppression. However, there is a lack of data to substantiate this claim. We investigate the movement patterns of insects from native vegetation (NV) and discuss the implications of these patterns for pest control services. Using bi-directional interception traps we quantified the number of insects crossing an NV/crop ecotone relative to a control crop/crop interface in two agricultural regions early in the growing season. We used these data to infer patterns of movement and net flux. At the community-level, insect movement patterns were influenced by ecotone in two out of three years by region combinations. At the functional-group level, pests and parasitoids showed similar movement patterns from NV very soon after crop emergence. However, movement across the control interface increased towards the end of the early-season sampling period. Predators consistently moved more often from NV into crops than vice versa, even after crop emergence. Not all species showed a significant response to ecotone, however when a response was detected, these species showed similar patterns between the two regions. Our results highlight the importance of NV for the recruitment of natural enemies for early season crop immigration that may be potentially important for pest suppression. However, NV was also associated with crop immigration by some pest species. Hence, NV offers both opportunities and risks for pest management. The development of targeted NV management may reduce the risk of crop immigration by pests, but not of natural enemies.