Individual Plant Characteristics Research Articles

Look after gardens and they look after you: Cultivating wellbeing in a pandemic through a popular TV gardening programme

Over the past few years there has been intense policy interest in the idea that nature-related activities such as gardening are good for wellbeing. Several studies have indeed found links between such activities and self-reported wellbeing. However, there are also sympathetic critiques of the limited conceptions of what kinds of activities are considered beneficial. Therefore, more attention should be paid to the social and cultural roots of the assumption that nature is good for us rather than treating connection to nature as an innate need. This article contributes to this task by showing how commonly held ideas about gardening and wellbeing were reproduced in the long-running and popular UK TV gardening programme Gardeners’ World ( GW) during 2020. As an exemplar of lifestyle programming, GW provides both information and entertainment and appeals to viewers to try out the techniques they observe on screen in their own gardens. Within the programme there is an emphasis on gardens as secluded havens from the outside world and on the attractive characteristics of individual plants. However, in many cases it is the work involved and the challenge that interests gardeners, as much as the qualities of the plants. Gardeners design a space and use it to express their identity. But the results of their actions are not guaranteed. Gardening can therefore be understood through a political ecology lens as a process whereby the social and nature constitute each other.

Distribution and characteristics of wastewater treatment plants within the global river network

Abstract. The main objective of wastewater treatment plants (WWTPs) is to remove pathogens, nutrients, organics, and other pollutants from wastewater. After these contaminants are partially or fully removed through physical, biological, and/or chemical processes, the treated effluents are discharged into receiving waterbodies. However, since WWTPs cannot remove all contaminants, especially those of emerging concern, they inevitably represent concentrated point sources of residual contaminant loads into surface waters. To understand the severity and extent of the impact of treated-wastewater discharges from such facilities into rivers and lakes, as well as to identify opportunities of improved management, detailed information about WWTPs is required, including (1) their explicit geospatial locations to identify the waterbodies affected and (2) individual plant characteristics such as the population served, flow rate of effluents, and level of treatment of processed wastewater. These characteristics are especially important for contaminant fate models that are designed to assess the distribution of substances that are not typically included in environmental monitoring programs. Although there are several regional datasets that provide information on WWTP locations and characteristics, data are still lacking at a global scale, especially in developing countries. Here we introduce a spatially explicit global database, termed HydroWASTE, containing 58 502 WWTPs and their characteristics. This database was developed by combining national and regional datasets with auxiliary information to derive or complete missing WWTP characteristics, including the number of people served. A high-resolution river network with streamflow estimates was used to georeference WWTP outfall locations and calculate each plant's dilution factor (i.e., the ratio of the natural discharge of the receiving waterbody to the WWTP effluent discharge). The utility of this information was demonstrated in an assessment of the distribution of treated wastewater at a global scale. Results show that 1 200 000 km of the global river network receives wastewater input from upstream WWTPs, of which more than 90 000 km is downstream of WWTPs that offer only primary treatment. Wastewater ratios originating from WWTPs exceed 10 % in over 72 000 km of rivers, mostly in areas of high population densities in Europe, the USA, China, India, and South Africa. In addition, 2533 plants show a dilution factor of less than 10, which represents a common threshold for environmental concern. HydroWASTE can be accessed at https://doi.org/10.6084/m9.figshare.14847786.v1 (Ehalt Macedo et al., 2021).

The individual‐based network structure of palm‐seed dispersers is explained by a rainforest gradient

How species interactions change in space and time is a major question in ecology. In tropical forests, plant individuals share mutualistic partners (pollinators or seed dispersers), yet we have little understanding of the factors affecting these individual interaction patterns. We used a seed dispersal individual‐based network describing interactions between individuals of a palm species and bird species to investigate how intrinsic and extrinsic characteristics of individual plants influence the network structure. We evaluated if average canopy height, number of fruits, distance to forest gap and habitat type influence the role of palm individuals in the network. From 102 palms, 62 individuals had their seeds dispersed at least once: 17 individual palms in the restinga, 15 in the lowland and 30 in the pre‐montane habitat. Twelve bird species were recorded dispersing Euterpe edulis seeds. No palm characteristics influenced interaction patterns in the network, characterized by the level of centrality of each palm. At the network level, modularity with qualitative data was reproduced by the null models which consider the variation in the number and distribution across interactions. Three of the seven identified modules were associated with a particular habitat. Indeed, habitat type explained 50% of network modularity. Habitat association with modularity was driven by differences in species composition across habitats. Palm individuals did not differ greatly in central positions, indicating that bird species are not selecting palm individuals by their characteristics. When using the weighted network, modularity level was higher than expected by the number of interactions, and frequency of interactions was positively correlated with canopy height. Our results suggest that the organization of this individual‐based network is mostly driven by habitat type. We hypothesize that extrinsic characteristics, such as habitat type, may affect the network organization of populations of sessile organisms with potentially unanticipated consequences to ecological and evolutionary dynamics.

Development of a Low-Cost System for 3D Orchard Mapping Integrating UGV and LiDAR.

Growing evaluation in the early stages of crop development can be critical to eventual yield. Point clouds have been used for this purpose in tasks such as detection, characterization, phenotyping, and prediction on different crops with terrestrial mapping platforms based on laser scanning. 3D model generation requires the use of specialized measurement equipment, which limits access to this technology because of their complex and high cost, both hardware elements and data processing software. An unmanned 3D reconstruction mapping system of orchards or small crops has been developed to support the determination of morphological indices, allowing the individual calculation of the height and radius of the canopy of the trees to monitor plant growth. This paper presents the details on each development stage of a low-cost mapping system which integrates an Unmanned Ground Vehicle UGV and a 2D LiDAR to generate 3D point clouds. The sensing system for the data collection was developed from the design in mechanical, electronic, control, and software layers. The validation test was carried out on a citrus crop section by a comparison of distance and canopy height values obtained from our generated point cloud concerning the reference values obtained with a photogrammetry method. A 3D crop map was generated to provide a graphical view of the density of tree canopies in different sections which led to the determination of individual plant characteristics using a Python-assisted tool. Field evaluation results showed plant individual tree height and crown diameter with a root mean square error of around 30.8 and 45.7 cm between point cloud data and reference values.

Considering the Effect of Land-Based Biomass on Dune Erosion Volumes in Large-Scale Numerical Modeling

This paper presents and validates a novel root model which accounts for the effect of belowground biomass on dune erosion volumes in XBeach, based on a small-scale wave flume experiment that was translated to a larger scale. A 1D-XBeach model was calibrated by using control runs considering a dune without vegetation. Despite calibration, a general model–data mismatch was observed in terms of overestimated erosion volumes around the waterline. Furthermore, the prediction of overwash had to be induced by increasing the maximum nearshore wave height within the XBeach simulation. Subsequently, applying the root model resulted in a good agreement with the belowground biomass cases, and the consideration of spatially varying rooting depths further improved the results. Predictions of the root model while using locally increased friction coefficients were in line with the aboveground and belowground biomass cases. However, the effect of the root model on the erosion predictions varied among the hydrodynamic conditions, so further improvements are required. Therefore, future research should focus on quantifying the effects of land-based biomass and individual plant characteristics, such as root density, on dune erodibility at large scales, along with their influences on the temporal evolution of dune scarping and avalanching.

Frozen naturae: floral motives in Mayan terracotta of the First Millennium A.D.

The article is devoted to the analysis of various plant motives on Mayan terracotta figurines of the 1st millennium A.D. Two basic types of plant motives are identified, which are represented by plants that are independent subjects of the image, as well as those that are secondary in nature, supplementing the plot composition. A characteristic is given of voluminous, bas-relief and flat forms of the image with a detailed characteristic of their localization, which differ in great variety: costume, hair-style, jewelry, headdress, tattoo, attributive objects, weapons, etc. The Jaina materials provide statistical data on the frequency of occurrence of all the above indicators. Attention is paid to the characteristics of individual plants and their elements, both domesticated and growing near humans, which can be identified and correlated with real prototypes. Quantitative and percentage characteristics of the occurrence of various plants are given, indicating their names in cases when they are definable. Iconographic features in the images of plants are described in detail, consisting both in "photographic" copying of the features of real plants, and in significant artistic stylization of images characteristic rather of images on stelae painted with polychrome ceramics. Conclusions are made about the features of images of plant motives, which are expressed in places of localization, their role in the plot and composition of terracotta, and the semantic load that the visual embodiment of a particular plant or its image carried.

Prescribed fires cause minimal damage to a threatened cactus (Tobusch fishhook cactus, Sclerocactus brevihamatus ssp. tobuschii, Texas, USA)

The effects of fire on cacti depend on individual plant characteristics, fire intensity, and local conditions. Tobusch fishhook cactus (Sclerocactus brevihamatus ssp. tobuschii) is a small (<~7 cm diameter), globose cactus endemic to the Edwards Plateau of central Texas. This species grows in open sites with shallow, rocky soils, surrounded by oak-juniper woodlands and shrublands. Fire is thought to maintain the open character of the sites, but few studies have examined the effects of fire on this species. We investigated the effects of two prescribed fires on Tobusch fishhook cacti (n > 600) in long-term monitoring plots. The fires killed only one cactus and visibly damaged <28% of cacti, none of which died within the first two growing seasons. Visibly damaged cacti grew less than undamaged cacti in the first and/or second growing seasons, but fruit set was not reduced. Fire damage was best predicted by cactus diameter (>1 cm), cactus height (>1 cm), and proximity to bunchgrasses (<3 cm). Prescribed fire can be used to maintain Tobusch fishhook cactus habitat but should avoid flowering/fruiting seasons (~January through May) and years with above-average rainfall that create high fuel loads.

Characterization of Origanum vulgare SUBSP. hirtum (LINK) Iestwaart Population and Determination of A Clones

Identification of the high yielding and the good quality clones of one population (B population) of Origanum vulgare subsp. hirtum (Link) Iestwaart was one of the purposes in this study and furthermore some agronomic and quality characteristics of individual plants were examined during two years (2014-2015). Annual performances were determined according to the minimum and maximum values of the first, second and non-flowering harvests of the population. Also for second year, minimum, maximum and mean values of the individual plants of the population were stated in the paper. The aim was to reveal if the high yield and quality characteristics of plants are based on the genotype. Individual plants of the B population, the mean plant height was found as 39 cm, canopy value as 30.5 cm, Fresh herb yield as 167.9 g/plant, Drog herb yield as 65.5 g/plant, Drog leaves yield as 32.2 g/plant and the mean rate of the essential oil as 4,01%. Considering the two years’ results of the B population, A clones were created in 2016 by selecting the high yielding and of good quality genotypes. On A clones, the plant height, fresh herb yield, Drog herb yield, essential oil rate and essential oil yield values were determined between 13-52.5 cm, 8-624 g/plot, 4-218.4 g/plot, 1.6-100.1 g/plot, 1.08-7.92 % and 0.03-5.74 L/parcel, respectively.

3D model processing for high throughput phenotype extraction – the case of corn

High resolution RGB imagery collected using a UAV and a handheld camera was used with structure from motion to reconstruct 3D canopies of small groups of corn plants. A methodology for the automated extraction of phenotypic characteristics of individual plants is presented based on these 3D reconstructed canopies. Such information can enhance the evaluation of crop traits and provide accurate and frequent statistics for in-season assessment of their changes with growth stage. Industries that target yield optimization and crop hybrid production can benefit greatly from this approach. The use of 3D models provides elevated information content, when compared to alternative planar methods, mainly due to the alleviation of leaf occlusions. High resolution images of corn stalks are collected and used to obtain 3D models for individual plants. Based on those extracted 3D point clouds, the calculation of phenotypic characteristics are obtained, such as the number of plants in an area, the Leaf Area Index (LAI), the individual and average plant height, the individual leaf length, the location and the angles of leaves with respect to the stem. An experimental validation using both artificial corn plants emulating real world scenarios and real corn plants in different growth stages, supports the accuracy of the proposed methodology.Our experiments conclude that phenotypic characteristics of individual plants can be extracted automatically with high accuracy based on a 3D model. The results include the individual plant segmentation and counting from a given 3D reconstructed field scene with 88.1% accuracy, the Leaf Area Index (LAI) estimation with 92.5% accuracy, the individual plant height computation with 89.2% accuracy, the leaf length extraction with 74.8% accuracy, the measurement of angles between leaves and stems, and the distance between the leaves of the same plant. We interpret the last two variables qualitatively to show that the method can show the trend of the angles to change with respect to the leaf position on the stem as the crops grow.

POLYSACCHARIDES IN TISSUES AMARANTHUS RETROFLEXUS, AGASTACHE RUGOSA AND THLASPI ARVENSE IN THE CONDITIONS OF CENTRAL YAKUTIA

Isolated fraction of polysaccharides, such as water-soluble polysaccharides, pectins, hemicelluloses A and B from the vegetative mass of plants Amaranthus retroflexus, Agastache rugosa and Thlaspi arvense, grown in the conditions of Central Yakutia. According to the obtained IR spectra it was established that the isolated fractions of polysaccharides from Amaranthus retroflexus, Agastache rugosa and Thlaspi arvense belong to water-soluble polysaccharides, pectins and hemicelluloses. Shows the monosaccharide composition of isolated fractions of polysaccharides from plants grown under conditions of Central Yakutia. The main monomers of the isolated polysaccharides are arabinose (Ara), galactose (Gal), rhamnose (Rha), mannose (Man), xylose (Xyl), glucose (Glc), galacturonic acid (GalA). Revealed the degree of ethrerification of the galacturonic acid in water-soluble polysaccharides and pectins by IR spectra. Shows the differences in the quantitative content and monosaccharide composition of the isolated fractions of polysaccharides, which can be associated with both adaptive rearrangements in the body and with individual plant characteristics.

Response of canopy structure, light interception and grain yield to plant density in maize

AbstractGood canopy structure is essential for optimal maize (Zea maysL.) production. However, creating appropriate maize canopy structure can be difficult, because the characteristics of individual plants are altered by changes in plant age, density and interactions with neighbouring plants. The objective of the current study was to find a reliable method for building good maize canopy structure by analysing changes in canopy structure, light distribution and grain yield (GY). A modern maize cultivar (ZhengDan958) was planted at 12 densities ranging from 1.5 to 18 plants/m2at two field locations in Xinjiang, China. At the silking stage (R1), plant and ear height increased with plant density as well as leaf area index (LAI), whereas leaf area per plant decreased logarithmically. The fraction of light intercepted by the plant (F) increased with increasing plant density, but the light extinction coefficient (K) decreased linearly from 0.61 to 0.39. Taking the optimum value ofF(95%) as an example, and using measured values ofKfor each plant density at R1 and the equation from Beer's law, the corresponding (theoretical) LAI for each plant density was calculated and optimum plant density (9.72 plants/m2) obtained by calculating the difference between theoretical LAIs and actual observations. Further analysis showed that plant density ranging from 10.64 to 11.55 plants/m2yielded a stable GY range. Therefore, taking into account the persistence time for maximum LAI, the plant density required to obtain an ideal GY maize canopy structure should be increased by 10–18% from 9.72 plants/m2.

Ridge and furrow planting pattern optimizes canopy structure of summer maize and obtains higher grain yield

Ridge and furrow planting patterns could improve the micro-environment effectively, and ultimately affect maize grain yield. Previous studies mainly focused on planting only on ridges or in furrows aiming to improve the water and temperature conditions, while research on effects of planting in both ridges and furrows on canopy structure and photosynthetic characteristics of individual plants was relatively few. Hence, we hypothesized that planting in both ridges and furrows would (1) optimize maize canopy structure (better light conditions within canopy and delayed leaf senescence), (2) enhance individual leaf photosynthetic characteristics during grain filling, and (3) obtain higher grain yield. To test this hypothesis, we conducted ridge and furrow planting pattern experiments in 2013, 2014 and 2015 growing seasons in Shaanxi, a province in the Northwest of China. Zhengdan958, a corn cultivar planted widely across China, was grown at a density of 67500 plants ha−1. Three planting patterns were arranged as follows: the conventional planting pattern with row spacing of 60 cm (T0 as control), the ridge and furrow planting pattern with one row plants in each ridge and furrow (T1) and the ridge and furrow planting pattern with one row in a ridge and two rows in a furrow (T2). The three-year investigations found that significantly higher relative chlorophyll content and green leaf area per plant were observed in plants of furrows compared to T0 as well as those on ridges, leading to an advantage in terms of individual photosynthetic capacity for plants in furrows, while no significant differences about them in furrows were found between T1 and T2. In addition, we also found that plants in ridge and furrow planting patterns (T1 and T2) exhibited a significantly higher transmission of light to lower layers of the canopy (LT) than that of conventional planting pattern (T0), leading to better light conditions within canopy. Moreover, plants in furrows maintained significantly higher LAI during grain filling, leading to longer LAI duration in T2 planting pattern than other treatments due to more plants in furrows. The highest yield was observed for T2 planting pattern during three experimental years. Relative to control, plants in T2 treatment obtained 27.2%, 18.3% and 31.9% higher grain yield in 2013, 2014 and 2015 growing seasons, respectively. In conclusion, for the tested growing conditions, the planting pattern with one row in a ridge and two rows in a furrow (T2) optimized canopy structure (higher LT and longer duration of LAI), enhanced photosynthetic capacity per plant (higher Pn) during grain filling, and accumulated higher aboveground dry matter at physiological maturity, leading to a greater grain yield.

Особливості лінійного приросту однорічних пагонів верби шерстистопагінцевої (Salix dasyclados Wimm.)

Різні форми і гібриди верби шерстистопагінцевої масово вирощуються на спеціальних плантаціях для отримання енергетичної біомаси. Однак останнім часом інтерес до верб як джерела біоенергетичної сировини помітно знизився. Однією з головних причин цього є нестабільність врожайності плантацій. Водночас відомо, що стабільний урожай фітомаси може бути забезпечений шляхом створення поліклональних насаджень з використанням клонів з різними ритмами розвитку.&#x0D; За результатами проведених досліджень вивчено типи динаміки наростання лідерських пагонів верби шерстистопагінцевої на відносно вирівняному одновіковому матеріалі, в однорідних едафо-фітоценотичних умовах.&#x0D; Встановлено, що динаміка росту пагонів верби шерстистопагінцевої характеризується наявністю трьох чітко виражених максимумів. Перший максимум в усіх пагонів припадає на кінець травня, у першій декаді липня спостерігається другий максимум, а у другій половині літа проявляються індивідуальні особливості в динаміці наростання пагонів: у особини da 2 третій максимум припадає на кінець липня, а у da 5 – на першу декаду серпня.&#x0D; Довгоперіодичними компонентами динаміки середньодобового приросту характеризуються не різні особини, а різні пагони. Усі короткоперіодичні компоненти характеризуються наявністю чотирьох максимумів, які загалом збігаються з фактичними максимумами.&#x0D; Довгоперіодичні компоненти визначають загальний тренд розвитку пагонів, а короткоперіодичні – спричиняють модуляційний вплив на динаміку наростання пагонів. Саме короткоперіодичні компоненти визначають індивідуальні відмінності в динаміці наростання пагонів.

Roadside verges as habitats for endangered lizard-orchids (Himantoglossum spp.): Ecological traps or refuges?

Alterations in traditional land use practices have led to severe declines in the area of semi-natural grasslands, thereby seriously threatening plant and animal species dependent on these habitats. Small anthropogenic managed habitats, like roadsides can act as refuges and might play an important role in conserving these species. Colonization of roadside verges by endangered lizard orchids (Himantoglossum spp.) has long been known, but few studies have systematically explored the suitability of roadside habitats for these orchids and the impact of roads on them. In this paper we present results of targeted surveys of three lizard orchid taxa on roadsides from eight European countries. During these surveys we searched for lizard orchids inhabiting roadside verges and recorded their distance from road, aspects of the roadside environment, as well as vegetative and reproductive characteristics of individual plants. We found large numbers of lizard orchids on roadside verges. Distance from roads was not uniformly distributed: orchids occurred more closely to roads than expected by chance. This suggests that regular management of roadsides (e.g. mowing) might enhance colonization and survival of lizard orchids. On the other hand, we also found that close proximity to roads negatively affects reproductive success, suggesting that the immediate vicinity of roads might act as an ecological trap (i.e. favorable in terms of colonization and survival but unfavorable in terms of reproduction). Nonetheless, the fact that significant and viable populations are maintained at roadsides suggests that traditionally managed roadside verges may allow long-term persistence of lizard orchid populations and may serve as refuges in a landscape context.

A Novel Route Controlling Begomovirus Resistance by the Messenger RNA Surveillance Factor Pelota.

Tomato yellow leaf curl virus (TYLCV) is a devastating disease of tomato (Solanum lycopersicum) that can be effectively controlled by the deployment of resistant cultivars. The TYLCV-resistant line TY172 carries a major recessive locus for TYLCV resistance, designated ty-5, on chromosome 4. In this study, the association between 27 polymorphic DNA markers, spanning the ty-5 locus, and the resistance characteristics of individual plants inoculated with TYLCV in 51 segregating recombinant populations were analyzed. These analyses localized ty-5 into a 425 bp region containing two transversions: one in the first exon of a gene encoding the tomato homolog of the messenger RNA surveillance factor Pelota (Pelo), and a second in its proximal promoter. Analyses of susceptible and resistant lines revealed that the relative transcript level of the gene remained unchanged, regardless of whether the plants were infected with TYLCV or not. This suggests that the polymorphism discovered in the coding region of the gene controls the resistance. Silencing of Pelo in a susceptible line rendered the transgenic plants highly resistant, while in the resistant line TY172 had no effect on symptom development. In addition, over-expression of the susceptible allele of the gene in the resistant TY172 line rendered it susceptible, while over-expression of the resistant allele in susceptible plants had no effect. These results confirm that Pelo is the gene controlling resistance at the ty-5 locus. Pelo, implicated in the ribosome recycling-phase of protein synthesis, offers an alternative route to promote resistance to TYLCV and other viruses.

The gravity of pollination: integrating at-site features into spatial analysis of contemporary pollen movement.

Pollen-mediated gene flow is a major driver of spatial genetic structure in plant populations. Both individual plant characteristics and site-specific features of the landscape can modify the perceived attractiveness of plants to their pollinators and thus play an important role in shaping spatial genetic variation. Most studies of landscape-level genetic connectivity in plants have focused on the effects of interindividual distance using spatial and increasingly ecological separation, yet have not incorporated individual plant characteristics or other at-site ecological variables. Using spatially explicit simulations, we first tested the extent to which the inclusion of at-site variables influencing local pollination success improved the statistical characterization of genetic connectivity based upon examination of pollen pool genetic structure. The addition of at-site characteristics provided better models than those that only considered interindividual spatial distance (e.g. IBD). Models parameterized using conditional genetic covariance (e.g. population graphs) also outperformed those assuming panmixia. In a natural population of Cornus florida L. (Cornaceae), we showed that the addition of at-site characteristics (clumping of primary canopy opening above each maternal tree and maternal tree floral output) provided significantly better models describing gene flow than models including only between-site spatial (IBD) and ecological (isolation by resistance) variables. Overall, our results show that including interindividual and local ecological variation greatly aids in characterizing landscape-level measures of contemporary gene flow.

MONOPSONISTIC BEHAVIOR IN CHILEAN MANUFACTURING

This paper uses a firm-specific method for measuring monopsonistic behavior developed by Brummund (2012) using data for Chilean manufacturing plants for the period 2001-2006. We find that there is significant heterogeneity in labor market power across plants and that nearly a quarter of the plants have a significant level of labor market power. It is also shown that individual plant characteristics explain more of the variation in monopsonistic behavior than do the characteristics of the accompanying labor market. These results are relevant for labor market policy since and suggest that a binding minimum wage could have ambiguous effects on welfare.

不同起始状态对草原群落恢复演替的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同起始状态对草原群落恢复演替的影响 DOI: 10.5846/stxb201202220241 作者: 作者单位: 内蒙古大学生命科学学院,内蒙古大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家科技支撑计划项目(2011BAC02B03);国家自然科学基金项目(31160476, 31060076);内蒙古自治区自然科学基金重点项目(2010Zd16) The effects of different original state on grassland community restoration succession Author: Affiliation: College Of Life Sciences Of Inner Mongolia University,College Of Life Sciences Of Inner Mongolia 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:内蒙古典型草原,由于过度放牧利用,绝大部分草原处于退化状态。为了使退化草原得到较好的恢复,以锡林郭勒盟白音锡勒牧场典型草原为研究对象,比较分析了在不同起始状态下的草原群落,经过6a的自然恢复,其各自的群落组成,地上生物量及共有种的植株高度、节间长、叶长、叶宽,土壤紧实度和容重。结果表明:1)不同放牧率的植物群落,经过6a的禁牧恢复,群落类型发生了变化且群落趋于一致。2)当放牧率SR≤5.33羊/hm2(SR4)时,演替起始状态对草原群落地上生物量的恢复没有影响;当放牧率SR＞5.33羊/hm2时,演替起始状态对草原群落地上生物量的恢复产生影响,其结果是导致当前生物量降低,不利于草原的恢复。3)不同放牧率植物群落的植物个体特征趋于一致, "个体小型化"现象消失。同时,也说明群落恢复演替的起点不同,正常化的时间没有太大的变化。4)不同放牧率植物群落的土壤紧实度和容重经过6a的禁牧恢复,没有得到完全恢复,但均达到一致的水平。 Abstract:The Xilinggol steppe is one of the four biggest grasslands in China, and is representative of the semi-arid grasslands in Asia. To discover whether the initial state (6 years previously) of various degraded grassland communities has had an effect on recovery of these communities and in what way this effect is evidenced, research was undertaken on vegetation that has undergone 6 years of recovery through non-grazing, after varying degrees of degradation under different grazing rates. The experimental study site is in the middle reaches of the Xilin River, 500 meters west of the Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences, from 43°26'-44°08'N and 116°04'-117°05'E. The following is the general situation of the surveyed land. The grazing experiment at the study site began in summer 1989. The sample plot is degraded grassland, in which Artemisia frigida and small grasses dominate, and the experimental grazing animal was sheep. There are 6 conditions, including five different stocking rates (1.33, 2.67, 4.00, 5.33 and 6.67 sheep/hm2) and a non-grazing control. Having been grazed at various rates for 16 years through 2005, the structure and function of the ecological system (plant community, soil physical and chemical properties) have experienced significant changes. Grassland ecological systems are in different degrees of degradation. To examine the recovery process of such grassland ecological systems after suspension of grazing, the grazing experiment was stopped in 2005. By 2011, the grassland ecosystems had recovered to their natural state. Investigation and sampling were conducted in August 2011. In recent years, under the influence of high use and adverse natural factors, the majority of the Inner Mongolian steppe has been in a state of degradation. In order to facilitate recovery of the degraded grasslands, the present research was conducted on a typical steppe at Baiyinxile Ranch in Xilinggol. The author analyzed a series of indicators of the state of various grassland communities (each after 6 years of natural recovery), which include plant community composition, aboveground biomass, plant height, internode length, main species leaf length, leaf width, soil compactness, and soil bulk density. The findings suggest that: 1) After 6 years of non-grazed recovery, communities of different stocking rates have changed their community type, and the communities tend to be consistent. 2) Initial successional stages have no significant effect on aboveground biomass recovery when the stocking rate is less than 5.33 sheep/hm2; however, if the stocking rate is more than 5.33 sheep/hm2, the initial successional stages lead to a decrease in current biomass. In other words, a higher stocking rate is unfavorable to the recovery of grassland. 3) Individual plant characteristics of communities at different grazing rates tend to be consistent, and the individual miniaturization phenomenon disappear. At the same time, this shows that even though the starting point of community recovery and succession is variable, the normalization time is nearly constant. 4) After 6 years of recovery, the soil compactness and bulk density of communities with different grazing rates did not fully recover, but tended to be consistent. 参考文献 相似文献 引证文献

Species-area curves revisited: the effects of model choice on parameter sensitivity to environmental, community, and individual plant characteristics

Species-area curves are often employed to identify factors affecting biodiversity patterns. The aim of this study was to determine how model choice affects biological interpretation of SAC parameters at a small scale in wet, temperate meadows (Železne hory Mts, Czech Republic). We estimated 88 species-area curves in nested plots on areas ranging from 0.01 to 4 m2 at 22 localities using four different models (Arrhenius, Gleason, and their log transformations). Relationships were tested between the parameters of the fitted curves (slope and intercept) and a number of environmental and vegetation characteristics (environmental—water table, pH, nutrient availability, organic matter content; community—productivity, evenness; and individual plant—shoot cyclicity, persistence of connection among ramets, multiplication rate, dispersal ability). Species diversity was calculated for 0.01, 1, and 4 m2. The corrected Akaike information criterion was used to identify the best model. The models differed in their sensitivity to environmental, community, and individual plant characteristics. The spatial scale that was the most suitable for revealing the factors underlying species diversity was the smallest considered (0.01 m2). The most important factors were spatial pattern in community structure (evenness, lateral spread), plant mobility (lateral spread and persistence), and soil properties. Although Gleason model showed better fit to data (both non-log and log transformation) and its intercept was more sensitive to tested biological characteristics, the Arrhenius model was more sensitive when correlating biological characteristics and slope. Choice of model according to best fit criteria restricts possibilities of biological interpretation and deserves further study.

Deeply gapped vegetation patterns: On crown/root allometry, criticality and desertification

The dynamics of vegetation is formulated in terms of the allometric and structural properties of plants. Within the framework of a general and yet parsimonious approach, we focus on the relationship between the morphology of individual plants and the spatial organization of vegetation populations. So far, in theoretical as well as in field studies, this relationship has received only scant attention. The results reported remedy to this shortcoming. They highlight the importance of the crown/root ratio and demonstrate that the allometric relationship between this ratio and plant development plays an essential part in all matters regarding ecosystems stability under conditions of limited soil (water) resources. This allometry determines the coordinates in parameter space of a critical point that controls the conditions in which the emergence of self-organized biomass distributions is possible. We have quantified this relationship in terms of parameters that are accessible by measurement of individual plant characteristics. It is further demonstrated that, close to criticality, the dynamics of plant populations is given by a variational Swift–Hohenberg equation. The evolution of vegetation in response to increasing aridity, the conditions of gapped pattern formation and the conditions under which desertification takes place are investigated more specifically. It is shown that desertification may occur either as a local desertification process that does not affect pattern morphology in the course of its unfolding or as a gap coarsening process after the emergence of a transitory, deeply gapped pattern regime. Our results amend the commonly held interpretation associating vegetation patterns with a Turing instability. They provide a more unified understanding of vegetation self-organization within the broad context of matter order–disorder transitions.