Shoot Biomass Ratio Research Articles

The overlooked effects of environmental impacts on root:shoot ratio in experiments and soil-crop models

Process-based soil-crop models are becoming increasingly important to estimate the effects of agricultural management practices and climate change impacts on soil organic carbon (C). Although work has been done on the effects of crop type and climate on the root:shoot (biomass) ratio, there is a gap in research on the effects of specific environmental or management conditions such as drought, temperature, nutrient limitation, elevated CO2 or tillage on the root:shoot ratio and thus, atmospheric C sequestration. In this study, we quantified the effects of these factors on the root:shoot biomass ratio by reviewing the current literature, presented common simulation approaches and performed model simulations using different examples. Finally, we identified different research gaps with respect to the root:shoot ratio with the aim of better estimating and predicting atmospheric C sequestration. A predominantly positive response of the root:shoot ratio was observed in case of elevated CO2 (~12 %), low soil N levels (~44 %), and drought (~14 %). Soil tillage did not affect root:shoot ratio of the major field crops but increased it by ~15 % in case of wheat. There are only few field studies on air temperature increase and the results vary widely (mean − 48 %). The responses of tested models to the mentioned effects root:shoot ratio were slightly positive in case of CO2 elevation (0 to 2 %) and tillage (0 to 8 %), slightly to clearly positive in the case of drought and N limitation depending on the model (1 to 40 %), and very variable in case of the air temperature scenarios. Our study reveals large model uncertainty (especially on temperature effects), particularly for below ground processes that highlight knowledge gaps in simulating root:shoot ratio. We advocate for the need of more model-oriented specific experiments under abiotic stresses to help model improvement. Such research effort would enable more robust and reliable root:shoot ratio simulations.

Assemblages of rhizospheric and root endospheric mycobiota and their ecological associations with functional traits of rice.

The assembly processes and functions of root-associated mycobiota are among the most fascinating yet elusive topics in microbial ecology. Our results revealed that stochastic forces (dispersal limitation or ecological drift) act on fungal community assembly in both the rice rhizosphere and root endosphere at the early stage of plant growth. In addition, high covariations between the rhizosphere fungal community compositions and plant functional trait profiles were clearly demonstrated in the present study. This work provides empirical evidence of the root-associated fungal assembly principles and ecological relationships of plant functional traits with rhizospheric and root endospheric mycobiota, thereby potentially providing novel perspectives for enhancing plant performance.

Correlations of the root–shoot ratio with soil water content in the patchy alpine grassland of the north‐eastern Qinghai–Tibetan Plateau using electrical resistivity tomography

AbstractThe root–shoot biomass ratio (R:S) changing the soil water redistribution is not well understood due to a lack of nondestructive technology to characterize the coexistence of plants and soil. This study aims to assess the correlations of the R:S ratios of Achnatherum splendens with soil water content by electrical resistivity tomography (ERT) on the north‐western Qinghai–Tibet Plateau (QTP). During the growing season, an experimental plot including bare patches (BK) and low‐ (LD) and high‐density (HD) A. splendens subplots was designed to quantify soil volumetric water content under different soil depths and antecedent total precipitation conditions for 7 days (AP7). The results showed that the R:S ratio was positive with soil water content in the surface soil layer of 0–10 cm. The synergistic effect of the R:S ratio on soil water in the surface soil layer promoted an increase in surface soil water. However, the nonsynergistic effect in the middle soil layer weakened the soil water increasing, and the effect of the R:S ratio on soil water in the deep soil layer of 40–80 cm was not obvious. In HD, soil water increased between 0.08% and 0.95% and was highest under AP7 > 20 mm conditions. In LD, soil water increased in the surface and deep soil layers but decreased in the middle soil layer, especially under AP7 = 10–20 mm conditions (−1.23%). These findings provide valuable insights that patchy alpine grass survival strategy under future climate change on the QTP, and the results are beneficial to the development of soil–plant–atmosphere continuum models.

Effects of Drought on the Growth of Lespedeza davurica through the Alteration of Soil Microbial Communities and Nutrient Availability.

Lespedeza davurica (Laxm.) is highly important for reducing soil erosion and maintaining the distinctive natural scenery of semiarid grasslands in northwest China. In this study, a pot experiment was conducted to investigate the effects of drought (20% water-holding capacity) on biomass and its allocation, root characteristics, plant hormones, and soil microbial communities and nutrients after L. davurica was grown in a greenhouse. Drought reduced the total biomass of L. davurica but increased the root:shoot biomass ratio. In addition, drought altered the composition and structure of microbial communities by limiting the mobility of nutrients in non-rhizosphere soils. In particular, drought increased the relative abundances of Basidiomycota, Acidobacteria, Actinobacteria, Coprinellus, Humicola and Rubrobacter, which were closely positively related to the soil organic carbon, pH, available phosphorus, ammonia nitrogen (N) and nitrate N under drought conditions. Furthermore, soil fungi could play a more potentially significant role than that of bacteria in the response of L. davurica to drought. Consequently, our study uncovered the effects of drought on the growth of L. davurica by altering soil microbial communities and/or soil nutrients, thus providing new insights for forage production and natural grassland restoration on the Loess Plateau of China.

Complementary Nutrients in Decoupled Aquaponics Enhance Basil Performance

Aquaponics combines raising fish and growing plants by recycling water and nutrients to reduce water consumption and reliance on chemical fertilizers. Coupled aquaponics systems recirculate water between fish and plant crops, whereas decoupled systems send mineralized fish effluent and wastewater unidirectionally to an independent hydroponic loop. Decoupling enables changes to the water, such as pH adjustments and complementary nutrient additions, to promote plant performance. In this study, basil, Ocimum basilicum (L.), was transplanted into 4 L containers filled with decoupled aquaponic (DAP), nutrient-complemented decoupled aquaponic (DAP+), or chemical-based conventional hydroponic (CON) nutrient solutions and grown for 21 days at pH 5.8. Plants grown in DAP+ and CON had greater biomass, height, and Soil Plant Analysis Development (SPAD) chlorophyll index and lower root:shoot biomass ratios than those in DAP. Shoot fresh and dry biomass was 11% greater for CON than DAP+, while height, SPAD chlorophyll index, and root:shoot ratio did not differ. We concluded that added nutrients in DAP+ enhanced performance compared to DAP, and the biologically derived nutrition in DAP+ enhanced performance to be similar, but not equal, to CON. We cannot recommend specific adjustments to the targeted blend of complementary nutrients tested, but findings suggest that complementary nutrients are effective in decoupled aquaponics.

Assessment on Carbon Stock of Natural and Plantation Forest in Setema District, Jimma Zone, South West Ethiopia

A Carbon Stock of Natural and Plantation Forest in Setema District, Jimma, South West Ethiopia was conducted. Carbon (C) densities of the biomass and soil (0–40 cm) in the natural forest and plantations of E.globulus and C. lusitanica in the Setema forest were determined and compared. In the stratum or forest stand, sample plots of 20 m x 20 m,(square) were randomly laid to measure the biomass of woody plants, a total of 90 (30 in each stratum) sample plots were taken for C stock inventory. Biomass C densities were estimated from total tree height, breast height diameter and wood density using allometric functions developed for tropical species and an assumed C content of 50%. Belowground biomass C densities were estimated using root: shoot biomass ratios. Soil organic C (SOC) densities were calculated from measured organic carbon contents (0–20 and 20–40 cm layers) and modeled bulk density values. Mean total biomass C densities for natural forest were greater than those of the plantations, and mean total SOC densities for plantations were greater than those of the natural forest, and the difference was significant (p < 0.05) in the cases of plantation and natural forest, but not significant in SOC in the case of E. globulus plantation species. Natural forests can store more total C stocks than plantations of exotic species, but the difference between natural forest and plantation of exotic was depended on plantation species. Therefore, species selection is vital when establishing tree plantations with the aim of the restoration of degraded soils and biomass carbon stocks. Conservation of the natural forest will have an imperative implication to the total C density and ensuring its viability. Keywords: biomass; carbon stocks ; C. lusitanica; E. globulus; natural forest ; soil carbon stocks DOI: 10.7176/JETP/12-1-01 Publication date: January 31 st 2022

A global map of root biomass across the world's forests

Abstract. As a key component of the Earth system, roots play a key role in linking Earth's lithosphere, hydrosphere, biosphere and atmosphere. Here we combine 10 307 field measurements of forest root biomass worldwide with global observations of forest structure, climatic conditions, topography, land management and soil characteristics to derive a spatially explicit global high-resolution (∼ 1 km) root biomass dataset, including fine and coarse roots. In total, 142 ± 25 (95 % CI) Pg of live dry-matter biomass is stored belowground, representing a global average root : shoot biomass ratio of 0.25 ± 0.10. Earlier studies (Jackson et al., 1997; Robinson, 2007; Saugier et al., 2001) are 44 %–226 % larger than our estimations of the total root biomass in tropical, temperate and boreal forests. The total global forest root biomass from a recent estimate (Spawn et al., 2020) is 24 % larger than this study. The smaller estimation from this study is attributable to the updated forest area, spatially explicit aboveground biomass density used to predict the patterns of root biomass, new root measurements and the upscaling methodology. We show specifically that the root shoot allometry is one underlying driver that has led to methodological overestimation of root biomass in previous estimations. Raw datasets and global maps generated in this study are deposited at the open-access repository Figshare (https://doi.org/10.6084/m9.figshare.12199637.v1; Huang et al., 2020).

Effects of Sediments Phosphorus Inactivation on the Life Strategies of Myriophyllum spicatum: Implications for Lake Restoration

Eutrophication often results in the loss of submerged vegetation in shallow lakes and turns the lake to be a turbid state. Recovery of submerged macrophytes is the key in the restoration of shallow eutrophic lakes to create a clear water state. However, internal loading control was considered as the critical process for the recovery of submerged macrophytes in shallow lakes after the external nutrient reduction. Phoslock® (Lanthanum modified bentonite) is a useful passivation material in controlling the internal loadings (release of phosphorus from the sediments), which was applied to restore the eutrophic lakes. However, the effects of Phoslock® on the growth and life strategies of submerged macrophytes are less focused so far. In the present study, we studied the responses in the growth and morphological characteristics of Myriophyllum spicatum to the addition of Phoslock® to the sediments. Our results showed that the addition of Phoslock® significantly decreased the contents of bioavailable forms of phosphorus in the sediments, such as redox-sensitive phosphorus bound to Fe and Mn compounds (BD–P), phosphorus bound to aluminum (Al–P) and organic phosphorus (Org–P). However, the concentration of the non-bioavailable forms of phosphorus in the sediments, such as calcium bound phosphorus (Ca–P), increased significantly in the Phoslock® treatments compared with the controls. At the end of the experiments, the total biomass, aboveground biomass and relative growth rate (RGR) of M. spicatum decreased significantly in the Phoslock® mesocosms compared with the controls. In contrast, the wet root biomass, root–shoot biomass ratio, root numbers and root length of M. spicatum were significantly higher in the Phoslock® treatments than that in the controls. Our results indicated that the growth of M. spicatum was suppressed by the addition of Phoslock®, and thus the biomass was decreased; however, the increase of root biomass might be beneficial to the inhibition of phosphorus release and resuspension of sediments and to the restoration of the lake ecosystem.

Hydrochar from sugarcane industry by-products: assessment of its potential use as a soil conditioner by germination and growth of maize

BackgroundHydrothermal carbonization (HTC) is a thermochemical process to convert biomass in carbon-rich materials (hydrochar). The use of sugarcane industry by-products in HTC has been evaluated, generating a hydrochar rich in nutrients, which could be used as a soil conditioner. We raised the hypothesis that the application of hydrochar in soil can improve its nutrient characteristics, bringing a better environment and favouring plant growth, expecting a development similar to that one observed in anthropogenic soils.ResultsGermination studies were performed expecting a species-dependent response, using maize and tomato seeds, whose development was assessed in two soluble fractions obtained from hydrochar aiming to evaluate different rhizosphere conditions. The results showed a better development of maize, especially in the aqueous soluble fraction, whose nutrient concentration was lower than that of the acid soluble fraction, as well as the organic composition. Maize growth in soils showed a better initial development in ultisol compared to oxisol, this being inferred by root:shoot biomass ratio and by scanning electron microscopy (SEM) images. However, the development of maize was better in anthropogenic soil compared to soils that received hydrochar.ConclusionThe maize growth, compared with that carried out in anthropogenic soil, suggests that during the period evaluated the addition of hydrochar in soil did not have a negative effect upon maize development in its initial phase, and could have even favoured rooting in ultisol.

Aboveground and belowground biomass and its' allometry for Salsola passerina shrub in degraded steppe desert in Northwestern China

AbstractKnowledge of the biomass allometry and partitioning is essential for understanding shrub adaptive strategies to degraded habitats as well as for estimating organic carbon storage. We studied biomass accumulation, allocation patterns, and allometric models of Salsola passerina shrub in the Alxa Desert steppe, Northwestern China. We measured aboveground and belowground biomass accumulation across different ages (0–50 years) by destructive sampling. The biomass allocation patterns between aboveground biomass, leaves, branches, and roots were studied by fitting allometric functions for both pooled and age‐classed data. Allometric biomass models were developed by regressing on single‐input variable of basal diameter, crown area, height, and age alone or on the pairwise variables of above four parameters. Biomass accumulation increased with age, aboveground components represented 86–89% of the total biomass, root to shoot biomass ratios increased with shrub age. Allometry patterns of S. passerina were relatively constant, and the growth rate of root was faster than that of aboveground components. Allometric models with two‐input variables were obviously better than single variable models. Crown area and basal diameter were the best predictors for biomass of S. passerina shrub.

Effects of Soil Microbes on Functional Traits of Loblolly Pine (Pinus taeda) Seedling Families From Contrasting Climates.

Examining factors that influence seedling establishment is essential for predicting the impacts of climate change on tree species’ distributions. Seedlings originating from contrasting climates differentially express functional traits related to water and nutrient uptake and drought resistance that reflect their climate of origin and influence their responses to drought. Soil microbes may improve seedling establishment because they can enhance water and nutrient uptake and drought resistance. However, the relative influence of soil microbes on the expression of these functional traits between seedling families or populations from contrasting climates is unknown. To determine if soil microbes may differentially alter functional traits to enhance water and nutrient uptake and drought resistance between dry and wet families, seeds of loblolly pine families from the driest and wettest ends of its geographic range (dry, wet) were planted in sterilized sand (controls) or in sterilized sand inoculated with a soil microbial community (inoculated). Functional traits related to seedling establishment (germination), water and nutrient uptake and C allocation (root:shoot biomass ratio, root exudate concentration, leaf C:N, leaf N isotope composition (δ15N)), and drought resistance (turgor loss point, leaf carbon isotope composition (δ13C)) were measured. Then, plants were exposed to a drought treatment and possible shifts in photosynthetic performance were monitored using chlorophyll fluorescence. Inoculated plants exhibited significantly greater germination than controls regardless of family. The inoculation treatment significantly increased root:shoot biomass ratio in the wet family but not in the dry family, suggesting soil microbes alter functional traits that improve water and nutrient uptake more so in a family originating from a wetter climate than in a family originating from a drier climate. Microbial effects on photosynthetic performance during drought also differed between families, as photosynthetic performance of the dry inoculated group declined fastest. Regardless of treatment, the dry family exhibited a greater root:shoot biomass ratio, root exudate concentration, and leaf δ15N than the wet family. This indicates that the dry family allocated more resources belowground than the wet and the two family may have used different sources of plant available N, which may be related to their contrasting climates of origin and influence their drought resistance. Examination of variation in impacts of soil microbes on seedling physiology improves efforts to enhance seedling establishment and beneficial plant-microbe interactions under climate change.

Direct and indirect effect of seed size on seedling survival along an experimental light availability gradient

Theoretical models of life-history strategies assume a positive relationship between seed size and subsequent offspring survival (seed size–survival relationship). There is limited empirical evidence, however, on how this relationship changes across environments or in relationship to seedling traits. Moreover, characterizing the dynamics of seedling recruitment under natural conditions is central to understanding how seedling recruitment may in turn affect large-scale ecological processes. Here, first-year seedling survival was monitored from emergence for 303 angiosperms species originated from alpine and sub-alpine meadows of the eastern Tibetan Plateau grasslands, across an experimental light gradient consisting of four treatments. We used linear models (LM) and phylogenetic generalized linear models (PGLM) to test for the seed size–survival relationship, and how this relationship differed across light treatments. We also used path analysis (PA) and phylogenetic confirmatory path analysis (PPA) to assess how seed size interacted with other seedling traits (seedling emergence time, specific leaf area, root: shoot biomass ratio, and biomass growth) to either directly or indirectly affect seedling survival. We found seed size to be positively associated with seedling survival only under low to medium light treatments only in LM (not in PGLM). PA and PPA revealed that the positive effect of seed size on seedling survival was indirect, mainly acting via biomass growth. Under low light, larger seeds exhibited greater biomass growth, which in turn increased seedling survival. In contrast, the direct effect of seed size on seedling survival is negative. In sum, the seed size–survival relationship appears to be both environmentally and phylogenetically dependent. The survival advantage of large seeds appears to be the result of their ability of higher biomass growth after emergence in low resource environments. However, our results also suggest there may be an underlying trade-off with larger seeds facing a lesser, but direct risk of increased mortality. The influence of environment on seedling traits, the interaction among traits, and phylogeny should be taking into consideration when modeling the dynamics of seedling recruitment.

Phenotypic plasticity of four Chenopodiaceae species with contrasting saline-sodic tolerance in response to increased salinity-sodicity.

It is unknown whether phenotypic plasticity in fitness‐related traits is associated with salinity–sodicity tolerance. This study compared growth and allocation phenotypic plasticity in two species with low salinity–sodicity tolerance (Chenopodium acuminatum and C. stenophyllum) and two species with high salinity–sodicity tolerance (Suaeda glauca and S. salsa) in a pot experiment in the Songnen grassland, China. While the species with low tolerance had higher growth and allocation plasticity than the highly tolerant species, the highly tolerant species only adjusted their growth traits and maintained higher fitness (e.g., plant height and total biomass) in response to increased soil salinity–sodicity, with low biomass allocation plasticity. Most plasticity is “apparent” plasticity (ontogenetic change), and only a few traits, for example, plant height:stem diameter ratio and root:shoot biomass ratio, represent “real” plasticity (real change in response to the environment). Our results show that phenotypic plasticity was negatively correlated with saline–sodic tolerance and could be used as an index of species sensitivity to soil salinity–sodicity.

Influence of sediment types on <i>Vallisneria spiralis</i>, <i>Radix auricularia</i> and their relationships with herbivory

沉水植物和螺类都是水生生态系统的重要组成部分，两者的牧食关系也是水生食物网中重要的一环，而不同的基质类型可能会影响两者的生长和改变沉水植物对螺类牧食的防御策略.以耳萝卜螺（Radix auricularia）和苦草（Vallisneria spiralis）为对象，研究基质类型、螺类牧食对沉水植物的生长及防御策略的影响，以及基质类型及沉水植物对螺类生长和生理特征的影响.研究发现，螺类牧食和基质类型对苦草生长和元素特征具有显著的影响，存在螺类牧食时，泥沙基质和沙基质苦草的相对生长速率显著降低，泥沙、沙和泥基质苦草地上生物量分别减少了67.74%、58.58%和17.84%，根冠比分别升高了177.51%、217.23%和1.44%；且泥沙基质中苦草的叶片数显著低于无牧食组.不同基质类型下，牧食对苦草总碳含量无显著影响，但泥和泥沙组中，螺类牧食使苦草的总氮含量均显著降低，碳氮比均显著升高；沙基质下，螺类牧食使苦草总酚含量显著降低.基质类型对螺类的形态特征（除壳宽外）、生长及元素含量均无显著影响.总体来看，基质类型对耳萝卜螺牧食和苦草防御策略具有一定程度的影响，但对螺类的生长及元素特征基本无影响.本研究可以为牧食理论的研究提供基础数据支持，也可为沉水植被恢复、水生生态系统稳定提供参考，但基质类型对螺草牧食关系的长期影响，仍需进一步深入研究.;Submerged plants and snails both are important components of aquatic ecosystems. Their relationships with herbivory also play an important role on the aquatic food web, and different sediment types may affect the growth of them and change the defensive strategy of submerged plant against snail herbivory. By taking Vallisneria spiralis and Radix auricularia as the research object in this research, we studied the effects of sediment types, snail herbivory on the growth submerged plants and the defensive strategies change, and also studied the effects of sediment types on snail growth and physiological characteristics. Our results showed that snail herbivory and sediment types have a significant impact on the growth and elemental characteristics of V. spiralis. In the presence of snail herbivory, the relative growth rate of V. spiralis in mixture and sand sediment both were significantly reduced. The shoot biomass of V. spiralis in mixture, sand and mud sediment were decreased by 67.74%, 58.58% and 17.84%, respectively, and the root:shoot biomass ratio increased by 177.51%, 217.23% and 1.44%, respectively. The leaves number of V. spiralis in mixture was significantly reduced with snail herbivory. Under different sediment types, the herbivory had no significant effect on the total carbon content of V. spiralis. However, the snail herbivory significantly reduced the total nitrogen content of V. spiralis, and C/N increased significantly in mud and mixture sediment. The total phenols content of V. spiralis was significantly reduced in sand sediment. The sediment types had no significant effect on the morphological characteristics (except for shell width), growth and element content of R. auricularia. In conclusion, the sediment types influenced on the snail herbivory and the defense strategy of V. spiralis in some extent, but had no effect on the growth and elemental characteristics of R. auricularia. This study can provide basic data support for the research of herbivory theory, and also provide reference for submerged vegetation restoration and aquatic ecosystem stability. However, the long-term effects of sediment types on submerged plants, snails, and their relationships with herbivory need to be further studied.

Effectiveness of pig sludge as organic amendment of different textural class mine tailings with different periods of amendment-contact time

The present study assesses the effect of tailing texture (loamy sand (LT) and sandy loam (ST)), dose of pig sludge (0, 50, 100 and 200 t ha−1) and amendment-contact time (14, 28 and 42 days) on physicochemical quality of amended substrate using Lolium perenne var Nui as a bioindicator. The main properties of LT differed of ST in levels of total organic carbon (0.19 and 0.58%), in pH (4.6 and 8.5), total Cu (202 and 1647 mg kg−1) and Zn content (31 and 137 mg kg−1). Soil pore water of experimental substrates was characterized for pH, electrical conductivity (EC) and Cu2+ ion activity (pCu2+) while ammonium nitrogen (NH4+-N), infiltration rate and general physicochemical characteristics were measured in substrates. Shoot biomass (SB), root biomass (RB) and the RB:SB ratio was calculated for L. perenne. The results showed there to be a significant interaction (p < 0.05) between tailing texture, sludge dose and amendment-contact time for pCu2+, infiltration rate, SB, RB, and RB: SB ratio, but not for pH, EC, or NH4+-N. However, sludge dose and amendment-contact time significantly affected all variables. By increasing dosages of pig sludge, pore water pH increased, and this was associated with decreases in pCu2+ and the infiltration rate. High doses of pig sludge (100 and 200 t ha−1) impaired growth of L. perenne irrespective of tailing texture and amendment-contact time, likely because of the rise of EC (up to 14 mS cm−1). For both tailing textures, the highest biomass was obtained after incorporation of 50 t ha−1 of pig sludge, with increasing values as amendment-contact time rose. In conclusion, effective management of pig sludge for tailing reclamation should guarantee doses <50 t ha−1 and amendment-contact time >28 days, irrespective of tailing texture.

Short-term effects of tillage and residue on spring maize yield through regulating root-shoot ratio in Northeast China

In recent years, yield instability of spring maize becomes increasingly pronounced under the traditional cropping system. In 2014 and 2015, short-term effects of tillage (plow-till, rotary-till and no-till) and residue (removal and incorporation) on soil properties, maize growth and yield were investigated in a brown soil region. Our results indicated that short-term reduced tillage (rotary-till and no-till) and residue incorporation promoted soil properties and maize growth. Compared with plow-till, rotary-till and no-till decreased soil bulk density and compaction below the plough layer (~30 cm). The soil organic carbon (SOC), total nitrogen and C:N of surface soil layers increased under the rotary-till (0–20 cm) and no-till (0–10 cm), which were higher in 0–30 cm soil layers for residue incorporation. For both years, root characteristics of root diameter (RAD) and root surface area density (RSD), biomass indexes of root biomass (RB), shoot biomass (SB) and root-shoot ratio (R:S) were increased under these short-term treatments. Although there were positive relationships between soil water content (SWC), C:N, RAD, RSD, RB, SB, R:S and yield, structural equation modeling showed maize yield was directly controlled by R:S. These findings will have important implications for improving the current cropping system (i.e., plow-till with residue removed) in this area.

Dominance of an alien shrub Rhus typhina over a native shrub Vitex negundo var. heterophylla under variable water supply patterns.

Temporal heterogeneity of a resource supply can have a profound effect on the interactions between alien and native plant species and their potential invasiveness. Precipitation patterns may be variable and result in a higher heterogeneity of water supply with global climate change. In this study, an alien shrub species, Rhus typhina, introduced to China from North America and a native shrub species, Vitex negundo var. heterophylla, were grown in monoculture and mixed culture under different water supply regimes, with four levels of water supply frequencies but with a constant level of total supplied water. After 60 days of treatments, the alien species was found to be the superior competitor in the mixed culture and was unaffected by changes in the water supply pattern. The dominance of R. typhina was mainly owing to its greater biomass and effective modulation of leaf physiology. However, in the mixed culture, V. negundo var. heterophylla exhibited both leaf- and whole-plant-level acclimations, including higher leaf length to petiole length and root to shoot biomass ratios, and lower specific leaf weight and leaf length to leaf width ratio. Plant height of V. negundo var. heterophylla was comparable to that of R. typhina in the mixed culture, which is a strategy to escape shading. Although water treatments had little effect on most traits in both species, the possible influence of water regimes should not be neglected. Compared with high-frequency water supply treatments, more individuals of V. negundo var. heterophylla died in low-water-frequency treatments when in competition with R. typhina, which may lead to species turnover in the field. The authors recommended that caution should be exercised when introducing R. typhina to non-native areas in the context of global climate change.

Insights into the functional relationship between cytokinin-induced root system phenotypes and nitrate uptake in Brassica napus

Root system architecture is the spatial arrangement of roots that impacts the capacity of plants to access nutrients and water. We employed pharmacologically generated morphological and molecular phenotypes and used in situ 15N isotope labelling, to investigate whether contrasting root traits are of functional interest in relation to nitrate acquisition. Brassica napus L. were grown in solidified phytogel culture media containing 1mM KNO3 and treated with the cytokinin, 6-benzylaminopurine, the cytokinin antagonist, PI-55, or both in combination. The pharmacological treatments inhibited root elongation relative to the control. The contrasting root traits induced by PI-55 and 6-benzylaminopurine were strongly related to 15N uptake rate. Large root proliferation led to greater 15N cumulative uptake rather than greater 15N uptake efficiency per unit root length, due to a systemic response in the plant. This relationship was associated with changes in C and N resource distribution between the shoot and root, and in expression of BnNRT2.1, a nitrate transporter. The root:shoot biomass ratio was positively correlated with 15N cumulative uptake, suggesting the functional utility of root investment for nutrient acquisition. These results demonstrate that root proliferation in response to external nitrate is a behaviour which integrates local N availability and the systemic N status of the plant.

Seedling stability in waterlogged sediments: an experiment with saltmarsh plants

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 590:95-108 (2018) - DOI: https://doi.org/10.3354/meps12463 Seedling stability in waterlogged sediments: an experiment with saltmarsh plants Regine Redelstein1,*, Gerhard Zotz2, Thorsten Balke2,3 1Plant Ecology and Ecosystems Research, University of Göttingen, 37077 Göttingen, Germany 2Institute of Biology and Environmental Sciences, University of Oldenburg, 26111 Oldenburg, Germany 3School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK *Corresponding author: regine.redelstein@biologie.uni-goettingen.de ABSTRACT: Saltmarsh seedlings are exposed to extreme soil conditions in combination with mechanical disturbance by waves and tides, especially at the seaward fringe. We tested whether soil waterlogging affects resistance of seedlings to physical disturbance, thereby potentially influencing the distribution of saltmarsh species. A mesocosm experiment was conducted to investigate effects of waterlogging on plant traits, in particular root growth, and tolerance of seedlings to sediment erosion. Three species, each dominating different elevations in NW European salt marshes (Salicornia europaea, Atriplex portulacoides and Elytrigia atherica), were selected for the experiments. Individual seedlings were grown under different waterlogging treatments and finally subjected to an erosion treatment. The depth of erosion at which the seedlings toppled (Ecrit) was determined and related to above- and below-ground morphological traits of the seedlings. Resistance to erosion decreased in all 3 species from drained to completely waterlogged soil conditions, with the strongest negative impact of waterlogging on the upper marsh species E. atherica. Root length and biomass, shoot biomass and the root:shoot biomass ratio were the most important traits positively affecting Ecrit. The experiment demonstrates that rapid root growth is essential for the stability of seedlings, and is presumably of great importance for their successful establishment on tidal flats where sediment erosion may be a limiting factor. Root growth is in turn affected by a species-specific response to waterlogging. Our study suggests that this species-specific effect of waterlogging on seedling stability contributes to species sorting along the inundation gradient of coastal ecosystems. KEY WORDS: Coastal ecosystems · Erosion · Root growth · Species distribution · Tidal inundation · Vegetation establishment Full text in pdf format Supplementary material PreviousNextCite this article as: Redelstein R, Zotz G, Balke T (2018) Seedling stability in waterlogged sediments: an experiment with saltmarsh plants. Mar Ecol Prog Ser 590:95-108. https://doi.org/10.3354/meps12463 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 590. Online publication date: March 12, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Assessing the effect of phosphorus application on early growth of maize at Sunderbazar, Lamjung, Nepal

Phosphorus (P) is an essential nutrient element for maize production. A pot experiment was conducted during May-June, 2015 to assess the effects of different rates of P on early growth of maize plant at Sundarbazar, Lamjung. Two maize varieties (Rato Makai and Poshilo Makai-1) were subjected to four P levels (0 kg ha-1,13 kg ha-1, 18 kg ha-1, and 23 kg ha-1) in randomized complete block design with four replications. The effects of different P level on root elongation, root biomass, plant height, root shoot biomass ratio and total dry matter were investigated at 45 days after sowing. For all parameters, the maximum value was obtained when soil was added with 18 kg P ha-1 &amp; the minimum value under the control of 0 kg P ha-1. Maize varieties differed significantly in terms of all the parameters under study, and Poshilo Makai-1 performed better than Rato Makai at all P levels. So, from this result, it can be concluded that Poshilo Makai-1 appeared to be P efficient over Rato Makai at early growth stage. However, it would be necessary to look at the response of crop up to maturity and at wider range of P to have the better insight of their relative performance.