High Food Availability Research Articles

Ancestral ecological regime shapes reaction to food limitation in the Least Killifish, Heterandria formosa.

Populations with different densities often show genetically based differences in life histories. The divergent life histories could be driven by several agents of selection, one of which is variation in per‐capita food levels. Its relationship with population density is complex, as it depends on overall food availability, individual metabolic demand, and food‐independent factors potentially affecting density, such as predation intensity. Here, we present a case study of two populations of a small live‐bearing freshwater fish, one characterized by high density, low predation risk, low overall food availability, and presumably low per‐capita food levels, and the other by low density, high predation risk, high overall food availability, and presumably high per‐capita food levels. Using a laboratory experiment, we examined whether fish from these populations respond differently to food limitation, and whether size at birth, a key trait with respect to density variation in this species, is associated with any such differential responses. While at the lower food level growth was slower, body size smaller, maturation delayed, and survival reduced in both populations, these fitness costs were smaller in fish from the high‐density population. At low food, only 15% of high‐density fish died, compared to 75% of low‐density fish. This difference was much smaller at high food (0% vs. 15% mortality). The increased survival of high‐density fish may, at least partly, be due to their larger size at birth. Moreover, being larger at birth enabled fish to mature relatively early even at the lower food level. We demonstrate that sensitivities to food limitation differ between study populations, consistent with selection for a greater ability to tolerate low per‐capita food availability in the high‐density population. While we cannot preclude other agents of selection from operating in these populations simultaneously, our results suggest that variation in per‐capita food levels is one of those agents.

Diminished growth and vitality in juvenile Hydractinia echinata under anticipated future temperature and variable nutrient conditions

In a warming climate, rising seawater temperatures and declining primary and secondary production will drastically affect growth and fitness of marine invertebrates in the northern Atlantic Ocean. To study the ecological performance of juvenile hydroids Hydractinia echinata we exposed them to current and predicted water temperatures which reflect the conditions in the inter- and subtidal in combination with changing food availability (high and low) in laboratory experiments. Here we show, that the interplay between temperature stress and diminished nutrition affected growth and vitality of juvenile hydroids more than either factor alone, while high food availability mitigated their stress responses. Our numerical growth model indicated that the growth of juvenile hydroids at temperatures beyond their optimum is a saturation function of energy availability. We demonstrated that the combined effects of environmental stressors should be taken into consideration when evaluating consequences of climate change. Interactive effects of ocean warming, decreasing resource availability and increasing organismal energy demand may have major impacts on biodiversity and ecosystem function.

Soil priming effect and its responses to nutrient addition along a tropical forest elevation gradient.

Priming plays important roles in terrestrial carbon cycling, but the patterns and drivers of priming and its responses to nutrient addition in tropical forests remain unclear. By collecting soils along a tropical forest elevation gradient, we conducted an incubation experiment with 13 C-labeled glucose and nutrient (N and/or P) additions. Results showed that priming effects increased soil organic matter decomposition by 44±12% across elevations, and priming intensity decreased significantly with elevation. Among soil and microbial properties, soil organic carbon (SOC) content and pH were two key factors negatively and positively regulating priming, respectively. Across elevations, the additions of N, P, or both of them (NP) did not significantly change priming. However, the variations in the effects of nutrient (N and/or P) addition on priming significantly correlated with initial soil nutrient (N or P) availability. The intensity for the effects of N addition on priming decreased significantly with initial soil N availability, and that for the effects of P and NP addition on priming decreased with initial soil P availability. Based on these relationships, we proposed a conceptual framework linking stoichiometric decomposition and nutrient mining hypotheses, in which the former dominates in low-nutrient availability soils and the latter dominates in high-nutrient availability soils. This conceptual framework can help to explain the contrasting effects of nutrient addition on priming. Collectively, our findings highlight the roles of SOC content and soil pH in regulating priming intensity, and the role of initial soil nutrient availability in regulating the effects of nutrient addition on priming.

Contribution of anecic and epigeic earthworms to biological control of Fusarium graminearum in wheat straw

Earthworms have proved to contribute to plant health indirectly, by improvement of soil physical and chemical properties, as well as directly, through suppression of plant pathogens. Fusarium Head Blight, caused primarily by Fusarium graminearum, is one of the most important cereal diseases, with severe detrimental effects on yield and grain quality worldwide, and significant effect on grain safety due to the accumulation of mycotoxins produced by the fungus. Earthworms could reduce the residue-borne inoculum density of F. graminearum through different mechanisms, including direct competition by residue consumption, growth inhibition caused by the earthworm coelomic fluid, mechanical disruption of fungal hyphae, and burying crop residue which reduce the chances for the fungus to release spores for head infection. Thus, the aim of this study was to assess the effects of anecic and epigeic earthworms on wheat straw and on F. graminearum inoculum. For this, PVC cylinders (microcosms 14.5 cm diameter, 30 cm height) were filled with moist soil mix, wheat straw was evenly distributed on the soil surface (inoculated with Fusarium, soil microorganisms or sterile) and three earthworm species (Aporrectodea longa, Lumbricus rubellus or Lumbricus terrestris) were tested. Since the response of earthworms may change according to conditions of soil moisture and food availability, two different experiments were arranged. The first Experiment represented a sub-optimal situation for earthworms regarding soil moisture and feeding conditions, which was obtained by scarce watering of the microcosms with a consequent decrease in soil water content during incubation, and by not adding cow manure as supplementary food source. In the second experiment, soil was enriched with cow manure as feed for the earthworms and soil moisture was maintained above 25%. Results from qPCR analysis revealed that F. graminearum inoculum on straw was reduced to undetectable amounts by L. rubellus and A. longa when the feeding conditions were limited, while no significant differences compared with the control without earthworms were found when earthworms had high food availability (α = 0.05). Straw coverage on soil surface was reduced by L. rubellus (epigeic) in both experiments (p < 0.0001), while A. longa (anecic) just did so under optimal conditions. L. terrestris (anecic), only tested under optimal conditions, reduced soil cover significantly more than the other two species (p < 0.0001). Negative effect of this fungus was not observed on the studied earthworms. Both anecic and epigeic earthworms tested showed potential to contribute to biological control of F. graminearum in wheat straw. This control may occur by reducing straw on surface, reducing the pathogen inoculum on straw, or both, depending on the environmental conditions and their response according to their ecological group and species. The possibilities to optimize earthworm capacity for biological control of fungal diseases in practical agriculture, under changing weather and organic matter supply conditions, are discussed.

Variability in strength of byssus attachment and index condition of subtidal mussels during the maximum growth stage

Local environmental conditions can have strong effects on ecophysiological responses in bivalve molluscs. Molluscs must allocate the energetic resources acquired in their habitats to survival and fitness. In this study, we investigated the spatial and temporal patterns of response in relation to byssus strength and soft tissue weight during the maximum growth stage in the subtidal mussel Mytilus galloprovincialis between March and July 2015 in the Ría de Arousa (NW Spain). Mussels growing in high-energy environments secreted stronger byssus than those inhabiting low-energy sites. The integrated values of wave height and food availability for the previous 15 days showed a positive relationship explaining 45% and 9% of total variability in tenacity of the byssus threads. Differences in condition index were greatest between the northern (highest values) and southern sites at the mouth of the ria owing to differences in food availability. Despite similar hydrodynamic energy values, the high food availability in the exposed northern zones supplied sufficient energetic resources for both strong byssus secretion and high CI. Despite lower food availability, high CI values were also reached in mussels in the innermost, sheltered sites, because of the low need for survival with strong attachment. The condition index was positively correlated with temperature and food availability integrated during 45 previous days prior explained a 57% and 13% of total variance, respectively, while wave height explained 2% but with an inverse relationship. Environmental differences between the geographical zones of the estuary modulated byssus secretion functionality affecting the soft tissues status of mussels.

Fasting and fasting-mimicking treatment activate SIRT1/LXRα and alleviate diabetes-induced systemic and microvascular dysfunction.

Homo sapiens evolved under conditions of intermittent food availability and prolonged fasting between meals. Periods of fasting are important for recovery from meal-induced oxidative and metabolic stress, and tissue repair. Constant high energy-density food availability in present-day society contributes to the pathogenesis of chronic diseases, including diabetes and its complications, with intermittent fasting (IF) and energy restriction shown to improve metabolic health. We have previously demonstrated that IF prevents the development of diabetic retinopathy in a mouse model of type 2 diabetes (db/db); however the mechanisms of fasting-induced health benefits and fasting-induced risks for individuals with diabetes remain largely unknown. Sirtuin 1 (SIRT1), a nutrient-sensing deacetylase, is downregulated in diabetes. In this study, the effect of SIRT1 stimulation by IF, fasting-mimicking cell culture conditions (FMC) or pharmacological treatment using SRT1720 was evaluated on systemic and retinal metabolism, systemic and retinal inflammation and vascular and bone marrow damage. The effects of IF were modelled in vivo using db/db mice and in vitro using bovine retinal endothelial cells or rat retinal neuroglial/precursor R28 cell line serum starved for 24h. mRNA expression was analysed by quantitative PCR (qPCR). SIRT1 activity was measured via histone deacetylase activity assay. NR1H3 (also known as liver X receptor alpha [LXRα]) acetylation was measured via western blot analysis. IF increased Sirt1 mRNA expression in mouse liver and retina when compared with non-fasted animals. IF also increased SIRT1 activity eightfold in mouse retina while FMC increased SIRT1 activity and expression in retinal endothelial cells when compared with control. Sirt1 expression was also increased twofold in neuronal retina progenitor cells (R28) after FMC treatment. Moreover, FMC led to SIRT1-mediated LXRα deacetylation and subsequent 2.4-fold increase in activity, as measured by increased mRNA expression of the genes encoding ATP-binding cassette transporter (Abca1 and Abcg1). These changes were reduced when retinal endothelial cells expressing a constitutively acetylated LXRα mutant were tested. Increased SIRT1/LXR/ABC-mediated cholesterol export resulted in decreased retinal endothelial cell cholesterol levels. Direct activation of SIRT1 by SRT1720 in db/db mice led to a twofold reduction of diabetes-induced inflammation in the retina and improved diabetes-induced visual function impairment, as measured by electroretinogram and optokinetic response. In the bone marrow, there was prevention of diabetes-induced myeloidosis and decreased inflammatory cytokine expression. Taken together, activation of SIRT1 signalling by IF or through pharmacological activation represents an effective therapeutic strategy that provides a mechanistic link between the advantageous effects associated with fasting regimens and prevention of microvascular and bone marrow dysfunction in diabetes.

Lithological and Topographic Impact on Soil Nutrient Distributions in Tectonic Landscapes: Implications for Pleistocene Human-Landscape Interactions in the Southern Kenya Rift

Tectonically active regions are characterized by complex landscapes comprising soils with heterogeneous physicochemical properties. Spatial variability of nutrient sources enhances landscape biodiversity and creates heterogeneous habitats potentially attractive for animals and humans. In this study, we analyze the role of geological processes in the distributions of soil nutrients in the southern Kenya Rift, a key region in the interpretation of early human-landscape interactions. Our aim is to determine how spatial variations in rock chemistry, as well as topographic gradients and localized zones of rock fracturing from tectonic faulting determine the distributions of plant-available soil nutrients in soils. We hypothesize that present-day soil nutrient levels reflect the long-term chemical and geomorphological characteristics of the landscape and underlying parent material, and that regions with high nutrient availability occur along pathways correlating with locations of hominin fossil sites. Analyses of 91 topsoil samples from the main geological units show that Calcium (Ca) deficiencies predominately occur in shallow soils developed on trachytic volcanic rocks and granitic gneisses, while high Ca levels are associated with basaltic parent material and sedimentary deposits of mixed sources. XRF analysis of rock samples confirms that CaO levels in trachyte rocks are significantly lower than those in basalts, and Ca mobilization in basalt is more effective than in trachyte. Along two toposequences in densely faulted basaltic and trachytic rocks, we observed slope dependent soil nutritional gradients and a systematic increase of the concentrations of Ca, Mg and SOC in topsoils of colluvial sediments downslope of active normal faults. Known hominin sites in the region are located either along corridors of long-term Ca availability or at short-term nutrient hotspots potentially related to active CO2 degassing along active fault zones. This implies a strategic advantage of Ca-rich regions for hominin subsistence strategies, such as provision of predictable constraints on the distribution and mobility of grazing animals in complex tectonic landscapes. Our study implies that geological processes impact nutrient distributions in the southern Kenya Rift. Results of this study have further implications for understanding the role of soils in the interpretation of hominin-landscape interactions in the early stages of human evolution.

Lianas have more acquisitive traits than trees in a dry but not in a wet forest

Abstract Lianas are increasing in relative abundance and biomass in many tropical forests. We tested the hypothesis that lianas conform to the fast and acquisitive end of the continuum of plant strategies, allowing lianas to acquire resources faster than trees. We assessed functional traits representative of the leaf (LES) and wood economics spectrum (WES), including plant hydraulics, in 16 liana and 16 tree species in the canopy of two tropical forests at the extremes of the climatic and geological gradient across the Isthmus of Panama. For both forests, we observed a trade‐off between the construction of more productive leaves with rapid turnover and expensive leaves with slower turnover. We also found trait variation associated with wood and hydraulic traits. These two axes were orthogonal, suggesting that trade‐offs at the leaf and stem, including plant hydraulics, operate independently. For the dry forest, lianas had cheaper and more efficient leaves than trees. For the wet forest, lianas and trees overlapped in leaf and stem characteristics. Moreover, the duration of green foliage highly explained the variation between dry forest species, reflecting different adaptations to drought. In the wet forest, fast‐growing species benefited from a higher return on investments of leaf vascular tissues than slow‐growing species and they had a higher capacity to transport water through the leaf. A higher capacity to construct more productive leaves and display leaves with lower costs may favour lianas over trees in light interception, photosynthetic rates, and growth under high light and nutrient availability in dry forests. Synthesis. Lianas in a dry tropical forest had a more acquisitive strategy than trees, characterized by more productive leaves and more efficient display for light interception. In dry environments, lianas appear to benefit from high‐light and nutrient‐rich soils and thus take advantage of higher resource conditions compared to trees. By contrast, in a wet tropical forest, lianas and trees overlapped in leaf and stem characteristics and lianas were not more acquisitive than trees. In wet environments, low light availability and nutrient‐poor soils in a context of low water limitation may constrain variation in resource acquisition strategies between lianas and trees.

Biological Impact of Ocean Acidification in the Canadian Arctic: Widespread Severe Pteropod Shell Dissolution in Amundsen Gulf

Increasing atmospheric CO2, cold water temperatures, respiration, and freshwater inputs all contribute to enhanced acidification in Arctic waters. However, ecosystem effects of ocean acidification (derived from anthropogenic and/or natural sources) in the Arctic Ocean are highly uncertain. Zooplankton samples and oceanographic data were collected in August 2012–2014 and again in August 2017 to investigate the pelagic sea snail,Limacina helicina, a biological indicator of the presence and potential impact of acidified waters in the Canadian Beaufort Sea. Between 2012 and 2014L. helicinaabundance ranged from &amp;lt;1 to 1942 Ind. m–2, with highest abundances occurring at stations on the Canadian Beaufort Shelf in 2012. The majority of individuals (66%) were located between 25 and 100 m depth, corresponding to upper halocline water of Pacific origin. In both 2014 and 2017, &amp;gt;85% ofL. helicinaassessed (n= 134) from the Amundsen Gulf region displayed shell dissolution and advanced levels of dissolution occurred at all stations. The severity of dissolution was not significantly different between 2014 and 2017 despite the presence of larger individuals that are less prone to dissolution, and higher food availability that can provide some physiological benefits in 2014. Corrosive water conditions were not widespread in the Amundsen Gulf at the time of sampling in 2017, and aragonite undersaturation (Ωar&amp;lt; 1) occurred primarily at depths &amp;gt;150 m. The majority of dissolution was observed on the first whorl of the shells strongly indicating that damage was initiated during the larval stage of growth in May or early June when sea ice is still present. Evidence of shell modification was present in 2014, likely supported by abundant food availability in 2014 relative to 2017. The proportion of damagedL. helicinacollected from coastal embayments and offshore stations is higher than in other Arctic and temperate locations indicating that exposure to corrosive waters is spatially widespread in the Amundsen Gulf region, and periods of exposure are extreme enough to impact the majority of the population.

Declines in occurrence of plants characteristic for a nutrient-poor meadow habitat are partly explained by their responses to nutrient addition and competition.

Species losses and local extinctions are alarmingly common, frequently as a consequence of habitat destruction. Nevertheless, many intact habitats also face species losses, most likely due to environmental changes. However, the exact drivers, and why they affect some species more than others in apparently intact habitats, are still poorly understood. Addressing these questions requires data on changes in occurrence frequency of many species, and comparisons of the responses of those species to experimental manipulations of the environment. Here, we use historic (1911) and contemporary (2017) data on the presence–absence of 42 plant species in 14 seemingly intact Molinia meadows around Lower Lake Constance to quantify changes in occurrence frequency. Then, we performed a common‐garden experiment to test whether occurrence frequencies in 1911 and changes therein by 2017 could be explained by responses of the 42 species to nutrient addition and competition with the acquisitive generalist grass Poa pratensis. Within the 14 still intact Molinia meadows, 36 of the 42 species had declined since 1911. As expected, nutrient addition generally led to increased biomass production of the 42 target species, and competition with P. pratensis had a negative effect. The latter was stronger at high nutrient availability. The more frequent species were in 1911 and the more they declined in frequency between 1911 and 2017, the less above‐ground biomass they produced in our experiment. Competition with P. pratensis magnified this effect. Our work highlights that environmental change can contribute to local extinction of species in otherwise intact habitat remnants. Specifically, we showed that increased nutrient availability negatively affected formerly widespread Molinia‐meadow species in competition with P. pratensis. Our study thus identified a likely mechanism for the decline in occurrence frequency of species in the remaining Molinia meadows.

Enhancement in yield and nutritive qualities of strawberry fruits by the application of organic manures and biofertilizers

The present study was carried out to elucidate the effects of organic manures (FYM, vermicompost and forest litter) and biofertilizers (Azotobacter chroococcum and Pseudomonas fluorescens) on plant growth, yield and fruits quality of strawberry (Fragaria ananassa Duch. cv. Chandler) under field conditions. Sixteen treatments (including a control) were used in this study. Among these, treatment T13 (50 % FYM + 50 % Vermicompost + Azotobacter + Pseudomonas) was found most effective to enhance plant growth parameters viz. plant height, plant spread, leaf area per plant, and induced early flowering. Maximum increase in yield per plant and yield per plot were achieved by the application of 50 % FYM + 50 % Vermicompost + Pseudomonas (T12), which was at par of T13. However, fruit quality parameters including ascorbic acid, total sugar, total phenolic content, and antioxidant capacity were found significantly higher in T13. Higher availability of nutrients (Nitrogen, Phosphorus and Potassium) in soil was also recorded in this treatment. Principle component analysis revealed that different treatments (T9 -T13, T15 and T16) showed positive effects on plant growth, yield and fruit quality parameters. Among these, T13 and T15 were found most effective to increase yield and fruit quality parameters. The PCA analysis also revealed that ‘Days to flowering’ was independent and negatively correlated to other planting value parameters. Similarly, total acid content in fruit did affect other fruit quality parameter, including antioxidant capacity. The combination of manures and biofertilizers has shown potential to increase crop yield and its nutritive properties under field conditions. Therefore, we concluded that the combination of biofertilizers with organic manures (especially, FYM and vermicompost) should be used for sustainably higher production of quality strawberries especially under organic farming system. Such approaches have a higher rationale with small farm or hill agriculture system where farmers are generally resource poor and have low input capacity.

Ecophysiological Performance of Proteaceae Species From Southern South America Growing on Substrates Derived From Young Volcanic Materials.

Southern South American Proteaceae thrive on young volcanic substrates, which are extremely low in plant-available phosphorus (P). Most Proteaceae exhibit a nutrient-acquisition strategy based on the release of carboxylates from specialized roots, named cluster roots (CR). Some Proteaceae colonize young volcanic substrates which has been related to CR functioning. However, physiological functioning of other Proteaceae on recent volcanic substrates is unknown. We conducted an experiment with seedlings of five Proteaceae (Gevuina avellana, Embothrium coccineum, Lomatia hirsuta, L. ferruginea, and L. dentata) grown in three volcanic materials. Two of them are substrates with very low nutrient concentrations, collected from the most recent deposits of the volcanoes Choshuenco and Calbuco (Chile). The other volcanic material corresponds to a developed soil that exhibits a high nutrient availability. We assessed morphological responses (i.e., height, biomass, and CR formation), seed and leaf macronutrient and micronutrient concentrations and carboxylates exuded by roots. The results show that G. avellana was less affected by nutrient availability of the volcanic substrate, probably because it had a greater nutrient content in its seeds and produced large CR exuding carboxylates that supported their initial growth. Embothrium coccineum exhibited greater total plant height and leaf P concentration than Lomatia species. In general, in all species leaf macronutrient concentrations were reduced on nutrient-poor volcanic substrates, while leaf micronutrient concentrations were highly variable depending on species and volcanic material. We conclude that Proteaceae from temperate rainforests differ in their capacity to grow and acquire nutrients from young and nutrient-poor volcanic substrates. The greater seed nutrient content, low nutrient requirements (only for G. avellana) and ability to mobilize nutrients help explain why G. avellana and E. coccineum are better colonizers of recent volcanic substrates than Lomatia species.

Drivers of land use complexity along an agricultural transition gradient in Southeast Asia

Agricultural systems in Southeast Asia are rapidly transitioning from subsistence-oriented to market-oriented agriculture. Driven by the highly complex and variable decision processes of individual farm households, these transitions have produced a diverse landscape mosaic across the region. Elucidation and characterization of underlying decision-making processes, and the factors that influence land use choices, are thus essential for sustainable land use planning. To enable a study that seeks to understand these linkages, data on plot-level 10-year land use history, management and farm performance indicators were collected from 163 households in the Northern Lao uplands and in the Central Highlands of Vietnam, areas chosen to represent two extremes of the transition gradient. The objectives of the study were (i) to describe plot-level sequence patterns of seasonal variation of land use over several years, (ii) to apply a sequence dissimilarity metric, the complexity index (CI), to measure land use transition in an agricultural system, and (iii) to identify the key drivers of land use change and their linkages with farm performance indicators and plot level characteristics through multi-dimensional analysis. CI allowed compressing historical land use data and quantifying land use complexity in a simple and efficient manner. Land use dynamics varied strongly between the two sites, with 66% of the land use types in the Laos site being completely replaced by others during the recall periods, compared to only 15% in the Vietnam site. Associated key drivers of land use change also differed significantly: while end use of agricultural products was the main driver behind land use changes in the Vietnam site, a more complex relationship between topography and management vs. land use change was evident in the Laos site. Likewise, land use complexity does not exhibit the same relationship with farm performance in the two sites: in the Central Highlands, households with higher food availability are half as likely to transition, while in the Lao uplands, land use complexity was significantly correlated with the Progress out of Poverty index. Multidisciplinary studies remain necessary to assess the impact of innovative sustainable intensification options on system performance and environmental sustainability, before policies are enacted to support their dissemination in Southeast Asian smallholder agricultural systems. Context-specific CI thresholds associated with system quality indicators could support this by informing decision-makers on the pace of agricultural transformation and its environmental impacts.

The incorporation of lime and NPK fertilizer on shallot production in peat soil

High acidity level and low nutrient availability are the most challenging factors of shallot production in peat soils. The purpose of this study was to find out the best lime material and the level of NPK fertilizer on shallot production in peat soil in Central Borneo, Indonesia. The experiment used was a Split Plot Design with three replications. The main plot was three types of lime material: 3 t ha−1 dolomite, 3 t ha−1 agriculture limestone and 1.5 t ha−1 calcium hydroxide. The subplots were ten combinations of NPK fertilizers. The results showed that lime materials and doses of NPK fertilizer had a significant effect on shallot growth and yield. Hydrated lime doses 1.5 t ha−1 and NPK fertilizer dose 100 kg N ha−1, 100 kg P2O5 ha−1 and 100 kg K2O ha−1 gave the highest bulb yield (7 t ha−1) compared to other trials. However, this bulb yield was lower compared to different adaptive cultivars from previous studies. Further experiments using higher levels of lime and adapted varieties are necessary to get the optimum bulb yield.

Response of shallots growth and yield to phosphate fertilizer and Trichoderma application on peat soil

Cultivating shallots on peat soils is quite challenging since it is considered less fertile regarding its high organic acid content and low nutrient availability. Trichoderma, as one of the plant-growth-promoting fungi (PGPF), is beneficial to promote shallots growth. However, there is still lack of information concerning its effectiveness and interaction effect with inorganic P fertilizer in peat soils. This study aimed to investigate the effect of Trichoderma application and P fertilization on the growth and yield of shallots on peat soils. A pot experiment arranged in a completely randomized design was conducted with two treatment factors. The first factor was P fertilizer comprised four application rates: 0, 100, 200, and 300 kg ha−1. Meanwhile, as the second factor, Trichoderma treatment consisted of four application rates: 0, 2, 4, and 6 g plant−1. The results showed an interaction effect of P treatment and Trichoderma on shallots growth and yield. A treatment combination of 2 g plant−1 Trichoderma without P fertilizer addition increased yield by 34% compared to control. This yield was relatively similar to 100 kg ha−1 P fertilizer without Trichoderma addition. It is proved that the Trichoderma application could reduce inorganic P fertilizer input.

Soil nutrients differentially influence root colonisation patterns of AMF and DSE in Australian plant species

This study determined the influence of soil nitrogen and phosphorus on the colonisation dynamics of arbuscular mycorrhizal fungi (AMF) and Dark Septate Endophytes (DSE) in plant species adapted to nutrient poor soils. Plant colonisation dynamics were investigated using a field experiment and a manipulative greenhouse experiment on Australian native seedlings. Tubestock of Poa labillardierei were transplanted into the field to large tracts of land of high and low nutrient availability, near Sydney, Australia, and root colonisation was determined from monthly plant collections over three months, between late austral autumn and through winter. In the greenhouse experiment, two native shrubs and one grass, respectively, Rhagodia candolleana, Dodonaea triquetra and P. labillardierei, were germinated from seeds and grown under a full factorial nitrogen and phosphorus fertilisation experiment for three months before root colonisation was determined. The selected study species were of varied mycotrophy. AMF colonisation in both experiments was lowest in plants from high nutrient treatments. Removal of either nitrogen or phosphorus from the fertiliser resulted in the same patterns of colonisation, with AMF being greater when either nutrient was removed. DSE colonisation was greatest in high nutrient soils. However, colonisation did not vary with nutrient treatments in the glasshouse experiment, suggesting that nitrogen and phosphorus minimally affect DSE colonisation. The difference in AMF and DSE colonisation patterns demonstrates a distinction in how different fungal symbionts are affected by abiotic factors. Both nitrogen and phosphorus are important drivers of colonisation dynamics of AMF. The results indicate the potential for disparate controls of AMF and DSE root associations.

Prolonged growth during the food-restricted dry season in a small African mammal

Abstract Studying how different environmental parameters, such as resource availability and ambient temperature, affect growth rates aids to understand the evolution of different growth strategies. Low levels of food availability restrict growth, and high ambient temperature can constrain growth via trade-offs between body temperature maintenance and heat produced during digestion. We studied growth of African striped mice (Rhabdomys pumilio), a small mammal living in a seasonally arid habitat. Striped mice are born during spring with high food availability and low ambient temperature, and typically enter the food-restricted dry season before reaching adulthood. We predicted low food availability and high ambient temperature would negatively affect growth. We therefore expected an extended period of slow growth during the long dry season. We repeatedly measured body length of 369 free-living individuals, examined how ambient temperature and food availability influenced growth rate, and seasonal changes in growth rate. In addition, we investigated whether mice (N = 27) born in summer (atypical breeding season) have slower growth rates than those born in spring. Growth rate increased with increasing food availability and decreased with increasing ambient temperature. Individuals born in summer grew slower than those born in spring. Sexes reached asymptotic body length at 258 days (females) and 285 days (males), which is an unusually long growth period compared with other small rodents. As most striped mice live for less than 1 year, this period encompasses the entire life for most individuals, but stops at old age, which could indicate senescence. Our results demonstrate a positive influence of food availability on growth, a relationship mediated by ambient temperature. We conclude that striped mice enter the food-restricted dry season before postnatal growth is terminated, and early exposure to harsh environmental conditions during the long dry season likely explains the prolonged growth period in striped mice.

Away from the city: habitat selection of badgers in mountainous area around Beijing

The habitat selection of wild animals residing in suburban area reflects their behavioral adaptation strategies to urbanization and socio-economic development, affecting individual’s fitness and population development. Despite declining population of Asian badgers (Meles leucurus) in China, there are increasing cases in human badger conflict with only few studies examining their potential causes and impacts. In this study we compared and analyzed 19 ecological parameters from 212 blank available plots and 45 active plots conducted through transect survey in the surrounding mountainous area of Beijing. Additionally, we assessed summer habitat selection and use patterns of Asian badgers and the interactions with human activities. In summer, active plots of badgers were in higher elevation (867.86 ± 49.49 m a.s.l.) compared with the available plots, and lower ground-plants coverage (42.00 ± 5.00%). To ensure the high food availability in hot summer, badgers preferred gentle upper slope with moist soil and good lee condition (p 1500 m) from the community and road avoiding the anthropogenic disturbances. Further, our study showed that they tended to select habitats close to cropland (< 500 m; p = 0.053) in the higher elevation of the mountainous area. The habitat selection of badgers around Beijing is a comprehensive tradeoff of their ecological needs in summer, including food availability, security, hydrothermal suitability. Therefore, changing the interference and type of human activities in low-altitude and protecting forest edges in high-altitude are conducive to mitigate human badger conflicts and thus maintain the biodiversity conservation.

NIGER (GUIZOTIA ABYSSINICA L.) – A PROMISING RABI SEASON CROP UNDER RICE-FALLOW SYSTEM IN NORTH-EAST INDIA

Assam is one of the major niger producing sates of India. Wide spread rice fallow and retreating northeast monsoon are the advantages for cultivation of rabi niger crop in Assam. However, niger yield under rainfed situation of Assam decreases drastically for every 15 days delay in sowing of the crop from 15th November to 30th December. The highest seed (4.1 q/ha) and stover (31.0 q/ha) yield could be obtained from 15th November sown crop. Nevertheless, sali rice is harvested late in Assam and so, delay sowing of next rabi crop leads to lower productivity of the crop. Application of 50% recommended dose of fertilizers (RDF) along with 50% nitrogen through FYM considerably increases yield attributing parameters that in the end maximize the stover and seed yield of niger crop. This can give 19.3 and 4.3% increase in stover and seed yield of niger respectively, over RDF. Thus, half of chemical fertilizers required for niger crop could be substituted through organic nutrient sources, which has also lead to an improvement in soil physico-chemical properties and higher availability of nutrients in soil. This review reported the detail management strategies for successful cultivation of rabi niger crop under rainfed situation of Assam of North-East region of India.

Predation by an omnivorous fish and food availability alter zooplankton functional diversity: a microcosm approach.

Studies considering the functional traits of organisms, populations, and communities functional indices increase the understanding of many factors on ecosystem functioning. Here, we analyze the predation effect (by fish) on zooplankton functional diversity and the effects of biomass and density of periphytic algae on zooplankton feeding type trait and body size. We expect that intense predation by fish on zooplankton leads to higher values of zooplankton functional diversity and that food resource will be positively related to the abundance of zooplankton trait and body size. For that, microcosms were established (T1- fish-absence, and T2- fish-presence, both with periphytic algae as food). We observed that fish presence decreased zooplankton functional diversity through modifications in the availability of nutrients and algae, through the middle-out effect. We also observed that body size had a negative relationship with the food resource, reaffirming that high food availability in subtropical lakes is linked to small-bodied zooplankton. The raptorial copepods covariate positively with the periphytic algae, which was an alternative food resource and, in this case, the main form of carbon input into the system. In this study, omnivorous fish reduced zooplankton functional traits, which can alter the energy stock and energy flow in aquatic ecosystems.