Lower Relative Growth Research Articles

Spatial coherence and change of opposite white spruce temperature sensitivities on floodplains in Alaska confirms early-stage boreal biome shift

Since the mid 1970s, Interior Alaska white spruce trees experienced markedly lower growth than during the 19th and early 20th centuries. This observation raises the question of forest persistence on certain sites of lowland central and eastern Alaska. We analyzed white spruce growth across a 36-site network (540 trees) on three major river floodplains in boreal Alaska along a longitudinal gradient from eastern Interior to the southwest tree limit to test for the presence of tree growth patterns and climate sensitivities. Chronologies are compared for temperature sensitivity at both stand and individual tree levels, using data from Bethel, McGrath, and Fairbanks NWS stations during the common period of 1952–2001. Cross-dated stand-level ring width chronologies indicate three regions of common signal in tree growth across the gradient. Temperature sensitivity of stand- and individual-tree chronologies is spatially coherent. Most downriver chronologies correlate positively with spring mean monthly temperatures (MMT) at Bethel, mid- and upriver chronologies correlate negatively with MMT of May and previous year July at either McGrath or Fairbanks, and an area in between is a mixed population of positive and negative responders. In downriver positive responders, recent increases from suboptimal cool temperatures accelerated tree growth, while in mid- and upriver negative responders, recent increases from optimal or above-optimal temperatures decreased growth. Fairbanks negative responders are also negatively correlated with a 200-yr index of recorded and reconstructed Fairbanks summer temperatures, and recent sustained record high summer temperatures are associated with the lowest relative growth. Until the 1940s, absolute growth rate of negative responders was greater than positive responders, but from the 1970s the positive responders grew more. These results explain why northern ring width samples can display opposite temperature sensitivity and contribute to understanding recent “divergence” or loss of temperature sensitivity in a changing climate. We find that July MMT and annual precipitation at Fairbanks are now outside the limits that previously characterized the North American distribution of white spruce, and are near the reported physiological limits of the species. Our results of the spatial and temporal change of white spruce temperature sensitivity provide strong empirical evidence of previously proposed early stage biome shift in boreal Alaska due to clear climatic causes. Already, western Alaska, previously extending to tree limit, has become the optimum climate region for the species. With modest additional warming widespread tree death will be unavoidable on warmer lowland interior sites, where persistence of white spruce is unlikely.

Plant invasive success associated with higher N-use efficiency and stoichiometric shifts in the soil–plant system in the Minjiang River tidal estuarine wetlands of China

The tidal estuarine wetlands of China are rich in plant diversity, but several human-driven processes, such as species invasion, can affect the biogeochemical cycles of these ecosystems, and by changing soil conditions can inhibit the regeneration of native vegetation. We seasonally analyzed the carbon (C), nitrogen (N) and phosphorus (P) concentrations in soils and in leaves, stems and roots of the invasive species Spartina alterniflora and of the native species Cyperus malaccensis var. brevifolius Boeckeler. This latter species was analyzed both in natural non-invaded stands and in stands that had been invaded by Spartina but from which it had been removed and replaced by Cyperus. The aim was to investigate the effect of plant invasion, subsequent removal and replanting with a native species on C, N and P stoichiometry of the plant–soil system in the tidal wetlands of the Minjiang River. C and N concentrations averaged across seasons did not differ significantly among the plant species. P concentration was lower in the stems of Spartina than in the stems of the native species Cyperus but was not significantly different in the roots of the two species. The soil C and N concentrations were higher in the Spartina stand than in the Cyperus stand, whereas the soil P concentrations were not significantly different. The invasive species had a higher N-resorption capacity, N:P ratios in stem and roots, biomass, absolute growth and biomass N and had a lower relative growth rate and litter production than the native species. After the removal of the invasive plants, the regenerating native plants have a higher capacity to resorb N and lower relative growth rates. All these traits show that a conservative strategy and a high N-use efficiency and internal plant control of the N in the ecosystem underlie the invasive success of Spartina in this N-limited wetland. Relative growth rate was associated with lower plant N:P ratios, whereas absolute growth rate was associated with higher nutrient-use efficiency and lower C and N turnover and storage capacities in the biomass. Changes in soil properties produced by the establishment of an invasive plant can condition the later regeneration of native plants.

Herbivory and relative growth rates of Pieris rapae are correlated with host constitutive salicylic acid and flowering time.

Treatment of plants with exogenous salicylic acid (SA) improves resistance to many bacterial pathogens, but can suppress resistance to insect herbivores. While plants vary naturally in constitutive SA, whether such differences are predictive of resistance to insect herbivores has not been studied previously. We examined the possible role of this endogenous SA in structuring the interactions between the cabbage white butterfly, Pieris rapae, and ten hosts in the mustard family (Brassicaceae). Because P. rapae has multiple generations that utilize different hosts across the year, we included five spring-flowering mustards and five summer-flowering mustards that co-occur in ruderal habitats in upstate New York. Under common garden conditions, the spring flowering mustards (Capsella bursa-pastoris, Draba verna, Cardamine impatiens, Barbarea vulgaris, and Arabidopsis thaliana) were significantly more resistant to P. rapae, supporting 42 % less herbivory (P = 0.015) and 64 % lower relative growth rates (P = 0.007), relative to the summer flowering mustards (Sisymbrium altissimum, Brassica nigra, Sinapis arvense, Lepidium campestre, and Arabis canadensis). Leaf total constitutive SA explained significant variation in larval herbivory (R2 = 75.3 %, P = 0.007) and relative growth rates (R2 = 59.4 %, P = 0.043). The three species with the lowest levels of constitutive SA (Capsella bursa-pastoris, Draba verna, and Cardamine impatiens) were the most resistant to larvae. Barbarea vulgaris and Arabis canadensis were notable exceptions, exhibiting high SA concentrations and intermediate resistance to P. rapae. These results suggest a curvilinear relationship between leaf constitutive SA and the herbivory by P. rapae, and they provide some insight into the ecology and possible management of this economically important crop pest.Electronic supplementary materialThe online version of this article (doi:10.1007/s10886-015-0572-z) contains supplementary material, which is available to authorized users.

Lithium, Vanadium and Chromium Uptake Ability of Brassica juncea from Lithium Mine Tailings

The potential for phytoremediation and phytostabilization of lithium in lieu with vanadium and chromium on a formulated acidic heterogeneous growth media engineered around lithium mine tailings, was investigated in four phases: (1) overall efficiency of the removal of the three metals, (2) bioaccumulation ratios of the three metals, (3) overall relative growth rate, and (4) translocation index of the three metals in the physiology of the hyperaccumulator plant. A pot study was conducted to assess the suitability of Brassica juncea (Indian mustard) in a phytoremediation process whereby it was lingered for eighty-six days under homogeneous growth conditions and irrigated bidaily with organic fertilizer amended with LiCl. A post harvest data analysis was achieved through ashing and the implementation of cold digestion procedure in a concentrated hydrochloric acidic matrix. In physiological efficiency parameters, the hyperaccumulator plant was twice as able to phytostabilize chromium and four times was able to phytostabilize vanadium in comparison to lithium. Moreover, it was extremely efficient in translocating and accumulating lithium inside its upper physiological sites, more so than chromium and vanadium, thereby demonstrating Indian mustard, as a hyperaccumulator plant, for phytoextraction and phytostabilization in an acidic heterogeneous rhizosphere, with an extremely low relative growth rate.

Carbon acquisition strategies uncoupled from predictions derived from species life-cycle

We compare carbon use strategies of congeneric annual (P. gracilis and P. angustifolia) and perennial (P. mendocina and P. pinetorum) Physaria (Brassicaceae), to evaluate the relevance of eco-physiological traits as determinants of differences in growth and to add information on the current debate on the agro-ecological suitability of perennial species for grain production in low resource ecosystems. Because of differences in growth and in seed-output previously found within this genus, we hypothesized that C acquisition strategies would not be fully coupled with predictions derived from a species life-cycle. Further, we expected to find different suites of traits related to C-acquisition among perennial species of Physaria. We found species with high (P. gracilis and P. pinetorum) and low (P. mendocina and P. angustifolia) relative growth rate (RGR) and biomass. The variation in RGR was linked to differences in specific leaf area (SLA) and allocation to leaves (leaf mass ratio, LMR) and roots (root mass ratio, RMR), but not to the species life-cycle. Physaria gracilis had high allocation to leaf area (leaf area ratio, LAR), LMR, high SLA, and low RMR and carbohydrates reserves. The slow-growth strategy found in P. mendocina was linked to low LAR, low SLA and large below-ground allocation. The other species showed intermediate strategies between these two. The sets of traits present in P. gracilis and in P. mendocina are extremes in the C acquisition–conservation trade-off, and may allow them to cope with low resource environments in different ways. SLA, LMR and RMR were the main determinants of RGR, while total non-structural carbohydrates (TNC) and leaf longevity were linked to the life-cycle. Taken together these characters define the intermediate growth strategies of P. angustifolia and P. pinetorum. These intermediate strategies were not dependent on the species life cycle and support the hypothesis of uncoupled relationships between growth, C acquisition strategies and life-cycle.

Arbuscular mycorrhizas increase survival, precocity and flowering of herbaceous and shrubby species of early stages of tropical succession in pot cultivation

Abstract:Arbuscular mycorrhizal fungi (AMF) are an important biotic factor that influences tropical ecological succession and differently affect the woody species belonging to different successional stages. However, little is known about the influence of AMF on growth and reproduction of herbaceous and shrubby species of early phases of tropical succession. Thus, we assessed the effect of AMF on the development of 27 heliophilous herbaceous and shrubby tropical species. Plants were grown in greenhouse, in low- and high-fertility soils, with or without AMF, for 100 d. Most species grown with AMF exhibited high root infection intensity (≈80%), irrespective of soil fertility. In the low-fertility soil, non-mycorrhizal plants exhibited about 88% less shoot dry mass (SDM) than mycorrhizal plants, and AMF were crucial for the survival of most species. Non-mycorrhizal plants also had lower relative growth rate (RGR), total leaf area (TLA), leaf area expansion (LAE) and total root length (TRL). Six species flowered in the low-fertility soil, and flowering increased with AMF in one plant species and four species only flowered when mycorrhizal. In the high-fertility soil, non-mycorrhizal plants exhibited about 13% less SDM than mycorrhizal plants and also exhibited lower TLA, LAE, and nutrient concentrations in shoots. On the other hand, no major changes were observed for RGR, TRL and root dry mass for most of the species. Sixteen plant species flowered in the high-fertility soil, but most had earlier (11) and more abundant (10) flowering when mycorrhizal. Thus, AMF have different influences on the survival, growth and flowering of herbaceous and shrubby tropical species, depending on soil fertility: in low-fertility soil, AMF especially affect the survival, growth and flowering, whereas in high-fertility soil, AMF mainly influence the shoot nutrient concentrations and flowering.

상수리나무 임분 내에서 벌채 유형에 따른 조림목의 생장 특성

Abstract The objective of this study was to evaluate the effect of cutting types on microclimate and growth characteristics of afforested tree in Quercus acutissima stand after different types of cutting. The difference in temperature reaching 5.2℃ was shown in between clear cutting and selective cutting treatments. On July and August days with temperatures more than 35℃often appeared in clear cutting stand. The values of VPD in July and August were higher than those in other months. Maximum VPD of 3.99 kPa was shown in clear cutting stand on May 23 as a prolonged rainless days appeared. However, VPD in selective cutting stand always stayed under 3.0 kPa throughout growing season. A higher intensity was shown in clear cutting and strip clear cutting stands, reaching to more than 1,600 μmol m -2 s -1 at midday on early August, while that in selective cutting stand stayed about 1,500. In relative growth rate selective cutting stand showed a significantly higher relative growth rate in plant height than those in other cutting stands (p<0.05). The number of leaf in current-year branches significantly increased in selective cutting stand, whereas no increase was shown in clear cutting and strip clear cutting stands (p<0.05). In addition, relative elongation rate of current year branch also showed higher values in selective cutting stand compared with that in strip clear cutting stand (p<0.05). However, leaf mass per unit area (LMA) was higher in order of strip clear cutting, clear cutting, and selective cutting stands. From these results it is concluded that environmental conditions in clear cutting and strip clear cutting stands during growing season are more stressful to afforested tree species, resulting in lower relative growth in plant height, elongation of current-year branches, and leaf number per branch compared with those in selective cutting stand. Consequently, more data must be accumulated in the field to find out best cutting type in plantation considering the adaptational characteristic of each tree species varies with species and life span of tree is long.

Improvement in lettuce growth by light diffusion under solar panels

Power generation by roof-mounted photovoltaic (PV) modules may provide additional income to farmers if the crop production is comparable to production under normal greenhouse conditions. However, fluctuating irradiance caused by the partial shade of PV modules has been reported to reduce crop production. In the present study, we have shown for the first time the possibility of improving lettuce growth by using light diffusion films under roof-mounted PV modules. The effects of different light conditions (direct but fluctuating and diffused but uniform irradiations) under PV modules on the morphology, yield, and photosynthesis of hydroponically grown lettuce were investigated. Lettuce growth was inhibited, resulting in lower dry weight and relative growth rate (RGR) with longer leaves, under the fluctuating light by roof-mounted PV modules compared to normal greenhouse conditions. On the other hand, the ratio of leaf width to length increased under diffused light conditions and the values were comparable to those in the control in spring, summer, and fall cultivations. Although the net photosynthetic rate of fully expanded leaves of lettuce grown under diffused light was lowest, their dry weight and RGR were comparable to the control in summer and fall cultivations. Diffused light might penetrate into the lower layers of the leaf canopy, thereby increasing the CO2 fixation of the whole canopy. Our results suggest that the application of light diffusion films is a viable option for improving crop productivity under roof-mounted PV modules.

The effect of irradiance on the carbon balance and tissue characteristics of five herbaceous species differing in shade-tolerance.

The carbon balance is defined here as the partitioning of daily whole-plant gross CO2 assimilation (A) in C available for growth and C required for respiration (R). A scales positively with growth irradiance and there is evidence for an irradiance dependence of R as well. Here we ask if R as a fraction of A is also irradiance dependent, whether there are systematic differences in C-balance between shade-tolerant and shade-intolerant species, and what the causes could be. Growth, gas exchange, chemical composition and leaf structure were analyzed for two shade-tolerant and three shade-intolerant herbaceous species that were hydroponically grown in a growth room at five irradiances from 20 μmol m−2 s−1 (1.2 mol m−2 day−1) to 500 μmol m−2 s−1 (30 mol m−2 day−1). Growth analysis showed little difference between species in unit leaf rate (dry mass increase per unit leaf area) at low irradiance, but lower rates for the shade-tolerant species at high irradiance, mainly as a result of their lower light-saturated rate of photosynthesis. This resulted in lower relative growth rates in these conditions. Daily whole-plant R scaled with A in a very tight manner, giving a remarkably constant R/A ratio of around 0.3 for all but the lowest irradiance. Although some shade-intolerant species showed tendencies toward a higher R/A and inefficiencies in terms of carbon and nitrogen investment in their leaves, no conclusive evidence was found for systematic differences in C-balance between the shade-tolerant and intolerant species at the lowest irradiance. Leaf tissue of the shade-tolerant species was characterized by high dry matter percentages, C-concentration and construction costs, which could be associated with a better defense in shade environments where leaf longevity matters. We conclude that shade-intolerant species have a competitive advantage at high irradiance due to superior potential growth rates, but that shade-tolerance is not necessarily associated with a better C-balance at low irradiance. Under those conditions tolerance to other stresses is probably more important for the performance of shade-tolerant species.

Reperfusion after 4·5 Hours Reduces Infarct Growth and Improves Clinical Outcomes

The currently proven time window for thrombolysis in ischemic stroke is 4.5 h. Beyond this, the risks and benefits of thrombolysis are uncertain. To determine whether thrombolysis and reperfusion were beneficial after 4.5 h, we examined clinical and radiological outcomes in patients treated with tissue plasminogen activator or placebo within 4.5-6 h, using data from the Echoplanar Imaging Thrombolytic Evaluation Trial. In the Echoplanar Imaging Thrombolytic Evaluation Trial, ischemic stroke patients presenting three to six-hours after stroke onset were randomized to tissue plasminogen activator or placebo, without knowledge of magnetic resonance imaging results. This analysis was restricted to patients treated between 4.5 and 6 h. The effect of tissue plasminogen activator and reperfusion on infarct growth between baseline diffusion-weighted imaging and day 90 T2 imaging was assessed, along with good neurological outcome (≥8 point reduction or reaching 0-1 at 90 days on National Institutes of Health Stroke Scale) and functional outcome (modified Rankin scale). The effect of tissue plasminogen activator on reperfusion was also analyzed. Sixty-nine patients were treated 4.5-6 h after onset, and infarct growth was assessed in 63. Tissue plasminogen activator was associated with lower relative growth (94% vs. 168%, P = 0.03) and a trend to lower absolute growth (-0.17 ml versus 9.6 ml, P = 0.07). Reperfusion was increased in the tissue plasminogen activator group (58% versus 25%, P = 0.03) and was associated with increased rates of good neurological (86% versus 28% P < 0.001) and functional (modified Rankin scale 0-2 73% versus 34%, P = 0.01) outcomes. Reperfusion was strongly associated with lower relative (80% versus 189%, P < 0.001) and absolute (-2.5 ml versus 40 ml, P < 0.001) infarct growth. Thrombolysis 4.5-6 h after stroke onset reduced infarct growth and increased the rate of reperfusion, which was associated with good neurological and functional outcome.

A Discussion on the Influence Mechanism of Iron to Algal Blooms in Natural Raw Water

Through designing orthogonal tests, the influence mechanism of iron to the growth of fresh water algae was studied. The results indicated that the initial Fe concentration of 0.3mg/L or above can lead to high algae relative growth rate while the initial Fe concentration under 0.3mg/L can only generate low algae relative growth rate. The consumption of iron in Group LNLP under low initial Fe concentration and Group HNHP under high initial Fe concentration was in synchronism with the consumption of nitrogen and phosphorus. However, in Group HNHP under low initial Fe concentration and Group LNLP under high initial Fe concentration the concentration of iron decreased with the increase of algal biomass before reaching the peak value of algal biomass and it increased after reaching the peak value in contrary. Among all those 25 groups the order of the peak value of algal biomass from big to small is as follows:All-rich Group&gt;Nitrogen-lacked Group&gt;Phosphorus-lacked Group&gt;Iron-lacked Group&gt;All-lacked Group. The lack of Fe content will restrain the growth of algae. In certain concentration rage algal biomass increased with the increasing of Fe content while Fe content will restrain the growth of algae in contrary if beyond the concentration rage.

Effect of silicon soil amendment on performance of sugarcane borer,Diatraea saccharalis(Lepidoptera:Crambidae) on rice

The sugarcane borer, Diatraea saccharalis (F.), is a pest of graminaceous crops in the southern USA, including sugarcane, maize, and rice. This study was conducted to investigate the effect of silicon (Si) soil amendments on performance of sugarcane borer, D. saccharalis, on two rice cultivars, Cocodrie and XL723. There was a significant increase in the Si content of rice plants supplemented with calcium silicate as compared to non-treated plants. Soil Si amendment led to lower relative growth rates (RGRs) and reduced boring success of sugarcane borer larvae. Effects of soil Si amendments on borer success and RGR appeared to be more pronounced in 'Cocodrie', the cultivar relatively susceptible to borers, than in the moderately resistant cultivar, XL723. Soil Si amendment may contribute to the management of D. saccharalis through reduced feeding injury and increased exposure to adverse environmental conditions and natural enemies arising from reduced boring success.

Afforestation of Boreal Open Woodlands: Early Performance and Ecophysiology of Planted Black Spruce Seedlings

Open lichen woodlands (LWs) are degraded stands that lack the ability to regenerate naturally due to a succession of natural and/or anthropogenic disturbances. As they represent both interesting forest restoration and carbon sequestration opportunities, we tested disc scarification and planting of two sizes of containerized black spruce (Picea mariana Mill. (BSP)) seedlings for their afforestation. We compared treatment of unproductive LWs to reforestation of harvested, closed-crown black spruce-feathermoss (BSFM) stands. After one year, seedling survival and nutritional status were equivalent among stand types but despite higher root elongation index (REI), planted seedlings in LWs had lower relative growth rate, smaller total biomass and stem diameter than those in BSFM stands. Soil fertility variables, soil temperature, nor seedling water potential, helped at explaining this early growth response. Disc scarification significantly improved seedling first-year survival, biomass and foliar nutrient concentrations of P, Ca, and Mg. Smaller planting stock showed higher REI, higher shoot water potential, and higher foliar nutrient concentration of all but one of the measured nutrients (N, P, K and Mg). Hence, preliminary results suggest that planting of smaller containerized black spruce stock, combined with disc scarification, shows potential for afforestation of unproductive LWs. The impact of the lichen mat and other potential growth limiting factors on afforestation of these sites requires further investigation.

Low relative growth rates predict future mortality of common beech (Fagus sylvatica L.)

For many tree species, growth patterns derived from tree-ring time series have been shown to be good indicators of tree mortality. Although tree rings of common beech (Fagus sylvatica) have been widely used to answer complex questions of forest ecology, there are only few studies using growth characteristics, such as growth decline or growth variability, as informative predictors of tree mortality in old-growth beech forests. To do this, we used dendrochronological data of living and dead trees from a nature reserve in eastern Germany. Using a logistic regression model, we predicted tree mortality based on growth characteristics (basal area increment; variance, autocorrelation, mean sensitivity of ring widths; growth trends) over different time horizons. Beech mortality could reliably be predicted up to 20years in advance on the basis of relative basal area growth. Trees that grew slower in relative basal area than 0.95cm2/cmy on average over a 20-year-period had a much higher mortality risk than faster-growing trees. Other statistical characteristics of the dendrochronological time series, such as the variance or autocorrelation of ring widths, the mean sensitivity or growth trends, did not convey significant additional information and did not lead to better mortality predictions.

Changes in growth rate, root morphology and water use efficiency of potted Callistemon citrinus plants in response to different levels of water deficit

Callistemon is widely used as a flowering shrub in gardening and landscaping in the Mediterranean area. However, prolonged or severe water stress may alter its physiological and morphological behaviour. Callistemon citrinus plants were grown in nursery conditions and subjected to three irrigation treatments: a control (watered to container capacity) and two water deficit treatments of 50 and 25% of the amount of water supplied in the control treatment (moderate and severe deficit irrigation, respectively). After 53 weeks, the moderate deficit irrigation plants showed a lower relative growth rate but increased root/shoot ratio, improved the root system and increased water use efficiency, while flowering and leaf colour were unaffected. However, severe deficit irrigation reduced flowering and affected leaf colour. Both deficit irrigation treatments reduced stomatal conductance, suggesting an efficient and adaptive stomatal control in this species. These reductions were marked after longer periods in plants submitted to severe deficit irrigation, which decreased photosynthesis and could delay plant recovery and cause permanent damage. Differences between stem and leaf water potential values have seen to be a good indicator of instantaneous shoot transpiration. Water consumption was influenced by the active periods of growth and inflorescence formation. It is concluded that moderate deficit irrigation can be used successfully in C. citrinus plant production to reduce water consumption while maintaining good overall quality.

Crescimento e fenologia de espécies de Jatropha durante a estação chuvosa

Jatropha curcas L., Jatropha mollissima (Pohl) Baill e Jatropha gossypiifolia L. são Euforbiáceas com potencial para produção de biodiesel e uso na indústria farmacêutica e em cosméticos. Objetivou-se, com este trabalho, avaliá-las em termos de crescimento e fenologia em pesquisa de campo. Adotou-se o delineamento experimental em blocos casualisados contendo na parcela 18 plantas e tendo área útil de 15 m². Nos estudos fenológicos das plantas foram consideradas as seguintes fases: estabelecimento/crescimento vegetativo, floração, frutificação e maturação/colheita. As fases fenológicas das espécies diferiram cronologicamente. Jatropha mollissima cresceu mais do que as outras espécies em altura de plantas enquanto Jatropha curcas cresceu mais em diâmetro caulinar. As maiores taxas de crescimento relativo em altura de plantas ocorreram durante o crescimento vegetativo com os maiores valores sendo registrados em Jatropha mollissima enquanto as maiores taxas de crescimento relativo, também no crescimento vegetativo, foram registradas em Jatropha curcas. As menores taxas de crescimento relativo em altura de plantas e diâmetro caulinar das espécies estudadas coincidiram com as fases reprodutivas.

Changes in relative organ weights and intestinal transporter gene expression in embryos from white Plymouth Rock and WENS Yellow Feather Chickens

This study was conducted to evaluate the embryonic development of broilers with different growth rates and correlate the differences between the amino acid transporter and peptide transporter gene expression patterns to the growth of the small intestine. The results showed that the body and yolk weights of the White Plymouth Rock (WPR) embryos were higher than those of the WENS Yellow Feather Chicken (WYFC) embryos although the relative embryonic body weights were inversely correlated. We studied nine organs and classified them into four clusters according to their changes in relative weight during the hatching process. The levels of gene expression of SLC7A9, SLC1A1 and SLC15A1 in the small intestine increased during embryo development and were affected by breed. Breed-specific differences in embryonic development were observed for SLC7A9, SLC1A1 and SLC15A1 gene expression. When represented as a function of SLC7A9, SLC1A1 or SLC15A1 gene expression, strong correlations were observed for the weight of small intestine. We conclude that WPR embryos have a higher absolute growth rate but a lower relative growth rate in comparison with WYFC embryos. Moreover, the expression levels of the SLC7A9, SLC1A1 or SLC15A1 genes can be used as indicators for the growth of the small intestine.

Little evidence for local adaptation to soils or microclimate in the post-fire recruitment of three Californian shrubs

Background: Seedling recruitment following fire is an infrequent yet critical demographic transition for woody plants in Mediterranean ecosystems.Aims: Here we examine whether post-fire seedling recruitment of three widespread Californian chaparral shrubs is affected by local adaptation within an edaphically and topographically complex landscape.Methods: We reciprocally transplanted 6-month-old seedlings of Adenostema fasciculatum, Ceanothus cuneatus and Eriodictyon californicum to serpentine and sandstone soils, and cool northerly and warm southerly slopes.Results: At the age of 2 years, none of the species manifested higher survival or growth on ‘home’ compared with ‘away’ soils or slopes, indicating an absence of local adaptation with respect to seedling recruitment in these environments. Seedlings of all species manifested lower survival and relative growth on serpentine soils regardless of seedling source, as well as a variety of other destination and source effects.Conclusions: The ability of these three species to recruit in new environments, such as in restoration settings or in response to shifting climates, is unlikely to be impeded by a need for seeds from sources that closely match their edaphic or topographic destination.

Limits of pine forest distribution at the treeline: herbivory matters

Herbivores can affect future forest composition by feeding selectivity. At temperature-sensitive treelines, herbivory can exacerbate or constrain climate-driven distributional shifts in tree species. This study analyses the impact of herbivory in a Mediterranean treeline of widespread Pinus sylvestris and P. nigra pinewoods, testing whether herbivory damage reinforces or inhibits the climatic responses of these trees. We used naturally occurring sapling pairs of similar size and age of both species, thereby isolating plant characteristics from environmental effects in herbivore behaviour. Herbivory damage by ungulates proved higher than that caused by insects in saplings of both species. Low plant density and extreme abiotic conditions at the treeline could in part be responsible for the observed low incidence of insect herbivory. Ungulates preferred P. sylvestris over P. nigra, implying heavier browsing damage for a large number of P. sylvestris saplings, suffering reduced internode growth as a consequence. In addition, P. sylvestris could not compensate height-growth reductions due to browsing with higher growth rate than P. nigra. In fact, P. sylvestris showed similar or lower relative height growth with respect to P. nigra. Under a scenario of increasing aridity and maintenance of ungulate populations, the upward migration of P. sylvestris in its southern range could be restricted by higher drought vulnerability than P. nigra, a situation exacerbated by ungulate herbivory. Our results indicate that ungulate herbivory reinforces climatic response of coexisting P. sylvestris and P. nigra at treeline, favouring a potential change in community dominance towards Mediterranean P. nigra.

Relative Growth Rate and Functional Traits of a Hybrid Species Reflect Adaptation to a Low-Fertility Habitat

Hybrid species provide a unique opportunity to examine trait evolution. We previously demonstrated that the hybrid species Helianthus anomalus is more fit than its ancestral parents, Helianthus annuus and Helianthus petiolaris, in its habitat and hypothesized that nutrient limitations have been a major selective agent in that adaptive evolution. In this glasshouse study, we asked whether H. anomalus has more conservative growth and resource use traits than its ancestral parents, as expected for low-nutrient-adapted species. Helianthus anomalus had a lower maximum relative growth rate, leaf area ratio, and specific leaf area as well as less of a decrease in relative growth rate with nitrogen limitation than its ancestral parents. Helianthus anomalus also had higher nitrogen use efficiency, largely because of a longer mean residence time, as well as greater leaf toughness and longer leaf life span. However, H. anomalus did not have a lower photosynthetic rate, higher ratio of fine root length to leaf area, ...