We present a meta-analysis of plant responses to fertilization experiments conducted in lowland, species-rich, tropical forests. We also update a key result and present the first species-level ...analyses of tree growth rates for a 15-yr factorial nitrogen (N), phosphorus (P), and potassium (K) experiment conducted in central Panama. The update concerns community-level tree growth rates, which responded significantly to the addition of N and K together after 10 yr of fertilization but not after 15 yr. Our experimental soils are infertile for the region, and species whose regional distributions are strongly associated with low soil P availability dominate the local tree flora. Under these circumstances, we expect muted responses to fertilization, and we predicted species associated with low-P soils would respond most slowly. The data did not support this prediction, species-level tree growth responses to P addition were unrelated to species-level soil P associations. The meta-analysis demonstrated that nutrient limitation is widespread in lowland tropical forests and evaluated two directional hypotheses concerning plant responses to N addition and to P addition. The meta-analysis supported the hypothesis that tree (or biomass) growth rate responses to fertilization are weaker in old growth forests and stronger in secondary forests, where rapid biomass accumulation provides a nutrient sink. The meta-analysis found no support for the long-standing hypothesis that plant responses are stronger for P addition and weaker for N addition. We do not advocate discarding the latter hypothesis. There are only 14 fertilization experiments from lowland, species-rich, tropical forests, 13 of the 14 experiments added nutrients for five or fewer years, and responses vary widely among experiments. Potential fertilization responses should be muted when the species present are well adapted to nutrient-poor soils, as is the case in our experiment, and when pest pressure increases with fertilization, as it does in our experiment. The statistical power and especially the duration of fertilization experiments conducted in old growth, tropical forests might be insufficient to detect the slow, modest growth responses that are to be expected.
Carbonates are only a minor sink of oceanic lithium, yet the presence of this element and its abundance relative to other metal cations in natural carbonate minerals is routinely used as a ...paleo-environmental proxy. To date, however, experimental studies on the influence of physicochemical parameters that may control lithium incorporation in calcite, like pH and precipitation rate, are scarce. Therefore, we experimentally studied Li incorporation in calcite to quantify the apparent partitioning coefficient (DLi∗=cLi/cCacalcitemLi+/mCa2+solution) between calcite and reactive fluid as a function of calcite growth rate and pH. The obtained results suggest that DLi∗ increases with calcite growth rate, according to the expression:LogDLi∗=1.331(±0.116)×LogRate+6.371(±0.880)(R2=0.87;10-8.1≤Rate≤10-7.1molm-2s-1)
Additionally the experimental results suggest that DLi∗ values exhibit a strong pH dependence. For experiments conducted at similar growth rates (i.e. Rate = 10−7.7±0.2 mol m−2 s−1), DLi∗ decreases with increasing pH as described by:LogDLi∗=-0.57(±0.047)×pH+0.759(±0.366)(R2=0.90;6.3<pH<9.5)
The positive correlation of DLi∗ with calcite growth rate is consistent with an increasing entrapment of traces/impurities at rapidly growing calcite surfaces, although the incorporation of monovalent cations such as Li+ and Na+ does not necessarily imply a substitution of Ca2+ ions in the calcite crystal lattice. The dependence of DLi∗ on pH can be considered as an indication that activity of aqueous HCO3− controls the incorporation of Li+ in calcite. The proposed coupled reaction can be explained by charge balance of these monovalent species, which is likely valid at least during the initial step of adsorption on the crystal surface. These new findings shed light on the mechanisms controlling Li incorporation in calcite and have direct implications on the use of Li partitioning coefficients in natural carbonates as an environmental proxy.
The incorporation of magnesium and sulfate in calcite is frequently used to characterize and trace the environmental conditions occurring during carbonate mineral formation. Although both ions are ...simultaneously incorporated in the growing calcite, the effect of sulfate on magnesium incorporation in calcite is still under-explored. In this study, we examine the Mg incorporation in low-Mg calcite as a function of growth rate at 25 °C and 1 bar pCO2 in the presence and absence of aqueous sulfate. The obtained results suggest that high calcite growth rates induce a significant increase in the partitioning coefficient of Mg between the precipitated low-Mg calcite and aqueous solution (i.e. DMg=nMg/nCacalciteMg2+/Ca2+solution). Obtained DMg values exhibit similar dependence to mineral growth rate for experiments performed in the presence and absence of sulfate, however a systematic shift to lower DMg values is observed for calcites formed in the presence of sulfate. The lower DMg values of calcites formed in sulfate-bearing solutions are attributed to the incorporated SO4 ions which provoke expansion in the unit cell along the c-axis of the newly formed calcite. A larger unit cell is unfavorable for the substitution of Ca by smaller Mg ions in calcite. The coupled effect of (i) sulfate uptake during calcite growth and (ii) precipitation rate on DMg can be expressed by the equation DMg=0.03726-0.02345×-logrp-7-XSO4×0.004607+0.002109×-logrp-7; (−8 ≤ log(rp) ≤ −7; 0 ≤ Xso4 ≤ 2.6; T = 25 °C) and is valid for 0.01 ≤ DMg ≤ 0.04. In analogy to Mg also SO4 ions are inhibiting calcite growth, thus promoting the formation of aragonite due to adsorption phenomena and blocking of calcite surface sites. These results improve our understanding on physicochemical parameters controlling CaCO3 composition and mineral polymorphism and are discussed in their relevance for the use of magnesium and sulfate environmental proxies in natural surroundings.
Calcite and aragonite growth rate experiments have been performed in the presence of aqueous Ba at 25 °C using the constant addition technique as a function of CaCO3 mineral growth rate (mol/m2/s). ...The partitioning of Ba in calcite at −8.4 ≤ Logrcalcite ≤ −7.3 exhibits a weak dependence on growth rate that can be expressed as:
LogDBa,calcite=0.2477±0.0543×Logrcalcite-0.2949±0.4222;R2=0.81
In the case of aragonite, Ba partitioning at −9.0 ≤ Lograragonite ≤ −7.8, exhibits a much stronger dependence on growth rate that can be described as:
LogDBa,aragonite=0.4458±0.0563×Lograragonite+3.3407±0.4668;R2=0.84
The determined DBa,aragonite values are systematically lower than unity and come in contrast to previous experimental works where Ba partitioning studied during aragonite nucleation. They are, however, in excellent agreement with the theoretical free energy correlation model by Wang and Xu (2001) that considers the effect of ionic radii size on DBa,aragonite. The defined growth rate dependence of Ba incorporation in aragonite provides new insights on the role of ionic radii size during the incorporation of trace elements and the formation of solid-solutions from aqueous solutions at low oversaturation degrees. The data presented here shed light on the process controlling the elevated DBa,aragonite values occurring at high saturation degrees of natural fluids with respect to aragonite that have been recorded in natural samples. Furthermore, the trend experimentally obtained herein has the potential to record variations in growth rate regimes in natural occurring aragonites and to provide information on the environmental conditions of natural waters in the past.
The incorporation of Ni and Co in aragonite was experimentally investigated as a function of mineral growth rate using the constant addition technique at 25 °C and 1 bar pCO2. The distribution ...coefficients of Ni and Co (i.e., DMe=Me/CasolidaMe2+/aCa2+fluid) exhibit a linear correlation with mineral growth rate in the range −9.1 ≤ Log rp ≤ −7.5 mol/m2/s. The obtained results suggest a stronger dependency of DNi to growth rate compared to that observed for DCo. These dependencies can be described as:
Log DNi = 1.247 (±0.152) Log rp + 7.448 (±1.212); R2 = 0.82
Log DCo = 0.312 (±0.047) Log rp + 1.664 (±0.383); R2 = 0.81
The DMe-aragonite values for both Ni and Co are systematically lower than unity and their increase with increasing growth rate is in agreement with the incorporation of elements incompatible with the host mineral structure. Using the dependency of DNi and DCo to the saturation indices (SI) of the reactive solution with respect to aragonite, the DMe under equilibrium were estimated. These estimates yield equilibrium Log DMe values of −3.9 and − 1.0 for Ni and Co, respectively. These experimentally defined Deq values are 1.3 to 4.3 orders of magnitude lower compared to theoretical estimates that were earlier published in the literature. Similar to other incompatible elements, the observed increase of DNi and DCo values with degree of saturation, points towards incorporation related to the density of defect sites on the mineral surface. Finally, the dependencies recorded in this study suggest that DNi and DCo have the potential to be used as a proxy for saturation degree of the reactive solution.
A rapidly changing climate has the potential to interfere with the timing of environmental cues that ectothermic organisms rely on to initiate and regulate life history events. Short‐lived ectotherms ...that exhibit plasticity in their life history could increase the number of generations per year under warming climate. If many individuals successfully complete an additional generation, the population experiences an additional opportunity to grow, and a warming climate could lead to a demographic bonanza. However, these plastic responses could become maladaptive in temperate regions, where a warmer climate could trigger a developmental pathway that cannot be completed within the growing season, referred to as a developmental trap. Here we incorporated detailed demography into commonly used photothermal models to evaluate these demographic consequences of phenological shifts due to a warming climate on the formerly widespread, multivoltine butterfly (Pieris oleracea). Using species‐specific temperature‐ and photoperiod‐sensitive vital rates, we estimated the number of generations per year and population growth rate over the set of climate conditions experienced during the past 38 years. We predicted that populations in the southern portion of its range have added a fourth generation in recent years, resulting in higher annual population growth rates (demographic bonanzas). We predicted that populations in the Northeast United States have experienced developmental traps, where increases in the thermal window initially caused mortality of the final generation and reduced growth rates. These populations may recover if more growing degree days are added to the year. Our framework for incorporating detailed demography into commonly used photothermal models demonstrates the importance of using both demography and phenology to predict consequences of phenological shifts.
We incorporated demographic components into commonly used phenology models to predict the demographic consequences (i.e. developmental trap vs. demographic bonanza) of phenological shifts in a native multivoltine butterfly under a warming climate. We predicted that populations in the southern limits of its range could become resilient against a warming climate by adding a fourth generation resulting in a demographic bonanza. In the northern ranges, this species may experience diametrically opposed consequences where initial warming would expand the thermal window causing a developmental trap followed by a demographic bonanza if warming continues.
Density-independent and density-dependent population regulation has long been a subject of investigation. We examined density-dependent and density-independent factors on growth rates of pronghorn ( ...Antilocapra americana (Ord, 1815)) using a retrospective analysis of population survey data. Across Idaho, we found that as the proportion of the subpopulation harvested the previous year increased, growth rates increased. Similarly, as fawn recruitment increased, growth rates increased. We also found when the growth rate in the previous year increased, the growth rate the subsequent year decreased. When subpopulations were examined independently, we found that in a low-elevation desert subpopulation, growth rates were influenced by growth the previous year. In an agricultural-dominated site, growth rates were influenced by fawn recruitment in the current year and maximum temperature the previous fall. Growth rates in a mid-elevation shrub–steppe site were influenced by drought severity prior to parturition and the growth rates from the previous year. Growth rates in two mountain valley subpopulations were influenced by measures of vegetative greenness. At the statewide scale, while managers may strive for increased numbers of pronghorn, density dependence will limit the ability for a region-wide numerical response. On the localized scale, drivers of growth were temporally and spatially explicit, and biologists must consider site-specific actions.
A new model is presented to predict hydrogen-assisted fatigue. The model combines a phase field description of fracture and fatigue, stress-assisted hydrogen diffusion, and a toughness degradation ...formulation with cyclic and hydrogen contributions. Hydrogen-assisted fatigue crack growth predictions exhibit an excellent agreement with experiments over all the scenarios considered, spanning multiple load ratios, H2 pressures and loading frequencies. These are obtained without any calibration with hydrogen-assisted fatigue data, taking as input only mechanical and hydrogen transport material properties, the material’s fatigue characteristics (from a single test in air), and the sensitivity of fracture toughness to hydrogen content. Furthermore, the model is used to determine: (i) what are suitable test loading frequencies to obtain conservative data, and (ii) the underestimation made when not pre-charging samples. The model can handle both laboratory specimens and large-scale engineering components, enabling the Virtual Testing paradigm in infrastructure exposed to hydrogen environments and cyclic loading.
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•A new phase field-based model for hydrogen-assisted fatigue crack growth is presented.•Model predictions are compared against fatigue crack growth experiments in H2.•An excellent agreement is attained across H2 pressures, loading ratios and frequencies.•The impact of hydrogen pre-charging the samples is quantified.•The sensitivity to frequency is elucidated, mapping regimes of conservative testing.
According to the invasion criterion, stable coexistence requires that all species in a community increase in abundance when rare, which occurs when stabilizing mechanisms cause intraspecific ...competition to be stronger than interspecific competition. This simple principle has traditionally been applied to tests of local coexistence in a narrow range of ecological systems. However, new theory founded on the invasion criterion is emerging across ecological fields ranging from eco-evolutionary dynamics to global change to macroecology. Concurrently, straightforward methods for testing the invasion criterion have been proposed, but remain underused. Here, we identify the invasion criterion as a common thread linking emerging ecological theory, and we bring this theory together with the methods that can be used to test it.
The invasion criterion has historically been applied to tests of local coexistence in a narrow range of ecological systems.New theory based on the invasion criterion is rapidly emerging, while new methods that allow researchers to test this principle across a broader range of systems have been introduced.We identify the invasion criterion as a common thread that links emerging theory across a range of ecological fields, and we bring this theory together with the methods that can be used to test it.We hope to facilitate the empirical application of the invasion criterion to a range of questions that reach beyond tests of local coexistence.
We consider log-growth rates of Romanian cities’ populations for all cities in the country in the period 1992-2019 on an annual basis. We construct annual, quinquennial and decennial log-growth rates ...and fit to them thirty-one different statistical distributions. The best results with Kolmogorov–Smirnov, Cramér–von Mises and Anderson–Darling statistics are obtained by a mixture of five stretched Gaussian distributions (5sG) with some fixed parameters, and with the AIC, BIC, HQC information criteria are obtained with mixtures of three logistic distributions (3L), that may have or may have not exponential tails. Just as an illustration, we propose a generating stochastic mechanism for the 3L. Dedicated to Laura Andrés Alcalde
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