Can arbuscular mycorrhizal fungi from non-invaded montane ecosystems facilitate the growth of alien trees?

It is generally assumed that recruitment and expansion of alien species along elevation gradients are constrained by climate. But, if plants are not fully constrained by climate, their expansion could be facilitated or hindered by other factors such as biotic interactions. Here, we assessed the composition of arbuscular mycorrhizal fungi (AMF) in soils along an elevation gradient (i.e. 900 m, 1600 m, 2200 m and 2700 m a.s.l.) through a fungal DNA meta-barcoding approach. In addition, we studied in the greenhouse the effects of AMF on growth and phosphorous (P) nutrition of seedlings of the alien trees Gleditsia triacanthos, Ligustrum lucidum and Pyracantha angustifolia cultivated in soils from those elevations, spanning the elevation at which they already form monospecific stands (below 1450 m a.s.l.) and higher elevations, above their current range of distribution in montane ecosystems of Central Argentina. For comparison, we also included in the experiment the dominant native tree Lithraea molleoides that historically occurs below 1300 m a.s.l. Arbuscular mycorrhizal fungal community composition showed strong community turnover with increasing elevation. The effects of these AMF communities on plant growth and nutrition differed among native and alien trees. While P nutrition in alien species' seedlings was generally enhanced by AMF along the whole gradient, the native species benefited only from AMF that occur in soils from the elevation corresponding to its current altitudinal range of distribution. These results suggest that AMF might foster upper range expansion of these invasive trees over non-invaded higher elevations.

[Research on morphological characteristics change of quercetin and polyphenols of accumulation dynamic of spines of Gleditsia sinensis].

To study morphological characteristics change of the development process and quercetin and polyphenols of accumulation dynamic of the spines of Gleditsia sinensis, measure and compare morphological indexes using Vernier caliper, ruler and balance, calibrate and analysis quercetin and polyphenols content using HPLC and colorimetric method. The spines of G. sinensis development process is divided into formation period (the beginning of August to the beginning of November), dormant period (the beginning of November to the end of March in the following year), germination period (the end of March to the middle of April), fast growth period (the middle of April to the middle of August), browning period (the middle of August to the end of August) and mature period (the beginning of September to the end of December). Formation period the spines primordium divides and forms the scale bubs; dormant period the scale bubs are in a dormant state; germination period the bubs scales fall off, spines primordium began to development; fast growth period rapid growth to maximum; browning period browning from the tip and browns until the whole becomes brown; mature period The early stage of maturity is full of luster, gradually the color deepened and the luster faded. The accumulation of quercetin was gradually decreasing after increasing. The total polyphenol accumulation was significantly decreased and then gradually increased, decreased finally. The content of quercetin was increased from 0.000 4%-0.002 6%, and the polyphenol content decreased from 0.761 9%-0.049 1% and then slowly increased to 0.286 9% in the fast growth period.The quercetin continuous increase to 0.004 3% and total polyphenol increased to 0.421 6% in the browning period. In the mature period, the quercetin content significantly decreased after reaching 0.009 6% in September, and the polyphenols content decreased after reaching 0.723 5% in October. Using principal component analysis results: September first, October 2nd, November 3rd. The morphological characteristics change of the development process and quercetin and polyphenols accumulation were determined. The development process is divided into six periods, the best harvest time is the early stage of mature period. Provide theoretical support for the utilization of the spines of G. sinensis and cultivation techniques of high yield.

Comparison and characterization of galactomannan at different developmental stages of Gleditsia sinensis Lam.

Pods from a Gleditsia sinensis Lam. tree were collected and the galactomannan content and other properties were determined at their different developmental stages. In green and immature seed, galactomannan was substituted to a great extent with a mannose to galactose (M/G) ratio of 2.4 from crude polysaccharides. During late galactomannan deposition, it was substituted to a lower extent and this ratio increased rapidly, reaching a M/G ratio of 3.1. Average molecular weight (Mw) of the extracted polysaccharides first increased, reached the maximum (1.19 × 106) at 17 weeks after flowering (WAF), and then decreased. These changes might result from primary galactomannan biosynthesis and from galactose removal by α-galactosidase in the endosperm. The solubility of crude polysaccharides decreased with increased M/G ratio and maximum solubility was more than 89% that collected at 13 WAF. Rheological properties showed that apparent viscosity was largely influenced by the molecular weight and M/G ratio of galactomannans.

Growth rate and survivorship of drought: CO2 effects on the presumed tradeoff in seedlings of five woody legumes.

Traits that promote rapid growth and seedling recruitment when water is plentiful may become a liability when seedlings encounter drought. We tested the hypothesis that CO2 enrichment reinforces any tradeoff between growth rate and drought tolerance by exaggerating interspecific differences in maximum relative growth rate (RGR) and survivorship of drought among seedlings of five woody legumes. We studied invasive species of grasslands that differ in distribution along a rainfall gradient. Survivorship of drought at ambient CO2 concentration ([CO2]) was negatively related to RGR in well-watered seedlings in one of two experiments, but the relationship was weak because interspecific differences in RGR were small. Contrary to our hypothesis, there was no significant relationship among well-watered seedlings between RGR at ambient [CO2] and either the relative or absolute increase in RGR at elevated [CO2]. As predicted, however, CO2 enrichment reinforced interspecific differences in survivorship of seedlings exposed to similar rates of soil water depletion. Doubling [CO2] improved seedling survivorship of the most drought-tolerant species throughout the period of soil water depletion, but did not consistently affect survivorship of more drought-sensitive species. Midday xylem pressure potentials of drought-treated seedlings were less negative at elevated [CO2] than at ambient [CO2], but no other measured trait was consistently correlated with improved survivorship at high [CO2]. Carbon dioxide enrichment may not reinforce species differences in RGR, but could exaggerate interspecific differences in drought tolerance. To the extent that seedling persistence in grasslands correlates with drought survivorship, our results indicate a positive effect of CO2 enrichment on recruitment of woody legumes that are currently tolerant of drought.

Modelling biological invasions: species traits, species interactions, and habitat heterogeneity.

In this paper we explore the integration of different factors to understand, predict and control ecological invasions, through a general cellular automaton model especially developed. The model includes life history traits of several species in a modular structure interacting multiple cellular automata. We performed simulations using field values corresponding to the exotic Gleditsia triacanthos and native co-dominant trees in a montane area. Presence of G. triacanthos juvenile bank was a determinant condition for invasion success. Main parameters influencing invasion velocity were mean seed dispersal distance and minimum reproductive age. Seed production had a small influence on the invasion velocity. Velocities predicted by the model agreed well with estimations from field data. Values of population density predicted matched field values closely. The modular structure of the model, the explicit interaction between the invader and the native species, and the simplicity of parameters and transition rules are novel features of the model.

[Effects of NaCl stress on the seedling growth and K(+)- and Na(+) -allocation of four leguminous tree species].

Taking the pot-cultured seedlings of four leguminous tree species (Albizia julibrissin, Robinia pseudoacacia, Sophora japonica, and Gleditsia sinensis) as test materials, this paper studied their growth indices, critical salt concentration (C50), and K+ and Na+ allocation under different levels of NaCl stress, aimed to understand the difference of test tree species in salt tolerance. NaCl stress inhibited the seedling growth of the tree species. Under NaCl stress, the dry matter accumulation decreased, while the root/shoot ratio increased, especially for A. julibrissin and G. sinensis. Quadratic regression analysis showed that the C50 of A. julibrissin, R. pseudoacacia, S. japonica, and G. sinensis was 3.0 per thousand, 5.0 per thousand, 4.5 per thousand, and 3.9 per thousand, respectively, i.e., the salt tolerance of the four tree species was in the order of R. pseudoacacia > S. japonica > G. sinensis > A. julibrissin. In the root, stem, and leaf of the four tree species seedlings, the Na+ content increased with the increase of NaCl stress, while the K+ content (except in the root of A. julibrissin) decreased after an initial increase, resulting in a larger difference in the K+/Na+ ratio in the organs. Under the same NaCl stress, the allocation of Na+ in different organs of the four tree species seedlings decreased in the order of root>stem>leaf, while that of K+ differed with tree species and NaCl stress, and leaf was the main storage organ for K+. The K+/Na+ ratio in different organs decreased in the sequence of leaf>stem>root. R. pseudoacacia under NaCl stress accumulated more K+ and less Na+ in stem and leaf, and had higher K+/Na+ ratio in all organs and higher dry mass, being assessed to be more salt-tolerant. In contrast, A. julibrissin under high NaCl stress accumulated more Na+ in stem and leaf, and had a lower K+/Na+ ratio in all organs and lower dry mass, being evaluated to be lesser salt-tolerant. The K+ accumulation in seedling stem and leaf and the Na+ retention in seedling root could be the main reasons for the salt tolerance of leguminous tree species under NaCl stress.

[Effects of NaCl stress on Hovenia dulcis and Gleditsia sinensis seedlings growth, chlorophyll fluorescence, and active oxygen metabolism].

With potted Hovenia dulcis and Gleditsia sinensis seedlings as test materials, their plant growth, chlorophyll fluorescence characteristics, and active oxygen metabolism under stress of different concentration (0, 0.15%, 0.30%, 0.45%, and 0.60%) NaCl were studied. The results showed that with increasing concentration of NaCl, the plant growth, leaf chlorophyll content, photochemical efficiency of PS II (Fv/Fm), quantum yield of PS II (phi(PS II)), and photochemical quenching (q(P)) decreased gradually, while the non-photochemical quenching of fluorescence (q(N)) was in adverse. After 10 days of 0. 15% NaCl stress, the leaf chlorophyll content, Fv/Fm, phi(PS II), and q(P) of H. dulcis seedlings decreased by 19.77%, 2.94%, 29.03%, and 8.16%, respectively, with significant differences (P<0.05) to the control, while no significant differences were observed for G. sinensis seedlings. Compared with the control, the Fv/Fm and phi(PS II), of G. sinensis seedlings in treatment 0.30% NaCl decreased significantly by 1.91% and 14.66%, and the chlorophyll content and q(P) of the seedling in treatment 0.45% NaCl decreased significantly by 29.28% and 11.36%, respectively (P<0.05). With increasing concentration of NaCl, the SOD activity of G. sinensis seedlings showed a consistent increasing trend, and that of H. dulcis seedlings increased first and decreased then. The POD and CAT activities of G. sinensis and H. dulci seedlings tended to increase first and decrease then, with the increment being higher for G. sinensis than for H. dulci, while the MDA content of the seedlings had an increasing trend, with the increment being higher for H. dulcis than for G. sinensis, suggesting that the cell membrane lipid peroxidation of H. dulcis was more serious than that of G. sinensis. It was concluded that G. sinensis had greater salt tolerance than H. dulcis, which was related toits higher anti-oxidation enzyme activities.

The regeneration structure and biodiversity of trees and shrub species in understory of pure plantations of oak and mixed with hornbeam in the Hyrcanian forests of Iran.

The regeneration structure and biodiversity of trees and shrub species in under story of pure and mixed Oak plantations were investigated in Chamestan Forest and Rangeland Research Station of Iran. Planted species including Oak (as main species) and Hornbeam (as associated species). This species were planted in five proportions (100Q, 70Q:30C, 60Q:40C, 50Q:50C, 40Q:60Z) in Northern of Iran in 11 years ago. All of regenerating seedlings and saplings of woody plants were divided into two height classes of 15-200 cm and more than 200 cm. In biodiversity study dominance index of Berger-Parker, diversity index of Fisher alpha, richness index of Margalef and evenness index of Equitability J were used. The results showed that abundance and diversity of regenerated species in under story of all plantations of oak were more than unplanted control plots and also under 50Q:50C were more than pure stand of oak. The presence of primary forest species in under stories of mixed plantation showed the usage of these plantations in development of succession in natural