Bacterial endophytes diversity of tree legumes from Argentina

Increased intrinsic water use efficiency enhances tree growth of native species, but not that of non-native species under warming and drying climates in Northeast China. Climate change significantly affects forest ecosystems. However, little is known about whether non-native and native tree species show similar responses to global warming. We found different trends in the basal area increment (BAI) and tree-ring stable carbon isotope ratio (δ13C) of two non-native (Pinus sylvestris var. mongolica and Populus × xiaozhuanica) and two native (Pinus tabuliformis and Ulmus pumila) tree species during the warming and drying periods from 1985 to 2014. The BAI of non-native tree species was stable, whereas that of the native tree species exhibited a significant increase. A significant increase in tree-ring δ13Ccorr (corrected for atmospheric changes in δ13C) for non-native tree species indicated increasing water stress. The intrinsic water use efficiency (iWUE, derived from tree-ring δ13C) of both non-native and native tree species increased significantly. However, the magnitude of the increase in iWUE was higher in non-native tree species than in native tree species, indicating that non-native tree species suffered stronger water stress. Increasing iWUE but no increase in BAI for non-native tree species suggested that water stress reduced stomatal conductance and, consequently, reduced carbon uptake. In contrast, increased iWUE accompanied by an enhanced BAI for native tree species indicated an increase in photosynthetic capacity induced by CO2 fertilization. These findings suggest that non-native tree species would experience greater mortality under extreme drought conditions once water stress passes a physiological threshold. However, native tree species would suffer only slightly due to benefiting from CO2 fertilization.

Since the 19th century to date, the fungal pathogens have been involved in causing devastating diseases in plants. All types of fungal pathogens have been observed in important agricultural crops that lead to significant pre and postharvest losses. The application of synthetic fungicide against the fungal plant pathogens (FPP) is a traditional management practice but at the same time these fungicides kill other beneficial microbes, insects, animal, and humans and are harmful to environment. The antagonistic microorganism such as bacteria are being used as an alternate strategy to control the FPP. These antagonistic species are cost-effective and eco-friendly in nature. These biocontrol bacteria have a broad mechanism against fungal pathogens present in the phyllosphere and rhizosphere of the plant. The antagonistic bacteria have different strategies against the FPP, by producing siderophore, biofilm, volatile organic compounds (VOCs), through parasitism, antibiosis, competition for limited resources and induce systemic resistance (ISR) in the host plant by activating the immune systems. The commercial bio-products synthesized by the major bacterial species Pseudomonas syringae, Burkholderia cepacia, Streptomyces griseoviridis, Pseudomonas fluorescens and Bacillus subtilis are used to control Fusarium, Pythium, Rhizoctonia, Penicillium, Alternaria, and Geotrichum. The commercial bio-formulations of bacteria act as both antifungal and plant growth regulators. The Plant growth-promoting rhizobacteria (PGPR) played a significant role in improving plant health by nitrogen-fixing, phosphorus solubilization, phytohormones production, minimizing soil metal contamination, and by ACC deaminase antifungal activities. Different articles are available on the specific antifungal activity of bacteria in plant diseases. Therefore, this review article has summarized the information on biocontrol activity of bacteria against the FPP and the role of PGPR in plant growth promotion. This review also provided a complete picture of scattered information regarding antifungal activities of bacteria and the role of PGPR.

For most forest species the irregularity of fruiting, low seed production and spatial distribution of trees, make it impossible to supply seeds to meet seedling production programs. On the other hand, to prevent subsequent years of low production and maintain seed viability, it is necessary to adopt adequate storage procedures. Therefore, the objectives of the study were to evaluate the influence of water content and storage conditions on the physiological potential of seeds of Colubrina glandulosa Perkins (Rhamnaceae), Chloroleucon dumosum (Benth.) G.P. Lewis (Fabaceae), Enterolobium contortisiliquum (Vell.) Morong (Fabaceae), Mimosa bimucronata (DC.) O. Kuntze (Fabaceae) and Sapindus saponaria L. (Sapindaceae), which are native tree species in tropical forests in South America. The seeds were placed in paper packaging and glass packaging and stored in a laboratory environment (uncontrolled), during storage periods of zero (recently harvested), three, six, nine, 12 and 15 months. For each storage period, the water content and physiological potential of the seeds were evaluated. The design was entirely randomized with four repetitions of 25 seeds. The germination (G) and germination uniformity (U) data were subjected to analysis of variance in a 2 x 6 factorial arrangement (two types of packaging x six storage periods), and application of polynomial regression. Seeds of Colubrina glandulosa, Chloroleucon dumosum, Enterolobium contortisiliquum, Mimosa bimucronata and Sapindus saponaria, packed in paper packaging or glass packaging, and stored under uncontrolled conditions of natural environment, presented higher G and U, in the storage period of 15 months. The physiological potential of the seeds can be maintained for a long time, as long as they are packed in a glass container with an adequate initial water content. With a water content of 8.2, 8.1, 7.9, 8.4% and 12.1%, the seeds of Colubrina glandulosa, Chloroleucon dumosum, Enterolobium contortisiliquum, Mimosa bimucronata and Sapindus saponaria, respectively, maintain the viability during storage. Therefore, the solution to store these seeds would be to rigorously dry them, and then use waterproof packaging. It is recommended that for the storage of seeds of these tree species, they are previously packaged in glass containers

Most farmers in Uruguay do not appreciate the benefits offered by native tree species and do not consider trees, pastures and livestock as a system. Since forests are renewable natural resources, sustainable use may be attained by the application of principles that ensure the perpetuation of resources through time. National information for the adoption, adaptation or technological development of silvopastoral systems is scarce. Technological proposals involving the native forests, livestock management and grassland do not exist. Native tree species (Acacia caven, Prosopis sp.) may be preserved, replanted and managed in traditional pastoral systems, as a valuable complement for sustainable animal husbandry.

Life-history traits of invasive exotic plants are typically considered to be exceptional vis-à-vis native species. In particular, hyper-fecundity and long range dispersal are regarded as invasive traits, but direct comparisons with native species are needed to identify the life-history stages behind invasiveness. Until recently, this task was particularly problematic in forests as tree fecundity and dispersal were difficult to characterize in closed stands. We used inverse modelling to parameterize fecundity, seed dispersal and seedling dispersion functions for two exotic and eight native tree species in closed-canopy forests in Connecticut, USA. Interannual variation in seed production was dramatic for all species, with complete seed crop failures in at least one year for six native species. However, the average per capita seed production of the exotic Ailanthus altissima was extraordinary: > 40 times higher than the next highest species. Seed production of the shade tolerant exotic Acer platanoides was average, but much higher than the native shade tolerant species, and the density of its established seedlings (≥ 3 years) was higher than any other species. Overall, the data supported a model in which adults of native and exotic species must reach a minimum size before seed production occurred. Once reached, the relationship between tree diameter and seed production was fairly flat for seven species, including both exotics. Seed dispersal was highly localized and usually showed a steep decline with increasing distance from parent trees: only Ailanthus altissima and Fraxinus americana had mean dispersal distances > 10 m. Janzen-Connell patterns were clearly evident for both native and exotic species, as the mode and mean dispersion distance of seedlings were further from potential parent trees than seeds. The comparable intensity of Janzen-Connell effects between native and exotic species suggests that the enemy escape hypothesis alone cannot explain the invasiveness of these exotics. Our study confirms the general importance of colonization processes in invasions, yet demonstrates how invasiveness can occur via divergent colonization strategies. Dispersal limitation of Acer platanoides and recruitment limitation of Ailanthus altissima will likely constitute some limit on their invasiveness in closed-canopy forests.

Soil-litter arthropods are critical for ecosystem functioning and sensitive to land use change, and hence to the variations in soil physicochemical properties. The relationships between soil-litter arthropod communities and soil physicochemical properties, however, remain poorly studied in Rwanda. We explored the relationships between the families of soil-litter arthropods and soil properties in exotic and native tree species, and in varieties of coffee and banana plantations. Soil-litter arthropods were sampled by using Berlese funnels, hand sorting, and pitfall traps, and were identified to the family level. Soil cores were collected and analysed for soil pH, available phosphorus, total nitrogen, soil organic carbon, silt, clay and sand. A total of 3176 individuals of soil-litter arthropods were collected, identified and classified into 13 orders and 23 families. Higher abundance was found in soil and litter sampled in plots of native tree species and banana plantations compared to exotic tree species and coffee plantations. Higher diversity was found in plots of native and exotic tree species. The analysis of soil physicochemical properties indicated that native tree species offer suitable conditions of studied soil properties. The study of the relationships between the land use, soil properties and families of soil-litter arthropods indicated positive correlations and relationships mainly in native tree species. We conclude that forest with native tree species play an important role in the conservation of soil-litter arthropods and for maintenance of better soil conditions.

Differentiation of rhizobia isolated from native legume trees in Uruguay

Growth rate, resource partitioning, and several biological traits related to biological N2 fixation for six native or non-native tree species were compared using 15N isotope dilution techniques. The trees were field grown for six years in a semiarid mediterranean-climate region with five to six months a year of absolute drought. Trees were tested as candidates for new agroforestry systems being developed in central Chile to improve soil fertility and land ‘health’, while also increasing productivity and profitability for landowners and animal breeders. Four nitrogen-fixing legume trees (NFTs) were tested: Acacia caven (Mol.) Mol.Prosopis alba Griseb., P. chilensis (Mol.) Steuntz. emend. Burk., and Tagasaste ( Chamaecytisus proliferus L.f. subsp. palmensis (Christ.)Kunkel). Additional, non-nitrogen-fixing trees were the slow-growing native Huingan (Schinus polygamus (Cav.) Caberera and the fast-growing European Ash (Fraxinus excelsior L.). Among the NFTs, highly contrasting patterns in biological nitrogen fixation (BNF) were detected, for Ndfa (proportion of N derived from atmosphere), nodule efficiency (NE = gN fixed g−1 nodules), and N content in leaves, stems and roots. Tagasaste produced 2.5–25 times more biomass and fixed 4.5 to 30 times more atmospheric nitrogen than the South American Acacia and Prosopis species. Ndfa reached 250 g plant−1 in Tagastaste, in the sixth year, with NE = maximum 2.68 in the 4th year, and 1.12 in the 6th year. In contrast, Acacia caven had by far the highest NE of the four NFTs – 12.13 in the 4th year and 6.6 in the 6th year. Whereas BNF in Tagasaste peaked in the fourth year, and declined thereafter, BNF in Acacia caven increased steadily over six years. Fraxinus excelsiorand Schinus polygamus had growth rates and biomass accumulation intermediate between that of Tagasaste and the South American NFTs.Results are discussed in relation to agroforestry, restoration of soil fertility, and ecological and economic rehabilitation of damaged ecosystems and landscapes.

Some forest plantations with native species are established in semiarid central Chile to compensate for industrial activities such as those of mining. Two of those operational forest plantations were monitored from age 1 to 3 years-old (2014–2016). Some plant attributes and soil volumetric water content (VWC) were monitored for eight native tree species (Acacia caven, Schinus polygamus, Porlieria chilensis, Lithraea caustica, Quillaja saponaria, Cryptocarya alba, Drimys winteri and Maytenus boaria), and a water balance model fitted to assess plant water use. Site preparation comprised planting holes of 40 cm × 40 cm by 50 cm in depth dug with a backhoe. Substrate was removed and mixed with compost in proportion 70:30 before mixing it in the planting hole. Planting holes acted as water reservoirs over the study period with soil VWC generally increasing with soil depth being also less variable deeper than in the upper soil layers. The ratio of adaxial (upper leaf side) to abaxial (lower leaf side) stomatal conductance approximately followed a species gradient from xeric to mesic. Irrigation represented about 26% and 53% of the total water input for the sclerophyll and the D. winteri plantation, respectively. At the plant level (0.4 × 0.4 m), soil evaporation and transpiration of D. winteri (273 and 232 mm year−1, equivalent to 43.7 and 37.1 L plant−1, respectively) were about twofold the values for the sclerophyllous/malacophyllous plantation (138 and 128 mm year−1, 22.1 and 20.5 L plant−1, respectively). We suggest the water budget for the sclerophyll/malacophyllous plantation was tight but feasible to be adjusted while for D. winteri irrigation was excessive, could be drastically reduced, and suppressed altogether if planted in gullies. We believe water balance models and soil moisture content sensors could be used to better plan and manage irrigation frequency and amounts in compensation forest plantations in semiarid central Chile.

Increasing human population and various developmental activities in the Indian state of Arunachal Pradesh, which lies in one of the most bio-diverse regions of the world, has caused large-scale deforestation, pushing a large number of native tree species to the serious verge of elimination from their native forest. In such tribal-dominated landscapes around the world, myriads of studies have emphasized the potential of homegardens as a site for local biodiversity conservation as they are known to have a huge Indigenous Knowledge System (IKS) on the use of diverse native floras. The present study was, therefore, undertaken to investigate if the native communities of the Mishmi tribe conserved native indigenous tree species in their homegardens and if they are grown then what is the future of these tree species? It was hypothesized that harbouring greater indigenous knowledge implies greater domestication of tree species in their homegardens. Altogether, 103 species of trees were recorded from 243 homegardens in the present study. Although the native species constituted more than half of the species diversity, they, however, greatly lagged in all other aspects of the study such as population share, frequency distribution and regeneration potential. Native tree species constituted just 37% of the total tree population. Only two species, Bauhinia variegata L. and Alnus nepalensis D. Don, made up the major bulk of the native population. In terms of frequency distribution, only a handful of native species maintained a decent presence in the homegardens. Most of the native species grew naturally in unmanaged homegardens. The regeneration potential of all native species was very poor, including B. variegata. The study demonstrates that out of the 76 native species recorded from the region, only 7 species can rightfully be regarded as being domesticated by virtue of IKS of the Mishmi community. Our study concludes that the native species do exist in large number in homegardens of the rural tribal areas, but most of the native wild species exist in the rural homegardens not because they are planted/preferred but because they just happen to randomly grow there since most of the homegardens of tribal household are unmanaged or poorly managed, thereby giving way to wild species to germinate, at least until the owner decides to weed them out.

Invasive plants may have variable effects within a given environment depending on their interactions with the dominant native species, yet little research has examined such species-species interactions within a site. Savanna trees with nonoverlapping canopies offer an ideal opportunity to assess associated changes in the ecosystem processes that result from interactions between an invasive species and different native tree species. We examined the influence of the exotic invasive shrub Lonicera maackii on decomposition dynamics under three native tree species: Fraxinus quadrangulata, Quercus muehlenbergii, and Carya ovata. Litter decomposition rates and litter C and N were evaluated over two years using single- and mixed-species litterbags (L. maackii and individual tree species litter); microarthropod abundance was measured at 6 weeks using Tulgren funnels. Litter from the invasive L. maackii decomposed and lost N more rapidly than the litter of the three native tree species. The rate at which L. maackii decomposed depended on its location, with L. maackii litter decomposing and losing N more rapidly under C. ovata than under the other two native tree species. Mixing L. maackii with the native species' litter did not accelerate litter mass loss overall but did result in synergistic N losses at variable times throughout the experiment, further highlighting the variable interaction between native species and L. maackii. Nitrogen loss was significantly higher than expected in mixtures of C. ovata + L. maackii litter at 6 weeks, in F. quadrangulata + L. maackii litter at 12 weeks, and in Q. muehlenbergii + L. maackii litter at 24 weeks. If the effects of invasive species on certain ecosystem processes, such as litter decomposition, are strongly influenced by their association with native species, this could suggest the need for a more nuanced understanding of the vulnerability of ecosystem processes to invasions of L. maackii and potentially other invasive species.

AimsLigustrum lucidum, native to China, is one of the dominant exotic and invasive tree species in secondary forests in Argentina. (1) We assessed its invasion during 20 yr in post‐agricultural secondary forests dominated by native tree species, and (2) evaluated tree demographic rates of native individuals under and away from L. lucidum trees that invaded these forests.LocationsFour 1‐ha permanent plots of secondary forests, subtropical Andes of Tucumán, Argentina.MethodsWe quantified the invasion of L. lucidum individuals (≥10‐cm diameter) from 1991 to 2011 within four 1‐ha plots of secondary forests and analysed annual growth and mortality rates of native tree individuals (≥10‐cm diameter) under and away from L. lucidum trees. For this, we compared tree demographic rates of all native individuals together (community level) under and away from individuals of L. lucidum, referred to as exotic and native neighbourhoods, respectively. Then, we described the relative growth rate of native tree species in exotic/native neighbourhoods (species level) and related them to their demographic life histories and morpho‐physiological traits.ResultsBoth density and basal area of L. lucidum increased from 0.1% to 4% between 1991 and 2011. Native tree individuals grew 65% less in exotic neighborhoods compared to native neighborhoods. Relative growth rate showed negative values under L. lucidum individuals for the abundant species Ocotea porphyria, Parapitadenia excelsa, Juglans austalis and Allophylus edulis, indicating competition; while less abundant species Terminalia triflora, Cupania vernalis and Blepharocalix saliscifolius showed positive growth values under L. lucidum, suggesting a facilitation process. Thus, L. lucidum competes efficiently with some native tree species, particularly with those abundant species that dominate the canopy.ConclusionsLigustrum lucidum is invading post‐agricultural secondary forests dominated by native tree species. While invading, L. lucidum competes with native abundant tree species that dominate the main structure of the forest canopy. As this invasive trend will likely increase in the near future, L. lucidum may alter forest structure, composition and dynamics, as well ecosystem functioning.

URban Biotopes of Aotearoa New Zealand (URBANZ) II: Floristics, biodiversity and conservation values of urban residential and public woodlands, Christchurch

The root nodules are a unique environment formed on legume roots through a highly specific symbiotic relationship between leguminous plants and nodule-inducing bacteria. Previously, Rhizobia were presumed to be the only group of bacteria residing within nodules. However, recent studies discovered diverse groups of bacteria within the legume nodules. In this report soybean nodule-associated bacteria were studied in an effort to identify beneficial bacteria for plant disease control and growth promotion. Analysis of surface-sterilized single nodules showed bacterial diversity of the nodule microbiome. Five hundred non-rhizobial colonies from 10 nodules, 50 colonies per nodule, were tested individually against the tomato wilt causing bacterial pathogen Clavibacter michiganensis subsp. michiganensis (Cmm) for inhibition of pathogen growth. From the initial screening, 54 isolates were selected based on significant growth inhibition of Cmm. These isolates were further tested in vitro on another bacterial pathogen Pseudomonas syringae pv. tomato (Pst) and two fungal pathogens Rhizoctonia solani and Sclerotinia sclerotiorum. Bacterial metabolites were extracted from 15 selected isolates with ethanol and tested against pathogen Cmm and Pst. These isolates were identified by using MALDI-TOF mass spectrometry and 16S rRNA gene sequencing. Pseudomonas spp. were the dominant soybean nodule-associated non-rhizobial bacterial group. Several isolates imparted significant protection against pathogens and/or plant growth promotion on tomato seedlings. The most promising nodule-associated bacterial isolate that suppressed both Cmm and Pst in vitro and Pst in tomato seedlings was identified as a Proteus species. Isolation and identification of beneficial nodule-associated bacteria established the foundation for further exploration of potential nodule-associated bacteria for plant protection and growth promotion.

Many tropical invasive species have allelopathic effects that contribute to their success in native plant communities. Pyrolyzed biomass (“biochar”) can sorb toxic compounds, including allelochemicals produced by invasive plants, potentially reducing their inhibitory effects on native species. Strawberry guava (Psidium cattleianum) is among the most important allelopathic invasive species on tropical islands and recognized as the most serious threat among invasive species in the global biodiversity hotspot of Mauritius. We investigated the effects of additions of locally produced biochar on native tree species in a field experiment conducted in areas invaded by strawberry guava within Mauritius’ largest national park. Growth and survivorship of native tree species were monitored over 2.5 years in plots subjected to four treatments: non-weeded, weeded, weeded + 25 t/ha biochar, and weeded + 50 t/ha biochar. Native tree growth and survivorship were strongly suppressed by strawberry guava. Biochar treatments dramatically increased native tree performance, with more than a doubling in growth, and substantially increased native tree survivorship and species diversity, while suppressing strawberry guava regeneration, consistent with growth-promoting properties and sorption of allelochemicals. We conclude that biochars, including “sustainable biochars” produced from locally accessible biomass using low-tech pyrolysis systems, have considerable potential to counteract effects of allelopathic invaders and increase the capacity for native species regeneration in tropical island ecosystems.