Acaciapollenites acaciae sp. nov., una nueva políade de mimosoidea del neógeno, en la Cuenca del Colorado, Argentina

Fossil mimosoid polyads have been recently recovered from Neogene deposits in the Colorado Basin, Argentina, and the new species Acaciapollenites acaciae sp. nov. is described, which is closely similar to polyads of species included in Acacia Miller subgenus Acacia Vassal. It is characterized by colporate apertures on the distal face of the pollen grains, a typical polyad of the subgenus Acacia species. The new polyad species is very similar to those of the extant Acacia curvifructa Burkart. Comparing the habitat of subgenus Acacia extant species, the Acaciapollenites acaciae occurrence suggests drier and warmer paleoclimatic conditions than today for the Late Miocene-Early Pliocene in the Colorado Basin. Paleogeographic data of Acacia pollen diversity are discussed. A similar early diversification and distribution of Acacia genus is recognized for the new and old worldPolíades afines a Mimoisoideas fueron recuperadas de depósitos del Neógeno de la cuenca del Colorado, Argentina. Por sus detalles morfológicos es reconocida una nueva especie con afinidad botánica a las especies actuales del género Acacia, subgénero Acacia. Acaciapollenites acaciae sp. nov. se distingue por presentar aperturas colporadas sobre la superficie distal de sus granos de polen, políade típica de las especies del subgénero Acacia. La nueva especie de políade se compara con las de la especie actual Acacia curvifructa. Comparando el hábitat de las actuales especies del subgénero Acacia, la presencia de Acaciapollenites acaciae en el Neógeno de la cuenca del Colorado, sugiere condiciones paleoclimáticas mas áridas y cálidas que las de hoy día. Se discuten los datos paleogeográficos de la diversidad de Acacia. Es reconocida tanto para el nuevo como para el viejo mundo, una temprana diversificación y dispersión del género.Fil: Caccavari, Marta Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Guler, Maria Veronica. Universidad Nacional del Sur. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Nematofauna as indicator of soil N availability in mixed plantations? A case study from tropical forest of Eucalyptus and Acacia in Congo. [P2.179]

Nitrogen is a limiting factor for the growth of Eucalyptus plantations, particularly in subtropical areas characterized by very low soil fertility (e.g.degraded pastures). The association with N2- fixing species such as Acacia mangium is an alternative for ecological intensification of these ecosystems. Enhancement of Eucalyptus trees growth may happen by direct transfer of N fixed by Acacia trees or indirectly through litter decomposition. Field assessments in Congo showed that the productivity of Eucalyptus trees in mixed plantations was significantly increased compared with Eucalyptus alone. Higher N contents in soil of mixed plantations explained such positive impact. In a microcosm experiment, we measured N mineralization in soil sampled from pure stands of Acacia, pure stands of Eucalyptus and from the mixed plantations. The results showed an accumulation of nitrate in the rhizosphere of Acacia. We found that the introduction of Acacia trees changed significantly the structure of the community of nematodes by increasing the proportion of bacterial-feeding nematodes. Similar results were obtained in mixed-plantations in Brazil and in France, suggesting that nematofauna could be a key indicator of N availability in soil. Microbial communities involved in nitrification were also studied by targeting AOA and AOB genes using the quantitative PCR method. An increase of the number of copies of AOA gene was observed in the rhizosphere of Acacia while AOB gene was difficult to detect. This suggests that Archae communities may play an important role in N cycling in soil of Eucalyptus plantations. Our results demonstrate that the introduction of Acacia in mixed plantations systems influences the N cycle in the soil and associated biological activities. (Résumé d'auteur

L´impact des aires protégées et des utilisations anthropogènes du sol sur la regeneration des terrains boisés à Acacia dans l´est du Burkina Faso

Regeneration success, persistence strategies (seedlings vs. coppicing), and population trend of Acacia spp. were tested under two land-use regimes in eastern Burkina Faso: (i) protected areas shielded to livestock grazing pressure, to logging, and using early annual fire as a management system; (ii) areas with high human impact (heavily and extensive livestock grazing, harvesting for wood and for medicinal plants). Generally, a good regeneration rate of Acacia species was observed in protected areas and a poor regeneration rate in areas with high human impact. Nevertheless, some species affiliated to the subgenus Aculeiferum as A. dudgeoni and A. polyacantha showed a good regeneration under both land use regimes. Juvenile plants less than 25 cm height of A. dudgeoni and A. gourmaensis increased by 116 to 50 % in areas with human impact as compared to their populations in protected areas. With SCD slopes varying from –0.40 to -0.70, the protected Acacia woodland displayed a stable population structure due to abundance of recruitment, and coppicing persistence (more common in the subgenus Aculeiferum) favoured by early annual fire. Consequently, the protected areas are favourable for Acacia woodland regeneration. Conversely, SCD slopes are positive or close to zero in areas of anthropogenic regime and showed a declining population, especially more marked with the subgenus Acacia due to permanent seed and seedling removal by livestock grazing. Nevertheless, the number of seedlings of some species was higher in areas under human pressure than in protected areas, especially for the subgenus Aculeiferum, improving the genetic variability and thus the long-term maintenance of the population. Key words: Acacia, early fire, land use, sudano-sahelien zoneLe statut de la régénération, les stratégies de persistance et la dynamique des Acacia spp. ont été évalués suivant deux modes d’utilisation dans la région est du Burkina Faso: (i) les zones protégées soustraites du pâturage extensif et de la coupe du bois, mais sont parcourues annuellement par des feux précoces ; (ii) les zones à forte impact anthropique (fort pâturage extensif, exploitations humaines diverses). En général, les zones protégées montrent un taux de régénération élevé des Acacia spp. alors que les zones anthropogéniques présentent une faible régénération. Néanmoins, certaines espèces affiliées au sous genre Aculeiferum comme A. dudgeoni et A. polyacantha montrent une bonne régénération dans les deux modes d’utilisation des terres. La population juvénile de moins de 25 cm de hauteur des espèces tel que A. dudgeoni et A. gourmaensis est 116 à 50 % plus élevée dans les zones anthropisées que dans les zones protégées. Avec des pentes de régression variant entre -0.40 à -0.70 dans les zones protégées, les populations présentent une structure stable due à l’abondance des plantules, et des rejets de souches maintenues par les feux précoces (plus fréquent dans le sous genre Aculeiferum). Par conséquent, les zones protégées sont plus favorables à la régénération des formations d’Acacia. A l’opposé, les pentes de régression sont positives ou proche de 0 dans les zones anthropisées montrant des populations peu stables particulièrement pour le sous genre Acacia à cause du prélèvement des semences et des plantules due au pâturage extensif. Néanmoins, les plantules issues de la germination de certaines espèces du sous Aculeiferum sont plus nombreuses dans les zones anthropisées que dans les zones protégées et pourraient améliorer la variabilité génétique pour la conservation à long termes des peuplements. Key words: Acacia, feux précoces, pâturage, utilisation des terres, zone soudano-sahélienn

Symbiotic and phylogenetic diversity of rhizobia associated with native and introduced Acacias in Algeria

In the arid zones were crop production is reduced due to drought combined to low soil fertility, the use of symbiotic native legume trees adapted to such harsh conditions could enhance the productivity of agroforestry systems. In North Africa, Acacia species are good candidates for this purpose since they can grow on N-deficient soils and improve their N balnce due to their symbiotic association with rhizobia, nitrogen-fixing soil bacteria. In order to identify and select. Efficient acacia-rhizobia symbiotic associations, soil samples and root nodules from seven Acacia species, five native (A ehrenbergiana, A laeta, A. niIotica, A. seyal, A. tortimis) and two introduced (A. karroo, A. saligna). were collected in arid and semi-arid regions of Algeria from Oran to Tamanrasset. A collection of 22 bacteria1 strains was obtained after trapping on Acacia seedlings inoculated with soil samples originating from nine geographic sites. 16S rDNA sequencing revealed that the new strains represented different species in Sinorhizobium and Rhizobium. This genetic diversity was confirmed by phenotypic characterisation through biochemical assays and host spectrum. Some strains were particularly tolerant to low pH and high NaCl concentrations. temperature and osmotic stress in vitro conditions. In a next step, selection of efficient rthizobia displaying a high nitrogen-fixing potential under stress conditions will be carried out in controlled conditions before testing them in field conditions. (Texte intégral

Floristics and distribution of Wattle Dry Sclerophyll Forests and Scrubs in north-eastern New South Wales

Acacia blakei forests and scrubs of north-eastern NSW are described and compared to similar vegetation found in the south-east of the state, primarily dominated by Acacia silvestris. Like those in the south, Northern Wattle Dry Sclerophyll Forests form often discrete stands with abrupt margins on steep slopes in rugged terrain on shallow often rocky soils. The structure is usually of a cohort with stems of an even height and size up to 20 m tall, and a sparse understorey with few grasses, herbs or shrubs. These systems are potentially maintained by infrequent extreme fire events. Notes are made on their management and conservation

Cross-amplification and characterization of polymorphic microsatellite markers from Acacia (Senegalia) mellifera and Acacia brevispica to Acacia senegal (L.) Willd.

Seven polymorphic microsatellite markers isolated from Acacia brevispica and Acacia mellifera were successfully cross-amplified in Acacia senegal. The loci were surveyed for polymorphism using 30 samples. Allelic diversity ranged from 4 (Ame02, Ab06 and Ab18) to 13 (Ab26) per locus. The expected heterozygosity (HE) ranged from 0.543 (Ame02) to 0.868 (Ab26) while observed heterozygosity (HO) ranged from 0.516 (Ame05) to 0.800 (Ame03). Cross amplification of these loci represents a potential source of co-dominant marker and will be useful in the study of genetic diversity, structure, gene flow and breeding systems of this important Acacia species

Properties and functions of organic materials in poor agricultural soil condition

A field experiment was conducted under different soil strata in poor agricultural soil condition. Each soil stratum was treated separately with different organic material for soil fertility management. These organic materials are cow dung, sheep dung, goat dung, donkey dung, rice husks, millet husks, Acacia albida, Acacia nilotica, wood ash, house refuses, and combination of all ‘ani-cro-ber’. In the first assessment, soil structure, texture, colour, consistency, bulk density were determined in the field, while in the second assessment N, P, K, Na, Ca, OC, OM and pH were determined under specific laboratory analysis. It is believed that the use of organic materials in soil management is a good way to improve and maintain soil quality and soil fertility rehabilitation in poor agricultural soil condition

Can species richness be maintained in logged endemic Acacia Heterophylla forests (Reunion Island, Indian Ocean) ?

It is assumed that forests can serve multiple uses, including wood production and maintenance of high biodiversity level. We tested this hypothesis by studying eradication methods of invasive plants currently implemented in exploited endemic Acacia heterophylla forests located in a tropical highland forest region on the island of Réunion. We also compared species richness in logged (over time) and natural forests. Our results show that all individuals of the widespread alien invasive plant Rubus alceifolius were generated from cuttings. We quantifi ed the high growth capability of this species by comparing with those of Acacia heterophylla along with Rubus apetalus var. apetalus, a close non-invasive congener. The substantial multiplicative and vegetative growth ability of R. alceifolius enabled it to form monospecific patches in only 2.5 years. The species richness of the exploited Acacia heterophylla forest was thus very affected. Although the species richness increased over time after logging, the extent of the resulting richness was not as great as that in natural forests which, moreover, included numerous exotic plants. The authors assess the impact of highly disturbing logging operations and, based on the results of the comparisons, are very pessimistic about the possibility of maintaining species richness in logged forests. Nevertheless, the results indicate that the situation is not beyond hope and an eradication program specifi cally tailored to this kind of forest is proposed if exploitation will stop

Seed production, infestation, and viability in Acacia tortilis (synonym: Vachellia tortilis) and Acacia robusta (synonym: Vachellia robusta) across the Serengeti rainfall gradient

Tree recruitment in savannas proceeds in multiple stages characterized by successive filters occurring at the seed and seedling stages. The “demographic bottleneck” hypothesis suggests that such filters ultimately restrict tree density and prevent trees from dominating grasses in savannas, but many of the demographic transitions underlying this assumption have not been quantified. We investigated how short- (1–2 years) and long-term (40 + years) rainfall patterns influenced seed production, infestation, and viability for two dominant species, Acacia robusta and Acacia tortilis across the Serengeti ecosystem mean annual precipitation gradient over a two-year period. We found that neither production, nor infestation, nor viability was influenced by rainfall. Pod production differed between species and increased with tree height in A. robusta. Mean infestation proportion in 2013 was higher (mean ± SE; 0.28 ± 0.08) in A. tortilis than in A. robusta (0.11 ± 0.05) but the trend reversed in 2014, when A. tortilis (0.33 ± 0.10) had lower infestation than A. robusta (0.61 ± 0.09). Under laboratory conditions, A. tortilis and A. robusta seeds had maximum germination (= viability) proportions of 70 and 20%, respectively. Mean seed viability was more than five-fold higher (0.46 ± 0.19) in A. tortilis than in A. robusta (0.08 ± 0.10). Our study has produced important estimates for seed stage demographic dynamics that can be used for modeling tree dynamics in Serengeti system, and savannas in general

KEANEKARAGAMAN TUMBUHAN LUMUT (BRYOPHYTA) PADA BERBAGAI KETINGGIAN HUBUNGANNYA DENGAN KONDISI LINGKUNGAN DI WILAYAH LERENG SELATAN MERAPI PASCA ERUPSI

Penelitian ini bertujuan untuk mengetahui jenis-jenis tumbuhan lumut, indeks keanekaragaman tumbuhan lumut, keanekaragaman jenis tumbuhan lumut, serta hubungan kondisi lingkungan yang meliputi faktor klimatik (intensitas cahaya, suhu udara, kelembaban udara) dan faktor edafik (suhu tanah, kelembaban tanah, pH tanah) dengan keanekaragaman jenis tumbuhan lumut diwilayah lereng selatan Merapi pasca erupsi. Penelitian ini merupakan penelitian dengan metode observasi dan hasilnya dianalisis secara deskriptif. Populasi penelitian adalah semua jenis lumut terrestrial pada berbagai ketinggian di wilayah lereng selatan Merapi pasca erupsi. Sampel penelitian ini adalah semua tumbuhan lumut terrestrial yang teramati di 30 plot pengamatan pada berbagai ketinggian sepanjang wilayah penelitian. Penelitian dilakukan dengan menentukan lokasi pengamatan dan menentukan batasan-batasan pada masing-masing ketinggian (1000 m dpl, 1200 m dpl dan 1400 m dpl). Mengambil sampel secara purposive sampling dengan membuat ukuran plot 1 x 1 m 2 dan melakukan pengukuran faktor lingkungan yaitu klimatik yang meliputi : Suhu udara, kelembaban udara, dan intensitas cahaya, dan untuk faktor edafik meliputi : Suhu tanah, kelembaban tanah, dan pH tanah. Kemudian melakukan identifikasi jenis tumbuhan lumut lalu menghitung luas penutupan setiap jenis pada tiap plot sekaligus perhitungan luas penutupan seluruh jenis pada masing-masing plot. Mencatat jenis tumbuhan pelindung pada plot yang diamati. Hasil penelitian dianalisis secara deskriptif dengan menentukan indeks keanekaragaman tumbuhan untuk menentukan keanekaragaman tumbuhan lumut di wilayah lereng selatan Merapi pasca erupsi. Hasil penelitian diperoleh bahwa ditemukan 11 jenis tumbuhan lumut terrestrial di lereng selatan Merapi pasca erupsi. Indeks keanekaragaman tumbuhan lumut pada ketinggian 1000 m dpl, 1200 m dpl, dan 1400 m dpl sebesar 0,810, 0,675 dan 0,471. Keanekaragaman tumbuhan lumut adalah rendah. Faktor klimatik pada berbagai ketinggian di wilayah lereng selatan Merapi pasca erupsi berpengaruh terhadap keanekaragaman jenis tumuhan lumut. Karena semakin tinggi tempat, intensitas cahaya semakin tinggi, suhu semakin tinggi, kelembaban semakin rendah. Maka keanekaragaman jenis tumbuhan lumut juga semakin rendah. Kata Kunci : Keanekaragaman jenis, Tumbuhan lumut (Bryophyta), Ketinggian