Tropical dryland agroforestry on clay soils: : Analysis of systems based on Acacia senegal in the Blue Nile region, Sudan

Acacia senegal, the gum arabic producing tree, is the most important component in traditional dryland agroforestry systems in the Blue Nile region, Sudan. The aim of the present study was to provide new knowledge on the potential use of A. senegal in dryland agroforestry systems on clay soils, as well as information on tree/crop interaction, and on silvicultural and management tools, with consideration on system productivity, nutrient cycling and sustainability. Moreover, the aim was also to clarify the intra-specific variation in the performance of A. senegal and, specifically, the adaptation of trees of different origin to the clay soils of the Blue Nile region. In agroforestry systems established at the beginning of the study, tree and crop growth, water use, gum and crop yields, nutrient cycling and system performance were investigated for a period of four years (1999 to 2002). Trees were grown at 5 x 5 m and 10 x 10 m spacing alone or in mixture with sorghum or sesame; crops were also grown in sole culture. The symbiotic biological N2 fixation by A. senegal was estimated using the 15N natural abundance (δ15N) procedure in eight provenances collected from different environments and soil types of the gum arabic belt and grown in clay soil in the Blue Nile region. Balanites aegyptiaca (a non-legume) was used as a non-N-fixing reference tree species, so as to allow 15N-based estimates of the proportion of the nitrogen in trees derived from the atmosphere. In the planted acacia trees, measurements were made on shoot growth, water-use efficiency (as assessed by the δ13C method) and (starting from the third year) gum production. Carbon isotope ratios were obtained from the leaves and branch wood samples. The agroforestry system design caused no statistically significant variation in water use, but the variation was highly significant between years, and the highest water use occurred in the years with high rainfall. No statistically significant differences were found in sorghum or sesame yields when intercropping and sole crop systems were compared (yield averages were 1.54 and 1.54 ha-1 for sorghum and 0.36 and 0.42 t ha-1 for sesame in the intercropped and mono-crop plots, respectively). Thus, at an early stage of agroforestry system management, A. senegal had no detrimental effect on crop yield, but the pattern of resource capture by trees and crops may change as the system matures. Intercropping resulted in taller trees and larger basal and crown diameters as compared to the development of sole trees. It also resulted in a higher land equivalent ratio. When gum yields were analysed it was found that a significant positive relationship existed between the second gum picking and the total gum yield. The second gum picking seems to be a decisive factor in gum production and could be used as an indicator for the total gum yield in a particular year. In trees, the concentrations of N and P were higher in leaves and roots, whereas the levels of K were higher in stems, branches and roots. Soil organic matter, N, P and K contents were highest in the upper soil stratum. There was some indication that the P content slightly increased in the topsoil as the agroforestry plantations aged. At a stocking of 400 trees ha-1 (5 x 5 m spacing), A. senegal accumulated in the biomass a total of 18, 1.21, 7.8 and 972 kg ha-1of N, P, K and OC, respectively. Trees contributed ca. 217 and 1500 kg ha-1 of K and OC, respectively, to the top 25-cm of soil over the first four years of intercropping. Acacia provenances of clay plain origin showed considerable variation in seed weight. They also had the lowest average seed weight as compared to the sandy soil (western) provenances. At the experimental site in the clay soil region, the clay provenances were distinctly superior to the sand provenances in all traits studied but especially in basal diameter and crown width, thus reflecting their adaptation to the environment. Values of δ13C, indicating water use efficiency, were higher in the sand soil group as compared to the clay one, both in leaves and in branch wood. This suggests that the sand provenances (with an average value of -28.07 ) displayed conservative water use and high drought tolerance. Of the clay provenances, the local one (Bout) displayed a highly negative (-29.31 ) value, which indicates less conservative water use that resulted in high productivity at this particular clay-soil site. Water use thus appeared to correspond to the environmental conditions prevailing at the original locations for these provenances. Results suggest that A. senegal provenances from the clay part of the gum belt are adapted for a faster growth rate and higher biomass and gum productivity as compared to provenances from sand regions. A strong negative relationship was found between the per-tree gum yield and water use efficiency, as indicated by δ13C. The differences in water use and gum production were greater among provenance groups than within them, suggesting that selection among rather than within provenances would result in distinct genetic gain in gum yield. The relative δ15N values ( ) were higher in B. aegyptiaca than in the N2-fixing acacia provenances. The amount of Ndfa increased significantly with age in all provenances, indicating that A. senegal is a potentially efficient nitrogen fixer and has an important role in t agroforestry development. The total above-ground contribution of fixed N to foliage growth in 4-year-old A. senegal trees was highest in the Rahad sand-soil provenance (46.7 kg N ha-1) and lowest in the Mazmoom clay-soil provenance (28.7 kg N ha-1). This study represents the first use of the δ15N method for estimating the N input by A. senegal in the gum belt of Sudan. Key words: Acacia senegal, agroforestry, clay plain, δ13C, δ15N, gum arabic, nutrient cycling, Ndfa, Sorghum bicolor, Sesamum indicum

Läksi puut ylenemähän : Metsien hoidon historia Suomessa keskiajalta metsäteollisuuden läpimurtoon 1870-luvulla

Tutkimuksen tavoitteena on historiantutkimuksen menetelmiä käyttäen selvittää metsänhoidon teorian sekä käytännön metsänhoidon kehitysvaiheet ja näihin vaikuttaneet tekijät, keskiajalta lähtien 1870-luvulla tapahtuneeseen metsäteollisuuden läpimurtoon saakka. Tutkimus tarkastelee Suomen metsiä, niiden käyttöä ja metsänhoidon alkuvaiheita Ruotsin ja Venäjän vallan aikoina. Vastauksia haetaan erityisesti seuraaviin pääkysymyksiin: - miten eri metsänkäyttömuodot ja -käyttäjät vaikuttivat metsiin ja metsänhoidon edistymiseen? - millä tavoin maanomistuksen kehitys vaikutti metsien käyttöön ja hoitoon? - millaisiin päämääriin ja yhteiskunnallisiin taustatekijöihin metsien käytön julkinen ohjaus perustui? - mitä käytännön vaikutuksia valtion metsäpolitiikalla ja ohjauksella oli metsänhoidon kehitykseen? - missä ja miten kehittyivät Suomessa sovellettu metsänhoidon teoria ja käytännön menetelmät? - mitkä tekijät säätelivät metsänhoidon teorioiden soveltamista käytäntöön? - mikä oli naapurimaiden metsänhoidon sekä kansainvälisten yhteyksien merkitys metsänhoidon kehitykselle Suomessa? - miten vuosisatainen pelko metsien ja puun loppumisesta vaikutti metsänhoidon kehitykseen? - millainen merkitys puun arvon kehityksellä oli metsänhoidon alkuun saattamiselle ja edistymiselle? Suomessa harjoitettiin 1870-luvulle saakka pääasiassa talonpoikaista metsänkäyttöä. Maaseudun väestö hankki toimeentulonsa metsistä eränkäynnin, kaskiviljelyn, laiduntamisen, rakennushirsien valmistamisen, tervantuotannon ja paikoin myös potaskan tai sysien valmistamisen avulla. Erityisesti rannikkoseuduilla tuotettiin "isorakennuksen puita", lehtereitä, mastopuita ja muuta erikoispuutavaraa. Lautojen ja lankkujen sahaus laajeni vähitellen, saavuttaen 1800-luvun lopulla hallitsevan aseman myyntiin tarkoitettujen metsäntuotteiden tuotannossa. Polttopuun sekä muun kotitarvepuun kulutus säilyi suurimpana puunkäytön ryhmänä pitkälle 1900-luvulle saakka. Mainituista metsänkäyttömuodoista erityisesti kaskeaminen ja sitä seuraava laiduntamisvaihe sekä tervaspuiden koloaminen "autioittivat" laajoja metsäalueita. Tiheimmin asutuilla seuduilla esiintyi pulaa poltto- ja rakennuspuusta myöhäiskeskiajalta alkaen. Nämä ongelmat sekä laivanrakennuksen ja vuoriteollisuuden puunsaannin turvaamisen tarve johtivat 1600-luvun puolivälissä pysyvään metsänkäytön julkiseen ohjaukseen. Tuolloin Ruotsin valtakunnan metsälainsäädännön kivijalaksi tuli kestävyyden periaate, josta kruunu kylläkin joutui tinkimään moneen otteeseen. Valtion jatkuva rahantarve oli käytännössä metsäpolitiikan tärkein taustavoima sekä Ruotsin vallan että autonomian aikana. Jo 1600-luvulla ruvettiin vaatimaan talonpoikien yhteismaiden jakamista omistajilleen vastuullisemman metsänkäytön nimissä. Isoajakoa saatiin Suomessa odottaa 1770-luvulle saakka. Etelä-Suomessa se valmistui melko nopeasti, 1800-luvun puoliväliin mennessä. Sillä olikin myönteinen, metsien säästävämpään käsittelyyn johtava vaikutus. Valtiosta tuli isonjaon myötä erityisesti Pohjois-Suomessa merkittävä metsänomistaja 1800-luvun jälkipuoliskolla. Valtion metsähallinto, jota maaherrat ja sivistyneistö vaativat perustettavaksi jo 1700-luvun puolivälissä, aloitti toimintansa maanlaajuisesti 1860-luvulla. Se oli ensimmäinen merkittävä metsänhoidon organisaatio, ja vasta sen myötä metsänkäyttöä ohjaavilla säädöksillä ja ohjeilla alkoi olla käytännön merkitystä. Yksityismetsiä varten ei tällaista organisaatiota vielä perustettu, niitä rasittivat pahoin nousevan sahateollisuuden määrämittahakkuut pitkälle 1900-luvun puolelle. Turun Akatemiassa tehtiin mittavaa metsänhoidon menetelmiä koskevaa sekä myös metsäpoliittista tutkimustyötä 1700-luvun jälkipuoliskolla. Tulokset eivät vielä sanottavasti siirtyneet käytäntöön, lähinnä puun alhaisen arvon ja tarvittavien organisaatioiden puuttumisen takia. Kun valtion metsähallintoa ja Suomen omaa metsäopetusta ryhdyttiin perustamaan 1800-luvun puolivälissä, haettiin metsänhoidon mallia alan johtavaksi maaksi kehittyneestä Saksasta. Tultaessa 1870-luvulle, oli Evolla jo käynnissä voimakas kehitystyö maamme olosuhteisiin soveltuvien menetelmien luomiseksi saksalaisen teorian pohjalta. Metsänhoidon tiedot ja taidot olisivat jo tässä vaiheessa riittäneet kestävän metsätalouden harjoittamiseen kaikkien omistajaryhmien metsissä, jos tarvittavat organisaatiot olisi kyetty perustamaan ja metsäammattilaisia olisi koulutettu tarpeeksi. Metsänhoidon kehitystä hidastivat 1800-luvun lopulla lähinnä valtion heikko talous ja poliittiset näkemyserot. Metsäteollisuuden 1870-luvulta alkanut voimakas kasvu ja lisääntyvä puuntarve pakottivat kuitenkin valtiovallan pitämään huolta puuntuotannon jatkuvuudesta. Metsäteollisuuden kasvavan viennin kautta lisääntyvät verotulot ja kan-santalouden myönteinen kehitys antoivat vähitellen mahdollisuuden metsänhoidon edistämiseen ammattilaisten koulutuksen, kansalaisten neuvonnan, lainsäädännön ja viranomaisten toiminnan kautta. Tämä tutkimus lähestyy aihettaan metsähistorian, taloushistorian, yhteiskuntahistorian ja ympäristöhistorian näkökulmista. Ajankohtaista merkitystä sillä on kehitysmaiden sekä Itä-Euroopan siirtymätalouksien metsänhoidon edistämiselle, missä suomalaiset metsäammattilaiset ovat mukana lukuisten kehityshankkeiden asiantuntijoina. Kymmenissä maissa metsätalous kamppailee samanlaisten ongelmien kanssa kuin Suomessa ja naapurimaissa 100 - 300 vuotta sitten. Meidän kokemuksistamme on näille kansantalouksille hyötyä valtion- ja yksityismetsätalouden metsänhoito-organisaatioita sekä metsälainsäädäntöä kehitettäessä.

Association study of the dystrobrevin-binding gene with schizophrenia in Australian and Indian samples

Numerous studies have reported association between variants in the dystrobrevin binding protein 1 (dysbindin) gene (DTNBP1) and schizophrenia. However, the pattern of results is complex and to date, no specific risk marker or haplotype has been consistently identified. The number of single nucleotide polymorphisms (SNPs) tested in these studies has ranged from 5 to 20. We attempted to replicate previous findings by testing 16 SNPs in samples of 41 Australian pedigrees, 194 Australian cases and 180 controls, and 197 Indian pedigrees. No globally significant evidence for association was observed in any sample, despite power calculations indicating sufficient power to replicate several previous findings. Possible explanations for our results include sample differences in background linkage disequilibrium and/or risk allele effect size, the presence of multiple risk alleles upon different haplotypes, or the presence of a single risk allele upon multiple haplotypes. Some previous associations may also represent false positives. Examination of Caucasian HapMap phase II genotype data spanning the DTNBP1 region indicates upwards of 40 SNPs are required to satisfactorily assess all nonredundant variation within DTNBP1 and its potential regulatory regions for association with schizophrenia. More comprehensive studies in multiple samples will be required to determine whether specific DTNBP1 variants function as risk factors for schizophrenia.

Ode to a Skylark: Agricultural intensification and farmland birds in the Baltic region

Intensification of agricultural land-use has been was shown to be the key reason behind declines in wildlife species associated with farmland. Accession to the European Union is regarded as a potential threat to the farmland biota of its new member states. In my thesis I looked at scenarios of agricultural development across the Baltic states of Estonia, Latvia and Lithuania, and the ways they are seen to affect farmed environments as a habitat of farmland bird species. I looked at the effects of major farmed habitats across the region, and assessed the role of spatial organisation of farmed habitats. I also evaluated the direction and magnitude of changes in bird communities following progression of farmland land-use from a relatively less intensive to the most intensive type within each country. Different aspects of the structural complexity of farmland were critical for supporting farmland birds. There was a clear indication that the more intensively farmed areas across the region provided habitat for fewer bird species and individuals, and intensification of field management was reflected in a tangible decrease in farmland bird abundance. The second part of the thesis, based on interviews in Estonia and Finland, is devoted to farmers interest in and knowledge of farmland wildlife, their understanding of the concept of biodiversity, and awareness of causes behind species declines. I examined the relationship between farmers interest and their willingness to undertake practices favouring farmland wildlife. Many farmers viewed biodiversity from a narrow perspective. In Finland farmers expressed higher concern about the decline in common farmland species than in Estonia. In both countries farmers rated intensification of agriculture as the major driving force behind declines. The expressed interest in wildlife positively correlated with willingness to undertake wildlife-friendly measures. Only farmers with agri-environment contracts targeted specifically at biodiversity were more knowledgeable about practical on-farm activities favouring wildlife, and were more willing to employ them that the rest. The results suggest that, by contributing to simplification of the farmland structure, homogenisation of crops, and increase in intensity of field use, EU agricultural policies will have a detrimental effect on farmland bird populations in Eastern Europe. Farmers are on the whole positive to the idea of supporting wildlife on their farms, and are concerned about declines, but they require payments to offset their income loss and extra work. I propose ways of further improving and better targeting of the agri-environment schemes in the region. I argue that with a foreseen tripling of cereal yields across the region, the EU Council s target of halting biodiversity decline in the EU by 2010 may not be realistic unless considerable improvements are made in conservation safeguards within the EU agricultural policy for the region.

Performance of Pinus elliottii, Pinus caribaea, their F-1, F-2 and backcross hybrids and Pinus taeda to 10 years in the Mesopotamia region, Argentina

Performances of Pinus taxa were studied to 10 years of age in two trials in each of Misiones and Entre Rios provinces across the Mesopotamia region of Argentina. Taxa comprised 22 populations from sources in Argentina, Australia, Brazil and Zimbabwe including Pinus elliottii var. elliottii (Pee), Pinus caribaea var. hondurensis (Pch), their four, inter-specific hybrids (F-1, F-2 and backcrosses from F-1 to Pch and to Pee-all as broadly based bulks); other Pee and Pinus taeda (Pt) comprised narrower or unspecified bulks. Variable numbers of taxa were missing at each site. Mean survival across sites at age 10 years ranged 53.2-91.3% averaging 74.2%. Analysis of variance of plot means indicated population effect was statistically significant (p < 0.05) for all or most growth and quality traits at all sites. However, significant differences from the nominated check seedlot at the Entre Rios sites (Pee, Australia) were extremely rare, while quite common at the northern, Misiones sites (check seedlot a Pt population). In the Misiones trials, F-1, F-2 and both backcross hybrids showed better stem straightness than Pee and Pt from Argentina, generally with statistically significant differences (p < 0.05). Pt showed lowest forking scores (desirable). Taxon x environment interaction was statistically significant (p < 0.01) for growth traits only (p > 0.05). However, this interaction contributed an average of only 34.1% of the taxon variance suggesting a lack of practical importance. Taxa most suitable for deployment in the Mesopotamia region, Argentina are suggested.

Surface instability of a current-carrying plasma under the influence of a high-frequency electric-field

Surface instability of a collisionless semi-infinite current carrying plasma is studied. The semi-infinite plasma bounded by a plane surface is under the influence of a high frequency (hf) field. There are two classes of surface modes. One is a normal extension of zero high frequency field and the other due entirely to the presence ofhf field. As expected, with the increase in thehf field, the growth rates of the surface instabilities decrease. There are regions defined by the electron drift velocityu where the unstable surface and bulk regions overlap. The interesting result is that unlike the bulk plasma, there is a stable region on theu-axis flanked by two unstable regions. The width of this stable region increases with the increase in the field strength.

Effect of rodents on seed fate of five hornbill-dispersed tree species in a tropical forest in north-east India

Hornbills are important dispersers of a wide range of tree species. Many of these species bear fruits with large, lipid-rich seeds that could attract terrestrial rodents. Rodents have multiple effects on seed fates, many of which remain poorly understood in the Palaeotropics. The role of terrestrial rodents was investigated by tracking seed fate of five horn bill-dispersed tree species in a tropical forest in north-cast India. Seeds were marked inside and outside of exclosures below 6-12 parent fruiting trees (undispersed seed rain) and six hornbill nest trees (a post-dispersal site). Rodent visitors and seed removal ere monitored using camera traps. Our findings suggest that several rodent species. especially two species of porcupine were major on-site seed predators. Scatter-hoarding was rare (1.4%). Seeds at hornbill nest trees had lower survival compared with parent fruiting trees, indicating that clumped dispersal by hornbills may not necessarily improve seed survival. Seed survival in the presence and absence of rodents varied with tree species. Some species (e.g. Polyalthia simiarum) showed no difference, others (e.g. Dysoxylum binectariferum) experienced up to a 64%. decrease in survival in the presence of rodents. The differing magnitude of seed predation by rodents can have significant consequences at the seed establishment stage.

First report of a Trichinella papuae infection in a wild pig (Sus scrofa) from an Australian island in the Torres Strait region

Multiple Trichinella species are reported from the Australasian region although mainland Australia has never confirmed an indigenous case of Trichinella infection in humans or animals. Wildlife surveys in high-risk regions are essential to truly determine the presence or absence of Trichinella, but in mainland Australia are largely lacking. In this study, a survey was conducted in wild pigs from mainland Australia's Cape York Peninsula and Torres Strait region for the presence of Trichinella, given the proximity of a Trichinella papuae reservoir in nearby PNG. We report the detection of a Trichinella infection in a pig from an Australian island in the Torres Strait, a narrow waterway that separates the islands of New Guinea and continental Australia. The larvae were characterised as T. papuae (Kikori strain) by PCR and sequence analysis. No Trichinella parasites were found in any pigs from the Cape York Peninsula. These results highlight the link the Torres Strait may play in providing a passage for introduction of Trichinella parasites from the Australasian region to the Australian mainland. (C) 2011 Elsevier B.V. All rights reserved.

Ravenelia acaciae-arabicae and Ravenelia evansii are distinct species on Acacia nilotica subsp. indica in India

The two rust fungi, Ravenelia acaciae-arabicae and R. evansii, were both found on Acacia nilotica subsp. indica in southern (Tamil Nadu) and northern (Gujarat) India. R. acaciae-arabicae has been often incorrectly synonymised with R. evansii, although each has distinctive urediniospores, viz. echinulate in R. acaciae-arabicae and verruculose in R. evansii. Both species are re-described and illustrated from fresh specimens collected in India. Herbarium specimens of R. evansii from South Africa, including the holotype, were also examined. The difficulty in connecting different anamorphic spore stages to either of these teleomorphic rusts is highlighted by the presence of similar aecidia on plants of A. robusta infected with R. evansii in South Africa and on A. nilotica subsp. indica infected with R. acaciae-arabicae in India. It is not known whether these aecidial rusts represent the same species, nor is it known if they represent an aecidial stage of either R. acaciae-arabicae, R. evansii or other rusts.

The nonequilibrium region of a mixing layer

Experiments were conducted in the nonequilibrium region of a free mixing layer with unequal freestream velocities. Four velocity ratios U(1)/U(2) of 0.32, 0.46, 0.74, and 0.96 were used in this investigation. The growth of the shear layer as well as the velocity adjustment in the near wake were examined. There was reasonable agreement between the measured mean velocity profiles and those computed using the K-epsilon turbulence model. Some periodic turbulence velocity fluctuations were observed in the mixing layer, but their frequency remained the same along the flow.