Canopy structure analysis for estimating forest regeneration dynamics and growth in <Emphasis Type="Italic">Nothofagus pumilio</Emphasis> forests

•Introduction   

Silviculture systems applied in Nothofagus pumilio forests are based on opening the canopy to stimulate natural regeneration by modifying light and soil moisture. The objective is to evaluate regeneration dynamics of N. pumilio along different forest canopy and solar radiation gradients.     

Stand biometry and leaf area distribution in an old olive grove at Andria, southern Italy

The objectives of this paper were (1) to provide general biometry data for an 80-year-old olive (Olea europea L., cv. Coratina) grove in Andria, southern Italy, and (2) to compare different methods for estimating leaf area distributions. Stand biometry was represented by a stocking density of 132 trees ha^?1, mean spacing of 8.7 m and mean social area (proportional to spacing and tree size) of about 76 m² per tree. Trunk total circumference averaged 110 cm and after subtraction of missing or dead parts of stems averaged 81 cm, projected area of crowns averaged 17.7 m² and the mean tree height was 4.9 m. Leaf distribution was evaluated using calibrated ground-based side photographs through image analysis and through using a simple canopy-layer model (considering hollow volume within tree crowns) and double-Gaussian curves. The mean leaf size was about 5 cm² (distributed in a log-normal manner over the range of 2 to 12 cm²). Considering whole tree crowns, the mean leaf density was about 2.6 m²m^?3; the maximum leaf area occurred in canopy layers between 1.5 to 3 m, tailing with a steeper slope to the crown base and a less steep slope to the tree-top. The foliated volume of olive crowns (mean 33.2 m³) contained on average 145 thousand leaves of the total area of 72.6 m². The corresponding leaf area index on the stand level (LAI _grove = 0.96), was rather low due to low stocking density. However when taking into account only the projected crown areas (and avoiding free space between trees), the mean LAI reached about 3.5 (range from 1–7). The radial pattern of leaf distribution derived from image analysis indicated peak LAI _rad values at a distance from the stem of about 60 to 70% of crown radius in trees of different size. The applicability of different approaches to the estimation of the necessary allometric parameters is discussed.     

Effects of associated fungi Sclerophoma pythiophila and Cenangium ferruginosum on Gremmeniella abietina dieback in Spain

The interactions between Gremmeniella abietina and either Sclerophoma pythiophila or Cenangium ferruginosum, fungi frequently isolated from diseased twigs along with G. abietina, were studied under laboratory (dual cultures) and greenhouse conditions (double‐inoculations). Virulence of each species was also evaluated in greenhouse experiments by means of single‐inoculations. In vitro interactions were assessed on Petri dishes containing malt agar with pine needle extract, and greenhouse experiments were performed on 1‐year‐old Pinus halepensis seedlings. In vitro growth of G. abietina was inhibited by both fungi when grown in dual culture. In single‐inoculations, G. abietina caused the greatest necrosis length on P. halepensis seedlings, followed by S. pythiophila, whereas C. ferruginosum did not cause significant necrosis. In double‐inoculations, C. ferruginosum was able to reduce the length of necrosis caused by G. abietina on the P. halepensis seedlings. In contrast, necrosis length was greater in seedlings inoculated with both S. pythiophila and G. abietina than in those inoculated with G. abietina alone. Therefore, S. pythiophila seems to play a role in disease expression caused by G. abietina on P. halepensis in Spain.     

Learning by doing: a participatory methodology for systematization of experiments with agroforestry systems, with an example of its application

Participatory research methods have helped scientists to understand how farmers experiment and to seek partnerships with farmers in developing technologies with enhanced relevance and adoption. This paper reports on the development of a participatory methodology to systematize long-term experimentation with agroforestry systems carried out in a hotspot of biodiversity by non-governmental organizations and local farmers. A methodological guide for systematization and techniques used for Participatory Rural Appraisal formed the basis of our work. We propose an analytical framework that recognizes systems of reflexive and learning interactions, in order to make the learned lessons explicit. At the process level, the main lessons and recommendations are as follows. It is important to establish partnerships to conduct innovative and complex experimentation with agroforest. Participatory systematization allows us to improve the methodological aspects of design, implementation and management of on-farm participatory experimentation. It also serves to synthesize the main findings and to extract lessons from agroforestry systems experiments. It fosters the technical improvement of agroforestry systems. It creates possibilities for reflection on agroforestry systems by farmers, extensionists and researchers, as well as their learning with respect to management of such systems. The findings are placed in the context of current theory on participatory experimentation in agriculture. Extractive and interactive approaches help to produce rich insights of mutual interest through collaboration by identifying local, regional and global convergences, complementarities, and conflicts of interest; which affect the advance of new eco-friendly technologies, to both improve the livelihoods and to reverse biodiversity loss and environmental degradation.     

Alternative silvicultural practices with variable retention improve bird conservation in managed South Patagonian forests

Alternative silvicultural approaches to timber management, such as regeneration treatments with different degrees of stand retention, may mitigate negative effects of clear-cutting or shelterwood cuts in forested ecosystems, including changes in old-growth forest bird communities. The aims of this work were: (a) to compare bird species richness and densities among different silvicultural designs with variable retention (dispersed and/or aggregated) and unmanaged primary forests, and (b) to assess temporal changes at community and species levels before and after treatments. A baseline avian survey was conducted prior to harvesting to evaluate canopy gap presence and forest stand site quality influences. Subsequent to harvesting, data on bird species richness and density were collected by point-count sampling during the summer season for 5 consecutive years (4 treatments × 5 years × 6 sampling points × 5 counts). Bird species richness and density (15 species and 9.2 individuals ha⁻¹) did not change significantly with forest site quality of the stands and canopy gap presence in unmanaged forests. However, both variables were significantly modified in managed forests, increasing over time to 18 species and reaching to 39 individuals ha⁻¹. Inside the aggregated retention, bird communities were more similar to unmanaged primary forests than those observed within the dispersed retention or in clear-cuts. Opting for a regeneration method with dispersed and aggregated retention has great potential for managing birds in Nothofagus pumilio forests. This method retained enough vegetation structure in a stand to permit the establishment of early successional birds (at least in dispersed retention), and to maintain the bird species of old-growth forests which could persisted in the retention aggregates.     

When the ground cover brings guests: is <Emphasis Type="Italic">Anaphothrips obscurus</Emphasis> a friend or a foe for the biological control of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> in clementines?

Biological control of Tetranychus urticae Koch (Acari: Tetranychidae), a key pest of clementines, can be improved in this crop with the establishment of a ground cover of Festuca arundinacea Schreber (Poaceae). This cover houses an abundant and diverse community of predatory Phytoseiidae mites including Euseius stipulatus (Athias-Henriot), Neoseiulus barkeri Hughes, Neoseiulus californicus (McGregor) and Phytoseiulus persimilis Athias-Henriot and a dense population of the grass thrips Anaphothrips obscurus Müller (Thysanoptera: Thripidae) throughout the year. The aim of this study was to determine whether the presence of this thrips species could be related to the improvement in the biological control of T. urticae. Therefore, the capacity of the abovementioned phytoseiids to feed and reproduce on A. obscurus and their feeding preferences when T. urticae and A. obscurus were simultaneously offered, were analyzed. The results show that E. stipulatus, N. barkeri and N. californicus have a type II functional response when offered A. obscurus nymphs, whereas P. persimilis barely feeds on this thrips species. Furthermore, N. barkeri and N. californicus can reproduce feeding only on thrips. Regarding prey preference, the Tetranychus spp.-specialist P. persimilis preferably preyed on T. urticae, the generalists N. barkeri and E. stipulatus preferred A. obscurus, and the selective predator of tetranychid mites N. californicus showed no preference. Therefore, we hypothesize that the enhanced biological control of T. urticae observed could be related to A. obscurus becoming an alternative prey for non-specialist phytoseiids, without altering the control exerted by the T. urticae-specialist P. persimilis and likely reducing intraguild predation.     

Thinning decreased soil respiration differently in two dryland Mediterranean forests with contrasted soil temperature and humidity regimes

The effects of a thinning treatment on soil respiration (Rs) were analysed in two dryland forest types with a Mediterranean climate in east Spain: a dry subhumid holm oak forest (Quercus ilex subsp. ballota) in La Hunde; a semiarid postfire regenerated Aleppo pine (Pinus halepensis) forest in Sierra Calderona. Two twin plots were established at each site: one was thinned and the other was the control. Rs, soil humidity and temperature were measured regularly in the field at nine points per plot distributed into three blocks along the slope for 3 years at HU and for 2 years at CA after forest treatment. Soil heterotrophic activity was measured in laboratory on soil samples obtained bimonthly from December 2012 to June 2013 at the HU site. Seasonal Rs distribution gave low values in winter, began to increase in spring before lowering as soil dried in summer. This scenario indicates that with a semiarid climate, soil respiration is controlled by both soil humidity and soil temperature. Throughout the study period, the mean Rs value in the HU C plot was 13% higher than at HU T, and was 26% higher at CA C than the corresponding CA T plot value, being the differences significantly higher in control plots during active growing periods. Soil microclimatic variables explain the biggest proportion of variability for Rs: soil temperature explained 24.1% of total variability for Rs in the dry subhumid forest; soil humidity accounted for 24.6% of total variability for Rs in the semiarid forest. As Mediterranean climates are characterised by wide interannual variability, Rs showed considerable variability over the years, which can mask the effect caused by thinning treatment.

     

Eine Methode zur integrierten Bekämpfung des Rüsselkäfers (Hylobius abietis L.)

Zusammenfassung Es wird gezeigt, da? es m?glich ist, durch die Anwendung subletaler Konzentrationen des Insektizids DTHP, d. h. durch eine allgemeine Schw?chung des Organismus erwachsener Rüsselk?fer (Hylobius abietis L.), eine geeignete Disposition dieses Sch?dlings zur Infektion durch den parasitischen PilzBeauveria bassiana (Bals-Criv.) Vuill. herbeizuführen. Die K?fer, die in Fangrinden oder Fallen an Kiefern? stchen — welche in ein kombiniertes Pr?parat einer 0,05% DTHP-Suspension (Organophosphorverbindung vom Dipterex-Typ, technischer Block 0,0-Dimethyl-2,2,2-trichlor-1-hydroxy?thyl-phosphonat) mit 0,1% Sporen vonBeauveria bassiana getaucht worden waren — konzentriert wurden, nahmen keine Nahrung mehr auf und starben allm?hlich ab. Wie die histologischen Untersuchungen gezeigt haben, wurden Erkrankung und Tod der K?fer durch den genannten parasitischen Pilz herbeigeführt. Obwohl nur zwei Vergleichsfl?chen zur Verfügung standen, ist aus dem obengesagten klar, da? bei der Anwendung des kombinierten Pr?parates mit einer gewissen selektiven Wirkung gerechnet werden kann: W?hrend an der nur mit 1% DTHP behandelten Versuchsfl?che ungef?hr 2,5% nützlicher Insekten unter den get?teten K?fern festgestellt wurden (vor allem Laufk?fer der GattungPterostichus), betrug der Prozentsatz der get?teten nützlichen Insekten bei der Anwendung des kombinierten Pr?parates (DTHPBeauveria bassiana-Sporen) nur 0,25%. Die angeführten Versuche bewiesen die Anwendbarkeit der Kombination von Insektiziden — in subletalen Dosen oder Konzentrationen — mit Sporen parasitischer Pilze.     

Artificial inoculation and susceptibility of Pinus armandii to Dothistroma septosporum

Dothistroma needle blight (DNB) is a serious needle disease of conifers that primarily affects pine species (Pinus spp.). Dothistroma septosporum is one of the DNB pathogens that has a diverse range of host species excluding Pinus armandii. In 15 inoculated P. armandii seedlings, D. septosporum acervuli were observed in 43 infected needles of ten seedlings with a mean disease severity of 1.11% at 25 weeks after inoculations, demonstrating the potential of D. septosporum to cause symptoms on the needles of P. armandii via artificial inoculation. The disease severity of P. armandii was similar to the positive control, Pinus nigra (median 0.75 for P. armandii to 0.70 for P. nigra), thus, P. armandii acts under artificial conditions as a susceptible host species.