Further observations on sudden diebacks of Scots pine in the European Alps

Since the beginning of the 1990s, significant mortality of Scots pine trees has been observed in inner valleys of the Alps. The objectives of this work were to investigate and describe the aetiology of a Scots pine dieback in the Aosta Valley (western Italian Alps) in 2005. Surveys were conducted in three forest stands. Crown transparency was assessed to evaluate the incidence and severity of dieback symptoms. Phytosanitary surveys were also performed. The time series of the major climatic parameters was analyzed in order to identify common climatic anomalies between the dieback of 2005 and similar dieback episodes in other periods and in other areas of the western Alps. Dendrochronological analyses were performed to assess the relationship between tree-ring widths and climatic parameters. The lack of primary biotic agents and the low frequency of secondary pathogens suggest an abiotic origin of diebacks. The time series analysis shows that two consecutive years with a value of summer dryness index below 1.5 preceded the diebacks. Tree-ring width and summer dryness index were strongly and significantly associated. Key words: climate change, forest dieback, Scots pine, crown transparency, ecophysiology, tree-ring width

Salt-wind induced wave regeneration in coastal pine forests in New Zealand

Strong onshore winds and airborne sea salt can gradually defoliate trees at the exposed margin of temperate pine stands in New Zealand and induce a slowly moving front of dieback and regeneration. Overcrowded mature stands are vulnerable to crown abrasion: abrasion affects trees 20 m ahead of the dieback front; suppressed trees 12 m ahead die before the front reaches them. At the stand margin, trees die from abrasion and salt wind induced dieback. The dieback zone lets sunlight enter the stand; light-demanding pine seedlings establish, but a gradient of increasing litter depth from the dieback front and summer dryness restrict successful seedling establishment to a narrow zone that moves parallel with the dieback front and 11-13 m ahead of it. Further seedlings establish for 4-10 years before the juveniles form a closed canopy; competing vegetation is partly suppressed by infrequent cattle browsing. Regenerating juvenile maritime pine (Pinus pinaster Ait.), show a strict age-related gradation from the dieback front and indicate that wind and salt deposition have been constant for 30 years. Stands further from the sea, with lower stocking rates and other pine species, did not have a clear-cut regeneration zone, because there were no strong gradients of litter depth and light intensity.

Evaluation of dryland species and new ryegrass cultivars to increase pasture productivity in coastal Taranaki

Seasonal and annual DM production of direct drilled dryland species 'Grasslands Maru' phalaris (Phalaris aquatica L.) and 'Grasslands Roa' tall fescue (Festucuurundinuceu Schreb.) and perennial ryegrass (Loliumperenne L.) cultivars 'Grasslands Pacific', 'Droughtmaster' and 'Yatsyn-1' was compared with that of established pasture in an environment prone to summer dry spells. Two methods of establishment using only Yatsyn-1 were examined: either the elimination of existing pasture with glyphosate and drilling, or drilling without spraying (undersowing). Average annual DM production (over 3 years) of Yatsyn-1 drilled into pasture previously sprayed with glyphosate was 12% more productive than established pasture. Maru phalaris, Droughtmaster and Pacific had similar annual DM production to established pasture, and Roa tall fescue produced 25% less. Yatsyn-1 undersown intopastures without previous spraying with glyphosate produced 9% less than Y atsyn- 1 established by the spray and drill technique. Phalaris established well but after 3 years the content of phalaris had declined markedly, suggesting poor persistency. Tall fescue was slow establishing but had good persistency, as did all ryegrass cultivars. Yatsyn-1 direct drilled into pastures eliminated with glyphosate before drilling is recommended for an environment prone to summer dryness to increase annual DM production. Keywords pasture production,established pasture, ryegrass cultivars, phalaris, tall fescue, establishment techniques, summer droughts