Talis Gaitnieks

Occurrence and impact of the root-rot biocontrol agent Phlebiopsis gigantea on soil fungal communities in Picea abies forests of northern Europe

The aim of this study was to assess belowground occurrence, persistence and possible impact of the biocontrol agent Phlebiopsis gigantea (Fr.) Jülich on soil fungi. Sampling of soil and roots of Picea abies (L.) H. Karst. was carried out at 12 P. gigantea-treated and five nontreated control sites representing 1- to 60-month-old clear-cuts and thinned forest sites in Finland and Latvia. The 454-sequencing of ITS rRNA from fine roots, humus and mineral soil resulted in 8626 high-quality fungal sequences. Phlebiopsis gigantea represented 1.3% of all fungal sequences and was found in 14 treated and nontreated sites and in all three substrates. In different substrates, the relative abundance of P. gigantea at stump treatment sites either did not differ significantly or was significantly lower than in nontreated controls. No significant correlation was found between the time elapsed since the tree harvesting and/or application of the biocontrol and abundance of P. gigantea in different substrates. In conclusion, the results demonstrate that P. gigantea occasionally occurs belowground in forest ecosystems but that stump treatment with the biocontrol agent has little or no impact on occurrence and persistence of P. gigantea belowground, and consequently no significant impact on soil fungi.

Diplodia sapinea is colonizing the native Scots pine (Pinus sylvestris) in the northern Baltics

For the northern Baltic region, Diplodia sapinea (Fr.) Fuckel, a well-known around the world pine pathogen, was first recorded in Estonia on Austrian pine (Pinus nigra Arn.) in 2007. Wider monitoring of the fungus was promptly started. Shortly, in 2012, the native Scots pine (P. sylvestris L.) was found symptomatic: first in Estonia, then in Latvia, and in 2013 in north-west Russia. Several individuals of exotic Mountain pine (P. mugo Turra) and some Bosnian pines (Pinus leucodermis Ant.) were also found to be infected. By the end of 2013, the front of the northward enlargement of the range of D. sapinea had reached to central Estonia. Early detection and continuous monitoring of this pathogen on native and introduced ornamental pine species will support forest and green belt management specialists with timely information, if an epidemic, as it occurred previously with the invasive Dothistroma needle blight, would emerge.

Heart-rot and associated fungi in Alnus glutinosa stands in Latvia

Abstract The interest in Alnus glutinosa (L.) Gaertn. as plantation species has increased during last years, but its prospects should be evaluated from the perspective of forest health. The aims of the present study were to: (1) estimate the incidence of stem decay in Latvian A. glutinosa stands, (2) measure the extent of decay within individual stems and on a stand level and (3) identify decay-causing fungi. In four A. glutinosa stands, 450 trees were randomly sampled with an increment borer and the presence/absence of decay was recorded. As a result, 112 sound-looking and 338 decayed trees were detected, and a corresponding number of wood samples were collected for fungal isolations. A total of 34 stems with decay symptoms were cut to measure the extent of internal decay. The incidence of decayed stems in studied stands was 75.1% on average. The length of the decay column was 7.7±5.4 m on average, and that of spongy rot was 4.2±4.5 m on average, implying that yield losses for fully stocked 80-years-old A. glutinosa stand would comprise 49.2% of the total stand volume, and the losses from spongy rot alone – 30.5%. In total, 1134 isolates representing 68 fungal taxa were obtained. The most common decay-causing fungi were Inonotus radiatus and Armillaria sp.

Analysis of Norway spruce dieback phenomenon in Latvia – a belowground perspective

ABSTRACT In 2010, dieback of Norway spruce (Picea abies) was observed in Latvia. As mostly stands on seasonally or permanently water-saturated soils were damaged, we hypothesized that the recorded foliar damage might be associated with belowground factors. We established 48 sample plots in stands with damage symptoms for soil parameter evaluation and fine root sampling to determine the number of fine roots in different growth stages and to describe the associated fungal community. Among sample plots on organic soils, there were fewer viable older fine roots and greater number of dead fine roots in more damaged sites than in less damaged. These root parameters were significantly correlated with higher groundwater level and soil pH. The fungal community was dominated by ectomycorrhizal (ECM) species (the most common was Tylospora asterophora), the endophyte Oidiodendron maius and saprotrophic species Cryptococcus magnus. Saprotrophic species had higher abundance in more damaged sites, suggesting a shift in fungal communities from ECM fungi. In conclusion, the results of this work suggest Norway spruce root system response to short-term climatic stress, which should be considered when planning spruce forest management, especially on organic soils with a high groundwater level.