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Articles by Jurģis Jansons

Category: Research note

article id 9911, category Research note
Tālis Gaitnieks, Indulis Brauners, Kristīne Kenigsvalde, Astra Zaļuma, Lauma Brūna, Jurģis Jansons, Natālija Burņeviča, Andis Lazdiņš, Rimvydas Vasaitis. (2018). Infection of pre-commercially cut stumps of Picea abies and Pinus sylvestris by Heterobasidion spp. – a comparative study. Silva Fennica vol. 52 no. 1 article id 9911. https://doi.org/10.14214/sf.9911
Highlights: In pre-commercial thinnings both Heterobasidion infection frequency and the extent of surface colonization correlated positively with stump diameter of both Norway spruce and Scots pine; Spruce stumps were significantly more often subjected to primary infections than pine stumps; The pathogen exhibited more extensive surface colonization of spruce stumps than of pine stumps.

The aim was to investigate relative susceptibility of stumps of spruce and pine to airborne infections by Heterobasidion following pre-commercial thinnings. The proportions of infected stumps and colonized stump surface areas were analysed in 16 forest stands. In total, 746 spruce and 1063 pine stumps were sampled, and 184 and 105 infected stumps, respectively, were analysed. In conclusion, the present study demonstrated that in the investigated area: i) both Heterobasidion infection frequency and the extent of surface colonization correlated positively with stump diameter of both spruce and pine; ii) spruce stumps were significantly more often subjected to primary infections than pine stumps; iii) the pathogen exhibited more extensive surface colonization of spruce stumps than of pine stumps.

  • Gaitnieks, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: talis.gaitnieks@silava.lv (email)
  • Brauners, JSC “Latvia’s State Forests”, 1 Vainodes str., Riga, LV-1004, Latvia ORCID ID:E-mail: i.brauners@lvm.lv
  • Kenigsvalde, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: kristine.kenigsvalde@silava.lv
  • Zaļuma, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: astra.zaluma@silava.lv
  • Brūna, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: lauma.bruna@silava.lv
  • Jansons, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: jurgis.jansons@silava.lv
  • Burņeviča, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: natalija.arhipova@silava.lv
  • Lazdiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils, LV-2169, Latvia ORCID ID:E-mail: andis.lazdins@silava.lv
  • Vasaitis, Swedish University of Agricultural Sciences (SLU), P.O. Box 7026, SE-75007 Uppsala, Sweden ORCID ID:E-mail: Rimvys.Vasaitis@slu.se
article id 7798, category Research note
Jānis Liepiņš, Jānis Ivanovs, Andis Lazdiņš, Jurģis Jansons, Kaspars Liepiņš. (2017). Mapping of basic density within European aspen stems in Latvia. Silva Fennica vol. 51 no. 5 article id 7798. https://doi.org/10.14214/sf.7798
Highlights: Stem bark is significantly denser than wood and does not follow the same variation patterns along the stem; The main trend in radial variation of wood density was the increase from pith to bark; There is a weak relationship between mean basic density and commonly measured stand and tree parameters.

The objective of this study was to investigate basic density and its within-stem variation by studying 84 European aspen stems from 28 forest stands in Latvia. The studied forest stands covered all age classes from young stands to matured forests in representative growth conditions of European aspen. The densities of 2722 wood and 1022 bark specimens were measured from the sampled trees. Only the knot-free wood specimens without obvious wood defects were chosen for analyses. A map of basic density summarizing its radial and axial variations was constructed to show species-specific, within-stem variability and the relationships between density and tree and stand variables were examined. Stem wood and bark of the European aspen show different patterns of basic density variation along the tree stem. Wood density increases from pith to bark up to certain dimensions and shows a slight decrease afterwards. The weighted basic density of bark (446 ± 39.6 kg m–3) was higher than stem wood density (393 ± 30.4 kg m–3). Our results suggest that wood and bark density measurements obtained at breast height can be used for reliable estimation of the densities of whole-tree stem components, while tree parameters such as diameter at breast height (DBH), tree height and social status or stand parameters, including number of trees, basal area and age, are weak predictors in this context.

  • Liepiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia ORCID ID:E-mail: janis.liepins@silava.lv (email)
  • Ivanovs, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia ORCID ID:E-mail: janis.ivanovs@silava.lv
  • Lazdiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia ORCID ID:E-mail: andis.lazdins@silava.lv
  • Jansons, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia ORCID ID:E-mail: jurgis.jansons@silava.lv
  • Liepiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia ORCID ID:E-mail: kaspars.liepins@silava.lv

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