Articles containing the keyword 'hemiboreal'

Impact of drainage of organic soils in forest land on soil carbon (C) stock changes is of high interest not only to accurately estimate soil C stock changes, but also to provide scientifically based recommendations for forest land management in context of climate change mitigation. To improve knowledge about long-term impact of drainage on nutrient-rich organic soils in hemiboreal forests in Latvia, 50 research sites representing drained conditions (Oxalidosa turf. mel. (Kp) and Myrtillosa turf. mel. (Ks) forest site types) and undrained conditions as control areas (Caricoso-phragmitosa, Dryopterioso-caricosa and Filipendulosa forest site types) were selected. Soil C stock changes after drainage was evaluated by comparing current C stock in drained organic soils to theoretical C stock before drainage considering impact of soil subsidence. During the 53-years period after drainage, the peat subsidence was higher in nutrient-rich Kp forest site type compared to moderate nutrient-rich Ks forest site type (peat subsided by 37.0 ± 4.8 and 23.3 ± 4.8 cm, respectively). In nutrient-rich Kp forest site type, soil C stock decreased by 4.98 ± 1.58 Mg C ha^-1 yr^-1 after drainage, while no statistically significant changes in soil C stock (0.19 ± 1.31 Mg C ha^-1 yr^-1) were observed in moderate nutrient-rich soils in Ks forest site type. Thus, in Ks forest site type, the main driver of the peat subsidence was the physical compaction, while in Kp forest site type contribution of organic matter decomposition and consequent soil C losses to subsidence of the peat was significant.

• Lazdiņš, Latvian State Forest Research Institute ‘Silava’ (LSFRI Silava), Rigas str. 111, Salaspils, LV-2169, Latvia https://orcid.org/0000-0002-7169-2011 E-mail: andis.lazdins@silava.lv
• Lupiķis, Latvian State Forest Research Institute ‘Silava’ (LSFRI Silava), Rigas str. 111, Salaspils, LV-2169, Latvia E-mail: ainars.lupikis@inbox.lv
• Polmanis, Latvian State Forest Research Institute ‘Silava’ (LSFRI Silava), Rigas str. 111, Salaspils, LV-2169, Latvia https://orcid.org/0000-0003-2579-353X E-mail: kaspars.polmanis@silava.lv
• Bārdule, Latvian State Forest Research Institute ‘Silava’ (LSFRI Silava), Rigas str. 111, Salaspils, LV-2169, Latvia https://orcid.org/0000-0003-0961-5119 E-mail: arta.bardule@silava.lv
• Butlers, Latvian State Forest Research Institute ‘Silava’ (LSFRI Silava), Rigas str. 111, Salaspils, LV-2169, Latvia https://orcid.org/0000-0003-3118-1716 E-mail: aldis.butlers@silava.lv
• Kalēja, Latvian State Forest Research Institute ‘Silava’ (LSFRI Silava), Rigas str. 111, Salaspils, LV-2169, Latvia E-mail: santa.kaleja@silava.lv

Since fire frequency is expected to increase globally due to climate change, it is important to understand its effects on forest ecosystems. We studied the long-term patterns in species diversity, cover and composition of vascular plants and bryophytes after forest fire and the site-related factors behind them. Research was carried out in northwestern Estonia, using a chronosequence of Scots pine (Pinus sylvestris L.) stands, located on nutrient poor sandy soils, where fires had occurred 12, 23, 38, 69, 80 and 183 years ago. In every stand three 100 m² vegetation plots were established to collect floristic and environmental information. The effects on floristic characteristics of time since fire, light, and soil variables were evaluated with linear mixed models, followed by backward variable selection. Compositional variation was analysed with non-metric multidimensional scaling, Multi-response Permutation Procedures, and Indicator Species Analysis. Altogether, 31 vascular plant and 39 bryophyte species were found in vegetation plots. The cover of the vascular plant and bryophyte layers increased with a longer time since fire. Soil and light variables impacted the richness of several vascular plant and bryophyte groups, whereas only the richness of liverworts and dwarf-shrubs correlated with time since fire. Considerable compositional differences were observed in vascular plant and bryophyte assemblages between recently vs. long-time ago burned stands. To conclude, time since fire significantly impacted compositional patterns of vascular plants and bryophytes in pine forests on nutrient poor soils, although time-related trends in species richness were less evident.

• Orumaa, Institute of Forestry and Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51006, Tartu, Estonia E-mail: argo.orumaa@emu.ee
• Köster, Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111 (Yliopistokatu 7), 80130, Joensuu, Finland E-mail: kajar.koster@helsinki.fi
• Tullus, Department of Botany, Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, Tartu, 51003, Estonia E-mail: arvo.tullus@ut.ee
• Tullus, Institute of Forestry and Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51006, Tartu, Estonia E-mail: tea.tullus@emu.ee
• Metslaid, Institute of Forestry and Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, 51006, Tartu, Estonia E-mail: marek.metslaid@emu.ee

Considering the increasing use of wood biomass for energy and the related intensification of forest management, the impacts of different intensities of biomass harvesting on nutrient leaching risks must be better understood. Different nitrogen forms in the soil solution were monitored for 3 to 6 years after harvesting in hemiboreal forests in Latvia to evaluate the impacts of different biomass harvesting regimes on local nitrogen leaching risks, which potentially increase eutrophication in surface waters. In forestland dominated by Scots pine Pinus sylvestris L. or Norway spruce Picea abies L. (Karst.), the soil solution was sampled in: (i) stem-only harvesting (SOH), (ii) whole‐tree harvesting, with only slash removed (WTH), and (iii) whole‐tree harvesting, with both slash and stumps harvested (WTH + SB), subplots. In agricultural land, sampling was performed in an initially fertilised hybrid aspen (Populus tremula L.× P. tremuloides Michx.) short-rotation coppice (SRC), where above-ground biomass was harvested. In forestland, soil solution N (nitrogen) concentrations were highest in the second and third year after harvesting. Mean annual values in WTH subplots of medium to high fertility sites exceeded the mean values in SOH subplots and control subplots (mature stand where no harvesting was performed) for the entire study period; the opposite trend was observed for the low-fertility site. Biomass harvesting in the hybrid aspen SRC only slightly affected NO₃^–-N (nitrate nitrogen) and NH₄⁺-N (ammonium nitrogen) concentrations in the soil solution within 3 years after harvesting, but a significant decrease in the TN (total nitrogen) concentration in the soil solution was found in plots with additional N fertilisation performed once initially.

• Kļaviņš, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia; University of Latvia, Raiņa blvd 19-125, LV 1586, Riga, Latvia E-mail: ivars.klavins@silava.lv
• Bārdule, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia; University of Latvia, Raiņa blvd 19-125, LV 1586, Riga, Latvia E-mail: arta.bardule@silava.lv
• Lībiete, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: zane.libiete@silava.lv
• Lazdiņa, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: dagnija.lazdina@silava.lv
• Lazdiņš, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: andis.lazdins@silava.lv

Fire as disturbance of forests has an important ecological and economical role in boreal and hemiboreal forests. The occurrence of forest fires is both climatically and anthropogenically determined and shifts in fire regimes are expected due to climate change. Although fire histories have been well documented in boreal regions, there is still insufficient information about fire occurrence in the Baltic States. In this study, spatio-temporal patterns and climatic drivers of forest fires were assessed by means of spatial and time-series analysis. The efficiency of Canadian Fire Weather (FWI) indices as indicators for fire activity was tested. The study was based on data from the literature, archives, and the Latvian State Forest service database. During the period 1922–2014, the occurrence and area affected by forest fires has decreased although the total area of forest land has nearly doubled, suggesting improvement of the fire suppression system as well as changes in socioeconomic situation. The geographical distribution of forest fires revealed two pronounced clusters near the largest cities of Riga and Daugavpils, suggesting dominance of human causes of ignitions. The occurrence of fires was mainly influenced by drought. FWI appeared to be efficient in predicting the fire occurrence: 23–34% of fires occurred on days with a high or extremely high fire danger class, which overall had a relative occurrence of only 4.3–4.6%. During the 20th century, the peak of fire activity shifted from May to April, probably due to global warming and socioeconomic reasons. The results of this study are relevant for forest hazard mitigation and development of fire activity prediction system in Latvia.

• Donis, LSFRI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: janis.donis@silava.lv
• Kitenberga, LSFRI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: mara.kitenberga@gmail.com
• Šņepsts, LSFRI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: guntars.snepsts@silava.lv
• Matisons, LSFRI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: robism@inbox.lv
• Zariņš, LSFRI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: juris.zarins@silava.lv
• Jansons, LSFRI “Silava”, Rigas str. 111, Salaspils, Latvia, LV2169 E-mail: aris.jansons@silava.lv

In managed European hemiboreal forests, windstorms have a notable ecological and socio-economic impact. In this study, stand properties affecting windstorm damage occurrence at the stand-level were assessed using a Generalized Linear Mixed model. After 2005 windstorm, 5959 stands dominated by birch (Betula spp.), Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.), with mean height > 10 m were inventoried. Windstorm damage was positively associated with spruce and pine-dominated stands, increasing mean height, fresh forest edges, decreasing time since the last thinning and stronger wind gusts. Tree species composition – mixed or monodominant – was not statistically significant in the model; while, the admixture of spruce in the canopy layer was positively associated with higher windstorm damage. Stands on peat soils were more damaged than stands on mineral soils. Birch stands were more damaged than pine stands. This information could be used in forest management planning, selection of silvicultural treatments to increase forest resilience to natural disturbances.

• Donis, Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, Latvia, LV-2169 E-mail: janis.donis@silava.lv
• Kitenberga, Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, Latvia, LV-2169 E-mail: mara.kitenberga@gmail.com
• Šņepsts, Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, Latvia, LV-2169 E-mail: guntars.snepsts@silava.lv
• Dubrovskis, Latvia University of Life Sciences and Technologies, Liela iela 2, Jelgava, Latvia, LV-3001 E-mail: edgars.dubrovskis@llu.lv
• Jansons, Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, Latvia, LV-2169 E-mail: aris.jansons@silava.lv

Dwarf shrub layer is an important component of boreal and hemiboreal forest ecosystems that has received little attention, particularly regarding its structural diversity, which, however, could serve as an additional proxy for habitat quality. Dimensions of bilberry (Vaccinium myrtillus L.) ramets were assessed in two sites in Latvia covered by dry oligotrophic Scots pine (Pinus sylvestris L.) stands 10–230 years of age. In total, 20 sampling plots (10×10 m) with 156 subplots (1×1 m) were sampled and 630 bilberry ramets analysed. The dimensions of ramets (age, diameter, and height) and cover of bilberry increased with stand age. The age of the studied ramets ranged 2–13 years; 5–6 years-old ramets were most frequent in all stands. The skewness of the distribution of the ramet dimensions shifted with stand age, leaning towards the higher values. Lower structural diversity of ramets was observed in stands 50–100 years of age. The highest diversity of ramet age structure occurred in stands younger than 150 years, whereas the oldest and largest ramets mostly occurred in the older stands (>150 years). Considering structural diversity of ramets, recovery of bilberry after stand-replacing disturbance (e.g. clearcut) was a continuous process, similarly to that observed in tree layer.

• Robalte, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: robalte.l@gmail.com
• Jansone, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia; University of Latvia, Faculty of Biology, Jelgavas Str. 1, LV 1004, Riga, Latvia E-mail: diana.jansone13@gmail.com
• Elferts, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia; University of Latvia, Faculty of Biology, Jelgavas Str. 1, LV 1004, Riga, Latvia E-mail: didzis.elferts@lu.lv
• Matisons, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: roberts.matisons@silava.lv
• Jansons, Latvian State Forest Research Institute “Silava”, 111 Rigas Str., LV 2169, Salaspils, Latvia E-mail: aris.jansons@silava.lv