Mats Varik

• PhD
• Researcher at Estonian University of Life Sciences

Shelterwood cutting (SC) has been highlighted as an alternative method to clear-cut (CC)-based even-aged forest management. However, compared to CC, the effect of SC on stand carbon (C) balance is still poorly understood at the ecosystem level. We examined the prompt effect of SC versus CC on ecosystem net primary production (NEP) on a short-term s...

Information on the capacity of organic soils to capture and store carbon in old‐growth forests in the hemiboreal forest zone is scarce and fragmented. However, fine‐root data can provide valuable insights into soil carbon fluxes. Thus, the aim of the current study was to provide estimates of the fine‐root biomass (FRB), fine‐root production (FRP),...

Pre-commercial thinning (PCT) is a common silvicultural practice for directing the development of the young stand in Nordic and Baltic countries. However, its impact on the stands carbon (C) cycling is still poorly studied. We carried out a comprehensive case study for estimating net ecosystem production (NEP) in unthinned control plot and in moder...

Clear-cutting is an extensively used silvicultural method in the Nordic and Baltic countries, which strongly influences the site’s carbon (C) budget. In the current study, C budgets for a young silver birch stand chronosequence (2–8-year-old) were compiled using the C budgeting method. High variability of annual NEP between stands of similar ages o...

Canopy litterfall represents an essential aboveground flux in every forest ecosystem, affecting soil carbon and nutrient dynamics as well as soil fertility. However, despite the important role of the canopy litter flux in ecosysteḿs functioning and carbon sequestration, litterfall dynamics is still poorly studied in hemiboreal forests. The main aim...

To evaluate the impact of stand age on the ecosystem's C budget, as well as the post-harvest recovery of the C storages and fluxes, a chronosequence of Scots pine stands from the clear-cut stage up to the age of 110 years was studied. An age-related trend of net primary production (NPP) demonstrated effective C accumulation in the young and middle-...

Thinning is the main silvicultural method for improving stand growth and wood quality, however, despite the relevance and extensive use of thinning in forest management, its effect on stand carbon (C) balance is still poorly studied at the ecosystem level. The present case study estimated the two-year post-thinning effect on the C balance of a pole...

Although thinning is a widely used silvicultural method, its effect on stand carbon (C) cycling is still poorly studied at the ecosystem level. The present case study estimated the two-year post-thinning effect on the C balance of a pole and a middle-aged silver birch stand. The results demonstrate the multifaceted impact of thinning on the differe...

Thinning changes the functioning of the whole forest ecosystem, including carbon and nitrogen (N) cycling. The input of organic matter and N into soil, as well as soil temperature and moisture regimes change, which may have an impact on the intensity of the net nitrogen mineralization (NNM) process. The main aims of this study were to estimate the...

Grey alder (Alnus incana) is a highly productive indigenous tree species, potential for short-rotation forestry in the Baltic and Nordic countries. The aim of the study was to investigate the development of a new forest generation, as well as the nitrogen (N) and carbon (C) storages and fluxes in a grey alder regenerating coppice (COP) after clear-...

Processes determining the carbon (C) balance of a forest ecosystem are influenced by a number of climatic and environmental factors. In Northern Europe, a rise in atmospheric humidity and precipitation is predicted. The study aims to ascertain the effect of elevated atmospheric humidity on the components of the C budget and on the C-sequestration c...

Clear-cutting is a conventional method of forest management which significantly changes carbon (C) cycling at the ecosystem level for a long time. Estimation of the interim period during which the ecosystem turns from a C source to a C sink is crucial for clarifying the environmental effects of management on forest C cycling. The current study prov...

The main aim of the current study was to estimate the annual net nitrogen mineralization (NNM) flux in stands of different tree species growing on drained peatlands, as well as to clarify the effect of tree species, soil properties and litter on annual NNM dynamics. Three study sites were set up in May 2014: a downy birch (Betula pubescens Ehrh.) s...

The decomposition of the leaf litter, fine roots (d < 2 mm) and coarser roots (2 ≤ d < 5 mm) of grey alder and silver birch, as well as of α-cellulose sheets using the litterbag method was studied in two experimental stands on Podzoluvisol soils in Southern Estonia. For both tree species, the coarser roots decomposed faster than the fine roots, (p...

Accurate carbon-balance accounting in forest soils is necessary for the development of climate change policy. However, changes in soil organic carbon (SOC) occur slowly and these changes may not be captured through repeated soil inventories. Simulation models may be used as alternatives to SOC measurement. The Yasso07 model presents a suitable alte...

Estimation of the carbon (C) storages and fluxes in different forest ecosystems is essential for understanding their C sequestration ability. The net ecosystem production (NEP) and the net primary production (NPP) in five downy birch (Betula pubescens) stands, aged between 12 and 78 years, growing on fertile well-drained Histosols, were studied. Dr...

Estimation of the carbon (C) storages and fluxes in different forest ecosystems is essential for understanding their C sequestration ability. Grey alder (Alnus incana (L.) Moench) is a fast growing tree species with a great potential for short-rotation forestry in the Nordic and Baltic countries and its stands are considered C accumulating ecosyste...

- The tree root–mycorhizosphere plays a key role in resource uptake, but also in the adaptation of forests to changing environments. - The adaptive foraging mechanisms of ectomycorrhizal (EcM) and fine roots of Picea abies, Pinus sylvestris and Betula pendula were evaluated along a gradient from temperate to subarctic boreal forest (38 sites betwee...

Stumps of conifer trees are a prospective source of bioenergy and stump harvesting is a novel practice in forestry management in the Baltic and Nordic countries. However, as stump harvesting may cause possible environmental risks there has emerged a clear need for research focusing on sustainable forest management. Three Norway spruce (Picea abies)...

Silver birch (Betula pendula Roth.) is one of the main pioneer tree species occupying large areas of abandoned agricultural lands under natural succession in Estonia. We estimated aboveground biomass (AGB) dynamics during 17 growing seasons, and analysed soil nitrogen (N) and carbon (C) dynamics for 10 year period in a silver birch stand growing on...

In the Northern and Baltic countries, grey alder is a prospective tree species for short-rotation forestry. Hence, knowledge about the functioning of such forest ecosystems is critical in order to manage them in a sustainable and environmentally sound way. The 17-year-long continuous time series study is conducted in a grey alder plantation growing...

At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. In 2006 an unique experimental facility for free air humidity manipulation (FAHM) was established in Estonia to study the functioning of deciduous forest ecosystem under altered humidity conditions. The experimental site co...

The influence of forest ageing on fine-root morphology and relations between fine-root and leaf characteristics is poorly studied. The aim of this study was to analyse age-driven changes in ectomycorrhizal roots (EcM roots) and leaf morphology in a chronosequence of silver birch (Betula pendula Roth.), which would provide a better understanding of...

The aim of the study was to determine the density of oven dry stemwood (moisture content 0%) of two fast-growing tree species, grey alder (Alnus incana (L.) Moench) and hybrid alder (Alnus hybrida A. Br.), growing on abandoned agricultural land. The study is based on two 16-year-old experimental stands located in Southern Estonia (N 58°32 E 27°12)....

Owing to its ability to produce large amounts of biomass in a short period of time, grey alder can be considered to be a prospective tree species for short-rotation forestry (SRF) in Eastern Europe and the Nordic countries. Relatively scanty data is available about grey alder yield and growth dynamics. Seven yield-tables from six countries and seve...

A facility for free air humidity manipulation (FAHM) was established to investigate the effect of increased air humidity on belowground biomass and turnover in silver birch (Betula pendula Roth.) forest ecosystems with respect to rising air humidity predicted for Northern Europe. Fine root and rhizomes are short-lived and recognized as the most imp...

a b s t r a c t During recent decades, studies of the carbon (C) balance of forest ecosystems have became more actual, mainly in connection with the global increase of CO 2 in the atmosphere. In the present study the stand chronosequence approach was applied to analyse C sequestration dynamics. Study was made of C accu-mulation both in biomass and...

Several studies about stands growing on abandoned agricultural lands are induced by extensive afforestation of agricultural lands and more intensive use of biomass. Overview of above-ground biomass production of grey alder, hybrid alder and silver birch young stands growing on former agricultural areas are presented in current paper. The results of...

Biomassi produktsioon jänesekapsa kasvukohatüübi arukaasikutes Present study was carried out in three silver birch ( Betula pendula Roth.) stands in the Oxalis site type in South-Estonia. The above-ground biomass, above-ground biomass production and foliar characteristics of 14-, 32- and 45-year-old silver birch natural stands were studied. The abo...