Modeling Forest Stand Dynamics, Growth and Yield

The world’s forests are diverse and serve myriad purposes; however, regardless of the management objective, reliable models of forest stand dynamics, growth and yield are required [...]

Spatiotemporal Structure Features of a Pine Stand on the South Slope of the Eastern Sayan Mountain

Due to relatively long development and long life of forest-forming species most of the conclusions on stand dynamics are based on the data collected by indirect methods of comparative research and analysis of cenosis forming theoretically temporal and spatial succession sequences and need to be verified and clarified. The most reliable results on the stand dynamics can be received on stationary objects such as permanent sample areas. The article presents the analysis results of long-term monitoring (1968–2012) of a pine (Pinus sylvestris L.) stand in low-mountain Eastern Sayan on the south slope with a steepness of 7–8º. The intermittent test of morphometric indicators of trees mapped on the permanent sample area was used. It is shown that the sum of tree trunk cross-section areas at breast height (1.3 m) varied by no more than 10 % with timber reserves on the lower, central and upper equal sites of the sample area during the entire observation period. At the same time heterogeneity of ecological conditions, taking place even on a small section of a smooth slope, influences the plantation self-thinning intensity. In the 42-year-old stand density ratio at lower, central and upper sites was 1:1.5:2.1. Stand density difference along the slope had been decreasing gradually over time, although it remained around 30 % at the time of the last observation. Over the years of observation, 53, 47, and 32 % of pines on the lower, central, and upper sites, respectively, have survived. The calculated average age of the died trees showed that in all groups of natural diameter classes, there was an earlier die-off of pines at the bottom of the slope with an increase in dying age up to the slope. Trees with larger trunk diameter (first telling) died later. All this led to a rearrangement of the horizontal structure of the plantation, a decrease in the average diameter and average volume of trees up to the slope. Typical for mountain forests clinal tree distribution, which affects their morphological indicators, is important to consider when studying and modeling forest ecosystems, as well as when implementing forest management measures. For citation: Ovchinnikova N.F. Spatiotemporal Structure Features of a Pine Stand on the South Slope of the Eastern Sayan Mountains. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 34–47. DOI: 10.37482/0536-1036-2021-5-34-47

Current Status and Recent Stand Structure Dynamics in Mixed Silver Fir—European Beech Forests in Croatian Dinarides: Are There Differences between Managed and Unmanaged Forests?

The environmental, social and economic potential of Dinaric uneven-aged forests along with the complex stand dynamics influenced by different long-term management approaches and environmental factors require comprehensive forest monitoring. This study aimed to explore differences in the current status and recent past dynamics of stand structures between unmanaged and managed mixed fir-beech forests in the Croatian part of the Dinaric Alps using large-scale data from an established monitoring system. From the 74 permanent sample plots distributed within the forest type measured in 2008 and re-measured in 2019, we stratified four strata (types of management regimes): (1) forests out of regular management and tree harvest for at least 30 years, (2) managed state forests on carbonate bedrock, (3) managed state forests on non-carbonate bedrock and (4) managed private forests. In each sample plot, 34 structural attributes were computed to assess indicators of their current status and recent past dynamics of stands in the studied forests. An increasing Q shape diameter distribution with a high number of large and very large trees characterize unmanaged forests and managed forests on non-carbonate bedrock. In managed state forests and private forests, variable (rotated sigmoid) and constant (negative exponential) results were obtained, respectively. Principal component analysis (PCA) distinguished managed and unmanaged forests with decreasing harvest volume and recruitment, increasing basal area, number of very large trees, average diameter at breast height (DBH), crown defoliation of firs and basal area of died beech trees. The current structure, recent and expected stand dynamics in the unmanaged forests (accumulation of standing volume, increase of large diameter trees and large snags, large share of beech, large mean DBH) can be recognized as old-growth attributes. The differences between the studied forest types, potential of both unmanaged and state managed fir-beech forests and approaches to sustain multifunctional forest management in the Dinaric region were discussed.

Distribution attributes of natural canopy gaps in the Hyrcanian mixed-oriental beech forests

One of the most important issues indicating the quality and quantity of forest ecosystems is the distribution of natural disturbances resulting in canopy gaps (CGs). The present study was conducted in one of the Hyrcanian beech forests in northern Iran in summer 2018. The gap areas were classified into small (< 200 m²), medium (200‒500 m²) and large gaps (500–1 000 m²) on the basis of full inventory. The univariate Ripley’s L-function was used for introducing the CG spatial pattern. Furthermore, mark correlation function (MCF) and density function (DC) in turns were used for verifying the correlation and frequency of CG size classes in each pattern. The results showed patterns of the gaps in each size class and integrated by the three size classes, they were random and cluster, respectively. Furthermore, the MCF revealed that the gap size classes were independently located in the clusters. The total frequency of the small, medium and large gaps in turns was 32, 49 and 19%, respectively. Although the density share of medium and small gaps in turns was more frequent than the large gap density in the study forest, the results of DC indicated that the frequency of each gap size class was random within each cluster, regardless of their density share. Based on the natural gap aggregations, the base circular mosaic with an area of 5 000 m² can be introduced for monitoring and specifying the forest stand dynamics.

The social drift of trees. Consequence for growth trend detection, stand dynamics, and silviculture

Recently, many studies worldwide tapped tree ring pattern for detection of growth events and trends caused by weather extremes and climate change. As long-term experiments with permanent survey of all trees are rare, growth trend analyses are mostly based on retrospective measurements of growth via increment coring or stem analyses of the remaining individual trees in older forest stands. However, the growth of the survivor trees in older stands may only unsufficiently represent the course of growth of the dominant trees throughout the stand development. Here, the more than 100 years survey data of the European beech (Fagus sylvatica L.) thinning experiment Fabrikschleichach in South Germany are used to show the long-term changes in social ranking of trees and their consequences for growth trend detection by retrospective tree ring analyses, for stand dynamics and silvicultural management. Firstly, a significant social upwards drift of initially medium-sized trees till 2010 is shown based on the trees' percentiles in the stem diameter distribution in 1904 versus 2010. The social climbing is stronger on the thinned compared to the unthinned plots. Secondly, we show that 40–60% of the 100 tallest trees in 1904 were replaced by social climbers and down-ranked below the 100 tallest trees till 2010. Linear mixed model analyses reveal that the long-term trend of the diameter growth of the 100 dominant survivors in 2010 was on average by 23% steeper than the trend of the 100 tallest starters in 1904. This indicates that the survivors had a steeper and longer lasting growth than the originally dominant trees. Thirdly, the diameter growth trend in the last 20 years, from 1990 to 2010, is analyzed in dependency on the current and past social position. A linear model shows that early subdominance or suppression can significantly steepen the growth trend a century later and vice versa.Finally, we discuss the implications of the social drift for the survivor-based growth trend analyses, for the stand dynamics, and silvicultural management.