Methods for Quantification of the Decline Phenomenon and Determination of the Vulnerability Degree for the Oak Stands in Northwestern Transylvania, Romania

Abstract

The decline phenomenon of stands can be defined as the totality of effects that damage the normal vegetation state of trees and stands. There are two types of decline, the acute one, with fast development, and the chronical one, with slow development in space and time. The accurate capture of the phenomenon has direct implications for the forest management measures. A first step in this direction is the analysis of the development type and of its dynamics. Forests which have Quercus species in composition are affected more by this phenomenon. There were identified oak stands presenting decline phenomenon in 9 Forest Districts in Northwestern Transylvania and 22 experimental plots were analyzed. These plots were located in middle aged stands that were affected in different ways. The study was performed during 2013-2015 and focused on crown level assessments of trees, taking into consideration the shape and size, defoliations, percentage of dead or missing slender branches, number of dead thick branches, presence of epicormic branches or dormant buds on the stem, presence of pathogens or pests. These elements were used for calculating some technical indicators of the health and vegetation state: degree of dieback, damage and devitalization, synthetic index damage, annual mortality rate. In 7 out of 22 stands, the overcoming of the incipient stage and beginning of active dieback stage was observed. The strongest correlation occurred between the annual mortality rate and the synthetic index damage.

Identifying and Describing the Main Climatic and Stress Factors That Are Affecting Forest and Viticultural Ecosystems

“…The most affected areas affected in the period 2001-2010 were oak forests (67%) and resinous forests (14%). Annual oak dryings on a surface of over 30.000 hectares represents a low percentage in comparison with the previous period, both as surface as well as intensity (Chira & Chira 1998, Simionescu et al 2001, Danescu et al 2015, Constandache et al 2016, Simonca et al 2017. This area is also characterized by the presence of natural and artificial shrubby associations composed of whitesea buckthorn (Constandache et al 2016), red sea buckthorn, small locust etc.…”

The Effectiveness of Phytosanitary Treatments in the Control of Oak Mildew, in the Current Climate Context

“…In order for the damage to be at the lowest level, a series of measures and treatments are usually applied: using seeds obtained from resistant parents, crop rotation, bathing the seeds and applying treatments of seedlings with various fungicides (Marcais, 2014). The complex constituted by the host plant and the parasite that attacks it is subject to the direct influence of the environment, through its various factors, acts both on the plant, changing its resistance, and on the pathogen, changing its virulence (Bobeș, 1983;Șimonca, 2017). For this reason, the study of plant diseases must be done in close connection with the microclimates in the nursery area, which gives it a pronounced regional character, certain particularities of the environment decisively influencing the success of certain treatments, schemes or technologies to combat and control diseases (Tăut, 2001;Demeter, 2021).…”

Genetic Diversity and Structure of Quercus petraea (Matt.) Liebl. Populations in Central and Northern Romania Revealed by SRAP Markers

“…Approximately 30-40 years ago, a phenomenon of dieback affecting several species within the Quercus genus, including Quercus petraea, was documented in Europe, as well as in Romania [18][19][20]. This dieback phenomenon, characterized by the gradual decline in tree health, is likely attributed to climate-change-associated factors like droughts [21], pest infestations by organisms such as Tortrix viridana and Lymantria dispar [22][23][24][25], or pathogenic fungi [26]. Although the dieback phenomenon has been considered as a natural selection process driven by climate change for Q. petraea populations [27,28], it also exerts a detrimental impact on the species' genetic diversity.…”