First-level Permanent Observation Plots (POPs I)
List of POPsI
There are 1461 of first-level Permanent Observation Plots (POPs I) located in pine, spruce, fir, oak, beech and birch stands aged 20 years and over, it gives an average of one plot per 60 km2 of the national forest area. The distribution of plots reflects spatial, species and age structures of forests in Poland. Within the total, some 431 plots are distributed in a 16 x 16 km grid system and fall into the European monitoring network.
Each first-level POP is a part of a forest and comprises a group of 20 trees selected from the dominating stand. The centre of the plot is marked permanently in the field and the trees are numbered. A circular plot covering area related to the stand age was established within each POP: 0.005 ha in stands 21 - 30 years, 0.1 in stands 31 - 40 years, 0.02 in stands 41 - 60 years and 0.04 in stands 60 years old and more. All trees with diameter at breast height 7 cm or more located within these circular plots were numbered.
Second-level Permanent Observation Plots (POPs II)
List of POPs II
In total 148 second-level Permanent Observation Plots (POPs II) were established in 50 - 60 year old pine and spruce stands, and 70 - 90 year old oak and birch stands. They are located in such a way that 56 from 59 natural-forest regions of Poland are represented by 2 plots. In the case of certain extensive districts 3 plots were established. Each second-level Permanent Observation Plot comprises 400-450 trees covering area approximating a square or a rectangle with the known side length and angle size of the quadrilateral.
Third-level Permanent Observation Plots (POPs III)
(Ecological monitoring)
Third-level Permanent Observation Plots somewhat link the forest monitoring and integrated monitoring systems with the research programmes aimed at the analysis of forest ecosystems under changing environmental conditions. Each of these plots should comprise a small river basin and make possible the matter cycle to balance. Bearing in mind high costs of the establishment and maintenance of such plots, about 10-15 POPs chosen from among POPs II are planned to be established during the next 5 years.