Tree-rings mirror management legacy: dramatic response of standard oaks to past coppicing in Central Europe

Abstract

Background: Coppicing was one of the most important forest management systems in Europe documented in prehistory as well as in the Middle Ages. However, coppicing was gradually abandoned by the mid-20(th) century, which has altered the ecosystem structure, diversity and function of coppice woods.

Methodology/principal findings: Our aim was to disentangle factors shaping the historical growth dynamics of oak standards (i.e. mature trees growing through several coppice cycles) in a former coppice-with-standards in Central Europe. Specifically, we tried to detect historical coppicing events from tree-rings of oak standards, to link coppicing events with the recruitment of mature oaks, and to determine the effects of neighbouring trees on the stem increment of oak standards. Large peaks in radial growth found for the periods 1895-1899 and 1935-1939 matched with historical records of coppice harvests. After coppicing, the number of newly recruited oak standards markedly grew in comparison with the preceding or following periods. The last significant recruitment of oak standards was after the 1930s following the last regular coppicing event. The diameter increment of oak standards from 1953 to 2003 was negatively correlated with competition indices, suggesting that neighbouring trees (mainly resprouting coppiced Tilia platyphyllos) partly suppressed the growth of oak standards. Our results showed that improved light conditions following historical coppicing events caused significant increase in pulses of radial growth and most probably maintained oak recruitment.

Conclusions/significance: Our historical perspective carries important implications for oak management in Central Europe and elsewhere. Relatively intense cutting creating open canopy woodlands, either as in the coppicing system or in the form of selective cutting, is needed to achieve significant radial growth in mature oaks. It is also critical for the successful regeneration and long-term maintenance of oak populations.

Figure 1. Typical oak standard with a large straight stem and spreading branches in an abandoned coppice-with-standards.

Photo by R. Hédl.

Figure 2. Location of the study site.

The aerial photograph of Děvín Wood from 1938 (Military Geographical and Hydrometerological Office, Dobruška) depicts the last coppicing (a). The sample area (b) is visible as lighter rectangle with darker dots representing oak standards. c) shows the cored oak standards. The date of the last harvest is marked in each forest compartment.

Figure 3

(A) Percentage of trees showing release in 5-year intervals, as identified with the boundary-line release criteria. The two main releases closely followed coppicing events. Releases in the 1970s and 1990s coincide with the major singling-out of coppice stools. (B) Number of trees established in individual decades (age was determined on the basis of increment cores taken at breast height). With two exceptions, all oak standards originated before or shortly after the last regular coppicing in 1935/1937. The two main coppicing events are indicated by black arrows.

Figure 4. The average annual radial growth of Q. petraea standards (dashed line) and values of boundary-line for this mean growth (red line).

The two main coppicing events are indicated by black arrows.

Figure 5. Average tree-ring growth for 22-year time periods.

Arrows mark the last two historical coppicing events. The periods after coppicing had significantly higher average tree-ring increments than the periods not following coppice events. Columns sharing the same letter are not significantly different at p<0.01 (ANOVA followed by Tukey's HSD post-hoc tests). Error bars represent standard error. The period 1917–1935 includes a 19-year time span, because there are no more years before the first coppicing event (1935).

Figure 6. Comparison of stem diameter, relative growth rate (RGR) and competition indices (sum of basal area of all living and dead neighbours, and the density of dead neighbouring stems) of oaks established before 1886 (A), between 1886 and 1930 (B), and after 1930 (C).

Boxes represent 25–75% of values, black dots medians, whiskers 1.5 interquartile ranges, and open dots outliers.

Figure 7. Mean cumulative stem diameter growth curves for three groups of oak standards established before 1886, between 1886 and 1930, and after 1930 with respect to the two coppicing events (marked by thick arrows).

Figure 8. Relationships between: (a) diameter increment from 1953 to 2003 (AGR, absolute growth rate) and stem diameter in 1952; (b) AGR and tree age in 1952; (c, d) relative growth rate (RGR) of diameter increment and the intensity of neighbourhood competition (crowding) within 10 m; where in (c) basal areas (in m²) of all dead trees were considered, while in (d) Tilia platyphyllos living and dead trees were analysed.