Canopy thinning, light climate and distribution of Calamagrostis epigejos (L.) ROTH in a Scots pine forest (Pinus sylvestris L.)

Osnabrück

1999

S. 9-18

7 Abb., 2 Tab., 50 Lit. Ang.

Bandaufführung

136544

The effects of canopy thinning and below-canopy light climate on the distribution of Wood Small-reed [Calamagrostis epigejos] were studied in an irregularly thinned 45-years-old Scots pine forest of the north-eastern German lowlands. Along a 160 m x 10m transect, occurrence and above-ground biomass of the dominating ground vegetation species Avenella flexuosa and Calamagrostis epigejos were assessed. Digital analysis of hemispherical photos was used to estimate the sum of global radiation during the vegetation period (15th July to 15th September). Additionally, canopy gaps along the transect were mapped using aerial color infrared photos. The appearance of Calamagrostis patches at the north-(eastern) edges of canopy gaps and in the adjacent areas under canopy indicates effects of direct radiation on the ground vegetation. The radiation estimates show a high small-scale variation between less than 10 % and more than 30 % relative to open-field radiation. Considering the biomass distribution, an ecological competition threshold between Avenella flexuosa and Calamagrostis epigejos of approximatly 30 % of open-field radiation sum could be identified. Beyond this threshold, the biomass of Calamagrostis epigejos strongly increases. This indicates the competitive success over Avenella flexuosa with stagnating or even increasing biomass storage. The site, climate and deposition conditions of the plot are typical for many middle-aged Scots pine forests of the region. Therefore, a representative estimation of a threshold for the distribution of Calamagrostis epigejos in these forests can be presented.