Soil scarification shortly before a rich seed fall improves seedling establishment in seed tree stands of Pinus sylvestris

The effect of timing of soil scarification on establishment of Scots pine ( Pinus sylvestris L.) in relation to amount of seed fall was studied in two seed-tree stands in central Sweden. The seed trees were released in autumn 1989. The treatments were: (i) scarification the autumn following cutting a nd before a seed fall expected to be poor; (ii) scarification in autumn 2 y rs after release, before a seed fall expected to be rich; and (iii) no soil preparation (control). Seedling establishment, mortality and height growth were monitored for 7 yrs from the start of the experiment. After 7 yrs, th e seedling density was highest (c. 69000 ha(-1)) in the area where soil sca rification preceded a rich seed fall, whereas scarification immediately aft er cutting resulted in 34000 seedlings ha(-1). The frequency of plots (size 3.14 m(2)) without seedlings was 5 and 7.5% where scarification was made b efore the rich seed fall and before the poor seed fall, respectively. Unsca rified plots showed the poorest result according to number of seedlings (60 00 ha(-1)) and number of plots without seedlings (52.5%). There was no sign ificant difference in mortality of germinated seedlings between treatments. Height growth was significantly improved by scarification. The time elapse d since scarification clearly affected seed germination: The germination pe rcentage of viable seeds dispersed on exposed mineral soil varied from 28.6 % in the first year following scarification to 0.8% in the 7th year. The me an germination percentage in unprepared humus (control) was only 0.9% durin g the monitored period.