Skład gatunkowy i biomasa nadziemna krzewów w podszycie drzewostanów Puszczy Niepołomickiej

摘要

Wzrost stężenia dwutlenku węgla w atmosferze jest powszechnie uważany za podstawową przyczynę obserwowanych w ostatnich dekadach zmian klimatu. Dla zminimalizowania niekorzystnych jego skutków podejmowane są działania zmierzające do ograniczenia wielkości emisji gazów cieplarnianych. Temu służą między innymi zobowiązania do oceny wielkości emitowanego i pochłanianego dwutlenku węgla ponad 150 państw, które podpisały sporządzony w Kioto w 1997 roku protokół do konwencji w sprawie zmian klimatu [Protokół... 2005]. Gospodarka leśna, ze względu na przewagę akumulacji nad wielkością uwalnianego dwutlenku węgla w skali globalnej, wymieniana jest jako istotne narzędzie sterowania wielkością jego stężenia w atmosferze. Sporządzane bilanse dwutlenku węgla, z uwagi na możliwość „handlu uprawnieniami do wielkości emisji gazów cieplarnianych", mogą, poza monitoringowym, mieć także konkretny wymiar ekonomiczny. Podejmowane także w Polsce badania biomasy ekosystemów leśnych [Orzeł i in. 2005a, b; Turski i in. 2008; Zasada i in. 2008, 2014; Bronisz i in. 2009; Orzeł 2009; Jagodziński i in. 2012, 2014; Ochał i in. 2013, 2014; Pietrzykowski, Daniels 2014; Woziwoda i in. 2014; Gazda i in. 2015] mają więc, poza poznawczym, istotne znaczenie utylitarne. Ich wyniki stanowią obiektywne źródło informacji o wielkości akumulowanego węgla oraz mogą być wykorzystane do modelowania jej zmian [Kauppi i in. 1992; Grotę 2002].%The understory, a layer composed predominantly of shrubs that perform an important phytome-liorative function, has rarely been the subject of research on the productivity and biomass. The aim of this paper was to specify the occurrence of understory aged ≥10 years as well as its species composition and the share of individual species in the biomass in the Niepołomice Forest (S Poland). The analysed features were related to the age and site conditions of the stands. The research material consisted of dry biomass of shrubs growing within circular sample plots spaced 500 m apart from each other. Dead and live (damaged and undamaged) shrubs of dbh＜7 cm were cut at a ground level to determine their wet mass and samples were taken to determine the dry mass. The mass of live shrubs was calculated based on empirical formulas. 368 sample plots were set up in total. Shrubs (13 species) were observed on 76.1% of plots. Shrubs were the most common in the stands of Ⅱ and Ⅳ age groups (87% of plots). No shrubs were observed on the plots with stands older than 160 years. The most common species was Frangula alnus (56.8% of the plots). Quite common ones included Sorbus aucuparia (21.1%) and Padus avium (12.8%). Cornus sanguinea, Prunus spinosa, Salix caprea and Viburnum opulus were observed on less than 1 % of the sample plots. Frangula alnus and Padus avium were inventoried in as many as 8 forest site types. The largest amount of shrubs (10 species) were observed in moist broadleaved forest stands, while the fewest (2 species) in boggy mixed broadleaved and ash-alder swamp stands. Over 56% of the aboveground biomass were live shrubs of dbh ＜7 cm (868.6 kg/ha), almost 29% (444.1 kg/ha) were shrubs of the dbh ≥7 cm, and around 15% (227.6 kg/ha) of the biomass were dead shrubs. The total aboveground biomass of shrubs in the understory of the analysed stands equaled, on average, to 1,540 kg/ha. 94% of the biomass was the aboveground woody biomass including bark (1,448 kg/ha). The dry mass of leaves amounted to 92 kg/ha (6%). Due to high variability of the understory biomass, the estimation error of its average amount was almost 11.4% for total biomass and 13.5% for leaves.