sön 23 dec 2018, 09:18#539900
Om kol...
Jurevics, A., Peichl, M., & Egnell, G. (2018). Stand Volume Production in the Subsequent Stand during Three Decades Remains Unaffected by Slash and Stump Harvest in Nordic Forests. Forests, 9(12), 770.
http://doi.org/10.3390/f9120770"Abstract: The renewable energy policies of the European Union rely on forest biomass in achieving
climate mitigation targets. In Sweden, where secondary residues from the forest industries are
fully utilized, primary residues following harvest such as stumps and slash offer a potential as an
additional biomass source. Stump and slash harvest may, however, have adverse effects on site
productivity due to increased nutrient loss from the site which could negatively impact the stand
volume production of the subsequent stand. Stand volume production is also affected by seedling
survival, seedling input from natural regeneration and management of the regenerated stand. In
this study, we evaluate the effects of stump and slash harvest on stand volume production of the
subsequent stand based on data from eight experimental sites across Sweden planted with Scots pine
(Pinus sylvestris L.) or Norway spruce (Picea abies (L.) Karst.) over period of 31–34 years after clearcut
with (1) traditional stem-only harvest; (2) stem and stump harvest; (3) stem and slash harvest; and
(4) stem, stump and slash harvest. With the goal to explain treatment differences in stand volume
production, treatment effects on site productivity estimated through initial height growth (10–19
years after planting), seedling survival, and input of seedlings through natural regeneration were also
analyzed. We found that stand volume production was higher following stump harvest as compared
to slash harvest, but stand volume production for the more intense harvest treatments (2)–(4) did not
differ from stem-only harvest (1). Initial height growth (i.e., site productivity) did not differ between
treatments, but followed the trend in stand volume production with (2) > (4) > (3) > (1). Survival
of planted seedlings was not affected by the treatments, whereas natural regeneration after 5 years
was significantly increased after both treatments including slash harvest (3) and (4) in comparison to
stem-only harvest. However, since most of that natural regeneration was removed in subsequent
pre-commercial thinnings, this initial increase did not affect stand volume production. The absence of
a significant interaction between treatment and species planted for all independent variables tested
suggests that there were no species related response differences. Since the experimental design did
not allow for site-level analyses, we cannot exclude the possibility that site-specific harvest treatment
effects might have masked general effects across all sites. Thus, slash and stump harvest effects at the
site level need to be further studied. These results suggest, at least over a 3-decade perspective, that
logging residues like stumps and slash can provide an additional renewable energy source to help
achieving climate change mitigation goals in the Nordic countries without depleting the future forest
biomass resource."
Åker och skogsmark fungerar helt olika. Huvuddelen av skogsmarken är podsol på morän där näringsupptaget huvudsakligen sker uppe i humustäcket. Det finns i princip inget kväve nere i mineraljorden. Våra skogsväxter är helt anpassade till det. På åkermark är det organiska materialet blandat med den ursprungliga sedimentjorden och kvävet finns inblandat i hela det övre jordlagret. På åkermark vill man ha kol i marken för att förbättra vattenhållning, syretillgång och tillgängligheten av NPK.
Om ljus...
Nej, ljus är inte begränsande för tillväxten. Tillväxten skulle inte höjas om man satte upp strålkastare över skogen.