Skógræktarritið - 15.12.1998, Side 66

* Þakning með plastdúk bætir
vöxt alaskaaspar á framræstri
mýri.
* Þar sem hætta er á næturfrost-
um, eykur sinuflóki eða illgresi
umhverfis ungarasparplöntur
hættu á skemmdum og van-
höldum.
* Með jarðvinnslu eða jarð-
vinnslu og plastþakningu má
draga úr hættu á vanhöldum
vegna næturfrosta.
* Þakning með heyi eða mykju
eykur líkur á skemmdum og
vanhöldum vegna næturfrosta í
flatlendri, framræstri mýri.
* Kanna verður betur möguleika
á því að nota beina stungu
græðlinga við asparskógrækt,
í stað plantna sem ræktaðar
hafa verið í gróðrarstöðvum.
* Þeim mun sterkara og
þroskaðra sem rótarkerfi aspar-
plantna er við gróðursetningu,
því betri eru lífslíkur og vaxtar-
möguleikar þeirra, að öðru
jöfnu.
* Þegar asparskógur er ræktaður
á bersvæði, er enginn ávinning-
ur í því fólginn að nota stálp-
aðar beðplöntur, fremur en
smávaxnar, ársgamlar
fjölpottaplöntur.
Þakkir
Við þökkum jarðeigendum að
Búlandi í Austur-Landeyjum og
að Þrándarholti í Gnúpverja-
hreppi fyrir afnot af landi til
tilrauna og aðstoð við undir-
búning tilraunar. Þórarni
Benedikz, Árna Bragasyni,
Guðmundi Halldórssyni og
öðrum þeim sem aðstoðuðu
við uppsetningu tilraunar og
mælingar eru færðar bestu
þakkir. Rannsóknir þær sem hér
segir frá voru styrktar af sérstakri
fjárveitingu á fjárlögum íslenska
ríkisins, til s.k. „Iðnviðarverkefnis"
(Notkun alaskaaspar f skógrækt
til iðnviðar). Höfundar vilja þakka
Ásu L. Aradóttur fyrir vandaðan
yfirlestur á handriti.
SUMMARY
Sigurgeirsson, A. and Ásgeirsson,
S. 1998. Establishment methods
for black cottonwood (Populus trich-
ocarpa Torr. & Gray). I. A compari-
son of different planting stock and
methods of mulching on contrast-
ing site-types in South lceland.
In 1992, two plantations were
established in South lceland to
determine the effects of three
types of mulching (hay, manure
and plastic sheet) and fourtypes of
planting stock (cuttings, 2-month
old containerized seedlings, 1-year
old containerized seedlings and 4-
year old bare-root seedlings) on
the survival and growth of a single
clone of Populus trichocarpa Torr. &
Gray. One of the plantations was
established on a recently drained,
ploughed and harrowed peatland
(Sandlækjarmýri = Sd). The other
plantation was established on a
sparsely vegetated, glacio-fluvial
outwash plain (Markarfljótsaurar =
Mk). Survival, climatic damage and
height-growth was followed over a
period of three years. On both
sites, mortality among cuttings
and 2-month old seedlings mainly
occurred during the year of establ-
ishment. At Sd, however, seedlings
were also killed during a night of
severe, ground-level, radiative frost
in Mid-August of 1993. Method of
mulching and planting stock had
significant effects on survival and
height over the whole period, and
interactions were significant
between plantation, method of
mulching and growing stock.
Mulching methods mainly im-
proved seedling growth rather than
survival. At Sd, hay mulching and
manure mulching contributed to
increased mortality and frost
damage during a night of radiative
frost in August 1993, compared to
that observed with control and
plastic-sheet mulching. Afterthree
years, seedlings treated with hay
mulching were, over all stock
types, 51%, 85% and 124% as high
as control seedlings, respectively.
At Mk (the glacio-fluvial outwash
plain), mulching methods had
rather minor effects on seedling
survival, however, all kinds of
mulching improved significantly
height growth in comparison with
control. Three years after establish-
ment, seedlings were 55, 36 and
30% taller for hay mulching,
manure mulching and plastic sheet
mulching, respectively, over
control.
Differences in survival and
height at the end of the third year
were significant between planting
stock types and appeared to be
related to the level of root develop-
ment at planting. Cuttings showed
poorest survival, with 22% and 29%
survival at Sd and Mk, respectively.
At Mk, 1-year old seedlings culti-
vated in 150 cm! multi-pot con-
tainers survived 30% better than
seedlings cultivated for 2 month in
the same type of container. At Sd,
differences between these two
stock types were small and non-
significant. One-year old seedlings
were significantly taller than 2-
month old seedlings at both sites
(30% taller at Sd and 24% taller at
Mk). At Mk, 4-year old bare-rooted
seedlings were also compared to
the other three stock types. During
the first winter after estabiishment,
these seedlings suffered extensive
stem die-back owing to wind-
blasting. However, although their
survival was 100%, and their height
at age 3 years 60% greater than
seedlings planted as 1-year old
containerized seedlings, they were
growing at a similar rate. The
results are discussed in relation
the opportunities for developing
new methods of establishing black
cottonwood forests on nutrient-
deficient, wind-exposed sites in
South lceland, especially on
glacio-fluvial outwash plains.
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SKÓGRÆKTARRITIÐ 1998