Jurij Diaci, Tomaž Adamič, Andrej Rozman, Dušan Roženbergar

Gradual conversion of black pine plantations in Karst region of Slovenia

Map of Slovenia and neighboring regions with position of the North Adriatic Karst(Kaligarič et al. 2006)

Karst in the 17th century: a barren, treeless rocky landscape and NE wind burja (bora)

Black pine afforestation in 1895

1. Introduction

• 16,500 ha of black pine stands within the Karst region• increasing management risks (disease, fire),

transformation is challenging (oaks?) • research within the region: Prebevšek (1981, 1998), Škulj (1988),

Košiček (1992), Ferlin et al. (1998)

• research of natural and planted black pine stands: Vallauri (2002), Anić (2003), Zlatanov et al. (2010), Prevosto et al. (2011), Tiscar in Linares (2011), Kerr et al. (2012), Herrero et al. (2013), Portoghesi et al. (2013)

• research on scotc pine stands in succession: Mosandl in Kleinert (1998), Lust et al. (1998), Dobrowolska (2006)

• few studies relied on detailed ground vegetation assessment and direct measurement of ecological factors as light climate and soil moisture

1. Introduction

Research objectives: - analyze the structure of regeneration and its dependence on abiotic (light, soil moisture, relief...) and biotic factors (competitive plants including herbs, seed trees ...) - propose guidelines for the transformation of black pine stands based on natural regeneration

2. Methods

Geology: carbonate with some silicate (chert, flysch)Soil: variable (rendzinas and brown soils)Recent / Potential natural vegetation (Daskobler in Kutnar, 1998):-Seslerio autumnalis-Qercetum petraeae-Ostryo-Qercetum pubescentis-Seslerio-OstryetumClimate: Godnje (12.00; 1234 mm)Senj – CRO (14.90; 1212 mm), Bulgaria – Balkan (10.00; 650 mm),Abruzzi (10.10; 1130 mm), F Alps (10.20; 787 mm), Pyrenees (480 mm)

Stand structure: 87% black pine, 2% oaks, 1% noble broadleaves, 10% other b. / two story standsgrowing stock: 200 (100) m3/ha; increment 5 (2.3) m3/ha/year

2. Methods

• 44 plots 25 x 25 m in size• 4 plot categories: closed stand - 14 pl., opened stand - 15 pl.,

gap edge - 15 pl., gap center - 7 pl. (1.2-4.4 ha)• 6 herb plots (center) and from 0-12 oak subplots (1.5 x 1.5

m) were placed on each plot

• plots: typical dendrometric data and some ecological features

• 477 subplots: vegetation coverage according to the species, density of natural regeneration, typical ecological features, relative irradiance and soil water content

Sketch of plot with subplotsN

S

Gap 5

3. ResultsDensity of regeneration per hectare according to height classes and three species (28 trees, 31 shrubs, 120+ herbs)

Herb subplots

H. Class F_Ash H_Hor Oak Elm N_Brd Other Sum

< 20 cm 9616 321 1859(14%) 270 710 152 12928

< 130 cm 9632 1724 794(6%) 253 676 84 13164

> 130 cm 1335 422 68(3%) 17 51 68 1960

Total 20583 2467 2721(10%) 541 1436 304 28052

Oak subplots

H. Class F_Ash H_Hor Oak Elm N_Brd Other Sum

< 20 cm 8494 353 4237 166 228 42 13520

< 130 cm 6397 1059 6044 332 187 145 14164

> 130 cm 748 602 166 0 0 21 1537

Total 15639 2015 10447 498 415 208 29221

Legend: F_Ash – Flowering Ash, H_Hor – Hop Hornbeam, N_Brd – Noble Broadleaves

Share of tree species according to height classes

< 20 cm 20-130 cm > 130 cm

OtherN_BrdElmOakH_HorF_Ash

Legend: F_Ash – Flowering Ash, H_Hor – Hop Hornbeam, N_Brd – Noble Broadleaves

Plot of Means

kras$sklepf

mea

n of

kra

s$hr

20

0.0

0.6

1.2

skl vr_st rob vrz

kras$transf

centhr

Plot of Means

kras$sklepf

mea

n of

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21

0.0

1.0

2.0

skl vr_st rob vrz

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Plot of Means

kras$sklepf

mea

n of

kra

s$cg

20

0.00

0.10

0.20

skl vr_st rob vrz

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centhr

Plot of Means

kras$sklepfm

ean

of k

ras$

cg21

0.0

0.5

1.0

1.5

skl vr_st rob vrz

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centhr

Plot of Means

kras$sklepf

mea

n of

kra

s$m

jes2

0

02

4

skl vr_st rob vrz

kras$transf

centhr

Plot of Means

kras$sklepf

mea

n of

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s$m

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12

34

skl vr_st rob vrz

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centhr

DIF 15% 28% 29% 52%

Oak < 20 cm

Mean tree species density and SE per ha according to height class and stand type

Oak > 20 cm

Hop Hornbeam > 20 cmHop Hornbeam < 20 cm

Flowering Ash < 20 cm Flowering Ash > 20 cm

closed opened gap edge gap center Stand type

closed opened gap edge gapclosed opened gap edge gap center Stand type

closed opened gap edge gap center Stand type

closed opened gap edge gap center Stand type

closed opened gap edge gap center Stand type

closed opened gap edge gap center

herb s.oak s.

herb s.oak s.

herb s.oak s.

herb s.oak s.

herb s.oak s.

herb s.oak s.

Share of (browsing) damage on regeneration according to species and height class

F_ash H_Hor Elm Oak N_Br Other

Legend: F_Ash – Flowering Ash, H_Hor – Hop Hornbeam, N_Brd – Noble Broadleaves

< 20 cm20-130 cm

Effect display for terms in the negative binomial regression mixed model for the oak seedling < 20 cm density data. The gray color denotes 95-percent confidence envelopes around the fitted effects. Only statistically significant factors are presented.

Stand type effect plot

closed opened gap edge gap center Stand type

Soil depth effect plot

Sessleria coverage effect plot

Seed tree distance effect plot

Rock coverage effect plot Organic soil horiz. depth effect plot

Effect display for terms in the negative binomial regression mixed model for the oak seedling > 20 cm density data. The gray color denotes 95-percent confidence envelopes around the fitted effects. Only statistically significant factors are presented.

clos. op. edge center Stand type

Ordination-biplot of the principle coordinate analysis for vascular plant cover in the herb layer (Bray-Curtis distance measure). Green arrows represent

Ellenberg indicator values, red arrows represent regeneration density and blue arrows represent measured ecological factors.

Closed standOpened standGap edgeGap center

Legend:HR – OakCGA – Hop HornbeamMJES – Flowering AshBREST – ElmEllenberg indicatorvalues:N – nitrogenF – soil moistureR – soil reactionH – humus

4. Discussion• significant density of oak (2700 ha-1) and noble broadleaves• mast year of 2011 didn't yield any one-year-old seedlings• oak < 20 cm: closed stand (DIF 15%), deeper soils, thicker

humus, seed trees• oak > 20 cm: open stands and gap edge (DIF 30%), humid

and developed soils• similar results: e.g. Vallauri 2002, Anic 2003, Zlatanov 2010;

Mosandl & Kleinert 1998, Dobrowolska 2006

5. Conclusion

Gradual conversion by means of natural regeneration is feasible:

(1) regular thinnings for stability and advance regeneration (15-20% DIF)

(2) creation of smaller gaps (0.05-0.10 ha, 30-40% DIFF)

(3) protection of seedlings from

harvesting and browsing

damage, regulation of

competitors