© Acta hydrotechnica 22/36 (2004), Ljubljana
ISSN 1581–0267
1
UDK/UDC: 556.52:630*1 Prejeto/Received: 21. 9. 2004
Izvirni znanstveni članek – Original scientific paper Sprejeto/Accepted: 23. 6. 2005
DOLO ČANJE INDEKSA LISTNE POVRŠINE LISTNATEGA GOZDA NA
POVODJU DRAGONJE – 2. DEL: REZULTATI IN DISKUSIJA
ESTIMATING LEAF AREA INDEX OF THE DECIDUOUS FOREST IN THE
DRAGONJA WATERSHED – PART II: RESULTS AND DISCUSSION
Mojca ŠRAJ
Meritve in dolo čanje indeksa listne površine (LAI) so se izvajale v listnatem gozdu na
eksperimentalnem povodju Dragonje. Poleg teh meritev so bile so časno narejene natan čne meritve
in analize posameznih komponent hidrološkega kroga gozda in drugih parametrov vegetacije s
sodobno mersko opremo. V prvem delu članka (Šraj, 2003b) so bile predstavljene metode dolo čanja
indeksa listne površine in meritve LAI. Prav tako so v prvem delu članka natan čno opisane lastnosti
dreves na obeh izbranih raziskovalnih ploskvah. V tem delu članka so predstavljeni rezultati
meritev in dolo čanja indeksa listne površine ter njihova analiza. Meritve so se za čele v jeseni 2000.
Najpogostejšim drevesnim vrstam (hrast, jesen, gaber, javor, dren) je bila dolo čena specifi čna
površina listov SLA. Indeks listne površine LAI se je dolo čal po treh metodah: neposredni metodi
zbiranja odpadlega listja, metodi hemisferi čnega fotografiranja in metodi merjenja fotosintetskega
aktivnega sevanja (PAR). Z analizami je bilo ugotovljeno, da metodi hemisferi čnega fotografiranja
in merjenja fotosintetskega aktivnega sevanja PAR v obdobju z listjem podcenjujeta vrednosti LAI.
Dobljeni vrednosti za LAI po metodi zbiranja listja sta 6,7 za južno pobo čje in 7,3 za severno.
Manjša vrednost LAI na južnem pobo čju je bila pri čakovana, saj ima gozd na tem pobo čju bolj
odprt zna čaj kot na severni strani.
Klju čne besede:  indeks listne površine (LAI), specifi čna listna površina (SLA), Dragonja, gozdna
hidrologija, raziskovalno polje
Measurements and estimation of leaf area index (LAI) were carried out in the deciduous forest in
the experimental watershed of the Dragonja River. At the same time precise measurements and
analysis relevant to single elements of the forest hydrological cycle and other vegetational
parameters with modern measuring equipment were made. In Part 1 of the paper (Šraj, 2003b) the
methods of delineation of the leaf area index and measurements of LAI were discussed. An accurate
description of characteristical features of trees on both chosen plots was also given. In this part of
the paper, results of measurements, LAI estimation and analysis are given. The measurements
commenced in autumn 2000. The specific leaf area (SLA) was estimated for the most abundant tree
species (for example oak, ash, hornbeam, maple, cornelian cherry dogwood). Leaf area index was
estimated according to three methods: direct method of litterfall collection, method of
hemispherical photography, and method of measuring photosynthetically active radiation (PAR).
The analyses revealed that the methods of hemispherical photography and of photosynthetically
active radiation (PAR) underestimated the value of LAI in the full-leaf period. LAI estimated
according to the litterfall collection method was 6.7 on the south plot and 7.3 on the north plot. The
lower value of LAI on the south plot was expected, since the forest on the south plot has a more
open character than the one on the north plot.
Key words: leaf area index (LAI), specific leaf area (SLA), Dragonja, forest hydrology,
experimental plot

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
2
1. REZULTATI MERITEV IN
RAZPRA V A
1.1 SPECIFI ČNA POVRŠINA LISTOV
SLA
Za izra čun indeksa listne površine po
neposredni metodi je potrebno najprej dolo čiti
specifi čno površino listov SLA (Šraj, 2003b).
SLA se je dolo čila za pet najbolj tipi čnih
drevesnih vrst na vsaki ploskvi posebej (hrast,
gaber, jesen, javor, rumeni dren), poleg tega pa
tudi za kategorijo “ostali listi” ter za droben
listni material. Dobljene vrednosti SLA so
prikazane v preglednici 1. Kot je razvidno iz
dobljenih rezultatov, so specifi čne površine
listov posameznih drevesnih vrst na severnem
pobočju ve čje kot na južnem, z izjemo gabra.
Razlike v SLA med obema pobo čjema se
gibljejo od 2 % (hrast) do 30 % (rumeni dren).
Vrednosti specifi čnih površin za listopadne
vrste dreves je v literaturi malo. Eden od
razlogov je tudi vedno ve čje število raziskav,
kjer se uporablja posredne metode dolo čanja
LAI, kjer specifi čna površina listov ni
potrebna. Drug razlog pa je gotovo zamudnost
metode. Za približno primerjavo so bile
najdene le vrednosti Chasona in sodelavcev
(1991), ki so za hrast v ZDA dobili vrednosti
SLA 10–12 m
2
/kg, za rde či javor pa 16,5
m
2
/kg.
1. RESULTS OF MEASUREMENTS
AND DISCUSSION
1.1 SPECIFIC LEAF AREA SLA
For calculation of the leaf area index
according to the direct method one first has to
estimate the specific leaf area SLA (Šraj,
2003b). SLA was estimated for the five most
typical tree species on each plot separately
(oak, hornbeam, maple, ash, cornelian cherry
dogwood), and also for the “other leaves”
category and for fine foliage material. SLA
values are shown in Table 1. As is apparent
from the results obtained, the specific leaf area
of single tree species on the north plot is
higher than that on the south plot, with the
exception of hornbeam. Differences in SLA
between both slopes are from 2 % (oak) to
30 % (cornelian cherry dogwood).
SLA values for deciduous tree species are
not often found in the literature. One of the
reasons is that a growing number of studies
use the indirect methods of LAI estimation,
where the estimation of specific leaf area is not
needed. Another reason is that the direct
method tends to be time-consuming. For an
approximate comparison only the values by
Chason et al. (1991) were available, who
acquired for oak (in USA) the SLA values of
10–12 m
2
/kg, and for red maple 16.5 m
2
/kg.
Preglednica 1. Specifi čna površina listov SLA za posamezne drevesne vrste na južni in severni
raziskovalni ploskvi.
Table 1. Specific leaf area SLA for each tree species on the south and north research plots.
DREVESNA VRSTA/
TREE SPECIES
JUŽNA PLOSKEV/
SOUTH PLOT
[m
2
kg
-1
]
SEVERNA PLOSKEV/
NORTH PLOT
[m
2
kg
-1
]
Hrast/oak 15.95* 16.25*
Gaber/hornbeam 30.60* 26.27*
Javor/maple 32.41 37.61
Jesen/ash 36.61 48.90
Rumeni dren/cornelian cherry
dogwood
30.63 43.47
Ostali listi/other leaves 26.55 27.68
Droben listni material/fine
foliage material
5.35* 5.01*
* te Linde (2001)

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
3
Preglednica 2. Povpre čne koli čine zbranega odpadlega listja [kg/m
2
] po posameznih drevesnih
vrstah v sezoni 2001/02 na severni raziskovalni ploskvi.
Table 2. Average quantity of collected litterfall [kg/m
2
] of single trees species in the season
2001/2002 on the north research plot.
Datum/date
HRAST/
OAK
GABER/
HORNBEAM
JAVOR/
MAPLE
JESEN/
ASH
DREN/
DOGWOOD
OSTALI LISTI/
OTHER
LEAVES
DROBEN
LISTNI
MATERIAL/
FINE LEAF
MATERIAL
SKUPAJ
LISTJE/
TOTAL
LITTERFALL
7.9.01 0.006 0.028 0.005 0.000 0.000 0.003 0.003 0.046
23.10.01 0.011 0.007 0.001 0.000 0.001 0.001 0.003 0.023
8.11.01 0.006 0.004 0.001 0.000 0.001 0.001 0.003 0.016
30.11.01 0.037 0.026 0.014 0.004 0.003 0.003 0.012 0.099
11.12.01 0.081 0.020 0.011 0.005 0.003 0.002 0.003 0.125
19.12.01 0.002 0.002 0.000 0.000 0.000 0.000 0.000 0.004
9.1.02 0.001 0.000 0.000 0.000 0.000 0.001 0.000 0.002
30.1.02 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001
8.3.02 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.002
22.5.02 0.001 0.000 0.000 0.000 0.000 0.005 0.001 0.008
SKUPAJ/
TOTAL
0.145 0.088 0.033 0.010 0.008 0.017 0.026 0.326
% 44.52 26.96 10.01 3.01 2.35 5.16 7.99 100.00
Preglednica 3. Povpre čne koli čine zbranega odpadlega listja [kg/m
2
] po posameznih drevesnih
vrstah v sezoni 2001/02 na južni raziskovalni ploskvi.
Table 3. Average quantity of collected litterfall [kg/m
2
] of single trees species in the season
2001/2002 on the south research plot.
Datum/date
HRAST/
OAK
GABER/
HORNBEAM
JAVOR/
MAPLE
JESEN/
ASH
DREN/
DOGWOOD
OSTALI LISTI/
OTHER
LEAVES
DROBEN
LISTNI
MATER./
FINE LEAF
MATERIAL
SKUPAJ
LISTJE/
TOTAL
LITTERFALL
7.9.01 0.004 0.001 0.000 0.000 0.000 0.001 0.001 0.007
23.10.01 0.005 0.002 0.000 0.002 0.007 0.001 0.003 0.021
8.11.01 0.001 0.002 0.000 0.003 0.003 0.000 0.001 0.010
30.11.01 0.009 0.010 0.000 0.047 0.008 0.004 0.004 0.082
11.12.01 0.061 0.001 0.000 0.014 0.004 0.005 0.003 0.088
19.12.01 0.036 0.000 0.000 0.004 0.000 0.003 0.001 0.044
9.1.02 0.006 0.000 0.000 0.001 0.000 0.001 0.000 0.008
30.1.02 0.002 0.000 0.000 0.000 0.000 0.001 0.000 0.004
8.3.02 0.009 0.000 0.000 0.001 0.000 0.002 0.000 0.012
22.5.02 0.007 0.000 0.000 0.000 0.000 0.001 0.000 0.008
SKUPAJ/
TOTAL
0.140 0.016 0.000 0.071 0.023 0.021 0.013 0.284
% 49.24 5.80 0.10 25.10 7.97 7.23 4.56 100.00

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
4
1.2 LAI PO METODI ZBIRANJA
ODPADLEGA LISTJA
Iz rezultatov tehtanja odpadlega listja je
razvidno (preglednica 2; slika 1), da skoraj
polovico zbranega listja [kg/m
2
] na severni
strani predstavljajo hrastovi listi. Dobra
četrina je gabrovih listov, 10 % javorjevih,
medtem ko je vseh ostalih vrst manj kot 10
%. To se na videz ne ujema popolnoma z
deležem zastopanosti posameznih dreves na
severnem pobo čju, kjer gabrova drevesa
predstavljajo 47 %, hrastova pa 34 % vseh
dreves. To lahko razložimo z ve čjo
specifi čno površino listov gabrovih dreves
(preglednica 1), kar pomeni, da so gabrovi
listi lažji od hrastovih, to pa rezultira k ve čji
masi zbranih hrastovih listov. Drug razlog
pa bi lahko bil v naklju čnosti razporeditve
desetih zbiralnih košar.
Tudi na južni strani približno polovico
zbranega listja [kg/m
2
] predstavljajo
hrastovi listi (preglednica 3; slika 2).
Četrtina je jesenovih listov, vse ostale vrste
pa predstavljajo manj kot deset odstotkov.
Tudi na južnem pobo čju prihaja do
navideznih neujemanj z deležem
zastopanosti posameznih drevesnih vrst,
kjer imamo 54 % jesena ter 26 % hrasta.
Razlog je enak. Specifi čna površina
jesenovih listov je ve č kot enkrat ve čja od
specifi čne površine hrastovih listov
(preglednica 1), kar nam da precej ve čjo
maso zbranih hrastovih listov.
Če pogledamo koli čine odpadlega listja
v odvisnosti od časa, ugotovimo, da ve čina
listja odpade v obdobju od za četka
novembra do konca decembra, torej v dveh
mesecih (sliki 1 in 2; preglednici 2 in 3).
Primerjava obeh ploskev kaže na nekoliko
ve čje koli čine listja na severnem pobo čju (~
0,04 kg/m
2
). Na severnem pobo čju imajo
vse drevesne vrste višek odpadanja listja v
prvi tretjini decembra (slika 1). Na južnem
pobočju pa listi jesena in gabra dosežejo
višek odpadanja približno 14 dni prej, torej
v drugi polovici novembra, listi ostalih
drevesnih vrst pa tako kot na severnem
pobočju v začetku meseca decembra (slika
2).
1.2 LAI ESTIMATED WITH DIRECT
LITTERFALL COLLECTION METHOD
The results of weighing the leaf litterfall
show (Table 2, Figure 1) that almost half of
the leaves collected [kg/m
2
] on the north plot
consists of oak leaves. Over a quarter of leaves
are represented by hornbeam, 10 % by maple,
while all other species make up less than 10 %.
Apparently, this does not completely coincide
with the representation of single species on the
north plot, where hornbeam trees represent 47
%, and oak 34 % of all trees. This can be
explained by larger specific leaf area of
hornbeam (Table 1), meaning that hornbeam
leaves are lighter than oak leaves, which
results in bigger mass of collected oak leaves.
The other reason could be the randomness of
distribution of 10 collection baskets.
Oak leaves represent approximately a half
of collected leaves [kg/m
2
] on the south plot as
well (Table 3, Figure 2). A quarter is
composed of ash leaves, all other tree species
represent less than 10 percent. There are
apparent discrepancies in the share of
representation of single species on the south
plot as well, where ash is represented by 54 %
and oak by 26 %. The reason remains the
same. Specific leaf area of ash is more than
one time the size of specific leaf area of oak
leaves (Table 1), which results in a greater
mass of collected oak leaves.
By considering the litterfall quantity in
dependence of time, it can be established that
most of the leaves falls off in the period from
the beginning of November to the end of
December, that is in two months (Figures 1
and 2; Tables 2 and 3). Comparison of both
plots shows somewhat higher litterfall volume
on the north plot (by approx. 0.04 kg/m
2
). On
the north plot all tree species reach their peak
in litterfall in the first third of December
(Figure 1). On the south plot, however, ash
and hornbeam leaves reach their peak in
litterfall approx. 14 days earlier, that is in the
second half of November, whereas leaves of
other tree species reach their peak in the
beginning of December (Figure 2), as is the
case on the north plot.

© Acta hydrotechnica 22/36 (2004), Ljubljana
ISSN 1581–0267
5
Slika 1. Kumulativna vsota odpadlega listja za posamezne drevesne vrste v odvisnosti od časa na
severni raziskovalni ploskvi v sezoni 2001/02 (Šraj, 2003a).
Figure 1. Cumulative total of litterfall for single tree species as a function of time on the north
research plot in the 2001/02 season (Šraj, 2003a).
Slika 2. Kumulativna vsota odpadlega listja za posamezne drevesne vrste v odvisnosti od časa na
južni raziskovalni ploskvi v sezoni 2001/02 (Šraj, 2003a).
Figure 2. Cumulative total of litterfall for single tree species as a function of time on the south
research plot in the 2001/02 season (Šraj, 2003a).

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
6
Preglednica 4. Indeks listne površine, dobljen z metodo zbiranja odpadlega listja v sezoni 2001/02
za vsako posamezno raziskovalno ploskev po posameznih datumih zbiranja.
Table 4. Leaf area index acquired by the method of litterfall collection in season 2001/02 for each
research plot and different collection dates.
SEVERNA PLOSKEV/
NORTH PLOT
JUŽNA PLOSKEV/
SOUTH PLOT
Datum/date SKUPAJ LISTJE/
TOTAL LITTERFALL
[kg/m
2
]
LAI SKUPAJ LISTJE/
TOTAL LITTERFALL
[kg/m
2
]
LAI
7.9.01 0.046 1.150 0.007 0.121
23.10.01 0.023 0.462 0.021 0.490
8.11.01 0.016 0.306 0.010 0.291
30.11.01 0.099 2.306 0.082 2.541
11.12.01 0.125 2.691 0.088 1.802
19.12.01 0.004 0.096 0.044 0.797
9.1.02 0.002 0.045 0.008 0.154
30.1.02 0.001 0.029 0.004 0.084
8.3.02 0.002 0.043 0.012 0.228
22.5.02 0.008 0.185 0.008 0.151
SKUPAJ/
TOTAL
0.326
( ± 0.045)
7.312
( ± 0.99)
0.284
( ± 0.032)
6.658
( ± 0.84)
Preglednica 5. Indeks listne površine, dobljen z metodo zbiranja odpadlega listja v sezoni 2001/02
za vsako posamezno raziskovalno ploskev po posameznih drevesnih vrstah (Šraj, 2003a).
Table 5. Leaf area index determined with the method of litterfall collection in the season 2001/02
for each research plot and for single tree species (Šraj, 2003a).
SEVERNA PLOSKEV/
NORTH PLOT
JUŽNA PLOSKEV/
SOUTH PLOT
VRSTA/
SPECIES
SKUPAJ LISTJE/
TOTAL LITTERFALL
[kg/m
2
]
LAI SKUPAJ LISTJE/
TOTAL LITTERFALL
[kg/m
2
]
LAI
HRAST/OAK 0.145 2.362 0.140 2.230
GABER/
HORNBEAM
0.088 2.311 0.016 0.504
JAVOR/MAPLE 0.033 1.229 0.000 0.009
JESEN/ASH 0.010 0.480 0.071 2.608
DREN/
DOGWOOD
0.008 0.333 0.023 0.693
OSTALI LISTI/
OTHER LEAVES
0.017 0.466 0.021 0.545
DROBEN LISTNI
MATERIAL/
FINE LEAF MATERIAL
0.026 0.131 0.013 0.069
SKUPAJ/
TOTAL
0.326
( ± 0.051)
7.312
( ± 0.95)
0.284
( ± 0.049)
6.658
( ± 1.04)

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
7
Zgodnejše odpadanje listja na južnem
pobočju je bilo zaznati v obeh letih merjenja.
Po vsej verjetnosti je to posledica pomanjkanja
vode v zemljini na južnem pobo čju, kar izhaja
tudi iz ve čje evapotranspiracije na tej ploskvi.
Primerjava obeh sezon merjenja daje zelo
podobno sliko, tako po času kot v koli činah.
Časovna primerjava sicer v ozkem časovnem
obdobju kaže manjša odstopanja, ki so po vsej
verjetnosti posledica vpliva burje, kažejo pa se
tako na severni kot južni strani.
Z množenjem specifi čne površine listov
posameznih drevesnih vrst s koli čino zbranega
listja dobimo indeks listne površine LAI.
Dobljeni vrednosti za najve čji indeks listne
površine sta 6,66 za južno pobo čje in 7,31 za
severno pobo čje (na višku rastne dobe)
(preglednici 4 in 5). Manjša vrednost LAI na
južnem pobo čju (za približno 10 %) je bila
pri čakovana, saj ima gozd na tem pobo čju bolj
odprt zna čaj. Podobno se tudi skupna koli čina
zbranega listja na obeh ploskvah razlikuje za
približno enako vrednost.
1.3 METODA HEMISFERI ČNEGA
FOTOGRAFIRANJA
Izra čunane vrednosti LAI za posamezna
časovna obdobja po metodi hemisferi čnega
fotografiranja so zbrane v preglednicah 6 in 7.
Dobljeni vrednosti najve čjega indeksa listne
površine v sezoni 2000/01 sta 5,24 za južno
pobočje in 4,81 za severno pobo čje, v
naslednji sezoni pa 3,50 oziroma 3,22.
1.4 MERJENJE FOTOSINTETSKEGA
AKTIVNEGA SEVANJA (PAR)
Za merjenje fotosintetskega aktivnega
sevanja PAR je bil uporabljen Sunflect
Ceptometer (Vrije Universiteit Amsterdam).
LAI se je izra čunal iz razmerja med
izmerjenim PAR pod krošnjami (prepuš čeno
sevanje) in nad krošnjami (vpadlo sevanje),
koeficienta pojemanja posamezne vegetacije
(angl. org. extinction coefficient) in Beer-
Lambertovega zakona. Uporabljeni koeficient
pojemanja svetlobe skozi krošnje κ je bil
privzet 0,70 (po Campbell, 1986; Ross, 1975).
Meritve so bile izvedene le na južnem
pobočju, saj na severnem pobočju v času
meritev skozi krošnje ni prehajalo ni č
Earlier falling off of leaves on the south
plot was recorded in both years of
measurements. In all likelihood, this resulted
from water shortage in the soil on the south
plot, which is also the consequence of bigger
evapotranspiration on the plot.
Comparison of both seasons of
measurements gives a very similar picture in
terms of time and quantity. Comparison in
terms of time shows minor deviations, which
are probably the result of the north-east burja
wind, and they occur on north and south plots
alike.
The specific leaf area of single tree species
multiplied by the quantity of collected litterfall
gives the leaf area index LAI. The highest
values of leaf area index were 6.66 for the
south plot and 7.31 for the north plot (at the
peak of growth) (Tables 4 and 5). Smaller LAI
value on the south plot (by approx. 10 %) was
expected, because the forest in the area is of
more open character. Similarly, the total
quantity of collected litterfall on both plots
differentiates for approximately the same
value.
1.3 HEMISPHERICAL PHOTOGRAPHY
The values of LAI for each time period
according to the method of hemispherical
photography are given in Tables 6 and 7. The
highest values of the leaf area index in the
season 2000/01 were estimated at 5.24 for the
south plot and 4.81 for the north plot, and
during the next season 3.50 and 3.22,
respectively.
1.4 PHOTOSYNTHETICALLY ACTIVE
RADIATION (PAR)
The Sunflect Ceptometer (Vrije Universiteit
Amsterdam) was used for measuring the
photosynthetically active radiation PAR. LAI
was calculated from the relationship between
PAR measured below canopy (transmitted
solar radiation) and above canopy (incoming
solar radiation), extinction coefficient and the
Beer-Lambert Law. The extinction coefficient
κ was set at the default value of 0.70
(according to Campbell, 1986; Ross, 1975).
The measurements were carried out on the
south plot only, since on the north plot there
was no direct solar radiation transmitted

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
8
neposrednega son čnega sevanja. Izra čunana
povpre čna vrednost LAI po tej metodi znaša
3,86 ( ± 0,24) (te Linde, 2001).
during the time of measurements. The
calculated average value of LAI according to
the method was 3.86 ( ± 0.24) (te Linde, 2001).
Preglednica 6. Izra čunane vrednosti LAI s pomo čjo hemisferi čnega fotografiranja
za sezono 2000/01 (te Linde, 2001).
Table 6. LAI values calculated by the method of hemispherical photography
for the season 2000/01 (te Linde, 2001).
DATUM/
DATE
SEVERNA PLOSKEV/
NORTH PLOT
JUŽNA PLOSKEV/
SOUTH PLOT
27.9.00 4.65 ( ± 0.48) 5.24 ( ± 0.78)
4.10.00 4.83 ( ± 0.71) 4.22 ( ± 0.35)
13.10.00 4.45 ( ± 0.21) 3.70 ( ± 0.26)
20.10.00 4.81 ( ± 0.17) 4.31 ( ± 0.35)
26.10.00 4.49 ( ± 0.23) -
Preglednica 7. Izra čunane vrednosti LAI s pomo čjo hemisferi čnega fotografiranja
za sezono 2001/02 (Šraj, 2003a).
Table 7. LAI values calculated by the method of hemispherical photography
for the season 2001/02 (Šraj, 2003a).
DATUM/
DATE
SEVERNA PLOSKEV/
NORTH PLOT
JUŽNA PLOSKEV/
SOUTH PLOT
7.9.01 3.22 ( ± 0.46) 3.50 ( ± 0.55)
5.12.01 2.19 ( ± 0.39) 2.07 ( ± 0.43)
11.12.01 1.20 ( ± 0.26) 1.56 ( ± 0.25)
18.12.01 0.89 ( ± 0.19) 1.34 ( ± 0.30)
9.1.02 1.06 ( ± 0.19) 1.52 ( ± 0.42)
Preglednica 8. Primerjava vrednosti LAI, dobljenih po razli čnih metodah za 20.–23.oktober.
Table 8. Comparison of LAI values obtained by different methods for 20–23 October.
ZBIRANJE
LISTJA/
LITTERFALL
COLL.
HEMISFERI ČNO
FOTOGRAFIRANJE/
HEMISPHERICAL
PHOTOGRAPHY
MERITVE PAR/
PAR
MEASUREMENTS
SEVERNA PLOSKEV/
NORTH PLOT
5.70 ( ± 0.49) 4.81 ( ± 0.17) -
JUŽNA PLOSKEV/
SOUTH PLOT
6.05 ( ± 0.26) 4.31 ( ± 0.35) 3.86 ( ± 0.24)
1.5 PRIMERJAVA VREDNOSTI LAI
DOBLJENIH PO RAZLI ČNIH
METODAH
Primerjava vseh treh metod za kratko
obdobje (20.–23. oktober), v katerem so bile
izvedene vse tri meritve, kaže, da dobimo
1.5 COMPARATION OF LAI OBTAINED
WITH DIFFERENT METHODS
Comparation of all three methods during a
short period (20–23 October), when all three
sets of measurements were carried out, shows
that the highest values were obtained by the

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
9
najvišje vrednosti po metodi zbiranja
odpadlega listja, najmanjše pa z merjenjem
fotosintetskega aktivnega sevanja (PAR).
Meritve PAR nam dajo skoraj za polovico
manjši LAI, hemisferi čno fotografiranje pa v
povpre čju okrog 20 % manjši LAI od metode
zbiranja odpadlega listja (preglednica 8). Torej
obe posredni metodi podcenjujeta vrednosti
LAI. To ni presenetljivo, saj so do podobnih
ugotovitev prišli tudi drugi raziskovalci po
svetu (Chason in ostali, 1991; Chen in ostali,
1997; Levy in Jarvis, 1999). Chason s
sodelavci (1991) je za mešani listnati gozd
(hrast, hikori, bukev, javor) v ZDA dobil
vrednosti LAI po metodi zbiranja odpadlega
listja 4,89, z dvema razli čnima posrednima
metodama merjenja prepuš čenega sevanja pa
3,79 oziroma 2,91 (Šraj, 2003a).
Časovna primerjava meritev skozi celo
sezono nam kaže celotno sliko (sliki 3 in 4). V
za četnem obdobju odpadanja listja, tj. nekje do
sredine novembra, lahko vidimo, da nam
metoda hemisferi čnega fotografiranja res daje
konstantno nižje vrednosti kot metoda zbiranja
odpadlega listja, kar smo že ugotovili pri
prejšnji primerjavi. Na višku sezone odpadanja
listja, tj. v drugi polovici novembra do sredine
decembra, pa lahko vidimo, da se vrednosti
LAI obeh metod ujemajo precej dobro. Po tem
obdobju metoda fotografiranja precenjuje
vrednosti LAI, kar je seveda pri čakovano, saj
so pri tej metodi v površino krošenj zajeti tudi
deblo in veje. Podobno ugotavljata v svoji
raziskavi tudi Levy in Jarvis (1999). Ugotovila
sta, da posredne metode (hemisferi čno
fotografiranje, Ceptometer) podcenjujejo LAI
pri velikih vrednostih in precenjujejo pri
majhnih.
Dobljene vrednosti so primerljive z rezultati
študij, narejenih drugod po svetu v približno
podobnih klimatskih razmerah za podobne
gozdne združbe listopadnih dreves. Le Dantec
s sodelavci (2000) je za hrastove in bukove
gozdove v Franciji izmeril vrednosti LAI od
0,5 do 8,1, v povpre čju pa med 6 in 8. Chason
s sodelavci (1991) je za mešani listnati gozd
(hrast, bukev, javor) v ZDA dobil vrednosti
LAI po metodi zbiranja odpadlega listja 4,9. Za
listnati gozd na Nizozemskem je bil izmerjen
LAI 4,9 (Lankreijer in ostali, 1993). Karlik in
Mckay (2002) poro čata o vrednostih 4–6,75 za
hrastov gozd v Sredozemlju (Šraj, 2003b). V
študiji, ki je zajela raziskave dolo čanja LAI od
leta 1932 do 2000 po celem svetu (Scurlock in
ostali, 2001), pa so za listopadne gozdove v
zmernem podnebju ugotovili povpre čno
vrednost 5,12 ( ± 1,84).
litterfall collection method, and the lowest
values with the method of photosynthetically
active radiation (PAR). PAR measurements
give LAI values smaller almost by half, and
hemispherical photography on average 20 %
lower LAI values from the litterfall collection
method (Table 8). This is not surprising, since
other scientists worldwide have come to
similar conclusions (Chason et al., 1991; Chen
et al. 1997; Levy & Jarvis, 1999). Chason et
al. (1991) obtained for the mixed deciduous
forest (oak, hickory, beech, maple) in USA
according to the litterfall collection method
LAI values of 4.89, and with two different
indirect methods of transmitted solar radiation
3.79 and 2.91, respectively (Šraj, 2003a).
Temporal comparison of measurements
throughout the whole seasons serves as an
overview (Figures 3 and 4). In the beginning
of the leaves falling-off period, i.e. by mid-
November, it can be established that the
method of hemispherical photography indeed
gives constantly lower values than the
litterfall collection method, as established in
previous comparison. At the peak of the
season of leaves falling off, i.e. in the second
half of November to mid-December, there is a
good correlation between values of LAI
acquired by both methods. After that the
method of hemispherical photography
overestimates the LAI values, which is to be
expected, because the tree trunks and branches
are incorporated into the canopy surface. Levy
& Jarvis (1999) have reached a similar
conclusion in their study. They concluded that
indirect methods (hemispherical photography,
Ceptometer) underestimate LAI with high
values and overestimate with low values.
The values obtained are comparable with
the results of studies carried out elsewhere in
approximately similar climate conditions for
similar deciduous forests. However, Le Dantec
et al. (2000) measured LAI values between 0.5
and 8.1 for oak and beech forest in France, and
on average between 6 and 8. Chason et al.
(1991) obtained LAI 4.9 for mixed deciduous
forest (oak, beech, maple) in USA according
to the the litterfall collection method. For the
deciduous forest in the Netherlands LAI was
estimated at 4.9 (Lankreijer et al., 1993).
Karlik & Mckay (2002) recorded values
between 4–6.75 for an oak forest in the
Mediterranean (Šraj, 2003b). In the study that
incorporated the LAI estimation from 1932 to
2000 worldwide (Scurlock et al., 2001) the
average value of 5.12 ( ±1.84) was estimated
for deciduous forests in moderate climate.

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
10
Slika 3. Primerjava meritev LAI po obeh metodah za severno raziskovalno ploskev.
Figure 3. Comparation of LAI obtained with different methods on the north plot.
Slika 4. Primerjava meritev LAI po vseh treh metodah za južno raziskovalno ploskev.
Figure 4. Comparation of LAI obtained with different methods on the south plot.

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
11
Slika 5. Prostorska spremenljivost LAI pri merjenju PAR za južno raziskovalno ploskev (serije
predstavljajo razli čne časovne meritve, n je število merskih to čk).
Figure 5.  Spatial variability of LAI in PAR measurements on the south research plot (series
represent different time measurements, n is the number of measuring points).
Slika 6. Prostorska spremenljivost LAI pri hemisferi čnem fotografiranju krošenj na severni
raziskovalni ploskvi (serije predstavljajo razli čne časovne meritve, n je število merskih to čk).
Figure 6. Spatial variability of LAI in hemispherical photography of canopy on the north research
plot (series represent different time measurements, n is the number of measuring points).

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
12
Slika 7. Prostorska spremenljivost LAI pri hemisferi čnem fotografiranju krošenj na južni
raziskovalni ploskvi (serije predstavljajo razli čne časovne meritve, n je število merskih to čk).
Figure 7. Spatial variability of LAI in hemispherical photography of canopy on the south research
plot (series represent different time measurements, n is the number of measuring points).
Slika 8. Prostorska spremenljivost LAI po metodi zbiranja odpadlega listja
v sezoni 2001/02 na severni raziskovalni ploskvi
(serije predstavljajo razli čne časovne meritve, n je število merskih to čk).
Figure 8. Spatial variability of LAI according to the method of litterfall collection in season
2001/02 on the north research plot (series represent different time measurements, n is the number
of measuring points).

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
13
Slika 9. Prostorska spremenljivost LAI po metodi zbiranja odpadlega listja v sezoni 2001/02 na
južni raziskovalni ploskvi (serije predstavljajo razli čne časovne meritve, n je število merskih to čk).
Figure 9. Spatial variability of LAI according to the method of litterfall collection in season
2001/02 on the south research plot (series represent different time measurements, n is the number
of measuring points).
1.6 PROSTORSKA SPREMENLJIVOST
LAI
Prostorska spremenljivost LAI pri merjenju
PAR na južnem pobo čju je razvidna iz slike 5.
Serije na sliki 5 predstavljajo razli čne časovne
meritve tekom sezone odpadanja listja. V
istem času se LAI po prostoru spreminja za
približno 2,5 m
2
/m
2
. Izstopa prva meritev, ki
pa je bila izvedena le v štirih to čkah, zato
verjetno tako majhen raztros.
Precej manjšo prostorsko spremenljivost
dobimo pri hemisferi čnem fotografiranju
krošenj, predvsem na severnem pobo čju.
Spremenljivost na severnem pobo čju se giblje
do 1,5 m
2
/m
2
, v ve čini serij pa pod 0,5 m
2
/m
2
(slika 6). Na južnem pobo čju pa je
spremenljivost ve čja, in sicer se giblje od 1–
2,5 m
2
/m
2
 (slika 7). To lahko razložimo z bolj
odprtim zna čajem gozda na južni strani.
Po metodi zbiranja odpadlega listja na
severnem pobo čju v ve čini serij dobimo zelo
majhno prostorsko spremenljivost, okrog 0,25
1.6 SPATIAL VARIABILITY OF LAI
Spatial variability of LAI in PAR
measurements on the south plot is shown in
Figure 5. Series on Figure 5 represent different
time measurements during the period of leaves
falling off. During the same time, LAI changes
by approximately 2.5 m
2
/m
2
 in space. The first
measurement stands out, it was carried out in
only in four points, and thus the small
fragmentation.
Fairly less significant spatial variability is
achieved with hemispherical photography of
canopy, primarily on the north plot. Variability
on the north plot is estimated at up to 1.5
m
2
/m
2
, in majority of sets, however, it is below
0.5 m
2
/m
2
(Figure 6). On the south plot the
variability is higher, i.e. from 1 to 2.5 m
2
/m
2
(Figure 7). This can be explained by the more
open character of the forest on the south plot.
According to the litterfall collection method
on the north plot in majority of sets a very
small spatial variability is achieved, which is
about 0.25 m
2
/m
2
, with the exception of three
sets, i.e. the first set in September and two sets

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
14
m
2
/m
2
, z izjemo treh serij, tj. prve septembrske
in dveh serij na višku odpadanja listja konec
novembra in v sredini decembra, ko je bila
spremenljivost malo manj kot 2 m
2
/m
2
 (slika
8). Nekaj podobnega se pojavlja tudi na
južnem pobo čju, kjer pa je v povprečju
prostorska spremenljivost ve čja od tiste na
severni strani. Podobno je bilo ugotovljeno že
pri metodi hemisferi čnega fotografiranja. Na
južni strani je spremenljivost v ve čini serij
manjša od 0,5 m
2
/m
2
, z izjemo štirih serij v
oktobru, konec novembra in v decembru, ko
znaša do 2 m
2
/m
2
 (slika 9).
2. ZAKLJU ČKI
Med gozdoma na severno in južno leže čih
pobočjih so bile pri čakovane ve čje razlike, saj
se opazno razlikujeta tako v strukturi, gostoti
in velikosti dreves kot v sami sestavi.
Primerjava rezultatov vseh treh metod
dolo čanja indeksa listne površine je pokazala,
da obe posredni metodi podcenjujeta LAI v
obdobju odpadanja listja in precenjujeta v
obdobju brez listja. To ni presenetljivo, saj so
do podobnih ugotovitev prišli tudi mnogi drugi
raziskovalci. Torej se z gotovostjo lahko
zanesemo le na neposredno metodo dolo čanja
LAI z zbiranjem odpadlega listja.
Z meritvami LAI in analizami bi bilo
potrebno nadaljevati še dve do tri leta, da bi
dobili potrditev rezultatov. Predvsem bi bilo
potrebno narediti ve č meritev fotosintetskega
aktivnega sevanja PAR in pove čati število
merskih to čk na obeh raziskovalnih ploskvah.
ZAHVALA
Za angleški prevod se zahvaljujem g. Mojci
Vilfan, za finan čno podporo pa Slovenskemu
komiteju IHP UNESCO in Ministrstvu za
šolstvo, znanost in šport Republike Slovenije.
Zahvaljujem se tudi izr. prof. dr. Damjani
Drobne iz Biotehniške fakultete Univerze v
Ljubljani za prijazno pomo č in uporabo
njihovega laboratorija. Prav tako bi se rada
zahvalila prof. dr. L.A. Bruijnzeelu in mag.
A.H. te Linde iz Vrije University v
Amsterdamu za strokovno pomo č.
at the peak of leaves falling off at the end of
November and mid-December, when the
variability was a little less than 2 m
2
/m
2
(Figure 8). Something similar was observed on
the south plot, where on average the spatial
variability is higher than that on the north side.
This was established earlier for the method of
hemispherical photography. On the south plot
the variability in the majority of sets was lower
than 0.5 m
2
/m
2
, with the exception of four sets
in October, at the end of November and in
December, when it was estimated up to 2
m
2
/m
2
 (Figure 9).
2. CONCLUSIONS
Greater differences were expected between
the forests on the north and south-facing plots,
since there are considerable differences in
terms of structure, density, tree size as well as
composition. The comparison of results of all
three methods of estimating the leaf area index
revealed that both indirect methods
underestimated LAI values in the period of
leaves falling off and overestimated LAI in the
leafless period. This comes as no surprise,
since many other experts have come to the
same conclusion. It appears that the only
highly reliable method of estimating LAI is the
direct method of litterfall collection.
For verification of results, LAI
measurements and analyses should be carried
out for another two or three years. Further
measurements of photosynthetically active
radiation PAR should be carried out in
particular and the number of measuring points
on both plots should be increased.
ACKNOWLEDGMENTS
I thank Ms. Mojca Vilfan for the translation
into English, and I greatly acknowledge the
financial support of the Slovenian National
Committee for the IHP UNESCO and the
Ministry od Education, Science and Sport of
the Republic of Slovenia. Furthermore, I
would like to thank Assoc. Prof. Damjana
Drobne from the Biotechnical Faculty of the
University of Ljubljana for her kind support
and access to their laboratory. I would also
like to thank Prof. dr. L.A. Bruijnzeel and
Msc. A.H. te Linde from Vrije University in
Amsterdam for their professional support.

Šraj, M.: Dolo čanje indeksa listne površine listnatega gozda na povodju Dragonje – 2. del: Rezultati in diskusija –
Estimating Leaf Area Index of the Deciduous Forest in the Dragonja Watershed – Part II: Results and Discussion
© Acta hydrotechnica 22/36 (2004), 1–15, Ljubljana
15
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Naslov avtorice – Author's Address
dr. Mojca ŠRAJ
Univerza v Ljubljani – University of Ljubljana
Fakulteta za gradbeništvo in geodezijo – Faculty of Civil and Geodetic Engineering
Katedra za splošno hidrotehniko – Chair of Hydrology and Hydraulic Engineering
Jamova 2, SI-1000 Ljubljana, Slovenia
E-mail: msraj@fgg.uni-lj.si