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P ozna ń skie T o warzyst w o P rzy j aci ó ł N auk
Wydział Nauk rolniczych i leŚnych
Forestry Letters
dawniej
Prace komisji nauk rolniczych i komisji nauk leśnych
Tom 105 – 2013
Bogna Zawieja, Katarzyna Kaźmierczak
THE EFFECT OF PRECIPITATION
ON THE HEIGHT INCREMENTS OF EIGHT AGE CLASSES
OF SCOTS PINE (Pinus sylvestris L.)
Abstract. Annual increments of the height of Scots pine are the main dendrometric characteristic because
the annual radial increments can be clearly determined in this way.
The meteorological conditions occurring at the time of budding, as well as the growth of trees, are important to the size of the increments. In this study, the dependence of annual increments on precipitation were
examined. In order to determine this dependence, correlation coefficients were designated, in addition a forward stepwise regression analysis was used. On the basis of the conducted analysis it can be concluded that
the Scots pine has greater increments when precipitation is more abundant in the July of the year preceding
the vegetation season. Moreover, the Scots pine has longer increments when the vegetation season is drier.
Key words: correlation, regression, tree increments, meteorological conditions, Pinus sylvestris
INTRODUCTION
The magnitude of height increments of the Scots pine is a very important characteristic used to determine volume increments. For example, it is needed to determine the
productivity of a stand [Bruchwald 1999]. It is a variable characteristic and depends on
several factors [Beker 1997, Kaźmierczak 2005, Najgrakowski 1998]. One of them is
meteorological conditions appearing in both years before and during vegetation. Many
scientists have considered the effect of atmospheric conditions on radial increment in
trees. For example, in Poland, Zienkiewicz [1946] and Ermich [1953] were scientists
who dealt with this issue. The effect of meteorological conditions on radial growth of
trees growing in peat soils was written on by Jasnowska [1977] and Zielski [1996,
1997]. Next, Cedro [2001] dealt with a similar problem covering the period of 1949-1998 in north-western Poland.
In Poland, pines tolerate annual precipitation from 200 to 1000 mm, as shown by
Jasnowska [1977], Białobok et. al. [1993] and Wilczyński [1999]. Too much water in
the soil adversely affects the diameter growth of trees. Scots pine is a northern tree type
(boreal-arctic northern) and a mountain tree type, and it grows in climates in which the
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Bogna Zawieja, Katarzyna Kaźmierczak
temperature ranges from -60 to +40ºC. The influence of meteorological conditions on
height increments was analyzed by Kaźmierczak and Zawieja [2011] for a 24-year pine
stand. Moreover, in the paper by Kaźmierczak and Zawieja [2008] the dependence between height increments and diameter increments was showed.
Pines grow during the period from May to September in Poland. Increments of
height and lateral branches develop from buds formed in the anterior vegetation season.
Because of the fact that after the vegetation season the increments lignify, its length
does not change in the following season. The length of annual shoots depends on the
weather during growth (in the vegetation year) as well as in the previous year. In the
period of July-September of the antecedent year buds are formed and reserve substances
are accumulated, which in large part will be used for the height increment in the next
year [Assmann 1968].
The aim of the study was to determine the dependence between annual increments in
the length of the main shoot (annual increment in height) and meteorological conditions
(especially precipitation) both in the anterior year and in the vegetation season. All eight
age classes of trees are considered.
EXPERIMENTAL DATA AND METHOD
The experimental materials are measurements of annual height increments made for
eight age classes of Scots pine. In all of these classes a ten-year period is considered,
and 25 trees selected following the methodology developed by Draudt [Lemke 1971].
Altogether, in the experiment of ten-year measurements, 200 Scots pine stems were
tested. The tested trees were taken from fresh mixed coniferous forest located in the
Zielonka Experimental Forest District. Measurements relate to the period from 1989 to
1998. In order to eliminate the effects of additional factors, the same vegetation period
was considered for all age classes of trees.
In dendrometrics the individual characteristics are determined in five-year periods.
Therefore, the ten-year period that was under consideration was divided into two fiveyear periods. For all age groups and all considered years of research, the average of
annual increments were calculated, which are presented in Table 1. Correlation coefficients between monthly precipitation and average annual height increments are designated separately in each age group and five-year terms. Next, the forward stepwise regression procedure was used to assess the impact of monthly precipitation on increments.
For this purpose the SAS software package was used. Each age class of tress is named
after the age of the tree of last measurement. For example, the group designated
24 means trees, whose first measurement applied to trees aged 15 at the start of a given
ten-year period and in 20 after the first five-year period. Particular months are marked
by Roman numerals.
9
The Effect of Precipitation on the Height Increments
Tab. 1. Average height increments [m] of individual age classes of trees in the ten-year period
Year
1989
Age groups – age of trees in least increments year
24
33
43
55
62
72
84
92
0.614
0.457
0.414
0.345
0.256
0.166
0.208
0.124
1990
0.519
0.342
0.278
0.279
0.24
0.154
0.144
0.097
1991
0.701
0.530
0.347
0.354
0.252
0.165
0.160
0.108
1992
0.588
0.434
0.317
0.310
0.211
0.170
0.167
0.096
1993
0.445
0.255
0.234
0.226
0.175
0.120
0.115
0.079
1994
0.562
0.404
0.294
0.264
0.213
0.142
0.133
0.088
1995
0.648
0.486
0.398
0.388
0.248
0.222
0.203
0.129
1996
0.584
0.421
0.413
0.374
0.288
0.243
0.228
0.144
1997
0.530
0.414
0.422
0.370
0.290
0.249
0.236
0.162
1998
0.534
0.433
0.458
0.365
0.292
0.256
0.271
0.177
RESULTS
In Figures 1 and 2 the average total monthly precipitation is presented respectively
in the first (Figure 1) and second (Fig. 2) half in all the research years under consideration. Precipitation in 1988 is also shown, because meteorological conditions in this year
could have affected the increments in the following year.
As can be seen in these Figures, in the given months of subsequent years, the fluctuations in precipitation were small, but in others they were very large. In the elevenyear period the smallest fluctuations of precipitation in any given month were in November (41.5 mm) and in February (41.9 mm), whereas the largest were in July
(155.2 mm). On the other hand, in the first six-year period the smallest fluctuations in
precipitation were in October (29 mm) and November (25.3 mm), while the largest were
in July (108.3 mm). In the second six-year period the smallest precipitation fluctuations
were in April (23.3 mm) and February (31.4 mm), while the largest were again in July
(137.4 mm). In the time considered, the most stable in terms of precipitation were the
months of November and February, whereas the most variable in this respect was July
(one year 16.5 mm another 171.7 mm). The second most unstable month was December
(minimum 9.1 mm, maximum 107.7 mm).
Correlation coefficients between monthly precipitation and both considered five-year
increment periods are shown in Figures 3 and 4. All values of coefficients greater than
0.88 are significant at the level 0.05. Both months before the vegetation season and during vegetation are considered, so in the first case before the number of the month the
letter p is placed and in the second one the letter a.
In the first five-year increment period, precipitation in July, September, November
and December at the time of tying buds (pVII, pIX, pXI and pXII) had a positive influence on height increments. In these months, apart from November, the correlation coef-
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Bogna Zawieja, Katarzyna Kaźmierczak
Fig. 1. Total monthly precipitation [mm] in the first half of the considered years.
Fig. 2. Total monthly precipitation [mm] in the second half of the considered years
Fig. 3. The correlation coefficients (r) and their significances between height increments of trees and monthly
precipitation in 1989-1993 incremental period
ficients were greater than 0.5 (50%) in all age-group of trees. Moreover, a positive influence was noted in April too. Precipitation in other months had a negative influence on
increments. In the second period, correlation coefficients were large, but negative in
August (pVIII), then from November to January and March in the case of the oldest
trees. There were positive correlations in October and February in the case of oldest
trees too. For the youngest trees the precipitation in spring and in the summer months of
the vegetation season had a greater effect on increments. The general trend was as follows, in the first period almost all correlations had large values, but in the second peri-
11
The Effect of Precipitation on the Height Increments
Fig. 4. The correlation coefficients (r) and their significances between height increments of trees and monthly
precipitation in 1994-1998 incremental period
Tab. 2. Monthly average precipitation [mm] in five-year periods
period
pVII
pVIII
pIX
pX
1989-1993
51.1
39.9
34.4
28.3
1994-1998
114
59.1
66.7
25.2
pXI
pXII
aI
38.6
38.5
21.4
25.1
23.3
43.6
28
33.4
period
aIII
aIV
aV
aVI
aVII
aVIII
aIX
1989-1993
33.1
31.3
34.6
56.9
58.3
51.2
36.1
1994-1998
37.5
27.2
59.1
55.6
97.9
59.7
70.3
aII
ods only in the months from November to March. These values were quite large, apart
from the trees from age groups 24 and 33. Moreover, they were at the time negative,
apart from February.
The total precipitation concerning each considered month in five-year periods is given in Table 2 and Figure 5. In the first period, the sum of the precipitation was smaller
than in the second one, only in November was it noticeably greater, and a little in the
October, April and June of preceding years. On the basis of the result shown, it can be
concluded that an increase of precipitation, to some degree, in months pVII, pVIII and
pIX contributed to larger height increments, but if the precipitation is too heavy (second
period) then it did not have a major impact on the growth of trees in the following year.
In the autumn months, more precipitation, especially in November, gave a positive effect in terms of the length increments. But too much rain in months aVII, aVIII and aIX
inhibited the growth of trees.
Since many of the correlation coefficients had a high value, especially in the first
five-year period, forward stepwise analysis of regression was used to find months which
had a significant impact on increments. This analysis was chosen because in each step
one variable is added or deleted from the model, and due to the large number of variables analyzed, backward analysis can not be used. This analysis was made separately in
each age group and considered period. The effects (coefficients of regression and determination) of this analysis are presented in Table 3 for the first period and Table 4 for the
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Bogna Zawieja, Katarzyna Kaźmierczak
Fig. 5. Monthly total precipitation in five-year periods
Tab. 3. The regression coefficients of dependences between mean height increments [m] and monthly total
precipitation [mm] in 1989-1993 incremental season
Age
groups
p-value
19
0.62045
+ 0.00206
p-value
0.0037
0.0376
28
0.68293
– 0.00652
p-value
0.0008
0.0029
38
0.45561
– 0.0235
p-value
0.0007
0.0059
50
0.40124
– 0.00085
p-value
0.0001
0.0036
57
0.30124
– 0.00181
p-value
0.0024
0.0067
67
0.18291
– 0.00076
p-value
0.0001
0.0281
79
0.25699
– 0.00256
p-value
0.0001
0.0020
0.0364
+ 0.00022
– 0.0277
0.053
87
p-value
adjR2
Equations of regression
pXI
– 0.00231
aVIII
0.9611
0.0479
aII
– 0.000572
aV
0.0129
pVIII
– 0.00360
– 0.00121
aVII
1.0000
aIV
0.9999
0.0023
pX
0.0031
aIII
– 0.00165
+ 0.00185
0.0026
aVII
0.9973
0.0007
aI
– 0.000844
aII
0,0379
aI
– 0.000199
– 0.00043
aIII
0.9987
0.0178
aVII
0.9863
aVIII
0.9967
pXII
0.9978
0.0479
pX
– 0.00050
0.0082
pIX
+ 0.00304
0.0013
second one. In the first period, the biggest impact on increments was noted in October
of the year that preceded the increments, and in January, February, March and July of
the increments year. In the second period it was noted in November and December of
the year that preceded increments and September in the vegetation season. In this period
all coefficients of regression were negligible. Because the explanatory variables – precipitation – can be correlated in different months, a correlation matrix was determined.
13
The Effect of Precipitation on the Height Increments
Tab. 4. The regression coefficients of dependences between mean height increments [m] and monthly total
precipitation [mm] in 1989-1993 incremental period
Age
groups
p-value
43
p-value
55
adjR2
Equations of regression
0.58560
– 0.00636
0.005
0.0168
0.40228
– 0.00115
p-value
0.0002
0.0447
62
0.30289
– 0.00084
p-value
0.0001
0.0232
72
0.28894
+ 0.00042
p-value
0.0026
0.0321
84
0.40636
– 0.00609
p-value
0.0008
0.0023
92
0.27907
– 0.00401
p-value
0.0027
0.0082
pXI
0.8490
pXII
0.7161
pXII
0.8135
pX
– 0.00180
pXI
– 0.00071
pXI
– 0.00065
pXI
0.0147
– 0.00081
pXII
0.9999
0.0066
aIX
0.9910
aIX
0.9677
0.0080
0.0341
The significant correlations were only between pVII and pIX, pXI and pIX, aI and aV,
aVII and aIX in the first period, and in the second period pVII and aIX, pIX and aV,
pXII and aI, aI and aIII, but no designated model contains these pairs.
The comparison of the received results and fluctuations of precipitation through the
years separately in each months, given in Figures 1 and 2, allows us to conclude that
there was a major impact on increments in the months of the year in previous increments in which fluctuations were small or medium, and in the months of a given incremental year in which fluctuations were medium or large.
In Figure 6, the sums of precipitation in each considered year and average annual
increments are presented. The sums of precipitation are given for the year that preceded
the increments season in this Figure. In both considered periods (1989-1993, 1994-1998)
some similarities can be seen. In Table 5, the correlation coefficients between these factors are shown. Most of them have a high value. In the first period, these dependences
were positive, but in the second one they were negative. The results confirm the earlier
proposal, that too much precipitation is not conducive to the growth of Scots pine
trees.
Weather conditions have a definite impact on radial growth of pine trees. Cedro
[2001] in her paper examined the effect of temperature and precipitation on diameter
increments of Scots pine. She received the following results: higher precipitation in June
and July, with a dry September during the growing season, had positive influence on the
radial increments of trees. In the February of the preceding year she observed a high
relationship between low precipitation and large increments in diameter. Zielski [1996]
indicated a significant relationship between radial growth of pine and precipitation in
14
Bogna Zawieja, Katarzyna Kaźmierczak
Fig. 6. Average annual height increments and sum of preceding year annual precipitations
Tab. 5. The correlation coefficients and their significances between height increments [m] of trees and total
precipitations [mm] of the year that preceded the increments
Age groups – age of trees in least increments year
period
19
28
1989-1993
0.74
0.75
38
50
57
67
79
87
0.95
0.76
0.64
0.53
0.81
0.74
Age groups – age of trees in least increments year
period
24
33
43
55
62
72
84
92
1994-1998
-0.11
-0.47
-0.91
-0.96
-0.85
-0.95
-0.86
-0.83
June and July. Similar results were obtained by Feliksik [1988] for pines from Dąbrowa
Tarnowska. Namely, increments in the width of the wood were strongly dependent on
precipitation (period April to August). Wilczyński [2004] found that warm, short winters
and moist, warm summers resulted in the formation of wide annual rings, and the years
with long, frosty winters followed by hot, dry summers caused a reduction of increments.
CONCLUSIONS
On the basis of the results the following statements can be formulated:
In the testing of height increments analyzed in this paper, a positive impact of a wet
July and dry November in the preceding incremental year was reported (see table 1 and
figures 1 and 2).
In all analyzed age groups, the smallest increments in trees were observed in 1993,
and in this case, the July of the preceding year was relatively dry, but from May to Sep-
The Effect of Precipitation on the Height Increments
15
tember of the incremental season (and particularly in July) there was a great deal of
precipitation.
In the drier five-year period, precipitation in the October of the previous vegetation
season and in the January, February, March and July of the vegetation season had the
biggest impact on increments, but in the wetter five-year period, the biggest impact on
height increments was in November and December of the pervious year and in the September of the given incremental year (see tables 3 and 4).
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Bogna Zawieja, Katarzyna Kaźmierczak
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Coresponding address:
Bogna Zawieja
e-mail: [email protected]
Department of Mathematical and Statistical Methods
Poznań University of Life Sciences,
Wojska Polskiego 28
60-637 Poznań
Katarzyna Kaźmierczak
e-mail: [email protected]
Department of Forest Management
Poznań University of Life Sciences
Wojska Polskiego 71C
60-625 Poznań