Phenology

In agrometeorology, phenology data are used along with meteorological data as a basis for studying how weather and climate affect growth and development of plants. To determine favourability of agroclimatic conditions of an area to grow a certain crop requires years of phenological observation. Phenology data are integral to agroclimatic analyses, but they also serve as indicators that enable better understanding of climate characteristics of certain areas.

Type and distribution of plants indicate certain macroclimate characteristics of an area. To talk about local characteristics, it is necessary to consider not only the plant species, but also dynamics of their development. It is well known that plants flower earlier in southern exposures, meaning they enjoy certain “advantage”. Descending of cool air down the slope and into the valley, in environments of more prominent relief, may lead to creation of so-called „heat islands“ causing early onset of life processes in plants; therefore, plants may lead up to several days compared to same species in the valley.

Phenology is also used in tillage, pomiculture, agroclimatic and agroecological zoning, agrometeorological forecasting, viticulture, apiculture, protection of plants from disease and vermin. Phenological observations conducted on a group of forest trees and bush may also provide many benefits, not only in forestry. In agrometeorology, special focus is on observing phenological objects of this group, which are of the same genetic origin, of the same material, reproduced vegetatively, in order to eliminate hereditary traits and reduce it to the influence of the external environment only.

Phenology in Bosnia and Herzegovina dates back to the 19th century, when individual enthusiasts, mostly ornithologists, conducted observations on a very limited territory.

The first phenology paper in Bosnia and Herzegovina, Phytophänologische Beobachtungen, J.Zoch, was published in 1881.

After the WWII, phenology service of Bosnia and Herzegovina was organised and developed. Common network, in line with the WMO standards, started in 1951, and Ivan-Sedlo, international phenological garden, also in accordance with the WMO standards, was established in 1953. Results of phenological observations conducted at stations and in the garden of Ivan-Sedlo were published in almanacs, starting from 1951, and they were presented as ordinal number of days since the beginning of the year, which basically meant the starting date of a phenological phase. Observations were conducted on wild herbaceous plants, forest trees and bush, crops, and fruit and vine. In addition, starting dates of some field works were observed and recorded.

In addition, certain plant diseases and pests, migratory birds and bees were subject to observation, but over time the data proved to be rather poor and unreliable, so this part was omitted from the programme in the early 1980's.

During the 1992-1995 aggression against Bosnia and Herzegovina, the phenological network was completely destroyed and has not been restored to this day.

In the period 1961-1990, the number of phenological observation sites in Bosnia and Herzegovina varied and ranged from 80 to more than 110; in the years just before the aggression against Bosnia and Herzegovina, it settled on 84.

The data were regularly published in the form of phenological almanacs, based on dates at first, but once the service developed in the entire country, the format switched to the ordinal number of a day in a year.

Since weather and climate affect the plants, phenological observations are usually conducted nearby or at the same sites of meteorological observations, that is, at selected agrometeorological observation sites. There is a special part of the programme of observation of phenological phases focused on international phenological gardens which was conducted in the period 1961-1990 at the Ivan-Sedlo meteorological station; the site is interesting for being located in the transition zone between the continental and the Mediterranean climate.

Phenological facilities used for observation are grouped in the following categories:

  • Wild and herbaceous plants
  • Forest trees and bush
  • Crops
  • Grass and legumes
  • Fruit trees
  • Vine
  • General field works

Phenology is specific for distinguishing more than four seasons. The beginning of each season is identified according to phenological phases of leaf development, flowering, ripening of fruit or falling of leaves from certain plants growing in the nature. Their beginning and end depend on meteorological parameters, humidity of air being particularly important. Thus, phenological data equivalent to the beginning of a season is the date on which a certain temperature value was achieved, that is, the day on which the mean daytime temperature of air goes above the benchmark value. If mean air temperature is t, seasons can be phenologically defined as follows:

  • Winter t ≤ 0°C
  • Pre-Spring and Pre-Winter 0°C < t < 5°C
  • Spring and Autumn 5°C < t < 15°C
  • Summer 15°C ≤ t

Phytophenological maps, the goal of which is to identify principles governing the development of plants, are made using mean values for multiple years. Changes in multi-annual indicators are presented using isophenal lines that link locations with the same date of commencement of a certain phenological phase for certain phenological subjects.

The Atlas provides a table view of mean, earliest, and latest date of phenological phases for different plant species with accompanying standard deviation, as well as cartographic representation of spatial distribution of onset for different phenological phases in the period 1961–1990, which is supposed to outline possible climate differences which would go unnoticed by the analysis of climatological elements. Phytophenological maps will therefore complement climatological maps to provide more detailed representation of the climate of the Federation of Bosnia and Herzegovina. Since forest trees and bush are non-cultivated, in order to avoid anthropogenic influence, the focus was put on this particular group of plants, that is, species that provide data of sufficient quality to meet the standards.

Vegetation cycle of horse-chestnut (aesculus hipocastanum l.) and small-leaved lime (tilia parvifolia ehrh.) at the Sarajevo-Bjelave site
Vegetative stages of black locust (robinia pseudoacacia) at the site of the international phenological garden Sarajevo-Bjelave
Onset dates for different phenological phases in the group of forest trees and bush

PERIOD 1961-1990

STATION

Horse-Chestnut

Aesculus hipocastanum L.

Silver birch

Betula verrucosa Ehrh.

BEGINNING OF LEAF UNFOLDING

BEGINNING OF FLOWERING

GENERAL COLOURING OF LEAVES

BEGINNING OF LEAF UNFOLDING

BEGINNING OF FLOWERING

GENERAL COLOURING OF LEAVES

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

Bugojno

19.IV.

8,1

28.III.

29.IV.

6.V.

8,8

11.IV.

18.V.

5.X.

10,9

16.IX.

29.X.

Livno

21.IV.

11,0

15.III.

4.V.

11.V.

8,9

17.IV.

25.V.

18.X.

7,7

1.X.

30.X.

24.IV.

6,8

10.IV.

8.V.

27.IV.

9,8

31.III.

11.V.

11.X.

7,2

27.IX.

23.X.

Sarajevo

18.IV.

10,7

1.IV.

9.V.

1.V.

10,3

7.IV.

17.V.

16.X.

5,7

2.X.

30.X.

23.IV.

7,4

11.IV.

6.V.

17.IV.

18,3

15.III.

14.V.

22.X.

14,7

18.IX.

24.XI.

Bihac

8.IV.

10,6

18.III.

28.IV.

29.IV.

8,7

15.IV.

11.V.

22.X.

6,4

7.X.

31.X.

12.IV.

10,4

25.III.

28.IV.

21.IV.

12,5

28.III.

8.V.

25.X.

4,7

15.X.

2.XI.

Drvar

24.IV.

7,6

5.IV.

4.V.

8.V.

9,0

20.IV.

29.V.

17.X.

9,7

2.X.

30.X.

21.IV.

11,1

30.III.

10.V.

5.IV.

11,4

11.III.

22.IV.

22.X.

12,5

5.X.

16.XI.

Zenica

9.IV.

8,3

23.III.

20.IV.

2.V.

8,5

18.IV.

17.V.

14.X.

10,4

30.IX.

10.XI.

13.IV.

7,7

30.III.

22.IV.

Mostar

29.III.

6,3

11.III.

10.IV.

15.IV.

8,4

22.III.

3.V.

21.X.

12,7

28.IX.

12.XI.

21.IV.

12,5

28.III.

8.V.


PERIOD 1961-1990

STATION

Dandelion/

Taraxacum officinale

Pussy Willow

Salix carpea

Common Hazel

Corylus avellana

Common Lilac/

Syringa vulgaris L

Small Leaved Lime

Tilia parvifolia Ehrh

BEGINNING OF FLOWERING

BEGINNING OF FLOWERING

BEGINNING OF FLOWERING

FIRST RIPE FRUITS

BEGINNING OF FLOWERING

BEGINNING OF FLOWERING

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

AVG

STD

MIN

MAX

Bugojno

11.IV.

13,6

7.III.

25.IV.

29.III.

13,2

3.II.

18.IV.

13.III.

12,5

27.II.

8.IV.

9.IX.

6,7

30.VIII.

20.IX.

2.V.

10,1

8.IV.

17.V.

20.VI.

8,3

10.VI.

12.VII.

Livno

13.IV.

17,6

20.III.

3.V.

31.III.

18,5

13.II.

25.IV.

17.III.

15,4

26.II.

10.IV.

12.IX.

4,6

5.IX.

17.IX.

7.V.

8,3

20.IV.

21.V.

25.VI.

8,4

12.VI.

09.VII.

Sarajevo

9.IV.

13,1

16.III.

1.V.

11.III.

19,5

16.II.

1.IV.

15.III.

21,3

12.II.

12.IV.

9.IX.

7,6

25.VIII.

25.VIII.

28.IV.

8,7

09.IV.

14.V.

18.VI.

10,8

27.V.

03.VII.

Bihac

2.IV.

13,4

10.III.

25.IV.

14.III.

13,8

9.II.

22.IV.

1.III.

17,1

6.II.

10.IV.

5.IX.

8,9

21.VIII.

19.IX.

21.IV.

12,3

21.III.

14.V.

20.VI.

10,8

19.V.

30.VI.

Drvar

2.IV.

14,9

7.III.

24.IV.

25.III.

21,6

13.II.

14.IV.

6.III.

14,3

10.II.

2.IV.

7.IX.

9,6

20.VIII.

18.IX.

28.IV.

9,2

08.IV.

13.V.

21.VI.

10,4

6.VI.

05.VII.

Zenica

31.III.

17,1

8.II.

2.V.

16.III.

11,8

13.II.

2.IV.

24.II.

9,5

13.II.

7.III.

27.VIII.

8,6

18.VIII.

4.IX.

25.IV.

10,0

23.III.

12.V.

20.VI.

7,4

9.VI.

03.VII.

Mostar

19.III.

10,7

28.II.

25.IV.

13.II.

14,8

15.I.

15.III.

20.II.

5.IV.

11,3

13.III.

9.V

30.V.

14,4

17.IV.

12.VI.


During the processing of phenological data, it should be kept in mind that this type of observation is susceptible to subjectivity since it involves visual observation where experience and reliability of the observer significantly affect the data quality. During long-term observations, many interruptions disrupted the continuity, which was one of the criteria taken into account when selecting the appropriate method of processing the collected phenological data. For determining multi-annual mean values presented in the Atlas, the Schnelle method was used to calculate multi-annual mean values of onset of phenological phases using annual corrective values, without filling in the missing years.

Phytophenological maps show that the relief is one of the major factors affecting the development rhythm of plants. Altitude causes vertical change of climate elements, and temperature decrease with higher altitudes is the most important phenomenon. Onset dates of different phenological phases are moved forward as the altitude increases. The delay for each 100 m is quantified by vertical phenological gradients. In warmer regions, where temperature decreases with altitude, vertical gradients are greater than in cooler regions, where altitude-related thermal changes are not as prominent. (Otorepec). At same altitudes, phenological phases start earlier on southern slopes, because of their better exposure to direct sunlight, than on northern (Schnelle, 1955).

Data in the table of onset dates for different phenological phases show that, e.g. the beginning of flowering of the Horse-Chestnut (Aesculus hipocastanum) in the south of the country 15.04. (Mostar station, altitude 99 m), while in the continent (Livno station, altitude 724 m), the average flowering onset date for Horse-Chestnut is not before 11.05. All phenological subjects show similar dynamics of different phenological phases, depending on the observed climatic area, and phenology data as such are useful in agroclimatic zoning.