changes in the seasonal rhythm of two forest communities during secondary succession

Biologia, Bratislava, 62/4: 416—423, 2007Section BotanyDOI: 10.2478/s11756-007-0081-9

Changes in the seasonal rhythm of two forest communitiesduring secondary succession

Branislav Schieber

Institute of Forest Ecology, Slovak Academy of Sciences, Štúrova 2, SK-96053 Zvolen, Slovakia;e-mail:[email protected]

Abstract: Changes in the seasonal rhythm of two plant phytocoenoses in a submountain beech forest during secondarysuccession were studied. Investigations were done on four monitoring plots with different stand density over the period of foursuccessive years. The rhythm of the associations Dentario bulbiferae-Fagetum and Carici pilosae-Fagetum reflects the courseof succession processes running six years after the human impact (cutting) in the ecosystem. Results of the phenologicalobservations of the understorey species with the focus on the changes in flowering and colour spectrum allowed to make thecomparisons between both associations in connection with different phyto-climatic conditions and in dependence on time.The most conspicuous changes in the seasonal rhythm and structure of the examined associations were found in conditionsof the former clear-cut, currently in succession phase. A clear decrease (56%) in number of taxons with the dominance > 1%in one association towards the end of the 4-year study period was detected here. Simultaneously, a decrease in the numberof flowering species was observed, while the relative rate of species being in the vegetative stage increased considerably(from 6 to 67%) over the growing season. The course of flowering of both of the associations missed discernible trends andpeaks as well as colour spectra were partially changed during four monitored successive years on the formerly unstockedarea.

Key words: Dentario bulbiferae-Fagetum; Carici pilosae-Fagetum; beech forest; flowering; seasonal rhythm; secondarysuccession

Introduction

Phenological or seasonal rhythm of plants reflects theadaptation process to the ecological conditions in theenvironment. In areas where the seasonal course of cli-mate is characterised by considerable fluctuations (tem-perate and boreal zone), the influence of climate “sea-sonality” on the rhythm of plants is evident (Battey2000). Certain seasonal variability can also be observedin many areas without conspicuous time-dependent cli-mate changes -equatorial and tropical zone (Lieberman1982; Sakai 2001). It is well recognised that the sea-sonal rhythm of individual plant species as well as theseasonal rhythm of their associations are influenced bya number of endogenous and exogenous factors (Fig.1).The first group comprises the biological properties at-tained in the course of the species historical devel-opment. The exogenous factors are primarily climatefactors (Diekmann 1996; Tyler 2001), soil conditions(Schwartz 1992; Sierra et al. 1996; Wielgolaski 1999),structure of phytocoenose (Eliáš 1987; Kawarasaki &Hori 2001; Routhier & Lapointe 2002; Kikuzawa 2003).In deciduous forests of the temperate climatic zone,

the altering between the vegetation rest and growingseason is in correlation with the rhythm of external cli-

matic factors. Natural submountain beech forests arecharacterised by their “nude” look. In most of them,the cover of the herbal layer is lower than 15%. Onlywhen such a stand is opened, the rate of literfall de-composition increases, which results in improved con-ditions for the development of both herbs and woodyplants. The following succession is reflected in struc-tural changes of the plant associations – the speciesdiversity increases, and the density of plants belongingto the individual taxons increases too. Every changein the conditions is also reflected in the vitality of in-dividual species. Number of flowering and fructifyingspecies is often increased, shifts within the individualphenophases were observed as well (Schieber 1996).Spontaneous succession processes lead to restorationof ancient forest conditions after relatively long time(Bossuyt & Hermy 2000). In spite of these facts, littleis known about the changes in the seasonal rhythm ofthe communities during secondary succession in forestecosystems.The aim of the paper is to analyse the changes in

the seasonal rhythm of two plant associations – Den-tario bulbiferae-Fagetum and Carici pilosae-Fagetumduring four successive years in a submountain beechforest with different density of its tree layer.

c©2007 Institute of Botany, Slovak Academy of Sciences

Changes in the seasonal rhythm of forest communities 417

temperature

Biological characteristics

Endogene

age

origin

life form

physiological characteristics

Exogene

Pedoclimatic conditions Structure of phytocoenose

precipitation

photoperiode

sun radiation

soil conditions

density

canopy

Factors

composition

Fig. 1. Scheme of selected factors affecting the seasonal rhythm of plants.

Material and methods

Study siteInvestigations were carried out at the Beech Ecological Ex-perimental Site (BEES), which is located in the SE partof the Kremnické vrchy Mts (48◦38′N, 19◦04′E, 450–520m a.s.l.) on a west-southwest oriented slope with an in-clination of 5–15◦. This area belongs to the moderatelywarm region, moderately warm and humid, hilly land sub-region (Lapin et al. 2002). The mean annual air temper-ature and mean annual precipitation are 6.8◦C and 780mm, respectively. The mean month air temperatures are−4◦C in January and 17◦C in July. About 55% of the an-nual precipitation total falls from April to September. Thesoil cover is formed from skeletal cambisols with moder-ate acid reaction. The skeleton content ranges from 10 to60% ( Kukla et al. 1998). A shelterwood cutting of vary-ing intensity was performed in the year 1989 with theaim to obtain five separate partial plots (PP) with differ-ent degrees of stocking. The plots were separated by iso-lation strips. The dominant tree is Fagus sylvatica (85%)old about 100 years, associated species are: Abies alba(8%), Quercus dalechampii (6%), Carpinus betulus (1%)and Tilia cordata (0.5%). According to Barna (2004), thestocking values in 1996 were: PP K – 0.87 – original stock-ing; PP M – 0.78; PP S – 0.62; PP I – 0.4; PP H –former clear-cut plot, currently with intensively develop-ing young generation of woody plants. Naturally regen-erated woody plants growing on the plot PP H, besidesthose which grow on the other plots, are represented bySalix caprea, Populus tremula, Betula verrucosa, Acer pseu-doplatanus, Prunus avium and Picea abies. The decreaseof the density of natural regeneration among the plots iscorrelated with the density increase of the parent trees.The vegetation cover consists mainly of patches of asso-ciations Carici pilosae-Fagetum and Dentario bulbiferae-Fagetum with permanent elements of Carex pilosa, Carexdigitata, Carex sylvatica, Dentaria bulbifera, Galium odor-

atum, Athyrium filix-femina, Dryopteris filix-mas (Kontrišet al. 1993).

Fieldwork and analyses of the dataThe monitoring of seasonal periodicity in plant associationswas carried out on 8 mini-plots established within the fourpartial plots (PP-K, PP-S, PP-I and PP-H) – two mini-plots on each partial plot. The mini-plots had dimensions ofthe standard phytocoenological relevé – 400 m2. The firstrepresents the association Carici pilosae- Fagetum, the sec-ond Dentario bulbiferae-Fagetum, or their succession phases,respectively. The observations on understorey herb species(except the ferns) were started in early spring 1995, de-pending on the day of the last snow melting, and they werepursued up to the first frosts (the end of October – the firstdays of November). In spring, the records were made in reg-ular 2 or 3–day intervals, later once a week. Observationswere repeated in 1998, after three successive years.

Analysis of the obtained phytocenological relevés re-sulted in a classification of all examined species in two ba-sic groups. The first group consisted of the species withdominance higher than 1%, which determines the charac-ter of the seasonal rhythm. The “accessory species” of thesecond group with lower dominance than 1% were takeninto account in the case of analysis of curves of flowering aswell as colour spectra. Both vegetative (germinating, vege-tative growth or leafing, discolouring of leaves, dieback) andgenerative stage (flower buds, flowering, fruiting, dissemina-tion) of the species within the associations were recorded.The beginning of phenophases was considered as the daywhen the phenophases were present in at least 10 % ofindividuals of the studied species (Lieth 1974). Floweringphase was analysed separately and visualized by the flower-ing curves constructed according to Bottlíková (1975). Thecolour spectrum consists of five colours – blue, white, yel-low, red and green appended with a category of colourlessflowering graminoids. The species nomenclature follows thatby Marhold & Hindák (1998).

418 B. Schieber

Table 1. Species composition of the associations Dentario bulbiferae-Fagetum (Db-F ) and Carici pliosae-Fagetum (Cp-F ) on thestudied plots (plus sign means the presence of a taxon).

Plots PP-K PP-S PP-I PP-HAssociations Db-F Cp-F Db-F Cp-F Db-F Cp-F Db-F Cp-F

Understorey speciesAjuga reptansAtropa bella-donaBrachypodium sylvaticumCalamagrostis epigejosCampanula persicifoliaCampanula rapunculoidesCampanula tracheliumCarduus acanthoidesCarex digitataCarex pilosaCarex sylvaticaCephalanthera longifoliaCirsium arvenseCoronilla variaDentaria bulbiferaDigitalis grandifloraEpilobium montanumEupatorium cannabinumFragaria vescaGalium odoratumGalium schultesiGeranium robertianumGeum urbanumGlechoma hederaceaHypericum hirsutumChamerion angustifoliumJuncus effususLathyrus vernusLuzula pilosaMelica nutansMelitis melisophyllumMycelis muralisMyosotis sylvaticaOxalis acetosellaPetasites albusPlatanthera bifoliaPoa nemoralisPolygonatum multiflorumPulmonaria officinalisRanunculus lanuginosusRubus hirtusRubus idaeusSanicula europaeaScrophularia nodosaSenecio fuchsiiSymphytum tuberosumTithymalus amygdaloidesTussilago farfaraVeronica officinalisViola reichenbachiana

+.............+...++.+...........+....+.+.......++

+........+....+...++..+....+.....+....+.+.+.....++

+.+...+.+.+...+.+.++++..+..++.+++...+++++++++.+.++

+....+..++.+..+...+++......+.++....+..+.+....+..++

+.....+.+.....+.+.++....+......++.....+.+..+....++

++......+++...++..++.......++.....++..+.++.+....++

++.+....+.+..++.++++...++++...........+.++++....++

++..+..+++..+.+...++....+.............+.+...+.++++

Results

Composition of the associations and changes in life de-velopment of the speciesThe composition of both associations Dentario bulbi-ferae-Fagetum and Carici pilosae-Fagetum is shown inTable 1. Species diversity varied in relation to densityof a tree layer. The lowest number of taxons was ob-served on control PP-K, while the highest diversity wasobserved on the plot S with a medium density (relatedto control PP-K) of a tree layer. Total number of tax-ons within both communities on the observation plots

moved from 16 (PP-K) to 35 (PP-S).Relative rate of taxons with dominance > 1% in

the association Dentario bulbiferae-Fagetum was quitestable among the plots, only on PP-H the number wasdecreased. Temporal changes in life development of thespecies within this association are evident from Table 2.The highest increase of the number of taxons remain-ing in vegetative stage was observed on both of theplots PP-H and PP-K and reached the 50% and 60%,respectively. On the other hand, distinct decrease ofthe number of taxons with dominance higher than 1%,which were passing through the generative cycle, was


Table 2. Changes in a structure of the association Dentario bulbiferae-Fagetum (A) and Carici pilosae-Fagetum (B) on the studiedplots between 1995 and 1998.

A. PP-K PP-S PP-I PP-HTrait 1995 1998 1995 1998 1995 1998 1995 1998

Absolute number of all taxons 10 10 29 29 15 15 22 21

Relative rate (in %) of taxons with dominance >1 %(related to number of all taxons) 90 100 52 55 87 87 50 28

Relative rate of taxons in vegetative stage(related to number of all taxons) 20 60 0 14 7 7 5 50

Relative rate of taxons with generative cycle(related to number of taxons with dominance >1 %) 78 40 100 100 93 100 100 100

B. PP-K PP-S PP-I PP-HTrait 1995 1998 1995 1998 1995 1998 1995 1998

Absolute number of all taxons 13 13 18 17 17 19 18 18

Relative rate (in %) of taxons with dominance >1 %(related to number of all taxons) 92 92 67 70 82 79 4 4

Relative rate of taxons in vegetative stage(related to number of all taxons) 0 66 6 6 0 14 6 67

Relative rate of taxons with generative cycle(related to number of taxons with dominance >1 %) 83 34 100 100 100 100 100 75

found out only in the case of the control PP-K. Simi-lar pattern was observed within the association Caricipilosae-Fagetum – the highest increase of the number oftaxons remaining in vegetative stage observed on bothof the plots PP-H and PP-K and a distinct decrease ofthe number of taxons passing through the generativecycle on PP-K.

Changes in floweringTemporal course of flowering within both associationsis shown in Figure 2. The curves of flowering of both as-sociations differed essentially between 1995 and 1998 inthe case of PP-H. Also certain differences were detectedon the PP-K. One single peak in spring was observedin both compared years on PP-K, but curve is less dis-tinct in 1998 than in 1995. In the case of the PP-S, theflowering curve of the association Dentario bulbiferae-Fagetum had one primary peak in full-late spring andtwo secondary peaks in early and late summer. On theother hand, the curve of the association Carici pilosae-Fagetum had one primary peak in full-late spring andone secondary peak in early summer. Similar coursewas also detected on PP- I within both associations.The differences in flowering course of both associationson PP-H were the most striking. While in 1995, theflowering curves had two peaks – in late spring and infull summer, three years later, they missed discernibletrends and peaks.

Colour spectra of the associationsDominant colours in both associations were blue andwhite in the case of all studied plots (Table 3). Thepoorest colour spectra were detected on PP-K. The pro-

portion of blue and white colour from the colour spectraof both associations was 45–60% and 35–50%, respec-tively. These two colours are supplemented with yellowand red, together with a flowering graminoid Carex pi-losa in the association Carici pilosae-Fagetum. On PP-S, relative rate of both blue and white colour rangedfrom 32 to 38% and from 28 to 45%, respectively, com-pleted with yellow and flowering graminoids. Figuresof 3% for red and green colour were also recorded inthe association Dentario bulbiferae-Fagetum. Both blueand white colours with proportions of 38–58% and 21–28% respectively, were also detected in both associa-tions on PP-I, with admixed yellow, green and flower-ing graminoids. In the case of the PP-H, in 1995, thedominant colour was blue (35%), together with white(17–22%) and yellow (5–24%) in both associations,red and flowering graminoids are fairly frequent. Thecolour spectrum of the association Dentario bulbiferae-Fagetum in 1998 consisted of equal proportions of blueand white (30%), and somewhat lower proportions ofred and flowering graminoids (each 20%). The prevail-ing colour in the second association was yellow (50%),mixed with blue (33%) and flowering graminoid (Carexdigitata).

Discussion

The different ecological conditions induced at the BEESby means of the human impact (cutting) with vary-ing intensity had been reflected on the structure of thestudied plant associations. The lowest number of taxonswas recorded on the control PP-K – without interven-tion. In both associations, together 16 taxons (included

420 B. Schieber

N

2 2

1 3

N

R

5 2

SDD

Dentario bulbiferae-Fagetum 1995


3

2

N

N

2

1

Carici pilosae-Fagetum 1995


K-plot

7 5 6

2

N

7 4 3

3

N



N

5

3

3

N

4

33



S-plot

N

2 2 3

4 2

N



44 3

N

4

2

2

N



I-plot

6 4 3

N Dentario bulbiferae-Fagetum 1995


N

2 2

Period March-August

4

3

5

N

N

2

1 1



Period March-August

H-plot

Fig. 2. Curves of flowering of two phytocoenoses on the studied plots in 1995 and three years later (SDD – span of dominance degree,N – number of species).


Table 3. Temporal changes in relative rate (in %) of coloursin colour spectra within the associations Dentario bulbiferae-Fagetum (Db-F ) and Carici pilosae-Fagetum (Cp-F ).

1995 1998Associations Db-F Cp-F Db-F Cp-F

Studied plots Colourspectra

PP-K bluewhiteyellowredgreengraminoids

5038.12..

453510..10

6040....

5050....

PP-S bluewhiteyellowredgreengraminoids

3228173317

35416..18

3630123316

3845...17

PP-I bluewhiteyellowredgreengraminoids

572114.8.

42236.623

58217.77

38286.622

PP-H bluewhiteyellowredgreengraminoids

3522514519

35172412.12

3030.20.20

33.50..17

0

20

40

60

80

100

PP-K PP-S PP-I PP-H

Plots

Deg

ree

of s

hadi

ng [

%] 1995

1998

Fig. 3. Changes in degree of shading of the parent stand andwoody regeneration (PP-H) on the studied plots between 1995and 1998.

taxons with dominance lower than 1%) were identified.Rather poor species spectrum can be reasoned by theleast favourable light conditions on this plot. The de-gree of shading by the parent beech stand on PP-Kis about 95% (Fig.3). While in 1995 the proportion ofthe species observed in the associations was only inthe vegetative phase 16–22%, in 1998 it was already65–72%. It is suggested, that the cause of this differ-ence lies in the fact that, in spite of the shading bythe parent stand, in 1995 a rather narrow stripe in the

PP-K was exposed to side-light from isolating stripesseparating the individual partial plots of the BEES.These conditions were probably similar to those whichexist in forest gaps (Hull 2002; Ritter et al. 2005). In1998, separating stripes had already been grown withnatural regeneration, which resulted in a considerabledecrease in the side-light intensity. Střelec (1992) re-ported that the light amount illuminating the herballayer on this plot in the time of full development ofleaves, represents only 1% of the light energy comparedto the open plot. This fact also influences the develop-ment of generative phases on the studied plant species.The herbs seek more favourable light conditions beforethe full leaf development in the stand. Consequently,the flowering curve of the associations has a singlepeak in spring. Kubíček & Šimonovič (1975) studyingthe associations Primulae veris-Carpinetum and Caricipilosae-Carpinetum in Báb observed in the first asso-ciation a single conspicuous peak in spring, in the sec-ond they also detected a secondary, less conspicuouspeak in early summer. The association Carici pilosae-Carpinetum also had a considerably higher proportionof flowering species in comparison to the first associ-ation. Falinska (1975) reported that the structure ofphytocoenoses affected the behaviour of the species. Inthe association Pino-Quercetum there was significantlylower ratio of the species in vegetative stage than inassociation Tilio-Carpinetum stachyetosum. As for thelow presence of yellow and red colour in 1995 and theirabsence in 1998 on PP-K, it is probably connected withthe fact that these colours occur more frequently inmore heliophilous species. White flowers are often ob-served for woody species, especially for those with lowlight demands. This phenomenon probably reflects therelation plant-pollinator developed in woody ecosys-tems throughout the evolution (Abe & Kamo 2003).The richest species spectrum observed on PP-S re-

flects the relative favourable conditions in understoreylayer with a sufficient number of free niches, while lowerrichness of species on PP-I can be explained by highercompetition capacity of the species Carex pilosa, whichis most intensively expanding namely over this plot.Also the competition capacity of the natural regenera-tion of woody plants on this plot is considerable, andthe developing woody plants are partially shading thelower vegetation layers (see Davis et al. 1998). The flow-ering curves of associations on PP-S and PP-I have sev-eral peaks. The first peak occurs immediately after thebeginning of leaf development in the stand, the sec-ond or also third occurs in the period of full leaf devel-opment in the summer. This can be explained by thefact that the parent stand shelter has not yet been fullclosed even under full leaf development, consequentlylight conditions in the stand are still favourable for de-velopment of the summer species.The most remarkable changes were detected on

PP-H. The total removal of tree layer opened the grow-ing space for vigorously developing natural regenera-tion. According to Kodrík (1997), the height of natu-ral regeneration on plot H in 1994 was from 60 to 110

422 B. Schieber

cm. In the following years this trend was even accel-erated: in spring 1998 the natural regeneration heightreached from 200 cm (Fagus sylvatica) to 400 cm (Salixcaprea). Because the density of the natural regenera-tion is considerably high, the sunlight supply to theherb layer is getting more limited (Fig. 3). This facthas also been reflected on cover and phenology of thespecies in the observed associations. In 1995 the numberof the species with dominance higher than 1% in the as-sociation Dentario bulbiferae-Fagetum was 11, in 1998there were only six (decrease by almost 45%). Whilein 1995 the number of flowering species in the associa-tion Dentario bulbiferae-Fagetum was 22 (including thespecies with dominance lower than 1%), in 1998 therewere only 10 (45% of the amount in 1995). Similarly,in the association Carici pilosae-Fagetum, 17 floweringspecies were found in 1995, in 1998 only 6 (35% com-pared with 1995). From the species with higher light de-mands, in 1998 primarily flowering high herbs (Atropabella-donna, Eupatorium cannabinum, Chamerion an-gustifolium) were able to catch at least minimum lightintensity necessary for the flowering. The strategy ofthe heliophilous species Calamagrostis epigejos was in-teresting. In 1995 this species was dominant in the asso-ciation Dentario bulbiferae-Fagetum, but in 1998, it wasalready almost pushed out from the stand – remainingonly in the vegetation phase, by the stand edge. Thebetter light conditions in this zone manifested itself inthe fructification of some individuals of this species.It is clear, that responses of the understorey

herb layer reflect the different ecological conditions inthe studied forest ecosystem. The method of forestmanagement affects following changes in the ecosys-tems (Brunet 1998). Destructive forms of managementcaused more expressive changes in comparison to lessdisturbed micro-sites with more favourable conditionsfor survival of sensitive species. Clear-cut areas arecharacterised by a considerable increase in biomassamount and species spectrum (Pykala 2004). But thesubsequent succession processes cause gradual decreasein the species diversity, changes in biometric charac-teristics, as well as changes in phenological traits of theindividual species in dependence on the intensity of dis-turbance of the original status. The results of this work,despite of a relatively short study period are consistentwith this fact.

Acknowledgements

The author is grateful to the Slovak Grant Agencyfor Science (VEGA) for support of this work (GrantsNos 2/7161/27 and 2/7185/27) and APVV agency (GrantNo. 0102-06).

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Received April 5, 2006Accepted Feb. 19, 2007

changes in the seasonal rhythm of two forest communities during secondary succession

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