How To Study The History Of A Sandy Old Field

Transcription

1 Ph.D. thesis STUDY OF SECONDARY SUCCESSION ON SANDY OLD-FIELDS IN THE KISKUNSÁG Anikó Csecserits Institute of Ecology and Botany of HAS Vácrátót 2007

2 Ph.D. School: Head of the Ph.D. School: Eötvös Loránd University, Faculty of Sciences, Biology Ph.D. School Dr. Anna Erdei Associate professor Ph.D. Program: Head of the Ph.D. Program: Theoretical Biology and Ecology Dr. János Podani Associate professor ELTE Department of Plant Taxonomy and Ecology Supervisor: Dr. Miklós Kertész Scientific advisor Institute of Ecology and Botany of HAS

3 1. Motivation and goals Humans are continuously transforming their environment and creating new areas which results in habitats only suitable to few species. Therefore, many species have become extinct or are drawn to the edge of extinction. This process is occurring to the same extent as it was during the geological extinctions, but now it has a much faster rate (Standovár and Primack 2001). Today, the extension of human-transformed areas (settlements, roads, agricultural areas etc.) is so large that all of the remaining natural or semi-natural areas must be protected in order to increase the chance of survival of the remaining species. Is there a way back? That is, what kind of community can colonise a human-altered environment, if humans stop managing (using, cultivating) it? Is it possible that semi-natural, stable communities could spontaneously develop again? The answers to these questions are important for nature protection and also for the farmers using these areas, because this knowledge can contribute to more advanced landuse. These answers are equally important for the science of ecology as well; as furthering scientific knowledge of plant- and animal communities is essential to understand their regeneration, dispersion and stability properties. Besides the intensive land-conversions (e.g. road building, urban development, greenfield investment), many landscapes have been abandoned in Hungary, which induces the spontaneous development of animal and plant communities. These spontaneous processes can be evaluated in many ways; they can be declared good or bad depending upon the observer. For instance, shrub encroachment on a previously grazed grassland would be considered a deterioration by a farmer, while an entomologist would consider this process an improvement, as an increase in the number of habitats provides an increase in insect diversity. Based on their species composition and structure of evolving plant communities, a plant ecologist can evaluate the spontaneous development of the abandoned areas. During my research, I studied the plant communities developing in place of the disintegrating farm system of the Danube-Tisza Interfluve in a 60 hectare sampling area. Most of the farms of this area have settled on the habitats of the open sandy grassland, a bit more humusrich closed sandy grassland or the dry sandy forests (Biró 2003). However, agriculture is not profitable anymore on these dry sandy soils due to a drop in the groundwater level and economic changes. Therefore, farms have been, and are still becoming abandoned on large areas. The remains of the semi-natural stands of sandy grasslands or sandy forests can often be found adjacent to agricultural land which later becomes abandoned, or are embedded among them. It is important to understand the size of the regeneration potential of the above mentioned areas;

4 which type of plant communities can develop on the abandoned fields, and which factors control their succession, because with this information, more well-developed management plans can be prepared for the whole of the Danube-Tisza Interfluve. My research was carried out in an area where many abandoned fields of different ages and states, and a relatively large amount of natural vegetation can be found next to each other. We could not find a reference area with a flat surface and with a similar area and abiotic background to the old-fields. Thus, we compared the old-fields with one of their target communities, the open sandy grassland, at a smaller scale which refers to the minimal area of the dry grasslands (patch-scale). At the same time, we studied the entire species pool of an old-field and it s changes (stand-scale), in order to get a more complete picture of the vegetation establishing during the succession. Many times there is only a short time to carry out research supporting nature conservation management. For this reason the different states of the successional process must be compared indirectly, instead of by direct, long-term observations (monitoring). This method, the space-for time substitution, is widely used to study succession. In the case of old-fields, we used this method to compare fields abandoned at different times and considered them as parts of a chronosequence. In my dissertation I made a comparative analysis of these two methods in order to obtain more accurate knowledge regarding their validity. Only a species poor plant community consisting of mainly generalist species can spontaneously develop on numerous Western-European old-fields, probably due to the lack of natural propagule sources. Several specialist species have poor dispersal ability, thus they only have a chance to establish on an abandoned field if there is a refugium in the surrounding area where they could survive. The part of the landscape I studied contains several remnants of different types of natural vegetation with varying sizes, which provided an opportunity to examine the role of these refugia in the development of the specialist species pool establishing on the old-fields. The main questions of my research were: How much does the vegetation of the sandy old-fields of different ages compare to the open sandy grassland? How does the vegetation of the sandy old-fields change during the successional process and which plant traits determine the vegetation composition and change?

5 Are the results of the static, space-for-time substitution-based and the dynamic, monitoringbased study similar or different? Among the background factors influencing succession, how does the soil composition of the old-fields and the spatial position of the propagule sources influence the species composition of the old-fields? 2. Study site and methods My research was carried out in the Kiskunság National Park near Fülöpháza within a 60 hectare area, which is a mosaic of agricultural fields, abandoned fields, vineyards, farms, plantations and semi-natural grassland and forest patches that can be considered as refugia. I identified 54 abandoned fields using aerial photographs and persistent landscape features. Based on the available aerial photographs I created four age-groups in 1998: old-fields abandoned years ago, years ago, years ago and years ago. I recorded the complete species list of vascular plants in each field twice a year between 1998 and 2003, and estimated the cover of the species on a five-degree scale. In 2004, I made 10 phytosociological relevés of 4 m by 4 m in each of the four age-groups, and 12 in the large open sandy grasslands close to the old-fields. In 2002, we took soil samples together with the Soil Research Institute from four old-fields from each age-group. The position and habitat type of the refugia patches were surveyed in I classified the vascular plant species based on several plant traits that are considered important during succession and which have enough verifiable records. These traits can be related partly to the dispersal ability of the species (seed mass, seedbank-type, clonality and origin), and partly to their long-term establishment ability (life-form, canopy height, disturbance tolerance, habitat preference). The grouping was made based on data from literature and field experience, for example, in the case of different life-form or habitat preference values I used the value typical in the Danube-Tisza Interfluve. Instead of the commonly used specialist, generalist and weed categories we developed a more objective category-system in co-operation with other botanists, which describes the relation of species to regular, but small, human disturbance. This system based on disturbance tolerance was an effective tool in characterising the naturalness of a given vegetation.

6 The ordination of the phytosociological relevés was carried out with the principal coordinate analysis ordination (PcoA, binary data, Sorensen-dissimilarity) and with the centered principal component analysis (centered PCA, quantitative data). The relevés were clustered by average linkage (UPGMA) algorithm and Bray-Curtis dissimilarity. Afterwards, I developed block clustering based on the presence of the species, where the age-groups provided the basis of the grouping of the columns. The five species groups created by the block clustering were separated by their presence in the relevés, that is by their behaviour during succession. I also analysed the distribution of the life-form, habitat preference and disturbance tolerance in these species groups. Finally, I depicted the species number of the lifeform types and disturbance tolerance groups depending on the total species number of the relevés, and based on this I examined the position of each age-groups. I analysed the soil samples taken from four old-fields in each age-group with canonical correspondence analysis. I examined which are the most frequent species on the old-fields and what kind of protected or rare sandy grassland species were able to colonise them. In the case of the space-for-time substitution, I studied the change of the species groups by comparing the age-groups with the Kruskal-Wallis test. Each old-field had a different size, thus I described the species number-area relation with the Arrhenius equation (MacArthur & Wilson 1967) when analysing the changes of the species numbers. Taking into account all of the sampled old-fields (54) I fit the curve according to this equation, and after I calculated the residuals and used them in the Kruskal-Wallis test to compare the age-groups. Based on the results of the survey in 1998, I made predictions about successional trends for the following years. In order to determine the direction and time of the fluctuations and to decide if the continuous monitoring is better than repeating the sampling only once following the initial survey, I compared the data of each year with the starting year (1998) and used the Wilcoxon test to detect if they differed significantly. When examining the changes of the 5-year long period, assuming that the relationship between the species number, the abundance and the time elapsed since the first sampling is linear, I used linear regression to determine the rate of the changes. I used one-sampled Wilcoxon test to detect if there were significant changes during the monitoring of the old-fields belonging to a given age-group. Finally, I compared the results of the monitoring with the predictions based on the space-for-time substitution study carried out in 1998.

7 I studied the relationship between the plant species and the successional age of the oldfields with canonical correspondance analysis and tested the importance of successional age as an environmental variable with the Monte-Carlo permutation test. The position of the plant species along the first ordination axis indicates successional behaviour, while the fit value shows the fitting. In further analysis, I included the species having higher fit values than 0.02 (66 species) or 0.01 (118 species). To investigate which traits are the best predictors of the appearance of certain species during succession, I used a regression tree analysis with the function ctree available in the party package in the R statistical environment. I used the loglink function of the generalised linear models (Poisson distribution) to describe the relationship of the quality of the propagule sources (open sandy grassland, closed sandy grassland, all dry grasslands, all natural refugia) and their area from 50, 100, 150 and 200 m distance from the edge of the old-fields with the number of low disturbance tolerant species occurring on the old-fields. Besides the above mentioned variables, I used the size of the oldfields as a continuous independent variable and the age of the old-fields (age-groups) as a grouping variable. 3. New scientific results 1. On the patch-scale, the regeneration of the sandy old-fields is quick; patches similar to the open sandy grassland can develop in years. Thus, patches similar to the open sandy grassland can be found on the older, years old old-fields, while these patches are missing from the younger fields, abandoned 3-12 years ago. Based on their species pool, some of the older old-fields did not differ from the open sandy grassland on the patch scale. 2. The young, 2-11 years old, sandy old-fields are characterised by the dominance of Poa angustifolia, Bromus tectorum, Cynodon dactylon and Asclepias syriaca, while the older fields, abandoned years ago, are characterised by the dominance of Secale sylvestre, Festuca vaginata and Stipa borysthenia, in addition to Cynodon dactylon and Asclepias syriaca. I have found that 16 protected or rare sandy grassland species are able to establish on old-fields. 3. Based on their behaviour during succession, we identified five species groups: (1) species connected to young old-fields, (2) species occurring only in semi-natural grasslands, (3) common species of old-fields and grasslands, (4) species occurring in old-fields of different ages and (5)

8 common species of older old-fields and semi-natural grasslands. There is no species group that is connected solely to the older abandoned fields. 4. The patch-scale average species number of the young old-fields is not different from that of the open sandy grassland, but there are much more species on young old-fields which are anthropogenic and require human disturbance. 5. In the soil of the youngest old-fields (5-8 years old in 2002), the potassium, phosphorous and humus content was higher than in the soil of the other old-fields. The differences in the soil also explains the variation in vegetation of the old-fields at the different ages. 6. Based on the space-for time study, the annual, disturbance requiring species are dominant on young abandoned fields, however, some perennial species also occur. Regarding both the species number and abundance, changes can be detected mostly on the youngest old-fields (between 1. and 2., or 1. and 3., 4. age groups). Either considering the species number or the abundance, approximately half of the plant traits did not change. 7. The space-for time study was a good predictor of the main successional trends, as was verified by the monitoring. Most of the predicted species number and abundance changes were verified. However, the predicted stability did not occur in several cases; during the monitoring we experienced numerous unexpected species number and abundance changes even on the older abandoned fields. 8. Our results have shown that the summary of the continuous, long-term monitoring gives more information about vegetation development and more predictions have been fulfilled. In comparison, the result of repeating the sampling only once following the initial survey is more incidental and confirmed less predictions. 9. According to our study, the advantages of the space-for time substitution approach are that it shows the general trends of successional change and it describes a process that has already occurred, but the disadvantage of this method is that it results in a more static view of the successional process. In comparison, the advantages of monitoring are that it shows a more dynamic, detailed view of succession and records finer details of variation, but the disadvantages

9 of monitoring are that it is affected by local conditions, gives less information about the future and is difficult to discriminate between trends and fluctuations. 10. Among the studied plant traits, the disturbance tolerance and the habitat preference influenced mostly the successional behaviour of the plant species. This means that, in the studied spatial and temporal scale, the factor which determines the vegetation development on old-fields is not dispersal ability, but the success of the long-term establishment. 11. Besides the age and size of an abandoned field, the species number of disturbance tolerant species is determined by the size of the remnants of dry grasslands found within a 150 m distance of the old-fields. 4. Conclusions During spontaneous succession on sandy old-fields, a habitat with a species pool similar to the open sandy grassland can develop. The dry grassland dominated by perennial grass species can develop rapidly, even within years, but the establishment of the woody species is slow. The species number does not change during succession, but considerable shifts can be observed: species requiring disturbance decline, while the number of low disturbance tolerant species increases. The annuals are continuously present, even 35 years after the abandonment, however the anthropogenic annuals are replaced by the annuals typical to sandy grasslands. The occurrence of the plant species in the studied landscape are not determined by their dispersal abilities, but rather by the traits connected to establishment and long-term persistence. This means that the successional process is not propagule limited, but rather determined by competition and other biotic relationships. Not only the semi-natural habitats that are closest to the old-fields, but the ones that are located further, m from the old-fields, can serve as propagule sources. When planning nature conservation management, it is worth considering spontaneous succession as a possible treatment alternative. However, in the case of the invasion of alien species, intervention into the spontaneous successional processes can be necessary. In place of the unprofitable ploughland cultivation and obligate cultivation, allowing spontaneous succession is a more profitable and environmentally friendly solution.

10 References for the thesis BIRÓ, M A Duna-Tisza közi homokbuckások tájtörténete az elmúlt kétszázötven évben. In: Molnár Zs. (szerk.) A Kiskunság száraz homoki növényzete. TermészetBúvár Alapítvány Kiadó, Budapest, pp MACARTHUR, R.H. & WILSON, E.O The theory of island biogeography. Princeton University Press, Princeton, New Jersey, USA. STANDOVÁR, T. & PRIMACK, R.B A természetvédelmi biológia alapjai. Nemzeti Tankönyvkiadó, Budapest.

11 5. Bibliography Articles in reviewed journals CSECSERITS, A. & RÉDEI, T Secondary succession on sandy old-fields in Hungary. Applied Vegetation Science 4: p CSECSERITS, A., RÉDEI, T., HALASSY, M. & SZABÓ, R Testing the validity of successional predictions on an old-field chronosequence in Hungary. Community Ecology 8(2): Articles in other journal RÉDEI, T., BARABÁS, S., CSECSERITS, A., & KUN, A A hegylábi löszvegetáció maradványai a Budai-hegységben - tájtörténeti rekonstrukciós kísérlet. Kitaibelia 3: BARTHA, S., KERTÉSZ, M., MOLNÁR, ZS., CSECSERITS, A., HENERBY, G. & KOVÁCS-LÁNG, E. 1999/2000. Homoki gyepek dinamikájának rekonstrukciója felhagyott szántóföldek és zavart ősgyepek mintázataiból. Botanikai Közlemények 86-87: CSECSERITS, A., HALASSY, M., SZABÓ, R., KERTÉSZ, M., & VAN DIGGELEN, R Sikeresen megtelepedő évelők felhagyott homoki szántókon - ki és miért pont ők? Botanikai Közlemények. 90 (1-2): BARTHA, S., BAUER, N., BÖLÖNI, J., CSECSERITS, A. HÁZI, J., HORVÁTH, A., ILLYÉS, E., KUN, A., PAPP, B., RÉDEI, T. & RUPRECHT, E Felismerhetők-e a parlagokon fejlődő másodlagos gyepek mikrocönológiai módszerekkel? Botanikai Közlemények 90: Book chapters CSECSERITS, A., VÁCZI, O., KATONA, K. & ALTBÄCKER, V Optimális legelési intenzitás vizsgálata homokpusztagyepben. Gyepgazdálkodási Társaság évkönyve. pp CSECSERITS A. & RÉDEI T Az Aranyribiszke. in: Botta-Dukát, Z. & Mihály B. (szerk.) Biológiai Inváziók Magyarországon Özönnövények II. A KVVM Természetvédelmi Hivatalának Tanulmánykötetei 10., Budapest. Conference presentations and posters CSECSERITS, A Amikor a természet visszatér - másodlagos szukcesszió felhagyott szántókon. In: A táj változásai a Kárpát-medencében II. Nyíregyháza. pp CSECSERITS, A., MOLNÁR, ZS., & RÉDEI, T Secondary succession on old fields on sandy soil. Spontaneous succession in ecosystem restoration, International workshop in Ceske Budejovice, Czech Republic. RÉDEI, T., BARABÁS, S., CSECSERITS, A., & KUN, A Land use and succession processes on loess-covered dolomite rocks in an old culture landscape near Budapest. Spontaneous succession in ecosystem restoration, International workshop in Ceske Budejovice, Czech Republic. BOTTA-DUKÁT, Z., MOLNÁR, ZS. & CSECSERITS, A. 1999: Changes of coarse scale compositional pattern diversity during old-field succesion. Spontaneous succession in ecosystem restoration, International workshop in Česke Budejovice.

12 CSECSERITS, A Szukcesszió vizsgálata kétféle módszerrel egy esettanulmány homoki szántókról. Aktuális flóra és vegetációkutatás Magyarországon IV. Jósvafő. CSECSERITS, A. & SZABÓ, R Felhagyott szántók és legelt, illetve nem legelt nyílt homokpusztagyepek összehasonlítása. V. Magyar Ökológus Kongresszus, Debrecen. BARTHA, S., KERTÉSZ, M., MOLNÁR, ZS., CSECSERITS, A., GEOFFREY, H. & KOVÁCS-LÁNG, E A primer és a szekunder szukcesszió összefüggései homoki gyepekben. V. Magyar Ökológus Kongresszus, Debrecen. CSECSERITS, A Different species composition during the regeneration of open sandy grassland after two different disturbance. 44 th IAVS Symposium, Freiburg-Weihenstephan, Németország, Abstracts. p.45. CSECSERITS, A. & RÉDEI, T Spontaneous succession on sandy old-fields: the experience of 4 years. 3 rd European Conference on Restoration Ecology, Budapest, Conference Abstracts. p. 82. CSECSERITS, A., BOTTA-DUKÁT, Z., BÖLÖNI, J., CSONTOS, P., KALAPOS, T., KENDERES, K., KUN, A., MORSCHHAUSER, T., PAPP, L., RÉDEI, D., RÉDEI, T. & VARRÓNÉ DARÓK, J. 2003: Hungarian plant trait database- structure. 46 th IAVS Symposium, 8-14 June 2003, Neaples, Italy. Conference Abstracts. p. 65. BARTHA, S., BAUER, N., BÖLÖNI, J., CSECSERITS, A., HÁZI, J., HORVÁTH, A., ILLYÉS, E., KUN, A., PAPP, B., RÉDEI, T., RUPRECHT, E. & SZABÓ, R. 2003: A vegetáció szünmorfogenezise magyar és amerikai felhagyott szántókon. VI. Magyar Ökológus Kongresszus, Gödöllő, Előadások és poszterek összefoglalói. p.43. CSECSERITS, A., HALASSY, M., SZABÓ, R. & RÉDEI, T Szukcessziós jóslatok tesztelése hosszútávon mit lehet gyorsan felmérni és mit nem. VI. Magyar Ökológus Kongresszus, Gödöllő, Előadások és poszterek összefoglalói. p. 59. RÉDEI, T., & CSECSERITS, A Az Alföld vegetációjának jellegtelenedése. Aktuális Flóraés Vegetációkutatás a Kárpát-medencében VI. Keszthely. Előadások és poszterek. Összefoglaló kötet. p. 28. SZABÓ, R., HALASSY, M. CSECSERITS, A. SZITÁR, K. & TÖRÖK, K Applicability of species groups as indicators of restoration efficiency in sandy oldfields. Abst. of The World Conference on Ecological Restoration, Zaragoza, Spain. p SZABÓ, R., CSECSERITS, A., HALASSY, M. & RÉDEI, T Növényi életmenet-tulajdonságok magyarországi adatbázisa és felhasználása. In: Aktuális Flóra- és Vegetációkutatás a Kárpát-medencében VII. Debrecen. Összefoglaló kötet. p. 37. Reports not published BOTTA-DUKÁT, Z., CSECSERITS, A., HALASSY, M., HORVÁTH, A., KRÖEL-DULAY, GY., RÉDEI, T., SZABÓ R., SZITÁR, K. & TÖRÖK, K Döntéstámogató szakértői rendszer. NKFP 3B/8/2002 projekt 30. részfeladatának keretében kidolgozva, kézirat. Popular articles CSECSERITS, A Parlag nem marad parlagon. Élet és Tudomány 59(2):