Leaf litter decomposition along the Porsuk River, Eskisehir, Turkey

Nuket Akanil and Beth Middleton

Abstract: The leaf litter decomposition of Typha latifolia L., Phragrnites australis (Cav.) Trin. ex Steud., Acacia longifolia Willd., Populus alba L., and Salix alba L. along the Porsuk River, Eskisehir, Turkey was studied using the fibreglass bag technique. After 180 days, soft-leaved species such as Acacia longifolia decomposed more quickly (0.52% loss . day-') than the tougher leaved species such as Typlzn lntifolia and Plzragnlires a~rstralis (0.31 and 0.37% loss. day-', respectively). Typha larifolia had the toughest while Acacia longifolia had the softest leaves among the five species as measured with a penetrometer (428.0 versus 128.2 g). Both leaf toughness and time were related to percent loss per day ( F = 4.4, p < 0.01 and F = 37.0, p < 0.01, respectively). World trends in percent loss per day for Typlza latifolia do not fit predictions based solely on latitude.

Key words: leaf toughness, fiberglass technique, Phragrnites australis, Typha latifolia.

Resum& : A I'aide de la technique du sac de fibre de verre, les auteurs ont CtudiC la dCcomposition des litikres des Typha latifolia L., Phragrnites australis (Cav.) Trin. ex Steud., Acacia longifolia Willd., Populus alba L. et Salix alba L., le long de la rivikre Porsuk, i Eskisehir, en Turquie. Aprks 180 jours, les feuilles tendres d'espkces telles que 1'A. longifolia se dCcomposent plus rapidement (0,52% de perte par jour) que celles d'especes 2 feuilles plus robustes telles que le T. latifoliu et le Phragrnites australis (0,31 et 0,37% de perte par jour, respectivement). Le T. latifolia posskde les feuilles les plus robustes et I'A. longifolia les feuilles les plus tendres tel que mesurC avec un ptnttromktre (428,O vs. 128,2 g). La robustesse foliaire ainsi que le temps sont relies au pourcentage de perte par jour (F = 4,4, p < 0,01 et F = 37,0, p < 0,01, respectivement). Les tendances mondiales en pourcentage de perte par jour pour le T. latifoliu ne correspondent pas aux predictions bastes uniquement sur la latitude.

Mots clr's : robustesse foliaire, technique de la fibre de verre, Plzrngrnites a~istralis, Typha latifolia. [Traduit par la rtdaction]

Introduction material, which is eventually transformed into fungal proto-

In woodland streams, the majority of energy comes from allochthonous input of streamside plants (Peterson and Cummins 1974; Vannote et al. 1980; Cummins et al. 1984, 1995). Ultimately, the level of input of energy into a riverine ecosystem is controlled by primary production and energy flow as regulated by decomposition. Movement of energy into secondary levels of the food chain can be facilitated by high primary production coupled with high rates of decom- position (Murkin 1989).

There are several steps of decomposition that can be generalized for all ecosystems and substrate types including leaching, microbial decomposition, and long-term break- down (Webster and Benfield 1986). After immersion in water, dead plant material immediately begins to lose weight in the first 24 h by leaching (van der Valk and Attiwill 1983; Webster and Benfield 1986). As soon as litter contacts water, the materials of higher molecular weight hydrolyse. After a brief period of leaching, fungi colonize on and in the leaf

plasm (Saunders 1975). while bacteria and fungi a;e equally important in the breakdown of litter, within 4 months of decomposition, bacteria become more important than fungi in the breakdown process. Studies of tree leaves in streams suggest that during the decomposition process, fungi actually make the litter more amenable to bacterial colonization (Polunin 1984). These bacteria have enzymes that can break high molecular weight compounds into less complex ones (Anderson and Swift 1983). The last stage of decomposition is long-term breakdown, and this final process can take many years depending on the species and its environment (Webster and Benfield 1986).

In aquatic systems, the rate of decomposition of organic matter is controlled by several factors including leaf tough- ness, inherent differences among plant parts, as well as major environmental variables such as water and air temperature, dissolved nutrient concentration, invertebrates, dissolved oxygen, and acidity. The techniques used in the study can also affect the rate of decomposition (Brinson 1977; Polunin 1984; Webster and enf field 1986). '

Received February 10, 1997. This study tested the hypothesis that aquatic species with tough leaves decompose more slowly than species with soft

N. ~ k a n i l ' and B. ~ idd le ton . ' Department of Plant Biology, leaves. The objective of this study was to conduct a decom- Southern Illinois University at Carbondale, IL 62901, U.S.A. position study of genera with large worldwide distributions ' Present address: Dumlupinar University, 43 100, Turkey. including Acacia longifoia Willd, Phragmites australis (Cav.)

Author to whom all correspondence should be addressed. Trin. ex Steud, Populus alba L., Typha latifolia L., and e-mail: bmiddleton@plant.siu.edu Salix alba L. Another purpose of this study was to set up a

Can. J . Bot. 75: 1394- 1397 (1997) O 1997 NRC Canada

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Notes 1395

Fig. 1. Percent remaining over time (days) for Typha latifolia, Phragrnites australis, Pop~il~is alba, Salix alba, and Acacia longifolia, July 1995 through January 1996, Porsuk River, Turkey.

I l l I I I I ( I 7 30 60 90 120 150 180

Time (in days)

Acacia longifolia

25

7 30 60 90 120 150 180 Time (in days)

Populus alba

$ 25

I I I I

7 30 60 90 120 150 180 Time (in days)

decomposition study in Turkey where few ecological studies have been undertaken.

Materials and methods

Study area Rivers and their floodplains are mostly highly altered in Europe, but in Turkey, a few remain in a natural or nearly natural state (wenger et al. 1990). This study took place along the Porsuk River in the northwestern part of central Anatolia in Eskisehir, Turkey (39- 4OoN, 29-32"E). Within the study area, the river was free flowing with a wooded buffer area mostly exceeding 30 m. Some water was diverted upstream (personal observation).

Eskisehir, at 790 m in altitude, is surrounded by five mountains: the Bozdag, Sundiken, Sivrihisar, Turkmen, and Kirgiz. There are three large plateaus surrounding Eskisehir: the Porsuk, Sarisu, and Sakarya. Both the Porsuk and Sakarya rivers run through Eskisehir (Onpeker 1992). December through May is the rainy season in Eskisehir. In summer, the temperature is approximately 30°C with the temperature differential between night and day as much as 20°C. The mountain vegetation is mainly forest with Pinus spp. and Quercus spp. Salix spp. and Populus spp. grow along the Porsuk and Sakarya Rivers (Onpeker 1992). The nomenclature follows Davis (1965).

Leaf decomposition and toughness Five sites were selected for the decomposition study along the Porsuk River, Eskisehir, Turkey. Sites with ephemeral water, human disturbance, or with no natural tying structures (trees) were rejected so that all available sites within a 2-km stretch were used.

Several kilograms of whole leaf blades each of Acacia longi- folia, Phragmites australis, Populus alba, Salk alba, and Typha latifolia were collected and air-dried. For each species, 50 fibre- glass bags (1 x 1 mm mesh) were filled with 10 g of leaf material. This leaf material was placed into the river at each of the five sites and tied to trees so that a total of 50 bags were tied at each site, 10 bags of each species. Five bags of each species, one from each site, were collected after 1, 3, 7, 15, 30, 60, 90, 120, 150, and 180 days starting on July 26, 1995, until January 21, 1996. The

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7 30 60 90 120 150 180 Time (in days)

Salix alba

.- .-

$ 25

7 30 60 90 120 150 180 Time (in days)

leaves in the litterbags were washed and rinsed in water to remove foreign materials such as soil and insects, oven-dried at 70°C, and weighed.

The leaf toughness of each species was tested with a penetro- meter (Fenny 1970). The weight of the water (g) at the time the rod punched through the leaf measured relative toughness. The test was repeated with four different leaves. At each site, temperature, dis- solved oxygen, and pH were measured on July 26, 1995.

Data analysis Percent loss per day was calculated as the total percent loss by the end of the experiment divided by the total number of days of the experiment (1 80 days).

ANOVA (SAS Institute Inc. 1988) was performed on percent loss and leaf toughness with species, site, and time as main effects (Cody and Smith 1991). Least significant differences (LSDs) were performed on means to detect differences in the percent loss between species and time because the means differed from one another. An ANOVA was first performed to determine if the per- cent loss among the five species was different (H,). After the H, was rejected (p < 0.05), each of the pairwise contrasts was tested to see if it differed from zero (Nelson 1990).

Results

The percent loss varied for the five species (F = 4.4, p < 0.01; Table 1). However,. based on LSD analysis, percent loss for leaf decomposition of Acacia longifolia, Populus alba, and Typha latifolia did not differ among each other nor did it for Phragmites australis, Salix alba, and Typha lati- folia. However, Acacia longifolia and Salix alba lost most of their original biomass (0.51 and 0.52 g, respectively; Fig. 1; LSD = 11.36) more rapidly than Phragmites australis and Typha latifolia (0.37 and 0.31 g, respectively).

The percent loss for all five species varied over time along the Porsuk River, Turkey. The initial weight loss in the first week for all five species was higher in days 0-7 than in days 90-180 (3.3-5.0 and 0.04-0.13% loss. day-',

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Table 1. ANOVA for mean percent loss per day for leaf decomposition of Typha latifolia, Phragmites australis, Populus alba, Salix alba, and Acacia longifolia, July 1995 through January 1996, Porsuk River, Turkey.

Source d f F P

Species 4 4.4 0.004* Block 4 0.1 1 .OOO Species X block 16 0.1 1 .OOO Time 3 37.0 0.001* Block x time 12 0.3 0.989 Error 60 Total 99

Note: *, significant at P < 0.05.

respectively; Fig. 1; F = 37.0, p < 0.01; Table 1). The mean rates of leaf decomposition based on percent

loss per day did not differ for the five common species between site positions (blocks) along the Porsuk River, Eskisehir, from July 1995 through January 1995 ( F = 0.01, p = 1.00; Table 1).

Leaf toughness differed anlong the species ( F = 25 377.5, p < 0.01). Typha latifolia had the toughest leaves (428.0 g) followed by Phragmites australis (318.5 g), Popul~ls alba (282.7 g), Salix alba (135.0 g), and Acacia longifolia (128.2 g).

Discussion

Leaf quality has a significant impact on decomposition rate, so that species with tough leaves decompose more slowly than species with soft leaves (Fenny 1970). Characteristics of the litter are often responsible for intrinsic differences in rates of breakdown (Day 1982). In this study along the Porsuk River, Turkey, the rate of decomposition varied for five common species (Table 1) mainly because of differences in leaf quality. The toughest leaves, Typha latifolia and Phragmites australis had a lower rate of decomposition as reflected in percent losses per day in comparison with the other three species (Fig. 1, Table 1).

In this study, the initial rates of breakdown in days 1-7 were much faster than in days 90-180 (Fig. 1, Table 1). Fast initial rates of weight loss are commonly observed in decomposition studies and often result from leaching (van der Valk and Attiwill 1983; Webster and Benfield 1986; Middleton et al. 1992; Steinke et al. 1993).

The genera Acacia, Phragmites, Popuhs, Salix, and Typha are widely distributed and have been used throughout the world in studies of decomposition. One would anticipate that, all else being equal, decomposition rates would slow moving from the equator to the poles (Brinson et al. 1981). Typha sp. does not show latitudinal trend, in that to the north in Manitoba, Canada, the rates of decomposition were faster than in Turkey (50°N versus 40°N, respectively; 0.3901 versus 0.2377% . dayp1, respectively; Murkin 1989 and this study, respectively). To the south of Turkey, in Jaipur, India, the rates of decomposition were slower (27"N; 0.2277% . day-'; Sharma and Gopal 1982) than in this study. However, specific rates of decomposition depend on

an array of factors, e.g., moisture and frequency of flooding, so that latitudinal comparisons become difficult (Webster and Benfield 1986).

Conclusions

Species with soft leaves such as Populus, Acacia, and Salix decompose faster than species with tough leaves such as Typha and Phragmites. The initial rates of decomposition (days 0-7) are much faster than at subsequent times. Con- trary to expectations, for Typha, the rates of decomposition in Turkey are faster than one study to the north and slower than another to the south, so that decomposition rate in not purely a function of latitude.

Acknowledgments

Dumlupinar University in Turkey provided financial support for this graduate program. Dr. Walter Schmid, Dr. David Gibson, and Dr. Donald Tindall critically reviewed this paper, and Dr. Roger Beck assisted in the statistical analysis of the data. We thank Dr. Yavuz Kilic, Suhli Ozkutuk, and Aydogan Akanil for their field assistance in Turkey.

References

Anderson, J.M., and Swift, M.J. 1983. Decomposition in tropical forests. In Tropical rain forest: ecology and management. Edited by S.L. Sutton, T.C. Whitmore, and A.C. Chadwick. Blackwell Scientific Publications, Boston, Mass. pp. 287-309.

Brinson, M.M. 1977. Decomposition and nutrient exchange of litter in an alluvial swamp forest. Ecology, 58: 601 -609.

Brinson, M.M., Lugo, A.E., and Brown, A.E. 1981. Primary productivity, decomposition, and consumer activity in fresh- water wetlands. Annu. Rev. Ecol. Syst. 12: 123-161.

Cody, R.P., and Smith, J.K. 1991. Applied statistics and the SAS programming language. Prentice Hall, Englewood Cliffs, N.J.

Cummins, K.W., Minshall, G.W., Sedell, J.R., Cushing, C.E., and Petersen, R.C. 1984. Stream ecosystem theory. Verh. Int. Ver. (Theor. Angew. Limnol. No. 22. pp. 1818- 1827.

Cummins, K.W., Cushing, C.E., and Minshall, G.W. 1995. Introduction: an overview of stream ecosystems. 111 River and stream ecosystems. Ecosyst. World No. 22. Edited by C.E. Cushing, K.W. Cummins, and G.W. Minshall. Elsevier, Amsterdam, The Netherlands. pp. 1-8.

Davis, P.H. (Editor). 1965. Flora of Turkey. University Press, Edinburgh, Scotland.

Day, F.P. 1982. Litter decomposition rates in the seasonally flooded Great Dismal Swamp. Ecology, 63: 670-678.

Fenny, P. 1970. Seasonal changes in oak leaf tannins and nutrients as a cause of spring feeding by winter moth caterpillar. Ecology, 51: 565-581.

Middleton, B.A., van der Valk, A.G., Davis, C.B., Mason, D.H., and Williams, R.L. 1992. Litter decomposition in an Indian monsoonal wetland overgrown with Paspalurn distichum. Wet- lands, 12: 37-44.

Murkin, H.R. 1989. The basis for food chains in prairie wetlands. In Northern prairie wetlands. Edited by A.G. van der Valk. Iowa State University Press, Ames, Iowa. pp. 316-338.

Nelson, P.R. 1990. Design and analysis of experiments. 111 Hand- book of statistical methods for engineers and scientists. Edited by H.M. Wadsworth. McGraw-Hill Publishing Co., New York.

Onpeker, H. 1992. Ilimiz Eskisehir (Our City Eskisehir). Metinler Matbacilik, Eskisehir, Turkey. (In Turkish.)

Peterson, R.C., and Cummins, K.W. 1974. Leaf processing in a woodland stream. Freshwater Biol. 4: 343-368.

O 1997 NRC Canada

Can

. J. B

ot. D

ownl

oade

d fr

om w

ww

.nrc

rese

arch

pres

s.co

m b

y U

NIV

ER

SIT

Y O

F N

OR

TH

TE

XA

S L

IBR

AR

Y o

n 11

/30/

14Fo

r pe

rson

al u

se o

nly.

Polunin, N.V.C. 1984. The decomposition of emergent macro- phytes in freshwater. Adv. Ecol. Res. 14: 115- 166.

SAS Institute Inc. 1988. SASISTAT user's guide, release 6.03 edi- tion. SAS Institute Inc., Cary, N.C.

Saunders, G.W. 1975. Decomposition in freshwater. In The role of terrestrial and aquatic organisms in decomposition process. Edited by J.M. Anderson and A. Macfadyen. Blackwell Scien- tific Publications, London, England. pp. 341 -373.

Sharma, K.P., and Gopal, B. 1982. Decomposition and nutrlent dynamics in Typha elephantina Roxb. under different water regimes. 111 Wetlands: ecology and management. Edited by B. Gopal, R.E. Turner, R.G. Wetzel, and D.F. Whigham. International Science Publishers, Jaipur, India. pp. 321 -335.

Steinke, T.D., Holland, A.J., and Singh, Y. 1993. Leaching losses

during decomposition of mangrove litter. S. Afr. J . Bot. 59: 21 -25.

van der Valk, A.G., and Attiwill, P.M. 1983. Decon~position of leaf and root litter of Avicenrzia marina at Westernport Bay, Victoria, Australia. Aquat. Bot. 18: 205-221.

Vannote, R.L., Minshall, G.W., Cummins, K.W., Sedell, J.R., and Cushing, C.E. 1980. The river continuum concept. Can. J. Fish. Aquat. Sci. 37: 130- 137.

Webster, J.R., and Benfield, E.F. 1986. Vascular plant breakdown in freshwater ecosystems. Annu. Rev. Ecol. Syst. 17: 67-94.

Wenger, E.L., Zinke, A,, and Gutzweiler, K.-A. 1990. Present sit- uation of the European floodplain forests. For. Ecol. Manage. 33/34: 5-12.

O 1997 NRC Canada

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. J. B

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oade

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