Different Nutrient Use Strategies of Expansive Grasses Calamagrostis
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Biologia 67/4: 673—680, 2012 Section Botany DOI: 10.2478/s11756-012-0050-9 Different nutrient use strategies of expansive grasses Calamagrostis epigejos and Arrhenatherum elatius Petr Holub1*, Ivan Tůma2, Jaroslav Záhora2 &KarelFiala3 1Global Change Research Centre, Academy of Sciences of the Czech Republic, Bělidla 4a, CZ-60300 Brno, Czech Republic; e-mail: [email protected] 2Department of Agrochemistry, Soil Science, Microbiology and Plant Nutrition, Faculty of Agronomy, Mendel University in Brno, Zemědělská 1,CZ-61300 Brno, Czech Republic 3Department of Vegetation Ecology, Institute of Botany, Academy of Sciences of the Czech Republic, Lidická 25, CZ-60200 Brno, Czech Republic Abstract: Enhanced nitrogen (N) levels accelerate expansion of Calamagrostis epigejos and Arrhenatherum elatius,highly aggressive expanders displacing original dry acidophilous grassland vegetation in the Podyjí National Park (Czech Repub- lic). We compared the capability of Calamagrostis and Arrhenatherum under control and N enhanced treatments to (i) accumulate N and phosphorus (P) in plant tissues, (ii) remove N and P from above-ground biomass during senescence and (iii) release N and P from plant material during decomposition of fresh formed litter. In control treatment, significantly higher amounts of total biomass and fresh aboveground litter were observed in Calamagrostis than in Arrhenatherum. Contrariwise, nutrient concentrations were significantly higher (11.6–14.3 mg N g−1 and 2.3 mg P g−1)inArrhenatherum peak aboveground biomass than in Calamagrostis (8.4–10.3 mg N g−1 and 1.6–1.7 mg P g−1). Substantial differences be- tween species were found in resorption of nutrients, mainly P, at the ends of growing seasons. While P concentrations in Arrhenatherum fresh litter were twice and three times higher (1.6–2.5 mg P g−1)thaninCalamagrostis (0.7–0.8 mg Pg−1), N concentrations were nearly doubled in Arrhenatherum (13.1–15.6 mg N g−1)incomparisonwithCalamagrostis (7.4–8.7 mg N g−1). Thus, the nutrients (N and mainly P) were retranslocated from the aboveground biomass of Calama- grostis probably more effectively in comparison with Arrhenatherum at the end of the growing season. On the other hand, Arrhenatherum litter was decomposed faster and consequently nutrient release (mainly N and P) was higher in comparison with Calamagrostis which pointed to different growth and nutrient use strategies of studied grass species. Key words: competition; decomposition; dry grassland; fertilization; N:P ratio; tissue nutrient concentration Introduction lic). Elevated nutrient levels accelerate the expansions of tall grasses Calamagrostis epigejos (L.) Roth and Ar- Atmospheric input may substantially affect biogeo- rhenatherum elatius (L.) P.Beauv. in this locality (Fiala chemical cycling, especially in areas subjected to high et al. 2004). C. epigejos, a rhizomatous perennial grass, concentrations of air pollutants. One of the major often tolerates dry sites with a very low content of or- threats to the structure and functioning of ecosystems ganic matter in the soil and low to very low contents are the high levels of air-borne nitrogen (N) pollution of N (Rebele & Lehmann 2001). However, its growth (Bobbink & Roelofs 1995; Bobbink et al. 1998). Al- is enhanced under moist and nutrient rich (especially though some improvements have been made with re- N) conditions (Br¨unn 1999). A. elatius,atuftsform- spect to the reduction of the amount of pollutants in ing perennial grass, is often found on well-aerated soils Central Europe (Květ 1993; Fanta 1997), acid deposi- of high to moderate fertility (Pfitzenmeyer 1962). Both tion still occurs and current N loads can exceed the mentioned grasses represent plant species of global im- critical loads of plant nutrition in some regions (e.g., portance due to their aggressive colonization of various Eugster et al. 1998; Balestrini et al. 2000; Hůnová ecosystems in Europe and North America (ten Harkel et al. 2004). Bobbink & Roelofs (1995) assessed 7–15 & van der Meulen 1996; Rebele 2000; Wilson & Clark kg N ha−1 per year as N critical load to species-rich 2001; Fiala et al. 2003; S¨uss et al. 2004). The conversion acid grasslands. Fabšičová et al. (2003) reported higher of native vegetation to an expansive species following capture of mineral N through interception from dewfall eutrophication (e.g., Bobbink & Willems 1988; Aerts (9–18 kg N ha−1) in dry acidophilous grassland in the 1989; Bobbink et al. 1998) suggests that the expander Podyjí National Park (South Moravia, Czech Repub- can take up more nutrients than the displaced resident * Corresponding author c 2012 Institute of Botany, Slovak Academy of Sciences 674 P. Holub et al. Table 1. Mean values of pH, contents of total C and N (%), P, Ca, Mg (mg g−1) and C:N ratio in soils of Calamagrostis epigejos and Arrhenatherum elatius stands in October 2002. Stands pH (H2O) pH (KCl) C N P Ca Mg C:N C. epigejos 6.9 6.6 14.7 0.52 0.32 3.7 0.45 28 A. elatius 5.6 4.9 12.7 0.43 0.12 1.5 0.21 30 species. Species replacement during succession can also ground parts of stands (in July) in the 2002 and 2003 grow- have major effects on the N cycle according to van der ing seasons. Samples of aboveground biomass for estimation Krift et al. (2001). They stressed that differences in N of fresh aboveground litter production (FAL) were collected mineralization and nitrification were not simply a func- at the end of the growing seasons (in November). Above- × tion of the net plant biomass production but probably ground biomass was taken from five 20 40 cm quadrates in all control and N fertilized sub-plots. In the second year also of differences in biomass turnover and litter decom- of the experiment, biomass samples were taken from the posability. Rees et al. (2005) reported that N addition different place than in the first year. Collected aboveground to grasses adapted to high soil fertility doubled rhizode- biomass was separated to living and dead plant parts of the position of carbonaceous substances, whereas low soil dominant species. At the end of the growing season, simul- fertility grass species (e.g., Festuca ovina)showedno taneous to sampling the aboveground biomass, five below- response. These changes in the rhizodeposition can ac- ground samples were taken in the harvested plots with a celerate microbial activities, biomass turnover and en- root sampler (diameter 9-cm) to the depth of 15 cm, be- courage even more expansive species. cause roots were not able to penetrate deeper. The total The main objectives of this study was to compare belowground biomass (TBB) was sorted into rhizomes and roots. Aboveground and belowground plant material was the capability of C. epigejos and A. elatius to (i) ac- dried for at least 48 h at 60 ◦C prior to weighing. Collected cumulate nutrients (N and P) in plant tissues, (ii) ef- plant samples were pulverized before analysis. The plant- ficiently remove N and P from aboveground biomass biomass analyses of N and P were performed from an ex- during senescence (nutrient resorption) and (iii) release tract obtained by wet combustion of dried plant material, N and P from plant material during decomposition of N by micro-Kjeldahl technique, P colorimetrically using the freshformedlitter. ammonium vanadate method. At the end of the growing season, representative soil samples from the top 15 cm were taken using a special soil Material and methods sampler for taking undisturbed soil samples. Four soil sub- Study site samples were randomly collected per each sampling plot. Our studies were carried out in the Podyjí National Park Each mixed sample was placed in a plastic bag in the field ◦ near the town of Znojmo (Czech Republic). The study site and kept cool at 4 C until processed in the laboratory. Soil is a dry grassland located near the village Havraníky (48◦49 samples taken from each plot were united as one composite N, 16◦01 E; 320 m a.s.l.) with nutrient-poor shallow soils sample and analysed. Soil characteristics were estimated on of Ranker type (Sedláková & Chytrý 1999). The shallow 2-mm fraction and included pH (in H2O and KCl). Total soils are often called A/C soils, as the topsoil or A horizon C content was determined according to the Kononova and is immediately over a C horizon (unaltered parent mate- Belcikova method, adapted from Novak. Calcium (Ca) and rial on the granitic bedrock). Basic soil characteristics are magnesium (Mg) contents were determined by the method presented in Table 1. The studied locality was character- according to Mehlich II and using GBC933 atomic absorp- ized by annual mean air temperature 9.0 ◦C and 600 mm tion spectrometer. Content of P was determined photo- (2002) and 322 mm (2003) of sum of precipitation during metricaly as a molybdate-phosphate-complex and total N growing season. A great part of the area is covered with content by distillation after mineralization (Kjeldahl tech- dry acidophilous short grass vegetation represented by the nique). plant community Potentillo arenariae-Agrostietum vinealis (Kučera & Šumberová 2010). The great part of original Estimation of decomposition and element release short grass vegetation has been already replaced by nearly The amount of decomposed plant biomass was assessed by monospecific stands of tall grasses Calamagrostis epigejos the mesh-bag method (Tesařová 1993). In each experimental and Arrhenatherum elatius (hereafter referred to as Calam- plot one nylon mesh-bag containing fresh aboveground litter agrostis and Arrhenatherum). Studied stands were not reg- (6 g of dry weight) of corresponding grass species was placed ularly mown before establishment of the experiment. Ten horizontally on soil surface (6 replications for species and permanent plots 6.0 × 2.0 m were laid out in five stands treatment).