Species in Acclimation to a New Habitat
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ACTA BIOLOGICA CRACOVIENSIA Series Botanica 52/1: 45–54, 2010 DOI: 10.2478/v10182-010-0006-8 CANOPY BEHAVIOR OF THREE MILKVETCH (ASTRAGALUS)SPECIES IN ACCLIMATION TO A NEW HABITAT TADEUSZ ANISZEWSKI* Department of Biology, University of Eastern Finland, P.O.Box 111, 80101 Joensuu, Finland Received April 24, 2009; revision accepted November 11, 2009 Empirical data on functional growth dynamics are extremely limited for herbaceous plants and do not exist for milkvetch (Astragalus) species, although they are essential to an understanding a plant's ability to acclimate to a new habitat, which we need to know in order to predict its performance in future climate scenarios. The paper examines how species spread to a habitat in which they do not initially occur. It presents results on changes in growth, canopy behavior, competition ability and morphological traits of Cicer milkvetch (Astragalus cicer L.), Sweet milkvetch (Astragalus glycyphyllos L.) and Russian milkvetch (Astragalus falcatus Lam.) from a ten-year experiment. They successfully acclimated to a new habitat and presented clearly similar growth dynamics and similar strategies for establishing and maintaining populations. Developmental and reductional perennial phas- es were noted. The developmental phase showed slow and fast subphases. Canopy cover area peaked at the height of the developmental phase. Morphological parameters measured from parts of plants growing outside the experimental plot were greater than for plants growing inside it. Milkvetch species are good competitors. Unlike invasive species, their expansion strategy is not colonization-oriented. The data suggest that systematic and evolutionary studies on these species should pay attention to morphological changes. Key words: Astragalus, autecology, biometrics, canopy behavior, developmental perennial phase, growth dynamics, new habitat, plant strategy, population ecology, reductional perennial phase. INTRODUCTION legumes are a group of plant species with a world- wide distribution. These species, both annuals and Long-term experiments are important in evolution- perennials, are part of the third largest family of ary biology, botany and ecology (Aniszewski, 2000; flowering plants, Fabaceae, and have a good adap- Rozen and Lenski, 2000; Dudley, 2007; Philippe et tive system. They are able to grow dynamically with al., 2007). They cannot in every case be set up with a high photosynthetic rate (Aniszewski, 1988b,c; hypothesis-driven approaches as in a molecular Aniszewski, 1995a,b; Aniszewski et al., 1996; biology assay. Such experiments and the data they Aniszewski et al.,1998; Aniszewski et al., 2001a) in yield are critical to understanding important factors different climates, environments and soil condi- affecting plant growth dynamics and some aspects of tions. They have great potential for breeding in heterogeneity, competition and invasiveness in com- Northeastern Europe, where growth conditions for munities (Aniszewski, 1988a), and even yield new plants are generally extreme (Aniszewski, 2004). It findings in ultrastructural and molecular research has been hypothesized that plants have their own of plant organs (Aniszewski, 2006; Aniszewski et growth strategies for extreme environmental condi- al.,2006; Sahbaz et al., 2009). Although plant behav- tions. They can form durable structures such as ior plays a vital role in the processes of natural and seeds or position-resilient organs at more sheltered managed habitats, plant functional dynamics are not places, or can develop adaptations on the basis of understood well enough to predict plant perform- anatomical, morphological and physiological futures ance in future climatic scenarios (Osmond et al., (Schurr et al., 2006). This problem has not been 2004). Nor can crop resources be exploited effi- studied empirically in legumes; hence the motiva- ciently without a deep understanding of plant func- tion for establishing long-term experiments with tional dynamics (Schurr et al., 2006). Perennial species belonging of the genus Astragalus. This *e-mail:[email protected] or [email protected] PL ISSN 0001-5296 © Polish Academy of Sciences and Jagiellonian University, Cracow 2010 46 Aniszewski genus contains herbs and small shrubs occurring eastern Fennoscandia (Mossberg and Stenberg, throughout the world, with the greatest concentration 2005) and were totally new to the experimental habi- of species in Southwest and Central Asia, though tat. The species studied are an integral part of the some species occur in Europe and western North Caucasian flora, but it is not precisely known how America (Heywood and Ball, 1968; Heywood, 1993; they came to the Caucasus or whether they are true Zomlefer, 1994; Kholoptseva and Mihkiev, 1995; endemics there. Decker, 2005; Akan et al., 2008; Riahi and Zarre, The experiment was established in 1998 in 2009). The genus Astragalus is very diverse in its Botania, the botanical garden of the University of species adaptation to environments, and many wild Joensuu in Finland (62°36'00"N, 29°45'50"E), species are rare and locally conserved; many are employing standard procedures for plant acclimation known as important useful plants and many as strong and measurement, with some modifications. The toxicants. There are no literature data on the poten- experimental site was in the center of the botanical tial spread (natural or artificial) of these species into garden, in a research area near a wild area with trees habitats where they did not initially occur, nor any and bushes. The plots were laid out on two east-west data on how they adapt to new conditions and cope transects, with buffer plots on the easternmost and with competition from other species which are native westernmost ends of both transects. The seeds of or well adapted to the given habitat. Such data are three different species were sown in 1 m2 plots in four needed for comparisons of earlier results related to replicates randomly (by lottery), together with the any scientific evidence of anticipated climate change, buffer plots. To enable comparison of the vegetation and they can help avoid potential problems in nature between plots, the roots of the experimental plants conservation. Habitat-forming invasive species can were prevented from growing outside the plots with produce novel transformations of the environment boards 3 cm thick on all sides of the plots, blocking (Wright et al., 2010). As milkvetch species have not egress down to 30 cm depth. The soil was tilled man- previously been studied, it is not known whether they ually down to the same depth. In each plot, 100 seeds can establish permanent and aggressive populations per m2 were sown at 3 cm depth on May 15, 1998. in nature and survive in a new habitat. These species, especially cicer milkvetch (Astragalus cicer L.), sweet NEW HABITAT CHARACTERISTICS AND POTENTIAL milkvetch (Astragalus glycyphyllos L.) and Russian PLANT NEIGHBORS milkvetch (Astragalus falcatus Lam.) are viewed as potentially useful plants in many European countries, The new habitat (Botania) for the milkvetch species is America and Australia, and are suggested as econom- located in the Finnish boreal zone, strongly influ- ic crops (Townsend, 1993; Loeppky et al., 1996; enced by the Gulf Stream from the Atlantic and by Aniszewski, 2004; Acharya et al., 2006; Laurence, gentle southwestern winds producing a climate 3–4°C 2006). Uses for them in revegetation and restoration warmer than other areas at the same northern lati- programs are proposed (Bhattarai et al., 2008), and tude. The climate is continental with cold winters and commercial production is expected to increase hot summers (Tab. 1). around the world (Acharya et al., 2006). This makes The soil in each plot was natural and typical gar- the question examined here topical and important, den soil with fine sand, sand, silt, clay and organic both for theory and for practical applications. In this matter fractions, and with its own seed bank (Tab. study I assess long-term growth dynamics and their 1). Seeds of 11 perennial species were found in soil functionality in the acclimation of three milkvetch samples taken from the experimental area (depth species to a new habitat, examining long-term canopy 0–30 cm, sample size 1 cm2, 4 replicates) immediate- behavior, morphological traits and competition abili- ly before the milkvetches were sown. These species ty. Three basic questions are addressed: (1) what are were expected to be neighbor competitors for the the perennial growth dynamics and canopy behavior three milkvetch species sown. All plants in the exper- of these milkvetch species, (2) is there any evidence of imental area were allowed to grow freely during each their canopy expansion strategy and competition abil- annual growing period. The species studied and their ity, and (3) are there morphological changes associat- neighbors were cut at the height of 5 cm from the ed with their population spread in a new habitat? soil surface each year on October 15. The green mass of the cut plants was transported out of the experimental area. Long-term observations and MATERIAL AND METHODS measurements were performed. PLANT MATERIAL AND ACCLIMATION EXPERIMENTS MEASUREMENT AND DATA COLLECTION Cicer milkvetch (CM), sweet milkvetch (SM) and Pod and seed samples were collected for measure- Russian milkvetch (RM) were used in the long-term ments. The plants were measured ten times during experiments. These species do not occur in nature in each growing season for ten years