Forest Snow and Landscape Research ISSN 1424-5108 Volume 79, Issue 3, 2005 195–415 Growth Rings in Herbs and Shrubs: life span, age determination and stem anatomy Fritz Hans Schweingruber and Peter Poschlod Publishers Swiss Federal Research Institute WSL, Birmensdorf Haupt, Berne, Stuttgart, Vienna Cerastium semidecandrum L., Caryophyllaceae. Collected April 6th 2005 in a vineyard in Fully, Valais, Switzerland. Transverse section of a 0.9 mm thick root collar stained with Astrablue and Safranin. Magnification 120x. The xylem in the center is surrounded by a cambium, a phloem, a cortex, an exodermis and an epidermis. The xylem is characterized by a rayless, unlignified parenchymatic tissue (blue), in which slightly lig nified vessels are embedded (reddish). The concentration of vessels at the periphery of the xylem indicates that the annual herb germinated in fall, stopped growth in winter and finished its life period in spring. The cambium is one to two cells wide. Typical for the phloem is the composition of very small sieve elements and the small parenchymatic cells. The thick belt with large cells represents the cortex (dark blue). It is surrounded by the exodermis, where the cell walls are intensively lignified (red). The outermost thin- walled cells represent the epidermis. For. Snow Landsc. Res. 79, 3: 195–415 (2005) 197 Growth Rings in Herbs and Shrubs: life span, age determination and stem anatomy Fritz Hans Schweingruber1 and Peter Poschlod2 1 WSL Swiss Federal Research Institute, Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland. [email protected] 2 Institute of Botany, Faculty of Biology and Preclinical Medicine, University of Regensburg, D-93040 Regensburg, Germany. [email protected] Revised manuscript accepted 17 October, 2005 Abstract Growth Rings in Herbs and Shrubs: life span, age determination and stem anatomy Can the age of herbs, dwarf shrubs and shrubs be determined, and if so, how old can they get? And what possibilities exist for answering ecological questions about plants and populations using the ages of such plants? These and many more questions prompted us to analyse the growth rings observed in central European herbs, dwarf shrubs and shrubs, and also, more generally, to review the state of the art for classifying and determining the age of plants. We also explore how the knowl- edge of the presence of growth rings can be applied to ecological and biological conservation ques- tions, and which factors may limit the lifespan of plants. We present techniques and prerequisites for identifying growth rings and for validating that they are actually annual rings. The limitations of growth-ring analysis are discussed. The anatomy of the root collars of about 800 central European species is given. The methods of age classification/determination reviewed include: annual ring and other chrono- logical methods, growth form analysis, permanent plot research, and historical and genetic analy- ses. The application of growth-ring analysis to describe population structures allows the current status of a population to be assessed. Several examples are given. Physiological and environmental factors that may limit a plant’s lifespan are reviewed. Preliminary results evaluating our data set show that lifespan may be limited by temperature and nutrients. Keywords: life span, growth-ring analysis, annual rings, plant anatomy, ontogeny, herbs, dwarf shrubs, shrubs, plant population structure, temperature, nutrients, moisture For. Snow Landsc. Res. 79, 3 (2005) 199 Preface Life span is a key trait in the life history of plants. What determines a plant’s survival under specific environmental conditions? Many factors affect a plant’s life span and help us ident- ify its age, such as: morphological, anatomical, ontogenetic, physiological and ecological fac- tors, and even the structure of populations. Until now, there has been no overview taking into account all these aspects and only a few studies of the life span of non-trees. Such an overview would, we thought, be an exciting challenge in which we could draw on our experience in dif- ferent fields. For the first author this has been in dendrochronology and wood anatomy, and for the second in population biology and vegetation ecology. This overview is, in our opinion, long overdue. Until recently ecologists seem to have largely ignored the fact that the age of non-woody plants can also be determined, and plant physiologists still cite MOLISCH (1929, 1938) when they discuss the life span of a whole plant or plant ageing. Our main aim is to encourage scientists from different disciplines to ask new questions by offering them not only a catalogue of species whose annual rings can be analysed, but also to encourage a state-of-the-art overview of how to measure the life span and persistence of a number of plant species. In the future we hope that it will be possible to determine the life span and persistence of plants with primary roots possessing growth rings, as well as to analyse the short-term demography of perennial species. Where annual growth rates and vegetation carbon storage can be measured in the herb and shrub layer, it should also be possible to examine issues such as the extent to which plant life span depends on habitat quality or the effect of different environmental conditions on population structures. Analyses of population structures should also help us to evaluate the success, or otherwise, of conservation or resto - ration management treatments. Finally, we hope that this overview and review will encourage plant physiologists to give further thought not just to the death of a cell or an organ such as a leaf, but also to the whole plant and various related aspects. Meeting this challenge would not have been possible without the help of many colleagues and friends: Stephan Krebs (LEL, Schwäbisch Gmünd, Germany) introduced us to Ernst Rieger (Blaufelden, Germany), without whose generous support we would not have been able to prove that annual rings in herbs are really annual rings. He let us dig in the fields where he cultivates an innumerable number of “wild species”, with exact sowing dates recorded for individuals of about 30 species. Anne-Kathrin Jackel (Regensburg, Germany) provided data on growth forms from the BioPop database and “managed” the “Swiss data”. Christine Römermann (Regensburg, Germany) put together data on vegetation types and life forms. During the literature search we found a huge amount of material in Russian on these topics, which was translated from Russian into German by Wioletta Moggert (Regensburg, Germany). Her telephone calls to Russia are already legendary: they made it possible for us to consult missing volumes of the Biological Flora of Moscow. Frantisek Krahulec (Prague and Pruhonice, Czechia), from the Institute of Botany at the Czech Academy of Sciences, provided the first paper by Rabotnov on the ontogenetic classification of species, which was available neither in Germany nor in Switzerland. Nina Ulanova (Moscow) also sent some Russian literature. The discussions we had with her (by e-mail) on the ontogenetic concepts of Rabotnov were very helpful. We also thank Bertil Krüsi, who provided unpublished data from studies on the growth rate and age of Brachypodium pinnatum patches and Jeremy Flower-Ellis, who provided a copy of his thesis. Tanja Donaubauer, Oliver Geuss, Isabel Hoffmann, John Hoffmann (all Regensburg, Germany), Claudia Baumberger (Biel, Switzerland), Marion and Richard Joss-Petersdorf (Schlatt, Winterthur, Switzerland), Andrea Münch and Ruth Schwarz (Würzburg, Germany) and Yvonne Steiner (Basel, Switzerland) provided unpublished data from their theses and research work. Karl-Friedrich Schreiber helped Tanja Donaubauer and the second author in the field to dig up individuals for annual- 200 ring analysis. Special thanks go to the Swiss Federal Institute for Snow and Avalanche Research (SLF) in Davos and the Swiss Federal Institute WSL in Birmensdorf. Both insti - tutions have allowed the first author to work in their laboratories since his retirement. The Swiss National Science Foundation supported the first author for 15 years in his collection of plant material and preparation of slides. Finally, we have to thank Vanessa Winchester (Oxford, UK), and Silvia Dingwall (Nussbaumen, Switzerland), who have patiently corrected our English. Their nice comments have been refreshing and stimulating. We are also grateful for the helpful feedback from two anonymous reviewers. Many thanks also to Ruth Landolt for editing the large manuscript and to Sandra Gurzeler, Margrit Wiederkehr, and Jacqueline Annen for their careful layout. Birmensdorf and Regensburg, October 2005 Fritz Schweingruber and Peter Poschlod For. Snow Landsc. Res. 79, 3 (2005) 201 Contents Abstract 197 Preface 199 1 Introduction 203 2 Age classification and determination of herbs, dwarf shrubs and shrubs – 205 the state of the art 2.1 Soft classifications 205 2.2 Hard classifications 208 2.3 Age determination 211 3 Determining the age and growth dynamics of herbs and shrubs by the analysis 223 of growth rings 3.1 Are annual rings annual rings? 223 3.2 Limitations on using ring counting to estimate the age of an individual 228 3.3 Crossdating 231 4 Morphological pre-requisites of growth-ring analysis 233 5 Analysis and anatomy of growth rings 237 5.1 Preparation and microscopic techniques 237 5.2 Stem anatomy 240 5.3 Growth-ring characteristics in the xylem and phloem 250 6 Age structure of Central European herbs and dwarf shrubs 263 7 Population age structure: examples of the application of growth-ring analysis 265 to issues in ecological and biological conservation 7.1 Age structure of populations and successional stage 268 7.2 Age structure of populations and management 270 7.3 Age structure of populations and restoration management 273 7.4 Age structure and reconstruction of landscape history 275 8 What restricts the life span of a plant? State of the art and analysis of 277 our data set 8.1 Physiological factors 277 8.2 Ecological/environmental factors 278 9 Conclusions 285 10 Summary 287 11 References 289 Appendices 301 Glossary 302 Table A 1 306 Atlas 315 For.