Natural Vegetation of South Carolina.

The Grass Cover of India.

In 1947 I began my doctoral studies to determine the causes of early old- field succession in the North Carolina Piedmont. I present here a review of the research that led me to undertake those studies and a synopsis of the research on patterns and mechanisms of old-field succession which followed. Although a few species are ubiq- uitous among old fields, the patterns and rate of species replacement vary considerably among and within regions. In few areas are stages as distinct or progress so rapid as in North Carolina. I expect the mechanisms are also varied and suggest that factors such as site history, farming practices and seed availability have been underrated. In general, much of the variation in old-field composition appears to be related to varia- tions among species in germination requirements and life histories. PRE- 1947 RESEARCH In the autumn of 1947, as a graduate student at Duke University, I began working on the causes of old-field succession in North Carolina. The sequence of species in- vading and dominating abandoned farmland in North Carolina had been determined by Crafton and Wells (1934) and Oosting (1942) with little disagreement. Crabgrass (Digitaria sanguinalis (L.) Scop.) usually occupies fields in the late summer and autumn following the last cultivation. Horseweed (Erigeron canadensis L.) dominates fields the 1st year of abandonment, followed in turn by aster (Aster pilosus Willd.) and broomsedge (Andropogon virginicus L.) in the 2nd and 3rd years. Broomsedge fields are invaded by pines of several species, which usually form a complete canopy in 10 or 15 years. After one generation pines are replaced by hardwoods. Dr. Oosting admitted (pers. comm.) that although he knew the sequence of species in early old-field succession, he did not know what caused these distinct and fast changes and challenged me to find the causes. Clements (1916) had proposed that pioneer species change the environment and make it more suitable for species that invade by increasing the humus in the soil, pro- viding shade and improving water and mineral conditions. This idea was widespread and generally accepted until the 1940s as the major cause of succession. Crafton and Wells (1934) found that one of the causes of old-field succession is competition for water. Coile (1940) and Oosting and Kramer (1946) had investigated the role of water and light in the replacement of pines by hardwoods. At about the same time the idea that one plant may produce some chemicals which are inhibitory or toxic to other plants (allelopathy) had been advanced by Davis (1928), Went (1942), Bonner and Galston (1944) and others. Such toxins could be the cause of one species replacing another in the old-field sequence. Perhaps horseweed produces a toxin that delays the invasion of aster, or aster produces a toxin that helps eliminate horseweed from the old- field succession in North Carolina. Drew (1942) worked out the sequence of species on abandoned farm fields in Missouri and speculated on the causes of variations from field to field. He concluded that the only event that correlated with the differences was what the last crop had been. From my research (Keever, 1950) I concluded that the early dominants are largely determined by the capability of their seeds to germinate at the time of year a suitable habitat is available. After the germination of seeds, the entrance and exit of each

A retrospective view of old-field succession after 35 years [North Carolina].

Beside the articles in scientific journals and the monographs within publication series covering most of the original progress in vegetation science, a growing number of reviews and outlines on particular topics are collected in symposium reports and similar volumes; they recently treat mosaics of plant communities (TUXEN, 19 78a), vegetation and climate (DIERSCHKE, 1977), vegetation on wet sites of inland areas (DYKYJOVa and KVET, 1978; GEHU, 1978a; GOOD et al., 1978) and of coastal regions (CHAPMAN, 1977; CLARK, 1977), portions of Africa (WERGER, 1978) and some other fields mentioned later. Systematic and complete texts on ample fields can be attained in volumes by single experienced authors. One example is the volume on the vegetation of central Europe including the Alps by ELLENBERG (1978), emphasizing in the new revised edition physiologic-ecologic processes within vegetation. The amplified integration of vegetation science in university curricula is reflected by the highly augmented parts on vegetation (EHRENDORFER, 1978) in the new edition of the well-known botany textbook of Strasburger. A new Russian textbook (RABOTNOV, 19 78a) accentuates coenologic aspects within vegetation (also RABOTNOV, 1978b), whereas the work of DAUBENMIRE (1978) refers mainly to North America. Numerical considerations continue to be frequently published in books of mostly limited size (e.g., FRENKIEL and GOODALL, 1978; INNIS, 1978; ORLOCI, 1978; DE WIT and GOUDRIAAN, 1978). The central position of vegetation science in nature conservation is documented in the texts of BOHN et al. (1978), GODWIN (1978), HILLESHEIM-KIMMEL et al. (1978), LONDO (1977), and TRAUTMANN et al. (1978). The increasing amount of publications and information makes bibliographies on particular fields of vegetation science more and more indispensable, representing recent root studies in vegetation (TUXEN and WILMANNS, 1978), paleosociology (TUXEN and WOJTERSKA, 1979), syntaxonomy (TUXEN et al., 1979), hydrology in plant communities (TUXEN and GROOTJANS, 1978; also TUXEN, 1978e), symphytosociology (TUXEN, 1978f), vegetational productivity (KNAPP and TUXEN, 1979), dynamics and reproduction in vegetation (KNAPP, 1978a, 1979a), plant communities of bryophytes (VON HUBSCHMANN and TUXEN, 19 78) and in bogs (TUXEN, 1978d). A series of bibliographies collects the literature on several countries (France: GEHU et al., 1978; India: MEHER-HOMJI and GUPTA, 1978; outline on Yemen: HEPPER, 1977; Senegal, Mauretania, Mali, Upper Volta, Chad, East Africa: KNAPP, 1979a; Chile: RAMIREZ, 1979).

Vegetation Science (Sociological Geobotany)

Accelerated fundamental changes of the vegetational cover are becoming apparent in more and more countries or regions. The study of these changes, including their causes and the investigation of methods to prevent undesirable consequences, is increasingly becoming a central theme of vegetation science. The partial destruction or regional extinction of several plant communities is obvious; it necessitates, for instance, the compilation;of “red lists” of endangered syntaxa (associations, etc.) in need of conservation and protection (e.g. for Schleswig-Holstein: DIERSSEN 1983; for western Czechoslovakia: MORAVEC 1983). But equally important is the emergence of new species assemblages and plant communities adapted to the changed environmental conditions. Examples and results of such studies are given here.

Vegetation Science (Sociobiological Geobotany)

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Rüdiger Knapp

Author Tools

Chat about Author

Papers

Vegetation Science (Sociological Geobotany)

Vegetation Science (Sociobiological Geobotany)