35. Vitaceae

Cyphostemma rhodesiae (Gilg & Brandt) Descoings. = Cissus rhodesiae Gilg. & Brandt). Small shrub or perennial herb, stems about 65 cm tall, tillering base at the soil surface. Buds, owers and leaves in October, then a full development of plant.

Tap root tuberous in the upper part 2.5 up to 8 (?) cm in diameter, with some lateral roots. Hemicryptophyte. Tab. 3 – Appendix 1; Fl. Zamb.: Erected herb to c. 1–3 m tall; Herbarium of Zambia University (UNZA): Specimen de ned as shrubs or subshrubs.

A notice: below in the text, a er the plant names, in parenthesis are numbers – they indicate the plant’s adherence to adequate family, according to the speci cation in the chapter above.

Common features of studied vegetation oristic composition

Number of plants in particular families On both studied plots of savanna 95 species of vascular plants were noticed. Ŀey are shortly described above and mentioned in phytosociological tables No 2 and 3, or – in the case of sporadic species – in the text. All of those plants belong to 35 families, represented in the studied plots chie y by a single taxon. Most numerous species – 22 were classi ed in the family of grasses – Poaceae (1), the lower number – 13 were found in Fabaceae (16), and 7 by Asteraceae (10), as well as in Cyperaceae (2), 6 other species were noticed in Rubiaceae (28), 3 in the families of Orchidaceae (4) and Acanthaceae (5), and at least 2 in Apiaceae (8), as well as in Polygalaceae (26). Ŀe comparison with data from temperate climate conditions may be interesting: the meadow Arrhenatheretum elatioris near Cracow (Poland), in time of investigations of Medwecka-Kornaś and Kornaś (1963), contained 71 plant species from 21 families, among them 18 various grasses, and a xerothermic grassland hvalictro-Salvietum on Małopolska Highland – 83 plant species from 23 families, with 12 species of grasses (Medwecka-Kornaś 1959). hvalictro-Salvietum belongs to a vegetation type formerly o en burned o.

Quantitative share of observed species On the rst studied savanna plot apart from the 73 herbaceous plant species, 5 taxa of trees and chie y shrubs were found, and on the second plot apart from 80 herbaceous species, 8 taxonomic units of shrubs and 3 of small trees were ascertained. Ŀe grasses included 22 species – 15 on the rst and 19 on the second studied plot. Ŀe low share of trees was partly due to their exploitation – on the second studied plot the single felled trunks were observed. Several trees were growing in the adjacent, and further situated parts of the savanna; soil and climate conditions were, therefore, suitable for plants of this type.

Ŀe quantity of particular plant species in the two studied plots of vegetation was uneven, chie y among the grasses (Tab. 2). Ŀe most important of them – Hyparrhenia lipendula attained the 4'ḩ degree of coverage (on Plot 2), other components of this group had a lower part, estimated even as only 1 or +. Among other species, belonging mostly to Magnoliopsida (Dicotyledones), the quantitative role was rather levelled – estimated as the 2"ª or lower degree of coverage (Tab. 3 – Appendix 1). Ŀe second plot of investigations was distinguished by a slightly richer ora – only there were found e.g. the tree Strychnos cfr. cocculoides (19) and among the herbaceous plants e.g. Indigofera vicioides (16), Vigna antunesii (16), and hvesium unyikense (29). During the author’s investigations in Zambia, the pyrophytes were noticed not only on the selected studied plots but also – chie y by Jan Kornaś – in numerous other localities (see pages 48–52).

Ecological types and classi cation of plants on the studied plots Ŀe observed plants were able to endure con agrations owing to various features connected with their structure, seasonal development, and ways of regeneration. Ŀe type and structure of underground parts were very important (cfr. enclosed pictures), as well as the location of renovating buds, a basic criterium in the Raunkiaer’s plant classi cation (considered here below and in chapter with plant descriptions). Concerning this, on the investigated plots the following groups of species can be distinguished:

Phanerophytes – trees, and shrubs – can survive res owing to the resistant bark and sometimes also the resistant leaves or buds. Shrubs have more o en also the possibility of regeneration by new sprouts regrowing from the parts in the soil. On the studied plots 11 species of the mentioned group were found, belonging – with some exceptions – to the family Fabaceae: e.g. the tree Erythrina abyssinica (16), as well as two taxa occurring as tree or shrub – Albizia cfr. glaberrima (16) and Strychnos coculloides (19). Ŀe tall shrubs with a height above 50 cm were represented chie y by Acacia pilispina (16), Dichrostachys cinerea (16), and Vitex mombassae (34). As a small shrub Desmodium velutinum (16) was noticed.

Chamaephytes – plants with woody stems up to 50 cm high – were observed only in the additionally distinguished group of geoxylic su rutices (located below on the last position) – to such chamaephytes there were classi ed e.g. Lannea edulis (6) and Parinari capensis (12).

Hemicryptophytes – perennial plants with regenerating buds on, or near the soil surface, where they can be protected by plant litter, small parts of the soil, old leaves, and some basic parts of stems. Ŀis group was the most numerous on the studied plots and numbered about 60 species. Owing to some di erences in structure and the way of re survival, the following ecological groups can be distinguished among them: plants with clusters of leaves and clusters of rather thin roots e.g. Andropogon schirensis (1), Brachiaria humidicola (1), and Justicia elegantula (5), plants with similar structure, but with stolons on the soil surface or rhizomes in the soil. To the group belongs a majority of noticed grasses (1), e.g. Hyparhenia lipendula, Setaria sphacelata, Tragopogon spicatus, and among non-grassy species Annona stenophylla (7). At least it can be mentioned a group with roots partially thickened (mostly in the upper part) and single shoots represented by species belonging to various families e.g. Brachiaria brizantha (1), Aspilia pluriseta (10), Dicoma plantaginifolia (10) and Trichodesma ambacense (11). Ŀe hemicryptophytes were distinguished also among further described “geoxylic su rutices”.

Geophytes (terrestrial part of a larger group – cryptophytes) – plants with renovating buds localised in the soil. On the studied plots, they were not numerous, numbered 7 species noticed chie y sporadically. Among them there can be distinguished some plants with relatively small tubers, namely Gloriosa superba (3), with tubers about 1–1.5 cm in diameter: Littonia littonioides (3), Eulophia pyrophila (4), and only one species: Adenia goetzei (23) with larger tubers of about 6 cm in diameter, located deeper, 4–7 cm under the soil surface. As a plant of transitional character between geophytes and hemicryptophytes Eulophia cfr. livingstoneana (4) with tubers on the short rhizomes, situated on – or below – the soil surface, can be considered. To this group, it can also be included some part of “geoxylic su rutices”, distinguished additionally and treated here below. In spite of this, the share of geophytes in the vegetation of studied plots is considered as low. It is connected with the fact that unfavourable high soil temperatures (evolved under re in uence, noticed in the tropics) occur not so deep under the earth’s surface as the frost impact in the regions with cold winter.

ffierophytes – the annual plants regenerating (also a er a re) from the seeds protected by plant litter, or saved in the soil. Ŀis group was not numerous on the studied plots, numbered only 6 species, e.g. the grass Dactyloctenium aegyptium (1) and from Magnoliopsida e.g. Polygala petitiana (26) as well as Spermacoce dibrachiata (28). It is worth noting that several plant species can develop the perennating buds not only in one location and therefore represent more than one plant type in the Raunkiaer’s classi cation. And so as hemicryptophyte or geophyte were classi ed e.g. Abildgaardia lementosa (2), Cyperus margaritaceous (2), Eulophia livingstoneana (4), and Diplolophium zambesianum (8). As chamaephyte or hemicryptophyte there were considered Lannea edulis (6) and Pygmaeothamnus zeyheri (28), as phanerophyte or hemicryptophyte Ectadiopsis oblongifolia (25) and as hemicryptophyte – geophyte Eulophia livingstoneana (4). Such a situation may be found also in the ecological unit described below.

Geoxylic su rutices – a group of plants distinguished additionally, independently of the Raunkiaer’s classi cation. Ŀis group includes plants with low, above-ground herbaceous stems (in the author’s study noticed as 45–75 cm high) and with woody underground parts. Among them there can be distinguished the species with woody taproot relatively thin like Hibiscus rhodanthus (20, Medwecka-Kornaś 2013) or thickened, found e.g. in Lannea edulis (6), Cussonia corbisieri (9) – with root-trunk 4 cm in diameter and Clerodendron pusillum (34). A similar root, located horizontally was found in the case of Ectadiopsis oblongifolia (25). Some of the other groups of geoxylic su rutices include plants with woody rhizomes or trailing rootstocks: namely Parinari capensis (12) and Combretum platypetalum (13) as well as Ochna leptoclada (22), Pygmaeothamnus zeyheri (28) and Psychotria spithamea (28). Ŀe discussed group, speci ed as “African geoxylites”, concerning plants belonging to Proteaceae in Southern Africa was described by Lamont et al. (2017). From the point of view of Raunkiaer’s classi cation (1934), the particular geoxylic su rutices can be considered as chamaephytes, hemicryptophytes, geophytes, or as combined – two or even three – ways of regeneration (Burt, Davy, 1972). Description according to their ecological features is illustrated in gure (36).

Explanations:on the le margin = family numbers according to the text on pages 18–38; * – samples taken from plants out the permanent studied plots; the water measurements apart from the plant roots, comprised samples of bulb and rhizome by Gloriosa superba and of a bulb by Pachycarpus lanceolatus; measurements carried out in the second year of investigations are bolded; XI–III – months of the rainy season

Water content in plant underground parts Ŀe important features of plants – especially in dry, even seasonally climate conditions (as in Zambia), belong to their water regime and content of water (e.g., Wiliamson, 1987). Ŀis second feature was measured by the author concerning selected species (Tab. 4).

Plant roots and in some cases bulbs or rhizomes, parts the most important for re survival and regeneration, were taken into consideration. Ŀeir samples were of various sizes regarding the di erent dimensions of particular species. Ŀe di erence between fresh weight (at the beginning) and the dried samples was considered as the result of water loss and simultaneously as their former content in plants.

Ŀe mentioned values were in some parts depending on the time interval between the rst and the second measurement. Ŀe important fact is that the majority of samples revealed higher than 50% or 60% and sometimes even about 70% of water content. Samples from the studied plots provided from the dry season (April to October) revealed similar values: 51–72%. For comparison the water content in potato bulbs may be quoted: it equals 77%.

Seasonal development of the observed species, occurrence of seedlings

Soon (in 2–3 weeks) a er burning the degree of soil coverage by vegetation on the studied plots was low and measured 30–40%. Some plants were however in the stage of

owering and attained 20–30 cm high. Ŀe res in August and October before the rainy season, with favourable plant living conditions, were very favourable for their further development. In the phenological development, there were, however, some similarities, as well as di erences between species and species groups (cfr. Tab. 5 – Appendix 1 and data in chapter with plant descriptions).

Grasses (1) had (and usually play) the most important role in the development of savanna vegetation a er a re. About two weeks a er con agration (on the rst plot at the end of August), and still in the dry season: their young leaves (usually in clusters) were up to 10 cm high. In the rainy season, at the beginning of January, their turfs attained 30–40 cm, and their owering shoots 50–70 cm in height. At the end of this month, tu s of grasses were fully developed and some of them produced stolons. Near the end of February, the discussed plants were up to 2 m high on the rst, and still taller on the second plot (see chapter – a structure of vegetation in full development). Ŀe fructi cation of grasses (like e.g. Hyparhenia lipendula on Tab. 5 – Appendix 1) was observed mainly in the rainy season, from November (or next months) until April.

Sedges (2) on the studied plots occurred scarcely. Ŀey were visible mainly in the rainy season (November-March). At the beginning of this time, new leaves appeared e.g. in Abildgaardia hispidula. In November the owering and the beginning of fructi cation took place. Some owers and fruits were observed also later – in December and January. In other sedges, e.g. Cyperus margaritaceous and Scleria bulbifera, owers and fruits occurred mostly in January, and in Abildgaardia lamentosa they were registered in April. Ŀose observations are consistent with the description and diagram of Medwecka-Kornaś and Kornaś (1985). Specimens of Cyperaceae from the described studied plots, as a rule, had distinct re traces: burned up leaves and stems with charred remnants 1–1.5 cm above the soil surface.

In other species (families 3–35), it is worth noting that numerous observed plants developed owers and o en also fruits soon (in two-three weeks) a er the occurrence of re, at the end of the dry season. At the end of October, the fruits or seeds were observed e.g. in Dicliptera melleri (5), Launaea nana (10), and Hibiscus rhodanthus (20). Ŀeir dissemination took place therefore mostly before the rainy season. Owing to this, the following development of seedlings was possible in moist conditions. Noteworthy is the fact (also described in the literature) that plants owering from short shoots a er re di er greatly from those that “escaped” and did not burn for two or more years.

Ŀe seedlings, which are of the greatest importance for the development of annual plants, were rarely noticed in the research plots. And so, e.g. the seedlings of Diplolophium zambesianum (8) with dimensions of 7 cm, were noticed in December. More complete observations concerned a rather common species Triumfetta heliocarpa (32). Its relatively large fruits were developed in the second half of October, as well as in November, then they fell on the soil surface. Ŀe seedlings appeared at the end of February. Seedlings of Fadogia cienkowskii (28) about 13 cm high were found at the end of May. Ŀerefore the dissemination took place before the rainy season and the development of young plants a erward. Ŀe young plants can survive res at least in some not burned fragments of vegetation.

Common phenological aspects of the studied savanna plots In connection with the seasonal development of species quoted above, the whole plant community has changed its aspects, so that at least its three distinct phonological phases can be distinguished:

1) Ŀe early stage of development of vegetation, 1–2 weeks a er a re, which was the period of owering of several non-grassy species; it fell in the second half of the

dry season, in August and September. Bare ground, covered with ash in places, was at this time visible between the low tu s of grasses which had been partly burned o, but already developed the rst new leaves. About half of all non-grassy species were then in bloom. Ŀey produced owers before the leaves or simultaneously with them. Most parts of the owers were situated on the soil surface or just above it (in the so-called “basi orous position”). Some plants set already fruits, but the main period of fructi cation occurred slightly later, just before or at the beginning of the rains in October and November (it does not concern the grassy species with seeds ripening a erward).

2) Ŀe stage of the optimal development of grasses, occurring from October through the middle of the rainy season, to February. At that time ground was completely covered with dense vegetation, dominated by owering and fruit-bearing plants of Poaceae. Most of the dicotyledonous species, very low at the time of owering, had well-developed assimilating organs of considerable dimensions (e.g. Lannea edulis (6) with leaves up to 40 cm long).

3) Ŀe period of gradual drying of vegetation a er the rainy season, from April-May till the next con agration; only some species had then owers and/or preserved fruits. Ŀe grasses were turning yellow and wiry at the beginning of that time, and the majority of other plants lost their leaves or herbaceous shoots. Ŀere were only very few specimens that retained green leaves or owers till the next re. Ŀe soil remained then completely shaded by the densely crowded dead shoots of grasses.

ffie structure of the studied plant cover in full development During the full development of studied vegetation (phase 2 in the chapter above) the coverage of ground by plants attained 90–95%. Some dominating grasses (cfr. family 1) were more than 1 m (up to 2 m) tall. To the highest ones belong Brachiaria humidicola, Digitaria milanjiana, Hyparrhenia lipendula, Hyperthelia dissoluta, Setaria sphacelata, and Trachypogon spicatus. Relatively tall was also Psorospermum baumii (17). Lower, a medium layer of vegetation about 40–80 cm high was formed e.g. by Annona stenophylla (7), Cyphostema rhodesiae (35), Scutellaria schweinfurthii (18), and Sesamum angustifolium (24). Ŀe lowest layer comprised plants up to 20–30 cm high and had some sedges, but occurring scarcely, as well as several other species e.g. Indigofera vicioides (16), Hibiscus rhodanthus (20), Parinari capensius (12), hvesium unyikense (29) and Tricliceras longipedunculatum (33). Ŀe soil surface was then covered by stolons of some plants, e.g. of grass Brachiaria humidicola (1) and dicotyledons: Astripomea malvacea (14), Gardenia subacaulis (28), Pygmaeothamnus zeyheri (28). Ŀe height of some registered plants was lower than that described in the literature, e.g. in Flora Zambesiaca. Perhaps the observations cited there were made at longer intervals a er the re or even in unburned places. It is noteworthy that other plants could grow underneath the plots, despite the relatively dense layer of grasses. Ŀis brings to mind some of the elds in Europe, in particular those with old tall cereal varieties and with numerous weeds, much lower.

Some phytosociological features of the observed vegetation Ŀe oristic composition of plant communities on both studied plots is presented in the table (2) and (3) – Appendix 1. Ŀe rst one contains the grasses, treated separately concerning the limited number of their concerning phytosociological records. Such a situation resulted from the di culties related to the problem of species identi cation during their vegetative phases, without spikelets – owers and seeds. Among grasses, the most important – in terms of quantity – turned out to be: Hyparhenia lipendula, Eragrostis racemosa, and Setaria sphacelata. Sedges were represented so scarcely that information about their occurrence is presented with one exception of Cyperus margaritaceous (2).

Ŀe phytosociological table contains the representants of Liliopsida and chie y Magnoliopsida (Tab. 3 – Appendix 1). Ŀe highest constancy degree attained 4 species, e.g. a shrub Securidaca longipedunculata (26 – family number), and among the herbaceous plants 15 species, e.g. Trichodesma ambacense (11), Triumfetta heliocarpa (32) and Annona stenophylla (7). Perhaps species unnoticed in some records were – during the particular investigations – undeveloped or underdeveloped, without owers or fruits, thus di cult to observe. Ŀe mosses Bryophytes were found very scarcely. Some phytosociological records revealed small di erences between plots 1 and 2. Ŀe rst one had a lower share of trees and shrubs and a slightly lower number of other species – 48, in comparison with 54 on Plot 2.

Additional information about the pyrophytic plants

beyond the studied plots Ŀe species which grew on the studied plots, as well as several other plants of a similar ecological character, were found in Zambia in various localities with the occurrence of re: in savannas and grasslands, shrublands, and even in some parts of the miombo forests. Ŀere are two methods of determination of such species and their distribution: eld observations on the burned plots and study of plants with re scars in the herbarium. Both methods were applied to ferns, grasses and sedges, mentioned below. In the case of other plants, the rst way of treatment was mainly adopted – concerning them the studies based on the large herbarium material would be too di cult.

Ferns and some others Pteridophyta Information about the occurrence of those plants in Zambia may be found chie y in several publications of Jan Kornaś; drawings of the mentioned plants and maps of their distribution are included in some of them. In the main paper (Kornaś, 1979), the re is broadly taken into account. Ŀe author wrote that more than 20% of Zambian pteridophytes at least occasionally survive burning; information about their distribution is presented in the text and on dot maps. A list of 25 pyrophytic fern species is supplemented to the 1978 and 1988 publications. For 18 of them, detailed information about the localities in Zambia may be found in the schedule of Kornaś (1977a, b). To the described pyrophytic ferns belongs, e.g. Pteridium aquilinum a rhizome geophyte and cosmopolite, known in Europe, including Poland. Ŀe information – in the notebook of Jan Kornaś – about the presence of 9 species of ferns in the Forest Reserve with re experiments near Ndola (Northern Zambia, Trapnell, 1959) is also interesting. Ŀere was reported, e.g. Nephrolepis undulata, a species highly re-resistant, growing on sites that are burnt in each dry season (Kornaś, 1978).

In 1975 Kornaś drew attention to the ecology of a very interesting species of the Pteridophyta, a club-moss Lycopodium carolinianum var. tuberosum, which has subterranean tubers not accessible for re. Ŀe large population of this species was found in Zambia (also by the present author) on the burned grasslands at the Great East Road.