Macroscopic and microscopic study of mature

Macroscopic and microscopic study of mature

Floristic and ecology study of vacant lots of Mexico City
Martha Eugenia Díaz Betancourt
Considering 100 floristic samples colected in
urban lots in Mexico we recorded a total of
317 species of spontaneous vascular
plants.The majority of the registered species
(227) are native of Mexico (71%) mean while
the rest 90 species, are introduced from
different countries.While analyzing the flora
of the Valley of Mexico of Rzedowski &
Rzedowski (1979, 1985, 1990), there were
considered a total of 1019 species for the
metropolitan area with 898 native species
(88.1%) and 121 alien species. In both urban
lots and metropolitan area, most of the
species belong to the families Compositae
(18%) and Gramineae (12 % to 14%).
In urban lots the majority of the species are
perennials (65%), almost 30% are annualsbiannuals and only 5% are considered
annuals-perennials mean while in the
metropolitan area 70.5% of species are
perennials, 22% are annuals-biannuals and
6.8% are annuals-perennials.
The native component represent 30% of the
flora in vacant lots and 44% in the
metropolitan area. Within the alien species the
European element was the highest (22% for
the vacant lots and 34% for the metropolitan
area).
Species with highest distribution and
frequency (91%) in vacant lots was the
aggressive grass Pennisetum clandestinum
introduced from Africa.
Weeds and the incipient aggressive species
represent nearly 58% of total flora of vacant
lots and 42% for the flora of metropolitan
area.
Correlation analysis between the species
richness and the environmental variables
shows no significant results. However, there
are several tendencies to take under
consideration to test various hypothesis in the
future. Among these, the increase of species
richness and the relation with the lot size and
the effect of the rubbish over the pioneer
species number.
http://www.biotaneotropica.org.br
About the rain factor it can be expected that
the vacant lots located in the more humid area
of the city (south west) could have a larger
number of species. However, this fact is
present only for the native species. This
phenomenon can be explained partly due to
moister areas located in the suburbubs of the
city have a major influence of the peripherical
vegetation that is basically formed by native
elements.
Finally, classification analysis resulted in
three groups, associated to an anthropological
gradient separating censuses with a higher
human activity and with the presence of the
European species Malva parviflora of the most
distant suburban areas and relatively less
disturbed.
Key-words: Alien, annuals, flora, natives,
perennials, species richness, vacant lots,
urban ecology.
DATOS DEL CATALOGO DE
PUBLICACIONES
Sistema Bibliotecario de la Facultad de Ciencias
de la Universidad Nacional Autónoma de
México
Diaz Betancourt, Martha Eugenia
Estudio florístico y ecológico de los terrenos
baldíos de la Ciudad de México. México,1999.71 p.
Tesis Maestría (Maestría en Ciencias (Biología).
Universidad Nacional Autónoma de MéxicoUNAM, Facultad de Ciencias
Asesor: López Moreno, Ismael Raúl
Titulo en ingles: Floristic and ecology study of
vacant lots of Mexico City
Palabras clave: México, estudio florístico, ecología.
e-mail autora: [email protected]