Identification of site-types important for rare ferns in an area of deciduous woodland in northwest Spain

The Eume woods in northwest Spain are an important refuge for a number of endangered ferns, including Culcita macrocarpa, Cystopteris diaphana, Dryopteris aemula, Dryopteris guanchica, Hymenophyllum tunbrigense and Woodwardia radicans. Because some of these species are inconspicuous or difficult to identify in the field, we attempted to develop simple floristic criteria to identify sites important or potentially important for these species (high-value sites). Having drawn up field-layer vascular plant inventories for 44 plots in the study area, we considered two major strategies. Under strategy 1, we looked for those conspicuous species which best discriminated between plots containing the endangered species (current-high-value plots) and all other plots. Under strategy 2, we first carried out a global plots-by-species classification using indicator species analysis (Hill et al. 1975) and then looked for those conspicuous species which best discriminated between groups containing current-high-value plots and all other groups. For our data set, the second strategy proved more effective. The best criterion identified was If two or more of Luzula sylvatica, Viola riviniana and Rubus spp. are present, then that plot is high-value. We include a listing of a BASIC program for the discriminant analysis algorithm, which we consider to have a number of potential applications in vegetation science and biogeography.     

An indirect gradient analysis of the ecological relationships between ancient and recent reiverine woodlands to the south of Bruges (Flanders,Belgium)

Summary Riverine forests to the south of Bruges were sampled according to the principles of the Braun-Blanquet approach. Cartographic data allowed a distinction between old (pre-1775) and recent (planted after 1775) woodland. Using a chi-square criterion and/or a Fisher exact probability test, the association of species with the two historical types of woodland was tested. Corylus avellana, Lamium galeobdolon, Primula elatior, Anemone nemorosa, Deschampsia cespitosa and Thamnium alopecurum are confined to ancient woodland. Glechoma hederacea, Prunus padus, Lysimachia nummularia, Ribes rubrum and Lychnis floscuculi have a significant affinity for recent woods.R-type prineipal components analysis produced an effective ordination of species and relevés. Interpretation of the scatter diagrams was performed using indicator values for the species and some environmental parameters for the relevés. Two major gradients were detected: the first one is the coenocline from wet, basic clay soils towards drier, more acidic, sandy soils. Anthropogenic dynamics, through the general management which effects the micro-climate in the wood, particularly the relative light intensity, has been recognized as the second ecological parameter.The potential natural vegetation of the valleys is thus determined primarily by soil texture and soil moisture, and secondarily by former land use (and age). It takes at least 200 years before old woodland species start to colonize recent woodland.We are much indebted to Prof. Dr. P. Van der Veken for his criticism of the manuscipt and to B. Kuziel en G. Dujardin for reviewing the English text.Nomenclature follows De Langhe et al. (1978) for vascular plants and Margadant (1973) & Margadant & During (1973) for bryophytes.Dedicated to the memory of Dr. Ir. G. Sissingh (1912–1979).This study was supported by a grant from the Instituut tot aanmoediging van het Wetenschappelijk Onderzoek in Nijverheid en Landbouw and since 1 October 1979 from the Nationaal Fonds voor Wetenschappelijk Onderzoek.     

Are habitat types compatible with floristically‐derived associations?

Abstract. The habitat type system developed by R. Daubenmire has been widely adopted throughout the western United States. Habitat types result from a site classification derived from the classification of late seral plant communities using selected indicator species. It has been suggested that the classification of late successional vegetation used to derive habitat types does not substantially differ from phytosociological classification in the sense of Braun‐Blanquet approach, and that habitat types can be adopted in their present form into floristically‐based vegetation classifications. Despite the many commonalities between the two systems, however, the classification methods, and specifically the use of indicator species in the habitat type system, yield a significantly different classification than the phytosociological approach. This is demonstrated in the comparison of a habitat type classification with the results of a recent phytosociological classification of forest vegetation in the northern Salish Mountains of Montana.     

Forest species in an agricultural landscape in the Netherlands: Effects of habitat fragmentation

Abstract. For 312 forest patches on sandy soils in the Netherlands, effects of fragmentation are studied of forest habitat in the past on the present occurrence of forest plant species. Using regression techniques, the numbers of forest edge, interior, zoochorous and anemochorous species, as well as occurrence of 24 individual species were related to patch area and connectivity measures. Connectivity was defined as the amount of forest habitat around patches within three zones up to 1000 m. Plant categories were distinguished by habitat type and dispersal mechanism. The results showed that number of total species and number of species of all habitat and dispersal categories increased with area. The occurrence of ten individually studied species were also positively related to area. Most of them were interior species. The number of zoochorous species increased with increasing connectivity. Also occurrence of ten individually studied species were affected by connectivity. Interior zoochorous species showed the highest percentage of affected species. The relationship of interior, animal-dispersed plants to connectivity can be explained by the limited distances covered by their dispersal agents (forest birds and ants) in a non-forest habitat. Also, some anemochorous plants appeared to be affected by connectivity, especially those with heavy seeds and potentially short distance dispersal. As not all species within a certain dispersal or habitat category react similar to area or isolation, it is suggested that differences in underlying processes of fragmentation such as local extinction and colonization need more focus.     

Do life history traits predict responses to defoliation in co‐occurring prairie grasses?

Abstract. This study examines whether competition between the unpalatable grass Hilaria mutica and three co‐occurring, palatable grasses in a Texan mixed prairie is altered by non‐selective or selective defoliation. In this four‐year study, plants were grown in monoculture or in combination with the unpalatable Hilaria in a replacement design. Under no defoliation, the unpalatable Hilaria had a lower growth potential than Bouteloua curtipendula and Nassella leucotricha that were of equal stature, and produced only as much as the shorter grass, Buchloe dactyloides. Bouteloua had the highest growth potential under no‐defoliation and was defoliation tolerant, except when defoliated at ground level. Nassella was more productive than the unpalatable Hilaria, since the ability to grow earlier in the year enabled it to compete successfully with Hilaria. These results indicate that with adequate deferment Bouteloua and Nassella should compete successfully with Hilaria and Buchloe should be able to maintain itself in the presence of Hilaria. Under non‐selective defoliation, Hilaria was able to compete successfully only with Buchloe. Hilaria was sensitive to defoliation, despite being rhizomatous, and competed less successfully with Buchloe after non‐selective defoliation than it did when not defoliated. This indicates that the management practice of burning and stocking heavily with livestock until Hilaria is avoided, resulting in non‐selective defoliation, will not cause Hilaria to be more competitive with the more palatable Bouteloua, Buchloe or Nassella. Hilaria was able to compete most successfully under selective defoliation when it was not defoliated. Under selective defoliation, by avoiding herbivory, Hilaria is able to compete strongly with at least Buchloe and Nassella. The reaction of Nassella and Buchloe to selective defoliation indicates that they may have been displaced by Hilaria in the past. In contrast, under the short‐term and non‐limiting growth conditions of this study, Bouteloua competed successfully with Hilaria even under selective defoliation. These results do not rule out the possibility that, through selective defoliation, Hilaria may have displaced other grasses including Bouteloua in the past.     

What helps Opuntia stricta invade Kruger National Park,South Africa: Baboons or elephants?

Question : Is Opuntia stricta more frequent, and its patches larger, under trees suitable for baboon roosting? If so, does it mean that baboons are major dispersal agents and that plants established under these trees are important foci of Opuntia stricta spread? Location: Skukuza, Kruger National Park, South Africa. Method: We surveyed an area invaded by Opuntia stricta in the Skukuza region of KNP. The survey included plots under potential baboon roosting trees,plots under trees unlikely to support baboons,and paired randomly located open sites. Results: The null hypothesis ‐tree‐Opuntia spatial independence – can be rejected for Acacia nilotica, but not for Spirostachys africana. Opuntia plants are positively associated with Acacia trees suitable for baboon roosting. However, there is no significant difference between frequency of Opuntia under Acacia trees suitable and unsuitable for baboon roosting.It appears that all Acacia trees can serve as nurse trees for Opuntia. Compared to plots under Acacia trees, frequencies of old and robust Opuntia plants are significantly higher in open areas and under dead trees. Conclusions: While baboons may be responsible for long distance Opuntia dispersal (over km),their role is not detectable at a local scale.On the other hand, elephants seem to contribute substantially to the local vegetative propagation of this species. Opuntia establishment and growth are more influenced by micro‐habitat than previously thought.