Flowering dynamics of Orchis morio L. and Herminium monorchis (L.) R.Br. at two sites in eastern England

Abstract

Information taken from two long-term demographic studies on Orchis morio L. and Heminiurn monorchis (L.) R.Br. is used to explore some of the factors which influence flowering. The proportion of plants which flowered each year varied considerably between species, flowering in 0. morio exceeding 40% in all years except one over an 18 year period; over a 30 year period , the number of plants of Herminium in flower never exceeded 36% of the population and no inflorescences were produced in 1977 and 1991. The relationship between flowering in Heminiurn in a given year and the monthly rainfall and temperature for the current and 3 previous years was analysed using logistic regression. Best fits were obtained using data for the summer months in the previous year, with an increasing flowering rate with rainfall and a decline with temperature. It is hypothesized that drought and high temperatures in the summer reduce leaf area and cause premature senescence and the death of leaves, with the result that not enough carbohydrates are stored to enable plants to support or initiate inflorescences the following year. For species such as Orchis morio which produce leaves in the autumn and remain green, summer drought causes no problems as they have no above ground organs. Factors which influence flowering in this species are as yet unknown. 0 1998 The Linnean Society of London ADDITIONAL KEY WORDS:--climatic factorsdroughtinflorescence initiation logistic regressionorchidsplant performance.

The intimacy between sexual traits and Grime’s CSR strategies for orchids coexisting in semi-natural calcareous grassland at the Olive Lawn

“…Despite persisting for several years plants are in many ways 'analogous to winter annual plants' (Hutchings 1987). Early flowering has also been recorded in British populations of A. morio and interpreted as an adaptation to avoid summer heat and drought, using essentially a Mediterranean life cycle (Wells et al 1998). At the opposite extreme A. pyramidalis and N. tridentata had large leaves and intermediate leaf Fig.…”

Demographic responses of boreal-montane orchid Malaxis monophyllos (L.) Sw. populations to contrasting environmental conditions

“…Despite growing interest in this problem, empirical evidence is relatively scarce. In the case of orchids, the influence of climate has most often been studied in the context of reproductive traits, which both in case of terrestrial and epiphytic orchids suggest precipitation as the main factor [98,99]. Connections of M. monophyllos with wet environments, together with an increase in large-scale precipitation in northeast Europe in the coming decades [15] suggest that populations in the boreal part of its range will presumably possess optimal conditions to persist.…”

Variation in size-dependent fitness components in a terrestrial orchid, Dactylorhiza majalis (Rchb.) Hunt et Summerh., in relation to environmental factors

“…In some species, increased plant size leads to higher flowering pro-bability and/or greater production of flower or greater allocation of resources to flowering (Calvo 1990;Willems and Ellers 1996;Willems and Melser 1998;Primack and Stacy 1998;Wells et al 1998;Brzosko 2002Brzosko , 2003Gregg 2004;Hrivnák et al 2006). According to Wells et al (1998), Willems and Dorland (2000) and Kull (2002), in some terrestrial orchids, achievement of a threshold size for reproduction is required for flowering.…”

“…In some species, increased plant size leads to higher flowering pro-bability and/or greater production of flower or greater allocation of resources to flowering (Calvo 1990;Willems and Ellers 1996;Willems and Melser 1998;Primack and Stacy 1998;Wells et al 1998;Brzosko 2002Brzosko , 2003Gregg 2004;Hrivnák et al 2006). According to Wells et al (1998), Willems and Dorland (2000) and Kull (2002), in some terrestrial orchids, achievement of a threshold size for reproduction is required for flowering. However, flowering does not only depend on the condition of a plant (expressed in size), but is also determined by external factors such as habitat, community structure and climate (Willems and Ellers 1996;Dijk and Grootjans 1998;Wells et al 1998;Brzosko 2002Brzosko , 2003Janečková et al 2006).…”

“…According to Wells et al (1998), Willems and Dorland (2000) and Kull (2002), in some terrestrial orchids, achievement of a threshold size for reproduction is required for flowering. However, flowering does not only depend on the condition of a plant (expressed in size), but is also determined by external factors such as habitat, community structure and climate (Willems and Ellers 1996;Dijk and Grootjans 1998;Wells et al 1998;Brzosko 2002Brzosko , 2003Janečková et al 2006). Since there is general lack of information about the importance of environmental factors in size-dependent reproduction in terrestrial orchids, the objective of this study is to explore the effect of soil, topography and site management variables on the variation in size-dependent flowering probability and flower production of terrestrial orchid, Dactylorhiza majalis.…”