The demography of space occupancy: measuring plant colonization and survival probabilities using repeated pin‐point measurements

Abstract

Summary1. The study of plant demography has long been an important component of plant ecological studies. However, in plant communities, e.g. grasslands, where individual plants are not easily distinguished and often vary in size, a convenient method of describing the demography and its ecological consequences has been lacking. 2. The aim of this study was to discuss the potential for using the change in the probability of space occupancy as a measure of ecological success in plant population biology. This will be done by demonstrating how the change in the probability of space occupancy depends on the processes of colonization and survival, and demonstrating how colonization and survival probabilities may be estimated from repeated pin-point recordings at the same pin-position. Furthermore, it will be demonstrated how to calculate the sensitivity and elasticity of the change in the probability of space occupancy to colonization and survival probabilities. 3. The method is applied to a case of repeated pin-point data of the perennial grass Brachypodium phoenicoıdes that underwent different grazing regimes from 2001 to 2008 on xero-halophytic grasslands. 4. It was demonstrated that grazing affected both plant survival and colonization probabilities so that the estimated colonization and survival probabilities of B. phoenicoıdes were highest in the nongrazed regime. Furthermore, using the calculated elasticity of the change in space occupancy, we found that survival was more important than colonization events in determining the ecological success of B. phoenicoıdes in the non-grazed regime, whereas colonization events were more important than survival in the grazed regime. 5. Synthesis and applications. We expect that the relatively simple method may be widely used on existing and future repeated pin-point recordings from the same pin-position and, consequently, that plant demographic questions may be addressed with larger precision in plant communities where individual plants are not easily distinguished.

Comparing the accuracy of three non-destructive methods in estimating aboveground plant biomass

“…The point intercept method provides information about three dimensional vegetation structure (Godínez-Alvarez et al 2009, Jonasson, 1988, and repeated point intercept method is also suitable for plant demography studies due to its precise positioning within the sampling unit (Damgaard et al 2011). However, we found that the method is not superior over other methods in the accuracy of biomass estimation.…”

The Effect of Nitrogen and Glyphosate on Survival and Colonisation of Perennial Grass Species in an Agro-Ecosystem: Does the Relative Importance of Survival Decrease with Competitive Ability?

“…The quantitative effect of survival and colonization processes on population growth of individuals is most effectively summarized using population models [28], and the calculation of elasticity (the relative contribution of different demographic parameters on population growth rates) has particularly been shown to be a powerful tool to investigate the importance of different demographic variables in determining population growth [18].…”

“…grasslands, it is often difficult to distinguish individual plants due to their vegetative growth pattern and, consequently, to obtain reliable demographic data. Instead, it is possible to measure “colonization” and “survival” by considering the turnover of a species at a specific spatial point [18]. Considering such a specific spatial point, then if the species was present at time t but absent at time t +1, we may loosely speak of a mortality event, and if the species is absent from a specific pin-position at time t and present at time t +1, we may loosely speak of a colonization event [18].…”

“…Instead, it is possible to measure “colonization” and “survival” by considering the turnover of a species at a specific spatial point [18]. Considering such a specific spatial point, then if the species was present at time t but absent at time t +1, we may loosely speak of a mortality event, and if the species is absent from a specific pin-position at time t and present at time t +1, we may loosely speak of a colonization event [18]. We have chosen to use the term “colonization” rather than “recruitment”, since the event is defined by a novel occurrence in space [19], [20].…”

Self-reseeding annual legumes for cover cropping in rainfed managed olive orchards

“…The ground covered by the sown species relative to weeds and uncovered bare soil was assessed by the pin point method, which measures the proportion of ground occupied by a perpendicular projection on to it of the aerial parts of the plants (Damgaard et al, 2011). A frame with a fixed grid pattern was placed randomly…”