Dynamic management needs for long‐lived, sporadically recruiting plant species in human‐dominated landscapes

Abstract

Societal Impact Statement Long‐lived, iconic plant species like the baobab, welwitschia, the saguaro cactus or the dragon's blood tree are perceived to be everlasting landscape features due to their pronounced longevity. However, these species are exceptional because new reproductive generations of these plants are infrequently incorporated into existing populations. A strong mismatch exists between the timescale at which these species provide services to society and ecosystems, and the timescale at which their reproductive stages and population development occurs. Here, we draw attention to these mismatches and their relevance for nature conservation and restoration. We argue that more dynamic management programs are necessary to preserve these iconic species for future generations. Summary Plants inhabiting variable environments have to adapt their physiology or demography to maintain fitness and, thus, long‐term population viability. Demographic storage through long‐lived seeds, juveniles, or adults help to overcome periods where unfavorable environmental conditions preclude successful recruitment into reproductive stages. Such storage components can foster long‐term population viability of sporadic recruiters, defined here as species with infrequent recruitment caused by a sporadic release from otherwise prevailing resource limitation. However, the beneficial effect of environmental variation reaches a limit when the species' physiological limits are exceeded or the demographic storage components are not sufficient to overcome periods of unfavorable environmental conditions. This can threaten species' long‐term population viability in an increasingly variable, human‐dominated world. At the same time, long‐lived, sporadically recruiting species provide numerous cultural, socio‐economic, and ecological services by being part of local myths and beliefs, or by providing habitat, food, wood, fiber, cosmetic, or medical products. In this contribution, we seek to raise awareness of what we call the ‘syndrome of long‐lived sporadic recruiters’ and the relevance of this syndrome for nature conservation and restoration. We outline key demographic features and highlight the main environmental threats for these plants, exemplified for a set of globally distributed charismatic plant species. We propose that fostering the long‐term population viability of long‐lived, sporadically recruiting plants will require the adaptive implementation of a dynamic management scheme where management actions, monitoring objectives, public outreach and research on the key demographic features of the species are coordinated.

Keywords

• climatic predictability
• disequilibrium
• disturbance
• ecological memory
• extinction debts
• historical legacies