Restoration of biogeomorphic systems by creating windows of opportunity to support natural establishment processes

In degraded landscapes, recolonization by pioneer vegetation is often halted by the presence of persistent environmental stress. When natural expansion does occur, it is commonly due to the momentary alleviation of a key environmental variable previously limiting new growth. Thus, studying the circumstances in which expansion occurs can inspire new restoration techniques, wherein vegetation establishment is provoked by emulating natural events through artificial means. Using the salt-marsh pioneer zone on tidal flats as a biogeomorphic model system, we explore how locally raised sediment bed forms, which are the result of natural (bio)geomorphic processes, enhance seedling establishment in an observational study. We then conduct a manipulative experiment designed to emulate these facilitative conditions in order to enable establishment on an uncolonized tidal flat. Here, we attempt to generate raised growth-promoting sediment bed forms using porous artificial structures. Flume experiments demonstrate how these structures produce a sheltered hydrodynamic environment in which suspended sediment and seeds preferentially settle. The application of these structures in the field led to the formation of stable, raised sediment platforms and the spontaneous recruitment of salt-marsh pioneers in the following growing season. These recruits were composed primarily of the annual pioneering Salicornia genus, with densities of up to 140 individuals/m2 within the structures, a 60-fold increase over ambient densities. Lower abundances of five other perennial species were found within structures that did not appear elsewhere in the pioneer zone. Furthermore, recruits grew to be on average three times greater in mass inside of the structures than in the neighboring ambient environment. The success of this restoration design may be attributed to the combination of three factors: (1) enhanced seed retention, (2) suppressed mortality, and (3) accelerated growth rates on the elevated surfaces generated by the artificial structures. We argue that restoration approaches similar to the one shown here, wherein the conditions for natural establishment are actively mimicked to promote vegetation development, may serve as promising tools in many biogeomorphic ecosystems, ranging from coastal to arid ecosystems

The interaction of lexical and phrasal prosody in whispered speech

The production and perception of Dutch whispered boundary tones, i.e., phrasal prosody, was investigated as a function of characteristics of the tone-bearing word, i.e., lexical prosody. More specifically, the disyllabic tone-bearing word also carried a pitch accent, either on the same syllable as the boundary tone (clash condition), or on the directly adjacent syllable (no clash condition). In a statement/question classification task listeners showed moderate, but above-chance performance for both conditions in whisper, which, however, was much worse as well as slower than in normal speech. The syllabic rhymes of speakers' productions were investigated for acoustic correlates of boundary tones. Results showed mainly secondary cues to intonation, that is, cues that are present in whisper as in normal speech, but minimal compensatory cues, which would reflect speakers' efforts to enhance their whispered speech signal in some way. This suggests that multiple prosodic events in close proximity are challenging to perceive and produce in whispered speech. A moderate increase in classification performance was found when that acoustic cue was enhanced that whispering speakers seemed to employ in a compensatory way: changing the spectral tilt of the utterance-final syllable improved perception of especially the poorer speakers and of intonation on stressed syllables. (C) 2014 Acoustical Society of America