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Ben-Gurion University of the Negev (2010)

Spatial and temporal effects on recruitment of the Palestine oak Quercus calliprinos within pine plantations in Israel

Ben-Yair Shani

Titre : Spatial and temporal effects on recruitment of the Palestine oak Quercus calliprinos within pine plantations in Israel

Auteur : Shani Ben-Yair

Université de soutenance : Ben-Gurion University of the Negev

Grade : Master of Science 2010

Résumé
Recruitment of native species in forest understory may have an important positive effect on forest sustainability. Factors controlling sapling recruitment are usually divided to limitations on the availability of seeds vs. limitations on the availability of establishment sites. Forest structural complexity may affect both the spatial pattern of seed and site availability, through the modification of biotic (such as seed predator activity) and abiotic (such as light level) conditions. Light level in particular is a key factor in the recruitment of many populations, especially in water-limited ecosystems. and several hypotheses predict plant response to shade in water limited conditions. Temporal variation among years in climate conditions or during the season in seed arrival time may also affect recruitment. The aim of this research is to study the recruitment of Q. calliprinos, the dominant tree of the Mediterranean woodland in Israel, in planted pine-forest understory. I tested the combined effect of spatial forest complexity due to pine density and of temporal variation in climatic conditions (among years) and seed arrival (during the dispersal season) on post dispersal acorn predation, seedling emergence, seedling establishment and development. I performed two sowing experiments, one in plots protected from predation, to test for seedling emergence, establishment and development, and another in unprotected plots to test for acorn predation. I also surveyed natural population structure, including adult density and seed production in the forest and the neighbor woodland to estimate the natural recruitment success and population growth. I hypothesized that following seed arrival, forest complexity in pine density affects recruitment of native species through (1) the effect of tree density on the spatial pattern of seed loss by predation, and through (2) the effect of variation in forest canopy and light levels on the spatial distribution of sites. An overlap between the spatial pattern of seeds and sites may be crucial for the recruitment success. I also hypothesize that the relative importance of seed vs. site limitation will vary among years or within the year due to variation in the time of seed arrival. Early seed arrival may improve the probability of seeds to escape from predation, to emerge and establish. My research showed the importance of both spatial and temporal effects on seedling recruitment. According to my results the suitability of a patch for seed survival, seedling survival and development may not overlap, which restricts oak recruitment within the forest. In particular I found that conditions that are suitable for seedling survival do not promote vigorous development, and vice versa, resulting in a "tradeoff" between seedling development and survival. These results suggest that oaks require shade at early stages to improve seedling survival, and light at later stages to enable vigorous development.

Mots Clés : European Turkey oak — Israel. — Forest ecology — — Pine — Breeding — Plantations — Experiments. — Understory plants — Israel

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Page publiée le 7 janvier 2012, mise à jour le 22 novembre 2018