Fruit maturation patterns of Carya spp. (Juglandaceae): an intra-crown analysis of growth and reproduction.

Fruit survival patterns, from fertilization to maturation, were examined for Carya ovata and C. tomentosa in a New Jersey USA forest. We observed fruiting and shoot growth characteristics over a 3-yr period to determine: (1) the patterns of fruit survivorship (from initiation to maturity) within and among years, (2) the relationships between shoot growth, fruit initiation, and fruit survival to maturity, and (3) the influence of phytophagous insects on fruit survival. We found that within years, smaller infructescences (1-2 fruits) exhibited greater relative survivorship than larger ones (3-4 fruits); however, absolute nut production was greatest for mid-sized infructescences (2-3 fruits). Among years, fruit survivorship varied considerably within populations. Across the 3-yr period we observed average fruit survivorship to be convex, linear, and concave, respectively. Likewise, shoot characteristics (length, width, number of leaves) varied concomitantly (decreasing fruit survivorship was accompanied by decreasing shoot length and number of leaves). Within years, we found no strong relationship between shoot characteristics and infructescence size and survival. The patterns of tree-to-tree variation suggested a strong genetic basis to shoot growth and fruit maturation. However, patterns of variation within and among years also indicated a strong environmental influence on these traits as well. Natural phytophagy by insects was observed to be low (<5%); however, shoot defoliations of 10-25% were not uncommon. Experimental defoliations (ambient, 10-15%, 20-40%, and 75-100%) did not result in reduced survival to maturity. Collectively, the data suggest that year-to-year variability in shoot growth has a greater influence on fruit maturation patterns than within year fruit-shoot relations.