Soil Resource Heterogeneity Effects on Early Succession

Abstract

Heterogeneous soil resources may cause vegetation heterogeneity on abandoned fields and grasslands. We tested effects of resource enrichment and heterogeneity at scales from a single plant to small plot community on vegetation composition and rate of early succession on two fields. Enriched plots of three heterogeneity scales were established by fertilizing alternate trenched subplots. Unenriched plots were established with trenched but unfertilized subplots as controls for trenching heterogeneity. Vegctation was censused every other year for six years. We asked if nutrient enrichment or heterogeneity affects vegetation diversity or rate of succession. and if resource effects change over time. Species richness was lower in fertilized plots on both fields. Species turnover reflected an early gain of species on one field and loss on the other. Turnover differed between enriched and unenriched plots. but not over heterogeneity scales. Plot enrichment, but not heterogeneity, influenced initial abundance and establishment of a a dominant Ambrosia trifida, on one field and the later dominant Solidago altissima on the other field. Ambrosia responses slowed. and Solidago responses increased. succession on enriched plots. There was a weak trend of increasing strength of soil resource effects over time in both fields. We found no strong evidence that vegetation tracks soil resource heterogeneity of the patch sizes. arrangement. and contrast tested. However. differential growth of the dominant species and richness of minor taxa between enriched and unenriched plots created vegetation heterogeneity on both fields through early succession.