Removal of organic matter from the forest floor in loblolly pine plantations increased ground-layer richness and diversity 16 years after treatment

Abstract

Forest floor organic matter (forest floor, understory, and slash material) often serves as an indicator of soil quality and contributes to soil productivity. Silvicultural activities can affect this layer through common manipulations of slash on the forest floor. Few studies examine the long-term effects of changes in the organic matter on the ground-layer vegetation (below 1.4 m tall). We investigated the impact of forest floor organic matter manipulation after 16 years in a loblolly pine (Pinus taeda L.) plantation. We examined the cover, richness, diversity, and biomass of the ground-layer vegetation. Twelve 0.16 ha plots were established in a randomized complete block design following clearcutting of the previous 33-year-old plantation. The three treatments were: control (leaving unaltered), removing, and doubling the forest floor and slash material. In each plot, we established 15 1 m2 subplots. Ground-layer diversity in the doubled treatment was less than in the other treatments. Similarly, plant richness, total plant cover, and the cover of herbaceous, graminoid, and woody species were all significantly greater in the removed treatment. The removal of organic matter overall increased the understory richness, cover, and diversity but had a negative effect on stand yield compared to the doubled treatment and no effect compared to the control.