Effects of Row Spacing and Debris Distribution on Vegetative Communities in Newly Established Loblolly-pine Plantations in Louisiana

Commercial pine (Pinus spp.) forests in the southeastern United States are critical to providing fiber for global wood supply needs. Intensive forest management techniques including row spacing and woody debris distribution can impact plant communities. Therefore, we quantified response of plant communities in replanted P. taeda stands to mechanical site preparation at two levels of row spacing (narrow and wide) and two methods of distributing woody debris (piling and scattering) following harvest in Louisiana. Sites were prepared with a combination of row spacing between planting beds (n = 2; 4.3 m and 6.1 m) and distribution of logging debris (n = 2; piled and scattered). We examined structural, compositional and speciesspecific characteristics of plant communities in each of four replicate stands for four years post-treatment. We documented 124 genera or species of plants and species richness and Shannon-diversity estimates were similar between site preparation methods. However, species richness and diversity varied among years and were reflective of successional changes. Placing woody debris in large piles throughout the stand appeared to influence stand structure by reducing woody plant growth, whereas scattering debris between rows of seedlings resulted in a more developed woody component. Variation in row spacing affected abundance of some individual species, but did not affect stand structure. Our results demonstrate that mechanical site preparation involving stand structure and distribution of logging debris influences plant communities and may change the trajectory of succession. However, plant species richness and diversity may not be strongly affected by row spacing or debris distribution. Therefore, we suggest that piling debris into isolated locales throughout the stand may increase availability of early successional vegetation through reduction of non-pine woody growth.

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