Underplanting degraded exotic <i><scp>P</scp>inus</i> with indigenous conifers assists forest restoration

Abstract

Summary We propose that nonharvest plantations could provide important opportunities for restoration of indigenous forest cover and related ecosystem services. We assessed the relative performance of three P odocarpaceae (podocarps) species planted into a degraded Ponderosa Pine ( P inus ponderosa ) plantation, central N orth I sland, N ew Z ealand. We hypothesised that the degraded pine plantation overstorey could provide suitable conditions for the development of a podocarp‐dominated forest structure within ca . 50 years of underplanting and that podocarp growth would differ depending on the species suitability to the site. Rimu ( D acrydium cupressinum ) significantly outperformed both T otara ( P odocarpus totara ) and K ahikatea ( D acrycarpus dacrydioides ) in height and diameter growth. Rimu was now the structurally dominant tree where it occurred rather than pine. Per annum scaled carbon storage within R imu stands was significantly greater than the T otara, K ahikatea or P ine stands. All podocarp species had attained a greater stand density compared to the pine overstorey. Possible reasons for the differing podocarp growth performance include different light requirements, response to soil nutrients, elevational distributions and frost susceptibility. There were significant differences in understorey species richness among the different stands of podocarp species. Underplanting accelerated successional development by incorporating late‐successional indigenous canopy dominants within the forest succession and overcame limitations imposed on forest succession at the site from its isolation from indigenous forest tree seed sources.