Carbon sequestration potential of plantation forests in New Zealand - no single tree species is universally best.

BACKGROUND: Plantation forests are a nature-based solution to sequester atmospheric carbon and, therefore, mitigate anthropogenic climate change. The choice of tree species for afforestation is subject to debate within New Zealand. Two key issues are whether to use (1) exotic plantation species versus indigenous forest species and (2) fast growing short-rotation species versus slower growing species. In addition, there is a lack of scientific knowledge about the carbon sequestration capabilities of different plantation tree species, which hinders the choice of species for optimal carbon sequestration. We contribute to this discussion by simulating carbon sequestration of five plantation forest species, Pinus radiata, Pseudotsuga menziesii, Eucalyptus fastigata, Sequoia sempervirens and Podocarpus totara, across three sites and two silvicultural regimes by using the 3-PG an ecophysiological model. RESULTS: The model simulations showed that carbon sequestration potential varies among the species, sites and silvicultural regimes. Indigenous Podocarpus totara or exotic Sequoia sempervirens can provide plausible options for long-term carbon sequestration. In contrast, short term rapid carbon sequestration can be obtained by planting exotic Pinus radiata, Pseudotsuga menziesii and Eucalyptus fastigata. CONCLUSION: No single species was universally better at sequestering carbon on all sites we tested. In general, the results of this study suggest a robust framework for ranking and testing candidate afforestation species with regard to carbon sequestration potential at a given site. Hence, this study could help towards more efficient decision-making for carbon forestry.

Combined effects of cotyledon excision and nursery fertilization on root growth, nutrient status and outplanting performance of Quercus variabilis container seedlings.

Artificial excision of the distal part of acorns in order to promote germination is well researched in oak seedling cultivation studies. However, studies of combined effects of cotyledon excision and nursery fertilization on container seedlings are lacking, especially for seedling root growth and outplanting performance. This study aimed to explore the main effects of cotyledon excision on Quercus variabilis seedling emergence characteristics and demonstrated the combined effects of cotyledon excision and nursery fertilization on seedling quality to improve Quercus variabilis seedling outplanting performance. Four cotyledon excision treatments and two classes of nursery fertilization were implemented. Seedling emergence was noted every week after sowing. Seedling dry mass, morphology, and nutrient status were assessed at the end of the nursery season. After the first outplanting season, the aforementioned measurements along with seedling survival were determined once again. The results showed that cotyledon excision generally induced greater and more rapid seedling emergence, but did not affect shoot emergence synchronicity. The highest total emergence and emergence rate occurred with Intermediate excision (1/2 of the distal end of acorn was excised). Effects of nutrient loss due to cotyledon excision on seedling quality and outplanting performance were somewhat compensated by nursery fertilization. Nursery fertilization promoted dry mass increment (the net increment from T0 to T2 for dry mass) for excised seedlings after outplanting, resulting in better performance for Slight (1/3 of the distal end of acorn was excised) and Intermediate excision treatments in the field. Thus we conclude Intermediate excision combined with reasonable nursery fertilization can be recommended for production of nursery grown seedlings for afforestation.

Radiographic and histologic analysis of the tibial tunnel after allograft anterior cruciate ligament reconstruction in goats.

BACKGROUND: Several problems have been reported with use of allogenic grafts in anterior cruciate ligament reconstruction, including local immune response to allograft tendon within the synovial fluid, delayed maturation and ligamentization, and progressive tibial tunnel enlargement. HYPOTHESIS: There is a correlation between the use of allograft and tibial tunnel enlargement. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty healthy adult female goats underwent allograft anterior cruciate ligament reconstruction and were followed with serial radiographs at 6-week intervals. Animals were randomly chosen for sacrifice between 18 and 36 weeks for histologic assessment. RESULTS: Significant radiographic increases in tunnel size were noted within the first 6 weeks of healing and remained up to 36 weeks with no further remodeling noted. Histologic analysis showed progressive ligamentization of the allografts with tendon-to-tunnel wall biologic fixation with dense connective tissue. Remodeling and incorporation of the bone plug was seen in all cases. The allograft tendon underwent early fibrous attachment within the tunnel and remodeled toward ligament histologic structure. Remodeling and incorporation of the bone plug was seen by 18 weeks. CONCLUSION: Tibial tunnel enlargement, consistent with that seen in humans after allograft anterior cruciate ligament reconstruction, did not appear to affect the ultimate incorporation of the allograft on a histologic level.