Suchergebnisse

Invasion of introduced lineage of common reed ( Phragmites australis ) into water-saturated communities in the Great Plains has modified habitats and ecosystem services. In several areas it grows alongside and out-competes its native counterpart. We investigated ecophysiological responses of the two lineages to nitrogen (N) fertilization and temperature (19°, 25°, and 32°C). Photosynthesis (A max ) did not differ between lineages at temperatures of 19° and 25°C but was higher in the native lineage at 32°C. Fertilization improved A max at all temperatures, and was more pronounced in the native than in the introduced lineage. Native P. australis had higher δ 13 C and water use efficiency (wue) compared to the introduced lineage. Differences in maximum photochemical efficiency of photosystem II (F v /F m ), carboxylation efficiency (V cmax ), and electron transport (J max ) were observed between lineages, and generally responded positively to treatments. Our results indicated that the native P. australis may better withstand water fluctuations and warmer temperatures than its introduced counterpart, and could contribute to diverse plant communities under warmer climate scenarios. In contrast, under cool temperatures, the introduced lineage has an advantage that could lead to further displacement of native species in water-saturated communities.

The modelling community has identified challenges for the integration and assessment of lake models due to the diversity of modelling approaches and lakes. In this study, we develop and assess a one-dimensional lake model and apply it to 32 lakes from a global observatory network. The data set included lakes over broad ranges in latitude, climatic zones, size, residence time, mixing regime and trophic level. Model performance was evaluated using several error assessment metrics, and a sensitivity analysis was conducted for nine parameters that governed the surface heat exchange and mixing efficiency. There was low correlation between input data uncertainty and model performance and predictions of temperature were less sensitive to model parameters than prediction of thermocline depth and Schmidt stability. The study provides guidance to where the general model approach and associated assumptions work, and cases where adjustments to model parameterisations and/or structure are required. (c) 2017 Published by Elsevier Ltd. ; Australian Research Council (ARC)Australian Research Council [DP130104078, LP130100756] ; GLM development and funding support for LCB, BDB, CB and MRH was provided by the Australian Research Council (ARC) (grants DP130104078 & LP130100756). Additional contributions from individuals and organisations as well as sources of data, provided from a variety of organisations are summarised in Appendix D. This study was made possible through the sharing of ideas, data and models across the AEMON and GLEON networks as well as discussions and working groups held during AEMON workshops and GLEON meetings. ; Public domain authored by a U.S. government employee