Climate Change Effects On Height-Diameter Allometric Relationship Vary With Tree Species And Size For Larch Plantations In Northern And Northeastern China

Background: Tree height-diameter relationship is very important in forest investigation, understanding forest ecosystem structure and estimating carbon storage. Climate change may modify the relationship. However, our understanding of the effects of climate change on height-diameter allometric growth is still limited at large scale.Methods: In this study, we explore how the climate change effects on height-diameter allometric relationship vary with tree species and size for larch plantations in northern and northeastern China. Based on the repeated measurement data of 535 plots from the 6th to 8th national forest inventory of China, climate-sensitive tree height-diameter models of Larix plantations in north and northeast China were developed by two-level nonlinear mixed effect (NLME) method. The final model was used to analyze the height-diameter relationship of different Larch species under RCP2.6, RCP 4.5, and RCP8.5 climate change scenarios from 2010 to 2100.Results: The values of B(adjusted coefficient of determination), MAE(mean absolute error) and RMSE(root mean squared error) of the NLME models for calibration data were 0.92, 0.76m and 1.06m, respectively. The inclusion of climate variables MAT (Mean annual temperature), CMD (Hargreaves climatic moisture deficit) with random effects was able to increase a by 19.5% and reduce the AIC (Akaike’s information criterion), MAE and RMSE by 22.2%, 44.5% and 41.8%, respectively. The climate sensitivity was ranked as L. gmelinii > the unidentified species group > L. pincipis-rupprechtii > L. kaempferi > L. olgensis under RCP4.5, but L. gmelinii > L. pincipis-rupprechtii > the unidentified species group > L. olgensis > L. kaempferi under RCP2.6 and RCP8.5. Conclusion: According to the climate sensitivity, tree species could be classified as group I(L. gmelinii, L. pincipis-rupprechtii and the unidentified species group) with large c (from -4.77% to 18.17%) and group II (L. kaempferi and L. olgensis) with small k (from -6.37% to 9.4%).Large trees were more sensitive to climate change than small trees.

Solar and Anthropogenic Influences on Climate: Regression Analysis and Tentative Predictions

The paper aims to quantify solar and anthropogenic influences on climate change, and to make some tentative predictions for the next hundred years. By means of double regression, we evaluate linear combinations of the logarithm of the carbon dioxide concentration and the geomagnetic aa index as a proxy for solar activity. Thereby, we reproduce the sea surface temperature (HadSST) since the middle of the 19th century with an adjusted R2 value of around 87 percent for a climate sensitivity (of TCR type) in the range of 0.6 K until 1.6 K per doubling of CO2. The solution of the double regression is quite sensitive: when including data from the last decade, the simultaneous occurrence of a strong El Niño and of low aa values leads to a preponderance of solutions with relatively high climate sensitivities around 1.6 K. If these later data are excluded, the regression delivers a significantly higher weight of the aa index and, correspondingly, a lower climate sensitivity going down to 0.6 K. The plausibility of such low values is discussed in view of recent experimental and satellite-borne measurements. We argue that a further decade of data collection will be needed to allow for a reliable distinction between low and high sensitivity values. In the second part, which builds on recent ideas about a quasi-deterministic planetary synchronization of the solar dynamo, we make a first attempt to predict the aa index and the resulting temperature anomaly for various typical CO2 scenarios. Even for the highest climate sensitivities, and an unabated linear CO2 increase, we predict only a mild additional temperature rise of around 1 K until the end of the century, while for the lower values an imminent temperature drop in the near future, followed by a rather flat temperature curve, is prognosticated.