Generalized nonlinear height–diameter models for a &amp;lt;i&amp;gt;Cryptomeria fortunei&amp;lt;/i&amp;gt; plantation in the Pingba region of Guizhou Province, China

Zhu

et al. 2020

Forests

Low temperature (LT) is an important abiotic factor affecting plant survival, growth and distribution. The response of Cryptomeria fortunei (Chinese cedar) to LT is not well known, limiting its application in production and ornamental value. In this study, we first screened ten clones (#3, #25, #32, #42, #54, #57, #68, #66, #74, #X1), originating from five different locations in China, for their degrees of cold resistance. We then selected the two showing the highest (#32) and lowest (#42) cold resistance to see the physiological and morphological response of different cold-resistant C. fortunei clones to LT. We found that the electrolyte leakage of all ten clones increased strongly between 0 and −8 °C, while below −8 or between 4 and 0 °C did not yield additional increases. Under cold stress, clones #32 and #42 showed different degrees of needle browning. From 25 to −20 °C, maximum and effective quantum yields of photosystem II (Fv/Fm and YII) and photochemical and non-photochemical quenching (qP and NPQ) decreased continuously in two clones with decreasing temperature, where #42 was more strongly affected compared with #32. The chlorophyll content first decreased significantly to the lowest from 25 to −12 °C, then increased significantly at −16/−20 °C compared with −12 °C. We observed changes in needle cellular ultrastructure at −8 °C, with chloroplasts of #32 swelling, while those of #42 were destroyed. Correlation analysis indicated that needle browning and chlorophyll fluorescence were closely related to temperature, and cellular ultrastructure changed notably around semi-lethal temperature (LT50), which can be used as physiological indicators for the identification of cold resistance. We found a clear difference in cold tolerance between clones of #32 and #42, with #32 being more tolerant, which can be exploited in breeding programs. We conclude that strongly cold-resistant clones have more stable physiological states and a wider adaptability to LT compared with weak ones.

mentioning

confidence: 99%

Individual Cryptomeria fortunei Hooibrenk Clones Show Varying Degrees of Chilling Stress Resistance

Zhu

et al. 2020

Forests

“…Models with the lowest averages of RMSE, MAPE, AIC and BIC and with the highest averages of R 2 and R 2 -adj. are recognized as the best (Aertsen et al 2010, Ahmadi et al 2013, Chai et al 2018. All analyses of data were performed using Python programming language, version 3.5, as well as Pandas, NumPy, SciPy, and scikit-learn software packages (Python 2020, Pandas Development Team 2020, NumPy 2020, SciPy 2020, Pedregosa et al 2011).…”

Section: Methodsmentioning

confidence: 99%

New generalized height-diameter models for birch in European Russia

Лебедев

2020

BALT FOR

Height and diameter at breast height are basic variables that are measured in a forest inventory. Generalized models do not require measuring tree heights or number of measurements is minimal. The purpose of this study was to obtain 24 new generalized height-diameter models based on simple basic models, compare them with 9 generalized models selected from other studies, and develop an appropriate height-diameter model for birch in the European Russia. To select models which better describe the relationship between the heights and diameters of the trees, six metrics were used – root mean square error (RMSE), mean absolute percentage error (MAPE), coefficient of determination (R2), adjusted coefficient of determination (R2-adj.), Akaike information criterion (AIC) and Bayesian information criterion (BIC). Results show that there are slight differences between all models. The performance statistics showed that model M24 is the most suitable and recommended for predicting the height-diameter relationships for birch trees in this study area. The predicting variables for applying developed generalized models to estimate total tree height require less sampling effort and are derived from conventional forest inventory data which allows to reduce costs and time consumption in field work.

“…In general, models with the lowest averages of RMSE, MAPE, AIC and BIC and with the highest averages of R 2 and R 2 -adj. are recognised as the best (Aertsen et al 2010;Ahmadi et al 2013;Chai et al 2018). All analyses of data were performed using Python version 3.5 and Pandas, NumPy, SciPy, scikit-learn packages.…”

Section: Methodsmentioning

confidence: 99%

Verification of two- and three-parameter simple height-diameter models for birch in the European part of Russia

Лебедев¹,

Кузьмичев²

2020

J. For. Sci.

The accuracy of determining the height of trees is essential both in forestry and in scientific research. Height is usually determined using specific models, where it is a function of the diameter at breast height. On the materials of 23 sample plots with the measurement of model trees in birch stands, the parameters were determined for 29 two-parameter and three-parameter models that are most often found in literary sources. The following metrics evaluated the quality of the models: root mean square error, mean absolute percentage error, coefficient of determination, adjusted coefficient of determination, Akaike information criterion, and Bayesian information criterion. Three-parameter models of the dependence of height on diameter by a set of metrics show somewhat better quality than two-parameter models. Nevertheless, in general, the differences between most models are minor. Along with the models selected as the best, the Näslund and Chapman-Richards equations, which are often used in the literature as the most flexible, showed good quality. The methodology of this study allows you to repeat the same work for tree species and forest conditions, for which information on the nature of the relationship of height with diameter is incomplete or missing.