Estimating Forest Aboveground Biomass Using Gaofen-1 Images, Sentinel-1 Images, and Machine Learning Algorithms: A Case Study of the Dabie Mountain Region, China

Quantitatively mapping forest aboveground biomass (AGB) is of great significance for the study of terrestrial carbon storage and global carbon cycles, and remote sensing-based data are a valuable source of estimating forest AGB. In this study, we evaluated the potential of machine learning algorithms (MLAs) by integrating Gaofen-1 (GF1) images, Sentinel-1 (S1) images, and topographic data for AGB estimation in the Dabie Mountain region, China. Variables extracted from GF1 and S1 images and digital elevation model data from sample plots were used to explain the field AGB value variations. The prediction capability of stepwise multiple regression and three MLAs, i.e., support vector machine (SVM), random forest (RF), and backpropagation neural network were compared. The results showed that the RF model achieved the highest prediction accuracy (R2 = 0.70, RMSE = 16.26 t/ha), followed by the SVM model (R2 = 0.66, RMSE = 18.03 t/ha) for the testing datasets. Some variables extracted from the GF1 images (e.g., normalized differential vegetation index, band 1-blue, the mean texture feature of band 3-red with windows of 3 × 3), S1 images (e.g., vertical transmit-horizontal receive and vertical transmit-vertical receive backscatter coefficient), and altitude had strong correlations with field AGB values (p < 0.01). Among the explanatory variables in MLAs, variables extracted from GF1 made a greater contribution to estimating forest AGB than those derived from S1 images. These results indicate the potential of the RF model for evaluating forest AGB by combining GF1 and S1, and that it could provide a reference for biomass estimation using multi-source images.

Topotaxial intergrowth and origin of antiperthite in monzogranite

&lt;p&gt;The crystallographic orientation of antiperthite (squared alkali feldspar inclusions grow inside plagioclase host) in Tiantangzai monzogranite from Dabie Mountain was investigated. The morphology of alkali feldspar inclusions is hexahedron, three pairs of parallel faces are controlled by the (010), (001) and (110) planes of the host plagioclase, respectively. Some plagioclase develops albite polysynthetic twin, defined the twinned individuals as Pl(1) and Pl(2), respectively; some alkali feldspar inclusions are related by Carlsbad twin, the twinned individuals are also defined as Kfs(1) and Kfs(2), respectively. Pl(1) is oriented similarly to Kfs(1). The topotaxial relationship between Pl(2) and Kfs(1) is similar to albite-twin. The topotaxial relationship between Kfs(2) and Pl(1) is similar to Carlsbad-twin. Kfs(2) and Pl(2) would form a topotaxial relationship similar to Carlsbad-albite-twin. Pl(1) generally becomes thinner or disappears in the regions where alkali feldspar inclusions developed. The development sequence of the alkali feldspar inclusions and the polysynthetic albite twin needs to be further investigated. Electron microprobe line scanning shows a homogeneous K, Ca and Na distribution in a single plagioclase grain with inclusions developed, suggesting that the origin of alkali feldspar inclusion may not be related to exsolution. The fractures in the host plagioclase are well developed, but most fractures do not pass through the embedded alkali feldspar. The precipitated alkali feldspar may be a result of alkali-bearing fluids penetrating through fractures and replacing plagioclase. The rim of some larger anhedral alkali feldspar inclusions has many voids, the local average misorientation map indicates there is a rectangular area with low misorientation difference inside the anhedral inclusions. The anhedral alkali feldspar inclusions are presumed to form by secondary replacement on top of the original rectangular inclusions.&lt;/p&gt;

Identification of twins in muscovite: an electron backscattered diffraction study

Twins in micas are difficultly identified due to mica’s hexagonal pseudosymmetry. Many theoretic studies on mica twins have been reported but experimental observations are very limited. In this paper, we present an electron backscattered diffraction analysis to identify twins in the muscovite in a quartz schist occurring in the UHP-HP metamorphic rock belt in Dabie Mountain, China. A trilling twin with twin law <310>/{110} is common in the muscovite. A six-couplet twin consisting of two trilling twins related by twin laws <110>/{130} and <001>/{001}(or <100>/{100}) has been discovered. This six-couplet twin contains many cross-twin relationships among the most common mica twin laws <310>/{110}, <110>/{130} and <001>/{001}. The composition plane for twin laws <110>/{130} and <001>/{001} is {001} which is reasonable in mica structure to form a twin by rotation around twin axes, and that for twin law <310>/{110} is irregular based on EBSD resolution. A possible misindexation of a trilling twin or a 3T polytype during EBSD test is discussed, which is helpful to distinguish a twin from a polytype in micas. The occurring frequency of twin law <310>/{110} is higher than that of twin laws <110>/{130} and <001>/{001}, which is consistent to the deducing result from mica structure analysis. This research provides a convenient and effective EBSD method to identify mica twins and an experimental method to distinguish a twin from a polytype in micas, which is a problem confusing researchers for many years.