Characterizing scale-specific environmental factors affecting soil organic carbon along two landscape transects
Soil organic carbon (SOC) is one of the most important soil properties affecting many other soil and environmental properties and processes. In order to understand and manage SOC effectively, it is important to identify the scale-specific main factors affecting SOC distributions, which in this study occurred in a watershed on the Loess Plateau. Two transects were selected that passed along the upper slopes on each side of the main gully of the Liudaogou watershed. Transect 1 (3411-m length) had 27 sampling sites at 131-m intervals; transect 2 (3597 m length) had 30 sampling sites at 124-m intervals. The two transects were chosen in order to compare landscape patterns of differing complexity that were in close proximity, which reduced the effects of factors that would be caused by different locations. The landscape of transect 1 was more complex due to the greater diversity in cultivation. Multivariate empirical mode decomposition (MEMD) decomposed the total variation in SOC and five selected environmental factors into four intrinsic mode functions (IMFs) and a residual according to the scale of occurrence. Scale-specific correlation analysis was used to identify significant relationships between SOC and the environmental factors. The dominant scales were those that were the largest contributors to the total SOC variance; for transect 1, this was the IMF 1 (scale of 403 m), whereas for transect 2, it was the medium scale of the IMF 2 (scale of 688 m). For both transects, vegetation properties (vegetation cover and aboveground biomass) were the main factors affecting SOC distributions at their respective dominant scales. At each scale, the main effective factors could be identified although at the larger scales, their contributions to the overall variance were almost negligible. The distributions of SOC and the factors affecting it were found to be scale dependent. The results of this study highlighted the suitability of the MEMD method in revealing the main scale-specific factors that affect SOC distributions, which is necessary in understanding and managing this important soil property.
Spatial filtering of a legacy dataset to characterize relationships between soil organic carbon and soil texture
The spatial distribution of soil properties often displays complex and multiscale patterns of variation. It results from multiple soil processes acting simultaneously but at different scales. Hence, characterizing the influence of a given controlling factor on the soil property is made more difficult by the variation due to other controlling factors. In this context, separating the variation of the soil properties by spatial scales could allow disentangling the combined effect of controlling factors and would provide a qualitative and quantitative characterization of controlling factors separately. In this paper, geostatistical tools have been used to separate the scales of variation of two soil properties (i.e. SOC and texture) coming from a legacy dataset in the Belgian Loess Belt. Scale components were predicted separately and the relationships between soil properties were analyzed at different scales. Results illustrated that the contents of a given soil property in different depth layers were typically more correlated when only the long range components were compared. Similarly, the link between SOC and texture components was also clearer for the long range components. This means that soil processes acting at local or landscape scale influence soil properties differently according to their nature or to the depth considered. Eliminating the variation at this scale allows to better characterize the relationships between depth layers and soil properties. The study gives insights for further spatial mapping of SOC by focusing on more appropriate variables at specific spatial scales. Furthermore, we raise the interest of spatial filtering for detecting inconsistencies inside composite datasets.
Vertebral Fusion in Two Early Jurassic Sauropodomorph Dinosaurs from the Lufeng Formation of Yunnan, China
Here we describe two instances of pathological vertebral fusion in two genera of sauropodomorph dinosaurs from the Early Jurassic Lufeng Formation in Yunnan, China. The first is a specimen, of Lufengosaurus huenei with two fused cervical vertebrae, and the other is a specimen of the Lufeng basal sauropod, with two fused caudal vertebrae. Both pathologies are consistent with spondyloarthropathy and represent the earliest known occurrence of that disease in dinosaurs. The two specimens affirm that early dinosaurs suffered from the same bone diseases as living vertebrates. Spondyloarthropathy in these dinosaurs may have been induced by long-term mechanical stress, such as weight bearing, and/or limited motion at the joint that would otherwise have inhibited such remodeling. In both cases, surface remodeling suggests that the animals survived well beyond the initiation of spondyloarthropathy.