A preliminary study on in-stream large woody debris in broadleaved and Korean pine forest in Changbai Mountain, Northeast China

This study was conducted in Erdaobaihe River passing through the broadleaved and Korean pine forest located on the north slope of Changbai Mountain. In-stream large woody debris (LWD) in two segments of the river channel was investigated with base diameter, top diameter, length, and decay class. To study relationship between in-stream LWD and adjacent riparian forest, species of each log of LWD in segment 1 was identified, and the riparian forest was examined by setting a 32m?4 m quadrat consisting of twelve 8m?m small quadrats. The results showed that, in segment 1, in-stream LWD loading was 1.733 m3/100m or 10.83 m3hm-2, and in segment 2, it was 1.709m3/100m or 21.36 m3hm-2. In-stream LWD in decay class III and IV were accounted for a high proportion, which was different from that in the broadleaved and Korean pine forest, and the possible reason might be different decomposing velocities due to different decomposing conditions. Logs of LWD in stream and living trees in riparian forest declined as diameter increased, and it was in a reverse J-shaped distribution except logs of LWD in segment 1 in the first diameter class. Volumes of LWD in stream and living trees in riparian forest increased as diameter increased, and it was in a typical J-shaped distribution. Loading and species component of in-stream LWD were correlative to status of riparian forest to a certain extent, and there also existed difference. Comparing the correlation and difference was helpful to study on dynamic of the riparian forest.

Spatial-temporal differences in in-stream flow requirement based on GIS： A case study of Yan＇an region, northern Shaanxi

Although water has the central function of the bloodstream in the biosphere especially in arid or semi-arid regions such as Yah＇an region in northwestern China, yet the very limited attention is paid to the role of the water-related processes in ecosystem. In this research, based on continuous nearly 50-year data including runoff volume, sediment discharge as well as sediment accretion from hydrographic stations, and 10-year information of water quality from pollution monitoring stations, the method for measuring in-stream flow requirement has been put forward supported by experiential models and GIS spatial analysis. Additionally, the changes of in-stream flow requirement for environment and economic development have been addressed from spatial-temporal dimensions. The results show that： （1） According to the central streams in Yan＇an region, mean annual in-stream flow requirement reaches 1.0619 billion m^3, and the surface water for economic exploitation is 0.2445 billion m3 （2） Mean annual in-stream flow requirement for sediment transfers in flood period occupies over 80% of the integrated volume in a year. （3） From the 1950s to 1970s, in-stream flow requirement for sediment transfers is comparatively higher, while from the 1980s to 1990s, this requirement presents a decreasing tendency.

Estimating the minimum in-stream flow requirements via wetted perimeter method based on curvature and slope techniques

Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement （MEIFR） is deduced. Based on the analytical solution, the uncertainty of the wetted perimeter method is analyzed by comparing the two techniques for the determination of the critical point on the relationship curve between wetted perimeter, P and discharge, Q. It is clearly shown that the results of MEIFR based on curvature technique （corresponding to the maximum curvature） and slope technique （slope being 1） are significantly different. On the P-Q curve, the slope of the critical point with the maximum curvature is 0.39 and the MEIFR varied prominently with the change of the slope threshold. This indicates that if a certain value of the slope threshold is not available for slope technique, curvature technique may be a better choice. By applying the analytical solution of MEIFR in the losing rivers of the Western Route South-to-North Water Transfer Project in China, the MEIFR value via curvature technique is 2.5%-23.7% of the multi-year average annual discharge, while that for slope technique is 11%-105.7%. General conclusions would rely on the more detailed research for all kinds of cross-sections.

Scaly-sided Merganser(Mergus squamatus)equalizes foraging costs with depth by switching foraging tactics

Throughout evolutionary history,animals are finely tuned to adjust their behaviors corresponding to environmental variations.Behavioral flexibility represents an important component of a species'adaptive capacity in the face of rapid anthropogenetic environmental change,and knowledge of animal behaviors is increasingly recognized in conservation biology.In aquatic ecosystem,variation of water depth is a key factor affecting the availability of food;thus,the foraging behaviors of many waterbirds,especially piscivores.In this study,we compared the foraging behaviors of the Scaly-sided Merganser(Mergus squamatus),an endangered migratory diving duck endemic to East Asia,in habitats with different water depths(Shallow waters:0–40 cm;Deep waters:40–300 cm),using video camera records obtained from the known wintering sites during three winters from 2018 to 2020.Further,the energy expenditure of foraging behavior profile and energy intake based on fish sizes were calculated to study the foraging energetics.In total,200 effective video footages that contained 1086 min with 17,995 behaviors and 163 events of catching fish were recorded.Results showed that:1)time length for fishing(including eye-submerging,head-dipping,diving and food handling)of M.squamatus in shallow waters was significantly more than in deep waters;2)M.squamatuss spent significantly more time for preparing(including vigilance,preening and swimming)in deep waters than in shallow waters;3)the mean catch rate was 0.28 fish/min in shallow waters,which is significantly higher than the value of 0.13 fish/min in deep waters;4)despite the distinct foraging behavior profiles and energy intakes,M.squamatus showed similar energetics in shallow and deep waters.We concluded that M.squamatus is a good example of behavioral flexibility that aligns with expectations of optimal foraging theory,in that it behaves in accordance to resource availability in different environments,resulting in high foraging efficiency.

Sampling-Based Approaches to Estimating Two-Dimensional Large Wood Area from UAS Imagery

Large in-stream wood (LW) is a critical component of riparian systems that increases heterogeneity of flow regimes and provides high quality habitat for salmonids and other fishes. We present four sampling-based methods to estimate two-dimensional LW for a 61-hectare river restoration project on the South Fork McKenzie River near Rainbow, OR (USA). We manually delineated LW area, from unoccupied aircraft systems (UAS) multispectral imagery for 40 randomly selected 51.46 m2 hexagonal plots. Seven auxiliary variables were extracted from the imagery and imagery derivatives to be incorporated in four estimators by summarizing spectral statistics for each plot including Random forest (RF) classification of segmented imagery (Cohen’s kappa = 0.75, balanced accuracy = 0.86). The four estimators were: difference estimator, simple linear regression estimator with one auxiliary variable, general regression estimator with seven auxiliary variables, and simple random sample without replacement. We assessed variance of the estimators and found that the simple random sample without replacement produced the largest estimate for LW area and widest confidence interval (17,283 m2, 95% CI 10,613 - 23,952 m2) while the generalized regression approach resulted in the smallest estimate and narrowest confidence interval (16,593 m2, 95% CI 13,054 - 20,133 m2). These methods facilitate efficient estimates of critical habitat components, that are especially suited to efforts that seek to quantify large amounts of these components through time. When combined with traditional sampling methods, classified imagery acquired via UAS promises to enhance the temporal resolution of the data products associated with restoration efforts while minimizing the necessity for potentially hazardous field work.