DOI: 10.5061/dryad.nk98sf7vq
title: Soil physicochemical properties in Chushandian reservoir

description: The impoundment of dams can significantly alter shorelines, hydrological
 regimes, sediment settling, and the soil nutrient cycle. With the
 completion of the Chushandian Reservoir Dam, land-use types around the
 reservoir have been profoundly affected by inundation. As yet, the changes
 due to inundation in soil properties for different land-use types have not
 been fully explored. We investigated the variation of soil physicochemical
 properties of different land-use types (abandoned cropland, grassland, and
 woodland) near the Chushandian Reservoir at several distances after
 short-term inundation and found that soil pH varied in the range of 5-6.5.
 The soil texture of abandoned cropland and grassland was dominated by silt
 particles, but the soil texture of woodland was dominated by sand
 particles. The ranges of variation in soil TC and TN for different
 land-use types were 5.26-33.91 and 0.59-2.68 g/kg, respectively. Woodland
 soil was characterized by low NH4-N and high NO3-N, which may be related
 to denitrification. In addition, we observed that inundation affected the
 soil nutrient status of the different land-use types in the riparian zone
 in the short-term after reservoir impoundment, especially in abandoned
 cropland and grassland. However, woodland showed better tolerance to
 inundation. Furthermore, there are two different mechanisms of soil
 properties in response to inundation at the distance scales for the
 woodland land-use type. Soil properties are dominated by microbial
 activity in the far-away region and by chemical properties in the
 near-water region. By contrast, the soil properties in abandoned cropland
 and grassland are dominated by physical properties. Finally, we found that
 microbial biomass may be an essential indicator that can characterize the
 ability of riparian zone soil to respond to inundation.
description: We conducted our soil survey
 on December 11, 2020, which was two months after the first controlled
 flood of the reservoir area reached its predetermined normal storage
 level. This meant that all corresponding land-use types were under
 short-term inundation. Sample plots of three different land-use types
 (abandoned cropland, grassland, and woodland) that border the watershed
 were selected along the riparian zone on the west side of the reservoir
 (which has no dike protection), with three replicated for each type
 (Figure 1), sampling vertically according to the distance from the water
 (0m, 2m, 20m). For convenience of expression, we write land-use types and
 distance scales together as woodland: W0, W2, W20; grassland: G0, G2, G20;
 abandoned cropland: C0, C2, C20. We collected 27 soil samples in
 total. Taking the boundary between water and land as a
 sampling point of 0 m, we took our samples using a Petersen grab, and
 three adjacent soil samples were selected for each location and mixed into
 one. A five-point sampling method was used to mix the soil into one
 portion at 2m and 20m, and an additional copy was kept with the soil core
 intact and brought back to the laboratory immediately for measurement of
 BD (soil bulk density) and SM (soil moisture). All soil samples were
 divided into two sections. One was kept in a self-sealed bag and placed in
 a refrigerator at 4° C for the determination of
 NH<sub>4</sub>-N, NO<sub>3</sub>-N, DOC (dissolved
 organic carbon), MBC (microbial biomass carbon), and MBN (microbial
 biomass nitrogen) content. And the other one was stored in a self-sealed
 bag and brought back to the laboratory for air drying. Stones and roots
 were picked out with forceps, and each soil sample was divided into two
 portions using a 2 mm sieve. One portion was used to determine the soil
 particle structure, and the other was screened through a 0.25 mm sieve and
 refrigerated at 4°
 C for pH, TC (total
 carbon), TN (total nitrogen), TP (total phosphorus) determination. All
 tests were conducted within two weeks after
 sampling.
description: The soil bulk density and soil moisture at 0m were missing due to
 immersion in water.