Soil Carbon, Nitrogen and Phosphorus Concentrations and Stoichiometries Across a Chronosequence of Restored Inland Soda Saline-Alkali Wetlands, Western Songnen Plain, Northeast China

Soil carbon(C), nitrogen(N) and phosphorus(P) concentrations and stoichiometries can be used to evaluate the success indicators to the effects of wetland restoration and reflect ecosystem function. Restoration of inland soda saline-alkali wetlands is widespread, however, the soil nutrition changes that follow restoration are unclear. We quantified the recovery trajectories of soil physicochemical properties, including soil organic carbon(SOC), total nitrogen(TN), and total phosphorus(TP) pools, for a chronosequence of three restored wetlands(7 yr, 12 yr and 21 yr) and compared these properties to those of degraded and natural wetlands in the western Songnen Plain, Northeast China. Wetland degradation lead to the loss of soil nutrients. Relative to natural wetlands, the mean reductions of in SOC, TN, and TP concentrations were 89.6%, 65.5% and 52.5%, respectively. Nutrients recovered as years passed after restoration. The SOC, TN, and TP concentrations increased by 2.36 times, 1.15 times, and 0.83 times, respectively in degraded wetlands that had been restored for 21 yr, but remained 29.2%, 17.3%, and 12.8% lower, respectively, than those in natural wetlands. The soil C∶N(RC N), C∶P(R CP), and N∶P(R NP) ratios increased from 5.92 to 8.81, 45.36 to 79.19, and 7.67 to 8.71, respectively in the wetland that had been restored for 12 yr. These results were similar to those from the natural wetland and the wetland that had been restored for 21 yr(P > 0.05). Soil nutrients changes occurred mainly in the upper layers(≤ 30 cm), and no significant differences were found in deeper soils(> 30 cm). Based on this, we inferred that it would take at least 34 yr for SOC, TN, and TP concentrations and 12 yr for RC N, R CP, and RN P in the top soils of degraded wetlands to recover to levels of natural wetlands. Soil salinity negatively influenced SOC(r =-0.704, P < 0.01), TN(r =-0.722, P < 0.01), and TP(r =-0.882, P < 0.01) concentrations during wetland restoration, which indicates that reducing salinity is beneficial to SOC, TN, and TP recovery. Moreover, plants were an important source of soil nutrients and vegetation restoration was conducive to soil nutrient accumulation. In brief, wetland restoration increased the accumulation of soil biogenic elements, which indicated that positive ecosystem functions changes had occurred.

Characteristics of land use conversion in soda saline-alkali soil region of central Northeast China

Since the 1970s,the soda saline-alkali soil region,which is located in the semiarid-arid region of the central Northeast China,has experienced drastic climate variability.Meanwhile,human activities and socio-economic development have led to an increase in water consumption.These factors have brought out considerable land use change and a lot of soil salinize-alkalization.The land use types were obtained from remote sensing images interpretation based on Landsat MSS in 1970s,TM,ETM in 1990s and 2010s.The characteristics of land use conversion and its response to climate change and influence of human activities were explored in the study area during 1970-2010.The results include:(1)The land use types had changed significantly,especially farmland and grassland,with annual growth rates of 0.31% and 0.35%,respectively.In terms of the saline-alkali land,the area increased greatly during 1970-1990,and its increase was mainly from grassland.There was a decrease from 1990 to 2010,and the loss of saline-alkali was replaced by farmland and grassland.(2)Climate change in the study area is obvious,showing a trend of decreasing precipitation and increasing temperature.The change of saline-alkali land area is closely related to the precipitation,with R2=0.78,passed a passing the 0.01 significance test.(3)The correlation of land use degree index and human activity index with saline-alkali land was not obvious,and the changes in these indices only reflected the land use patterns.Under sufficient rainfall,the saline-alkali land was developed into farmland by humans,which caused the decrease of the saline-alkali land.Therefore,climate change is the main driving force of land salinization in the study area.

Effects of different soil amendments on physicochemical property of soda saline-alkali soil and crop yield in Northeast China

Soil amendment is one of the most effective methods to improve saline-alkali soil.In this study,laboratory experiments were conducted to verify the effect of 13 kinds of amendments and their combinations(Citric acid(NM),Phosphogypsum(LS),Aluminum sulfate+citric acid(AL+NM),Aluminum sulfate+phosphogypsum(AL+LS),Aluminum sulfate+citric acid+phosphogypsum(HH),Zeolite(Z),Acidified zeolite(ZH),Aluminum sulfate(AL),Aluminum sulfate+zeolite(AL+Z),Aluminum sulfate+acidified zeolite(AL+ZH),Poly Aluminum chloride(ALCL),Polyaluminium chloride+zeolite(ALCL+Z),Polyaluminium chloride+acidified zeolite(ALCL+ZH))on soil pH,metal cations content,exchangeable Na+,exchangeable sodium percentage(ESP)in the lab.And then the five most effective amendments(Z,ZH,AL,AL+Z,and AL+ZH)were chosen applying both in dry field(maize field)and paddy field to evaluate their improvement on soda saline-alkali soil and crop yield in the northeast Songnen Plain,China.The lab results showed that AL,AL+Z and AL+ZH treatments could significantly reduce the pH in soil solution and increase the content of metal cations.Z and ZH treatments could adsorb metal cations in soil.Both in dry and paddy fields,all five treatments could increase the soil saturated hydraulic conductivity(Ks),increased from 9.63 to 60.02 mm/d and 0.18 to 33.25 mm/d,respectively,of which the AL treatment was the best;all five treatments could reduce the content of exchangeable Na+in soil,and decrease by 38.62%-61.33%and 25.24%-71.53%,respectively,of which the AL+ZH treatment was the best;all treatments could reduce soil exchangeable sodium percentage,and decrease by 0.14-0.22 and 0.14-0.41,respectively,of which the AL+ZH treatment was the best;AL,AL+Z and AL+ZH treatments could improve soil organic matter content;all treatments could effectively improve the yield of crops,and increase 23.98%-60.75%and 52.51%-260.21%,respectively,of which the AL treatment was the best in dry field and the AL+ZH treatment was the best in paddy field.The effect of AL treatment was the best in dry field and AL+ZH treatment was the best in paddy field of soda saline-alkali soil.This study could provide instructive information for the chemical improvement and agricultural utilization of soda saline-alkali soils in the world.

苏打盐碱湿地两种栽培方式下3种水生植物生理生态和养分吸收特征的比较

为了提高苏打盐碱地区稻田—苏打盐碱湿地复合系统的水资源利用效率,消减灌区退水的环境影响,针对苏打盐碱生境水、土资源的特点,开展3种水生植物的引种实验研究。通过引种水芹(Oenanthe javanica)、雍菜(Ipomoea aquatic)和茭白(Zizania caduciflora),观测其在水培和土培方式下的生长指标、光合生理指标和产量,并对氮、磷吸收特征进行研究。研究结果表明,在水培方式下,水芹和雍菜的生长速率、光合速率、叶绿素含量、生长指标和产量都比土培方式下大,水芹和雍菜平均每亩产量分别比土培方式下多1148.11 kg和863.76 kg;在土培方式下,茭白的生长速率、光合速率、叶绿素含量、生长指标和产量明显大于水培方式下,茭白平均每亩产量比水培方式下多1043.34 kg;水培方式下3种水生植物的根部全氮含量显著大于土培方式下的含量,水芹、雍菜和茭白根部全氮含量分别比土培方式下大136.26%、106.82%和24.51%;在土培方式下,3种水生植物的全磷含量明显大于水培方式下的含量,水芹地上部和根部全磷含量分别比水培方式下的含量大28.57%和33.33%,雍菜地上部全磷含量比水培方式下大77.78%,茭白地上部和根部全磷含量分别比水培方式下大100.00%和77.78%;在土培方式下,3种水生植物的可溶性糖含量显著大于水培方式下的含量,水芹、雍菜和茭白可溶性糖含量分别比水培方式下的含量大50.98%、43.21%和22.90%。