Multi-function evolutions of arable land and its driving forces based on different functional types of cities
[Background] In order to know the multi-function changes of arable land and compare the differences of three different functional types of cities, Changsha (capital of Hunan province), Zhuzhou and Zhangjiajie are selected as research areas, representing three different functional cities as political and economic type, industrial type and tourism type, and the multi-functions of arable land in these three cities were evaluated. [Methods] We constructed evaluation index system of arable land multi-functions from four aspects of production, society, culture and ecology, collected and dealt with data, analyzed the driving factors of arable land function changes in three cities using grey correlation analysis method. [Results]1) From 2007 to 2016, the productive function score of arable land in Changsha decreased from 0.271 to 0.077, then recovered to 0.274; the social function score decreased from 0.117 to 0.032; the cultural function score increased from 0.026 to 0.150; the ecological function score increased from 0.085 to 0.160. From 2007 to 2016, the productive function score of Zhuzhou arable land decreased from 0.249 to 0.126, and then increased to 0.252; the social function score decreased from 0.106 to 0.010; the cultural function score increased from 0.037 to 0.133; the ecological function score increased from 0.094 to 0.175, and then decreased to 0.040. From 2007 to 2016, the productive function score of arable land in Zhangjiajie decreased from 0.301 to 0.165, then recovered to 0.272; the social function score decreased from 0.117 to 0.056; the cultural function score increased from 0.009 to 0.106; the ecological function score decreased from 0.172 to 0.126. 2) The correlation degrees of population, urbanization rate, total fixed asset investment, total tourism income, effective irrigation area, GDP and the evolution of arable land function in Changsha were 0.805, 0.767, 0.652, 0.628, 0.601, and 0.584 respectively. The correlation degrees of effective irrigation area, number of industries above designated scale, urbanization rate, population and the evolution of arable land function in Zhuzhou were 0.824, 0.741, 0.659, and 0.632 respectively. The correlation degrees of urbanization rate, total tourism revenue, number of tourists, population, effective irrigation area, GDP and the evolution of cultivated land function in Zhangjiajie were 0.774, 0.758, 0.735, 0.716, 0.707, 0.696 respectively. [Conclusions] 1) The production function of arable land in Changsha, Zhuzhou and Zhangjiajie declined first and then increased, the social function declined, the cultural function increased, and the ecological function changed differently from 2007 to 2016. 2)The driving forces of Changsha which affect the change of cultivated land function are population, urbanization rate and investment in fixed assets. 3) The driving forces of cultivated land function change in Zhuzhou are effective irrigated area, the number of industries above the scale, and urbanization rate, and those in Zhangjiajie are urbanization rate, tourism revenue, and the number of tourists. The arable land multi-function changes and its driving factors in three cities with different functions are different. The study result could provide practical basis for the cultivated land protection and the multi-functional management in different functional cities.
LI Qinggui, LI Rui, SHANG Chongju, ZHANG Yin, CHEN Yang
Effects of organic mulching measures on soil moisture conservation of sloping farmland in karst areas of northwest Guizhou
[Background] Considering the problem of "engineering" water shortage in karst areas, understanding the effects of organic mulch on soil moisture of sloping farmland in karst areas is of great significance to improve the utilization efficiency of regional natural precipitation and to increase crop yield. [Methods] The maize monoculture was set as control (CK), 5 straw mulch treatments (SM1 by straw 1 111 kg/hm2,SM2 by straw 2 222 kg/hm2,SM3 by straw 3 889 kg/hm2, SM4 by straw 5 556 kg/hm2, and SM5 by straw 6 944 kg/hm2) and 4 biochar mulch treatments (BM1 by biochar 1 389 kg/hm2,BM2 by biochar 2 778 kg/hm2, BM3 by biochar 5 556 kg/hm2,and BM4 by biochar 11 111 kg/hm2) were set, and alfalfa (AI), chicory (CI) and ryegrass intercropping (RI) in maize were set as 3 grain and grass intercropping treatments according to the difference of intercropping plants, 13 treatments in total. During the whole growing season, the soil moisture dynamics in the cultivated layer was observed in the field and 46 observations were recorded in the whole year of 2018. [Results] 1) With the increase of straw mulch application rate, the soil moisture in tillage layer showed an upward trend. When the straw mulch application rate was up to SM5, the soil moisture reached the maximum, which was significantly higher than CK and SM1-SM3 (P<0.05), but not significantly higher than SM4, that was, when the straw mulch application rate increased from 5 556 (SM4) to 6 944 kg/hm2 (SM5), the soil moisture did not increase significantly. 2) With the increase of biochar mulch application rate, the soil moisture also showed an increasing trend, but did not reach a significant level (P>0.05). 3) Soil moisture under AI was higher than that of CK, CI and RI, but did not reach the significant level (P>0.05). 4) Among the three different organic mulches, the overall effect of SM on soil moisture conservation was better than that of BM and GI, but did not reach the significant level (P>0.05). [Conclusions] The straw mulch of about 6 000 kg/hm2presents promising effect on soil moisture conservation, and might be an appropriate reference mulch application rate for karst areas in Southwest China. The effect of biochar mulch and grain and grass intercropping on soil moisture conservation is not significant, however, biochar mulch might be a suitable organic mulch to conserve soil moisture during critical phenological or drought periods.
ZHOU Ziye, XIA Jihong, YE Jibing, DOU Chuanbin, ZHOU Zhiyue, LIU Han, ZHU Zhuo, WANG Jie
REMM-based compensation and optimization of widths on the rural riparian zones of plain, Zhejiang province
[Background] Riparian zones play a key role in removing none-point pollution and improving water quality. It is well known that these functions largely depend on the widths of riparian zones. However, due to farm land-use, building construction, road construction and other reasons, some riparian zones have been occupied in some rural areas. It results in that none-point pollution cannot be intercepted efficiently and water quality could be degraded. [Methods] We investigated 3 rivers in Baimatang village of Tongxiang city, Zhejiang province, where is attributed as flat rural area. After we divided the 3 rivers into 6 reaches (T1, T2, T3, T4, T5, and T6) according to the land use patterns and cross-section, the removal rate of total nitrogen in each riparian zone were calculated with Riparian Ecosystem Management Model (REMM). [Results] 1) The removal rate in T6 was the biggest, 76.03%. But in other 5 reaches, the removal rates of total nitrogen were <75%. In practice, lands outside the riparian zones were used as farm field or house field along the 5 reaches, the riparian zones were limited and could not been widened. In order to remedy the width deficits, we set 5 experimental blocks with concrete sector bricks, ecological concrete balls, concrete bricks, Wufeng bricks and ecological bags in reach T1, T2, T3, T4, and T5, respectively. 2) Experiments showed that the removal rates by the combined measures of vegetation with ecological concrete balls or ecological bags were improved to 76.07%, 79.71% and their remedied widths were 10.34 m and 11.64 m, respectively. However, the removal rates by other three measures were still < 75% and their remedied widths were not obvious. The combined measures of vegetation with ecological concrete balls or ecological bags presented much better nitrogen removal efficiency. Meanwhile, these measures reduced the width deficits of current widths to satisfy the objectives of buffering the water quality. Among the 5 artificial ecological materials, the ecological concrete ball demonstrated the greatest increase in the nitrogen removal rate per unit width, which was 0.751 9%/m, and the compensation width was >10 m, and the width compensation efficiency was the highest, and the effect of width compensation was the best. [Conclusions] In order to further improve the width compensation effect of the riparian zone in the study area, ecological concrete balls can be arranged in the riparian zone to optimize the construction measures of the riparian zone. Additionally, the fitting equations of optimal widths have been presented, it would be helpful to definite the exact width of a riparian zone for river restorations or managements.
ZHAO Yuming, CHENG Liping, LI Jiajia, CHU Chunjie, HUANG Fang, CHE Jiangbo, ZHANG Chuang, LI Changchun
Research on the definition of soil types in typical black soil regions of Northeast China
[Background] The definition of main soil types, which was one of the most important reference for the delineation of typical black soil regions of Northeast China, is quite controversial at present, thus it is necessary to conduct in-depth research. [Methods] Taking the national digital soil map with the scale 1∶1 000 000 drawn by the Nanjing Soil Research Institute, Chinese Academy of Sciences as the base map, the study counts the area and spatial distribution of black soil, chernozem and meadow soil in Northeast China, and points out that. [Results] 1) The total area of black soil in Northeast China is 60 434.78 km2. Black soil, which has two concentrated distribution regions and located in the eastern-northeastern part of Songnen Plain (51 807.20 km2) and the Sanjiang Plain (7 075.73 km2) accounting for 97.43% of the total area, can be used as one important reference for delineation of typical black soil regions. 2) The area of chernozem in Northeast China is 92 680.32 km2. Chernozem, which also has two concentrated distribution regions and located in the western part of Songnen Plain (45 368.20 km2) and the East Four Alliance (46 881.22 km2) cities based on the Hulun Buir League in Inner Mongolia Autonomous Region, accounting for 99.53% of the total area, can be used as another reference for the delineation of typical black soil regions. 3) The area of meadow soil is 225 980.75 km2. Meadow soil, which is almost linear shape throughout all the valley lowlands in Northeast China and does not have concentrated distribution characteristics, can't be used the reference for the delineation of typical black soil areas in Northeast China. [Conculsions] The typical black soil regions of Northeast China, including four typical black soil regions of Hulun Buir, western Songnen Plain, eastern Songnen Plain and Sanjiang Plain, can only be delineated around black soil and chernozem. The meadow soil, which although accounts for a high proportion in the four typical black soil regions, cannot be used as a reference for demarcation. In order to maintain the consistency of the delineation and definition of the typical black soil area in Northeast China, meadow soil should be excluded the definition of soil types. The research results are conducive to guiding the production practice in typical black soil regions of Northeast China, and have a certain theoretical guidance for the in-depth study of typical black soil regions of Northeast China.
Effect of phosphorus addition on the functional traits of Dicranopteris dichotoma
[Background] Red soil region of southern China is the severe soil and water erosion region following the Loess Plateau. Dicranopteris dichotoma, which plays an important role in soil and water conservation in the red soil area of southern China, is an excellent soil and water conservation plant. The phosphorus mass fraction in the soil is an important factor affecting the distribution and growth of D. dichotoma. However, the effect of phosphorus on the functional traits of D. dichotoma has not received much attention. In order to give full play to the water and soil conservation function of D. dichotoma, further study in this area is urgently needed. [Methods] The pot experiment was used to set up the 6 gradients of phosphorus addition treatment control (CK), P1, P2, P3, P4 and P5. The soil used in the experiment came from Hetian town, Changting county, Fujian province. Each pot was filled with 7 kg soil and one seedling of D. dichotoma. From the CK group to the P5 group, 0, 400, 600, 1 000, 1 600, and 2 400 mg of phosphate fertilizer were applied respectively. Four replicates were set up per group and a total of 24 pots were planted and cultivated. The pot culture period was 90 d, then the indexes of D. dichotoma’s functional traits were measured. All data were collated using Excel 2010 and analyzed using IBM SPSS 22.0. The different data were examined by One-way ANOVA and LSD method or nonparametric Kruskall-Wallis method, and the correlation of data was analyzed using Pearson method. All illustrations were generated using Origin 9.0. [Results] 1) Phosphorus addition significantly increased the leaf area and root length of D. dichotoma (P<0.05), which were 2.29 times and 1.12 times that of the corresponding CK group, respectively. While there was little effect on specific leaf area, leaf tissue density, and specific root length, and the increase in root tissue density was small. 2) Phosphorus addition now increased the plant height of D. dichotoma (P<0.05), with the largest plant under P4 treatment being up to 20.43 cm, and significantly reduced the root-to-shoot ratio (P<0.05). The growth rate of D. dichotoma also increased with the increase of the phosphorus addition gradient. 3) The phosphorus mass fraction in various organs of D. dichotoma showed the characteristics of leaf> petiole> underground stem and root. Phosphorus mass fraction in the leaves, petioles, and underground stems and roots of D. dichotoma increased with the increase of phosphorus addition gradient, in which the phosphorus mass fraction of underground stems and roots increased at a relatively high rate, and it reached 1.8 g/kg in P4 treatment. There was no obvious regular change in the C∶N of the underground stems and roots and leaves of D. dichotoma, while petiole C∶N increased with increasing phosphorus addition gradient. The C∶P and N∶P of organs of D. dichotoma had the characteristic of significantly decreasing with the increase of phosphorus addition (P<0.05).[Conclusions] This study reveals that the functional traits of D. dichotoma may respond to the changes of phosphorus elements in the surrounding environment, and it has stable material acquisition capabilities and strong environmental adaptability in different environments, thus it can adapt to harsh living environment.
Advances in research on effects of biochar on soil nitrogen leaching
[Background] In agricultural activities, due to the unilateral pursuit of high food production, the environmental problems from excessive use of nitrogen fertilizer have become increasingly serious. As a highly effective soil amendment, biochar affects the retention of nitrogen nutrients in the soil and affects the nitrogen fixation capacity of the soil. This review aims to clarify the prior research results, and to provide reference for the future research work on soil nitrogen leaching. [Methods] By focusing on the effects of biochar on soil nitrogen fixation capacity, we combined external conditions (soil environment, biochar type, amount and mode of addition, crop type, etc.) and intrinsic conditions (physical properties of biochar, microbial action), and conducted in-depth discussion and clarification of the four mechanisms of biochar's ability of affecting soil nitrogen fixation, and prospected the future research directions.[Results] 1) There are 4 mechanisms of biochar's ability to affect soil nitrogen fixation. a) The microporous structure of biochar and its large specific surface area give it strong physical adsorption properties, which can greatly increase the nitrogen content in soil. The retention time of nutrients reduces the loss of nitrogen caused by leaching. b) Biochar is added to the soil to improve the water-holding capacity of the soil and to avoid the loss of nitrogen nutrients with water migration. c) The oxygen-containing acidic functional groups formed on the surface of the biochar increase the CEC value, pH value, etc. of the soil, thereby enhancing the chemical adsorption performance of the soil. d) The interaction between biochar and microorganisms indirectly affects the circulation and utilization of nitrogen in the soil. 2) The future research direction of biochar nitrogen fixation technology and suggestions for the scientific use of biochar in agricultural production are in followings. a) We should actively carry out medium and long-term outdoor tests of biochar, and conduct in-depth research on the stability of biochar. b) We should study the interaction between soil nitrogen nutrients and other nutrients, and verify whether the biochar's retention of nitrogen nutrients is affected by other nutrient elements. c) We need to consider the environmental problems caused by the biochar production process, which is related to the sustainable development of biochar, which may have certain practical significance. d) Biochar may have a certain upper limit on the ability of nutrient adsorption, and we need to further explore it. e) In agricultural production activities, we should pay attention to the use of biochar, learn to adapt to local conditions, and rationally apply biochar according to different soil conditions to improve the effectiveness of fertilizer nutrient utilization. f) We should try to establish a biochar-soil-crop joint research system to better serve agricultural production. Explore new ways to produce cheaper biochar, and strive to reduce their production costs and maximize their economic benefits. [Conclusions] The relevant works are summarized and 4 mechanisms and 6 prospects are clarified, which may provide the references for the future research on soil nitrogen leaching.
Trade-offs in forest ecosystem services: Cognition, approach and driving
[Background] Trade-off relationship among forest ecosystem services is one of the important factors causing regionally and globally ecological and environmental problems. Scientifically understanding trade-off relationships of forest ecosystem is significant to enhance human well-beings and achieve win-win situation of ecological protection and social and economic development. [Methods] On the basis of comprehending domestic and foreign research literatures, we expounded the connotation of forest ecosystem service trade-off, and clarified the basic characteristics and main steps of trade-off analysis of forest ecosystem services. Then we sorted the principles, techniques and main functions of trade-off analysis methods, as well as their scope of application, and analyzed the driving roles of natural and human factors in trade-off of forest ecosystem services.[Results] 1) Human choice preferences lead to trade-offs among forest ecosystem services. The trade-offs among forest ecosystem services are characterized by universality, reversibility, time-space scale, uncertainty and externality. Universality refers to the general existence of trade-offs between various forest ecosystem services,and reversibility indicates the resilience of damaged forest ecosystem services. Time-space scale shows the spatial and temporal scale characteristics of trade-off relationship, and uncertainty means that the trade-off relationship is not constant. Externality reveals the impact of trade-off management on ecosystem services in non-target areas. 2) The main research procedure of forest ecosystem trade-off includes evaluation index selection, data acquisition quantitative and evaluation trade-off analysis. The research methods mainly include eco-economic integration model method, statistical method, mapping of ecosystem services, scenario analysis and service liquidity analysis. The eco-economic integration model is suitable for analyzing trade-off relationship between the supply services and regulation services convenient for marketization, the statistical method for analyzing correlation relationship between various forest ecosystem services, and mapping of ecosystem services for revealing trade-off spatial heterogeneity. Scenario analysis holds for scenario analysis and finding the best optimization scheme, and service liquidity analysis method for analyzing trade-off occurrence mechanism and ecological process. 3) The driving factors for trade-offs among forest ecosystem services can be divided into natural factors and human factors. Natural factors containing ecological factors and environmental factors are the basis of trade-offs among forest ecosystem services, while human factors include human choice preference, human activity mode and human activity behavior are main ones for trade-offs among forest ecosystem services. [Conclusions] The trade-offs among forest ecosystem services are generated by co-driving or direct interaction of driving factors. The trade-offs among forest ecosystem services are insufficient in temporal scales terms of uncertainty of evaluation results, driving factors and spatial and temporal scaling effects of mechanisms. Forest ecosystem trade-offs assessment methods, quantitative models, spatiotemporal scaling effect of driving factors and their mechanisms will be the focus of future research in forest ecosystem services trade-offs.
