Wang Qiao,Liu Xiume, Wang Huatian, Meng Xianpeng, Cao Guiping, Li Jian, Huang Changbao
Effects of drought and waterlogging on growth and photosynthesisof potted young Pinus tabulaeformis Carr.
Drought and waterlogging are the main ecological adversities which affect the survival, growth and vigor of Pinus tabulaeformis Carr. In order to determine the influence of water condition on the growth and physiological adaptation to water stress of P. tabulaeformis trees, the growth of roots and needles,biomass distribution and photosynthesis of 4-year-old potted young trees under continuous drought,waterlogging and normal conditions were studied. We also measured indexes including soil water potential, branch water potential, net photosynthetic rate, transpiration rate, stomatal conductance,intercellular CO2 concentration, root mass, stem mass, leaf mass, total biomass, caliper and the length,surface area, and diameter of needles and roots. The results showed that: 1) The roughness and number of fine roots increased at the early stage of drought stress, but when the drought stress was prolongated,the growth vigor gradually declined with reduced number of fine roots. The soil water potential and branch water potential were also significantly reduced. The plants were easier to die when the stress time was more than 50 days. During water stress, net photosynthetic rate, transpiration rate, stomatal conductanceand intercellular CO2 concentration showed a continuous decline. 2) A short period of waterlogging stresshad no significant effect on growth, but chlorosis content descended and needle color turned yellow withsoil water potential and branch water potential increasing under long term of drought stress. Moreover,when the waterlogging lasted for more than 20 days, the fine roots began to decompose and the plantswent to die. During the waterlogging stress, stomatal conductance decreased with net photosynthetic rateapproaching to zero, but intercellular CO2 concentration increased. 3) Drought and waterlogging stressinhibited the growth significantly, and the biomass of roots, stems and needles decreased with stress time increasing. The descending range of drought stress treatment was larger than waterlogging treatment. In consequence,during dry seasons, soil moisture condition should be controlled in order to promote the growth of fine roots and enhance water use efficiency of P. tabulaeformis trees. When the rainy seasons come, high temperature and soil moisture content lead to more anaerobic respiration and rotted roots with tree vigor declining. More seriously, the P. tabulaeformistrees could die. Therefore we should control the amount of soil moisture content, pay attention to checking whether the rhizosphere soil is subjected to waterlogging. If necessary, drainage measures should be taken in time to ensure that the drainage depth is below concentrated distribution layer of roots, so as to ultimately optimize the cultivating method and raise survival rate of P. tabulaeformisseedlings.
Luan Lili, Zhang Guanghui, Sun Long, Liu Fa,Wang Hao
Spatial variation of typical plant litters in the Loess Plateau
Severe soil and water loss in the Loess Plateau caused by the most highly erodible soil,inappropriate land use and low vegetation cover, pose a great pressure to the sustainability of agro-ecosystem and society and economy. Great efforts have been made to restore vegetation cover to reduce soil and water loss in the Loess Plateau over the past several decades. Consequently, the near soil surface characteristics (e. g. soil properties, biomass production, plant litter, and root system) have beenchanged significantly. Plant litter is effective in reducing soil and water loss by enhancing water infiltration, retarding the velocity of overland flow and increasing the water holding capacity. The weight of accumulated plant litter is of spatial heterogeneity, but so far few studies have been conducted to quantify the distribution of plant litter accumulation among different slope positions and on a regional scale. Therefore, in order to investigate the spatial distribution patterns and influencing factors of weight of accumulated plant litter on a regional scale,seven survey sites were selected from south to north in the Loess Plateau along the decreasing gradient of mean annual precipitation. The mass of accumulated plant litter of typical species of arbor, shrub, and herb among different slope positions were investigated and the influencing factors including mean annual precipitation, mean annual temperature, altitude,aboveground biomass, vegetation density and canopy density were analyzed. The result showed that the differences of the weight of accumulated plant litter among typical species of arbor, shrub, and herb were significant with the litter mass ranked as arbor (440.5~840.1 g/m2) > shrub (105.9~217.9 g/m2)> herb (12.2~67.6 g/m2). The weight of accumulated plant litter was significantly affected by the terrain conditions. The weights of accumulated plant litter of arbor, shrub, and herb communities at the shady slope were 14.9%, 39.3%, and 27.5% more than that at the sunny slope. The weight of accumulated plant litter in the middle slopes was greater than that in the base and the top of the slopes.The weight of accumulated plant litter showed a decreasing trend with the altitude increasing and the accumulated litter fall of arbor, shrubs, and herbs were reduced from 808.6 g/m2, 145.1g/m2, and 67.6g/m2 to 478.7 g/m2, 118.6 g/m2, and 12.2 g/m2, respectively. The weight of accumulated plant litter increased with the mean annual precipitation, and was significantly correlated with the mean annual temperature, canopy density, vegetation density, aboveground biomass and altitude. The fitting equations well predicted the weight of accumulated plant litter of typical plants in the Loess Plateau. The Nash coefficients of the fitting equations were greater than 0.61. The results are helpful to understanding the spatial distribution patterns of accumulated plant litter and its influencing factors and evaluating the soil and water conservation and ecological benefits of vegetation restoration in the Loess Plateau.
Wang Yu, Zhu Qingke, Zhao Weijun, Wang Lina, Ma Huan, Liang Feifan, Zhao Xingkai,Li Anyi
Vertical distribution of soil moisture in artificial forestsin loess region of northern Shaanxi
Soil moisture is one of the main factors that restrict vegetation growth, vegetation restoration and stand stability on the Loess Plateau in northern Shaanxi province. It also shows obvious temporal-spatial characteristics under different land use types, to pography and geomorphology, and vegetation conditions due to the effects of rainfall, surface runoff, plant transpiration, root absorption and so on.The vertical distribution of soil moisture in artificial forests reflects the characteristics of soil water consumption and stability of forest lands. Thus, the study of soil moisture in vertical profiles is important for understanding the utilization of soil moisture in artificial forests. The aim of this study was to investigate the distribution and the hierarchical characteristics of soil moisture at the 0-180 cm layer invertical profiles. In order to analyze it,three types of typical artificial forests on the Loess Plateau innorthern Shaanxi province,namely Pinus tabulaeformis,Armeniaca sibirica and Hippophae rhamnoides,were selected as the research object. Meanwhile, waste grassland in the same stand conditions was used as a reference group. The time domain reflection (TDR) was chosen to measure the soil moisture between 0 cm and 180 cm in vertical profiles. During the period from August 2010 to June 2013, the soil moisture contents were measured 3 times in every 20 cm layer. Moreover, in each observation, the probe of TDR was rotated 120 in horizontal direction. The sequential clustering method and the variation coefficient method were combined in this study in order to classify the soil layer by moisture. Results show that the soil moisture contents of Pinus tabulaeformis and Armeniaca sibirica forests were decreased respectively by 0.0193%/cm and 0.0209% /cm with increasing soil depth (0-180 cm), while the soil moisture contents of Hippophaer hamnoides forest and waste grassland were increased with the rate of 0.0046% /cm and 0.0863% /cm, respectively. Nevertheless, the soil moisture contents of the three types of artificial forests were all less than those of waste grassland between 80 cm and 180 cm in vertical profiles.Thus, studies should pay more attention to soil moisture below the 80cm soil layer in the Loess Plateau of northern Shaanxi province and determining whether it will be absorbed by the root system of the three kinds of artificial forests. Using variation coefficient method, our observation also suggests the soil layersin 0-180 cm vertical profiles can be divided into three groups, which are quickly changing layer, active layer and subactive water layer. Moreover, the soil layers can also be divided into three groups using sequential clustering method. And the grouping result is comparatively consistent with that by variationcoefficient method and by sequential clustering method. Thus, the sequential clustering method is likelyto be reasonable when used in classification of soil layer. The result of this research would provide basic theory for selecting species in near-natural affore station.
Soil moisture and nutrient characteristics of soil and water conservationforests in Loess Plateau of western Shanxi Province
In order to explore soil moisture and nutrient characteristics of soil and water conservation forests, we investigated soil moisture, soil nutrients and root density of three types of forests, i. e. ,Pinus tabulaeformis plantation,Robinia pseudoacacia plantation and secondary forest in Loess Plateau of western Shanxi Province, using EnviroSMART soil moisture monitoring system. The results showed that: 1) Theaverage moisture content of 0 -150 cm soil layer in three types of forests was ranked as secondary forest >P. tabulae formisplantation >R. pseudoacacia plantation. 2) In general, the monthly changes of soil moisture in secondary forest and R. pseudoacacia plantation were consistent, while it was more volatile in the P. tabulae formisplantation. The soil moisture contentin secondary forest was higher than that in the R. pseudoacacia plantation.3)The total root density in 0 -30 cm soil layer followed the order of secondary forest >R. pseudoacacia plantation >P. tabulaeformis plantation, and the density decreased with the increase of soil depth. 4) In all the three forest types, there was a significantly negative correlation between soil moisture content and root density in 0 -30 cm soil depth. 5) In the 0 -30 cm depth,the contents of soil organic matters, total phosphorus and total potassium in secondary forest were significantly higher than those in the R. pseudoacacia and P. tabulae formisplantations, with little difference between the latter two types of plantation. 6) Contents of organic matters and total potassium decreased with the increase of soil depth, while no obvious change in total phosphorus content was found with the increase of soil depth in three types of forests.
Bai Xiaofang, Xu Fuli, Wang Weiling, Zhao Yafang, Wang Lingling, Sun Pengyue
Ecological stoichiometry of soil carbon,nitrogen and phosphorus in aLarix principis rupprechtii plantation
Large areas of plantations have been cultivated in China since 1950s, which provide tremendous ecological and economic services such as soil and water control, wood production, carbon sequestration and environment protection. Many problems such as soil degradation, tree diseases and wood production decline, however, also appeared after several decades of cultivation due to lack of effective management practices, which seriously threatens the stability and sustainability of plantation development and imposes severe influence on ecological and economic achievements. As the main elements circulation and nutrients turn over pool for plant growth, soil is essential in forest management.The soil fertilization maintenance and promotion have been and still are of significant interest for plantation management. A number of studies concerning spatial pattern of soil nutrients have been conducted in woodland, while little is known about the temporal pattern of soil nutrient status and stoichiometric ratios in plantations which has the important implications for dynamic balance of soil nutrients. The objective of this study was to clarify the seasonal pattern of soil stoichiometric characteristics of a 20-year-old Larix principis rupprechtii plantation in Qinling. The soil organic carbon(C), total nitrogen (N), total phosphorous (P) contents and stoichiometric ratios were measured to explore their seasonal variation and vertical distribution. The results show that: 1) The contents of C,N and P decreased with soil depth throughout the entire growing season (May to October). The contents of C, N and P have obvious seasonally dynamic changes from May to October. Soil C and Nvaried greatly in the 0-20 cm soil layer (coefficient of variance (Cv) of C and N was 0.28 and 0.22,respectively) compared to 20-40 cm and 40-60 cm soil layers (Cvfor C 0.11 -0.18; for N 0.13 -0.14), while soil P fluctuated significantly in the 40 - 60 cm layer (0.18) in comparison with theother two layers. The contents of C and P in the 0-20 cm soil layer reached the top value in October.Also, seasonal variations of C (0.11 - 0.28) and N (0.15 - 0.22) were greater than P (0.06 -0.18). 2)C/N, C/P and N/P ratios in the 0 -20 cm soil layer was significantly higher than those in 20 -40 cm and 40 -60 cm layers (P<0.05). In these three soil layers, the seasonal variation of C/N was the smallest and not obvious. The seasonal variation of N/P was the biggest. In May, C/P and N/P in both 0 -20 cm and 20 -40 cm soil layers were significantly higher than in other months (P<0. 05). In May and June, C/P and N/P in 40 -60 cm soil layer were significantly higher than in July and August. 3) The relative analysis implies that the contents of C, N and P have obvious positivecorrelation (P<0.01). Moreover, C content and C/N, C content and C/P, N content and C/N, Ncontent and N/P, P content and C/P all have obvious positive correlations, but P content has norelation with N/P.
Tang Hui, Li Zhanbin1, Song Xiaoqiang, Tong Xinqi, Wang Tian, Yang yuanyuan, Yao Jingwei
Distribution characteristics of the content of available Mn in Yingwugou watershed,Shaanxi Province
Manganese (Mn) is one of important elements in soil and its transportation process is an reflection of soil and water loss. In order to understand more deeply about the process of soil and water loss, the content of available Mn in Yingwugou watershed located in Shaanxi Province was investigated.This study employed DTPA-atomic absorption fire spectrophotometry to measure the content of available Mn in different topography and land use types of the watershed. Then fractal dimension of the content of available Mn in a few directions was calculated and finally the distribution of the content of available Mn was clarified. The results showed that the content of soil available Mn at the Yingwugou watershed ranged from 7.43-57.67 mg/kg, 39-52 mg/kg on average. 1) Middle elevation had the highest content(41-61 mg/kg) and the value of the coefficient variation (CV) from high to low was ordered distinctively as low, middle, and high, suggesting that the available Mn in soil is moved from high to low elevations by runoff in the watershed after leaching, gathers at middle or low elevation are as, and finally the available Mn at low elevation are as is carried away by flowing river. The highest content of available Mn(43.32mg/kg) could be found on slopes with degree ranging from 8-14° and the value of CV from high to low was ranked as very gentle slope, micro-slope, very steep slope, steep slope and gentle slope; the available Mn was easier to aggregate at very gentle slope, micro-slope, and steep slope. The upslope position had the highest content (42-16mg/kg) and the value of CV from high to low was ordered as downslope, middle slope, upslope, indicating that runoff is the main force to move the available Mn. 2) The woodland had the highest content of 42.07mg/kg and the value of CV from high to low was ranked as farmland, woodland, grassland. The woodland and the grassland had more complicated soil structures because of more biocenoses and less disturbance. The grass roots have a high ability to utilize the available Mn and the soil texture of farmland is highly uniform. All of these reasons lead to the current distribution characteristics of content of available Mn in the different landuse types. 3) The fractal characteristics wereobvious at the 45° direction, and extent of variation was the highest. The high content of Mn was distributed in the west, south, and north of the watershed. The total spatial pattern of the watershed was that the content of available Mn increased from east to west and then decreased, but still higher than the east. These results would provide reference to describe the process of soil and water loss.
Shao Yongchang, Zhang Jinchi, Sun Yongtao, Li Juanjuan, Zhuang Jiayao, Li Erhuan, Xue Xue
Comparison of transpiration characteristics and cooling and humidifying functions of the main greening tree species in summer in Shanghai
In order to quantitatively explore the characteristics of transpiration water consumption and functions of cooling and humidification for the typical urban greening tree species in summer, we selectedseventeen main greening tree species in Shanghai and measured their transpiration characteristics by using LI-6400 photosynthetic apparatus. The correlation between transpiration and the main influencing factors was analyzed, and the functions of cooling and humidification were estimated quantitatively by clustering analysis. The results showed that:1) The daily variation of transpiration rate showed a pattern of “low in the morning and evening but high around noon, presenting unimodal or bimodal distribution.Ilexchinensis,Zelkova schneideriana, andMagnolia albahad a high mean daily transpiration rate, whileMagnolia grandiflora,Koelreuteria paniculata,Distylium racemosum, and Michelia maudiaehad a muchlower value. 2) Except for a very few tree species, the transpiration rate had a positive correlation with net photosynthetic rate, stomatal conductance, leaf temperature, solar radiati on, air temperature, etc.3) In terms of the capacity of daily cooling and humidifying per unit of land area,Ilex chinensis and Cinnamomum camphora were the higher, while that of Koelreuteria paniculata,Ginkgo biloba,Micheliamaudiae,Distylium racemosum,Elaeocarpus decipiens,Magnolia grand if lorawere relatively lower.When it comes to selecting tree species considering the capacity of cooling and humidifying,Ilexchinensis,Cinnamomum camphora,Magnolia alba,Sapindus mukorossi,Zelkova schneideriana,Liriodendron chinense,Platanusspp. ,Acer buergerianum,Bischofia polycarpa,Osmanthus fragrans,Photinia serrulataoutperform others such as Koelreuteria paniculata,Ginkgo biloba,Michelia maudiae Distylium racemosum,Elaeocarpus decipien sand Magnolia grandiflora.
Zhang Songsong, Hu Xuli, Zhang Guangcan, Xing Wei, Liu Xia, Yao Xiaoyou
Effects of different tillage methods on the project of changing slope intoterrace in small watersheds
In order to understand the implementation effects of different tillage methods on terracing project in small watersheds, we surveyed the amount of soil loss, hydrology and physical properties of soiland crop yield of the terrace where different tillage methods (furrow and ridge tillage, non-tillage and embankment tillage) had been applied after the implementation of the project, in Dayu small watershed of Yishui Cunty in Yimeng mountainous area, Shandong Province. The concept of economic index in soiland water conservation was introduced to analyze ecological and economic coupling effects in soil and water conservation of terrace with different tillage methods. The results show that: tillage methods had significant impacts on ecological and economic effects in soil and water conservation of the terracing project after the implementation of the project. 1) Compared to slope terrace (with embankment stillage), the field soil loss and field nutrient loss of fruit terrace (without tillage) were 7.1% and 9.6%respectively, which were much smaller than those of crops terrace (with furrow and ridge tillage) of22.1% and 24.8%. That was to say, the control effect of non-tillage was significantly greater than that of furrow and ridge tillage. 2) Compared with slope farmland, crops terrace and fruit terrace increased the soil particles fractal dimension, soil capillary porosity and soil total porosity by more than 30%. Butthe effect of the latter on the improvement of hydrologically physical properties of soil was greater than the former. 3) The ecological and economic index in soil and water conservation (Ec) of slope terrace (with embankment tillage) was 19% of that of the crop terrace (with furrow and ridge tillage). The ecologicaland economic index in soil and water conservation (Ec) of fruit terrace (non-tillage) was 18.87 times as high as that of crops terrace (with furrow and ridge tillage). The effects of non-tillage in controlling soil erosion and nutrient loss, improving hydrologically physical properties of soil and improving soil and water conservation economy coupling were significantly greater than embankment tillage. The way of furrow and ridge tillage that destroyed embankments and ridges could significantly reduce the ecological and economic effects in soil and water conservation of terracing project, including increasing amount of soiland nutrient loss, reducing the hydrologically physical properties of soil and the ecological and economicindex in soil and water conservation. This research mainly illustrated that after carrying out terracingproject, terraces with different tillage methods have effects to varying extent in controlling soil erosion and nutrient loss, improving hydrologically physical properties of soil, and coupling soil and water conservation and economy. Our study would provided basis and reference for understanding the relationship between terracing project and ecological and economic effect.
Evaluation on comprehensive benefit of forests in Taihang Mountains area:A case study of Youyu County, Shanxi Province
Based on the comprehensive review and comment of benefit assessment theory and method of forest resources, and using the theories of forest ecology and environmental economics, the index system to evaluate comprehensive benefits of forest resources was proposed in combination with field survey,investigation and consultation, analytic methods and computational models were established taking advantage of the market value method, and alternative hypothetical market assessment techniques as well as the comprehensive benefits of forest resources in Youyu County were evaluated. The results show thatwood value and product out put value of forests in Youyu County are 6.83*10 8 and 1.91*10 8yuan/arespectively. Value of forest ecological benefits is 3.45*10 9 yuan/a. Social benefit of forest is 3. 90*10 8yuan/a. The proportion of values of the economic, ecological and social benefits of forest resources iscalculated as 1.00:18.03:2.04.
Niu Yaobin, Gao Zhaoliang, Liu Zizhuang, Zhang Shaojia
Hydrodynamic characteristics of soil erosion on depositslope under engineering measures
Engineering deposit formed during the process of engineering construction has unique soil composition and complex underlying surface. This sort of deposit is characterized by weak anti-scourabilty due to loose texture, which may cause severe soil erosion. Hydrodynamic parameters and their relationships with runoff in steep engineering slope show different characteristics in response to hydrodynamic conditions. Most physically based soil erosion prediction models established so far are onthe basis of hydraulic characteristics. A detailed study of the hydrodynamic characteristics is the precondition and foundation to understand erosion processes on engineering deposit. Study on the characteristics of hydrodynamic parameters of soil erosion on deposit slope under different engineering measures would be helpful to provide an optional theoretical reference for selection of suitable measures.Moreover, in order to explore the optimal hydrodynamic parameters for describing the process of soilerosion under different engineering measures (fish-scale pit and level terrace), a field scouring-erosion experiment was conducted on steep slopes under three slope gradients of 24°, 28° and 32°. Runoff kinetic energy, flow shear stress and runoff power were selected as main parameters to analyze the hydraulic process of rill flow stripping surface soil particles. Results showed that on slopes under measures of fish-scale pit and level terrace, soil erosion amount was reduced because of higher soil anti-erodibility. Soil detachment rate showed a good linear relationship with both flow shear stress and streampower, while it had a logarithmic relationship with flow kinetic energy. The rill erodibility of engineeringdeposit under the condition of fish鄄scale pit was calculated to be 1为1*10-3s/m and 2.6 *10-3s2/m2,and the rill erodibility of engineering deposit under the condition of level terrace was calculated to be 5*10 -4s/m and 1.7 *10-3s2/m2. Under the same slope of engineering deposit, protection of level terracewas better than that of fish-scale pit, but the effects of these two measures had limitation in time.
Impacts of wood vinegar on enzyme activity in saline alkaline soil
Salt toxicity is one of the major edaphic factors limiting crop production and eco-environmentalquality in salinized and/or sodic soils throughout the world. Application of organic fertilizer to salinealkaline soil is considered as a good practice for soil remediation. Wood vinegar, as a new kind of liquidorganic fertilizer, plays an important role in reducing soil pH and salt content, increasing soil organic matter content and promoting plant growth in saline alkaline soil. Soil enzyme stimulates the decomposition of organic matter and the transformation of nutrient substances, can reflect the function of soil microbe, and is regarded as a potential index for monitoring soil quality in a short time.Nevertheless, the impacts of wood vinegar on enzyme activity in saline alkaline soil remain unknown. The objectives of the present study were to investigate the impacts of different wood vinegar contents onenzyme activity in saline and alkaline soil. In our study, five treatments with different contents of woodvinegar, namely 100% (not diluted), 20% (diluted 5 times), 10% (diluted 10 times), 5% (diluted20 times) and 0 (CK) were mixed with soil at a wood vinegar liquid (mL)- to- soil (g) ratio of 1:4,respectively. The soil chemical properties, such as the dissolved organic carbon, phenol, and sever alkinds of hydrolases and oxido reductase activity were measured after 20 days indoor culture. In addition, the relationship between the soil chemical properties and soil enzyme activities was analyzed by the linear regression analysis. The results showed that all the different contents of wood vinegar could significantly decrease soil pH, and increase the content of soil dissolved phenol, soil readily oxidizable carbon, soil dissolved carbon and nitrogen, NH+4and NO-3. However, the change of soil available phosphorus content was not significant. The activities of soil glycosidase and urease were inhibited at 100% wood vinegar.For soil glycosidase activity, it was decreased with the decline of wood vinegar content at the rate below 20%. The urease activities at 20% and 10% wood vinegar were significantly higher than that at 5% and CK. The activities of soil acid phosphatase and phenol oxidase were enhanced with the increasing woodvinegar content. However, alkaline phosphatase activity was significantly decreased at 20% and 10% wood vinegar. These results demonstrated the changes of soil readily oxidizable carbon and NO-3-N werepositively related to the activity of soil glycosidase. The changes of soil pH and available phosphorus hada significantly negative correlation with soil acid phosphatase activity, but a significantly positive correlation with alkaline phosphatase activity. On the other hand, the change of soil dissolved phenol hada significantly positive correlation with phenol oxidase activity. In conclusion, the application of woodvinegar in the saline alkaline soil can stimulate enzyme activity. The long-term impacts of the application of wood vinegar on soil enzyme activities should be concerned in the future since our conclusion isobtained by a short indoor culture manipulation.
Impact of row grade on losses of nitrogen and phosphorus under seepage condition
The existence of row grade in the contour ridge system results in that runoff from side slopes accumulates in the low areas along furrows. When the collected rainfall exceeds the storage capacity of soil,that is, when soil becomes saturated, seepage flows through ridges and then leads to the collapse of the contour ridge system. In this study, we conducted rainfall simulation experiments to evaluate effects of rowgrade on nitrogen and phosphorus losses in runoff for brown soil during different erosion stages (seepageerosion, inter-rill and rill erosion) under seepage condition, using the runoff box by which row grade and field slope can be adjusted simultaneously. Results showed that:1) During seepage erosion stage, NO3-N,NH4-N and PO4-P losses under different row grades were in the order of 2° > 10° > 6°, while differences in their concentrations ranked in the sequence of 10° >6° >2°; for inter-rill and rill erosion stages, thesequence of NO3-N loss under different row grades was 10° >2° >6°, while the order of NH4-N and PO4-P losses among row grades was 6° >10° >2° and 2° >6° >10°, respectively. 2) For seepage erosionstage, difference in runoff was the dominant factor that induced the variation of nutrient loss among row grades, while for inter-rill stage it was concentration. 3) The variation of row grade only altered NH4-N lossmechanism during inter-rill and rill erosion stages. These findings in our study would provide scientific guidance for evaluating soil conservation benefit and for implementing the contour ridge system.
Farmers’ selection response to the economic compensationpattern for the cultivated land preservation scheme:A case study of Chengdu City
The selection of compensation pattern is one of the most important processes in the design of economic compensation for cultivated land preservation mechanism, which would also contribute to the achievement of cultivated land preservation and the sustainability of the project. On the other hand, from the perspective of farmers in the project area, the selection of compensation pattern would bring important impact on their enthusiasm of agricultural production activities and the improvement of welfare. Besides,from a national perspective, as a typical pilot area of economic compensation for cultivated land preservation in China, Chengdu's experience in economic compensation for cultivated land preservation would exert important significance for the promotion of this scheme in other areas. So, through there search of farmers' reaction to the policy in Chengdu, we can provide a reference for improving the efficiency of economic compensation for cultivated land preservation scheme. In this paper, based on the investigation of 223 households in Shuangliu and Congzhou areas, two important districts in central Chengdu, the multinomial logistic model (MNL) was used to analyze the preference and the factors offarmers' behavior when they participated in the economic compensation for cultivated land preservationscheme, and farmers' characteristics, households' characteristics, agricultural production characteristics and farmers' perception characteristics were chosen as four main independent variables to measure thedegree of influence on the compensation pattern. The conclusions are as follows: 1) Farmers have astrong preference for the monetary compensation and endowment or agricultural insurance compensation,which account for 47.4% and 39.6% of the total samples respectively, because they think these twopatterns are more convenient and securer than other patterns. Comparatively, the inclination to other patterns is relatively weak, such as the material compensation, technological ( intelligence )compensation, policy compensation and so on, which only accounts for 13% of all the samples. 2) The multinomial logistic model result shows that, farmers' selection preference changes with the attribute of their educational level, age, economic conditions, agricultural production characteristics and their perception for the scheme. Other factors such as the population structure, number of farming and off-farmlabors, arable land size, economics and the proportion of non-agricultural income all have significant influence on the selection of compensation pattern. However, farmers' perception for agricultural policyand their understanding of farmland ecological function are not significant in the model. 3) Farmers' features of land transfer have important effects on the choice of compensation pattern. That is to say,farmers, who are involved in land transfer, have a stronger preference to the endowment insurance compensation pattern, for the reason that they think endowment insurance compensation pattern is more sustainable and affordable when they get old.
Investigation of shrub germplasm resources and community successionin Kongtong Mountain,eastern Gansu Province
In the region of Kongtong Mountain of eastern Gansu Province, there are various and complextypes of plants with seed plants 702 species in 356 genera of 90 families, in which 662 species in 343genera of 88 families are wild type. It is a valuable natural species gene pool. The forest coverage rateincreased from 37.4% in 1996 to 45.8% in 2011, and shrub land area increased from 3216hm21996 to 3 865hm2 in 2011. Accompanying with the shrub land area increasing is the complex successional change of community structure. In order to clarify the structure and community of shrubs and vegetation landscape change of Kongtong Mountain under different habitat conditions, we conducted a resource scensus in the Kongtong Mountain forest region with rich shrub resources banned for many years. Theregion was divided into four different habitat types according to the aspect and location, i. e. , sunny,semi-sunny, semi-shady and shady. According to the detailed investigation of habitat types, a basesurvey line was selected along each of the channels, slope moldings, ridges and other typical geomorphology. Finally, 13 sample lines and 115 determination sections were set. We systematicallyanalyzed the relationship among shrub community, ecological environment, shrub communitycomposition, structure and community succession in the Kongtong Mountain under various ecologicalconditions. The results showed that there are a total of 142 species of shrub, sub-shrub and liana plants,belonging to 39 families and 74 genera. Except for one family, one genus and two species that belong to the gymnosperms, they are all angiosperms with most species belonging to North China Flora. Various shrubspecies have their certain spatial distribution features. There is a certain hierarchy along the verticaldistribution that can be divided into three elevation zones: 1 393-1 496 m, 1 796-1 946 m and 1 946-2046 m. Shrub community compositions are different under four slope conditions with 12 main species distributed in sunny slopes and Sophora davidiias the constructive species, 14 main tree species in semi-sunny slopes and the sea buckthorn as constructive species,12 main tree species in semi-shady slopes, and 15 main tree species in shady slopes and the ostryopsis as constructive species. In the case without disturbance, the succession of shrub community began from the bare wasteland during the period, and hasprobably experienced natural grassland, mixed shrub and grass, shrub community, sub-shrub community and the ultimate succession of arbor community. It is a complicated system for the development andutilization of shrub resources in Kongtong Mountain and therefore we must strengthen the protection anddevelopment of shrub resources and plan utilization, vigorously protect the suitable shrubs such asSophoradavidii, sea buckthorn,Prunus davidiana, caragana,Ostryopsisand so on, expand the scale ofresources, and ensure the sustainable development and succession of shrub community in the region.
Reconstruction of early summer temperature and annualaridity index at Mulan Weichang in northern China
The Mulan Weichang National Nature Reserve, located in northern Hebei province, adjacent to southeastern Inner Mongolia, is an important ecological barrier and nature reservoir for Beijing-Tianjin-Hebei region. Cognizing the historical climate change of this area will benefit the ecological protection and management of North China Plain. As an essential research technique for the climate variability and predictability (CLIVARl), dendroclimatology tackles problems of present and past climate withinformation of dated tree-rings. According to the theories of dendroclimatology, we developed two-groupstandard chronologies (STD), residual chronologies (RES) and autoregressive chronologies (ARS)based on tree-ring widths of Chinese pine (Pinus tabuliformis) and Yeddo spruce (Picea jezoenssisvar.komarovii) from two sampling points in the nature reserve and all the chronologies were significantly correlated with each other. The correlation analyses between chronologies and climate factors showed thatthe radial growth of both arbor species was closely related to summer temperature and annual precipitation. Among all the calculations, STD of Chinese pine ( STDpine) and May-June meantemperature had the maximum correlation coefficient (r=-0.654,P<0.01). Additionally, wein vestigated the relationship between chronologies with ecoclimatic indices. The analysis suggested that tree-ring growth was highly influenced by humidity index and aridity index. Using regression analysis, the mean temperature of May to June, the temperature of May and annual aridity index from 1909 to 2008 were reconstructed on the basis of STD pine. After calibration, the explained variances of the three reconstructions value were 48.1%, 39.9% and 33.8% respectively. The trend of change of eachestimated series was consistent with the observed data. In addition, the estimated and observed aridity indexes were both better correlated with temperature than precipitation, indicating that the contribution of temperature to the aridity of the study area was larger than precipitation. During the entirere constructed series, the most distinctively warm period occurred between the 1910s and 1930s. Soon afterwards, the temperature had a rapid fall and reached the lowest point in 1935. After that, it gradually increased and lasted for the next five years, then began to decrease again. Although there wasa slight rise from 1957 to 1968, the series showed a moderate descending tendency for the next 40years. The temperature has increased rapidly since the middle 1990s, showing a warming period.There were four xerothermic periods and three clammy periods in the past one hundred years. Theintervals above average of each reconstructed series comprised 1909—1929, 1939—1948, 1980—1989 and 1997—2008, while the below ones were consisted of 1930—1938, 1949—1979 and 1973—1979. A significant cycle of quasi 21 year was also detected in the series. Moreover, spatial correlation analyses revealed that the reconstructions were regionally representative. The estimated May-June mean temperature and May temperature can be well comparable with previous research of surrounding areas, as well as the historical drought events.
