A Fractal Method of Estimating Soil Structure Changes Under Different Vegetations on Ziwuling Mountains of the Loess Plateau, China

Fractal method is a new method to estimate soil structure. It has been shown to be a useful tool in studies related to physical properties of soil as well as erosion and other hydrological processes. Fractal dimension was used to study the soil structure in soil at different stages of vegetative succession on the Ziwuling Mountains. The land use and vegetation types included cultivated land, abandoned land, grassland, two types of shrub land, and three types of forests. The grassland, shrub land, and forested areas represented a continuum in vegetative succession that had occurred naturally, as the land was abandoned in 1862. Disturbed and undisturbed soil samples were collected from ten vegetation types from depths of 0-10, 10-20, and 20-30 cm on the Ziwuling Mountains, at a site with an elevation of about 1 500 m. Particle size distribution was determined by the pipette method and aggregate size distribution was determined by wet sieving. The results were used to calculate the particle and aggregate fractal dimension. The results showed that particle and aggregate fractal dimensions varied between vegetation types. There was a positive correlation between the particle fractal dimension and the weight of particles with diameter 〈 0.001 mm, but no relationship between particle fractal dimension and the other particle size classes. Particle fractal dimension was lower in vegetated soils compared to cropland and there was no consistent relationship between fractal dimension and vegetation type. Aggregate fractal dimension was positively correlated with the weight of 〉 0.25 mm aggregates. Aggregate fractal dimension was lower in vegetated soils compared with cropland. In contrast to particle fractal dimension, aggregate fractal dimension described changes in soil structure associated with vegetative succession. The results of this study indicate that aggregate fractal dimension is more effective in describing soil structure and function compared with particle fractal dimension.     

Impact of Microbial Inoculants on Microbial Quantity,Enzyme Activity and Available Nutrient Content in Paddy Soil

The experiment was conducted to study the impact of application of microbial inoculants, compared with no microbial fertilizer, on enzyme activity, microbial biomass and available nutrient contents in paddy soil in Heilongjiang Province. The application of soil phosphorus activator was able to increase the quantity of bacteria and fungi in soil, but its effect on actinomycetes in soil was not significant. The application of microbial inoculants increased the urease and sucrase activities in soil over the growing season, but only at the maturing stage soil acid phosphatase activity was enhanced with the applying soil phosphorus activator. The application of soil phosphorus activator increased alkali-hydrolyzable nitrogen and available phosphorus contents in soil, but did not increase available potassium content in soil. The optimal microbial inoculant application rate as applied as soil phosphorus activator was 7.5 kg·hm~(-2).     

Spatial variability of soil properties in red soil and its implications for site-specific fertilizer management

Assessing spatial variability and mapping of soil properties constitute important prerequisites for soil and crop management in agricultural areas. To explore the relationship between soil spatial variability and land management, 256 samples were randomly collected at two depths(surface layer 0–20 cm and subsurface layer 20–40 cm) under different land use types and soil parent materials in Yujiang County, Jiangxi Province, a red soil region of China. The pH, soil organic matter(SOM), total nitrogen(TN), cation exchange capacity(CEC), and base saturation(BS) of the soil samples were examined and mapped. The results indicated that soils in Yujiang were acidified, with an average pH of 4.87(4.03–6.46) in the surface layer and 4.99(4.03–6.24) in the subsurface layer. SOM and TN were significantly higher in the surface layer(27.6 and 1.50 g kg~(–1), respectively) than in the subsurface layer(12.1 and 0.70 g kg~(–1), respectively), while both CEC and BS were low(9.0 and 8.0 cmol kg~(–1), 29 and 38% for surface and subsurface layers, respectively). Paddy soil had higher pH(mean 4.99) than upland and forest soils, while soil derived from river alluvial deposits(RAD) had higher pH(mean 5.05) than the other three parent materials in both layers. Geostatistical analysis revealed that the best fit models were exponential for pH and TN, and spherical for BS in both layers, while spherical and Gaussian were the best fitted for SOM and CEC in the surface and subsurface layers. Spatial dependency varied from weak to strong for the different soil properties in both soil layers. The maps produced by selecting the best predictive variables showed that SOM, TN, and CEC had moderate levels in most parts of the study area. This study highlights the importance of site-specific agricultural management and suggests guidelines for appropriate land management decisions.     

Effect of Different Vegetation Types on the Rhizosphere Soil Microbial Community Structure in the Loess Plateau of China

The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows：two natural grassland （Artemisia capillaries and Heteropappus altaicus）, two artificial grassland （Astragalus adsurgens and Panicum virgatum）, and two artificial shrubland （Caragana korshinskii and Hippophae rhamnoides） species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids （PLFAs） and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative （G-） bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive （G＋） bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal：bacterial PLFA ratio. Correlation analysis indicated a signiifcant positive relationship among the microbial biomass C, G- bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions signiifcantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.     

黑麦草-白三叶人工草地退化趋势研究(英文)

[Objective] The study aimed to explore the degradation law and trend of artificial grassland. [Method] Taking the ryegrass (Lolium perenne)-white clover (Trifolium repens) artificial grassland in Maiping Township, Guizhou Province as the research object, the grassland vegetation of 40 quadrats from different areas (area around the sheep shed, hilltop, hillside, flatland at the foot of the hill) were analyzed by comparing the dominance and richness index. [Result] Degradation of different degrees appeared in various areas of this artificial grassland. To be specific, the degradation of grassland around the sheep shed was not serious for less consumption by the sheep; however, the areas on the hilltop and hillside degenerated to the grassland types of dallis grass (Paspalum dilatatum Poir.)-Indian lovegrass (Eragrostis pilosa) and dallis grass-cogongrass [Imperata cylindrica (Linn.) Beauv.], respectively, and the area at the foot of the hill degenerated to the grassland type dominated by garland chrysanthemum (Chrysanthemum coronarium L.) and knotgrass (Paspalum distichum L.). [Conclusion] This study provided a basis for grassland improvement as well as the efficient and sustainable utilization of grazing-type artificial grassland in South China.     

Studies on the Root Characteristics of Maize Varieties of Different Eras

Experiment was conducted at the Gongzhuling Experimental Station of Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Jilin Province, China, during 2009-2010. Six representative varieties of maize (Baihe in the 1950s, Jidan 101 in the 1960s, Zhongdan 2 in the 1970s, Yedan 13 in the 1980s, Zhengdan 958 in the 1990s, and Xianyu 335 in the 2000s) were each planted under two different densities (52 500 and 82 500 plants ha-1) and two different nitrogen application levels (150 and 300 kg ha-1). Root characteristics and distribution among soil layers were studied by the field root digging method. The results showed that root mass increased with the process of the growth and development of the plant, and it peaked at kernel filling stage, and decreased at maturity due to the root senesces. Root mass of different maize varieties from the 1950s to 1980s had a trend of increase, while it decreased for the modern varieties. Root length and root surface areas had the similar changing trend. The study suggested that early maize varieties may have root redundancy, and reducing root redundancy may be a direction for variety improvement for high yield. Root characteristics were affected by nitrogen application level and density; modern varieties were more suitable for higher fertilizer application level and density conditions. Root characteristics distribution among soil layers decreased by an exponent equation, but the regression coefficients of different varieties were different. Though the root length density (RLD) of every soil layer of different varieties also decreased by an exponent equation, there were large variations of RLD in every part of a layer.     

Studies on Fast Remediation of Soda Meadow Alkaline Soil

Researches on models of remediation quickly in soda meadow alkaline soil, and dynamic variation of water-salt in saline soil of Zhaozhou County were studied systematically from 2001 to 2006. Realize the vegetation cover of those years through the artificial planting, mixed seeding lyme grass （Elymus dahuricus Turcz） and melilot in the mode of rotary tillage and deep loosening in lower and medium saline soils. The results showed that there was remarkable relationship between net evaporation （difference of precipitation and evaporation） and total salt content in the soil. The net evaporation could be used as a new method to forecast the dynamics variation of salt to ensure the pasture optimum sowing time. Realize the autumnal vegetation cover of those years through direct planting on the bourgeon layer of soda meadow alkaline soil, on the other hand, the covered pasture made the function of restraining salt and alkaline content to realize the biology reverse succession quickly. Forage seeds were seeded directly on the seeding bed of soda alkaline meadow at the end of July. In fall of the same year, a certain amount of biomass was obtained. The model, which has remarkable economical efficiency and use widely, represented the innovative model for the fast vegetation restoration on the soda alkaline meadow soil.     

Vertical Migrating and Cluster Analysis of Soil Mesofauna at Dongying Halophytes Garden in Yellow River Delta

For the first time,we used Tullgren method made a study on vertical migrating and cluster analysis of the soil mesofauna in Dongying Halophytes Garden in the Yellow River Delta(YRD),Shandong Province.The results showed that the soil mesofauna tended to gather on soil surface in most samples at most times,but the vertical migrating greatly varied in different seasons or environment conditions.Acari was the dominant group.The index of diversity of the soil fauna was correlated with the index of evenness.The Acari’s number of individuals infected other species and numbers.Dominant group-Acari made greater contribution to the result of cluster analysis,and there were significant differences between communities in different habitats by cluster analysis with both Bray-Curtis and Jaccard similarity coefficient.     

The main physical properties of planosol in maize(Zea mays L.) cultivation under different long-term reduced tillage practices in the Baltic region

The impact of sustainable reduced tillage(RT) on the physical properties of soil is well documented worldwide; however, there is no precise information about the influence of long-term RT or no-till(NT) on the soils at the boundary for grain maize-growing in the semi-humid subarctic climate conditions of the Baltic states, especially on the formation of a hardened upper soil layer(10–15 cm in depth)- "loosening hardpan". This study was carried out at the Research Station of Aleksandras Stulginskis University, Lithuania from 2009–2012. The investigations were based on a long-term(since 1988) field experiment. The aim of the investigation was to ascertain the influence of reduced primary tillage on the main soil's physical properties. This study examined soils that were deep ploughing(DP), shallow ploughing(SP), deep cultivation(DC), shallow cultivation(SC), and no-till(NT). Reducing the tillage intensity to NT had no significant effect on the structural soil's composition; however, the stability of the structure of the 1 and 0.25 mm-size fractions was significantly higher in the non-reversibly tilled(DC, SC) and NT plots. The penetration resistance of the DP soils was less after primary tillage and wintering, and became similar to the NT plots at the end of the maize growth season. After primary tillage and wintering, the soil moisture content in the upper soil layer(0–5 cm depth) of the NT plots was 17–49 and 16–18% higher than that in the DP. Long-term reduction of primary tillage up to NT generally had no significant effect on the moisture content and soil bulk density of the 0–10 and 10–20 cm layers. The results showed that long-term RT stabilized the physical quality of soil. Less soil penetration resistance was established in the DP plots compared to both RT and NT, however, indicators of the formation of a uniform "loosening hardpan" layer were not found. It is summarized that long-term RT or NT systems stabilize, or may increase, the physical quality of soil in crop cultivation with low inter-row coverage potential(maize), and could be applied in semi-humid subarctic climate conditions as a good option to prevent soil degradation.     

Long Term Effects of Farming System on Soil Water Content and Dry Soil Layer in Deep Loess Proifle of Loess Tableland in China

Soil water is strongly affected by land use/cover in the Loess Plateau in China. Water stored in thick loessal soils is one of the most important resources regulating vegetation growth. However, soil water in the deep loess proifle, which is critical for maintaining the function of the“soil water pool”is rarely studied because deep proifle soil samples are dififcult to collect. In this study, four experimental plots were established in 2005 to represent different farming systems on the Changwu Tableland：fallow land, fertilized cropland, unfertilized cropland, and continuous alfalfa. The soil water content in the 15-m-deep loess proifles was monitored continuously from 2007 to 2012 with the neutron probe technique. The results showed that temporal variations in soil water proifles differed among the four farming systems. Under fallow land, the soil water content increased gradually over time, ifrst in the surface layers and later in the deep soil layers. In contrast, the soil water content decreased gradually under continuous alfalfa. The distributions of soil water in deep soil layers under both fertilized and unfertilized cropland were relatively stable over time. Thus farming system signiifcantly affected soil water content. Seven years after the start of the experiment, the soil water contents in the 15-m-deep proifles averaged 23.4%under fallow land, 20.3%under fertilized cropland, 21.6%under unfertilized cropland, and 16.0%under continuous alfalfa. Compared to measurements at the start of the experiment, both fallow land and unfertilized cropland increased soil water storage in the 15-m loess proifles. In contrast, continuous alfalfa reduced soil water storage. Fertilized cropland has no signiifcant effect on soil water storage. These results suggest that deep soil water can be replenished under the fallow and unfertilized farming systems. Dry soil layers （i.e., those which have soil water content less than the stable ifeld water capacity） in the subsoil of the Changwu Tableland region can be classiifed as either temporary dry soil layers or persistent dry soil layers. Temporary dry soil layers, which typically form under annual crops, often disappear during wet years. Persistent dry soil layers generally develop under perennial vegetation. Even after removing the vegetation, persistent dry soil layers remain for several decades. This study provides information useful for the conservation and utilization of soil water resources in the Loess Tableland.     

宁夏沙坡头人工植被区土壤真菌种群的动态研究

[目的]研究宁夏沙坡头人工植被区不同沙丘土样在不同时间、不同土层真菌的变化情况。[方法]以9个沙地土样与1个土壤土样作比较,对不同时间、不同土层真菌的种类、数量和分布进行了比较分析。[结果]同一样地环境、不同空间层次以及不同样地环境、相同空间层次草地土壤真菌数量变化均较大,而各土壤类型的真菌数量分布均以翠柳沟(天然荒漠草原)最多、流沙最少;在不同固沙地类型中,翠柳沟真菌种类和数目最多。[结论]人工植被区土壤真菌的数量随固沙年代的增加而增加,因此加强沙地的植被建设和人工管理有助于改善沙漠化现状。     

人工固沙植被区土壤酶活性研究

[目的]研究人工固沙植被区土壤酶的活性。[方法]通过采集流沙,自然植被区,1956、1964、1981、1987、1990年人工固沙植被的土壤表层样品（0～5 cm）,对各类型土壤的脲酶、蔗糖酶、磷酸酶、纤维素酶、多酚氧化酶、淀粉酶、过氧化氢酶活性进行了研究。[结果]不同固沙年代土壤表层（0～5 cm）酶活性大小依次为自然植被区〉1956年人工植被区〉1964年人工植被区〉1981年人工植被区〉1987年人工植被区〉流沙区;同一年代固沙植被区,不同地形之间土壤表层（0～5 cm）酶活性大小依次为迎风坡〉背风坡。[结论]该研究结果为提高人工植被固定沙丘工程系统的稳定性提供了依据。     

鄂尔多斯高原北部沙区生长季土壤水分特征分析

土壤水分是沙地植被稳定性的决定因素之一。在鄂尔多斯高原北部沙区选择地形或植被类型各异的24块样地进行生长季土壤水分监测与分析。结果表明，研究区土壤水分具有极高的时空异质性，不同样地、不同层之间的土壤体积含水量在0．7％～39．4％之间变化，且多数样地存在0～10cm厚的干土层；0～70cm厚度土层的平均水分含量大于10％的样地的等值线图具有极大的相似性，小于10％的样地差异较大却分布了研究区的主要植被类型；土壤水分对降水有明显的响应作用，在三维等值线图上表现出典型的凹陷（干季）和凸起（雨季）。进一步探究该区域以土壤水分为主的自然植被分布格局、人工植被配置、生态水文过程转变、人工生态系统的演替等问题，将有助于完善该区域的生态安全格局。     

浑善达克沙地不同龄级沙柳灌丛土壤有机碳研究

[目的]研究浑善达克沙地不同龄级人工沙柳灌丛土壤有机碳分布规律,为进一步研究干旱区群落演替过程中碳收支以及生态恢复过程中的植被类型选择提供科学依据。[方法]对浑善达克沙地不同龄级(2、4、6、8 a)人工沙柳灌丛土壤p H、容重、有机碳、碳密度进行研究。[结果]土壤p H在7.34~7.60,且与土壤有机碳的变化无明显相关性。同一龄级植被垂直分布上,表层土壤容重较底层低,与土壤有机碳含量的变化呈负相关。土壤有机碳在0.44~1.10 g/kg,不同龄级沙柳灌丛不同土层土壤有机碳含量均随林龄的增加出现先减低后升高的趋势,同一龄级沙柳灌丛不同土层的土壤有机碳含量无明显的变化规律。表层土壤碳密度随着龄级的增大呈先降低后增加的趋势。8 a沙柳灌丛土壤碳密度最高,为9.59 kg/m~2;随着土层的加深土壤碳密度不断增大。[结论]沙柳灌丛对沙地植被恢复、土壤碳库有重要作用。     

毛乌素沙地樟子松人工林土壤物理性质的时空变异规律

以毛乌素沙地榆林沙区樟子松人工林土壤为研究对象,分析不同林龄樟子松人工林土壤质量含水量、土壤体积质量、孔隙度时空变异规律。结果表明,土壤质量含水量在流沙地为丘间地>迎风坡>背风坡>丘顶,在樟子松人工林为丘间地>背风坡>迎风坡>丘顶,并随土层深度增加而增加,0～5cm土层质量含水量樟子松人工林高于流沙地,5～25cm和25～50cm土层低于流沙地。土壤体积质量在流沙地为丘顶>迎风坡>背风坡>丘间地,在樟子松人工林为丘顶>中部(迎风坡、背风坡)>丘间地,随土层深度增加而增加,且樟子松人工林对应各层土壤体积质量均小于流沙地。毛管孔隙度均为丘间地>中部(迎风坡、背风坡)>丘顶,土壤孔隙度(总孔隙度、毛管孔隙度、非毛管孔隙度)随土层深度增加而降低,樟子松人工林对应各层土壤孔隙度均大于流沙地。随樟子松林龄增加,质量含水量和孔隙度分别增加1.32%～21.82%、2.88%～12.00%,土壤体积质量降低1.16%～7.12%。统计分析表明,所测指标总体上存在显著差异。     

间作芳香植物对沙地梨园土壤微生物数量与土壤养分的影响

【目的】探讨间作芳香植物对梨园土壤微生物数量和土壤养分的影响。【方法】以沙地梨园间作香矢车菊、香薄荷、香荆芥、藿香蓟和柠檬罗勒为处理,自然生草为对照,分别于梨树幼果期、果实膨大期和果实成熟期,测定分析不同土层土壤中微生物的数量和土壤养分的含量及其相互关系。【结果】梨园间作香矢车菊和柠檬罗勒较对照显著提高各个发育时期和各土层中土壤微生物的数量,调节土壤微生物群落中真菌、细菌、放线菌的比例。和对照相比,其它处理对各发育时期和各土层中土壤微生物数量和比例的影响呈现出多态效应。不同处理条件下梨树果实膨大期和果实成熟期各土层中微生物数量都高于幼果期,而且土壤微生物群落中真菌、细菌和放线菌的比例优于幼果期;不同处理条件下梨园0—20 cm土层内土壤微生物数量显著高于20—40 cm土层。各处理和对照相比对土壤养分的效果呈现多种差异;随着梨树发育时期变化,土壤养分含量在不同处理条件下和梨园不同土层中的变化趋势不同。相关分析表明,在沙地梨园间作芳香植物条件下,土壤中各类微生物的数量与土壤养分诸元素间也存在着多种显著的相关关系。【结论】间作芳香植物对于沙地梨园土壤微生物数量及其群落中真菌、细菌和放线菌的比例与土壤中有效态养分含量具有良好的调节作用,其中柠檬罗勒对提高梨园土壤微生物数量、土壤养分含量的综合效果最佳。     

黄土高原区煤矿复垦地乔灌木根区土壤特性研究

采用化学分析、微生物平皿培养,研究了黄土高原区准格尔煤田黑岱沟露天煤矿人工复垦区9种乔灌草不同配置下的土壤0～20cm及20～40cm土层60个土样的土壤性质及微生物的数量与组成。结果表明：①黄土高原区露天煤矿人工复垦区与裸地土壤中仍然生存着数量较多的细菌、放线茵及真菌,其中各类群的数量排序为：细菌〉放线茵〉真菌;②不同树种下的土壤中细菌、放线茵及真菌数量不同,土壤微生物的数量按灌木林〉乔木林排序;③黄土高原“果树人工林-微生物-土壤”生态系统微生物数量大,种类较多,生物活性强,对土壤物质转化及肥力提高有明显作用。在恢复黄土高原植被时应将沙棘作为先锋树种。     

茯苓栽培场土壤微生物区系与酶活性变化初探

[目的]探索茯苓栽培场不能连续使用的原因和解决办法。[方法]在茯苓生产的主产区安徽省岳西县选择了3个栽培样地,在茯苓栽培前、后期两次从窖底50 cm和窖中25 cm两层采取土样,测定细菌、放线菌和真菌的数量以及土壤脲酶、酸性磷酸酶、脱氢酶和过氧化氢酶的活性。[结果]栽培前、后微生物总数平均下降了14.8%,细菌增加了2.3%,放线菌和真菌分别下降了52.6%、66.8% 两层比较,50 cm层比25 cm层放线菌下降多6.6个百分点,真菌下降多18.2个百分点。脲酶和酸性磷酸酶活性平均降低了11.6%和12.2%,脱氢酶和过氧化氢酶降低了90.4%和91.7%。此外,根据微生物数量变化推测,茯苓可能产生化感物质。[结论]土壤微生物数量和酶活性的降低以及化感物质的产生,反映了土壤生态环境质量明显变差,应该都是茯苓栽培场不能连续使用的一些原因。     

晋西黄土区不同水文年土壤水分特征及其主要影响因子分析

  目的  晋西黄土区生态环境脆弱,土壤水分是制约植被生长的重要因子。为深入了解该区域土壤水分年际变化,明确制约该区域土壤储水量的关键因子,探讨晋西黄土区不同植被类型在生长季节内土壤含水量的变化。  方法  以定位观测法为主,对人工刺槐Robinia pseudoacacia林、天然三角槭Acer buergerianum林和野艾蒿Artemisia lavandu-laefolia草地生长季(5?10月)内0~400 cm土壤含水量进行监测;在此基础上,根据含水量标准差对土壤进行活跃层划分,并通过生长季前后储水量的对比探究年际土壤储水量盈亏状况;测定了典型样地的土壤性质,并结合地形、不同水文年旱涝特征对土壤储水量的影响因子进行冗余分析。  结果  ①人工刺槐林、天然三角槭林和野艾蒿草地平均土壤含水量分别为8.36%~9.63%、10.01%~13.19%和15.43%~19.17%,野艾蒿草地表层土壤含水量显著高于人工刺槐林和天然三角槭林(P＜0.05)。②天然三角槭林土壤水分活跃层最深可达180 cm,人工刺槐林和野艾蒿草地土壤水分活跃层较浅;中等湿润年土壤水分活跃层最深,严重干旱年土壤水分活跃层次之,平水年土壤水分活跃层最浅。③严重干旱年,人工刺槐林、天然三角槭林和野艾蒿草地土壤水分亏缺土层深度分别为100~300、0~200和0~100 cm;平水年土壤水分的输入和输出达到平衡;中等湿润年0~200 cm土层水分得到不同程度补给,而200~400 cm土层的水分补给量接近于0。④不同深度土层土壤储水量受不同环境因子影响,其中植被类型和土壤容重是0~100 cm土层水分的主导因素,100~200 cm土层水分主要受容重和坡向控制,而不同水文年旱涝程度、土壤黏粒和粉粒含量是200~400 cm土层水分的主导因素。  结论  干旱水文年土壤水分亏缺严重,平水年及湿润年亏缺现象有所缓解,植被类型对土壤储水量影响最大。今后黄土高原地区的造林,不仅要考虑树种的耐旱能力,更应充分考虑地形、土质及生长季降水的分配情况带来的影响。图5表5参33     

莽山不同次生林土壤有机碳分布与土壤物理性质的相关性

[目的]探讨湖南莽山国家级自然保护区三类次生林土壤有机碳(SOC)分布特征与土壤物理性质的关系,为该地区森林土壤碳储量的准确计量及森林土壤固碳增汇提供参考依据.[方法]在海拔1230~1300 m区域内的杉木、粤松林和竹林内设9个固定标准地,采集不同层次土壤样品32个,测定其SOC、土壤容重及田间持水量,运用方差分析、相关分析及回归分析法研究不同植被类型SOC分布特征及其与土壤容重和田间持水量间的关系.[结果]杉、松、竹三类林地不同土层SOC含量存在显著差异(P<0.05,下同),随土壤深度增加呈递减趋势;不同林分变化幅度差异不同,且各土层间的差异达显著水平.三类林地0~40 cm土层SOC存贮有机碳在整个土层所占比重不同,分别为77.7%、77.1%和85.9%.经回归分析发现,杉、松、竹三类林地SOC和土壤容重拟合值R分别为0.632、0.727和0.615,杉木林SOC含量与土壤容重呈极显著相关(P<0.01,下同);三类林地SOC含量与田间持水率均呈极显著或显著正相关.方差分析结果表明,黏粒、粉粒、砂粒含量在同一土层中的三类林地间存在极显著差异;黏粒、粉粒、砂粒含量与SOC含量相关不显著(P>0.05),而砂粒与黏粒、粉粒存在极显著负相关.杉、松、竹三类林地砂粒含量在土壤垂直剖面各层均高于黏粒、粉粒含量.[结论]莽山不同次生林SOC与土壤物理性质密切相关,土壤容重、田间持水量、土壤机械组成等物理性质可作为营林和增加森林土壤碳汇的参考指标.