Eff ect of prescribed burning on the small-scale spatial heterogeneity of soil microbial biomass in Pinus koraiensis and Quercus mongolica forests of China

Prescribed burning can alter soil microbial activity and spatially redistribute soil nutrient elements.However,no systematic,in-depth studies have investigated the impact of prescribed burning on the spatial patterns of soil microbial biomass in temperate forest ecosystems in Northeast China.The present study investigated the impacts of prescribed burning on the small-scale spatial heterogeneity of microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)in the upper(0–10 cm)and lower(10–20 cm)soil layers in Pinus koraiensis and Quercus mongolica forests and explored the factors that infl uence spatial variations of these variables after prescribed burning.Our results showed that,MBC declined by approximately 30%in the 10–20 cm soil layer in the Q.mongolica forest,where there were no signifi cant eff ects on the soil MBC and MBN contents of the P.koraiensis forest(p>0.05)after prescribed burning.Compared to the MBC of the Q.mongolica forest before the prescribed burn,MBC spatial dependence in the upper and lower soil layers was approximately 7%and 2%higher,respectively.After the prescribed burn,MBN spatial dependence in the upper and lower soil layers in the P.koraiensis forest was approximately 1%and 13%lower,respectively,than that before the burn,and the MBC spatial variability in the 0–10 cm soil layer in the two forest types was explained by the soil moisture content(SMC),whereas the MBN spatial variability in the 0–10 cm soil layer in the two forests was explained by the soil pH and nitrate nitrogen(NO_(3)^(–)-N),respectively.In the lower soil layer(10–20 cm)of the Q.mongolica forest,elevation and ammonium nitrogen(NH 4+-N)were the main factors aff ecting the spatial variability of MBC and MBN,respectively.In the 10–20 cm soil layer of the P.koraiensis forest,NO_(3)^(–)-N and slope were the main factors aff ecting the spatial variability of MBC and MBN,respectively,after the burn.The spatial distributions of MBC and MBN in the two forests were largely structured with higher spatial autocorrelation(relative structural variance C/[C 0+C]>0.75).However,the factors infl uencing the spatial variability of MBC and MBN in the two forest types were not consistent between the upper and lower soil layers with prescribed burning.These fi ndings have important implications for developing sustainable management and conservation policies for forest ecosystems.

Spatial heterogeneity of soil chemical properties between Haloxylon persicum and Haloxylon ammodendron populations

Spatial heterogeneity is a ubiquitous feature in natural ecosystems, especially in arid regions. Different species and their discontinuous distribution, accompanied by varied topographic characteristics, result in soil resources distributed differently in different locations, and present significant spatial heterogeneity in desert ecosystems. In this study, conventional and geostatistical methods were used to identify the heterogeneity of soil chemical properties in two desert populations, Haloxylon persicum Bunge ex Boss., which dominates on the slopes and tops of sand dunes and Haloxylon ammodendron (C. A. Mey.) Bunge, which inhabits interdunes in the Gurbantunggut Desert of Xinjiang, China. The results showed that soil pH, electrical conductivity (EC), soil organic carbon (SOC), available nitrogen (AN) and available phosphorus (AP) were significantly higher in H. ammodendron populations than that in H. persicum. The coefficient of variation (CV) indicated that (1) most parameters presented a moderate degree of variability (10% 【 CV 【 100%) except pH in both plots, (2) the variability of soil pH, EC and AP in H. ammodendron populations was higher than that in H. persicum populations, and (3) SOC and AN in H. ammodendron populations were lower than that in H. persicum populations. Geostatistical analysis revealed a strong spatial dependence (C0/(C0+C) 【 25%) within the distance of ranges for all tested parameters in both plots. The Kriging-interpolated figures showed that the soil spatial distribution was correlated with the vegetation distribution, individual size of plants, and the topographic features, especially with the plants nearest to sampling points and the topographic features. In each plot, soil EC, SOC, AN and AP presented similar distributions, and fertile islands and salt islands occurred in both plots but did not affect every individual plant, since the sampling distance was larger than the size of such fertile islands. The results of topographic effects on soil heterogeneity suggested significant differences between the interdunes and dune-tops. Different topographic characteristics (physical factors) between plots result in the differences in SOC, AN and AP, while the heterogeneity of soil pH and EC arise from plant species and their distribution (biotic factor). Such biotic and physical factors did not occur in isolation, but worked together on soil heterogeneity, and played important parts in improving the soil properties. Hence these factors were ecologically valuable in the highly resource-stressed arid study area.

Spatial variation and soil nitrogen potential hotspots in a mixed land cover catchment on the Chinese Loess Plateau

Soil nitrogen(N) is critical to ecosystem services and environmental quality. Hotspots of soil N in areas with high soil moisture have been widely studied, however, their spatial distribution and their linkage with soil N variation have seldom been examined at a catchment scale in areas with low soil water content. We investigated the spatial variation of soil N and its hotspots in a mixed land cover catchment on the Chinese Loess Plateau and used multiple statistical methods to evaluate the effects of the critical environmental factors on soil N variation and potential hotspots. The results demonstrated that land cover, soil moisture, elevation, plan curvature and flow accumulation were the dominant factors affecting the spatial variation of soil nitrate(NN), while land cover and slope aspect were the most important factors impacting the spatial distribution of soil ammonium(AN) and total nitrogen(TN). In the studied catchment, the forestland, gully land and grassland were found to be the potential hotspots of soil NN, AN and TN accumulation, respectively. We concluded that land cover and slope aspect could be proxies to determine the potential hotspots of soil N at the catchment scale. Overall, land cover was the most important factor that resulted in the spatial variations of soil N. The findings may help us to better understand the environmental factors affecting soil N hotspots and their spatial variation at the catchment scale in terrestrial ecosystems.

Spatial Variability of Soil Organic Carbon in Different Hillslope Positions in Toshan Area, Golestan Province, Iran: Geostatistical Approaches

Accessibility to organic carbon(OC) budget is required for sustainable agricultural development and ecosystem preservation and restoration. Using geostatistical models to describe and demonstrate the spatial variability of soil organic carbon(SOC) will lead to a greater understanding of this dynamics. The aim of this paper is to present the relationships between the spatial variability of SOC and the topographic features by using geostatistical methods on a loess mountain-slope in Toshan region, Golestan Province, northern Iran. Hence, 234 soil samples were collected in a regular grid that covered different parts of the slope. The results showed that such factors as silt, clay, saturated moisture content, mean weighted diameter(MWD) and bulk density were all correlated to the OC content in different slope positions, and the spatial variability of SOC more to slope positions and elevations. The coefficient of variation(CV) indicated that the variability of SOC was moderate in different slope positions and for the mountain-slope as a whole. However, the higher variability of SOC(CV = 45.6%) was shown in the back-slope positions. Also, the ordinary cokriging method for clay as covariant gave better results in evaluating SOC for the whole slope with the RMSE value 0.2552 in comparison with the kriging and the inverse distance weighted(IDW) methods. The interpolation map of OC for the slope under investigation showed lowering SOC concentrations versus increasing elevation and slope gradient. The spatial correlation ratio was different between various slope positions and related to the topographic texture.

Spatial heterogeneity and source apportionment of soil metal(loid)s in an abandoned lead/zinc smelter

Metal smelting have brought severe metal(loid)s contamination to the soil.Spatial distribution and pollution source analysis for soil metal(loid)s in an abandoned lead/zinc smelter were studied.The results showed that soil was contaminated heavily withmetal(loid)s.The mean of lead(Pb),arsenic(As),cadmium(Cd),mercury(Hg)and antimony(Sb)content in topsoil is 9.7,8.2,5.0,2.3,and 1.2 times higher than the risk screening value for soil contamination of development land of China(GB36600-2018),respectively.Cd ismainly enriched in the 0–6mdepth of site soil while As and Pbmainly deposited in the 0–4mlayer.The spatial distribution of soil metal(loid)s is significantly correlated with the pollution source in the different functional areas of smelter.As,Hg,Sb,Pb and copper(Cu)were mainly distributed in pyrometallurgical area,while Cd,thallium(Tl)and zinc(Zn)was mainly existed in both hydrometallurgical area and raw material storage area.Soil metal(loid)s pollution sources in the abandoned smelter are mainly contributed to the anthropogenic sources,accounting for 84.5%.Specifically,Pb,Tl,As,Hg,Sb and Cumainly from atmospheric deposition(55.9%),Cd and Zn mainly from surface runoff(28.6%),While nickel(Ni)mainly comes from parent material(15.5%).The results clarified the spatial distribution and their sources in different functional areas of the smelter,providing a new thought for the risk prevention and control of metal(loid)s in polluted site soil.

Spatial Distribution of Surface Soil Moisture in a Small Forested Catchment

Predicting the spatial distribution of soil moisture is an important hydrological question. We measured the spatial distribution of surface soil moisture (upper 6 cm) using an Amplitude Domain Reflectometry sensor at the plot scale (2 × 2 m) and small catchment scale (0.84 ha) in a temperate forest. The spatial variation of soil water content was higher during dry conditions than that during wet conditions. Results indicated 3.1 samples at the plot scale were sufficient to estimate mean soil water content when the precision was 0.1. Soil water content increased with increasing topographic index (TI) and soil-topographic index (STI) at the small catchment scale. The correlation between soil water content and TI was higher than that between soil water content and STI. This suggests that topography is more important for estimating surface soil moisture than soil depth as formation of surface soil moisture occurs at ≤6 cm.

Driving forces and their interactions of soil erosion in soil and water conservation regionalization at the county scale with a high cultivation rate

Soil erosion control based on county scale Soil and Water Conservation Regionalization(SWCR)is an essential component of China's ecological civilization construction.In SWCR,the quantitative analysis of the spatial heterogeneity and driving factors of soil erosion among different regions is still lacking.It is of great significance for soil erosion control to deeply examine the factors contributing to soil erosion(natural,land use,and socioeconomic factors)and their interaction at the county and regional levels.This study focused on a highly cultivated area,Hechuan District of Chongqing in the Sichuan Basin.The district(with 30 townships)was divided into four soil and water conservation regions(Ⅰ-Ⅳ)using principal component and hierarchical cluster analysis.The driving factors of soil erosion were identified using the geographical detector model.The results showed thatⅰ)the high cultivation rate was a prominent factor of soil erosion,and the sloping farmland accounted for 78.4%of the soil erosion in the study area;ⅱ)land use factors demonstrated the highest explanatory power in soil erosion,and the average interaction of land use factors explained 60.1%of soil erosion in the study area;ⅲ)the interaction between natural factors,socioeconomic factors,and land use factors greatly contributes to regional soil erosion through nonlinear-enhancement of double-factor enhancement.This study highlights the importance of giving special attention to the effects of land use factors on soil erosion at the county scale,particularly in mountainous and hilly areas with extensive sloping farmland and a high cultivation rate.

典型喀斯特白云岩小流域土壤-表层岩溶带厚度空间异质性特征

土壤-表层岩溶带厚度是喀斯特地球关键带的关键指标,明确其空间异质性特征对于理解地球关键带结构演化机理以及评估水源涵养功能具有重要意义。在广西环江木连小流域1.4 km 2范围内,通过高密度电法(ERT)探测45条样线,共获取1731个样点的土壤-表层岩溶带厚度及环境因子数据资料,研究了土壤和表层岩溶带厚度的空间分布格局及其影响因素。结果表明,土壤和表层岩溶带厚度平均值分别为1.15 m和6.44 m,且分别呈现强变异程度和中等变异程度。地统计分析结果表明球状模型和指数模型分别可以反映土壤和表层岩溶带的空间结构特征。土壤厚度呈现中等空间自相关性,变程长,空间连续性好;而表层岩溶带呈现强烈的空间自相关性,变程短,空间依赖性强。土壤厚度受到环境因子(地形湿度指数、垂直曲率、曲率、坡向、坡度、高程、覆盖度、出露基岩率和植被归一化指数)的多重影响,而表层岩溶带厚度受部分环境因子影响的同时,与土壤厚度和植被类型的相关性更高。研究结果有助于喀斯特区土壤-表层岩溶带演化机理认识,并为土壤-表层岩溶带厚度的空间预测提供科学依据。

黑木相思家系适地适树品种综合评价

[目的]为选出适宜南方山地的黑木相思家系,揭示黑木相思长势土壤养分的空间分异规律与地形变化的关系。[方法]本文以杉木采伐迹地上营造的15年生7个黑木相思家系(M1~M7)为研究对象,采用经典统计学、描述性统计、地统计学方法和GIS技术,研究了7个黑木相思家系分别在不同坡位的土壤理化性质的变化规律和土壤养分的空间分布,并通过因子分析法和模糊评价法对7个黑木相思家系进行综合评价选优。[结果]7个黑木相思家系的理化性质在不同坡位的含量大多表现为下坡位>中坡位>上坡位,下坡位显著高于其他坡位;家系间土壤结构和养分含量均表现出M7、M6和M5较好;研究区各养分含量总体呈块状或条带状分布,呈现从东北和西北方向往南方向递增的趋势。[结论]综合评价值在上下坡位黑木相思家系M7值最高,其生长对土壤理化性质的改良效果最佳,在中坡位黑木相思家系M6最佳。研究结果对南方山地适地适品种和可持续发展研究具有参考价值,可用于黑木相思人工林经营管理实践中。

雅鲁藏布江上游干、支流沉积物总有机碳分布特征初探

为探究雅鲁藏布江(雅江)上游干、支流沉积物总有机碳(TOC)含量分布特征及其影响因素,研究了雅鲁藏布江上游干、支流沉积物TOC含量对粒度的响应,并基于随机森林分析(RFA)解释了流域内土地利用类型对沉积物TOC含量空间变化趋势的影响。结果表明,雅江上游沉积物TOC含量均值[(6.56±6.37)g·kg^(-1)]低于其他地区大中型河流[范围为5.95~49.06 g·kg^(-1),均值为(19.77±14.05)g·kg^(-1)]。其中,河源段沉积物TOC含量均值最低[(2.57±0.97)g·kg^(-1)],所有采样点沉积物TOC含量与黏土含量占比呈极显著正相关(r=0.64,P<0.01)。根据统计结果,包括雅江上游在内,河流沉积物TOC含量与粒径小于63μm颗粒含量具有极显著指数相关关系(r=0.77,P<0.01)。随机森林分析进一步表明,雅江上游沉积物TOC陆源贡献率中草地贡献率最大(48.12%),且受土地利用方式从以低覆盖度草地、裸土地为主导(上游头段)逐渐过渡到以中、高覆盖度草地和农、牧、一类工业用地(M1类)等为主(上游中、末段)的影响,沉积物TOC含量在空间上表现为随流向逐渐增加的趋势。总体上,人为干扰因素少及河流沉积物以砂质为主体是雅江上游沉积物TOC含量较低的重要原因。本研究深化了对雅鲁藏布江上游沉积物总有机碳含量分布特征及其影响因素的理解,可为进一步探究高原河流碳循环、生态环境保护以及区域可持续发展提供科学依据。

近江平原区土壤水力参数及相关理化性质空间分布与影响因素

为研究土壤水力参数的空间分布特征,并揭示相关影响因素,以江汉平原典型近江农业区为研究单元,采集不同类型农用地的浅层(0~40 cm)原状和扰动土样,测定其水力参数和相关理化性质,揭示各水力参数及相关理化性质的空间分布特征,比较不同样地各参数和性质的差异,并分析相关影响因素。结果表明:研究区土壤各基本理化性质(土壤机械组成、有机质含量、容重、直径>0.1 mm和>0.3 mm大孔隙含量)和水力参数(饱和含水量(θ_(s))、残余含水量(θ_(r))、水分特征曲线拟合参数α和n、田间持水量(θ_(f))、凋萎系数(θ_(w))和最大有效水含量(θ_(AW)))均具有明显的空间异质性;近江区土壤机械组成、有机质含量、容重等部分理化性质与距江远近具有较强的空间相关性;直径>0.1 mm和>0.3 mm大孔隙含量,θs和θr,以及θf和θ_(AW)的空间分布特征相似。不同样地的有机质含量、容重和直径>0.3 mm大孔隙含量具有显著差异。土壤理化性质的差异显著影响了Ks和水分特征曲线参数(特别是θs和n)。不同农用地土壤的水力性质也存在差异,稻田和旱地的入渗性能较好,表现为最高的中位Ks(18.7 cm/h),其他样地的Ks差异较小(9.2~10.5 cm/h)。菜地的持水能力最强,表现为较高的θf(0.46 cm^(3)/cm^(3))、θw(0.07 cm^(3)/cm^(3))和θAW(0.39 cm^(3)/cm^(3)),其他样地的土壤水力参数差异较小。河流冲积物的分布显著影响了研究区农用地的土壤机械组成,对容重和有机质含量分布也有一些影响;而人类耕作活动可以显著改变土壤的有机质含量、大孔隙含量和容重,但对机械组成影响较小;自然要素和人为活动的共同作用影响了各水力参数的分布特征。在近江农业区开展土壤调查和农业生产规划时,需要考虑河流冲积物的分布特征。

黑龙江省冻融侵蚀强度分级评价及空间分布特征

黑龙江省肩负维护国家生态安全、保障国家粮食安全的重任,近年来因冻融侵蚀影响,自然环境和黑土资源受到严重威胁。为了定量揭示黑龙江省冻融侵蚀强度的空间异质性及其影响因素,该研究选取10个冻融侵蚀强度评价指标,并确定其权重。通过构建多元回归模型得到冻融侵蚀下限,将权重和赋值结果代入综合评价指数模型,利用自然断点法对冻融侵蚀强度进行分级。研究结果表明:1)黑龙江省冻融侵蚀总面积为1.917×10~5 km^(2),占全省面积的40.53%,其中强烈和极强烈侵蚀分别占冻融侵蚀总面积的20.66%和10.54%。2)黑龙江省中度冻融侵蚀以上的区域呈现三区一带的特征。三区分别为大兴安岭地区、小兴安岭地区和张广才岭地区;一带为西北—东南走向的“三岭一平原”廊道。3)黑龙江省冻融侵蚀强度在空间上表现出明显的正相关和集聚性特征,强度相近的冻融侵蚀区在空间上积聚,高强度和低强度的冻融侵蚀区在空间上分异,产生了多个高强度和低强度的冻融侵蚀区。4)植被覆盖度的增加可以降低冻融侵蚀强度,在植被覆盖度小于20%的地方,冻融侵蚀尤为剧烈;冻融侵蚀主要发生在土壤含水量为0.2~0.3 m^(3)/m^(3)的区域,而极少发生在土壤水分含量小于0.2 m^(3)/m^(3)的区域。研究结果通过对比验证显示出较高的可靠性,可为该地区冻融侵蚀的防护和管理提供依据,并为类似区域提供借鉴方法和技术参考。

昌黎黄金海岸国家级自然保护区土壤理化性质空间分布及影响因素

【目的】探究昌黎黄金海岸国家级自然保护区土壤理化性质空间分布特征,为建立保护区植被生态系统的良性循环提供科学参考。【方法】采用1000 m×1000 m网格取样的方法确定57个采样点,分别采集0~10 cm和10~20 cm土壤样品进行理化性质测定,利用克里金插值法进行空间制图,根据相关分析和方差分析探讨影响因素。【结果】保护区土壤理化性质水平分异明显,距海越远,部分理化性质指标值越高;土壤质地主要分为砂土、壤质砂土、砂质壤土及粉壤土四类,其中砂土占70%左右,砂粒含量达到85%~100%;七里海实验区西部为盐土,全盐量为5.22 g/kg,沿海以非盐化和轻度盐化为主。各指标间显著相关,其中土壤容重与含水量、养分指标呈显著负相关;除容重外,土壤含水量与其他6种指标之间呈显著正相关;4种养分指标之间互为正相关关系,pH值与有效磷、速效钾及全盐量呈显著正相关。此外,土壤理化性质分布格局受距海岸线距离、土地利用类型、土壤类型等因素的影响。其中距海岸线距离因素所起作用较大;耕地土壤含水量和养分含量显著高于林地、草地和未利用地;与潮土和滨海盐土相比,滨海风沙土的土壤容重较高,但含水量、有机质含量、全盐量和pH值较低。【结论】七里海实验区西部树种选择应以耐盐碱植物为主,陆域缓冲区、陆域核心区南部和金沙湾实验区应选择耐旱、抗风的良种壮苗。

Spatial heterogeneity of DTPA-extractable zinc in cultivated soils induced by city pollution and land use

The spatial heterogeneity of DTPA-extractable zinc in the cultivated soils of Shenyang suburbs in Liaoning Province of China was investigated, and its map was drawn by the methods of geostatistics combined with geographic information system. The data of soil DTPA-extractable zinc fitted normal distribution after logarithm transformation, and its semivariogram fitted a spherical model. The semivariogram indicated that the spatial dependence of soil DTPA-extractable zinc content was moderate, with the spatial dependence range of 1.69 km and the fractal dimension of 1.96. Stochastic factors contributed to 49.9% of the spatial variability, while structural factors contributed to 50.1% of it. The spatial heterogeneity of soil DTPA-extractable zinc shown by a kriged interpolation map was deeply influenced by stochastic factors such as city pollution, land use pattern and crop distributions. For example, the average content of Zn in vegetable garden soils was 2.5-4 times as much as in their originated soils, and was lower in paddy soils than in their originated soils. The areas with a higher content of soil DTPA-extractable zinc appeared in the near suburbs and the riverside along Hunhe River and the wastewater drainage of Xihe River, and the extremely high values in the near suburb of the city's residential area were a striking feature, indicating the key role of city pollution in the spatial heterogeneity of soil DTPA-extractable zinc. When recorded in the form of a soil pollution map,the results of such a survey make it possible to identify the unusually polluted areas, and to provide more information for precise agriculture and environmental control.

Pedogenic Carbonate and Soil Dehydrogenase Activity in Response to Soil Organic Matter in Artemisia ordosica Community

Little attention has been paid to the role of soil organic matter (OM) in the formation of pedogenic carbonate in desert soils.The relationships among soil OM,soil dehydrogenase activity (DHA),and soil CaCO 3 in a plant community dominated by Artemisia ordosica,located on the eastern boundary of Tengger Desert in the Alxa League,Inner Mongolia,China,were studied to understand whether OM was directly involved in the formation of pedogenic carbonate.The results showed that DHA and CaCO 3 positively correlated with OM content,and DHA,OM,and CaCO 3 were correlated with each other in their spatial distribution,indicating that abundant OM content contributed to the formation of CaCO 3.Therefore,the formation of pedogenic CaCO 3 was a biotic process in the plant community dominated by A.ordosica.

Land Use and Soil Organic Carbon in China’s Village Landscapes

Village landscapes, which integrate small-scale agriculture with housing, forestry, and a host of other land use practices, cover more than 2 million square kilometers across China. Village lands tend to be managed at very fine spatial scales (≤ 30 m), with managers both adapting their practices to existing variation in soils and terrain (e.g., fertile plains vs. infertile slopes) and also altering soil fertility and even terrain by terracing, irrigation, fertilizing, and other land use practices. Relationships between fine-scale land management patterns and soil organic carbon (SOC) in the top 30 cm of village soils were studied by sampling soils within fine-scale landscape features using a regionally weighted landscape sampling design across five environmentally distinct sites in China. SOC stocks across China’s village regions (5 Pg C in the top 30 cm of 2 × 10 6 km 2 ) represent roughly 4% of the total SOC stocks in global croplands. Although macroclimate varied from temperate to tropical in this study, SOC density did not vary significantly with climate, though it was negatively correlated with regional mean elevation. The highest SOC densities within landscapes were found in agricultural lands, especially paddy, the lowest SOC densities were found in nonproductive lands, and forest lands tended toward moderate SOC densities. Due to the high SOC densities of agricultural lands and their predominance in village landscapes, most village SOC was found in agricultural land, except in the tropical hilly region, where forestry accounted for about 45% of the SOC stocks. A surprisingly large portion of village SOC was associated with built structures and with the disturbed lands surrounding these structures, ranging from > 18% in the North China Plain to about 9% in the tropical hilly region. These results confirmed that local land use practices, combined with local and regional variation in terrain, were associated with most of the SOC variation within and across China’s village landscapes and may be an important cause of regional variation in SOC.

Scale correlation between vegetation and soil in larch forest, NE China

After the analysis on the linages of species, the fractal dimensions of vegetation and soil in a managed larch(Larix gmelini) forest in Daxingan Mountains, NE China were estimated separately, and their scale correlation was discussed. (1) The dominant species of the larch forest, larch and the important accompany species, birch (Betula platyphylla) were homogeneously distributed along the transect. The other species were heterogeneous, and can be divided into three groups located on the right, left and central parts of the transect respectively. The transect can be separated into two parts at the position for the 29th quadrat(580m). (2) The fractal dimension in the large scale range from 200 to 400m was lower than that in the small scale range from 0 to 200m in the forest, indicating the different variation regularities of spatial heterogeneity in different scale ranges. The inflection point at 200m was one of the key scales of spatial hierarchy of the larch forest. (3) The scale variation of the forest was correlated with that of soil pH on large scales, which reflected the indirect control of the dominant species to the spatial pattern and species distribution of understorey by changing soil acidity in the forest and the indirect effects of forest management.

Vegetation Spatial Heterogeneity of Different Soil Regions in Inner Mongolia, China

The vegetation spatial heterogeneity and ecological characteristics in different soil regions were analyzed by surveying the vegetation in 12 different soil regions of Inner Mongolia, China, including coniferous-broadleaf deciduous forests, shrub, grassland, and desert regions with 1122 large 2 cm × 2 cm quadrats （actual size 30 km × 30 km, referred to as L-quadrat hereafter） in about 1.18 million km2. Each L-quadrat was divided into four small 1 cm × 1 cm quadrats （actual size 15 km × 15 km, S-quadrat）. The vegetation was analyzed based on the beta-binomial distribution to describe the frequency of occurrence and spatial heterogeneity for each kind of vegetation. The weighted average of the heterogeneity of all vegetation in the same soil region provides a measure of the soil regional landscape level heterogeneity which describes the spatial complexity of the regional landscape composition of the existing vegetation. Comparison of the vegetation characteristics in the 12 soil regions shows that, the calcic gray soil has the highest average vegetation type per quadrat. The largest soil region is calcic chestnut soil and has the most vegetation types. Every soil region has its own dominant vegetation sequence which dominates in occurrence and dominant vegetation types which dominates in spatial heterogeneity. For the Inner Mongolian vegetation, the weighted average of the heterogeneity is 0.60 and the vegetation diversity index is 4.47.

Spatial heterogeneity in soil particle size:does it affect the yield of plant communities with different species richness?

Aims Soil heterogeneity is ubiquitous in many ecosystems.We hypothesized that plant communities with higher species richness might be better adapted to soil heterogeneity and produce more biomass than those with lower richness.This is because there is niche differentiation among species and different species can complement each other and occupy a broader range of niches when plant species richness is high.However,no study has tested how soil particle heterogeneity affects the yield of plant communities,and whether such effects depend on the spatial scale of the heterogeneity and the species richness within the communities.Methods In a greenhouse experiment,we sowed seeds of four-species or eight-species mixtures in three heterogeneous treatments consisting of 32,8 or 2 patches of both small(1.5 mm)and large quartz(3.0 mm)particles arranged in a chessboard manner and one homogeneous treatment with an even mixture of small and large quartz particles.Important Findings Biomass production was significantly greater in the communities with high species richness than those with low species richness.However,soil particle heterogeneity or its interactions with patch scale or species richness did not significantly affect biomass production of the experimental communities.This work indicates that plant species richness may have a bigger impact on plant productivity than soil particle heterogeneity.Further studies should consider multiple sets of plant species during longer time periods to unravel the potential mechanisms of soil heterogeneity and its interactions with the impacts of species richness on community yield and species coexistence.

区域土壤锌空间分布的异质性及制约因素分析

了解区域土壤锌(Zn)元素的地球化学特征及其空间分布的区域性特点对土壤生态环境管理具有重要的指导意义。通过查阅目前相关文献的研究成果,对我国西南地区土壤Zn的含量水平、空间分布的异质性及制约因素进行了分析及归纳总结。结果表明:不同地质年代的地层及岩性组合变化是制约区域土壤Zn含量水平及空间异质性的自然因素,碳酸盐岩发育的微碱性土壤Zn含量明显高于碎屑岩发育的酸性土壤,不同地层中碳酸盐岩与碎屑岩分布的占比大小是导致区域土壤Zn空间分布异质性的主要原因。此外,矿产资源开发及加工利用是制约区域土壤Zn含量水平及空间异质性的人为因素,铅锌矿区及冶炼区土壤Zn存在明显的污染风险。区域土壤Zn元素分布存在明显的空间异质性,根据土壤Zn含量水平可划分为低锌区(1~50 mg/kg)、中锌区(50~80 mg/kg)、富锌区(80~200 mg/kg)、高锌区(>200 mg/kg);在高锌土壤区应加强土壤Zn污染的生态风险评估,富锌土壤区宜规划及发展成为富锌农产品的重要产区,而中低锌土壤区则要强化土壤Zn元素的养分管理及优化施肥技术。