林分密度对毛乌素沙地樟子松人工林林分结构和林下植被的影响

[目的]研究不同密度下,樟子松人工林林分结构和林下物种多样性的变化,以期为毛乌素沙地以樟子松为建群种的植物固沙模式提供理论依据。[方法]以毛乌素沙地榆林地区5种不同密度25a生樟子松人工林为研究对象,采用样方调查和测试分析法,探究樟子松人工林林分结构和林下物种多样性随林分密度的变化特征。[结果]樟子松人工林密度与平均胸径呈幂函数递减关系,与高径比呈显著的线性正相关关系。樟子松人工林林下共出现植物8科13属16种。草本以禾本科的狗尾草为优势种,草本丰富度、多样性指数随着密度的不断减小,表现出明显的增加趋势。林分密度与物种丰富度指数、多样性指数呈显著的负相关关系,Shannon多样性指数对密度变化最为敏感。[结论]毛乌素沙地樟子松人工林的林分密度与林分结构、林下物种多样性的相关关系十分显著,可以将林下物种多样性指数作为衡量林分密度是否合理的参考指标。     

Changes in soil properties related to conversion of savannah woodland into pine and eucalyptus plantations,Northern Nigeria

Soil properties associated with six age-grade plantations of Pinus oocarpa Schiede and Eucalyptus camaldulensis Dehnh., respectively, including nearby natural vegetation, were compared in the savannah zone of Nigeria. The soil organic matter, total nitrogen and exchangeable nutrients first show declining values with the increasing age of the plantation, then an increase and finally steady or declining values in the 0–15 cm soil depth. Usually the differences between the two youngest plantations and the oldest plantations, and the natural vegetation, were significant. In the 20–30 cm soil depth the properties showed a decrease or steady values over time, with the three oldest plantations showing significant differences from the natural vegetation. The soil pH showed an increased acidity over time. There was little difference in the soil properties between the two tree species. The implications of the results are discussed in relation to sustaining productivity and soil fertility. © 1998 John Wiley & Sons, Ltd.     

INTRODUCED EUCALYPTUS UROPHYLLA PLANTATIONS CHANGE THE COMPOSITION OF THE SOIL MICROBIAL COMMUNITY IN SUBTROPICAL CHINA

Fast‐growing tree species are widely used as pioneers for reforestation. These plantations strongly affect the ecosystem productivity and nutrient cycling, whereas their effect on the soil microbial community is still unclear. In a reforestation chronosequence in subtropical China consisting of Eucalyptus plantation with ages of 1, 2, 4 or 5 years, we examined the response of the soil microbial community and its function. The results showed that soil bulk density and dissolved organic carbon decreased significantly along the chronosequence. Soil pH was highest in the 5‐year‐old plantation. The amount of bacterial phospholipid fatty acids (PLFAs) and arbuscular mycorrhizal fungal PLFAs increased, but the ratio of fungal‐to‐bacterial PLFAs decreased with increasing forest age. The composition of the soil microbial community obviously changed after 5 years' development. Redundancy analysis showed that dissolved organic carbon was the major factor associated with the changes of soil microbial community composition. The short‐rotation Eucalyptus plantation could affect the composition of soil microbial communities through changing soil available carbon when planted in subtropical region at the early developmental stage. We suggest that soil microbial community composition should be taken into consideration in the large‐scale reforestation activities. Copyright © 2012 John Wiley & Sons, Ltd.     

南亚热带5种典型人工林凋落物水文效应

以广西国有高峰林场的5种不同人工林(马尾松林、杉木林、桉树林、米老排林、红锥林)为研究对象,结合野外调查和室内浸水法,对各人工林凋落物层的水文效应进行定量分析。结果表明:(1)5种林分凋落物蓄积量范围在1.96～9.05 t/hm~2,大小顺序为红锥林杉木林马尾松林桉树林米老排林。(2)5种林分凋落物中,杉木林最大持水量最大,为14.23 t/hm~2,马尾松林最小,为6.26 t/hm~2;米老排林凋落物最大持水率最大,为577.98%,红锥林最小,为135.46%。(3)杉木林凋落物的有效拦蓄量最大,为10.18 t/hm~2,马尾松林最小,为4.07 t/hm~2;米老排林凋落物有效拦蓄率最大,为463.35%,红锥林最小,为92.38%。(4)回归分析表明,凋落物持水量与浸水时间的关系符合对数函数关系(Q=aln t+b(R~20.773)),凋落物吸水速率和浸水时间的关系符合幂函数关系(V=kt~n(R~20.997))。持水过程中,各林分凋落物均表现为在1 h内持水量迅速增加,1 h后增加速度变慢,在10～12 h之后,吸水基本停止。综上,杉木林、米老排林凋落物层水源涵养功能较强。     

CHANGES IN SOIL ORGANIC CARBON UNDER EUCALYPTUS PLANTATIONS IN BRAZIL: A COMPARATIVE ANALYSIS

Proper assessment of environmental quality or degradation requires knowledge of how terrestrial C pools respond to land use change. Forest plantations offer a considerable potential to sequester C in aboveground biomass. However, their impact on initial levels of soil organic carbon (SOC) varies from strong losses to gains, possibly affecting C balances in afforestation or reforestation initiatives. We compiled paired‐plot studies on how SOC stocks under native vegetation change after planting fast‐growth Eucalyptus species in Brazil, where these plantations are becoming increasingly important. SOC changes for the 0–20 and 0–40 cm depths varied between −25 and 42 Mg ha⁻¹, following a normal distribution centered near zero. After replacing native vegetation by Eucalyptus plantations, mean SOC changes were −1·5 and 0·3 Mg ha⁻¹ for the 0–20 and 0–40 cm depths, respectively. These are very low figures in comparison to C stocks usually sequestered in aboveground biomass and were statistically nonsignificant as demonstrated by a t‐test at p < 0·05. Similar low, nonsignificant SOC changes were estimated after data were stratified into first or second rotation cycles, soil texture and biome (savanna, rainforest or grassland). Although strong SOC losses or gains effectively occurred in some cases, their underpinning causes could not be generally identified in the present work and must be ascribed in a case basis, considering the full set of environmental and management conditions. We conclude that Eucalyptus spp. plantations in average have no net effect on SOC stocks in Brazil. Copyright © 2012 John Wiley & Sons, Ltd.     

Interrelations of vegetal cover,silicophytolith content and pedogenesis of Typical Argiudolls of the Pampean Plain,Argentina

Knowledge of the origin, evolution and weathering of Pampean soils is still limited. There are few prior studies of silicophytoliths, even though they could be important pedogenetic indicators that provide information about the role of amorphous silica in the reestablishment of soil structure. The aim of this work is to determine the silicophytolith content in Typical Argiudolls of the Pampean Plain, Argentina, its relation with vegetal cover and its effect on pedogenesis. We worked in three plots with different vegetal cover: grasses and shelter-belt plantations of Acacia melanoxylon – Celtis tala and Eucalyptus globulus – Celtis tala. In the study area, morphological characterization and particle size distribution analysis of soils were completed, and pH and organic matter content were determined. The heavy liquid separation was realized with sodium polytungstate (δ = 2.3 g/cm³) and an average of around 500 mineral grains were counted under optical microscope for the quali-quantitative analysis. There were no differences between profiles with respect to their morphological properties, organic matter content and particle size distribution, except for the higher organic horizon development of the forest plots as compared with the grass plot. The silicophytolith content was higher in the forest plots than in the grass one; within each profile, this fraction content decreased from the surface (63–40%) to the subsurface levels (23–5%) of soils. This decrease parallels the pieces of amorphous silica (< 7.5 μm) distribution in all plots analyzed. Afforestation over the past 50 years does not affect either the morphological or the physico-chemical properties of soils. These forest species, through the organic horizons, preserve soil conditions, which insures a higher representativity of silicophytoliths in comparison with the grass plot.     

茶树土壤的某些生物地球化学特性

Characteristics of the element abundance, material cycling, element budget in tea soils were discussed based on investigations of six tea plantations and the adjacent waste lands in the Three Gorges region. The plantations have different soil-forming parent materials, but similar landforms, and the same tea variety and close ages. The results showed that tea growing could increased the contents of organic matter, total and available N, P, Al and Mn; the elements enriched by tea trees were in the following descending sequence: P>Ca>K>Mn>Mg>Zn>Al>Fe; elements returned through litter of tea were in the sequence of Ca>Mn>P>Zn>Mg>K>Al>Fe; in the nutrient budget of the soil-tea system, P and K were in deficit, whereas Al, Ca, Fe and Mn in surplus.     

添加凋落物对杨树人工林土壤氮、磷矿化的影响初探

采用室内培养方法,在30℃和土壤含水量为田间持水量的70％的条件下研究杨树人工林的枯叶或枯枝、枯地被植物、杨树根系以及混合凋落物的添加对土壤氮和磷矿化的影响.结果表明:(1)培养42 d后,不同处理间的土壤有效磷含量存在一定差异,呈现枯叶+土＞枯地被植物+土＞混合凋落物+土＞根+土＞枯枝+土＞对照的趋势;(2)不同处理间的土壤铵态氮含量差异比较小;(3)各种处理的硝态氮含量占总无机氮的78％以上;(4)在培养初期,除添加枯枝处理外,添加其他凋落物处理的土壤硝态氮和总无机氮含量明显下降,后期逐渐升高;(5)土壤无机氮、磷含量及其矿化速率与土壤和凋落物的性质密切相关.     

半干旱区人工固沙灌丛发育过程土壤水分及水量平衡研究

在野外条件下测定了不同林龄小叶锦鸡儿人工固沙灌丛区生长季节土壤水分动态和蒸散量变化。结果表明:不同林龄灌丛区土壤水分状态和蒸散量存在明显差异,土壤水分含量随着植被林龄增加而降低,16年生、19年生灌丛区土壤含水量随着深度增加呈下降趋势,在70cm深度产生低含水区,土壤转变为非淋溶性土壤;生长季土壤水分受降水和植被双重影响,在6月期间含水量最低;生长季节蒸散量随着植被林龄增加而增大,以19年生灌丛区最高,所有灌丛区生长季节蒸散量均低于同期降水量,占同期降水量的95%以上。流动沙丘生长季节土壤水分含量高于灌丛区,蒸散量低于灌丛区。     

红松人工林腐殖质组成及其结合形态研究

 运用野外调查与实验分析相结合的方法,对不同生长发育阶段红松人工林（林龄25、45、58、68 a）和红松混交林（林龄60a）根际与非根际土壤有机质含碳量、腐殖质组成与结合形态进行了研究。结果表明:不同年龄阶段红松人工纯林、红松混交林土壤有机质含碳量、腐殖质各组分含碳量随土层深度的加深而降低,并且根际土壤高于非根际土壤。就土壤腐殖质组成而言,除林龄58a红松人工林根际土壤和45a红松人工林非根际土壤外,其他林型土壤胡敏酸含碳量均高于富里酸含碳量;胡敏酸与富里酸比值（HA/FA）在1.00～2.45之间;土壤重组腐殖质、松结态腐殖质、稳结态腐殖质含碳量大小顺序为林龄58>68>25>45a;红松混交林除紧结态腐殖质外,其他腐殖质各组分含碳量均高于红松人工林。     

The importance of former land use in determining successful re-creation of lowland heath in southern England

In order to reverse losses of lowland heathland substantial areas of former agricultural and forestry land are currently being targeted for restoration. In this study we assessed the success of heathland re-creation on 37 former arable, improved grassland and conifer plantation sites in southern England, UK. The similarity between the vegetation and seed banks of the re-creation sites and undisturbed heathland controls were examined in relation to former land use, soil properties and re-creation management. Former land use was found to be the most important determinant of re-creation success. On former arable, and to a lesser extent improved grassland, antecedent management had caused significant changes to seed bank and soil properties. As a result, regeneration of Calluna heath had been minimal, even on sites where appropriate management (e.g. cropping, addition of pH amendments) had been undertaken and heathland species introduced. In contrast, former plantation seed banks and soils were similar to heathland controls, and, as a result, rapid regeneration of Calluna heath had taken place. It was concluded that conifer removal provides the most practical and cost-effective means of re-creating Calluna heath on former heathland, although further research is required to assess the effect of litter removal and the rate at which heather seed banks decline following conversion to forestry. In contrast, re-creation on former agricultural sites will require effective management to reduce soil pH, fertility and the abundance of competitive species as well as the introduction of heathland propagules. Given limited resources a more realistic objective for these sites is likely to be reversion to an acid grassland or grass-heath.     

巨桉人工林下土壤团聚体稳定性及分形特征

选择3年生巨桉纯林、巨桉+粮食作物、巨桉+果树土壤作为研究对象,农耕地作为对照,运用标准化平均质量直径及分形理论,分析不同巨桉人工林下的土壤团聚体稳定性及分形维数特征。结果表明,不同林地模式下,水稳性团聚体平均质量直径的变化顺序为农耕地>林粮>巨桉纯林>林果,农耕地与不同林地模式下水稳性团聚体平均质量直径差异显著,农耕地在退耕成巨桉人工林后不利于土壤大团聚体的形成;3种林地模式与农耕地比较有效磷、容重差异显著,土壤有机质、碱解氮、有效钾含量差异不显著,说明林地覆盖增强了土壤的紧实度;相关分析表明,影响土壤稳定性的最重要因素为大团聚体的含量,而其他因素影响不显著;分形维数与<0.25mm团聚体含量、容重呈显著、极显著正相关,与1～2mm团聚体含量、平均质量直径呈极显著负相关,说明土壤团聚体的分形维数越小,土壤大团聚体含量越高,土壤团聚体稳定性越强;团聚体的分形维数值能反映土壤性质的变化,通过对土壤分形维数特征的研究可以定量揭示不同巨桉模式下土壤质量的特点。     

Acidity,nutrient stocks,and organic‐matter content in soils of a temperate deciduous forest with different abundance of European beech (Fagus sylvatica L.)

The production and composition of leaf litter, soil acidity, exchangeable nutrients, and the amount and distribution of soil organic matter were analyzed in a broad‐leaved mixed forest on loess over limestone in Central Germany. The study aimed at determining the current variability of surface‐soil acidification and nutrient status, and at identifying and evaluating the main factors that contributed to the variability of these soil properties along a gradient of decreasing predominance of European beech (Fagus sylvatica L.) and increasing tree‐species diversity. Analyses were carried out in (1) mature monospecific stands with a predominance of beech (DL 1), (2) mature stands dominated by three deciduous‐tree species (DL 2: beech, ash [Fraxinus excelsior L.], lime [Tilia cordata Mill. and/or T. platyphyllos Scop.]), and (3) mature stands dominated by five deciduous‐tree species (DL 3: beech, ash, lime, hornbeam [Carpinus betulus L.], maple [Acer pseudoplatanus L. and/or A. platanoides L.]). The production of leaf litter was similar in all stands (3.2 to 3.9 Mg dry matter ha^–1 y^–1) but the total quantity of Ca and Mg deposited on the soil surface by leaf litter increased with increasing tree‐species diversity and decreasing abundance of beech (47 to 88 kg Ca ha^–1 y^–1; 3.8 to 7.9 kg Mg ha^–1 y^–1). The soil pH_(H2O) and base saturation (BS) measured at three soil depths down to 30 cm (0–10 cm, 10–20 cm, 20–30 cm) were lower in stands dominated by beech (pH = 4.2 to 4.4, BS = 15% to 20%) than in mixed stands (pH = 5.1 to 6.5, BS = 80% to 100%). The quantities of exchangeable Al and Mn increased with decreasing pH and were highest beneath beech. Total stocks of exchangeable Ca (0–30 cm) were 12 to 15 times larger in mixed stands (6660 to 9650 kg ha^–1) than in beech stands (620 kg ha^–1). Similar results were found for stocks of exchangeable Mg that were 4 to 13 times larger in mixed stands (270 to 864 kg ha^–1) than in beech stands (66 kg ha^–1). Subsoil clay content and differences in litter composition were identified as important factors that contributed to the observed variability of soil acidification and stocks of exchangeable Ca and Mg. Organic‐C accumulation in the humus layer was highest in beech stands (0.81 kg m^–2) and lowest in stands with the highest level of tree‐species diversity and the lowest abundance of beech (0.27 kg m^–2). The results suggest that redistribution of nutrients via leaf litter has a high potential to increase BS in these loess‐derived surface soils that are underlain by limestone. Species‐related differences of the intensity of soil–tree cation cycling can thus influence the rate of soil acidification and the stocks and distribution of nutrients.     

阔叶幼林取代杉木林后的土壤肥力研究

研究了3种阔叶混交幼林的土壤肥力，并将其肥力特征与杉木幼林进行对比研究。3种林分的立地条件相似常绿阔叶混交林1由12种观赏树种组成，常绿阔叶混交林2由7种速生乡土阔叶树种组成，常绿阔叶混交林3由12种阔叶树种组成。结果表明，各林地的土壤呈强酸性。常绿阔叶混交林1的土壤有机质、全氮和有效磷含量居各林地之首，其余的养分含量也大于或近似于杉木林地；常绿阔叶混交林2的全磷、全钾、有效氮、有效钾含量在4种林分中最高，有机质、全氮和有效磷含量也较高，说明这两种阔叶混交林有效地改善了土壤养分状况。常绿阔叶混交林3的土壤有机质、全氮和有效氮含量大于杉木林地，但是全磷、全钾、有效磷、有效钾含量小于后者。常绿阔叶混交林地1和常绿阔叶混交林地2的细菌、真菌和放线菌数量大于杉木林地，脲酶、磷酸酶、过氧化氢酶活性也较高，表明这2种阔叶混交林显著地改善了林地肥力。     

Effects of beech and ash on small‐scale variation of soil acidity and nutrient stocks in a mixed deciduous forest

Trees interact in a complex manner with soils: they recycle and redistribute nutrients via many ecological pathways. Nutrient distribution via leaf litter is assumed to be of major importance. Beech is commonly known to have lower nutrient concentrations in its litter than other hardwood tree species occurring in Central Europe. We examined the influences of distribution of beech (Fagus sylvatica L.), ash (Fraxinus excelsior L.), lime (Tilia cordata Mill. and T. platyphyllos Scop.), maple (Acer spp. L.), and clay content on small‐scale variability of pH and exchangeable Ca and Mg stocks in the mineral soil and of organic‐C stocks in the forest floor in a near‐natural, mature mixed deciduous forest in Central Germany. The soil is a Luvisol developed in loess over limestone. We found a positive effect of the proportion of beech on the organic‐C stocks in the forest floor and a negative effect on soil pH and exchangeable Ca and Mg in the upper mineral soil (0 to 10 cm). The proportion of ash had a similar effect in the opposite direction, the other species did not show any such effect. The ecological impact of beech and ash on soil properties at a sample point was explained best by their respective proportion within a radius of 9 to 11 m. The proportion of the species based on tree volume within this radius was the best proxy to explain species effects. The clay content had a significant positive influence on soil pH and exchangeable Ca and Mg with similar effect sizes. Our results indicate that beech, in comparison to other co‐occurring deciduous tree species, mainly ash, increased acidification at our site. This effect occurred on a small spatial scale and was probably driven by species‐related differences in nutrient cycling via leaf litter. The distribution of beech and ash resulted not only in aboveground diversity of stand structures but also induced a distinct belowground diversity of the soil habitat.     

章古台地区樟子松人工林林下草本植物群落动态

[目的]探究樟子松人工林林龄与林下草本植物多样性指数的关系,分析樟子松林林下草本植物群落动态,为樟子松林下的植被管理提供参考。[方法]以科尔沁沙地南部章古台地区不同林龄(8,18,27,35,48a)樟子松人工林为研究对象,调查林下草本植被的植物种类、数量、盖度和生物量特征,定量分析林龄对林下草本植物的影响。[结果]在樟子松人工林林下,马唐Digitaria sanguinalis的重要值高于其它草本植物,能更好地适应林下环境,是最主要的优势种。随着樟子松林龄的增长,林下草本植被的生物量和多样性呈先减少后增加的趋势,其中27a生樟子松林的林下草本植被生物量和多样性最低。林龄与Patrick丰富度指数、Shannon-Wiener指数、Pielou均匀度指数和Simpson优势度指数均呈显著的二元回归关系。[结论]樟子松人工林中龄林与近熟林林下草本植被存在退化现象,需要通过间伐、中耕、围封等方法人工促进草本植被的生长与演替。     

不同人工林对黄河三角洲滨海盐碱地土壤理化性质的影响

为了探讨人工林对黄河三角洲滨海盐碱地土壤理化性质的改良效果,采用野外取样和室内分析测定相结合的方法,以林龄8年的4种人工林为研究对象,未造林空地为对照,对各样地的土壤理化性质指标进行分析。结果表明:(1)4种人工林均能改善黄河三角洲滨海盐碱地的土壤理化特性。与对照空地相比,人工林的平均土壤容重、含盐量、pH值分别降低了4.8%,44.4%,2.5%,平均总孔隙度、毛管孔隙度分别提高了6.0%,4.7%;(2)不同人工林对土壤阳离子交换性能及碱化度的影响效果各异,其碱化度大小依次为:柽柳(27.4%)杜梨(23.3%)对照(19.5%)白蜡(16.0%)盐柳(13.3%)。     

C‐Factors of the Universal Soil Loss Equation for olive plantations in Western Anatolia (central Ege Region)

In the course of investigations into soil erosion and its prediction in Western Anatolia (Ege region), C‐factors of the Universal Soil Loss Equation (USLE / ABAG) were also determined for various agricultural culture systems, including olive orchards. Because of the extreme level of input and expenditure required for field tests in such an investigation, the necessary information was instead acquired from surveys of agricultural organizations and local experts, along with additional own assessments. The information collected was analyzed in the form of a partly analogous application of specific values available in the USLE and ABAG, respectively. So the C‐factor estimation was performed dependent on analogous deductions. Necessary information about the seasonal course of rainfall erosivity in the area under investigation was acquired from a relevant Turkish study. Erosion problems in olive plantations result particularly from the intensity of soil tillage practices and from the treatment of the undergrowth (= weed and grass). That the level of the C‐factor of an olive plantation can be substantially influenced by this value alone is demonstrated by a comparison with the effect of the simultaneously determined second C‐factor component, namely the canopy effect of the trees themselves. The information gained can be used as a basis for recommendations to control erosion in olive plantations.