The influence of trees on soil fertility on two contrasting semi-arid soil types at Matopos,Zimbabwe

An investigation into the influence of indigenous trees on soil fertility was conducted in an area of semi-arid tropical savanna in Zimbabwe on two contrasting soil types: dystrophic savanna soils (sandy soils) and eutrophic savanna soils (fine-textured soils). The study adds further support to the growing literature showing that trees have a positive influence on soil fertility. The study suggests that tree clearance, as advocated in these agropastoral systems, may not necessarily result in long-term benefits. It is argued that the primary mechanism by which soil fertility is improved is through increased litter and soil organic matter compartments under trees. The influence of trees on cation levels is greater on sandy soils than fine-textured soils because the exchange capacity of fine-textured soils is determined largely by soil texture whereas organic matter is the prime determinant of exchange capacity in sandy soils. The present study demonstrates that fertility improvement under trees is not at the expense of fertility decline in the surface soils of the zone around the tree. Leaf quality, as reflected simply in leaf C:N ratio, influences decomposition rates but the activities of termites probably confound any simple relationship. Litter quality of tree species is probably important in determining levels of soil organic matter under canopies, with higher levels under species with lower leaf quality.     

Tree effects on the chemical topsoil features of oak, beech and pine forests

We aimed to study tree effects on the chemical properties of forest soils. We compared soil features of three types of forest ecosystems, each with four stands (replicates): beech forests (Fagus sylvatica), oak forests (dominated by Quercus pyrenaica) and pine plantations (Pinus sylvestris). Five samples from the top 10 cm of soil were taken per stand, from which pH, organic matter content (O.M.), total nitrogen (N) and available calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺) and sodium (Na⁺) were determined. Litter layer depth was measured at each soil sampling point. We also measured tree density and crown diameters at each stand. Our results indicated that soil samples from the four pine plantation stands were more similar while oak and beech stands were characterised by great variability in terms of soil properties and leaf litter depth. Although the identity of the dominant tree species significantly influenced several topsoil chemical properties (increase in pH and available cations in oak forests and higher organic matter and total nitrogen in beech and pine ecosystems), there were other important factors affecting soil features that may be taken under consideration. Differences between soil properties of the three types of forest ecosystems were mainly related to the characteristics of the litter layer and less related to the tree layer structure. Finally, the establishment of pine plantations in naturally deciduous tree areas made the topsoil features more homogeneous.     

不同植被类型土壤理化性质及水源涵养功能研究

对丽水实验林场3种植被类型的土壤理化性质和涵养水源的功能进行了实验研究，结果表明，阔叶林、毛竹林土壤有机质含量相对较高，这2种林分可较好改善土壤养分状况；马尾松下的土壤pH值较低，酸性较强，土壤有效P含量高，各植被类型下的林地枯落物持水量大小依次是：阔叶林（16．453t／hm^2）〉毛竹林（7．142t／hm^2）〉马尾松林（2．656t／hm^2）；土壤持水量大小依次是：毛竹林〉阔叶林〉马尾松林。     

Comparison of organic matter dynamics in soil between Japanese cedar (Cryptomeria japonica) forest and adjacent Japanese red pine (Pinus densiflora) forest established on flatland

In order to clarify the effects of tree species on organic matter dynamics in soil, we investigated the amount of forest floor material, leaf litter decomposition rate, soil chemical characteristics, soil respiration rate and cellulose decomposition rate in a Japanese cedar forest (cedar plot) and an adjacent Japanese red pine forest (pine plot) established on a flatland. The amount of forest floor material in the cedar plot was 34.5 Mg ha⁻¹ which was greater than that in the pine plot. Because the leaf litter decomposition rate was higher in the pine plot than in the cedar plot, it is likely that the difference in the amount of forest floor material between the plots is caused by the difference in the leaf litter decomposition rate. The C concentrations of soil in the cedar plot were 1.2–2.1 times higher than those in the pine plot. Soil pH(H₂O)s in the cedar plot were significantly higher than those in the pine plot. The soil respiration rates and the rates of mineralized C in the cedar plot byin vitro incubation were higher than those in the pine plot. From this result, it is assumed that soil organic matter in the cedar plot was decomposed relatively faster compared with the pine plot. Furthermore, microbial activities, which were reflected as cellulose decomposition rates in the cedar plot, were higher than those in the pine plot. A part of this paper was presented at the 109th Annual Meeting of the Japanese Forestry Society (1998).     

Single-tree influences on soil properties in agroforestry: lessons from natural forest and savanna ecosystems

Climate, organisms, topographic relief, and parent material interacting through time are the dominant factors that control processes of soil formation and determine soil properties. In both forest and savanna ecosystems, trees affect soil properties through several pathways. Trees alter inputs to the soil system by increasing capture of wetfall and dryfall and by adding to soil N via N₂-fixation. They affect the morphology and chemical conditions of the soil as a result of the characteristics of above- and below-ground litter inputs. The chemical and physical nature of leaf, bark, branch, and roots alter decomposition and nutrient availability via controls on soil water and the soil fauna involved in litter breakdown. Extensive lateral root systems scavenge soil nutrients and redistribute them beneath tree canopies. In general, trees represent both conduits through which nutrients cycle and sites for the accumulation of nutrients within a landscape. From an ecological perspective, the soil patches found beneath tree canopies are important local and regional nutrient reserves that influence community structure and ecosystem function. Understanding species-specific differences in tree-soil interactions has important and immediate interest to farmers and agroforesters concerned with maintaining or increasing site productivity. Lessons from natural plant-soil systems provide a guide for predicting the direction and magnitude of tree influences on soil in agroforestry settings. The challenge for agroforesters is to determine under what conditions positive tree effects will accumulate simultaneously within active farming systems and which require rotation of cropping and forest fallows.     

沙地疏林草地和樟子松人工林土壤中不同形态磷素含量和磷酸单酯酶活性的比较

为评价我国北方大规模人工造林对土壤磷素转化及磷素有效性的影响,对半干旱沙地樟子松人工林和天然植被(疏林草地)不同层次(0～5 cm, 5～20 cm)土壤中不同形态磷组分和磷酸单酯酶活性进行了比较.结果表明:除人工林土壤中活性有机磷不受土壤深度影响外,各样地表层土壤中各种磷素含量和酶活性均显著高于低层土壤,但分层效应在人工林中低于疏林草地;与疏林草地土壤相比,除Al-P外,人工林土壤中各种磷素绝对含量和酶活性均显著降低,总有机磷和Ca-P在全磷中的比例显著下降,而活性磷,Al-P和Fe-P占全磷的比例增加.可见表层土壤是磷素转化最活跃的区域,凋落物分解是土壤磷的主要来源;用樟子松进行人工造林促进了有机磷的矿化和Ca-P的溶解,提高了土壤磷素的有效性,同时导致土壤总磷库逐渐耗竭.要维持该人工防护林功能和稳定性,必须对地被物予以保护,并进行适当施肥.表3参38.     

Temporal changes in litterfall, litter decomposition and their chemical composition in Sasa dwarf bamboo in a natural forest ecosystem of northern Japan

We investigated the dynamics of litterfall and litter decomposition of Sasa dwarf bamboo (Sasa senanensis) and trees to clarify the characteristics of organic matter and nitrogen cycling between plant and soil in a natural cool-temperate mixed forest ecosystem dominated by an understory vegetation of Sasa. Mean annual Sasa litterfall over the 3-year study period was 164 g m^?2 year^?1, which accounted for approximately 29% of total litterfall. Litter decomposition of Sasa leaf and Sasa culm was significantly slower than that of tree leaf during first and second years. The slow decomposition rates of both Sasa litter types were caused by a significantly higher silicate than in tree leaf. Nitrogen concentration in litter increased as decomposition progressed, especially in Sasa leaf and tree leaf. As a result of the slow decomposition of both Sasa litter types, 111 and 73% of nitrogen to the initial amounts were retained in Sasa leaf and Sasa culm after 3 years, respectively. The amounts of retained nitrogen in Sasa leaf, Sasa culm, and tree leaf after 3 years were 1.29, 0.47, and 3.92 g N m^?2, respectively, indicating that the differences of litter decomposition rates among the litter types influence on the nitrogen cycling in forest ecosystem through the differences of the nitrogen release from litter.     

Changes in soil properties and vegetation characteristics along a forest-savanna gradient in southern Venezuela

Vegetation cover in the Gran Sabana highlands (southern Venezuela) appears as a complex mosaic of tall to low forests, bush vegetation and savannas. In this study we described the changes in structure and floristic composition along a forest-savanna gradient consisted of tall forest (TF), medium forest (MF), low forest (LF) and open savanna (S), and analyse the possible reasons for the observed changes. The results showed no obvious differences in the soils properties along the vegetation gradient. All sites presented shallow soils (<50 cm depth) with high percentage of sand and with dominance of quartz, kaolinite and oxides of iron and aluminum. The soil chemical characteristics were unfavorable and similar along the vegetation gradient. The major soil difference was related with the presence of an organic layer on the soil surface of TF and MF and their absence on the soils of LF and S. Abundant residues of large trees were found on the forest floor of TF, MF and LF. These residues presented no signs of burning in TF, while in MF and particularly in LF were charred. This observation joined to the presence of charcoal within the mineral soil of S and the absence of the organic surface layer in LF and S indicated that fire has affected with different intensity or frequency the studied vegetation gradient. Large differences in the structure and floristic composition were found between TF, MF, LF and S. These differences could not be explained by changes in the mineralogical and chemical characteristics of the soil but only by fire which triggers the conversion. We concluded that the studied vegetation gradient represents stages in a temporal change from forest to savanna caused by fire, and this change has implied an impoverishment of tree species, a drastic reduction of biomass in terms of basal area, a drastic change of the floristic composition and the loss of the organic surface layer, which play an important role to maintain the fertility of these soils.     

Change in soil macrofauna and vegetation when fast-growing trees are planted on savanna soils

Many forest species can be found in understory vegetation of old plantation plots, despite the fact that the native vegetation was a poor savanna growing on highly nonfertile sandy soils. The aim of the present paper is to describe the changes that occur in the environmental conditions when savanna is planted with fast-growing trees, and is particularly concerned with vegetation and soil macrofauna. The study was carried out in industrial eucalyptus plantations, and in experimental Acacia and pine plantations. Most plots were located on sandy soil, but some measurements were also carried out on clay soil planted with the same species in order to assess the influence of soil type.

A strong correlation was shown between the age of the eucalyptus trees and the percentage of forest species in undergrowth, emphasizing the progressive change from savanna vegetation towards forest vegetation.

Biomass and density of macrofauna were very low in both sandy and clayey savanna soils, total biomass being 3.3 and 5.8 g/m² respectively. Soil macrofauna became more important as the age of plantations increased, and biomass reached 29 g/m² in the 20-year-old eucalyptus plot on sandy soil, and 74 g/m² in 26-year-old eucalyptus plantation on clay soil, compared to 33 g/m² in the natural forest plot on sandy soil; however, frequency of occurrence and number of taxa were lower in old eucalyptus plot as compared to forest. Large differences in the abundance of macrofauna were observed in relation to planted species. Acacia was most favourable to soil macrofauna, with a total biomass of 60 g/m² on sandy soil and many taxa present. Pine plantations had a poor macrofauna and several taxa were lacking, particularly in the sandy soil.

Total macrofauna frequency was significantly correlated with the percentage of forest species in understory vegetation. Both were correlated with soil pH and soil organic-matter content. The results suggest that soil organic matter and litter quality are of main importance in changing the above- and below-ground habitat in plantations.     

孟加拉国库克斯巴扎(Cox's Bazar)和兰加马蒂(Rangamati)地区森林区和采伐区土壤属性比较

比较了天然林和森林采伐区土壤理化性质,评价了森林采伐对土壤的影响。采集了自然林和邻近的采伐林地三个土层（表层、中层和底层）土壤,对其属性进行了调查。森林土壤颗粒大小分布无显著变化。森林表层土和中层土体积密度存在显著差异。林地内表层土和中层土壤pH、表层土有机质和中层土有效磷均显著高于采伐林地的值。两块林地内可交换Na＋和阳离子交换能力没有变化。这些结果表明,两块林地内表层和亚表层土壤变化较明显。森林采伐降低土壤理化性质。     

海南4种典型林分土壤化学性质比较研究

保持和提高土壤质量是实现林业可持续发展的前提.森林封不仅起着支持和固家林森林生长的作用,而县供给林森林在生长发育过程中所需要的营养与环境条件.     

Soil factors influencing yields of Eucalyptus camaldulensis on former tin-mining land in the Jos Plateau region,Nigeria

Plantations of Eucalyptus growing on reclaimed tin-minning spoil were compared with similar stands established on undisturbed farmland soils in the north of the Jos Plateau, Nigeria. Soils were collected from sample plots in both situations to determine their physical and chemical properties, while destructive harvests of representative stems were used to calculate tree yields.A principal components analysis of the soils data revealed wide variations in texture and base status, and was supported by a cluster analysis from which five major soil groups were defined. One such group, which contained a majority of mining site plots, was characterised by shortages of organic matter and low levels of available phosphorus. Farmland plantation sites had a wider range of texture and fertility, but on the whole gave similar yields to those of mining sites.The relationship between forest yield and selected soil variables was investigated using multiple regression analysis. This showed that the best yields occurred on fine-textured soils with good reserves of organic matter, while moderately base-saturated soils and high available-iron concentrations were associated with poor growth. There were indications that soil chemistry was modified by tree growth, with high-yielding stands increasing cation exchange capacity but significantly lowering soil pH.The implications for future tree growth are discussed, and suggestions given for the improvement of currently derelict mining sites.     

The Growth of Sitka Spruce on Poorly Drained Soils in Northern Ireland

A soil survey of Lisnaskea Forest, Co. Fermanagh, showed thatgrowth of Sitka spruce was far from uniform on areas of apparentlyuniform soil. The relation between soil factors, tree growth,and foliar nutrient status on two blocks of trees growing ongleyed soils was therefore studied. Simple regression showed that tree growth was poor when thelevels of foliar nutrients were low and when there was a matof undecomposed needles on the forest floor. It is thereforeconsidered that lack of organic matter breakdown in the soilis causing poor tree nutrition and growth. Multivariate statistical analysis also showed highly significantregressions between tree growth, level of foliar nutrients,and depth of litter layer. The correlations between soil factorsalone and tree growth were barely significant and the multivariatetechnique did not give an acceptable method of predicting treegrowth from soil measurements. Methods of improving soil conditions are discussed.     

The role of fire and nutrient loss in the genesis of the forest soils of Tasmania and southern New Zealand

The dominant soil patterns in forested or previously forested landscapes in southern New Zealand and Tasmania are described. Soil properties on adjacent sunny and shady aspects in hill country of the South Island of New Zealand are compared to soil properties under adjacent ‘dry’ and ‘wet’ eucalypt forest in Tasmania.

A soil contrast index or SCI is defined for comparing soil contrasts on parent materials of different absolute nutrient contents. Three soil groups are defined using the SCI. Group 1 soil pairs are stable New Zealand soils in which exchangeable Ca + Mg + K values are higher on drier sunny aspects than on moister shady aspects. Group 2 soil pairs are New Zealand soils in which soils on sunny aspects display evidence of topsoil erosion by wind; consequently some soil pairs on dry (sunny) aspects have lower levels of exchangeable Ca + Mg + K than soils on moister (shady) aspects. Group 3 soil pairs are Tasmanian. Soils on drier sites (under dry eucalypt forest) invariably have lower exchangeable Ca + Mg + K values than soils on moister sites (under wet eucalypt forest), which is the reverse of the pattern in SCI Group 1 soils in New Zealand.

Except on clay-rich parent materials, Tasmanian soils under dry forest generally have texture-contrast profiles and a mean C/N ratio in topsoils (A1 horizons) of 29. Soils under wet forest generally have uniform or gradational texture profiles and a mean topsoil C/N ratio of 15. The texture-contrast soils show strong clay eluviation with sand or sandy loam textures in upper horizons and clayey textures in lower horizons. However, in New Zealand texture-contrast soils are all but absent, and do not occur in the previously forested areas described in this paper. Topsoils (Ah horizons and soils sampled to 7.5 cm depth) in New Zealand areas sampled in this study have a mean C/N ratio of 15, regardless of whether they occur on sunny or shady aspects.

We propose that the frequency and spatial occurrence of fire are the dominant processes causing: (1) the marked difference in levels of nutrients and different topsoil C/N ratios in soils of Tasmania; (2) the development of texture-contrast soils under dry forests in Tasmania; and (3) the difference between soil patterns in New Zealand and Tasmania. Fire depletes nutrients in forests by causing losses to the atmosphere, losses by runoff, and losses by leaching. Nutrient loss by fire encourages fire-tolerant vegetation adapted to lower soil nutrient status, so frequent fire is a feedback mechanism that causes progressive soil nutrient depletion. By destroying organic matter and diminishing organic matter supply to the soil surface fire inhibits clay–organic matter linkages and soil faunal mixing and promotes clay eluviation. Fire frequency is likely to have increased markedly with the arrival of humans at ca. 34 000 years B.P. in Tasmania and ca. 800 years B.P. in New Zealand. We argue that texture-contrast soils have not formed in New Zealand because of the short history of frequent fires in that country. A corollary of this conclusion is that texture-contrast soils in Tasmania are, at least in part, anthropogenic in origin.     

Effects of soil pH gradient caused by stemflow acidification on soil microarthropod community structure in a Japanese red cedar plantation: An evaluation of ecological risk on decomposition

Effect of acidic stemflow input on soil biological properties around cedar tree trunk were examined in a 34 year old Japanese red cedar plantation forest. Average soil pH of soil around cedar trunk (stemflow soil) was 3.88 and that of soil between trees (throughfall soil) was 4.97, and this suggested soil acidification due to proton load via stemflow. Soil microarthropod density in soil was higher as close to tree trunk, whereas microbial biomass of surface soil was reduced ca. 30 % around trunk. Abundance of Collembola and Gamasid mites showed positive correlation to amount of soil organic matter, while Oribatida had strong negative correlation to soil pH.Tectocepheus velatus (Oribatida) was dominant in soils pH under 4.0. Annual decomposition rate of cedar foliage was reduced ca. 16% in stemflow soil compared to throughfall soil. More litter accumulation was observed in stemflow soil, but it was not significant, though low microbial activity and retarded litter decomposition may be responsible to the accumulation of organic matter in stemflow soil. Soil biological community and soil process have been changed due to stemflow, the affected area corresponded to ca. 9.4 % of the forest. Thus, ecological risk of acidification in the sense of decrease in decomposition rate is 1.4%. This study was partly supported by Grant-in-Aid for Scientific Research (A)(1), No.08506001 by The Ministry of Education, Science, Sports, and Culture, Japan, and by the research project “Establishment of a scientific framework for the management of toxicity of chemicals based on environmental risk-benefit analysis” supported by Core Research for Evolutional Science and Technology (CREST).     

The effect of thinning on microbial biomass C, N and basal respiration in black pine forest soils in Mudurnu, Turkey

Reducing the canopy cover (e.g., forest thinning) is one of the most commonly employed forest silvicultural treatments. Trees are partially removed from a forest in order to manage tree competition, thus favoring the remaining and often the most valuable trees. The properties of the soil are affected by forest thinning as a result of changes in key microclimatic conditions, microbial communities and biomass, root density, nutrient budgets and organic matter turnover. The aim of this study was to determine the soil microbial biomass C, N and respiration (basal respiration) in a black pine (Pinus nigra Arn. subsp. pallasiana) forest in the Mudurnu district of Bolu Province (Western Black Sea Region, Turkey). Whereas forest thinning was found to cause increases in the soil temperature, microbial biomass C and N and organic C, it was found to decrease the soil moisture, basal respiration and metabolic quotient (qCO₂). As expected, soil organic C exhibited a strong impact on soil microbial biomass C, N and basal respiration. It was concluded that the influence of forest thinning on the microbial biomass and soil respiration was the combined result of changing microclimatic conditions and soil properties, such as forest litter, soil temperature, soil moisture, soil pH and soil organic matter.     

西樵山森林改造对林地土壤理化性质的影响

文章研究了西樵山森林改造对林地土壤理化性质(包括土壤物理性质、化学性质及微生物含量等)的影响。结果表明：森林改造后，林地枯落物增多，土壤容重、毛管持水量、总孔隙度及非毛管孔隙度等物理性状都得到了改良；林地土壤有机质含量增加，土壤全N、有效N及有效K等养分指标普遍比对照样地高；且随着造林时间延长，效果越来越显著。但林地土壤pH值、全P、全K及有效P等养分指标规律性不明显，土壤微生物含量差异不大，这可能与造林整地引起暂时的局部水土流失及林木生长年限尚短有关。     

Deforestation effects on biological and other important soil properties in an upland watershed of Bangladesh

Deforestation occurs at an alarming rate in upland watersheds of Bangladesh and has many detrimental effects on the environment. This study reports the effects of deforestation on soil biological properties along with some important physicochemical parameters of a southern upland watershed in Bangladesh. Soils were sampled at 4 paired sites, each pair representing a deforested site and a forested site, and having similar topographical characteristics. Significantly fewer(p≤0.001) fungi and bacteria, and lower microbial respiration, active microbial biomass, metabolic and microbial quotients were found in soils of the deforested sites. Soil physical properties such as moisture content, water holding capacity, and chemical properties such as organic matter, total N, available P and EC were also lower in deforested soils. Bulk density and pH were significantly higher in deforested soils. Available Ca and Mg were inconsistent between the two land uses at all the paired sites. Reduced abundance and biomass of soil mesofauna were recorded in deforested soils. However, soil anecic species were more abundant in deforested soils than epigeic and endogeic species, which were more abundant in forested soils than on deforested sites.     

The effects of teak monoculture on forest soils: a case study in Bangladesh

Teak plantations date back to 1871 in Bangladesh.This study was designed to assess how teak monoculture has impacted the soil properties in Bangladesh.Multiple linear regression and correlation matrices were estimated to evaluate these impacts.The means of soil physicochemical properties were compared across various attributes of the plantations.Older plantations accumulated more organic carbon in the soils than the younger plantations.Excessive removal of litter from the forest floor resulted in reduced levels of N, P, K, and other nutrients in the soils.Since bulk density was continuously decreasing deeper into the soil, the penetration of mineral nutrients into the soil was low.Furthermore, moisture content in the topsoil was significantly lower than that in the bottom layers due to the exposed and dry condition of the forest floor under teak plantations.For improving depleted teak plantation soils, teak could be planted with other tree species rather than just in monocultures.In addition, the forest floor could be enriched with leguminous herbs and shrubs to improve soil health in these plantations.     

Effects of elevated concentrations of atmospheric CO2 and tropospheric O3 on leaf litter production and chemistry in trembling aspen and paper birch communities

Human activities are increasing the concentrations of atmospheric carbon dioxide ([CO2]) and tropospheric ozone ([O3]), potentially leading to changes in the quantity and chemical quality of leaf litter inputs to forest soils. Because the quality and quantity of labile and recalcitrant carbon (C) compounds influence forest productivity through changes in soil organic matter content, characterizing changes in leaf litter in response to environmental change is critical to understanding the effects of global change on forests. We assessed the independent and combined effects of elevated [CO2] and elevated [O3] on foliar litter production and chemistry in aspen (Populus tremuloides Michx.) and birch-(Betula papyrifera Marsh.) aspen communities at the Aspen free-air CO2 enrichment (FACE) experiment in Rhinelander, WI. Litter was analyzed for concentrations of C, nitrogen (N), soluble sugars, lipids, lignin, cellulose, hemicellulose and C-based defensive compounds (soluble phenolics and condensed tannins). Concentrations of these chemical compounds in naturally senesced litter were similar in aspen and birch-aspen communities among treatments, except for N, the C:N ratio and lipids. Elevated [CO2] significantly increased C:N (+8.7%), lowered mean litter N concentration (-10.7%) but had no effect on the concentrations of soluble sugars, soluble phenolics and condensed tannins. Elevated [CO2] significantly increased litter biomass production (+33.3%), resulting in significant increases in fluxes of N, soluble sugars, soluble phenolics and condensed tannins to the soil. Elevated [O3] significantly increased litter concentrations of soluble sugars (+78.1%), soluble phenolics (+53.1%) and condensed tannins (+77.2%). There were no significant effects of elevated [CO2] or elevated [O3] on the concentrations of individual C structural carbohydrates (cellulose, hemicellulose and lignin). Elevated [CO2] significantly increased cellulose (+37.4%) input to soil, whereas elevated [O3] significantly reduced hemicellulose and lignin inputs to soil (-22.3 and -31.5%, respectively). The small changes in litter chemistry in response to elevated [CO2] and tropospheric [O3] that we observed, combined with changes in litter biomass production, could significantly alter the inputs of N, soluble sugars, condensed tannins, soluble phenolics, cellulose and lignin to forest soils in the future.