Nitrogen and phosphorus constrain labile and stable carbon turnover in lowland tropical forest soils

Tropical forests contain a large stock of soil carbon, but the factors that constrain its mineralization remain poorly understood. Microorganisms, when stimulated by the presence of new inputs of labile organic carbon, can mineralize (‘prime’) soil organic matter to acquire nutrients. We used stable carbon isotopes to assess how nutrient demand and soil properties constrain mineralization of added labile (sucrose) carbon and pre-existing (primed) soil carbon in tropical forest soils. In a series of lowland tropical forest soils from Panama, we found that the mineralization of fresh labile carbon was accelerated foremost by phosphorus addition, whereas the mineralization of pre-existing soil carbon was constrained foremost by nitrogen addition. However, there was variation in the relative importance of these nutrients in different soils and the largest effects on the acceleration of sucrose metabolism and constraint of priming occurred following the addition of nitrogen and phosphorus together. The respiration responses due to sucrose or primed soil carbon mineralization were reduced at pH below 4.8 and above 6.0. We conclude that in these tropical forest soils, phosphorus availability is more important in promoting microbial mineralization of sucrose carbon, whereas nitrogen availability is more important in constraining the priming of pre-existing soil organic carbon. This response likely arises because nitrogen is more closely coupled to organic matter cycling, whereas phosphorus is abundant in both organic and inorganic forms. These results suggest that the greatest impact of priming on soil carbon stocks will occur in moderately acidic tropical forest soils of low nitrogen availability. Given long-term changes in both atmospheric carbon dioxide and nitrogen deposition, the impact of priming effects on soil carbon in tropical forest soils may be partially constrained by the abundance of nitrogen.     

西双版纳热带雨林次生林的生物养分循环

本文获得了西双版纳热带雨林，砍伐后２块处于恢复演替阶段不同年代的次生林的生物量、生长量、年凋浇物量及它们的主要营养元素含量、对土壤养分状况的影响、以及土壤微生物状况和土壤生化活性等一系列资料。阐明了次生林生物物质和养分吸收、积累和归还的特点及对土壤养发状况的影响，研究了土壤微生物对凋落物的分解作用，从而对热带雨林次生林的生物养分循环作了一初步的探讨，为热带森林生态系统研究奠定了基础。研究表明：１．     

不同水稻灌溉模式和氮肥减量对还田麦秸腐解特性及土壤养分的影响

为了探讨不同水稻灌溉模式和氮肥减量对还田小麦秸秆腐解特性及土壤养分的影响，通过田间试验，设置了水稻灌溉模式（常规灌溉，W1；干湿交替灌溉，W2）和施氮水平（不施氮，N0；常量施氮，N1；减量20%施氮，N2）处理，采用尼龙网袋法研究了不同处理下小麦秸秆腐解动态、养分释放规律及土壤养分含量。结果表明，干湿交替灌溉和氮肥施用均可促进还田小麦秸秆的腐解，减量20%施氮处理小麦秸秆累积腐解率低于常量施氮处理。相同施氮水平下，干湿交替灌溉模式小麦秸秆碳与氮磷钾累积释放率高于常规灌溉模式；与常量施氮相比，减量20%施氮处理小麦秸秆碳与氮磷钾累积释放率降低。干湿交替灌溉和施氮使土壤有机质、全氮、碱解氮和有效磷含量提高，而减量20%施氮对土壤养分含量的影响较小。综上可见，干湿交替灌溉和氮肥施用促进了还田小麦秸秆腐解和养分释放，有利于土壤养分提升；而减量20%施氮对小麦秸秆腐解与养分释放以及土壤养分无明显影响。     

Allelopathic effects of artemisinin on ectomycorrhizal fungal isolates in vitro

The anti-malarial drug artemisinin is extracted from the leaves of Artemisia annua L. The release of artemisinin into forest soils could produce a potential risk for forest ecosystems, including effects on ectomycorrhizal fungal nutrient uptake, in areas where commercial and continual cultivation of the medicinal plant A. annua L. is practiced. Therefore, growth, proton and oxalate efflux, and nutrient uptake (nitrogen, phosphorus and potassium) of three isolates of Suillus luteus (S. luteus 1, S. luteus 13, and S. luteus 11) and of one isolate of Suillus subluteus (S. subluteus 12) were compared in culture solutions with different nominal artemisinin concentrations. The results showed that artemisinin inhibited significantly the growth of all studied fungi. With 25 mg artemisinin L⁻¹ added, fungal biomass was decreased by 78.6% (S. luteus 1), 96.7% (S. luteus 13), 77.8% (S. luteus 11) and 86.8% (S. subluteus 12) compared with the control (without artemisinin). This could explain, at least in part, why ectomycorrhizal fungal sporocarps in forests are consistently not found near cultivated A. annua L. fields. The amount of proton efflux by the fungal isolates also decreased as nominal artemisinin concentrations increased, indicating the limited ability of ectomycorrhizal fungi to mobilize nutrients from soil minerals. However, nominal artemisinin significantly increased the rate of fungal oxalate efflux, suggesting membrane damage and the abnormal opening of anion channels on hyphae cell membranes. Nominal artemisinin also decreased the uptake of nitrogen, phosphorus and potassium by the fungal isolates, which may not benefit from the nutrient uptake by ectomycorrhizae. Therefore, artemisinin released from large A. annua L. plantations may inhibit ectomycorrhizal fungal growth, nutrition and functions in forest ecosystems in Southwest China.     

Effects of climatic and soil properties on cellulose decomposition rates in temperate and tropical forests

Cellulose decomposition experiments were conducted under field conditions to analyze the effects of climatic and soil properties on rates of organic matter decomposition in temperate and tropical forests. The mass loss rates of cellulose filter papers buried in the soil surface were measured to estimate the respiratory C fluxes caused by cellulose decomposition and mean residence time (MRT) of cellulose. The rates of cellulose decomposition increased with soil temperature, except for during the dry season, while rate constants of decomposition (normalized for temperature) decreased with decreasing pH because of lower cellulase activity. The estimated MRTs of soil cellulosic carbohydrates varied from 81 to 495 days for the temperate forests and from 31 to 61 days for the tropical forests. As a major organic substrate, the C fluxes from cellulose decomposition can account for a substantial fraction of heterotrophic (basal) soil respiration. However, the respiratory C fluxes can be limited by the low substrate availability and low pH in tropical soils, despite high microbial activity. The rate-regulating factors of cellulose decomposition, i.e., temperature, soil pH, and substrate availability, can accordingly influence the rates of heterotrophic soil respiration.     

长期氮肥施用对农田黑土NLFA与PLFA特性的影响

以不施肥与休闲处理为对照,通过对土壤微生物磷脂脂肪酸（PLFA）、中性磷脂脂肪酸（NLFA）、NLFA/PLFA比值及各菌群特定PLFA比值的测定,研究不同氮肥处理条件下东北黑土微生物群落变化规律.PLFA测定结果表明,氮磷配施能促进土壤微生物生长;氮磷钾配施未表现出促进土壤微生物生长的作用;单施氮肥处理因有效磷等养分过度消耗而抑制真菌生长.不同菌群之间PLFA比值表明,真菌较细菌更能适应养分贫瘠条件,而氮肥与磷肥的施入则能促进细菌生物量增加.不同氮肥处理NLFA含量及个别NLFA/PLFA比值存在较大差异,可用来说明土壤微生物生理状态和土壤养分水平.     

Carbon mineralization is promoted by phosphorus and reduced by nitrogen addition in the organic horizon of northern hardwood forests

Limitations to the respiratory activity of heterotrophic soil microorganisms exert important controls of CO₂ efflux from soils. In the northeastern US, ecosystem nutrient status varies across the landscape and changes with forest succession following disturbance, likely impacting soil microbial processes regulating the transformation and emission of carbon (C). We tested whether nitrogen (N) or phosphorus (P) limit the mineralization of soil organic C (SOC) or that of added C sources in the Oe horizon of successional and mature northern hardwood forests in three locations in central New Hampshire, USA. Added N reduced mineralization of C from SOC and from added leaf litter and cellulose. Added P did not affect mineralization from SOC; however, it did enhance mineralization of litter- and cellulose- C in organic horizons from all forest locations. Added N increased microbial biomass N and K₂SO₄-extractable DON pools, but added P had no effect. Microbial biomass C increased with litter addition but did not respond to either nutrient. The direction of responses to added nutrients was consistent among sites and between forest ages. We conclude that in these organic horizons limitation by N promotes mineralization of C from SOC, whereas limitation by P constrains mineralization of C from new organic inputs. We also suggest that N suppresses respiration in these organic horizons either by relieving the N limitation of microbial biomass synthesis, or by slowing turnover of C through the microbial pool; concurrent measures of microbial growth and turnover are needed to resolve this question.     

Decoupled stoichiometric,isotopic, and fungal responses of an ectomycorrhizal black spruce forest to nitrogen and phosphorus additions

Many northern forests are limited by nitrogen (N) availability, slight changes in which can have profound effects on ecosystem function and the activity of ectomycorrhizal (EcM) fungi. Increasing N and phosphorus (P) availability, an analog to accelerated soil organic matter decomposition in a warming climate, could decrease plant dependency on EcM fungi and increase plant productivity as a result of greater carbon use efficiency. However, the impact of altered N and P availability on the growth and activity of EcM fungi in boreal forests remains poorly understood despite recognition of their importance to host plant nutrition and soil carbon sequestration. To address such uncertainty we examined above and belowground ecosystem properties in a boreal black spruce forest following five years of factorial N and P additions. By combining detailed soil, fungal, and plant δ¹⁵N measurements with in situ metrics of fungal biomass, growth, and activity, we found both expected and unexpected patterns. Soil nitrate isotope values became ¹⁵N enriched in response to both N and P additions; fungal biomass was repressed by N yet both biomass and growth were stimulated by P; and, black spruce dependency on EcM derived N increased slightly when N and P were added alone yet significantly declined when added in combination. These findings contradict predictions that N fertilization would increase plant P demands and P fertilization would further exacerbate plant N demands. As a result, the prediction that EcM fungi predictably respond to plant N limitation was not supported. These findings highlight P as an under appreciated mediator of the activity of denitrifying bacteria, EcM fungi, and the dynamics of N cycles in boreal forests. Further, use of δ¹⁵N values from bulk soils, plants, and fungi to understand how EcM systems respond to changing nutrient availabilities will often require additional ecological information.     

河北雾灵山5种人工纯林土壤养分综合评价

通过河北雾灵山5种人工纯林的土壤养分分析,研究了不同林分类型对土壤pH值、有机质、全量养分和速效养分的变化,并对不同土壤养分进行了主成分分析。结果表明:5种不同林分类型的土壤pH值均为弱酸性,其变化范围为4.61～6.31;不同土层土壤有机质表现为:表层（0—10 cm）> 中层（10—20 cm）> 下层（20—40 cm）,有机质均值在2.53～9.60 g/kg之间;土壤全磷含量均值为0.20～0.70 g/kg;土壤全氮含量均值为2.38～3.45 g/kg;土壤速效钾含量均值为67.54～169.88 mg/kg;土壤速效磷含量均值在0.84～6.84 mg/kg之间;土壤碱解氮含量均值在65.68～147.88 mg/kg之间;不同林分类型土壤养分综合效应评价,白桦纯林最大,为1.122;落叶松纯林最小,为-0.819。综合来看,随土层厚度增加土壤养分含量减少;阔叶林土壤养分含量大于针叶林。     

Recovery of woody plant diversity in tropical rain forests in southern China after logging and shifting cultivation

Logging and intense shifting cultivation have caused major degradation of tropical forests and loss of biodiversity. Understanding the direct and indirect effects of those land uses on plant biodiversity is essential to the restoration of tropical forests. We compared the species diversity, community composition and basal area of all stems ?1 cm dbh among 18 1-ha tropical lowland and montane rain forest plots with a well-recorded long-term history of shifting cultivation and logging on Hainan Island, south China. We also explored the relative importance of disturbance and environmental factors in determining forest recovery. We found that the species density and diversity in old growth forests were higher than in shifting cultivation fallows (55 years old) but lower than in logged forests (35–40 years since logging). The species composition of shifting cultivation fallows was distinct from other forest types but logged forests were similar to old growth forests, especially in lowland forests. Disturbance intensity was the most frequently important factor in determining species composition, species density, diversity, and basal area accumulation. Soil nutrient availability explained some of the variation in species composition and diversity. Stem density was related to multiple factors including disturbance history, soil nutrients, and distance to old-growth forest. In general, we found that disturbance intensity was a better predictor of forest structure and diversity than edaphic environmental variables, highlighting the importance of human impacts in shaping tropical forest successional pathways.     

滴灌棉田根系与土壤氮磷钾养分的分布特征

为了解滴灌棉田根系与土壤养分的分布特征,选择壤土和砂壤土两种质地土壤,定期调查滴灌棉田不同生育时期的棉花根系与土壤氮磷钾养分在水平和垂直方向的分布规律。结果表明:第一次滴灌水前棉花根系体系构建完成,棉花根系水平分布均匀,在3~20 cm土层垂直分布较多,疏松土壤中可深入到40 cm土层;根系分布与基肥分布吻合,基肥能被有效利用。各生育期棉田养分垂直方向分布总体规律是0~30 cm土层中有效氮磷钾养分分布一致且较高;30~40 cm土层中养分略低,是过渡层;40 cm以下土层中养分较低。0~30 cm土层与40~60 cm土层养分间差异显著。棉田在垂直滴灌带的水平方向土壤养分含量差异不显著;滴肥后0~30 cm土层氮磷钾养分增加明显,及时提供了棉花生长的养分,维持了土层中养分水平。     

Responses of extracellular enzymes to simple and complex nutrient inputs

Soil microbes produce extracellular enzymes that mineralize organic matter and release carbon and nutrients in forms that can be assimilated. Economic theories of microbial metabolism predict that enzyme production should increase when simple nutrients are scarce and complex nutrients are abundant; however, resource limitation could also constrain enzyme production. We tested these hypotheses by monitoring enzyme activities and nutrient pools in soil incubations with added simple and complex nutrient compounds. Over 28 days of incubation, we found that an enzyme's activity increased when its target nutrient was present in complex but not simple form, and carbon and nitrogen were available. β-Glucosidase and acid phosphatase activities also increased in treatments where only carbon and nitrogen were added. Glycine aminopeptidase and acid phosphatase activities declined in response to ammonium and phosphate additions, respectively. In some cases, mineralization responses paralleled changes in enzyme activity—for example, β-glucosidase activity increased and respiration was 5-fold greater in soil incubations with added cellulose, ammonium, and phosphate. However, a doubling of acid phosphatase activity in response to collagen addition was not associated with any changes in phosphorus mineralization. Our results indicate that microbes produce enzymes according to ‘economic rules’, but a substantial pool of mineral stabilized or constitutive enzymes mediates this response. Enzyme allocation patterns reflect microbial nutrient demands and may allow microbes to acquire limiting nutrients from complex substrates available in the soil.     

辽西北沙地苹果-花生间作系统土壤养分空间分布特征及间作效应

[目的] 研究辽西北沙地农林复合系统土壤养分的空间分布及其效应，从土壤养分角度探讨果农间作系统中果树和农作物对土壤养分的相互作用关系，为该区农林复合系统的可持续经营提供科学合理的依据。[方法] 以苹果与花生间作、花生单作、苹果单作为研究对象，对0-60 cm土层深度，0-300 cm水平距离范围内土壤养分含量进行测定和分析。[结果] 沙地间作系统中土壤有机质、速效钾极缺乏，全氮、碱解氮很缺乏，全磷缺乏，有效磷含量中等；间作系统在水平方向上，苹果树和花生植株对总养分有机质、氮、磷的竞争激烈位点位于果树带区，对有效养分氮、磷、钾的竞争激烈位点位于近果树作物区；在垂直方向上，各养分总体表现出了表聚性，间作系统对有机质、有效磷的竞争主要位于深土层，对全磷、速效钾的竞争主要位于表土层，对全氮、碱解氮表现为合作效应，表土层效应更高；与苹果单作、花生单作相比较，间作系统速效钾和有效磷含量呈现负效应。[结论] 沙地苹果-花生间作系统土壤养分贫瘠，应在果树带区施用有机肥、磷肥，作物区施入钾肥，以减轻养分竞争，提高养分效应。     

Macro‐ and micronutrients removed by upland and lowland rice cultivars in West Africa

Abstract

Plant analysis is an important component of soil fertility and plant nutrition research. Plant analysis at harvest of the crop forms the basis for constructing nutrient balances and assessing the nutrient needs of production systems. Amounts of macro‐ and micronutrient elements removed by improved, upland and lowland rice cultivars were determined in field experiments at two sites in Ivory Coast. Amounts of nitrogen (N), zinc (Zn), and manganese (Mn) removed for 11 rice grain yield by upland and lowland rice cultivars were similar, but the amounts of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) removed were higher for lowland than upland rice. The nutrient element harvest indexes (amount in grain/amount in grain plus straw) varied between the cultivars, but more importantly, among nutrient elements. On average the nutrient harvest index was highest for P (69%) and lowest for K (10%). The results suggest that the nutrient requirement of rice for K can be met to a large extent through the recycling of K in rice straw. The amounts of other major nutrients, N and P in the straw were small and hence less scope for supplying these nutrients through the recycling of rice straw.     

北方山区主要森林类型树木叶片氮、磷回收效率研究

养分回收是植物养分利用策略的重要驱动力,可减少养分流失,降低其对环境的依赖性,对植物种群和群落稳定性、生态系统养分循环都具有重要的生态学意义。本文在收集北方山区(黄土高原、太行山区、京北山区)天然林、人工林等各种森林成熟叶片和凋落物氮、磷养分含量等资料的基础上,根据群落生活型和管理方式将各类森林进行归并,对其养分回收效率进行了综合评估。结果表明,各类森林植被通过成熟叶片和落叶中氮、磷含量计算得到的叶片氮、磷回收效率分别是24.5%~71.3%和18.1%~75.4%,均值分别是45.5%和47.4%。北方山区天然林和人工林成熟叶片的平均氮含量分别是11.6 g·kg~(-1)和21.6 g·kg~(-1),人工林成熟叶片氮含量显著高于天然林,养分在人工林生长过程中可能基本处于消耗状态。不同地区天然林与人工林叶片磷含量存在差异:太行山区天然林成熟叶片和枯落叶片磷含量显著高于人工林,而京北山区人工林成熟叶片磷含量较高,枯落叶片磷含量较低。灌木成熟和枯落叶片中氮含量显著高于乔木,而两者间磷含量无显著差异;灌木叶片氮回收效率高于乔木。通过3个地区的比较发现,京北山区树木叶片氮、磷回收效率分别是62.1%和67.8%,高于其他两个地区。相关分析表明,北方山区森林枯落叶片氮含量是影响叶片氮、磷回收效率的重要因子。通过对不同树种养分回收效率的比较发现,针叶树种养分回收效率大于阔叶树种,这说明在土壤养分贫瘠山区针叶树种的养分回收效率更高,更能适应这种贫瘠的土壤环境。在山区进行人工建植时,针叶树种高的养分利用效率应该被考虑进来。     

物元模型在玉树地区林地土壤养分评价中的应用

选择玉树区林地土壤有机质,全氮,全磷,全钾,速效氮,速效磷和速效钾7项测试数据作为土壤养分评价指标,采用偏相关分析法确定权重,应用物元分析建模对玉树地区林地土壤养分进行评价。结果表明玉树地区整体林地土壤养分状况良好,除速效磷含量极贫乏外,其余养分指标含量均达到丰富水平;有机质、氮素和速效磷是影响土壤养分的主要因子。建议平衡地区土壤养分状况,优先考虑提高速效磷养分水平。     

Quantification of pyrophosphate in soil solution by pyrophosphatase hydrolysis

A commercial pyrophosphatase from Saccharomyces cerevisiae selectively hydrolyzed sodium pyrophosphate, but showed no significant activity towards a range of other organic and condensed inorganic phosphorus compounds. Pyrophosphate determined by pyrophosphatase hydrolysis accounted for 38 ± 12% (mean ± standard error of 19 sites) of the non-reactive phosphorus in soil solution obtained by centrifugation from a series of lowland tropical rain forest soils. Pyrophosphate concentrations were up to 89 μg P l⁻¹ and correlated positively with microbial phosphorus, soil solution pH, and native phosphomonoesterase activity in soil solution, but not with total soil pyrophosphate determined by NaOH–EDTA extraction and solution ³¹P NMR spectroscopy. In summary, we identify pyrophosphate as a major constituent of soil solution phosphorus in lowland tropical rain forests, and demonstrate that a commercial pyrophosphatase can be used as a selective tool to quantify trace concentrations of pyrophosphate in soil solution.     

云南玉溪植烟土壤速效养分空间变异特征及应用

为探讨烟田土壤养分空间变异特征及利用空间变异进行分区管理的技术路线,以全国烤烟种植典型产区云南省玉溪市烟田土壤为例,形成土壤养分空间变异分析—空间分布—肥料养分推荐—分区配方的技术思路。基于烟区土壤养分数据,应用地理信息系统(GIS),采用地统计学方法研究烟区耕作层(0~20 cm)土壤碱解氮、有效磷和速效钾的变异特征和空间分布。以乡镇作为管理单元,依据烟田土壤肥力评价及养分管理指标体系,计算出乡镇烤烟养分管理的氮、磷、钾肥料推荐量。采用聚类分析方法,结合烤烟养分管理"核心是氮、品质元素是钾"的特点,提出玉溪烤烟养分管理5个管理分区、5个基肥配方、2个追肥配方。研究表明:玉溪烟田土壤速效养分为中等强度空间变异,拟合模型为指数模型,变异来源于结构性因素和施肥等人为因素;土壤有效磷的变异最大,高于速效钾和碱解氮,与氮肥和钾肥用量相对稳定,而磷肥相对随机等农艺措施相关;超过67%的土壤碱解氮、有效磷和速效钾含量处于高和极高水平,肥料氮、磷、钾推荐量低于云南省烤烟养分管理平均水平11%左右;提出5个烤烟养分管理分区及相应的基肥和追肥配方,以满足"大配方、小调整"原则,实现分类指导和分区管理。     

石羊河尾闾(青土湖)水面形成后土壤养分的空间特征

通过测定青土湖不同土层、不同水面距离的土壤有机质、全氮、全磷、全钾、速效氮、速效磷和电解质,对比不同土层和水面距离的土壤养分差异,分析其空间变异性以及相关关系。结果表明：１）青土湖的土壤各养分含量均较低,水面形成的干扰改变了原状土壤的理化性质,水面的形成对土壤养分垂直分布的影响范围在0~40cm。;2）0-60cm土层深度的有机质、全氮、速效氮、全磷、全钾和土壤溶液电导率分别在距水面100-150m和300 m处达到最大值,在距水面200 m处为最小,呈波浪式变化,这种波浪式变化与其原湖泊沉积和区域气候环境相符合。;32）土壤养分含量存在显著空间变异性,各养分指标含量随土层深度变化规律明显,不同水面距离0～40cm土层土壤有机质、全氮等含量均比40~80cm高,土壤各养分含量除了土壤全钾含量在0~80cm、土壤全磷在60~80cm为弱变异外,其他均属于中等变异。;43）在0~40cm土层深度,有机质与全氮、全钾,速效氮、电导率呈正相关;电导率和速效磷、全磷呈正相关。青土湖的土壤各养分含量均较低,水面形成的干扰改变了原土壤的理化性质,水面的形成对土壤养分垂直分布的影响范围在0~40cm。     

Factors determining soil nutrient distribution in a small-scaled watershed in the purple soil region of Sichuan Province, China

Determining soil nutrient distribution is critical to identify sites which are at risk of N and P loading. Equally important are determining factors that influence such distribution (e.g. land use, land management, topography, etc.). In this research, soil nutrient distribution and its influencing factors were studied in a small-scaled watershed in the purple soil region of Sichuan Province, China. The watershed is 1.3 km² with a complex land management system including agriculture and forestry. Surface soil samples (0–20 cm) from 48 sites within the watershed were collected in the spring of 1999 and analysed for chemical properties. When spatial distribution patterns of soil organic matter and soil nutrients were considered, several patterns were evident. Soil organic matter and total nitrogen coincided with high soil nutrients in the center of the watershed. Total phosphorus was linked to low soil nutrient contents on hilltops, while total potassium was characterized by low variability and high soil nutrient content throughout the watershed. Water-soluble nutrients in soils were highly variable throughout the watershed. Results of this study indicate that land use, topography and other variables play important roles in controlling the spatial distribution of most soil nutrients. However, the relative roles of these indices were nutrient specific. The relationship was therefore complex. Land use, silt, and sand content contributed to a high level of heterogeneity for soil organic matter and total nitrogen with the former being the dominant factor. Land use, particle size distribution (silt and sand) and topographic factors (slope and elevation) contributed to the variability of total phosphorus. However, particle size distribution and topographic factors were the dominant factors affecting total phosphorus. Elevation influenced the concentration of total potassium and land use controlled the concentration of dissolved phosphorous. No significant relationship was found between the studied characteristics and nitrate nitrogen.