Partitioning of rainwater and chemicals into throughfall and stemflow in different forest stands

The flow of nutrients throughout different components of forests was characterized using 13 years of data from a nutrient-cycling study involving three hardwood (broadleaved) and six softwood (conifer) forest stands. Included in this report is information on the distribution and chemistry of rainwater as it affects the quantity of nutrients cycled as throughfall and stemflow in different stands. A general formula empirically derived for partitioning rainwater into throughfall and stemflow is also described.

The empirically derived equations were found to be suitable for calculating without rain data on an event basis, the weekly or monthly quantity of throughfall and stemflow reaching the ground under different stands. These equations were evaluated to increase their portability and applicability to forest stands of different regions. The results obtained with these calculations validated the among-species differences in the measured values of throughfall and stemflow. The differences among tree species with respect to their abilities to alter rain chemistry were also found to be significant. The differences in the concentrations of hydrogen and sulfate ions and total dissolved solids in the throughfall and stemflow samples as compared to those in the rainwater are also reported.     

Influence of nitrogen and phosphorus fertilizers on amount and nutrient content of litterfall in a regrowth eucalypt forest

The effects of fertilizer treatment on nutrient transfers to the forest floor were examined in regrowth Eucalyptus diversicolor F. Muell. forest. Dry weight and nutrient content of leaf litterfall and total litterfall were measured for 3 years in a stand to which two levels of N (0, 200 kg ha^-1 year^-1) were applied each year at each of three levels of a single initial application of P (0, 30, 200 kg ha^-1). Annual accessions of litter to the forest floor were significantly increased by additions of both N (by 17%, 18% and 21% in the 3 years) and 200 kg P ha^-1 (by 8%, 8% and 4% in the 3 years) but there was no interaction between effects of N and P treatments. Fertilizer application also had a significant effect on the nutrient content of leaf litterfall and total litterfall. Concentration of N in leaf litterfall was 9% to 23% greater on plots treated with N fertilizer compared to untreated plots. The amounts of N in litterfall were about 30% greater on N-treated compared to untreated plots. On plots treated with 200 kg P ha^-1, P concentrations in leaf litter were 50% to 100% greater than in litter from plots receiving no P. Application of 200 kg P ha^-1 increased the amounts of P in annual litterfall by 32% to 87%. The greatest increase in P accessions occurred soon after fertilizer treatment. The amounts of Ca, K, and Na in litterfall were also significantly increased by fertilizer application. For Ca and K this was due partly to increases in element concentrations in litterfall following application of treatments. The effect of fertilizers on internal recycling of plant nutrients and on litter accumulation and nutrient dynamics in forest floor litter is discussed.     

降雨在杉木和马尾松人工林养分循环中的作用

本文对杉木和马尾松林内、外雨树干茎流及迳流所含各种养分物质量进行了测定,其结果表明:林内雨的各种养分物质浓度显著地高于林外雨。林外雨的各养分物质含量是 N>Ca>K>Mg>P,杉木林内雨的各种养分物质量是 K>N>Ca>Mg>P。皆伐迹地迳流中养分流失量显著地高于林地的流失量。雨水养分含量与降雨量存在着半对数函数关系。由降雨输入的养分量显著地大于迳流输出的养分量。林内雨和树干茎流淋溶的养分量占还原养分总量的 48—53％。林内雨和树干淋溶的K、Mg、N的养分量超过凋落物归还的养分量。     

长宁竹海主要林分林冠降雨分配格局

对长宁竹海楠竹林、黄竹林、苦竹林、杉木林和栎林5种林分林冠降雨分配格局进行了对比。回归结果表明:穿透雨量和干流与林外降雨量呈线性关系,并都达到极显著水平(p-0.01)。在降雨量为1204.7 mm时,5种林分穿透雨的最小响应雨量分别为:斑苦竹(Pleioblastus amarus Kengf)林为3.0 mm,硬头黄竹(Bambusa rigida Keng et Kengf)林为1.0 mm、白栎(Quercus fabri Hance)林为0.9 mm、楠竹(Phyllostachy spubescen)林为0.8 mm、杉木(Cunninghamia lanceolata Hook)林为0.7 mm。干流量随树干胸径的增加而增大,两者关系可用Q=B0 B1D B2D2 B3D3进行描述。与其它的林种相比,竹林干流量远高于栎林和杉木林。苦竹林干流量达105.3 mm,干流率为8.74%,黄竹和楠竹干流量均为82.4 mm,干流率为6.84%,栎林分别为42.4 mm和3.49%,杉木林最小,仅为8.8 mm和0.73%。截留量和截留率从大至小的排序为:苦竹林为384.3 mm和31.9%,栎林355.5 mm和29.51%,黄竹280.7 mm和23.3%,楠竹274.1 mm和22.75%,杉木林254.8 mm和21.15%。     

亚热带杉木、马尾松人工林水文功能的研究

1984-1990年,在江西省分宜县山下林场,对22年生杉木,马尾松人工林中的主要水文要素:降雨、林冠截留、树干茎流、土壤水分含量、径流及各种水的养分含量进行了测定,结果表明:人工林林冠的截留率为10.20-17.56％,茎流率为0.98-1.40％。土壤层较薄,含水率低,水文物理性质较差,土壤蓄渗性能较弱。林地径流量较小,且多为表层流。降雨输入林地的养分量大于径流的输出量。林内雨和树干茎流淋溶的养分量占养分还原总量的48-53％。其淋溶的K、Mg、N的养分量超过凋落物归还量。     

Interception loss, throughfall and stemflow chemistry in pine and oak forests in northeastern Mexico

Interception loss, gross precipitation, throughfall and stemflow solution chemistry beneath pine (Pinus pseudostrobus Lindl.), oak (Quercus sp.) and pine-oak natural forest canopies in northeastern Mexico were measured. Coefficients of variation for throughfall were 12% in pine and oak canopies and 17% in the mixed pine-oak canopy. The variability of stemflow averaged 66, 126 and 73% for pine, oak and the mixed pine-oak canopies, respectively. Linear regression analysis of net versus gross precipitation for the three canopies showed highly significant correlations (r = 0.974-0.984). Total precipitation during the experimental period was 974 mm and estimated interception loss was 19.2, 13.6 and 23% for the pine, oak and pine-oak canopies, respectively. Stemflow did not occur following rainfall events of less than 4 mm and, in all canopies, stemflow represented a minimal proportion of gross precipitation (0.60, 0.50 and 0.03% for pine, oak and pine-oak, respectively). Throughfall pH in pine (6.2), oak (6.3) and pine-oak (6.3) canopies was significantly more acidic than gross precipitation (6.6). Stemflow pH ranged from 3.7 (pine) to 6.0 (oak). The pine-oak canopy registered the highest throughfall and stemflow electrical conductivities, 104 and 188 microS cm(-1), respectively. Net nutrient leaching of K, Mg, Na, Fe, Mn and Zn was significantly higher from the pine-oak canopy than from the pure pine and oak canopies. Mean depositions of Ca and Cu in throughfall behaved similarly among the three types of canopies. A greater proportion of Zn in gross precipitation was absorbed by the oak canopy than by the pine and pine-oak canopies. Enrichment factors beneath the pine-oak canopy relative to gross precipitation varied from 1.2 to 3.2 for macro-nutrients (Ca, K, Mg and Na) and from 1.4 to 3.1 for micro-nutrients (Cu, Fe, Mn and Zn). Stemflow depositions of Ca, K, Mg and Cu were higher in the pine-oak canopy, whereas stemflow depositions of Na, Fe, Mn and Zn were higher in the pine canopy.     

Atmospheric nutrient inputs to three forest types in East Texas

The effect of forest type on atmospheric nutrient inputs to the forest ecosystem was measured for individual storm events for 1 year in three East Texas forest types: beechmagnolia, pine-mixed hardwoods and loblolly pine plantation. Total annual bulk precipitation inputs (kg/ha) for Ca, Mg, N, K and Na were, respectively: 5.0, 1.1, 4.1, 3.3 and 9.9. Total througfall inputs were increased by forest type, but the magnitude differed with each nutrient. Over $\text{3}\text{4}$ of the total K and $\text{1}\text{2}$ the total Mg throughfall input were due to the forest canopy. However $\text{2}\text{3}$ of the Ca and most of the Na throughfall input resulted from bulk precipitation. Although stemflow nutrient concentrations (ppm) were higher than throughfall and bulk precipitation, total annual stemflow nutrient inputs were only a minor component of the loblolly pine plantation ecosystem.     

长白山北坡阔叶红松林林冠对降雨及其养分的影响

在2001年森林生长季(6-9月),通过测量降雨各分量,分析了中国吉林省长白山北坡红松阔叶林冠层对降水分配各分量的影响。结果表明:干流量(37.39 mm),透流量(326.02 mm)和截留量(105.67 mm),分别占同期降雨量(469.08 mm) 的7.97%、69.50%和22.53%。林冠对降雨的月份分配规律是:树干茎流率的月变化为七、八月份大于其它月份,穿透率从6-9月份有逐渐减少的趋势,而截留率的变化正好与穿透率相反,从19.43%增加到31.02%。林内降雨中的养分元素浓度发生显著变化,除Ca、Mg外,其它元素的浓度都有所增加。经分析得出,大气降雨中养分元素的浓度序列为:Ca> Mg> N> K> Fe > P> Cu > Mn;而穿透雨中养分元素的浓度序列为:K>N>Mg>Ca>P>Fe>Mn>Cu;在林冠淋溶中各养分元素的浓度序列为:Mn> P>K>Cu>Fe>N>Mg>Ca。图1表5参13。     

黑龙江省东部山地白桦人工林对水质的影响

对黑龙江省东部山地白桦人工林生态系统的大气降水、穿透水、树干茎流和地表径流中的pH值、溶解氧、浊度、总溶解固体、电导率、氧化还原电位、K、Na、Ca、Mg、Cu、Zn、Mn和Fe等水质指标进行了测定.结果表明:大气降水经过白桦人工林生态系统后,浊度和总溶解固体值逐渐升高.穿透水除Ca元素外,其他化学元素含量均有不同程度的增加,化学元素含量排序为:K＞ Ca＞ Na＞ Mg＞ Mn＞ Fe ＞Zn＞ Cu.树干茎流中各化学元素含量排序为:K＞Ca＞Mg ＞Na＞Fe ＞Mn ＞Zn ＞Cu.地表径流中各化学元素含量为:K＞ Ca＞ Na＞ Mg＞ Fe＞ Mn＞ Zn＞ Cu.除Na、Ca元素外,大气降水中其他元素的变异系数均较大.穿透水和树干茎流中Cu元素的变异系数大于其他元素,地表径流中Zn元素的变异系数最大.根据淋溶系数的大小排列,穿透水中各化学元素的淋溶序列是:Mn＞K＞Mg＞Fe＞Cu ＞Zn＞ Na＞ Ca.树干茎流中各化学元素的淋溶序列是:K ＞Mn＞ Mg＞ Fe ＞Cu ＞Zn＞ Ca＞ Na.经过淋洗后,穿透水和树干茎流中K和Mg元素增加较多,Ca元素出现负淋溶.     

Nutrient cycling in a clonal stand of Eucalyptus and an adjacent savanna ecosystem in Congo: 2. Chemical composition of soil solutions

The dynamics of nutrients were compared over three years in a clonal Eucalyptus plantation and in a native savanna in Congo. This paper focuses on the changes in the chemical composition of solutions during their transfer through the soil in both ecosystems. The main characteristics of the soil (Ferralic Arenosol) were similar in the two ecosystems, and the low inter-stand variability allowed reliable comparisons of the influence of afforestation on the soil solution chemistry.

Rainfall amounted to about 1400 mm per year during the experimental period. In both ecosystems, an enrichment was observed for most elements during the transfer of solutions through the foliage, but N uptake occurred. Concentrations of H⁺ and dissolved organic carbon (DOC) in solutions increased through the litter layer in both stands. In the Eucalyptus ecosystem, a quick uptake of nutrients by a dense root mat inside the forest floor likely explained why the concentrations of gravitational waters were not enhanced markedly for ‘base cations’, despite the mineralization of high amounts of nutrients during the litter decay.

Soil solutions were collected by zero tension lysimeters (ZTL) at a depth of 15 cm, but these lysimeters were inefficient at collecting gravitational solutions beyond this depth. By contrast, tension lysimeters (TL) maintained at a suction of −60 kPa, collected soil solutions at the depths of 15, 50 cm, 1, 2, 3, 4 m in both ecosystems and 6 m in the plantation. In the topsoil of both stands, the nutrient concentration decreased sharply when the time of residence of solutions increased. This pattern highlighted the crucial role of the inputs by throughfall, stemflow and mineralization of the litter layer for the nutrition of these stands.

A combination of high nutrient requirements of the stands and low availability of exchangeable cations in this highly weathered soil might account for the extremely low nutrient concentrations in solutions collected by TL, regardless of the depth.     

Nitrogen deposition in Casuarina equisetifolia (Forst.) plantation stands in the dry tropics of Sonbhadra, India

Periodic variations in the concentration, deposition and canopy impact of different forms of N on annual N deposition through rainfall, throughfall and stemflow in 5 and 8 year old stands of Casuarina equisetifolia were studied. Throughfall and stemflow ranged from 70 to 76% and 5–6% of annual precipitation respectively. The total N deposition by rainfall was 11.1 kg ha⁻¹ year⁻¹, and by throughfall was 13.6 kg ha⁻¹ year⁻¹ and 16.5 kg ha⁻¹ year⁻¹ in 5-year-old and 8-year old plantations, respectively. The quantities of N deposited through stemflow in the two plantations were nearly identical, accounting for 1.6 kg ha⁻¹ year⁻¹. Observations of the monthly deposition of NH₄,N, NO₃-N, Kjeldahl-N and organic-N revealed that maximum deposition occurred in July and the minimum in September. Organic-N deposition was 17% less (5-year) than the rainwater content. Net deposition of N, as an effect of canopy, was 7–8.7 kg ha⁻¹ year⁻¹, which was added directly to the available nutrient pool of soil.     

Mineral nutrient fluxes in rainfall and throughfall in a lowland Atlantic rainforest in southern Brazil

The ecosystems occurring on dystrophic soils, such as sandy soils, are highly dependent on nutrients from the atmosphere and those cycled by their own biota. Nutrient inputs from rainfall and throughfall were measured between October 2001 and August 2003 in a secondary Atlantic rainforest in southern Brazil. Canopy interception (rainfall minus throughfall) was 17.3% of the annual rainfall of 2,235 mm. Monthly interception ranged from 12 to 31% during the rainiest months (precipitation above 200 mm) and from 1 to 45% during the driest months (precipitation below 50 mm) indicating relatively high variability during this period. The studied site may be susceptible to water stress in this period due to the high permeability of the sandy soil. Approximately 80% of the Ca and Na and 57% of Mg were mainly from rainfall (bulk deposition) whereas the main input source for K was net throughfall (about 78%). Mean annual inputs via throughfall (in kg ha⁻¹) were: 90.6 for Na, 29.1 for K, 7.1 for Ca, and 2.9 for Mg. The highest nutrient inputs occurred during the rainy season. Na fluxes were relatively high, while K, Ca, and Mg inputs were low, compared with other tropical and subtropical forests. Information on nutrient fluxes for different forest ecosystems are fundamental for building up a database that can give support to environmental diagnosis, to forest management, and to conservation and restoration techniques.     

Carbon concentrations of tree components,forest floor and understorey in young Pinus sylvestris stands in north-western Turkey

Abstract

This study examines the carbon concentrations of various above-ground biomass components (stem, bark, living branch, dead branch, needle and above-ground biomass), the forest floor and understorey. The research was carried out on Scots pine (Pinus sylvestris L.) stands in north-western Turkey. Sample trees were cut, and forest floor and understorey samples were collected from the 13 sampling areas in the 31-year-old Scots pine stands. Carbon contents of these samples were determined. Carbon concentrations of all tree components were found to be higher than 50%. This value is referred to as the general carbon conversion factor (CF). The weighted mean carbon concentration was found to be 51.96%. Consequently, if the CF for a single tree is taken to be 50%, carbon storage in the above-ground parts of the tree would have been underestimated by 3.77%. Carbon concentration, which was 53.02% in needles, was reduced to 50.08% in the litter plus fermentation layer of the forest floor and to 40.08% in the humus layer owing to decomposition. In the understorey, carbon concentration was determined to be 47.64%. There was a significant difference between the carbon concentrations of the tree components, forest floor and understorey.     

Throughfall,stemflow and interception loss in a mixed white oak forest (Quercus serrata Thunb.)

Throughfall and stemflow measurements in a 60-year-old white oak stand (Quercus serrata Thunb.) were carried out during two periods totalling eleven months, from August to November 1993 and from May to November 1994, in order to clarify the rainfall partitioning of this forest. Troughs and spiral-type stemflow gauges connected to tipping bucket-gauges were used for throughfall and stemflow measurements. Seventy-five storms were analyzed individually. Coefficients of variation for throughfall and stemflow ranged between 5–25% and 20–70% respectively. Partitioning of net rainfall in throughfall and stemflow represent 72% and 10% of the gross rainfall respectively. Multiple regression analyses were carried out to determine the stemflow variability. In was determined that maximum rain intensity was highly correlated with stemflow and this variable explained a further 5.5% of the stemflow variation. Estimates of averaged lag time and drainage after rain cease for stemflow were 290 and 164 min, while estimates for throughfall were 60 and 104 min. respectively. The canopy saturation was estimated from continuous storms and showed a value of 0.6 mm. The trunk storage capacity was estimated at a value of 0.2 mm. The interception loss from the forest canopy was estimated in 18%. Interception loss was heighly correlated with rainfall characteristics such as duration and intensity.     

Litterfall and nutrient return in five tree species in a common garden experiment

Canopy litterfall is a significant pathway for return of nutrients and carbon (C) to the soil in forest ecosystems. Litterfall was studied in five even-aged stands of Norway spruce, Sitka spruce, Douglas-fir, European beech and common oak at three different locations in Denmark; two sandy sites, Ulborg and Lindet in Jutland, and one loamy site, Frederiksborg on Zealand. Litterfall was collected during three years from 1994 to 1996 in all five species and during six years from 1994 to 1999 in Norway spruce, Sitka spruce and European beech. The average total litterfall was in the range of 3200–3700 kg ha⁻¹ yr⁻¹ and did not differ significantly among tree species. There were no significant differences in total litterfall among sites during the short period, but during the longer period the richer site Frederiksborg had significantly higher total and foliar litterfall amounts compared to the more nutrient-poor sites Lindet and Ulborg. There were close relationships between foliar and total litterfall suggesting that foliar litterfall can be reliably estimated from total litterfall. Beech and oak bud scale litter was significantly related to foliar litterfall. The amount of branch and twig litter was significantly higher in oak than in other tree species. The average foliar litterfall was well related to the annual volume increment. The relationship differed markedly from previously reported relationships based on global litterfall data suggesting that such relationships are better evaluated at the regional level. Nutrient concentrations and fluxes in foliar litterfall were not significantly different among the five tree species. However, there was a significant effect of site on most nutrient concentrations of the three litterfall fractions, and foliar fluxes of P, Ca and Mn were all significantly highest at Frederiksborg and lowest at Ulborg. The similarity in litterfall inputs to the forest floor under these five tree species suggested that previous reports of large variability in forest floor accumulation should primarily be attributed to differences in litter decomposition.     

两种经济林中的穿透雨与茎流特征研究

本文观测了桃李两种经济林的穿透雨和茎流特征。结果表明,两种经济林的穿透雨量、林冠截留量、茎流量与降雨量均存在极显著的正相关关系。用幂函数方程能较好的拟合林冠截留量与降雨量之间的关系,而用线性方程能较好的拟合穿透雨量、茎流量和降雨量之间的关系;桃李两种经济林穿透雨量分别占降雨量的93.29%、85.34%,林冠截留量分别占降雨量的5.60%和12.04%,茎流量分别占降雨量的1.11%和2.62%。     

Spatio-temporal dynamics of gross rainfall partitioning and nutrient fluxes in shaded-cocoa (<Emphasis Type="Italic">Theobroma cocoa</Emphasis>) systems in a tropical semi-deciduous forest

Land-use change from forest to cocoa agroforestry and other tree-based farming systems alters the structure of forest stands and influences the magnitude of canopy water fluxes and subsequent bio-element inputs to the forest floor. The partitioning of incident rainfall (IR) into throughfall (TF), stemflow (SF) and canopy interception loss (IL_C) and their associated nutrient element concentrations and fluxes was examined along a replicated chrono-sequence: forest, 3, 15 and 30-year-old smallholder shaded-cocoa systems in Ashanti Region, Ghana. Mean annual precipitation during the 2-year observational period (2007 and 2008) was 1376.2 ± 93.8 mm. TF contributed between 76.5–90.4%, and SF between 1.4–1.7% of the annual IR to the forest floor. There were significant differences in IR, TF and SF chemistry. While TF and SF were enriched in phosphorus (1.33–5.67-fold), potassium (1.1–5.69 fold), calcium (1.35–2.65 fold) and magnesium (1.4–2.68 fold) relative to IR, total N (NH₄ ⁺+NO₃ ^?) declined (0.5–0.91) of IR values in TF and SF in forest and shaded cocoa systems. Incident rainfall was significantly more acidic than TF and SF in both forest and shaded-cocoa systems. Mean annual total N, P, K, Ca and Mg inputs to the forest floor through IR were 5.7, 0.14, 13.6, 9.43 and 5.6 kg ha^?1year^?1 respectively. Though an important source of available nutrients for plant growth, incident rainfall provides only a small percentage of the annual nutrient requirements. With declining soil fertility and pervasive low cocoa yields, possible effects of the reported nutrient fluxes on nutrient budgets in cocoa systems merit further investigation. Against the background of increased TF and decreased IL_C following forest conversion to shaded-cocoa, it is also recommended that more studies be carried out on rainfall partitioning and its impact on ground water recharge as a way of establishing its influence on the availability of moisture for agriculture in these systems.     

Dynamics and potentials of carbon sequestration in managed stands and wood products in Finland under changing climatic conditions

Carbon (C) sequestration was studied in managed boreal forest stands and in wood products under current and changing climate in Finland. The C flows were simulated with a gap-type forest model interfaced with a wood product model. Sites in the simulations represented medium fertile southern and northern Finland sites, and stands were pure Scots pine and Norway spruce stands or mixtures of silver and pubescent birch.

Changing climate increased C sequestration clearly in northern Finland, but in southern Finland sequestration even decreased. Temperature is currently the major factor limiting tree growth in northern Finland. In southern Finland, the total average C balance over the 150 year period increased slightly in Scots pine stands and wood products, from 0.78 Mg C ha⁻¹ per year to 0.84 Mg C ha⁻¹ per year, while in birch stands and wood products the increase was larger, from 0.64 Mg C ha⁻¹ per year to 0.92 Mg C ha⁻¹ per year. In Norway spruce stands and wood products, the total average balance decreased substantially, from 0.96 Mg C ha⁻¹ per year to 0.32 Mg C ha⁻¹ per year. In northern Finland, the total average C balance of the 150 year period increased under changing climate, regardless of tree species: in Scots pine stands and wood products from 1.10 Mg C ha⁻¹ per year to 1.42 Mg C ha⁻¹ per year, in Norway spruce stands and wood products from 0.69 Mg C ha⁻¹ per year to 0.99 Mg C ha⁻¹ per year, and in birch stands and wood products from 0.43 Mg C ha⁻¹ per year to 0.60 Mg C ha⁻¹ per year.

C sequestration in unmanaged stands was larger than in managed systems, regardless of climate. However, wood products should be included in C sequestration assessments since 12–55% of the total 45–214 Mg C ha⁻¹ after 150 years' simulation was in products, depending on tree species, climate and location. The largest C flow from managed system back into the atmosphere was from litter, 36–47% of the total flow, from vegetation 22–32%, from soil organic matter 25–30%. Emissions from the production process and burning of discarded products were 1–6% of the total flow, and emissions from landfills less than 1%.     

自然侵入阔叶树对琉球松人工林碳素及氮素动态的影响

对日本冲绳岛北部相同土壤条件下的琉球松纯林及其混交林的土壤氮素及有机碳素、地表凋落物量、枯枝落叶量以及土壤氮素矿化速率进行了比较研究。结果表明 ,琉球松纯林的地表凋落物层氮、碳平均贮量分别为133kg·hm- 2 和 7199kg·hm- 2 ,混交林则分别为 10 5kg·hm- 2 和 6 14 3kg·hm- 2 。然而 ,混交林地表 10cm矿质土层的氮、碳贮量则显著高于纯林 ,氮素比纯林多 4 93kg·hm- 2 ,碳素多 5 5 5 4kg·hm- 2 。在 30d的实验室培养实验中 ,混交林表层土壤的氮素矿化速率高于纯林 18% ;而且 ,混交林的落叶和土壤的碳氮比值亦明显低于松纯林。混交林土壤的年平均矿化氮素 (NH4 NO3- )浓度高于纯林 2 2 %。与松纯林相比 ,混交林通过枯枝落叶年平均氮素归还量多 4 3 7kg·hm- 2 ,碳素归还量多 16 5 5kg·hm- 2 。混交林具有较高的氮素归还量 ,主要是混交林的针叶含氮含量较高以及大量的高含氮量的阔叶落叶所致。上述结果充分说明针阔混交导致了林分氮素循环的变化。     

Canopy composition as a measure to identify patterns of nutrient input in a mixed European beech and Norway spruce forest in central Europe

The influence of canopy composition on litterfall and throughfall was investigated in a mixed spruce beech forest in central Germany. We hypothesised that different parts of the mixed canopy created distinct patterns of element inputs via litterfall and throughfall. The investigation was carried out in two plots, representing the most contrasting cases of mixed forests: a stand greatly dominated by spruce (SDP) and a stand greatly dominated by beech (BDP). The canopies of the two plots were classified in four categories: pure beech, pure spruce, mixed canopy and gap. Amounts of throughfall water were lower and major element fluxes were higher under spruce than under beech in both plots, indicating that the nutrient inputs under the canopies of individual trees are driven by species-specific properties of the canopies and are quite independent of the degree of admixture. With the exception of K⁺, mixed canopies showed intermediate element inputs via throughfall, compared with pure canopy classes. The K⁺ input was significantly greater under mixed canopies, and these differences were more pronounced in the SDP than in the BDP. Results suggest that individual spruce trees in the BDP induce greater spatial heterogeneity of throughfall input than individual beech trees in the SDP. Nutrient inputs via foliar litterfall were similar among the different canopy classes, but the Mg input was lower under spruce canopy. This effect was balanced by higher Mg input via spruce throughfall. In our study, throughfall was the main source of heterogeneity in nutrient inputs, while foliar litterfall had a homogenising effect.