模拟氮沉降下南方针叶林红壤的养分淋溶和酸化

以中国科学院红壤生态实验站林草生态试验区针叶林红壤为研究对象,在恒温(20 ℃)条件下,通过大土柱（直径10 cm、高60 cm）,8个月间隙性淋溶试验模拟研究了不同氮输入量（0、7.8、26和52 mg N/月/柱）对针叶林红壤NO₃^-、NH₄⁺、H⁺和土壤盐基离子(Ca²⁺、Mg²⁺、K⁺、Na⁺⁾淋溶以及土壤酸化的影响.结果表明,土壤交换态盐基总量、Ca²⁺和Mg²⁺淋溶量随氮输入量的增加而增加,土壤交换态Na⁺和K⁺则无明显影响.4种N输入处理的土壤交换态盐基总量净淋溶（淋溶出的盐基与淋洗液累计输入的盐基之差）分别占土壤交换性盐基总量的13.9%、18.6%、31.8% 和57.9％,土壤交换态Ca²⁺净淋溶分别占土壤交换性Ca²⁺总量的19.6%、25.8%、45.3%和84.8%,土壤交换态Mg²⁺净淋溶分别占土壤交换性Mg²⁺总量的4.4%、6.1%、10.9%和17.1%.随氮输入量增加,表层土壤pH值逐渐下降,4种N输入处理的表层土壤pH（KCl）分别为3.85、3.84、3.80和3.75;随氮输入量增加,淋溶液中无机氮、NO₃^-和H⁺逐渐增加.氮沉降可促进针叶林红壤的有机氮矿化,加速养分淋失和土壤酸化.     

Composition and deposition of throughfall in a flooded forest archipelago

The sources of spatial and temporal variation and rates of nutrient deposition via throughfall were studied for 9 months in the Anavilhanas archipelago of the Negro River, Brazil. A total of 30 events was sampled individually for rain and throughfall chemistry in a 1-ha plot of flooded forest. Throughfall samples were collected in 40 collectors distributed in five parallel transects in the study plot, while rain was collected in 4 collectors in an adjacent channel. Volume-weighted mean (VWM) concentrations of solutes in rain were consistently lower than in throughfall, except for H⁺, NO ₃ ^– and NH ₄ ⁺ . Ratios of VWM concentrations of rain to throughfall indicated that K⁺, followed by Mg²⁺ and PO ₄ ^3– , were the most enhanced solutes as rain passed through the forest canopy. The deposition of solutes varied significantly among transects, except for Na⁺ and Ca²⁺, and was significantly correlated with maximum flooding depth, foliar nutrient content, soil fertility and canopy closure for most solutes. The concentrations of PO ₄ ^3– and most major ions were higher in throughfall compared to those in rain due to canopy exchange and dry deposition. In contrast, NO ₃ ^– , NH ₄ ⁺ and H⁺ were retained due to immobilization by leafy canopy and ion exchange processes. Solute inputs via throughfall (not including stemflow) to a floodplain lake (Lake Prato) of the archipelago accounted for 30 to 64% of the total for most solutes in the lake at high water, which indicates that throughfall is an important source of nutrients to the aquatic ecosystem of the Anavilhanas archipelago.     

The sensitivity of water chemistry to climate in a forested,nitrogen-saturated catchment recovering from acidification

Fluxes of major ions and nutrients were measured in the N-saturated mountain forest catchment-lake system of Čertovo Lake (Czech Republic) from 1998 to 2014. The lake has been rapidly recovering from atmospheric acidification due to a 90% decrease in sulphate (SO₄²⁻) deposition since the late 1980s and nitrate (NO₃⁻) contribution to the pool of strong acid anion and leaching of dissolved organic carbon (DOC) have increased. Present concentrations of base cations, phosphorus (P), total organic N (TON), and ionic (Al_i) and organically bound (Al_o) aluminium in tributaries are thus predominantly governed by NO₃⁻ and DOC leaching. Despite a continuing recovery lasting 25 years, the Čertovo catchment is still a net source of protons (H⁺), producing 44 mmol m⁻² yr⁻¹ H⁺ on a catchment-area basis (corresponding to 35 μmol L⁻¹ on a concentration basis). Retention of the deposited inorganic N in the catchment averages 20%, and ammonium consumption (51 mmol m⁻² yr⁻¹) and net NO₃⁻ production (28 mol m⁻² yr⁻¹) are together the dominant terrestrial H⁺ generating processes. In contrast, the importance of SO₄²⁻ release from the soils on terrestrial H⁺ production is continuously decreasing, with an average of 47 mmol m⁻² yr⁻¹ during the study. The in-lake biogeochemical processes reduce the incoming acidity by ∼40%, neutralizing 23 μmol L⁻¹ H⁺ (i.e., 225 mmol m⁻² yr⁻¹ on a lake-area basis). Denitrification and photochemical and microbial decomposition of DOC are the most important in-lake H⁺ consuming processes (50 and 39%, respectively), while hydrolysis of Al_i (from tributaries and photochemically liberated from Al_o) is the dominant in-lake H⁺ generating process. Because the trends in water chemistry and H⁺ balance in the catchment-lake system are increasingly related to variability in NO₃⁻ and DOC leaching, they have become sensitive to climate-related factors (drought, elevated runoff) and forest damage that significantly modify the leaching of these anions. During the study period, increased exports of NO₃⁻ (accompanied by Al_i and base cations) from the Čertovo catchment occurred after a dry and hot summer, after forest damage, and during elevated winter runoff. Increasing DOC export due to decreasing acid deposition was further elevated during years with higher runoff (and especially during events with lateral flow), and was accompanied by P, TON, and Al_o leaching. The climate-related processes, which originally “only” confounded chemical trends in waters recovering from acidification, may soon become the dominant variables controlling water composition in N-saturated catchments.     

Trajectory analysis of forest canopy effects on chemical flux in throughfall

Short interval sampling of precipitation inputs and stem flow-throughfall (SF-TF) outputs was conducted in a subalpine balsam fir forest to analyze the controls on canopy ion flux. A canopy hydrology model was used to separate the effects of abiotic and biotic processes. The time lag between precipitation inputs and SF-TF outputs caused by the storage of water in the canopy required that time-course patterns of SF-TF flux be examined graphically. The resulting trajectory analyses disclosed patterns from which we generalized about canopy processing of precipitation inputs. Changes in the ion concentration gradient across canopy tissue surfaces appeared to be an important factor in regulating the rate of flux of ions between canopy tissues and SF-TF. These changes were in turn determined by changes in such factors as apoplast ion concentrations and the residence time of water in the canopy. These generalizations permit qualitative predictions of SF-TF flux in other canopies over time based on only rudimentary knowledge of canopy structure and function.     

氮沉降对森林生态系统碳吸存的影响

工业化带来的大气氮沉降增加是影响森林生态系统碳吸存的重要因素。将森林碳库分为地上和地下两部分,从3个方面综述了国内外氮沉降对森林生态系统碳吸存影响的研究现状。(1)地上部分:氮限制的温带森林,氮沉降增加了地上部分碳吸存。氮丰富的热带森林,氮沉降对地上部分碳吸存没有影响。过量的氮输入会造成森林死亡率的上升,从而降低地上部分碳吸存。(2)地下部分:相比地上部分研究得少,表现为增加、降低和没有影响3种效果。(3)目前的结论趋向于认为氮沉降促进森林生态系统碳吸存,然而氮沉降所带来的森林生态系统碳吸存能力到底有多大依然无法确定,这也将成为未来氮碳循环研究的重点问题。分析了氮沉降影响森林生态系统碳吸存的机理,介绍了氮沉降对森林生态系统碳吸存影响的4种研究方法。探讨了该领域研究的不足及未来的研究方向。     

Modelling the hydro-geochemistry of acid-sensitive catchments in Finland under atmospheric deposition and biomass harvesting scenarios

The dynamic hydro-geochemical Model of Acidification of Groundwater in Catchments (MAGIC) was used to predict the response of 163 Finnish lake catchments to historic and future atmospheric deposition (1880–2100) and future tree harvesting practices. Deposition was assumed to follow current legislated European emission reduction policies (CLe) and a scenario based on maximum (technically) feasible reductions (MFR). Future harvesting was assumed to shift from stem-only harvesting (SOH) to whole-tree harvesting (WTH) owing to the potential increased utilisation of biofuels. Despite the modest changes in atmospheric deposition under CLe (compared to current day), these reductions are predicted to halt the decline in soil base saturation; however, further reductions are required to improve soil and lake water chemistry. The MFR scenario predicted a significant long-term improvement in soil base saturation leading to continued long-term recovery in surface waters (all lakes with ANC > 0 by 2100). However under the WTH scenario, significant long-term impacts (re-acidification) were predicted for soil and surface water chemistry (14 lakes with ANC < 0 by 2100). To some extent the long-term negative impacts were reduced under MFR, indicating that increased utilisation of biofuels will necessitate ‘trading emissions for timber’, or soil amendment, to maintain ecosystem quality and sustainable forest growth. The current practice of SOH is close to the sustainable maximum harvesting under current (legislated) atmospheric deposition in Finland.     

边缘效应及其对森林生态系统影响的研究进展

边缘效应是生态学和生物保护的重要概念之一,它在研究生态系统尺度和景观生态系统尺度的能量流和物质流等生态过程中具有重要作用.本文对边缘效应的内涵、特征、定量评价(包括定量分析基础、强度、影响区、模型等)、应用研究等方面进行阐述,分析了边缘效应研究中存在的不足,总结了边缘效应对森林生态系统的影响及其研究方向,以期为森林经营、保护区管理等生产实践提供借鉴.     

氮沉降对森林生物多样性的影响

从3个方面论述了氮沉降对森林生物多样性影响：（1）森林植物多样性,包括乔木层植物、林下层植物和隐花植物;（2）土壤微生物多样性,主要是细菌和真菌;（3）森林动物多样性：主要包括地下土壤动物和地上草食动物。综合来看,氮沉降改变了物种组成,过量氮沉降降低了生物多样性。同时,也对氮沉降影响生物多样性的机理进行了分析。最后,还探讨了当前在氮沉降对森林生物多样性影响的研究方面存在的问题以及今后研究的方向。     

Growth of ectomycorrhizal mycelia and composition of soil microbial communities in oak forest soils along a nitrogen deposition gradient

Deciduous forests may respond differently from coniferous forests to the anthropogenic deposition of nitrogen (N). Since fungi, especially ectomycorrhizal (EM) fungi, are known to be negatively affected by N deposition, the effects of N deposition on the soil microbial community, total fungal biomass and mycelial growth of EM fungi were studied in oak-dominated deciduous forests along a nitrogen deposition gradient in southern Sweden. In-growth mesh bags were used to estimate the production of mycelia by EM fungi in 19 oak stands in the N deposition gradient, and the results were compared with nitrate leaching data obtained previously. Soil samples from 154 oak forest sites were analysed regarding the content of phospholipid fatty acids (PLFAs). Thirty PLFAs associated with microbes were analysed and the PLFA 18:2ω6,9 was used as an indicator to estimate the total fungal biomass. Higher N deposition (20 kg N ha⁻¹ y⁻¹ compared with 10 kg N ha⁻¹ y⁻¹) tended to reduce EM mycelial growth. The total soil fungal biomass was not affected by N deposition or soil pH, while the PLFA 16:1ω5, a biomarker for arbuscular mycorrhizal (AM) fungi, was negatively affected by N deposition, but also positively correlated to soil pH. Other PLFAs positively affected by soil pH were, e.g., i14:0, a15:0, 16:1ω9, a17:0 and 18:1ω7, while some were negatively affected by pH, such as i15:0, 16:1ω7t, 10Me17:0 and cy19:0. In addition, N deposition had an effect on the PLFAs 16:1ω7c and 16:1ω9 (negatively) and cy19:0 (positively). The production of EM mycelia is probably more sensitive to N deposition than total fungal biomass according to the fungal biomarker PLFA 18:2ω6,9. Low amounts of EM mycelia covaried with increased nitrate leaching, suggesting that EM mycelia possibly play an important role in forest soil N retention at increased N input.     

离子树脂法测定森林穿透雨氮素湿沉降通量——以千烟洲人工针叶林为例

穿透雨是大气氮素输入森林生态系统的重要途径之一,穿透雨中氮素含量的定量评估在森林生态系统氮素循环研究中的作用不可忽视。穿透雨中氮沉降通量的空间异质性很强,传统降水收集法工作量大,且容易带来测定误差。分析了国产离子树脂测定大气氮素湿沉降的可行性,并以千烟洲人工针叶林为例探讨离子树脂法测定森林穿透雨的适用性。结果表明,离子交换树脂法和传统降水收集法测定值之间的相关性显著,离子交换树脂法可以很好的反映大气氮沉降通量和季节变化特征,并且在采样周期较长时也能准确测定氮沉降组分,是适用于野外站点林内穿透雨氮沉降通量的观测方法。千烟洲人工针叶林穿透雨的氮沉降通量为9.19 kgN?hm-2?a-1,夏季的5—7月份和冬季的1—2月份出现氮沉降通量高峰。夏季穿透雨氮沉降以铵态氮为主,而冬季以硝态氮为主。千烟洲人工针叶林的氮沉降通量与附近地区针叶林穿透雨氮沉降通量近似,低于临近区域阔叶林穿透雨的氮沉降通量水平,但已可能接近森林生态系统氮输出出现强烈反应的氮沉降临界值。     

氮沉降对森林土壤磷循环的影响

磷是生物体必需的大量元素之一,也是许多生态系统的主要限制因子。近年来,大气氮沉降日益加剧,已对森林生态系统磷循环产生了不可忽视的影响。关于氮沉降对生态系统磷循环的影响已开展了一系列的研究,然而尚缺少对其整体的认识。因此,通过收集国内外已发表的相关文章,从以下五个方面综述氮沉降对森林生态系统土壤磷循环的影响及其机理:1)阐述了森林生态系统土壤磷循环的概念;2)介绍了氮沉降对森林土壤磷循环影响的研究方法,包括长期定位模拟氮沉降法、自然氮沉降梯度法和同位素示踪法等;3)概述了氮沉降对森林生态系统土壤磷循环的影响。目前的研究结论趋向于认为长期氮沉降使森林土壤磷循环速率加快。长期氮输入易于使土壤中可溶性磷向非活性磷酸盐库迁移而难以被利用。因此,为了满足需求,土壤磷酸酶活性将增加以加速有机磷的矿化,从而加速磷素在土壤-植物-微生物之间的周转。4)探讨了氮沉降影响森林土壤磷循环的机制。氮沉降可通过改变土壤有机质的性质、微生物群落组成、磷酸酶活性以及阳离子的流动性等途径影响森林土壤磷循环;5)指出了当前研究存在的问题及未来的研究方向。     

长白山森林生态系统大气氮素湿沉降通量和组成的季节变化特征

2009—2010年期间,利用雨量计收集法在长白山森林生态系统定位站开展定位观测,分析降水中氮素浓度,研究了该区域大气氮素湿沉降通量和组成的季节变化特征。结果表明,各形态氮素月均浓度之间差别较大,具有明显的季节性;其降水中浓度主要受降水量和降水频次的影响。全年氮素湿沉降中TN、TIN和TON的沉降量分别为27.64 kg N hm-2a-1、11.05 kg N hm-2a-1和16.59 kg N hm-2a-1,TON为沉降主体,占60.02%;其大气氮沉降量主要由降水量和降水中氮素浓度共同决定。该地区氮湿沉降量已处于我国中等水平,考虑到氮素的干湿沉降比例,本区域的年氮沉降量已接近或超过本区域的营养氮沉降临界负荷,存在一定的环境风险。该地区生长季(5—10月)的氮沉降量(16.59 kg N hm-2a-1)占全年氮沉降量的比例达到73.20%。生长季的氮沉降对于促进植物生长直接生态意义重大,而非生长季的氮沉降对于大量补充次年植物生长初期所需养分的间接生态意义明显。     

长白山红松云冷杉林林内降水的养分输入

1 引言 在林地里,树木的叶子、枝条、树皮、果实,有时甚至整株树木都周期性地归还土壤,这种凋落物养分归还是森林生态系统的一个重要特点。但林木吸收的大部分养分,除由凋落物归还土壤外,还能由树冠淋洗归还土壤,在我国东北地区森林生态系统研究工作中,红     

The fate of15N enriched throughfall in two coniferous forest stands at different nitrogen deposition levels

The stable isotope¹⁵N was added as (¹⁵NH₄)₂SO₄ to throughfall water for one year, to study the fate of the deposited nitrogen at different levels of N deposition in two N saturated coniferous forests ecosystems in the Netherlands. The fate of the¹⁵N was followed at high-N (44–55 kg N ha^–1 yr^–1) 1) and low-N (4–6 kg N ha^–1 yr^–1) deposition in plots established under transparent roofs build under the canopy in a Douglas fir (Pseudotsuga menziesii (Mirb.) Franco.) and Scots pine (Pinus sylvestris L.) forest.The applied¹⁵N was detectable in needles and twigs, the soil and soil water leaching below the rooting zone (90 cm depth). Total¹⁵N recovery in major ecosystem compartments was 71–100% during two successive growing seasons after the start of a year-round¹⁵N application to throughfall-N. Nine months after the year-round¹⁵N application, the¹⁵N assimilated into tree biomass was 29–33% of the¹⁵N added in the Douglas fir stand and less than 17% in the Scots pine stand. At the same time total¹⁵N retention in the soil (down to 70 cm) of the high-N plots was about 37% of the deposited¹⁵NH₄-N, whereas 46% and 65% of the¹⁵N was found in the soil of the low-N deposition plots at the Douglas fir and Scots pine stand, respectively. The organic layers accounted for 60% of the¹⁵N retained in the soil. The total N deposition exceeded the demand of the vegetation and microbial immobilization. Total¹⁵N leaching losses within a year (below 90 cm) were 10–20% in the high-N deposition plots in comparison to 2–6% in the lowered nitrogen input plots. Relative retention in the soil and vegetation increased at lower N-input levels.Species differences in uptake and tree health seem to contribute to lower¹⁵N recoveries in the Scots pine trees compared to the Douglas fir trees. The excessive N deposition and resulting N saturation lead to conditions were the health and functioning of biota were negatively influenced. At decreased N deposition, lower leaching losses together with increased soil and plant retention indicated a change in the fate of the¹⁵N deposited. This may have resulted from changes in ecosystem processes, and thus a shift along the continuum of N saturation to N limitation.     

大气氮沉降对阔叶林红壤淋溶水化学模拟研究

在氮饱和的森林生态系统中,氮沉降的增加将导致NO3-淋溶的增加及土壤酸度的提高,从而影响土壤质量及林业的可持续发展。然而,大气氮沉降对我国南方红壤地区森林生态系统中土壤的影响研究还很少,尤其是氮沉降引起的土壤淋溶液化学组成方面。研究中,以中国科学院红壤生态实验站林草生态试验区阔叶林红壤为对象,在恒温(20℃)条件下,通过土壤淋洗柱(直径10cm、高60cm)进行了8个月间隙性淋溶试验,来模拟研究不同氮输入量(0、7.8、26mg月-1.柱-1和52mg月-1柱-1)对阔叶林红壤NO3-、NH4 、SO42-、H 和土壤盐基离子(Ca2 、Mg2 、K 和Na )的淋溶和土壤酸度的影响。结果表明,随氮输入量增加,淋溶液中NO3-、EC、H 和总盐基离子逐渐增加,但淋溶液中无NH4 。不同氮处理时,土壤有机氮总表观矿化量分别为189.6、263.9、372.8mg月-1.柱-1与554.2mg柱-1,氮输入明显促进了土壤有机氮的矿化,且土壤有机氮的表观矿化量与氮输入量间呈正线性相关(R2=0.997**)。无氮(0mg月-1柱-1)、低氮(7.8mg月-1柱-1)、中氮(26mg月-1柱-1)和高氮(52mg月-1柱-1)输入处理下,土壤交换态盐基淋溶总量分别占土壤交换性盐基总量的13.6、18.4、27.7%和48.1%。不同的盐基离子对氮输入的反应不同,Ca2 和Mg2 淋溶量随氮输入量的增加而增加,对Na 和K 则无明显影响。土壤交换态离子中随淋洗液输出最多的为Ca2 (无氮、低氮、中氮和高氮输入处理的土壤交换态输出量占土壤交换态的比例分别为22.6、31.4、46.7%和82.5%),其次为Na (无氮、低氮、中氮和高氮输入处理的土壤交换态输出量占土壤交换态的比例分别为16.0、10.7、17.6%和26.3%),最少的为Mg2 (无氮、低氮、中氮和高氮输入处理的土壤交换态输出量占土壤交换态的比例分别为5.0、6.9、11.1%和16.9%),几乎没有土壤交换性K 输出。与对照相比,有氮处理后土壤中硫酸根离子的淋失量明显减少(p<0.05)。表层土壤pH值随氮输入量的增加而显著下降,各处理间差异极显著(p<0.01)。可见,大气氮沉降的增加将加速阔叶林红壤的养分淋失和土壤酸化的程度。     

On the importance of incorporating forest edge deposition for evaluating exceedance of critical pollutant loads

The concept of critical load (CL) was defined to express the tolerance of natural and semi‐natural habitats for anthropogenic air pollution. Correct evaluation of the exceedance of critical loads is fundamental for the long‐term protection of ecosystems by limiting emissions of potential acidifying and eutrophying pollutants. For forest ecosystems, the exceedance of critical loads is often calculated using deposition data measured in the forest interior. However, several studies report forest edges acting as ‘hotspots’ of acidifying and nitrogen deposition, showing up to fourfold increases in atmospheric deposition compared to the forest interior. This paper estimates the relevance of considering the higher deposition load in forest edges for calculating exceedance of critical loads for nitrogen and potential acidifying deposition. If measures to control and reduce atmospheric deposition are based on mean deposition fluxes within forest stands, deposition reductions will not be enough for preventing adverse effects. In fact, emission reductions should be adjusted to deposition values at the forest edge, since these zones are most threatened. We thus conclude that there is an urgent need to reconsider the calculation of exceedance of critical loads, taking into account edge enhancement of deposition. This is an issue of high relevance, particularly in highly fragmented regions, such as Flanders (Belgium).     

亚热带常绿阔叶林和杉木人工林茎流与穿透雨的养分特征

亚热带常绿阔叶林和杉木人工林树干茎流和穿透雨养分含量均表现季节动态变化。养分含量中,K^ 、Ca^2 、NO3%-浓度高,Na^ 、Mg^2 居中,HPO4^2-含量低,相对于林外雨,养分均出现富集化,但树干茎流养分富集化高于穿透雨。树干茎流出现强烈的酸化,而穿透雨酸化现象不明显。树种之间的茎流养分特征表现不一样,樟树和枫香总的养分浓度较高,其次为刨花楠,最后为青冈和红栲。     

森林生态系统碳循环对全球氮沉降的响应

森林土壤和植被储存着全球陆地生态系统大约46%的碳,在全球碳平衡中起着非常重要的作用。过去几十年来,森林生态系统的碳循环和碳吸存受到了全球氮沉降的深刻影响,因为氮沉降改变了陆地生态系统的生产力和生物量积累。以欧洲和北美温带森林区域开展的研究为基础,综述了氮沉降对植物光合作用、土壤呼吸、土壤DOM及林木生长的影响特征和机理,探讨了森林生态系统碳动态对氮沉降响应的不确定性因素。热带森林C、N循环与大部分温带森林不同,人为输入的氮对热带生态系统过程的影响也可能不同,因此指出了在热带地区开展碳氮循环耦合研究的必要性和紧迫性。     

森林土壤氮素转换及其对氮沉降的响应

近几十年人类活动向大气中排放的含氮化合物激增 ,并引起大气氮沉降也成比例增加。目前 ,氮沉降的增加使一些森林生态系统结构和功能发生改变 ,甚至衰退。近 2 0 a欧洲和北美有关氮沉降及其对森林生态系统的影响方面的研究较多 ,而我国少有涉及。森林土壤氮素转换是森林生态系统氮素循环的一个重要的组成部分 ,而矿化、硝化和反硝化作用是其核心过程 ,氮沉降作为驱动因子势必改变森林土壤氮素转换速度、方向和通量。根据国外近 2 0 a有关研究 ,首先介绍了森林土壤氮素转换过程和强度 ,论述森林土壤氮素在生态系统氮素循环中的作用 ,然后在此基础上 ,介绍了氮沉降对森林土壤氮素循环的研究途径 ,探讨了氮沉降对森林土壤氮素矿化、硝化和反硝化作用的影响及其机理     

The effect of nitrogen and phosphorus addition on the growth,reproduction, and nutrient dynamics of two ericaceous shrubs

Summary Aboveground growth, reproduction, and foliar nitrogen and phosphorus contents of two ericaceous shrub species were compared over two seasons in (a) an undisturbed shrub bog (pocosin), and (b) a factorial fertilization design in which three levels each of nitrogen and phosphorus were added in all possible combinations. One species, Zenobia pulverulenta, is deciduous whereas the other species, Lyonia lucida, is evergreen. In the nutrient-poor undisturbed pocosin the two species exhibited similar foliar nitrogen and phosphorus concentrations and aboveground growth rates. Neither species flowered. In response to nutrient-addition Zenobia increased growth rates more than Lyonia. Foliar phosphorus concentrations of both species increased in response to enhanced phosphorus availability. in the first season neither species flowered in any treatment. In the second season Zenobia flowered only in the fertilized plots, with the most flowering in the high phosphorus treatments. I conclude that, by virtue of high growth rates and efficient use of nutrients and despite differences in leaf phenology and morphology, both Lyonia and Zenobia are successful in a competitive community under conditions of extremely low phosphorus availability. However, unlike Lyonia, Zenobia can take advantage of temporarily increased nutrient availability, which occurs following fire in the pocosin, to increase growth and reproduction.