Water and element input into native, agri- and silvicultural ecosystems of the Brazilian savanna

The interaction of rain water with the vegetation canopy results in changes of the water quantity and quality. We examined these canopy effects in different ecosystems of the Brazilian savanna, the Cerrado. The ecosystems were 20 yr-old Pinus caribaea Morelet plantations (PI), productive (PP) and degraded Brachiaria decumbens Stapf pastures (DP), continuous corn-soybean rotation (CC), and native typical cerrado (CE). We collected rainfall, throughfall, and, in PI and CE, stemflow from three plots of each ecosystem. Dry deposition and canopy leaching were estimated with a Na-tracer method. Between May 1997 and April 1999, the mean annual rainfall was 1656 mm of which 145 mm fell during the dry season (May–September). The throughfall percentage of the rainfall increased in the order, PI (75–85%) < CC (76–89%) < CE (89–100%) < PP (90–100%) < DP (99–100%); stemflow was < 1% of the rainfall. The volume-weighted mean (VWM) pH in rainfall was higher in the dry (6.5) than in the rainy season (5.4). The VWM pH in throughfall decreased in the order, CC (rainy season: 5.9/dry season: 6.2) > PP (5.5/6.0) > CE (5.2/6.0) > DP (5.2/5.6) > PI (4.8/5.7). The rainfall deposition of the dry season contributed one third of the annual element input with rainfall because of higher element concentrations than in the rainy season. The mean Na deposition ratios, i.e. the ratio of throughfall (+ stemflow) to rainfall deposition as a measure for dry deposition, increased in the order, CE (1.5) = CC (1.5) < PP (1.7) < PI (1.9) < (DP 2.1). Total deposition (rainfall + dry deposition) accounted for 104–164% of the K and Ca fertilizer application in PP and for 6.1–12% of the K, Ca, and Mg fertilizer application in CC. The P concentrations were below the detection limit of 0.2 mg L^–1 in all samples. Net canopy uptake, i.e. a smaller throughfall(+ stemflow) than rainfall + dry deposition, of Ca, K, Mg, S, Cu, and Zn in at least one of CE, PI, DP, and PP indicate that plant growth may be limited in part by these nutrients. During the vegetation period, between 28 and 50% of the applied K and Ca were leached from the canopy in PP and between 8.7 and 17% of the applied K, Ca, Mg, and S in CC. Our results demonstrate that PI causes larger water losses and enhanced acid inputs to the soil compared with all other ecosystems. However, the PI and pasture canopies scavenge more nutrients from the atmosphere than CE and CC.     

鼎湖山季风常绿阔叶林水相沉积元素分布及其相关性研究

2001年2月~ 2002年3月在鼎湖山季风常绿阔叶林对大气降水、穿透水、土壤水 (30和 80cm层 ) 和溪水中的沉积元素进行监测, 拟通过不同水相元素浓度的比较及相关关系分析, 揭示系统的营养循环功能状况以及对区域化学条件变化的响应, 阐明因素在环境中的迁移转化规律。结果表明 :林冠与大气间强烈的相互作用, 极大地提高穿透水中Mn2 + 、Sr2 + 、K+ 、Mg2 + 、Ca2 + 浓度。水与土壤作用后, 极大地提高水相中Al3 + 的浓度。 30cm土壤溶液和溪水中的Al3 + 浓度分别是大气降水 (0.32 9mg·L-1) 的 4.8和 3.7倍。溪水中的Al3 + 主要来源于土壤的淋溶。大气降水平均Pb2 + 浓度为 0.0 6 2mg·L-1, 存在着一定程度的Pb2 + 污染, 其浓度分别是穿透水和溪水的 5倍和 10倍。林冠吸收和土壤过滤吸附是森林生态系统净化Pb2 + 等重金属污染物的主要过程。大气降水、穿透水、土壤水和溪水中Na+的浓度逐步增加, 但增幅不大。元素浓度的变异系数在 5 1.1%~ 2 36.7%之间。水相中的离子浓度与雨量有关, 大气降水、穿透水、土壤水中的沉积元素浓度大部分是干季大于湿季, 而溪水中是干季小于或近等于湿季。元素相关分析发现, 与元素Mg相关的元素最多, 穿透水所含相关元素对最多, 不同水相间元素相关状况差异与其元素的来源和外部环境条件有关系。Pb与金属元素Al、Mn在大气降水中极显著相关, Mn_Al、Mn_Mg、Mg_K在所有水相中显著相关, Al_Sr、Mn_Sr、Ca_K、Ca_Mg在除溪水外的所有水相中显著相关, Na_K、Na_Mg在除大气降水外的所有水相中显著相关, 而Pb_Na、Pb_K在所有水相中都无相关关系。结果说明, 季风常绿阔叶林系统已经遭受一定的外界环境压力, 但是其物质循环功能依然稳定。     

鼎湖山酸沉降背景下主要森林类型水化学特征初步研究

雨水的水质在通过森林后会发生变化．如果雨水是酸性的,这种变化会更加明显．通过一年多时间在鼎湖山主要森林类型采样分析发现,鼎湖山大气降水pH值低,酸雨频率高;阔叶林穿透雨pH值比大气降水高,树干径流和地表水pH值比大气降水低,土壤自然酸化非常严重;混交林穿透雨和地表水酸度比大气降水低,树干径流酸度则大于大气降水;针叶林穿透雨和树干径流都有进一步酸化趋势,但地表水pH值比大气降水高．3种林型比较,阔叶林林冠缓冲能力最强,针叶林土壤缓冲能力最大．3种林型,林内降水和地表水养分N、P、K、Ca、Mg和Na含量除N外都明显高于大气降水．各林型树干径流对养分富集能力强于穿透水,养分在大气降水中的浓度低于在地表水中的浓度．针叶林林内降水比混交林和阔叶林养分含量高,但地表水中养分浓度比后两者低．从地表水的养分浓度看,阔叶林和混交林养分亏损更为严重．     

模拟降雨条件下玉米植株对降雨再分配过程的影响

为系统测定玉米(Zea mays)不同生长阶段的穿透雨、茎秆流和冠层截留,采用室内模拟降雨法测定了不同降雨强度、不同叶面积指数玉米冠下穿透雨和茎秆流,采用喷雾法测定了玉米不同生长阶段的冠层截留。对其进行了量化分析,并探讨了三者与玉米叶面积指数和降雨强度的关系,阐明了玉米冠下穿透雨的空间分布特征。结果表明:玉米冠下穿透雨量占冠上总降雨量比例为30.97%—94.02%,平均为63.92%;茎秆流量占降雨量比例的变化范围为5.68%—75.70%,平均为35.28%;冠层截留量在其全生育期内变化范围为0.02—0.43 mm,平均为0.16 mm,所占总降雨量比例最大仅为1%。随玉米生长,穿透雨量逐渐降低,茎秆流量和冠层截留量逐渐增加。穿透雨与茎秆流呈现此消彼长的关系,其中穿透雨率平均由93.55%降至36.23%;茎秆流率平均由5.98%增加至70.42%。降雨强度与穿透雨量和茎秆流量呈正相关关系,但是二者占总降雨量的比例与降雨强度关系不显著(P0.05)。随着玉米生长,穿透雨冠下空间分布由均匀逐渐趋向于不均匀,使降雨经过冠层后趋于向行中汇集,但在玉米生长后期,集中于行中的穿透雨量也因叶片衰败而随之降低。揭示了玉米对降雨的再分配作用特征,可为农田水分有效利用、农田生态水文过程机理和坡耕地土壤侵蚀防治提供理论依据。     

Nutrient content of throughfall and stemflow in fertilized and irrigatedPinus resinosa ait. Stands

Summary The P, K, Ca, and Mg contents of throughfall and stemflow from K-fertilized and/or irrigated plots from adjacent sites differing in productivity in 39-year-oldPinus resinosa plantations were determined. The amounts of these elements leached from the tree canopies (throughfall plus stemflow) during April through October varied significantly according to site and treatment. These amounts ranged in kg per ha from −0.03 to 0.23 for P, 2.05 to 8.78 for K, 1.55 to 3.63 for Ca, and 0.02 to 0.44 for Mg. Leaching of P, K, and Ca from the trees was usually greater on the more productive site than on the poorer one. In general, the fertilization treatment was correlated with increasing amounts of P, K, and Ca leached, whereas the irrigation treatment was correlated with decreasing amounts of P, K, and Ca leached. For Mg, leaching was consistently greater on the poorer site than on the more productive one; further, it was greatest on the control plots and least on plots both fertilized and irrigated. Gross precipitation of 61.26 cm contained P, K, Ca, and Mg in amounts of 0.33, 0.84, 2.96, and 0.83 kg per ha, respectively. Volumes of both throughfall and stemflow were significantly affected by site conditions. Although throughfall was not affected by treatment, stemflow varied significantly according to plot treatment and was also highly and positively correlated with tree diameter. Stemflow accounted for about 2 per cent of the total water volume collected beneath the canopies, and contained, on a relative basis, considerably less P, an equivalent amount of K, twice as much Mg, and four times as much Ca as throughfall. Contribution of the Northeastern Forest Experiment Station, Forest Service, USDA, and Department of Silviculture and Forest Influences, State University of New York College of Environmental Science and Forestry, Syracuse, New York, 13210.     

鼎湖山季风常绿阔叶林大气降雨、穿透雨和树干流的养分特征研究

对鼎湖山季风常绿阔叶林大气降雨、穿透雨和树干茎流中的5种养分元素K、Ca、Mg、N、P进行了测定,结合水量分配规律,研究了森林降雨过程中养分在水相中的含量变化特征和输入规律。结果表明：(1)所有离子浓度均为大气降水<穿透雨<树干流,且增幅较大,而平均浓度以K+和总氮(TN)含量最高;总磷(TP)、磷酸盐(HPO42-)、总有机磷(TOP)含量均最低。(2) 大气降雨中的离子平均浓度中以总有机氮(TON)的变异系数最大,为1.282;最小的是NO3-(0.502);穿透雨中变异系数最大的是TOP(2.357);最小的是TN(0.621)。树干流中各养分元素浓度与树种的相关性不显著(P>0.05)。(3) 季风常绿阔叶林树干流和穿透雨各养分对森林土壤的年输入量为TN>K+>Ca2+>Mg2+>TP,树干流和穿透雨对森林土壤层Ca2+的输入大于凋落物分解输入。因此,大气降雨是养分从林冠层转移到土壤层的重要因素。     

韶山针阔叶混交林凋落物层的淋溶及缓冲作用

在韶山森林设立4个10m×10m的标准样地,分别收集凋落物、凋落物层淋滤液和冠层穿透水,研究了韶山森林凋落量季节动态,凋落物淋滤液和冠层穿透水特征以及凋落物层对酸沉降的缓冲作用.结果表明:(1)韶山森林凋落高峰出现在秋季,凋落量随着海拔增加而增加;(2)凋落物淋滤液中盐基阳离子浓度除夏季K ＞Ca2 外,其余季节均为:Ca2 ＞K ＞NH 4 ＞Mg2 ＞Na ,与冠层穿透水中阳离子浓度分布基本是一致的;(3)除Ca2 外,凋落物淋滤液和穿冠水中各阳离子浓度相关性显著,K 达到了极显著相关水平,证实了韶山森林通过凋落物养分归还的K 主要来自森林冠层的滤出;(4)除个别点外,凋落物淋滤液中各阳离子总浓度较冠层穿透水均有不同程度的增加,秋季增幅最大,冬季次之,这与凋落物量变化一致;(5)韶山森林冠层穿透水pH值变动范围为4.58～7.13,最低值出现在冬季,最高值出现在夏季,凋落物淋滤液pH值变动范围为5.02～6.69,均高于韶山表层土壤pH平均值5.0,且最低值出现在春季,最高值出现在秋季;(6)冬季凋落物淋滤液pH值较冠层穿透水均增加,增幅范围在0.06～1.35之间,而其他季节(除样地C的秋季外)pH值均有所下降,这表明韶山森林凋落物层冬季具有较强的酸缓冲作用,而其他季节由于盐基阳离子的滤出不足以抵消凋落物本身分解产生的有机酸类物质的酸化作用,而使凋落物淋滤液pH值降低.     

Impact of Phytophthora agathidicida infection on canopy and forest floor plant nutrient concentrations and fluxes in a kauri‐dominated forest

Kauri dieback, caused by Phytophthora agathidicida, is a biotic disturbance that poses a recent threat to the survival of kauri (Agathis australis) forests in New Zealand. Previous studies have shown that throughfall and stemflow play an important role in the kauri forests’ internal nutrient cycle. However, the effects of P. agathidicida infection on canopy and forest floor nutrient fluxes in kauri forests remain unknown. Here, we measured throughfall, stemflow and forest floor water yield, nutrient (potassium, calcium, magnesium, manganese, silicon, sulfur, sodium, iron) concentrations and fluxes of ten kauri trees differing in soil P. agathidicida DNA concentration, and health status. We did not observe an effect of soil P. agathidicida DNA concentration on throughfall, stemflow, and forest floor water yield. Throughfall and forest floor nutrient concentrations and fluxes decreased (up to 50%) with increasing soil P. agathidicida DNA concentration. We found significant effects on potassium and manganese fluxes in throughfall; calcium and silicon fluxes in forest floor leachate. A decline in canopy and forest floor nutrient fluxes may result in soil nutrient imbalances, which in turn may negatively impact forest productivity and may increase the susceptibility of trees to future pathogen infection in these ecologically unique kauri forests. Given our findings and the increasing spread of Phytophthora species worldwide, research on the underlying physiological mechanisms linking dieback and plant–soil nutrient fluxes is critical.     

槟榔林冠穿透雨空间格局的时间稳定性

槟榔林是热带地区广泛种植典型经济林,独特的树冠结构改变了穿透雨的空间格局,但针对穿透雨空间格局的时间稳定性研究很少,影响对穿透雨生态效应的认识与调控。以海南岛槟榔林为研究对象,基于33场降雨数据,研究了穿透雨的空间格局及时间特性,结果显示:(1)槟榔树冠内不同位置穿透雨差异极显著(P0.01),穿透雨率分别为:树干附近(85.6%)、冠幅中央(48.3%)、冠幅边缘(59.8%),穿透雨空间格局表现为向树干附近汇集的特点;不同方位的穿透雨率仅东面显著高于南面(P0.1),表明风向对穿透雨空间格局具有一定影响。(2)槟榔树冠下各位点穿透雨时间变异程度大(65.7%),但槟榔树冠幅中央穿透雨时间稳定性较好(55.6%),而树干旁边和冠幅边缘穿透雨时间稳定性较差(25%、19.4%),各方位穿透雨的时间稳定性相差不大(约1/3)。(3)距树干距离和降雨量影响穿透雨的时间稳定性,距树干不同距离平均叶片倾斜角度的差异是造成穿透雨在时间上不稳定的关键因素,平均叶片倾斜角度与穿透雨时间不稳定程度呈现显著正相关关系(P0.05);穿透雨时间稳定性在中等降雨条件下最差,随着降雨量增加,冠层对穿透雨的"屏蔽效应"减弱,"滴水效应"增加。揭示槟榔植株个体穿透雨的空间格局及时间稳定性,可为认识乔木个体尺度穿透雨时空特征提供参考,也可为解释林地小尺度土壤水分和土壤侵蚀的空间格局及时间动态提供依据。     

Rainfall partitioning into throughfall and stemflow and associated nutrient fluxes: land use impacts in a lower montane tropical region of Panama

Land-use change alters catchment hydrology by influencing the quality and quantity of partitioned rainfall. We compared rainfall partitioning (throughfall, stemflow and interception) and nutrient concentrations in rainfall, throughfall and stemflow in three land-use types [primary forest (PF), secondary forest (SF) and agriculture (A)] in Panama. Measurements of throughfall were highly variable which may have masked seasonal and land use differences but it was clear that throughfall at agricultural sites made up a larger proportion of gross precipitation than at forest sites. Of incident precipitation, 94% became throughfall in agriculture sites while 83 and 81% of gross precipitation became throughfall in PF and SF, respectively. The size of the precipitation event was the main driver of variation in throughfall and stemflow. Consistent patterns in nutrient cycling were also difficult to identify. Vegetation has a vital role in delivering nutrients as throughfall deposition of K was often larger than precipitation deposition. A canopy budget model indicated that canopy exchange was often more dominant than dry deposition. Throughfall was generally enriched with nutrients, especially K and Mg, with enrichment factors of up to 17 and 5 for K and Mg, respectively, in PF. In contrast, Ca was sometimes taken up by the canopy. Values of nutrient deposition were high (with up to 15, 3, 30 and 15 kg ha^?1 month^?1 in stand deposition of Ca, Mg, K and Na, respectively in PF), possibly due to the slash-and-burn agricultural practices in the area or marine inputs. Throughfall and stemflow are vital sources of nutrients in these ecosystems.     

大兴安岭北部兴安落叶松(Larix gmelinii)林下穿透雨空间分布特征

森林冠层对降雨的水量和水质再分配是生态水文学研究的热点问题之一。为了研究兴安落叶松林下穿透雨的空间分布规律,探究森林冠层结构对穿透雨影响的生态机制,利用在兴安落叶松林下布设38个雨量筒,测定19场不同降雨事件的穿透雨数据(2013年7—8月),通过统计学方法分析冠层结构各因子与穿透雨的空间变异性规律,结果表明:观测期间,兴安落叶松林穿透雨量为148.3 mm,占同期大气降雨量的80.62%,穿透雨率随着降雨量的增加呈增加趋势;兴安落叶松林下穿透雨具有较大空间异质性,其变异程度随降雨量的增加而减小,以对数方程拟合较好(P0.01);冠层结构特征是影响穿透雨空间变异的重要因素,冠层复杂程度与穿透雨量呈负相关关系(P0.01);距树干距离、冠层厚度、叶面积指数等因素均可影响穿透雨的空间分布,以距树干距离影响最大,其与穿透雨率呈正相关关系(P0.01),而冠层厚度、叶面积指数则均与穿透雨率呈负相关关系(P0.01),但拟合效果不佳;从影响穿透雨的生态学机制来考虑,在冠层结构特征因子中,冠层厚度是决定穿透雨空间分布的最主要因素。     

Nutrient cycling in Pinus sylvestris stands in eastern Finland

Nutrient cycling within three Pinus sylvestris stands was studied in eastern Finland. The aim of the study was to determine annual fluxes and distribution of N, P, K, Ca, Mg, Zn, Fe, B, and Al in the research stands. Special emphasis was put on determining the importance of different fluxes, especially the internal cycle within the trees in satisfying the tree nutrient requirements for biomass production. The following nutrient fluxes were included, input; free precipitation and throughfall, output; percolation through soil profile, biological cycle; nutrient uptake from soil, retranslocation within trees, return to soil in litterfall, release by litter decomposition. The distribution of nutrients was determined in above- and belowground tree compartments, in ground and field vegetation, and in soil.The nitrogen use efficiencies were 181, 211 and 191 g of tree aboveground dry matter produced per g of N supplied by uptake and retranslocation in the sapling, pole stage and mature stands, respectively. Field vegetation was more efficient in nitrogen use than trees. Stand belowground/aboveground and fine root/coarse root biomass ratios decreased with tree age. With only slightly higher fine root biomass, almost three times more nitrogen had to be taken-up from soil for biomass production in the mature stand than in the sapling stand.The annual input-output balances of most nutrients were positive; throughfall contained more nutrients than was lost in mineral soil leachate. The sulphate flux contributed to the leaching of cations, especially magnesium, from soil in the mature stand.Retranslocation supplied 17–42% of the annual N, P and K requirements for tree aboveground biomass production. Precipitation and throughfall were important in transferring K and Mg, and also N in the sapling stand. Litterfall was an important pathway for N, Ca, Mg and micro nutrients, especially in the oldest stands.     

Accession and cycling of elements in a coastal stand ofPinus radiata D. Don in New Zealand

Summary The accession and cycling of elements in a 14-year-old coastal stand ofPinus radiata D. Don was measured for one year. The element contents (mg m^–2 year^–1) of bulk precipitation and throughfall respectively were: NO₃–N 41, 12; NH₄–N 133, 154; organic-N 157, 396; Na 4420, 9700; K 387, 2900; Ca 351, 701; Mg 486, 1320. Of the increase in element content of rainwater beneath the forest canopy 20% (NH₄–N), 70% (organic-N), 3% (Na), 90% (K), 20% (Ca) and 30% (Mg) was attributed to leaching; the remainder to washing of aerosols filtered from the atmosphere by the vegetation. The canopy absorbed approximately 40 mg m^–2 year^–1 of NO₃–N. Litterfall was the major pathway for the above-ground biogeochemical cycle of N (93%), Ca (96%) and Mg (74%), and leaching was the major (73%) pathway for K.     

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     

Topography strongly affects atmospheric deposition and canopy exchange processes in different types of wet lowland rainforest,Southwest Costa Rica

Bulk precipitation and throughfall were collected in a wet lowland rainforest in SW Costa Rica on an event basis to allow modelling the contributions of dry deposition and canopy exchange to nutrient inputs and internal cycling of nutrients. Estimates based on bulk precipitation underestimated total atmospheric deposition to tropical rainforests by up to 10-fold ignoring the contributions of dry deposition. Canopy exchange contributed most of the aboveground inputs to the forest soil of Na⁺, about half for K⁺, 10% for P and Mg²⁺ and negligible for N, C and other elements. Tree species composition did not account for the differences found in net throughfall between forest sites, and vegetation structure (plant area index) had only a small effect on net throughfall. Forest regrowth affected net throughfall through reduced soil fertility and differences in leaf traits. Topography most significantly affected net throughfall via increased dry deposition at sites of higher elevation and via soil fertility and increased canopy exchange at down slope sites.     

Soil respiration under climate change: prolonged summer drought offsets soil warming effects

Climate change may considerably impact the carbon (C) dynamics and C stocks of forest soils. To assess the combined effects of warming and reduced precipitation on soil CO₂ efflux, we conducted a two‐way factorial manipulation experiment (4 °C soil warming + throughfall exclusion) in a temperate spruce forest from 2008 until 2010. Soil was warmed by heating cables throughout the growing seasons. Soil drought was simulated by throughfall exclusions with three 100 m² roofs during 25 days in July/August 2008 and 2009. Soil warming permanently increased the CO₂ efflux from soil, whereas throughfall exclusion led to a sharp decrease in soil CO₂ efflux (45% and 50% reduction during roof installation in 2008 and 2009, respectively). In 2008, CO₂ efflux did not recover after natural rewetting and remained lowered until autumn. In 2009, CO₂ efflux recovered shortly after rewetting, but relapsed again for several weeks. Drought offset the increase in soil CO₂ efflux by warming in 2008 (growing season CO₂ efflux in t C ha^?1: control: 7.1 ± 1.0; warmed: 9.5 ± 1.7; warmed + roof: 7.4 ± 0.3; roof: 5.9 ± 0.4) and in 2009 (control: 7.6 ± 0.8; warmed + roof: 8.3 ± 1.0). Throughfall exclusion mainly affected the organic layer and the top 5 cm of the mineral soil. Radiocarbon data suggest that heterotrophic and autotrophic respiration were affected to the same extent by soil warming and drying. Microbial biomass in the mineral soil (0–5 cm) was not affected by the treatments. Our results suggest that warming causes significant C losses from the soil as long as precipitation patterns remain steady at our site. If summer droughts become more severe in the future, warming induced C losses will likely be offset by reduced soil CO₂ efflux during and after summer drought.     

Water inputs across a tropical montane landscape in Veracruz,Mexico: synergistic effects of land cover,rain and fog seasonality,and interannual precipitation variability

Land‐cover change can alter the spatiotemporal distribution of water inputs to mountain ecosystems, an important control on land‐surface and land‐atmosphere hydrologic fluxes. In eastern Mexico, we examined the influence of three widespread land‐cover types, montane cloud forest, coffee agroforestry, and cleared areas, on total and net water inputs to soil. Stand structural characteristics, as well as rain, fog, stemflow, and throughfall (water that falls through the canopy) water fluxes were measured across 11 sites during wet and dry seasons from 2005 to 2008. Land‐cover type had a significant effect on annual and seasonal net throughfall (NTF <0=canopy water retention plus canopy evaporation; NTF >0=fog water deposition). Forest canopies retained and/or lost to evaporation (i.e. NTF<0) five‐ to 11‐fold more water than coffee agroforests. Moreover, stemflow was fourfold higher under coffee shade than forest trees. Precipitation seasonality and phenological patterns determined the magnitude of these land‐cover differences, as well as their implications for the hydrologic cycle. Significant negative relationships were found between NTF and tree leaf area index (R²=0.38, P<0.002), NTF and stand basal area (R²=0.664, P<0.002), and stemflow and epiphyte loading (R²=0.414, P<0.001). These findings indicate that leaf and epiphyte surface area reductions associated with forest conversion decrease canopy water retention/evaporation, thereby increasing throughfall and stemflow inputs to soil. Interannual precipitation variability also altered patterns of water redistribution across this landscape. Storms and hurricanes resulted in little difference in forest‐coffee wet season NTF, while El Niño Southern Oscillation was associated with a twofold increase in dry season rain and fog throughfall water deposition. In montane headwater regions, changes in water delivery to canopies and soils may affect infiltration, runoff, and evapotranspiration, with implications for provisioning (e.g. water supply) and regulating (e.g. flood mitigation) ecosystem services.     

Water balance of conifer logs in early stages of decomposition

Seasonal and long-term changes in the water balance of conifer logs during the first 8 years of decomposition were studied in an old-growth Pseudotsuga/Tsuga forest in the Oregon Cascade Mountains. Measurements were made of the moisture content of outer bark, inner bark, sapwood, and heartwood and of the flow of water into and out of logs of four species (Abies amabilis, Pseudotsuga menziesii, Thuja plicata, and Tsuga heterophylla). After the logs had decomposed from 1 to 2 years, 38–47% of the canopy throughfall landing upon them ran off the surface, 29–34% leached from the bottom, and 21–30% was absorbed and evaporated. After 8 years of decomposition, water entering and then leaching from logs increased 1.3 times while runoff decreased a similar amount. The proportion of water stored by and evaporated from logs in this study indicates that in old growth forests they may intercept 2–5% of the canopy throughfall to the forest floor and that, even in early stages of decomposition, they may affect the hydrological cycle of Pacific Northwest old-growth forests.This is paper 2945 of the Forest Research Laboratory, Oregon State University, Corvallis     

川东红池坝地区红三叶和鸭茅人工草地土壤和植物营养元素含量特征的研究

川东红池坝地区红三叶（Ｔｒｉｆｏｌｉｕｍｐｒａｔｅｎｓｅ）和鸭茅（Ｄａｃｔｙｌｉｓｇｌｏｍｅｒａｔａ）人工草地土壤和植物营养元素的含量特征如下：（１）土壤中的元素含量以铁、钾和镁较高,钠、钙、氮、锰和磷较低,硫、锌、硼、铜和钼微少;（２）从元素的富集特征来看,该区土壤中的钙、硫为重度淋溶元素,钾、磷、镁、锌、钠为中度淋溶元素,铁、铜属轻度淋溶元素,锰属富集元素;（３）根据元素的生物吸收系列,红三叶属氮－钙型植物,鸭茅属氮－钾－磷型植物。（４）两种牧草的生物吸收系数,均以钙、硫、磷较高,钠、铁较低,其余７种元素介于二者之间。     

The effect of stand age on throughfall chemistry in spruce stands in the Potok Dupniañski catchment in the Silesian Beskid Mountains, southern Poland

The chemical composition of throughfall depends on the age of the Norway spruce (Picea abies Karst) stands and season of the year. The pH of throughfall decreased and the amount of hydrogen ion in throughfall deposited to the soil increased with increasing age of spruce stands, especially in the winter season. Concentrations of K+, H+, SO4(2-), Mn2+, and NH4(+) in throughfall were higher than bulk precipitation for the whole year and K+, H+, and Mn2+ concentrations were higher in throughfall in winter and the growing season. This indicates that these ions were washed out or washed from the surface of needles and/or the bark, and that NO3(-), NH4(+), Ca2+, Mg2+, Fe2+, and Zn2+ were absorbed in the canopy. The effect of high nitrogen deposition, above critical loads, and an increase in the amount of sulfur and in the sum of the strong acids (S-SO4(2-) and N-NO3(-)) that reached the soil with throughfall may have implications for the vitality of spruce stands, especially in older age classes. The application of Principal Component Analysis (PCA) has led to identification of five factors responsible for the data structure ("mineral dust", "acidic emissions", "heavy metals-dust particles", "ammonium [NH4(+)]", and "H+"). They explain more than 60% of the total variance system. The strong positive correlation between stand age class and ionic concentrations in throughfall occurs for all year and the winter period for ions within the following categories: "acidic emissions", SO4(2-) + NO3(-); "heavy metals-dust particles", Fe2+ + Mn2+ + Zn2+; "mineral dust", Na+ + K+ + Ca2+ + Mg2+; "NH4(+)"; and "H+". The strength of the relationship decreases in the growing period, probably due to processes occurring in the canopy (adsorption, leaching, etc.).