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.     

Characteristics of canopy interception and its simulation with a revised Gash model for a larch plantation in the Liupan Mountains,China

Canopy interception is a significant proportion of incident rainfall and evapotranspiration of forest ecosystems. Hence, identifying its magnitude is vital for studies of eco-hydrological processes and hydrological impact evaluation. In this study, throughfall, stemflow and interception were measured in a pure Larix principis-rupprechtii Mayr.(larch) plantation in the Liupan Mountains of northwestern China during the growing season(May–October) of 2015, and simulated using a revised Gash model. During the study period, the total precipitation was499.0 mm; corresponding total throughfall, stemflow and canopy interception were 410.3, 2.0 and 86.7 mm,accounting for 82.2, 0.4 and 17.4% of the total precipitation, respectively. With increasing rainfall, the canopy interception ratio of individual rainfall events decreased initially and then tended to stabilize. Within the study period, the simulated total canopy interception, throughfall and stemflow were 2.2 mm lower, 2.5 mm higher and0.3 mm lower than their measured values, with a relative error of 2.5, 0.6 and 15.0%, respectively. As quantified by the model, canopy interception loss(79%) mainly consisted of interception caused by canopy adsorption, while the proportions of additional interception and trunk interception were small. The revised Gash model was highly sensitive to the parameter of canopy storage capacity,followed by the parameters of canopy density and mean rainfall intensity, but less sensitive to the parameters of mean evaporation rate, trunk storage capacity, and stemflow ratio. The revised Gash model satisfactorily simulated the total canopy interception of the larch plantation within the growing season but was less accurate for some individual rainfall events, indicating that some flaws exist in the model structure. Further measures to improve the model's ability in simulating the interception of individual rainfall events were suggested.     

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.     

Transfer characteristics of nutrient elements through hydrological process of a Pinus tabulaeformis stand in the West Mountain of Beijing

Forest precipitation chemistry is a major issue in forest hydrology and forest ecology. Chemical contents in precipitation change significantly when different kinds of external chemical materials are added, removed, translocated and transformed to or in the forest ecosystem along with precipitation. The chemistry of precipitation was monitored and analyzed in a 31-year-old Pinus tabulaeformis forest in the West Mountain of Beijing. Movement patterns of nutrient elements in hydrological processes can be discovered by studying this monitored data. Also, the information is useful for diagnosing the function of ecosystems and evaluating the impact of the environment on the ecosystem. Samples of rainfall, throughfall and stemflow were collected on the site. In the lab, Ca²⁺ and Mg²⁺ were analyzed by flame atomic absorption and K⁺ and Na⁺ by flame emission. NH₄ ⁺-N was analyzed by indophenol blue colorimetry and NO₃ ⁻-N was analyzed by phenoldisulfonic acid colorimetry. The results showed that: 1) The concentration gradient of nutrient elements clearly changed except for Na⁺. The nutrients in stemflow were significantly higher than those of throughfall and rainfall as the precipitation passed through the P. tabulaeformis forest. The monthly patterns showed distinct differentiation. There are indications that a large amount of nutrients was leached from the canopy, which is a critical function of intra-ecosystem nutrient cycling to improve the efficiency of nutrient use. 2) The concentrations of NO₃ ⁻-N and K⁺ changed more than those of the other nutrient elements. The concentration of NO₃ ⁻-N in throughfall and stemflow was 4.4 times and 9.9 times higher than those in rainfall, respectively. The concentration of K⁺ in throughfall and stemflow was 4.1 times and 8.1 times higher than those in rainfall, respectively. 3) The leaching of nutrient elements from the stand was an important aspect of nutrient return to the P. tabulaeformis forest, which returned a total amount of nutrient of 54.1 kg/hm², with the contribution of Ca²⁺ and K⁺ much greater than that of other elements. Also, K⁺ was the most active element in leaching intensity. 4) Nutrient input through precipitation was the main source in the West Mountain of Beijing and the amount of nutrient added was 66.4 kg/hm², of which Ca²⁺ and N contributed much more than the other nutrient elements. When precipitation passes through the P. tabulaeformis forest, 121 kg/hm² of nutrient is added to the forest floor. Ca²⁺ recorded the greatest nutrient increase, with 61.2 kg/hm², followed by N (NH₄ ⁺-N and NO₃ ⁻-N), K⁺ and Mg²⁺, with 31.3 and 16.5, and 8.11 kg/hm², respectively. The least was Na⁺, 3.34 kg/hm². Translated from Acta Ecologica Sinica, 2006, 26(7): 2,101–2,107 [译自: 生态学报]     

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.     

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.     

Nutrient accessions to the forest floor in karri (Eucalyptus diversicolor F. Muell.) forests of varying age

Nutrient accessions to the forest floor in rainfall, throughfall and stemflow from the understorey and tree strata were measured in karri (Eucalyptus diversicolor F. Muell.) forest of south-west Western Australia. These data, for stands aged 2, 6, 9, and 40 years and for mature forest, were compared with annual accessions of nutrients in litterfall.

With increasing age of the stands, the concentration and amounts of Ca, K, Mg, Na and Cl in throughfall increased. The amounts of Mg, Na and Cl in stemflow from the overstorey were also greatest in the older stands. Although concentrations of nutrients in stemflow from the tree stratum were higher than from the understorey, the quantities of nutrients transported to the forest floor in stemflow from the understorey were greater because of its greater volume.

Rainfall is the major source of Na (64–91%) and Cl (51–79%) and it also contributes significantly to Mg (19–50%) accessions. Of the nutrient pathways between canopy and forest floor, litterfall accounts for the largest proportion of N (89–93%), Ca (80–87%) and P (67–79%) recycled in the karri forest. About equal amounts of K are transferred in litterfall, throughfall and stemflow with approximately 80% of stemflow K originating from the understorey strata.     

川西亚高山原始云杉林内降雨分配研究

穿透雨、茎流和林冠截留在森林生态系统水文循环和水量平衡中占有极其重要的地位 (VanDijketal .,2 0 0 1) ,因而从生理学、生态学和水文学的观点来看 ,研究一定区域内植被与降雨之间的相关性具有重要的意义 (Aboaletal .,1999)。川西亚高山针叶林处于我国东南半壁湿润地区与西北半壁干旱地区的过渡地带上 ,且多分布于江河上游 ,在涵养水源、保持水土、稳定河川流量、维护生态平衡等方面具有重要的地位 ,被誉为庇护四川及长江流域的“绿色万里长城”(杨玉坡 ,1990 )。马雪华 (1987)对米亚罗地区亚高山冷杉林的林冠截留做了一些初步的观测 …     

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%。     

Response of the N and P cycles of an old-growth montane forest in Ecuador to experimental low-level N and P amendments

Atmospheric nitrogen (N) and phosphorus (P) depositions are expected to increase in the tropics as a consequence of increasing human activities in the next decades. In the literature, it is frequently assumed that tropical montane forests are N-limited, while tropical lowland forests are P-limited. In a low-level N and P addition experiment, we determined the short-term response of N and P cycles in a north Andean montane forest on Palaeozoic shists and metasandstones at an elevation of 2100 m a.s.l. to increased N and P inputs. We evaluated experimental N, P and N + P additions (50 kg ha⁻¹ yr⁻¹ of N, 10 kg ha⁻¹ yr⁻¹ of P and 50 kg + 10 kg ha⁻¹ yr⁻¹ of N and P, respectively) and an untreated control in a fourfold replicated randomized block design. We collected litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall and litterfall before the treatment began (August 2007) until 16 months after the first nutrient application (April 2009). Less than 10 and 1% of the applied N and P, respectively, leached below the organic layer which contained almost all roots and no significant leaching losses of N and P occurred to below 0.15 m mineral soil depth. Deposited N and P from the atmosphere in dry and wet form were retained in the canopy of the control treatment using a canopy budget model. Nitrogen and P retention by the canopy were reduced and N and P fluxes in throughfall and litterfall increased in their respective treatments. The increase in N and P fluxes in throughfall after fertilization was equivalent to 2.5% of the applied N and 2% of the applied P. The fluxes of N and P in litterfall were up to 15% and 3%, respectively, higher in the N and N + P than in the control treatments. We conclude that the expected elevated N and P deposition in the tropics will be retained in the ecosystem, at least in the short term and hence, N and P concentrations in stream water will not increase. Our results suggest that in the studied tropical montane forest ecosystem on Palaeozoic bedrock, N and P are co-limiting the growth of organisms in the canopy and organic layer.     

Deposition pattern of precipitation and throughfall in a subtropical evergreen forest in south-central China

The effects of dry deposition, canopy leaching, precipitation ion concentration, and precipitation H⁺ concentration on net throughfall flux (NTF, throughfall minus bulk precipitation) were evaluated on a seasonal basis by using a multiple regression analysis approach based on an observation period of 4 years in Shaoshan subtropical mixed evergreen forest, south-central China. Regression analysis results indicated that the estimated canopy exchange flux was the dominant factor regulating the NTF and the calculated dry deposition was a minor term. The seasonal dry deposition of base cations accounted for 15%–43% of the NTF. The NTF analysis showed that K⁺, Ca²⁺, Mg²⁺, Na⁺, and weak acids in throughfall were derived from foliar leaching and the canopy uptakes of H⁺, NH₄ ⁺, and NO₃ ⁻ were from precipitation. The retention rate of proton (H⁺ and NH₄ ⁺) in the canopy was close to the canopy leaching rate of base cations when corrected for weak acids because weak acid-induced canopy leaching did not exchange with protons, which suggested that the canopy leaching processes neutralized acid precipitation in Shaoshan forest.     

Nitrogen cycling in Pinus sylvestris stands exposed to different nitrogen inputs

The objective of this study was to quantify the effects of high nitrogen (N) inputs on N cycling in a 35–45-yr-old Scots pine (Pinus sylvestris L.) forest. Nitrogen was added annually (single doses) as NH₄NO₃ in doses of 0 (N0), 30 (N1) and 90 (N2) kg N ha^?1 yr^?1. The only N input to the N0 plots was atmospheric deposition of 10 kg N ha^?1 yr^?1. The N cycle in these plots was tight, with almost complete retention of the incoming N. In the N1 plots the N retention was 83% after 9 yrs of N addition. The trees were the major sink, but the soil also contributed to the N retention. In the N2 plots the N retention was 63%, being mainly accounted for by accumulation in the soil. The leaching of N from the N2 stands was as high as 35 kg N ha^?1 yr^?1. The N2 system was N saturated.     

Atmospheric deposition and leaching of nitrogen in Chinese forest ecosystems

Data have been compiled from published sources on nitrogen (N) fluxes in precipitation, throughfall, and leaching from 69 forest ecosystems at 50 sites throughout China, to examine at a national level: (1) N input in precipitation and throughfall, (2) how precipitation N changes after the interaction with canopy, and (3) whether N leaching increases with increasing N deposition and, if so, to what extent. The deposition of dissolved inorganic N (DIN) in precipitation ranged from 2.6 to 48.2 kg N ha⁻¹ year⁻¹, with an average of 16.6 kg N ha⁻¹ year⁻¹. Ammonium was the dominant form of N at most sites, accounting for, on average, 63% of total inorganic N deposition. Nitrate accounted for the remaining 37%. On average, DIN fluxes increased through forest canopies, by 40% and 34% in broad-leaved and coniferous forests, respectively. No significant difference in throughfall DIN inputs was found between the two forest types. Overall, 22% of the throughfall DIN input was leached from forest ecosystems in China, which is lower than the 50–59% observed for European forests. Simple calculations indicate that Chinese forests have great potential to absorb carbon dioxide from the atmosphere, because of the large forest area and high N deposition.     

Export of Nutrients in Plant Biomass Following Harvest of Eucalypt Plantations in Kerala,India

Abstract

Pools of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) were examined in the soil and above-ground plant biomass at the end of a 7 year rotation at two E. tereticornis lowland sites and two E. grandis highland sites in Kerala, India. Potential export rates of these nutrients were also examined for different biomass removal scenarios from the plantations. Pools of nutrients were measured in the above-ground components of the tree crop, forest floor and understorey, and in soil down to 1 m depth. At harvest, large quantities of biomass and nutrients are removed from eucalypt plantation sites, with the quantities of nutrients exported unlikely to be replaced through natural atmospheric and weathering inputs. Between 24 Mg ha^-1 and 115 Mg ha^-1 of biomass was exported in stem wood across the sites, and this increased to 40-145 Mg ha^-1 in scenarios where all of the branches, bark and understorey were also exported. Stem wood had the lowest concentration of nutrients and had a relatively low export of nutrient per kg of biomass. On average, 54 kg, 12 kg and 65 kg of N, P and K were removed per hectare in stem wood only, equivalent to 0.46%, 0.17%, and 6.7%, respectively, of above- and below-ground (to 1 m depth) site pools. Export increased to 194 kg, 30 kg, and 220 kg of N, P and K per hectare if the branches, bark and understorey were also removed (equivalent to 1.6%, 0.5% and 24.7% of above- and below-ground site pools down to 1 m depth). Export of Ca and Mg was also high, with an average of 88 kg and 11 kg of Ca and Mg removed per hectare if only the stem wood was taken (3.12% and 1.34% of total above-ground and exchangeable below-ground to 1 m depth), increasing to 501 kg ha^-1 and 66 kg ha^-1 if the branches, bark and understorey were also removed (21.7% and 11.3% of total above-ground and available below-ground to 1 m depth). Removals of this magnitude represent a significant proportion of site nutrient pools and have the potential to reduce future plantation productivity unless steps are taken to promote retention of biomass and nutrients on site and/or replacement of nutrients through fertilizer application.     

Gradual forest edges can mitigate edge effects on throughfall deposition if their size and shape are well considered

For the protection and promotion of biodiversity in forest edges and interiors, forest edge management practices are put forward like the creation of gradual forest edges (i.e., edges with a gradual increase of vegetation height from open area to forest, e.g., by means of a fringe, a belt, and a mantle). In this study, we tested the mitigating effect of gradual forest edges on the atmospheric deposition of inorganic nitrogen (N) and the potentially acidifying pollutants SO₄²⁻, NO₃⁻, and NH₄⁺ (N + S). We conducted field experiments at three exposed forest edges in Flanders and the Netherlands and compared throughfall deposition at steep edges (i.e., edges with an abrupt transition from open area to forest) and at adjacent gradual edges. Along transects perpendicular to the edges, during three months in both winter and summer, throughfall deposition of Cl⁻, SO₄²⁻, NO₃⁻, and NH₄⁺ was monitored in the forest between 0 and 64 m from the edges and in the gradual edge vegetation. At the smoothest and best fitting gradual edge, the extra N + S throughfall deposition the forest received due to edge effects was lower than at the adjacent steep edge, with on average 80 and 100% in winter and summer, respectively. This was due to a halving of the depth of edge influence and an almost full reduction of the magnitude of edge influence. This decrease in throughfall deposition in the forest was not compensated by the additional throughfall deposition on the gradual edge vegetation itself, resulting in a final decrease in throughfall deposition in the forest edge by 60% in winter and 74% in summer. While this result confirms that gradual edges can mitigate edge effects on atmospheric deposition, the results of the other sites indicate the importance of size and shape of the gradual edge vegetation in mitigating edge effects on deposition: due to insufficient height (‘size’) or inadequate shape of the gradual edge vegetation, only small or insignificant decreases in throughfall deposition were observed. Hence, for mitigating edge effects on N + S and N deposition, our results support the recommendation of creating gradual edges at forests with poorly developed, abrupt edges, but it stresses the importance of a thorough consideration of the shape and size of the gradual edge vegetation in the design and management of gradual forest edges.     

Growing woody biomass for bioenergy in a tree-based intercropping system in southern Ontario, Canada

During the spring of 2006, three willow varieties (SV1, SX67 and 9882-41) were established on marginal land in an agroforestry tree-intercropping arrangement where plots of short rotation willows were planted between rows (spaced 15?m apart) of 21-year-old mixed tree species. As a control, the same varieties were established on an adjacent piece of land without established trees (conventional willow system). This study investigated the magnitude of carbon pools, fine root and leaf biomass inputs and clone yields in both the tree-based intercropping (agroforestry) and conventional monocropping systems. Willow biomass yield was significantly higher in the agroforestry field (4.86?odt?ha^?1?y^?1) compared to the conventional field (3.02?odt?ha^?1?y^?1). In both fields, varieties SV1 and SX67 produced higher yields than the variety 9882-41. Willow fine root biomass in the top 20?cm of soil was significantly higher in the intercropping system (3,062?kg?ha^?1) than in the conventional system (2,536?kg?ha^?1). Differences in fine root biomass between clones were similar to that observed for differences in biomass yield: SV1?>?SX67?>?9882-41. Leaf input was higher in the intercropping system (1,961?kg?ha^?1) than in the conventional system (1,673?kg?ha^?1). Clonal differences in leaf inputs followed the same trends as those for root biomass and yield: SV1?>?SX67?>?9882-41. Soil organic carbon was significantly higher in the agroforestry field (1.94?%) than in the conventional field (1.82?%). A significant difference in soil organic carbon was found between the three clones: soils under clone 9882-41 had the lowest soil organic carbon at 1.80?%.     

Dissolved organic carbon and nitrogen in precipitation, throughfall and stemflow fromSchima superba andCunninghamia lanceolata plantations in subtropical China

Despite growing attention to the role of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in forest nutrient cycling, their monthly concentration dynamics in forest ecosystems, especially in subtropical forests only were little known. The goal of this study is to measure the concentrations and monthly dynamics of DOC and DON in precipitation, throughfall and stemflow for two plantations ofSchima superba (SS) and Chinese fir (Cunninghamia lanceolata, CF) in Jianou, Fujian, China. Samples of precipitation, throughfall and stemflow were collected on a rain event base from January 2002 to December 2002. Upon collection, all water samples were analyzed for DOC, NO₃ ⁻−N, NH₄ ⁺−N and total dissolved N (TDN). DON was calculated by subtracting NO₃ ⁻−N and NH₄ ⁺−N from TDN. The results showed that the precipitation had a mean DOC concentration of 1.7 mg·L⁻¹ and DON concentration of 0.13 mg·L⁻¹. The mean DOC and DON concentrations in throughfall were 11.2 and 0.24 mg·L⁻¹ in the SS and 10.3 and 0.19 mg·L⁻¹ in the CF respectively. Stemflow DOC and DON concentrations in the CF (19.1 and 0.66 mg·L⁻¹ respectively) were significantly higher than those in the SS (17.6 and 0.48 mg·L⁻¹ respectively). No clear monthly variation in precipitation DOC concentration was found in our study, while DON concentration in precipitation tended to be higher in summer or autumn. The monthly variations of DON concentrations were very similar in throughfall and stemflow at both forests, showing an increase at the beginning of the rainy season in March. In contrast, monthly changes of the DOC concentrations in throughfall of the SS and CF were different to those in stemflow. Throughfall DOC concentrations were higher from February to April, while relatively higher DOC concentrations in stemflow were found during September–November period. Foundation item: This study was supported by the Teaching and Research Award program for MOE P.R.C. (TRAPOYT). Biography: Guo Jian-fen (1977-), female, Ph. Doctor in College of Life Science, Xiamen University, Xiamen 361005, P.R. China. Responsible editor: Zhu Hong     

Carbon, nitrogen, organic phosphorus, microbial biomass and N mineralization in soils under cacao agroforestry systems in Bahia, Brazil

Large amounts of plant litter deposited in cacao agroforestry systems play a key role in nutrient cycling. Organic matter, nitrogen and phosphorus cycling and microbial biomass were investigated in cacao agroforestry systems on Latosols and Cambisols in Bahia, Brazil. The objective of this study was to characterize the microbial C and N, mineralizable N and organic P in two soil orders under three types of cacao agroforestry systems and an adjacent natural forest in Bahia, Brazil and also to evaluate the relationship between P fractions, microbial biomass and mineralized N with other soil attributes. Overall, the average stocks of organic C, total N and total organic P across all systems for 0?C50?cm soil depth were 89,072, 8,838 and 790?kg?ha^?1, respectively. At this soil depth the average stock of labile organic P was 55.5?kg?ha^?1. For 0?C10?cm soil depth, there were large amounts of microbial biomass C (mean of 286?kg?ha^?1), microbial biomass N (mean of 168?kg?ha^?1) and mineralizable N (mean of 79?kg?ha^?1). Organic P (total and labile) was negatively related to organic C, reflecting that the dynamics of organic P in these cacao agroforestry systems are not directly associated with organic C dynamics in soils, in contrast to the dynamics of N. Furthermore, the amounts of soil microbial biomass, mineralizable N, and organic P could be relevant for cacao nutrition, considering the low amount of N and P exported in cacao seeds.     

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。     

Spatial variability of throughfall in a Pinus tabulaeformis plantation forest in Loess Plateau,China

Throughfall varies in space, which complicates measurements and makes it difficult to achieve accurate spatial representation. In the present research, we measured gross rainfall and throughfall from May 2011 to September 2012, leaf area index, and locations of trees within a Pinus tabulaeformis plantation forest in the Loess Plateau of northwestern China. The spatial heterogeneity of throughfall and related factors, as well as the minimum number and locations of collectors needed to measure throughfall accurately, were analyzed by statistical techniques. The results indicated that the throughfall was concentrated at the canopy edge, indicating that the edge of the canopy of P. tabulaeformis had a convergence effect on throughfall. The analysis of semivariance of throughfall demonstrated that canopy structure was a key factor influencing spatial variation of throughfall in low rainfall events, but measurement errors and other nonspatial variables were the primary factors affecting the variation of throughfall in high rainfall events. Based on the mean throughfall at different proportions of canopy radius centered on the individual tree stem, the minimum number and locations of collectors needed to accurately measure throughfall was estimated. In this study, four rain collectors (diameter 20?cm) at the 3/5 canopy radius could reasonably represent the average throughfall under the individual P. tabulaeformis canopy.