Nitrification and denitrification as sources of gaseous nitrogen emission from different forest soils in Changbai Mountain

The contributions of nitrification and denitrification to N₂O and N₂ emissions from four forest soils on northern slop of Changbai Mountain were measured with acetylene inhibition methods. In incubation experiments, 0.06% and 3% C₂H₂ were used to inhibit nitrification and denitrification in these soils, respectively. Both nitrification and denitification existed in these soils except tundra soil, where only denitrification was found. The annually averaged rates of nitrification and denitrification in mountain dark brown forest soil were much higher than that in other three soils. In mountain brown coniferous soil, contributions of different processes to gaseous nitrogen emissions were Denitrification N₂O>nitrification N₂O>Denitrification N₂. The same sequence exists in mountain soddy soil as that in the mountain brown coniferous soil. The sequence in mountain tundra soil was Denitrification N₂O>Denitrification N₂. Foundation item: This paper was supported by the National Natural Science Foundation of China (No.49701016) and the “Hundred Scientists” Project of Chinese Academy of Sciences. Biography: XU Hui (1967-), male, Ph. Doctor, associate research fellow in Laboratory of Ecological Process of Trace Substance in Terrestrial Ecosystem, Institute of Applied Ecology, Chinese Academy of sciences, Shenyang 110015, P. R. China. Responsible editor: Song Funan     

Effects of different N sources on growth, nutrient uptake and ionic balance ofLarlix gmelini seedlings

The effect of different sources and levels of N on dry matter production, nutrient uptake and ionic balance ofLarlix gmelini was studied. The results showed that the growth of the plants fertilized with ammonium was not as good as the control treatment. The growth of the plants fertilized with ammonium nitrate did not differ significantly from that in control or nitrate treatment, but was better than that in the ammonium treatment. Total cation concentrations in shoots varied little with N level in the ammonium and ammonium nitrate treatments, while those in the shoot increased with N level in the nitrate treatment. The treatments had little effect on the anion concentrations in the shoot. In the roots, the concentrations of both cations and anions changed little except for SO₄ ²⁻ and Ca²⁺. There existed a higher carboxylate production in the plants fertilized with nitrate. The ratio between the production of carboxylate and the production of organic N Δ(C-A)/ΔN_org was constant with N supply in the plants receiving nitrate, but obviously declined with N supply for ammonium-fed plants. Δ (C-A)/ΔN_org values were intermediate between those of the nitrate and the ammonium-fed plants as for the mixed N source. Foundation item: This paper was supported by “Hundred Scientists” Project of Chinese Academy of Sciences. Biography: CHEN Yong-liang (1969-), male, Ph. Doctor, lecture of Northeast Forestry University, Harbin 150040, Post-doctor in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P.R. China. Responsible editor: Song Fuman     

Effects of elevated CO2 concentrations on photosynthesis, dark respiration and RuBPcase activity of three species seedlings in Changbai Mountain

Two-year-old seedlings ofPinus koraiensis, Pinus sylvestriformis andFraxinus mandshurica were treated in open-top chambers with elevated CO₂ concentrations (700 μL·L⁻¹, 500 μL·L⁻¹) and ambient CO₂ concentrations (350 μL·L⁻¹) in Changbai Mountain from June to Sept. in 1999 and 2001. The net photosynthetic rate, dark respiration rate, ribulose-1,5-bisphosphate carboxlase (RuBPcase) activity, and chlorophyll content were analyzed. The results indicated the RuBPcase activity of the three species seedlings increased at elevated CO₂ concentrations. The elevated CO₂ concentrations stimulated the net photosynthetic rates of three tree species exceptP. sylvestriformis grown under 500 μL·L⁻¹ CO₂ concentration. The dark respiration rates ofP. koraiensis andP. sylvestriformis increased under concentration of 700 μL·L⁻¹ CO₂, out that ofF. mandshurica decreased under both concentrations 700 μL·L⁻¹ and 500 μL·L⁻¹ CO₂. The seedlings ofF. mandshurica decreased in chlorophyll contents at elevated CO₂ concentrations. Foundation item: This paper was supported by the National Natural Science Foundation of China (No. 30070158). Knowledge Innovation Item of Chinese Academy of Sciences (KZCX2-406) and “Hundred Scientists” Project of Chinese Academy of Sciences. Biography: Zhou Yu-mei (1973-) Ph. Doctor, Assistant Research fellow Institute of Applied Ecology. Chinese Academy of Sciences. Shenyang 110016. P.R. China. Responsible editor: Song Funan     

Effects of soil moisture and temperature on CH4 oxidation and N2O emission of forest soil

Soil samples were taken from depth of 0–12 cm in the virgin broad-leaved/Korean pine mixed forest in Changbai Mountain in April, 2000. 20 μL·L⁻¹ and 200 μL·L⁻¹ CH₄ and N₂O concentration were supplied for analysis. Laboratory study on CH₄ oxidation and N₂O emission in forest soil showed that fresh soil sample could oxidize atmospheric methane and product N₂O. Air-dried soil sample could not oxidize atmospheric methane, but could product N₂O. However, it could oxidize the supplied methane quickly when its concentration was higher than 20 μL·L⁻¹. The oxidation rate of methane was increased with its initial concentration. An addition of water to dry soil caused large pulse of N₂O emissions within 2 hours. There were curvilinear correlations between N₂O emission and temperature (r²=0.706, p<0.05), and between N₂O emission and water content (r²=0.2968, p <0.05). These suggested temperature and water content were important factors controlling N₂O emission. The correlation between CH₄ oxidization and temperature was also found while CH₄ was supplied 200 μL·L⁻¹ (r²=0.3573, p<0.05). Temperature was an important factor controlling CH₄ oxidation. However, when 20 μL·L⁻¹ CH₄ was supplied, there was no correlation among CH₄ oxidization, N₂O emission, temperature and water content. Foundation item: This paper was supported by Chinese Academy of Sciences. Biography: ZHANG Xiu-jun (1960-), female, Ph. Doctor, lecture in Laboratory of Ecological Process of Trace Substance in Terrestrial Ecosystem, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110015, P.R. China. Responsible editor: Song Funan     

Effects of thinning on wind damage in Pinus thunbergii plantation ——Based on theoretlcal derlvation of risk—ratios for assessing wind damage

Based on paper of “Theoretical derivation of risk-ratios for assessing wind damage in coastal forest“,wind damage in the pine coasteal forest,which was thinned at four levels in December of 1997,was investigated for four successive growing seasons.Besides wind damage,the wind profiles outside and inside the coastal forest stand and the distributions of optical stratification porosity (OSP) were also observed.Based on these data,risk-ratios of wind damage for both individual trees and stands were estimated according to the methods developed in “Theoretical derivation of risk-ratios for assessing wind damage in a coastal forest“.The results showed that risk-ratios of wind damage,which were calculated from the meen height and diameter only and from the combination of wind and stand sructure profiles,accurately predicted wind damage in the plantation.Relationships between different thinning ratios and incidence of wind damage showed that stand stability decreased soon after the thinning.This was due to the immediate effects of thinning on increasing the canopy roughness and wind load,and on decreasing the sheltering effects from surrounding trees.However,thinning strategies could improve the stability by long-term effects on growthand development of trees against extreme wind.Only canopy damage was recorded during the experimental period,no stem damage was found,even though the maximum 10-min wind speed outside the coastal forest attained 30.2m s^-1.The results obtained in this study indicate that thinning is the most effective silvicultural strategy available for managing coastal forest despite the increased probability of wind damage soon after thinning.     

Effect of water stress on N2O emission rate of 5 tree species

The N₂O emission rates, photosynthesis, respiration and stomatal conductance of the dominant tree species from broadleaf/Korean pine forest in Changbai Mountain were measured by simulated water stress with the closed bag-gas chromatography. A total of five species seedlings were involved in this study, i.e.,Pinus koraiensis Sieb. et Zucc,Fraxinus mandshurica Rupr,Juglans mandshurica Maxim,Tilia amurensis Rupr, andQuercus mongolica Fisch. ex Turcz.. The results showed that the stomatal conductance, net photosynthetic rate and N₂O emission of leaves were significantly reduced under the water stress. The stoma in the leaves of trees is the main pathway of N₂O emission. N₂O emission in the trees mainly occurred during daytime. N₂O emission rates were different in various tree specie seedlings at the same water status. In the same tree species, N₂O emission rates decreased as the reduction of soil water contents. At different soil water contents (MW, LW) the N₂O emission rates ofPinus koraiensis decreased by 34.43% and 100.6% of those in normal water condition, respectively. In broadleaf arbor decreased by 31.93% and 86.35%, respectively. Under different water stresses N₂O emission rates in five tree species such asPinus koraiensis, Fraxinus mandshurica, Juglans mandshurica, Tilia amurensis, andQuercus mongolica were 38.22, 14.44, 33.02, 16.48 and 32.33 ngN₂O·g⁻¹DW·h⁻¹, respectively. Foundation item: This project was supported by the National Natural Science Foundation of China (No. 30271068), the grant of the Knowledge Innovation Program of Chinese Academy of Sciences (KZ-CX-SW-01-01B-10), and the Special Funds for Major State Basic Research Program of China (No. G1999043407) Biography: Wang Miao (1964-), male, associate professor in Institute of Applied Ecology, Chinese Academy of Science, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

长白山北坡不同海拔植物群落物种丰富度估计

应用梯度格局法在长白山北坡海拔700-2600 m 之间，海拔每上升100 m设置一块样地，共20块样地。以具体的样地观测数据为基础，应用刀切法和自助法等非参数估计法对各海拔群落的物种丰富度进行了估计，结果表明，用自助法所得到的物种估计数，与客观实际更为接近。同时，根据各海拔群落观测物种数与估计物种数的差异，进一步验证了最小取样面积的合理性。     

Response of seedlings of different tree species to elevated C02 in Changbai Mountain

Eco-physiological responses of seedlings of eight species,Pinus koraiensis, Picea koraiensis, Larix olgensis, Populus ussuriensis, Betula platyphylla, Tilia amurensis, Traxinus mandshurica andAcer mono from broadleaved/Korean pine forest, to elevated CO₂ were studied by using open-top chambers under natural sunlight in Changbai Mountain, China in two growing seasons (1998–1999). Two concentrations of CO₂ were designed: elevated CO₂ (700 μmol·mol⁻¹) and ambient CO₂ (400 μmol·mol⁻¹). The study results showed that the height growth of the tree seedlings grown at elevated CO₂ increased by about 10%–40% compared to those grown at ambient CO₂. And the water using efficiency of seedlings also followed the same tendency. However, the responses of seedlings in transpiration and chlorophyll content to elevated CO₂ varied with tree species. The broad-leaf tree species were more sensitive to the elevated CO₂ than conifer tree species. All seedlings showed a photosynthetic acclimation to long-term elevated CO₂. Foundation item: The project was supported by National Key Basic Development of China (G1999043400) and the grant KZCX 406-4, KZCX1 SW-01 of the Chinese Academy of Sciences Biography: WANG Miao (1964-), maie, associate professor in Institute of applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

GIS在生态土地分类中的作用

This paper depicted the physiographic landscape features and natural vegetation situation of study area (the eastern Jilin Province), and expatiates the definition, basic characters and its development of Ecological Land Classification (ELC). Based on the combination of relief map, satellite photography for study area and vegetation inventory data of 480 sample sites, a 5-class and a 15-class ecological land type map was concluded according to 4 important factors including slope, aspect, vegetation and elevation. Ecological Classification System (ECS) is a method to identify, characterize, and map ecosystems. The Ecological Land Type (ELT) was examined and applied initially in eastern Jilin Province. Foundation item: This paper was supported by Chinese Academy of Sciences “100 people” project and the Open Research Station of Changbai Mountain Forest Ecosystem. Biography: XIAO Bao-ying (1974-), female, postgraduate in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China Responsible editor: Zhu Hong     

Stomatal response ofPinus sylvestriformis to elevated CO2 concentrations during the four years of exposure

Four-year-oldPinus sylvestriformis were exposed for four growing seasons in open top chambers to ambient CO₂ concentration (approx. 350 μmol·mol⁻¹) and high CO₂ concentrations (500 and 700 μmol·mol⁻¹) at Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences at Antu Town, Jilin Province, China (42°N, 128°E). Stomatal response to elevated CO₂ concentrations was examined by stomatal conductance (g _s), ratio of intercellular to ambient CO₂ concentration (c _i/c _a) and stomatal number. Reciprocal transfer experiments of stomatal conductance showed that stomatal conductance in high-[CO₂]-grown plants increased in comparison with ambient-[CO₂]-grown plants when measured at their respective growth CO₂ concentration and at the same measurement CO₂ concentration (except a reduction in 700 μmol·mol⁻¹ CO₂. grown plants compared with plants on unchambered field when measured at growth CO₂ concentration and 350 μmol·mol⁻¹CO₂). High-[CO₂]-grown plants exhibited lowerc _i/c _a ratios than ambient-[CO₂]-grown plants when measured at their respective growth CO₂ concentration. However,c _i/c _a ratios increased for plants grown in high CO₂ concentrations compared with control plants when measured at the same CO₂ concentration. There was no significant difference in stomatal number per unit long needle between elevated and ambient CO₂. However, elevated CO₂ concentrations reduced the total stomatal number of whole needle by the decline of stomatal line and changed the allocation pattern of stomata between upper and lower surface of needle. Foundation Item: This research was supported by National Basic Research Program of China (2002CB412502), Project of Key program of the National Natural Science Foundation of China (90411020) and National Natural Science Foundation of China (30400051). Biography: ZHOU Yu-mei (1973-), female, Ph. Doctor, assistant research fellow, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

Artificial incubation and growth observation for the nestlings of Great Bustard （Otis tarda）

Growth indicators including weight, body length, wings length, tail length, tarsus, gape, the third toe and head width of 21 nestlings of Great Bustard (Otis tarda) were measured and investigated in Harbin Zoo, Harbin, China during 1999–2002, and methods on successfully fostering nestlings of the bird were also summarized in this article. The results showed: the Great Bustard is a kind of premature bird and its birth weight was 86.31 ±3.56g (N=21); environmental temperature for the neonatal nestlings should be controlled at 36°C; the feeding principle “having many meals but little food at each” for the nestlings should be followed; since six weeks after birth, nestlings of both gender began to show significant difference in body weight, the weight of male was 1.8 times of that of the female after fourteenth week, and by weight and body figure sexual identity could be easily discerned when 3 or 4 months old; There is no significant difference in growth and development of all organs between male and female nestlings and organ growth curves were fit into Logistic equation. Foundation items: This research was supported by “the 100-Young-Researcher Project” of Chinese Academy of Sciences (BR0301) and National Natural Science Foundation (30371149).     

The contribution of root respiration of<Emphasis Type="Italic">Pinus koraiensis</Emphasis> seedlings to total soil respiration under elevated CO<Subscript>2</Subscript> concentrations

The impacts of elevated atmospheric CO₂ concentrations (500 μmol·mol⁻¹ and 700 μmol·mol⁻¹) on total soil respiration and the contribution of root respiration ofPinus koraiensis seedlings were investigated from May to October in 2003 at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, Jilin Province, China. After four growing seasons in top-open chambers exposed to elevated CO₂, the total soil respiration and roots respiration ofPinus koraiensis seedlings were measured by a Li-6400-09 soil CO₂ flux chamber. Three PVC cylinders in each chamber were inserted about 30 cm into the soil instantaneously to terminate the supply of current photosynthates from the tree canopy to roots for separating the root respiration from total soil respiration. Soil respirations both inside and outside of the cylinders were measured on June 16, August 20 and October 8, respectively. The results indicated that: there was a marked diurnal change in air temperature and soil temperature at depth of 5 cm on June 16, the maximum of soil temperature at depth of 5 cm lagged behind that of air temperature, no differences in temperature between treatments were found (P>0.05). The total soil respiration and soil respiration with roots severed showed strong diurnal and seasonal patterns. There was marked difference in total soil respiration and soil respiration with roots severed between treatments (P<0.01); Mean total soil respiration and contribution of root under different treatments were 3.26, 4.78 and 1.47 μmol·m⁻²·s⁻¹, 11.5%, 43.1% and 27.9% on June 16, August 20 and October 8, respectively. Foundation item: This study was supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (KZCX1-SW-01) and the National Natural Science Foundation of China (30070158). Biography: LIU Ying (1976-), female, Ph. D. Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

Effect of elevated CO2 concentration on growth course of tree seedlings in Changbai Mountain

One-year-old seedlings ofPinus koraiensis, Pinus sylvestriformis, Phellodendron amurense were grown in open-top chambers (OTCs) with 700 and 500 ώmol/mol CO₂ concentrations, control chamber and on open site (ambient CO₂, about 350 ώmol/mol CO₂) respectively at the Open Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, and the growth course responses of three species to elevated CO₂ and temperature during one growing season was studied from May to Oct. 1999. The results showed that increase in CO₂ concentration enhanced the growth of seedlings and the effect of 700 (ώmol/mol CO₂ was more remarkable than 500 ώmol/mol CO₂ on seedling growth. Under the condition of doubly elevated CO₂ concentration, the biomass increased by 38% in average for coniferous seedlings and 60% for broad-leaved seedlings. With continuous treatment of high CO₂ concentration, the monthly-accumulated biomass of shade-tolerantPinus koraiensis seedlings was bigger in July than in August and September, while those ofPinus sylvestriformis andPhellodendron amurense seedlings showed an increase in July and August, or did not decrese until September. During the hot August, high CO₂ concentration enhanced the growth ofPinus koraiensis seedlings by increasing temperature, but it did not show dominance in other two species. Foundation Item: This paper was supported by Chinese Academy of Sciences and the Open Research Station of Changbai Mountain Forest Ecosystem.     

长白山阔叶红松林CO2廓线和CO2贮存的动态

从1999年8至10月,2000年的4至6月,2002年8月至2003年9月,在平均树高为26米的长白山阔叶红松林内,用红外气体分析仪(2250D,LI-CORInc.和LI-COR,820)测定了不同高度的二氧化碳浓度。根据测定的数据,分析了阔叶红松林二氧化碳廓线的日变化和季节变化动态。结果表明:CO2浓度的垂直分布在白天和夜间是不同的,在接近地面处CO2浓度始终最大。从季节CO2廓线看出,在植物生长季节林冠处CO2浓度有明显的成层现象,不同高度(60~2.5m)的CO2浓度3月份变化较小差值为10mmol穖ol-1,而在7月份变化较大,差值为60mmol穖ol-1。7月份林冠处(22,26,32m)CO2浓度梯度较大,浓度差为8mmol穖ol-1。计算位于涡度相关仪器之下的40米高空气柱中CO2贮存状况表明,年际贮存是负值,但对NEE的贡献很小。图4参11。     

Photosynthetic response ofPinus sylvestriformis to elevated carbon dioxide and its influential factor analysis

The photosynthetic response of 12-year oldPinus sylvestriformis to elevated CO₂ and its influential factors were tested and analyzed in the forest region of Changbai Mountain in 1999. Trees grown at the natural condition were controlled at three levels of CO₂ concentration (350 μL·L⁻¹, 500 μL·L⁻¹ and 700 μL·L⁻¹) by CO₂ rich settlement designed by us. Net photosynthetic rates (NPR), temperature, relative humidity, stomatal conductance, intercellular CO₂ concentration and photosynthetic active radiation (PAR) were measured at 6:00, 8:00, 10:00, 14:00, 16:00 and 18:00 hours a day. Experimental results showed that the NPR ofPinus sylvestriformis increased by 32.6% and 123.0% at 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ concentration respectively, compared to ambient atmospheric CO₂ concentration (350 μL·L⁻¹). The relations between NPR and influential factors, including temperature, relative humidity, intercellular CO₂ concentration and photosynthetic active radiation, were analyzed respectively by regression analysis at different CO₂ concentrations. Foundation Item: This project was supported by Chinese Academy of Sciences. Biography: WANG Chen-rui (1970-), male, Assistant Research Fellow in Institute of Applied Ecology, Chinese Academy of Sciences. Responsible editor: Chai Ruihai     

海岸林风害危险率评价的理论推导

本文在对间伐和风害之间关系的讨论和以往有关研究结果的基础上,确定了一种林木风害危险率的估计方法,用于评价间伐对林木风害的影响。这种对单株黑松及整个黑松林分的风害危险率估计,是根据风速廓线、枝条分布和透光分层疏透度(OSP)系数推导出来的。结果表明:如果枝条分布模型中的参数β等于单株树冠中风速廓线模型的衰减系数αs,参数H/D1.33可用于比较和评价对单株树木的风害危险率。这一原理也同样适用于整个林分,即用林分内风速廓线衰减系数α和透光分层疏透度(OSP)的分布中的衰减系数ν,结合D1.33估计和比较林分风害危险率。文中对间伐与非间伐单株黑松风害危险率进行了估计,得出了间伐两年后可以降低单株黑松风害危险率的结论;同时给出了确定林分风害危险率估计的过程图。图3参45。     

风对林木的影响

风除对森林造成了危害外,还对树木的生长、形态以及森林生态等产生影响。随着全球气候变化的发展,更多和更强的暴风出现的危险性日益增加。为了更好地理解风害对树木、林分和森林生态系统的影响,为森林经营管理提供依据,本文对近10年来国际上有关风对林木影响内容进行归纳总结。结果表明,风对林木影响的研究主要在以下几个方面取得了重要的进展：1)风与林木的空气动力学关系;2)树木在风力荷载下其适应性的生长机理;3)树木对风的生理响应：4)森林风害的危险评估。所有这些研究大都在人工用材林中进行的。此外,本文还介绍了该研究领域需要开展的其它研究,如1)天然林或天然次生林的风害研究;2)风害形成的林窗和森林动态研究;3)风害对森林生态主要过程的影响研究;4)．风害与森林管理研究。图3参61。     

Ecophysiological responses and carbon distribution ofPinus koraiensis seedlings to elevated carbon dioxide

The net CO₂ assimilation rate, stomatal conductance, RuBPcase (ribulose 1,5-biphosphate carboxylose) activity, dry weight of aboveground and belowgroud part, plant height, the length and diameter of taproot ofPinus koraiensis seedlings were measured and analyzed after six-week exposure to elevated CO₂ in an open-top chamber in Changbai Mountain of China from May to Oct. 1999. Seedlings were planted in four different conditions: on an open site, control chamber, 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ chambers. The results showed that the total biomass of the seedlings increased whereas stomatal conductance decreased. The physiological responses and growth to 500 μL·L⁻¹ and 700 μL·L⁻¹ CO₂ varied greatly. The acclimation of photosynthesis was downward to 700 μL·L⁻¹ CO₂ but upward to 500 μL·L⁻¹ CO₂. The RuBPcase activity, chlorophyll and soluble sugar contents of the seedlings grown at 500 μL·L⁻¹ CO₂ were higher than that at 700 μL·L⁻¹ CO₂. The concentration 500 μL·L⁻¹ CO₂ enhanced the growth of aboveground part whereas 700 μL·L⁻¹ CO₂ allocated more carbon to belowground part. Elevated CO₂ changed the carbon distribution pattern. The ecophysiological responses were significantly different between plants grown under 500 μL·L⁻¹ CO₂ and 700 μL·L⁻¹ CO₂. Foundation Item: This paper was supported by Chinese Academy of Sciences. Biography: HAN Shi-jie (1956-), male, Ph. Doctor, Professor in Laboratory of Ecological Process of Trace Substance in Terrestrial Ecosystem, Institute of Applied Ecology, Chinese Academy of Sciences. Responsible editor: Chai Ruihai     

农田防护林主要间距离的确定——基于林带结构与风速降低的关系

Relative windspeed reduction was measured behind nine relatively narrow, homogenous tree windbreaks with porosities between 0.13–0.33, and behind 28 combinations of model stubble barriers representing 25 different optical porosities (0.00–0.80). The optimum porosities observed were 0.25 and 0.13 for tree windbreaks and stubble barriers respectively. Based on the relationship between windbreak structure (optical porosity) and wind reduction, the chief indices for determining spacing interval, i.e., the windbreak structure index (δ) and the parameter of microclimate, represented by the problem wind (L _rp ), were determined. Additionally, investigations on shelterbelt trees were carried out, and stem-analysis techniques were used, to develop a method for determining the mature height of tree windbreaks (H ₀). Optimal spacing intervals between windbreaks could be predicted from the indices of a given windbreak structure, percentage of reduction of windspeed desired and tree growth model. A hypothetical example for determining the spacing interval of principal poplar windbreaks is given at the end of this paper. The results can be applied not only to tree windbreak design but also to other plant materials and artificial barriers for wind protection. Foundation item: This study was supported by Innovation Research Project of Chinese Academy of Sciences Biography: ZHU Jiao-jun (1965-), male, Ph. Doctor, PhD advisor. Professor of Institute of Applied Ecology, the Chinese Academy of Sciences, China, Scholar researcher of Faculty of Agriculture, Niigata University, Japan. Responsible editor: Song Funan     

不同浓度氨源引起的红松苗木根际pH变化及其对Fe、Mn、Cu、Zn有效性和吸收的影响

Dark brown forest soil was collected from the upper 20 cm soil layer in Changbai Mountain Research Station of Ecosystem, Chinese Academy of Sciences. The soil was amended with two different forms of nitrogen fertilizers: NO₃ as Ca(NO₃)₂, NH₄ ⁺ as NH₄Cl at the concentrations of 50, 100, 200 and 400 mg kg⁻¹respectively. The experiment was carried out with 2-yr-oldPinus koraiensis seedlings in pot. The pH change of rhizosphere soil and the contents of available Fe, Mn, Cu, and Zn in soil and leaves were analyzed. The result indicated that the addition of NH₄-N decreased the rhizosphere pH value, while the addition of NO₃-N increased the rhizosphere pH value in contrast with the control treatment. The direction and extent of the pH change mainly depended on N source and its concentrations applied. The rhizosphere pH change had a remarkable influence on the availability of the micronutrients in the rhizosphere, and thereafter affected the nutrient uptake by the seedlings. The contents of available mineral nutrients had a negative correlation with the pH value in the rhizosphere soil. The contents of available mineral nutrients in leaves were positively correlated to the levels of the available nutrients in the rhizosphere soils. Foundation item: This paper was supported by National Natural Science Foundation of China (Grant No. 30170167). Biography: CHEN Yong-liang (1969-), male, Ph. Doctor, lecture of Northeast Forestry University, Harbin 150040, Post-doctor in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan