Introduction

The mineral status of plants is directly related to their growth and productivity.It is controlled by their genetically fi xed nutrient uptake potential,the nutrient availability in the soil,and other environmental factors(Cernusak et al.2010).Stand ages,soil variability,and changes in slope,elevation,topographic position,and climate interact to affect the mineral nutrition of trees.The complexity and site speci fi city of such interactions is probably the reason why the mineral nutrition of forest trees is still poorly understood.Therefore,it is not yet clear which of the environmental factors in Forest Ecosystems controls the nutrition of trees.Similarly,very little information is available on the relative amounts of nutrients taken up from the soil by forest trees.

“回首向来萧瑟处，也有风雨也有晴”。改革开放40年是中国制造业从低端走向中高端的关键发展阶段，在这个伟大的历史变革过程中，我们的制造业通过大浪淘沙涌现了一批有影响力的优秀企业。正是他们的坚守、成就与贡献，推动了行业转型升级，引领了行业发展方向，从而真正促进了中国制造业大踏步从高速度增长向高质量发展迈进。

Previous studies have reported that the mineral nutrient concentration in each component(leaf,stem,branch,and root)of forest trees varies widely due to stand age and environmental conditions,particularly heterogeneous soil properties(Masunaga et al.1998a;Domínguez et al.2010;You et al.2013).Vitousek and Sanford(1986)found that nutrient concentrations in individual components of forest trees are more likely to re fl ect the in fl uence of soil fertility.They added that,where a single species is found on two soils that differ in soil fertility,nutrient concentrations in individual components are usually quite similar.

Grubb(1977)observed that mountain forest trees are generally adapted to a relatively poor supply of N and P and thus,tend to have low concentrations of these mineral nutrients.Masunaga et al.(1998a,b)provided new insights into the nutrient characteristics of tropical rain forest trees although they did not relate these to the environmental conditions.The study found that concentrations of most elements were higher in the leaves than in the bark.The authors were also able to classify the trees as accumulators or excluders based on a novel statistical method they employed.In conclusion,among other things,differences in stand age result in wide variations in the nutritional characteristics of trees.In the literature,we could not fi nd similar studies that relate the nutrient status of the trees to environmental factors.

表1为条带SAR、定点聚束SAR、滑动聚束SAR三种工作模式下方位分辨率、方位测绘带宽及作用距离等指标对照情况，可看出定点聚束SAR模式天线波束地面照射区域固定，波束移动速度为0，方位向分辨率与天线波束方位向扫描角度范围有关，而其方位向测绘带宽Ls为方位向波束地面照射范围，Ls=R·θ，其中R为作用距离，θ为方位向波束宽度[2]。

Information on the mineral nutrition of temperate coniferous forest tree species is necessary for understanding the response of forest ecosystems to natural and anthropogenic perturbations,the selection of suitable native reforestation species of degraded areas,and sustainable forest management.Franzaring et al.(2010)found that mineral nutrition is the most important factor limiting the early growth of indigenous forest trees on degraded soils,which underscores the need for more information on the mineral nutrition of native tree species to enhance the use of such trees for the purpose of reforestation.

The objectives of this paper were to evaluate the nutrient status of the dominant tree species in the temperate coniferous forest of northwestern China and to determine its relationship with stand age and environmental factors such as elevation,slope,landscape position,soil pH and soil available nutrients.

表姐早动了心，她在大队当老师年底也就几百斤粮食。3 0 0块钱得一个公家人不吃不喝一年攒。表姐心里已经计划好这笔钱的用途，先买两个小猪娃，再把厨屋搭起来。到了过年，猪一卖，家里就缓过劲了……

Materials and methods

The study site is located on Qilian Mountain,northwestern China.Three forest districts were selected according to different stand ages and tree species(Fig.1).The sites were chosen because they were relatively undisturbed with no observable anthropogenic in fl uence and because of their landscape diversity and varying stand ages.

Study site

景天属（Sedum L.）植物的生命力旺盛，其具备对生长土壤要求不严、耐旱、抗寒、生长适应性强、易于栽培、管理方便等优点[1，2]。景天品种用途广泛，部分品种可代替草坪成片栽植，是北方目前有很好应用前景的园林观赏地被植物[3]。在景天草毯生产适宜品种筛选实验中，由于景天茎段扦插繁殖中，其生根率和根系发育状况与扦插基质、处理插穗的激素种类、浓度等因素有关。本实验运用了不同配比的栽培基质，对实验的6个景天品种茎段插条，采用了不同的IBA浓度处理，实验目的旨在探究不同栽培基质中，不同的IBA浓度处理对6个景天品种茎段扦插生根的影响。

Within the elevation range of 2100–3000 m,high vegetation biodiversity exists,indicating a phenomenon of vegetation(Franzaring et al.2010;Li et al.2012).Soils in these sites are arsenic and organic,according to the IUSS Working Group WRB(2006).Climatic data collected from May 2011 to October 2013 from four meteorological stations at altitudes of 1500,2100,2400,and 3000 m showed obvious differences in temperature and precipitation at these four elevations.They also showed a range in annual rainfall from 368.5 mm to 800 mm and a range in mean air temperature from 0.5 to 12.5°C.More detailed information on the forest status is presented in Table 1.

Figure 4 showed the average nutrient concentration of each component in the different aged stands.The order of N,P and K concentrations of the three tree species was middle-age＞young＞mature.The order of total nutrient concentration(N+P+K)of the different stand ages was also middle-age＞young＞mature.

Collection of plant tissue and soil samples

According to different stand ages(young 10–20 a,middleage 20–30 a,mature 30–40 a)and tree species(Picea crassifolia,Pinus armandii,Pinus tabuliformis),29 plots were set in the three forest regions with an area of 25 m×25 m.The subplots(sampling plots)were distributed as follows:9 in the Diebu forest region(34°01′N,103°16′E),10 in the Xiaolongshan Mountains(34°47′N,106°23′E),and 10 in the Qilian Mountains(38°32′N,100°15′E).

Soil properties were analyzed following the USDANRCS methodsas follows:soil pH by applying the potentiometric method to soil–water and soil-KCl solution mixtures in a ratio of 1:1;organic C by the modi fi ed Walkley–Black method;exchangeable K by extraction with 1 M ammonium acetate(pH 7.0)and determined by AAS(Hitachi,180-30 type);and available N by extractionwith 4 M KCl following incubation at 40°C for 7 days and then determined using the Kjeltec Autosampler System 1035 Analyzer;and available P and K by the Bray No.1 and the Mehlich No.1 methods,respectively(Soil Survey Laboratory Staff 1996).

We measured N,P,K in the soil by pro fi ling,according to each layer at 0–10,10–20,20–40,40–60,and 60–80 cm.We also used strati fi ed sampling:at each layer,three replicate samples of soil were taken,from which N,P,K values were measured.All plant tissue and soil samples were carried out from May 2013 to October 2013.This work was conducted,based on the following forestry standard,‘Observation Methodology for Long-term Forest Ecosystem Research’of the People′s Republic of China.

Chemical analysis

Elemental concentrations of powdered leaf and wood samples were measured after wet digestion,using an H2O2/H2SO4mixture(Jones Jr et al.1990)and atomic absorption spectrophotometry(AAS)for K;an auto sampler(Kjeltec auto sampler 1035 analyzer,Tecator)for N;and photometry for P after color development,following the molybdenum blue method(Murphy and Riley 1962).

Based on the method of scaling for each tree,we chose more than 2 cm in DBH and determination of DBH,tree height,crown width,and height under branch in the sample plot.Combined with the growth factor in the sample plot,we selected three standard sample trees to sample leaves,branches,trunks,roots.Annual leaves and perennial leaves were sampled and then fully mixed.Annual branches and perennial branches were sampled and then fully mixed.The dry samples of trunks were sampled at each 2 m.At each soil layer(20 cm divided 1 layers)we dug up all the roots,which include rootstock,coarse root(DR＞2.0 cm),middle root(1.0 cm＜DR≤2.0 cm),rootlet(0.5 cm＜DR≤1.0 cm),and fi brous roots(DR≤0.5 cm).We then determined the fresh weight of the samples,and crushed,bottled,and labelled the samples.

Fig.1 Geographical location of the long-term ecological research site in northwestern China

Table 1 The structural characteristics of vegetation at the different study sites

Stand ages:Yong(P.tabulaeformis,P.armandii and P.crassifolia:10–20 a);Middle-aged(P.tabulaeformis,P.armandii and P.crassifolia:20–30 a);Mature(P.tabulaeformis,P.armandii and P.crassifolia:30–40 a) Different standard deviation indicate signi fi cant level at p≤0.05 among different stand age in same location aPer 1000 trees

Location Species Stand ages densitya Heighta(m) Basal iametera(cm)Diebu Pinus tabulaeformis Young 879 2100–2200 300 18 0.52± 0.12 12.1± 1.4 7.4± 1.2 Midage No.of tree/ha Elevation(m)Aspect(°)Slope(°)Canopy 764 2100–2200 250 15 0.53± 0.11 14.9± 1.1 10.2± 1.1 Mature 791 2100–2200 260 22 0.62± 0.06 18.7± 0.9 14.6± 1.6 Xiaolongshan mountains 526 2350–2400 70 20 0.44± 0.09 16.4± 1.3 10.7± 1.5 Mature 734 2350–2400 200 15 0.76± 0.13 20.7± 2.1 15.6± 2.4 Qilian mountains Picea crassifolia Mature 811 2800–3000 340 7 0.83± 0.2 25.7± 2.4 18.4± 2.9 Pinus armandii Young 647 2350–2400 290 15 0.75± 0.15 11.7± 0.8 8.9± 1.3 Midage

Statistical analysis

最后借用何显斌教授的一句话:“只有当刑罚以正义和人道为基本价值取向的时候，刑法的价值—秩序和自由才能实现并确保和谐的共生关系。”［8］我们设立刑法是为了很好的维护正常的自由、秩序，而不是滥用刑罚。

The distribution pattern and concentration of mineral nutrients in the trees

We focused on the leaf,branch,stem,and root nutrient concentrations.Figure 2 shows the distribution of leaf,branch,stem,and root concentrations of P.tabulaeformis,P.armandii and P.crassifolia(we calculated the weighted average of the 3 stand ages).The results showed that the nutrient concentrations of P.tabulaeformis leaf,stem,and root were K＞N＞P,and those in the branch were N＞K＞P;for P.armandii,leaf,branch and root,we had N＞K＞P,and stem was N＞K＞P;and for P.crassifolia,leaf,stem and root,we had N＞K＞P,and branch was N＞K＞P.

For P.armandii and P.crassifolia,N,P,K content change trend were similar in the young forest,middle-age forest,and mature forest.The N,P,K content increased fi rst and then decreased from the young forest to mature forest,the N,P,K content of middle-age forest was highest.Figure 3 also showed that the leaves exhibited higher nutrient concentrations than the other components for the three species,P concentration were lower those of than N and K for each component in the different aged stands.

Concentration of mineral nutrients in different aged stand

Figure 3 shows statistical analysis of N,P,K content changes of P.tabulaeformis,P.armandii and P.crassifolia in different ages.For P.tabulaeformis:(1)the N,P content of leaves increased fi rst and then decreased from the young forest to the mature forest,The N,P content of the middleage forest was highest,but K content of leaves decreased from the young forest to mature forest;(2)the N,P,K content of branches increased fi rst and then decreased from the young forest to mature forest,the N,P,K content of mature forest was lowest;(3)the N,K content of stems decreased fi rst and then increased from the young forest to mature forest,the N,K content of middle-age forest was lowest,P had no obvious change;(4)the N content of roots increased from the young forest to mature forest,and the P,K content of roots increased fi rst and then decreased from the young forest to mature forest.

In general,among the macronutrients,P exhibited the lowest and narrowest concentration in each component(0.039–0.28 g kg-1,mean=0.12),whereas N exhibited the highest(0.095–1.72 g kg-1,mean=0.51).Among components,the leaves had the highest mineral nutrient concentration,and the order of the nutrient concentrations was leaf(0.54 g kg-1)＞branch(0.32 g kg-1)＞root(0.21 g kg-1)＞stem(0.14 g kg-1).P.armandii(0.45 g kg-1)had a higher nutrient concentration than P. tabulaeformis (0.19 g kg-1) and P. crassifolia(0.29 g kg-1).

采用机械挖土将基坑开挖至水层约-1.5m处，测量确定井点位置，然后在井位挖一个土坑，深度约为0.5m，以利于冲击孔时集水、埋管和灌砂，并将小坑之间用水沟与集水坑连接排水[2]。

Relationship between nutrient concentrations of trees and environmental factors

Fig.2 Nutrient concentrations distribution of leaf,branch,stem and root of P.tabulaeformis,P.armandii and P.crassifolia.Values=mean±SD(P.tabulaeformis,n=90;P.armandii,n=120;P.crassifolia,n=200)

Fig.3 Nutrient concentrations in each component of different age groups.a–d Leaf,branch,stem and root of P.tabulaeformis;e–h leaf,branch,stem and root of P.armandii;i–l leaf,branch,stem and root of P.crassifolia

Fig.4 Average nutrient concentration in different age groups of studied plant species

The environmental factors that we evaluated included slope,elevation,vegetation type,and soil nutrient status of the 0–10,10–20,20–40,40–60,and 60–80 cm layers in the A horizon,such as organic carbon,and available N,P,and K.Our data for the 5 soil depths revealed very similar relationships between these variables and the nutrient concentrations of each component,apparently due to very similar values of pH and nutrients across these 5 soil depths(Table 2).Hence,for the discussion,we placed emphasis on the fi rst soil depth(0–10 cm)only.It can also be seen in Table 2 that the soil at the study site is weakly basic and contains relatively high mineral nutrient concentrations.

Table 3 shows the Pearson’s correlation coef fi cients between the leaf,branch,stem,and root-nutrient concentrations and the environmental factors.Basically,it showed a negative association between the N,P,and K concentrations of each component and each item.Foliar N,P,and K were negatively correlated(p＜0.001)with available soil N,P,and K,respectively,while no relationships were found between the foliar nutrients and the slope.There wasa signi fi cant(p＜0.001)negative association between branch N and soil N,branch P and soil P(p＜0.05),as well as branch K and soil K(p＜0.01).Stem P and K were negatively correlated(p＜0.001)with elevation and soil K,respectively.Root N,P,and K were negatively correlated(p＜0.001)with elevation,and soil pH had a strong impact on the nutrient concentration in the roots.The soil available nutrients also affected the root nutrients.

Table 2 Average values of soil pH and nutrient status of the study sites(P.tabulaeformis was used as an example)

Different letters indicate signi fi cant different level at p≤0.05 among different treatments

Soil layer(cm) Location pH N(g kg-1) P(g kg-1) K(g kg-1)0–10 Xiaolong mountain 7.77b 2.28a 0.49a 13.22a Diebu 8.21b 1.27b 0.41a 17.71a Qilian mountain 7.60a 0.50ba 0.060b 12.14bc 10–20 Xiaolong mountain 7.74b 1.11a 0.63b 13.54a Diebu 8.02a 0.235a 0.42a 19.71b Qilian mountain 7.88b 0.58ab 0.061b 12.33b 20–40 Xiaolong mountain 7.85b 0.84a 0.38bc 13.28a Diebu 7.91b 0.21a 0.432a 15.53a Qilian mountain 8.00a 0.54bc 0.062a 12.33a 40–60 Xiaolong mountain 7.06b 0.69b 0.52ab 13.57bc Diebu 8.05b 0.12a 0.29ab 15.54b Qilian mountain 8.00b 0.44b 0.061a 12.25b Xiaolong mountain 7.25ab 0.99a 0.66b 12.31b Diebu 8.42a 0.067ab 0.33b 16.00ab Qilian mountain 8.00ab 0.35b 0.060ab 12.33ab

Table 3 Pearson correlation coef fi cients between nutrient concentration and environmental factors(P.tabulaeformis was used as an example)

*p＜0.05;**p＜0.01;***p＜0.001(n=90)

Component Nutrient concentration Elevation Slope Vegetation pH N P K Leaf N -0.34** -0.08 0.46** -0.29* -0.51*** -0.26* -0.21*P-0.45** -0.12 0.49** -0.30* -0.22* -0.64*** -0.34**K-0.31** -0.13 0.34** -0.29* -0.14 -0.08 -0.57***Branch N -0.42** -0.09 0.34** -0.35** -0.57*** -0.33** -0.24*P-0.31** -0.21* 0.41** -0.26* -0.33** 0.29* -0.15 K-0.21* -0.23* -0.40** -0.11 -0.24* -0.34** -0.36**Stem N -0.46** -0.16 0.35** -0.14 -0.26* -0.56*** 0.21*P-0.53*** -0.24* 0.21* -0.12 -0.48** -0.42** -0.24*K-0.26* -0.14 0.36** -0.04 -0.24* -0.34** -0.51***Root N -0.64*** -0.16 0.33** -0.56*** -0.58*** -0.25* -0.33**P-0.61*** -0.15 0.34** -0.44** -0.56*** 0.44** -0.24*K-0.57*** -0.24* -0.33** -0.59*** -0.31** -0.36** -0.61***

Discussion

We collected leaf,stem,branch,and root samples for nutrient analysis.Our results indicated that the analysis of each component was good,showed correlations with the nutrient concentrations in each component as well as with the environmental factors.This con fl icts with reports on the value of foliar analysis for the assessment of the nutritional status of forest trees(He et al.2008;Gartzia-Bengoetxea et al.2009).Some authors considered that the leaf is the focal point of many plant functions and is a relatively sensitive indicator of mineral nutrient status(Hessen et al.2007).Our results suggested that data on nutrient accumulation in plant components,including the leaf,branch,stem and root,can be useful in comparing nutrient status between different species and soils.

Comparing the mean values of the nutrient concentrations measured in this study with those reported for other temperate coniferous forests(Kang et al.2011;Mediavilla et al.2011)indicates that our values are in close agreement,especially with those of generally comparable geology and soil conditions.This implies that it is possible to compare the nutrient status of temperate coniferous forests with comparable environmental conditions despite considerable differences in species composition.This will allow the establishment of optimal and de fi cient levels of nutrients for temperate,coniferous forest stands,which were not clearly delineated until now(Michopoulos et al.2007;Minocha et al.2010;Li et al.2014).

The tendency for foliar nutrient concentrations in most tree species to occur at the higher end of their observed ranges can be ascribed to the low fertility of the soil,implying that soil directly in fl uences the nutrient concentrations of the trees.This also suggests that plants are able to depend on the high nutrient status of the soil by absorbing more nutrients.Chapin(1980)reported that slow-growing wild plant species,characteristic of low fertility soils,usually exhibit low nutrient absorption.

One-way ANOVA was performed to examine the differences in the investigated variables among forests,ecosystem components,and growth strategy.Pearson’s correlation coef fi cients were calculated between the nutrient concentration of each component and the environmental factors.All analyses were conducted using SPSS Statistics 18.0 for Windows.Statistically signi fi cant differences were set at a p value of 0.05 unless otherwise stated.

Temperate coniferous forests on low fertile sites have low nutrient concentrations and nutrient cycling ef fi ciency associated with nutrient limitations in forest ecosystems(Chapin 1980).Ecologists consider that low nutrient concentration in temperate coniferous forests is a defense mechanism to prevent the destruction of herbivores;it has recently been found that the frequency of this destruction was still high in temperate coniferous forests ecosystems(Chávez and Macdonald 2010).

The leaves of all three species had higher nutrient concentrations compared with the other plant components,and the leaves are the focal point of many plant functions and are also an accumulator organ.Wu et al.(2007)grouped tree species and organs into accumulators and excluders based on their nutrient status.Those with the ability to absorb relatively high amounts of nutrients are called accumulator species or organs.They found that the leaf and root are accumulator organs.

Grubb(1977)suggested that the selective uptake system in plant roots has a greater effect than leaf anatomy on the concentration of several mineral elements.On the other hand,the genus Helicia,with a very low concentration of nutrients,may be tolerant of such site conditions and are thus considered to be good species for reforestation.The absorption mechanisms of these tree species(those that can absorb high amounts and those that absorb very little)are scienti fi cally interesting and deserve further study.

The order of total nutrient concentration(N+P+K)in the different stand ages was the following:midage＞young＞mature,which is in accordance with natural laws.The middle-age forest is a vigorous growth period:the physiological function and nutrients absorptive capacity are very strong,so they need a lot of nutrient elements in soil t to meet the needs for their normal growth(Sariyildiz and Anderson 2005).The young forest is undergoing development,vitality is low,there is poor resistance to outside conditions,environmental factors affect normal growth,leading to poor soil nutrient absorption and insuf fi cient utilization(Vitousek et al.2010;Yu and Sun 2013).As forests mature,the result is poor physiological function digestion and poor absorption ability.Their absorption utilization rate is low to soil nutrient,so their nutrient content are low(Zhang et al.2012).

子虚手指一轮，一枚黑子直射到棋盘上，正是“东五南九”的腹地，虽然是孤军犯险，但跳出重围，弃子争先，也妙。

The very low concentration of P in the trees may be attributed to the low P availability in the soil.However,the narrow concentration range in the trees implies low nutrient absorption and requirement by the forest trees regardless of species.P is known to be the most limiting nutrient in many forest soils(Susaya and Asio 2005)and has been hypothesized to limit the productivity of forests(Wardle et al.2004).Our results tend to support this hypothesis.

土壤生态环境也具一定抗风险能力。其土壤微生物可促进Bt蛋白的降解。从转Cry1Ac基因水稻种植田土壤中得到降解Cry1Ac蛋白的细菌FJSB3，为寡养单胞菌(Stenotrophomonas sp.)，4 d内水稻秸秆中Cry1Ac蛋白降解率达到92. 86%[5-6]。新疆阿克苏盐碱地土壤细菌资源丰富，已分离培养盐碱地土壤中的细菌103株[7]，但目前新疆棉田Cry1Ac蛋白的降解研究鲜有报导。因此对Cry1Ac毒蛋白的降解细菌进行筛选和鉴定将可对长期种植转Bt棉田土壤的生态治理提供参考。

The effects of geomorphic factors are interrelated,and it is dif fi cult to isolate these factors.Slope is also related since it varies with topographic position.The variation in geomorphic factors results in considerable variation in soil properties and nutrient status.It is likely that vegetation differs in terms of composition at different elevations in response to these variations in environmental conditions(Webb and Donoghue 2005).Nevertheless,it appears that topographic position,vegetation type and soil nutrient status had the greatest effect on the nutrient concentration of the trees.The latter factor,however,was only true for some nutrients.

Conclusions

The P content in three species was the lowest,while N content was the highest.The nutrient content of leaves was the highest and the total nutrient elements of each organ were as follows:leaf＞branch＞root＞stem.From the young forest to mature forest,For P.tabulaeformis,the N,P content of leaves,the N,P,K content of branches and the P,K content of roots increased fi rst and then decreased;the N,K content of stems decreased fi rst and then increased;and P had no obvious change.The N content of roots increased from the young forest to the mature forest.For P.armandii and P.crassifolia,the N,P,K content increased fi rst and then decreased from the young forest to mature forest.Overall,P.armandii had a higher nutrient concentration than P.tabulaeformis and P.crassifolia.The nutrient content of each species is highest in the young forest,but lowest in the mature forest.The nutrient content of each tree species was signi fi cantly affected by soil nutrient content,and negatively correlated with soil-available nutrients.In addition,elevation and soil pH had a greater effect on root and dry nutrients.

Acknowledgements We appreciated the reviewer’s comments on the previous version of the manuscript,which helped us greatly improve the quality and readability of the paper.

所设计的低压变频器集成监控系统安装于测试现场使用。经一段时间的测试，系统稳定可靠，计算节能节电水平较好。系统通过对变频器运行过程与参数状态的监控，实现了对低压变频器的集成监控，该系统具备监控不同品牌、不同型号、只需具备MODBUS或USS两种通讯协议中任意一种低压变频器的功能。在变频器集成监控系统使用过程中，减少了人工巡检的工作量，提高了系统性的自动化水平，对工业系统的自动化水平提高具有一定的促进意义。

References

Cernusak LA,Winter K,Turner BL(2010)Leaf nitrogen to phosphorus ratios of tropical trees:experimental assessment of physiological and environmental controls.N Phytol 185(3):770–779

Chapin FS(1980)The mineral nutrition of wild plants.Annu Rev Ecol Syst 11:233–260

Chávez V,Macdonald SE(2010)The in fl uence of canopy patch mosaics on understory plant community composition in boreal mixedwood forest.For Ecol Manag 259(6):1067–1075

Domínguez MT,Marañón T,Murillo JM,Schulin R,Robinson BH(2010)Nutritional status of Mediterranean trees growing in a contaminatedandremediatedarea.Water AirSoilPollut205(1–4):305–321

Franzaring J,Holz I,Zipperle J,Fangmeier A(2010)Twenty years of biological monitoring of element concentrations in permanent forest and grassland plots in Baden-Württemberg(SW Germany).Environ Sci Pollut Res 17(1):4–12

Gartzia-Bengoetxea N,Gonzalez-Arias A,Mart ınez de Arano I(2009)Effects of tree species and clear-cut forestry on forestfl oor characteristics in adjacent temperate forests in northern Spain.Can J For Res 39(7):1302–1312

Grubb PJ(1977)Control of forest growth and distribution on wet tropical mountains:with special reference to mineral nutrition.Annu Rev Ecol Syst 8(1):83–107

He JS,Wang L,Flynn DF,Wang XP,Ma WH,Fang JY(2008)Leaf nitrogen:phosphorus stoichiometry across Chinese grassland biomes.Oecologia 155(2):301–310

Hessen DO,Jensen TC,Kyle M,Elser JJ(2007)RNA responses to N-and P-limitation;reciprocal regulation of stoichiometry and growth rate in Brachionus.Funct Ecol 21(5):956–962

IUSS Working Group WRB(2006)World reference base for soil resources 2006,2nd edn.World Soil Resources Reports No.203.FAO,Rome

Jones Jr JB,Case VW(1990)Sampling,handling and analyzing plant tissue samples.In:Westerman RL(ed)Soil testing and plant analysis,3rd edn.Soil Science Society of America,Madison,pp 389–427

Kang HZ,Zhuang HL,Wu LL,Liu QL,Shen GR,Berg B,Man RZ,Liu CJ(2011)Variation in leaf nitrogen and phosphorus stoichiometry in Picea abies across Europe:an analysis based on local observations.For Ecol Manag 261(2):195–202

Li LI,Xu XW,Sun YQ,Han W,Tu PF(2012)Effects of parasitic plant Cistanche deserticola on chlorophyll a fl uorescence and nutrient accumulation of host plant Haloxylon ammodendron in the Taklimakan Desert.J Arid Land 4(3):342–348

Li Y,Jing C,Mao W,Cui D,Wang X,Zhao X(2014)N and P resorption in a pioneer shrub(Artemisia halodendron)inhabiting severely deserti fi ed lands of Northern China.J Arid Land 6(2):174–185

Masunaga T,Kubota D,Hotta M,Wakatsuki T(1998a)Nutritional characteristics of mineral elements in leaves of tree species in tropical rain forest,West Sumatra,Indonesia.Soil Sci Plant Nutr 44(3):315–329

Masunaga T,Kubota D,William U(1998b)Spatial distribution pattern of trees in relation to soil edaphic status in tropical rain forest in west Sumatra,Indonesia.I.Distribution of accumulation.Tropics 7:209–222

Mediavilla S,González-Zurdo P,Escudero A(2011)Morphological and chemical leaf composition of Mediterranean evergreen tree species according to leaf age.Trees 25(4):669–677

Michopoulos P,Baloutsos G,Economou A,Samara C,Thomaidis NS,Grigoratos T(2007)Nutrient cycling and foliar status in an urban pine forest in Athens,Greece.Plant Soil 294(1–2):31–39

Minocha R,Long S,Thangavel P,Minocha SC,Eagar C,Driscoll CT(2010)Elevation dependent sensitivity of northern hardwoods to Ca addition at Hubbard Brook Experimental Forest,NH,USA.For Ecol Manag 260(12):2115–2124

Murphy J,Riley JP(1962)A modi fi ed single solution method for the determination of phosphate in natural waters.Anal Chim Acta 27:31–36

Sariyildiz T,Anderson JM (2005)Variation in the chemical composition of green leaves and leaf litters from three deciduous tree species growing on different soil types.For Ecol Manag 210(1):303–319

Soil Survey Laboratory Staff(1996)Soil Survey Laboratory methods manual.Soil survey investigations report,vol 42.National Soil Survey Center,Lincoln,NE,Version 3.0,USDA-NRCS

Susaya JP,Asio VB(2005)Status of phosphorus in the rain forest ecosystem of Mt.Pangasugan,Leyte,Philippines.Annals of Tropical Research

Vitousek PM,Sanford RL(1986)Nutrient cycling in moist tropical forest.Annu Rev Ecol Syst 17:137–167

Vitousek PM,Porder S,Houlton BZ,Chadwick OA(2010)Terrestrial phosphorus limitation:mechanisms,implications,and nitrogen–phosphorus interactions.Ecol Appl 20(1):5–15

Wardle DA,Walker LR,Bardgett RD(2004)Ecosystem properties and forest decline in contrasting long-term chronosequences.Science 305(5683):509–513

Webb CO,Donoghue MJ(2005)Phylomatic:tree assembly for applied phylogenetics.Mol Ecol Notes 5(1):181–183

Wu CC,Tsui CC,Hseih CF,Asio VB,Chen ZS(2007)Mineral nutrient status of tree species in relation to environmental factors in the subtropical rain forest of Taiwan.For Ecol Manag 239(1):81–91

You WZ,Wei WJ,Zhang HD,Yan TW,Xing ZK(2013)Temporal patterns of soil CO2 ef fl ux in a temperate Korean Larch(Larix olgensis Herry.)plantation,Northeast China.Trees 27(5):1417–1428

Yu M,Sun JXO(2013)Effects of forest patch type and site on herblayer vegetation in a temperate forest ecosystem.For Ecol Manag 300(300):14–20

Zhang YT,Li JM,Chang SL,Li X,Lu JJ(2012)Spatial distribution pattern of Picea schrenkiana population in the Middle Tianshan Mountains and the relationship with topographic attributes.J Arid Land 4(4):457–468