马鹿和狍饲料植物的营养质量

本项研究测定了１４种木本植物的枝和叶以及苔草、非禾本和莎草科草、蕨、榆树皮的粗蛋白（ＣＰ）、中性洗涤纤维（ＮＤＦ）、酸性洗涤纤维（ＡＤＦ）、钙（Ｃａ）、磷（Ｐ）、钠（Ｎａ）、钾（Ｋ）等营养成分和体外干物质消化率（ＩＶＤＤＭ）。结果表明,各类饲料植物中营养成分的含量存在显著的差异（Ｐ＜０．０５）。木本植物叶中ＣＰ的含量在全年呈最高趋势,枝条中ＣＰ含量为最低;木本植物枝条中ＮＤＦ和ＡＤＦ的四季含量最高,非禾本和莎草科草中的ＮＤＦ和ＡＤＦ的含量最低。Ｃａ在木本植物的枝条和非禾本及莎草科草中的四季含量最高,在苦草中的含量最低;Ｋ在非禾本和莎草科草以及蕨类中的四季含量最高,在木本植物枝条中的含量最低;Ｐ和Ｎａ在各类饲料植物中的四季含量变化很大。木本植物枝条中ＣＰ含量的季变化很小,木本植物的叶、苔草、非禾本和莎草科草及蕨中ＣＰ的含量从春到秋逐渐减少。各类饲料植物中ＮＤＦ和ＡＤＦ在春季的含量明显地低于其它季节。Ｋ在各类饲料植物中的含量由春季到冬季呈下降趋势,而Ｃａ、Ｐ、Ｎａ在不同饲料植物中的含量表现出不同的季节变化。马鹿和狍对饲料植物干物质的体外消化率与饲料植物中ＣＰ的含量存在显著的正相关,与ＡＤＦ存在显著的负相关。     

闪电河流域6种农作物磷元素含量动态变化规律研究

本文报道了闪电河流域１５种植物磷含量特征及６种农作物含磷量的动态变化规律。结果表明：闪电河流域植物平均含磷量为１．３８±０．６２ｍｇ·ｇ￣（－１）,最高达２．２５ｍｇ·ｇ￣（－１）,最低只有０．８８ｍｇ·ｇ￣（－１）,与海河流域及锡林河流域植物磷含量基本一致。６种农作物在整个生长期间的磷含量变化规律表现为三种类型：禾本科植物小麦（Ｔｒｉｔｉｃｕｍａｅｓｔｉｖｕｍ）、莜麦（Ａｖｅｎａｎｕｄａ）和油料作物类亚麻（Ｌｉｎｕｍｕｓｉｔａｔｉｓｓｉｍｕｍ）,果实成熟期＞幼苗期＞营养期（Ｐ＜０．０５）;豆科作物豌豆（Ｐｉｓｕｍｓｅｔｉｖｕｍ）和蚕豆（Ｖｉｃｉａｆａｂａ）幼苗期＞营养期≥果实成熟期（Ｐ＜０．００１）;块茎类作物马铃薯（Ｓｏｌａｎｕｍｌｕｂｅｒｏｓｕｍ）则表现为营养期＞幼苗期＞果实成熟期（Ｐ＜０．００１）。６种农作物不同器官部位中根、茎、叶表现为幼苗期＞营养期＞果实成熟期（马铃薯除外）,而果实则为成熟后期＞果实形成期。不同器官磷含量比率的变化可反应磷在根、茎、叶、果４个器官的迁移清况,研究认为植物磷在幼苗期及营养期,通过根→茎→叶迁移,而在果实成熟期则通过根→茎叶→果途径运输。     

东灵山地区辽东栎叶养分的季节动态与回收效率

为探讨辽东栎叶的养分回收对种群的适应能力和生态系统的养分循环的意义,在东灵山地区分析了辽东栎叶中Ｎ、Ｐ、Ｋ、Ｃa、Ｍg、Fe等６种元素的浓度和单位叶面积含量,确定了了辽东栎叶养分的季节动态与回收效率。结果发现：１）６种元素的浓度和单位叶面积含量在叶的生活史中都发生了明显的季节变化,其中Ｎ、Ｐ、Ｋ等３种元素的浓度在展叶初期下降很快,阴后逐渐下降的,但单位叶面积含量是在７月下旬达到最大值;２）Ｃa浓度和单位叶面积含量整个生长季中一直保持上升趋势,Ｍg的季节变化无一定规律;３）Ｎ、Ｐ、Ｋ、Ｍg都有一定程度的回收,其中Ｎ、Ｐ的回收率分别为６７％和８７％,Ｃa、Ｆe在叶有所积累。为探讨叶养分回收效率在常绿和落叶植物中的差异,对栎属植物养分动态进行了比较分析。结果表明：１）落叶植物成熟叶中的Ｎ浓度稍高于常绿植物,但不显著,Ｎ的回收率与成熟叶中的浓度成显著正相关,;２）栎属植物的成熟叶和落叶中的Ｎ、Ｐ浓度间呈显著正相关。     

广西英罗湾红树植物幼苗矿质元素含量初步研究

木榄、秋茄、红海榄、白骨壤和桐花树幼苗是广西英罗湾红树林幼苗库中的主要成分。对这５种幼苗的Ｎ、Ｐ、Ｋ、Ｎａ和Ｃｌ进行了测定,结果表明：（１）Ｃｌ和Ｎａ的含量较高;（２）Ｃｌ和Ｎａ、Ｃｌ和Ｋ以及Ｎ和Ｐ含量之间存在着显著的相关性;（３）Ｎ的富集系数较高。     

青藏高原掌叶大黄和丽江大黄及其土壤的主要元素含量

采集掌叶大黄（Ｒｈｅｕｍ ｐａｌｍａｔｕｍ）和丽江大黄（Ｒｈｅｕｍ ｌｉｋｉａｎｇｅｎｓｅ）根茎、叶及根部土壤,应用ＩＣＰ测定主要元素含量特征,研究了２种大黄及其土壤的元素含量特征。结果表明,２种大黄土壤Ｐ含量远低于大黄根茎和叶,Ｆｅ含量则为土壤〉根茎〉叶,其中根茎与叶相差不大,但它们与土壤相差５０～１１０倍;Ｎａ、Ｍｎ、Ｃｕ含量在２种大黄中都表现为土壤〉叶〉根茎,Ｃａ含量在掌叶大黄中为土壤〈叶〈     

2,4—D和乙烯利对玉米幼苗抗旱性效应的研究

水分胁迫下,２０ｍｇ／Ｌ２,４－Ｄ和４００ｍｇ／Ｌ乙烯利（ＣＥＰＡ）分别不同程度地降低和提高玉米幼叶生长部位的相对含水量（ＲＷＣ）、水势（ψｗ）和渗透调节能力（ＯＡ）。胁迫后期,玉米幼叶中脯氨酸含量（Ｐｒｏ）为：ＣＥＰＡ〉对照（ＣＫｓ）〉２,４－Ｄ。随胁迫宾进行,２,４－Ｄ处理幼叶的膜相对透性（ＲＰ）始终处于较高水平且增长幅度较大,叶片延伸生长速率（ＬＥＲ）对ＲＰ的变化较为敏感;而ＣＥＰＡ处理则与     

菹草（Potamogeton crispus）对水中氮、磷的吸收及若干影响因素

菹草（Ｐｏｔａｍｏｇｅｔｏｎ ｃｒｉｓｐｕｓ）对水中氮、磷的吸收与ｐＨ、光照、水温、根／茎生物量比及底泥间隙水与上覆水中营养盐浓度比有关。在ｐＨ为８．０－９．５、水温为１９－２８Ｃ的实验条件下,水中ＮＨ＿４－Ｎ浓度低于０．３５ｍｇ·１左右时;菹草茎、叶优先吸收ＮＯ＿３－Ｎ;水中ＮＨ＿４－Ｎ浓度大于０．３５ｍｇ·１￣（－１）左右时,菹草则优先吸收ＮＮ＿４－Ｎ,这一选择吸收与ＮＨ＿４－Ｎ／ＮＯ＿３－Ｎ比值无关。强光照、高温（３０℃）和高ｐＮ的协同作用严重影响菹草硝酸盐还原酶活性。在自然条件下,菹草根部主要从底泥中吸收ＮＨ＿４－Ｎ、ＰＯ＿４－Ｐ,对ＮＯ＿３－Ｎ吸收甚微;茎、叶主要从水层中吸收ＮＯ＿３－Ｎ,对ＰＯ＿４－Ｐ吸收甚少。一般情况下,浮游植物和菹草对水体中的氮、磷吸收无多大矛盾。菹草倒伏后腐败分解释放大量营养盐,为浮游植物的增殖创造了条件。     

鼎湖山马尾松林营养元素的分布和生物循环特征

较系统地研究了鼎湖山马尾松林营养元素的分布和生物循环情况。马尾松林内各组分营养元素浓度总的规律为：针叶－细根－林下层植物－凋落物－树皮－树干;在树皮,树干和凋落物组分中各营养元素的排序为：Ｎ－Ｃａ－Ｋ－Ｍｇ－Ｐ,其它组分中则为：Ｎ－Ｋ－Ｃａ－Ｐ－Ｍｇ。马尾松林各营养元素的总贮量（ｋｇ／ｈｍ＾２）为：２２７８．５１（Ｎ＊）,２８０．０１（Ｐ）,５６７．９０（Ｋ）,４５６．８４（Ｃａ）,１４４．７６（     

有机物料在维持土壤微生物体氮库中的作用

采用室内和田间培养试验,研究了有机物料矿化过程中土壤微生物体氮的变化,测定结果表明,有机物料对矿化过程和微生物体氮的影响,既与有机物料本身性质和组成有关,也与土壤肥力水平和施氮与否有关。加入Ｃ／Ｎ比高的有机物料后,微生物对矿质氮的净固定持续时间长,而加入Ｃ／Ｎ比小的则固定时间短;高肥力土壤上的固定时间比低肥力土壤短。不同有机物料对土壤微生物体氮的影响不同。从加绿豆茎叶、小麦茎叶、未腐解马粪、腐熟马粪、腐熟猪粪到厩肥,土壤微生物体氮依次减小,提供的有效能源物质丰富（如绿豆茎叶）或Ｃ／Ｎ比较高（如小麦茎叶）时影响效果突出。土壤肥力不同,有机物料对微生物体的影响效果不同,在低肥力土壤的效果突出,约为高肥力土壤的４倍,因此,在评价有机物料对土壤微生物体氮的影响时,既考虑有有机物料的性质和组成,也考虑土壤力水平、矿质氮含量和培养时期。     

青心酮对妊娠高血压综合征胎盘血管内皮和平滑肌细胞内一氧化氮合酶的影响

本文对正常孕妇、妊娠高血压综合征（ＰＩＨ）患者和经青心酮（ＤＨＡＰ）治疗的ＰＩＨ患者等共２４例,应用组织化学分析方法观察胎盘血管内皮细胞（ＶＥＣ）和平滑肌细胞（ＶＳＭＣ）内一氧化氮合酶（ＮＯＳ）活性的变化。结果表明：正常孕妇胎盘ＶＥＣ和ＶＳＭＣ内ＮＯＳ活性较高;ＰＩＨ胎盘ＶＥＣ和ＶＳＭＣ内ＮＯＳ活性明显减弱,并伴有组织和细胞的形态学损伤;经ＤＨＡＰ治疗后的ＰＩＨ胎盘ＶＥＣ和ＶＳＭＣ细胞ＮＯＳ活性较未经ＤＨＡＰ治疗者明显增加,其组织和细胞损伤也减轻。本研究结果提示胎盘内ＶＥＣ和ＶＳＭＣ细胞的ＮＯＳ减少可能与ＰＩＨ的发生和／或发展有关,青心酮治疗ＰＩＨ的作用可能与ＤＨＡＰ促进胎盘ＶＥＣ和ＶＳＭＣ内一氧化氮（ＮＯ）合成有关。     

Changes in nutrient use efficiency, status and retranslocation in young post-fire regeneration Pinus halepensis in response to sudden N and P input, irrigation and removal of competing vegetation

The capacity of Mediterranean species to adapt to variable nutrient supply levels in a global change context can be a key factor to predict their future capacity to compete and survive in this new scenario. We aimed to investigate the capacity of a typical Mediterranean tree species, Pinus halepensis, to respond to sudden changes in N and P supply in different environmental conditions. We conducted a fertilisation, irrigation and removal of competing vegetation experiment in a calcareous post-fire shrubland with an homogeneous young (5 years old) population of P. halepensis in order to investigate the retranslocation and nutrient status for the principal nutrients (N, P, Mg, K, S, Ca and Fe), and the nutrient use efficiency (NUE) of the most important nutrients linked to photosynthetic capacity (N, P, Mg and K). P fertilisation increased P concentration in needles, P, N, Mg and K retranslocations, and NUE calculated as biomass production per unit of nutrient lost in the litterfall. The P fertilisation was able to increase the aboveground biomasses and P concentration 3 years after P fertiliser application. Those responses to P fertilisation were enhanced by the removal of competing vegetation. The N needle and litterfall concentration decreased after P fertilisation and this effect was greater when the P fertilisation was accompanied by removal of competing vegetation. The increase of P availability decreased the P-NUE and increased the N-NUE when these variables were calculated as aboveground biomass production per unit of P present in the biomass. Both P-NUE and N-NUE increased when calculated as total aboveground production per unit of nutrient loss. The results show that it is necessary to calculate NUE on a different basis to have a wider understanding of nutrient use. The irrigation did not change the needle nutrient concentrations and the litterfall production, but it significantly changed the nutrient litterfall concentrations and total aboveground contents (especially P and K). These results show a high capacity of P. halepensis to quickly respond to a limiting nutrient such as P in the critical phases of post-fire regeneration. The increase in P availability had a positive effect on growth and P concentrations and contents in aboveground biomass, thus increasing the capacity of growth in future periods and avoiding immediate runoff losses and leachate. This capacity also strongly depends on neighbour competition.     

神农架常绿落叶阔叶混交林凋落物养分特征

凋落物是联结陆地生态系统植物与土壤养分的重要媒介,了解凋落物养分特征有助于理解陆地生态系统物质循环的机理。该研究于2015年收集了神农架地区常绿落叶阔叶混交林的新鲜凋落物及现存凋落物,测定其不同器官中大量元素(C、N、P、K、Ca、Mg)的含量,据此分析其养分含量、养分归还量、养分储量及化学计量比的特征。结果发现:该常绿落叶阔叶混交林新鲜凋落物的C、K养分含量显著高于现存凋落物,N、P、Ca、Mg养分含量显著低于现存凋落物;其凋落物大量元素的养分归还量及养分储量大小顺序均为C Ca N Mg K P,分别为1569.84、52.44、34.82、6.24、5.24、1.30 kg hm~(-2) a~(-1)及1835.29、87.87、51.17、12.12、3.90、1.95 kg hm~(-2) a~(-1);其新鲜凋落物及现存凋落物的C∶N∶P分别为1307.33∶27.73∶1及976.48∶26.77∶1,新鲜凋落物的C∶N、C∶P显著高于现存凋落物,N∶P无显著区别。研究表明,新鲜凋落物与现存凋落物养分含量之间的差异与不同元素在分解过程中的可淋溶性及生物固持等因素有关。该地区常绿落叶阔叶混交林凋落物养分归还量及养分储量相对于亚热带阔叶林平均水平较低;且显著低于喀斯特地区同类型森林,主要与其凋落物产量、降水量及植被类型有关。该森林生态系统新鲜凋落叶与中国及全球范围内阔叶树种凋落叶相比C∶N较低,C∶P、N∶P较高,这可能是由于该地区N沉降及P限制现象较为严重所致。     

亚热带红壤侵蚀区马尾松针叶养分含量及再吸收特征

叶片衰老过程中的养分再吸收是植物适应养分贫瘠生境的一种重要策略,一直是生态学领域的研究热点。以亚热带红壤侵蚀区生态恢复先锋树种马尾松为研究对象,分析4种不同恢复水平下马尾松叶片养分含量随叶龄的变化情况及养分再吸收特征。结果表明:(1)叶片中N、P、K含量变化范围分别在(6.10±0.52)—(12.02±0.85)mg/g、(0.17±0.03)—(1.02±0.01)mg/g、(1.58±0.49)—(9.46±0.90)mg/g,随叶龄增长整体呈先增加后降低的趋势,具有一个快速积累期和一个相对漫长衰减期的动态特征,这表明叶龄也是影响叶片养分含量的重要因素;(2)叶片N、P、K含量随生境恢复水平的提高而增加,且N、P含量在除凋落叶外的叶龄阶段均表现出显著正相关,表明叶片中这两种营养元素在动态变化上存在协同性;(3)在叶片N、P、K再吸收效率中,P、K再吸收效率较高,而N相对较低。养分再吸收受生境中营养元素的含量水平、循环方式等因素的综合影响表现出一定选择性,对生境中较为贫瘠或使其生长受到限制的元素具有较高的再吸收效率。这不仅可以减小植物对外源养分的依赖性,同时也维持了体内重要营养元素的平衡。随叶龄增长叶片中N/P逐渐增大,反映出在叶片衰老过程中对限制元素P具有较强的再吸收能力,这种反馈调节提高了马尾松对养分贫瘠环境的适应性。本文的研究结果可为亚热带红壤侵蚀退化区先锋物种在贫瘠生境条件下的养分利用机制与适应对策方面的研究提供理论依据。     

Evaluation of sewage sludge, septic waste and sludge compost applications to corn and forage: yields and N, P and K content of crops and soils

This paper presents the data from two years of experiments concerned with the application of aerobically-digested sewage sludge, anaerobic lagoon septic sludge, sewage sludge compost or fertilizer to soils for grass forage and feed corn (Zea mays L.) production at two different sites 45 km from Truro, Nova Scotia. Crop yields, plant tissue and Mehlich-1 extractable soil nutrients were evaluated; 15 elements were analyzed in the plant tissue and nine elements in the soil extracts. This paper describes the results of crop yields, plant N, P and K content and Mehlich-1 extractable P and K. The research demonstrated the fertilizer produced higher yields of grass forage than the sludge and the compost but equivalent to the sludge in corn yields. Forage and corn N, P and K contents, however, varied with treatment, crop and year, while the compost-amended soils were highest in extractable nutrients. Both sludges and the compost, therefore, could be effective sources of N, P and K for crop production. Compared to the conventional fertilizer, the nutrient availability from the organic amendments (especially N and P) was considerably lower than the 50% assumed at the start of the experiment; the sludges however, provided higher nutrient availability than the compost.     

西双版纳望天树林土壤养分含量及其季节变化

 对西双版纳望天树(Shorea chinensis)林地0～10 cm和10～25㎝土层的有机质,全氮、磷、钾,速效氮、磷、钾等几种营养元素的含量状态及雨季前后的变化进行了研究。结果表明：土壤的养分含量变化为旱季结束＞雨季结束,沟谷地带雨林＞低山地带雨林,并且差异显著;表土0～10 cm是养分富集区,10 cm以下土层的养分含量锐减,两层养分含量对比,除钾元素以外均差异显著,表明望天树热带雨林生存的环境与植被的生活习性,对土壤养分的含量都有一定的影响。雨季对林地土壤的全钾和速效磷含量影响很大,对有机质、全磷和速效钾的含量影响较小,对氮素的影响是低山雨林＞沟谷雨林。雨季期间土壤中的磷素消耗到严重缺乏的水平。     

Nutrient balance and P,K, Ca,Mg, S and B accumulation in a Norway spruce stand following ammonium sulphate application,fertigation, irrigation,drought and N-free-fertilisation

The nutrient balance and above ground accumulation of macro nutrients, except for N, resulting from improved or deteriorated availability of water and nutrients in a 25 year old Norway spruce stand in SW Sweden is presented. The site and the productivity of the stand is typical for the area. Treatment include irrigation (I); artificial drought (D1); ammonium sulphate addition (NS); N-free-fertilisation (V) and irrigation with liquid fertilisers including a complete set of nutrients according to the Ingestad principle (IF). At start of the experiment the stand contained 86.5 t dry mass, 342 kg N, 33 kg P, 142 kg K, 172 kg Ca, 36 kg Mg and 34 kg S ha^-1. Enhanced accumulation vs control of S was seen in the NS and IF treatments. In the V and IF treatments P accumulation was 7–9 times higher and Ca and Mg, 2–4 times higher compared to the control. K accumulation was increased for the IF treatment. B that accumulated in the needles was decreased in the NS and D1 treatments and increased in the IF and V treatments, as compared to the control. The gross accumulation of nutrients relative to the amounts added was in the IF and V treatments 56 and 47% for P, 40 and 64% for K, 40 and 24% for Mg and, 22 and 8% for S, respectively. We conclude that application with N-free fertilizer, Skogvital (V), including macro nutrients and essential micro nutrients, results in a fast and efficient accumulation above ground of P, K, Ca, Mg and B. The treatment is efficient when aiming at restoring nutrient imbalances in Norway spruce. Application with ammonium sulphate at a rate of 5–6 times higher than the current deposition of N and S did not lead to decreased accumulation above ground of any of the macro nutrients P, K, Ca or Mg. The accumulation of B, however, was significantly reduced. Results from this and other studies indicate that today, N alone, generally is a growth limiting nutrient for Norway spruce in Southern Sweden.     

Dry matter production and partitioning in potato plants subjected to combined deficiencies of nitrogen, phosphorus and potassium

Three experiments examined effects on growth, dry matter partitioning and nutrient uptake in potato plants grown in large pots under different combinations of adequate and deficient levels of nitrogen, phosphorus and potassium. N supply affected the growth of all leaves, with low N reducing both the size of individual leaves and the extent of branch growth. P and K availability affected the growth of later formed leaves and only when both were deficient was branch growth substantially reduced. At later stages of growth, total green leaf area was significantly reduced by deficiency of each of the nutrients. Partitioning of dry matter to tubers was markedly reduced by K deficiency and increased in one experiment by P deficiency. When both P and K were deficient, partitioning approximated that under non‐limiting conditions. Leaf weight ratio (LWR) was higher under K deficiency, but not when P was also deficient, and was consistently higher when the ratio of K : P in dry matter was less than approximately five. In these experiments, LWR was not consistently related to shoot N% and N supply had relatively little effect on partitioning. There were large treatment effects on tuber dry matter percentage, characterised by significant interactions especially between N and K. Deficiency of one nutrient increased the concentration of others but uptake was highly regulated as crop content of all three nutrients was reduced when the supply of any one was deficient. The results show that the response of potatoes to single deficiencies may be influenced greatly by the levels of other nutrients.     

Nutrient distributions and bio-cycle characteristics in both natural and artificial Pinus tabulaeformis Carr. forests in hilly loess regions

Pinus tabulaeformis Carr. forest, the dominant community in Ziwuling Mountain lying in the hilly loess region, was studied for its nutrient distributions and bio-cycle characteristics in both natural and artificial forms. The results showed that the changes in the nutrient contents for different components in the same Pinus tabulaeformis Carr. forest stood in the order of needles > branches > bark > roots > bole. The aboveground nutrient elements in needles, branches, bark bole and litterfalls stood in the order of Ca > N > K > Mg > P, but the nutrients stored in the soil stood in the order of Ca > K > Mg > N > P. The accumulated amounts of nutrients increased first and then decreased with the increased age of the forest. The nutrient amounts reached their maximum when the stand was 30 years old, and decreased greatly when it was 50 years old. The 30-year-old artificial Pinus tabulaeformis Carr. forest had the highest annual accumulated amount of nutrients, and different stands stood in the order of II > III > IV > I. Comparatively, annual accumulated nutrients in different components stood in the order of needles > branches > roots > bark > bole. It was also suggested that the amounts of nutrients annually taken in from and retained in the natural Pinus tabulaeformis Carr. forest were significantly higher than those in artificial forests. The coefficients of nutrient use in various Pinus tabulaeformis Carr. stands stood in the order of Ca > Mg > N > K > P, but the nutrient use efficiency (NUE) of the same element decreased with increased age of the forest. There were no differences in the utilization coefficient and the turnover period of nutrients in both natural and artificial matured Pinus tabulaeformis Carr. forests.     

川西亚高山林线交错带植被凋落物量及养分归还动态

从2006—2008年,研究了川西亚高山林线交错带群落凋落物产量及N、P、K、Ca和Mg主要养分归还动态。结果表明:林线交错带植被凋落物年产量为389.83kg.hm-2.a-1,5种主要养分年归还量总量为15.82kg.hm-2.a-1,归还量排序为Ca>N>K>Mg>P。其中,叶、枝和其他混合杂物分别占凋落物总量的72.2%、17.9%和9.9%,占养分归还总量的87.4%、7.0%和5.6%。凋落物各组分及养分归还月动态均呈单峰曲线型变化,叶高峰期在9月,而枝、杂物则在10月。凋落物养分含量季节动态因不同凋落物组分和养分元素而异。叶凋落物中N、P、K和Mg含量在生长高峰的6、7月较高,而Ca含量较低;枝凋落物各元素含量总体上月变化不显著,其他混合杂物各元素含量6与10月相对较高,其余各月则无显著差异。     

Nutrient distributions and bio-cycle characteristics in both natural and artificial Pinus tabulaeformis Carr. forests in hilly loess regions

Pinus tabulaeformis Carr. forest, the dominant community in Ziwuling Mountain lying in the hilly loess region, was studied for its nutrient distributions and bio-cycle characteristics in both natural and artificial forms. The results showed that the changes in the nutrient contents for different components in the same Pinus tabulaeformis Carr. forest stood in the order of needles > branches > bark > roots > bole. The aboveground nutrient elements in needles, branches, bark bole and litterfalls stood in the order of Ca > N > K > Mg > P, but the nutrients stored in the soil stood in the order of Ca > K > Mg > N > P. The accumulated amounts of nutrients increased first and then decreased with the increased age of the forest. The nutrient amounts reached their maximum when the stand was 30 years old, and decreased greatly when it was 50 years old. The 30-year-old artificial Pinus tabulaeformis Carr. forest had the highest annual accumulated amount of nutrients, and different stands stood in the order of II > III > IV > I. Comparatively, annual accumulated nutrients in different components stood in the order of needles > branches > roots > bark > bole. It was also suggested that the amounts of nutrients annually taken in from and retained in the natural Pinus tabulaeformis Carr. forest were significantly higher than those in artificial forests. The coefficients of nutrient use in various Pinus tabulaeformis Carr. stands stood in the order of Ca > Mg > N > K > P, but the nutrient use efficiency (NUE) of the same element decreased with increased age of the forest. There were no differences in the utilization coefficient and the turnover period of nutrients in both natural and artificial matured Pinus tabulaeformis Carr. forests.