Effect of nitrogen and phosphorus addition on leaf nutrient concentrations and nutrient resorption efficiency of two dominant alpine grass species

Nitrogen(N)and phosphorus(P)are two essential nutrients that determine plant growth and many nutrient cycling processes.Increasing N and P deposition is an important driver of ecosystem changes.However,in contrast to numerous studies about the impacts of nutrient addition on forests and temperate grasslands,how plant foliar stoichiometry and nutrient resorption respond to N and P addition in alpine grasslands is poorly understood.Therefore,we conducted an N and P addition experiment(involving control,N addition,P addition,and N+P addition)in an alpine grassland on Kunlun Mountains(Xinjiang Uygur Autonomous Region,China)in 2016 and 2017 to investigate the changes in leaf nutrient concentrations(i.e.,leaf N,Leaf P,and leaf N:P ratio)and nutrient resorption efficiency of Seriphidium rhodanthum and Stipa capillata,which are dominant species in this grassland.Results showed that N addition has significant effects on soil inorganic N(NO_(3)^(-)-N and NH_(4)^(+)-N)and leaf N of both species in the study periods.Compared with green leaves,leaf nutrient concentrations and nutrient resorption efficiency in senesced leaves of S.rhodanthum was more sensitive to N addition,whereas N addition influenced leaf N and leaf N:P ratio in green and senesced leaves of S.capillata.N addition did not influence N resorption efficiency of the two species.P addition and N+P addition significantly improved leaf P and had a negative effect on P resorption efficiency of the two species in the study period.These influences on plants can be explained by increasing P availability.The present results illustrated that the two species are more sensitive to P addition than N addition,which implies that P is the major limiting factor in the studied alpine grassland ecosystem.In addition,an interactive effect of N+P addition was only discernable with respect to soil availability,but did not affect plants.Therefore,exploring how nutrient characteristics and resorption response to N and P addition in the alpine grassland is important to understand nutrient use strategy of plants in terrestrial ecosystems.

Effects of Different Fertilization Treatments on Soil, Leaf Nutrient and Fruit Quality of Citrus grandis var. longanyou

The five-year-old “Longanyou” trees were used as the experimental material to study the effects of different fertilization treatments. The nutrient contents in soil and leaves, fruit yield and quality were determined, and then the correlations were analyzed. The results showed that: 1) The soil nutrient contents of 0 - 20 cm depth were more than the 20 - 40 cm, and the trends of nutrient contents of the 0 - 20 cm soil layers were as follows: treatment 2 (T2) > treatment 3 (T3) > treatment 4 (T4) > treatment 1(T1) > control (CK). However, the 20 - 40 cm depth had not significant difference between different treatments, but T2, T4 and T3 were higher than T1 and CK. It indicated that the soil effective nutrient content increased in T2 and T3. 2) Compared with the control, the content of K and B elements was improved obviously in leaves with the increase of organic manure application. The contents of P (1.60 g·kg-1), B (26.00 mg·kg-1) and Mg (1.18 g·kg-1) were the highest, and other nutrients contents were also higher, indicating that T2 could effectively improve the leaves’ nutrient contents. 3) The fruit yield per plant was the highest in T2 (95.40 kg plant-1), and the single fruit weight, total sugar, sugar and acid ratio, vitamin C were also the highest, but titratable acid was lower. It indicated that T2 effectively improved fruit yield and quality. 4) There were positive correlations between multiple factors of soil nutrients and the quality index, such as fruit peel thickness, total sugar, solid acid ratio, sugar and acid ratio, Vc content and single yield etc. There was significant correlation between K, B, Zn, Fe contents and fruit yield and quality index, and the contents of B, Zn and Fe in leaves were significantly correlated with soil nutrient, indicating that the contents of K, B, Zn, Fe in soil and leaf were closely related to fruit yield and quality. In sum, the T2 was the best fertilization scheme for orchard management practice of “Longanyou”.

Soil Nutrient Status and Leaf Nutrient Diagnosis in the Main Apple Producing Regions in China

Soil and leaf nutrient analysis are widely used as effective methods of diagnosing nutrient deficiency in fruit trees,the results of which are used to properly manage fertilizer application.Therefore,a survey was conducted for assessment of the soil nutrient status and leaf nutrient concentration in 2 827 apple orchards in the Bohai Bay and Loess Plateau apple production regions of China.The soil organic matter,alkali hydrolyzable N,available P,and available K were 10.91 g·kg^(-1),73.21 mg·kg^(-1),70.22 mg·kg^(-1),and 169.23 mg·kg^(-1)in the Bohai Bay region,respectively,and 11.72 g·kg^(-1),56.46 mg·kg^(-1),14.91 mg·kg^(-1),and 135.78 mg·kg^(-1)in the Loess Plateau region,respectively.Soil organic matter was at a medium-to-low level in both regions,whereas the soil alkali hydrolyzable N was low.In the Bohai Bay region,soil available P was high,but soil available K was deficient.In contrast,both soil available P and K were insufficient in the Loess Plateau region.The Diagnosis and Recommendation Integrated System(DRIS)diagnostic results indicated that the most deficient elements were Ca and K in low-yielding orchards(<35 t·hm(-2))of the Bohai Bay region followed by Fe,N,and Zn;however in the Loess Plateau region,the most deficient elements were P and K followed by N,Zn,and Cu.The findings imply that the application of Ca,K,Fe,N,and Zn fertilizer should be increased in the Bohai Bay region,whereas P,K,N,Zn,and Cu fertilizer should be enhanced in the Loess Plateau region.Meanwhile,use of organic manure is recommended to improve soil quality in the two apple producing regions.

Soil and Leaf Micronutrient Composition in Contrasting Habitats in Podzolized Sands of the Amazon Region

Plant macronutrient distribution in podzolized sands of the Amazon caatinga has received attention in several studies;however, the distribution of micronutrients has not been assessed. Soil micronutrient availability has been hypothesized to reflect contrasting habitat characteristics as well as fundamental differences in substrate, and leaf micronutrient composition may reflect the macronutrient content needed to maintain balance for leaf cell functions. In this study, soil and leaf samples were obtained in a toposequence (valley, slope, and mound). Available soil micro- and macronutrients as well as total leaf content were measured by inductively coupled plasma-atomic emission spectrometer and mass spectroscopy. Soil Zn (-1) and B (-1) as well as Cu (-1) levels were very low. Soil Mn was low in the valleys and slopes (0.62-0.87 mg·kg-1), but higher in the mound (6.59 mg·kg-1). Soil Fe (11.48-21.13 mg·kg-1) was well above the critical level in all of the habitats. Leaf micronutrients Cu, B, Zn, and Fe were below the critical levels for tropical crops of 3-7, 20-70, 15-20, and 72 mg·kg-1, respectively. Leaf Mn (88 mg·kg-1) and Al (<50 mg·kg-1) were below the accumulators level. A strong relationship between leaf micro- and macronutrients suggests the maintenance of a homeostatic elemental composition, which may favour photosynthetic function. Therefore, the local distribution of species may be shaped by their abilities to maintain a balance of micronutrient collected through roots under critically low levels of available Zn, B, and Cu whilst excluding potentially deleterious ions of Mn, Fe, and Al.

Standardization of Leaf Sampling Technique in Jackfruit Nutrient Status Diagnosis

In China, little information is known about the nutrient requirements of jackfruits and the traditional nutrient management usually depends on the experience. Therefore, in this study, an attempt was made to standardize the leaf sampling technique and the suitable range of leaf nutrient concentrations for jackfruit (Artocarpus heterophyllus Lam.) nutrient status diagnosis. The sampling result was affected by canopy height, leaf age and time of sampling. Therefore, the three factors were studied. The results illustrated that the stability in level of nutrient concentrations was in 3 - 6 month-old leaves from the central part of the canopy. The most stable period was from April to May for leaf sampling. It was recommended that the stable intracanopy and stable period of nutrient concentrations could be used as the standards of leaf sampling technique. Based on the leaf sampling technique, the standard of leaf nutrient concentrations was summarized, and could be used as the standard of nutrient suitability evaluation.

Determination of Nutrient Contents in the Leaf Litter of <i>Diospyros crassiflora</i>S. (Hiern-FWTA) Plantation in Okwuta-Ibeku, Umuahia, Abia State, Nigeria

Determination of nutrient contents in Diospyros crassiflora leaf litter was carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku, Umuahia, Abia State, Nigeria in 2016 and 2017. Three 1 m × 1 m trays were randomly positioned for collection of leaf litter production from 4/5 years old Diospyros crassiflora species in each block (10 m × 25 m) within the plantation totaling 1.5 ha. A Randomised Complete Block Design (RCBD) with three replicates was used to study the mean monthly leaf litterfall of Diospyros crassiflora. Leaf litter was collected from each of the three litter trays per block and placed in paper bags every 28th day of each month from January-December in 2016 and in 2017. Fifteen grammes (15 g) of properly mixed and oven-dried samples of D. crassiflora leaf litter were milled and sieved in 1 mm sieve;0.3 g was used to determine nutrient elements and their concentrations. The data obtained from mineral nutrient contents of D. crassiflora leaf litter was analysed using analysis of variance. Result reveals the mean concentrations of nitrogen (1.41 and 1.41 mg·l-1), phosphorus (0.18 and 0.18 mg·l-1), potassium (0.68 and 0.68 mg·l-1), sodium (0.35 and 0.30 mg·l-1), calcium (1.57 and 1.56 mg·l-1), magnesium (0.32 and 0.31 mg·l-1), chlorine (0.25 and 0.24 mg·l-1), Organic carbon (0.03 and 0.03 mg·l-1) and Organic matter (1.17 and 1.18 mg·l-1) etc. in D. crassiflora leaf litter in January-December (2016 and 2017). The study shows almost uniform distribution of mineral elements concentrations in 2016 and 2017.

控释尿素与普通尿素配施对橡胶树叶片和胶乳养分及产量的影响

为了明确控释尿素与普通尿素配施在橡胶树上的应用效果,通过2年田间试验,研究了减氮条件下控释尿素与普通尿素不同比例配施对橡胶树产量、叶片和胶乳矿质养分及土壤氮含量的影响,为橡胶树栽培管理中合理施氮提供技术支撑。结果表明:控释尿素与普通尿素配施可提高橡胶树干胶产量和叶片氮含量,与常规施肥相比,橡胶树干胶产量增幅为16.28%~39.13%(2021年)和7.94%~9.69%(2022年),叶片氮含量增幅为10.54%~19.17%(2021年)和10.24%~21.50%(2022年),控释尿素与普通尿素配施处理叶片氮含量均处于正常值以上。控释尿素与普通尿素配施还能够增加胶园肥穴土壤碱解氮含量,较常规施肥增加了11.27%~80.36%。控释尿素与普通尿素配施比例为50∶50时,橡胶树干胶产量(2022年)、叶片氮含量(2021—2022年)和土壤碱解氮含量(2021—2022年)均显著高于常规施肥。综上所述,在本试验条件下,控释尿素与普通尿素配施比例为50∶50能够获得较高的干胶产量,可改善叶片营养状况,维持土壤氮水平,有利于实现橡胶树施肥管理的绿色协同增效。

高接换种对核桃枝条和根系生理特征的影响

为探究高接换种对核桃枝条和根系生理特征的影响,对定植10年的实生砧+‘香玲’进行高接换种‘清香’,以短截更新为对照,成活3年后比较分析1年生枝和根系生理特征差异。结果表明:(1)高接后1年生枝导管密度为76.82 N/mm^(2),平均长度为39.85 cm,叶片N、K元素含量分别为27.20、7.17 g/kg,显著高于更新处理(P<0.05),说明高接提高了养分运输和树冠恢复效率。(2)更新处理20~40 cm土层根系导管直径为86.55μm,0~20 cm土层根系导管平均密度为149.33 N/mm^(2),显著高于高接处理(P<0.05),说明高接‘清香’一定程度上改变了根系结构。(3)高接后0~20 cm土层根系韧皮部厚度/枝条半径比例为0.39,其根系平均长度、直径、周皮厚度分别达到10.64 cm、2.36 mm和70.09μm,显著高于更新处理(P<0.05),说明高接‘清香’后,光合产物倾向于分配到0~20 cm土层根系。(4)高接‘清香’核桃后,1年生枝和20~40 cm土层根系形成层厚度分别达到36.26、76.42μm,显著高于更新处理(P<0.05),说明其具有较强的增粗生长潜力。综上,高接‘清香’核桃改变了‘香玲’核桃1年生枝和根系输导结构,提高了养分运输效率,促进了树冠和地表根系的生长。

Degree of shade tolerance shapes seasonality of chlorophyll, nitrogen and phosphorus levels of trees and herbs in a temperate deciduous forest

Forest productivity is closely linked to seasonal variations and vertical differentiation in leaf traits.However,leaf structural and chemical traits variation among co-existing species,and plant functional types within the canopy are poorly quantified.In this study,the seasonality of leaf chlorophyll,nitrogen(N),and phosphorus(P)were quantified vertically along the canopy of four major tree species and two types of herbs in a temperate deciduous forest.The role of shade tolerance in shaping the seasonal variation and vertical differentiation was examined.During the entire season,chlorophyll content showed a distinct asymmetric unimodal pattern for all species,with greater chlorophyll levels in autumn than in spring,and the timing of peak chlorophyll per leaf area gradually decreased as shade tolerance increased.Chlorophyll a:b ratios gradually decreased with increasing shade tolerance.Leaf N and P contents sharply declined during leaf expansion,remained steady in the mature stage and decreased again during leaf senescence.Over the seasons,the lower canopy layer had significantly higher chlorophyll per leaf mass but not chlorophyll per leaf area than the upper canopy layer regardless of degree of shade tolerance.However,N and P per leaf area of intermediate shade-tolerant and fully shade-tolerant tree species were significantly higher in the upper canopy than in the lower.Seasonal variations in N:P ratios suggest changes in N or P limitation.These findings indicate that shade tolerance is a key feature shaping inter-specific differences in leaf chlorophyll,N,and P contents as well as their seasonality in temperate deciduous forests,which have significant implications for modeling leaf photosynthesis and ecosystem production.

3种寄主植物对白刺夜蛾生长发育、繁殖和寿命的影响

白刺夜蛾Leiometopon simyrides是荒漠植物白刺的重要害虫,为明确寄主植物对白刺夜蛾生长发育的影响,以便对其进行科学监测和防控,本研究在27℃下,利用3种寄主植物(大果白刺、泡泡刺、唐古特白刺)饲养白刺夜蛾,观察记录白刺夜蛾幼虫的取食量、各阶段的发育历期、存活率、羽化率、雌雄性比和成虫寿命等生物学特性,同时测定各寄主植物叶片的营养和次生代谢物质含量。结果表明,白刺夜蛾幼虫取食大果白刺叶片的总量最少,取食唐古特白刺的量最多。取食唐古特白刺的白刺夜蛾幼虫发育历期最短,其次为取食泡泡刺,取食大果白刺时历期最长。取食泡泡刺和唐古特白刺后,白刺夜蛾幼虫的存活率和羽化率较高,取食大果白刺存活率最低,且无成虫羽化。在唐古特白刺上,白刺夜蛾雌虫占比较高,成虫寿命较长。大果白刺的叶片总酚含量和简单酚含量最高,各营养物质含量最低,不利于白刺夜蛾的生长发育;唐古特白刺和泡泡刺酚类物质含量较低,营养物质含量较高,较适宜白刺夜蛾的生长发育和繁殖。唐古特白刺为白刺夜蛾的最适宜寄主植物,其次为泡泡刺。

不同微生物添加剂对辣木茎叶青贮感官评价、营养成分及发酵品质的影响

试验旨在研究不同微生物添加剂对辣木茎叶青贮感官评价、营养成分及发酵品质的影响。试验以辣木茎叶为底物,对照组中不添加微生物制剂,试验组分别添加植物乳杆菌(A组)、酵母菌(B组)、枯草芽孢杆菌(C组)、植物乳杆菌+酵母菌(D组)、酵母菌+枯草芽孢杆菌(E组)、植物乳杆菌+枯草芽孢杆菌(F组)、植物乳杆菌+酵母菌+枯草芽孢杆菌(G组),每组3个重复,青贮30 d,测定辣木茎叶青贮的感官、营养成分及发酵品质。结果显示:对照组辣木茎叶青贮感官评价分数最低,为12分,D组、E组、F组、G组辣木茎叶青贮得分为18~19分,等级为一级优良。与对照组比较,除A组外,其余微生物添加剂组辣木茎叶青贮的粗蛋白(CP)含量均显著升高(P<0.05),D组、E组、F组和G组中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)含量显著降低(P<0.05),所有微生物添加剂组木质素(ADL)含量均显著降低,相对饲喂价值(RFV)显著升高(P<0.05)。与对照组比较,所有微生物添加剂组辣木茎叶青贮的pH值均显著低于对照组(P<0.05),且低于4.2,D组、E组、F组和G组青贮饲料的氨态氮(NH3-N)含量显著降低(P<0.05),所有微生物添加剂组辣木茎叶青贮的乳酸(LA)含量均显著升高(P<0.05);所有微生物制剂组辣木茎叶青贮中的植酸含量均显著降低(P<0.05)。研究表明,辣木茎叶青贮过程中添加植物乳杆菌、酵母菌及枯草芽孢杆菌均可不同程度地改善感官评分、营养品质及发酵品质,且以植物乳杆菌+酵母菌+枯草芽孢杆菌组效果最好。

黄芪茎叶提取物对仔猪生长性能、养分表观消化率及免疫指标的影响

文章旨在探究添加不同水平黄芪茎叶提取物对断奶仔猪生长性能、养分表观消化率及免疫机能的影响。试验将120头健康的体重(25±0.5)kg的“杜×长×大”三元杂交仔猪随机分成4组,每组3个重复,每个重复组10头,试验分别在基础日粮中添加0(1组)、1.0%(2组)、1.5%(3组)、2.0%(4组)黄芪茎叶提取物,预饲期10d,整个试验为期56d。结果表明:(1)试验3、4组平均日增重较1组分别显著提高11.6%、10.1%(P <0.05),其料重比较1组分别显著降低9.4%、7.0%(P <0.05);(2)试验3、4组粪便中的粗蛋白质、粗脂肪、粗纤维的养分表观消化率较1组分别显著提高10.9%、10.8%、10.8%、11.2%、16.5%、15.9%(P <0.05);(3)试验3、4组血清中IgA、IgG、IL-2含量较1组分别显著提高10.8%、11.7%、12.0%、13.7%、22.9%、25.1%(P <0.05),其血清中TNF-α含量较1组分别显著降低20.8%、22.1%(P <0.05)。综上所述,添加1.5%黄芪茎叶提取物可以提高“杜×长×大”二元杂交仔猪的生长性能、养分表观消化率及免疫机能。

Relationship between Leaf Micro- and Macro-Nutrients in Top Canopy Trees in a Mixed Forest in the Upper Rio Negro in the Amazon Region

The mixed forests of the upper Rio Negro at the northern of the Amazon basin grow in oxisol soils that are extremely infertile. These areas exhibit deficiencies in several macro-nutrients, and may also be characterized by the shortage or toxic excess of some micronutrients. The overall goal of this research is to collect more comprehensive information regarding the micronutrient composition of the upper Rio Negro forests as well as discern the relationship between leaf micro- and macro-nutrients that may contribute to the homeostasis and balance of the ionome. Firstly, the nutrient composition within the oxisol soil and leaf tissues of two top canopy tree species from the mixed forests was determined. We then analyzed the relationship between leaf micronutrient composition with N and P levels of the two species and that of species inhabiting the Amazon caatinga. Extractable soil Zn, B, Mn and Cu were very low in the mixed forest. In contrast, Fe and Al levels were potentially toxic. The analysis of leaf N/P ratios revealed for the first time the co-limitation of N and P in the mixed forest. This contrasts with species from the adjacent Amazon caatinga toposequence that are characterized by strong N limitation. All micronutrients within leaves of species inhabiting the mixed forest were also found to have low concentrations. Moreover, Fe and Al were detected at concentrations well below those reported for accumulator species. This suggested that leaf ion homeostasis was maintained under potentially toxic soil Fe and Al conditions. Leaf micronutrient (Fe, Zn and B) contents mirrored that of leaf N and P contents, and comparable Fe/N, Fe/P, Zn/N, Zn/P, B/N as well as B/P ratios were found across species and forest types. Therefore, forest species exhibited the capability to maintain leaf nutrient balances under soil conditions with deficient or toxic levels of micronutrients.

动物源营养液对卷叶霸王空气凤梨新叶生长及矿质元素含量影响

为分析动物源营养液在空气凤梨上的应用效果,以‘卷叶霸王’空气凤梨为研究对象,以清水作对照,研究动物源营养液、磷酸二氢钾、尿素喷施后对空气凤梨新叶生长、单株增重、光泽度及矿质元素含量等的影响。结果表明,动物源营养液中含有钙、镁、铁、锌、硼和锰等矿质元素,空气凤梨在各种处理后3月内都没有新根萌出,均未出现肥害与微量元素中毒现象,光泽度没有明显差异。2.50‰营养液处理的第1小叶生长率增加41.58%,增加幅度最大。0.10‰动物源营养液处理单株增重率最高,2.50‰、0.50‰营养液处理次之;不同浓度动物源营养液处理间单株增重率差异不显著。与CK相比,3.33‰营养液处理、1.00‰营养液处理显著增加空气凤梨新叶内钙、镁、铁和锰含量,3.33‰动物源营养液处理的钙含量增加27.80%,镁含量增加23.71%,铁含量增加10.75%,锰含量增加104.41%。3.33‰营养液处理新叶内钙、镁、锰和硼含量显著高于1.00‰营养液处理,但铁和锌含量显著低于1.00‰营养液处理,生产上可以将动物源营养液作为卷叶霸王空气凤梨新型叶面营养肥进行合理开发与利用。

不同油茶品系叶片C、N、P生态化学计量及其重吸收效率研究

对不同油茶(Camellia oleifera)品系叶片C、N、P养分和生态化学计量特征及其重吸收效率进行分析,旨在阐明不同油茶品系的养分利用策略。以岑软2号、岑软3号和香花1号3个不同油茶品系为研究对象,分析成熟叶、衰老叶、凋落叶C、N、P含量、生态化学计量特征及养分重吸收效率。结果表明,3个品系中,香花1号的3种叶片的C、N、P含量、生态化学计量特征表现为最高,各品系间的成熟叶养分含量和老叶、凋落叶的N含量均存在显著差异;岑软2号3种叶片的C∶N均表现为较高,成熟叶以岑软3号最低,老叶和凋落叶均为香花1号最低;3个品系成熟叶的N∶P、凋落叶的各化学计量比值均存在显著性差异,老叶的C∶N和N∶P各品系间差异均未达到显著性水平;N、P重吸收率均表现为岑软2号>岑软3号>香花1号,P的重吸收率在3个品系间均有显著性差异。总体上3个品系成熟叶片的N∶P均介于14~16,其生长受到N、P双重限制;从3种叶片的养分含量和重吸收率来看,尽管不同油茶品系具有不同的养分吸收策略,但均表现出养分主要来源于土壤,在抚育管理中应注重N、P的施用量;岑软2号更能适应所在地区的低N、P限制。

荒漠草原植物在氮磷添加下叶功能性状特征及其可塑性

探究荒漠草原植物在N、P添加下叶功能性状特征及其变异,对揭示植被对环境的响应机制至关重要。以宁夏盐池县荒漠草原植物群落为研究对象,分析了N、P添加对植物群落叶片形态和化学性状的影响。结果表明:植物群落叶片氮磷比<14,表明研究区植物生长受到N限制,P添加对植物群落叶片功能性状无显著影响,N+P共同添加显著增加了叶片碳磷比,N添加下植物群落叶面积、比叶面积、叶组织密度和叶片氮含量显著上升,反映了植物在环境的变化下采取了较快的养分循环策略;根据可塑性指数排序结果可知,植物群落叶面积、比叶面积、叶片干物质含量、叶组织密度、叶片碳含量和叶片氮含量为响应N、P添加的敏感性状(PI>0.5),其中变异性较大的性状为叶面积、比叶面积和叶组织密度,表明植物群落主要通过改变自身形态来应对环境的变化;相关性分析结果表明,植物群落叶片性状之间存在显著的相关性,并且表现出应对养分环境变化的协同作用。本研究为预测植物和生态系统对全球变化因素的反应提供了理论依据,对探讨区域植被分布、恢复进程至关重要。

赖草草地叶片养分、碳组分和防御性化合物对氮添加的响应

本研究依托山西右玉黄土高原赖草(Leymus secalinus)草地2017年建立的氮(Nitrogen, N)添加梯度试验平台(0~32 g·m^(-2)·a^(-1)),探究N添加对优势植物赖草叶片养分[N、磷(Phosphorus, P)、钾(Potassium, K)]、非结构性碳水化合物、结构性碳水化合物和防御性化合物含量的影响。结果表明:N素输入显著提高叶片N,K含量和N∶K和N∶P比值,降低叶片P含量和P∶K比值;N素输入显著降低叶片非结构性碳水化合物和结构性碳水化合物含量;N素输入显著增加叶片总酚、单宁和黄酮类化合物含量;PCA分析表明低N(≤8 g·m^(-2)·a^(-1))和高N(>8 g·m^(-2)·a^(-1))输入下赖草叶片性状存在显著差异,土壤无机N含量、土壤有效N∶P和N∶K是其主要影响因子。以上结果表明N素输入改变了盐渍化草地赖草叶片养分-碳组分-防御性化合物的分配策略。

喀斯特常绿落叶阔叶混交林凋落叶养分含量时空分布特征

森林生态系统中凋落物养分含量通常具有明显的时空异质性,为探究喀斯特常绿落叶阔叶混交林凋落叶养分含量的时空分布特征及其影响因素,以广西木论喀斯特常绿落叶阔叶混交林25hm2动态监测样地内151个凋落物收集器所收集的凋落叶为研究对象,选取连续12个月的凋落叶进行元素含量分析。结果显示:该森林群落凋落叶元素含量大小顺序为碳(C)>钙(Ca)>氮(N)>镁(Mg)>钾(K)>硫(S)>磷(P),分别介于471.85—496.33、20.27—28.29、17.34—23.10、2.79—5.49、1.80—4.38、1.82—2.22、0.96—1.21g/kg之间,呈现高Ca、Mg,低P、K的分布规律,并且随时间出现明显波动,其中C、N、P、S和Ca元素均在4月出现较大值,而K、Mg则在1月出现峰值。生物因子在5m和10m邻域范围内对凋落叶含量的影响基本一致,但10m尺度上地形因子和土壤因子对凋落叶元素含量的影响更为明显。10m邻域范围内生物和非生物因子对凋落叶P元素的随机森林累积解释率最高,达80.27%,C元素累积解释率最低,仅10.49%,其中海拔和坡度对凋落叶C、N、P、S、K、Ca和Mg含量均有强烈影响,岩石出露率和土壤铁(Fe)含量也会在一定程度上对凋落叶元素含量产生较大影响。综上所述,喀斯特常绿落叶阔叶混交林不同月际间凋落叶养分含量存在显著差异,10m尺度上海拔和坡度是凋落叶养分含量产生空间变异的主要原因。

生物有机肥与化肥减量配施对土壤养分及烟叶产质量的影响

为减少化肥的过量施用,提高湖南宜章植烟土壤肥力和烟叶生产效益,以烤烟品种‘K326’为材料,采用田间试验研究了不同比例生物有机肥与化肥减量配施对土壤养分及烟叶产量与品质的影响。结果表明:增施适当比例生物有机肥配合化肥减量能不同程度地改善土壤肥力质量,促进烟株的生长。随着生物有机肥比例的增加与化肥用量的减少,烤烟的各项生长农艺性状、感官评吸质量、产量、产值以及上等烟比例呈先升后降的趋势。其中,以减量20%化学追肥的T2处理对烟株的生长和烟叶的品质表现最好。与常规施肥的对照(CK)相比,烟草株高、有效叶片数和最大叶面积分别增加8.24%~17.00%、13.81%~23.22%和12.63%~16.86%,C3F烟叶中总糖和钾含量分别达到26.51%~30.01%和2.16%~2.86%,C3F和B2F烟叶的感官评吸质量分别提高1.67%~2.98%和3.12%~4.10%,烟叶产量、上等烟比例和产值分别提高3.76%~6.58%、3.38%~3.79%和8.24%~9.58%。研究结果为湘南植烟区应用生物有机肥与化肥减量配施提供了科学参考依据。

氮肥形态对山苍子幼苗生长及生理的影响

【目的】筛选适宜的氮素肥料,为山苍子苗期施肥提供参考。【方法】以同一家系1年生山苍子幼苗为试验材料,设置不施肥、硝态氮、铵态氮、硝铵态氮、酰胺态氮、氨基酸态氮共6个处理,施肥处理结束3个月后,测定苗高、地径生长量、地上部生物量、地下部生物量、叶绿素a含量、叶绿素b含量和总叶绿素含量、叶片光合气体交换参数、光响应曲线参数和叶片养分含量指标,分析山苍子幼苗生长及生理特性对不同形态氮肥的响应。【结果】与不施肥的对照相比,不同形态氮肥处理均不同程度地促进了山苍子幼苗生长,增大了其生物量,以酰胺态氮处理的效果最为显著;仅酰胺态氮处理显著增加了叶片叶绿素的含量;不同形态氮肥对叶片光合作用的影响不同,所有氮肥处理均提高了净光合速率,酰胺态氮处理显著提高了气孔导度,硝态氮、铵态氮、硝铵态氮显著降低了蒸腾速率且显著提高了水分利用效率;酰胺态氮处理显著提高了最大净光合速率、铵态氮显著降低最大净光合速率,各处理中表观量子效率、光补偿点、暗呼吸速率无显著差异;所有氮肥处理均显著提高了叶片氮含量,硝铵态氮、酰胺态氮处理降低了叶片磷含量,除氨基酸态氮处理外其余氮肥处理显著提高了叶片钾含量。【结论】不同形态氮肥对山苍子幼苗生长和生理特性的影响不尽相同,按照肥效由优到劣排序依次为酰胺态氮、硝铵态氮、铵态氮、氨基酸态氮、硝态氮、对照,酰胺态氮更有利于促进山苍子幼苗生长发育。