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 ...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.展开更多
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 determine...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”.展开更多
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 cond...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.展开更多
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 ...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.展开更多
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 standardi...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.展开更多
Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia Sta...Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia State, Nigeria in 2016 and 2017. Three 1<span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 1</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m trays were randomly positioned for collection of leaf litter production from 4/5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">years old <i>Diospyros crassiflora</i> species in each block (10</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 25</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m) within the plantation totaling 1.5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">ha. A Randomised Complete Block Design (RCBD) with three replicates was used to study the mean monthly leaf litterfall of <i>Diospyros crassiflora</i>. Leaf litter was collected from each of the three litter trays per block and placed in paper bags every 28<sup>th</sup> day of each month from January-December in 2016 and in 2017. Fifteen grammes (15</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g) of properly mixed and oven-dried samples of <i>D. crassiflora</i> leaf litter were milled and sieved in 1</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">mm sieve;0.3</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g was used to determine nutrient elements and their concentrations. The data obtained from mineral nutrient contents of <i>D. crassiflora</i> leaf litter was analysed using analysis of variance. Result reveals the mean concentrations of nitrogen</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.41 and 1.41 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), phosphorus (0.18 and 0.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), potassium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.68 and 0.68 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), sodium (0.35 and 0.30 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), calcium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.57 and 1.56 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), magnesium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.32 and 0.31 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), chlorine (0.25 and 0.24 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), Organic carbon (0.03</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">and 0.03 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) and Organic matter</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.17 and 1.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) etc. in <i>D. crassiflora</i> leaf litter in January-December (2016 and 2017). The study shows almost uniform distribution of mineral elements concentrations in 2016 and 2017.</span></span></span>展开更多
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 characterize...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.展开更多
To explore the relationship between soil nutrients,plant nutrients,and the growth and development of Trichosanthes kirilowii,the soil pH,organic matter,available nitrogen,available phosphorus,available potassium conte...To explore the relationship between soil nutrients,plant nutrients,and the growth and development of Trichosanthes kirilowii,the soil pH,organic matter,available nitrogen,available phosphorus,available potassium content,and leaf total nitrogen,total phosphorus,total potassium,and SPAD in different growth stages of T.kirilowii in the main production area of Shishou City were measured and analyzed.The changes in soil nutrient content and leaf nutrient content at different growth stages of T.kirilowii were compared,and correlation analysis was conducted.The results showed that the average soil pH,organic matter content,alkaline nitrogen content,available phosphorus content,and available potassium content during the entire growth period of T.kirilowii were 7.03,14.01 g/kg,98.79 mg/kg,14.84 mg/kg,and 135.20 mg/kg,respectively;the average total nitrogen content,total phosphorus content,total potassium content,and SPAD of the leaves were 0.55%,0.23%,1.78%,and 77.66,respectively.The nutrient dynamics of T.kirilowii at different growth stages exhibited certain regularity,with most nutrients reaching their maximum values during the flowering and fruiting stages,and then showing a decreasing or stabilizing trend.There was a varying degree of correlation between the nutrient content of leaves and soil,among which the nitrogen,phosphorus,and potassium contents of leaves were significantly or extremely significantly correlated with soil organic matter and alkaline nitrogen content.It can be seen that the nutrient abundance or deficiency level of soil in T.kirilowii field significantly affected the nutrient content of the leaves at different growth stages,thereby restricting its growth and development status.展开更多
The productivity of Robinia pseudoacacia（R.p.） pure forest usually declines at the late growth stage,and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tre...The productivity of Robinia pseudoacacia（R.p.） pure forest usually declines at the late growth stage,and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tree species that can be mixed with R.p., the interspecific relationship is an important issue. Therefore, we gathered the autumn litter fall from R.p. and 10 other species from the Loess Plateau of China were mixed in dual species litterbags（R.p.＋each other species） and buried them in soil for a 345 days lab decay incubation. We measured the litter mass loss and nutrient contents to determine whether the nutrient release was affected by mixed species litter decomposition. The impacts of mixed litter decomposition on macro-elements release were more obvious than on micro-elements. The litters with similar substrate quality might show variable impacts on nutrients release in mixed decomposition. The C loss and release of nutrient was improved by descending order when R.p. litter was mixed with Hippophae rhamnoides, Ulmus pumila, Populus simonii, Larix principis-rupprechtii and Quercus liaotungensis（Q.l.）. But, except for Q.l., only the other species were recommended as suitable mix-plants for R.p. since promoting a high turnover of the nutrient in the litter compartment and a rapid availability for tree.展开更多
Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The ob...Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The objective of this research was to assess litterfall production,the potential deposition of macro and micronutrients through leaf and twig fall as well as macronutrient—use efficiency in three forest ecosystems at different altitudes： a pine forest mixed with deciduous species（S1）; a Quercus spp.forest（S2）; and,a Tamaulipan thornscrub forest（S3）.Total annual litterfall deposition was 594,742 and 533 g m^（-2） for S1,S2 and S3.Leaf litter was higher （68%） than twigs（18%）,reproductive structures（8%） or miscellaneous material（6%）.Micronutrient leaf deposition was higher for Fe followed by Mn,Zn and Cu.Macronutrient leaf deposition was higher for Ca followed by K,Mg and P.Even though P deposition in leaves and twigs was lower than other macronutrients,its nutrient use efficiency was higher than Ca,Mg or K.Altitude and species composition determine litter and nutrient deposition,with higher values at mid-altitudes（550 m）.Altitude is an important factor to consider when analyzing litter production as well as nutrient deposition as shown in this study.Litter production and nutrient deposition are expected to change in a scenario of global warming.展开更多
Nitrogen （N） and phosphorus （P） are the major nutrients that constrain plant growth and development, as well as the structure and function of ecosystems. Hence, leaf N and P patterns can contribute to a deep under...Nitrogen （N） and phosphorus （P） are the major nutrients that constrain plant growth and development, as well as the structure and function of ecosystems. Hence, leaf N and P patterns can contribute to a deep understanding of plant nutrient status, nutrient limitation type of ecosystems, plant life-history strategy and differentiation of functional groups. However, the status and pattern of leaf N and P stoichiometry in N-deficiency desert ecosystems remain unclear. Under this context, the leaf samples from 57 plant species in the Karamori Mountain Ungulate Nature Reserve, eastern Junggar Desert, China were investigated and the patterns and interrelations of leaf N and P were comparatively analyzed. The results showed that the average leaf N concentration, P concentration, and N：P ratio were 30.81 mg/g, 1.77 mg/g and 17.72, respectively. This study found that the leaf N concentration and N：P ratio were significantly higher than those of studies conducted at global, national and regional scales; however, the leaf P concentration was at moderate level. Leaf N concentration was allometrically correlated with leaf P and N：P ratio across all species. Leaf N, P concentrations and N：P ratio differed to a certain extent among plant functional groups. C4 plants and shrubs, particularly shrubs with assimilative branches, showed an obviously lower P concentration than those of C3 plants, herbs and shrubs without assimilative branches. Shrubs with assimilative branches also had lower N concentration. Fabaceae plants had the highest leaf N, P concentrations （as well as Asteraceae） and N：P ratio; other families had a similar N, P-stoichiometry. The soil in this study was characterized by a lack of N （total N：P ratio was 0.605）, but had high N availability compared with P （i.e. the available N：P ratio was 1.86）. This might explain why plant leaves had high N concentration （leaf N：P ratio〉16）. In conclusion, the desert plants in the extreme environment in this study have formed their intrinsic and special stoichiometric characteristics in relation to their life-history strategy.展开更多
To investigate the effects ofMoringa oleifera leaf meal （MOLM） on the performance and haematology of broiler finisher using 120 Cobb chicks of 4 weeks old broiler chicks. The birds were assigned randomly into four d...To investigate the effects ofMoringa oleifera leaf meal （MOLM） on the performance and haematology of broiler finisher using 120 Cobb chicks of 4 weeks old broiler chicks. The birds were assigned randomly into four dietary treatments containing MOLM at 0, 6%, 8%, and 10% （treatments 1, 2, 3 and 4） inclusion levels, respectively, in a complete randomized design experiment. The effect of the dietary treatments on the growth performance and blood parameters of the broiler finisher was determined. MOLM at a rate of 6% （T2）, 8% （T3）, and 10% （T4） of the diets （as fed basis） to replace 3.2%, 5.6% and 8.6% of the crude protein （CP） of the control diet. The daily feed, dry matter and CP intake of the chicks fed MOLM diets were higher （p〈0.05） than those fed the control diet. Average weight gain （AWG） of birds fed MOLM diets reduced as inclusion levels increases 09〈0.05） than those fed the control diet. Chicks fed T2 showed higher （p〈0.05） AWG than those on T3 and T4. Feed conversion ratios （FCR, weight gain/g and feed intake） were higher for chicks fed MOLM. MOLM showed minimal deleterious effects in birds. However, birds fed T2 （6%） diets recorded significantly （p〈0.05） the highest body weight gain. There were significant differences （p〈0.05） among groups in packed cell volume （PVC） of birds. The haemoglobin （Hb）, mean corpuscular volume （MCV）, mean corpuscular haemoglobin （MCH） and mean corpuscular haemoglobin concentration （MCHC） counts showed no significant difference （p〉0.05） among treatments. The results indicated that at 10% in the diets of broiler finisher chick, MOLM could be substituted with expensive conventional protein sources without any deleterious effects on performance and blood parameters of broiler finisher chicken.展开更多
Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in nort...Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in northern hardwood forests along an elevation gradient of decreasing temperature and increasing soil N availability to evaluate how this critical nutrient cycling process can be expected to respond to global and regional environmental changes.Foliar N resorption proficiency(NRP)increased significantly at lower elevations for both sugar maple and American beech,the dominant species in these forests.Foliar N resorption efficiency(NRE)also decreased with increasing elevation,but only in one year.Both species exhibited strong negative relationships between NRP and soil N availability.Thus,we anticipate that with climate warming and decreasing N inputs,northern hardwood forests can be expected to exhibit stronger N conservation via foliar resorption.Both species also exhibited strong correlations between resorption efficiency of N and C,but resorption of both elements was much greater for beech than sugar maple,suggesting contrasting mechanisms of nutrient conservation between these two widespread species.展开更多
基金This research was supported by the National Natural Science Foundation of China(41807335)the Shandong Provincial Natural Science Foundation,China(ZR2020MC040)+2 种基金the National Key Technology Research and Development Program of China(2019YFC0507602-2)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2020434)the National Postdoctoral Program for Innovative Talents(BX201700279).
文摘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.
文摘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”.
基金supported by the National Key Research and Development Program of China(2017YFD0200200/08)the National Natural Science Foundation of China(31501713)+1 种基金the Natural Science Foundation of Shandong Province(ZR2015PC001)the Modern Agro-industry Technology Research System(CARS-27)
文摘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.
文摘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.
文摘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.
文摘Determination of nutrient contents in <i>Diospyros crassiflora</i> leaf litter was <span>carried out in the Forestry Research Institute of Nigeria (FRIN), Okwuta-Ibeku,</span> Umuahia, Abia State, Nigeria in 2016 and 2017. Three 1<span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 1</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m trays were randomly positioned for collection of leaf litter production from 4/5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">years old <i>Diospyros crassiflora</i> species in each block (10</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m </span></span></span><span><span><span style="font-family:;" "="">×<span> 25</span></span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">m) within the plantation totaling 1.5</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">ha. A Randomised Complete Block Design (RCBD) with three replicates was used to study the mean monthly leaf litterfall of <i>Diospyros crassiflora</i>. Leaf litter was collected from each of the three litter trays per block and placed in paper bags every 28<sup>th</sup> day of each month from January-December in 2016 and in 2017. Fifteen grammes (15</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g) of properly mixed and oven-dried samples of <i>D. crassiflora</i> leaf litter were milled and sieved in 1</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">mm sieve;0.3</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">g was used to determine nutrient elements and their concentrations. The data obtained from mineral nutrient contents of <i>D. crassiflora</i> leaf litter was analysed using analysis of variance. Result reveals the mean concentrations of nitrogen</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.41 and 1.41 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), phosphorus (0.18 and 0.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), potassium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.68 and 0.68 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), sodium (0.35 and 0.30 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), calcium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.57 and 1.56 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), magnesium</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(0.32 and 0.31 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), chlorine (0.25 and 0.24 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>), Organic carbon (0.03</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">and 0.03 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) and Organic matter</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "="">(1.17 and 1.18 mg<span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#F7F7F7;">·</span>l<sup><span style="color:#4F4F4F;font-family:-apple-system, "font-size:16px;white-space:normal;background-color:#FFFFFF;">-</span>1</sup>) etc. in <i>D. crassiflora</i> leaf litter in January-December (2016 and 2017). The study shows almost uniform distribution of mineral elements concentrations in 2016 and 2017.</span></span></span>
文摘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.
基金Unveiling Project of"Advanced Technology Integration Demonstration Base Construction and Targeted Research and Development"in Pioneer Counties of Shishou City(SS202307).
文摘To explore the relationship between soil nutrients,plant nutrients,and the growth and development of Trichosanthes kirilowii,the soil pH,organic matter,available nitrogen,available phosphorus,available potassium content,and leaf total nitrogen,total phosphorus,total potassium,and SPAD in different growth stages of T.kirilowii in the main production area of Shishou City were measured and analyzed.The changes in soil nutrient content and leaf nutrient content at different growth stages of T.kirilowii were compared,and correlation analysis was conducted.The results showed that the average soil pH,organic matter content,alkaline nitrogen content,available phosphorus content,and available potassium content during the entire growth period of T.kirilowii were 7.03,14.01 g/kg,98.79 mg/kg,14.84 mg/kg,and 135.20 mg/kg,respectively;the average total nitrogen content,total phosphorus content,total potassium content,and SPAD of the leaves were 0.55%,0.23%,1.78%,and 77.66,respectively.The nutrient dynamics of T.kirilowii at different growth stages exhibited certain regularity,with most nutrients reaching their maximum values during the flowering and fruiting stages,and then showing a decreasing or stabilizing trend.There was a varying degree of correlation between the nutrient content of leaves and soil,among which the nitrogen,phosphorus,and potassium contents of leaves were significantly or extremely significantly correlated with soil organic matter and alkaline nitrogen content.It can be seen that the nutrient abundance or deficiency level of soil in T.kirilowii field significantly affected the nutrient content of the leaves at different growth stages,thereby restricting its growth and development status.
基金supported by the National Science Foundation of China (No. 31070630)
文摘The productivity of Robinia pseudoacacia（R.p.） pure forest usually declines at the late growth stage,and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tree species that can be mixed with R.p., the interspecific relationship is an important issue. Therefore, we gathered the autumn litter fall from R.p. and 10 other species from the Loess Plateau of China were mixed in dual species litterbags（R.p.＋each other species） and buried them in soil for a 345 days lab decay incubation. We measured the litter mass loss and nutrient contents to determine whether the nutrient release was affected by mixed species litter decomposition. The impacts of mixed litter decomposition on macro-elements release were more obvious than on micro-elements. The litters with similar substrate quality might show variable impacts on nutrients release in mixed decomposition. The C loss and release of nutrient was improved by descending order when R.p. litter was mixed with Hippophae rhamnoides, Ulmus pumila, Populus simonii, Larix principis-rupprechtii and Quercus liaotungensis（Q.l.）. But, except for Q.l., only the other species were recommended as suitable mix-plants for R.p. since promoting a high turnover of the nutrient in the litter compartment and a rapid availability for tree.
基金supported by the PAICYT Grant CT259-15National Science and Technological Council(Grant250732)
文摘Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The objective of this research was to assess litterfall production,the potential deposition of macro and micronutrients through leaf and twig fall as well as macronutrient—use efficiency in three forest ecosystems at different altitudes： a pine forest mixed with deciduous species（S1）; a Quercus spp.forest（S2）; and,a Tamaulipan thornscrub forest（S3）.Total annual litterfall deposition was 594,742 and 533 g m^（-2） for S1,S2 and S3.Leaf litter was higher （68%） than twigs（18%）,reproductive structures（8%） or miscellaneous material（6%）.Micronutrient leaf deposition was higher for Fe followed by Mn,Zn and Cu.Macronutrient leaf deposition was higher for Ca followed by K,Mg and P.Even though P deposition in leaves and twigs was lower than other macronutrients,its nutrient use efficiency was higher than Ca,Mg or K.Altitude and species composition determine litter and nutrient deposition,with higher values at mid-altitudes（550 m）.Altitude is an important factor to consider when analyzing litter production as well as nutrient deposition as shown in this study.Litter production and nutrient deposition are expected to change in a scenario of global warming.
基金financially supported by the National Natural Science Foundation of China(41201056)the National Basic Research Program of China(2014CB954202)+2 种基金the West Light Foundation of the Chinese Academy of Sciences(XBBS-2014-20)the Program of Joint Foundation of the National Natural Science Foundationthe Government of Xinjiang Uygur Autonomous Region of China(U1503101)
文摘Nitrogen （N） and phosphorus （P） are the major nutrients that constrain plant growth and development, as well as the structure and function of ecosystems. Hence, leaf N and P patterns can contribute to a deep understanding of plant nutrient status, nutrient limitation type of ecosystems, plant life-history strategy and differentiation of functional groups. However, the status and pattern of leaf N and P stoichiometry in N-deficiency desert ecosystems remain unclear. Under this context, the leaf samples from 57 plant species in the Karamori Mountain Ungulate Nature Reserve, eastern Junggar Desert, China were investigated and the patterns and interrelations of leaf N and P were comparatively analyzed. The results showed that the average leaf N concentration, P concentration, and N：P ratio were 30.81 mg/g, 1.77 mg/g and 17.72, respectively. This study found that the leaf N concentration and N：P ratio were significantly higher than those of studies conducted at global, national and regional scales; however, the leaf P concentration was at moderate level. Leaf N concentration was allometrically correlated with leaf P and N：P ratio across all species. Leaf N, P concentrations and N：P ratio differed to a certain extent among plant functional groups. C4 plants and shrubs, particularly shrubs with assimilative branches, showed an obviously lower P concentration than those of C3 plants, herbs and shrubs without assimilative branches. Shrubs with assimilative branches also had lower N concentration. Fabaceae plants had the highest leaf N, P concentrations （as well as Asteraceae） and N：P ratio; other families had a similar N, P-stoichiometry. The soil in this study was characterized by a lack of N （total N：P ratio was 0.605）, but had high N availability compared with P （i.e. the available N：P ratio was 1.86）. This might explain why plant leaves had high N concentration （leaf N：P ratio〉16）. In conclusion, the desert plants in the extreme environment in this study have formed their intrinsic and special stoichiometric characteristics in relation to their life-history strategy.
文摘To investigate the effects ofMoringa oleifera leaf meal （MOLM） on the performance and haematology of broiler finisher using 120 Cobb chicks of 4 weeks old broiler chicks. The birds were assigned randomly into four dietary treatments containing MOLM at 0, 6%, 8%, and 10% （treatments 1, 2, 3 and 4） inclusion levels, respectively, in a complete randomized design experiment. The effect of the dietary treatments on the growth performance and blood parameters of the broiler finisher was determined. MOLM at a rate of 6% （T2）, 8% （T3）, and 10% （T4） of the diets （as fed basis） to replace 3.2%, 5.6% and 8.6% of the crude protein （CP） of the control diet. The daily feed, dry matter and CP intake of the chicks fed MOLM diets were higher （p〈0.05） than those fed the control diet. Average weight gain （AWG） of birds fed MOLM diets reduced as inclusion levels increases 09〈0.05） than those fed the control diet. Chicks fed T2 showed higher （p〈0.05） AWG than those on T3 and T4. Feed conversion ratios （FCR, weight gain/g and feed intake） were higher for chicks fed MOLM. MOLM showed minimal deleterious effects in birds. However, birds fed T2 （6%） diets recorded significantly （p〈0.05） the highest body weight gain. There were significant differences （p〈0.05） among groups in packed cell volume （PVC） of birds. The haemoglobin （Hb）, mean corpuscular volume （MCV）, mean corpuscular haemoglobin （MCH） and mean corpuscular haemoglobin concentration （MCHC） counts showed no significant difference （p〉0.05） among treatments. The results indicated that at 10% in the diets of broiler finisher chick, MOLM could be substituted with expensive conventional protein sources without any deleterious effects on performance and blood parameters of broiler finisher chicken.
基金National Science Foundation supported this research through the Long Term Ecological Research(LTER)Grant to Hubbard Brook(NSF DEB1114804,1637685,and 2224545)by the project grant(NSF DEB,2020397).
文摘Foliar resorption is a principal nutrient conservation mechanism in terrestrial vegetation that could be sensitive to ongoing changes in climate and atmospheric nitrogen(N)deposition.We quantified N resorption in northern hardwood forests along an elevation gradient of decreasing temperature and increasing soil N availability to evaluate how this critical nutrient cycling process can be expected to respond to global and regional environmental changes.Foliar N resorption proficiency(NRP)increased significantly at lower elevations for both sugar maple and American beech,the dominant species in these forests.Foliar N resorption efficiency(NRE)also decreased with increasing elevation,but only in one year.Both species exhibited strong negative relationships between NRP and soil N availability.Thus,we anticipate that with climate warming and decreasing N inputs,northern hardwood forests can be expected to exhibit stronger N conservation via foliar resorption.Both species also exhibited strong correlations between resorption efficiency of N and C,but resorption of both elements was much greater for beech than sugar maple,suggesting contrasting mechanisms of nutrient conservation between these two widespread species.
