Concentrations and resorption patterns of 13 nutrients in different plant functional types in the karst region of south-western China

Background and Aims

Elucidating the stoichiometry and resorption patterns of multiple nutrients is an essential requirement for a holistic understanding of plant nutrition and biogeochemical cycling. However, most studies have focused on nitrogen (N) and phosphorus (P), and largely ignored other nutrients. The current study aimed to determine relationships between resorption patterns and leaf nutrient status for 13 nutrient elements in a karst vegetation region.

Methods

Plant and soil samples were collected from four vegetation types in the karst region of south-western China and divided into eight plant functional types. Samples of newly expanded and recently senesced leaves were analysed to determine concentrations of boron (B), calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), N, sodium (Na), P, sulphur (S) and zinc (Zn).

Key Results

Nutrient concentrations of the karst plants were lower than those normally found in other regions of China and the rest of the world, and plant growth was mainly limited by P. Overall, four nutrients revealed resorption [N (resorption efficiency 34·6 %), P (48·4 %), K (63·2 %) and Mg (13·2 %)], seven nutrients [B (–16·1 %), Ca (–44·0 %), Cu (–14·5 %), Fe (–205·5 %), Mn (–72·5 %), Mo (–35·6 %) and Zn (–184·3 %)] showed accumulation in senesced leaves and two nutrients (Na and S) showed no resorption or accumulation. Resorption efficiencies of K and Mg and accumulation of B, Ca, Fe and Mn differed among plant functional types, and this strongly affected litter quality. Resorption efficiencies of N, P and K and accumulation of Ca and Zn increased with decreasing concentrations of these nutrients in green leaves. The N:P, N:K and N:Mg ratios in green leaves predicted resorption proficiency for N, K and Mg, respectively.

Conclusions

The results emphasize the fact that nutrient resorption patterns strongly depend on element and plant functional type, which provides new insights into plant nutrient use strategies and nutrient cycling in karst ecosystems.     

Increased precipitation modulates the influence of nitrogen and litter inputs on the nutrient resorption proficiency rather than efficiency of <Emphasis Type="Italic">Leymus chinensis</Emphasis>

Resorption of nutrients from senescing organs is an important conservation mechanism that is usually influenced by the supply of soil nutrients and plant growth requirements. Therefore, it is likely that increases in nitrogen (N), precipitation, and litter could lead to changes in nutrient resorption because of changes in nutrients in the soil and accelerated plant growth in response to the alleviation of water limitations in arid and semiarid environments. In the current study, we investigated the effects of water, N, and litter addition on the nutrient resorption efficiency and proficiency of N and phosphorus (P) in leaves and stems of Leymus chinensis in Inner Mongolia, China. Our results showed that N addition significantly decreased the N resorption efficiency in leaves under water addition, and increased P resorption efficiency under ambient precipitation conditions. There was no apparent influence of either litter or water addition on N and P resorption efficiencies. However, N and litter addition significantly altered N and P resorption proficiencies, and these effects were modulated by water availability. Furthermore, changes in resorption proficiencies were mainly associated with alterations in the nutritional status of green organs in response to water, N and litter addition, except for leaf P. Our findings highlight the importance of increased precipitation in modulating the nutrient resorption proficiency of plants under potentially increased nutrient availability in semiarid grasslands. Therefore, global changes in precipitation and N, and corresponding litter changes could result in complex effects on plant nutrient economies and, in turn, could influence the return of nutrients to the soil.     

Biogeographic patterns of nutrient resorption from Quercus variabilis Blume leaves across China

The variation in nutrient resorption has been studied at different taxonomic levels and geographic ranges. However, the variable traits of nutrient resorption at the individual species level across its distribution are poorly understood. We examined the variability and environmental controls of leaf nutrient resorption of Quercus variabilis, a widely distributed species of important ecological and economic value in China. The mean resorption efficiency was highest for phosphorus (P), followed by potassium (K), nitrogen (N), sulphur (S), magnesium (Mg) and carbon (C). Resorption efficiencies and proficiencies were strongly affected by climate and respective nutrients concentrations in soils and green leaves, but had little association with leaf mass per area. Climate factors, especially growing season length, were dominant drivers of nutrient resorption efficiencies, except for C, which was strongly related to green leaf C status. In contrast, green leaf nutritional status was the primary controlling factor of leaf nutrient proficiencies, except for C. Resorption efficiencies of N, P, K and S increased significantly with latitude, and were negatively related to growing season length and mean annual temperature. In turn, N, P, K and S in senesced leaves decreased with latitude, likely due to their efficient resorption response to variation in climate, but increased for Mg and did not change for C. Our results indicate that the nutrient resorption efficiency and proficiency of Q. variabilis differed strongly among nutrients, as well as growing environments. Our findings provide important insights into understanding the nutrient conservation strategy at the individual species level and its possible influence on nutrient cycling.     

Simulated climate change decreases nutrient resorption from senescing leaves

Nutrient resorption is the process whereby plants recover nutrients from senescing leaves and reallocate them to storage structures or newer tissues. Elemental resorption of foliar N and P has been shown to respond to temperature and precipitation, but we know remarkably little about the influence of warming and drought on the resorption of these and other essential plant macro‐ and micronutrients, which could alter the ability of species to recycle their nutrients. We conducted a 5 year manipulative field study to simulate predicted climate change conditions and studied the effects of warming (W), rainfall reduction (RR), and their combination (W+RR) on nutrient resorption efficiency in five coexisting shrub species in a semiarid shrubland. Both mature and senesced leaves showed significant reductions in their nutrient contents and an altered stoichiometry in response to climate change conditions. Warming (W, W+RR) reduced mature leaf N, K, Ca, S, Fe, and Zn and senesced leaf N, Ca, Mg, S, Fe, and Zn contents relative to ambient temperature conditions. Warming increased mature leaf C/N ratios and decreased N/P and C/P ratios and increased senesced leaf C/N and C/P ratios. Furthermore, W and W+RR reduced nutrient resorption efficiencies for N (6.3%), K (19.8%), S (70.9%) and increased Ca and Fe accumulation in senesced leaves (440% and 35.7%, respectively) relative to the control treatment. Rainfall reduction decreased the resorption efficiencies of N (6.7%), S (51%), and Zn (46%). Reductions in nutrient resorption efficiencies with warming and/or rainfall reduction were rather uniform and consistent across species. The negative impacts of warming and rainfall reduction on foliar nutrient resorption efficiency will likely cause an impairment of plant nutrient budgets and fitness across coexisting native shrubs in this nutrient‐poor habitat, with probable implications for key ecosystem functions such as reductions in nutrient retention in vegetation, litter decomposition, and nutrient cycling rates.     

Radial and vertical variation of wood nutrients in Bornean tropical forest trees

Nitrogen, phosphorus, potassium, calcium, and magnesium concentrations in woody tissue are poorly documented, but are necessary for understanding whole-tree nutrient use and storage. Here, we report how wood macronutrient concentrations vary radially and along the length of a tree for 10 tropical tree species in Sabah, Malaysia. Bark nutrient concentrations were consistently high: 2.9–13.7 times greater than heartwood depending on the nutrient. In contrast, within the wood both the radial (sapwood vs. heartwood) and vertical (trunk bottom vs. trunk middle) variation was modest. Higher concentrations in sapwood relative to heartwood provide empirical support for wood nutrient resorption during sapwood senescence. Dipterocarp species showed resorption rates of 25.3 ± 7.1% (nitrogen), 62.7 ± 11.9% (phosphorus), and 56.2 ± 12.5% (potassium), respectively, while non-dipterocarp species showed no evidence of nutrient resorption in wood. This suggests that while dipterocarps have lower wood nutrient concentrations, this family is able to compensate for this by using wood nutrient resorption as an efficient nutrient conservation mechanism. In contrast to other nutrients, calcium and magnesium tended to accumulate in heartwood. Wood density (WD) showed little vertical variation along the trunk. Across the species (WD range of 0.33 to 0.94 mg/cm³), WD was negatively correlated with wood P and K concentration and positively correlated with wood Ca concentration. As our study showed exceptionally high nutrient concentrations in the bark, debarking and leaving the bark of the harvested trees on site during logging operations could substantially contribute to maintaining nutrients within forest ecosystems.     

Nutrient resorption from senescing leaves in two Stipa species native to central Argentina

Abstract Nutrient resorption from senescing leaves enables plants to conserve and reuse nutrients. As such, it could be expected that plant species adapted to infertile soils have a higher nutrient resorption efficiency (percentage reduction of nutrients between green and senesced leaves) and/or higher nutrient resorption proficiency (absolute reduction of nutrients in senesced leaves) than those adapted to fertile soils. Our objective was to compare nitrogen (N) and phosphorous (P) resorption of two congener grasses that successfully occupy uplands of relatively low fertility (Stipa gynerioides) or lowlands of relatively high fertility (Stipa brachychaeta) in natural grasslands of central Argentina. The two Stipa species did not differ in N and P resorption efficiency, but S. gynerioides had a higher N and P resorption proficiency than S. brachychaeta. As a consequence, leaf‐level N and P use efficiency were higher in the species adapted to low fertility conditions than in the species adapted to high fertility conditions. The higher nutrient resorption proficiency of S. gynerioides was also associated with relatively low leaf‐litter decomposition and nutrient release rates found in a previous study.     

Does the Gradualness of Leaf Shedding Govern Nutrient Resorption from Senescing Leaves in Mediterranean Woody Plants?

To reveal the environmental and substrate quality effects on decomposition process and enzyme activities, litterbag experiments containing Nuphar and Carex leaves, Nuphar rhizome, and Ranunculus shoot, were carried in five-subalpine marshes in Lake Tahoe basin, USA. Alkaline phosphatase, β-glucosidase, and β-xylosidase activities were determined by a fluorogenic method using methyumbelliferyl substrates. Carex leaves, Nuphar rhizome and leaves, and Ranunculus shoots lost, respectively, 33, 67, 82 and 93% of original dry weight over 268 days. Decay rates were different among substrates but not among marshes. Nitrogen and carbon contents increased during the first 58 days and subsequently remained stable. Phosphorus content was stable during the experimental period except for a decrease in the first 16 days in Nuphar shoots. Enzyme activities in decomposing Carex and Nuphar leaves in four marshes were not significantly affected by environmental conditions. β-glucosidase and β-xylosidase activities in decomposing Carex leaves increased with time, but in other plant tissue these enzyme activities remained stable during experimental period. Enzyme activities were significantly different among decomposing substrates. Alkaline phosphatase activity was highest in Nuphar leaves (ca. 1286 μ-mole h⁻¹ g DW −1) but lower and similar in other plant tissues (ca. 100 and 10 μ-mole h −1 g DW −1, respectively). This study showed differences in decay rates and enzyme activities rely on substrate and not the environment conditions of the study area. Decomposition rates in the early stage of decomposition were related to cumulative enzyme activities.     

Inefficient nitrogen resorption in genets of the actinorhizal nitrogen fixing shrubComptonia peregrina: physiological ineptitude or evolutionary tradeoff?

Nutrient resorption was measured in an actinorhizal nitrogen-fixing shrub,Comptonia peregrina, for five years in the understory of a deciduous oak forest in Rhode Island, USA. Mean resorption of nitrogen was extremely inefficient (11%) compared to most deciduous species (50%+), yet resorption of phosphorus was efficient (53%) and comparable to other species. Of the seven additional nutrients studied, only copper (6%) and zinc (10%) were resorbed from senescing leaves. Resorption of nitrogen (5%–20%) and phosphorus (40%–71%) varied significantly among years. Copper was resorbed from leaves in three years and accreted into leaves in two years. Five-year resorption means differed among individual genets by as much as a factor of 2.5 for nitrogen, and 1.3 for phosphorus. Resorption of nitrogen, copper, and zinc were highly correlated, yet resorption of phosphorus remained autonomous from other nutrients. The ecophysiological tradeoffs inComptonia which have resulted in the cooccurence of actinorhizal nitrogen fixation, inefficient nitrogen resorption, and efficient phosphorus resorption suggest that plant nutrient status does have an impact on resorption efficiency and that the evolution of nutrient conservation strategies is nutrient-specific.     

重庆石灰岩地区主要木本植物叶片性状及养分再吸收特征

以重庆石灰岩地区15种常绿木本植物和14种落叶木本植物为研究对象,对两种生活型植物叶片衰老前后叶干物质含量(LDMC)、比叶面积(SLA)和叶片厚度(LT)进行了比较,并采用不同的计算方法(单位质量叶片养分含量、单位面积叶片养分含量)分析了两类植物叶片衰老前后养分含量及再吸收特征,最后对养分再吸收效率与其他叶性状因子之间的关系进行了相关分析。结果表明:常绿植物成熟叶LDMC、LT及衰老叶LT显著低于落叶植物,落叶植物成熟叶和衰老叶SLA均显著高于常绿植物(P0.05);基于单位质量叶片计算的养分含量,常绿植物成熟和衰老叶N、P量均低于落叶植物,而基于单位面积叶片计算的N、P含量则表现出相反的趋势;基于不同方法计算的N、P再吸收效率差异不明显,其中常绿植物基于单位质量叶片养分含量计算的N、P平均再吸收效率为39.42%、43.79%,落叶植物的为24.08%、33.59%;常绿和落叶植物N、P再吸收效率与LDMC、SLA、LT和成熟叶N、P含量之间没有显著相关性,但与衰老叶养分含量存在显著负相关(P0.05)。研究发现,无论是常绿植物还是落叶植物,衰老叶N、P含量均较低,表明石灰岩地区植物具有较高的养分再吸收程度。     

Resorption of foliar nutrients in a regenerating southern Appalachian forest

Summary Leaves were sampled in a successional, southern Appalachian forest to estimate autumn foliar nutrient dynamics. Resorption of N and P in a successional forest equaled, or exceeded, resorption estimates for a more mature control forest. Foliar nutrient leaching was not sufficient to account for changes in autumn leaf N, P, Ca and Mg concentrations. The resorption process conserves nutrients by reducing nutrient losses from leaching and litter-fall, thereby closing the nutrient cycle in successional forests. We hypothesize that rapid recovery of primary productivity early in forest regeneration is the result of maximum nutrient resorption of limiting nutrients. Implications of these results for successional nutrient cycling theory are discussed.     

Nutrient resorption and stoichiometric responses of poplar (Populus deltoids) plantations to N addition in a coastal region of eastern China

中国东部沿海杨树人工林养分重吸收和化学计量对氮添加的响应 叶片养分重吸收对土壤养分的变化很敏感。然而,我们尚不清楚氮沉降如何影响植物大量元素重吸收率。杨树(Populus deltoids)是世界上栽培最广泛的阔叶树种之一。本文研究了在氮添加条件下,杨树重吸收率及其化学计量比的规律和主要驱动因素。通过一个4年的氮添加实验,我们探究中国东部沿海两个林分(8和12年)杨树人工林重吸收率及其化学计量比对氮添加的响应。我们测定了在一系列氮添加浓度水平(0、50、100、150、300 kg N ha⁻¹ yr⁻¹)下,土壤和叶片(包括绿叶和落叶)中氮、磷、钾、钙、镁的浓度。研究结果表明,除钙元素重吸收率和钙、镁元素重吸收率化学计量比外,氮添加对两个林分大量元素重吸收率及其化学计量比都没有显著影响。氮、磷重吸收率尺度斜率在不同氮添加水平下均小于1,表明氮添加条件下,氮、磷元素重吸收率解耦。养分重吸收率与绿叶中养分含量显著正相关,表明重吸收主要受到绿叶养分调控。我们的研究结果为中国东部沿海地区12年生杨树人工林的生长受氮限制提供了直接证据。     

Leaf nutrient dynamics and nutrient resorption: a comparison between larch plantations and adjacent secondary forests in Northeast China

Aims Conversion of secondary forests to pure larch plantations is a common management practice driven by the increasing demand for timber production in Northeast China, resulting in a reduction in soil nutrient availability after a certain number of years following conversion. Nutrient resorption prior to leaf senescence was related to soil fertility, an important nutrient conservation strategy for plants, being especially significant in nutrient-poor habitats. However, the seasonal dynamics of leaf nutrients and nutrient resorption in response to secondary forest conversion to larch plantations is not well understood.Methods A comparative experiment between larch plantations (Larix spp.) and adjacent secondary forests (dominant tree species including Quercus mongolica, Acer mono, Juglans mandshurica and Fraxinus rhynchophylla) was conducted. We examined the variations in leaf nutrient (macronutrients: N, P, K, Ca and Mg; micronutrients: Cu and Zn) concentrations of these tree species during the growing season from May to October in 2013. Nutrient resorption efficiency and proficiency were compared between Larix spp. and the broadleaved species in the secondary forests.Important findings Results show that the seasonal variation of nutrient concentrations in leaves generally exhibited two trends, one was a downward trend for N, P, K, Cu and Zn, and another was an upward trend for Ca and Mg. The variations in foliar nutrient concentrations were mainly controlled by the developmental stage of leaves rather than by tree species. Resorption of the observed seven elements varied among the five tree species during leaf senescence. Nutrient resorption efficiency varied 6–75% of N, P, K, Mg, Cu and Zn, while Ca was not retranslocated in the senescing leaves of all species, and Mg was not retranslocated in Larix spp. Generally, Larix spp. tended to be more efficient and proficient (higher than 6–30% and 2–271% of nutrient resorption efficiency and resorption proficiency, respectively) in resorbing nutrients than the broadleaved species in the secondary forests, indicating that larch plantations had higher leaf nutrient resorption and thus nutrient use efficiency. Compared with Larix spp., more nutrients would remain in the leaf litter of the secondary forests, indicating an advantage of secondary forests in sustaining soil fertility. In contrast, the larch plantation would reuse internal nutrients rather than lose nutrients with litter fall and thus produce a positive feedback to soil nutrient availability. In summary, our results suggest that conversion from secondary forests to pure larch plantations would alter nutrient cycling through a plant-mediated pathway.     

To recycle or steal? Nutrient resorption in Australian and Brazilian mistletoes from three low‐phosphorus sites

Resorption is the process by which nutrients are withdrawn from leaves prior to leaf fall. Mistletoes are generally thought not to rely on nutrient resorption; being xylem‐tapping parasites, they instead derive the nutrients required for new growth from their host plant, at little or no cost. We measured nutrient (N, P, K, Ca, Mg) resorption in 18 parasitic mistletoe–host species pairs distributed across three sites with notably low‐P soil, also quantifying relationships with leaf lifespan (LL) and specific leaf area (SLA). There was little or no evidence of N, Ca or Mg resorption. By contrast, on average ～30% of P and ～20% of K were resorbed prior to leaf fall. Longer LL in mistletoes was associated with lower N and P concentrations in mistletoes and in host leaves. We provide evidence that, even though mistletoes are relatively inefficient in terms of nutrient resorption compared to non‐parasite species, on low‐P soils their ecological and evolutionary strategies for conserving phosphorous involve modulation of both leaf lifespan and P concentration in senesced leaves.     

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。     

Foliar Nutrient Dynamics and Resorption in Naturalized Lonicera maackii (Caprifoliaceae) Populations in Ohio,USA

Foliar phosphorus (P) and nitrogen (N) concentrations and nutrient resorption in the forest understory shrub Lonicera maackii (Rupr.) Maxim (Caprifoliaceae) were measured along contiguous topographic gradients in two southwestern Ohio forests during 1992–1994. Mean summer foliar P varied significantly among topographic positions (but not sites or years), with uplands having greatest P concentrations and bottomlands exhibiting the lowest. Unlike for P, the mean summer foliar N concentrations varied little among sites, topographic positions, and years. Mean absolute and proportional P resorption ranged from 0.48 mg/dm² (33.7%) in slope positions to 0.80 mg/dm² (53.1%) in bottomland positions. Repeated-measures analysis of variance (RMANOVA) for P resorption indicated significant topographic and year effects, a site × year and a site × year × topographic interaction. Mean absolute and proportional foliar N resorption ranged from 6.82 mg/dm² (30.7%) in bottomlands to 8.41 mg/dm² (37.3%) in slope positions. RMANOVA indicated a significant topographic effect for both absolute and proportional N resorption and a significant year effect for absolute N resorption. These significant year effects for P and N stemmed from lowest resorption of nutrients in 1993. The results for P resorption support the hypothesis that foliar resorption is greater in forested sites with lower P fertility. However, resorption rates for N did not support the hypothesis clearly, as slopes with intermediate N availability had greater N resorption rates than did N-rich bottomlands.     

Relationship between the Relative Limitation and Resorption Efficiency of Nitrogen vs Phosphorus in Woody Plants

Most previous studies have ascribed variations in the resorption of a certain plant nutrient to its corresponding environmental availability or level in tissues, regardless of the other nutrients’ status. However, given that plant growth relies on both sufficient and balanced nutrient supply, the nutrient resorption process should not only be related to the absolute nutrient status, but also be regulated by the relative limitation of the nutrient. Here, based on a global woody-plants dataset from literature, we test the hypothesis that plants resorb proportionately more nitrogen (or phosphorus) when they are nitrogen (or phosphorus) limited, or similar proportions of nitrogen (N) and phosphorus (P) when co-limited by both nutrients (the relative resorption hypothesis). Using the N:P ratio in green foliage as an indicator of nutrient limitation, we found an inverse relationship between the difference in the proportionate resorption of N vs P and this foliar N:P ratio, consistent across species, growth-forms, and vegetation-types globally. Moreover, according to the relative resorption hypothesis, communities with higher/lower foliar N:P (more likely P/N limited) tend to produce litter with disproportionately higher/lower N:P, causing a worsening status of P/N availability; this positive feedback may somehow be counteracted by several negative-feedback mechanisms. Compared to N, P generally shows higher variability in resorption efficiency (proportion resorbed), and higher resorption sensitivity to nutrient availability, implying that the resorption of P seems more important for plant nutrient conservation and N:P stoichiometry. Our findings elucidate the nutrient limitation effects on resorption efficiency in woody plants at the global scale, and thus can improve the understanding of nutrient resorption process in plants. This study also suggests the importance of the foliar N:P ratio as a key parameter for biogeochemical modeling, and the relative resorption hypothesis used to deduce the critical (optimal) N:P ratio for a specific plant community.     

江西阳际峰30种阔叶树叶片氮磷含量及再吸收效率

养分再吸收是植物养分利用的重要策略,体现了植物对养分留存、利用和适应环境的能力.为研究亚热带不同生活型(常绿与落叶)阔叶树养分含量与养分再吸收的关系,以江西阳际峰国家级自然保护区内30种阔叶树为研究对象,测定成熟和衰老叶片氮(N)和磷(P)含量,分析常绿和落叶树种叶片N和P含量及其再吸收效率差异,揭示阔叶树种叶片养分再...     

浙江天童常绿阔叶林、常绿针叶林与落叶阔叶林的C:N:P化学计量特征

以浙江天童常绿阔叶林、常绿针叶林和落叶阔叶林为对象, 通过对叶片和凋落物C:N:P比率与N、P重吸收的研究, 揭示3种植被类型N、P养分限制和N、P重吸收的内在联系。结果显示: 1)叶片C:N:P在常绿阔叶林为758:18:1, 在常绿针叶林为678:14:1, 在落叶阔叶林为338:11:1; 凋落物C:N:P在常绿阔叶林为777:13:1, 常绿针叶林为691:14:1, 落叶阔叶林为567:14:1; 2)常绿阔叶林和常绿针叶林叶片与凋落物C:N均显著高于落叶阔叶林; 叶片C:P在常绿阔叶林最高, 常绿针叶林中等, 落叶阔叶林最低, 常绿阔叶林和常绿针叶林凋落物C:P显著高于落叶阔叶林; 叶片N:P比也是常绿阔叶林最高、常绿针叶林次之, 落叶阔叶林最低, 但常绿阔叶林凋落物N:P最低; 3)植被叶片N、P含量间(N为x, P为y)的II类线性回归斜率显著大于1 (p < 0.05), 表明叶片P含量的增加可显著提高叶片N含量; 凋落物N、P含量的回归斜率约等于1, 反映了凋落物中单位P含量与单位N含量间的等速损耗关系; 4)常绿阔叶林N重吸收率显著高于常绿针叶林与落叶阔叶林, 落叶阔叶林P重吸收率显著高于常绿阔叶林和常绿针叶林。虽然植被的N:P指示常绿阔叶林受P限制, 落叶阔叶林受N限制, 常绿针叶林受N、P的共同限制, 但是N、P重吸收研究结果表明: 受N素限制的常绿阔叶林具有高的N重吸收率, 受P限制的落叶阔叶林并不具有高的P重吸收率。可见, 较高的N、P养分转移率可能不是植物对N、P养分胁迫的一种重要适应机制, 是物种固有的特征。     

Alternate Bearing Affects Nitrogen, Phosphorus, Potassium and Starch Storage Pools in Mature Pistachio Trees

The relationship between crop load and the functional storageof selected macronutrients and starch was assessed to developnutrient budgets and best management fertilization practicesin orchards. Functional storage represents the amount of nutrientsand starch redistributed from perennial tree parts in supportof the spring growth flush. Functional storage was influencedby:(a)nutrient and starch accumulation prior to dormancy; and(b)nutrientand starch demand by vegetative and reproductive organs in spring.Lightly cropping (off-year) trees stored 7, 14 and 2 times asmuch N, P and K, respectively, as heavily cropping (on-year)trees. Similar to many biennial plant species, nutrients thataccumulated during the vegetative phase in off-year trees wereused to support reproductive growth during the subsequent on-year.Soil nutrient uptake contributed more to storage pools thanleaf nutrient resorption in off-year-trees, while the reversewas true in on-year trees. Net nutrient resorption from senescingleaves accounted for all of the N and P and a third of the Kstored in on-year trees. Only between 20–33% of the N,P and K stored in perennial tissues of off-year trees couldbe attributed to leaf nutrient resorption. This is the firststudy to determine the amounts of nutrients stored in the perennialparts of mature, field-grown trees and the relative contributionsof leaf nutrient resorption and soil nutrient uptake to functionalstorage in trees.Copyright 1998 Annals of Botany Company Pistacia vera, nutrient storage, biennial bearing, crop load, leaf nutrient resorption, source-sink relationships.