Deposition pattern of precipitation and throughfall in a subtropical evergreen forest in south-central China

The effects of dry deposition, canopy leaching, precipitation ion concentration, and precipitation H⁺ concentration on net throughfall flux (NTF, throughfall minus bulk precipitation) were evaluated on a seasonal basis by using a multiple regression analysis approach based on an observation period of 4 years in Shaoshan subtropical mixed evergreen forest, south-central China. Regression analysis results indicated that the estimated canopy exchange flux was the dominant factor regulating the NTF and the calculated dry deposition was a minor term. The seasonal dry deposition of base cations accounted for 15%–43% of the NTF. The NTF analysis showed that K⁺, Ca²⁺, Mg²⁺, Na⁺, and weak acids in throughfall were derived from foliar leaching and the canopy uptakes of H⁺, NH₄ ⁺, and NO₃ ⁻ were from precipitation. The retention rate of proton (H⁺ and NH₄ ⁺) in the canopy was close to the canopy leaching rate of base cations when corrected for weak acids because weak acid-induced canopy leaching did not exchange with protons, which suggested that the canopy leaching processes neutralized acid precipitation in Shaoshan forest.     

Review of dry deposition measurements of ammonia and nitric acid to forest

The paper describes some general aspects of the estimation of dry deposition fluxes and reviews the measurements of dry deposition of atmospheric gaseous ammonia and nitric acid in relation to forests. The dry deposition of ammonia is shown to be a bi-directional surface flux, i.e. the forest receives a nitrogen input from ammonia in the air, though some ammonia apparently is also emitted from the forest. Still, atmospheric ammonia originating from agricultural activities contributes with large amounts of nitrogen to the ecosystems. Nitric acid seems to deposit very fast, though only very few flux measurements above forest are reported. The method for estimating the fluxes of nitric acid might be questionable for some conditions. For the investigations reported the concentration levels of nitric acid have been relatively low and this compound has contributed with moderate loads of nitrogen to the ecosystem.     

Calibration and assessment of seasonal changes in leaf area index of a tropical dry forest in different stages of succession

A simple measure of the amount of foliage present in a forest is leaf area index (LAI; the amount of foliage per unit ground surface area), which can be determined by optical estimation (gap fraction method) with an instrument such as the Li-Cor LAI-2000 Plant Canopy Analyzer. However, optical instruments such as the LAI-2000 cannot directly differentiate between foliage and woody components of the canopy. Studies investigating LAI and its calibration (extracting foliar LAI from optical estimates) in tropical forests are rare. We calibrated optical estimates of LAI from the LAI-2000 with leaf litter data for a tropical dry forest. We also developed a robust method for determining LAI from leaf litter data in a tropical dry forest environment. We found that, depending on the successional stage of the canopy and the season, the LAI-2000 may underestimate LAI by 17% to over 40%. In the dry season, the instrument overestimated LAI by the contribution of the woody area index. Examination of the seasonal variation in LAI for three successional stages in a tropical dry forest indicated differences in timing of leaf fall according to successional stage and functional group (i.e., lianas and trees). We conclude that when calculating LAI from optical estimates, it is necessary to account for the differences between values obtained from optical and semi-direct techniques. In addition, to calculate LAI from litter collected in traps, specific leaf area must be calculated for each species rather than from a mean value for multiple species.     

森林冠层结构与功能及其时空变化研究进展*

林冠是森林与外界环境相互作用最直接和最活跃的界面层 ,同时 ,它本身又承载了森林生物多样性的主体部分。森林冠层研究的方法和技术在近些年取得了长足发展 ,从而促进了有关林冠结构与功能的研究。这些研究深化了人们对于林冠结构与光能截获以及群落干物质积累之间关系的认识 ,同时 ,对于森林冠层的物质循环和能量传输以及冠层内各营养级之间相互关系动态也有了更为深入的理解。考察森林冠层的结构与功能及其时空变化是深入理解整个森林生态系统的格局、过程及其运作机制的重要基础。     

Nutrient fluxes in rainfall,throughfall and stemflow in Eucalyptus stands on the Zululand coastal plain,South Africa

Atmospheric deposition was assessed at two sites over a four-year period in post-canopy-closure (mature) Eucalyptus stands in the northern Dukuduku and southern KwaMbonambi commercial plantation forestry areas of Zululand, South Africa. The aim of this study was to determine the magnitude and relevance of nutrient addition with rainfall, throughfall and stemflow to commercial forestry in this region. Canopy cation exchange was used with rainfall and canopy drainage to derive wet, dry and total atmospheric deposition. Nutrient concentrations measured in the rainfall, throughfall and stemflow varied widely throughout the study period, and between sources and sites. Rainfall was slightly acidic at both sides, but became less acidic upon passing through the tree canopies. Canopy exchange and collection of dry deposition resulted in increased cation concentrations under the tree canopy, while the canopy generally absorbed nitrogen (N), from the rainfall, reducing the below canopy concentrations. Atmospheric deposition was shown to be responsible for large quantities of nutrients added to the eucalypt stands at each site. Annualised deposition averaged across all years at each site amounted to N, calcium, magnesium, and potassium (K) fluxes of 11.0, 6.0, 2.7 and 10.2 kg ha^?1 y^?1 at Dukuduku and 10, 10.6, 7.5 and 18.8 kg ha^?1 y^?1 at KwaMbonambi, respectively. Organic N fluxes contributed a further 8.1 kg ha^?1 y^?1 at Dukuduku and 7.1 kg ha^?1 y^?1 at KwaMbonambi to the total N deposition. Although K deposition values were high, additions of all other nutrients, although also high, were within the ranges reported in local and international research. Over the course of a full rotation, the atmospheric deposition levels recorded at these sites may have potential to supply a large proportion of the nutrients that are lost during stem-wood harvesting. This study adds value to understanding of nutritional sustainability of fast-growing plantation forests, demonstrating the importance of atmospheric deposition as a nutrient addition source to plantation-grown eucalypts along the Zululand coastal plain.     

Effect of nitrogen addition on DOC leaching and chemical exchanges on canopy leaves in Guangdong Province,China

The impact of nitrogen(N)deposition on dissolved organic carbon(DOC)fractions in throughfall is not well understood.We performed a laboratory experiment and compared DOC leaching from canopy leaves after dipping leaves in pure water(control)and NH4NO3 solution(N-treatment)for 18 h.Net changes of DOC,NH4^+,NO3^-,SO4^2-,K^+,Mg^2+,Ca^2+and H^+contents after dipping leaves were determined by comparing solutions with and without leaves.We recorded no differences of DOC leaching between control and N-treatment,implying that N deposition had minor impacts on canopy DOC production.This confirmed that previous experiments testing the effects of N addition on DOC dynamics without considering the effects of the canopy reaction successfully described the real situation.We also confirmed the previously-reported canopy exchange process in spite of a high background N deposition at our study site.N-treatment significantly increased base cation leaching,especially K^+,and the increase was positively correlated with foliar NH4?retention.Net leaching of H^+and SO4^2-was not affected by the N-treatment.     

Copper and zinc dynamics in foliar litter during decomposition from gap center to closed canopy in an alpine forest

Forest gap in alpine forests may redistribute the hydrothermal conditions in winter and growing season, which may affect the releases of copper and zinc in foliar litter during decomposition. However, the details of this process are largely unknown. Foliar litters of willow (Salix paraplesia), larch (Larix mastersiana), fir (Abies faxoniana), azalea (Rhododendron lapponicum), birch (Betula albosinensis) and cypress (Sabina saltuaria) were selected in an alpine forest of eastern Tibetan Plateau. The litterbags were placed on the forest floor from gap center, canopy gap edge and expanded gap edge to closed canopy. Zinc and copper contents were studied as litter decomposition proceeded. After one year of decomposition, zinc accumulated in all foliar litters regardless of gap positions, but copper accumulated in the litters of fir, azalea and cypress. Separately, copper was released from all foliar litters in winter, whereas zinc in litters of larch, azalea, birch and cypress was released in winter. Moreover, both copper and zinc accumulated during the growing season regardless of litter species. Nevertheless, higher accumulation rates were observed under closed canopy compared with other gap positions. These results suggest that forest gap slows the releases of copper and zinc in foliar litter during forest regeneration in these cold biomes.     

森林冠层叶片氮浓度高光谱遥感反演研究进展

氮素是植物生命活动所需的重要营养元素,在森林植被的光合作用和生态系统固碳方面起着关键作用。因此,理解森林叶片氮浓度在叶片和冠层（遥感像元）尺度上的高光谱特征,是开展森林冠层叶片氮浓度（CNC）遥感反演、优化森林碳循环模拟、应对气候变化的重要基础工作。当前,森林CNC的光谱特征提取受到冠层结构因素的影响,其高光谱遥感反演的理论亦不明确。文中通过梳理国内外大量植被叶氮高光谱反演的代表性研究成果,以时间为轴线从叶片和冠层2个尺度上进行文献综述,详细阐述当前国内外森林叶氮浓度高光谱遥感反演的主要方法、研究热点和面临的问题,并对近年来学界关于森林冠层结构在冠层叶片氮浓度遥感反演中的影响进行综述,并展望森林冠层叶氮浓度高光谱遥感反演的发展方向。     

High Productivity in a Polestage Sitka Spruce Stand and its Relation to Canopy Structure

1. The net annual above ground dry matter production of a 17 yearplantation of Sitka spruce in Scotland was 26.7 t ha^–1y^–1.Total annual production which includes estimates for roots,was 35 t ha^–1y^–1, one of the highest values reportedfor coniferous forest in the temperate zone.
2. When comparedwith other forests with high rates of net productionthis standhad the highest foliage and branch biomass and lowestrate ofproduction per unit of foliage.
3. Gross foliage increment tothe canopy declined following thetime of maximum stand basalarea increment, which coincidedwith the onset of competitionbetween individual trees. Thesechanges in canopy and standstructure are discussed in relationto the decline in net productionwhich has been observed inpolestage conifer plantations.
4. Foliageand branch production were greatest in the top 6 whorlsof thecanopy; over the period studied new foliage became concentratednearer to the top of the trees. Significant branch wood incrementceased below the height where needle death balances needle production.
5. New needles produced at increasing depth in a canopy weighedless per unit needle area. Generally needles lost weight asthey aged. All needles survived for three years, the greatestmortality was of 5-year-old needles but some survived for 8years.
6. Needle area index was 10–11 at age 16, 7–8at age18. Branch area index was 3.6 and the ratio of main stembarksurface area to ground area was 0.4 at age 16.

     

无人机作业航速对喷雾雾滴在竹林中沉降分布及害虫防效的影响

采用无人机开展竹林喷雾施药防治试验,通过设置5个不同无人机作业航速,分析雾滴在竹林中的沉降率、覆盖密度、密度变异系数、有效喷幅和防治效果,明确无人机的作业航速对喷雾雾滴沉积分布及防效的影响,为构建无人机喷雾施药关键技术体系提供技术支撑。结果表明：无人机作业航速对雾滴沉积分布和防效有较大的影响,当无人机作业航速为2.0 m/s时,竹冠水平与垂直方向雾滴的沉积分布最好,可获得较理想的防治效果。     

Carbon loads, forms and sequestration potential within ash deposits produced by wildfire: new insights from the 2009 ‘Black Saturday’ fires, Australia

Forest fires release substantial amounts of carbon (C). Much of it is emitted to the atmosphere, but some is deposited within ash on the ground. Little is known about amount and types of C deposited in ash. Here, we quantify total C, and total inorganic, water-soluble and particulate organic fractions deposited in ash during the catastrophic 2009 ‘Black Saturday’ wildfires in Australia. These fires coincided with the highest air temperatures and lowest humidity ever recorded in the local area, which, combined with high fuel loads of mostly long unburnt eucalypt forests, generated extreme burning conditions. In three mixed-species eucalypt forest sites sampled, the canopy, understorey and litter fuels were almost completely consumed, resulting in substantial ash deposition (mean, 81.9 t ha^?1), with 5.9 t ha^?1 of C being transferred from vegetation to the forest floor. In five temperate rainforest sites sampled, the canopy was not burnt and ash deposition was lower (mean, 48.3 t ha^?1) than in the mixed-species eucalypt forest, but overall their higher C content resulted in higher C deposition (8.1 t ha^?1). In all cases, most C contained in ash was organic and its pyrogenic nature infers increased resistance to degradation. Pyrogenic C is viewed by many as an important C sink, which could contribute to long-term C sequestration when incorporated into soils or sediments. Our results highlight the potential importance of the pyrogenic C pool in freshly deposited ash and, therefore, the necessity of a systematic and detailed analysis of ash deposition and C forms in ash to improve our understanding of C fluxes by forest fires.     

Response of the N and P cycles of an old-growth montane forest in Ecuador to experimental low-level N and P amendments

Atmospheric nitrogen (N) and phosphorus (P) depositions are expected to increase in the tropics as a consequence of increasing human activities in the next decades. In the literature, it is frequently assumed that tropical montane forests are N-limited, while tropical lowland forests are P-limited. In a low-level N and P addition experiment, we determined the short-term response of N and P cycles in a north Andean montane forest on Palaeozoic shists and metasandstones at an elevation of 2100 m a.s.l. to increased N and P inputs. We evaluated experimental N, P and N + P additions (50 kg ha⁻¹ yr⁻¹ of N, 10 kg ha⁻¹ yr⁻¹ of P and 50 kg + 10 kg ha⁻¹ yr⁻¹ of N and P, respectively) and an untreated control in a fourfold replicated randomized block design. We collected litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall and litterfall before the treatment began (August 2007) until 16 months after the first nutrient application (April 2009). Less than 10 and 1% of the applied N and P, respectively, leached below the organic layer which contained almost all roots and no significant leaching losses of N and P occurred to below 0.15 m mineral soil depth. Deposited N and P from the atmosphere in dry and wet form were retained in the canopy of the control treatment using a canopy budget model. Nitrogen and P retention by the canopy were reduced and N and P fluxes in throughfall and litterfall increased in their respective treatments. The increase in N and P fluxes in throughfall after fertilization was equivalent to 2.5% of the applied N and 2% of the applied P. The fluxes of N and P in litterfall were up to 15% and 3%, respectively, higher in the N and N + P than in the control treatments. We conclude that the expected elevated N and P deposition in the tropics will be retained in the ecosystem, at least in the short term and hence, N and P concentrations in stream water will not increase. Our results suggest that in the studied tropical montane forest ecosystem on Palaeozoic bedrock, N and P are co-limiting the growth of organisms in the canopy and organic layer.     

Long-term trends of phosphorus nutrition and topsoil phosphorus stocks in unfertilized and fertilized Scots pine (Pinus sylvestris) stands at two sites in Southern Germany

For two Scots pine (Pinus sylvestris) ecosystems in S Germany with different atmospheric N deposition (Pfaffenwinkel, intermediate N deposition; Pustert, large N deposition), the supply with phosphorus (P) has been monitored for unfertilized and fertilized plots over more than four decades by foliar analysis (1964–2007). Additionally, topsoil concentrations and stocks of total P and plant-available P (citric-acid-extractable phosphate) were quantified in 10-year intervals (1982/1984, 1994, 2004). At both sites, fertilization experiments, including the variants control, NPKMgCa + lime, PKMgCa + lime + introduction of lupine, corresponding to an addition of 75 and 90 kg ha⁻¹ P in Pustert and Pfaffenwinkel, respectively had been established in 1964. Our study revealed different trends of the P nutritional status for the pines at the two sites during the recent four decades: At Pustert, elevated atmospheric N deposition together with small topsoil P pools resulted in significant deterioration of Scots pine P nutrition and in an increasingly unbalanced N/P nutrition. At Pfaffenwinkel a trend of improved P nutrition from 1964 to 1991 was replaced by an opposite trend in the most recent 15 years. For our study sites, which are characterized by acidic soils with thick O layers, the forest floor stock of citric-acid-extractable phosphate showed a strong and significant correlation with the P concentration in current-year pine foliage, and thus was an appropriate variable to predict the P nutritional status of the stands. Total P stocks as well as the concentrations of total P in the forest floor or in the mineral topsoil were poorly correlated with pine foliar P concentrations and thus inappropriate predictors of P nutrition. P fertilization in the 1960s sustainably improved the P nutritional status of the stands. At Pfaffenwinkel, foliar P concentrations and topsoil stocks of citric-acid-extractable phosphate were increased at the fertilized plots relative to the control plots even 40 years after fertilization; at Pustert, foliar P concentrations were increased for about 20 years.     

Germination and seedling growth of Quercus (section Erythrobalanus) across openings in a mixed-deciduous forest of southern New England, USA

In this study three species of the genus Quercus section Erythrobalanus (Quercus coccinea, Quercus rubra, Quercus velutina) were investigated. All occur together as canopy trees in forests of southern New England. Acorns of each Quercus species were planted in plots located in five zones that represent a range of forest gap/canopy conditions that can occur within a southern New England forest. These five zones were demarcated adjacent to and across large openings of two physiographic sites—valley and ridgetop. Experiments were designed to monitor germination and initial growth of seedlings for the first three growing seasons. During the start of the first growing season germination was monitored. At the end of the first growing season measurements of height and number of flushes were taken and destructive samples of seedlings made for dry mass of root, stem and leaves. At the end of the third growing season height was recorded for surviving seedlings. Comparisons were made of germination and growth of seedlings located in the different gap/canopy conditions.

Results demonstrated clear differences in patterns of germination and early growth among species and among gap/canopy conditions of the sites. All species showed an increased lag in germination with reduced amounts of light. Highest growth and flushing rate were in the center conditions of the openings for all species during the first growing season. Quercus rubra had the greatest height growth the first growing season but a lower number of flushes than Q. velutina and Q. coccinea. In comparison with the other species, Q. rubra had the greatest total dry mass in most gap/canopy conditions after the first growing season. However, Q. velutina had the greatest total dry mass in the center of the ridgetop opening. In almost all gap/canopy conditions Q. velutina had greater proportions of dry mass allocated to roots compared with the other species.

After 3 years, greatest height growth in any of the gap/canopy conditions was recorded for all three species in the center of the valley site. Under this condition Q. rubra had significantly greater growth than Q. velutina and Q. coccinea. Quercus rubra also had significantly greater height growth and survival beneath the canopy conditions of the valley site than the other species. On the ridgetop site regeneration failed to establish beneath canopy conditions that provided low amounts of light. Quercus velutina showed greatest height growth after three years in the center and edge conditions of the ridgetop opening compared with the other species. Environmental influences that determine species germination and growth performance are suggested.     

无人机喷雾作业定高对雾滴在竹林中沉降分布及防效的影响

为探究无人机低空喷雾不同作业高度对雾滴在竹林中沉降分布及防效的影响,揭示无人机喷雾施药关键技术,在福建省三明市沙县区建立试验区,运用无人机开展喷雾施药防治试验。结果表明：无人机喷雾作业定高对雾滴在竹林中的沉降分布影响较大,当无人机作业高度为6.5 m时,其雾滴在林冠的沉降率和覆盖密度的水平分布与垂直分布最佳,雾滴在林冠层的穿透性最强,有效喷幅最大,喷药后的防治效果最理想。无人机在竹林喷雾作业最佳定高为6.5 m。     

Foliar delta(13)C and delta(18)O reveal differential physiological responses of canopy foliage to pre-planting weed control in a young spotted gum (Corymbia citriodora subsp. Variegata) plantation

Weed control may improve the growth of forest plantations by influencing soil water and nutrient availability, but our knowledge of leaf-level physiological responses to weed control at different within-canopy positions is limited for tropical and subtropical plantations. Foliar carbon (delta(13)C) and oxygen (delta(18)O) isotope compositions, gas exchange, and nitrogen (N(mass)) and phosphorus (P(mass)) concentrations at four canopy positions were assessed in a young spotted gum (Corymbia citriodora subsp. Variegata (F. Muell.) A.R. Bean & M.W. McDonald) plantation subjected to either weed control or no weed control treatment, to test if leaves at different positions within the tree canopy had the same physiological responses to the weed control treatment. Weed control increased foliar delta(13)C but lowered delta(18)O in the upper-outer and upper-inner canopy, indicating that weed control resulted in a higher foliar photosynthetic capacity at upper-canopy positions, a conclusion confirmed by gas exchange measurements. The increased photosynthetic capacity resulting from weed control can be explained by an increase in foliar N(mass). In the lower-outer canopy, weed control reduced foliar delta(13)C while lowering delta(18)O even more than in the upper-canopy, suggesting strong enhancement of the partial pressure of CO(2) in the leaf intercellular spaces and of foliar stomatal conductance in lower-canopy foliage. This conclusion was supported by gas exchange measurements. Foliar photosynthesis in the lower-inner canopy showed no significant response to weed control. The finding that leaves at different canopy positions differ in their physiological responses to weed control highlights the need to consider the canopy position effect when examining competition for soil nutrient and water resources between weeds and trees.     

Litterfall and nutrient return in five tree species in a common garden experiment

Canopy litterfall is a significant pathway for return of nutrients and carbon (C) to the soil in forest ecosystems. Litterfall was studied in five even-aged stands of Norway spruce, Sitka spruce, Douglas-fir, European beech and common oak at three different locations in Denmark; two sandy sites, Ulborg and Lindet in Jutland, and one loamy site, Frederiksborg on Zealand. Litterfall was collected during three years from 1994 to 1996 in all five species and during six years from 1994 to 1999 in Norway spruce, Sitka spruce and European beech. The average total litterfall was in the range of 3200–3700 kg ha⁻¹ yr⁻¹ and did not differ significantly among tree species. There were no significant differences in total litterfall among sites during the short period, but during the longer period the richer site Frederiksborg had significantly higher total and foliar litterfall amounts compared to the more nutrient-poor sites Lindet and Ulborg. There were close relationships between foliar and total litterfall suggesting that foliar litterfall can be reliably estimated from total litterfall. Beech and oak bud scale litter was significantly related to foliar litterfall. The amount of branch and twig litter was significantly higher in oak than in other tree species. The average foliar litterfall was well related to the annual volume increment. The relationship differed markedly from previously reported relationships based on global litterfall data suggesting that such relationships are better evaluated at the regional level. Nutrient concentrations and fluxes in foliar litterfall were not significantly different among the five tree species. However, there was a significant effect of site on most nutrient concentrations of the three litterfall fractions, and foliar fluxes of P, Ca and Mn were all significantly highest at Frederiksborg and lowest at Ulborg. The similarity in litterfall inputs to the forest floor under these five tree species suggested that previous reports of large variability in forest floor accumulation should primarily be attributed to differences in litter decomposition.     

Historical fire and vegetation dynamics in dry forests of the interior Pacific Northwest,USA, and relationships to Northern Spotted Owl (Strix occidentalis caurina) habitat conservation

Regional conservation planning frequently relies on general assumptions about historical disturbance regimes to inform decisions about landscape restoration, reserve allocations, and landscape management. Spatially explicit simulations of landscape dynamics provide quantitative estimates of landscape structure and allow for the testing of alternative scenarios. We used a landscape fire succession model to estimate the historical range of variability of vegetation and fire in a dry forest landscape (size ca. 7900 km²) where the present-day risk of high severity fire threatens the persistence of older closed canopy forest which may serve as Northern Spotted Owl (Strix occidentalis caurina) habitat. Our results indicated that historically, older forest may have comprised the largest percentage of the landscape (∼35%), followed by early successional forest (∼25%), with about 9% of the landscape in a closed canopy older forest condition. The amount and condition of older forest varied by potential vegetation type and land use allocation type. Vegetation successional stages had fine-grained spatial heterogeneity in patch characteristics, with older forest tending to have the largest patch sizes among the successional stages. Increasing fire severities posed a greater risk to Northern Spotted Owl habitat than increasing fire sizes or frequencies under historical fire regimes. Improved understanding of historical landscape-specific fire and vegetation conditions and their variability can assist forest managers to promote landscape resilience and increases of older forest, in dry forests with restricted amounts of habitat for sensitive species.     

Genetic variation in foliar nutrient concentration in relation to foliar carbon isotope composition and tree growth with clones of the F1 hybrid between slash pine and Caribbean pine

The objectives of this study were: (1) to quantify the genetic variation in foliar nutrient concentration in relation to foliar carbon isotope composition (δ¹³C) and tree growth of 122 clones of ca. 4-year-old F₁ hybrids between slash pine (Pinus elliottii Engelm var. elliottii) and Caribbean pine (P. caribaea var. hondurensis Barr. et Golf.) grown at two experimental sites with different water and nutrient availability in southeast Queensland, Australia and (2) to examine the potential of using foliar nutrient concentration of the 4-year-old tree canopies for selecting elite F₁ hybrid pine clones with improved nutrient-use efficiency (NUE) and water-use efficiency (WUE), and ultimately enhanced tree growth under ambient growing conditions. There were significant differences in foliar nutrient concentrations between two canopy positions (upper outer and lower outer canopy) sampled, between summer and winter, and between the two sites. This highlights that foliar nutrient concentrations are influenced by sampling and environment. Significant genetic variations in foliar nutrient concentrations were detected between the clones, between the female parents, and between the male parents of the clones in both sampling seasons at both sites. Depending on the nutrient concerned, canopy position, season, and site sampled, the clones accounted for 4.7–33.9% of the total variation in foliar nutrient concentrations, the clone female parents for 0–25.1% and the clone male parents for 0–28.6%. The site-by-clone interactions were statistically significant for foliar N, P, Mg, Cu, Zn, Mn, Fe and mineral concentrations at the upper outer canopy in summer, and for foliar N concentration in winter. There were significant, positive correlations between clone means of foliar δ¹³C and N concentration at the upper outer canopy in summer for the wet site, while clone foliar δ¹³C was also positively related to clone foliar N concentration at both canopy positions in summer for the dry site. This suggests that clone WUE as reflected in foliar δ¹³C may be improved by selecting elite clones with higher foliar N concentration and increased photosynthesis, leading to enhanced tree growth when both water and N are the major growth-limiting factors. This is supported by the positive correlation detected between clone tree height and foliar N concentration at the upper outer canopy for both sites. Thus, foliar nutrient (particularly N) concentration, together with foliar δ¹³C, may be useful for assisting in selection of exotic pine clones with improved NUE and WUE, and enhanced tree growth under the nutrient- and water-limiting environments.