Juglans Mandshurica Research Articles

Coordination of xylem hydraulics and stomatal regulation in keeping the integrity of xylem water transport in shoots of two compound-leaved tree species

Hydraulic segmentation between proximal and distal organs has been hypothesized to be an important protective mechanism for plants to minimize the detrimental effects of drought-induced hydraulic failure. Uncertainties still exist regarding the degree of segmentation and the role of stomatal regulation in keeping hydraulic integrity of organs at different hierarchies. In the present study, we measured hydraulic conductivity and vulnerability in stems, compound leaf petioles and leaflet laminas of Fraxinus mandshurica Rupr. and Juglans mandshurica Maxim. growing in Changbai Mountain of Northeast China to identify the main locality where hydraulic segmentation occurs along the shoot water transport pathway. Stomatal conductance in response to leaf water potential change was also measured to investigate the role of stomatal regulation in avoiding extensive transpiration-induced embolism. No major contrasts were found between stems and compound leaf petioles in either hydraulic conductivity or vulnerability to drought-induced embolism, whereas a large difference in hydraulic vulnerability exists between compound leaf petioles and leaflet laminas. Furthermore, in contrast to the relatively large safety margins in stems (4.13 and 2.04 MPa) and compound leaf petioles (1.33 and 1.93 MPa), leaflet lamina hydraulic systems have substantially smaller or even negative safety margins (-0.17 and 0.47 MPa) in F. mandshurica and J. mandshurica. Under unstressed water conditions, gas exchange may be better optimized by allowing leaflet vascular system function with small safety margins. In the meantime, hydraulic safety of compound leaf petioles and stems are guaranteed by their large safety margins. In facing severe drought stress, larger safety margins in stems than in compound leaf petioles would allow plants to minimize the risk of catastrophic embolism in stems by sacrificing the whole compound leaves. A strong coordination between hydraulic and stomatal regulation appears to play a critical role in balancing the competing efficiency and safety requirements for xylem water transport and use in plants.

Juglone prevents metabolic endotoxemia-induced hepatitis and neuroinflammation via suppressing TLR4/NF-κB signaling pathway in high-fat diet rats

Juglone as a natural production mainly extracted from green walnut husks of Juglans mandshurica has been defined as the functional composition among a series of compounds. It showed powerful protective effect in various diseases by inhibiting inflammation and tumor cells growth. However, studies on its anti-inflammatory effect based on high-fat diet-induced hepatitis and neuroinflammation are still not available. In this regard, we first investigated whether juglone suppresses high-fat diet-stimulated liver injury, hypothalamus inflammation and underlying mechanisms by which they may recover them. SD rats were orally treated with or without high-fat diet, 0.25 mg/kg or 1 mg/kg juglone for 70 days. Subsequently, blood, hypothalamus and liver tissue were collected for different analysis. Also, the primary astrocytes were isolated and used to analyze the inhibitory effect of juglone in vitro. Analysis of inflammatory cytokines declared that the inhibition of TNF-α, IL-1β and IL-6 could be carried by juglone in response to high-fat diet rats. Meanwhile, TLR4 expression and NF-kappa activity also have been confirmed to be the key link in the development of hepatitis and nerve inflammation. The activation was significantly suppressed in treatment group as compared with model. These results indicated that juglone prevents high-fat diet-induced liver injury and nerve inflammation in mice through inhibition of inflammatory cytokine secretion, NF-kappa B activation and endotoxin production.

Identification, development, and application of 12 polymorphic EST-SSR markers for an endemic Chinese walnut (Juglans cathayensis L.) using next-generation sequencing technology

The Chinese walnut (Juglans cathayensis L.), valued for both its nut and wood, is an ecologically important tree species endemic temperate southern China. Investigation of the genetic diversity of Chinese walnut has been limited to natural population genetics and genetic germplasm resources. Here, we describe the development of 12 polymorphic microsatellite markers using next-generation sequencing to screen 96 Chinese walnut individuals collected from 11 natural populations. The number of alleles per locus ranged from 5 to 12. The observed heterozygosity (0.288–0.748) overlapped well with the expected heterozygosity (0.337–0.751). This species has high genetic diversity and gene flow among different populations (FST = 0.075, Nm = 3.088). These markers will be useful for future studies on population genetic structure, evolutionary ecology, and genetic breeding of this walnut tree or other Juglans species.

Seed trait and rodent species determine seed dispersal and predation: evidences from semi-natural enclosures

Abstract: Seed traits affect seed dispersal by animals. However, the combined role of seeds and dispersers in determining seed dispersal is not well explored. We attempted to test how seed traits and predators determine seed dispersal and predation interaction in a rodent-mediated seed dispersal system. Semi-natural enclosure experiments were conducted to investigate seed dispersal and predation of five sympatric tree species with different seed traits, Juglans mandshurica, Quercus mongolica, Pinus koraiensis, Corylus mandshurica and C. heterophylla by three rodent species, Apodemus peninsulae, Tamias sibiricus and Clethrionomys rufocanus showing different body sizes, hoarding behaviors and activity rhythms. Our results demonstrated that seed species with thick coat were removed more slowly than thin-coated seeds in regardless of rodent species, reflecting a consistent negative effect of seed coat on seed dispersal. Seeds with thick coat were less likely to be eaten both in situ and after removal by small rodents. Seeds with high caloric value were more likely to be larder-hoarded, whereas seed traits showed no influence on scatter-hoarding. Rodent species with large body size tended to eat more seeds in situ, while small-sized rodents preferred to eat seeds after removal. Large-sized rodent species scatter-hoarded more seeds, however, small-sized rodents larder-hoarded more seeds. Seeds with thick coat showed high mutualism but low predation with rodents, while rodents with large size showed low mutualism but high predation with seeds. Our results indicate that both seeds and predators play important roles in determining seed dispersal and predation in the seed-rodent dispersal system.

Two new conjugated ketonic fatty acids from the stem bark of JuglJuglans mandshurica

The present study was designed to isolate and characterize novel chemical constituents of the stem bark of Juglans mandshurica Maxim. (Juglandaceae). The chemical constituents were isolated and purified by various chromatographic techniques. The structures of the compounds were elucidated on the basis of spectral data (1D and 2D NMR, HR-ESI-MS, CD, UV, and IR) and by the comparisons of spectroscopic data with the reported values in the literatures. Two long chain polyunsaturated fatty acids (1 and 2) were obtained and identified as (S)-(8E,10E)-12-hydroxy-7-oxo-8,10-octadecadienoic acid (1) and (S)-(8E, 10E)-12-hydroxy-7-oxo-8,10-octadecadienoic acid methyl ester (2). To the best of our knowledge, this is the first report on the isolation and structural elucidation of the two new conjugated ketonic fatty acids from this genus.

담수직파에서 형질전환 CPPO06이벤트 벼의 안전성 및 잡초방제효과

This study was conducted to evaluate the efficacy of weed control and phytotoxicity of oxyfluorfen using a transgenic rice line (CPPO06 event) resistant to protoporphyrinogen oxidase (Protox) inhibiting herbicides in the direct-seeding flooded rice. Five annual weeds including Echinochloa oryzoides and two perennial weeds were occurred in the test field. Oxyfluorfen at 120 g a.i. ha -1 in the application timing of two days before sowing and 0 and five days after sowing showed more than 90% weed control value except for Juglans mandshurica. Total weed control value was more than 95% in any application timing indicating a highly effective herbicide in the direct-seeding flooded rice. When compared with untreated control, no visual injuries were detected at single and double dosage of oxyfluorfen. The agronomic characteristics and yield components of CPPO06 event was reasonable in any time of application in this study. Based on these data, oxyfluorfen application before and after sowing can be applied to provide effective weed management in the direct-seeding flooded field.

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

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. 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. 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.

Regeneration System for Axillary Bud of Juglans mandshurica Maxim.

Browning takes place generally in tissue culture of Juglans mandshurica Maxim. and influences the growth and proliferation of cultures. We established the regeneration system for axillary bud of J. mandshurica Maxim. and studied the factors influencing the browning of cultures by changing culture environment and adding anti-browning agents into the culture medium. The inducing rate of 1- 2 year axillary bud as explant was75. 8%,significantly higher than those of 10 and 30 year axillary buds. Browning rate was 56. 7%,which was significantly lower than the others. DKW + BA 2. 0 mg · L- 1+ IBA 0. 1 mg · L- 1culture medium reduced browning and promoted plant growth,and the browning rate was lowered by about 10%. Na2S2O3 and AC effectively alleviated the browning,while the alleviated effect of PVP and VC on browning was not significant.Five-day dark treatment after inoculation delayed browning time,and the browning rate reduced by about 10%.Adding 6 g·L- 1agar in culture medium resulted in browning rate of 56. 7%. After subculture on DKW + BA2. 0 mg·L- 1+ IBA 0. 01 mg·L- 1culture medium,the proliferation coefficient of seedlings was 14. 4,and the seedling height was 2. 33 cm. There was no significant difference between subculture cycles of 21 and 28 days,and a subculture cycle of 21- 28 days was suitable for proliferation culture.

Two new diarylheptanoids isolated from the roots of Juglans mandshurica

Two new diarylheptanoids, ( − )-threo-3′,4″-epoxy-1-(4-hydroxyphenyl)-7-(3-methoxyphenyl)heptan-2,3-diol (1) and (1α,3β,5α,6α)-1,5-epoxy-3,6-dihydroxy-1,7-bis(3-methoxy-4-hydroxy-phenyl)-heptane (2), along with one known diarylheptanoid, rhoiptelol B (3), were isolated from the roots of Juglans mandshurica. The structures of compounds 1 and 2 were identified based on HR-ESI-MS, 1D and 2D NMR including 1H–1H COSY, HMQC, HMBC and NOESY spectroscopic methods.

Effect of the hoarding behavior by rodent on distribution of walnut, Juglans mandshurica

Effect of the hoarding behavior by rodent on distribution of walnut, Juglans mandshurica

Enhanced eryptosis following juglone exposure.

Juglone, a quinone isolated from Juglans mandshurica Maxim, has previously been shown to be effective against malignancy. The effect is at least partially due to stimulation of suicidal death or apoptosis of tumour cells. On the other hand, juglone has been shown to counteract apoptosis, for example, of neurons. In analogy to apoptosis of nucleated cells, erythrocytes may enter eryptosis, a suicidal death characterized by cell shrinkage and breakdown of phosphatidylserine asymmetry of the cell membrane with phosphatidylserine exposure at the erythrocyte surface. Stimulators of eryptosis include increase in cytosolic Ca(2+) activity [(Ca(2+) )i]. This study explored whether juglone stimulates eryptosis. To this end, erythrocyte volume was estimated from forward scatter, phosphatidylserine exposure at the erythrocyte surface from FITC annexin V binding, ceramide abundance from binding of fluorescent antibodies in flow cytometry and cytosolic ATP with a luciferin-luciferase-based assay. As a result, a 24-hr exposure of human erythrocytes to juglone (5 μM) significantly decreased erythrocyte forward scatter. Juglone (1-5 μM) significantly increased the percentage of annexin V binding cells. Juglone (5 μM) significantly increased ceramide abundance at the erythrocyte surface and decreased erythrocyte ATP concentration. The effect of juglone (10 μM) on annexin V binding was slightly but significantly blunted by removal of extracellular Ca(2+) and by addition of protein kinase C (PKC) inhibitor staurosporine (1 μM). In conclusion, juglone stimulates suicidal erythrocyte death or eryptosis at least in part by upregulation of ceramide abundance, energy depletion and activation of PKC.

A new naphthalenone isolated from the green walnut husks of Juglans mandshurica Maxim.

Phytochemical study of green walnut husks of Juglans mandshurica Maxim. led to the isolation of a new naphthalenone, (4R)-3,4-dihydro-4-butoxy-5-hydroxy-naphthalen-1(2H)-one (1), together with 16 known compounds. Compounds 4–6, 13, 14 and 17 were isolated from the genus Juglans for the first time, and their chemotaxonomic significance was also evaluated.

Antitumor effects and immune regulation activities of a purified polysaccharide extracted from Juglan regia

A water-soluble polysaccharide, named as JRP1, was extracted and fractioned from the epicarp of immature fruit of Juglans mandshurica Maxim. The determination of the monosaccharide composition in JRP1 with gas chromatography (GC) showed that JRP1 was composed of Gal (43.1%), Glu (23.6%), Ara (16.2%), Rha (9.8%) and Fru (7.3%). The results in vitro showed that 25, 50 and 100μg/mL of JRP1 could present a significant inhibition on the growth of S180 cells, and furthermore, a significant improvement on the proliferation ability of lymphocytes and the phagocytic activity of macrophages. The results in vivo showed that compared with those in the control group, the inhibition rates of different doses of JRP1 on S180 cells in the tumor-bearing mice were 35.3%, 40.6% and 48.1%, respectively, and serum immune cytokine levels such as IL-2, TNF-α and IFN-γ were significantly improved. Our results confirm that JRP1 has the activities of effective antitumor and immunomodulatory function.

백두대간 조침령-신배령 구간 소나무림과 신갈나무림의 군락구조

백두대간 조침령-신배령 구간 소나무림과 신갈나무림을 대상으로 2012년 4월부터 2013년 8월까지 영구조사구(<TEX>$100m{\times}100m$</TEX>) 설치하여 조사하였다. 총 50개소의 산림식생조사 자료를 토대로 Z-M식물사회학적 방법에 의해 식생유형 분류를 수행하였던바, 최상위 수준에서 신갈나무군락군이 분류되었으며, 군락단위에서는 물푸레나무군락과 까치박달군락으로 세분되었다. 물푸레나무군락은 군단위에서 소나무군과 가래나무군으로 나누어지며, 소나무군은 다시 회나무소군과 머루소군으로 분류되었고, 까치박달군락은 시닥나무군과 사스래나무군으로 각각 세분되어, 총 5개의 식생단위로 분류되었다. 식생단위별 중요치를 분석한 결과 소나무림에서 소나무와 신갈나무의 중요치가 20%이상으로 높게 나타났으나 소나무가 신갈나무보다 상대피도가 50%이상으로 가장 높게 나타났다. 종간연관 분석결과 크게 4개의 유형으로 구분되었고, 이는 식생단위의 식별종 및 표징종과 일치하는 경향이었다. 또한 소나무림의 흉고직경급별 개체 분포에서 중간직경급에서 개체수가 가장 많은 정규분포를 나타낸 소나무와 이를 제외한 다른 수종은 직경이 커질수록 개체수가 감소하는 역 J자형의 분포유형을 나타내어 소나무림에서 신갈나무림으로 교체될 가능성이 크다 판단된다. 반면 신갈나무림에서는 신갈나무를 포함한 다른 수종 모두 역 J자형의 분포유형을 나타내어 신갈나무림은 당분간 안정된 상태로 지속될 것으로 판단되었다. The study was carried out to analyze vegetation structure of Pinus densiflora and Quercus mongolica forests located in Jochimryeong to Shinbaeryeong of the Baekdudaegan mountain range. The survey for 50 plots was conducted from April 2012 to August 2013 in the permanent plots (<TEX>$100m{\times}100m$</TEX>) using phytosociological analysis. As a result, the vegetations were classified into five vegetation units. In species composition, they were classified into Q. mongolica community group divided into 2 community such as Fraxinus rhynchophylla community and Carpinus cordata community, F. rhynchophylla community was subdivided Pinus densiflor group (into Euonymus sachalinensis subgroup, Vitis coignetiae subgroup) and Juglans mandshurica group. C. cordata community was subdivided Acer komarovii group and Betula ermanii group. In terms of importance value, P. densiflora and Q. mongolica were more than 20% respectively. P. densiflora was found to have the highest relative coverage. Analysis of interspecific association showed four types which were coincident with differential species and character species on the constancy table. Based on the diameter class distribution, P. densiflora forest presented a normal distribution pattern except for other species which showed a reverse Jshaped distribution pattern, therefore P. densiflora forest would likely be replaced by Q. mongolica forests. While in Q. mongolica forest, diameter class distribution of all species population presented a reverse J-shaped distribution pattern, therefore Q. mongolica forest could likely remain in the future.

Impact of tree litter decomposition on soil biochemical properties obtained from a temperate secondary forest in Northeast China

Conversion of secondary forests to larch plantations results in a reduction in quantity and quality of plant litters entering the soil and may reduce the soil nutrient cycling rate. As a major process influencing soil nutrient cycling and biochemical properties, leaf litter decomposition has received little attention in temperate secondary forest systems. This study aimed to assess the decomposition of tree litters of varying quality and its impacts on the chemical and biological properties of soils obtained from a temperate secondary forest in a short-term experiment. In this study, impact on soil biochemical properties of tree litter originating from five dominant tree species in Northeast China (Quercus mongolica, Juglans mandshurica, Fraxinus rhynchophylla, Fraxinus mandshurica, and Acer mono) were tested. A 42-day laboratory decomposition experiment was conducted to determine the short-term influences of the decomposition of the five tree species leaf litters on secondary forest soil carbon (C) decomposition, nitrogen (N) mineralization, soil microbial biomass, soluble organic compounds in microbial biomass, enzyme activities, soluble organic C, and pH. Carbon decomposition, equivalent to 29–41 % of leaf litter C, occurred during the incubation. F. mandshurica and A. mono leaf litters decomposed faster than those of Q. mongolica, J. mandshurica, and F. rhynchophylla due to their low lignin concentration and lignin-to-N ratio and high labile C pool. In contrast, F. mandshurica and A. mono leaf litters immobilized less N than the other three leaf litters, which affected N availability. Soil amended with F. mandshurica leaf litter had higher microbial biomass C than the other four leaf litters, indicating that F. mandshurica could increase soil nutrient cycling. The five leaf litter types all increased activities of exoglucanase, s-glucosidase, and N-acetyl-s-glucosaminidase, but there were no effects on phenol oxidase activity. This study suggested that litter of F. mandshurica incorporated in soils tends to decompose faster than litter of other species and increases the microbial biomass. F. mandshurica is, therefore, more advantageous than the other studied tree species for increasing nutrient cycling in a temperate secondary forest soil in this short-term laboratory incubation experiment. Future studies should consider the interactions among soil types, different climates, and long-term decomposition of leaf litters.

Contrasts between the phylogeographic patterns of chloroplast and nuclear DNA highlight a role for pollen-mediated gene flow in preventing population divergence in an East Asian temperate tree

Plant phylogeographic studies in East Asia have provided support for the biogeographic hypothesis that the complex landforms and climate of this region have provided substantial opportunities for allopatric speciation. However, most of these studies have been based on maternally inherited chloroplast DNA (cpDNA) markers and were therefore unable to reveal the role of pollen-mediated gene flow in preventing population divergence. Here, we investigate the phylogeography of the Chinese walnut Juglans cathayensis, a temperate deciduous tree widely distributed across disjunct montane sites in subtropical China. We genotyped 19 populations using seven cpDNA fragments and ten nuclear microsatellite loci and modeled the ecological niche of J. cathayensis. CpDNA analysis identified a total of nine haplotypes, and each of the 19 sampled populations was fixed for a single haplotype, displaying a prominent phylogeographic structure. The results of ecological niche modeling indicated that J. cathayensis populations survived the last glaciation in situ, although they were probably more fragmented than today. In contrast, we detected a much weaker, but nonetheless clear, genetic structure based on nuclear microsatellite data. Our study demonstrates how extensive pollen flow can erase the genetic imprint of long-term refugial isolation in maternal lineages, effectively preventing population differentiation in temperate, particularly wind-pollinated, forest trees in subtropical China.

Using Lignin Content, Cellulose Content, and Cellulose Crystallinity as Indicators of Wood Decay in Juglans mandshurica Maxim. and Pinus koraiensis

The main chemical indicators for healthy wood and rotted wood at different decay levels in two species, namely Juglans mandshurica Maxim. and Pinus koraiensis, were preliminary analyzed. The cellulose content, lignin content, and relative crystallinity were measured using the nitric acid-ethanol method, acid-insoluble lignin, and X-ray diffraction to further explore the process of wood decay. Results indicated that the cellulose content and relative crystallinity decreased and the acid-insoluble lignin content increased as wood decay increased. X-ray diffraction results showed that there were no significant changes in the lattice structure between healthy wood and rotted wood. Approximately 98.3% and 99.9% of the variations in wood decay for Juglans mandshurica Maxim. and Pinus koraiensis, respectively, can be explained by the comprehensive effect of the above chemical indicators.

Three new compounds from the stem bark of Juglans mandshurica

Three new compounds, 3,6-dihydroxy-4,5-dimethoxy-1,8-naphalic anhydride (1), 3,4,5,6-tetrahydroxy-1,8-naphalic anhydride (2), and methyl (7E,9E)-6,11-dioxononadeca-7,9-dienoate (3), were isolated from the stem bark of Juglans mandshurica. Their structures were elucidated on the basis of spectroscopic evidence, including 1D and 2D NMR, HR-TOF-MS, and by comparison with the literature data.

Tree Species Diversity and DBH Diversity of the Secondary Forests on the North Slope of Changbai Mountains

The tree species diversity and DBH diversity of the secondary forests on the north slope of Changbai Mountains were studied and compared with that of virgin Korean pine forest by using Margalef species richness index,Shannon Wiener diversity index,Pielou evenness index and Simpson dominance index through the methods of field investigation and indoor analysis. It was shown that:( 1) Tree species diversity index H and evenness index J were bigger,richness index S and ecological dominance index D were smaller in the secondary forest than those in virgin Korean pine forest. DBH ecological advantages index D,richness index S and diversity index H of the secondary forest were smaller than those of virgin Korean pine forest. DBH evenness index of the secondary forest was similar to that of virgin Korean pine forest. DBH richness index and diversity index of the poplar-birch forest were the biggest,and those of Juglans mandshurica Maxim. forest were the smallest among three secondary forests. DBH evenness index and dominance index changed oppositely to DBH richness index and diversity index among three secondary forests;( 2) Tree species diversity and DBH diversity changed with the same pattern. Tree species diversity index and evenness index,DBH richness index and diversity index increased gradually,tree species and DBH dominance index decreased gradually with forest age increased.( 3) Either virgin Korean Pine forest or secondary forests,tree species diversity would reduce after cutting,the stronger the cutting intensity,the greater the decrease degree. The response of the DBH diversity to the cutting intensity was complex,which was associated with the cutting methods.

Rapid sequestration and recaching by a scatter-hoarding rodent (Sciurotamias davidianus)

Many seed-hoarding species are faced with ephemeral pulses of seeds that result in competition at seed sources and the need to minimize hoarding time during the limited time seeds are available. Here we tested the hypothesis that a seed-hoarding species (Père David's rock squirrel [Sciurotamias davidianus]) rapidly scatter hoards seeds near seed sources to maximize harvest rate, and then subsequently recaches seeds to further reduce cache losses. We tracked the caches of wild walnut (Juglans mandshurica) scatter hoarded by S. davidianus, the exclusive dispersal agent of this highly preferred nut species. We followed dispersed nuts in both the field and in a large enclosure in a manner that allowed us to follow patterns of recaching through the scatter-hoarding process. In the field, S. davidianus initially cached close to nut sources and then subsequently recached nuts on multiple occasions progressively farther from sources, always in the same direction, at lower densities, and at sites with more vegetative cover (e.g., under shrubs). In enclosures, each of 6 squirrels first cached nuts closer to the nut source on the 1st day of observation, and then subsequently recached nuts closer to the nest, sometimes at decreasing densities. We suggest that, in addition to pilferage risk, cache spacing by S. davidianus may be influenced by the potential for competition at the seed source and proximity to the burrow or the core of the home range, and that caches might be managed to accommodate all of these factors. Future studies should consider how such recaching behavior influences patterns of cache recovery, the ultimate distribution of dispersed nuts, and seed fates.