Comments on relationships between native seed preferences of shrub-steppe granivores and seed nutritional characteristics

Summary Kelrick et al. (1986) argued that seed preferences of desert granivores are strongly influenced by soluble carbohydrate contents of native seed species. They assumed that bitterbrush (Purshia tridentata) seeds are eaten in their entirety by rodents, but in fact these granivores eat only embryos of bitterbrush seeds. Embryos have a much lower percentage of soluble carbohydrate than whole bitterbrush seeds, and the correlation between preference and soluble carbohydrate content of seeds for six native species becomes non-significant when embryo values are substituted for whole-seed values.     

Disproportionate allocation of mineral nutrients and carbon between vegetative and reproductive structures in Banksia hookeriana

We compared above-ground allocation patterns in mature shrubs of Banksia hookeriana from three 13-year-old populations, growing on nutrient-impoverished sands to determine whether C (dry mass) could be a substitute for mineral nutrients (N, P, K, Ca, Mg and NA). The percentage of reproductive structures to total above-ground growth (reproductive effort; RE) was integrated over nine successive reproductive cycles. Only 0.5% of above-ground dry mass was allocated to seeds compared with 31% to total RE. Allocations of N (24%) and P (48%) to seeds, and N (44%) and P (65%) to RE were much higher. Allocations of K, Ca, Mg and Na to seeds (<1–3%), and RE (21–35%) were closer to that of dry mass. Relative allocation (RA) is defined as the proportion of a nutrient element allocated to a structure relative to its dry mass. RA of P to seeds was 91 and N was 44, but for K, Ca, Mg and Na ranged from only 6 for K to<1 for Na. Thus P, and to a lesser extent N, provide a much more sensitive measure of the relative cost of reproduction than C in this nutrient-limited system.     

Nitrogen addition increases fecundity in the desert shrub Sarcobatus vermiculatus

Nutrients, in addition to water, limit desert primary productivity, but nutrient limitations to fecundity and seed quality in desert ecosystems have received little attention. Reduced seed production and quality may affect recruitment, population, and community processes. At the Mono Basin, CA, USA where the alkaline, sandy soil has very low availability of N, P, and most other nutrients, seed production, recruitment, and dominance of the desert shrub Sarcobatus vermiculatus decrease over a dune successional sequence. Concurrently, Sarcobatus leaf N, P, and Ca/Mg ratio decline from early to later successional dunes. At two later successional dune sites, we fertilized adult Sarcobatus shrubs for 2 years and determined which nutrient(s) limited growth, seed production, and seed quality. We also tested whether nutrient addition at these older sites made these fitness-related variables equivalent to a younger, high-fecundity site. Nitrogen addition, alone, increased Sarcobatus leaf N, growth, and seed production per shoot module. Any treatment including P, Ca, Mg, or micronutrients but not N had an insignificant effect on growth and fecundity. Nitrogen addition also increased filled seed weight, a predictor of potential seedling survival, at one of the sites. Nitrogen-limited seed production and seed mass may reduce Sarcobatus fitness and contribute to the observed successional changes in plant community composition in this alkaline desert ecosystem.     

Cache site selection by chipmunks (Tamias spp.) and its influence on the effectiveness of seed dispersal in Jeffrey pine (Pinus jeffreyi)

The effectiveness of Jeffrey pine (Pinus jeffreyi) seed dispersal performed by seed-caching yellow pine chipmunks (Tamias amoenus) and lodgepole chipmunks (Tamias speciosus) was compared to that of wind dispersal in the Sierra Nevada of western Nevada. Wind-dispersed seeds typically fall under or near the parent tree. Chipmunks removed 90 and 97% of 1064 radioactive seeds from each of two simulated wind-dispersed seed shadows in less than 24 h. Wind-dispersed seeds were deployed within 12 m of the two source trees, but chipmunk caches were found from 2–69 m from the trees. Chipmunks carried nearly all seeds away from source trees, greatly reducing the density of seeds under and near source trees. Caches contained from 1–35 seeds and most were buried 7–21 mm deep. Chipmunks cached in open bitterbrush shrubland with mineral soils much more than expected and cached in closed-canopy Jeffrey pine and lodgepole pine forests with thick needle litter much less than expected. Many Jeffrey pine seedlings and saplings grow in the bitterbrush habitat and few grow in the pine forests. Ten and 20% of the original caches survived until April, the time of seed germination, at the two sites. The movement of wind-dispersed seeds is random relative to environmental variables important in seedling survival, and the wind in coniferous forests cannot quickly bury seeds. The quality of seed dispersal rendered by chipmunks was superior to that provided by the wind because the chipmunks quickly harvested seeds on the ground, moved them away from source trees, and buried them in the ground in habitats and microhabitats where they were more likely to establish new seedlings. The increased quality of seed dispersal provided by animals relative to the wind may help explain why over twenty species of pines have evolved seeds and cones that are adapted for dispersal by seed-caching animals.     

The effects of phylogeny,life-history traits and altitude on the carbon,nitrogen, and phosphorus contents of seeds across 203 species from an alpine meadow

Seed reserves are very important to the earlier growth and survival of plants, and its variation in nutrient contents might make species to form different germination or seedlings growth strategies. Here, 203 species collected from an alpine meadow on the northeastern Qinghai–Tibet plateau were used to test the effects of phylogenetic groups, life-history traits, and altitude on carbon (C), nitrogen (N) and phosphorus (P) contents of seeds across species. The results showed that (1) seeds of Brassicaceae had the highest C content, those of Fabaceae had the highest N content, and Asteraceae had the highest P content, and family explained independently 32.7%, 46.4%, and 17.9% of the variation in C, N, and P contents of seeds, respectively; (2) the smaller seeds tended to have higher C and P contents, and seed mass explained independently 2.5% of variation in C, 4.3% in N, and 8.1% in P contents; (3) N content was explained 1% independently by life form, seeds N content of perennials was significantly higher than that of annals, but seeds C and P contents had non-significant difference between them; (4) seeds of wind-adapted species had higher N and P contents, and dispersal mode explained independently 1.7% of variation in C, 1.6% in N, and 5.6% in P contents; (5) seeds from high altitude had the highest N and P contents, and altitude explained independently 4.3% of the variation in N and 4% in P contents.     

Seed rain into upland plant communities in Hong Kong, China

Hong Kong is an extreme example of tropical landscape degradation, with no substantial remnants of the original forest cover and a highly impoverished disperser fauna. Seed availability is a potential limiting factor in vegetation recovery in such landscapes. To assess the quantity and quality of the seed rain of woody taxa, seed traps were placed in the major upland vegetation types: fire-maintained grassland, shrubland, and secondary forest. Within the grassland site, traps were placed under isolated trees, isolated male and female shrubs of Eurya chinensis, and in the open. Seeds were collected every 2 weeks for 2 years. The seed rain was highest under female shrubs in grassland (6455 seeds m⁻² year⁻¹), where it was almost entirely confined to their fruiting period. Next highest were isolated trees (890 seeds), followed by male isolated shrubs (611 seeds), shrubland (558 seeds), forest (129 seeds) and open grassland (47 seeds). The number of seed taxa was highest in shrubland (59), followed by isolated trees (42), forest (42), female isolated shrubs (28), male isolated shrubs (15), and open grassland (9). The seed rain differed in species composition between the forest, shrubland, and grassland sites, while the differences within the grassland site were largely in terms of quantity. Birds (particularly bulbuls, Pycnonotus spp.) are known or inferred to be the major dispersal agents for 85% of the seed taxa trapped, 99% of the total number of seeds trapped, and 99.8% of the seeds trapped in the grassland site. Few taxa and of the total seeds were dispersed by wind and no seed taxa were definitely dispersed by fruit bats. The results suggest that even in the most degraded landscape the seed rain is adequate for the development of woody vegetation cover, but that human intervention will be needed for the restoration of plant diversity.     

Mineral nutrient stoichiometric variability in Hedera helix (Araliaceae) seeds

Background and Aims

The analysis of variability in mineral allocation to seeds has rarely been considered in relation to allometric patterns and deviations from the allometric trajectory. Here, I examine the scaling of carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) with seed mass in field-collected seeds of Hedera helix, taking into account that brood size might influence the allocation patterns.

Methods

C, N and S contents of 56 individual seeds of different sizes were analysed by combustion using a standard automated CNHS procedure. P content was determined for 200 individual seeds using spectrophotometry after acid digestion of ashed samples. This sample included seeds from different brood sizes.

Key Results

C and N content both varied isometrically with seed mass and this variable explained most of the variation in their content in seeds. P and S, however, varied allometrically with seed mass. Additionally, seed mass only explained 37·3 % and 37·6 % of the total variance in P and S content, respectively. Seeds with higher mass contained proportionately more P and, furthermore, the seeds from small broods contained proportionally more P than those from large broods.

Conclusions

Although seed mass in this species can be used as a surrogate of investment in C and N, it does not account for variability in allocation of nutrients such as P and S. The fact that larger seeds increased their P concentration when found in smaller broods might be a consequence of intense competition for this nutrient among developing seeds. Then, brood size may influence the mineral nutrient concentration of seeds.     

The effect of mineral elements on the maturity of peanut seed

A greenhouse study was conducted to determine the effect, of certain nutrient elements, on the maturing peanut. Peanut fruits were grown in fruiting zones, which contained a complete nutrient medium, for 15 days. Individual plants were then cultured to maturity whilst allowing the fruit to develop in a nutrient medium which contained the complete nutrient (N, P, K, Ca, Mg and B) from which one element had been excluded. Except in the ‘minus B’ treatment, the basal seed weighed more than 500 mg. In the head seed the “minus Ca” treatment produced the lowest number of seeds which weighed 500 mg or more and P, K and B deficiencies produced not quite such low numbers of seeds above 500 mg. When basal and head seeds were grouped into 3 grades of fresh weights, those from Ca and K deficiencies produced smaller dry weights in seeds harvested on the 80th day. Seeds from a Ca deficient medium had a smaller lipid content and an increased sugar content. The starch content of the seed was decreased by K deficiency.     

川滇高山栎灌丛萌生过程中的营养元素供应动态

萌生更新是森林更新的重要方式, 是硬叶栎林受到干扰后植被恢复的主要机制。以位于青藏高原东南缘的川西折多山东坡川滇高山栎(Quercus aquifoliodes)灌丛为研究对象, 调查分析了砍伐后灌丛萌生过程中基株根系和萌株生物量动态、营养元素含量, 以及基株根系和土壤对萌株生长过程中的营养元素供应动态。结果表明, 川滇高山栎灌丛平均地上和地下生物量分别为(11.25 ± 0.92) t·hm^-2和(34.85 ± 2.02) t·hm^-2, 具有较大的根冠比(3.10:1); 萌生过程中, 萌株生物量呈线性增加趋势, 以灌丛活细根生物量变化为最大, 其次是活中根和活粗根, 树桩和根蔸生物量变化最小; 萌生过程中, 灌丛细根和中根N、P含量表现为先增加、后降低的变化趋势, 萌生初期树桩、粗根和根蔸中N和K的含量明显下降, 根蔸中Ca含量略有下降, 而P没有明显下降, 根系Mg含量变化幅度较大, 灌丛地下根系储存了较多的营养元素; 土壤、树桩、粗根和根蔸是川滇高山栎灌丛砍伐后0-120天萌生生长的主要营养来源, 砍伐后60天, 萌株生长所需的营养除K元素主要来源于根系外, 其余营养元素主要来源于土壤; 在砍伐后60-120天, 基株根系对萌株生长所需的N、K和Ca贡献较大, 而对P和Mg的贡献较小; 在砍伐后120-180天, 根系除K元素对萌生生长还保持较大的贡献外, 对其余营养元素的贡献均较小。高山栎林管理要注重加强地下根系的保护。     

Bottom-up effects of nutrient availability on flower production, pollinator visitation, and seed output in a high-Andean shrub

Soil nutrient availability directly enhances vegetative growth, flowering, and fruiting in alpine ecosystems. However, the impacts of nutrient addition on pollinator visitation, which could affect seed output indirectly, are unknown. In a nutrient addition experiment, we tested the hypothesis that seed output in the insect-pollinated, self-incompatible shrub, Chuquiraga oppositifolia (Asteraceae) of the Andes of central Chile, is enhanced by soil nitrogen (N) availability. We aimed to monitor total shrub floral display, size of flower heads (capitula), pollinator visitation patterns, and seed output during three growing seasons on control and N addition shrubs. N addition did not augment floral display, size of capitula, pollinator visitation, or seed output during the first growing season. Seed mass and viability were 25–40% lower in fertilised shrubs. During the second growing season only 33% of the N addition shrubs flowered compared to 71% of controls, and a significant (50%) enhancement in vegetative growth occurred in fertilised shrubs. During the third growing season, floral display in N addition shrubs was more than double that of controls, received more than twice the number of insect pollinator visits, and seed output was three- to four-fold higher compared to controls. A significant (50%) enhancement in vegetative growth again occurred in N addition shrubs. Results of this study strongly suggest that soil N availability produces strong positive bottom-up effects on the reproductive output of the alpine shrub C. oppositifolia. Despite taking considerably longer to be manifest in comparison to the previously reported top-down indirect negative effects of lizard predators in the same study system, our results suggest that both bottom-up and top-down forces are important in controlling the reproductive output of an alpine shrub.     

Nutrient content and dynamics in north Swedish shrub tundra areas

Forbs and leaves of deciduous shrubs had high concentrations of Ca, Mg, K, P, and N. Deciduous dwarf shrubs had intermediate concentrations but higher than evergreen dwarf shrubs. Monocots, cryptogams, woody and belowground tissues had low concentrations.
Plant nutrient concentrations and nutrient content in soil organic matter increased from dry towards moist tundra areas.
The residence time of nutrients was considerably less than ten years in surface litter, but several decades or centuries in total organic matter. The longest residence time was found in the moist part of the tundra.
N, K, and P in Betula nana leaves were translocated to a great extent prior to leaf fall, whereas Mg and particularly Ca were only slightly translocated. As on other tundra areas shortage of nutrients probably limits plant growth. In that case short supply of N and F seems most probable due to retention in litter and soil organic matter.     

Pre-emergence Growth of Genotypes of Sugarbeet (Beta vulgaris L.) Tolerant to Rhizomania

Growth during pre-emergence of three sugarbeet genotypes, alltolerant to the root disease rhizomania but with poor emergencefeatures, was studied. Dry mass, carbon and nitrogen content,and N isotope composition were measured for the seeds and eachseedling part. These results were compared with those obtainedfor Vega, a genotype with no emergence problems. The depletionof seed reserves and carbon use were similar for all genotypes.Tolerant genotypes had altered nitrogen absorption: the netnitrogen balance (total N in the seedling/N initial mass inthe seed) was 20% lower in these genotypes at the end of theexperiments. Differences in the natural abundance of¹⁵N in seedsand nutrient solutions were used to determine the proportionof N originating from seed reserves or from absorption by theorgans. N absorbed from the nutrient solution was found mainlyin the hypocotyl and radicle, with less in the cotyledons ofall genotypes. Tolerant genotypes had less absorbed N in allparts than non-tolerant genotypes. Hypocotyl and radicle elongationwas the same in all genotypes, but the emergence forces in rhizomania-tolerantgenotypes were smaller. These results suggest that breedingto introduce tolerance to rhizomania has also led to a loweredmineral absorption capacity. Copyright 2000 Annals of BotanyCompany Beta vulgaris L, carbon, nitrogen isotopic composition, rhizomania, seedling growth, seed reserves, sugarbeet.     

Seed preferences by rodents in the agri‐environment and implications for biological weed control

Post‐dispersal seed predation and endozoochorous seed dispersal are two antagonistic processes in relation to plant recruitment, but rely on similar preconditions such as feeding behavior of seed consumers and seed traits. In agricultural landscapes, rodents are considered important seed predators, thereby potentially providing regulating ecosystem services in terms of biological weed control. However, their potential to disperse seeds endozoochorously is largely unknown. We exposed seeds of arable plant species with different seed traits (seed weight, nutrient content) and different Red List status in an experimental rye field and assessed seed removal by rodents. In a complementary laboratory experiment, consumption rates, feeding preferences, and potential endozoochory by two vole species (Microtus arvalis and Myodes glareolus) were tested. Seed consumption by rodents after 24 h was 35% in the field and 90% in the laboratory. Both vole species preferred nutrient‐rich over nutrient‐poor seeds and M. glareolus further preferred light over heavy seeds and seeds of common over those of endangered plants. Endozoochory by voles could be neglected for all tested plant species as no seeds germinated, and only few intact seeds could be retrieved from feces. Synthesis and applications. Our results suggest that voles can provide regulating services in agricultural landscapes by depleting the seed shadow of weeds, rather than facilitating plant recruitment by endozoochory. In the laboratory, endangered arable plants were less preferred by voles than noxious weeds, and thus, our results provide implications for seed choice in restoration approaches. However, other factors such as seed and predator densities need to be taken into account to reliably predict the impact of rodents on the seed fate of arable plants.     

Dispersal mode constrains allocation of carbon and mineral nutrients in seeds of forest and savanna trees

• Species vary in seed size and content of stored reserves, which can be related to dispersal strategies and type of habitat in which they are found. We compare seed carbon and nutrient reserves of anemochorous and zoochorous trees from the Cerrado of central Brazil.
• We measured seed dry mass, lipids, non‐structural carbohydrates (starch and total soluble sugars), carbon and mineral nutrients in ten forest and 13 savanna species, each classified as having wind‐ or animal‐dispersed seeds. We used phylogenetically independent contrasts to test for correlations among these traits.
• Seeds of anemochorous species were lighter, with higher concentrations of C, N, P, Ca and Mg. Lipids were the dominant carbon reserve for most anemochorous species, underpinning the importance of allocation to compact carbon reserves. Starch, lipids or soluble sugars were the major carbon reserve in zoochorous seeds. Savanna and forest species did not differ in seed mass or in total carbon reserves. However, seeds of forest species had higher concentrations of starch than seeds of savanna species. Lipid and starch negatively correlated across species, suggesting a trade‐off between starch and lipids as major seed carbon reserves. Calcium was positively correlated with Mn and B, while Mg was positively correlated with C, N, P, K, S, Zn and B. Potassium, S and Cl were positively correlated, while P was positively correlated with Mg and Zn.
• Dispersal mode rather than vegetation type constrained seed mass and seed storage allocation patterns in forest and savanna trees. We provide evidence that similar mechanisms are involved in seed storage of carbon and mineral nutrients across species.

     

Genetic Regulation of Seed Dormancy in Purshia tridentata(Rosaceae)

Seeds of Purshia tridentata, a shrub of semi-arid North America,require chilling to become non-dormant. Using seeds producedfrom controlled crosses in a common garden, we examined effectsof ovule parent, pollen parent, and year of production on germinationpercentage in response to chilling for 2 weeks at 2°C. Differencesamong ovule parents accounted for most of the variance in chillingresponse, and these differences (2 to 83% germination) wereconsistent across years. Differences among pollen parents werealso significant, producing a two- to five-fold difference inmean germination percentage. Differences among years were significantbut small. Ovule parent by year interactions showed that among-yearvariation in ripening environment did not affect ovule parentsequally. There was no significant pollen parent by year interaction,suggesting that the effect of maturation environment was mediatedthrough maternal tissues. In reciprocal crosses, two plantsthat showed contrasting dormancy levels as ovule parents producedseeds with similar dormancy as pollen parents, indicating thatthe genetic difference between them was at the testa level.Two plants that produced seeds with contrasting dormancy aspollen parents showed a similar but stronger pattern of contrastas ovule parents, showing that the genetic difference betweenthem was at both embryo and endosperm or testa level. Testaor endosperm genotype was primarily responsible for chillingresponse of intact seeds, while embryo genotype affected chillingresponse and also exercised primary control over low temperaturegermination rate, whether of excised embryos or of intact seeds.Copyright 2000 Annals of Botany Company Antelope bitterbrush, bitterbrush, common garden study, germination     

Nutrient reabsorption efficiency and the response to phosphorus fertilization in the desert shrubLarrea tridentata (DC.) Cov.

A field fertilization experiment demonstrated that growth ofLarrea tridentata was not limited by phosphorus, even though soils contained high levels of pedogenic carbonates that can potentially fix high amounts of phosphorus. Nutrient reabsorption efficiencies in unfertilized shrubs ranged from 72–86% for P, making nutrient reabsorption a very effective nutrient conservation mechanism. Absolute amounts of N and P reabsorption increased with N and P concentrations in leaves, with reabsorption being greater during drought stress than during rapid leaf growth. However, only N reabsorption efficiency increased with increasing plant N status. A model was developed to explain patterns of nutrient reabsorption efficiencies over large gradients in nutrient availability.     

Seasonal Dynamics of the Accumulation, Distribution and Redistribution of Dry Matter and Mineral Nutrients in a Weedy Species of Gladiolus (Gladiolus caryophyllaceus)

The seasonal dynamics of the accumulation, distribution andredistribution of dry matter and 12 mineral nutrients by a weedyspecies of gladiolus (Gladiolus caryophyllaceus) were studiedat Perth, Western Australia, where it has colonized the nutrient-poorsandy soils. Parent corms sprouted in autumn, and the plantshad completed their growth cycle by early summer. The maturereplacement corm had 15-25% of the plant's P, Ca, Na, Zn andCu, 5-15% of its K, N, Cl, Mg, S and dry matter, and < 5%of its Fe and Mn. Seeds had 26% of the plant's dry matter, 60%of its N and P, 21-33% of its S, Mg, Cu and K, 5-20% of itsFe, Mn and Zn, and < 5% of its Ca and Na. The mature vegetativeshoot had 47% of the plant's dry matter and over 40% of eachnutrient, except for N, P and Cu. Phosphorus, K and N were redistributedfrom the parent corm with over 85% efficiency, S, Mg, Zn andCu with 60-70% efficiency, but there was < 10% redistributionof Ca, Na, Cl, Fe and Mn. The efficiency of redistribution fromthe leafy shoot was over 70% for N and P, 29-52% for K, Mg andCu, 16-20% for S, Zn and Cl, but negligible for Ca, Na, Fe andMn. Redistribution from the shoot could have provided the replacementcorm and seeds with 53-98% of their Cu, Mg, N, P and K, and29-38% of their S, Zn and dry matter. Seeds contained over 60%of each nutrient in a capsule, except for Ca, Na and Fe. Redistributionfrom the capsule walls could have provided 13-19% of the P,Cu and Zn, and 3-7% of the N, K, Mg and dry matter accumulatedby seeds. Each plant produced an average of 520 seeds. Removalof flowers and buds at first anthesis resulted in a larger replacementcorm containing a greater quantity of most nutrients, indicatingcompetition between the replacement corm and seeds for nutrients.Redistribution from parent to replacement cormlets in the absenceof shoot and root development was high, with over 50% of thedry matter and each nutrient, except for Ca, being transferred.Concentration of nutrients were low in all organs of G. caryophyllaceus,especially the replacement corm. It was concluded that the effectiveredistribution of key nutrients, such as N and P, to reproductivestructures and tolerance of low internal concentrations of nutrientscontribute to the capacity of G. caryophyllaceus to colonizeand persist on infertile soils.Copyright 1993, 1999 AcademicPress Gladiolus caryophyllaceus, corm, distribution, dry matter, gladiolus, mineral nutrients, nutrient accumulation, nutrient redistribution, seasonal growth, weed     

密云水库水源保护区板栗林主要养分元素生物循环研究

对密云水库北京集水区板栗林主要养分元素循环进行了研究。结果表明,22年生板栗林的生物量为38638kg·hm^-2;板栗林5种主要养分元素N、P、K、Ca、Mg贮存量为315．38kg·hm^-2,各器官中5种元素贮存量大小排序是干>枝>根>叶>花>果苞>果。板栗林生态系统乔木层每年从土壤中吸收的5种养分元素量为79．17kg·hm^-2,吸收量占0～30cm土层5种养分元素总量的0．15％,占0～30cm土层中5种元素有效养分量的1．95％。年吸收量中存留量为11．25kg·hm^-2,枯落物归还量为58．08kg·hm^-2。雨水及雨水淋溶输入到板栗林生态系统的养分元素量为38．63kg·hm^-2,果实输出量为9．84kg·hm^-2。雨水和雨水淋溶量与枯落物归还量之和大于吸收量,表明研究期间板栗林生态系统养分元素的收入略大于支出,5种元素的吸收系数排序为N>P>K>Ca>Mg,利用系数排序为K>N>Mg>P>Ca。循环系数排序为K>N>P>Mg>Ca。周转期排序是Ca>P>Mg>N>K。     

麻楝种子形态和营养特征遗传变异分析

为系统揭示麻楝种源间种子形态和营养成分的变异程度和变异规律,以8个国家26个种源麻楝种子为试验材料,对不同种源麻楝种子的形态特征和营养成分进行比较分析。多重比较结果表明,麻楝种源间种子的长、宽、厚、长宽比、百粒重以及可溶性蛋白质、可溶性糖和淀粉含量差异极显著;相关分析表明,种子百粒重与种子长、种子宽呈极显著正相关,可溶性蛋白质、可溶性糖和淀粉含量与百粒重均呈极显著正相关;主成分分析结果显示,影响麻楝种子品质的第1主成分主要是种子形态性状,即种子长、百粒重和种子宽,第2主成分是种子营养成分;通过分析麻楝种子形态特征及营养成分变异系数可知,麻楝种子形态变异系数大于营养成分变异系数,表明种子形态受外界环境影响较大。通过主成分聚类分析,将26个种源分为2个集群,第1集群包括澳大利亚和马来西亚2个种源,其特点是种子形态较大、百粒较重、养分含量较高;第2集群包括其余24个种源。结合聚类分析和种子形态与地理气候因子相关分析结果可知,麻楝种子形态变异具有一定的地理区域特征,与分布区的自然地理因素有一定的相关性,麻楝分布区南部种子较大而北部种子较小。     

Controls of Bedrock Geochemistry on Soil and Plant Nutrients in Southeastern Utah

The cold deserts of the Colorado Plateau contain numerous geologically and geochemically distinct sedimentary bedrock types. In the area near Canyonlands National Park in Southeastern Utah, geochemical variation in geologic substrates is related to the depositional environment with higher concentrations of Fe, Al, P, K, and Mg in sediments deposited in alluvial or marine environments and lower concentrations in bedrock derived from eolian sand dunes. Availability of soil nutrients to vegetation is also controlled by the formation of secondary minerals, particularly for P and Ca availability, which, in some geologic settings, appears closely related to variation of CaCO₃ and Ca-phosphates in soils. However, the results of this study also indicate that P content is related to bedrock and soil Fe and Al content suggesting that the deposition history of the bedrock and the presence of P-bearing Fe and Al minerals, is important to contemporary P cycling in this region. The relation between bedrock type and exchangeable Mg and K is less clear-cut, despite large variation in bedrock concentrations of these elements. We examined soil nutrient concentrations and foliar nutrient concentration of grasses, shrubs, conifers, and forbs in four geochemically distinct field sites. All four of the functional plant groups had similar proportional responses to variation in soil nutrient availability despite large absolute differences in foliar nutrient concentrations and stoichiometry across species. Foliar P concentration (normalized to N) in particular showed relatively small variation across different geochemical settings despite large variation in soil P availability in these study sites. The limited foliar variation in bedrock-derived nutrients suggests that the dominant plant species in this dryland setting have a remarkably strong capacity to maintain foliar chemistry ratios despite large underlying differences in soil nutrient availability.