Greater Water-holding Capacity Research Articles

Seasonal home range and habitat use of a critically endangered marsupial (Bettongia penicillata ogilbyi) inside and outside a predator-proof sanctuary

An understanding of the factors that influence the distribution of the woylie (Bettongia penicillata ogilbyi) at local and regional scales has been identified as a key knowledge gap, because such knowledge may assist in the recovery of this endangered species. We aimed to investigate the seasonal home-range size and habitat use of woylies to update current knowledge of the species in the context of a substantial decline. Specifically, we examined the home range and habitat use of woylies reintroduced into a sanctuary free from invasive predators and compared these data to those from an external reference site. Eight woylies inside the sanctuary and seven outside were radio-tracked in autumn 2011. The average home-range size was 65.4 (±8.2, s.e.) ha. There was little evidence to suggest any difference in home-range size between woylies inside and outside the sanctuary. Woylies were more likely to be found in the slope and low-lying valley habitats, which have greater water-holding capacity and sandier soils. These relatively large seasonal home ranges, compared with previously published estimates for the species, may be accounted for by low population density, lower seasonal food availability and clustered food distribution. Monitoring the home-range size of woylies within the sanctuary may assist in identifying the carrying capacity of the sanctuary, which has implications for how this population is managed.

Disponibilidade de carbono orgânico nos solos do cerrado brasileiro

Soil quality is a concern that every year becomes more and increasing current. With intensive f arming worldwide, mainly in tropical countries, systems that aim at conservation of the chemical, physical and biological soil become a viable alternative for maintaining soil quality and sustainability of ambeinte. Thus, the objective of this work is to expose a revision that demostre the relationship of physical and chemical properties of soils that have different rates of organic carbon in the conditions of Cerrado in Brazil. For these environments the levels of soil organic matter - MOS and organic carbon - CO are associated and dependent on the rates of addition of waste and the intensity of the processes of decomposition of soil organic matter - MOS. Therefore, managements seeking increased MOS as tillage - PD tends to accumulate the COS, as results observed an increasing of the aggregation index, greater water-holding capacity, higher porosity and greater resistance to erosion. In addition, the soils had better fertility and soil quality and hence greater productive capacity. However, the input MOS is also correlated with climatic conditions (rainfall, temperature, etc.), texture (clay, silt and sand), soil structure and biogeochemical factors of the environment.

Disponibilidade de carbono orgânico nos solos do cerrado brasileiro

Soil quality is a concern that every year becomes more and increasing current. With intensive f arming worldwide, mainly in tropical countries, systems that aim at conservation of the chemical, physical and biological soil become a viable alternative for maintaining soil quality and sustainability of ambeinte. Thus, the objective of this work is to expose a revision that demostre the relationship of physical and chemical properties of soils that have different rates of organic carbon in the conditions of Cerrado in Brazil. For these environments the levels of soil organic matter - MOS and organic carbon - CO are associated and dependent on the rates of addition of waste and the intensity of the processes of decomposition of soil organic matter - MOS. Therefore, managements seeking increased MOS as tillage - PD tends to accumulate the COS, as results observed an increasing of the aggregation index, greater water-holding capacity, higher porosity and greater resistance to erosion. In addition, the soils had better fertility and soil quality and hence greater productive capacity. However, the input MOS is also correlated with climatic conditions (rainfall, temperature, etc.), texture (clay, silt and sand), soil structure and biogeochemical factors of the environment.

Effect of rice husk biochar and coal fly ash on some physical properties of expansive clayey soil (Vertisol)

The objective of this work is to evaluate the effect of rice husk biochar (RHB) and coal fly ash (CAF) on the formation and stability of aggregates, pore size distribution, water retention, swell–shrinkage, consistency limit, and tensile strength of an expansive clayey soil (Vertisol). For this purpose, RHB and CAF are added to the clayey soil at four levels of 0, 2, 4, and 6% by weight, and incubated for 180days in a glasshouse. Results indicate that the RHB significantly increases macroaggregates with a diameter larger than 0.25mm and reduces microaggregates with a diameter of <0.25mm. Whereas CFA does not significantly affect the formation of macroaggregates. The RHB- and CFA-amended soils have significantly higher mean weight diameter (MWD) and geometric mean diameter (GWD) as compared with the control soil. The enhanced aggregate stability is attributed to a decrease in the aggregate breakdown by differential swelling and an increase in the aggregate resistance to mechanical breakdown. The RHB-amended soil has a greater water-holding capacity and higher available water content. Pore size distribution (PSD) of RHB- and CFA-amended soils, determined by the mercury intrusion porosimetry (MIP), indicates that the amendment enhances the formation of mesopores having a pore size range between 6 and 45μm. In the measured pore range (0.003–360μm), the amended soils are found to have considerably higher porosity than the control soil. The RHB and CAF affect the PSD of clayey soil by binding microaggregates together to form macroaggregate and combining carbon and fly ash particles with clay mineral phases to form a larger complex. Meanwhile, the RHB and CFA significantly decrease the tensile strength and coefficient of linear extensibility (COLE) of clayey soil. For example, adding a 6% RHB can reduce the tensile strength from 936.8 to 353.6kPa and COLE from 0.63 to 0.56, respectively. The RHB and CFA also decrease the plasticity index of clayey soil. The above results indicate that the RHB and CFA are able to improve the physical quality and swelling–shrinkage status of expansive clayey soils, being a potential soil amendment for improving poor physical characteristics of the clayey soil.

Soil Texture and Planting Depth Affect Large Crabgrass (Digitaria sanguinalis), Virginia buttonweed (Diodia virginiana), and Cock’s-comb Kyllinga (Kyllinga squamulata) Emergence

Greenhouse studies were conducted to explore soil texture and planting depth effects on emergence of large crabgrass, Virginia buttonweed, and cock’s-comb kyllinga. Soil textures examined were sand, loamy sand, and clay loam with planting depths of 0, 0.5, 1, 2, 4, 6, and 8 cm. Percent emergence was standardized relative to surface emergence to allow comparisons among tested weed species. The three-way interaction of weed species, planting depth, and soil texture was never significant for emergence. Significant interactions occurred between weed species and soil texture, weed species and planting depth, and soil texture and planting depth. For all weed species and soil textures, emergence decreased as planting depth increased with the greatest percent emergence at the soil surface. The planting depth at which weed emergence was decreased 50% [relative to surface emergence (D50)] was predicted by regression analysis. Large crabgrass emerged from deepest depths (8 cm) followed by Virginia buttonweed (6 cm) and cock’s-comb kyllinga (2 cm). Large crabgrass, Virginia buttonweed, and cock’s-comb kyllinga D50 occurred at 3.9, 1.1, and 0.8 cm, respectively. Sand, loamy sand, and clay loam D50 occurred at 0.9, 2.3, and 1.9 cm, respectively, with D50 higher in the soils with greater water-holding capacity.

Water-holding capacity and instrumental texture properties of m. Longissimus dorsi and m. Serratus ventralis from Iberian pigs as affected by the production system

Meat from Iberian pigs had a high quality and an important acceptance for consumers, but is affected enormously by production conditions. So, in this study, ninety Iberian pigs were randomly allotted into three batches – Montanera (free-range rearing and fed on acorns and grass), Intensive (confinement rearing and fed on concentrate) and Recebo (free-range rearing fed on acorn, grass and concentrate) – in order to characterize the influence of the production system on water holding capacity (WHC), drip loss, thaw loss and cook loss and instrumental texture traits of m. Longissimus dorsi and m. Serratus ventralis. Muscles from pigs raised in Montanera had greater WHC and lower water losses after thawing than those from Intensive system. Instrumental texture analysis showed that muscles from Montanera pigs had different characteristics as determined by instrumental Texture profile analysis (TPA) and with most resistance to cutting of the muscle fibres Warner–Bratzler (W–B). In all the cases, however, the type of muscle showed a different behaviour on water loss and rheological properties. So, these results suggest that meat quality of Iberian pig is highly influenced by the production system and type of muscle studied.

Structural and rheological properties of amaranth protein concentrate gels obtained by different processes

The heat-induced gelation of amaranth protein concentrates (APCs) by three processes was studied. The first was the conventional process for isolating protein (standard process-st), the second included an acid washing step prior to protein extraction (acid washing process-aw) and the third included heating (50 °C) during the alkaline extraction step (heat process-ht). The dispersions (12%, w/v) were heated to 55–90 °C and assessed by rheological measurements made under small deformations, whereas the gels obtained by heating at 70, 80 or 90 °C/30 min were subjected to uniaxial compression measurements (TPA and mechanical properties). The rheological parameters associated with the network structure, elasticity modulus (E) and storage modulus ( G′), increased with increasing gelation temperature. For the APCst and APCht gels, protein aggregation occurred in two steps, whereas for APCaw, gelation occurred in a single step. The APCht gels showed the highest fracturability, hardness and adhesiveness, followed by the APCst and APCaw gels ( p < 0.05). Similar results were obtained for the mechanical properties at fracture. Increasing the heat treatment temperature from 80 to 90 °C resulted in a more structured matrix with greater water-holding capacity as compared to gels obtained at 70 °C, and these properties were influenced by the extraction processes used to obtain the APCs. Heat extraction (APCht) improved the gelation and water-holding properties, whereas the acid treatment had the opposite effect.

¿CASTAÑAR PARA FRUTO O PARA MADERA? CONSIDERACIONES SOBRE SU AUTOECOLOGÍA

The autoecology of species has provided quantified information on the characteristics of the environment in which forest species grow. These studies have been carried out using research done on a regional basis, and the study of the sweet chestnut represents the first case that has arisen of the same species appearing in two such very different ways. The chestnut has been exploited by man since ancient times and continues to be of use to humans today as a source of edible chestnuts and/or timber production. This work examines the differences in autoecological characteristics between chestnut stands for the production of nuts and timber. The results indicate that chestnut orchards in Spain tend to be located at higher altitudes and on sites with a less pronounced slope than for trees used for timber production. Chestnut orchards are located under climates with greater winter precipitation, lower summer precipitation and greater excess precipitation, as well as lower average annual temperatures and potential evapotranspiration. From the soil point of view the orchards are found in soils which are significantly less sandy, more silty and clayey, and with a significantly lower permeability, as well as a greater water-holding capacity. Taking the whole set of ecological parameters analysed, it can be seen that it is not the soil or physiographic characteristics but rather the climatic characteristics which basically determine the use which the chestnut stands will be given. It therefore seems appropriate to continue using these climatic characteristics as a guide when assigning the most suitable use for a chestnut stand, whether for the production of nuts or timber.

Effect of Soil Type on Wines Produced fromVitisviniferaL. Cv. Grenache in Commercial Vineyards

In recent years, the wine industry has become increasingly interested in the influence of the terroir characteristics on the features of a wine and, in particular, the mechanisms by which a soil influences wine quality. Among published papers on this topic, most merely describe the effect of the soil; few explain it. In this study were conducted a sensory evaluation and phenolic composition and stilbene concentration tests in order to analyze the effects of soil on wine. Significant differences were found in the results of the tests conducted on two vineyards during two consecutive harvests in 2004 and 2005. The results, in line with previous reports, show that the more fertile of the two vineyards, which was also the one with the greatest water-holding capacity, produced wines that presented significantly lower color intensity and shade, as well as lower total phenolic composition and a smaller quantity of hydroxycinnamic compounds. In 2004, these wines presented significantly higher trans-resveratrol content, due to a fungal attack that was favored by the vineyard's soil characteristics. Extreme drought conditions in 2005 had a marked impact on the characteristics of the wines, increasing wavelength measurements significantly and reducing stilbene concentrations. Finally, sensory evaluations revealed significant differences between the wines produced on the two vineyards in both years for five of the seven attributes evaluated. No significant differences were found from one year to the next between the wines produced from the same vineyard, indicating that the attributes of these wines were maintained despite markedly different vintage conditions.

Effect of calcium concentration on textural properties of high and low acyl mixed gellan gels

Textural properties of 1% low and high acyl gellan gels and their mixtures were studied using compression tests and the microcentrifuge-microfiltration based water holding capacity (WHC) method. Low acyl (1% LA), high acyl (1% HA) gels and mixtures of 1% 25/75 LA/HA, 50/50 LA/HA, 75/25 LA/HA gels with calcium concentrations ranging from 2 to 80 mM were studied. HA or mixed gels with a lower LA/HA ratio had a greater WHC and failure strain than that of LA or mixed gels with a higher LA/HA ratio. Gellan gels with a higher LA/HA ratio had a larger initial Young's modulus. Our study also indicates that a higher LA/HA ratio does not necessarily result in a gel with a larger failure stress, although LA gels are generally firmer than HA gels. Gel strength and WHC of HA and LA/HA mixtures may reflect both stabilization and destabilization effects of glycerate groups positioned at one of the glucose residues in each repeating tetrasaccharide unit of HA gels.

Analysis of the benefits to wheat yield from assimilates stored prior to grain filling in a range of environments*

Grain yields of rainfed agriculture in Australia are often low and vary substantially from season to season. Assimilates stored prior to grain filling have been identified as important contributors to grain yield in such environments, but quantifying their benefit has been hampered by inadequate methods and large seasonal variability. APSIM-Nwheat is a crop system simulation model, consisting of modules that incorporate aspects of soil water, nitrogen (N), crop residues, crop growth and development. Model outputs were compared with detailed measurements of N fertilizer experiments on loamy soils at three locations in southern New South Wales, Australia. The field measurements allowed the routine for remobilization of assimilates stored prior to grain filling in the model to be tested for the first time and simulations showed close agreement with observed data. Analysing system components indicated that with increasing yield, both the observed and simulated absolute amount of remobilization generally increased while the relative contribution to grain yield decreased. The simulated relative contribution of assimilates stored prior to grain filling to grain yield also decreased with increasing availability of water after anthesis. The model, linked to long-term historical weather records was used to analyse yield benefits from assimilates stored prior to grain filling under rainfed conditions at a range of locations in the main wheat growing areas of Australia. Simulation results highlighted that in each of these locations assimilates stored prior to grain filling often contributed a significant proportion to grain yield. The simulated contribution of assimilates stored prior to grain filling to grain yield can amount to several tonnes per hectare, however, it varied substantially from 5–90% of grain yield depending on seasonal rainfall amount and distribution, N supply, crop growth and seasonal water use. High N application often reduced the proportion of water available after anthesis and decreased the relative contribution of remobilization to grain yield as long as grain yields increased, particularly on soils with greater water-holding capacity. Increasing the capacity or potential to accumulate pre-grain filling assimilates for later remobilization by 20% increased yields by a maximum of 12% in moderate seasons with terminal droughts, but had little effect in poor or very good seasons in which factors that affect the amount of carbohydrates stored rather than the storage capacity itself appeared to limit grain yield. These factors were, little growth due to water or N deficit in the weeks prior to and shortly after anthesis (when most of the assimilates accumulate for later remobilization), poor sink demand of grains due to low grain number as a result of little pre-anthesis growth or high photosynthetic rate during grain filling. Increasing the potential storage capacity for remobilization is expected to increase grain yield especially under conditions of terminal drought.

Termite soil preferences and particle selections: strategies related to ecological requirements

At the Lamto Savanna Ecological Station (Cote d'Ivoire), Odontotermes nr. pauperans (Termitidae, Macrotermitinae) was observed to build mounds enriched with fine particles. Using laboratory experiments we studied the selection of building materials by worker termites offered soil from two contrasting horizons: superficial soil (15-20 cm) and a deeper layer (70-80cm). The physical and chemical properties of the unused soil and subsequent termite constructions (foraging galleries and fungus-comb chambers) were compared in each case.¶When presented with a single soil type, the termites modified soil texture for different parts of their structure. Termite building activity increased when presented with both soil types and a notable selection was observed in the use of a given soil type for a specific part of the structure built.¶We conclude that termites utilise soil particles selectively, favouring finer particles and making constructions which match ecological, physiological, and behavioural needs. Compared with material from deeper horizons, less energy was expended when surface soil was used as a resource for gallery building and less C and N supplementation was needed. In contrast, termites preferred deeper soil for constructing fungus-comb chamber walls because this material has greater water-holding capacity.

Comparison of the water-holding capacity of wheat bran products prepared by wet and dry smashing methods in vitro and effect on the gastrointestinal retention time in rats in vivo.

Microfibril wheat bran (MFW) prepared by wet smashing of wheat bran using a colloidal mill has the advantages of being more palatable than other wheat bran and easier to apply to various foods. In this study, we investigated water-holding capacity (WHC) and physiological effects of a novel food material, MFW, focusing on shortening of the retention time of the gastrointestinal contents compared to those of dry smashing of wheat bran (DWB) prepared by conventional method, and wheat bran (WB), which is the raw materials. The mean particle size of MFW was 35 microns, and WHC was 5.1 g/g. In contrast, those of DWB were 61 microns and 3.0 g/g, respectively. Those of WB were 420 microns and 5.0 g/g, respectively. The WHC of MFW was 1.7 times greater than that of DWB and comparable to that of WB. The dietary fiber content in MFW, DWB, and WB were 73.5, 66.9 and 70.2%, respectively. Six-week-old Fisher rats were divided into three groups, and fed for 20 days with AIN-76 chow supplemented with MFW, DWB, or WB to a dietary fiber content of 10%. On days 14-16 of the experimental period, the mean retention time (MRT) of gastrointestinal content and fecal weight were measured using solid phase and liquid phase markers. On day 20 of the experimental period, animals were killed, and the water content, pH, composition of short chain fatty acids (SCFAs) in the cecal content and total amounts of SCFAs in the cecum were investigated. MRT in the MFW group was 15.2 +/- 0.8 h in the solid phase, which was significantly shorter than that in the DWB group (18.0 +/- 0.9 h) (p < 0.05), and comparable to that in the WB (15.5 +/- 2.4 h). MRT in the liquid phase was almost the same as that in the solid phase: 14.7 +/- 1.0, 18.4 +/- 0.8, and 16.0 +/- 2.5 h in the MFW, DWB, and WB groups, respectively. The fecal weight, pH, the concentration of SCFA in the cecal content and total amounts of SCFAs in the cecum did not differ among the groups, but the cecal water content was in the order of MFW > WB > DWB, showing a significant difference between each group (p < 0.05). The above finding suggested that MFW is a novel food material with a greater WHC and the ability of shortening the retention time of the gastrointestinal contents compared to DWB.

Chilled storage of high pressure and heat-induced gels of blue whithing (Micromesistius poutassou) muscle

Microbiological, rheological and chemical characteristics were examined in gels made from the muscle of blue whiting (Micromesistius poutassou) and subjected to three different combinations of pressure, temperature and time: 200 MPa at 3 °C for 10 min (lot L), 375 MPa at 38 °C for 20 min (lot H) and atmospheric pressure at 37 °C for 30 min followed by 90 °C for 50 min (lot T), and kept in chilled storage for 20 days. The microorganism content dropped at the outset as pressurizing took effect, the highest microbial content being found in lot L; however as the effect was not lethal, the total load increased over the following days. Microbial load was significantly lower in lot T. During chilled storage, the values of breaking deformation, breaking force and cohesiveness of lot L were higher than those of the other lots, although they did decrease with storage. The heat-induced gel was much harder, had greater water-holding capacity and was considerably more stable than the high-pressure-induced gels. The lightness value was higher in lot H than in the other two lots. In general, changes in protein solubility tended towards the cleavage of strong bonds as a result of microbial action. The electrophoretic profiles evolved differently in each of the lots over the chilled storage period. However, all of them exhibited large numbers of bands of lower molecular mass which could have been the result of degradation. This was particularly evident in lot H. The heat-induced gels exhibited a highly porous ultrastructure, quite different from the high-pressure-induced gels; these had a more compact matrix which expanded as storage progressed.

OPTIMIZATION OF DEHYDRATED EGG QUALITY BY MICROWAVE ASSISTED FREEZE-DRYING AND HYDROCOLLOID INCORPORATION

Enhancement of the physical and sensory properties of rehydrated egg products as a consequence of microwave assisted freeze-drying and addition of hydrocolloids to the formulation was assessed. When compared to conventional freeze-drying (CFD), microwave assisted freeze-drying (MFD) led to products with greater water-holding capacity and reduced elastic modulus. Comparisons were also made of moisture sorption rates. The addition of xanthan gum and, to a lesser extent, microcrystalline cellulose increased both water-holding capacity and elastic modulus. Magnitude estimation by a trained texture panel of critical sensory properties (chewiness, rubberiness, moistness, moisture release, and roughness) revealed that MFD samples were superior to CFD samples and that MFD samples containing xanthan were closest to the optimal for the egg products. It was concluded that the more uniform and less heat stressing process of microwave assisted freeze-drying coupled with the presence of xanthan gum leads to a rehydrated product that best retains its structural integrity and ability to bind (reabsorbed) water and that, in turn, has highly acceptable textural properties most similar to fresh eggs.

Growth of Bedding Plants in Sphagnum Peat and Coir Dust-Based Substrates

Abstract Water-holding capacity of substrates increased as the proportion of sphagnum peat and coir increased, and coir-based substrates had greater water-holding capacities than comparable peat-based substrates. There were no significant differences between coir and peat-based substrates with respect to bulk density, percent pore space and percent solids. Air-filled pore space and water-filled pore space decreased and increased, respectively, as the proportion of peat and coir increased. ‘Pink Elite’ geranium plants grown in coir-based substrates had greater root fresh weights than those grown in sphagnum-peat based substrates. Greatest root fresh weight occurred in an 80% coir and 20% perlite substrate. Days to flower, height, shoot fresh weight and number of axillary shoots were not significantly different between substrates. ‘Janie Bright Yellow’ marigold and ‘Blue Lace Carpet’ petunia plants had increased heights and shoot fresh weights when grown in coir-based substrates as compared with sphagnum peat-based substrates. Greatest heights and shoot fresh weights of petunia and marigold occurred in an 80% coir and 20% perlite substrate. Days to flower were reduced for marigold plants grown in coir-based substrates.

Replant Management Strategies Influence Early Growth of Apple Trees in a Sand Soil

Abstract Two field experiments were conducted to evaluate the influence of rootstock (seedling, M.26, MM.106), soil fumigation (metam-sodium, methyl bromide), and planting hole substrate (original soil, non-orchard soil, organic mix) on early growth of ‘Granny Smith’ apple trees (Malus domestica Borkh.) in a Quincy sand. Application of soil fumigants in the fall before tree planting the next spring or replacement of the original soil with non-orchard planting hole substrates having greater water-holding capacity and nutrient status significantly improved tree growth. Combination of fumigation and soil replacement had a synergistic positive effect on tree growth. The size-controlling characteristics of the rootstocks were evident in the non-orchard soil and organic mix treatments, but not when the trees were planted in the original orchard soil. Chemical name used: sodium N-methyldithiocarbamate (metam-sodium).

Sequence of bryophytes and lichens in relation to substrate variables of decaying coniferous wood in Northern Sweden

Söderström, L. 1988. Sequence of bryophytes and lichens in relation to substrate variables of decaying coniferous wood in Northern Sweden. ‐ Nord. J. Bot. 8: 89–97. Copenhagen. ISSN 0107–055X.The species sequence on decaying logs during the decay period has been investigated in a forest in Northern Sweden. The species present can be divided, by means of a weighted average technique, into four groups, facultative epiphytes, early and late epixylics, and ground flora species.Species sequence on several variables reflecting the wood decay, was measured for 25 species. Wood texture (degree of surface erosion) was the most important variable in separating species. Logs high above ground had very few species, probably due to low moisture content. Log diameter was important and several species did not occur, or only rarely occurred, on small logs. Small logs are more rapidly overgrown by ground flora species and very few reach late decay stages before being overgrown. Larger logs also have greater waterholding capacity which facilitates growth of many species sensitive to drought.

Effect of soil transfer on ectomycorrhiza formation and the survival and growth of conifer seedlings on old, nonreforested clear-cuts

Small amounts (150 mL) of soil from established conifer plantations and mature forest were transferred to planting holes on three clear-cuts in southwest Oregon and northern California to enhance mycorrihiza formation. The clear-cuts, 8–27 years old and unsuccessfully reforested, included a range of environmental conditions. At Cedar Camp, a high-elevation (1720 m) southerly slope with sandy soil, transfer of plantation soils increased 1st-year Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedling survival by 50%. Notably, soil from a plantation on a previously burned clear-cut doubled mycorrhiza formation and tripled seedling basal area growth. Soil from mature forest did not improve survival and growth. Less dramatic effects owing to soil transfer were evident on other sites, which were lower in elevation and had clayey soils with greater water-holding capacity, and where woody shrubs had apparently preserved mycorrhizal fungi. At Crazy Peak (1005 m), seedling survival was uniformly good, and soil from a previously burned plantation increased Douglas-fir mycorrhiza formation. At Wood Creek (500 m), soil from a plantation on a previously unburned clear-cut increased mycorrhizal branching on sugar pine (Pinuslambertiana Dougl.) seedlings, but there was no other effect. Results suggest that adequate mycorrhiza formation is critical to seedling growth and survival on cold, droughty sites. Populations of mycorrhizal fungi, and perhaps other beneficial soil biota, decline if reforestation is delayed or other host plants are absent. These declines can be offset by soil transfer from the proper source; in this study, soil from vigorous young plantations.

Sexual dimorphism and resource allocation in male and female shrubs of Simmondsia chinensis.

Desert populations of the evergreen dioecious shrub Simmondsia chinensis exhibit sex-related leaf and canopy dimorphisms not present in populations from more mesic coastal environments. Leaves on female shrubs have characteristically larger sizes, greater specific weights, and greater water-holding capacity than male leaves in desert habitats. In coastal scrub environments no significant difference is present, with leaf characteristics of both sexes similar to those of desert male shrubs. Desert female shrub canopies are typically relatively open with little mutual branch shading. In male shrubs canopies are more densely branched with considerable mutual shading of branches. Female plants allocate a greater proportion of their vegetative resources to leaves than do male plants. Considering total biomass, male plants allocate 10-15% of their resources (biomass, calories, glucose-equivalents, nitrogen, phosphorus) to reproductive tissues. Female allocation is dependent on seed set. At 100% seed set females would allocate 30-40% of their resources to reproduction, while female reproductive investment would equal that of males at approximately 30% seed set. Sexual dimorphism and the associated physiological characteristics in Simmondsia act as an alternative to differential habitat selection by male and female plants. Female plants respond to limited water resources in desert areas by increasing their efficiency in allocating limited resources to reproductive structures.