Academic literature on the topic 'Plants, Effect of soil moisture on – Western Australia – South-West'

The effect of sowing rate (60–320 kg/ha) on the growth and seed yield of kabuli chickpea (cv. Kaniva) was assessed at 11 sites for 4 seasons in the cropping regions of south-western Australia. The economic optimum plant density and yield potential were estimated using an asymptotic model fitted to the data and calculating the sowing rate above which the cost of additional seed was equivalent to the revenue that could be achieved from the extra seed yield produced, assuming a 10 and 50% opportunity cost. On average for all sites and seasons, plant densities ranged from 10 plants/m2 when sown at 60 kg/ha to 43�plants/m2 when sown at 320 kg/ha. Assuming a mean seed weight of 400 mg and a germination of 80%, then on average 75% of viable seeds sown (or 60% of sown seeds) established as plants. The poor establishment rates are thought to be associated with reduced viability caused by mechanical damage, storage conditions, fungal infection in the soil, and unfavourable seed bed moisture and temperatures. In general, there was a positive relationship between sowing rate and seed yield. Seed yield increases at higher sowing rates were mainly associated with the greater number of plants per unit area. There were fewer pods per plant at higher sowing rates, but there were more pods per unit area. Changing the sowing rate had little effect on mean seed weight and the number of seeds per pod. The economic optimum plant density varied from 8 to 68 plants/m2, depending on the location, but the mean (27�plants/m2) was within the range currently recommended in southern Australia (25–35 plants/m2). Due to the low establishment rates observed in this study, we estimate a sowing rate greater (160–185 kg/ha) than currently suggested (110–160 kg/ha) to achieve this density. There was a strong relationship between economic optimum plant density and seed yield potential (r2 = 0.66, P<0.01), which allows an estimation of the most profitable sowing rate, depending on the seed yield potential of the site. For most crops yielding about 1.0 t/ha in southern Australia, a plant density of 25 plants/m2 is most profitable, while in higher-yielding situations (>1.5 t/ha) plant densities >35�plants/m2 will produce the most profit.

Farmers often experience inconsistent responses when using herbicides to terminate an established lucerne pasture prior to cropping. In an attempt to redress this problem, a series of field experiments were conducted between 1999 and 2002 at various locations in southern and northern New South Wales, the Australian Capital Territory, and south Western Australia that aimed to identify management guidelines that improved the efficacy of herbicide mixtures commonly used to remove lucerne. Collectively, these studies indicated that herbicides were generally less effective when applied either early (less than 2 weeks) or late (6 weeks or more) in the regrowth cycle of lucerne after defoliation. Herbicide efficacy tended to be greatest if applied to regrowth 3–5 weeks after defoliation, which corresponds to a time when the lucerne crown and root reserves are likely to be in the process of being replenished by photoassimilates transported from the shoot. The impact of timing of herbicide application in relation to season was compared at a number of locations. Across all the sites and years, spring herbicide applications were generally the most effective, removing on average 87% of the lucerne (range 53–100%) compared with 72% in summer (24–100%) and 60% in autumn (7–92%). Spring applications were also more consistent in their effect, removing >80% of the lucerne plants in 9 out of 12 experiments, whereas similar rates of removal occurred on 4 occasions in 9 summer applications and only twice in 8 autumn applications. Some of the seasonal variation could be explained by differences in the amount of rainfall prior to herbicide applications. It was assumed that the relationship between rainfall and herbicide efficacy reflected the stimulation of lucerne shoot and root growth by the additional soil moisture before herbicide treatment. Herbicide mixtures that contained ingredients such as picloram that retain residual activity in the soil tended to be more effective and were less influenced by lucerne growth and season than those herbicides with little or no residual activity. However, such chemicals could potentially restrict which crops can subsequently be grown after a lucerne pasture has been removed. It was concluded that >80% of lucerne plants were likely to be removed using herbicides provided that the herbicide treatment was applied to actively growing lucerne 3–5 weeks after defoliation, and when greater than 70–95 mm rain had fallen in the 6–8 weeks prior to application.

The effects of 2 tree windbreaks on pasture production in adjoining paddocks were assessed over 4 years in a cool-temperate climate, perennial pasture area in south-western Victoria, Australia. The Willandra windbreak was 2 rows of direct-sown black wattle (Acacia mearnsii) aligned south-east–north-west. The Helm View windbreak was 4 rows of mixed Eucalyptus, Casuarina and Acacia spp., aligned east–west. Pastures at both sites had been sown to perennial ryegrass and subterranean clover. Wind direction data indicated that the north-eastern and south-western paddocks at Willandra were sheltered 39 and 28% of the time, respectively. The northern and southern paddocks at Helm View were sheltered 34 and 42% of the time, respectively. The relationship of rainfall with wind speed and direction was examined to indicate the potential of windbreaks of various orientations to protect livestock. The windbreaks had clear effects on pasture production in the competition zone along the margins of the windbreak. Average pasture production at Willandra in the zone 0.5–0.75 H (where H is the windbreak height) was 69% of open yield; production in the 0.9–1.5 H zone was 96%. At Helm View, production in the zone 0.7–1.0 H was 74% of open yield, with 81% in the zone 1.1–1.5 H. Averaged over all years, both windbreaks had no effect on pasture growth in the 2–10 H sheltered zone, although in some years there were small significant growth increases at parts of that zone in certain paddocks. Periodic soil moisture measurements at Willandra showed that water use was greater in the competition zone near the windbreak, with a difference in summer water content of the 1.2 m profile of at least 20 mm between soil 4.6 m from the windbreak and further away. The difference was due to greater water use from the deepest part of the profile. No other effects of the windbreak on soil water content were observed.

This paper examines the effect severing lateral tree roots (root pruning) has on crop and tree growth and soil water content at 2 sites in the south-west of Western Australia. Crop and tree growth and soil water content were assessed in a Pinus pinaster windbreak system growing on 0.45–1.00 m of sand over clay, and crop growth was assessed adjacent to Eucalyptus globulus windbreaks growing on 4–5 m of sand. Crop yield was depressed by 23–52% within 2.5 times the tree height (H) of unpruned pines and by 44% within 2.5 H of pruned eucalypts. Depressed yields made cropping uneconomical within 1.5 H of the eucalypts and 1 H of the pines. Root pruning most improved crop yields where lateral tree roots were confined close to the soil surface and decreased in effectiveness as the depth to confining layer (clay) increased. Crop losses within 2.5 H of the pines were reduced from 39 to 14% in the year the trees were root pruned and were 25% 1 year after root pruning. Subsequent root pruning of the eucalypts did not improve crop yield. While root pruning severed lateral pine roots, tree growth was not significantly reduced. The principal cause of reduced crop yield near the trees appeared to be reduced soil moisture in the area occupied by tree roots. Competition for nutrients and light appeared to have little effect on crop yield. Root pruning can spatially separate tree and crop roots where the tree roots are confined close to the surface, and significantly improve crop yields without reducing tree growth.

Twenty-one field experiments located in different rainfall zones on a range of soils that had been fertilised with copper (Cu) fertiliser 16-23 years previously were used to examine the effect of level of nitrogen (N) fertiliser on the grain yield of wheat. At 1 site (experiment 15), no Cu fertiliser had been applied. The effect of applied N on Cu concentrations in the youngest emerged blade (YEB) and in the grain was also studied. At 20 sites, there was no further response to currently applied Cu fertiliser. The highest level of N fertiliser applied (46-92 kg N/ha) did not induce Cu deficiency in wheat plants. The addition of Cu increased Cu concentration in the YEB and grain, whilst increasing the rate of N fertiliser generally decreased these concentrations of Cu. At 2 sites in the Jerramungup district, the addition of N induced Cu deficiency in wheat, which reduced grain yields. Increasing the rate of N fertiliser reduced Cu concentration in the YEB to deficient levels (< 1.0 mg Cu/kg); Cu concentrations in grain were <0.8 mg/kg. Only 50% of the recommended Cu fertiliser had been applied in previous years at 1 site (experiment 12). At the other site, Cu appears not to have been previously applied, because the ammonium oxalate soil-extractable Cu measured in soil samples collected from the site and adjacent uncleared soil were identical and very low (0.25 mg Cu/kg). At 1 high-yielding site (>3.0 t/ha), the highest level of N (92 kg/ha) reduced Cu concentration to 1.0 mgkg in the YEB and 1.0 mg/kg in the grain without reducing grain yield. It is concluded that high levels of N fertiliser application did not increase the wheat plants' requirement for Cu fertiliser where Cu fertilisers had been applied at the recommended level in the past 23 years. Where Cu fertiliser has been applied at lower-than- recommended levels in previous years, Cu deficiency occurred where high levels of N were applied.

A network of rainfall stations was selected across the Australian wheatbelt and monthly rainfall regressed with wheat yields from the surrounding shires for the period 1976-87. Yields were found to be strongly related to fluctuations in total rainfall amount and the seasonal distribution of rainfall through the year. These temporal relationships vary spatially and appear to be regulated by the water-holding capacity of regional soils. Sixteen agrometeorological zones were defined with similar rainfall-yield relationships. In all these, autumn rains that permit an early sowing, and finishing rains after July, are most important for higher yields. As the rainfall distribution becomes more winter-dominant, both crop yield variability and the usefulness of high winter rainfall decreases. Heavy rainfall in the month after sowing can have a negative effect in southern Australia, as plants are more prone to suffer potential yield losses from a wet soil profile. Waterlogging has a large negative effect in the south-west of Western Australia, such that the rainfall distribution can be more important than the rainfall amount. Rainfall-yield correlations are generally more positive in drier regions, and are enhanced by persistent rainfall anomalies between April and November during El Niño Southern Oscillation years.

This article continues the series of publications devoted to the classification of communities with invasive plant species in the Southern Urals (Abramova, 2011, 2015; Abramova, Golovanov, 2016b). The information on communities with four aggressive neophytes of North American origin Solidago canadensis L., S. gigantea Ait., Lupinus polyphyllus Lindl. and Phalacroloma annuum (L.) Dumort. s. l. (Table 1) is given. All species are included in the «black list» of the Republic of Bashkortostan (Abramova, Golovanov, 2016a), and the «Black book of the flora of Central Russia» (Vinogradova et al., 2010). The studies was conducted in the period 2016–2018 on the republic territory. The wide distribution of species and their naturalization in the meadow and semi-natural communities of the Southern Urals are noted (Abramova, 2011, 2014; Abramova et al., 2016; Abramova, Golovanov, 2018). In the centers of invasion of the studied species, 83 geobotanical relevés of communities were performed on sample areas of 10–100 mІ. Location, date, area of the described area, total cover, mean and maximum height of grass layer were indicated for each sample plot. The classification of communities involving these invasive species was carried according to Braun-Blanquet method with Kopecký–Hejný approach (Kopecký, Hejný, 1974). The identified syntaxa were compared with the units previously described in the studied area and other regions. Ecological regimes of communities are determined using the weighted average of the Landolt’s optimum ecological scales by IBIS 6.2 software (Zverev, 2007). The weighted average values are calculated according to the following scales: moisture (F), acidity (R), soil richness with mineral nutrients (N), humus content (H), light (L) and continentality (K). The Detrended correspondence analysis (DCA-ordination) method was applied using the CANOCO 4.5 software package to identify the patterns of ecological differentiation of invasive communities. Herbaceous perennials plants Solidago canadensis and S. gigantea left the decorative culture and now are naturalized in meadows along roadsides, forest edges, wastelands, fallow lands, around gardens near large cities. The most common species is S. canadensis, common in the vicinity of human settlements. S. gigantea is first recorded only in 2017 in the North-West of the republic, where it formed monodominant communities on the territory of abandoned garden plots. The ass. Rudbeckio laciniatae–Solidaginetum canadensis Tüxen et Raabe ex Anioł-Kwiatkowska 1974 (Tables 2, 3) with 2 variants: Solidago canadensis (Fig. 1) and Solidago gigantea and the derivate community Solidago canadensis–Poa angustifolia [Molinio-Arrhenatheretea/Artemisietea vulgaris] (Table 4, Fig. 2) is described. Association variants reflect the dominance of Solidago canadensis or S. gigantea, the derivative community is characterized by the presence of two large groups of species: meadow species of the class Molinio-Arrhenatheretea Tx. 1937 and sinanthropic two- and long-term species of the class Artemisietea vulgaris Lohmeyer et al. in Tx. ex von Rochow 1951. Lupinus polyphyllus is an ornamental herbaceous plant, also dissapeared fr om culture and naturalized in meadow communities. Within the studied area it is sporadically recorded in the Cis-Urals, but invasive populations of sufficiently large in size form only in the north-western districts of the republic on the territories of abandoned horticultural plots, along the roads on the meadows, occasionally on abandoned fields. A derivative community Lupinus polyphyllus[Arrhenatheretalia elatioris] (Tables 6, 7) with 2 variants: typica (Fig. 3) and Convolvulus arvensis, which represent meadow or ruderalized communities, has been identified. The annual Phalacroloma annuum is confined to the areas of the northern Cis-Urals, wh ere it is widely naturalized in meadows, but has no a transforming effect on the meadow coenoflora. Thay is why var. Phalacroloma annuum as part of the association of low-grass meadows of the hay and pasture use within ass. Agrostio tenuis–Festucetum pratensis Yamalov 2015 (Table 9) as well as derivate community Phalacroloma annuum–Cirsium setosum [Arrhenatheretalia elatioris/Artemisietea vulgaris] (Table 10) for semi-natural communities in abandoned garden plots and fields with a large proportion of synanthropic species in floristic composition are suggested. All four invasive species are intruded and naturalized in meadows of varying degrees of anthropogenic disturbance, as well as in semi-natural phytocenoses of the final stages of succession. The ordination analysis (DCA-ordination) confirmed the suggested floristic classification (Fig. 4). The first axis is associated with two differently directed factors — soil acidity (correlation coefficient — 0.10) and humus content (correlation coefficient — –0.29). The distribution of communities along the second axis is associated with the substrate moistening (correlation coefficient is 0.10) and the community light conditions (correlation coefficient is –0.57), these vectors also have different directions. All communities with these species are well differentiated in the space of the two main ordination axes, which indirectly confirms the correctness of the syntaxonomic decision, and also indicates the wide ecological amplitude of the species and their use of different ecological niches in similar types of meadow and semi-natural communities of the Southern Urals. The leading factors in the community distribution are both those characterizing the soil properties (moisture, acidity, humus content) and habitat ones (light conditions). The high invasive potential of these neophytes makes possible to predict their further distribution over the territory of the Republic of Bashkortostan.

Abstract African lovegrass [Eragrostis curvula (Schrad.) Nees] is an invasive weed that is threatening biodiversity around the world and will continue to do so unless its efficient management is achieved. Consequently, laboratory and field-based experiments were performed to analyse several measures of germination to determine the effect of drought stress, radiant heat stress and burial depth and duration (longevity) on E. curvula seeds. This study investigated seeds from four spatially varied populations across Australia: Maffra and Shepparton, Victoria; Tenterfield, New South Wales; and Midvale, Western Australia. Results showed that increasing drought stress reduced and slowed germination for all populations. Maffra (24% vs. 83%) and Shepparton (41% vs. 74%) were reduced at the osmotic potential of ≤-0.4 MPa, whilst Tenterfield (35% vs. 98.6%) and Midvale (32% vs. 91%) were reduced at ≤-0.6 MPa, compared to the mean of all other osmotic potentials. Radiant heat at 100 C significantly reduced and slowed germination compared to 40 C for Tenterfield (62% vs. 100%), Shepparton (15% vs. 89%) and Midvale (41% vs. 100%); whilst Maffra (75% vs. 86%) had consistent germination. For the effect of burial depth and duration (longevity), there was no significant difference across the fourteen-month period, however, the 0 cm burial depth had a significantly lower final germination percentage compared to depths of 3, 5 and 10 cm (24% vs. 55%). Although each trial was conducted independently, their results can be used to help identify efficient control measures to reduce infesting populations. Such measures recommended include using soil moisture monitoring to detect which conditions will promote germination, as germination is encouraged when the osmotic potential is >-0.6 MPa; exposing seeds to radiant heat (>100 C) using methods such as prescribed burning; and limiting soil disturbance over time to reduce seed establishment.

Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots. Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots.

[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.