Cortaderia selloana seed germination under different ecological conditions

Water bodies can mitigate urban heat island effects and allow terrestrial animals to access water during periods of insufficient precipitation. Because precipitation is expected to become increasingly scarce in many global regions, urban riparian areas in drylands may yield important insight into the dynamic role of water in terrestrial animal communities. Here, we first investigated the role of spatiotemporal variability in water availability in insect biomass and biodiversity in an urban riparian area—particularly, whether seasonality modulates the spatial effects of water availability. High water availability was characterized spatially by proximity to a river, and temporally by high-precipitation seasons. Second, we investigated whether the relationship between biomass and biodiversity shifts due to variation in water availability. We determined the biomass and biodiversity of an insect community across a riparian zone in Stockton, CA, USA, an urban drylands area characterized by hot, dry summers and cool, wet winters. Time (seasonality exhibiting dramatic variation in precipitation) exerted strong effects on ecological indices and a biodiversity-biomass relationship. Space (proximity to a fixed water source) had more modest effects on the community, and there was some evidence that space and time modulated the effects of one another on the community. Urban animal community dynamics may be more sensitive to larger-scale climate patterns than to local, landscape-level factors, and covariation between biomass and biodiversity may be influenced by resource (water) availability. Studying insect communities in the riparian zones of urban drylands may be critical to understanding how animal communities respond to a warmer, drier climate.

SummaryMicroclimatic effects (light, temperature) are often neglected in phenological studies and little information is known about the impact of resource availability (nutrient and water) on tree’s phenological cycles.Here we experimentally studied spring and autumn phenology in four temperate trees in response to changes in bud albedo (white‐painted vs black‐painted buds), light conditions (nonshaded vs c. 70% shaded), water availability (irrigated, control and reduced precipitation) and nutrients (low vs high availability).We found that higher bud albedo or shade delayed budburst (up to +12 d), indicating that temperature is sensed locally within each bud. Leaf senescence was delayed by high nutrient availability (up to +7 d) and shade conditions (up to +39 d) in all species, except oak. Autumn phenological responses to summer droughts depended on species, with a delay for cherry (+7 d) and an advance for beech (−7 d).The strong phenological effects of bud albedo and light exposure reveal an important role of microclimatic variation on phenology. In addition to the temperature and photoperiod effects, our results suggest a tight interplay between source and sink processes in regulating the end of the seasonal vegetation cycle, which can be largely influenced by resource availability (light, water and nutrients).

Little is known about the effect of water availability on P pools in the detritusphere. Detritusphere was generated with two plant residues: 100% barley straw, C/N 95, C/P 255; 75% barley straw with 25% young faba bean shoot, C/N 74, C/P 200. Residues were placed between two PVC caps filled with soil at − 0.078 MPa, separating them from the soil surface with fine nylon mesh. Unamended controls were without residue between the two meshes. After 2 weeks, soil at 0–2 mm distance from the surface was collected and the soil water availability was either maintained at − 0.078 MPa or reduced to − 0.320 and − 1.700 MPa by drying in a fan-forced oven. Bioavailable P pools, available N, and microbial N were measured 1, 14, and 28 days after adjusting to different water availabilities. Soil respiration was measured over 28 days. Soil water availability had a stronger effect on respiration, available N, and microbial biomass N (MBN) in the mix than the control or barley. With the mix compared with − 1.700 MPa, cumulative respiration from day 0 to 14, available N and MBN were five, two, and three-fold higher at − 0.078 MPa. In the control or with barley, differences between the two water contents were two or less fold. Low water availability limits microbial activity and nutrient fluxes at high substrate availability as in the mix but has little effect when substrate availability is low even at high water availability as in the control and with barley.

Research Highlights: Dedicated experiments to investigate how disturbances will affect Heterobasidion sp.—Norway spruce pathosystems are important, in order to develop different strategies to limit the spread of Heterobasidion annosum s.l. under the predicted climate change. Here, we report on a greenhouse experiment to evaluate the effects of water availability on the infection severity of Heterobasidion parviporum or Heterobasidion annosum, respectively, on Picea abies saplings. Background and Objectives: Changes in climatic conditions and intense logging will continue to promote H. annosum s.l. in conifer forests, increasing annual economic losses. Thus, our aim was to test if disease severity in Norway spruce was greater after infection with H. parviporum or H. annosum in low water availability conditions, compared to seedlings with high water availability. Materials and Methods: We performed inoculation studies of three-year-old saplings in a greenhouse. Saplings were treated as high (+) or low (−) water groups: High water group received double the water amount than the low water group. The necrosis observed after pathogen inoculation was measured and analyzed. Results: The seedling growth was negatively influenced in the lower water group. In addition, the water availability enhanced the necrosis length of H. parviporum in phloem and sapwood (vertical length) in the low water group. H. annosum benefited only in horizontal length in the phloem. Conclusions: Disturbances related to water availability, especially low water conditions, can have negative effects on the tree host and benefit the infection ability of the pathogens in the host.

• Environmental determinants of wood properties variation were examined in Eucalyptus globulus ,a globally important hardwood plantation species, in southern Tasmania, Australia. • Radial variation in wood properties, measured with the SilviScan system, were re-scaled from distance to time abscissa using stem radial growth data measured with dendrometers. With this re-scaled data it was possible to evaluate how water availability and temperature affected wood density, microfibril angle (MFA) and fibre and vessel transverse dimensions in irrigated and non-irrigated trees. • Wood density, fibre radial diameter and MFA were sensitive to water availability. Wood density increased and fibre radial diameter decreased in response to reduced water availability. When high water availability was maintained, wood density was negatively correlated with temperature. Together, temperature and soil matric potential explained about 60% of temporal variation in wood density variation. In contrast MFA was not related to temperature but decreased with increasing water stress. Slower growing trees also had lower MFA than faster growing trees. Slower growing trees had a larger number of vessels per unit area of wood than faster growing trees within this even aged stand. However, vessel radius to the 4th power was significantly higher in faster growing trees than in slower growing trees. • Overall, E. globulus wood properties were sensitive to temporal changes in environmental conditions (particularly water availability) and associated growth rates. The data provided support for the hypothesis that growth rates are hydraulically mediated.

The article presents the results of calculating the water consumption per year of 75% availability and during the growing season from May to September on the borders of village councils for the Muchkapsky municipal district of the Tambov region. The calculation was carried out over a 60-year period. The current article presents schematic maps for one municipal district, selected as a vivid example of displaying various degrees of water availability. For the first time, river runoff resources were calculated for each month of the growing season for the entire territory of the Tambov region. Maps-schemes of provision of rural areas of the Tambov region with river flow resources will allow water users to estimate the permissible volumes of water for economic use on the territory of each village council. Based on the existing classifications of water availability, the authors have compiled their own classification, which makes it possible to distribute the territories of rural councils in the year of 75% provision by categories of water availability. Thus, in a year 75% of the provision of the Muchkap municipal district has 75% of the territories with very high water availability and only 12.5% of the territories of the Muchkap municipal district belong to the categories with extremely low and low water availability. The conducted research allows us to conclude that, in general, the territory of the Muchkap municipal district for the most part allows for industrial water intake by local enterprises.

In Argentina, wheat (Triticum aestivum L.) is cropped over a wide range of climatic conditions. Considerable variability in the ratio of dry weight produced per unit of transpired water, usually referred to as water-use efficiency (WUE), is expected as variation in climatic factors affects photosynthesis and transpiration in different ways. Also, previous studies have shown that water supply limitations may affect WUE in wheat. The objective of this study was to quantify the effects of climatic environment and water availability on WUE in wheat crops. Six experiments were conducted at different locations of the Argentine wheat belt and crop dry weight and water use were measured in periods when water use was dominated by transpiration. Three of the experiments included both irrigated and rainfed treatments. Mean daily values of (i) pan evaporation, (ii) relative humidity, (iii) potential water use, and (iv) vapor pressure deficit, were used to find a general relationship that explained effects of the climatic environment on WUE. For experiments with high water availability, daytime vapor pressure deficit was better related to WUE than the other climatic factors. WUE was greater for experiments with water limitation, probably because stomatal closure to restrict transpiration rate occurred around midday when vapor pressure deficit was highest. As a consequence, relative dry weight under water limitation was not linearly related to relative water use as proposed in previous studies. A quadratic relationship that better represented this response was derived.

In Argentina, wheat (Triticum aestivum L.) is cropped over a wide range of climatic conditions. Considerable variability in the ratio of dry weight produced per unit of transpired water, usually referred to as water‐use efficiency (WUE), is expected as variation in climatic factors affects photosynthesis and transpiration in different ways. Also, previous studies have shown that water supply limitations may affect WUE in wheat. The objective of this study was to quantify the effects of climatic environment and water availability on WUE in wheat crops. Six experiments were conducted at different locations of the Argentine wheat belt and crop dry weight and water use were measured in periods when water use was dominated by transpiration. Three of the experiments included both irrigated and rainfed treatments. Mean daily values of (i) pan evaporation, (ii) relative humidity, (iii) potential water use, and (iv) vapor pressure deficit, were used to find a general relationship that explained effects of the climatic environment on WUE. For experiments with high water availability, daytime vapor pressure deficit was better related to WUE than the other climatic factors. WUE was greater for experiments with water limitation, probably because stomatal closure to restrict transpiration rate occurred around midday when vapor pressure deficit was highest. As a consequence, relative dry weight under water limitation was not linearly related to relative water use as proposed in previous studies. A quadratic relationship that better represented this response was derived.

This paper represents an empirical study on the effect of different leaf orientations on the daily carbon gain and transpirational water loss of desert winter annuals. Laboratory physiological data on Malvastrum rotundifolium (Gray) and Lupinus arizonicus (Wats) were combined with energy budget concepts and field measurements of water relations and leaf movements to predict carbon gain patterns for horizontally oriented, diaheliotropic and paraheliotropic leaf movement types. The results showed contrasting patterns of carbon gain and water loss. L. arizonicus, which is capable of both dia- and paraheliotropic leaf movements, had the lowest rates of daily carbon gain and water loss. But these low rates resulted in the highest water use efficiencies under early season conditions and high water availability. M. rotundifolium, a diaheliotropic species, was predicted as having the highest rates of carbon gain and water loss on a daily basis over a wide range of environmental conditions and water availability. Despite possessing the highest rates for transpiration, its water use efficiency was higher in relation to other leaf movement types, under a variety of conditions. This result was extremely sensitive to soil water availability. The results were discussed in relation to the ecological ramifications of leaf movements in arid land annuals.

Identifying environments where invasive plants are most invasive is key to understanding causes of invasion and developing effective management strategies. In mixed-grass prairie, invasive plants are often successful in relatively wet, nitrogen-rich areas, and areas protected from grazing. Dalmatian toadflax, a common invader of mixed-grass prairie, can also be favored by high water and nitrogen availability, but is thought to be relatively unpalatable to cattle, and therefore favored by grazing. We used spatially-adjusted model selection techniques to quantify relationships between toadflax cover (measured using very high-resolution aerial imagery), and relative snow deposition (estimated with a blowing snow model), slope, aspect, soil texture, and grazing intensity (estimated by proximity to water tanks). Toadflax was common throughout the 400 ha study site, occurring in 742 of 1,861 images. Toadflax cover was high on steeper slopes, particularly those with southern aspects. These two topographic variables were more effective in explaining toadflax distribution than modeled snow deposition, suggesting that factors other than snow deposition cause toadflax invasion on south-facing slopes. Toadflax cover was also high in areas further from water tanks, indicating that grazing may inhibit toadflax invasion. More broadly, this result suggests that grazing can reduce invasion of even relatively unpalatable species in ecosystems with long evolutionary histories of grazing.

Epiphytes are highly dependent on atmospheric inputs of water and nutrients. Reductions in water availability associated with warming and climate change and continual atmospheric nitrogen (N) deposition can affect plant growth but few studies have evaluated the effects of changes in both water and nutrient availabilities on epiphytes. We experimentally tested whether epiphyte growth is more water- or nutrient-limited, if nutrient limitation was stronger for nitrogen or phosphorus, and whether nutrient limitation interacts with water availability. We applied watering (high and low) and nutrient addition (control, +N, +P, +N+P) treatments to greenhouse-grown Asplenium nidus, a common epiphytic fern found in many tropical and subtropical wet forests. We measured leaf area production and leaf elemental concentrations to assess how A. nidus growth and physiology respond to changes in water and nutrient availabilities. We found that leaf growth of A. nidus was more affected by water availability than nutrient addition and the effect of adding nutrients was not fully realized under low-water availability. Among the different nutrient treatments, +N+P had the greatest effects on A. nidus growth and physiology in both watering treatments. Watering treatment changed leaf elemental concentrations but not their ratios (i.e. C:N and N:P). Nutrient addition altered C:N and N:P ratios and increased the concentration of the added elements in leaves, with more pronounced increases in the high-watering treatment. We conclude that the growth of A. nidus is more water- than nutrient-limited. When nutrient limitation occurs (i.e. under high-water availability), nutrient co-limitation is stronger than limitation by N or P alone. This result taken together with studies of other epiphytes suggests greater water than nutrient limitation is likely widespread among epiphytic plants. The limited effects of nutrient addition in the low-water treatment suggest that the effect of atmospheric N deposition on epiphyte growth will be limited when water availability is low.

Coastal sandplain heathlands are a rare plant community in the northeastern United States. Salt spray and water availability are likely important factors determining heathland distribution. Field surveys and manipulative experiments were performed to examine heathland species' responses to salt spray and water availability. We surveyed field distributions of four typical heathland species: Solidago puberula, Solidago rugosa, Gaylussacia baccata, and Myrica pensylvanica. The distributions of two native tree species, Pinus rigida and Quercus ilicifolia, were also surveyed because they succeed into coastal heathlands with low disturbance frequency. We then manipulated salt spray and water in the field and measured species' water status, necrosis, and growth responses to the treatments. Predawn xylem pressure potential and necrosis were strongly affected by high salt spray and low water availability. Shoot elongation was also limited in S. puberula and S. rugosa grown in high salt, low water treatments. Gaylussacia baccata and Q. ilicifolia were particularly sensitive to high salt spray and low water, suggesting that they might excluded be from areas with those conditions. The interaction between salt spray and water availability could affect the landscape scale and should be incorporated into conservation management plans.

Vegetation patterns in the high-altitude Himalayas are influenced by a complex set of biotic and abiotic factors. Anthropogenic disturbances are one of the primary factors influencing the community patterns and diversity, which are largely determined by the level of accessibility in the Himalayas. However, with advancing urbanization and accessibility, limited efforts have been made to quantify the impact of road constructions on the alpine flora of the Himalayas. To overcome this data gap, this study aimed to quantify the impact of anthropogenic disturbance on the alpine vegetation community pattern along the altitudinal gradient, i.e., 3264–4340 m in Kullu district and 3148–4634 m in Lahaul and Spiti district of Himachal Pradesh, Northwestern Himalayas. The impact of anthropogenic disturbance was assessed by comparing species diversity and richness between selected disturbed and undisturbed sites. The diversity profiles of disturbed sites (2.45), near roads and highways (within 25–50 m), were indicative of a higher level of anthropogenic disturbances than undisturbed sites (2.56), which were located at a farther distance (more than 25–50 m) from roads and highways. The variation in diversity profiles of disturbed and undisturbed sites was further favored by lower values of soil moisture, potassium, phosphorous, and nitrogen content in disturbed sites. In addition, the disturbed sites have lower numbers of threatened and endemic species (15 and 29, respectively) than undisturbed sites (30 and 15, respectively). Linear modelling between soil properties and density indicated a perfect linear relationship for both disturbed and undisturbed sites. Canonical correspondence analysis for disturbed sites indicated sand, silt, clay and bulk density as major controlling factors. The present study indicated a significant impact of anthropogenic disturbances on the alpine floristic diversity and soil properties which needs urgent mitigation actions to conserve the unique and threatened alpine floristic diversity of the Himalayas.

Forests in Southeast Asia have been disrupted by widespread deforestation and land use change. Most countries in this region attempt to return the forested areas through reforestation. However, planting trees efficiently is difficult because changing environmental conditions and tree size could affect the water consumption of different tree-species under climate change. Hence, the information regarding water use characteristics of different tree-species in different tree size classes is important to the selection of tree species for reforestation. Nonetheless, available information on species-specific water-use characteristics is less investigated, especially in secondary tropical forests. To gain the information on species-specific water-use characteristics in secondary forests, we estimated tree water use (T) of dominant tree species including Syzygium antisepticum and Adinandra integerrima, hereafter Sa and Ai, respectively, in a secondary tropical forest at Khao Yai National Park Thailand using sap flow data from custom-made thermal dissipation probes and compare T of both species in different tree size classes. Specifically, we evaluated the responses of T of both species in large and small sizes to environmental factors including soil moisture and vapor pressure deficit (VPD) which represent soil and atmospheric humidity, respectively. Results of different soil moisture conditions in both sizes showed consistently higher T in Sa compared to Ai at across VPD ranges. Our results imply that Ai may be suitable for reforestation in the area where droughts frequently occur in the downstream ecosystem through its conservative water-use behavior and may benefit downstream ecosystems with increasing runoff from the forest during drought. Moreover, Ai has conservative water-use behavior regardless of tree size. Thus, Ai would still provide these benefits to ecosystems when they grow larger in the future. In contrast, Sa seems suitable for reforestation in the area with frequent floods because it has high water consumption during high water availability which may slow down runoff from forest into downstream ecosystems when storms come. However, mixed planting species seem to be suitable for reforestation in the area that extreme events do not frequently occur because both species can maintain their water use at moderate soil moisture regardless of tree size which prevent the depletion of soil water availability. This study highlights that the response of T depends on species and tree size. Such information would benefit the selection of tree species for reforestation that could adapt well to certain environments and support policy design on the management of tropical forests and natural resources. Depending on reforestation purpose, Sa and Ai may provide either benefits or negative effects to the ecosystems.

Differential responses of species to environmental stress may interfere with restoration of prairie ecosystems or change community structure. The impact of increasing atmospheric ozone (O 3 ) concentrations and/or low water on the growth of Andropogon gerardii Vitm. (big bluestem) and Sorghastrum nutans (L.) Nash (indian grass), two common warm-season native grasses, and Setaria faberi Herrm. (giant foxtail), a vigorous annual weed species, were studied in replacement series. Giant foxtail grew better than either big bluestem or indian grass under all tested conditions. The leaf areas of all three species were primarily controlled by water availability. Big bluestem and indian grass accumulated biomass equally well under high water availability, but with low water, indian grass accumulated more biomass than did bluestem. Three-way analysis of variance showed biomass, leaf area, and leaf number differed among species; low water was significant in all cases except for indian grass leaf area; and the O 3 effect was significant only in the case of foxtail biomass. The interaction of O 3 concentration and low water was significant only for indian grass biomass and leaf number; the interaction of species combination and low water was significant only for big bluestem leaf area and biomass. Relative yield calculations indicated that under conditions of elevated O 3 and low water, big bluestem was the least competitive, while indian grass was most competitive. Intraspecific competition was common, each species apparently utilizing the environment in different ways. The results also suggest that giant foxtail at a low relative density may be used as a nurse species in prairie restorations as growth of big bluestem and indian grass were improved when in mixtures with foxtail.