Search

Water availability strongly influences the survival, growth, and reproduction of most terrestrial plant species. Experimental evidence has well documented the effect of changes in total amount of water availability on non‐native vs. native plants. However, little is known about how fluctuations in water availability affect these two groups, although more extreme fluctuations in water availability increasingly occur with prolonged drought and extreme precipitation events. Here, we grew seven non‐native and seven native plant species individually in the greenhouse. Then, we exposed them to four watering treatments, each treatment with the same total amount of water, but with different divisions: W1 (added water 16 times with 125 mL per time), W2 (8 times, 250 mL per time), W3 (4 times, 500 mL per time), and W4 (2 times, 1000 mL per time). We found that both non‐native and native plants produced the most biomass under medium frequency/magnitude watering treatments (W2 and W3). Interestingly, non‐native plants produced 34% more biomass with the infrequent, substantial watering treatment (W4) than with frequent, minor watering treatment (W1), whereas native plants showed opposite patterns, producing 26% more biomass with W1 than with W4. Differences in the ratio of root to shoot under few/large and many/small watering treatments of non‐native vs. native species probably contributed to their different responses in biomass production. Our results advance the current understanding of the effect of water availability on non‐native plants, which are affected not only by changes in amount of water availability but also by fluctuations in water availability. Furthermore, our results indicate that an increased few/large precipitation pattern expected under climate change conditions might further promote non‐native plant invasions. Future field experiments with multiple phylogenetically controlled pairs of non‐native and native species will be required to enhance our understanding of how water availability fluctuations impact on non‐native invasions. [ABSTRACT FROM AUTHOR]

Abstract Water availability strongly influences the survival, growth, and reproduction of most terrestrial plant species. Experimental evidence has well documented the effect of changes in total amount of water availability on non‐native vs. native plants. However, little is known about how fluctuations in water availability affect these two groups, although more extreme fluctuations in water availability increasingly occur with prolonged drought and extreme precipitation events. Here, we grew seven non‐native and seven native plant species individually in the greenhouse. Then, we exposed them to four watering treatments, each treatment with the same total amount of water, but with different divisions: W1 (added water 16 times with 125 mL per time), W2 (8 times, 250 mL per time), W3 (4 times, 500 mL per time), and W4 (2 times, 1000 mL per time). We found that both non‐native and native plants produced the most biomass under medium frequency/magnitude watering treatments (W2 and W3). Interestingly, non‐native plants produced 34% more biomass with the infrequent, substantial watering treatment (W4) than with frequent, minor watering treatment (W1), whereas native plants showed opposite patterns, producing 26% more biomass with W1 than with W4. Differences in the ratio of root to shoot under few/large and many/small watering treatments of non‐native vs. native species probably contributed to their different responses in biomass production. Our results advance the current understanding of the effect of water availability on non‐native plants, which are affected not only by changes in amount of water availability but also by fluctuations in water availability. Furthermore, our results indicate that an increased few/large precipitation pattern expected under climate change conditions might further promote non‐native plant invasions. Future field experiments with multiple phylogenetically controlled pairs of non‐native and native species will be required to enhance our understanding of how water availability fluctuations impact on non‐native invasions.

Global warming is predicted to change precipitation amount and reduce precipitation frequency, which may alter grassland primary productivity and biomass allocation, especially when interact with other global change factors, such as nitrogen deposition. The interactive effects of changes in precipitation amount and nitrogen addition on productivity and biomass allocation are extensively studied; however, how these effects may be regulated by the predicted reduction in precipitation frequency remain largely unknown. Using a mesocosm experiment, we investigated responses of primary productivity and biomass allocation to the manipulated changes in precipitation amount (PA: 150 mm, 300 mm, 450 mm), precipitation frequency (PF: medium and low), and nitrogen addition (NA: 0 and 10 g N m-2 yr-1) in a Leymus chinensis grassland. We detected significant effects of the PA, PF and NA treatments on both aboveground biomass (AGB) and belowground biomass (BGB); but the interactive effects were only significant between the PA and NA on AGB. Both AGB and BGB increased with an increment in precipitation amount and nitrogen addition; the reduction in PF decreased AGB, but increased BGB. The reduced PF treatment induced an enhancement in the variation of soil moisture, which subsequently affected photosynthesis and biomass formation. Overall, there were mismatches in the above- and belowground biomass responses to changes in precipitation regime. Our results suggest the predicted changes in precipitation regime, including precipitation amount and frequency, is likely to alter primary productivity and biomass allocation, especially when interact with nitrogen deposition. Therefore, predicting the influence of global changes on grassland structure and functions requires the consideration of interactions among multiple global change factors. [ABSTRACT FROM AUTHOR]

In mountain ecosystems, plant regeneration might be constrained by multiple factors that change along elevation gradients and promote traits differentiation. Drought is a strong filter for seedling establishment that might be modified by herbivory co-occurrence. Populations of the tree Maytenus boaria support lower soil moisture and higher herbivory pressure at low elevations than at mid-elevations in Córdoba Mountains, central Argentina. Consequently, we expect that populations from the low elevation perform better in response to drought than populations from mid-elevations and that herbivory modifies these responses. Seedlings from the two elevation origins were exposed to two levels of simulated drought and herbivory in a greenhouse experiment. The selected elevations corresponded to the lowest edge of species distribution (with driest soils and highest herbivory pressure) and the central mid-elevation. Performance-related variables, biomass allocation patterns and several morphological and physiological traits were measured. Mortality patterns and most of morphological and physiological variables showed that drought is a stressful factor at the regeneration stage of M. boaria. The drought effect was increased by simulated herbivory in some variables (LMF, RM:SM and SPAD). In most variables, origin did not influence seedling performance, suggesting that drought response of seedlings is independent of populations' elevation. Only leaf number and water potential were in line with our predictions and showed an origin response to drought. [ABSTRACT FROM AUTHOR]

The arid and semiarid grassland ecosystems are characterized by limited water resources and are generally vulnerable to climate change. Understanding how plants in arid and semiarid ecosystems respond to global climatic variation is crucial for ecological restoration under a changing climate. Although the effects of climate on aboveground biomass (AGB) and belowground biomass (BGB) have been widely explored, how AGB and BGB respond to climatic variation is seldom disentangled. There is still a need to understand how plant communities respond to global climate change. In this study, we conducted a transect survey across grasslands in Inner Mongolia to capture changes in AGB and BGB in plant communities. Then, we used structural equation modelling (SEM) to explore the relationship between environmental factors and the root:shoot ratio to understand how plant communities respond to ecological drought under global climate change. Our results showed that low precipitation use efficiency (LPUE) results in a high root:shoot (HRS) ratio, and BGB was more sensitive to environmental changes. By contrast, high precipitation use efficiency (HPUE) led to a low root:shoot (LRS) ratio, and environmental factors had a greater impact on AGB. For the LPUE pattern, soil water content (SWC), pH, and soil total nitrogen (STN) mainly affected the HRS ratio. Soil water content and STN influenced the HRS ratio through a positive effect on BGB. For the HPUE pattern, SWC, STN, and plant abundance (PA) predominantly regulate the LRS ratio, while biodiversity (plant abundance) affects the LRS ratio by positively affecting AGB. Our results highlight the differential impact of precipitation use efficiency on aboveground and belowground biomass allocation. This is important for monitoring the impact of drought events on plant biomass, improving productivity assessment models in arid and semi‐arid regions, and assessing local carbon storage accurately. [ABSTRACT FROM AUTHOR]

Background and Aims Our understanding of plant responses to biotic and abiotic drivers is largely based on above-ground plant traits, with little focus on below-ground traits despite their key role in water and nutrient uptake. Here, we aimed to understand the extent to which above- and below-ground traits are co-ordinated, and how these traits respond to soil moisture gradients and plant intraspecific competition. Methods We chose seedlings of five tropical tree species and grew them in a greenhouse for 16 weeks under a soil moisture gradient [low (drought), medium and high (well-watered) moisture levels] with and without intraspecific competition. At harvest, we measured nine above- and five below-ground traits of all seedlings based on standard protocols. Key Results In response to the soil moisture gradient, above-ground traits are found to be consistent with the leaf economics spectrum, whereas below-ground traits are inconsistent with the root economics spectrum. We found high specific leaf area and total leaf area in well-watered conditions, while high leaf dry matter content, leaf thickness and stem dry matter content were observed in drought conditions. However, below-ground traits showed contrasting patterns, with high specific root length but low root branching index in the low water treatment. The correlations between above- and below-ground traits across the soil moisture gradient were variable, i.e. specific leaf area was positively correlated with specific root length, while it was negatively correlated with root average diameter across moisture levels. However, leaf dry matter content was unexpectedly positively correlated with both specific root length and root branching index. Intraspecific competition has influenced both above- and below-ground traits, but interacted with soil moisture to affect only below-ground traits. Consistent with functional equilibrium theory, more biomass was allocated to roots under drought conditions, and to leaves under sufficient soil moisture conditions. Conclusions Our results indicate that the response of below-ground traits to plant intraspecific competition and soil moisture conditions may not be inferred using above-ground traits, suggesting that multiple resource use axes are needed to understand plant ecological strategies. Lack of consistent leaf–root trait correlations across the soil moisture gradient highlight the multidimensionality of plant trait relationships which needs more exploration. [ABSTRACT FROM AUTHOR]

Purpose: Roots are the mean absorbing organ of plants and an important part of material circulation in ecosystems. Understanding long-term root system development and its response to soil water availability can help to elucidate carbon cycling and plant resource uptake strategies in forest plantations under climate change. Methods: We created a soil water content (SWC) gradient in a poplar forest using irrigation. During the six-year rotation, we determined biomass allocation by dissecting 45 sample trees, and measured spatial–temporal distribution and morphology of fine roots through analysis of 3984 root samples. Observations occurred as stands developed through canopy closure and experienced increasing inter-tree competition. Results: Biomass allocation initially responded positively to low SWC while rooting depth was unaffected. As stands developed, biomass allocation differences gradually disappeared, and low SWC caused deeper root distribution. Morphological responses to depth emerged after the first year. In shallow soil, specific root length and fine-root diameter were lower while root tissue density was greater than those below 50 cm depth. Conclusion: Soil water availability can affect biomass allocation and determine the soil layer with high exploration intensity, but both of these effects depend on stand development. During development, horizontal root system expansion takes precedence over vertical expansion. Besides, our finding implies that functional divergence of fine roots may occur gradually with stand development, with finer diameter roots in shallow soil perhaps functioning mainly for absorbing soil resources while low-density, high-diameter roots in deep soil functioning primarily for expanding the root system and exploring for limiting soil moisture resource. [ABSTRACT FROM AUTHOR]

Elucidating the influence mechanisms of seed germination and seedling growth is important for revealing the natural regeneration of forest plantations. We collected the seeds from 58-year-old Quercus acutissima Carruth. forest, and the seeds were further divided into three classes: large, medium, and small, and sown under the forest gaps (I, 197.82 m2; II, 91.85 m2, III, understory) to observe seed germination and early seedling growth. Precipitation in the study area and soil moisture content in the forest gaps were also observed during the trial period. The results showed that the precipitation in 2019 was similar to that in 2020; both were significantly lower than the precipitation in 2021. The difference in soil water content between gaps I and II was not significant, and both were significantly lower than III. The order of seedling emergence rate in gaps was II > III > I, but the minimum was almost close to zero in I. Large and medium seeds showed significantly greater emergence rate than small seeds. The seedlings of II had higher seedling height, ground diameter, ground diameter relative growth rate, seedling biomass, root surface area, and root volume than those of III. Large seeds had the highest ground diameter, ground diameter relative growth rate, biomass, root mass ratio, root shoot ratio, and root surface area. Correlation analysis showed that seedling biomass was significantly and positively correlated with root surface area and root volume, and significantly and negatively correlated with specific root length and specific root surface area. The regulation of soil moisture in the gap and the adaptability related to seed size were two key factors influencing the seed germination and early seedling growth of Q. acutissima. [ABSTRACT FROM AUTHOR]

We aimed to investigate the water use strategies and the responses to water shortages in Glycyrrhiza uralensis, which is a dominant species in the desert steppe. Water stress gradients included control, mild, moderate, and severe. The time intervals were 15, 30, 45, and 60 d. Our study suggested that with the aggravation of water stress intensity, the total biomass of Glycyrrhiza uralensis gradually decreased and allometric growth was preferred to underground biomass accumulation. From 30 d and mild to moderate water stress, the water potential (WP) of leaves decreased considerably compared to the CK. The relative water content (EWC) decreased over time and had a narrow range of variation. Proline (PR) was continuously increased, then declined at 45–60 d under severe and more severe water stress. The δ13C values increased in all organs, showed roots > stems > leaves. The net photosynthetic rate (Pn) and transpiration rate (Tr) decreased to varying degrees. The instantaneous water use efficiency (WUEi) and limiting value of stomata (Ls) increased continuously at first and decreased under severe water stress. Meanwhile, severe water stress triggered the most significant changes in chloroplast and guard cell morphology. In summary, Glycyrrhiza uralensis could maintain water content and turgor pressure under water stress, promote root biomass accumulation, and improve water use efficiency, a water-conservation strategy indicating a mechanism both avoidable dehydration and tolerable drought. [ABSTRACT FROM AUTHOR]

Groundwater plays a significant role in influencing the growth and distribution of Robinia pseudoacacia L. plantations, with the largest planting area in the Yellow River Delta, by affecting the soil water–salt environment. This study aimed to clarify the mechanism of groundwater's influence on the growth of R. pseudoacacia under different levels of groundwater mineralization (GWM) and groundwater depth (GWD). We simulated GWM of 0, 2 and 4 g L−1, and GWD of 0.8, 1.3 and 1.8 m. As GWM increased, soil relative water content (SRWC) and soil salt (dissolved salt) content (SSC) increased; sapling biomass (SB), stem mass (SM), leaf mass (LM), photosynthesis characteristics (maximum net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (E) and water use efficiency (WUE)) decreased; root mass (RM), root mass ratio (RMR) and root–shoot ratio (RSR) first increased then decreased; stem mass ratio (SMR) first decreased then increased; and leaf mass ratio (LMR) increased. As GWD increased, SRWC decreased, but SSC first increased then decreased; SB, RM, RMR, RSR, and photosynthesis characteristics increased; SM and LM first increased then decreased; and SMR and LMR decreased. SRWC and SSC were negatively correlated with SB and photosynthesis characteristics. SRWC was negatively correlated with RMR and RSR, whereas it was positively correlated with LMR. SSC was negatively correlated with SMR, whereas it was positively correlated with LMR. The first principal component, including SB, RM, and photosynthesis characteristics, was related to sapling growth. The second principal component, including RMR, SMR, and RSR, was mainly related to biomass allocation. In conclusion, GWM and GWD affected the soil water and salt content, which were key factors influencing the photosynthesis and growth of R. pseudoacacia. Adjustments in biomass allocation and photosynthesis were the main adaptive strategies of R. pseudoacacia to salt, drought, and flooding stress. [ABSTRACT FROM AUTHOR]

Purpose: Climate models predict shifts in precipitation patterns characterized by increased precipitation amount and decreased frequency for semi-arid grasslands in northeast China. However, under these novel climatic conditions, potential differences in plant biomass and its allocation among different degraded grasslands remain unclear. Methods: We conducted a mesocosm experiment to test the effects of higher precipitation amount (increased by 50% from the long-term mean) and lower frequency (decreased by 50%) on plant biomass and allocation in the lightly, moderately, and severely degraded grasslands. Results: Lower precipitation frequency promoted belowground biomass but reduced aboveground biomass through enhancing soil water variability. Higher precipitation amount enhanced aboveground biomass in the lightly and moderately degraded grasslands, but not in the severely degraded grassland due to lower soil nitrogen availability. Lower precipitation frequency weakened or ended the positive effects of higher precipitation amount on aboveground and belowground biomass, and higher precipitation amount suppressed the enhancement of lower precipitation frequency on belowground biomass, which could be attributed to temporary waterlogging. Plants in the moderately degraded grassland preferred to adjust root vertical distribution, which was impacted by the changes in plant community composition. However, adjustment of aboveground biomass vs. belowground biomass was the primary biomass allocation strategy in the other two grasslands. Conclusions: Our findings emphasized the importance of considering the degradation level of grasslands when predicting responses of ecosystem functions to the projected changes in precipitation regimes. These findings are critical for making feasible decisions for the sustainable management of degraded grasslands. Legend: + and − indicate positive and negative relationships, respectively LDG, MDG and SDG-lightly degraded, moderately degraded and severely degraded grasslands, respectively DPF-decreased precipitation frequency treatment, IPA-increased precipitation amount treatment SWC and CVSWC-mean and variation of soil water content, respectively SINC-soil inorganic nitrogen content AGB and BGB-aboveground and belowground biomass, respectively fAGB-AGB / total biomass BGB0–10 (%)-belowground biomass proportion in the 0–10 cm soil layer, BGB 0 - 10 / BGB 0 - 30 × 100 RAGB-relative aboveground biomass [ABSTRACT FROM AUTHOR]

Natural regeneration is crucial for the development of sustainable forestry practices in light of the current global climate changes. In this paper, we compared the size distributions of Quercus acutissima seedlings in the understory of Q. acutissima forest plantations in Mount Tai in 2010 and 2017, studied the physiological and morphological responses of seedlings to the microenvironment, and explored the maintenance mechanisms of the seedling bank. The results showed that the density of understory seedlings in 2017 was only 61.63% of that in 2010, especially in the 20–40 cm height class. Between 2011 and 2016, the precipitation and soil water content were the highest in 2011, followed by 2013. The 2–4-year seedlings (height < 40 cm) were not significantly different in seedling biomass, biomass allocation, and root morphology (root total surface area, root volume, and root average diameter), and were significantly different in total root length, specific root length, specific root surface area, and nonstructural carbohydrate content of root, stem, and leaves. However, 5–6-year seedlings (height > 40 cm) showed the largest biomass. Principal component analysis indicated that altering root morphology, nonstructural carbohydrate, and biomass allocation played significant roles in the drought adaptation of seedlings in the understory. In conclusion, drought stress together with seedling adaptation influenced the dynamics of seedling bank in the understory of Q. acutissima plantations. [ABSTRACT FROM AUTHOR]

Surviving the seedling phase is crucial for the establishment of plant individuals and populations. In ecosystems with dynamic water availability such as temperate grasslands, seedlings should adjust their growth strategy not only to match the current conditions but also to secure resource acquisition in the future. Here, we explored evolutionary adaptations determining plant early growth strategies in herbaceous species of temperate grasslands differing in their requirements for soil water availability.We chose 15 plant genera, within which we selected species differing in their Ellenberg indicator values for moisture. We cultivated the seedlings under standard conditions with sufficient water supply for 4 weeks. Subsequently, we measured length‐based and mass‐based shoot:root ratio to investigate seedling growth strategy and its association with species ecological niche. Seed size and content of soil‐borne nutrients were considered as potential covariates affecting this association.Linear mixed‐effect models identified the length‐based shoot:root ratio of seedlings was positively associated with soil moisture requirements in a congeneric species comparison. Nitrogen and phosphorus seed concentrations had an additional negative effect on the shoot:root ratio. Neither of these trends was found for the mass‐based shoot:root ratio.We demonstrated for the first time that there might be a general adaptation modifying the seedling shoot:root ratio according to the species niche position on the soil moisture gradient in temperate grassland species across a broad range of angiosperm phylogeny. This adaptation seems to be affected by seed mineral nutrient reserves and may operate in parallel to the well‐known phenotypic plasticity. [ABSTRACT FROM AUTHOR]

Small semi-fossorial herbivores can affect plant aboveground biomass (AGB) in grasslands and possibly alter the allocation of AGB and belowground biomass (BGB). In this study, plateau pika (Ochotona curzoniae) was used to investigate such effects at three alpine meadow sites on the Eastern Tibetan Plateau, where pairs of disturbed vs. undisturbed plots were randomly selected and sampled. We also explored the relationships between soil properties and BGB/AGB across the plots in the presence and absence of plateau pikas, respectively. We found that BGB and BGB/AGB were 11.40 and 8.20% lower in the presence of plateau pikas than in their absence, respectively. We also found that the BGB/AGB was positively related to soil moisture and soil total nitrogen (STN) in the absence of plateau pikas. In contrast, BGB/AGB was positively related to STN, soil organic carbon (SOC), soil carbon/nitrogen (C/N), and soil total phosphorus in the presence of plateau pikas. These factors indicated plateau pika disturbance increased AGB allocation. The relationship between AGB and BGB of alpine meadow plants to soil variables was also different between sites with and without plateau pika disturbance. In conclusion, small semi-fossorial herbivore disturbance is likely to alter grassland carbon stock and should be well controlled for sustainable conservation and management of alpine meadows on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Biomass allocation affects the ability of plants to acquire resources and nutrients; a limited allocation of nutrients, such as nitrogen and phosphorus, affects ecological processes. However, little research has been conducted on how plant allocation patterns change and on the trade-offs involved in allocation strategies when microhabitat gradients exist. We selected a 3.6 km transect in the Ebinur Lake Wetland Natural Reserve of Xinjiang, China, to investigate the relationships between plant traits (biomass and N and P concentrations) of herbaceous plants and environmental factors (soil moisture, salinity and nutrient content), and to determine the allometric scaling of biomass and stoichiometric traits between the above- and below-ground plant parts. The results show that the biomass and stoichiometric traits of plants reflected both the change of micro-environment and the natural characteristics of plants. With a decrease of the soil water availability and salinity, above- and below-ground N and P concentrations decrease gradually; scaling relationships exist between above- and below-ground plant parts, for biomass and N and P concentrations. Biomass allocation is influenced by soil nutrient ratios, and the allocation strategy tended to be conserved for N and variable for P. Second, the scaling relationships also show interspecific differences; all scaling exponents of Suaeda prostrata are larger than for other species and indicate a 'tolerance' strategy, while other species tend to increase the below-ground biomass and N and P concentrations, i.e. a 'capture' strategy. [ABSTRACT FROM AUTHOR]

Aims: Drought events can alter the composition of plant and soil communities, and are becoming increasingly common and severe due to climate change. However, how droughts affect plant-soil feedbacks is still poorly understood. Plants accumulate species-specific rhizosphere communities, and droughts may have varying impacts across plant species and soil biota. We therefore tested the hypothesis that drought alters plant-soil feedbacks differently among closely related plant species that differ in their preferences for soil moisture. Methods: In a two-phase greenhouse experiment, we first conditioned grassland soil with seven Geranium species and, as controls, we conditioned soil with a grass species or left soil unplanted. In the second phase, we grew the Geranium species in conspecific, grass-conditioned and unplanted soil, maintained soil moisture at 5 %, 10 % or 20 % (w/w), and determined biomass responses after 35 days. Results: Independent of conditioning, plants showed a weaker performance with decreasing soil moisture. Under the driest conditions, soil conditioning by conspecifics most negatively affected relative root weight in comparison to plants growing in unplanted control soil, while the effects of conspecific conditioning on relative root weights were species-specific when compared to plants grown in grass-conditioned control soil. Conclusions: We conclude that decreased soil moisture modified plant-soil feedback effects on biomass allocation, and that these modifications acted in species-specific ways. However, drought effects on plant-soil feedbacks were subtle, and did not affect overall plant performance. Therefore, plant-soil feedback effects on plant performance during a drought event may be limited in comparison with the direct effects of drought. [ABSTRACT FROM AUTHOR]

Background: Invasive exotic species have caused significant problems, and the effects of extreme precipitation and drought, which might occur more frequently under the global climate change scenarios, on interspecific relationship between invasive and native species remain unclear. Results: We conducted a greenhouse experiment with three soil water levels (30–40%, 50–60%, and 70–80% of field capacity) and two cultivation treatments (monoculture pots, one seedling of either species and mixture pots, one seedling of each species) to investigate soil water content effects on the relationship between invasive Rhus typhina and native Cotinus coggygria. Rhus typhina had lower height but bigger crown area than C. coggygria in the monoculture treatment. Rhus typhina had higher height, bigger crown area and total biomass than C. coggygria in the mixture treatment. Drought decreased the growth parameters, total chlorophyll concentration, and leaf biomass, but did not change gas exchange and other biomass parameters in R. typhina. The growth parameters, leaf area index, biomass parameters, total chlorophyll concentration, and net photosynthetic rate of C. coggygria decreased under drought conditions. The log response ratio (lnRR), calculated as ln (total biomass of a target plant grown in monoculture/total biomass of a target plant grown in mixed culture), of R. typhina was lower than that of C. coggygria. The lnRR of R. typhina and C. coggygria decreased and increased with increase in soil water content, respectively. Conclusions: Rhus typhina has greater capacity to relatively stable growth to the drought condition than C. coggygria and has strong competition advantages in the mixture with C. coggygria, especially in the drought condition. Our study will help understand the causes of invasiveness and wide distribution of R. typhina under various moisture conditions and predict its expansion under climate change scenarios. [ABSTRACT FROM AUTHOR]

The river basin of Ebi Lake represents a typical ecosystem in arid land, a sensitive area for global change and a key protected area for biodiversity. The study of the relationship among biomass allocation of above-ground and below-ground plant, response mechanism of edaphic factor, and allometry helps understand the plants' survival and optimization strategies in terms of soil conditions and ecological functions. With excavation as the method that gave us adequate biomass information and the physical and chemical properties of the soil, four desert plants in the research area were analyzed: Suaeda salsa, Seriphidium kaschgaricum, Horaninowia ulicina, and Alhagi sparsifolia, among which the biomass, its allocation ratio in response to the edaphic factor, and allometric models were compared. The results were as follows:(1)There were significant differences in the biomass and its allocation ratios among the four plants, with Seriphidium kaschgaricum having the largest above-ground and below-ground biomass, while Horaninowia ulicina the smallest; The R/S(root-shoot ratio)showed Alhagi sparsifolia > Horaninowia ulicina and Seriphidium kaschgaricum > Suaeda salsa(P<0.05).(2)The effect of edaphic factor on R/S analyzed with RDA showed that the interpretability of edaphic factors towards R/S in terms of the four plants were 16.3%, 24.8%, 33.1% and 35.4%, respectively. Among them, the soil total nitrogen had a positive correlation with the R/S of Horaninowia ulicina (P<0.05), and the soil moisture a significantly positive correlation with the R/S of Suaeda salsa(P<0.01).(3)The four plants all had significant correlations with regards to AGB-BGB(P<0.01), where the AGB-BGB of Seriphidium kaschgaricum had a pattern of isometric scaling(α=1), while both Horaninowia ulicina and Alhagi sparsifolia showed an allometric scaling of α=3/4, and Suaeda salsa belonged to the allometric scaling of a non-3/4 power exponent(α<1). All the four plants shared a common allometric scaling index(0.767). The above results indicate that the desert plants in Ebi Lake have functional convergence, and the characteristics of their spatial distribution are species-specific in response to edaphic factors. [ABSTRACT FROM AUTHOR]

• Clonal integration improved photochemical activity and growth performance of ramets growing in unfavourable patches. • Clonal integration may be result in lower fitness for whole clonal fragments subjected to severe drought stress. • Capacity of division of labour for clonal plants is dependent on contrast of resource availability. Clonal integration allows translocation of water between interconnected ramets, improving fitness of clonal plants growing in heterogeneous water availability. However, few studies have been conducted to investigate the effects of clonal integration on physiological responses of clonal plants suffering from heterogeneous water availability. A greenhouse experiment was conducted by using clonal fragments of the stoloniferous herb Centella asiatica with two successive ramets. The basal ramets were grown in patches with 40% soil moisture (high water availability), while the apical ramets were grown in patches with 40% (high water availability), 20% (medium water availability) and 10% soil moisture (low water availability) respectively. Stolons between the basal and apical ramets were severed (clonal integration impeded) or retained intact (clonal integration allowed). Our results showed that clonal integration relieved negative impact of water deficiency on the apical ramets in terms of photochemical activity and growth performance. Clonal integration modified biomass partitioning both for the apical ramets growing in low water availability and the basal ramets growing in high water availability. In addition, significant cost of clonal integration was observed in terms of growth performance of whole clonal fragments. A possible explanation is that increased biomass allocation to root may reduce capturing of light energy, producing negative effect on biomass accumulation of the basal ramets under high water availability contrast between patches. The results suggest that the net benefit of clonal integration may depend on the contrast of resource availability between interconnected ramets. [ABSTRACT FROM AUTHOR]

Highlights • Four pines and four spruces in a 2 × 2 factorial of CO 2 and soil moisture. • Overall, pines respond better to eCO 2 and soil moisture stress. • Shade-tolerant spruces perform better in eCO 2 than shade-intolerant spruces. • Greater the mass, greater the response to eCO 2 and soil moisture. • Supports shift toward increased use of pines in NE N. America. Abstract Growth, components of growth, and biomass allocation were quantified for eight species in two commercially important genera, Pinus and Picea , grown in a 2 × 2 factorial of atmospheric CO 2 and soil moisture stress. Four of the pines and three of the spruces are native to eastern North America; a fourth spruce, Norway spruce (NS: P. abies), is native to Europe but is used for reforestation in northeastern North America. Height, basal diameter (BD), and total biomass response of pines were often more than two times greater than that of spruces under elevated CO 2 (eCO 2). A significant species × CO 2 interaction for total biomass was a result of species' differential response to eCO 2 : Pinus rigida had the greatest biomass stimulation (59%), followed by P. resinosa (39%), P. strobus (26%), and P. banksiana (19%). Among spruces, Picea glauca showed the greatest response (30%), and P. mariana the least response under eCO 2 (5%). Overall, soil moisture stress reduced total productivity by 12%. Most pines did have greater growth under moisture stress, and NS and BS grew well. Percent needle mass was lower under eCO 2 , but this was not due directly to eCO 2 but to ontological changes. Controlling for size, pines had 20% greater needle biomass than spruces, while having a negative relationship to total biomass. A comparison of total biomass under eCO 2 in relation to aCO 2 by species showed that overall, the greater the species mass, the greater the mass gain under eCO 2, and the greater the mass loss under drought conditions. In addition, our results for spruces lend strong support to the theory that late-successional species have greater growth response under eCO 2 than early to mid-successional species. A diverse portfolio of tree species for artificial reforestation would help forest management adapt to the many uncertainties over future environments and markets, but our results on responses in spruces and pines to eCO 2 and soil moisture stress support a shift toward increased use of pines in forest management and artificial reforestation. [ABSTRACT FROM AUTHOR]

The plant carbon balance depends on the coordination between photosynthesis and the long-distance transport of water and sugars. How plants modify the allocation to the different structures affecting this coordination under different environmental conditions has been poorly investigated. In this study, we evaluated the effect of soil water availability on the allocation to leaf, xylem and phloem structures in Fraxinus ornus L. We selected small individuals of F. ornus (height ~2 m) from sites contrasting in soil water availability (wet vs dry). We measured how the leaf (LM) and stem + branch biomass (SBM) are cumulated along the stem. Moreover, we assessed the axial variation in xylem (XA) and phloem tissue area (PA), and in lumen area of xylem vessels (CAxy) and phloem sieve elements (CAph). We found a higher ratio of LM : SBM in the trees growing under drier conditions. The long-distance transport tissues of xylem and phloem followed axial patterns with scaling exponents (b) independent of site conditions. PA scaled isometrically with XA (b ~ 1). While CAxy was only marginally higher at the wet sites, CAph was significantly higher at the drier sites. Our results showed that under reduced soil water availability, F. ornus trees allocate relatively more to the leaf biomass and produce more conductive phloem, which is likely to compensate for the drought-related hydraulic limitations to the leaf gas exchanges and the phloem sap viscosity. [ABSTRACT FROM AUTHOR]

Soil and water bioengineering techniques are now increasingly adopted worldwide for controlling riverbank erosion but have not yet been implemented in the Caribbean Islands biodiversity hotspot. The selection of suitable native plant species is critical for successful soil bioengineering designs on riverbanks, but few data are available regarding Caribbean species. This study aimed to characterize the performance and biotechnical traits of native Caribbean species potentially compatible with soil and water bioengineering. In a six-month shadehouse experiment, we measured the survival rate, biomass production and root growth of cuttings of ten native Caribbean shrub and tree species occurring naturally in a variety of riparian environments. All species appeared suitable for soil and water bioengineering but differed as to the specific bioengineering techniques they seemed particularly suited for, depending on their respective survival rates, growth performances and root system structures. Five tree species, Citharexylum spinosum, Cedrela odorata, Ficus citrifolia, Chimarrhis cymosa, Homalium racemosum , and three shrubs, Piper dussii, Piper dilatatum and Phyllanthus mimosoides , exhibited survival, growth and root characteristics compatible with a broad range of techniques, whereas Tabebuia heterophylla and Cordia sulcata may only be compatible with a few. We also propose using of the DEXi decision-support software for assessing species suitability to a series of widespread soil and water bioengineering techniques. Our results provide practical guidance for the integration of native species in soil and water bioengineering in the Caribbean and the Neotropics at large. • Caribbean riparian trees and shrubs are promising for soil bioengineering. • A new approach is proposed to assess species suitability to the main soil bioengineering techniques. • Among the ten species tested, eight possess characteristics that make them suitable for soil bioengineering techniques. • These results will greatly facilitate the development of soil bioengineering in the Caribbean. [ABSTRACT FROM AUTHOR]

We investigated the effects of simulated prospective increased temperatures and reduced soil moisture during the vegetation period on the early growth of three weed species that co-occur in spring crops and are currently spreading in Europe. Potted four-species crop-weed-communities of Abutilon theophrasti, Datura stramonium, Iva xanthiifolia, and maize were exposed to warming (ambient temperature + 2.5°C, treatment "warm") and drought (soil water potential of -0.1 to -1.5 MPa, "dry") versus ambient temperature (treatment "ambient") and a soil water potential of -0.0036 MPa ("moist"), in four soil types (clay, loess, peat, sand based mixtures) in greenhouse settings. We determined the performance of the weeds in terms of total biomass accumulation as well as their morphological acclimation regarding root length, leaf size and root-to-shoot ratio at various combinations of the experimental factors. Warm-dry conditions had a significant negative effect on total weed biomass and also resulted in a higher proportion of maize in total aboveground biomass. In D. stramonium, aboveground vs. belowground allocation and leaf size responded more strongly to the experimental factors than in the other two species. Total biomass values of individual plants in warm-dry conditions on average were > 50%, 40 to 55%, and < 40% of those in ambient-moist conditions for A. theophrasti, I. xanthiifolia, and D. stramonium, respectively. Soil and its interaction with moisture and temperature additionally had a significant effect on various traits of the weed species which highlights the importance of considering this factor when investigating plant responses to altered climate conditions. [ABSTRACT FROM AUTHOR]

Heterogeneity of precipitation could influence various physiological and ecological processes of plants. We present a comparative study on the ecophysiological responses of two congenerous species, Mosla chinensis (an endemic species) and M. scabra (a weedy species), to four soil water content (20%, 40%, 60% and 90% of water holding capacity (WHC), referred to as W20, W40, W60 and W90, respectively) to understand their ecophysiological responses and ecological differentiation. Results showed that both species grew well from W40 to W90, as they showed higher photosynthetic rate and biomass and bigger plants under these soil water content. However, biomass, chlorophyll a to b ratio ( Chl) and root to shoot ratio (R/S) of M. scabra but not M. chinensis were significantly reduced under W20, indicating M. chinensis showed stronger capacity of sun-acclimation under severe drought than M. scabra. M. chinensis showed priority in adapting severe drought in comparison with M. scabra. We hypothesize that the different adaptive abilities to soil water content are partly responsible for their ecological differentiation observed in the field and may affect their fate in their native habitat. [ABSTRACT FROM AUTHOR]

Centaurea solstitialis (yellow starthistle) has invaded rangelands and natural areas in the western USA. There is evidence that mowing is a more effective method of reducing growth and seed production, compared with the well-established and distributed bioagents. To test this hypothesis we measured C. solstitialis's growth and reproduction following two treatments (late spring and early summer bud/capitula destruction and shoot mowing) and measured C. solstitialis's growth and reproduction. We measured changes in soil moisture content to test the hypothesis that these manipulations differentially affect water usage by the invasive plant. Mowing produced shorter plants that weighed less. Bud damaged plants were not statistically different from untreated controls. The number of developed capitula was reduced 67% by mowing but was unaffected by bud damage. Mowed plants redistributed resources from root to flower production. Both treatments reduced mean capitulum diameter. This resulted in reductions of 76% and 21% in estimated seed number for mowed and bud damaged plants respectively. Root abundance decreased and root life-span was reduced by both treatments. Soil moisture depletion was greatest from mid-May to mid-July (from 21% to 9%) and occurred after maximum root abundance. Mowing resulted in a delay in soil moisture depletion compared with the bud damaged plants or the untreated controls. Bud/capitula damage did not affect C. solstitialis's requirement for soil water. Overall, this study supported the hypothesis that mowing reduced C. solstitialis growth and reproduction more than bud damage alone. This information will aid managers in selecting a strategy for managing C. solstitialis in a particular habitat. [ABSTRACT FROM AUTHOR]

Soil--plant water relations are crucial for understanding the mechanisms by which plants adapt to their environments. An experiment was conducted to understand the responses of 4 dominant psammophyte shrub species to different sandy environments. Pots were filled with tap water or sand, and pots planted with different species and filled with sand with and without pot covers were kept in 4 growth cabinets at 15/25 °C and with a water supply of 75 mm per month. Soil water content; dry weights of roots, shoots, and leaves; and leaf area were measured. The relative growth rate (0.039-0.042 g g-1 day-1) was higher for the 2 Artemisia Krasch. species and lower for Caragana korshinskii Kom. and Hedysarum laeve Maxim. (0.016-0.023 g g-1 d-1). The final soil water content of the 2 Artemisia species (1.3%-2.7%) was lower than that of H. laeve and C. korshinskii (14.7%-18.4%). Soil water content increased from the top of the profile to deeper levels for H. laeve and C. korshinskii. However, for the 2 Artemisia species, soil water was lower in the deeper profile compared with the upper profile. Considering water consumption, the 2 Artemisia species were similar while C. korshinskii and H. laeve were similar; this result was different from our hypothesis. [ABSTRACT FROM AUTHOR]

Changes in forest openings affect light quality and quantity, and the magnitude of rainfall that reaches the soil surface. Osmorhiza depauperata, a geophyte, acclimates to changes imposed because of forest openings. We studied which changes in biomass allocation allow acclimation of O. depauperata to the various environments that this species inhabits, and where it develops better. Three light intensities (I4 = 4 %, I26 = 26 %, I64 = 64 % of ambient sunlight) and two moisture levels (M40 = 40-60 %, M80 = 80-100 % field capacity) were evaluated on O. depauperata under greenhouse conditions. Plant biomasses per pot were 0.81, 0.56 and 0.48 g at I26, I4 and I64 light intensities, respectively, after one growing season. The biomass allocation to aboveground tissues and leaf area decreased as light intensity increased. Soil moisture modified only belowground biomass and weight of fine roots. The interaction between soil moisture content and light intensity was consistent. This was because of a significant reduction in total plant biomass under high both soil moisture content and high light intensity. Osmorhiza depauperata growth was favored most at medium light intensities. Changes in biomass allocation among various organs allow this species to inhabit forest habitats with different light intensities. [ABSTRACT FROM AUTHOR]

Background and aims Dioecious plants often show sex-specific differences in growth and biomass allocation. These differences have been explained as a consequence of the different reproductive functions performed by the sexes. Empirical evidence strongly supports a greater reproductive investment in females. Sex differences in allocation may determine the performance of each sex in different habitats and therefore might explain the spatial segregation of the sexes described in many dimorphic plants. Here, an investigation was made of the sexual dimorphism in seasonal patterns of biomass allocation in the subdioecious perennial herb Honckenya peploides, a species that grows in embryo dunes (i.e. the youngest coastal dune formation) and displays spatial segregation of the sexes at the studied site. The water content in the soil of the male- and female-plant habitats at different times throughout the season was also examined. Methods The seasonal patterns of soil-water availability and biomass allocation were compared in two consecutive years in male and female H. peploides plants by collecting soil and plant samples in natural populations. Vertical profiles of below-ground biomass and water content were studied by sampling soil in male- and female-plant habitats at different soil depths. Key Results The sexes of H. peploides differed in their seasonal patterns of biomass allocation to reproduction. Males invested twice as much in reproduction than females early in the season, but sexual differences became reversed as the season progressed. No differences were found in above-ground biomass between the sexes, but the allocation of biomass to below-ground structures varied differently in depth for males and females, with females usually having greater below-ground biomass than males. In addition, male and female plants of H. peploides had different water-content profiles in the soil where they were growing and, when differences existed (usually in the upper layers of the soil), the water content of the soil was higher for the female plants had than for the male plants. Conclusions Sex-differential timing of investment in reproduction and differential availability and use of resources from the soil (particularly water) are factors that probably offset the costs of reproduction in the above-ground growth in males and females of H. peploides. The results suggest that the patterns of spatial segregation of the sexes observed in H. peploides may contribute to maximize each sex's growth and reproduction. [ABSTRACT FROM AUTHOR]

The growth and reproduction of Pedicularis davidii Franch. var. pentodon Tsoong, a snowbank species in the eastern Tibetan Plateau, was studied along a snowmelt gradient of four segments. Soil water content in the snow-free period and amplitude of diurnal soil surface temperature in March to May were significantly different between the segments, whereas soil nutrients and pH showed no difference. The species did not occur at the early-melting segment. Stem height, leaf number per stem, leaf size and specific leaf area increased significantly along the remaining segments. Above-ground biomass and total biomass showed a similar trend, while below-ground biomass and the ratio of below- to above-ground biomass decreased along the gradient. Flower number, seeds per flower and 1000-seed weight increased in the lower and middle parts of an inflorescence, while they kept almost constant in upper part of an inflorescence along the gradient. As far as a whole inflorescence was concerned, these reproductive characteristics increased from early- to late-melting segments of the snowbank. Population density also increased along the snowmelt gradient. The distribution and growth pattern were mainly related to diurnal freeze–thaw cycles near the soil surface and soil water content. [ABSTRACT FROM PUBLISHER]

We assessed interactive effects of varying levels of applied phosphorus fertilizer and water stress on growth, productivity, and mineral accumulation in container-grown Dalbergia sissoo L. seedlings. Height, collar diameter, leaf size and area, root volume and total biomass were reduced, and dry matter allocation to root was increased with increasing levels of soil water stress. The reduction was >32% in growth, >50% in leaf, and >77% in biomass when seedlings were grown with <50% of soil field capacity. Phosphorus application at the level of 10 mg kg-1 soil enhanced stems and leaf biomass and nutrient accumulation at all irrigation levels, and thus tolerance to drought. Phosphorus responses to growth and biomass production increased with irrigation levels. Thus, 20 mg P kg-1 soil is beneficial at sufficient soil water availability and a lower dose (i.e., 10 mg P kg-1) is recommended under high soil water stress conditions to benefit growth and productivity of D. sissoo. [ABSTRACT FROM AUTHOR]

Abstract: In arid lands, the shifts in dominant plant types from grasses to shrubs can significantly alter the ecosystem function and biogeochemistry cycles. However, the magnitude of these alterations and its inherent mechanisms are still poorly understood. In this study, we measured soil respiration and NPP over two growing seasons in 2006–2007 in the co-occurring perennial grass and desert shrub ecosystems at the Ordos Plateau of Inner Mongolia, China. Over the two growing seasons, the desert shrub site presented higher aboveground biomass and NPP while lower soil respiration relative to the grass site (p < 0.05). In this paper, we can not determine that whether vegetation conversion or soil texture change drive the site difference in soil respiration because we did not control for soil texture. We suppose that the site difference in pulse response of soil respiration might play an essential role in regulating this soil respiration gap. In all the growing seasons, surface soil moisture (0–10 cm) was identified as the major driver of soil respiration at both sites. Compared to the linear soil moisture model, the integrated model incorporating both surface soil moisture and air temperature was performed better in predicting the dynamics of soil respiration. [Copyright &y& Elsevier]

A pot experiment was conducted to investigate the effects of different soil water supply on growth features and nutrient status in Parthenocissus tricuspidata (Siebold & Zucc.) Planch. seedlings. Decreased soil moisture had significantly reduced the length of stem, internode and petiole, but resulted in an increase of root length. Soil water supply appeared to affect stem biomass to a lesser extent than root and leaf. The seedlings grown under high water supply invested more biomass in leaf (in terms of leaf number and leaf area). The N concentration in various plant organs followed in the order leaf>stem>root>petiole while K and P concentrations remained relatively constant at different soil moisture levels. Soil water supply had significantly affected N use efficiency, but did not affect P and K use efficiency. Moreover, there was a higher P use efficiency than N or K. In addition, P. tricuspidata had a low K concentration (below 10 mg·g-1) in all its plant tissues, which may allow the plants to limit its stomatal opening and reduce its water loss. The growth and nutrient responses of P. tricuspidata to different soil water supply indicated that this species could resilient to water availabilities and adapt to water stress conditions very well. [ABSTRACT FROM AUTHOR]

Temporal environmental variation has profound influences on population dynamics and community structure. Examination of functional traits that influence resource uptake and allocation can illuminate how co-occurring species translate environmental variation into different demographic outcomes, yet few studies have considered interspecific differences in trait plasticity. We experimentally manipulated soil moisture to test the hypothesis that differences in morphological plasticity contribute to species differences in demographic response to unpredictable precipitation in Sonoran Desert winter annual plants. We compared plasticity of leaf traits and biomass allocation between Pectocarya recurvata (Boraginaceae) and Stylocline inicropoides (Asteraceae), co-occurring species that differ in long-term demographic patterns. The species with highly variable population dynamics, Siylodine, had striking increases in leaf area and root biomass in response to an experimental increase in soil moisture. In contrast, the species with buffered long-term population dynamics, Pectocarya, did not differ in leaf morphology or biomass allocation between soil moisture treatments. Regardless of water treatment, Pectocarya had earlier reproductive phenology and greater fecundity than Slylocline, suggesting that differences in the timing of the phenological transitions from vegetative to reproductive growth may affect species' responses to precipitation pulses. Combining long-term observations with experimental manipulations provides a window into the functional underpinnings and demographic consequences of trait plasticity. [ABSTRACT FROM AUTHOR]

Abstract: This study was conducted to determine the effect of both inter-cultivar and intra-cultivar competition on the growth of three spring wheat (Triticum aestivum L.) cultivars released in different periods that had different root:shoot ratios, differed in water extraction from dry soil, and differed in height. Two water regimes were imposed to compare competitive effects under irrigated and rainfed conditions. Our main hypotheses were that the different distribution of biomass between shoot and root in old and new wheat cultivars will alter their competitive ability, that differences in root size will alter their competitive ability through different water uptake patterns, and differences in the gradient for water uptake will alter their competitive ability in different environments by enabling water extraction from drier soil. In monoculture, the recent cultivars had significantly more grain yield and higher water use efficiency for grain (WUEG) than the old cultivar. Under the two water regimes the old cultivar had more root biomass, and extracted water in deeper soil layers, whereas the modern cultivars extracted more water in dry soil layers. The old cultivar benefited from inter-cultivar competition in terms of both grain yield and above-ground biomass accumulation at the expense of the modern cultivars, which showed significantly reduced growth in mixtures compared to in monoculture. Our study suggested that the below-ground competitive ability of cultivars may have a negative relationship with the grain yield and WUEG in monoculture. The yield superiority of modern and recent cultivars was mostly due to increased above-ground biomass, kernel number and WUEG and a smaller proportion of root biomass. Our results demonstrate that inter-plant competition is an important factor affecting spring wheat productivity in contrasting environments, but the extent and intensity of these effects depend on the adaptation of root traits to available soil water. Reducing root growth redundancy and enhancing the ability to deplete more soil water are clearly adaptive features for wheat for water-limited conditions. [Copyright &y& Elsevier]

Abstract: Cactus seedlings often establish under nurse plants which modify environmental conditions by increasing moisture and decreasing solar radiation, which may cause beneficial and detrimental effects, respectively, on seedling growth. Three soil moisture treatments (5%, 25% and 60%) and two solar radiation levels (100% exposure=243μmolm−2 s−1, and 40%=102μmolm−2 s−1) were used in a factorial design to analyze seedling growth response of three rare cactus species (Mammillaria pectinifera, Obregonia denegrii and Coryphantha werdermannii). The variables evaluated were relative growth rate (RGR), root/shoot ratio (R/S), and K (RGRroots/RGRshoot), obtained from an initial seedling harvest (6-month-old seedlings) and a final harvest 6 months after treatment application. All three species had slow RGRs (0.002–0.012gg−1 day−1). O. denegrii had the lowest RGR values, but was the only species for which R/S and K varied with soil moisture. While all seedlings responded markedly to soil moisture, no response was observed to radiation treatments. The latter might have been related to the relatively low solar radiation levels present in the greenhouse. Yet, our results suggest that the main benefit nurse plants offer to seedlings is the increase in soil moisture. [Copyright &y& Elsevier]

Identifying key ecophysiological traits that differ among dominant plant species and can be linked to species-specific responses to drought would improve our ability to forecast community and ecosystem responses to global climate change. The mesic grasslands of the central plains of North America are dominated by two C4 grass species, Andropogon gerardii and Sorghastrum nutans, which purportedly differ in their tolerance of water stress. Individuals of these two species were grown in the field under rain-out shelters and subjected to wet (watered every 2–3 d) or dry (repeatedly subjected to wilting before watering) soil moisture regimes. A range of ecophysiological traits potentially important for tolerating water stress were concurrently measured. Although few traits differed between the species in the wet treatment, several traits were identified in the dry treatment that may enable A. gerardii to better tolerate drought. These were greater allocation to roots, reduced allocation to flowering, more rapid leaf turnover, and more rapid recovery of photosynthesis after wilting. The latter two traits may be particularly important for coping with increased variability in rainfall regimes in the future and are consistent with recently documented responses of A. gerardii to experimental increases in soil moisture variability. [ABSTRACT FROM AUTHOR]

The effects of moisture availability on clonal growth and biomass investment in the bamboo Pleioblastus maculata were investigated over a four-year period by transplanting Pleioblastus maculata clones into soils with different levels of moisture availability in the field. The results showed that: (1) The higher the moisture availability, the greater the total biomass of P. maculata clones. Although fewer culms are produced at the higher moisture levels, mean tiller biomass is greater. (2) Under different levels of moisture availability, obvious differences in the total rhizome length (p < 0.01), spacer length (p < 0.05) and the sizes of bamboo culms (height, p < 0.01; diameter, p < 0.01) were observed. Thus, the higher the moisture availability, the shorter the rhizomes and the larger ramets. (3) In microhabitats with low moisture availability, bamboo allocated more biomass to underground organs, which promotes elongation of rhizomes and increases root production, thereby helping to capture underground resources essential to growth. In microhabitats of high moisture availability, the biomass is primarily allocated to the aboveground growth of ramets. (4) We suggest that soil moisture availability effects the foraging strategies of bamboo, that bamboo plants growing with low moisture availability produce longer rhizomes (that is, more, although shorter, spacers) with more biomass allocation than plants in high moisture and have a better ability to forage to increase the probability of locating adequate moisture patches. Also, longer length distance between shoots (that is, longer spacers) in high soil moisture than in low is adapted to avoid intense competition from faster growing aboveground growth in high moisture patches. [ABSTRACT FROM AUTHOR]

The structure of wetland plant communities is sensitive to patterns of precipitation. In some regions, climate change is expected to result in more large‐magnitude, infrequent precipitation events. Typically, the response of wetland plants to changing precipitation regimes is studied under alterations in the amount of precipitation (drought), rather than event frequency. Here, we seek to understand how changes in rainfall frequency affect (a) soil moisture variability, (b) plant performance, and (c) plant C and N concentrations. We conducted a greenhouse study using eight herbaceous plant species (three eudicots, five monocots) subject to three precipitation treatments: (a) 80 mm per month distributed in equal volumes every 3 days (control treatment), (b) 80 mm per month distributed every 15 days (infrequent treatment), and (c) 110 mm per month distributed every 15 days (large magnitude‐infrequent treatment). Infrequent treatments decreased soil moisture by >60% compared with the control. Rainfall frequency affected soil moisture losses to evapotranspiration, which differed between early‐ and late‐growing seasons. This soil moisture stress in the infrequent treatments contributed to a 10–49% decrease in biomass among all eudicot species and a 25–54% decrease in two monocots. In contrast, changes in C and N concentration were limited to two forb species. Our results show that changes in precipitation frequency can strongly impact some wetland species. For some impacted species increased magnitude can alleviate the negative effects of infrequent rainfall. These results provide insight into how forecasted changes in the frequency and magnitude of precipitation may affect wetland plant species. [ABSTRACT FROM AUTHOR]