Limited linkages of aboveground and belowground phenology: A study in grape

High temperature can improve the performance of invasive plants by facilitating root growth

PREMISE

The ever-increasing temperatures of the Anthropocene may facilitate plant invasions. To date, studies of temperature effects on alien plants have mainly focused on aboveground plant traits but ignored belowground traits, which may confound predictions of plant invasion risks.

METHODS

The temperature effects on the root growth dynamics of two alien shrubs, invasive Mimosa sepiaria and naturalized Corchorus capsulari, were studied using a 3D, transparent growth system under five temperature treatments (day/night: 18°C/13°C to 34°C/29°C) that cover the present and future warming temperature scenarios in China. We measured root depth and width growth in response to temperature treatments over 84 days. We also investigated intra- and interspecific competition of paired plants of the two species grown together at the five temperatures.

RESULTS

Shoot growth of M. sepiaria and C. capsularis was optimal at the mid-range temperature. Root growth, however, was faster at the highest temperature (34°C/29°C) for M. sepiaria, but decreased for C. capsularis as temperatures increased. Root depth growth was more sensitive than root width for both species during neighbor competition. Compared to C. capsularis, M. sepiaria had relatively greater advantage during intra- and interspecific competition with increasing temperature, possibly because of its better root growth at high temperatures.

CONCLUSIONS

These results suggest that temperature increases can improve the performance of some alien plants by facilitating width and depth growth of their roots. This enhancement requires serious attention when managing and predicting invasion risk.

Separating the effects of air and soil temperature on silver birch. Part I. Does soil temperature or resource competition determine the timing of root growth?

The aboveground parts of boreal forest trees mostly grow earlier, and the roots later, in the growing season. We aimed to experimentally test whether the extrinsic driver of soil temperature or the intrinsic driver (resource competition between plant parts) is a more important control for the root and shoot growth of silver birch (Betula pendula Roth) seedlings. Sixteen two-year-old seedlings were grown in controlled environment rooms for two simulated growing seasons (GS1, GS2). In GS1, all the seedlings were acclimatized under the same conditions, but in GS2, the soil temperature treatments were: (i) constant 10 °C (Cool); (ii) constant 18 °C (Warm); (iii) early growing season at 10 °C, switched to 18 °C later (Early Cool Late Warm, ECLW) and (iv) early growing season 18 °C, switched to 10 °C later (Early Warm Late Cool, EWLC). The treatments did not affect growth allocation between shoots and roots. Warm soil benefitted shoot elongation as it slowed down in EWLC and accelerated in ECLW after the soil temperature switch. However, whole-tree biomasses were similar to Cool and the seedlings grew largest in Warm. Phenology was not strongly affected by soil temperature, and root and shoot growth did not usually peak simultaneously. Short root mortality increased strongly in ECLW and decreased in EWLC after the soil temperature switch. Long root longevity was not significantly affected but long root growth ceased earliest in ECLW. Soil warming increased foliar nutrient contents. Growth dynamics were not solely driven by soil temperature, but resource competition also played a significant role. The study showed the importance of soil temperature for fine root dynamics not only through root growth but also via root mortality, as soil warming increased mortality even more than growth. Soil temperature has complex effects on tree and soil functioning, which further affects carbon dynamics in forest ecosystems that have a climate feedback.

Prediction of Nitrogen Dosage in ‘Alicante Bouschet’ Vineyards with Machine Learning Models

Vineyard soils normally do not provide the amount of nitrogen (N) necessary for red wine production. Traditionally, the N concentration in leaves guides the N fertilization of vineyards to reach high grape yields and chemical composition under the ceteris paribus assumption. Moreover, the carryover effects of nutrients and carbohydrates stored by perennials such as grapevines are neglected. Where a well-documented database is assembled, machine learning (ML) methods can account for key site-specific features and carryover effects, impacting the performance of grapevines. The aim of this study was to predict, using ML tools, N management from local features to reach high berry yield and quality in ‘Alicante Bouschet’ vineyards. The 5-year (2015–2019) fertilizer trial comprised six N doses (0–20–40–60–80–100 kg N ha⁻¹) and three regimes of irrigation. Model features included N dosage, climatic indices, foliar N application, and stem diameter of the preceding season, all of which were indices of the carryover effects. Accuracy of ML models was the highest with a yield cutoff of 14 t ha⁻¹ and a total anthocyanin content (TAC) of 3900 mg L⁻¹. Regression models were more accurate for total soluble solids (TSS), total titratable acidity (TTA), pH, TAC, and total phenolic content (TPC) in the marketable grape yield. The tissue N ranges differed between high marketable yield and TAC, indicating a trade-off about 24 g N kg⁻¹ in the diagnostic leaf. The N dosage predicted varied from 0 to 40 kg N ha⁻¹ depending on target variable, this was calculated from local features and carryover effects but excluded climatic indices. The dataset can increase in size and diversity with the collaboration of growers, which can help to cross over the numerous combinations of features found in vineyards. This research contributes to the rational use of N fertilizers, but with the guarantee that obtaining high productivity must be with adequate composition.

Under-Vine Vegetation Mitigates the Impacts of Excessive Precipitation in Vineyards

Excessive precipitation events have greatly increased in several grape growing regions due to human-caused climate change. These heavy downpours result in a myriad of problems in the vineyard including soil aggregate breakdown, soil runoff, nutrient leaching, excessive vine vegetative growth, and diseased fruit. The negative impacts of excessive precipitation events on vineyards are exacerbated by the maintenance of bare soil under the vines. Exposure of bare soil results in soil erosion and runoff which pollutes nearby watersheds; raindrops weaken and break apart soil aggregates, leading to increased soil erosivity and contributing to the formation of surface crusts. In addition to excessive precipitation events, some grape growing regions can be characterized by fertile soils. The availability of ample water and nutrients can lead to highly vigorous vines with shoot growth continuing through harvest. Long shoots and large leaves result in shaded fruit, a humid vine microclimate, and excessive cluster rot. In this review, we examined how either natural (i.e., resident) or seeded under-vine vegetation (UVV) can help mitigate many of the problems associated with excessive precipitation. Through providing vegetative coverage to reduce the force of raindrops, increasing soil organic matter and enhancing soil microbial diversity, UVV can reduce the soil degradation and off-site impacts caused by excessive precipitation events. Through competition for soil resources, UVV can reduce excessive vegetative growth of vines and decrease cluster rot incidence and severity, although grapevine response to UVV can be highly variable. We discussed recent advances in understanding below and aboveground vine response and acclimation to UVV and presented current evidence of factors influencing the impact of UVV on vine growth and productivity to assist practitioners in making informed decisions and maximize the ecosystem services provided by UVV.

Waterlogging and soil freezing during dormancy affected root and shoot phenology and growth of Scots pine saplings

Soil waterlogging is predicted to increase in the future climate in boreal regions due to increased precipitation. Snowmelt periods in winter may also become more common and further increase the amount of water in soil. It is not well known how waterlogging and soil freezing during winter affect the physiology, phenology and growth of trees. Our aim was to study the below- and aboveground responses of Scots pine (Pinus sylvestris L.) saplings to waterlogging (WL) in frozen (Fr) and unfrozen (NoFr) soils in a growth chamber experiment. The soil was either -2 °C or +2 °C and either waterlogged or not in a split-plot design for 6 weeks during dormancy, with similar air conditions in all treatments, which were Fr + WL, NoFr + WL, Fr + NoWL and NoFr + NoWL. Needles showed a shift towards a deeper dormancy in frozen than unfrozen soil in terms of chlorophyll fluorescence (Fv/Fm), water potential and apoplastic electrical resistance. In spring, initiation of shoot elongation started earlier if the soil was frozen during dormancy. In Fr + WL, initiation of root growth was delayed by 20 days compared with other treatments; after that, the root growth peaked at the same time as needle elongation. Needles remained smaller in Fr + WL than in the other treatments, indicating that roots formed a strong sink for carbon. Shoot and root biomass were not negatively affected by waterlogging if the soil remained unfrozen. In Fr + WL, survival and growth capacity of new terminal and whorl buds, the number of bud scales and the number of dwarf shoots were reduced. We conclude that soil freezing on sites prone to waterlogging should be considered in management of boreal forests, especially in the face of predicted climate change.

Unaltered phenology but increased production of ectomycorrhizal roots of Pinus elliottii under 4 years of nitrogen addition

Timing (phenology) and amount (production) are two integral facets of root growth, and their shifts have profound influences on below-ground resource acquisition. However, the environmental control and the effects of nitrogen (N) deposition on the production and phenology of ectomycorrhizal (ECM) roots remain unclear. Using a 4 yr minirhizotron experiment, we explored the control of the production and three phenophases (initiation, peak, and cessation of growth) of ECM roots in two soil layers and investigated their dynamic responses to N addition in a seasonally dry subtropical Pinus elliottii forest. We found a stronger control of water availability on the production and a stronger control of temperature on the phenology of ECM roots under ambient conditions. Temperature was correlated positively with initiation and negatively with cessation, especially in the shallow layer. N addition did not affect the phenology of ECM roots but increased their production by modifying N and phosphorus (P) stoichiometry in the soil and foliage. Our findings suggest a greater sensitivity of production than phenology of ECM roots to N addition. The increased production of ECM roots under N addition could be driven by N-induced P limitation or some combination of below-ground resources (P, N, water).