Understanding how climate influences plant reproduction and growth at contrasting range limits is crucial for predicting how species' ranges may shift in response to ongoing climate change. Trees and shrubs have shown warming‐induced increases in performance at upper elevation limits but reduced performance at lower distributional limits due to warming‐driven drought limitation. Whether these differential responses are also valid for alpine forbs exposed to accelerated warming remains largely unknown. We examined climate signal recorded in annual growth and recruitment over the past 60 years in the alpine forb Potentilla pamirica in Western Himalayas, and tested whether the responses to recent climate warming differ between dry steppe, wet alpine and cold subnival zone within the species 5,250–5,900 m elevation range. We reconstructed recruitment and growth chronologies from 1,019 individuals spanning 1–73 years, and more than 21,500 annual growth rings. We identified contrasting climatic controls of recruitment and growth at opposite elevation range margins, as well as contrasting demographic trends identified from age distributions. In lower‐elevation steppes, recruitment increased with high late‐winter snowfall and decreased with high summer temperatures, while growth increased with high summer precipitation. Conversely, warm winters and summers in higher‐elevation alpine and subnival zones support growth and recruitment, while snowy winters reduce them, especially at their upper elevation limit. The age distribution revealed greater numbers of younger individuals, indicating healthy growing populations, in the alpine habitat, while evidence of ageing plant populations was observed in steppe and subnival zones. Accelerated warming since the 1990s reduced growth and recruitment in dry steppes while supporting plant performance in the alpine habitat. The recruitment in the subnival zone did not peak during the past warmest decade due to concomitant extreme snowfall events. Synthesis. Our results provide novel information on population‐specific climate dependency of plant recruitment, growth and population dynamics, suggesting the high vulnerability of high‐elevation Himalayan ecosystems to climate change. This is partly balanced by high species longevity and slow radial growth securing a long‐term population persistence. Continuing trends of extreme snowfall events at higher elevations and droughts at lower elevations may lead to species range contraction.
1. How plants allocate their biomass to different organs is essential to understanding plant adaptations and distributions. Overall, biomass allocation may follow fixed rules across taxa. They are also likely to exhibit substantial departure from these rules during ontogeny and in response to particular limiting factors to optimize their growth and maximize their survival. However, how plants adjust their allocation priorities depending on size and age across stress gradients remain largely unknown in wild populations. 2. We examined ontogenetic variation in biomass allocation in Himalayan forb Potentilla pamirica across its 5,250-5,900-m elevation range, between populations from dry steppe, wet alpine and cold subnival zone. We evaluated whether biomass allocation followed optimal partitioning or fixed allometric rules using organ mass in 1,019 individuals spanning 1-73 years. 3. We found shifting biomass fractions with plant size and age, supporting the optimal partitioning theory. Young plants (<10 years) allocated similar proportions of biomass to leaves, stems and roots, intermediate-aged plants (10-30 years) allocated more biomass to roots, while the oldest plants had 90% biomass in belowground stems. 4. Major developmental processes including secondary thickening, branching and flowering begin 10-15 years earlier under more thermally favourable steppe conditions. Young steppe plants are larger than alpine and subnival plants, but these differences disappear in plants aged ~30, and the oldest alpine and subnival plants are larger than steppe plants. 5. Plant age exerted significant control over biomass allocation after controlling for plant size. While in steppe plants the preference for stem biomass allocation increases with both size and age, for large alpine and subnival plants the stem prioritization decreases with age in favour of root and leaf mass fractions. We interpret root and leaf prioritization in older plants as a way to reduce carbon imbalances and the risk of frost damage to secure long life. 6. Our analyses rejected ontogenetically fixed allometry and instead found high variation in biomass allocation depending on age, size and environment, supporting optimal partitioning theory. The uneven allocation of resources to different structures and functions during ontogenesis reflects plant adaptations | 33 Functional Ecology DOLEZAL Et AL.
Background and Aims Although the plant economic spectrum seeks to explain resource allocation strategies, carbohydrate storage is often omitted. Belowground storage organs are the centre of herb perennation, yet little is known about the role of their turnover, anatomy, and carbohydrate storage in relation to the aboveground economic spectrum. Methods We collected aboveground traits associated with the economic spectrum, storage organ turnover traits, storage organ inner structure traits, and storage carbohydrate concentrations for approximately eighty temperate meadow species. Key Results The suites of belowground traits were largely independent from one another, but there was significant correlation between the aboveground traits with both inner structure and storage carbohydrates. Anatomical traits diverged according to leaf nitrogen concentration on one side and vessel area and dry matter content on the other; carbohydrates separated along leaf nitrogen and plant height. Conclusions Contrary to our expectations, aboveground traits and not storage organ turnover were correlated with anatomy and storage carbohydrates. Belowground traits associated with the aboveground economic spectrum also did not fall clearly within the fast-slow economic continuum, thus indicating the presence of a more complicated economic space. Our study implies that the generally over-looked role of storage within the plant economic spectrum represents an important dimension of plant strategy.
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