Physiological and environmental control of seed germination timing in Mediterranean mountain populations of Gundelia tournefortii

Fruit and seed morphology interact with embryo physiology and environmental conditions to control seed germination timing. This interaction plays a pivotal role in ecosystems with narrow windows for seedling establishment, such as the Mediterranean mountains. In this study, we investigated the germination responses of the secondary capitula (disseminules) of Gundelia tournefortii from East Mediterranean mountain populations. When incubated at 15 °C, intact capitula did not reach 20% of final germination, with or without the addition in the germination substrate of GA3 (250 mg L−1), while extracted fruits reached 50% of germination, which increased to ca. 70% when treated with GA3. Cold stratification enhanced final germination of the capitula at 15 °C to ca. 65%, although almost half of the initially sown capitula germinated during the second month of stratification at 5 °C. During the stratification at 5 °C, peak puncture force needed to pierce the basal part of the capitula decreased linearly and capitula started germinating after one month, which corresponded to a peak puncture force of 0.41–0.35 N. These findings highlight the presence of mechanical and hormonal components of physiological seed dormancy. The morphology of the disseminules controls seed germination timing, by interacting with cold winter temperatures and starting seed germination only in early winter. These findings not only provide new insights on the reproduction from seeds of this plant, but by highlighting high germination of cold-stratified intact capitula, can also support plant propagation programmes for this key wild edible species, very important for food security and the livelihoods of local communities in the East Mediterranean region.

A Step-by-Step Guide to Initialize and Calibrate Landscape Models: A Case Study in the Mediterranean Mountains

The use of spatially interactive forest landscape models has increased in recent years. These models are valuable tools to assess our knowledge about the functioning and provisioning of ecosystems as well as essential allies when predicting future changes. However, developing the necessary inputs and preparing them for research studies require substantial initial investments in terms of time. Although model initialization and calibration often take the largest amount of modelers’ efforts, such processes are rarely reported thoroughly in application studies. Our study documents the process of calibrating and setting up an ecophysiologically based forest landscape model (LANDIS-II with PnET-Succession) in a biogeographical region where such a model has never been applied to date (southwestern Mediterranean mountains in Europe). We describe the methodological process necessary to produce the required spatial inputs expressing initial vegetation and site conditions. We test model behaviour on single-cell simulations and calibrate species parameters using local biomass estimations and literature information. Finally, we test how different initialization data—with and without shrub communities—influence the simulation of forest dynamics by applying the calibrated model at landscape level. Combination of plot-level data with vegetation maps allowed us to generate a detailed map of initial tree and shrub communities. Single-cell simulations revealed that the model was able to reproduce realistic biomass estimates and competitive effects for different forest types included in the landscape, as well as plausible monthly growth patterns of species growing in Mediterranean mountains. Our results highlight the importance of considering shrub communities in forest landscape models, as they influence the temporal dynamics of tree species. Besides, our results show that, in the absence of natural disturbances, harvesting or climate change, landscape-level simulations projected a general increase of biomass of several species over the next decades but with distinct spatio-temporal patterns due to competitive effects and landscape heterogeneity. Providing a step-by-step workflow to initialize and calibrate a forest landscape model, our study encourages new users to use such tools in forestry and climate change applications. Thus, we advocate for documenting initialization processes in a transparent and reproducible manner in forest landscape modelling.

Long-Term Tree-Ring Response to Drought and Frost in Two Pinus halepensis Populations Growing under Contrasting Environmental Conditions in Peninsular Italy

Pinus halepensis dominates coastal to mountain areas throughout the Mediterranean Basin. Its growth plasticity, based on polycyclic shoot formation and dynamic cambial activity, and tolerance to extreme drought and exceptional frosts, allows it to colonize a vast array of environments. We used tree-rings from codominant pines to compare lifespan, growth rates, age and size distribution in a typical coastal (i.e., prolonged drought, occasional low-intensity fires) vs. inland hilly (i.e., moister conditions, recurrent frosts) population. BAI trends, growth-limiting climate factors and tree-ring anatomical anomalies were analyzed considering the differences in climate and phenology obtained from multispectral satellite images. The species maximum lifespan was 100–125 years. Mortality was mainly due to fire on the coast, or heart-rot in the inland site. Populations differed in productivity, which was maintained over time despite recent warming. Site conditions affected the growing season dynamics, the control over ring formation by summer drought vs. winter cold and the frequency of anatomical anomalies. Recurrent frost rings, associated with temperatures below −10 °C, occurred only at the inland site. Pinus halepensis confirmed its remarkable growth plasticity to diverse and variable environmental conditions. Its ability to survive extreme events and sustain productivity confirmed its adaptability to climate change in coastal areas as well as on Mediterranean mountains.

Estimation of soil loss with RUSLE during a period of increasing rainfall erosivity (1997-2018) in two-contrasted Mediterranean watersheds (southern Spain).

<p>During the last 25 years, an increasing rainfall erosivity occurred in South of Spain according to recent studies. This fact may rendered in an increment of the derived threatens from water erosion and, consequently, soil loss processes, one of the main geomorphic agent in that geographical area. This study deals with the application of RUSLE equation in two-contrasted Mediterranean mountainous watershed from 1997 to 2018. Both of them are characterised with very common ecogeomorphologic features from Mediterranean mountains but differs in the rainfall regime: one watershed shows an altitudinal gradient from dry-Mediterranean to subhumid Mediterranean climate, and the other one from semiarid to dry-Mediterranean climate.</p><p>From the methodological point of view, RULSE was applied but some modifications were introduced in its calculation: i) rainfall intensity calculated in 10-minutes instead of 30-minutes for Factor R; ii) vegetation cover estimated by means of NDVI for Factor C; and iii) validation using field inventory of soil surface components.</p><p>The results indicated differences between both watersheds given their different ecogeomorphologic conditions. The precision of using I10 let valuate better the soil loss estimation and its spatial and temporal variability. The validation with the soil surface components obtained better results in the rainiest watershed with more biotic ecogeomorphological conditions. This study is of great useful to detect priority areas to carry out revegetation plans to control erosion and floodings.</p>