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Weed control is a key aspect that influences seedling response in newly-established plantations. Tree shelter protection may be an effective complement to weed control with a positive effect on the overall response of seedlings. Our study focused on assessing the morpho-physiological response of Holm oak (Quercus ilex L. ballota [Desf.] Samp.) plantations to weed control and individual protection as a combined cultural technique on a cropland site in southern Spain. The weed control treatments (cultivation, herbicide and mulch) were also applied in combination with tree shelters. Morpho-physiological variables including survival, aerial and root morphology, water potential, gas exchange and chlorophyll fluorescence were monitored over a 2-year period. Results showed that weed competition management treatments improved the seedling survival rate compared to the control treatment. Moreover, shelter was associated with a greater height growth. At early stages of establishment, and particularly under combined treatments, all plants invested more resources in their aerial parts than in their root system. Seedlings did not regulate water loss as a result of water stress, contrary to what would be expected in Mediterranean areas. Under all treatments, especially those combined with tree shelters, seedlings took up to 2 years to achieve morpho-physiological adaptation (i.e. height and diameter growths, water stress behavior) to site conditions. In addition, tree shelters promoted an increase in net photosynthesis compared to non-shelter treatments during the winter period. The tree shelters also limited the emergence of photo-inhibition phenomena in seedlings so that plants under combined treatments showed greater photo-chemical efficiency. Thus, this study supports the effectiveness of tree shelter protection as a complement to weed control treatments. More specifically, it suggests that combining individual protection (shelter) and weed control around seedlings is an interesting technique for reforestation of forest ecosystems in Mediterranean areas.

Weed control is a key aspect affecting seedling response in newly-established plantations. Tree shelter protection may be an effective complement to weed control with a positive effect on the overall response of seedlings. Our study focused on assessing the morpho-physiological response of Holm oak (Quercus ilex L. ballota [Desf.] Samp.) plantations to weed control and individual protection as a combined cultural technique on a cropland site in southern Spain. The weed control treatments (cultivation, herbicide and mulch) were also applied in combination with tree shelters. Morpho-physiological variables including survival, aerial and root morphology, water potential, gas exchange and chlorophyll fluorescence were monitored over a 2-year period. Results showed that weed competition management treatments improved the seedling survival rate compared to the control treatment. Moreover, shelter protection was proven to enhance the height growth of seedlings. At early stages of establishment, and particularly under combined treatments, all plants invested more resources in their aerial parts than in their root system. Seedlings did not regulate water loss as a result of water stress, contrary to the expectations in Mediterranean areas. Under all treatments, especially those combined with tree shelters, seedlings took up to 2 years to achieve morpho-physiological adaptation to site conditions, in terms of height and diameter growths, and water stress behavior. In addition, tree shelters promoted an increase in net photosynthesis compared to non-shelter treatments during the winter period. Tree shelters also limited the emergence of photo-inhibition phenomena in seedlings so that plants under combined treatments showed greater photo-chemical efficiency. Thus, this study supports the effectiveness of tree shelter protection as a complement to weed control treatments. More specifically, a combination of individual protection (shelter) and weed control around seedlings is an interesting technique for reforestation of agroforestry systems in the Mediterranean area. [ABSTRACT FROM AUTHOR]

This work investigates Aleppo pine performance under severe drought conditions according to seedling size and nutritional status, with special emphasis on potassium. The interaction of drought ameliorating measures such as hydrogels is also studied. Seven fertilization treatments applied in two nursery locations provided 14 stocklots, resulting in different seedling sizes for each nutrient concentration and vice versa. Stocklots were tested in a greenhouse experiment and a harsh site plantation experiment. In the greenhouse, seedlings given two hydrogel doses (0.01 and 0.1 per cent w/w) plus a control were allowed to dry and survival and soil moisture were measured. In parallel to this trial, the effects of hydrogel dosage, brand and soil texture on soil water properties were tested in a laboratory. Results show that large stock survived significantly better than conventionally sized stock in both experiments: 37 and 27 per cent more in the greenhouse and harsh site, respectively. Despite presenting wide variation, macronutrient concentration was not related to survival for a given size. Hydrogel effect on soil water was different according to factors, although in all cases, its effect diminished at suction tensions higher than 30 kPa. Results demonstrate the overriding effect of size over nutritional status on seedling survival in harsh environments. [ABSTRACT FROM AUTHOR]

There is a need for a better understanding of the primary role of macronutrients in Aleppo pine stock quality and for producing larger nutrient-loaded stock, which may be challenging for inland nurseries. The influence of nursery location and fertilization on nursery culture, growth, allometry and seedling quality of Aleppo pine was studied in seedlings cultivated over the 2006 growing year. Fertilization treatments considered how a K enrichment performed over common programs currently being practiced and divided into three levels of K/N ratio: 0.63–0.89 (normal), 1.81–1.89 (high), and 2.25–2.53 (very high). Results showed that fertilization had a minor effect on seedling growth and allometry in comparison with location, which was the governing factor. However, fertilizing treatments significantly affected final seedling attributes, which has its origin on the early treatment differences that were kept up to the end of culture. Higher nutrient supply treatments produced the highest nutrient concentration in seedlings but they were associated with lower fertilization efficiencies. Fertilizer efficiency was approximately twofold in the coastal nursery for the three macronutrients, although concentration was higher in the inland nursery due to lower seedling growth. It is concluded that warmer regions are more suitable for producing large stock more efficiently. [ABSTRACT FROM AUTHOR]