Coconut coir as a sustainable nursery growing media for seedling production of the ecologically diverse quercus species

Peat, a non-sustainable resource, is still predominately used in forest nurseries. Coconut coir might provide an alternative, renewable, and reliable growing media but few studies have evaluated this media type in forest nurseries. We assessed the influence of pure coir, in combination with various fertilization regimes, on the growth and physiology of three ecologically diverse Quercus species seedlings (Q. robur, Q. pubescens, and Q. ilex) during nursery cultivation. Seedlings were grown using peat and pure coir in combination with three fertilization treatments (standard, K-enriched, and P-enriched). Data were collected for: (1) growth and physiological traits; (2) detailed above- and below-ground morphological traits by destructive analysis; and (3) NPK content in leaves, shoot and roots, and in the growing media, following cultivation. Peat and coir in combination with the various fertilization treatments affected above- and below-ground morphology and, to a lesser extent, the physiological traits of Quercus seedlings. Large effects of the substrate occurred for most morphological variables, with peat being more effective than coir in all studied species. Fertilization also produced significant differences. The effect of K-enriched fertilization on plant growth was clear across the three species and the two growing media. P-enriched fertilization in peat was the only combination that promoted a higher amount of this element in the tissues at the end of cultivation. Despite their smaller size, seedlings produced in coir were compatible with standard Quercus forest stocktype size, and showed a proportionally higher root system development and fibrosity. Our results suggest that coir can be used as an alternative substrate to grow Quercus species seedlings, and that fertilization can offset coir deficiencies in chemical properties. As several functional traits drive planting performance under varying environmental conditions. according to the Target Plant Concept, coir might thus serve as an acceptable material for seedling cultivation in some cases

Should we use meshes or solid tube shelters when planting in Mediterranean semiarid environments?

Tree shelters in Mediterranean environments have a two-sided effect. They not only protect seedlings from browsing but also ameliorate microclimatic conditions, improving post-planting survival and growth. However, the ecophysiological basis of these effects are poorly understood. A factorial experiment combining light transmissivity and shelter type (solid tube vs. mesh wall) was carried out to assess the impact of contrasting microclimatic characteristics on seedling performance and physiological stress levels of shelters in two Mediterranean shrubland species (Quercus coccifera and Rhamnus lycioides) planted in a semiarid site. Even though seedlings in solid tube shelters experienced higher temperature and were slightly more photoinhibited, they had higher predawn water potential and, in general, better survival and growth than in mesh wall shelters. However, these effects were species-specific, with Rh. lycioides more favoured by solid wall shelters than Q. coccifera. However, root growth cannot explain these interactions between species and shelter type on seedling survival. Since light transmission had a marginal effect compared with wall type, we proposed that the observed effects and interaction with species are not dependent on light intensity or temperature but on other microclimatic differences like air velocity or light quality and distribution. Further studies should assess the importance of these factors on post-planting growth and physiological stress levels, which can be critical for matching the correct tree shelters type for each species in plantations in semiarid environments

Establishing Acacia salicina under dry Mediterranean conditions: The effects of nursery fertilization and tree shelters on a mid-term experiment with saline irrigation

The restoration of dry lands in the Mediterranean is a challenging task because harsh abiotic conditions hamper the counteraction of feed-back degradation processes. Active restoration through planting must be performed to deter this process. In this study, we tested the influence of mineral nutrition in the nursery (two formulations of controlled release fertilizer at two rates each) and tree protection after planting (by using tube shelters) on the nine-year performance of Acacia salicina irrigated with low-quality (saline) water. The overall survival at the end of the study period was 58.2%, with the electrical conductivity of the soil saturation extract reaching 5.4 dS·m-1 after nine years. The survival and growth (in height) were greater for seedlings fertilized with more than 1.5 g·L-1 of 9-13-18, although the survival differences became significant only after the seventh year. The basal stem diameter (BSD) of seedlings that were fertilized at higher rates was significantly greater than those that were fertilized at lower rates during the first two years of planting; the differences were no longer present thereafter. The seedlings in shelters had marginally superior survival, faster growth during the first four years, and smaller BSD values after the third year compared to those of the unprotected seedlings. In comparison with a parallel study that was conducted under drought conditions, irrigation reduced some differences among treatments, but it increased others. These results emphasize the importance of the size and mineral nutrient status of nursery stock in irrigated plantations under dry Mediterranean conditions, with highly fertilized seedlings showing superior performance. Long-term planting studies are crucial for gaining a greater understanding of seedling performance and for providing a better rationale for treatment recommendations.We gratefully acknowledge the financial support of the National Institute for Agriculture and Food Technology and Research (INIA, Spanish Department of Science and Innovation) through projects SC-94111 and OT98-001) and the Technical University of Madrid through its sabbatical program. The comments of three anonymous reviewers substantially improved this manuscript

Combined pre-hardening and fall fertilization facilitates N storage and field performance of Pinus tabulaeformis seedlings

Exponential fertilization during the pre-hardening stage and fall fertilization during the hardening stage have each been used independently to nutrient load seedlings. However, nursery and field responses of seedlings to the combination of exponential fertilization and fall fertilization have received little attention. Chinese pine (Pinus tabulaeformis Car.) container seedlings were exponentially fertilized with accumulated totals of 40, 80 or 120 mg N per seedling during pre-hardening, and fall-fertilized with 0, 12, 24 or 48 mg N per seedling, and were subsequently outplanted and followed for two growing seasons. Interactions of exponential and fall fertilization had significant effects on plant N content in the nursery and first-year height after outplanting. Fall fertilization promoted additional nutrient loading during hardening for the 40-80 mg N per seedling pre-hardening regimes. The highest exponential fertilization rate enhanced N concentration in foliage and roots compared to the other two rates. Maximum diameter was observed in the lowest exponential fertilization rate at the second year after outplanting. Fall fertilization enhanced foliar N concentration. Supplemental 12 and 24 mg N per seedling during fall were more effective in increasing height increment at the second year after outplanting. Our results indicate that pre-hardening fertilization is a useful tool to nutrient load Chinese pine in the nursery and facilitate outplanting performance in the field. In combination, fall fertilization has potential to further augment this response, although further research is needed to precisely match rates of pre-hardening and fall fertilization to optimize seedling performance

Linking nursery nutritional status and water availability post-planting under intense summer drought: the case of a South American Mediterranean tree species

Drought-avoidance traits of South American Mediterranean tree species are crucial attributes to be considered in nursery practices aimed at improving the performance of seedlings exposed to intense summer drought in dryland reforestation projects. In this study, we determined the relation between nursery fertilization doses and the development of drought-avoidance traits of the soapbark tree Quillaja saponaria (Mol.) under contrasting watering regimes following post-planting. Seedlings were grown for 6 months using four increasing doses of controlled-release fertilizer (0, 3, 6, and 12 g L-1 of Basacote® Plus 15:8:12). After outplanting, half of the seedlings were watered weekly and the other half were left unwatered for one growing season from September 2011 to May 2012. Seedlings were periodically measured for morphological and ecophysiological parameters, and carefully harvested for root measurements at the end of the study. Our results showed that high fertilization doses produced significantly larger seedlings in the nursery with high nitrogen and phosphorous foliar concentrations, which resulted in a significantly higher shoot dry mass after outplanting. Unfertilized seedlings grown with water application had a significantly higher stem diameter, root dry mass and lower shoot/root compared with seedlings with high fertilizer dose. These results highlight the ability of this species to maintain drought-avoidance traits, such as high xylem water potential and chlorophyll fluorescence, during the first 3 months of the 7-month drought period. High nutrient loading, although resulting in improved shoot productivity after outplanting, did not make a significant contribution to the early development of drought-avoidance traits in Q. saponaria

Establishing quercus ilex under Mediterranean dry conditions:sowing recalcitrant acorns versus planting seedlings at different depths and tube shelter light transmissions

Success of Mediterranean dry areas restoration with oaks is a challenging goal. Testing eco-techniques that mimic beneficial effects of natural structures and ameliorate stress contributes to positive solutions to overcoming establishment barriers. We ran a factorial experiment in a dry area, testing two levels of solid wall transmission of tube shelters (60 and 80 %) plus a control mesh, and two depths (shallow and 15 cm depth) of placing either planted seedlings or acorns of Quercus ilex. Microclimate of the planting or sowing spots was characterized by measuring photosynthetically active radiation, temperature and relative humidity. Plant response was evaluated in terms of survival, phenology, acorn emergence and photochemical efficiency (measured through chlorophyll fluorescence). We hypothesize that tube shelters and deep planting improve Q. ilex post-planting and sowing performance because of the combined effects of reducing excessive radiation and improving access to moist soil horizons. Results show that temperature and PAR was reduced, and relative humidity increased, in deep spots. Midsummer photochemical efficiency indicates highest level of stress for oaks in 80 % light transmission shelter. Optimum acorn emergence in spring was registered within solid wall tree shelters, and maximum summer survival of germinants and of planted seedlings occurred when acorns or seedlings were placed at 15 cm depth irrespectively of light transmission of shelter. Survival of germinants was similar to that of planted seedlings. The importance of techniques to keep high levels of viability after sowing recalcitrant seeds in the field is emphasized in the study

Light transmissivity of tree shelters interacts with site environment and species ecophysiology to determine outplanting performance in Mediterranean climates

Plastic tree shelters are commonly used in plantations under Mediterranean climates to protect against herbivory and enhance outplanting performance. However, effects on outplanting performance cannot be generalized due to the complexity of plant responses to microenvironmental conditions within the tube wall. The interactions between the light transmissivity of the tubes and species-specific responses to light and site environment on two-year outplanting performance were studied in two species with contrasting shade tolerance planted inside tree shelters with four different light transmissivities and a non-tree shelter control at two Mediterranean sites with contrasting rainfall and temperature. In general, increasing light transmissivity enhanced biomass accumulation, suggesting that the use of clear tubes might be advisable. However, the shade-tolerant Q. ilex did not benefit from the greater light transmissivity in the most arid site, indicating that the positive effect of clear tubes depends on water stress experienced by seedlings, which ultimately is determined by drought resistance strategies and site conditions. The growth of both species and survival of P. halepensis were higher within clear tubes in the continental site than in unsheltered plants, which suggests that factors other than light, such as warmer daytime temperatures or the prevention of dust deposition, can explain this beneficial site-dependent effect of tree shelters. In conclusion, our results confirm the hypothesis that the effect of tree shelter and its light transmission on outplanting performance is site and species-specific, but further research is needed to identify the effect of other effects not related to light transmission

Is light the key factor for success of tube shelters in forest restoration plantings under Mediterranean climates?

Tube shelters were designed to protect against browsing, but they improve seedling survival in Mediterranean dry climates. Mechanisms for this response, however, are not fully understood and this knowledge can be useful to help design optimal tube shelters for Mediterranean species and climates. Our objective in this study was to determine if the positive effect of tube shelters is due to enhanced growth during the wet season or to reduced light stress during the dry season. we performed two independent experiments. In the first, we assessed root growth during the wet season in two Mediterranean species with contrasting light tolerance (Quercus ilex L and Pious halepensis Mill.) growing in tubes with varying light transmissivity. In the second experiment, we studied the response of a Quercus ilex plantation to different shelter treatments. Root growth during the wet season was reduced with decreasing light transmissivity in the shade intolerant P. halepensis, but not in the shade tolerant Quercus ilex. Survival of Q. ilex shaded by a mesh shelter only during summer was higher than in unsheltered seedlings and similar to the survival in tube and mesh shelters during the whole season. This suggests that shade during the dry period was the main factor explaining survival in this species. This effect could be related to the lower leaf temperature recorded in sheltered seedlings. We conclude that Q. ilex (and perhaps other late successional, shade tolerant Mediterranean species) should be planted in tubes with the currently used light transmissivity because these shelters reduce light stress in summer without impairing root growth in the wet season. However, current tubes impair root growth in P. halepensis (and likely other pioneer, shade intolerant Mediterranean species), so higher transmissivity tubes may be necessary. Optimal transmissivity for tube shelter in Mediterranean climates is species-specific and identifiable as the point that minimizes light stress during summer without impairing root growth in the wet season. (C) 2010 Elsevier B.V. All rights reserved

Matching seedling size to planting conditions: interactive response with soil moisture

Seedling size is a very important issue when producing plants for restoration projects. Scientific evidence on the appropriate size for drylands is contradictory. Thus, the aim of this study was to evaluate the effect of seedling size during first establishment by conducting a short term greenhouse experiment with Pinus canariensis containerized seedlings. A selection of large (mean height: 33.7 cm) and small (14.3 cm) one-year-old seedlings were planted in pots under two volumetric water content regimes: dry (7%) and wet (15%). Midday shoot water potential was measured in two periods: 10 (prior to root protrusion) and 30 (once the roots had protruded from the plug) days after planting. The length of protruding roots was measured after 30 days. One month after planting, the large seedlings under the dry regime produced more new roots than the small seedlings, but also showed the highest midday water potential values. Therefore, the greater root growth of the former did not offset the higher transpiration demand when planted in dry soils. These results suggest that under uncertainty about the soil humidity levels of dry areas, using small seedlings can improve their short-term survival after planting