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T. Curt - One of the best experts on this subject based on the ideXlab platform.
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Six-year time course of light-use efficiency, carbon gain and growth of beech Saplings (Fagus sylvatica) planted under a Scots pine (Pinus sylvestris) shelterwood
Tree Physiology, 2007Co-Authors: Philippe Balandier, Hervé Sinoquet, Ela Frak, R. Giuliani, Marc Vandame, S. Descamps, L. Coll, Boris Adam, Bernard Prévosto, T. CurtAbstract:Two-year-old Fagus sylvatica L. Saplings were planted under the cover of a Pinus sylvestris L. stand in the Massif Central (France). The stand was thinned to different degrees to obtain a gradient of transmitted PAR (0-0.35). Eighteen Fagus Saplings were sampled in this gradient and their growth (basal stem diameter increment) were recorded during six years. In the same time morphological parameters (leaf area, number and arrangement in space) were monitored using 3D-digitizing. Photosynthesis parameters (leaf nitrogen content, Vcmax, Jmax, Rd) were estimated with a portable gas-exchange analyser. Sapling photosynthesis was mainly linked to light availability while their morphology was more driven by sapling size. Annual sapling stem diameter increment was related to the amount of light-intercepting foliage (silhouette to total leaf area ratio (STAR) * total sapling leaf area (LA)) and light availability above the Saplings (PARt). However, the light use efficiency, i.e. the slope of the relationship between STAR * LA * PARt and stem diameter increment, decreased over time. This decrease is due to a size effect, i.e. a relative decrease of the proportion of photosynthetic tissues in comparison with the total biomass of the sapling.
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Six-year time course of light-use efficiency, carbon gain and growth of beech Saplings (Fagus sylvatica) planted under a Scots pine (Pinus sylvestris) shelterwood
Tree Physiology, 2007Co-Authors: Philippe Balandier, Hervé Sinoquet, Ela Frak, R. Giuliani, Marc Vandame, S. Descamps, L. Coll, Boris Adam, Bernard Prévosto, T. CurtAbstract:Two-year-old Fagus sylvatica L. Saplings were planted under the cover of a Pinus sylvestris L. stand in the French Massif Central. The stand was differentially thinned to obtain a gradient of transmitted photosynthetically active radiation (PAR(t): 0-0.35). Eighteen Fagus Saplings were sampled in this gradient, and their growth (basal stem diameter increment) was recorded over six years. Over the same period, morphological parameters (leaf area, number and arrangement in space) were monitored by 3D-digitization. Photosynthetic parameters were estimated with a portable gas-exchange analyzer. Photosynthesis was mainly related to light availability, whereas sapling morphology was mainly driven by sapling size. Annual stein diameter increment was related to the amount of light-intercepting foliage (silhouette to total leaf area ratio (STAR) x total sapling leaf area (LA)) and light availability above the Saplings (PAR(t)). However, light-use efficiency. i.e.. the slope of the relationship between STAR x LA x PAR, and stem diameter increment, decreased over time as a result of a relative decrease in the proportion of photosynthetic tissues to total sapling biomass.
Christian Smit - One of the best experts on this subject based on the ideXlab platform.
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coarse woody debris facilitates oak recruitment in bialowieza primeval forest poland
Forest Ecology and Management, 2012Co-Authors: Christian Smit, Dries P J Kuijper, David Prentice, M J Wassen, Joris P G M CromsigtAbstract:While oaks contribute to the ecology and economy of temperate lowland forests, recruitment into larger size classes is generally scarce. Ungulate herbivory is a limiting factor for tree recruitment, thus natural structures protecting against ungulates may be important for recruitment success. We studied oak recruitment in relation to coarse woody debris (CWD) in the Bialowieza National Park, Poland, one of the last remaining reference sites for undisturbed temperate lowland forests in Europe that contains the full natural assemblage of large ungulate species and their predators. We compared two contrasting management types: one that excludes all forestry activities (the strict reserve) and one where sanitary cutting and removal of bark-beetle infested Picea abies occurs to prevent further spread. We sampled 4 m wide transects (19 ha in total, of which 15.8 ha in the strict reserve) and recorded sapling height and sapling browsing, distance from, height of and CWD encirclement, distance to and diameter of mature oaks, tree composition, distance to and diameter of nearest trees, canopy openness and cover of herbs, mosses, bare soil and litter in an equal number of plots with and without Saplings. We found 161 oak Saplings (8.5/ha). CWD was predominantly formed by P. abies. Sapling plots contained more often CWD than plots without Saplings. Also, the distance to CWD was smaller and the CWD encirclement was higher in sapling plots, while canopy cover did not differ. Sapling height increased and sapling browsing decreased with increasing presence of CWD. Both CWD and recruitment beyond 50 cm were reduced in the managed zone. Our study shows that CWD plays an essential role for the recruitment of oaks in old-growth temperate forest systems, predominantly via protection against ungulate browsing. Sanitary cutting of infested trees, a common management practice in temperate forests, prevents the natural accumulation of CWD and so can be counter-productive for the recruitment of appreciated species.
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From protégé to nurse plant: establishment of thorny shrubs in grazed temperate woodlands
Journal of Vegetation Science, 2011Co-Authors: Christian Smit, Jasper L. RuifrokAbstract:Question Thorny shrubs play keystone roles in grazed ecosystems by defending non-protected plants against herbivores, but their establishment in grazed ecosystems is poorly understood. Which factors control establishment of recruits of thorny nurse shrubs in grazed temperate woodlands? Location Ancient grazed temperate woodlands (52 degrees 32'N, 6 degrees 36'E), The Netherlands. Methods We surveyed biotic and abiotic factors for Saplings of thorny nurse shrubs in plots with and without Saplings. To disentangle these factors, we performed a transplantation experiment over two growing seasons with nurse shrub Saplings (Prunus spinosa and Crataegus monogyna) planted in two dominant vegetation types - tall unpalatable swards and short grazed lawns - half of them protected from herbivory via exclosures. Results Plots with shrub Saplings had taller surrounding vegetation, higher soil pH and higher soil moisture than plots without Saplings. These plots predominantly contained unpalatable sward species, while plots without Saplings mainly contained palatable lawn species. After transplantation, sapling survival was higher in exclosures than in the open, and higher in sward exclosures than in lawn exclosures. Sapling growth was higher in swards than in lawns, higher inside than outside exclosures, and higher for Prunus than Crataegus, while browsing on Saplings was higher in lawns. Conclusion Unpalatable swards form essential establishment niches for thorny shrubs in grazed temperate woodlands: they protect against herbivores before thorns fully develop in Saplings, and sapling growth is better due to improved micro-environmental conditions. Once established and thorny, shrub Saplings grow out of the protective range of the swards and in turn facilitate tree seedlings, which are essential for long-term persistence of grazed temperate woodlands. This study shows that nurse plants may start as proteges before becoming facilitators for other plants in a later life stage. This may be common for nurse plants in various ecosystems. We argue that improved understanding of establishment of nurse plants and their constraining factors is crucial for effective conservation and restoration in various ecosystems.
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nurse plants tree Saplings and grazing pressure changes in facilitation along a biotic environmental gradient
Oecologia, 2007Co-Authors: Christian Smit, Charlotte Vandenberghe, Jan Den Ouden, Heinz MullerscharerAbstract:Current conceptual models predict that an increase in stress shifts interactions between plants from competitive to facilitative; hence, facilitation is expected to gain in ecological importance with increasing stress. Little is known about how facilitative interactions between plants change with increasing biotic stress, such as that incurred by consumer pressure or herbivory (i.e. disturbance sensu Grime). In grazed ecosystems, the presence of unpalatable plants is reported to protect tree Saplings against cattle grazing and enhance tree establishment. In accordance with current conceptual facilitation-stress models, we hypothesised a positive relationship between facilitation and grazing pressure. We tested this hypothesis in a field experiment in which tree Saplings of four different species (deciduous Fagus sylvatica, Acer pseudoplatanus and coniferous Abies alba, Picea abies) were planted either inside or outside of the canopy of the spiny nurse shrub Rosa rubiginosa in enclosures differing in grazing pressure (low and high) and in exclosures. During one grazing season we followed the survival of the different tree Saplings and the level of browsing on these; we also estimated browsing damage to the nurse shrubs. Shrub damage was highest at the higher grazing pressure. Correspondingly, browsing increased and survival decreased in Saplings located inside the canopy of the shrubs at the high grazing pressure compared to the low grazing pressure. Saplings of both deciduous species showed a higher survival than the evergreens, while sapling browsing did not differ between species. The relative facilitation of sapling browsing and sapling survival – i.e. the difference between Saplings inside and outside the shrub canopy – decreased at high grazing pressure as the facilitative species became less protective. Interestingly, these findings do not agree with current conceptual facilitation-stress models predicting increasing facilitation with abiotic stress. We used our results to design a conceptual model of facilitation along a biotic environmental gradient. Empirical studies are needed to test the applicability of this model. In conclusion, we suggest that current conceptual facilitation models should at least consider the possibility of decreasing facilitation at high levels of stress.
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Unpalatable plants facilitate tree sapling survival in wooded pastures
Journal of Applied Ecology, 2006Co-Authors: Christian Smit, Jan Den Ouden, Heinz Müller-schärerAbstract:Summary 1. In endangered wooded pasture ecosystems established tree Saplings are frequently found in spatial association with protective structures, suggesting nurse effects. This associational resistance is thought to be a driving force behind tree regeneration in wooded pastures. Experimental evidence for associational resistance is, however, scarce. We studied the effects of unpalatable plants on tree sapling performance in a wooded pasture ecosystem in Switzerland and tested the associational resistance hypothesis experimentally. 2. We transplanted 600 Picea abies Saplings of two size classes (5 cm and 10 cm) in plots: (i) with unpalatable plants (either Gentiana lutea or Cirsium acaule, representing a chemically and mechanically defended species, respectively); (ii) with one of both unpalatable plants clipped to the ground; and (iii) without any unpalatable plants. Grazing intensity was measured once in each plot and tree sapling performance was followed for 2 consecutive years. 3. Grazing intensity was significantly higher in plots without unpalatable plants, and significantly higher in plots with Cirsium than with Gentiana. Correspondingly, sapling survival (21?5% and 10?6% after 1 and 2 grazing years, respectively) was significantly higher near unpalatable plants, and significantly higher in plots with Gentiana than with Cirsium . Large tree Saplings survived significantly better than small ones, and depended less on the unpalatable plants for survival. 4. Except for Saplings planted near Gentiana, sapling removal by cows and horses was the major cause of death, the extent varying between unpalatable species and treatments. 5. The growth in height of the Saplings was unaffected by the treatments. 6. Synthesis and applications. This study shows that unpalatable plants can enhance tree regeneration in wooded pastures. Sapling survival was significantly higher near unpalatable plants where grazing intensity was significantly lower. Protection against cattle is particularly important for small Saplings. These results have important management implications for the endangered and disappearing wooded pastures in western Europe. Transplanting tree Saplings near unpalatable plants could be an alternative reforestation technique in intensively grazed wooded pastures. On the other hand, removal of unpalatable plants and shrubs might prevent or slow down undesired tree encroachment in less intensively grazed areas. Key-words: associational resistance, cattle, Cirsium acaule, Gentiana lutea, grazing, Picea abies, tree regeneration
Philippe Balandier - One of the best experts on this subject based on the ideXlab platform.
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Six-year time course of light-use efficiency, carbon gain and growth of beech Saplings (Fagus sylvatica) planted under a Scots pine (Pinus sylvestris) shelterwood
Tree Physiology, 2007Co-Authors: Philippe Balandier, Hervé Sinoquet, Ela Frak, R. Giuliani, Marc Vandame, S. Descamps, L. Coll, Boris Adam, Bernard Prévosto, T. CurtAbstract:Two-year-old Fagus sylvatica L. Saplings were planted under the cover of a Pinus sylvestris L. stand in the Massif Central (France). The stand was thinned to different degrees to obtain a gradient of transmitted PAR (0-0.35). Eighteen Fagus Saplings were sampled in this gradient and their growth (basal stem diameter increment) were recorded during six years. In the same time morphological parameters (leaf area, number and arrangement in space) were monitored using 3D-digitizing. Photosynthesis parameters (leaf nitrogen content, Vcmax, Jmax, Rd) were estimated with a portable gas-exchange analyser. Sapling photosynthesis was mainly linked to light availability while their morphology was more driven by sapling size. Annual sapling stem diameter increment was related to the amount of light-intercepting foliage (silhouette to total leaf area ratio (STAR) * total sapling leaf area (LA)) and light availability above the Saplings (PARt). However, the light use efficiency, i.e. the slope of the relationship between STAR * LA * PARt and stem diameter increment, decreased over time. This decrease is due to a size effect, i.e. a relative decrease of the proportion of photosynthetic tissues in comparison with the total biomass of the sapling.
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Six-year time course of light-use efficiency, carbon gain and growth of beech Saplings (Fagus sylvatica) planted under a Scots pine (Pinus sylvestris) shelterwood
Tree Physiology, 2007Co-Authors: Philippe Balandier, Hervé Sinoquet, Ela Frak, R. Giuliani, Marc Vandame, S. Descamps, L. Coll, Boris Adam, Bernard Prévosto, T. CurtAbstract:Two-year-old Fagus sylvatica L. Saplings were planted under the cover of a Pinus sylvestris L. stand in the French Massif Central. The stand was differentially thinned to obtain a gradient of transmitted photosynthetically active radiation (PAR(t): 0-0.35). Eighteen Fagus Saplings were sampled in this gradient, and their growth (basal stem diameter increment) was recorded over six years. Over the same period, morphological parameters (leaf area, number and arrangement in space) were monitored by 3D-digitization. Photosynthetic parameters were estimated with a portable gas-exchange analyzer. Photosynthesis was mainly related to light availability, whereas sapling morphology was mainly driven by sapling size. Annual stein diameter increment was related to the amount of light-intercepting foliage (silhouette to total leaf area ratio (STAR) x total sapling leaf area (LA)) and light availability above the Saplings (PAR(t)). However, light-use efficiency. i.e.. the slope of the relationship between STAR x LA x PAR, and stem diameter increment, decreased over time as a result of a relative decrease in the proportion of photosynthetic tissues to total sapling biomass.
Mohammed Armani - One of the best experts on this subject based on the ideXlab platform.
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developmental constraints and resource environment shape early emergence and investment in spines in Saplings
Annals of Botany, 2019Co-Authors: Mohammed Armani, Tristan Charlesdominique, Kasey E Barton, Kyle W TomlinsonAbstract:BACKGROUND AND AIMS Herbivory by large mammals imposes a critical recruitment bottleneck on plants in many systems. Spines defend plants against large herbivores, and how early they emerge in Saplings may be one of the strongest predictors of sapling survival in herbivore-rich environments. Yet little effort has been directed at understanding the variability in spine emergence across Saplings. METHODS We present a multispecies study examining whether and how sapling size, spine type and species' environmental niche (light and precipitation environment) influence early emergence and biomass investment in spines. A phylogenetically diverse pool of 45 species possessing different spine types (spines, prickles and thorns; that are derived from distinct plant organs: leaf, epidermis or cortex, and branch, respectively), were grown under common-garden conditions, and patterns of spine emergence and biomass allocation to spines at 5 and 15 weeks after transplanting were characterized. KEY RESULTS Spine type and species' resource niche were the main factors driving early emergence and investment patterns. Spines emerged earliest in leaf spine-bearing species, and latest in thorn-bearing species. The probability of early spine emergence increased with decreasing precipitation, and was greater in species from open than from closed habitats. Sapling investment in spines changed with plant mass but was contingent on spine type and habitat type. CONCLUSIONS Different spine types have strikingly different timing of expression, suggesting that developmental origins of spines play a critical role in sapling defences. Furthermore, species from different precipitation and light environments (open vs. closed habitats) showed contrasting patterns of early spine expression, suggesting that resource limitation in their native range may have driven divergent evolution of early defence expression.
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Developmental constraints and resource environment shape early emergence and investment in spines in Saplings
Annals of Botany, 2019Co-Authors: Mohammed Armani, Tristan Charles-dominique, Kasey Barton, Kyle TomlinsonAbstract:Running title: Early emergence and investment in spines in Saplings Background and Aims Herbivory by large mammals imposes a critical recruitment bottleneck on plants in many systems. Spines defend plants against large herbivores and how early they emerge in Saplings may be one of the strongest predictors of sapling survival in herbivore-rich environments. Yet little effort has been directed at understanding the variability in spine emergence across Saplings.
Glenn R. Iason - One of the best experts on this subject based on the ideXlab platform.
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Pinus sylvestris sapling growth and recovery from mammalian browsing
Forest Ecology and Management, 2014Co-Authors: Julianne M. O’reilly-wapstra, Ben D. Moore, Mark J. Brewer, Joan R Beaton, D. A. Sim, Natasha L. Wiggins, Glenn R. IasonAbstract:Plants employ a range of resistance and tolerance mechanisms to counteract the effects of herbivory and research is still unravelling which strategies are most effective against which herbivores. In commercial forestry, research has focused on understanding the genetic basis of resistance traits and using resistance as a management strategy. However, there has been less focus on addressing the basis and utility of tolerance traits. Scots pine (Pinus sylvestris) is a well-studied forest tree due to its wide distribution, commercial importance and use in forest restoration of degraded lands as an important foundation tree species. Several herbivore species browse Scots pine and, here, we examine the genetic basis of recovery of Scots pine Saplings following browsing by red deer (Cervus elaphus) and attempt to describe which plant traits are associated with sapling tolerance. Three hundred Saplings from five different open pollinated mothers (five families) were offered to deer in a feeding trial and Saplings were left to recover from browsing for one and a half years (two annual growth seasons) in a randomised, replicated common garden. Seven sapling traits were assessed at this time: survival, stem diameter below the leading bud, stem diameter at the base of the sapling, total sapling height, length of the leading bud, average length of three lateral buds, and the total number of lateral buds. Results indicate that browsing of Scots pine by deer influences sapling survival and recovery ability. There were significant family differences in morphological growth traits and these differences were maintained in the presence and absence of browsing. For one recovery trait, length of the leading bud, overcompensation in response to browsing was evident in all families. These data, matched with our finding of no negative relationships between any recovery traits, indicate that Scots pine is quite robust to once-off browsing events by deer. We suggest that at the sapling stage, Scots pine do not employ resistance as a strategy against deer, but tolerate deer browsing to counteract the negative impacts of herbivory. Hence, the use of recovery traits as a management tool to mitigate the negative impacts of browsing is an option worthy of further investigation.
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The effect of sapling density, heather height and season on browsing by mountain hares on birch
Journal of Applied Ecology, 2003Co-Authors: Shaila J. Rao, Glenn R. Iason, Ian A. R. Hulbert, David A. Elston, Paul A. RaceyAbstract:Summary 1 When mammalian herbivores are present at high densities their browsing activity can have a negative effect on establishment or regeneration of native woodlands. The impact on Saplings of browsing by herbivores is known to vary in response to sapling density. Until now, experimental tests of the effect of sapling density have usually involved only one tree species and no alternative forages. In this study we used a planting experiment conducted in the field to test the effects of surrounding vegetation height, season and density of downy birch Betula pubescens on the extent of browsing damage by mountain hares Lepus timidus, in the presence of background vegetation that also represents an acceptable food source. 2 The experiment was conducted on heather Calluna vulgaris moorland between March 1998 and October 1999 in north-east Scotland. Birch Saplings (n = 6708) were planted in short and tall heather in arrays at low, medium and high sapling density within a 107-ha area from which large herbivores were excluded. The number of Saplings browsed was recorded monthly and individual sapling morphological measurements and characteristics of the ground vegetation were noted twice yearly, pre- and post-winter. 3 More Saplings were browsed in winter and spring than in summer, especially during the period immediately after planting. Saplings were browsed at a higher rate in short heather, which facilitated easier access by mountain hares. The proportion of Saplings that were browsed decreased with planting density in all seasons except winter, when it increased. 4 At the individual sapling level, larger Saplings were more likely to be attacked and to have more biomass removed than smaller Saplings. 5 Synthesis and applications. This study demonstrates that mountain hares browse birch throughout the year, but browsing is at its most intense during winter and in short heather, and this may potentially suppress tree growth and tree regeneration. This result has important management implications for the uplands of Scotland, where downy birch is used to establish and regenerate native woodlands, often on moorland supporting high densities of mountain hares. Damage to trees by hares can be minimized by planting in tall vegetation where trees are less visible and accessible to hares. Tree planting can be synchronized with temporary hare control; however, effective reduction in hare numbers may be difficult to achieve. Finally, planting density should be low, as during winter, when browsing is most frequent, the rate of browsing increases with increasing tree density.
