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     

Balandier P  Sinoquet H  Frak E  Giuliani R  Vandame M  Descamps S  Coll L  Adam B  Prevosto B  Curt T 《Tree physiology》2007,27(8):1073-1082

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 stem 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(t) and stem diameter increment, decreased over time as a result of a relative decrease in the proportion of photosynthetic tissues to total sapling biomass.  相似文献   

Influence of nurse birch and Scots pine seedlings on early aerial development of European beech seedlings in an open-field plantation of Central France     

Prevosto  Bernard; Balandier  Philippe 《Forestry》2007,80(3):253-264

Beech woodland can be restored by direct planting of beech (Fagussylvatica L.) seedlings in abandoned areas, but this methodis generally avoided in forestry because of the growth difficultiesof beech in full-light conditions. This study tested a methodthat consists of planting beech seedlings in full-light conditionswith silver birch (Betula pendula Roth.) or Scots pine (Pinussylvestris L.) as nurse trees. A total of 65 two-year-old beechseedlings surrounded by either 3, 4, 5 or 6 pine or birch seedlingsor without competitors were planted in bare-soil open-fieldconditions in Central France. Tree growth and light availabilitywere monitored at the end of each of the following 3 years,and soil moisture was also measured the last year. At the endof the experiment, aerial biomass measurements were made onthe beeches. Results showed that relative beech growth in termsof diameter was significantly reduced by the local neighbouringtrees and that this reduction was particularly noticeable inthe pine treatments where there was extensive pine seedlingdevelopment. In contrast, relative beech height did not exhibitany significant variations among the treatments. Light availabilitywas decreased by the neighbouring trees, especially in the pinetreatments. Light reduction was more pronounced in the last2 years and in the middle or lower parts of the canopy of thesubject beech. Soil water content was lower under the pine canopiesthan under the birch canopies, and was positively correlatedto beech relative diameter growth. Specific leaf area, height-to-diameterratio and crown length-to-crown width ratio weakly but significantlyincreased with competition from the neighbours. Beech biomasspartitioning was only weakly affected by the treatments. Thisstudy showed that nurse trees tend to reduce beech growth butimprove form although effects remained weak due to the insufficientlength of the experiment. Further studies are also needed toquantify the effects of the neighbourhood on the growth of competitiveherbaceous vegetation and on changes in the microclimatic conditions.  相似文献