Effects of stand density on ecosystem properties of subalpine forests in the southern Rocky Mountains, USA

Abstract

Abstract• Mixed coniferous, subalpine forest communities in the Rocky Mountains are historically dense and have experienced infrequent, high-severity fire. However, many of these high-elevation stands are thinned for a number of perceived benefits.• We explored the effects of forest stand density on ecosystem properties in subalpine forests in Colorado, USA, 17-18 y after forests were managed for timber.• Forest structure significantly altered the composition and chemical signature of plant communities. Previously managed stands contained lower density of overstory trees and higher ground cover compared to paired reference stands. Foliar phenolic concentration of several species was negatively related to basal area of overstory trees. Furthermore, reductions in stand density increased total foliar phenolic:nitrogen ratios in some species, suggesting that gap formation may drive long-term changes in litter quality. Despite significant changes in forest structure, reductions in stand density did not leave a strong legacy in surface soil properties, likely due to the integrity of soil organic matter reserves.• Changes in forest structure associated with past management has left a long-term impact on plant communities but has only subtly altered soil nutrient cycling, possibly due to trade offs between litter decomposability and microclimate associated with reductions in canopy cover. Mots-clés :chimie foliaire / composés phénoliques / cycle de l'azote du sol / densité du peuplement / biogéochimie Résumé -Effets de la densité du peuplement sur les propriétés des écosystèmes des forêts subalpines dans le sud des Montagnes Rocheuses aux USA.• Les communautés subalpines de forêts mixtes de conifères dans les Montagnes Rocheuses sont historiquement denses et ont peu connu de feux très sévères. Cependant, beaucoup de ces peuplements de haute altitude sont éclaircis pour de nombreux profits.• Nous avons étudié les effets de la densité des peuplements forestiers sur les propriétés des éco-systèmes dans les forêts subalpines du Colorado (USA), 17-18 ans après que les forêts aient été exploitées pour le bois.• La structure de la forêt a considérablement modifié la composition et la signature chimique des communautés végétales. Auparavant les peuplements exploités renfermaient une plus faible densité d'arbres de l'étage dominant et une couverture du sol plus importante par rapport aux peuplements de référence correspondants. La concentration des composés phénoliques foliaires de plusieurs espèces a été liée négativement à la surface terrière des arbres dominants. En outre, les réductions de la densité du peuplement ont augmenté les rapports composés phénoliques foliaires totaux : azote chez certaines espèces, ce qui suggère que la formation de trouée peut conduire à des changements à long terme de la qualité de la litière. Malgré d'importants changements dans la structure forestière, la réduction de la densité du peuplement n'a pas laissé un héritage solide dans les propriétés de surface du sol, probablement à cause de l'inté...

Plant interactions as biotic drivers of plasticity in leaf litter traits and decomposability of Quercus petraea

“…). It was, however, consistent with the increase of Pinus flexilis green leaf phenolics : N ratio in response to thinning observed by Hall and Marchand () in a coniferous subalpine forest ecosystem. These response patterns were generally consistent over a large scale and between humus types, highlighting that they were largely independent of soil fertility context in a range of acidic forest soils and could potentially be generalizable to a broad set of temperate forest ecosystems dominated by tree species with ecological features similar to Q. petraea (Symstad et al.…”

“…Further, many species favored by tree removal, such as various grass species and the fern P. aquilinum, have been reported to produce poorly decomposable leaf litter (Cornwell et al 2008). Hall and Marchand (2010) also found that tree removal increased the green leaf phenolic : N ratio of several common understory plants species, thus likely decreasing their leaf litter decomposability. Tree removal thus likely results in a shift toward less decomposable leaf litter of understory plants at the community level in relation to both species turnover and plasticity.…”

“…). Hall and Marchand () also found that tree removal increased the green leaf phenolic : N ratio of several common understory plants species, thus likely decreasing their leaf litter decomposability. Tree removal thus likely results in a shift toward less decomposable leaf litter of understory plants at the community level in relation to both species turnover and plasticity.…”

Inter-specific competition in mixed forests of Douglas-fir (Pseudotsuga menziesii) and common beech (Fagus sylvatica) under climate change — a model-based analysis

“…In stands that are not regulated through management, the stem densities are higher, the competition for water thus more intense and this increases the effect of climate change on competition. However, Douglas-fir stands are managed for wood production and show a structure and a biogeochemistry distinct from unmanaged stands (Hall and Marchand, 2010) and since we were interested in the response of managed forests to climate change, we only considered managed stands.…”

Increases in soil and woody biomass carbon stocks as a result of rangeland riparian restoration

“…This study employs a retrospective approach to understand the question of multi-decadal carbon accumulation in riparian restoration treatments. While retrospective studies may lack consistency in size or type of treatment, they are often used in managed landscapes to assess temporal changes in long-term processes with greater power and cost-effectiveness than can be achieved through short-term experimentation [26][27][28]. We examined patterns of carbon sequestration in biomass and soil resulting from riparian restoration in 42 stream reaches in northern California (Fig.…”