Forests2015, 6(10), 3582-3593; doi:10.3390/f6103582 (registering DOI) - published 12 October 2015 Show/Hide Abstract
Abstract: Douglas-fir (Pseudotsuga menziesii) seedlings are periodically challenged by biotic and abiotic stresses. The ability of endophytes to colonize the interior of plants could confer benefits to host plants that may play an important role in plant adaptation to environmental changes. In this greenhouse study, nursery-grown Douglas-fir seedlings were inoculated with diazotrophic endophytes previously isolated from poplar and willow trees and grown for fifteen months in nutrient-poor conditions. Inoculated seedlings had significant increases in biomass (48%), root length (13%) and shoot height (16%) compared to the control seedlings. Characterization of these endophytes for symbiotic traits in addition to nitrogen fixation revealed that they can also solubilize phosphate and produce siderophores. Colonization was observed through fluorescent microscopy in seedlings inoculated with gfp-and mkate-tagged strains. Inoculation with beneficial endophytes could prove to be valuable for increasing the production of planting stocks in forest nurseries.
Forests2015, 6(10), 3547-3581; doi:10.3390/f6103547 (registering DOI) - published 10 October 2015 Show/Hide Abstract
Abstract: Surface lignite coal mines in east Texas are commonly reforested using loblolly pine (Pinus taeda L.) following mining and reclamation activities. Due to the nature of such an extreme disturbance, altered growth patterns, growth rates, and productivity could be expected. We destructively sampled above- and belowground tissue to develop prediction equations specific to these sites. These prediction equations differed statistically from those found in the literature regarding unmined land. At the stand level, biomass and volume productivity appeared similar with young stands on reclaimed mineland performing slightly poorer than similarly managed unmined sites. Allometric partitioning of above- and belowground biomass differed statistically from the unmined allometric model previously studied. The allometric pattern on reclaimed mineland indicated greater partitioning of biomass belowground for young stands of low quadratic mean diameter relative to unmined stands. Older stands on reclaimed mineland exhibited no allometric partitioning differences from unmined stands, indicating the normal allometric pattern is resumed for stands greater than 10 years of age.
Forests2015, 6(10), 3528-3546; doi:10.3390/f6103528 - published 7 October 2015 Show/Hide Abstract
Abstract: There are few detailed carbon (C) budgets of mangrove forests, yet these are important for understanding C sequestration in mangrove forests, how they support the productivity of the coast and their vulnerability to environmental change. Here, we develop C budgets for mangroves on the islands of Twin Cays, Belize. We consider seaward fringing forests and interior scrub forests that have been fertilized with phosphorus (P), which severely limits growth of trees in the scrub forests. We found that respiration of the aboveground biomass accounted for 60%–80% of the fixed C and that respiration of the canopy and aboveground roots were important components of respiration. Soil respiration accounted for only 7%–11% of total gross primary production (GPP) while burial of C in soils was ~4% of GPP. Respiration by roots can account for the majority of soil respiration in fringing forests, while microbial processes may account 80% of respiration in scrub forests. Fertilization of scrub forests with P enhanced GPP but the proportion of C buried declined to ~2% of GPP. Net ecosystem production was 17%–27% of GPP similar to that reported for other mangrove forests. Carbon isotope signatures of adjacent seagrass suggest that dissolved C from mangroves is exported into the adjacent ecosystems. Our data indicate that C budgets can vary among mangrove forest types and with nutrient enrichment and that low productivity mangroves provide a disproportionate share of exported C.
Forests2015, 6(10), 3514-3527; doi:10.3390/f6103514 - published 7 October 2015 Show/Hide Abstract
Abstract: American chestnut (Castanea dentata), once a primary constituent of the eastern hardwood forest ecosystem, was nearly extirpated from the forest canopy by the accidental introduction of chestnut blight (Cryphonectria parasitica). An intensive breeding program has sought to breed blight resistance from Chinese chestnut into American chestnuts, while maintaining as much of the desirable American chestnut phenotypes as possible. Previous studies suggest that these blight resistant American chestnuts, termed “restoration chestnuts”, are capable of thriving on reclaimed surface mines. We direct seeded pure Chinese, pure American, and three backcross lines into brown sandstone minesoil on a mine site in Pike County, KY. To investigate the effects of tree sheltering on survival and growth, we installed tree shelters on half the plots, and left the rest of the plots unsheltered. Results indicated that shelters were highly effective at reducing initial mortality. In addition, while pure Chinese chestnut survival was highest, the three backcross lines have also survived well on this site. Our study demonstrates that American, Chinese, and backcrossed chestnuts can survive through five growing seasons on reclaimed surface mines with the use of tree shelters.
Forests2015, 6(10), 3501-3513; doi:10.3390/f6103501 - published 7 October 2015 Show/Hide Abstract
Abstract: Soil nitrogen and phosphorus are commonly limiting elements affecting plant species richness in temperate zones. Our species richness-ecological study was performed in alder-dominated forests representing temperate floodplains (streamside alder forests of Alnion incanae alliance) and swamp forests (alder carrs of Alnion glutinosae alliance) in the Western Carpathians. Species richness (i.e., the number of vascular plants in a vegetation plot) was analyzed separately for native and alien vascular plants in 240 vegetation plots across the study area covering Slovakia, northern Hungary and southern Poland. The relationship between the species richness of each plant group and total soil nitrogen content, plant-available phosphorus and carbon to nitrogen (C/N) ratio was analyzed by generalized linear mixed models (GLMM) with Poisson error distribution and log-link function. The number of recorded native and alien species was 17–84 (average 45.4) and 0–9 (average 1.5) species per plot, respectively. The GLMMs were statistically significant (p ˂ 0.001) for both plant groups, but the total explained variation was higher for native (14%) than alien plants (9%). The richness of native species was negatively affected by the total soil nitrogen content and plant-available phosphorus, whereas the C/N ratio showed a positive impact. The alien richness was predicted only by the total soil nitrogen content showing a negative effect.
Forests2015, 6(10), 3483-3500; doi:10.3390/f6103483 - published 30 September 2015 Show/Hide Abstract
Abstract: The current mountain pine beetle (MPB) (Dendroctonous ponderosae Hopkins) epidemic has severely affected pine forests of Western Canada and killed millions of hectares of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) forest. Generally, MPB attack larger and older (diameter > 20 cm or >60 years of age) trees, but the current epidemic extends this limit with attacks on even younger and smaller trees. The study’s aim was to investigate the extent of MPB attack in young pine stands and its possible impact on stand dynamics. Although MPB attacks were observed in trees as small as 7.5 cm diameter at breast height (DBH) and as young as 13 years old, the degree of MPB attack (percent stems ha−1) increased with increasing tree diameter and age class (13–20, 21–40, 41–60, and 61–80 years old) (6.4%, 49.4%, 62.6%, and 69.5% attack, respectively, by age class) which is greater than that reported from previous epidemics for stands of this age. The mean density of surviving residual structure varied widely among age classes and ecological subzones. Depending on age class, 65% to 77% of the attacked stands could contribute to mid-term timber supply. The surviving residual structure of young stands offers an opportunity to mitigate the effects of MPB-attack on future timber supply, increase age class diversity, and enhance ecological resilience in younger stands.