Growing‐season warming and winter soil freeze/thaw cycles increase transpiration in a northern hardwood forest

Abstract PurposePlant roots alter nutrient cycling within the soil surrounding them (rhizosphere). Recent studies have focused on nutrient uptake by plants in low-temperature seasons. This study aimed to reveal the nutrient dynamics in rhizosphere during low-temperature seasons in a northern hardwood forest in Japan.MethodsThe potential extracellular enzymatic activity, bacterial, fungal, and archaeal abundances, and soil chemical properties in the rhizosphere of canopy trees and understory vegetation and non-rhizosphere bulk soil were measured at the beginning of the dormant season (November), end of the dormant season (April and May), and middle of the growing season (August) in a northern hardwood forest in Japan.ResultsThe abundance of fungi and the activity of nitrogen- and phosphorus-degrading enzymes were higher in the rhizosphere than in non-rhizosphere bulk soil regardless of the season. The concentration of extractable organic and inorganic N was higher in the rhizosphere than in the non-rhizosphere bulk soil at the beginning and end of the dormant season, but this trend was not observed in the middle of the growing season. ConclusionSince the concentration of nutrients in the rhizosphere is determined by the balance between nutrient uptake by fine roots and root-induced acceleration of decomposition, our results suggest that plant roots would accelerate N and P cycles during the dormant season, even though the amount of nutrient uptake by plants was lower during the season.

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Effects of selective tree harvests on aboveground biomass and net primary productivity of a second-growth northern hardwood forest

Canadian Journal of Forest Research ◽

10.1139/x10-184 ◽

2010 ◽

Vol 40 (12) ◽

pp. 2360-2369 ◽

Cited By ~ 25

Author(s):

Jacob H. Dyer ◽

Stith T. Gower ◽

Jodi A. Forrester ◽

Craig G. Lorimer ◽

David J. Mladenoff ◽

...

Keyword(s):

Primary Productivity ◽

Net Primary Productivity ◽

Growing Season ◽

Hardwood Forest ◽

Northern Hardwood Forest ◽

Aboveground Net Primary Productivity ◽

Transition Zones ◽

Northern Hardwood ◽

Growing Seasons ◽

Second Growth

Restoring structural features of old-growth forests, such as increased canopy gap sizes and coarse woody debris, is a common management goal for second-growth, even-aged stands. We experimentally manipulated forest structure by creating variable-size canopy gaps in a second-growth northern hardwood forest in north-central Wisconsin following two growing seasons of pre-treatment monitoring. The objectives of this study were to quantify the influence of canopy gaps of different sizes (50–380 m2) on aboveground biomass and productivity of each vegetation stratum two growing seasons following treatment. Two years after treatment, ground layer biomass in canopy openings increased significantly relative to surrounding undisturbed transition zones. The response of ground layer biomass was greatest in the large versus the medium and small gaps. Sapling aboveground net primary productivity was significantly greater in undisturbed transition zones than within gaps across gap sizes following the second post-treatment growing season. Annual stem diameter increment was greatest for trees along gap borders and was correlated with crown class, percentage of crown perimeter exposed, gap area, and shade tolerance. Total aboveground net primary productivity was significantly lower in the gap addition plots the first year but by the second post-treatment growing season no longer differed from that in the control plots.

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