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We used dendroecological techniques to analyze the temporal pattern in diameter growth following selection harvests in stands dominated by Acer saccharum Marsh. in central Ontario and examined differences in growth responses related to tree size, damage, and orientation relative to canopy gaps. While dendroecological studies have commonly assumed that trees show immediate growth responses to gap creation (i.e., within 1–2 years), we found that the growth enhancement in A. saccharum was gradual and did not reach a peak until 3–5 years following gap creation. Trees of intermediate size showed the largest proportional growth increases after gap creation, with the largest responses observed in trees on the north side of gaps. Trees with visible damage to the crown or bole had significantly lower preharvest basal area increments than trees with little or no damage, but showed greater proportional growth responses to gap creation. Both the long observed time delay in tree growth response to canopy opening and the variability in response relative to tree size and damage have important implications for attempts to reconstruct disturbance history using dendroecological methods and to sustainable forest management under selection system silviculture.

Fractures are often leakage pathways for fluid in low‐permeability rocks that otherwise act as geologic barriers in the subsurface. Flow of fluids in chemical disequilibrium with fracture surfaces can lead to mineral precipitation and fracture sealing. To directly evaluate the role of small‐scale mineral heterogeneity on mineral precipitation, we measured CaCO3 precipitation in a transparent analog fracture that included randomly distributed small‐scale regions of CaCO3 on one of the borosilicate surfaces. Steady flow of a well‐mixed CaCl2‐NaHCO3 solution ( log(ΩnormalCaCO3) = 1.44) resulted in significant mineral precipitation during the 82 day experiment. Localized mineral precipitation reduced flow within regions of the fracture, but small‐scale reaction‐site heterogeneity allowed preferential flow to persist through pathways that contained 82% less area of CaCO3 regions than the fracture‐scale average. This resulted in a significant reduction in measured precipitation rate; excluding these effects results in more than an order‐of‐magnitude underestimation of fracture sealing timescales.

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