Leaf-On (formerly called Green Up)

Transcription

1 Leaf-On (formerly called Green Up) An important characteristic of forest fuels is the Foliar Moisture Content. The moisture content of conifers and other vegetation varies throughout the season with a dip in the Foliar Moisture Content occurring in the spring. Once this dip occurs, the moisture content of forest fuels begin to rise. This is called Leaf-On or spring flush and from that point forward forest fuels are considered to be in summer condition. The timing of this dip varies with location. For much of Ontario the dip typically occurs between mid- May and mid-june, however the potential exists in any given year to enter into summer conditions earlier than previous years by as much as 2 to 3 weeks (coinciding with an early snow free period) In general we can assume that summer conditions have arrived when forest fuels contribute to suppression efforts. In other words, forest growth has started and is advanced enough that it starts to exhibit the fire behaviour properties of summer conditions even though the fuels may not yet have their full moisture content. The following is a brief summary of some of the indicators that can be used in the field to determine if Leaf-On has been reached. Once it has been determined that Leaf-On has occurred, this information can be applied to the modified guidelines for forest/industrial operations. Leaf-On Condition Indicators New leaves on birch, willow, alder and red oak (where found) are fully developed on all sites. The leaves are full size and flat. These species are amongst the last to flush out. When observed from the air, deciduous tree leaves will appear darker than the brighter, almost neon green that can be seen in newer developing leaves. Herbaceous growth/plants on the forest floor have flushed and can also be observed in older cutover areas. Some examples of things to look for include: 1. Large Leafed Aster nearly full grown. 2. Labrador Tea leaves fully developed and possibly in flower. 3. Naked Mitrewort, Bunch Berry etc in bloom. 4. Beaked Hazel leaves are fully flushed and the flowers are well developed and\or nearing the end of their bloom. The new growth of conifer leaders (the new growth, or shoot, found at the end of the branches and tops of the tree) has reached one half of the total seasonal growth. A tree is considered to begin recovering moisture when it reaches approximately ½ of its estimated full year s growth. Try to observe the leaders at the tops of the trees and not just those lower to the ground. Some guidelines by species are; Spruce Immature Jack Pine Mature Jack Pine 4-6 leaders 2-12 leaders 3-6 leaders New needle growth on conifers will be well advanced. This can be determined by looking closely at the needles to observe the needle sheaths. In developing needles, needle sheaths (a thin membrane that will bind and cover the needles) will be present over much of the needle s length. As the needle growth becomes more advanced, the needle sheaths will be reduced to the base of the needles or, in the case of Red and White Pine, may be absent entirely. As this occurs the needles will become well separated from the other members of the cluster.

2 Tips and Tricks For Ensuring a Good Assessment Be sure to check for green up indicators in a variety of fuel types. Feel the duff to assess how much moisture there is and how far down it is wet. If the duff has a lot of moisture, it may mean that the trees have not yet flushed (i.e. not started growing) and are not yet taking water up from the soil. Check the ground in multiple locations. Higher ground may feel dry but lower areas may still have frost which means that trees in these locations will not have flushed yet. Use conifer trees as an indicator of the final stage of Leaf-On. Advanced needle development and leader growth typically occurs after all of the other indicators have occurred. However exercise caution especially if few or none of the other indicators are present. Check multiple areas across your District, both East and West as well as North and South. These conditions will be met at different times across the region. Fire Managers, Regional Duty Officers and Industry Representatives will need to work together to determine when these conditions have changed and should be applied to the Modified Industrial Operations Guidelines. There is a need for consistency across the region. For example if Abitibi has operations in both Fort Frances and Kenora and they are at similar latitudes and have similar conditions then both areas should be moved into Leaf-On at the same time. This type of communication is particularly important when Forest Management Units cross District Boundaries in a North and South direction. By having good communications between the FMHs, the Region and Industry we can ensure that the message is consistent, timely and applied fairly across District Boundaries.

3 Black Spruce (Sb) columnar shape, varies in height from 5 20 m to 30 m top of crown is club like found on dry-fresh sites to wet organic sites roots are shallow and spreading outer bark is dark greyish brown and flaky leaves are 4 sided needle like < 2 cm long dark bluish-green individually attached spirally around the branchlets covered with a brownish hair may reproduce by layering short, spreading to drooping and upturned at the tips poor natural pruner except in dense stands egg shaped cm long White Spruce (Sw) 17m 28 m in height conical crown rarely grows in pure stands associated with balsam fir, trembling aspen (poplar), white birch and black spruce found as an understory or scattered over story bark is light greyish-brown inner bark is silvery-white to reddish needles are 4 sided thick, stiff and sharp 2 cm long bluish-green colour with a powdery coating finer branches are hairless branches spread with a slight droop poor self-pruner

4 cm long Jack Pine (Pj) 19m 30 m in height found on dry to fresh, sandy or coarse loamy soils even aged stands associated with black spruce in pure conifer stands trunk is reddish-brown on young stems to dark brown and flaky with age needles are straight or slightly curved and sharp cm long in clusters of two light yellowish-green in colour branchlets are yellowish-green branches are spreading lower branches in thick stands will self-prune 3-5 cm long serotinous cones regenerates easily after a fire Red Pine (Pr) height averages 23 m mature trees have a clear bole up to ¾ of its height associated with white pine, jack pine, and/or trembling aspen (poplar) found in small stands on dry to fresh, rapidly drained sandy or coarse loamy soils (frequently found on stony soils as well) young bark scaly with a reddish to pinkish brown colour mature bark broad with scaly plates cm thick needles are straight, slender and sharp cm long clusters of 2 straight, egg-shaped 4 8 cm long

5 White Pine (Pw) average height 22 m usually clear bole for ½ of its height irregular crown shape deep, dry to fresh, rapidly drained coarse upland soils on young trees, bark is thin and smooth and grey-green in colour on older trees the bark is dark, thick and deeply furrowed into broad ridges needles are straight and slender bluish-green to a whitened colour 3 13 cm long cluster of five cylindrical cm Trembling Aspen (Po) also called Poplar average height 21 m broadleaf hardwood small spread out crown trunk has a clear bole up to the crown egg-shaped pointed on the end light wind will move leaves in a trembling fashion White Birch (Bw) average height is m small to open crown trunks are often leaning and clumped bark paper-like, white, flaky and very flammable triangular to egg shaped with single to double toothed edges sharp pointed tip leaves alternate but may appear to be opposite on the branch