Dry Weather and Its Effects on Maple

Table of Contents

1. Introduction
2. Young Trees in Maple Orchards and Along Roadways and Fencelines
3. Natural Sugar Bushes
4. Information Source
5. Related Links

Introduction

The combination of hot and dry weather, lack of overhead canopy and light and/or shallow soil conditions can cause very significant stress to maple trees. When exposed to these conditions, the trees respond by closing their leaf stomata and shutting down the process of photosynthesis. This can translate into lower starch reserves in the trees during the fall and winter months. Pre-mature leaf fall can also affect the nutritional status of the tree.

The visible effects of the hot, dry weather are often most noticeable in maple orchards, along roadways and fencelines, and in sugar bushes with an open canopy allowing penetration of solar radiation into the understory. Signs and symptoms of the hot dry weather include leaf scorch, yellow-brown discoloration of the foliage, drying of the foliage and premature leaf fall. In some open grown sugar bushes on thin or light soils, the hot, dry weather can cause drying of the woody tissue of regeneration and sapling sized trees. In addition to these effects, moisture stress can indirectly limit the availability of soil nutrients.

Young Trees in Maple Orchards and Along Roadways and Fencelines

In recent years,there have been reports of young trees as high as 15 meters tall showing signs of moderate to severe stress. Trees planted within the past several years are most at risk because their root systems are not fully established. These trees would definitely benefit from periodic watering until dry weather subsides. Without watering, it is expected that many recently planted or naturally seeded maple trees may suffer mortality. It is also expected that some of the well established maples growing on lighter soils or on soils with rooting depth restrictions, will suffer mortality. These trees will have less chance to recover from the effects of a mid to late season drought than they would from abnormally dry weather experienced earlier in the season.

Established maple trees growing on soils with a high productive capability-deep profile, fine texture and fertile, are considerably less vulnerable to the effects of extremely dry weather. This should be kept in mind when selecting sites for orchard establishment. It is also apparent that young maple trees with some overhead shelter provided by larger maple or non-maple species, are not as affected by the dry conditions.

Natural Sugar Bushes

Maple trees growing in managed sugar bushes on sites of medium to high capability, may not show visible signs of drought stress,especially early in the season. However, signs of stress and even mortality of the regeneration are evident in open grown sugar bushes where soil depth and soil moisture holding ability are limited. The effects of the dry weather are expected to be most felt by over-mature maple trees, or younger trees suffering from other types of stress (natural site limitations, soil compaction, disease, insect defoliation, etc.).

It is important to remember that there is some evidence that maple trees growing on very moist soils are somewhat more susceptible to the effects of very dry weather than maple growing on fresh sites. This is probably because their root systems are more confined and are less able to access the limited moisture which is available.

Over a period of time, it is the cumulative effects of multiple stress factors which can lead to a deterioration in tree health and/or tree mortality.

The extremely dry weather which has been experienced in parts of Eastern Ontario in some years since the 1998 ice storm may cause additional mortality of old and/or severely stressed trees and extend the recovery period for other trees. Trees which suffered more than 50% loss of their live crown as a result of the ice storm are most at risk. Close monitoring of weather and other environmental factors (e.g. insect defoliation) and their potential effects on ice damaged trees over the next few years is advisable.  

Information Source

OMAFRA is maintaining a section on their website which documents some of the effects of adverse weather on agricultural crops.

Related Links

• Adverse Weather OMAFRA