Many natural ecosystems are periodically exposed to fire.  After a fire, there is often reduced competition and increased nutrient availability (from ash etc.).  The plants and flowers that grow after a fire are visited more often by pollinators, such as bees and other insects.  This can result in increased production of fruits and seeds. Bushfires have been part of certain australian ecosystems for thousands of years and some native species are ‘fire adapted’.  They have come to 'rely' on fires as a means of reproduction and / or  dispersal. Whilst no one fire can be attributed to climate change alone, rising temperatures and aridity, lengthening of the ‘fire season’, combined with bursts of extreme ‘fire weather’, all combine to suggest climate change is implicated. As the frequency of fires increases, the possible benefits of fire to such ecosystems / species are being lost. Fire can help with the physical dispersal of seeds from the parent plant.  In some parts of the world, such as South Africa and Australia, fire and / or smoke can be the stimulus for seed dispersal and subsequent germination.  Plants such as some species of Protea, Banksia, certain members of the myrtle family (e.g. some Eucalypts), and some Pines and Sequoias 'make use' of fire to disperse their seeds. Seed dispersal involving fire is termed serotiny.  Many of these plants produce woody fruits or cones in which the seeds are held.  The mechanism underlying seed release varies but can be due to a resin that ‘seals’ the seeds inside the fruit or cone.  The resin ‘melts’ / liquefies on exposure to heat releasing the seed or there may be a structure called a seed separator (as in Banksia).  Serotinous conifers (like lodgepole pine), have mature cones in which the cone scales are naturally sealed shut with resin.   Most of the seeds stay in the canopy until the cones reach 122-140o F  (i.e 50 to 60oC).  At these temperatures, heat / fire  melts the resin and  the cone scales open to expose the seed. The seed can then drop or drift to a burned but cooling ash-rich soil bed. The seeds do well on the burnt soil available to them as the site offers reduced competition, more light, warmth plus the nutrients from the burning of leaves and litter.  Some species align their germination to immediate post-fire conditions - stimulated by chemicals present in the smoke.  The organic compounds karrikins,  products of the degradation of cellulose are  a germination ‘cue’ for some species.  Karrikins are thought to be present on the soil surface after a fire.  When it rains,  the karrikins are 'washed' into the soil, and seeds present in the soil seed bank are then stimulated to germinate. Thanks to Steve Sangster and John Cameron for images of woodland fire.  

Flowers of the woodland floor. Some woodland flowers enjoy the dappled light of the woodland floor beneath the canopy.  They grow in relatively shady, cool and damp conditions in the humus-rich soils.  Polish scientists at the Nicolaus Copernicus University have been studying four species that often grow together in European woodlands - namely Wood anemone Yellow anemone Lily of the valley Common may lily These are perennial plants that ‘come to life’ in Spring, producing a carpet  of flowers across the woodland floor.  However, as much as they share a liking for the shady, cool and moist conditions found there, they differ in their sensitivity / tolerance to rainfall / moisture levels in the summer months: which may change their distribution as summers become warmer and longer.  The team modelled various warming scenarios which suggested that the ranges of these species may change / contract with hotter and drier summers.  The common may lily is one that may be particularly affected and no longer share the same range or woodlands as the others studied.  If climate change takes a hold, it may be that ‘assisted migration’ may be needed to help such plants to find suitable ‘climatic refugia’. more on plant migration ...... With climate change, both plants and animals need to adapt.  With increasing warmth, many species may ‘need’ to move towards cooler latitudes.  Whilst many animals are mobile, they may be able [over time] to access new suitable areas, plants on the other hand are dependent on the dispersal of their fruits / seeds.  Fruit and seed dispersal may involve various animals, including birds.  If the birds are resident or non-migrating species, then it is probable that they will only disperse seeds over relatively short distances.   Migratory birds however travel great distances but often in the wrong direction.  Many birds that migrate at the end of the summer, travel south to warmer climes.  Work at the University of Exeter has studied a number of woodlands across Europe and bird species that feed on the fruits of 81 plants species (and help disperse their seeds).  They found that only about a third of the plants had fruits (seeds) that might be dispersed northwards by birds.  To benefit from this northward dispersal, the plants needed to either have a very long fruiting period (eg.holly, juniper) or a very late fruiting period (eg. Ivy). Full details of this study here Food production and food waste. As Sir David Attenborough has pointed out in a recent episode of Planet Earth III, producing food to feed the world comes at significant environmental cost.  Natural ecosystems are often burned (forests) or drained (peatlands) and then turned over to agriculture to produce crops or farm animals. The forests of the Amazon have been significantly affected by burning and logging,  with the concomitant loss of biodiversity.  But they are not alone. In Mexico, forests are being lost as the land is being turned over to avocado production.  Mexico’s neighbour, the USA has a voracious appetite for this fruit.  The forests are being turned into ‘avocado orchards’.  Avocado trees are ‘thirsty’, they need a generous supply of water.  They consume much more water than the natural species [eg. oyamel), so that natural aquifers are being depleted.  This affects local farmers growing crops such as tomatoes and corn. One particularly sad aspect of food production is that much of the food is wasted. Some is lost between harvest and reaching the retail sector, and then more is ‘lost’ in the home. Food may not be used, or not used in time so it starts to rot, become rancid etc.  A lot of food goes to land fill, where it may generate methane - a potent greenhouse gas. Sprouting sequoias. In recent times, there have been many images of the fires ravaging the forests of the west coast of the States.  Many thousands of hectares and millions of trees have been lost, including many of the giant redwoods.  However, recent studies have found that some of the burned Sequoias are producing new growth.  They are sprouting from roots and trunks, from dormant buds that have lain hidden under the thick bark for decades, this despite the loss of the canopies of the trees.  To fuel this growth, the trees are using reserve materials that have been stored for 50+ years.

There is evidence that trees lost to fires and drought are not returning to fire damaged areas.  Fire has been ‘part and parcel’ of  the dynamics of some forest ecosystems.  The fires take out smaller trees, giving space and light to others.  Fire (or the smoke associated with it) can even help the seeds of some species to disperse and/or germinate (eg. serotiny in certain Pines). Different chemicals from smoke such as karrikinolide and glyceronitrile are known to play key roles in smoke-stimulated germination of certain species, such as heather. However, climate change is affecting forests (and woodlands) across the globe. Fires are becoming more frequent (associated with increasing drought) and trees are struggling to return / regenerate after intense or repeated fires.  An analysis of a number of sites in the Rocky Mountains suggests that in some areas fire, moisture stress and increasing temperatures result in a loss of resilience so that forested areas are being replaced with shrubs, grassland and flowers.  "Fire refugia" are areas that somehow avoid significant or frequent damage; they burn less often and/or less intensely than the surrounding landscape.  Such areas are important in the recovery of the ecosystem after a fire - allowing re-population of the area with a variety of species.  [caption id="attachment_35352" align="aligncenter" width="650"] Woodland recovering from a fire[/caption] Consequently, studies have been directed towards understanding the physical and biological nature of such refugia.  The work has focused on mature, conifer dominated forests in the States (The Klamath-Siskiyou region)  and the fires that have occurred over a period of some 30 years.  It was found that refugia were associated with physical features of the habitat such as rocky outcrops, depressions in the landscape.  It was also noted that the density of the smoke that the fires generated was a factor in tree survival (perhaps dense smoke offered a degree of shade?).   The area studied has a complex and diverse geology,  with varied habitats that support considerable biodiversity.   Fire has always been a key factor in the maintenance of the varied landscape but with the climate becoming hotter and drier, there is concern that an increasing frequency of fires will ‘eat away’ at the forest’s ability to regenerate - with the loss of refugia and incineration of seed banks in the soil. Severe fire can reset the path of succession - so that forest can be reduced to bare soil. Complex and established communities of fungi, microbes, plants and animals are lost, reduced down to bare soil. Intense heat will damage the structure of the soil, reducing its organic content and its complex community of microbes. In extreme cases, this can lead to the erosion of the soil.  

Seeds are dispersed from a parent plant by a variety of means.  Some plants use wind dispersal (sycamore, dandelion), some use animals (burdock, herb bennet), some even use water (willow, silver birch, coconut and the famous coco de mer).  But in some parts of the world, such as South Africa and Australia, fire is a feature of certain ecosystems and the fire and/or smoke can be the stimulus for seed dispersal and germination.   Read more...

Monterey Pine or Radiata Pine (Pinus radiata) is found naturally in the coastal area around Monterey in California.  There, it is under threat from Pine Pitch Canker (a fungal disease), which makes them liable to attack by bark beetles.  Monterey pine is to be found growing in milder parts of the UK (where it grows faster than in its native habitat), and in coastal areas as it is resistant to salt spray. The pine is extensively and intensively used in forestry, especially in countries like New Zealand (like the Kaingaroa Forest on the North Island).  The monterey pine can be used for erosion control on steep slopes - as it has a widespread and fast growing root system The growth form of the tree is conic at first, but as the tree ages it becomes dome shaped with heavily, twisted branches. Read more...