buffer zones & buffer strips – what they are and why we need them

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photo credit: pubs.usgs

Buffer zones and buffer strips are the areas between aquatic and terrestrial zones.  The best-known buffer strips are wetlands and riparian zones.  They can consist of natural or planted vegetation and serve as a place for water and matter storage.  

The two types of limitations that impact buffer zones are internal limitations and external limitations.  Internal limitations are those that have to do with the qualities of the buffer zone itself e.g. the width, the soil qualities, the pH levels, the organic matter content and the soil porosity. The external limitations include outside influencing factors like the size of the basin, the geochemistry of a location, the climate, hydrology, slope and stream morphology.Some buffer zones can also link ephemeral (short-term) and perennial areas with non-point source loads via surface or groundwater paths.  

We need these unique natural treasures because they offer valuable services that man-made options and replacements simply cannot reproduce.  This means that existing buffer zones should be protected in an effort to benefit the majority, rather than the minority.  In areas that have buffer zones, the following benefits are enjoyed:

  • During warm periods, buffer zones cool in the summertime via evapotranspiration and shading
  • Many unique species of plants and animals have a place to live creating havens of biodiversity
  • Water is filtered water slowly through the dead and decomposing organic matter, as well as non-organic components
  • Sedimentation occurs which keeps water cleaner and reduces the likelihood that unwanted particles enter other water sources
  • Embankments are stabilized and coastlines are protected from storm and flood damage 
  • Groundwater recharge takes place which keeps aquifers full
  • Groundwater composition is changed as excess nitrogen and other nutrients/toxins are removed which improves water quality and reduces the need for artificial water filtration efforts
  • Litter and dead wood is allocated, concentrated and distributed to aquatic organisms
  • Carbon is sequestered

With so many positive benefits, it is clear that buffer zone protection is imperative.  This is especially true with the many environmental uncertainties that we are facing in the modern world making it essential to protect and preserve these valuable natural service providers.

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photo credit: elibrary.dep.state.pa.gov

 

question: what is the difference between plant resistance and plant tolerance?

Plant tolerance is the characteristic of a plant that allows a plant to avoid, tolerate or recover from attacks from insects, among other things, under conditions that would typically cause a greater amount of injury to other plants of the same species. These inheritable characteristics are what influence the ultimate degree of damage caused by a pest. Tolerance in terms of agricultural production means that despite stress from a pest or disease, the production levels will remain above the economic threshold.

Resistance means that a plant completely immunizes itself from a particular stress.  This is typically a biotrophic pathogen infection. The host has a resistance gene which prevents the proliferation of the pathogen. The pathogen typically contains an avirulence gene which triggers plant immunity.

Resistance and tolerance are the best defense mechanisms of plants against pests. 

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developing new plants that are resistant to freezing  photo credit: phys.org

There are two main types of resistance: ecological resistance/pseudo-resistance and genetic resistance. Ecological resistance is resistance related to favorable environmental conditions at a given location at a particular time. This type of resistance can be broken down into 3 forms:

  1. Host evasion – this phenomenon occurs when a host passes through the susceptible stages very quickly or during a period when pests are fewer.  This type of resistance applies to an entire species population.
  2. Induced resistance – this type of resistance is the result of some type of changed condition for the plant, such as an increase in available nutrients or water
  3. Escape – this is more or less luck as there is an absence of infestation or injury to a host plant as a result of incomplete infestation.

Genetic resistance is resistance related to (you guessed it) plant genetics.  There are several types of genetic resistance:

Resistance based on the number of genes

  • Monogenic – controlled by a single gene which makes it easy to both incorporate and exclude in plant breeding programs
  • Oligogenic – controlled by a few genes
  • Polygenic – controlled by several genes
  • Major Gene Resistance – controlled by one or a few major genes (vertical resistance) 
  • Minor Gene Resistance – controlled by many minor genes; the cumulative effect of minor genes is called adult/mature/field/horizontal resistance

Resistance based on biotype reaction

  • Vertical Resistance – specific resistance against specific biotypes
  • Horizontal Resistance – effective against all known biotypes; nonspecific resistance

Resistance based on miscellaneous factors

  • Cross-Resistance – when resistance against a primary pest results in resistance to a secondary pest
  • Multiple-Resistance – different environmental stresses (e.g. insects, diseases, nematodes, heat, drought, etc.) results in a new resistance

Resistance based on evolution

  • Sympatric Resistance – resistance that is acquired through the coevolution of a plant and insect (which is why it is important to protect our native pollinators!); governed by major genes
  • Allopatric Resistance – not governed by a co-evolution; governed by many genes

There are three mechanisms of resistance in plants.

Antixenosis (non-preference) resistance mechanisms are those by which host plant has characteristics that result in non-preference for insects in terms of shelter, oviposition, feeding, etc. There are morphological or chemical factors that influence insect behavior and results in the poor establishment of insects. Plant shape and color can also be an important influencing factor.

Antibiosis is the negative effect of a host plant on the biology of an insect. This can include decreased rates of survival, development and/or reproduction and is a result of biochemical and biophysical factors. Antibiosis may be a result of the presence of toxic substances, the absence of essential nutrients or a nutrient imbalance. Physical factors, such as thick cuticles, glandular hairs and silica deposits, also contribute to antibiosis.

Tolerance is a plant’s ability to grow and produce an acceptable yield despite a pest attack. Tolerance is typically attributed to plant vigor, regrowth of damaged tissue and a plant’s ability to produce additional stems/branches.

Both plant tolerance and plant resistance are extremely important to IPM efforts as it helps to reduce costs and amount of other control tactics that need to be implemented. This includes improving the efficacy of insecticides and promoting non-chemical benefits like shifts in predator-prey relationships and reduced pest populations.

The benefits of the use of resistant cultivars are numerous as this method has a high level of specificity, is eco-friendly, lower cost and adaptable to a given situation. The benefits are limited only by the amount of time required to develop new cultivars in breeding programs and by a lack of known resistance genes that can be used. To identify and capture relevant genes, crop wild relatives are often used.

an introduction to integrated pest management (IPM)

Integrated pest management (IPM) is a long-term pest prevention program that focuses on ecosystem-based strategies for the control of pest related issues. This is accomplished through a combination of techniques including biological control, habitat manipulation, modification of cultural practices and the use of resistant cultivars. The use of chemical pesticides is then restricted to applications only after strict monitoring that is based on established guidelines indicates that stronger measures are required for pest management. In the event that chemical agents are required, they are applied in a targeted manner intended to minimize risks to the environment, other organisms (especially beneficial and non-target organisms) and to human health.

The 8 principles of IPM are as followed:

  1. In an effort to prevent and/or combat pests, the following intelligent production practices shall be used: crop rotation, sustainable cultivation techniques, resistant/tolerant cultivars and certified seed production systems, balanced fertilization, irrigation and drainage techniques, proper hygiene measures and the protection and proliferation of beneficial organism.
  2. The use of biological, physical and non-chemical control methods must be preferred to chemical options as long as the non-chemical options provide acceptable pest control.
  3. In the event that pesticides must be applied, they shall be target-specific and strategically applied in an effort to reduce negative health outcomes.
  4. Pesticides shall be used only on an as-needed basis and the frequency and intensity of use  should be minimized in order to reduce the risk of resistance populations.
  5. In cases where pest resistance has been established and repeat pesticide application is necessary, anti-resistance strategies should be integrated into control efforts.  
  6. Record keeping is essential and should be based on detailed records in order to determine the efficacy of pest control programs – especially in the case of chemical inputs.
  7. Monitoring efforts are essential in order to track pest presence.  This can be accomplished via observations, forecasting and early diagnosis systems and information, as well as information from professionally qualified .  
  8. The information garnered by monitoring efforts shall be used to determine when and which plant protection measures will be taken.  There should be scientifically supported threshold values upon which to base decision making.  Said values should be adapted to local conditions including climate, crop type and topographical qualities.

sources:

https://www.nap-pflanzenschutz.de/en/practice/integrated-plant-protection/general-principles-integrated-plant-protection/
http://www.ipm.ucdavis.edu/GENERAL/ipmdefinition.html
http://www.fao.org/agriculture/crops/thematic-sitemap/theme/spi/scpi-home/managing-ecosystems/integrated-pest-management/ipm-how/en/

 

 

the importance of annual grasses

The family Poaceae is considered the most economically important plant family due to the fact that they produce the world’s food staples including domesticated cereal crops such as maize (corn), wheat, rice, barley and millet.  Poaceae plants also provide forage, building materials (bamboo, thatch, straw) and fuel (ethanol).  

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Photo Credit:  oxfordlearnersdictionaries.com

Agricultural grasses grown for their edible seeds are called cereals or grains (although the latter term, agriculturally, refers to both cereals and legumes). Of all crops, 70% are grasses.  Three cereals – rice, wheat, and maize (corn) – provide more than half of all calories eaten by humans.  Cereals constitute the major source of carbohydrates for humans and may also be the major source of protein.  Rice is the dominate crop in southern and eastern Asia, maize in Central and South America, and wheat and barley in Europe, northern Asia and the Americas.  Sugarcane is the major source of sugar production. Many other grasses are grown for forage and fodder for animal feed, especially for sheep and cattle which indirectly provides more calories for humans.

Flowering Poaceae plants are among the 5 most numerous families in the world.  There are an estimated 10,000+ species within family Poaceae that originate from Gondwanan more than 80 million years ago.  The grasses grow on every continent in the world in varying climates from deserts to riparian.  There are two types of grasses – C3 and C4.  C3 grasses are cool season grasses and C4 grasses are warm season grasses.  It is estimated that at least 20% of the world’s surfaces are covered in grasslands.  

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The plants  are typically wind-pollinated and have hollow stems called “culms” plugged at intervals by solid leaf-bearing nodes. Grass leaves are nearly always alternate and distichous (in one plane), and have parallel veins. Each leaf is differentiated into a lower sheath hugging the stem and a blade with entire (i.e., smooth) margins. The leaf blades of many grasses are hardened with silicaphytoliths which discourage grazing animals.  Some plants also produce silica crystals in their leaves to deter predation.  

It is theorized that the evolution of large grazing animals during the Cenozoic period contributed greatly to the spread of grasses.  Trampling grazers killed or consumed seedlings, but not grasses.  This prevented the colonization of fire-cleared areas by trees which prevented the shading out of grasses.

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Photo Credit: nature.org

Grasses also serve very important environmental purposes including erosion protection, nourishing and providing a habitat for animals and insects, cooling, water retention and nutrient enrichment via the dead root litter that is decomposed in the soil.

crop wild relatives – what they are and why we need them

Nature has been doing her thing for billions of years (maybe longer, I’m not sure).  It is only since about 200,000 years ago that humans entered the picture and it is only since about 15,000 years that humans have figured out agricultural production.  It is safe to say that nature may have a few tricks up her sleeves that we Homo sapiens cannot even begin to fathom – although our incredible brains are trying.

For the first 14,850 years of the human agricultural experience, seeds were simply saved from the plants that were growing.  Some cultures chose to save the seeds from the best-looking plants and others chose to save seeds from the smallest plants, so they could eat the best-looking seeds.  The latter was not the best decision and eventually all cultures began saving the seeds from the best and strongest plants.  This helped to improve production somewhat.

Then in the 1890s, we human folk decide that it might be wise to breed two plant types together in order to get even better production.  This gave birth to modern plant breeding. Soon after, during the Green Revolution, new types of staple crops were developed that were not sensitive to the number of daylight hours, produced larger amounts of above ground biomass and saved billions of people from starvation.  It was quite an accomplishment.

However, as a result of these scientific efforts, modern crops cannot grow without inputs from humans.  They lack the necessary defenses from the many surprises that the wild world has to offer.  This brings us to Crop Wild Relatives (CWR).  These are the wild relatives of the current crops.  They contain the valuable genetic information needed to maintain genetic diversity.  Such a quality is essential as monoculture practices continue to dominate the agricultural production landscape.  CWRs also continue to evolve in adaption to natural conditions – something that domesticated crops are incapable of doing.

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Photo Credit: agro.biodiver.se

The information provided by the CWRs also contribute the development of more desirable qualities in domesticated crops. Pest resistance is one of these important factors, as in the case of three peanut crops that helped in the development of a crop variety resistant to the root-knot nematode that previously cost growers an estimated $100 million annually.

Furthermore, even in their wild state, some CWRs provide valuable nutrition for humans and other animals in areas that are not suitable for cultivation. Strong examples include the use of wild cowpeas and yams in Africa to help sustain the large population, and the consumption of wild fruits, such as apples, throughout Asia.  CWRs also provide valuable fodder, fiber and medicines.

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sources:

http://www.cropwildrelatives.org/cwr/importance/

http://www.bioversityinternational.org/cwr/

the green revolution

There is no doubt about it – there are a lot of people in the world: more than 7 billion. The sheer number of humans is probably even too much for our brains to process. Still, we’re all here and more people are coming joining the global population and every day.

Feeding so many people is a daunting task. So much so that food security is one of the most prominent issues facing the world today – despite the fact that output is greater than ever before. Successful increases in output are retarded by issues with food waste, problems with logistics and the unequal distribution of resources. However, the biggest issue preventing lasting change is the use of unsustainable production practices like monoculture, the irrigation of arid and/or semi-arid locations and high chemical inputs. For true food security to be achieved alternatives that are better adaptable to dynamic conditions are required.

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Norman Borlaug   Photo credit: nytimes.com

That is not to say that the evolution of the current system is not a biological and technological wonder.  It is a result of the Green Revolution which started the 1940s. It was during this time that Norman Borlaug, a plant breeder from the University of Minnesota, developed a high yielding wheat variety that revolutionized crop production throughout the world. The new varieties were not sensitive to hours of sunlight each day which allowed farmers to grow wheat anywhere, had more above ground mass which increased yields and produced shorter plants so that more of the plant’s energy could be focused on the usable grain production.

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A comparison of dwarf and full-size wheat varieties Photo credit: http://www.lsuagcenter.com

These genetic improvements coupled with the use of newly developed irrigation systems, altered farm management techniques, hybrids and chemical pesticides and fertilizers resulted in unprecedented increases in output. For example, following the introduction of high-yielding wheat, Mexico was able to go from importing half its wheat in 1944 to exporting a 1/2 million tons of wheat in 1964. The success was so great that shortly after high producing rice varieties (with IR8 being the most notable) were introduced in other places throughout the world. The increase is estimated to be so great that these changes are credited with saving more than a billion people from starvation. It is also credited with allowing the population to continue to balloon out of control.

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Photo credit: yubanet.com

Depending on the person, this is a good thing or a bad thing. Many find that humans are the best thing in the world and that continued population growth can result in improved economic climates, expanded intellectual capital and ultimately an overall betterment of the world. Others see the human presence as a burden that the world cannot truly bear. With a continuing world hunger crisis and severe weather conditions across the globe, it is hard to argue for the former.

Still, continuing efforts are being made to improve the genetic potential of seeds. There are 16 centers throughout the world focusing on the continuing development of improved crops including maize, sorghum, and beans. Unfortunately, this has led to a rapid decrease in genetic diversity and it has resulted in plants that are only able to survive with human intervention and high inputs. This has and will continue to cause serious issues as a result of droughts, floods, pests and/or disease (ex. bananas). Furthermore, many of the inputs used are non-renewable (fossil fuel, water). There are also rapidly changing consumer demands as third world countries develop and demand lifestyle choices comparable to those enjoyed by westerners (ex. higher rates of meat consumption), environmental degradation concerns, a limited amount of arable land, and unchecked population growth threatens food security.

To address these issues, there is a call for a second Green Revolution that is based on sustainability. The new revolution is aimed at efforts to reduce dependence on synthetic inputs and reduce the use of non-renewable water sources. Success in this respect can be achieved with the use of nitrogen fixing cover crops, crop rotation, alternative cropping styles, reduced tillage and farm diversification. There is also a need for a Green Revolution in Africa in order to focus efforts on improving the output of common crops grown on the continent. This would also help to reduce the yield gap that plagues many African countries.

the benefits of fire

forest fire
photo courtesy of NOAA

We have all read about them…the insane, previously unseen and completely out of control fires that are ravaging parts of America’s west. The lack of water has taken its toll. Reservoirs are tapped. Rivers are running dry. Famous people are illegally hoarding water. Lakes are at all-time lows. Northern parts of states are at odds with the southern parts. The state of Colorado wants its fair share of the Colorado River to stay in Colorado while Los Angeles keeps growing which means a higher demand for water. And then there are the scorching temperatures. The combination of drought conditions and high temperatures have resulted in widespread blazes which are often unpredictable and (unfortunately and unlikely) unavoidable – even with the best of land management plans (although there is always room for improvement).

This makes fires scary things to use human folks – as is the case with many things that we cannot control. This fear makes it easy to overlook the benefits of fire. However, the valuable role that they play in ecosystem health is undeniable.

Here are four benefits of fire in the health of our natural systems:

  • Fires clear underbrush which enriches the soil with new nutrients. This is known as nutrient cycling.
  • Fires help to eliminate invasive/non-native species.
  • Fires change the carrying capacity of forests by removing old growth, which is relatively unproductive, and opening up space for new and more varied growth.
  • Fires play a pivotal role in the perpetuation of various species. Hickory and oak trees, for example, have very thick bark which is able to sustain periodic fires. Furthermore, seedlings from these varieties their seedlings need nutrient-rich soil free of shade to thrive. In some locations, certain seeds require fire to germinate.  Fire also leaves behind acidic ash which is needed for the growth of native plants in places such as the sand plains.
photo courtesy of npr.org
photo courtesy of npr.org