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Vietnamese has a locution that: “Forest is gold, ocean is silver, oceans of money”. To be honest that forests is very important to human life. It is not just about economic aspects, it is also about roles of forest when forest is a big deal such as Green lung of our world by many negative effects to environmental matters : reduce GHGs, global warming, climate change, provide Oxygen, and also protect our life by reduce natural disasters and so on. With mangrove forests, it also has many roles included by waves, storms and wind defensing, etc (Duy, 2014) . However, big question is that how can rise the value and to manage those gold, it become a big problem and it come to be very complicated. In that case, a greatest solution was taken that how to raise forest quality but not much negative effects of that solution?
VIETNAM NATIONAL UNIVERSITY OF FORESTRY FOREST RESOURCES AND ENVIRONMENTAL MANAGEMENT FINAL REPORT Title THINNING IMPACTS ON FOREST GROWTH Student: Nguyen Huu Dung Student ID: 1353091031 Subject : Forest Ecology Class: L03 Advanced Education Program Developed in collaboration with Colorado State University, USA Supervisor: Dr Pham Minh Toai Ha Noi, June /2017 I Introduction Vietnamese has a locution that: “Forest is gold, ocean is silver, oceans of money” To be honest that forests is very important to human life It is not just about economic aspects, it is also about roles of forest when forest is a big deal such as Green lung of our world by many negative effects to environmental matters : reduce GHGs, global warming, climate change, provide Oxygen, and also protect our life by reduce natural disasters and so on With mangrove forests, it also has many roles included by waves, storms and wind defensing, etc (Duy, 2014) However, big question is that how can rise the value and to manage those gold, it become a big problem and it come to be very complicated In that case, a greatest solution was taken that how to raise forest quality but not much negative effects of that solution? That solution which I mentioned about is thinning Thinning has considered to be a optimal solution for forest management by many positive effects that reduce wildfire risk, tree competitions for nutrients, water, and lights; or improving quality of trees for harvesting which considered to be profitable (B Parker et al 2008) A question that: “ what are negative impacts of thinning on forest growth which was considered as a optimal solution?” Thinning has defined that: “ In forestry, thinning is the selective removal of trees, primarily undertaken to improve the growth rate or health of the remaining trees Overcrowded trees are under competitive stress from their neighbors Thinning may be done to increase the resistance of the stand to environmental stress such as drought, insect infestation, extreme temperature, or wildfire.,etc” (Russell T Graham et al 1999) In other side, key factors impacts on tree growth rate are nutrients, water, lights etc In which their overpopulation of trees and with lack of nutrients, lights, and water It means that stress of forest So in this case, thinning has become the best choice for managers Base on secondary data from many authors who defined the thinning definition that we can clearly understand about roles of thinning in forest management However, in this study case, I inherited from a number of scientific research related to my study case I would like to give readers a deeper look about impacts of thinning on forest growth Hence: Thinning impacts on forest growth” will help you had a scientific knowledge about thinning and forest growth from their implications II Goals and objectives: Goal This report aims to prove hypothesis that thinning has closely inter-related to forest growth and how did they impacts on each other? Objectives - To indicate key factors impacts on thinning plans - To indicate and deeply explain about negative and positive impacts of thinning - on forest growth To indicate their implications between thinning and forest growth III Study methods Data collection + Secondary data: This study mainly depend on results from another authors In order to prove hypothesis that thinning impacts on forest growth, I have inherited those results from recognized researches which related to this report Results and discussions Key factors in order to establish thinning plans 1.1 Manager decisions in management objectives It has a belief for sure that manager decisions in management objectives is the IV - most important factor in order to establish thinning plans Because managers who investigate, evaluate and decide what stand will be thinned, how many trees and what species will be thinned, what are thinning methods will be - applied, etc With other aspect that economical, it has differences between landowners and forests belongs to government (Garry Kerr et al,2011) That means with forests belongs to private company or owners, the manager will be preferred to economic values more than sustainable management of those forests areas Private managers think about how to get more profits from thinning in shortterm in stead of main thinning objectives that reduce wildfire risk or improve forest health as well Figure Key factors to establish thinning plans - - - - Because thinning was considered to be profitable with no tax from government and related fees…etc (PhD, Advisor: John A Kershaw thesis) So that many managers based on this in order to get more profits Further more that thinning increase asset value of the remaining crop and also remaining trees increase in volume faster which allows clear felling to be completed as quickly as possible 1.2 Forest types with forest growth rate It is very easy to understand that why forest types with forest growth rate indirectly impacts on manager decisions and thinning plans Because we can clearly wondered with differences species, they also have differences growth rate For example with species that Santalum Album after 12 years we can harvest It means that less than 12 years it could be thinned But with species Pterocarpus santalinus upto 22 years we could be harvested.( Dr Vu Van Toai, 2015) So we can see that each species has different growth rate With planted forests that not much mixed species than natural forests That means with higher mixed vegetation ratio, we also have higher density of trees It also increase competitive between trees or stress of forests From this, we can be released that inter-relationship between thinning plans or thinning and forest growth In other way, we can prove that thinning impacts on forest growth and the both of them reacted to each other closely By components of species, density of stands, forest types, and their consequences from all of characteristics 1.3 Age of forest With another periods of time for thinning or for forest growth, we also have different of thinning plans Because of with another periods of time in forest growth, we have differences characteristics for growth abilities, regeneration, nutrients, lights, and water demanding (Gary Kerr et al 2011) Figure Age of forest stands with their growth (Sources: Gary Kerr et al 2011) - At the first stage, stand initiation with regenerate naturally, in this stage, tree has highest growth rate than any stage compare with second, third and fourth stage Especially in third stage that understory reinitiation, in this stage, trees has fruits and seeding can be growth well in this stage But in all-sized stage, self-thinning happened because of lack of nutrients, lights, water It make not good die included by seeding as well, regeneration and growth abilities in this stage was slowest Positive and negative impacts of thinning on forest growth 2.1 Positive impacts of thinning on forest growth - 2.1.2 Thinning is profitable Thinning is considered to be profitable which I mentioned in introduction In other words, we can say that thinning get more and more profits for managers In another periods of thinning, cause of improving quality of trees, total of profits increased over time: Figure Thinning with their economic value in period of time - (Sources: Forestry services Ltd, experienced professionals) With no taxes from government, from selling woods production in thinning, the manager can get more profits from 16th year is 400 € per hectare after years is 500 €/ But just after years, total of profits increased 1,100 €/ha and after 11 years has become 1,400 €/ha In order to get profits likes this, year by year from thinning, trees quality has increased about volume of trees by increasing growth rate over time So that from increasing whole of quality and volume and - price together, thinning is profitable with managers From that positive impact of thinning, profits could be improve manager’s behaviors with thinning and management objectives that in stead of preferred to focus on short-term benefits, managers could be though about long-term It means sustainable forest management 2.1.2 Thinning reduce wildfire risk - Thinning influences tree growth rates, economic potential, species composition, resistance to insects and disease, quality of wildlife habitat, forage production and visual appearance of a stand of trees Another very important purpose for thinning can be added to this list: increasing the ability of a forest to survive wildfire (B Parker et al 2008) Figure Thinning reduce wildfire risk (Sources: B Parker et al 2008) - Unthinned stand means no trees thinned, light thinning, moderate, heavy thinning respectively 90% , 90-110% and 110-140% MTI ( marginal thinning intensity) By reducing density of trees, understory, and fuel ladders that reduce wildfire risk, especially in dry season In unthinned stand with highest density of trees fire will be harder to control and faster in wildfire happen From tree to tree, if more space between trees, wildfire can be slower outbreak than unthinned stand So from reducing wildfire risk, thinning positively impacts on forest growth 2.1.3 Thinning increase photosynthetic rate - From reducing density of trees, thinning increase photosynthetic rate by make more spaces between tree to tree Compare between moderate and heavy thinning: Figure Photosynthetic rate related to thinning rate - Moderate thinning with 110% Marginal thinning intensity and with heavy thinning up to 110-140 % MTI, it always has photosynthetic rate higher than moderate thinning From that, we can see that total of trees thinned ratio with photosynthetic rate, and with higher trees thinned, it has higher photosynthetic rate included comparison with unthinned stands ( David J Suggett et al 2013) 2.2 Negative impacts of thinning on forest growth Beside positive impacts of thinning on forest growth, it also negatively impacts on tree growth when it used more big and heavy machines for transferring, and cutting By those consequences, forest growth could be indirectly effected Soil compaction From using some big and heavy machines go through the forest that make soil 2.2.1 - strength increased: - Figure Soil compaction with root stress threshold When we applied big and heavy machines, in thinning process those machines come to the forest and they need the roads for transferring Between stands, when machines go inside of stands by gravity force, it compacted to the soil It makes soil strength increased more than 1500 kPa and more than 2000 kPa It - negatively impacts on root systems and indirectly impacts on tree growth 2.2.2 Thinning increase soil erosion Also from reducing density of trees, thinned trees has removed, it make more spaces for direct drops from precipitation into soil From here, detachment process happened and overland flows carry soils and nutrients come down to water bodies May natural disasters happened in rain season with a high of rainfall at the short time: Figure Thinning rate related to erosion rate - Sources: Ygui Zheng et al 2005 With different thinning rate by MTI, we can see that erosion rate and thinning rate ratio to each other With light thinning at 90% MTI, the erosion rate is less than 0.15 ton/km2/yr But with higher thinning rate in moderate and heavy thinning 90-110% MTI and 110-140% MTI respectively , so the erosion rate increased up to 0.15 and 0.4 tons/km2/yr So with higher thinning rate, the - erosion rate also increased over time V Conclusion Thinning was known with many positive effects such as profitable with almost of managers, increase quality of wood productions, reducing wildfire risk by - reduce density of trees respected to improve forest growth by many ways This report also give a larger looks for readers by negative impacts of thinning by soil erosion, soil compaction as well However to be honest that thinning still a optimal solution in sustainable management because it resolve the both of - issues that economic and sustainability in forest development With further study, I would like to recommend a aspects that was a limitation of my research that effects of thinning on aquatic life and soil ecology cause by erosion and soil compaction and so on Reference: • B Parker et al 2008., Reducing hazardous fuels on woodland properties: thinning • David J Suggett et al 2013, Thinning effect on photosynthesis depends on needle ages in a Chinese fir (Cunninghamia lanceolata) plantation • • Gary Kerr et al 2011, Thinning Practice A Silvicultural Guide Josef Hakl et al 2007, The effects of the soil compaction […] on root biomass Tran Van Duy (2014), Environmental effects of tourism on Cuc Phuong National Park Ygui Zheng et al 2005,Effects of thinning on Erosion rate with aquatic life • • ... negative impacts of thinning on forest growth 2.1 Positive impacts of thinning on forest growth - 2.1.2 Thinning is profitable Thinning is considered to be profitable which I mentioned in introduction... look about impacts of thinning on forest growth Hence: Thinning impacts on forest growth will help you had a scientific knowledge about thinning and forest growth from their implications II Goals... Suggett et al 2013) 2.2 Negative impacts of thinning on forest growth Beside positive impacts of thinning on forest growth, it also negatively impacts on tree growth when it used more big and