One of the most important issues at the border involving existence and ecological sciences is how ecological unit will react to worldwide alteration in the face of ongoing decrease of biodiversity. Owing to their possibility to stock up huge amount of carbon in biomass and to avoid soil decomposition, forests are of particular significance but not easy to control experimentally. Global warming has caused an increase in concern over how carbon moves though specific natural ecosystems.
In this study I described forest structure for two upland Florida ecosystems, sandhill and a mixed hardwood hammock forest, through means of quantifying tree diversity, basal area, frequency, and heights. Than to quantify the function of these systems I determined the carbon flux of a well established mixed hardwood hammock, lawn, and agricultural sites in order to note how human influence is changing the rate at which carbon is cycling though an ecosystem. In both of these studies used I used a belt transect to survey and collect data on tree diversity and characteristics.
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Other tools that were used were clinometers, to determine tree height, DBH tape to determine tree diameter, and a Infrared Gas Analysis Chamber which was used to quantify the amount of carbon dioxide respired by plants and soil microorganisms. My results found that sandhill forest communities are less diverse than hardwood hammock communities and that forest were better carbon pools than lawns. I also discovered that the highest flux rate of carbon out of a system came from the area which was tilled every 40 years. In conclusion I found that forest store carbon very efficiently and that tillage is a good mechanism to speed up carbon flux out of a system.
The objective to put together the consequences from the two scheme part to achieve an improved mechanistic kind of how medium-term results of biodiversity loss on ecosystem performance may be connected to degree of difference of short-term reaction to environmental measures of forests with high vs. low tree diversity. This information outlines a base for management to increase forest steadiness and environmental maintenance, together with timber production and soil protection.
Introduction
The importance about the outlook of forests has mainly concentrate on the pressure to the continued existence of the strange biological diversity that set apart these ecosystems. An additional viewpoint highlights the responsibility that forests take part in the global carbon cycle. In spite of covering only about 8% of the ground level, forests are considered to control about 40% of the earthly biomass and allow for over 50% of the yearly net primary output of the biosphere (Williams et al., 1998).
In addition, current facts proposed that unlogged forests proceed as a sink of anthropogenic carbon discharge (Grace et al., 1995). On the other hand, the devastation of forests by land permission and forest fires is an important source of CO2, a point noticeably highlighted by the current huge fires that take place in forests internationally (Brown, 1998). The point of this review is to detail existing research relating to the issue that manipulates carbon dynamics in the forests.
Global warming has caused a heighten interest in the flux of carbon in and out of ecosystems in recent years. This spring of interest has been caused by the solidified statement that increasing carbon levels are directly related to anthropogenic carbon dioxide emissions. In this series of observational studies I will consider ecosystem function and structure and connect them to ecosystem carbon flux through means of biomass and respiration studies.
The objective for this research was to quantify tree diversity, basal area, frequency, and heights in sandhill and mixed hardwood forest ecosystems in attempts to describe their structure and secondly, to determine carbon flux though means of soil respiration in multiple Florida ecosystems and evaluate how changes in land use/cover could affect ecosystem cycling of the carbon.
Sandhill forests are arid fire climax communities that occur on elevated sloping ground composed of deep, marine deposited, yellowish sands that are well drained and relatively sterile. (Myers 1985) The vegetation consists mainly of longleaf pine (pinus palustris) deciduous oaks and with a typical ground cover of wiregrass (Aristida stricta) (Myers et al. 1987). Since sandills are a fire climax community they are dependent on low-intensity quick burns in order to reduce hardwood competition.
The larger pines and oaks over time developed thick insulating bark and developmental modifications that allow seedlings and seeds to be fire tolerant such as the grass like seedling stage of most pines (Myers, 1985). In Florida, this community has been extensively reduced and altered due to agriculture and development over the past 100 years. (Myers et al. 1987)
The second community I evaluated was a Florida mixed hardwood forest. These plant communities are found in areas where fire has been suppressed long enough to allow succession to move pass the pine stage and where limestone and phosphate deposits are outcropping ( Myers, 1985). Hardwood mixed forest varies highly in species composition since they are dependent on soil moisture and fertility. Therefore the most species diversity should be located in the mixed hardwood hammock rather than the sandhill environment because it is a more variable ecosystem that has more diverse soils and is less prone to selection by fires.
The main ecosystem function I focused on in this study was the flux of carbon dioxide from a Florida hardwood forest, lawn, an area that had been tilled every 10 years, and an area that had been tilled every 40 years. When plants photosynthesize they decrease levels of carbon in the atmosphere by collecting it via carbon dioxide and storing it in their biomass. Almost 50% of all living tissue accumulated in plants is comprised essentially of carbon so plant growth and photosynthesis are two direct causes of decreased levels of carbon dioxide in the atmosphere.
The process of respiration is another important mechanism which influences carbon flux by releasing carbon dioxide back into the atmosphere through processes of plant dark reactions and microbial and animal metabolic activates. Soil respiration, which is made up of organic matter decomposition and mineralization, root respiration and atmosphere respiration, is strongly influenced by temperature and moisture levels (Jabro et al. 2008) When soils are warm and moist microbial metabolic rates can increase allowing more respiration to occur than if they were dry and lower than ideal temperatures.
So the hardwood forest should have the highest amount of carbon storage because it contains the most plant biomass, while the plot of land that is plowed every 40 years should have the highest carbon flux rate because of the constantly aerated soils which allow high levels of microbial activity to occur to digest the grasses and shrubs with annual life cycles.
There is an obvious need of essential data on carbon storage in the woods and the amount of carbon released next to logging and burning. Carvalho et al. (1995; 1998) establish that a 1-ha area of forest hold about 200 tonnes of carbon in the above-ground biomass. A late dry period fire in wreckage three months following the forest had been vacant was set up to go through about 20% of the entire above-ground biomass and released 37.7, 121, and 8.6 tonnes per hectare of carbon, CO2 and CO, correspondingly. Kauffman et al. (1998) establish that the entire above-ground biomass of the main forest was between 290 and 435 tonnes per hectare and as soon as this biomass was cut and burned it dismissed, relying on restricted site conditions, between 58 and 112 tonnes of carbon per hectare.
The quantity of carbon stocked in forest soils in contrast to that stocked in forests transformed to cattle pasture remains uncertain. Assessment of accessible data led Fearnside and Barbosa (1998) to bring to a close that pasture adaptation naturally discharge about 12 tonnes of carbon per hectare in the forest, even though they note that the quantity of carbon stored or lost from the soil is predisposed by the method of pasture management.
The length of studies of transformed forest sites is necessary to give way to vigorous guess of soil carbon storage (Fearnside and Barbosa, 1998). There is also substantial indecision as to how forest soils will react to augmented CO2 and related climate change (Silver, 1998).
Evaluation of present facts led Silver to reason out that warmer climates features of a CO2-rich atmosphere will have an effect in increased soil respiration but it is indefinite how this will be counterbalance by increased carbon absorption by plants that will as a result return more organic matter to the soil. Silver (1998) comments that refusal in soil organic matter linked with increased respiration may affect the reduced ease of use of soil nutrients, therefore preventing the ability of forests to take the benefits of increased CO2– the so-called fertilizer consequence.
Methods
This investigation was conducted in the San Felasco Hammock State Preserve, where sandhill and a mixed hardwood forest arrange side by side. I used the belt transect to measure up the arrangement of sandhill and mixed hardwood forests. At every sample location, I’d put up a belt transect that was 100 meters long by 10 meters wide (Schuur et al, 2008). Then I divided the 100 meter by 10 meter area behind the center of its extended axis with numeral pin flags at 10 meter interval.
The external limitations of the transect were then marked at 10 meter interval in order to form pin flag grid where every “box”, consisting of 4 flags, created a 10 meter by 5 meter plot. These plots where then given a consistent numerical scheme in order to keep path of sampling site information. Once the two divided transects were recognized in every place, I began to bring together tree height and inventory information for the individual 10 meter by 5 meter scheme within each transect.
While determining tree height, first I recognized the tree species and then stand in an identified distance away from the tree. Then by means of a clinometer I documented the point of view from eye level to the top of the tree. By using this data in addition to my own height information I used plain trigonometry to generalize each individual tree height. When taking tree record I collected data relating to plant species and its DBH or diameter at breast height in every individual plot of the belt transect for species of tree that were active and had a width at least 2 inches wide. (Breast height is believed to be located at just about 1.37 meters.)
To compute CO2 flux, I set up a single 50m transect in a mixed hardwood forest, grass, 10 year old field, and 40 year old field all located at the University of Florida outside training laboratory. Next to each transect, I obtained six 15 second measurements at 10m intervals using an infrare gas examination soil respiration chamber. These measurements were used to duplicate the soil respiration from each site.
With the intend of evaluating the above earth biomass in a hectare of lawn to a hectare of woodland, formerly I used to established allometric equilibrium to estimate above ground biomass of trees with pliable or firm wood foundation only on their stem diameter. This process was used given that it is less time consuming and did not necessitate the devastation of the area in query. B= a DBHb Where B= biomass in tons, and a and b are constants values, and DBH= diameter at breast height (cm). Here are the constant values for the forest I used: Softwoods: (a=0.006, b=2.172), Hardwoods: (a=0.113, b=1.164). (Lab manual)
After that I measured every individual tree >2.5 cm DBH within 2m on either side of the transect, in 10m increment (Schuur et al, 2008). For the lawn and tilled plots I clipped and collected a 25 cm x 25 cm square sampling from the middle of every plot and multiplied this biomass number by 0.5 to get the quantity of carbon since biomass is just about 50% carbon. After computing the quantity of carbon at each plot I level this carbon into a 1 hectare area.
Results
The degree to verify the arrangement of every ecosystem I come across at I used a species-area curve. As the vicinity is reviewed in the mixed hardwood hammock increased, more species were noticed. Whereas in the sandhill species, the diversity is plateau at around 300 sq meters. The sandhill and hammock ecosystems together had declining basal area with an increase in tree number of trees (Fig. 2). In the mixed hardwood hammock ecosystem Laurel Oak (Quercus hemisphaerica) was the majority of influential species, with utmost relative significant value, relative supremacy, frequency and abundance (Fig. 3).
While in the sandhill ecosystem there was a relatively equal spread of importance between Loblolly Pine (Pinus taeda), Longleaf Pine (Pinus palustris), Slash Pine (Pinus elliottii) and Turkey Oak (Quercus laevis) while Laurel Oaks (Quercus hemisphaerica) though present were relatively non abundant (Fig. 4). When comparing tree height between the two ecosystems it was found that the hammock ecosystem (mean=17.977 meters/tree, variance 46.095) and the sandhill ecosystem (mean=18.715 meters/tree, variance 33.123) were on average very similar in height (paired t-test for means=1.833, p value one tailed =0.411).
When looking at ecosystem purpose in respect to carbon dioxide levels I found that forest had the largest carbon pools, while lawns had the smallest (Figure 5). Surprisingly, I found that the area that receives tillage every 40 years had the largest mean carbon loss at 39.48 Tons C/ha/yr with a St Dev. of 10.57. The lawn had the lowest mean carbon loss at 21.78 Tons C/ha/yr with a St. Dev. of 15.35 (Figure 5).
The longest turnover rate was found to be in the forest with it taking 65.31 years for carbon to return to the atmosphere. The shortest turnover time was held by the 40 year tillage patch with a turnover rate of 0.25 years. The largest biomass amount was found to be located in forests which had an average of 2329.797 Ton C/ha (St. Dev 2103.05). The lowest amount of biomass was located on the lawn with an average of 1.407 Ton C/ha (St Dev. 0.781).
Discussion
It has been discussed whether worldwide climate change and associated increased in CO2 height will have effect in considerable adjustment in the arrangement and group mixture of forests (Phillips, 1995). Roden et al. (1997) used a growth hall to replicate the outcome of a tree-fall hole on the growth of a pioneer species and a late sequences species from the subtropics in a CO2 rich environment. They discover that increased CO2 considerably deferred the capability of the shade-tolerant species to adapt to high light levels whilst the pioneer species was not so deprived. Such outcome flags the likelihood that under a CO2-rich atmosphere, pioneer species may proceed as a negative reaction system in the global carbon series since their ability swiftly to collect carbon in plant biomass and soil (Bazzaz, 1998).
Though, beneath a very deep shadow situation it has been revealed that one species of neotropical forest bush had larger growth and absorption rates in growth chamber with twice the present atmospheric property of CO2 in contrast to growth chambers with the surrounding atmosphere (Winter and Virgo, 1998). The dimensions of gas exchange of forest in the ‘Biosphere 2’ mesocosm have also made known to elevate carbon absorption under increased CO2 (Rosenthal, 1998), a outcome that proposed that forests may be a vital sinks of anthropogenic CO2.
On the other hand, countryside testing has shown that the reaction of plants to improved CO2 is more complex than many growth chamber trials suggest. For example, Lovelock et al. (1998) found that eminent CO2 resulted in no increase in plant biomass of ten neotropical forest tree seedlings from three sequence phase developed in open-top chambers generated in the ground. These authors perceived considerable modification in leaf chemistry in reaction to elevated CO2 and mainly where late rotational species had better leaf carbon to nitrogen proportion. This directs them to reason out that the outcome of high CO2 on forest may perhaps be indirect by means of change in nutrient interval and therefore soil nutrient accessibility.
Modelling is crucial to the knowledge of forest carbon financial plan, chiefly at local and worldwide balance. Though the forecast of representation are of basic necessity, given the difficulty of the connections and poor geographical extent of field statistics, they are practical in putting together suggestions and elucidating field measurements (Potter et al., 1998). For instance, a form of the soil–plant–atmosphere range was matched over ground measurements of CO2 and H2O found on eddy-covariance techniques in a virgin forest.
This model led Williams et al. (1998) to terminate that lesser carbon uptake in the dry season was due to reduced soil moisture materials, rather than due to change in leaf region indicator or low levels of moisture. Information on constant isotopic arrangement of carbon and oxygen in CO2 example across vertical outline during forest covering are believed to be crucial for rising global carbon budgets. Nevertheless, much more investigation is necessary to comprehend the foundation and implication of temporal and spatial inconsistency in these measurements (Buchmann et al., 1997).
The ‘Biosphere 2’ mesocosm has facilitate investigational validation of straightforward canopy representation used to discover the result of different levels of CO2 and light on net carbon uptake of the forests (Lin et al., 1998). This mesocosm facility permits the creation of data on carbon exchanges under a range of mixture of light and CO2 distribution that at present do not take place under normal conditions. Lin et al.’s (1998) short-term testing and modeling led them to determine that carbon exchange is not in a straight line and that previously atmospheric CO2 levels exceed 600ppm in the forest cannot act as a carbon sink.
This judgment is reliable with the soil–vegetation–atmosphere modelling by Cao and Woodward (1998) for the period 1861–2070. They established clear interaction consequence of climatic change and increased atmospheric CO2 on carbon storage and recommended that in the tropics the harmful consequence of climate change on carbon result will be counterbalance by more well-organized gas exchange under an ambiance enriched by CO2. On the other hand, they foresee that the capability of earthly scheme to store carbon would turn into concentrated once CO2 strengthening surpasses 600ppm.
Laurance et al. (1998) take on a modelling exercise to examine the significance on carbon discharge that biomass decline is greater on the limits of forest fragments in contrast to the entire centre of remains. Their modelling established that land interval that create numerous rain forest segregate (such as that caused by small-scale farms) causes two to five times more biomass decline on forest border than separation for large-scale cattle ranches, in spite of the total area cleared.
They recommend that this distinction is a major additional section of global carbon release that has been in the past unnoticed, perhaps in the order of 22–149 million tonnes per year for forests worldwide. Goldammer and Price (1998) used the outcome of a number of models of the importance of climate change following a repetition of atmospheric CO2. They accomplished that forests, mainly those ruined by logging and clearance, will develop into more fire prone given extended dry seasons, high frequencies of dearth and an increased significance of fires started by lightning. Recurring fires may affect considerable soil nutrient losses from minor forests, thus striking the capability of forests to take carbon (Kauffman etal., 1997).
Conclusion
In a current evaluation Bazzaz (1998) renowned that there can be ‘little doubt’ that forests will react to increases in atmospheric CO2 and related alteration in rainfall and temperature, even if accepting the particulars of these modification will necessitate substantial mutual research from scholars across a wide variety of regulation.
Houghton (1997) exemplify this position by disagreeing that, in order to undertake sufficiently the problem of carbon exchange amid the atmosphere and biosphere, the subsequent five research programmes that function at unusual spatial balance should be engaged:
- direct field measurements of carbon storage;
- direct field measurements of CO2 fluxes above different ecosystems;
- models of carbon cycling at the ecosystem level;
- geochemical modelling of the global carbon cycle; and
- modelling carbon flux on the basis of remote-sensing data on land-use changes (Bazzaz, 1998).
Obviously, to carry out such a complete set of research programmes the decision of an amount of considerable scientific, managerial and political problems is requisite. This is so since the worldwide nature of the question, the variety of methodologies and expertise, and the vast quantity of information concerned (Houghton, 1997). Additional, such included programmes are costly and need strong community support in a broad cross-section of rich and poor state all through the world.
Mazur (1998) offer a sobering report of the indecisiveness of the media in gathering together worldwide community support for forest protection. In spite of speed up there is proof devastation of tropical rain forests and matching release of CO2 that this once well-liked media ‘story’ has now turn into decayed. Recurring the fortune of tropical rain forests to the pinnacle of political program entail change in media attention to update the public and reason politicians.
With no extensive support there will be inadequate assets to undertake this grimly serious worldwide crisis. One more urgent subject crucial for the continued existence of forests is the making of financial device that make rich nations pay for ecological services provided by forests, such as carbon storage (Fearnside, 1997). At present, ecological services significant to the preservation of biosphere purpose are not accorded financial cost with the effect that poor nations have no financial inducement to relinquish the change of forests in their anxious mission for hard notes.
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