The hubbard brook ecosystem study essay
Each such zone functions essentially as a closed environmental system.
This policy has been largely responsible for the intellectual growth of the HBES, as well as its role as a center for undergraduate and graduate education in ecosystem science.
Also, some elements enter the ecosystems as dry rather than wet deposition e.
Hubbard brook experimental forest acid rain
Streamwater is usually characterized by low concentrations of suspended materials due to the coarse-grained texture of the soil. Bormann, G. At various places in the Forest, the C horizon exists as an impermeable pan. The early ecosystem monitoring was aimed at studying the effects of forest management practices on water flow and quality. At the same time, cooperating ecosystem scientists were interested in studying how entire watersheds respond to major disturbances. For these reasons as well as many logistical ones e. The numerous streams in the HBEF range from small ephemeral channels that often dry up during summer to a large perennial 5th-order stream Hubbard Brook. Forest biomass is estimated using allometric equations relating DBH to other tree dimensions e. In a catchment where the underlying bedrock is impermeable, water falling on the catchment leaves only by evapotranspiration ET or as stream discharge. Because of the large stocks and high spatial variability of elements in soil, detection of changes through time or in response to treatments is challenging. The second manipulation, beginning in , examined the effects of strip-cutting on forest processes, water yields, and elemental budgets. Depth to the C horizon averages about 0. The uniformity allows for comparisons to be made between watersheds, the watertight bedrock makes quantitative hydrologic and elemental budgets possible, and the similarity to surrounding ecosystems allows for extrapolations of results to a broader area. A prominent feature of the surface topography throughout the HBEF is the rough pit-and-mound appearance caused by the uprooting of trees.
A prominent feature of the surface topography throughout the HBEF is the rough pit-and-mound appearance caused by the uprooting of trees.
The pool or stock of an element is estimated from the product of mass and element concentration in various tissues.
The uniformity allows for comparisons to be made between watersheds, the watertight bedrock makes quantitative hydrologic and elemental budgets possible, and the similarity to surrounding ecosystems allows for extrapolations of results to a broader area.
Harsh winter conditions do not allow for rapid recovery, unlike more humid climates that recover net primary productivity within years, the northeastern version needs decades and in the case of the forest floor possibly centuries to recover.
Some of the dry deposition can be captured on artificial samplers or as canopy throughfall, but the calculation of dry deposition flux is complex and uncertain, and we refer the reader to detailed explanations in the literature Likens et al. The soil is carefully excavated manually from a 0.
Huntington and T.
At various places, the C horizon exists as an impermeable pan. Hubbard Brook weir at watershed 3.
Long term ecological research at the hubbard brook experimental forest
The initial development of the HBES was slow and deliberate. Hubbard Brook rain gauge. Ecological Monographs 44 2 Fuss, P. Hence, silica is retained and at times mixes with the forest floor. The soil is carefully excavated manually from a 0. The forest comprises nine individual watersheds, each of which drains into Hubbard Brook which flows eastward into the Pemigewasset River near West Thornton. Anderson, J. Litter is sorted by species, providing annual estimates of leaf biomass and leaf area index in these plots. At that time, there were no precedents to follow since comprehensive studies of ecosystems had not been initiated. The first stream in the forest was fitted with monitoring devices in Hubbard Brook weir at watershed 3. By quantifying the latter, annual ET can be calculated by difference: Eq. The first whole-watershed experiment is the focus of this activity, and involved the deforestation of "Watershed 2" to examine hydrologic and elemental watershed output.
Driscoll and T. Subsequently, seven additional headwater streams and their associated watersheds were delimited for study.
Hubbard brook study summary
Siccama, T. Flux of particulate matter is measured by removing accumulated material in the weir stilling pond periodically. Arthur, R. These dams form a stair-step pattern in stream channels, and they play important roles in regulating many physical, chemical, and biological processes in the streams. Battles, J. Yanai, R. In the summers of , , and , two herbicides were applied to the entire watershed to prevent the regrowth of any vegetation. Rodenhouse and L. Periodically, the chemistry of leaf litter is measured; combined with chemistry of live foliage from the plots, these measurements provide estimates of nutrient resorption from senescing foliage, a large internal ecosystem flux especially for N and P Ryan and Bormann Proceedings of the National Academy of Sciences 46 : doi Considering the role transpiration plays in forest ecosystem water budgets, hydrologists and forest managers were curious about the effects deforestation would have on downstream water supplies.
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