The NFMA of 1976, Sec. 6 (g), part C, states that the USDA, through research and continuous monitoring, must ensure that the effects of each management system have no substantial and permanent impairment of the productivity of the land. So, in 1989, the NFS and FS Research partnered together to design and implement a nationwide, long-term study on the effects of forest management practices on long-term soil productivity. The LTSP study in the South is 5-13 years old, which is the most critical time for research on site productivity. Much work has been done on early plantation productivity (<15 years), but not on stands well past canopy closure, which is when site quality begins to exert its greatest influence on stand growth and productivity.

The LTSP study was designed to answer the following questions:

• What is the inherent carrying capacity of a site?
• Is this capacity altered by management?
• If carrying capacity is degraded, can it be restored?
• How does soil disturbance affect soil functions?
• Can these processes be monitored with surrogates?

The founding principles of the study are that:

• Soil is the key factor controlling site productivity
• The fundamental measure of productivity is vegetative carrying capacity; all other uses dependent on forest
• Losses of organic matter and/or porosity most common causes of long-term productivity loss
• Past efforts to directly document productivity loss have been confounded by climate, weeds, stocking, management, etc.

The experimental design is a 3X3 factorial design with three levels of experimentally-induced soil compaction and three levels of organic matter removal. The three compaction levels were None, in which no mechanical equipment was allowed on the plots; Moderate, which consisted of six passes of a wobble-wheel road compactor with 3.6 Mg of ballast; Severe, which consisted of six passes of the compactor with 6.4 Mg of ballast.

The organic matter removal treatments ranged from merchantable bole-only, where all tops were left on-site, to whole-tree, in which all tops were removed as well as boles, and complete removal, where all aboveground organic matter was removed (trees, understory, forest floor).

Each experimental plot was 0.4 ha in size and planted on a 2.5 X 2.5 m spacing.  The main plots were split into two 0.2 ha split-plots, and one half was kept free from woody competition with manual removal and herbicides.

Locations of LTSP in US, Canada, and Southern Region
(each red star represents 3-4 locations)

 

Location	Forest	Year installed	Soil series
LA 1	Calcasieu RD, Kistachie NF, Louisiana	1990	Malbis
LA 2	Catahoula RD, Kistachie NF, Louisiana	1992	Glenmora
LA 3	Catahoula RD, Kistachie NF, Louisiana	1993	Metcalf
LA 4	Catahoula RD, Kistachie NF, Louisiana	1993	Mayhew
MS 1,2,3	Chickasawhay RD, DeSoto NF, Mississippi	1994	Freest
TX 1,2,3	Davy Crockett NF, Texas	1996	Kurth

 

Other LTSP Websites

North Carolina LTSP, Missouri LTSP, Rocky Mountain LTSP, British Columbia (Canada) LTSP
 

Gulf Coast LTSP Bibliography

 

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