1.2.1 Site and Site Classification

The ideal goal of silviculture is to place the right tree in the right place. Therefore, to understand the tree, place and their interactions is the main principle of silviculture.

A site means a whole environment of a special place. A forest site is a place where trees and other organisms live and interact. Generally, a site includes three aspect(s). That is (They are) geographic condition, climatic condition and biological condition.

See online APFNet Course 6: Forest Resource Management and Protection (http://blogs.ubc.ca/apfnet06/) Module I, Topic 1 Principles of silviculture, 1.1.1 Forest site. From that course you will know exactly what is forest site, how to know forest site, how to make a site classification.

Site Classes reflect the basic information for

• identification of the Natural Potential Vegetation, which would grow without human impact – only driven by the regional and local ecological conditions.
• Tree & Shrub Species selection as well as further on for the design of Afforestation Models;
• focusing on the interests of human society the site conditions also are defining the Forest Functions.

1.2.2 Technology of site classification

The main criteria & indicators defining the Site Classes are

• Elevation: Sub-compartment’s (SC) average and range by 10m accuracy: e.g. 2,450/2,300-2,500m; taken from Digital Terrain Model (DTM) or on site by GPS (Global Positioning System);
• Aspect: N, NE, E, SE, S, SW, W, NW by SC’s main aspect/followed by the range of sub-dominant aspects: e.g. SW/S,SE,W; taken from DTM or on site by GPS;
• Slope-Inclination: SC’s average /range by 1 °degree; taken from the DTM or on site by inclinometer;
• Mother-rock / pH-range: limestone; acidic rock; sediments (alluvial, dilluvial, aeolic/ Loess); identified from field survey or from reliable geologic data base;
• Soil Type, Depth, Texture & Moisture: identified from reliable soil data base or from field survey analyses to be taken on each SC – once at a representative location of all of the 6 topographic units (as below), if occurring within a SC:
  • type: e.g. “natural loess” or “chestnut-soil”;
  • depth: by 10cm accuracy; also indicates the fertility/concentration of nutrients of the site;
  • texture: (rocky), stony gravel, sandy, loamy sand, sandy loam, loam;
  • moisture: dry, moderate dry, moderate moist, moist.

Alternatively the soil depth & fertility, soil texture as well as soil moisture and erosion category as basic criteria of site classes need not to be measured at each SC,- it can also be concluded from the topographic micro-sites and slope aspects taken by (satellite image or aerial photograph based) DTM-remote sensing interpretation.

• Erosion category: taken from reliable erosion data base or from field survey according to the national standards given by the Soil & Water Conservation Department/ Bureau and calculated from soil type, inclination and vegetation cover.
• Topographic Micro-Sites (TMS; Fig.1) – 6 units: taken from DTM
  • convex 1   – specific slope area: “ ᴧ ”       (ridges; high – low diff. > 5m),
  • convex 2   – general slope area: “ Ç ”      (high – low diff. > 2m),
  • concave 1 – general slope area: “ È ”      (high – low diff. > 2m),
  • concave 2 – specific slope area: “ ↘ ”       (slope foot),
  • un-structured slope area: “ \ “         (high – low diff. < 2m),
  • plain, flat land: “ → “      (inclination < 5°)

Based on the topographic micro-sites the Site Classes can be concluded if including the ecological effects of the slope aspect, because the general topography-related site conditions are modified by the slope aspect concerning soil moisture: S-facing slopes are drier than N-facing slopes. So – we can assume, that N-facing convex slopes showing similar conditions like S-facing un-structured slopes, and N-facing un-structured slopes are similar to S-facing concave areas, et.

• Site Class (SCL) 1: very dry S-facing hill-top ridge – prone to (water) erosion
• Site Class 2: dry N-facing hill-top ridge or dry S-facing convex slope – prone to erosion
• Site Class 3: moderate dry N-facing convex slope or moderate dry S-facing un-structured slope area – prone to erosion
• Site Class 4: moderate moist N-facing un-structured slope area or moderate moist S-facing concave slope – prone to erosion
• Site Class 5: moist N-facing concave slope – prone to erosion
• Site Class 4-1: moderate moist S-facing slope foot – without erosion
• Site Class 5-1: moist N-facing slope foot or plain valley bottom area – without erosion

• the satellite image/aerial photo based Digital Terrain Model/DTM, or
• on site exactly by GPS, or
• from the topographic map 1:2,500.

Here in this course is to guide you found out the site condition in your local area.

1. Select a site suitable for establish a plantation.
2. Develop a site inventory plan which include: topographical factors (elevation, slope direction, slope inclination, slope position), soil conditions (soil depth, humus thickness, soil texture, content of rocks, pH, parent rock type, groundwater level, soil moisture), plant factors (coverage, height, diameter of dominant species, major pests and diseases).
3. Conduct an investigation to the site and data analyze.
4. Complete a site classification part for the assignment 1.