Data Collection and Estimation

In 2004 NEFD questionnaires were sent to all 120 forest owners and managers with at least 1000 hectares of planted production forest. The major questions contained in this questionnaire are shown in Appendix 2. A 99 percent response rate to the survey was achieved.

For forest owners with less than 1000 hectares, the data collected in the comprehensive 2003 NEFD survey continue to be used. Aside from new planting it is assumed that relatively minor changes in area will have occurred from these forest owners during the 12-month period ending 31 March 2004. For details of the 2003 NEFD survey refer to A National Exotic Forest Description as at 1 April 2003.

AgriQuality New Zealand recently completed 15 regional Small Forest Grower Surveys on behalf of MAF. These surveys collected data from smaller forest growers not represented in the NEFD survey. The results from the AgriQuality surveys have been incorporated into the 2004 NEFD database. Details on the methods used by AgriQuality are available in Small Forest Grower Survey Report (AgriQuality NZ, April 2005). This information replaces the results to the 1995 Statistics New Zealand Small Grower Survey which have been used in the NEFD database up until now.

New planting not directly captured in the 2004 NEFD survey has been imputed.

New Planting Imputation

Since 1992 the Ministry has conducted a new planting survey. This new planting survey measures the sale of planting stock from commercial forest nurseries. An estimate of national new planting is calculated from the numbers of seedlings sold. Details of how this survey is operated are described in Predicting and Measuring New Planting from Nursery Surveys (Eyre, 1995). This new planting survey provides the most complete indicator of the area of new forest established each year. The methodology was reviewed in 2003 (Review of New Forest Planting Estimates (Manley et al, 2003)).

It has been recognised that the areas of new planting were substantially underestimated in the NEFD databases prior to 1995.

In the 2004 NEFD database, adjustments have been made to the areas established between 1992 and 2003 to account for the areas of new planting not collected in the postal surveys. This same method of imputation has been used in the compilation of the NEFD databases since 1995.

Table 2: Comparison of Total New Planting with New Planting Collected in Postal Surveys (hectares)

  Year of Planting
  1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Total new planting1 50 200 61 600 98 200 73 900 83 600 63 700 51 200 40 000 33 600 30 100 22 100 19 900
New planting collected in postal surveys2 29 700 39 800 69 600 68 600 65 500 45 600 36 800 26 800 25 300 18 700 15 200 11 800
New planting adjustments3 20 500 21 800 28 600 15 300 18 100 18 100 14 400 13 200 8 300 11 400 5 900 8 100

Notes:

  1. As estimated from the nursery surveys undertaken by the Ministry of Forestry and the Ministry of Agriculture and Forestry.
  2. The area of planted forest as collected in postal surveys excluding restocking. Any new information captured in any subsequent year is deducted from the imputation in the appropriate year.
  3. The difference between total new planting and new planting collected in postal surveys.

The national new planting adjustments were distributed into territorial authorities using the proportions indicated from the new planting collected in the postal survey. Table 12 shows how the adjustments for recent new planting have been distributed across territorial authorities.

Within each territorial authority the imputed new planting was allocated to NEFD crop types using the postal survey results in the following way:

  • The imputed new planting was allocated into species groups based on the relative proportions of each species group within the 1 to 5 year age class.


  • For radiata pine the imputed new planting was allocated into the four NEFD tending regimes, based on the relative proportion of each of these tending regimes across all the age classes. All the Douglas-fir imputed new planting was allocated to the "without production thinning" tending regime.

Historically imputed new planting estimates are revised each year based on any new information on the area of young forest captured directly in the NEFD survey. This year, there have been extensive revisions as a consequence of the Small Forest Growers' Survey, which captured areas previously estimated (see Table 3).

Contact for Enquiries

MAF Information Services
Pastoral House
25 The Terrace
PO Box 2526
Wellington, NEW ZEALAND

Fax: +64 4 894 0721
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