Biomass Harvesting Impacts

Transcription

1 Biomass Harvesting Impacts H. Lee Allen ProFOR Consulting Cary, NC Progressive Forestry for Production Forests Biomass C CO 2 Conversions 1 ft 3 3 green tons wood 1 dry ton green tons 1 ton carbon = 2 dry tons biomass 1 ton carbon = 3.67 tons of CO 2 1 green ton wood (1% MC).25 ton C =.92 tons CO 2 1 ton = 2 lbs 1

2 Biomass Harvesting Questions about Sustainability and Nutrition Will repeated harvest of timber crops deplete soil organic matter and nutrients enough to reduce productivity? How do intensive management practices affect soil nutrient availability? How do we determine if a forest stand's growth is limited by nutrients? If nutrients are limiting, what elements, rates, sources, and timing of application should be used? Managing for Sustained Productivity Requires Replacing the Nutrients Removed during Harvest 2

3 Managing for Sus ained Productivity Requires Replacing the Nutrients Removed during Harvest" Henderson Site Productivity Study Vance Co., NC Cecil soil 22 year old loblolly pine, second rotation plantation Pine 4 trees/acre, 14 ft 2 /acre, 22 ft 3 /acre, Site index (25 years) = 6 ft Hardwoods 125 trees/acre, 42 ft 2 /acre, 9 ft 3 /acre Established

4 Biomass and Nutrient Content (Winter) Henderson Second Rotation Plantation Component Biomass N P K Ca Mg tons/acre lbs/acre AG Pine AG Hardwood AG Understory Total AG Vegetation Forest Floor Soil Total From Tew, Morris, & Allen, 1986; Soil Total N, Mehlich III extractable P, K, Ca, Mg top 24 inches Treatments Applied CHOP & BURN (CH) SHEAR/PILE& DISK (DI) COMPLETE TREE (CT) No Vegetation Vegetation No Vegetation Vegetation STEMWOOD (ST) No Vegetation Vegetation No Vegetation Vegetation 4

5 Design and Treatments Harvest (winter 198/81) Pine Stemwood vs Above ground Pine and Hwd Site Preparation Chop (and burn)(ch) vs Shear, Pile, Disc (DI) Vegetation None (NO) and Complete 1st 5 years + (HR) 49.2 x 98.4 ft (15 x 3 m) plots measurement plots 1st generation improved loblolly planted March x 9.8 ft (2 x 3 m) spacing (75 planted trees/plot) Henderson Site Productivity Study Harvest 22 years Biomass (dry tons/acre) C (dry tons/acre) Stem Only Complete Tree Additional Removal (tops) % Increase in Removal Nutrients Removed lbs/dry ton of stem Nutrients Removed lbs/dry ton of tops N (lbs/acre) P (lbs/acre) K (lbs/acre) Ca (lbs/acre) Mg (lbs/acre) Adapted from Tew, Morris, & Allen,

6 Henderson Site Productivity Study Biomass and Nutrient Removals Before Harvest Harvest Site Prep Stem Only CB Complete Tree CB Stem Only SPD Complete Tree SPD Adapted from Tew, Morris, & Allen, 1986 Biomass N P K Ca Mg tons/acre lbs/acre Vegetation, Forest Floor and Mineral Soil % Removal What happened after 22 years? 6

7 CHNO age 5 DINO age 5 CHHR age 5 DIHR age 5 7

8 8 Henderson Site Productivity Study 3 rd Rotation Pine Dominant Height (feet) DIHR CHHR DINO CHNO Age (years) Allen et al, in preparation 8

9 CUMULATIVE VOLUME (ft 3 /acre) Henderson Site Productivity Study 3 rd Rotation Pine DIHR CHHR DINO CHNO Allen et al, in preparation AGE (years) Stand Biomass (green tons/acre) Henderson Site Productivity Study Stand Biomass Age Hardwood Pine Roots Miller, Allen, & Maier, CJFR (26) CHNO DINO CHHR DIHR 9

10 Henderson Site Productivity Study Comparison of 2 nd and 3 rd rotations 14 pine biomass 3 rd rotation (tons/acre) CHNO CHVC DINO DIVC Allen et al, in preparation pine biomass 2 nd rotation (tons/acre) Managing for Sustained Productivity Requires Replacing the Nutrients Removed during Harvest 1

11 Big Questions What is the capacity of soils to supply nutrients to forest stands? What nutrient(s) already limit stand growth? Can fertilization be used to effectively ameliorate existing and future nutrient limitations? 18 Area fertilized annually acres x N+P Established P Established At Planting

12 Eight Year Cumulative Response to N and/or P Additions in Established Loblolly Pine Plantations 6 Volume response ft 3 /acre P Rate lbs/acre Nitrogen Rate lbs/acre Number of Studies Frequency Distribution of Annual Growth Response to additions of 2N+P in Established Stands Annual Volume Response ft 3 /acre/yr 12

13 Is Biomass Harvesting Sustainable? What we know > Biomass removal >> nutrient removal increase % of nutrient rich crown material easily calculated biomass x nutrient conc. One biomass harvest does not reduce subsequent production Most pine plantations in the SEUSA are responsive to nutrient (N,P,K,B) additions. Biomass Harvestings Uncertainties Will repeated biomass harvests deplete soil organic matter and nutrients enough to reduce productivity? Will mixed pine hardwood or hardwood stands respond to nutrient additions? What other management options do we have to increase nutrient availability in addition to fertilization? 13

14 Silviculture for the 21 st Century Manipulation of: Species composition Species, genotypes, clones Stocking Quantity and distribution of crop and non crop vegetation Site resource availability Quantity and quality of the soil rooting environment to optimize value for the current landowner and future generations 14