Varia'on in PS rates Produc'vity and Carbon Cycling Processes governing produc'vity and energy and material flow within communi'es. Last 'me we saw considerable varia'on among plants in PS rates What is the implica'on for plant community composi'on and dynamics? What is the implica'on for food web diversity and dynamics? What governs the varia'on in produc'vity from one place to another? Tundra has low produc'vity. Boreal forests are much higher than tundra but low for moist forests. April May High produc'vity in freshwater 'dal marshes. June July August 1
Some terminology Primary Produc'on (per unit area per yr) biomass produc'on by plants Secondary Produc'on (per unit area per yr) biomass produc'on by animals Detrital Flow consump'on of all dead organic mamer Biomass = standing crop Gross PP = all produc'on Net PP = GPP - respira'on CO2 Light PS Respira'on 1 Energy and Material Flow in Ecological Communi'es Plant Biomass 3 Soil Organics 2 Detri'vores & Decomposers Heat Herbivores & Higher Trophic Levels 1. Primary Produc'on 2. Secondary Produc'on 3. Detrital Flow Biomass distribu'ons in different communi'es. Wide range in values Dispropor'onately in either roots or shoots Leaves Highest % in herbs Next in shrubs Next in trop. trees Next in temp. trees evrgr>>decid Net Primary Produc'on varies by climate/communi'es Wetlands>terrestrial Tropical>temperate Evergreen>Deciduous Forests>grasslands Average ANPP for 11 sites in the LTER network Physical Environmental Aspects Governing Produc'vity (A) Long-term average (+SE) ANPP for 11 sites in the LTER network (Table 1; see table for site abbreviations). The inset shows the long-term average ANPP combined into biome types. A, arctic and alpine sites (ARC and NWT); D, desert sites (SEV and JRN); G, grassland sites (SGS, KNZ, and CDR); O, old field site (KBS); F, forest sites (HFR, HBR, and BNZ). In the grassland and forest biomes, where two similar community types were included (KNZ/CDR and HFR/HBR, respectively), these were averaged first before calculation of the biome average. (B) Range in ANPP for the 11 LTER sites. The inset denotes the average range by biome. (C) Inter-annual CV for the 11 LTER sites. The inset denotes the average CV by biome. 2
Average annual precipitation and average annual ANPP for 11 LTER sites. Magnitude of relative ANPP pulses (maxima) and declines (minima) for 11 LTER sites. Arctic Tundra (ARC), AK (Tussock tundra) Bonanza (BNZ), AK (Balsam poplar forest) Cedar Creek (CDR), MN (Oak savanna grassland) Harvard Forest (HFR), MA (Mixed deciduous forest) Hubbard Brook (HBR), NH (Mixed deciduous forest) Jornada (JRN), NM (Black gramma grassland) Kellogg (KBS), MI (Successional field -ann tilled) Konza Prairie (KNZ), KS (Tallgrass prairie -ann burned) Niwot Ridge (NWT), CO (Moist alpine meadow) Sevilleta (SEV), NM (Mixed desert grassland) Shortgrass Steppe (SGS), CO (Shortgrass steppe -swale) Conceptual model: continental-scale gradients in abiotic factors like the amount and variability of precipitation interacts with biotic factors such as production potential to result in maximal temporal variability in ANPP in central U.S. biomes dominated by herbaceous plants. Nemani et al. 2003; Science 300:1560 Climate change impacts to 1999; net increase globally of 6% Global terrestrial NPP is nega0vely correlated with CO 2 growth rates Terrestrial NPP linear trends (2000-2009). Global ANPP declines, especially in Southern Hemisphere. Global terrestrial NPP is a major driver of the interannual CO 2 growth rate Inter- annual anomaly varia0on (2000-2009) of annual total global terrestrial NPP and inverted global atmospheric CO2 annual growth M Zhao, S W Running Science 2010;329:940-943 rate. M Zhao, S W Running Science 2010;329:940-943 3
Photosynthe'c Efficiency (PS as a % of solar energy) Biological Aspects Governing Produc'vity GPP vs. Leaf area dura'on Evergreen vs. Deciduous Forests Do rates of Photosynthesis directly relate to overall produc'vity? Boreal Coniferous Deciduous broadleaf Pine Temperate Coniferous Evergreen broad leaf Frequency diagrams of produc'vity of stands represen'ng a variety of forest types. Note that evergreen systems are more produc've, regardless of whether they are boreal, temperate or subtropical. Data are from Japan, from the north to the south. Evergreen vs. Deciduous Forest Produc'vity PSrates/lf area Leaf Biomass Ann. C gain Biomass Prod. 4
Ques'ons: Why do deciduous forests dominate in temperate zones? Why do evergreen forests take over at higher eleva'ons? What happens to primary produc'on? 1) Consump'on by animals, pathogens, etc (herbivory or the first stage of secondary produc'on), or 2) Consump'on of plant ajer death or ajer limerfall by detri'vores and decomposers Detrital flow Large carbon flow in communi'es Normally 90% of leaf produc'on in communi'es goes to detritus LiMer quality cri'cal influence on rates of decomposi'on influenced by % lignin % inhibitory compounds Rela've amounts of carbon and nitrogen (C:N) LiMer Produc'on Similar to primary produc'on values Why would that be the case? LiMer Quality and Decomposi'on Species Wt. Loss % in 1 yr C:N ratio Bacteria millions/g Fungi thousand s/g B/F Morus Red Mulberry 90 25 698 2650 264 Cercis Redbud 70 26 286 1870 148 Quercus White Oak 55 34 32 1880 17 Pinus Loblolly Pine 40 43 15 360 42 Secondary Produc'on (food webs) Consump'on of plants by herbivores and other associated food web flows Plant consump'on limited by plant alloca'on pamerns, herbivore defenses, etc % Leaves in different systems 1-10% in trees 20-60% in shrubs 90+% in herbs Root/shoot ra'os strong influence on types of herbivores (posi've value=more root biomass) tundra 4.75 desert 5.3 forests 0.2-0.3 5
Secondary Produc'on CO2 Light PS Respira'on 1 Energy and Material Flow in Ecological Communi'es Plant Biomass 3 Soil Organics 2 Detri'vores & Decomposers Heat Herbivores & Higher Trophic Levels 1. Primary Produc'on 2. Secondary Produc'on 3. Detrital Flow Conclusions Primary produc'on related to environmental constraints and biological characteris'cs. Slower growing plants like conifers can accumulate more leaf area and with their longer growing season can create greater primary produc'on. Secondary produc'on influenced by alloca'on pamerns of plants (woody vs. herbaceous; root vs shoot; toxicity; other morphological issues). Detrital flow and rates of turnover influenced by construc'on characteris'cs of leaves like % lignin, by levels of secondary compounds and toxins, and by overall C:N ra'os. 6