docA peek down under: structural root architecture of some New
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A peek down under: structural root architecture of some New
A peek down under: structural root architecture of some New Zealand native plants Chris Phillips Mike Marden, Jagath Ekanayake & Alex Watson Disclaimer We are not botanists! We are not plant ecologists! We are on the edge! We play in the dirt! We are statistically challenged! Wadda ya know? In this talk…. • • • • • • Context – 3 strands What we’ve done – 2 trials How we do it What we’ve found How we use the information Wrap up Context 1 – hillslope stability • • • • Plantation forests for erosion control Pinus radiata and other exotics 1980’s to 1990’s Effectiveness, densities, harvesting etc Context 1 – hillslope stability Context 1 – hillslope stability Context 1 – hillslope stability Context 2 – river bank stabilisation • • • • Off the hills and into the rivers – ICM Riparian restoration/rehabilitation efforts Natives vs exotics, Ecology vs function Performance, build the K base Context 2 – river bank stabilisation Context 3 – Carbon & SLM • MAF – Govt policies - convergence • Climate change mitigation & Sustainable land management (SLM) >> HCE • What to use, how effective, how much C, what rate, where, management etc The Big Question? Can our New Zealand native plants perform E & SC functions as well as introduced plants? In geotechnical terms, how do we quantify the benefits of vegetation to soil stabilisation? With roots Without roots Shear displacement What we’ve been doing • Exotic species • 2 native trials • 1 MSc. on Cordyline What we’ve been doing - natives Riparian plant trial Common name Karamu Ribbonwood Kowhai Lemonwood Kohuhu Lacebark Mapou Fivefinger Cabbage tree Rewarewa Manuka Tutu Marden, Rowan, Phillips (2007; 2005) Phillips & Marden (2006) Podocarp trial Cabbage trees Common name Kauri Rimu Kahikatea Miro Totara Matai Puriri Titoki Sedge grass NZ Mountain flax Toe toe Still in progress Czernin (2002) Czernin & Phillips (2005) How we do it The old The hard The new What we’ve found • • • • • • General growth patterns Biomass Root length Root depth Site occupancy Root strength Root architecture Root definitions Root bole Lateral Sinker Sinker Taproot Root architecture Tree root forms • plateroot • heartroot • taproot What we’ve found – growth Cabbage tree (Cordyline australis) 25 13 7 5 Czernin (2002) Czernin & Phillips (2005) What we’ve found – growth (Psuedopanax arboreus) 3.35 m m m 1 year old 2 year old 3 year old 4 year old What we’ve found – growth Totara 4 yr old Kauri 1m 0 What we’ve found – growth Toe toe 3 year olds Kahikatea & Puriri Flax Carex 4m 1m What we’ve found – root spread 5 year old Pittosporum tenuifolium (kohuhu) Coprosma robusta (karamu) le m tu tu on w oo d a re pou w ar e fi v wa e. fin ge m an r uk ka a ra m ko u w la hai ca ceb bb a a g rk e. tre ko e rib hu bo h u nw oo d m Root Spread (m) What we’ve found – root spread Mean max. root spread – 5 year old 4 3 2 1 0 5 10 15 20 25 30 35 40 45 50 fiv e. fi u ca .tr ee oo d ge w u bo n bb a rib ka ra m ng er ko hu hu ko w ha i le m on w o m an od uk a re w ar ew a la ce ba rk tu tu 0 ap o (cm) m What we’ve found – root depth Mean max. root depth – 5 year old What we’ve found – root depth Ribbonwood Cabbage tree ou e fiv wa e. fin ge m an r uk ko a w ha la ce i ba r ko k le hu hu m on w oo ka d rib ram bo u nw oo d ca bb tutu ag e. tre e ar ap 14 12 10 8 (kg) 6 4 2 0 2 4 re w m What we’ve found – biomass 5 year old Above-ground Below-ground What we’ve found – root length 3 year old - woody What we’ve found – root length 3 year old - all What we’ve found – root length 3-5 year old - all What we’ve found – variation What we’ve found – variation What we’ve found – variation What we’ve found – variation 5 year old - woody Data range – max, mean, min ow ew ve f in ge r am ah i C K ar am u Willows 30 - 125 MPa Tu tu ar ew ab a ba g M e ou tr nt ee ai n be ec h D ou gl as R fir ib bo nw oo R ad d ia ta Le pi ne m m on w oo d R Fi K ha i M an uk a1 M an uk aR 2 ed be ec h K an uk a K oh uh u K at a La ce ba H rk ar d be ec h R Mean max. tensile strength (MPa) What we’ve found – root tensile strength (1-4 mm diameter) Riparian plant trial Old FRI data 60 50 40 Exotics 30 20 10 0 Watson & Marden (2005) How we use it – Knowledge delivery http://icm.landcareresearch.co.nz/ How we use it – management Planting types – radiata pine 3 yr old Watson & Tombleson (2004) How we use it – Allometry Cabbage tree root depth 200 y = 4.8813x 2 r = 0.9617 Rooting depth (cm) 175 150 125 100 75 50 11 yr Gisborne plant trial 25 0 0 10 20 30 Mean root collar diameter (cm) 40 How we use it – relative root reinforcement “Window of vulnerability” 1. Kanuka 16000 spha 2. Radiata 1250 spha 3. Radiata 800 spha 4. Radiata 500 spha Watson, Phillips, Marden (1999) How we use it – Models Root site occupancy 100% root site occupancy How we use it – Models Root site occupancy What about these bits? 100% root site occupancy Poplars 5 yr Cabbage tree ? ? ? 7 yr 4 yr 8 yr 25 yr Czernin & Phillips (2005) Totara ? 9.5 yr ? McIvor et al (2007) 4 yr Marden & Phillips (unpub.) How we use it – root site occupancy model “Effective” root spread radius 100% ? ? Site occupancy 0% Mean maximum root length radius Root reinforcement index (RFI) = Root surface area Root spread area Effective root spread measured & predicted using model equation 5-Finger 5-Finger Effective Root Spread distance from stump (cm) Cabage_Tree 120 Cabage tree Karamau Karamau 100 Kohuh Kohuhu 80 Kowhai Kowhai Lacebark 60 Lacebark Lemonwood 40 Lemonwood manuka 20 Manuka Mapou Mapou 0 2 3 4 5 Time (years) Rewarewa Rewarewa Ribbonwood Ribbonwood b c y = a + 0.5 + exp(x) x Tutu How we use it – root site occupancy & density Site occupancy (%) for planting density 1m x 1m 5-Finger Cabage tree Site occupancy (%) 100 Karamau Kohuhu Kowhai 75 Lacebark Lemonwood Rewarewa Ribbonwood Tutu Mapou 50 25 2 3 4 5 Time (years) 6 7 How we use it – root site occupancy & density Site occupancy (%) for planting density 2m x 2m 100 5-Finger Site occupancy (%) Cabage tree Karamau 75 Kohuhu Kowhai Lacebark 50 Lemonwood Rewarewa Ribbonwood 25 Tutu 0 2 3 4 Time (years) 5 6 How we use it – Visualisation Avondale Stream, existing channel, May 2004 Avondale Stream, Carex added Avondale Stream, Juncus added Avondale Stream, native trees added Existing channel has little in-stream cover Riparian grasses provide cover & spawning habitat Cabbage trees suitable above the wetland grasses Tree ferns also suitable above wetland grasses Chockie fish time… • What native had the greatest tensile root strength? • What do we call the gadget we use to expose the root systems of plants? • What’s so special about the root systems of cabbage trees? Fivefinger Wrap up • • • • • We know more than we did before Hard won data Natives can grow quickly Maybe need to look more at function Opportunities for further research – Optimisation for site reinforcement – Carbon modelling ….. – Modelling in general… “The unhealthiness in our world today is in direct proportion to our inability to see it as a whole.” Peter Senge
