The ratio of foliar nitrogen to foliar phosphorus: a determinant of leaf attributes and height in life-forms of subtropical and tropical plant communities
Ray L. Specht A C and Alison Specht BA Emeritus Professor of Botany, The University of Queensland, 107 Central Avenue, St Lucia, Qld 4067, Australia.
B Program Manager, Terrestrial Ecosystem Research Network, The University of Queensland, Queensland 4072, Australia.
C Corresponding author. Email: r.specht@uqconnect.net
Australian Journal of Botany 58(7) 527-538 https://doi.org/10.1071/BT07110
Submitted: 12 June 2007 Accepted: 21 July 2010 Published: 27 October 2010
Abstract
In the species-rich overstorey of tropical and subtropical closed-forests (rainforests), a series of life-forms (emergent trees, canopy trees, subcanopy trees, mid-stratum trees and shrubs, interlaced with lianes) of increasing basal area, height and foliage attributes (leaf area, leaf specific weight and internode length) develop in equilibrium with aerodynamic fluxes (frictional, thermal, evaporative ± atmospheric salinity) in the atmosphere as it flows turbulently over and through a plant community. In both closed-forest and open-forest communities in eastern Australia, the translocation of high-energy nitrogen and phosphorus compounds into developing leaves – during the driest season of the year – increases as soil water becomes more available in the climatic gradient from the subhumid to the per-humid zone. Foliage attributes (leaf area and leaf specific weight) of vertical shoots are determined by the rate of input of high-energy compounds into developing shoot apices. Increasing nutrient input in the transpiration stream results in a greater number of leaves (with similar leaf specific weights) on vertical foliage shoots. The leaf area index of the tree is thus enhanced and leads to increased biomass, basal area and height at maturity. In each life-form within a closed-forest, the size of the root system is allometrically related to aboveground attributes. The ability of the root system to explore available nitrogen and phosphorus stored in the surface soil thus determines the attributes of developing foliage shoots in each of these life-forms. Both leaf areas and leaf specific weights decrease from maxima in canopy trees to leaves of subcanopy and mid-stratum trees in the milder climate under the dense structure of per-humid rainforests. In contrast, in the open-structured, subhumid rainforests, although leaf areas decrease in the gradient from canopy to mid-stratum trees – all exposed to direct solar radiation – leaf specific weights increase as temperatures in the boundary layer around growth-apices increase. The production of nitrate ions in soil, exposed to solar radiation in gaps, increases the uptake of nitrogen into leaves of pioneer trees. Larger and thinner leaves, with higher foliar N : P ratios and nitrate reductase activity, result in and enable rapid regeneration of the rainforest.
Acknowledgements
Many scientists have investigated the dynamic processes in tropical and subtropical rainforests in Australia. The subtropical rainforest vegetation of south-eastern Queensland has been studied by the following scientists: Len Webb, Geoff Tracey, Bill Williams, Paul Forster and Peter Bostock (floristics), and Elwyn Hegarty (structure and phenology). Both rainforest and eucalypt open-forest–woodland vegetation in south-eastern Queensland has been examined by the following scientists: Ray Specht, Margarita Arianoutsou of the University of Athens and Santi Sabaté of the University of Barcelona (foliage attributes), Carles Gracia of the University of Barcelona (Chlorophyll a and b ratios), Ray Specht, Phil Rundel of University of California, LA, and Roger Reeves of Massey University, NZ (foliar nutrients), Phil Rundel and George Stewart (carbon isotope ratios), David Lamb (soil nitrogen dynamics), and George Stewart of the University College, London (nitrate reductase activity). The subtropical rainforests of north-eastern New South Wales have been studied by the following scientists: Alec Floyd, Len Webb, Geoff Tracey, Bill Williams and Alison Specht (floristics), Alison Specht (structure and phenology), Alison Specht (foliage attributes), Alison Specht, John Turner, M. J. Lambert and Len Webb (foliar nutrients), and Alison Specht (soil nitrogen dynamics and nitrate reductase activity). The ‘dry rainforests’ in wet-watered sites in the serpentinite outcrop of central Queensland have been studied by the following scientists: George Batianoff and Ray Specht (floristics and structure), Ray Specht (foliage attributes), Alison Specht and Roger Reeves (foliar nutrients), and George Stewart (carbon isotope ratios). The tropical rainforests of north-eastern Queensland have been studied by the following scientists: Len Webb, Geoff Tracey and Bill Williams (floristics), Geoff Stocker and Greg Unwin (structure), Heather Brasell (foliar nutrients), and David Doley, David Yates and Greg Unwin (photosynthesis). David Doley provided invaluable comments on the manuscript.
Brasell HM,
Unwin GL, Stocker GC
(1980) The quantity, temporal distribution and mineral-element content of litterfall in two forest types at two sites in tropical Australia. Journal of Ecology 68, 123–139.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
Hegarty EE
(1990) Leaf life-span and leafing phenology of lianes and associated trees during a rainforest succession. Journal of Ecology 78, 300–312.
| Crossref | GoogleScholarGoogle Scholar |
Hegarty EE
(1991) Patterns of productivity by liane and tree components of an Australian rainforest. Journal of Tropical Ecology 7, 201–214.
| Crossref | GoogleScholarGoogle Scholar |
Lamb D
(1980) Soil nitrogen mineralisation in a secondary rainforest succession. Oecologia 47, 257–263.
| Crossref | GoogleScholarGoogle Scholar |
Lambert MJ,
Turner J, Kelly J
(1989) Redistribution of nutrients in subtropical rainforest trees. Proceedings of the Linnean Society of New South Wales 111, 1–10.
Loveless AR
(1961) A nutritional interpretation of sclerophylly based on differences in the chemical composition of sclerophyllous and mesophytic leaves. Annals of Botany 25, 168–184.
|
CAS |
Loveless AR
(1962) Further evidence to support a nutritional interpretation of sclerophylly. Annals of Botany 26, 551–561.
Marshall JK
(1971) Drag measurements in roughness arrays of varying density and distribution. Agricultural Meteorology 8, 269–292.
| Crossref | GoogleScholarGoogle Scholar |
Specht A, Specht RL
(1993) Species richness and canopy productivity of Australian plant communities. Biodiversity and Conservation 2, 152–167.
| Crossref | GoogleScholarGoogle Scholar |
Specht A, Specht RL
(1994) Biodiversity of overstorey trees in relation to canopy productivity and stand density in the climatic gradient from warm temperate to tropical Australia. Biodiversity Letters 2, 39–45.
| Crossref | GoogleScholarGoogle Scholar |
Specht RL
(1972) Water use by perennial, evergreen plant communities in Australia and Papua New Guinea. Australian Journal of Botany 20, 273–299.
| Crossref | GoogleScholarGoogle Scholar |
Specht RL
(1981a) Growth indices – Their rôle in understanding the growth, structure and distribution of Australian vegetation. Oecologia 50, 347–356.
| Crossref | GoogleScholarGoogle Scholar |
Specht RL
(1983) Foliage projective covers of overstorey and understorey strata of mature vegetation in Australia. Australian Journal of Ecology 8, 433–439.
| Crossref | GoogleScholarGoogle Scholar |
Specht RL
(2001) Phosphorus toxicity and pollution: a threat to our Gondwanan heritage. Ecological Management & Restoration 2, 228–230.
Specht RL
(2007) Species richness of rainforest stands on non-serpentinite and serpentinite substrates in the Rockhampton – Marlborough area of central Queensland. Proceedings of the Royal Society of Queensland 113, 17–35.
Specht RL
(2009) Structure and species richness in wetland continua on sandy soils in subtropical and tropical Australia. Austral Ecology 34, 761–772.
| Crossref | GoogleScholarGoogle Scholar |
Specht RL, Brouwer YM
(1975) Seasonal shoot growth of Eucalyptus spp. in the Brisbane area of Queensland (with notes on shoot growth and litter fall in other areas of Australia). Australian Journal of Botany 23, 459–474.
| Crossref | GoogleScholarGoogle Scholar |
Specht RL, Morgan DJ
(1981) The balance between the foliage projective covers of overstorey and understorey strata in Australian vegetation. Australian Journal of Ecology 6, 193–202.
| Crossref | GoogleScholarGoogle Scholar |
Specht RL, Rundel PW
(1990) Sclerophylly and foliar nutrient status of mediterranean-climate plant communities in southern Australia. Australian Journal of Botany 38, 459–474.
| Crossref | GoogleScholarGoogle Scholar |
Specht RL, Specht A
(1989) Canopy structure in Eucalyptus-dominated communities in Australia along climatic gradients. Acta Oecologica Oecologia Plantarum 10, 191–202.
Specht RL, Yates DJ
(1990) Climatic control of structure and phenology of foliage shoots in dicotyledonous overstorey and understorey strata of subtropical plant communities in eastern Australia. Acta Oecologica 11, 215–233.
Specht RL,
Salt RB, Reynolds S
(1977) Vegetation in the vicinity of Weipa, north Queensland. Proceedings of the Royal Society of Queensland 88, 17–38.
Specht RL,
Clifford HT,
Arianoutsou M,
Bird LH,
Bolton MP,
Forster PI,
Grundy RI,
Hegarty EE, Specht A
(1991a) Structure, floristics and species richness of plant communities in south-east Queensland. Proceedings of the Royal Society of Queensland 101, 27–78.
Specht RL,
Yates DJ,
Sommerville JEM, Moll EJ
(1991b) Foliage structure and shoot growth in heathlands in the mediterranean-type climate of southern Australia and South Africa. Ecologia Mediterranea 16, 195–207.
Specht RL,
Batianoff GN, Reeves RD
(2006) Vegetation structure and biodiversity along the eucalypt forest to rainforest continuum on the serpentinite soil catena in a sub-humid area of central Queensland, Australia. Austral Ecology 31, 394–407.
| Crossref | GoogleScholarGoogle Scholar |
Stewart GR,
Hegarty EE, Specht RL
(1988) Inorganic nitrogen assimilation in plants of Australian rainforest communities. Physiologia Plantarum 74, 26–33.
| Crossref | GoogleScholarGoogle Scholar |
CAS |
Stewart GR,
Gracia CA,
Hegarty EE, Specht RL
(1990) Nitrate reductase activity and chlorophyll content in sun leaves of subtropical Australian closed-forest (rainforest) and open-forest communities. Oecologia 82, 544–551.
| Crossref | GoogleScholarGoogle Scholar |
Turnbull MH,
Schmidt S,
Erskine PD,
Richards S, Stewart GR
(1996) Root adaptation and nitrogen source acquisition in natural ecosystems. Tree Physiology 16, 941–948.
| PubMed |
Turner J, Kelly J
(1981) Relationships between soil nutrients and vegetation in a north coast forest, New South Wales. Australian Forestry Research 11, 201–208.
Turner J,
Lambert MJ, Kelly J
(1989) Nutrient cycling in a New South Wales subtropical rainforest. Annals of Botany 63, 635–642.
Webb LG,
Tracey JG,
Williams WT, Lance GN
(1967) The pattern of mineral nutrient return in leaf litter of three subtropical Australian forests. Australian Forestry 33, 99–110.
Webb LG,
Tracey JG, Williams WT
(1984) A floristic framework of Australian rainforests. Australian Journal of Ecology 9, 169–198.
| Crossref | GoogleScholarGoogle Scholar |
