The reproductive allocation (RA) of Haloxylon ammodendron (C.A. Mey.) Bunge was studied in different edaphic types of the Gurbantünggüt desert. Results showed that the RA had significant
hierarchical variation. Both RA and reproductive output (RO) were size-dependent, and relationships between above-ground total
biomass and RA/RO were represented by linear or exponential equations. The RA in loam increased with aboveground total biomass
increased. However, the RA showed a faint decrease in gravel soil and significant decrease in sandy soil with aboveground
total biomass increased. Then, the stability of the population was analyzed in three edaphic types.
H. ammodendron (C.A. Mey.) Bunge–Edaphic type–Reproductive allocation–Size-dependence
[Show abstract][Hide abstract] ABSTRACT: In plants, investment in height improves access to light, but incurs costs in construction and maintenance of the stem. Because the benefits of plant height depend on which other height strategies are present, competition for light can usefully be framed as a game-theoretic problem. The vertical structure of the world's vegetation, which is inefficient for plant growth, can then be understood as the outcome of evolutionary and ecological arms races. In addition, game-theoretic models predict taller vegetation on sites of higher leaf area index, and allocation to reproduction only after an initial period of height growth. However, of 14 game-theoretic models for height reviewed here, only one predicts coexistence of a mix of height strategies, a conspicuous feature of most vegetation. We suggest that game-theoretic models could help account for observed mixtures of height strategies if they incorporated processes for coexistence along spectra of light income and time since disturbance.
[Show abstract][Hide abstract] ABSTRACT: We excavated soil to study root distribution in Haloxylon ammodendron seedlings grown with different amounts of irrigation (35, 24.5 and 14 kg water for each plant each time) in the hinterland
of the Taklimakan Desert. The results indicated that: 1) With decreasing irrigation amounts, the root biomass tended to be
distributed in deeper soil layers. Underground biomass had a significantly negative logarithmic relationship with soil depth
under different irrigation amounts. 2) Maximum horizontal spread of roots was twice that of vertical root spread, and horizontal
distribution of root biomass was similar under all irrigation amounts. 3) Vertical distribution of fine roots was nearly consistent
with vertical changes in soil moisture, and all had a unimodal curve; but peak values of fine root biomass in different soil
layers varied with different irrigation amounts. The smaller the amount of irrigation, the deeper were the fine roots concentrated
in soil layers. 4) Root length, root surface area and root volume all exhibited a unimodal curve under different irrigation
amounts; the less the irrigation amount, the deeper the peak values appeared in soil layers. 5) Rootshoot ratio and ratio
of vertical root depth to plant height both increased as irrigation amounts decreased.
Frontiers of Forestry in China 02/2009; 4(1):60-67. DOI:10.1007/s11461-009-0002-x
[Show abstract][Hide abstract] ABSTRACT: Allocation is one of the central concepts in modern ecology, providing the basis for different strategies. Allocation in plants has been conceptualized as a proportional or ratio-driven process (‘partitioning’). In this view, a plant has a given amount of resources at any point in time and it allocates these resources to different structures. But many plant ecological processes are better understood in terms of growth and size than in terms of time. In an allometric perspective, allocation is seen as a size-dependent process: allometry is the quantitative relationship between growth and allocation. Therefore most questions of allocation should be posed allometrically, not as ratios or proportions. Plants evolve allometric patterns in response to numerous selection pressures and constraints, and these patterns explain many behaviours of plant populations.In the allometric view, plasticity in allocation can be understood as a change in a plant's allometric trajectory in response to the environment. Some allocation patterns show relatively fixed allometric trajectories, varying in different environments primarily in the speed at which the trajectory is travelled, whereas other allocation patterns show great flexibility in their behaviour at a given size. Because plant growth is often indeterminate and its rate highly influenced by environmental conditions, ‘plasticity in size’ is not a meaningful concept. We need a new way to classify, describe and analyze plant allocation and plasticity because the concepts ‘trait’ and ‘plasticity’ are too broad. Three degrees of plasticity can be distinguished: (1) allometric growth (‘apparent plasticity’), (2) modular proliferation and local physiological adaptation, and (3) integrated plastic responses. Plasticity, which has evolved because it increases individual fitness, can be a disadvantage in plant production systems, where we want to optimize population, not individual, performance.
Perspectives in Plant Ecology Evolution and Systematics 12/2004; 6(4-6):207-215. DOI:10.1078/1433-8319-00083 · 3.61 Impact Factor
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