scholarly journals Effects of Above- and Below-Ground Interactions of Plants on Growth of Tree Seedlings in Low-Elevation Tropical Rainforests on Hainan Island, China

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 905
Author(s):  
Xinghui Lu ◽  
Runguo Zang ◽  
Yue Xu ◽  
Shouchao Yu ◽  
Hongxia Zhao
Keyword(s):  
Seedling Growth ◽  
Growth Rates ◽  
Hainan Island ◽  
Tropical Rainforests ◽  
Tree Seedlings ◽  
Evergreen Species ◽  
Vegetation Removal ◽  
Below Ground ◽  
Monsoon Rainforest ◽  
Tropical Lowland Rainforest

Understanding the effects of above- and below-ground interactions on seedling growth is pivotal for identifying the key drivers of secondary forest succession. However, it is still unclear whether the effects of above- and below-ground interactions of plants are consistent for seedling growth of deciduous and evergreen species. There are two types of broadleaved forests (i.e., tropical lowland rainforest and tropical deciduous monsoon rainforest) in the low-elevation (<800 m) areas of Hainan Island in China. Here, 32 seedling transplanting plots (1 × 1 m2) were established in the tropical lowland rainforest and the tropical deciduous monsoon rainforest, respectively. Four treatments (each with 16 replicates) were carried out to reduce above- and below-ground interactions of plants in the low-elevation forests: removal of vegetation (R), root trenching (T), removal of vegetation and root trenching (R + T), and no vegetation removal or trenching (as the control) (C). Seedlings of four deciduous species and four evergreen species were planted to observe their performance in the experiments. The relative growth rates (RGR) of the seedlings were measured to distinguish the relative effects of above- and below-ground interactions. The photosynthetically active radiation (PAR) was measured as a proxy for above-ground interaction and the root biomass was used as a proxy for below-ground interaction. The relationships between seedling RGR and PAR/root biomass were examined. Results showed that: (1) R and R+T treatments significantly increased the seedlings RGR, but T treatment had no effect on the RGR; (2) the growth rates of deciduous species were greater than those of the evergreen species; and (3) seedling growth rates were increased with more PAR. Our study suggests that above-ground vegetation removal had a stronger effect than trenching on the growth and assembly of tree seedlings in the low-elevation tropical rainforests.

scholarly journals Nutrient deposition enhances post-fire survival in non-N-fixing savanna tree seedlings

2018 ◽  
Author(s):  
Varun Varma ◽  
Mahesh Sankaran
Keyword(s):  
Community Composition ◽  
Seedling Growth ◽  
Growth Rates ◽  
Seedling Survival ◽  
Tropical Dry Forest ◽  
Forest Tree ◽  
Dry Forest ◽  
Tree Seedlings ◽  
Tree Seedling ◽  
Nutrient Deposition

AbstractNutrient deposition can modify plant growth rates and potentially alter the susceptibility of plants to disturbance events, while also influencing properties of disturbance regimes. In mixed tree-grass ecosystems, such as savannas and tropical dry forests, tree seedling growth rates strongly influence the ability of seedlings to survive fire (i.e. post-fire seedling survival), and hence, vegetation structure and tree community composition. However the effects of nutrient deposition on the susceptibility of recruiting trees to fire are poorly quantified. In a field experiment, seedlings of multiple N-fixing and non-N-fixing tropical dry forest tree species were exposed to nitrogen (N) and phosphorus (P) fertilisation, and fire. We quantified nutrient-mediated changes in a) mean seedling growth rates; b) growth rates of the fastest growing individuals and c) post-fire seedling survival. N-fixers had substantially higher baseline post-fire seedling survival, that was unaffected by nutrient addition. Fertilisation, especially with N, increased post-fire survival probabilities in non-N-fixers by increasing the growth rates of the fastest growing individuals. These results suggest that fertilisation can lead to an increase in the relative abundance of non-N-fixers in the resprout community, and thereby, alter the community composition of tropical savanna and dry forest tree communities in the long-term.

Differential determinants of growth rates in subtropical evergreen and deciduous juvenile trees: Carbon gain, hydraulics and nutrient use efficiencies

2020 ◽  
Author(s):  
Jin-Hua Qi ◽  
Ze-Xin Fan ◽  
Pei-Li Fu ◽  
Yong-Jiang Zhang ◽  
Frank Sterck
Keyword(s):  
Tree Growth ◽  
Growth Rates ◽  
Tree Species ◽  
Nutrient Use Efficiency ◽  
Height Growth ◽  
Deciduous Tree ◽  
Carbon Gain ◽  
Evergreen Species ◽  
Nutrient Use ◽  
Use Efficiency

Abstract Growth rate varies across plant species and represents an important ecological strategy for competition, resource use and fitness. However, empirical studies often show a low predictability of functional traits to tree growth. We measured stem diameter and height growth rates of 96 juvenile trees (2 to 5 m tall) of eight evergreen and eight deciduous broadleaf tree species over three consecutive years in a subtropical forest in southwestern China. We examined the relationships between tree growth rates and 20 leaf/stem traits that associated with carbon gain, stem hydraulics and nutrient use efficiency, as well as the difference between evergreen and deciduous trees. We found that cross-species variations of stem diameter/height growth rate can be predicted by leaf photosynthetic capacity, leaf mass per area, xylem theoretical specific hydraulic conductivity, wood density and photosynthetic nutrient use efficiencies. Higher leaf carbon assimilation and lower leaf/stem constructing costs facilitate deciduous species to be more resource acquisitive and consequently faster growth within a relatively shorter growing season, whereas evergreen species exhibit a more conservative strategies and thus slower growth. Further, stem growth rates of evergreen species showed were more dependence on leaf carbon gains, whereas stem hydraulic efficiency were more important for deciduous tree growth. Our results suggest that physiological traits (photosynthesis, hydraulics, nutrient use efficiency) can predict tree diameter and height growth of subtropical tree species. The differential resource acquisition and use strategies and their associations with tree growth between evergreen and deciduous trees provide insights in explaining the co-existence of evergreen and deciduous tree species in subtropical forests.

Dormancy, germination and seedling growth of two Kalaharian perennials of the genus Harpagophytum (Pedaliaceae)

1988 ◽  
Vol 4 (2) ◽  
pp. 185-198 ◽  
Author(s):  
W. H. O. Ernst ◽  
T. Tietema ◽  
E. M. Veenendaal ◽  
R. Masene
Keyword(s):  
Gibberellic Acid ◽  
High Temperatures ◽  
Seedling Growth ◽  
Seed Coat ◽  
Growth Rates ◽  
Natural Conditions ◽  
Relative Growth ◽  
Relative Growth Rates ◽  
Respiration Rates ◽  
Drought Avoidance

ABSTRACTDormancy and germination ecology of two Harpagophytum species (Pedaliaceae) from an open Acacia savanna in Botswana were investigated. The maintenance of dormancy is governed partly by the seed coat but mainly by the endosperm and the embryo itself, as demonstrated by removal of the endosperm. Dissemination of the seed from the fruit can be delayed for several years without affecting the viability of the embryo, due to very low respiration rates.Germination can be enhanced slightly by high temperatures under natural conditions, and by gibberellic acid or removal of the endosperm under laboratory conditions. Relative growth rates for both Harpagophytum species are lower than for subtropical grasses and legumes, due to a strong investment in root and tuber biomass. Germination and seedling growth is discussed in relation to the drought avoidance syndrome and the animal disperser syndrome.

scholarly journals Disturbance is required for CO2-dependent promotion of woody plant growth in grasslands

2010 ◽  
Vol 37 (6) ◽  
pp. 555 ◽  
Author(s):  
Beth R. Loveys ◽  
John J. G. Egerton ◽  
Dan Bruhn ◽  
Marilyn C. Ball
Keyword(s):  
Plant Growth ◽  
Elevated Co2 ◽  
Seedling Growth ◽  
Woody Plant ◽  
Competitive Inhibition ◽  
Bare Soil ◽  
Tree Seedlings ◽  
Soil Resources ◽  
Canopy Area ◽  
Thermal Interference

The relative effects of disturbance (here defined as bare soil), competition for edaphic resources, thermal interference and elevated [CO2] on growth of tree seedlings in grasslands were studied under field conditions. Snow gum (Eucalyptus pauciflora Sieb. ex Spreng.) seedlings were grown in open-top chambers flushed with either ambient or elevated [CO2] from March 2004 to January 2005 (autumn to summer). These seedlings were planted into three treatments (i.e. bare soil, soil covered with straw or soil supporting a sward of live pasture grass) to separate effects of grass on seedling growth into those due to competition with grass for soil resources or to alteration of the thermal environment caused by a grassy surface (Ball et al. 2002). After the first major autumn frost, seedlings growing in competition with grass lost 59% of their canopy area, whereas those growing in bare soil or straw suffered negligible damage. These results reveal the complexity of competitive inhibition of plant growth in which ineffective competition for resources such as soil water enhances the vulnerability of the plant to abiotic stress, in this case frost. Tree seedlings growing in bare soil and straw commenced growth earlier in spring than those growing in competition with grass, where soil moisture was consistently lowest. Under ambient [CO2], growth was greater in bare soil than in straw, consistent with thermal interference, but these differences disappeared under elevated [CO2]. Elevated [CO2] significantly increased biomass accumulation for seedlings growing in bare soil and straw treatments, but not in grass. Thus, elevated [CO2] alleviated apparent thermal interference of seedling growth in spring but did not overcome adverse effects on seedling growth of either competitive reduction in soil resources or competitive enhancement of environmental stress. Nevertheless, elevated [CO2] could promote invasion of grasslands due to enhancement of woody plant growth in bare soil created by disturbances.

A study of phosphorus nutrition and water supply on the early growth and survival of buffel grass grown on a sandy red earth from south-west Queensland

1975 ◽  
Vol 15 (73) ◽  
pp. 239 ◽  
Author(s):  
EK Christie
Keyword(s):  
Seedling Growth ◽  
Growth Rates ◽  
Phosphorus Concentration ◽  
Root Penetration ◽  
Buffel Grass ◽  
Phosphorus Absorption ◽  
South West ◽  
Red Earth ◽  
Drought Survival ◽  
Phosphorus Application

The influence of phosphorus application on the growth and drought survival of buffel grass on a sandy red earth in south west Queensland was studied in a series of pot experiments. An omission nutrient trial showed phosphorus was the principal nutrient limiting seedling growth, the severity of the deficiency increasing with time. A further pot experiment showed that at rates greater than 24 kg P ha-1 luxury consumption occurred. The critical phosphorus concentration for the plant was estimated to be 0.26 per cent. The available (0.01 NH2SO4 extractable) soil phosphorus concentration corresponding to this critical tissue concentration was 25 p.p.m. Beyond the 2-leaf seedling stage, the seedling depended increasingly on external phosphorus for growth. Under conditions of phosphorus deficiency, phosphorus absorption rates were insufficient to maintain tissue phosphorus at the concentrations necessary for healthy growth, and relative growth rates were low. In the presence of phosphorus, absorption and growth rates increased. Maturity of phosphorus deficient plants was characteristically delayed but with little yield loss. The addition of phosphorus increased seedling growth rate, root development and drought survival. The depth of root penetration is considered to be the major factor responsible for survival.

Biology of Fire Ephemerals of the Sandplains of the Kwongan of South-Western Australia

1985 ◽  
Vol 12 (6) ◽  
pp. 641 ◽  
Author(s):  
JS Pate ◽  
NE Casson ◽  
J Rullo ◽  
J Kuo
Keyword(s):  
Life Cycle ◽  
Reproductive Biology ◽  
Seedling Growth ◽  
Western Australia ◽  
Growth Rates ◽  
Dry Matter ◽  
Dry Weight ◽  
Growing Season ◽  
Adaptive Significance ◽  
Sexually Dimorphic

The growth, longevity, mineral relationships and reproductive biology of 18 species of fire ephemerals were examined in sclerophyllous shrubland, located mainly within the Jurien : Badgingarra region of the Northern Sandplains of the kwongan of SW. Australia. Ten of the species were monocarpic, completing their life cycle within the 6-8 month winter growing season after a summer or autumn fire. The remaining species were polycarpic, commencing reproduction in their second season and surviving and reproducing for a further two to eight seasons (depending on species). Detailed study was made of growth and dry matter allocation in the dioecious, sexually dimorphic, polycarpic species Tersonia brevipes (Gyrostemonaceae). Monocarpic species tended to produce smaller seeds, and exhibited greater seed output per unit biomass and higher harvest indices for dry matter and minerals than polycarpic species. Certain monocarpic species showed great plasticity in final dry weight, e.g. a 2700-fold difference between largest and smallest individuals in a sample of 250 plants of Stipa elegantissima (Poaceae), and a 180-fold range in a similarly sized sample of Macarthuria apetala (Aizoaceae). The fire ephemerals studied generally exhibited faster seedling growth rates, greater concentrations of P and N (but not of Ca, Mg and K) in seedling dry matter, but usually lesser concentrations of P and N (but not of Ca, Mg and K) in seed dry matter than in cohabiting obligate seeder or sprouter species with potential life spans exceeding 15 years. The above-mentioned features of fire ephemerals are suggested to be of special adaptive significance within the context of exploitation of transiently non-limiting habitat resources immediately following fire.

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