Comparative studies of the response of larch and birch seedlings from two origins to water deficit

Abstract

Background: Early developmental stages of plants are expected to be a major bottleneck to recruitment. Information on the response of seedling to anticipated water availability is urgently needed in regions where tree seedlings may experience more frequent water deficits. In this paper, we focused on the influence of water deficit on different species (larch vs. birch) and origins (xeric vs. mesic). Methods: Prince Rupprecht's larch (Larix gmelinii var. principis-rupprechtii (Mayr) Pilg.) and white birch (Betula platyphylla Sukaczev) from northern China were selected to represent the xeric origin. Eastern larch (Larix laricina (Du Roi) K. Koch) and paper birch (Betula papyrifera Marshall) from eastern Canada were selected to represent the mesic origin. For each species, half of seedlings were assigned to a well-watered treatment (WW, 75% water holding capacity (WHC) and the other half to a low-watered treatment (LW, 35% WHC). After 20 weeks of treatment, we collected data on morphological indexes of shoot height, root collar diameter, total leaf area and total root area; measured photosynthetic rate (A sat ), transpiration rate (E), photosynthetic water-use efficiency (WUE) and apparent chlorophyll concentration (Chl); harvested seedlings and measured biomass allocation of leaf, stem and root. Results: We found that reduced photosynthetic rate, transpiration rate and increased water-use efficiency were physiological responses of the four species to drought, and the responses varied among the species. All larch seedlings appeared no leaf shedding, survived through the drought treatment and showed a longer duration and high tolerance to drought. In low-watered conditions, survival rate, biomass, shoot height, root collar diameter, total leaf area, total root area and chlorophyll concentration of birch seedlings were significantly decreased. The response of seedlings to water deficits also differed according to the seed origins. Xeric origin of Prince Rupprecht's larch was more affected than mesic origin of eastern larch, mainly because Prince Rupprecht's larch originated in a narrower range of mountainous regions, resulting in lower adaptation of this species to water deficits, whereas eastern larch was distributed widely along coastal regions, contributing to higher phenotypic plasticity to variable soil conditions. Similarly, higher plasticity of paper birch may be responsible for its better performance in the low-watered treatment than white birch. Conclusions: Larch seedlings were less sensitive to water deficit than birch seedlings. Larch seedlings were characteristics of a conservative water-use strategy, whereas birch seedlings responded with a profligate water-use strategy. Plasticity or adaptation of seedlings outweighs the seed origins in determining their drought responses.

Root foraging of birch and larch in heterogeneous soil nutrient patches under water deficit

“…The well-watered treatment was achieved by watering pots to full capacity every three days [ 36 ]. In the drought treatment, water deficit was brought about by watering seedlings every six days [ 36 ]. The amount of water irrigated to seedlings under deficit condition was 70 ml per pot.…”

“…Temperate forests in the Northern Hemisphere are expected to undergo future drought events with high frequency and increasing severity [ 33 ]. Birch and larch are two early successional timber species that are sensitive to climatic drought and are used as model plants to study tree response to water deficit [ 34 – 36 ]. Potted plants are commonly used in controlled experiments of studies that detected root foraging behavior in heterogeneous soil patches [ 11 , 23 , 25 , 26 , 37 ].…”

Forest Management In Mongolia – A Review Of Challenges And Lessons Learned With Special Reference To Degradation And Deforestation

“…Dorjsuren (2014) has found that also the quality of larch seeds in Mongolia has decreased since 1980 due to drought. Similarly, Gao et al (2017) conclude that birch seedlings are more sensitive to water deficit than larch seedlings, and Gradel et al (2017a) have shown that younger trees are more susceptible to drought than older trees, most likely due to their less-developed root architecture and other factors. These findings indicate which species or development stages of trees may be especially affected if the climate gets drier.…”

Responses to Drought in Seedlings of European Larch (Larix decidua Mill.) from Several Carpathian Provenances

“…Drought, as a consequence of climate change, is a threat to many forest stands, which will have to cope with new adverse environmental conditions within their current natural habitats [1][2][3][4][5]. European coniferous forests are among those ecosystems forecasted to be susceptible to the effects of global warming; the negative ones such as drought and disturbance risk will probably outweigh the favorable effects of increasing atmospheric CO 2 and warmer temperatures [6][7][8].…”

“…There is an urgent need to increase our knowledge on seedling responses of forest species to drought in areas where future extensive drought periods are forecasted. Responses to drought are heritable but variable within populations of one species [5], and are often being conditioned by the environmental conditions in which parental plants develop [15]. Therefore, for better management of forest stands, as well as for reforestation and afforestation programs, not only a genetic, but also a screening of the phenotype plasticity of different populations of the same species are highly recommended [16].…”