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2 Polish Journal of Ecology

2 2020

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Influence of Branch Death on Leaf Nutrient Status and Stoichiometry of Wild Apple Trees (Malus sieversii) in the Western Tianshan Mountains, China

Tao Ye, Nuerhailati Maziyirea, Zhang Yuan-Ming, Zhang Jing, Yin Ben-Feng, Zhou Xiao-Bing

Polish Journal of Ecology

2020

Vol. 68, nr 4

296--312

The wild apple tree Malus sieversii is a tertiary relict species and a key ancestor of the commonly cultivated apple trees today. In recent years, many M. sieversii individuals have died or have severe dead branches. Whether branch death would lead to the change in nutrient stoichiometry of M. sieversii remains unclear. In this study, the nitrogen (N), phosphorous (P), and potassium (K) stoichiometric traits of M. sieversii individual trees with different proportion of dead branches divided into three classes (Class I [< 20%], Class II [40-60%], and Class III [> 80%]) during annual growth period, elemental scaling relations, and the possible influencing factors were systematically analysed. Leaf N, P, and K decreased during growing season, and N and P did not show significant differences among the three classes; however, the Class III wild apple trees had the lowest K contents in both photosynthetic and reproductive organs. Flowers had higher P and K contents than leaves, whereas fruits had low N content. The growth of M. sieversii was always limited by N due to low N:P ratio and N resorption efficiency. The scaling exponents of leaf N-P, N-K, or P-K among the three classes did not show any significant differences, revealing an inherent property of M. sieversii. Most soil variables showed weak correlations with leaf nutrient parameters (except for K). Precipitation and relative humidity, rather than temperature, showed significantly positive effects on leaf nutrients. These findings suggest that increasing water input and plant K content may be conducive to enhance the resistance and recovery ability of diseased wild apple trees.

Humped Relationship between Herbaceous Species Richness and Biomass Reveals a Potential for Increasing Productivity in a Temperate Desert in Central Asia

Tao Ye, Zhou Xiao-Bing, Zhang Jing, Yin Ben-Feng, Wu Nan, Zhang Yuan-Ming

Polish Journal of Ecology

2020

Vol. 68, nr 1

67--83

Species richness-biomass relationship has become a primary focus in plant community ecology. The most commonly reported pattern of species richness and biomass is the humped relationship with a peak in richness at moderate biomass, although negative, positive, or no relationships exited in some cases. However, the richness-biomass relationship in the temperate deserts of Central Asia, where herbaceous species with different life forms are abundant, remains unclear. In this study, 21-214 plots with herbaceous richness and aboveground biomass for each of four plot sizes (0.25, 25, 100, and 400 m2) were surveyed in early summer and early autumn in the Gurbantunggut Desert, China. Linear and quadratic regressions were employed to examine the richness-biomass relationship and the location of the richness peak. Significantly unimodal species richness-biomass relationships were observed in all plot sizes and seasons (except for 0.25 m2 plot in summer). In most cases (9/11), the biomass at the richness peak was higher than half of the biomass range. Meanwhile, the percent of sampling plots where the biomass was less than the peak was considerably greater than 50% (72.7 to 100%) in all cases, and nine of them were more than 95%, indicating strong interspecific coexistence and weak interspecific competition. In conclusion, under the background of increasing precipitation and nitrogen deposition, the humped richness-biomass relationship and the high percent of sampling plots with low biomass jointly revealed a huge potential for increasing productivity, which is crucial for the carbon fixation and ecosystem stability in deserts of Central Asia.