Effects of Different Soils on the Biomass and Photosynthesis of Rumex nepalensis in Subalpine Region of Southwestern China

The performance of Rumex nepalensis, an important medicinal herb, varies significantly among subalpine grasslands, shrublands and forest ecosystems in southwestern China. Plant–soil feedback is receiving increasing interest as an important driver influencing plant growth and population dynamics. However, the feedback effects of soils from different ecosystems on R. nepalensis remain poorly understood. A greenhouse experiment was carried out to identify the effects of different soil sources on the photosynthesis and biomass of R. nepalensis. R. nepalensis was grown in soils collected from the rooting zones of R. nepalensis (a grassland soil, RS treatment), Hippophae rhamnoides (a shrub soil, HS treatment), and Picea asperata (a forest soil, PS treatment). The chlorophyll contents, net photosynthetic rates, and biomasses of R. nepalensis differed significantly among the three soils and followed the order of RS > HS > PS. After soil sterilization, these plant parameters followed the order of RS > PS > HS. The total biomass was 16.5 times higher in sterilized PS than in unsterilized PS, indicating that the existence of soil microbes in P. asperata forest ecosystems could strongly inhibit R. nepalensis growth. The root to shoot biomass ratio of R. nepalensis was the highest in the sterilized PS but the lowest in the unsterilized PS, which showed that soil microbes in PS could change the biomass allocation. Constrained redundancy analysis and path analysis suggested that soil microbes could impact the growth of R. nepalensis via the activities of soil extracellular enzymes (e.g., β-1,4-N-acetylglucosaminidase (NAG)) in live soils. The soil total soluble nitrogen concentration might be the main soil factor regulating R. nepalensis performance in sterilized soils. Our findings underline the importance of the soil microbes and nitrogen to R. nepalensis performance in natural ecosystems and will help to better predict plant population dynamics.

The First Conserved Mitochondrial Genome of Polygraphus Poligraphus (Coleoptera: Curculionidae) and Its Phylogenetic Implications

Background: Polygraphus poligraphus L., the four-eyed spruce bark beetle, belongs to the Curculionidae (Coleoptera), which mainly harms Picea asperata Mast and Pinus armandii Franch tree trunks. So far, there is no mitochondrial genome reported for P. poligraphus.Results: In this study, we sequenced and annotated the nearly complete mitogenome of P. poligraphus for the first time and predicted the secondary structures of its tRNAs. The results showed that the mitogenome of P. poligraphus was 15,302 bp (partial genome) in length with A + T content of 69.65% due to large-scale duplication. The nearly complete mitochondrial genome of P. Poligraphus contained a set of 36 genes typical of the insect mitogenome, including 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rRNAs), 21 transfer RNA genes (tRNAs) but lacked tRNA-Ile, as for the typical insect mitogenome. The results of nucleotide skew statistics showed that the AT-skews and GC-skew of P. poligraphus were positive and negative, respectively, which were similar to other Scolytinae insects. All PCGs were initiated with the standard start codon ATN. All tRNA genes had the typical cloverleaf structure, except for the trnS1, which lacked a dihydroxyuridine (DHU) arm. Furthermore, we reconstructed phylogenetic trees of P. poligraphus based on the data set of the mitogenome’s protein-coding gene sequences using the Bayesian inference (BI) method. Phylogenetic analysis indicated that the P. poligraphus mitogenome clustered with Gnathotrichus materiarius and Pityophthorus pubescens mitogenomes in a monophyletic manner. The phylogeny of these three genera of Scolytinae is presented as Polygraphus + (Gnathotrichus + Pityophthorus). Conclusions: The results presented herein will provide a reference for further molecular taxonomy, evolution and phylogenetic research of P. poligraphus. However, additional mitogenome samples are still needed to more satisfactorily resolve the phylogeny of the Scolytinae.

Dynamic Top Height Growth Models for Eight Native Tree Species in a Cool-Temperate Region in Northeast China

In this study, we developed dynamic top height growth models for the eight important Chinese tree species Larix gmelinii var. principis-rupprechtii, Pinus tabuliformis Carr., Pinus sylvestris var. mongolica Litv., Picea asperata Mast., Quercus mongolica Fisch. ex Ledeb, Betula platyphylla Suk., Betula dahurica Pall. and Populus davidiana Dode based on age-height relationships. For this purpose, commonly growth data from long-term observations of permanent experimental plots are used, which ideally cover all development stages from stand establishment to final harvest. As such data were not available in the research area of Hebei Province in Northeast China, we used stem analysis data as well as tree height and annual shoot length measurements. The dataset consisted of 72 stands, 233 dominant trees and 10,195 observations of stem discs and annual shoot length measurements. Five dynamic base-age invariant top height growth models were derived from four base models with the Generalized Algebraic Difference Approach and fitted to our age-height data using nested regression techniques. According to biological plausibility and model accuracy the Chapman–Richards model showed the best performance for Picea asperata. This selected model accounted for 99% of the total variance in age-height relationship with average absolute bias of 0.2322 m, root mean square error of 0.3337 m and of 0.9979, respectively. The distribution of the residuals was scattered around 0 and without visible trends, indicating that the fitness of the models was good. All developed models are able to generate top height growth curves representing the analyzed height growth data and can be utilized for predicting height growth on the base of current height and age of dominant trees. Additionally, they are the base for calculating the development of other relevant stand attributes such as basal area and volume growth. The determination of potential site productivity by the use of top height growth curves is a practical and convenient method for a simplified presentation of complex growth processes in stands and helps to create growth models, which facilitate implementing sustainable forest management practices in Mulan Forest.

Seasonal changes in the pigment composition of needles of representatives of the genus spruce in the Nizhny Novgorod region

Изучали характер и масштаб сезонных изменений пигментного состава хвои разных видов ели (Picea A. Dietr.) в условиях интродукции в Нижегородскую область, выявляли содержание и баланс пластидных пигментов фотосинтеза. Объектами исследования выступали 13 видов ели, относящихся к аборигенам и экзотам: ель европейская (Picea abies (L.) H. Karst.); ель сибирская (Picea obovata Ledeb.); ель Глена (Picea glehnii (F. Schmidt) Mast.); ель белая (Picea glauca (Moench) Voss); ель шероховатая (Picea asperata Masters); ель черная (Picea mariana Mill., Britton, Sterns & Poggenburg); ель колючая форма серебристая (Picea pungens Engelm., f. argentea); ель колючая форма голубая (Picea pungens Engelm., f. glauca Regel); ель сербская (Picea omorika (Pančić) Purk.); ель Энгельмана (Picea engelmannii Parry ex Engelm.); ель колючая (Picea pungens Engelm.); ель аянская (Picea jezoensis (Siebold & Zucc.) Carrière); ель корейская (Picea koraiensis Nakai). Отбор проб осуществлен рендомизированно с соблюдением принципа единственного логического различия. Использовали спектрофотометр СФ-2000. Установлено, что содержание и соотношение пластидных пигментов в хвое динамично в течение года. Определена эффективность влияния фаз сезонного развития растений на характеристики пигментного состава: по содержанию хлорофилла-a – 18,86±0,32%; по содержанию хлорофилла-b – 21,26±0,31%; по сумме хлорофиллов – 16,13±0,33%; по каротиноидам – 37,43±0,25%; по доле хлорофилла-a – 39,74±0,24% и доле хлорофилла-b – 39,74±0,24%. Эффект влияния межвидовых различий по показателям содержания и соотношения разных форм хлорофилла и каротиноидов достоверен и в достаточной мере выравнен при максимуме 23,56±0,91%. При общих тенденциях в сезонной динамике представители рода ель обладают заметной видоспецифичностью пигментного состава. We studied the nature and scale of seasonal changes in the pigment composition of needles of different spruce species (Picea A. Dietr.) under the conditions of introduction to the Nizhny Novgorod region, and revealed the content and balance of photosynthetic plastid pigments. The objects of the study were 13 species of spruce belonging to aborigines and exotics: Norway spruce (Picea abies (L.) H. Karst.); Siberian spruce (Picea obovata Ledeb.); Glen spruce (Picea glehnii (F. Schmidt) Mast.); white spruce (Picea glauca (Moench) Voss); Dragon spruce (Picea asperata Masters); black spruce (Picea mariana Mill., Britton, Sterns & Poggenburg); silver prickly spruce (Picea pungens Engelm., f. argentea); blue prickly spruce (Picea pungens Engelm., f. glauca Regel); Serbian spruce (Picea omorika (Pančić) Purk.); Engelman spruce (Picea engelmannii Parry ex Engelm.); Blue spruce (Picea pungens engelm.); Ayan spruce (Picea jezoensis (Siebold & Zucc.) carrière); Korean spruce (Picea koraiensis Nakai). Sampling was carried out in a randomized manner, following the principle of a single logical difference. A spectrophotometer SF-2000 was used. It was found that the content and ratio of plastid pigments in conifers is dynamic throughout the year. The effectiveness of the influence of the phases of seasonal plant development on the characteristics of the pigment composition is determined: by the content of chlorophyll-a-18.86±0.32%; by the content of chlorophyll-b-21.26±0.31%; by the sum of chlorophylls-16.13±0.33%; by carotenoids – 37.43±0.25%; by the proportion of chlorophyll-a – 39.74±0.24% and the proportion of chlorophyll-b – 39.74±0.24%. The effect of interspecific differences in the content and ratio of different forms of chlorophyll and carotenoids is significant and sufficiently equalized at a maximum of 23.56±0.91%. With General trends in seasonal dynamics, representatives of the spruce genus have a noticeable species-specific pigment composition.

The Vertical Distribution Pattern of Microbial- and Plant-Derived Carbon in the Rhizosphere in Alpine Coniferous Forests

Background and aimsWhile the quantitative assessment of plant- and microbial-derived carbon (C) in the soil organic C (SOC) chemical composition in soil profiles has been initially explored, the vertical distribution pattern of these two C sources and their dominant role in SOC formation based on the insights related to the rhizosphere are still lacking.MethodsWe quantified the divergent accumulation of microbial-derived C (i.e., microbial residues), plant-derived C (i.e., lipids and lignin phenols) and SOC in the rhizosphere at various depths (0-10 cm, 10-20 cm and 20-30 cm) in the upper mineral soil and analyzed its control factors in an alpine coniferous forest (Picea asperata. Mast). We further revealed the relative contribution of plant- or microbial-derived C to rhizosphere SOC in the soil profile.ResultsThe contents of microbial- and plant-derived C and SOC in the rhizosphere decreased with soil depth and were mainly regulated by root and microbial biomass. Moreover, the contribution of microbial-derived C dominated by fungal residues to rhizosphere SOC at each soil depth (more than 62%) was much higher than that of plant-derived C (less than 6%), implying that the soil microbial C pump was intensely stimulated in the rhizosphere.ConclusionsThese results indicated that microbial-derived C was the main contributor of rhizosphere SOC at various depths in the upper mineral soil. Our findings provide direct experimental evidence for assessing the dominant contribution of microbial- or plant-derived C to SOC in the soil profile from the perspective of the rhizosphere.

Forest biomass carbon pool dynamics in Tibet Autonomous Region of China: Inventory data 1999-2019

According to the forest resources inventory data for different periods and the latest estimation parameters of forest carbon reserves in China, the carbon reserves and carbon density of forest biomass in the Tibet Autonomous Region from 1999 to 2019 were estimated using the IPCC international carbon reserves estimation model. The results showed that, during the past 20 years, the forest area, forest stock, and biomass carbon storage in Tibet have been steadily increasing, with an average annual increase of 1.85×104 hm2, 0.033×107 m3, and 0.22×107 t, respectively. Influenced by geographical conditions and the natural environment, the forest area and biomass carbon storage gradually increased from the northwest to the southeast, particularly in Linzhi and Changdu, where there are many primitive forests, which serve as important carbon sinks in Tibet. In terms of the composition of tree species, coniferous forests are dominant in Tibet, particularly those containing Abies fabri, Picea asperata, and Pinus densata, which comprise approximately 45% of the total forest area in Tibet. The ecological location of Tibet has resulted in the area being dominated by shelter forest, comprising 68.76% of the total area, 64.72% of the total forest stock, and 66.34% of the total biomass carbon reserves. The biomass carbon storage was observed to first increase and then decrease with increasing forest age, which is primarily caused by tree growth characteristics. In over-mature forests, trees’ photosynthesis decreases along with their accumulation of organic matter, and the trees can die. In addition, this study also observed that the proportion of mature and over-mature forest in Tibet is excessively large, which is not conducive to the sustainable development of forestry in the region. This problem should be addressed in future management and utilization activities.