Larix Principis-rupprechtii Plantation Research Articles

Assessing the Impact of Soil Moisture on Canopy Transpiration Using a Modified Jarvis-Stewart Model

In dryland regions, soil moisture is an important limiting factor for canopy transpiration (T). Thus, clarifying the impact of soil moisture on T is critical for comprehensive forest—water management and sustainable development. In this study, T, meteorological factors (reference evapotranspiration, ETref), soil moisture (relative soil water content, RSWC), and leaf area index (LAI) in a Larix principis-rupprechtii plantation of Liupan Mountains in the dryland region of Northwest China were simultaneously monitored during the growing seasons in 2017–2019. A modified Jarvis—Stewart model was established by introducing the impact of RSWC in different soil layers (0–20, 20–40, and 40–60 cm, respectively) to quantify the independent contribution of RSWC of different soil layers to T. Results showed that with rising ETref, T firstly increased and then decreased, and with rising RSWC and LAI, T firstly increased and then gradually stabilised, respectively. The modified Jarvis—Stewart model was able to give comparable estimates of T to those derived from sap flow measurements. The contribution of RSWC to T in different soil layers has obvious specificity, and the contribution rate of 20–40 cm (13.4%) and 0–20 cm soil layers (6.6%) where roots are mainly distributed is significantly higher than that of 40–60 cm soil layer (1.9%). As the soil moisture status changes from moist (RSWC0–60cm ≥ 0.4) to drought (RSWC0–60cm < 0.4), the role of the soil moisture in the 0–20 cm soil layer increased compared with other layers. The impacts of soil moisture that were coupled into the Jarvis—Stewart model can genuinely reflect the environmental influence and can be used to quantify the contributions of soil moisture to T. Thus, it has the potential to become a new tool to guide the protection and management of forest water resources.

Effects of stand density on soil respiration and labile organic carbon in different aged Larix principis-rupprechtii plantations

BackgroundThe carbon pools of forest soils play a vital role in global carbon sequestration and emissions. Forest management can regulate the sequestration and output of forest soil carbon pools to a certain extent; however, the kinetics of the effects of forest density on soil carbon pools require further investigation.MethodsWe established sample plots with stand density gradients in three different aged Larix principis-rupprechtii plantations and quantified the soil respiration, soil organic carbon (SOC), soil dissolved organic carbon (DOC), microbial biomass carbon (MBC), light fraction organic carbon (LFOC), and readily oxidized carbon (ROC).Results and conclusionsDuring the growth and development of plantations, stand density is an essential factor that impacts soil respiration and its associated elements. Moderate density was observed to promote both the soil and heterotrophic respiration rates and the sequestration of MBC and LFOC, whereas it inhibited the sequestration of ROC. The soil, heterotrophic, and autotrophic respiration rates of older forest stands were relatively rapid, whereas the contents of SOC, MBC, LFOC, DOC, and ROC were higher and more sensitive to changes in stand density. The MBC, LFOC, and ROC in soil labile organic carbon were closely related to both the soil and heterotrophic respiration, but not the SOC. Among them, the LFOC and MBC played the roles of “warehouse” and “tool” and were significantly correlated with soil and heterotrophic respiration. The ROC, as a “raw material”, exhibited a significantly negative correlation with the soil and heterotrophic respiration. When the soil and heterotrophic respiration rates were rapid, the ROC content in the soil maintained the low level of a “dynamically stabilized” state. The stand density regulated heterotrophic respiration by affecting the soil labile organic carbon, which provided an essential path for the stand density to regulate soil respiration.

Multivariate path analysis of factors influencing Larix principis-rupprechtii plantation regeneration in northern China

Forest regeneration is a critical indicator of the overall health of forest ecosystems, and is considered to be a vital process in which old and senescent trees are replaced by young ones. The seed-to-seedling transition entails seedlings’ emergence from seeds and their establishment, this phase being the most vulnerable to mortality effects from biotic and abiotic factors. Larix principis-rupprechtii is a typical tree species in northern China, where the natural regeneration of artificial forests dominated by this species is very limited. This study explored the limiting factors affecting the natural regeneration of Larix principis-rupprechtii forests via field surveys of large-scale sampling plots. Redundancy analysis and structural equation models were developed and applied to determine the relative importance of direct and indirect factors affecting the regeneration of Larix principis-rupprechtii plantations. We found a negative relationship between the regeneration index and stand structure, for which the path coefficient was –0.54, the strongest correlation. Conversely, the regeneration index was positively correlated with the herb index, soil index, and elevation, having path coefficients of 0.06, 0.07, and 0.32, respectively. The soil index was negative correlated with both elevation and herb index, with path coefficients of –0.31 and –0.53, respectively, while stand structure was negatively correlated with the herb index and positively correlated with elevation (respective path coefficients: –0.62 and 0.29). Stand density and tree height to crown base were the main factors representing stand structure and, accordingly, the most important factors influencing forest regeneration of the species. At a stand density of ca. 200 trees·hm−2, the number and quality of seedling regeneration were robust. In later stages of stand management and thinning, the proper adjustment of stand density and timely pruning interventions can promote this tree’s natural regeneration to achieve the sustainable development of forest resources.

Changes of light response indicators and its impact factors of Larix principis-rupprechtii on Saihanba Forest Farm, China.

We examined the differences of maximum light use efficiency (LUEmax), most effective light intensity (PARe), light compensation point (LCP) and light saturation point (LSP) in diffe-rent vertical positions and different phenological periods of tree crown in Larix principis-rupprechtii plantation in Saihanba Mechanical Forest Farm of Hebei Province. We analyzed the main influencing factors for all the variables. The results showed that LUEmax increased with the increasing crown depth, and that PARe, LCP and LSP decreased with the increasing crown depth. Such a result indicated that upper crown had higher utilization efficiency to strong light and that the lower crown was more efficient to adapt to weak light environment. During the leaf development in the growth period, the LUEmax approximately increased except in July, while the changes of other photosynthe-tic-light factors showed a tendency of unimodal curve. Environmental factors were significantly correlated with the indices of light response, mainly due to the stress reaction of leaf stomata to surrounding environment. Understanding the spatial and seasonal changes of the photosynthetic-light indicators was important for formulating scientific management measures, optimizing stand structure, improving local microenvironment and maximizing forest productivity.

Effects of environment and canopy structure on stem sap flow in a Larix principis-rupprechtii plantation.

Accurately quantifying the impacts of environmental factors and canopy structure on stem sap flow is of great significance for deeply understanding water use strategies of trees in changing environment. The stem sap flow of Larix principis-rupprechtii plantation was observed using thermal diffusion probes from June to September of 2019 in the Xiangshuihe small watershed of Liupan Mountains, with the meteorological conditions, root-zone soil water content and canopy structure being simultaneously recorded. We first analyzed the relationships of sap flow rate (Jc) to potential evapotranspiration (PET), relative extract water (REW) and canopy leaf area index (LAI), and then quantified their relative contribution to Jc. The results showed that the response of Jc to PET, LAI, and REW conformed to binomial, linearly increase and saturated exponential function, respectively. The Jc model coupling multiple factors was established as a continuous multiplication of the response functions of Jc to PET, REW and LAI, which had good simulation precision. PET was the main factor leading to the difference of Jc in different weather conditions. The average contribution rate of PET had obvious difference in sunny (with a contribution rate of 40.3%), cloudy (4.3%), and rainy days (-26.3%). PET and LAI were the leading factors affecting the Jc variation among months. The ranges of the contribution rates of PET and LAI were from -23.1% to 16.8% and from -12.3% to 11.0%, respectively. The Jc model coupling the multi-factor effect developed in this study could be used to predict Jc, and quantify the impacts of each leading factor, which had the potential to be an effective tool to analyze the water use of trees in the changing environment.

Forest thinning and organic matter manipulation drives changes in soil respiration in a Larix principis-rupprechtii plantation in China

Plantation management practices may influence carbon dioxide (CO2) uptake dynamics; however, the responses of carbon losses, such as soil respiration, to management (e.g. thinning) have not been sufficiently studied. We evaluated the effects of forest thinning (no thinning (NT), low thinning (LT), medium thinning (MT), and high thinning (HT) and organic matter manipulation (intact soil (untreated control, UC), exclusion of aboveground litter (EL), and exclusion of both aboveground litter and roots (ELR)) on soil respiration in a Larix principis-rupprechtii plantation. During the period from 2015–2018, soil respiration was continuously monitored from May to October (growing season). Meanwhile, soil temperature and soil moisture at a depth of 5 cm were also measured. In addition, three soil samples were collected to measure biochemical properties of soil. We found that mean soil respiration (Rs) was significantly greater in MT than that in NT (by 21.5 %). RS in HT was significantly greater than NT in 2015 (by 25.0 %) and then finally lower than NT (14.8 %) in 2018. However, RS in LT compared with NT showed no response to thinning during our observation period. The organic matter manipulation also affected soil respiration. Mean reduction of soil respiration in EL (REL) and in ELR (RELR) compared to Rs ranged from 25.9%–39.2% and 40.8%–53.6% across all thinning regimes, respectively. The temperature sensitivity (Q10) values of RS, REL, RELR ranged from 2.23 to 2.72, 2.21–2.60, and 2.31–2.90, respectively. The model with the best fitting temperature and moisture factors explained 63.8 % - 75.4 % changes in RS, 65.9 % - 74.7 % changes in REL and 70.4 % - 74.1 % changes in RELR. Stepwise regression analyses showed that soil temperature, ratio of soil carbon and nitrogen in the topsoil explained the pattern of RS across the thinning scenarios. REL showed a high sensitivity to changing in some soil chemical properties and hydrolases activities, whereas RELR showed a high sensitivity to changing in microbial activity combined with temperature and pH of soil. Overall, our data show that the response of organic matter inputs to thinning has an important impact on soil CO2 fluxes of plantation, and emphasize the difference of the response between aboveground and underground organic matter inputs to soil CO2 fluxes.

Soil ecoenzymatic stoichiometry and microbial resource limitation driven by thinning practices and season types in Larix principis-rupprechtii plantations in North China

The extracellular ecoenzymatic stoichiometry (EES) of the soil are key indicators of the nutritional status and relative resource limitations of microbes that play important roles in biogeochemical cycling and ecosystem functions. However, our knowledge of the effects of forest thinning and the seasons on the variability of extracellular ecoenzymatic activities (EEA) and EES in the soil is limited. We examined the soils from Larix principis-rupprechtii plantations after nine years of treatments with four different thinning intensities (i.e., control (CK), low thinning (LT), moderate thinning (MT), and high thinning (HT)) in four different seasons. We measured the activities of one carbon (C) acquiring enzyme (β-1,4-glucosidase (BG)), two nitrogen (N) acquiring enzymes (β-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP)), and one phosphorus (P) acquiring enzyme (acid phosphatase (AP)), and examined potential factors (soil environment, nutrients, and microbial biomass) that may influence the activities of these enzymes. Our results showed that thinning significantly (p < 0.05) enhanced the activities of the BG, NAG + LAP, and AP. The EEA were higher in summer and autumn than those in spring and winter. Further, MT and HT stands exhibited lower BG:(NAG + LAP) and higher (NAG + LAP):AP ratios than the CK and LT stands, demonstrating that MT and HT caused a greater N limitation for soil microbes. The higher (NAG + LAP):AP ratio during winter indicated that the microbial N limitation was increased in this season. The variations in the EEA, EES, environment, nutrients, and microbial biomass in the soil among different thinning treatments demonstrated that thinning could markedly promote microbial activities and metabolism and improve nutrient cycling. Based on analyses of the BG:(NAG + LAP) ratio, (NAG + LAP):AP ratio, and the threshold element ratio, we found that the metabolism of soil microbes was limited by N in L. principis-rupprechtii plantations in North China. A redundancy analysis and a variation partitioning analysis revealed that variations in the EEA and EES of soils could attributed to the alterations in soil properties, especially soil nutrient and microbial biomass. Overall, the ecoenzymatic C:N:P stoichiometry was dependent on the resource availability in the soils rather than on homeostatic mechanisms. Our research highlights the importance of the effects of thinning practices and season types on ecoenzymes and microbial metabolism, and provides insights into the microbial resource limitation, nutrient cycling, and ecological processes in plantation forests after thinning.

Evaluation of potential versus realized site productivity of Larix principis-rupprechtii plantations across northern China

Site quality evaluation is a fundamental component of forest management and is also vitally important towards improved understanding of forest growth processes and optimizing silviculture practices. However, most site quality studies have focused on site index which cannot predict potential site productivity. In this study, a methodology that incorporates volume-related potential increment which accounts for optimal stand density index was used for site productivity assessment of Larix principis-rupprechtii plantations across Northern China. Based on 152 permanent sample plots, the models of potential and realized productivity of L. principis-rupprechtii plantation were established, and percentage of available growing space close to potential productivity in different regions were analyzed in different site classes. Growth models of stand dominant height and volume were developed by site classes based on biological and statistical rationality. The potential productivity was between 3.93 m3/ha/year and 6.84 m3/ha/year. The realized productivity was always lower than potential productivity, and the gaps between the two types of productivity measures decreased with increasing stand age. The available growing space percentage of volume productivity was between 0% and 94.52%, and this was higher in stands in the middle and young stage of stand development compared to the mature stage. The available growing space increased with the decline of site class. The values of potential productivity and available growing space could be used to effectively assess forest site productivity, and also provide highly reliable and valuable information for L. principis-rupprechtii plantation management.

Factors promoting the natural regeneration of Larix principis-rupprechtii plantation in the Lvliang Mountains of central China.

Given their complexity, targeted care and management of different areas and tree species are necessary for enhancing the natural regeneration of forests. Thus, an understanding of changes in the overstory and understory is essential for ensuring successful regeneration. Promoting the natural regeneration of Larix principis-rupprechtii plantations is considered challenging; indeed, regional sustainable development through natural regeneration of many stands has often been considered unattainable. Here, we studied several plots with varying extents of regeneration to identify the most important factors that affect regeneration. The plots were divided into three forest types based on the number of regenerating plants. For each type of plot, we measured various factors that might potentially affect regeneration. Representational difference analysis was used to identify the most important factors >9% contribution). Based on these factors, multiple corrections were made to construct a structural equation model of topography, stand structure, soil properties and litter to identify the most important factors driving variation in regeneration. Positive correlations were detected between regeneration with diameter at breast height (0.21) and litter thickness (0.57). Regeneration was negatively correlated with soil (−0.54) and slope (−0.48). Additionally, the number of regenerating plants and the height of regenerating plants were strongly positively correlated. However, there was no significant relationship between regeneration and litter accumulation, stand density, altitude, average tree height, total P and total N. Overall, our study showed that key factors for promoting natural regeneration include appropriate litter thickness, strong parent trees, a gentle slope and sufficient quantities of soil nutrients. Moreover, our findings provide a reference for the design of effective management and restoration plans.

Effects of forest thinning on interception and surface runoff in Larix principis-rupprechtii plantation during the growing season

Forest thinning is an important management strategy for altering the hydrological function of forests by redistributing of incident rainfall, and improving the capacity to store water on forest floor and in the soil. A study to analyze the water conservation functions of the forest canopy and forest floor was conducted on a 36-year-old Larix principis-rupprechtii plantation with different thinning treatments in the Taiyue Mountain of Shanxi Province. The results showed that the cumulative values of throughfall (TF) gradually increased with thinning intensity, whereas the cumulative values of stemflow (SF) and interception loss (Ic) decreased significantly. More importantly, the study revealed that combining Ic and interception loss of litter (Il) yields a total interception flux of 21.9%, 24.5%, 23.8% and 19.7% of GR during the growing season in control, lightly thinned, moderately thinned, and heavily thinned respectively. Surface runoff as a proportion of GR varies tremendously depending on the amount and intensity of rainfall. Our findings demonstrated that rainfall redistribution through the forest canopy and litter and the potential for surface runoff responded to thinning intensity independently of each other. The intensity of management and plant-mediated biological processes are of particular importance in evaluating the impacts of forest management on hydrological processes in forests.

Variations in stem radii of Larix principis-rupprechtii to environmental factors at two slope locations in the Liupan Mountains, northwest China

Relationships between stem growth and climatic and edaphic factors, notably air temperatures and soil moisture for different slopes, are not completely understood. Stem radial variations were monitored at the bottom and top slope positions in a Larix principis-rupprechtii plantation during the 2017 and 2018 growing seasons. Total precipitation during the growing season in 2017 and 2018 was 566 mm and 728 mm, respectively. Stem contractions typically occurred after mid-morning followed by swelling in the late afternoon in both plots, reflecting the diurnal cycle of water uptake and loss. Trees at the two locations showed the same growth initiation (mid-May) because of the small differences in air and soil temperatures. There were no significant differences in cumulative stem radial growth between the bottom plot (1.57 ± 0.34 mm) and the top plot (1.55 ± 0.26 mm) in 2018. However, in 2017, the main growth period of the bottom plot ceased 17 days earlier than in the top plot, while cumulative seasonal growth of the bottom plot (1.08 ± 0.25 mm) was significantly less than the top plot (1.54 ± 0.43 mm). Maximum daily stem shrinkage was positively correlated with air and soil temperatures, solar radiation, vapor pressure deficits, and negatively correlated with volumetric soil moisture content. The maximum daily shrinkage reflected transpiration rates as affected by environmental factors. Daily radial stem increment was correlated with precipitation and volumetric soil moisture in both years, but with air temperatures only in 2017. The seasonal growth of L. principis-rupprechtii Mayr thus shows interannual dynamics, while precipitation constitutes a key driving factor.

Thinning drives C:N:P stoichiometry and nutrient resorption in Larix principis-rupprechtii plantations in North China

Carbon (C):nitrogen (N):phosphorous (P) stoichiometry and nutrient resorption play an important role in terrestrial biogeochemical cycling and functioning. However, little information is available about the changes in C:N:P stoichiometry and nutrient resorption following thinning in plantation forests. Here, to reveal how thinning affects the C:N:P stoichiometry and nutrient resorption and their relationships, green leaves, senesced leaves and soil samples were collected from a pure Larix principis-rupprechtii plantation in North China after 9 years of four different thinning treatments, i.e., control (CK, 0% thinning), low thinning (LT, 14% thinning), moderate thinning (MT, 28% thinning) and high thinning (HT, 42% thinning). The results showed that excluding the green leaf C contents, thinning significantly increased the C, N, and P contents in green leaves, senesced leaves, and soil (p < 0.05). Thinning significantly decreased the C:N and C:P ratios in green leaves, C:P and N:P ratios in senesced leaves, and C:N, C:P, and N:P ratios in soil (p < 0.05), while thinning did not significantly affect green leaf N:P and senesced leaf C:N ratios (p > 0.05). The N resorption efficiency (NRE) showed no significant differences among different thinning treatments (p > 0.05), while thinning significantly decreased the P resorption efficiency (PRE, p < 0.05). There were different degrees of correlations between nutrient contents, stoichiometry ratios and nutrient resorption, and most of which were affected by soil properties (bulk density, soil water contents, available nitrogen and phosphorus, pH, electrical conductivity, soil microbial biomass C and N, and the activities of soil β-glucosidase, N-acetylglucosaminidase, and acid phosphatase). The N:P ratios of green leaves and senesced leaf litter and the nutrient resorption suggested that Larix principis-rupprechtii plantations in the study region were limited by N. Overall, the variations in nutrient contents, stoichiometry ratios, nutrient resorption, and soil properties demonstrate that thinning can significantly increase nutrient contents, promote nutrient cycling, and improve soil fertility. Among the four thinning treatments, in terms of nutrients, MT is recommended in Larix principis-rupprechtii plantations in North China. Furthermore, appropriate fertilization management strategies should be considered to improve N-limitation status.

Effects of thinning on soil active organic carbon contents and enzyme activities in Larix principis-rupprechtii plantation

The effects of thinning on soil active organic carbon and related soil enzyme activities were investigated in a Larix principis-rupprechtii plantation in Taiyue Mountain. With the increases of soil depth, the content of soil labile organic carbon, soil nitrogen content and enzyme activities all reduced. For each soil layer, moderate thinning increased soil carbon and nitrogen contents dramati-cally. The activities of sucrase (SC) and peroxidase (PEO) and the activities of polyphenol oxidase (PHO) and urease (UE) in the layer of 0-10 cm could be significantly improved by low thinning and moderate thinning, respectively. For the 10-50 cm layer, the activities of SC and UE were reduced by low thinning, while moderate thinning markedly reduced the activities of cellulase. Results from redundancy analysis showed that dissolved organic carbon (DOC) was the main factor affecting soil enzyme activity in both 0-10 cm and 20-30 cm soil layers and that soil organic carbon (SOC) contents affected the activities of PHO and SC in 10-20 cm soil layer. The microbial biomass nitrogen (MBN) mainly affected the activities of PHO, PEO and UE in 30-40 cm soil layer. The contents of total P (TP) and readily oxidized carbon (ROC) played an important role in affecting soil enzyme activities in 40-50 cm soil layer. The results indicated that thinning could dramati-cally affect soil active organic carbon content and soil enzyme activity in L. principis-rupprechtii plantation. Moderate thinning treatment could obtain the highest soil nutrients and achieve better soil chemical properties such as soil pH, water content and organic matter content than other treatments, which could improve vegetation structure, litter and nutrient cycling process. Therefore, we recommended moderate density adjustment (1404-1422 trees·hm-2) to L. principis-rupprechtii plantation to promote soil carbon and nitrogen retention.

Sap flow and responses to meteorological about the Larix principis-rupprechtii plantation in Gansu Xinlong mountain, northwestern China

The transpiration of trees plays a decisive role in the water balance of forest stands and in water yields from forested catchments, especially an artificial forest planted for the purpose of soil and water conservation in semiarid mountain ecosystem regions. For proper management of watershed ecosystems, quantification of water use, sensitivity and adaptation for artificial forest is needed. This study were monitored the sap flow for Larix principis-rupprechtii plantation by thermal dissipation probes (TDP), analyzed the correlation between the sap flow and the meteorological factors on daily and seasonal scale, and upscaled stand transpiration from individual sap flow measurements. Within a daily timescale, the net radiation (Ra), air temperature (AT), air humidity (AH), vapor pressure deficit (VPD) and wind speed (WS) showed a significantly positive correlation with sap flow velocity in day-time, but in the night-time sap flow had no significant correlation. Within a monthly timescale, the Ra, AT, WS, and VPD showed a significantly positive correlation with stand water use, whereas precipitation (Pr) showed a significantly negative correlation with stand water use. Our results also showed that the daily transpiration of L. principis-rupprechtii continued to increase with the increase of net radiation (Ra), until the late stages of growth season (except rainy and cloudy days), and the sap flow velocity showed an obvious hysteresis response to meteorological factors to alleviate plant water stress from June to October, while there was no significant correlation between day-time and night-time water use during the stage of germination and rapid growth in May. Besides, due to the relatively low temperature, the water consumption of forest stands was only about 151.05 mm during the whole growing season, and there was no obvious ‘noon break’ phenomenon in the whole growing season. These results indicated that L. principis-rupprechtii could manage the water consumption conservatively, and were appropriate for afforestation in the mountains ecosystem with high altitude and low temperature.

Microbial regulation of soil carbon properties under nitrogen addition and plant inputs removal.

BackgroundSoil microbial communities and their associated enzyme activities play key roles in carbon cycling in terrestrial ecosystems. Soil microbial communities are sensitive to resource availability, but the mechanisms of microbial regulation have not been thoroughly investigated. Here, we tested the mechanistic relationships between microbial responses and multiple interacting resources.MethodsWe examined soil carbon properties, soil microbial community structure and carbon-related functions under nitrogen addition and plant inputs removal (litter removal (NL), root trench and litter removal (NRL)) in a pure Larix principis-rupprechtii plantation in northern China.ResultsWe found that nitrogen addition affected the soil microbial community structure, and that microbial biomass increased significantly once 100 kg ha−1 a−1 of nitrogen was added. The interactions between nitrogen addition and plant inputs removal significantly affected soil bacteria and their enzymatic activities (oxidases). The NL treatment enhanced soil microbial biomass under nitrogen addition. We also found that the biomass of gram-negative bacteria and saprotrophic fungi directly affected the soil microbial functions related to carbon turnover. The biomass of gram-negative bacteria and peroxidase activity were key factors controlling soil carbon dynamics. The interactions between nitrogen addition and plant inputs removal strengthened the correlation between the hydrolases and soil carbon.ConclusionsThis study showed that nitrogen addition and plant inputs removal could alter soil enzyme activities and further affect soil carbon turnover via microbial regulation. The increase in soil microbial biomass and the microbial regulation of soil carbon both need to be considered when developing effective sustainable forest management practices for northern China. Moreover, further studies are also needed to exactly understand how the complex interaction between the plant and below-ground processes affects the soil microbial community structure.

Minimum data set for evaluation of stand density effects on soil quality in Larix principis-rupprechtii plantations in North China

Soil quality index (SQI) was an important tool for evaluating soil quality (SQ). The aim of the study was to evaluate the stand density effects on SQ for Larix principis-rupprechtii plantations in North China. After eight years of thinning, SQ evaluation was used a SQI method to provide targeted and theoretical basis for the reasonable management and soil restoration. The study was conducted on twelve experimental sample plots classified by four levels of stand density (CK, HD, MD, LD), which were formed by 0%, 14%, 28% and 42% thinning, respectively. Thirty-nine soil physical, chemical and biological properties were measured at 0–20 and 20–40 cm depths as potential SQ indicators. The SQI was calculated using a minimum data set (MDS), the non-linear scoring method, followed by weighted additive (SQIw) and nemoro (SQIn) integration. Fungi, OM (soil organic matter) and G+:G− (the concentration ratio of Gram-positive bacteria to Gram-negative bacteria) were identified as the MDS. Both SQIw and SQIn performed well, with significant differences (P < 0.001, at both soil depths) among four stand densities after 8 years of thinning. However, the SQIw was superior to the SQIn for showing differences among the four stand densities due to the higher F values and larger coefficient of variance. The results showed that decrease of stand density (caused by thinning) resulted in a positive effect on SQ, and the highest values of SQI occurred in MD stands. Density management of around 1495 trees ha−1 (MD) was beneficial to the maintenance of SQ for Larix principis-rupprechtii plantations in North China. Additionally, the SQI method could provide a practical, quantitative tool for evaluating SQ in plantations, and provide reference for other tree species or other regions.

间伐和凋落物处理对华北落叶松人工林土壤磷形态的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 间伐和凋落物处理对华北落叶松人工林土壤磷形态的影响 DOI: 10.5846/stxb201809061907 作者: 作者单位: 北京林业大学林学院,北京林业大学林学院,北京林业大学林学院,北京林业大学林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划（2016YFD0600205）；国家自然科学基金项目（N31700372） Effects of thinning and litter manipulation on soil phosphorus dynamicsin a Larixprincipis-rupprechtii plantation Author: Affiliation: Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University,Forestry College of Beijing Forestry University Fund Project: National Key Research and Development Program of China (2016YFD0600205) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤磷在维持生态系统功能稳定性中发挥重要作用，研究间伐和凋落物处理下的土壤磷组分特征及转化机理，对森林生态系统磷素管理和可持续发展具有重要意义。采用Tiessen改良的Hedley分级方法，探究了不同间伐强度（未间伐、轻度间伐、中度间伐、重度间伐）和凋落物处理（对照、加倍、去凋、切根去凋）下土壤磷形态的变化特征及其驱动因子。结果显示：随着间伐强度的增大，土壤活性磷（Resin-Pi、NaHCO3-Pi和NaHCO3-Po）、土壤微生物量磷和酸性磷酸酶活性呈先增加后降低的趋势，且在中度间伐最高。凋落物加倍（DL）显著增加了土壤活性磷（Resin-Pi、NaHCO3-Pi和NaHCO3-Po）、土壤微生物量磷和酸性磷酸酶活性。稳定态磷（HCl-Pi、浓HCl-Pi和浓HCl-Po）、残留态磷（Residual-P）不受间伐和凋落物处理的影响。冗余分析（RDA）显示，土壤微生物量磷、酸性磷酸酶活性和土壤有机碳是引起华北落叶松人工林表层土壤磷组分变化的重要因子。研究表明，适度的间伐和增加凋落物能够显著提高华北落叶松人工林表层土壤磷素的活化能力。本研究为华北落叶松人工林的可持续经营提供依据。 Abstract:Soil phosphorus (P) plays an important role in maintaining the stability of ecosystem functions. Understanding the effects of forest management practices (e.g., thinning) on soil phosphorus fractions is important for soil phosphorus management for sustainable development in forest ecosystems. In this paper, a modified Hedley phosphorus fractionation method was used to sequentially extract soil samples and investigate the characteristics of soil phosphorus fractions with different thinning intensities (control, T0; Low thinning, T15; Moderate thinning,T35; Heavy thinning,T50)and litter manipulation (control, CK; exclusion litter, NL; addition litter, DL; exclusion litter and roots, NRL) in a Larixprincipis-rupprechtii plantation and addressed its determining factors. The results showed that soil labile phosphorus(Resin-Pi, NaHCO3-Pi and NaHCO3-Po), soil microbial biomass phosphorus, and acid phosphatase activity increased first and then decreased with the increase of thinning intensity, and the maximum appeared in T35.DL treatment significantly increased soil labile phosphorus (Resin-Pi, NaHCO3-Pi and NaHCO3-Po), soil microbial biomass phosphorus, and acid phosphatase activity. No-labile phosphorus (HCl-Pi, concentrated HCl-Pi and concentrated HCl-Po) and residual phosphorus (Residual-P) were not affected by thinning or litter treatments. The redundancy analysis (RDA) indicated that the changes in phosphorus fractions were mainly driven by soil microbial biomass phosphorus, acid phosphatase activity, andsoil organic carbon in the surface soil of the Larixprincipis-rupprechtii plantation. The results suggested that moderate thinning and increased litter could significantly improve the activation of phosphorus in the surface soil of the Larixprincipis-rupprechtii plantation. 参考文献 相似文献 引证文献

Characteristics of soil phosphorus fractions under different thinning intensities in Larix principis-rupprechtii plantation and the affecting factors.

Thinning is an important plantation management strategy. Phosphorus (P) is one of the limiting nutrients in forest ecosystems. The impacts of thinning on soil P remain unclear. In this study, we investigated the characteristics of soil P fractions in topsoil (0-10 cm) of Larix principis-rupprechtii plantation in Taiyue Mountain, Shanxi Province under different thinning intensity (control, CK, 0%; low thinning, LT, 15%; moderate thinning, MT, 35%; high thinning, HT, 50%) and the affecting factors. The soil P fractions were measured using Tissen modified Hedley P fractionation method. The results showed that the total inorganic P content in soil was significantly higher in stands subjected to moderate thinning than in control. The soil acid phosphatase activity (APA) and the contents of Resin-Pi, NaHCO3-Pi, NaHCO3-Po, NaOH-Pi, and microbial biomass phosphorus (MBP) were significantly increased in LT and MT compared with CK, but the content of NaOH-Po showed an opposite trend. Thinning had no significant effect on soil total P, total organic P, non-available P and residual-P. Soil moisture, organic matter, MBP and APA were the important factors affecting soil P availability. Our results demonstrated that MT could enhance soil P availability in Larix principis-rupprechtii plantation.

Effects of seed traits and seed production on the seed predation and dispersal behavior of rodents.

To deeply understand the foraging behavioral strategies of the rodents in response to seeds of different sizes and tannin contents under different seed densities and its relationship with plant regeneration, field experiments were conducted to explore the effects of artificial seeds of different sizes (large and small) and tannin (T) contents (0%T, 2%T, 8%T, and 15%T) on seed predation and dispersal behavior of rodents during simulated non-mast and mast seeding year in Larix principis-rupprechtii plantation of Liupan Mountains in Ningxia. The results showed that seeds were consumed rapidly by rodents in non-mast seeding year but relatively slow in mast seeding year. No significant difference of in situ predation rate (ISPR) was observed between non-mast and mast seeding year. The predation rates of seeds after dispersal (PRAD) by rodents in non-mast year were significantly higher than those in mast year, while the hoarding rate of seed after dispersal (HRAD) of the former was significantly lower than the latter. Both seed predation distance after dispersal (PDAD) and hoarding distance after dispersal (HDAD) by rodents in non-mast year were substantially higher than those in mast year. In non-mast year, both PDAD and HDAD of large seeds were longer than those of small seeds. Significant difference of the former was observed between large and small seeds for all tannin content seeds, but significant difference of the latter between large and small seeds was detected only for seeds of 2% and 15% tannin. In mast year, significant difference of PDADs and HDADs between large and small seeds was found in all other seeds of tannin contents except for 0% Tannin seeds. The ISPR maximized in medium tannin seeds and minimized in high tannin seeds. Maximums of PRAD were observed in high tannin seeds in non-mast year and 0% tannin seeds in mast year respectively. High tannin seeds had the highest HRAD while medium tannin seeds had the lowest HRAD in both mast and non-mast year. Our results suggested that mast seeding year could delay the seed consumption rate of rodents and increase the HRAD, but reduce the dispersal distance. Hoarding preference of the rodents on large seeds was demonstrated in both mast and non-mast years and the dispersal distance of large seeds was longer than those of small ones. It is probably that rodents prefer to predate in situ seeds of medium tannin and disperse high tannin seeds during both mast and non-mast years.

Ectomycorrhizal fungi respiration quantification and drivers in three differently-aged larch plantations

Soil respiration (Rs) is generally partitioned into autotrophic respiration (by roots and mycorrhizae) and heterotrophic respiration (by decomposers). Boreal and temperate forests are widely associated with ectomycorrhizal (EM) fungi, which play a critical role in belowground carbon dynamics. However, the magnitude and factors controlling EM fungal respiration (Rem) have not been well studied in field experiments. In this study, we quantified Rem using the micro-pore mesh method in three Larix principis-rupprechtii plantations of different ages (i.e., 11-, 20-, and 45-year-old, representing sapling, young, and mature stands, respectively) during the growing seasons from 2014 to 2016 in North China. The results showed clear seasonality of Rem, with an initial increase in spring (May and June), peak in summer (July and August), and decrease in autumn (September and October). Rem represented 37, 47 and 39% of rhizosphere respiration in the sapling, young, and mature stands, respectively, with an average of 41% across the three stands, indicating that a significant portion of rhizosphere respiration originated from EM fungi in larch plantations. Rem was positively correlated with soil temperature and the annual fine root increment, but negatively correlated with soil moisture when values exceeded 0.055 cm3 cm–3. Stand age had no significant effects on Rem, but Rem and the contribution of Rem to Rs in summer in the sapling stand was significantly higher than values in the young and mature stands. These results may be due to the higher values of soil temperature and annual fine root increment and lower soil inorganic nitrogen in the sapling stand relative to the other two stands. Overall, our results emphasize the importance of partitioning and quantifying EM fungal respiration to improve our understanding and predictions of belowground carbon dynamics under global climate change.