Effects of three coniferous plantation species on plant-soil feedbacks and soil physical and chemical properties in semiarid mountain ecosystems

Background:Large-scale afforestation can significantly change the ground cover and soil physicochemical properties,especially the soil fertility maintenance and water conservation functions of artificial forests,which are very important in semi-arid mountain ecosystems.However,how different tree species affect soil nutrients and soil physicochemical properties after afforestation,and which is the best plantation species for improving soil fertility and water conservation functions remain largely unknown.Methods:This study investigated the soil nutrient contents of three different plantations(Larix principis-rupprechtii,Picea crassifolia,Pinus tabuliformis),soils and plant-soil feedbacks,as well as the interactions between soil physicochemical properties.Results:The results revealed that the leaves and litter layers strongly influenced soil nutrient availability through biogeochemical processes:P.tabuliformis had higher organic carbon,ratio of organic carbon to total nitrogen(C:N)and organic carbon to total phosphorus(C:P)in the leaves and litter layers than L.principis-rupprechtii or P.crassifolia,suggesting that higher C:N and C:P hindered litter decomposition.As a result,the L.principis-rupprechtii and P.crassifolia plantation forests significantly improved soil nutrients and clay components,compared with the P.tabuliformis plantation forest.Furthermore,the L.principis-rupprechtii and P.crassifolia plantation forests significantly improved the soil capacity,soil total porosity,and capillary porosity,decreased soil bulk density,and enhanced water storage capacity,compared with the P.tabuliformis plantation forest.The results of this study showed that,the strong link between plants and soil was tightly coupled to C:N and C:P,and there was a close correlation between soil particle size distribution and soil physicochemical properties.Conclusions:Therefore,our results recommend planting the L.principis-rupprechtii and P.crassifolia as the preferred tree species to enhance the soil fertility and water conservation functions,especially in semi-arid regions mountain forest ecosystems.

Conservation of challenging endemic plant species at high risk of extinction in arid mountain ecosystems:a case study of Rosa arabica Crép.in Egypt

Rosa arabica Crép.is a perennial shrub belonging to the family Rosaceae.It is endemic to the high mountain area of St.Catherine Protected Area(SCPA)in southern Sinai,Egypt,and is listed as one of the most 100 threatened plants in the world.Recently,it has been listed as critically endangered by IUCN Red List due to its small extent of occurrence and tiny population size.We reported the continuous decline in habitat quality for this species and the urgent need to carry out on-ground conservation actions.So,this research aims to conserve Rosa arabica through in situ practices by implementing the following steps,respectively:a)evaluate the current conservation status through IUCN Red List to extract the environmental factors controlling the species’distribution necessary for establishing the recovery program,b)determine the potential species habitat suitability under the current climate conditions using Maxent,and c)based on the previous two steps,the translocation process for R.arabica in the suitable habitat will be done after the simple layering process as one of the most effective traditional vegetative methods for wild cultivation for this species.These steps aimed to reduce the impact of threats and the risk of extinction through increasing the population size,the Extent of Occurrence(EOO),and the Area of Occupancy(AOO).We extracted the environmental factors controlling the target species’distribution and habitat suitability range using the IUCN Red List assessment and Species Distribution Model(SDM).The most suitable habitat for R.arabica is predicted in the middle northern parts of SCPA,with the highest suitability in the High Mountains.Precipitation of driest quarter,precipitation of wettest month,precipitation of coldest quarter,and aspect are the highest mean contributors determining the distribution of R.arabica in SCPA.Rosa arabica potential distribution covers 324.4 km^(2)(7.46%)of the total SCPA area(4350 km^(2)).This area is divided into:18.1 km^(2)high probability,124.3 km^(2)moderate probability,and 182 km^(2)low probability.After one year of the simple layering process,ten branches rooted and were translocated into three sites that had been previously identified to cover three habitat suitability ranges(high,moderate,and low suitability).After a year of translocation in the wild,the survival rate ranged from 66%to 100%,the geographical range increased by 65%,and the population size by 6.8%.Therefore,if the new individuals continue to grow and adapt it may lead to the expansion of other environmental factors such as climatic and topographical factors that probably increase the resilience of the global population of the species to adverse events.Detailed information is provided in this research about the recovery program,from planning to implementation and monitoring,and recommendations for best practices.

Height-diameter models for King Boris fir(Abies borisii regis Mattf.) and Scots pine(Pinus sylvestris L.) in Olympus and Pieria Mountains, Greece

In forest science and practice, the total tree height is one of the basic morphometric attributes at the tree level and it has been closely linked with important stand attributes. In the current research, sixteen nonlinear functions for height prediction were tested in terms of their fitting ability against samples of Abies borisii regis and Pinus sylvestris trees from mountainous forests in central Greece. The fitting procedure was based on generalized nonlinear weighted regression. At the final stage, a five-quantile nonlinear height-diameter model was developed for both species through a quantile regression approach, to estimate the entire conditional distribution of tree height, enabling the evaluation of the diameter impact at various quantiles and providing a comprehensive understanding of the proposed relationship across the distribution. The results clearly showed that employing the diameter as the sole independent variable, the 3-parameter Hossfeld function and the 2-parameter N?slund function managed to explain approximately 84.0% and 81.7% of the total height variance in the case of King Boris fir and Scots pine species, respectively. Furthermore, the models exhibited low levels of error in both cases(2.310m for the fir and 3.004m for the pine), yielding unbiased predictions for both fir(-0.002m) and pine(-0.004m). Notably, all the required assumptions for homogeneity and normality of the associated residuals were achieved through the weighting procedure, while the quantile regression approach provided additional insights into the height-diameter allometry of the specific species. The proposed models can turn into valuable tools for operational forest management planning, particularly for wood production and conservation of mountainous forest ecosystems.

Phosphorus Biogeochemical Cycle Research in Mountainous Ecosystems

Phosphorus(P),as a limiting nutrient,plays a crucial role in the mountainous ecosystem development.Its biogeochemical cycle in mountainous ecosystems determines the bioavailability and sustainable supply of P,and thus becomes a crucial process which needs to be fully understood and described for ecological and environmental conservation.However,most of research about P biogeochemical processes has been carried out in aquatic environment and agronomic field,but rare researches have been done in mountain ecosystem.In the present review,we summarize researches on P biogeochemical cycle concerning mountain ecosystem in recent decades,including rock weathering,the release,transformation and bioavailability of P,interactions between the P biological cycle and microbial and plant life,as well as the development of models.Based on the state of art,we propose the future work on this direction,including the integration of all these research,the development of a practical model to understand the P biogeochemical cycle and its bioavailability,and to provide a reference for ecological and environmental conservation of mountainous ecosystems and lowland aquatic systems.

Soil Properties and Land Capability Evaluation in a Mountainous Ecosystem of North-West Cameroon

Up to date, tropical mountainous ecosystems still lack in depth information on soil and environmental characteristics which are major factors limiting optimum crop production. The objective of this work was to study soil characteristics and to evaluate the land capability level for the production of some common tropical crops in mountainous ecosystem soils of North West Cameroon. Soil sampling was done following a randomized complete block design (RCBD) with four replications for three topographic positions (upslope, midslope and footslope) and at two depths (0 - 20 cm and 20 - 100 cm). It was completed by standard laboratory analyses. The fertility capability classification (FCC) system enabled to identify soil limitations and to classify soils into FCC units. Land and climate were evaluated by simple limitation and parametric methods. Globally, the soils were dark-colored, sandy clayey to clayey, compact and very acidic (pHH2O = 4.3 - 5.8). The organic matter (3.7% - 5.1% dry matter), total nitrogen (0.08% - 0.56%) and available phosphorus (22.1 to 30.9 mg?kg?1) recorded for the 0 - 20 cm depth then reduced with depth but midslope values were also lower. The C/N ratio varied between 9 and 45. Low C/N values appeared mostly in 0 - 20 cm depth at the upslope and downslope soils and subsurface soils of midslope position. Exchangeable Ca was very low to low (1.43 - 3.6 cmol + kg?1), Mg was very low to low (0.39 - 1.5 cmol + kg?1), K was low to medium (0.2 - 0.54 cmol + kg?1) and Na was very low (?1). The sum of exchangeable bases was very low (3.02 - 5.19 cmol + kg?1), cation exchange capacity was low to moderate (8.60 - 25.6 cmol + kg?1) and base saturation was very low to low (19.27% - 36.97%). Leaching of bases under heavy rainfall is a major cause of soil acidification under humid topical ecosystems. The Ca/Mg/K ratio was unbalanced and Mg was the most relatively concentrated base in all the soils. There was a clear variation of most of the soil properties along the slope and with depth. The soils were classified in the FCC system as aek for the upslope soils, Caek for the midslope soils and Cagk for the footslope soils. The principal limitations to production of huckleberry, beans, maize and potatoes were heavy rainfall, wetness, steep slope, soil texture/structure and low soil fertility. These constraints might be overcome by farming at the end of the raining season, contour ploughing, terracing, fertilization and liming.

Function of Rural Settlement Complex Ecosystem in Mountain Area:A Case Study of Raosi Village of Zuogong County,Tibet

Using energy analysis,the quantifying evaluation and study method on production, living and ecology functions and their sustainability of rural settlement ecosystem in mountain area is established with these energy index such as export of labor and products, export of water resource, internal energy reserve, energy consumption for human living, net energy of ecosystem function and net internal reserve. Taking rural settlement Raosi Village in Hengduan Mountains as a case study, and on the basis of the synthetic research into the ecological process of the complex ecosystem, the study shows that energy costs of production, human living and ecology functions are separately taking 1.36%, 13.59% and 85. 05% of the gross ecosystem functions, and the exertions of production and human living functions are close to a high-point state on the present using level of energy in the settlement. The study also shows that the most important function of a rural settlement in mountain area is its ecological rather productive function.

Carbon storage of a subtropical forest ecosystem: a case study of the Jinggang Mountain National Nature Reserve in south-eastern China

The carbon cycle of forest ecosystems plays a key role in regulating CO2 concentrations in the atmosphere. Research on carbon storage estimation of forest ecosystems has become a major research topic. However, carbon budgets of subtropical forest ecosystems have received little attention. Reports of soil carbon storage and topographic heterogeneity of carbon storage are limited. This study focused on the Jinggang Mountain National Nature Reserve as an example of a mid-subtropical forest and evaluated soil and vegetation carbon storage by field sampling combined with GIS, RS and GPS technology. We classified the forest into nine forest types using ALOS high-resolution remote sensing images. The evergreen broad-leaved forest has the largest area, occupying 26.5% of the total area, followed by coniferous and broad-leaved mixed forests and warm temperate coniferous forest, occupying 24.2 and 22.9%, respectively. The vegetation and soil carbon storage of the whole forest ecosystem were 1,692,344 and 5,514,707 t, with a carbon density of 7.4 and 24.2 kg/m^2, respectively, which suggests that the ecosystem has great carbon storage capacity. The topographic heterogeneity of the carbon storage was also analysed. The largest vegetation storage and soil storage is at 700–800 and 1000–1100 m, respectively. The vegetation carbon storage is highest in the southeast, south and southwest.

The value of vegetation ecosystem services:a case of Qinling-Daba Mountains

According to differences in vegetation types and their coverage, combining the latest research, using theory and method on the value of vegetation ecosystem services, this paper not only calculated goods produced by different types of vegetation but also estimated the value of various vegetation ecosystem services and set up database, GIS and eco-account of vegetation ecosystem. The result was as follows: the value of vegetation's primary productivity, soil and fertility conservation, water conservation, CO 2 fixation and O 2 release was 199.6 billion yuan/a, 22.64 billion yuan/a, 22.66 billion yuan/a, 352.24 billion yuan/a and 374.19 billion yuan/a, respectively. The total value of ecosystem services was 968.33 billion yuan/a. The temperate deciduous broad-leaved forest had the highest contribution rate, accounting for 16.42%. The result of value can reflect regional reality more exactly.

Analysis of solute preferential transport in a dark coniferous forest ecosystem of Gongga Mountain,Sichuan Province,southwestern China

We selected a dark coniferous forest ecosystem of Gongga Mountain in the upper reaches of the Yangtze River as our research area to study the preferential flow and solute preferential transport by adding the tracers KNO3 and KBr to the self-made soil column equipment in different ways to examine density and volume changes of inflows and outflows of a mass input （impulse input） and a stable, well-distributed input （step input））. The results showed that this dark coniferous forest ecosystem of Gongga Mountain is a typical area of preferential flow and solute preferential transport, a process that can be classified into five parts. A great amount of solute was transported at high speed as the result of preferential flow in the soil and caused the density of the solute in both deep water and in groundwater to rise rapidly, which definitely increased pollution in the deep soil layer.

喀斯特山地旅游地生态系统文化服务的空间分异及其影响因素——以黔西南州万峰林景区为例

喀斯特山地旅游地是一个典型的社会-生态系统,具有较高的生态系统服务价值,但针对其为公众提供的非物质收益却鲜有研究。该研究以黔西南州万峰林景区为典型案例地,采用Amazon Rekognition图像识别技术,结合社交媒体照片内容分析法、GIS空间分析法、地理探测器模型等方法,识别和分析喀斯特山地旅游地生态系统文化服务(CES)空间分异与影响因素。研究表明:(1)喀斯特山地旅游地具有美学、游憩、生物多样性、地方认同感、文化多元性和教育价值6种CES类型;(2)景区CES均存在显著的空间正相关性,总体CES热点区呈多核心分布态势,主要集聚在景区北部、中部和南部,且面积由北向南逐渐增大,形成了公众感知喀斯特峰林群和布依族文化景观的集聚区,而冷点区则少量集聚在景区中部东北向和南部东南向等区域;(3)距水系距离、距道路距离、高程和NDVI因子是影响总体CES的主导因子,土地利用类型、服务设施密度、村庄密度因子为次要因子,总体CES的多因子交互作用呈现出非线性增强多于双因子增强的交互类型特征,且自然与社会维度交互因子均提高了总体CES空间分异的解释力度。该研究为明晰和提升公众对喀斯特山地旅游地生态系统的非物质收益和社会文化福祉提供了实践参考。

“两山论”对发展理论创新的实践性分析——以生态系统服务价值实现的条件组态为视角

习近平的“两山论”作为对生态发展理念的全新诠释,其核心在于强调“和谐共生”的深刻内涵,同时更深刻地揭示了可持续发展的生态路径。研究通过理论模型和案例举证对这一创新的理论价值与实践价值进行了深入分析。研究发现,生态资源管控与迂回生产的结合,以及实际交易效率的提升,是实现生态价值的两组关键条件。研究不仅揭示了各因素间的相互作用及其对生态价值实现的影响机制,还通过对比不同地区的生态价值实现案例,提炼出成功实现生态价值的共性因素和条件组合。实践证明,“两山论”不仅为发展理论注入了新的活力,而且为当今世界的发展实践提供了宝贵的指导。

山地多中心城市公园绿地生态系统文化服务供需匹配特征

城市公园绿地为居民提供了重要的生态系统文化服务,在促进居民身心健康和提高社会福祉方面发挥着关键作用。以典型山地城市重庆中心城区为例,构建供需匹配评估体系,利用多源数据量化供给与需求,识别供需平衡与协调发展关系。结果表明:(1)重庆市中心城区城市公园绿地生态系统文化服务供需具有显著空间异质性,供给呈北高南低、分散布局的格局,需求呈中心高、外围低的格局;(2)生态系统文化服务供需失衡特征显著,其中52.38%的组团文化服务供给滞后,33.33%的组团属于供给超前状态;供需耦合协调指数平均值为0.50,协调发展程度空间分布呈“中心高、外围低”格局;(3)综合分析供需均衡与耦合协调结果发现,由于供给超前导致了外围城市组团的失调发展,而城市中心区域组团在供给滞后状态下维持了中等水平协调发展程度。总体来看,重庆市中心城区各组团存在不同程度的公园绿地生态系统文化服务供需错配,基于评估提出针对性的城市公园绿地优化策略,可为公园绿地的合理配置与规划提供重要支持。

贵州喀斯特山区农业生态效率测度及影响因素研究——基于生态系统服务改进的对比分析

以期望产出是否包括农业生态系统服务,对贵州喀斯特山区农业生态效率进行对比分析,以期为推动该区农业绿色发展提供理论参考与数据支持。采用超效率SBM模型、GML指数测度2000—2019年贵州9个市(州)2种农业生态效率,并利用Tobit回归模型探讨其影响因素。结果表明:①传统的农业生态效率只有贵阳有效,期望产出考虑了农业生态系统服务后,除六盘水、安顺、黔西南及黔南外,其余市州农业生态效率均值进入到有效区。②研究期内贵州传统的农业全要素生产率(GML)年均增长2%,尤其是2012年以后GML指数增长明显。除了遵义、黔东南和铜仁,其余市州传统的农业全要素生产率(GML)均大于1,各市州农业生态效率提高主要依靠技术进步提升带动。除了遵义和铜仁,其余各市州改进的GML指数均较传统的有所降低。③产业结构、财政支农水平、农业机械化密度与传统和改进的农业生态效率均呈正相关,农民收入水平、化肥使用强度与传统和改进的传统农业生态效率都呈负相关,人均耕地水平与植被覆盖度与改进的农业生态效率呈正相关,但与传统的农业生态效率呈负相关。

粤东北山地生态系统植被及其碳储量时空变化

根据遥感影像和实测土壤(选择林地、草地、耕地和建设用地等28个样地,采集112个土壤样品)有机碳含量数据,运用Sen氏趋势分析、Hurst指数、偏相关分析和InVEST模型等方法,探究粤东北山地生态系统植被及其碳储量时空变化特征。研究结果表明:1)研究区植被覆盖度较高,归一化植被指数(NDVI)变化范围为0.14~0.95,平均值为0.79。2000-2021年全域植被覆盖度呈上升趋势,空间分布存在差异,除梅州市区外,其他地区NDVI均有不同程度的增加,其中山地NDVI增加显著,且随海拔先上升后下降。研究区未来植被变化可能存在下降趋势(Hurst指数<0.5);2)2000-2020年研究区碳储量呈现减少趋势,共计减少1.33 Tg。土地利用变化,尤其林地、草地转化为耕地和建设用地是研究区碳储量减少的主要原因。研究结果可为我国亚热带生态系统碳汇功能变化研究提供基础数据。

贺兰山东、西侧典型植物群落物种多样性差异及其影响因子

深入理解干旱与半干旱地区山地植物群落的物种多样性特征及其环境影响因子,是全球气候变化下区域生物多样性保护的基础。贺兰山脉地处中国温带草原与温带荒漠的过渡带,其东、西侧受不同气候影响,各植被类型的物种多样性特征也存在差异。选取贺兰山东、西侧广泛分布的5个森林群落类型,通过群落组成、环境因子调查,分析贺兰山东、西侧典型植物群落物种多样性的差异及主要影响因子。结果表明,1)东、西侧典型植物群落在物种丰富度、水分生态类型构成上均存在较大差异:西侧群落的环境比东侧更干旱,因此水分生态类型构成上旱生植物的占比更高;在灰榆林、山杨林、青海云杉林中,相同取样面积时位于西侧的植物群落的物种丰富度明显高于东侧。2)物种多样性在东侧表现为随海拔升高先升后降,西侧则沿海拔升高而下降。灰榆林、油松林的物种丰富度在东、西侧存在显著差异。3)东、西两侧总体植物多样性空间分布格局与土壤含水量、速效磷、土壤容重的相关性相对较高。其中,土壤容重、海拔与乔木层多样性的相关性较高,海拔、土壤速效磷与灌木层多样性的相关性较高,草本层的多样性则主要受土壤速效磷、含水量的影响。贺兰山东、西侧典型森林群落的物种多样性与海拔、土壤理化特征具有相关性,因此改善土壤理化性质的林地管理措施可能有助于提高群落物种多样性。研究结果有助于深入理解干旱与半干旱山地生态系统的结构与功能,为脆弱山地生态系统的保育与恢复提供理论依据。

梵净山不同海拔土壤团聚体稳定性及影响因素

[目的]阐明土壤团聚体稳定性的海拔分布模式及其影响机制对评估山地自然生态系统生态功能稳定性至关重要。[方法]在梵净山900~2100 m海拔梯度下采集不同土层深度的土壤样品,借助干湿筛法和冗余分析(RDA)方法探讨了土壤环境因子与土壤团聚体稳定性的关系。[结果]在0—60 cm土层,土壤团聚体主要以>0.25 mm水稳性大团聚体为主,平均含量为86.78%;在0—20 cm土层各海拔梯度差异显著,且中海拔1 500~1 800 m处显著高于1 800~2 100 m(p<0.05)。土壤团聚体MWD,GMD和D与海拔存在显著相关性,随海拔的升高土壤团聚体MWD和GMD均呈先升高后降低的单峰分布模式,在中海拔1 500~1 800 m处达到峰值;且在0—10 cm和10—20 cm土层,1 500~1 800 m的MWD和GMD分别为5.03,3.64和4.79,3.52,显著高于900~1 200 m和1 800~2 100 m(p<0.05)。冗余分析显示,土壤团聚体稳定性沿海拔梯度变化主要受土壤SOC和pH值的影响,解释度分别为76.3%和1.3%,是影响土壤团聚体稳定性的主要环境因子。[结论]梵净山山地森林生态系统土壤团聚体稳定性沿海拔梯度具有明显差异,土壤化学性质是影响团聚体稳定性的重要因素。

供需关系下保定太行山区生态系统服务时空演化研究

为明确区域生态系统服务供给和需求的匹配关系,实现区域生态和社会经济的可持续发展,基于InVEST模型,量化太行山区保定段8个县域2005-2020年粮食供给和碳固定服务的供给量和需求量,对供需关系的时空特征进行研究,并为保定太行山区的生态系统服务管理提出合理建议。研究结果显示:(1)2005-2020年保定太行山区的粮食供给服务供给量呈现波动上升的趋势,需求量和供需比呈现持续上升的趋势;产水服务供给量和需求量呈现逐步上升的趋势,而供需比呈先上升后下降的趋势;碳固定服务供给量呈现先下降后上升的趋势,需求量呈现持续增长的趋势,供需比呈先上升后下降的趋势。(2)2005-2020年保定太行山区的粮食供给-产水-碳固定服务和3种生态系统服务的供需比均呈现"西北高,东南低"的分布特征。(3)2005-2020年保定太行山区的3种生态系统服务均以高供给低需求的供需特征为主,粮食供给-产水-碳固定服务的供需以供给大于需求为主。研究结果有助于了解保定太行山区的生态系统服务供需均衡匹配状况,并指导生态系统的管理和规划。

太行山典型流域森林生态系统碳储量分布特征

森林生态系统是陆地生态系统的主要碳库,准确评估其碳储量,探明其分布特征对区域碳汇管理及生态修复具有重要意义。本文以太行山区典型流域—柳林河流域的森林生态系统为研究对象,基于样地清查法,对区域内森林生态系统碳密度和碳储量分布特征展开研究。结果表明:1)柳林河流域森林生态系统碳密度为20.80 kg·m^(−2),碳储量为2.95×10^(6)t(C);2)在空间上,随海拔升高森林生态系统碳密度由15.12 kg·m^(−2)持续增加到27.34 kg·m^(−2),碳储量呈先增大后降低的变化趋势,并于700~900 m海拔处达最大,阴坡平均碳密度和碳储量均高于阳坡;3)在垂直组成上,灌木林与阔叶林中土壤层(0~100 cm)碳储量分别占森林总碳储量的77.87%和51.41%,而在针叶林中植被层碳储量占主导地位,占比为53.89%,各林型中土壤层碳密度和碳储量均随土壤深度的增加而减少,表层土壤(0~20 cm)碳储量占土壤层(0~100 cm)总碳储量的69.91%。柳林河流域森林生态系统碳密度与全国森林生态系统平均碳密度仍存在一定差距,未来应继续加强该区域特别是低海拔以及阳坡区域森林的经营管理和表层土壤的保护修复,以提升森林固碳增汇能力。该研究可为太行山流域碳储量评估、生态修复及多因素分析提供数据和理论支撑。

长白山温带森林生态系统关键要素耦合及演替过程动态模拟

认识生态系统内和生态系统间耦合机制,揭示复合生态系统功能规律,对促进我国山水林田湖草沙项目一体化修复和保护实践具有重要的意义。针对目前修复和保护工程中出现的缺乏系统性、连续性等问题,以拥有丰富生态资源的长白山温带森林生态系统为研究区域,对其关键要素“水土气生”进行耦合建模。通过分析模型的运行机理,探究重要子模块之间的相互作用以及子模块内部生态关键要素的耦合机制,并以长白山温带落叶阔叶林的组成树种和环境因素为对象构建模型参数,通过运行林窗模型1000次,得出长白山温带森林的动态演替过程。结果表明:在森林生态系统的演替过程中,“水土气生”体现为模型中有效积温、干旱天数(低于土壤凋萎点的天数)、土壤可利用氮以及可利用光,这些关键要素之间相互影响,综合决定着每棵树木的更新、生长、死亡过程。模拟结果显示在长白山温带针阔混交林的动态演替过程中0—70 a, 70—170 a, 170—280 a, 280—400 a四个阶段分别有不同的树种组成特征,与真实演替过程比较发现模拟林具有明显的阶段性。白桦、山杨为演替先锋树种,0—70 a期间生物量共占比为55%,70 a后生物量减少最后消失;紫椴、蒙古栎、水曲柳等为过渡树种,这些树种进一步改变了生长环境。红松在170 a前生物量占比仅为3%左右,随演替的发展生物量持续增加,170—280 a期间生物量占比15%,280 a之后红松生物量占总林分的50%。该结果模拟森林动态过程符合演替规律,充分说明多关键要素“水土气生”耦合机制的合理性,对于促进生态系统尺度上多生态要素耦合的相关研究提供了科学理论基础以及方法技术。

Allometric relationships between primary size measures and sapwood area for six common tree species in snow-dependent ecosystems in the Southwest United States

High-elevation,snow-dependent,semiarid ecosystems across southwestern United States are expected to be vulnerable to climate change,including drought and fi re,with implications for various aspects of the water cycle.To that end,much less is known about the dynamics of transpiration,an important component of the water cycle across this region.At the individual-tree scale,transpiration is estimated by scaling mean sap fl ux density by the hydroactive sapwood area(SA).SA also remains a key factor in eff ectively scaling individual tree water-use to stand level.SA across large spatial scales is normally established by relating SA of a few trees to primary size measures,e.g.,diameter at breast height(DBH),tree height(H),or canopy diameter(CD).Considering the importance of SA in scaling transpiration,the primary objective of this study was therefore to establish six species-specifi c(aspen,maple,white fi r,ponderosa pine,Douglas fi r,Englemann spruce)allometric relationships between SA and three primary size measures(DBH,CD,or H)across two high-elevation,snow-dependent,semiarid ecosystems in New Mexico and Arizona.Based on multiple statistical criteria(coeffi cient of determination,index of agreement,Nash–Sutcliff e effi-ciency)and ease of measurement in the forest,we identifi ed DBH as the primary independent variable for estimating SA across all sites.Based on group regression analysis,we found allometric relationships to be signifi cantly(p<0.05)diff erent for the same species(ponderosa pine,Douglas-fi r)across diff erent sites.Overall,our allometric relationships provide a valuable database for estimating transpiration at diff erent spatial scales from sap fl ow data in some of our most vulnerable ecosystems.