Relationships between plant colonization and soil characteristics in the natural recovery of an earthquaketriggered debris flow gully in the Wanglang National Nature Reserve,China

Fragmentation and loss of habitats due to natural disasters, like earthquakes and earthquaketriggered debris flows are existing threats to the long- term survival of the giant panda （Ailuropoda melanoleuca）. To better understand natural recovery processes of the damaged habitat, field investigation and laboratory analysis were used to analyze relationships between plant colonization and soil characteristics in an over 3o-year natural recovery of a damaged giant panda habitat in a debris flow gully after the 1976 Songpan-Pingwu earthquake in Sichuan Province, China. Four different damaged sites were selected that located at the center of the gully （center）, on a flat alluvial fan （fan）, in a side slope of the gully （slope）, and at the ecotone between the gully and native forest （ecotone）. Vegetation characteristics, soil physicochemical properties, and microbial biomass in the different sites and soil depths were measured. After the natural recovery, the soil fertility, water retention, and microbial biomass were highest at ecotone, followed by fan, slope, and center. Only a few perennial herbs colonized at center; shrubs started to invade at fan and slope, and the native trees dominated the community of ecotone. Furthermore, Fargesia spathacea （food for the giant panda） started to be re-established at ecotone, and the community characteristic of ecotone recovered similarly to the native habitat. These results suggested that improving the soil fertility, water retaining capacity and microbial biomass is fundamental to the plant colonization, particular for F. spathacea＇s re- establishment in a damaged giant panda habitat.

岷江上游人工植被恢复下高石砾弃渣边坡土壤质量变化特征研究

【目的】为研究岷江上游人工植被恢复下土壤养分及土壤质量状况。【方法】本研究以人工植被恢复措施5年后的高石砾弃渣边坡、原生植被自然边坡、高石砾弃渣场边坡为对象,测定了土壤容重、pH、饱和水含量、毛细管孔隙度、总孔隙度、有机碳、全氮、全磷、速效钾和有效磷含量等理化指标,分析了土壤化学计量特征,采用土壤质量综合指数法对土壤质量进行了评价。【结果】(1)人工植被恢复弃渣场土壤容重显著低于弃渣场边坡,土壤理化指标(土壤饱和水含量、毛细管孔隙度、总孔隙度、有机质含量、总氮含量、全磷含量、速效钾含量和有效磷含量)显著高于原生植被自然边坡和弃渣场边坡,说明人工植被恢复改善了土壤结构,提高了土壤养分含量。(2)人工植被恢复弃渣场土壤N∶P和C∶P显著高于弃渣场,土壤化学计量比处理平衡状态,不受C和P的限制。(3)土壤综合指数为植被恢复的弃渣坡面>原生植被坡面>弃渣场。【结论】表明人工植被恢复能改善土壤质量,在高石砾弃渣边坡治理土壤环境的改善中发挥了积极作用。

海拔对暗紫贝母物候及形态特征的影响

为探究暗紫贝母(Fritillaria unibracteata)在不同海拔的人工种植成效,拓展产业发展空间,减缓产量与市场需求间的矛盾,在5个海拔(1174、1784、2371、3076和3413 m)开展了野外盆栽试验。结果表明:经过一个生长季后,"一匹叶"阶段暗紫贝母萌芽期和展叶期随海拔降低显著提前(P<0.05);枯萎期随海拔降低显著提前(P<0.05),但高海拔地区(3076和3413 m)枯萎期差异不显著(P>0.05);生长季长度随海拔降低表现出先增加后减少的特征,在3076 m最长,为(114.83±3.59)天。暗紫贝母株高和单叶面积随海拔降低表现出先增加后减小的特征,均在海拔2371 m最大,分别为(11.00±0.70)cm和(7.71±0.87)cm^(2);鳞茎横轴长和纵轴长随海拔降低表现出先增加后减小的特征,均在海拔3076 m最大,分别为(10.63±0.87)mm和(12.11±0.72)mm。本研究表明,从暗紫贝母生长季长度和鳞茎大小的角度考虑,可以选择在2371~3076 m的范围开展低海拔人工种植。

Uptake and Recovery of Soil Nitrogen by Bryophytes and Vascular Plants in an Alpine Meadow

Due to their particular physiology and life history traits, bryophytes are critical in regulating biogeochemical cycles and functions in alpine ecosystem. Hence, it is crucial to investigate their nutrient utilization strategies in comparison with vascular plants and understand their responses to the variation of growing season caused by climate change. Firstly, this study testified whether or not bryophytes can absorb nitrogen(N) directly from soil through spiking three chemical forms of 15N stable isotope tracer. Secondly, with stronger ability of carbohydrates assimilation and photosynthesis, it is supposed that N utilization efficiency of vascular plants is significantly higher than that of bryophytes. However, the recovery of soil N by bryophytes can still compete with vascular plants due to their greater phytomass. Thirdly, resource acquisition may be varied from the change of growing season, during which N pulse can be manipulated with 15N tracer addition at different time. Both of bryophytes and vascular plants contain more N in a longer growing season, and prefer inorganic over organic N. Bryophytes assimilate more NH4+ than NO3– and amino acid, which can be indicated from the greater shoot excess 15N of bryophytes. However, vascular plants prefer to absorb NO3– for their developed root systems and vascular tissue. Concerning the uptake of three forms N by bryophytes, there is significant difference between two manipulated lengths of growing season. Furthermore, the capacity of bryophytes to tolerate N-pollution may be lower than currently appreciated, which indicates the effect of climate change on asynchronous variation of soil N pools with plant requirements.

Impacts of ontogenetic and altitudinal changes on morphological traits and biomass allocation patterns of Fritillaria unibracteata

Environmental variations and ontogeny may affect plant morphological traits and biomass allocation patterns that are related to the adjustments of plant ecological strategies. We selected 2-, 3-and 4-year-old Fritillaria unibracteata plants to explore the ontogenetic and altitudinal changes that impact their morphological traits(i.e., plant height, single leaf area,and specific leaf area) and biomass allocations [i.e.,biomass allocations of roots, bulbs, leaves, stems, and flowers] at relatively low altitudinal ranges(3400 m to 3600 m asl) and high altitudinal ranges(3600 m to4000 m asl). Our results indicated that plant height,root biomass allocation, and stem biomass allocation significantly increased during the process of individual growth and development, but single leaf area, specific leaf area, bulb biomass allocation, and leaf biomass allocation showed opposite trends.Furthermore, the impacts of altitudinal changes on morphological traits and biomass allocations had no significant differences at low altitude, except for single leaf area of 2-year-old plants. At high altitude,significantly reduced plant height, single leaf area and leaf biomass allocation for the 2-year-old plants,specific leaf area for the 2-and 4-year-old plants, and stem biomass allocation were found along altitudinal gradients. Significantly increased sexual reproductive allocation and relatively stable single leaf area and leaf biomass allocation were also observed for the 3-and 4-year-old plants. In addition, stable specific leaf area for the 3-year-old plants and root biomass allocation were recorded. These results suggested that the adaptive adjustments of alpine plants, in particular F. unibracteata were simultaneously influenced by altitudinal gradients and ontogeny.