Monitoring litter interception of rainfall using leaf wetness sensor under controlled and field conditions

Leaf litter interception of water is an integral component of the water budget for some vegetated ecosystems. However, loss of rainfall to litter receives considerably less attention than canopy interception due to lack of suitable sensors to measure changes in litter water content. In this study, a commercially available leaf wetness sensor was calibrated to the gravimetric water content of eastern redcedar (Juniperus virginiana ) litter and used to estimate litter interception in a subhumid eastern redcedar woodland in north‐central Oklahoma. Under controlled laboratory conditions, a strong positive correlation between the leaf wetness sensor output voltage (mV) and measured gravimetric litter water content (? _g) was determined: ? _g = (.0009 × mV²) ? (0.14 × mV) ? 11.41 (R ² = .94, p  < .0001). This relationship was validated with field sampling and the output voltage (mV) accounted for 48% of the observed variance in the measured water content. The maximum and minimum interception storage capacity ranged between 1.16 and 12.04 and 1.12 and 9.62 mm, respectively. The maximum and minimum amount of intercepted rain was positively correlated to rainfall amount and intensity. The continuous field measurements demonstrated that eastern redcedar litter intercepted approximately 8% of the gross rainfall that fell between December 16, 2014 and May 31, 2015. Therefore, rainfall loss to litter can constitute a substantial component of the annual water budget. Long‐term in situ measurement of litter interception loss is necessary to gain a better estimate of water availability for streamflow and recharge. This is critical to manage water resources in the south‐central Great Plains, USA where grasslands are rapidly being transformed to woodland or woody dominated savanna.     

Dieback affects forest structure in a dry Afromontane forest in northern Ethiopia

Forests are highly susceptible to dieback under ongoing climate warming. In degraded forests, dead standing trees, or snags, have become such prominent features that they should be taken into account when setting management interventions. This study investigated (1) the extent and spatial pattern of standing dead stems of Juniperus procera and Olea europaea subsp. cuspidata along an elevational gradient, and (2) the effect of dieback on forest stand structure. We quantified abundance, size, and spatial pattern of tree dieback in 57 plots (50 m × 50 m) established at 100 m intervals along five transects. The snag density and basal area (mean ± SE) of the two species combined were 147 ± 23 stems ha⁻¹ and 5.35 ± 0.81 m² ha⁻¹, respectively. The percentages of snags were extremely high for both J. procera (57 ± 7%) and O. europaea subsp. cuspidata (60 ± 5%), but showed a decreasing trend with increasing elevation suggesting that restoration is even more urgent at the lower elevations. Snags of the two species accounted for 31 and 45% of total stand density and basal area, respectively. Living stems exhibited truncated inverse-J-shaped diameter and height class distributions, indicating serious regeneration problems of these foundation species in the study area. In addition to direct interventions to assist recruitment of climax tree species, sites with high dieback would probably benefit from snag reduction to prevent fire incidents in the remaining dry Afromontane forests in northern Ethiopia.     

帕米尔东北部昆仑圆柏850年树轮宽度年表的建立及其气候意义

利用帕米尔高原东北缘的昆仑圆柏树轮资料建立了850 a的树轮宽度年表(1165—2014年),是目前新疆最长的树轮年表。树轮宽度指数与乌恰站的气象资料相关分析表明:树轮宽度主要受水分条件限制,与降水量、降水日数和水汽压呈一致的正相关,其中树轮宽度标准年表与乌恰上年10月—当年7月的降水量的相关系数达到0.671。宽度年表与最高气温和最低气温呈反相关:当年生长季及其前期的最高气温与轮宽指数负相关,而最低气温(当年5月以外)与树木的生长正相关,表明生长季的较高的最高气温和冬季的较低的最低气温不利于树木的生长。树轮宽度指数与CRU格点降水资料的空间相关分析表明其能较好地反映帕米尔高原东部的降水变化,其次与新疆天山山区中部和南疆平原区的降水也具有较好的相关性。     

丝绸之路青海道吐蕃时期墓葬出土木材记载的森林干扰史

森林动态与气候变化及人类活动有着紧密的联系,了解森林干扰的发生历史对准确预测全球变暖背景下的森林动态具有重要意义,也可为理解历史时期的气候变化和人地关系演变提供线索.文章利用丝绸之路青海道沿线吐蕃时期3个墓葬中出土的78棵祁连圆柏(Juniperus przewalskii Komarov)原木作为研究对象,利用树木年...