Aspects of forest restoration and hydrology:the hydrological function of litter

Although forests play important roles in the hydrological cycle,there is little information that relates the water retention capacity of litter in areas under passive restoration,especially in Cerrado savannas.This study relates litter levels to water holding capacity and effective water retention among forest fragments under different passive restoration stages:46,11,and 8 years to better understand litter hydrological functions in the Cerrado.Water retention capacity and effective water retention capacity of litters(unstructured materials,branches and leaves)in the field were monitored on a monthly basis.Total litter accumulation at 46 years was significantly higher than that of the other succession stages.Unstructured litter mass was significantly higher than that of leaves and branches.The 46-year stage had the highest water holding capacity in the leaf fraction,followed by unstructured material and branches.Although the water holding capacity was lower in the oldest resto-ration,this site showed the highest efficiency under field conditions.The process was quickly reestablished,as the 11-year restoration showed results closer to that for the 46-year stage in comparison to the area at 8 years.Thus,passive restoration plays a key role in soil water mainte-nance due to the influence of litter in Cerrado savannas.Deforestation and the imminent need of restoring degraded sites,highlight the need for further studies focused on bet-ter understanding of the process of forest restoration and its temporal effect on soil water recovery dynamics.

西秦岭森林生态旅游区不同林分类型土壤水文效应研究——以麦积山风景区为例

为揭示麦积山风景区不同林分土壤水文效应,采用环刀法对麦积山风景区5种林分林下土壤持水性进行研究。结果表明:5种典型不同林分类型林地土壤0~30 cm容重平均值范围为1.14~1.48 g·cm3,土壤总孔隙度均值为43.40%~54.86%,其中锐齿栎林最大,油松+锐齿栎林和油松林次之,油松+辽东栎林最小。不同林分林地土壤最大持水量以锐齿栎林(548.56 t·hm-2)最大,油松+辽东栎林(434.02 t·hm-2)最小,说明锐齿栎林土壤持水能力最强。土壤稳渗速率以油松+锐齿栎林最大(1.52 mm·min-1),油松林最小(1.21 mm·min-1)。5种不同林分林下土壤入渗时间和入渗速率存在着较好的幂函数关系。

Rainfall partitioning in young clonal plantations Eucalyptus species in a subtropical environment,and implications for water and forest management

Different canopy characteristics of industrial eucalyptus may lead to differences in water evaporation and availability to plants.This study aims to understand rainfall partitioning in a young clonal plantation(age of 2-4.5 years)of three eucalyptus species by relating tree parameters:diameter at breast height,total height,and leaf area index.We measured rainfall,throughfall,stemflow and litter interception,along with the tree parameters.The eucalyptus trees had rainfall interception varying between 22 mm(for 178 mm of rainfall)and 42 mm(for 87 mm of te rainfall),throughfall between 106 mm(for 186 mm of rainfall)and 44 mm(for 74 mm of rainfall),and stemflow between 0.5 mm(for 92 mm of rainfall)and 1.4 mm(for 24 mm of rainfall).For the three species,rainfall interception varied between 12 and 48%,throughfall between 57 and 90%,and stemflow between 0.3 and 5.4%.The coefficient of determination between interception and rainfall was 0.76,indicating interception depends on other variables,possibly including antecedent rainfall,rainfall intensity,and seasonality.Interception decreased with a reduction in leaf area index caused by eucalyptus defoliation.The E.benthamii had 0.75 mm of throughfall per 1 mm of rainfall,whereas in E.dunnii and E saligna,these ratios were 0.71 and 0.68,respectively.Stemflow in E.benthamii and E.dunii had a higher positive relationship with the diameter at breast height of the trees,whereas in E.saligna the highest relationship was with the rainfall.These results contribute to establishing management strategies,such as choosing suitable eucalyptus species to local climate,and to improve the synchronization of crop-demand versus soil-water-supply while maintaining streamflow to fulfill ecological and production needs.

Estimating tree and stand sapwood area in spatially heterogeneous southeastern Australian forests

Aims Natural and anthropogenic changes in forests can have important influences on transpiration and water production.Understanding the effects of increasing disturbances,due for example to climate change and forest harvesting,requires detailed information on how forest density and structural attributes relate to transpiration.Mean annual transpiration of eucalypt forest communities is often strongly correlated with total cross-sectional sapwood area.Our aim was to test an efficient method for estimating sapwood area at_(1.3)m height(SA_(1.3))in a large number of trees to understand the spatial heterogeneity of tree and stand sapwood area within and between forest communities,and develop allometric relationships that predict SA_(1.3)with forest inventory data.We also apply tree competition models to determine the degree to which the relationship between SA_(1.3)and tree basal area at_(1.3)m height(BABA_(1.3))is influenced by competition.Methods We visited 25 recently harvested southeastern Australian forest sites consisting of 1379 trees and 5 Eucalyptus species to evaluate a new efficient data collection method for estimating SA_(1.3)with tree taper and stump dimensions data using mixed effects models.The locations of 784 stumps within one 5-ha site were accurately mapped using an unmanned aerial vehicle(UAV),and four distance-dependent tree competition models were applied across the site to explain within-stand variation in the ratio of SA_(1.3)to BABA_(1.3).Data from 24 additional sites,consisting of ten 15 m radial plots per site,were used to analyse within-site variation in R_(Ha)(the ratio of stand sapwood area SA_(Ha)to stand basal area BABA_(Ha)).The radial plots were merged within each site to evaluate between-site variations in R_(Ha)across the landscape.For predicting SA_(Ha)with forest inventory data,we computed the relationship between SA_(Ha)and a new index of total stem perimeter per hectare,defined as√BA_(Ha)N_(T),where N_(T)is tree stocking density.Important Findings Our 1379 measured stems represent the most comprehensive measure of sapwood area,surpassing the 757 measured stems in native eucalypt forests published in literature.The species-specific R_(Ha) varied considerably across sites and therefore extrapolating SA_(Ha)with spatially distributed BABA_(Ha)maps and a generalized R_(Ha) would introduce local uncertainty.We found that the species-specific stem perimeter index was more effective at capturing variability in SA_(Ha)across the landscape using forest composition,structure and density data(R^(2):0.72–0.77).The strong correlation between tree SA_(1.3)and BABA_(1.3)improved slightly using tree competition models(R^(2)increased from 0.86 to 0.88).Relating SA_(Ha)to routinely measured forest inventory attributes within permanent plots and Light Detection and Ranging(LiDAR)data may provide opportunities to map forest water use in time and space across large areas disturbed by wildfire and logging.

Current Status and Trend of Forest Hydrological Services Market Research

Of the many services that forests provide, hydrological services are among the most valuable, and it becomes more scarce with the growing demands by human beings. As a kind of incentive measure for protecting forest, forest hydrological services markets have been developed in many countries around the world and some valuable experiences have been achieved. The paper reviews the experiments carried out in the world and their research findings on forest hydrological services market, and presents the issues to be studied for the establishment of future water services market.