黄土高原森林植被景观的特征分析

用1∶50万森林类型图为信息源,以G IS为手段,对黄土高原地区森林景观类型斑块的大小、形状以及空间特征进行了分析。结果表明:黄土高原地区27类森林总面积仅64 980.7 km2,共有斑块数5 890个,林斑平均面积较小,且分布不均,森林景观破碎化程度较高。森林景观以华北落叶松林、山杨林、油松林、辽东栎林等为优势类型。黄土高原森林景观类型的形状指数值都比较大,说明森林斑块的形状明显偏离于圆形和方形,多为狭长的不规则形,其斑块的边界率都比较高。不同类型森林分维数变化较大,这也表明黄土高原森林景观破碎化程度较高,景观异质性较大。     

Soil loss and displacement by heavy equipment in forest road subgrading projects

Forest soil is an important component of the natural environment, and is a primary medium for many biological activities. In this study, soil loss and displacement by excavator and bulldozer （heavy equipments） were measured on cut and fills slopes of forest roads located in Mazandaran province, lran. The volumes of soil losses were estimated by prismoidal analyses of cut and fill slopes deformation between two time treatments （under subgrading and two years later） in slope classes of 30-50% and 50-70%. Weights of soil losses were calculated by multiplying the volumes of soil losses （cm^3） to the general bulk density （1.3g/cm^3）. Soil displaced area by heavy equipment was evaluated according to earth working width. Results indicated that heavy equipment has significant effect on deformation of cut slope gradient and fill slope length （p〈0.0001）. During the two-year period, the cut （p〈0.0002） and fill （p〈0.0001） slope gradients were significantly deformed in different slope classes. The average soil loss by excavator and bulldozer were 160.35 t/ha·yr and 429.09 t/ha·yr, respectively. Moreover, the soil displaced area during the subgrading process by bulldozer was greater than excavator in both two slope classes （p〈0.05）. Soil loss and displacement in forest roads can be rednced by applying powerful excavators in subgrading project, especially in steep terrains.     

REDD+ and incentives: An analysis of income generation in forest-dependent communities of the Yasuní Biosphere Reserve,Ecuador

Reducing Emissions from Deforestation and Forest Degradation (REDD+) is considered a promising strategy to slow down deforestation rates, promote sustainable forest use, and support rural livelihoods under the umbrella of climate change mitigation. However, so far there is only little field-based knowledge on how REDD+ can go along with subsistence-based production systems and livelihoods of forest-dependent communities. We addressed this research gap by analyzing the income generation of three widespread ethnic groups (Colonists, Shuar, Kichwa) in the buffer zone of the Yasuní National Park in Ecuador to better understand their livelihoods and possible engagement in REDD+. We selected two communities of each ethnic group (close-to and far-from markets) and used household surveys to (a) calculate household incomes, (b) assess the degree of forest-dependency, and (c) discuss how REDD+ schemes can be designed along with traditional subsistence-based production systems. We found that the studied indigenous communities have a higher degree of forest-dependency and higher environmental income compared to Colonists. However, our assumption that close-to-market communities have a lower degree of forest dependency and higher cash income due to better market access and labor opportunities applies only to the Colonists and Shuar, but must be rejected for the Kichwas who gain income from timber sale. Despite these differences, all communities receive high off-farm revenues from unskilled labor provided by oil-companies and external aid. Therefore, dependency on agriculture and forestry is temporarily reduced. Under these circumstances, REDD+ provides only weak financial incentives so that the willingness to participate in REDD+ is low.     

Hydrology and related changes after harvesting native forest catchments and establishing pinus radiata plantations. Part 1. Introduction to study

The hydrology of eight small catchments (1.63–8.26 ha) has been monitored in Westland, New Zealand since 1975. Two of these catchments were left in indigenous beech-podocarp-hardwood forest and the rest were subjected to various harvesting and land preparation treatments before being planted with Pinus radiata. This paper introduces a series of papers on the hydrology of the indigenous forest catchments and the changes that occurred after treatment. The catchments, experimental programme, climate of the area and the rainfall regime experienced between 1975 and 1987 are described.     

Hydrology and related changes after harvesting native forest catchments and establishing pinus radiata plantations. Part 2. The native forest water balance and changes in streamflow after harvesting

Six small, steep, south-west facing catchments (1.63–4.62 ha) have been monitored in Westland, New Zealand since 1974. Two catchments were retained in native mixed evergreen forest and the rest were subjected to various harvesting and land preparation techniques before being planted with Pinus radiata between 1977 and 1980. The 11-year water balance for the native forest catchments was: rain = streamflow + interception loss + transpiration + seepage (2370mm = 1290mm + 620mm + 360mm + 100mm). In the year after treatment streamflow generally increased by 200–250 mm, except for one treatment (clearfelling, herbicide application, no riparian reserve) where the increase was 550 mm. The catchments were planted with Pinus radiata, but rapid colonization by bracken (Pteridium esculentum) and Himalayan honeysuckle (Leycesteria formosa) led to a rapid decline in streamflow, which returned to pre-treatment levels after an average of about five years. Streamflow yields then continued to decline for another two to three years before stabilizing at a level about 250mm yr^?1 lower than pre-treatment levels. At this time the catchments had a dense bracken/honeysuckle understorey beneath 5 m tall pine trees.     

神农架红桦林的孢粉学研究

本文是在鄂西神农架山区的红桦林中,进行的孢粉组合与植被关系,及其森林植被历史的实验研究。在孢粉统计中、计算了各种类成分的百分频度、浓度、“R”值及其置信区间。论证了由华山松林——红桦林的植被变化过程,各种植物成分间的生态关系。实验证明,研究当地现代花粉与植物间数量关系,以校正化石花粉数值,对于用孢粉学方法研究历史时期的植被与环境,是至关重要的。     

Monitoring spatial variability of forest interception

Field instrumentation was designed and installed to quantify the influence of forest interception on the spatial and temporal distribution of water flux onto and into the forest soil at the plot scale. An application is presented which demonstrates that the instrumentation has the required resolution to monitor the spatial variability and dynamics of the flux processes. The observations show that spatial variability of interception may play an important role, not only in small scale soil moisture heterogeneity, but also in the hydrological response of a forested catchment at the hillslope scale. They also highlight the need of gathering more field information on the effects of vegetation on the spatial variability of soil surface water input.     

Scaling smallholder tree cover restoration across the tropics

Restoring tree cover in tropical countries has the potential to benefit millions of smallholders through improvements in income and environmental services. However, despite their dominant landholding shares in many countries, smallholders’ role in restoration has not been addressed in prior global or pan-tropical restoration studies. We fill this lacuna by using global spatial data on trees and people, national indicators of enabling conditions, and micro-level expert information. We find that by 2050, low-cost restoration is feasible within 280, 200, and 60 million hectares of tropical croplands, pasturelands, and degraded forestlands, respectively. Such restoration could affect 210 million people in croplands, 59 million people in pasturelands and 22 million people in degraded forestlands. This predominance of low-cost restoration opportunity in populated agricultural lands has not been revealed by prior analyses of tree cover restoration potential. In countries with low-cost tropical restoration potential, smallholdings comprise a significant proportion of agricultural lands in Asia (∼76 %) and Africa (∼60 %) but not the Americas (∼3%). Thus, while the Americas account for approximately half of 21st century tropical deforestation, smallholder-based reforestation may play a larger role in efforts to reverse recent forest loss in Asia and Africa than in the Americas. Furthermore, our analyses show that countries with low-cost restoration potential largely lack policy commitments or smallholder supportive institutional and market conditions. Discussions among practitioners and researchers suggest that four principles – partnering with farmers and prioritizing their preferences, reducing uncertainty, strengthening markets, and mobilizing innovative financing – can help scale smallholder-driven restoration in the face of these challenges.     

Canopy foliar nitrogen retrieved from airborne hyperspectral imagery by correcting for canopy structure effects

A statistical relationship between canopy mass-based foliar nitrogen concentration (%N) and canopy bidirectional reflectance factor (BRF) has been repeatedly demonstrated. However, the interaction between leaf properties and canopy structure confounds the estimation of foliar nitrogen. The canopy scattering coefficient (the ratio of BRF and the directional area scattering factor, DASF) has recently been suggested for estimating %N as it suppresses the canopy structural effects on BRF. However, estimation of %N using the scattering coefficient has not yet been investigated for longer spectral wavelengths (>855 nm). We retrieved the canopy scattering coefficient for wavelengths between 400 and 2500 nm from airborne hyperspectral imagery, and then applied a continuous wavelet analysis (CWA) to the scattering coefficient in order to estimate %N. Predictions of %N were also made using partial least squares regression (PLSR). We found that %N can be accurately retrieved using CWA (R² = 0.65, RMSE = 0.33) when four wavelet features are combined, with CWA yielding a more accurate estimation than PLSR (R² = 0.47, RMSE = 0.41). We also found that the wavelet features most sensitive to %N variation in the visible region relate to chlorophyll absorption, while wavelet features in the shortwave infrared regions relate to protein and dry matter absorption. Our results confirm that %N can be retrieved using the scattering coefficient after correcting for canopy structural effect. With the aid of high-fidelity airborne or upcoming space-borne hyperspectral imagery, large-scale foliar nitrogen maps can be generated to improve the modeling of ecosystem processes as well as ecosystem-climate feedbacks.