Planting mahogany in canopy gaps created by commercial harvesting

Attempts at natural forest management of mahogany (Swietenia macrophylla King) have so far met with limited success, whilst many plantations are beset by the shoot borer Hypsipyla spp. In this paper we present preliminary results of an approach to enrichment planting that aims to balance economic returns (rapid growth and good silvicultural form) with intervention costs and changes to forest structure. Mahogany seedlings were planted in gaps created by selective timber harvesting and that ranged in vertical projected area from 91 to 542 m² (mean = 257 m²). Seedlings grew within the matrix of gap regrowth, with limited control of competing vegetation. Sixty-one percent of seedlings had survived by 4.4 years (equivalent to an annual mortality rate of 10.5% year⁻¹), and had reached a mean height of 4.5 m. Stocking levels of mahogany were similar to that of naturally regenerated commercial species in unplanted gaps of the same age, but mahogany seedlings were significantly taller. The incidence of shoot borer attack on mahogany stems was relatively low (54.7%), but, more importantly, most damaged stems (58%) responded by producing a single replacement leader. The cost of the proposed methodology (US$ 94 per gap over 4.4 years) was low compared to the high value of mahogany timber relative to other species in the forest. The implications of planting mahogany in gaps for forest management and the potential benefits to conservation of the species are considered.     

Toward a model for local stakeholder participation in landscape-level wildlife conservation

The conservation community is increasingly taking a landscape-level approach to wildlife conservation. This approach faces obstacles, including how to ensure transboundary wildlife conservation goals that can be realized through local management actions, and how and when to engage local stakeholders in landscape conservation planning processes. Currently, local stakeholder participation is not institutionalized within these processes. This paper examines the potential role of local stakeholders in landscape conservation. In this paper, we present a preliminary model of cross-level coordination that could facilitate development and implementation of conservation across social–ecological landscapes, highlighting the possible contributions of local stakeholders. The feasibility of this model is contingent on addressing a range of challenges associated with local stakeholder participation in extra-local conservation decisions. Ultimately, we present suggestions for future research examining the potential for a locally inclusive, participatory approach to wildlife conservation across complex landscapes.     

Invasion of Non-Commercial Tree Species After Selection Logging in a Bolivian Tropical Forest

Abstract

Single-tree selection logging will likely result in a 4.3% loss in the relative abundance and a 4.1% loss in basal area of trees of commercial species in one cutting cycle due to their removal by harvesting combined with their potential recolonization of only 31% of logging gaps in a Bolivian tropical dry forest. Densities of the most valuable species, Amburana cearensis and Cedrela fissilis, were particularly reduced by logging. To sustain the current harvesting rate, uses need to be developed for more non-commercial species and/or silvicul-tural treatments employed that increase regeneration of commercial species and remove non-commercial species using timber stand improvement techniques.     

Analysis of Water Non-limiting and Water Limiting Yields and Yield Gaps of Groundnut in India Using CROPGRO-Peanut Model

To assess the scope for enhancing productivity of groundnut (Arachis hypogaea L.) in India, well‐calibrated and validated CROPGRO‐Peanut model was used to assess potential yields (water non‐limiting and water limiting) and yield gaps of groundnut for 18 locations representing major groundnut growing regions of India. The average simulated water non‐limiting pod yield of groundnut for the locations was 5440 kg ha^?1, whereas the water limiting yield was 2750 kg ha^?1 indicating a 49 % reduction in yield because of deficit soil moisture conditions. As against this, the actual pod yields of the locations averaged 1020 kg ha^?1, which was 4420 and 1730 kg ha^?1 less than the simulated water non‐limiting and water limiting yields, respectively. Across locations, the simulated water non‐limiting yields were less variable than water limited and actual yields, and strongly correlated with solar radiation during the crop season (R² = 0.62, P ≤ 0.01). Simulated water limiting yield showed a significant positive, but curvilinear relationship (R² = 0.73, P ≤ 0.01) with mean crop season rainfall across locations. The relationship between actual yield and the mean crop season rainfall across locations was not significant, whereas across seasons for some of the locations, the association was found to be significant. Total yield gap (water non‐limiting minus actual yields) ranged from 3100 to 5570 kg ha^?1, and remained more or less unaffected by the quantity of rainfall received across locations. The gap between simulated water non‐limiting and water limiting yields, which ranged from 710 to 5430 kg ha^?1, was large at locations with low crop season rainfall, and narrowed down at locations with increasing quantum of crop season rainfall. On the other hand, the gap between simulated water limiting yield and actual farmers yield ranged from 0 to 3150 kg ha^?1. It was narrow at locations with low crop season rainfall and increased considerably at locations with increasing amounts of rainfall indicating that type of interventions to abridge the yield gap will vary with the rainfall regimes. It is suggested that improved agronomic management (such as high yielding cultivars, balance crop nutrition and control of pest and diseases) in high rainfall regimes and rainfall conservation and supplemental irrigations in low rainfall regimes will be essential components of the improved technologies aimed at abridging the yield gaps of groundnut.     

Mechanical cleaning and prescribed burning for recruiting commercial tree regeneration in a Bolivian dry forest

A critical component of sustainable forest management is the regeneration of commercially valuable tree species. Mechanical cleaning with machetes and chainsaws, prescribed burning, and a combination of both treatments were applied to recently-created logging gaps in a Bolivian dry forest to evaluate their impact on the natural regeneration of commercial tree species and on control of competing vegetation. The three treatments and an untreated control were applied to logging gaps during the dry season of 1998 and replicated ten times. Eight months following burning, the density of commercial tree regeneration in gaps did not differ statistically among treatments. Relative height growth of total commercial regeneration also did not differ among treatments, although it did vary by species. Reduction in competing vegetation following the application of site preparation treatments was significantly higher, but competing plant cover was beginning to converge among treatments after eight months. Despite better control of competing vegetation, early recruitment and growth responses to burning and cleaning of vegetation in logging gaps do not appear to justify application of these treatments in this forest, especially considering their high costs.     

子午岭油松林林隙更新特征研究

利用样地调查资料,以林下为对照,分析研究子午岭油松林的林隙更新特征,结果表明:1)子午岭油松林林隙内和林下更新树种在组成和数量上有较大差异,其中,油松在林隙内的重要值远远大于其在林下的重要值,是林隙更新的主要树种;2)油松幼苗幼树在林隙内生长良好,7年生以上的幼树在林下分布已很少,地径在1.0cm以上、高度在50cm以上的幼树数量分布在林隙内也远远大于林下,说明随着年龄的增长,油松幼苗幼树在林隙内存活的概率大于林下;3)方差分析表明,油松幼苗幼树在林隙内与林下的高度生长差异极为显著;4)相关性分析表明,林隙内油松幼苗幼树的更新数量与光照强度呈显著正相关,与植被总盖度呈显著负相关。     

茂兰喀斯特森林干扰状况与林隙特征

调查茂兰喀斯特森林林隙干扰特征,并对林隙特征、林隙的形成方式进行探讨。结果表明:1)林隙大小分布表现出以小林隙为主的偏正态分布,但在总林隙面积比例上,大林隙所占的比例较大;2)林隙大多数在20年前形成,估计林隙形成速率为0.55个·hm-2a-1,返回间隔期为270年;3)林隙密度约为20个·hm-2,林隙平均面积(69.7±45.71)m2,扩展林隙平均面积(152.7±79.43)m2,林隙和扩展林隙占所调查林分面积的比例分别为13.9%和30.6%;4)林隙形成方式以折干为主,但因地形差异,槽谷、坡地、漏斗的主要形成方式分别为干中折断、拔根倒和干基折断;5)大多数林隙由1～4株形成木形成,平均每个林隙的形成木为2.5株。大部分林隙形成木为森林建群种,常绿和落叶树种分别占61.5%和38.5%。林隙形成木以小径级为主,表明本地森林林隙干扰十分频繁。     

极端天气干扰下闽北人工林林隙形成方式及其特征

对福建省顺昌县宝庄村人工林在极端天气干扰下形成的林隙进行调查,研究人工林林隙分布及其特征。结果表明,在宝庄村人工林中,树木倒伏形成的林隙最为常见,占林隙总数的32．98％;其次是树木翻兜形成的林隙,占27．66％。林隙形状不规则,林冠空隙（CG）和扩展林冠空隙（EG）面积主要集中在600～800m。;形成木数量组成以100～150株为主,形成木分布最多的径级在10-15cm,构成形成木的主要树种是马尾松、杉木、毛竹。以林隙形成特征为参照,对受灾人工林的恢复提出建议。     

Human-scale structural heterogeneity induced by grazing in a Mediterranean woodland landscape

A set of structural criteria to differentiate among types of a heterogeneous woodland landscape that are shaped by goat and cattle grazing was studied in northern Israel. The landscape was described with relation to the “human scale” of the observer, by mapping the dimensions, basic shapes, and distribution of gaps between individual plants on sites with various grazing management systems. The shapes of the trees and the bushes were drawn in situ and the ratio between plant height and the width of the adjacent open space was measured in order to define the various structural profiles of the vegetation. All the structural criteria clearly and significantly differentiated among grazing systems that created closed (no grazing), half-open (cattle and modern goat grazing) and open (traditional goat grazing) landscapes. The diversity of plant shapes was highest under the cattle and modern goat grazing management systems. In the ungrazed treatment, more than 60% of the gaps were defined as ‘inaccessible’ compared with only 10–15% under cattle grazing and modern goat grazing. The diversity of gap proportions was high, but their absolute number was low. Under traditional heavy goat grazing, there were only wide and open gaps. Under cattle grazing and modern goat-grazing management systems, a relatively large number of wide and open gaps were found, with small numbers of narrow and closed gaps. Overall, the various grazing systems were differentiated most clearly according to their transparency, accessibility, height of Quercus calliprinos, and gap distribution. We conclude that structural criteria provide an efficient and objective methodology for evaluating the effects of grazing on different components of Mediterranean woodland mosaic landscapes. Nomenclature follows Feinbrun-Dothan and Danin (1991)     

基于“近自然林业”的红松林主要树种重要值的研究

以“近自然林业”为指导思想,对凉水自然保护区不同类型红松林主要树种的重要值进行了研究。结果表明：红松在天然林内并不占据优势地位;红松人工纯林内红松的重要值都很大,都大于同林分内的阔叶树主要树种的重要值之和;林隙透光抚育林内红松的重要值为107．98％,而其他几个阔叶树种色木、白桦、椴树和杨树的重要值相加为121．69％,主要树种中针叶树种和阔叶树种的比值接近1∶1,这种重要值的比率使整个林分的针阔比处于一种平衡的状态。