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林业是瑞典经济的重要组成部分,2017年林业GDP贡献率为2.2%。瑞典森林面积占土地面积的55%,根据2012年统计数据,75%的森林面积为个人所有,南部为78%[1]。合理的经营规划对于经济收益、环境保护和政策实行都有重要意义。Ollas[2]2016年的研究结果显示,合理的经营规划可以降低风险,提高林场主经济收益,同时对生态环境也可做出有效保护。Brukas等[3]认为除了确保经济收益和发挥生态保护功能,森林经营规划还可成为有效的政策调节工具。1994年之前,森林经营的重心为提高生产力。1994年之后,来自于国际、国家和社会等各方压力驱使生态保护逐渐成为森林经营的重要因素[1],多目标森林经营可以实现木材生产、生态保护、生活娱乐等多重经营目标。目前瑞典森林经营的主要目标为木材生产(57%)、生态保护(12%)、生活娱乐(15%)等[1],最常用的多目标经营方法为分级经营体系。2003年,Pukkala[4]对多目标森林规划进行了系统的介绍;2014年,Annika Kangas[5]介绍了基本规划和分级规划两种规划体系,同时根据对Virtanen的案例分析显示,分级规划体系更易达到预定的经营目标;Seely等[6]通过分级决策系统实现了对多目标经营规划的评估。
为实现Ostad区森林资源的可持续利用,本规划以木材收获和生态保护为目标,根据实地调查,ProdMod生长模拟所获得的数据,对Ostad区2017—2027年森林经营进行中期规划,确保在未来10年中,既可以通过木材收获达到足够的经济收益,也保证区域内的生态环境不受破坏。
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Ostad位于瑞典西南部,昼夜温差大,夏季多风,年平均气温为7 ℃,年降水量700 mm,土壤性质为中度湿润,东南部及西北部有明显裸露岩石及沼泽[7],森林面积为206.27 hm2,共有89个小班(图 1)。森林生长量及树种组成如表 1和表 2所示。
图 1 Ostad各经营类型和土地利用类型分布图
Figure 1. Overview of forest landscape as characterized by management objectives and land uses in the Ostad Estate
表 1 2017年Ostad区森林生长量与木材产量
Table 1. Growth and productivity of Ostad Estate with a reference year of 2017
变量Variable 数值Value 森林面积/hm2
Forest area/ha206.27 平均生长量(上一个10年规划期)
Mean growth(according to last ten-year planning)/
(m3·a-1)1 944.98 每公顷平均生长量/(m3·(hm-2·a-1))
Mean growth per hectare/(m3·(ha-1·a-1))9.43 连年生长量
Continuous annual growth/(m3·a-1)1 799.62 每公顷连年生长量/(m3·(hm-2·a-1))
Continuous annual growth per hectare/(m3·(ha-1·a-1))8.70 活立木蓄积
Living standing stock/m345 922.14 每公顷活立木蓄积/(m3·hm-2)
Living standing stock per hectare/(m3·ha-1)222.63 表 2 2017年树种组成及活立木蓄积
Table 2. Species composition and living standing stock in 2017
树种
Species蓄积
Volume/m3组成
Proportion/%欧洲赤松Scots pine 8 304.58 18.08 挪威云杉Norway spruce 28 474.78 62.00 白桦Birch 4 021.41 8.76 欧洲山毛榉Beech 102.96 0.22 重要阔叶树种
Nobel broadleaved species4 916.57 10.71 其他阔叶树种
Other broadleaved species101.84 0.22 总量Total 45 922.14 100.00 瑞典林业法通过后,为实现可持续林业的经营目标,达到木材利用和环境保护的双重目标,瑞典林业局和其他林业相关部门共同制定了绿色森林经营目标[8]。在绿色森林经营的总目标下根据不同林分的长期经营目标(一般为100年)和对于经济效益或生态效益的侧重点不同,将林分划分为4种类型,即满足一般生态保护要求的用材林(Production with general considerations,简称PG),如收获时,植株的胸径达到瑞典林业局最低要求即可[9];强生态保护用材林(Production with stronger considerations,PF),如皆伐时,每公顷留下3~5株高度大于30 cm的树桩为皆伐区域的昆虫提供临时栖息地等;轻微人工干预的生态保留地(Nature conservation with management,NS),这种经营类型旨在通过人工干预恢复或提高经营区生态环境,如通过控制立地条件较好林分内的针叶树,提高阔叶树比例。该经营类型中包含欧洲山毛榉等具有一般生态价值的阔叶树种和过熟龄个体;无人工干预的生态保留地(Nature conservation, free development,NO),该经营类型内一般包括具有高生态价值的阔叶树种如栎类(Quercus)和过熟龄个体。4种经营类型对于生态保护的能力依次递增,木材生产能力依次递减。根据绿色森林的经营目标,以NS和NO为目标的森林面积必须达到该区所有森林面积的5%,不可将NO的经营类型转变为其他类型,NS经营类型可调整为PG或PF,但面积不能超过其总面积的15%[10]。Ostad区现有林分同时包含以上4种经营类型(表 3)。
表 3 Ostad区各经营类型总面积
Table 3. Total area of each management type in Ostad Estate
类型
Type code面积/hm2
Area/ha比例
Percentage/%活立木蓄积
Living standing volume/m3NO 3 1.45 496.72 NS 9.52 4.65 2 313.70 PF 17.96 8.71 4 770.97 PG 175.79 85.22 38 340.75 总量Total 206.27 100 45 922.14 注:NO为无人工干预的生态保留地,NS轻微人工干预的生态保留地,PF为强生态保护用材林,PG为一般生态保护要求的用材林。下同。Notes: NO, nature conservation with no human intervention; NS, nature conservation with slight human intervention; PF, strong ecological protection timber forest; PG, general ecological protection timber forest. The same below. -
瑞典多目标森林经营规划流程主要是目标设定、数据搜集、生长预测、执行、执行结果评估、新目标设定。规划为分级体系,包括长期计划(几十甚至上百年)、中期计划(5~10年)和短期计划(几天、几周或几个月)。长期计划的主要目标是预测未来几十年甚至上百年的生态景观以及木材收获情况,以每5~10年为一个预测单位;中期规划则是制定未来每年的工作内容,如更新、间伐、皆伐等具体内容以达到预定的收获目标,以年为单位;短期计划则以周、月为单位,具体包括确定需要处理的样地、配备的人力资源、所采用的工具等[11]。本次规划为中期规划。
根据上一个10年规划中对2017年的预测结果,对Ostad全区的89个小班进行复查,获得2017年的林分数据,并将89个小班按照成熟等级进行分类。
在更新数据的基础上,使用ProdMod进行未来10年森林生长状态模拟,获得各小班每一年的年龄、优势树高、胸径、断面积、蓄积、每公顷株数等值。ProdMod是瑞典农业大学林学系研发的一款森林生长模拟软件,其原理是基于收获建立的林分生长回归模型。该软件通过输入林分所处的海拔、纬度等地理信息,土壤质地、主要林下植被、树种、断面积、每公顷株数、平均胸径、立地指数、历史经营信息、间伐计划等基本信息,即可得到未来林分断面积、蓄积、株数、平均生长量、连年生长量、优势树高、胸径等的模拟值,模拟结果还包括由于自疏作用造成的死亡损耗。每5年为一个预测单位。该软件可模拟混交林各林分因子的生长量,对于各个林分因子的计算是对每个树种该因子的加和,其基本概念可用以下公式表示:
$$ I = EWB $$ 式中:I为生长量,E为单位生物量中某因子的生长能力,W为生物量,B为地力影响因子。
基于以上基本概念,各生长因子的生长量可以用公式表示。以断面积生长量(IG)为例,计算公式为:
$$ \begin{array}{*{20}{c}} {\ln ({\rm{IG}}) = \ln c + \ln {f_1}\left( {{V_{\rm{y}}}\left( {{t_0}} \right), {V_{\rm{k}}}\left( {{t_0}} \right)} \right) + }\\ {\ln {f_2}\left( {{V_{\rm{y}}}\left( {{t_0}} \right)} \right) + \ln {f_3}\left( {{V_{\rm{b}}}, {V_{\rm{k}}}\left( {{t_0}} \right)} \right) + \varepsilon } \end{array} $$ 式中:f1为目标植物的生长力;f2为其他植物的生物量总量;f3为地力因子可能造成的影响;Vy为描述目标植物状态的变量;Vk为描述其他植物状态的变量;Vb为影响地力的变量;t0表示变量,应该根据上一个5年的状态确定;c为其他不可计算因子对结果的平均影响;ε为随机变量。
由于林分每一年的生长变化较为微小,可以通过内推法计算每一年各小班的各项数据。例如求某年的活立木蓄积:设2017年的蓄积初始值为V0,通过ProdMod获得第5年的蓄积为V5,则5年间的蓄积生长量为V5-V0,年生长量为i=(V5-V0)/5,则第n年的蓄积分别为Vn=V0+ni。其他数据也通过同样的方法获得[12]。根据历史经营信息和各小班的生长阶段(表 4),将所有小班分为8类,定义为8个成熟等级,以便后期根据该分类制定经营措施。该分级系统包括:未更新小班,简称K11;已更新但未复查的小班,简称K14;需要抚育或情况不明的幼龄林,简称R21;不需要抚育的幼龄林,简称R22;需要间伐或从未间伐过的小班,简称GA31;需要间伐的小班,简称GA32、GA33;不需要间伐的小班,简称GA34;需要皆伐收获的小班,简称S。
表 4 林分成熟等级划分依据
Table 4. Baseline of stand maturity classification
成熟等级
Maturity class划分原因
Classification reason[9, 11, 13]GA31 1.根据历史经营信息该部分从未被间伐过;2.每公顷株数达到2 500株;3.断面积仅达到31 m2/hm2;4.优势高为14 m;5.蓄积达到209 m3/hm2; 6.年龄均未达到规定的最低采伐年龄。以上指标均说明,以上林地未达到皆伐标准,需要间伐,经营采取的紧迫性根据小班的地位指数和优势树高决定
1. Never thinned before according to management history; 2. The stem number is over 2 500 per hectare; 3. The basal area just reaches 31 m2/ha;4. The top height is over(includes) 14 m; 5. The volume has reached 209 m3/ha; 6.The age is below regulated youngest year. All of these indicators show that the stand has not reached the clear cutting requirement, thinning is required, the thinning priority depends on site index and top heightGA32/
GA331.每公顷株数为1 936;2.优势树高仅为13.6 m;3.年龄距最后最低收获年龄还有19年。以上指标说明需要间伐,且遭受风害的可能性较低。根据紧迫性将其分为GA32和GA33两类
1. The stem number is 1 936; 2. The height of dominant tree is only 13.6 m; 3. There are 19 years before the required age of harvesting. All these indicators imply that stands with these characteristics have low possibility to be damaged by storm and wind throw, thinning can be implemented. According to the risk emergency, they could be grouped into GA32 and GA33K11 根据历史经营信息,该样地在更新后未作任何处理
Notreatment after regeneration according to the management historyK14 1.已更新且已做过防护或抚育工作
1. Regenerated, so did fencing or pre-commercial thinningR21 1.近期未核查过,但按照历史记录需要抚育;2.每公顷株数为2 700;3.立地条件较好,林下有大量杂草形成竞争;4.优势树高为4 m
1. It should get pre-commercial thinning according to management history; 2. The stem number is 2 700 per ha; 3. With high site index, weed competes with seedling; 4. The height of dominant tree is 4 mR22 1.树高已超过抚育的经营范围;2.年龄已超过0~5年的经营范围
1.The top height is over the height range of pre-commercial thinning; 2. The age is over 5 yearsS 1.优势树高为25 m;2.蓄积为370 m3/hm2;3.断面积为34 m2/hm2;4.每公顷株数为715株;5.年龄大于规定采伐最低年龄。为保证经济效益,以上指标均说明该林地急需皆伐,各小班采取经营措施的紧迫性主要根据树高、断面积和每公顷株数确定
1.The height of dominant tree is over 25 m; 2. The volume is 370 m3/ha; 3. The basal area is 34 m2/ha;4. The stem number is 715 per ha; 5. The age is over the thinning age. To purse the highest economic income, all stands with these characteristics need clear cut, priority depends on tree height, stem number and basal areaGA34 1.每公顷株数为557;2.断面积为32 m2/hm2;3.优势树高均超越22.7 m;4.立地条件好,地位指数为G34;5.达到或将在规划期内达到法案要求的采伐年龄。以上指标均说明林地不适宜再采取间伐措施,可根据具体情况进行收获或做其他安排
1. The stem number is 557 per ha; 2. The basal area is 32 m2/ha;3. The top height is over 22.7 m; 4. Nice stand, site index is G34; 5. Reached the required clear felling age. All these indicators show these stands don’t need to be thinned, the implementation could be done according to the specific condition注:GA31为需要间伐或从未间伐过的小班,GA32、GA33为需要间伐的小班,GA34为不需要间伐的小班,K11为未更新小班,K14为已更新但未复查的小班,R21为需要抚育或情况不明的幼龄林,R22为不需要抚育的幼龄林,S为需要皆伐收获的小班。Notes:GA31 is sublot need be thinned or never been thinned, GA32 and GA33 are sublots need be thinned, GA34 is sublot needn’t be thinned, K11 is no regenerated sublot, K14 is regenerated but no check sublot, R21 is young forest need foster or the situation is not clear, R22 is young forest needn’t foster, S is clear cutting harvesting sublot. Ostad区的4种经营类型是长期规划(100年)中为了达到经济和生态经营目标确立的。除第4类无人工干预的生态保留地(NO)面积不能减少,其他经营类型均可相互调整或调整为无人工干预的生态保留地,因此在本规划中将不对无人工干预的生态保留地做其他规划。由于各经营类型中均包含不同成熟等级的小班,因此经营措施的制定将主要基于各小班的成熟等级。根据小班数据,达到S、GA34、GA33的小班可以进行收获;达到GA31、GA32、GA33的小班可以进行间伐;K11和皆伐后的小班可以更新;K14、R21、R22和经过一定更新年限的小班可以进行抚育。
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按照成熟等级对全区4种经营类型下的89个小班进行分类(表 5),其中NO中仅包含2个S级小班;NS中包含3个S级和1个GA33级小班;PF包括7个S级小班和2个GA34级小班;PG中包含成熟等级各个阶段的小班。
表 5 Ostad区2017年林分成熟等级表
Table 5. Stand status by maturity classes of Ostad Estate in 2017
成熟等级
Maturity class小班个数
Sublot number总蓄积
Total volume/m3比例
Percentage/%经营类型
Managing typeGA31 9 2 822.72 6.15 PG GA32/G33 16 9 389.39 20.45 PG、NS K11 1 0.00 0.00 PG K14 6 19.69 0.04 PG R21 5 105.99 0.23 PG R22 3 226.39 0.49 PG S 36 25 521.52 55.58 PG、PF、NO、NS GA34 13 7 836.46 17.06 PG、PF 合计Total 89 45 922.14 100.00 -
根据各成熟等级所需采取的经营措施,将其分为5大类,即间伐、皆伐、更新、抚育和不采取任何措施(表 6)。
表 6 规划实施表
Table 6. Detailed management planning
经营措施
Management measure小班个数
Sublot number面积/
hm2
Area/ha筛选来源
Screening source小班筛选标准及实施标准[13-14]
Sublot screening criteria and implementation standard[13-14]间伐Thinning 15 43.26 GA31
GA33
GA321.为确保收获量,根据间伐表伐去15%~30%的断面积;2.未经过间伐,地位指数较大,林分优势高已超过11 m的小班,为避免遭受风害及雪害造成的经济损失,根据其紧迫程度安排实施时间;3.为避免风害,接近成熟的小班应跳过间伐等待收获;4.根据林分状态采用上层间伐和下层间伐结合的方式,确保个体的平均生长;5.将地位指数低或生态保护价值高的小班的经营目标转化为PF或NS;6.为降低经济风险,尽量在规划前期进行,同时可将收益用于后续经营
1. To make sure of the harvest volume, thinning amount will be among 15% to 30% of basal area; 2. To avoid the wind-throw and snow storm, arrange the thinning schedule according to the priority of management history, site index, and the top height; 3. Skip stands which are almost mature, wait for final felling; 4. Combine thinning from above and thinning from below to make stands grow evenly; 5. Transfer stands which have high nature conservation value or low site index to be PF or NS; 6. To reduce the economic risks, arrange thinning at the beginning of the plan, income could also be used for lateral output皆伐
Clear cut33 55.52 S
GA34
GA33根据林业局要求:1.林分年龄达到林业法案要求的最低年龄;2.平均胸径达到25 cm;3.根据平均胸径,断面积和林分密度确定各小班的经营紧迫性,以确保收益最大化;4.生态考虑:每公顷留下3~5株高度大于30 cm的树桩,为避免狩猎、蹄类动物的破坏,同时为更新小班建立微环境,在欧洲赤松的小班内留下5株母树,5年后伐除;5.皆伐后留下10%的蓄积量作为生态保护和缓冲区;6.转化具有生态保护价值小班的经营目标[4, 6-7];7.将部分皆伐收获用作后续经营支出
According to forest agency: 1.The stand age should reach the required year; 2. The average DBH should reach 25 cm; 3. The harvest priority depends on average DBH, basal area, stem density; 4. Nature considerations: Retain 3-5 high stumps, leave five retained trees for nature regeneration and avoiding damages from browsing and ungulate, cut these trees after 5 years; 5. Retain 10% volume to be buffer zone and nature reservation; 6. Transfer the management type for stands with high conservation values[4, 6-7]; 7. Part of income can be used for regeneration, fencing etc更新
Regeneration27 45.39 S
GA34
GA33
K111.皆伐后样地;2.皆伐后样地继续种植皆伐前的树种及比例;3.白桦采用自然更新的办法;4.更新密度根据瑞典林业局森林更新办法中不同立地条件对应的种植密度进行;5.通过推迟种植时间、整地、选择不同大小,种类的幼苗来降低由于象鼻虫造成的死亡损耗[6];6.建立围栏,防止狩猎和放牧对更新苗的影响;7.将生产力低的区域改为生态保护区
1. Stands after clear cut; 2. Keep the previous tree species and proportion; 3. Keep nature regeneration for birch; 4. Regeneration density will be decided according to Regenerate Act from Swedish Forest Agency; 5. Reduce mortality from pine-weevil attacks by delaying planting, scarification, choosing different seedling type, sizes[6];6. Build fence to avoid game browsing; 7. Transfer stands with low productivity to nature conservation area抚育
Pre-commercial thinning9 13.75 K14
R21
R221.皆伐更新后未经过抚育措施的样地;2.经营期内优势高为3~5 m;3.每公顷株数大于2 500株;4.清理林分内的过量白桦和发展不良的针叶树种
1. Stands without any treatment after regeneration; 2. The dominant tree height is 3-5 m; 3. Stem number is 2 500 per ha; 4. Remove quite a substantial amount of birch and bad quality conifers不采取措施
No implementation34 47.99 S
GA34
GA33
K14
K111.根据预测结果,所需要采取的经营措施在10年内未达到林业法规定,如采伐年龄未达到林业法要求的下限,或在规划期内不需要采取措施的小班,在本次规划中不作具体考虑;2.将经营目标调整为NS或NO的小班
1. According to the predicted result, all treatment should be implemented after 10 years according to the regulations, for example, the age is lower than the required cutting age, or the treatment would be in the next ten-years plan; 2.The objective has been changed to NS or NO规划中间伐的采伐量根据林业法[9]和FSC经营标准[14]提供的间伐表确定,间伐表已对间伐量的范围进行明确说明。以挪威云杉在立地指数为G30时的间伐表为例,如间伐量超过要求的最低范围(图中的灰色区域),则该小班的断面积和蓄积在间伐后将无法重新达到伐前水平,但间伐量过低,则无法起到提高单木质量和增加收获量的目标,同时可能会增加经营费用,因此建议将间伐量控制在红色区域内进行。本次的间伐量将在建议采伐范围内根据伐前的断面积水平伐去15%~30%(图 2)。
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Ostad地区有丰富的动植物资源,具有较高的自然保护价值。同时,大量的阔叶林和过熟针叶林为维持地区的生态完整性提供了重要条件,因此生态保护也是本次规划的重要组成部分。该部分是在保证原有NO和NS经营类型面积不变的基础上,将原木材生产区域内产量低下的小班调整为生态保护区域;将大面积阔叶林、具有重要阔叶树种和临近水域的小班设置为固定区域并对其进行保护。在立地条件较好的林地上由于针叶树种更新生长良好,因此在NS林地中进行轻度的人工干扰限制云杉纯林的形成,如伐去一部分针叶树种补植阔叶树种以提高阔叶树种比列[13-14]。具体操作措施如表 7所示,在这部分的规划中一共有13个面积为22.87 hm2的小班从木材生产的经营类型调整到生态保护的经营类型中。
表 7 Ostad区生态保护区设置
Table 7. Areas designated for conservation of nature values for Ostad Estate
小班号
Sublot No.面积/hm2
Area/ha立地指数
Site index旧规划目标
Previous objective新规划目标
Current objective原因
Reason1 161 1.01 T18 PG NO 生产力低下Low productivity 1 440 2.93 E22 PF NO 高比例重要阔叶树种High proportion of noble broadleaved species 1 450 0.68 E20 PF NO 高比例重要阔叶树种High proportion of noble broadleaved species 1 950 0.66 E22 PG NO 高比例重要阔叶树种High proportion of noble broadleaved species 2 000 0.78 T18 PF NS 生产力低下Low productivity 2 110 0.34 B20 PF NO 高比例其他阔叶树种High proportion of other broadleaved species 2 120 8.36 G32 PF NS 高比例重要阔叶树种High proportion of noble broadleaved species 2 140 0.44 G32 PF NO 高比例欧洲山毛榉High proportion ofbeech 2 220 4.46 G34 PG NS 高比例重要阔叶树种High proportion of noble broadleaved species 2 240 0.50 E19 PG NO 高比例重要阔叶树种High proportion of noble broadleaved species 2 300 2.22 G32 PF NS 大量重要阔叶树种和一定数量的针叶树种Significant amount of noble and conifers species 2 310 0.21 G35 PG NO 高比例其他阔叶树种High proportion of other broadlead species 2 330 0.28 T10 PG NS 高比例重要阔叶树种High proportion of noble broadleaved species 1 270 1.76 T14 NO NO 经营目的保持不变Management objective unchanged 1 300 1.48 E18 NS NS 1 390 1.24 E18 NO NO 1 400 6.27 E20 NS NS 1 430 0.92 E16 NS NS 2 210 0.85 G32 NS NS 总计Total 35.39 注:G为以云杉林定义的立地指数,T为以赤松定义的立地指数,E为以栎类为代表的重要阔叶树种定义的立地指数,B为以白桦为代表的一般阔叶树种定义的立地指数,数值越高则产量越大。Notes: G is the symbol of site index in spruce forest; T is the symbol of site index in pine forest; E is the symbol of site index in noble broadleaved forest, here means oak; B is the symbol of site index in other broadleaved forest, higher value indicates higher volume. -
截至2027年,通过皆伐和间伐共可收获14.80亿瑞典克朗,同时有35.39 hm2的面积可被作为生态保护区(表 7),相比上一规划期新增面积为22.87 hm2,同时规划前后的年龄分布图也表明既定的生产和自然保护目标可以在计划中实现。从图 3中可以看出,2027年该地区相当大比例的林分可于50~70年后被收获,可以实现稳定收获的经济目标。此外,规划地森林总面积31%的林龄低于20年,可以确保皆伐区域更新。另一方面,预计2027年森林总面积约69%的林分林龄为20年以上,可以确保收获(瑞典森林法规定皆伐林分中要求有50%以上面积的林龄在20年以上)[9]。
图 3 规划前后的龄级分布
Figure 3. Age class distribution at the beginning (2017) and the end (2027) of the planning period
规划未来10年的总收获量(15 497.00 m3)低于10年间用材林的蓄积生长量(16 556.50 m3),则将会有1 060 m3蓄积作为活立木继续保存以保证木材的可持续且平均收获。这种可持续木材生产收获可能会受到树种、生长以及人为和自然灾害的影响,但可以通过抚育和保留树来进行调节。
计划的另一个显著特点是对自然保护和环境敏感性的考虑。从龄级分布图(图 3)中可以看出,2027年Ostad区过熟林面积将大幅度增加,这将非常有利于该区域的动植物保护。鉴于此,我们希望通过用近自然的营林技术来保持阔叶林的活力,同时保留原生态文化遗存作为生物多样性保护的驱动因素。
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经分析,本规划依旧存在一些潜在风险,如自然灾害,包括风暴损害、根腐、冰暴以及蠹虫的影响。这些问题由于其突发性、不可预测性以及高额的修复费用,而未在规划中详细体现。最谨慎的做法是利用足够的收入来实行抢救工作。本规划通过及时间伐降低风害造成的经济损失和推迟更新时间降低虫害造成的经济损失,从一定程度上确保了收益最大化。因此,该规划的潜在优势是可以在规划期内提供巨大的潜在净收益应对突发情况(表 8)。但未来市场需求、木材价格加上利率等市场因素也可能改变这一规划的结果。然而,在瑞典和其他波罗的海地区,由于针叶木材(云杉和赤松)长期需求的发展轨迹,本次木材收获的经济收益基本处于安全状态。潜在的气候变化影响也可能会对更新树种的选择、树种混交比例的确定产生一定的影响,从而影响最后的经济收入。
表 8 造林规划及收益情况(2017—2027年)
Table 8. Summary of silvicultural operations and revenues (SEK) carried out in the plan (2017-2027)
年份Year 更新
Regeneration抚育
Pre-commercial thinning间伐
Thinning皆伐
Clearcut净现值/
瑞典克朗
Net present value (NPV)/
SEK面积/hm2
Area/ha支出/
瑞典克朗
Cost/SEK面积/hm2
Area/ha支出/
瑞典克朗
Cost/SEK面积/hm2
Area/ha净收入/
瑞典克朗
Net income/
SEK面积/hm2
Area/ha净收入/
瑞典克朗
Net income/
SEK2017 0.00 0.00 4.71 5 761.00 9.82 147 668.50 11.37 269 258 111.40 256 571 446.60 2018 5.21 213 916.00 1.72 1 892.00 11.33 20 878.70 11.06 314 008 125.10 284 637 819.30 2019 3.23 134 302.60 6.5 10 355.00 7.66 22 070.60 7.90 204 335 589.60 176 406 869.80 2020 11.06 367 475.00 0 0.00 0 0.00 3.79 237 081 449.30 194 745 172.50 2021 7.90 339 477.40 0.79 948.00 0 0.00 5.53 84 718 083.73 66 112 103.17 2022 7.40 357 841.90 0 0 0 0.00 0.98 36 536 422.42 24 593 769.59 2023 2.90 90 680.70 0 0 3.82 15 739.20 3.38 135 001 375.80 95 889 697.80 2024 3.38 129 102.70 0 0 5.74 34 222.20 0 0.00 -64 218.86 2025 0.00 0.00 0 0 0.49 1 387.00 1.79 15 879 763.16 10 237 130.99 2026 0.00 0.00 0 0 4.40 36 514.60 4.31 95 842 904.56 58 861 646.16 2027 4.31 171 946.60 0 0 0 0.00 5.41 89 034 012.55 51 955 809.55 总计Total 45.39 1 804 742.90 13.75 18 956.00 43.26 278 480.80 55.52 1 481 695 838.00 1 219 947 247.00 在生态保护方面,可以在未来的经营中通过调整收获方式来提高林区的生态保护能力,如避免采用皆伐。目前在瑞典国内较为热议的有4种收获方式:主要针对挪威云杉的异龄林经营;人工林到异龄林的过渡态经营;遮蔽木林业和欧洲赤松的棋盘式采伐。该类恒续林的经营模式通过持续覆盖的冠层为林地内的动物、昆虫和珍稀菌类提供栖息地,保证生态系统的完整性;持续的植被覆盖可以避免土质沙化和水土流失的风险;同时,老树遮蔽下的天然更新一方面可以降低人工更新的高昂费用,另一方面可以保护更新苗免受蹄类动物的迫害;最后,该类收获方式还可使经营的现金流更加稳定。
Medium term planning of multi-objective forest management in private forest of Ostad Estate, southern Sweden
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摘要:
目的根据瑞典私有林多目标经营的主要做法,对瑞典南部Ostad区进行为期10年的中期森林经营规划, 以期实现木材收获和生态保护的双重目标。 方法规划包括样地调查、ProdMod生长预测、结果分析和计划制定。调查开展的时间为2017年10—12月, 调查地点为Ostad区全区206.27 hm2的89个小班。 结果根据规划,截至2027年共有15个小班、2 136.40 m3的蓄积需要间伐,净收入为278 480.80瑞典克朗;33个小班、15 497.00 m3的蓄积需要进行皆伐收获,净收入为1 481 695 838.00瑞典克朗;27个小班、45.39 hm2的面积需要进行更新,共花费1 804 742.88瑞典克朗;9个小班、13.75 hm2的面积需要抚育,共花费18 956.00瑞典克朗;22.87 hm2的森林面积被增设为生态保护区范围。 结论截至2027年,Ostad区将有170.88 hm2的面积作为用材林,35.39 hm2的森林面积作为生态保护区,总收益为14.80亿瑞典克朗,净现值为12.19亿瑞典克朗。在本次规划中,10年间收获量小于生长量,实现了可持续的基本收获目标;规划期末林分合理的年龄分布确保了稳定的年收入,扩大的生态保护区面积为区域内的动植物保护提供了重要场所。规划基本达到了木材收获与生态保护的双重目标。此外,规划仍存在一些不确定因素可能会对经营结果产生影响,如自然灾害、市场波动和气候变化,经分析,本规划将通过提高收益和调整经营树种来应对这些不确定因素。 Abstract:ObjectiveThis paper takes the case of Ostad Estate in southern Sweden as an example to make a 10 year medium term forest management planning of multi-objective of timber harvest and nature conservation according to the main requirements and implementations of Sweden. MethodThe process included sample survey, growth forecast by ProdMod, result analysis and planning make. The field investigation was implemented during October 2017 to December 2017. ResultAccording to the panning, until 2027, there will be 15 sublots, 2 136.40 m3 volume will be thinned, net income is 278 480.80 SEK; 33 sublots, 15 497.00 m3 volume will be clear felled, net income is 1 481 695 838.0 SEK; 27 sublots, 45.39 ha need to be regenerated, the cost is 1 804 742.88 SEK; 9 sublots, 13.75 ha area young seedlings need pre-commercial thinning; 22.87 ha forest area will be added into nature conservation area. ConclusionAt the end of 2027, 170.88 ha of area will be used for wood production, and 35.39 ha of forest area for ecological reserve, the total net income is 1.48 billion SEK in ten years, the net present value is 1.22 billion SEK. In this planning, the total harvest amount will be smaller than growth amount during the period, sustainable harvest target could be reached, the reasonable age distribution makes sure of the stable annual income, the enlarged ecological reserve area provides a good protection on flora and fauna. Basically, the plan achieves the dual goals of timber harvesting and nature reservation. However, potential risks include natural hazard, market situation as well as climate change would influence the result of management, the strategies are improving the income and altering species. -
Key words:
- forest management planning /
- Sweden /
- multi-objective
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表 1 2017年Ostad区森林生长量与木材产量
Table 1. Growth and productivity of Ostad Estate with a reference year of 2017
变量Variable 数值Value 森林面积/hm2
Forest area/ha206.27 平均生长量(上一个10年规划期)
Mean growth(according to last ten-year planning)/
(m3·a-1)1 944.98 每公顷平均生长量/(m3·(hm-2·a-1))
Mean growth per hectare/(m3·(ha-1·a-1))9.43 连年生长量
Continuous annual growth/(m3·a-1)1 799.62 每公顷连年生长量/(m3·(hm-2·a-1))
Continuous annual growth per hectare/(m3·(ha-1·a-1))8.70 活立木蓄积
Living standing stock/m345 922.14 每公顷活立木蓄积/(m3·hm-2)
Living standing stock per hectare/(m3·ha-1)222.63 表 2 2017年树种组成及活立木蓄积
Table 2. Species composition and living standing stock in 2017
树种
Species蓄积
Volume/m3组成
Proportion/%欧洲赤松Scots pine 8 304.58 18.08 挪威云杉Norway spruce 28 474.78 62.00 白桦Birch 4 021.41 8.76 欧洲山毛榉Beech 102.96 0.22 重要阔叶树种
Nobel broadleaved species4 916.57 10.71 其他阔叶树种
Other broadleaved species101.84 0.22 总量Total 45 922.14 100.00 表 3 Ostad区各经营类型总面积
Table 3. Total area of each management type in Ostad Estate
类型
Type code面积/hm2
Area/ha比例
Percentage/%活立木蓄积
Living standing volume/m3NO 3 1.45 496.72 NS 9.52 4.65 2 313.70 PF 17.96 8.71 4 770.97 PG 175.79 85.22 38 340.75 总量Total 206.27 100 45 922.14 注:NO为无人工干预的生态保留地,NS轻微人工干预的生态保留地,PF为强生态保护用材林,PG为一般生态保护要求的用材林。下同。Notes: NO, nature conservation with no human intervention; NS, nature conservation with slight human intervention; PF, strong ecological protection timber forest; PG, general ecological protection timber forest. The same below. 表 4 林分成熟等级划分依据
Table 4. Baseline of stand maturity classification
成熟等级
Maturity class划分原因
Classification reason[9, 11, 13]GA31 1.根据历史经营信息该部分从未被间伐过;2.每公顷株数达到2 500株;3.断面积仅达到31 m2/hm2;4.优势高为14 m;5.蓄积达到209 m3/hm2; 6.年龄均未达到规定的最低采伐年龄。以上指标均说明,以上林地未达到皆伐标准,需要间伐,经营采取的紧迫性根据小班的地位指数和优势树高决定
1. Never thinned before according to management history; 2. The stem number is over 2 500 per hectare; 3. The basal area just reaches 31 m2/ha;4. The top height is over(includes) 14 m; 5. The volume has reached 209 m3/ha; 6.The age is below regulated youngest year. All of these indicators show that the stand has not reached the clear cutting requirement, thinning is required, the thinning priority depends on site index and top heightGA32/
GA331.每公顷株数为1 936;2.优势树高仅为13.6 m;3.年龄距最后最低收获年龄还有19年。以上指标说明需要间伐,且遭受风害的可能性较低。根据紧迫性将其分为GA32和GA33两类
1. The stem number is 1 936; 2. The height of dominant tree is only 13.6 m; 3. There are 19 years before the required age of harvesting. All these indicators imply that stands with these characteristics have low possibility to be damaged by storm and wind throw, thinning can be implemented. According to the risk emergency, they could be grouped into GA32 and GA33K11 根据历史经营信息,该样地在更新后未作任何处理
Notreatment after regeneration according to the management historyK14 1.已更新且已做过防护或抚育工作
1. Regenerated, so did fencing or pre-commercial thinningR21 1.近期未核查过,但按照历史记录需要抚育;2.每公顷株数为2 700;3.立地条件较好,林下有大量杂草形成竞争;4.优势树高为4 m
1. It should get pre-commercial thinning according to management history; 2. The stem number is 2 700 per ha; 3. With high site index, weed competes with seedling; 4. The height of dominant tree is 4 mR22 1.树高已超过抚育的经营范围;2.年龄已超过0~5年的经营范围
1.The top height is over the height range of pre-commercial thinning; 2. The age is over 5 yearsS 1.优势树高为25 m;2.蓄积为370 m3/hm2;3.断面积为34 m2/hm2;4.每公顷株数为715株;5.年龄大于规定采伐最低年龄。为保证经济效益,以上指标均说明该林地急需皆伐,各小班采取经营措施的紧迫性主要根据树高、断面积和每公顷株数确定
1.The height of dominant tree is over 25 m; 2. The volume is 370 m3/ha; 3. The basal area is 34 m2/ha;4. The stem number is 715 per ha; 5. The age is over the thinning age. To purse the highest economic income, all stands with these characteristics need clear cut, priority depends on tree height, stem number and basal areaGA34 1.每公顷株数为557;2.断面积为32 m2/hm2;3.优势树高均超越22.7 m;4.立地条件好,地位指数为G34;5.达到或将在规划期内达到法案要求的采伐年龄。以上指标均说明林地不适宜再采取间伐措施,可根据具体情况进行收获或做其他安排
1. The stem number is 557 per ha; 2. The basal area is 32 m2/ha;3. The top height is over 22.7 m; 4. Nice stand, site index is G34; 5. Reached the required clear felling age. All these indicators show these stands don’t need to be thinned, the implementation could be done according to the specific condition注:GA31为需要间伐或从未间伐过的小班,GA32、GA33为需要间伐的小班,GA34为不需要间伐的小班,K11为未更新小班,K14为已更新但未复查的小班,R21为需要抚育或情况不明的幼龄林,R22为不需要抚育的幼龄林,S为需要皆伐收获的小班。Notes:GA31 is sublot need be thinned or never been thinned, GA32 and GA33 are sublots need be thinned, GA34 is sublot needn’t be thinned, K11 is no regenerated sublot, K14 is regenerated but no check sublot, R21 is young forest need foster or the situation is not clear, R22 is young forest needn’t foster, S is clear cutting harvesting sublot. 表 5 Ostad区2017年林分成熟等级表
Table 5. Stand status by maturity classes of Ostad Estate in 2017
成熟等级
Maturity class小班个数
Sublot number总蓄积
Total volume/m3比例
Percentage/%经营类型
Managing typeGA31 9 2 822.72 6.15 PG GA32/G33 16 9 389.39 20.45 PG、NS K11 1 0.00 0.00 PG K14 6 19.69 0.04 PG R21 5 105.99 0.23 PG R22 3 226.39 0.49 PG S 36 25 521.52 55.58 PG、PF、NO、NS GA34 13 7 836.46 17.06 PG、PF 合计Total 89 45 922.14 100.00 表 6 规划实施表
Table 6. Detailed management planning
经营措施
Management measure小班个数
Sublot number面积/
hm2
Area/ha筛选来源
Screening source小班筛选标准及实施标准[13-14]
Sublot screening criteria and implementation standard[13-14]间伐Thinning 15 43.26 GA31
GA33
GA321.为确保收获量,根据间伐表伐去15%~30%的断面积;2.未经过间伐,地位指数较大,林分优势高已超过11 m的小班,为避免遭受风害及雪害造成的经济损失,根据其紧迫程度安排实施时间;3.为避免风害,接近成熟的小班应跳过间伐等待收获;4.根据林分状态采用上层间伐和下层间伐结合的方式,确保个体的平均生长;5.将地位指数低或生态保护价值高的小班的经营目标转化为PF或NS;6.为降低经济风险,尽量在规划前期进行,同时可将收益用于后续经营
1. To make sure of the harvest volume, thinning amount will be among 15% to 30% of basal area; 2. To avoid the wind-throw and snow storm, arrange the thinning schedule according to the priority of management history, site index, and the top height; 3. Skip stands which are almost mature, wait for final felling; 4. Combine thinning from above and thinning from below to make stands grow evenly; 5. Transfer stands which have high nature conservation value or low site index to be PF or NS; 6. To reduce the economic risks, arrange thinning at the beginning of the plan, income could also be used for lateral output皆伐
Clear cut33 55.52 S
GA34
GA33根据林业局要求:1.林分年龄达到林业法案要求的最低年龄;2.平均胸径达到25 cm;3.根据平均胸径,断面积和林分密度确定各小班的经营紧迫性,以确保收益最大化;4.生态考虑:每公顷留下3~5株高度大于30 cm的树桩,为避免狩猎、蹄类动物的破坏,同时为更新小班建立微环境,在欧洲赤松的小班内留下5株母树,5年后伐除;5.皆伐后留下10%的蓄积量作为生态保护和缓冲区;6.转化具有生态保护价值小班的经营目标[4, 6-7];7.将部分皆伐收获用作后续经营支出
According to forest agency: 1.The stand age should reach the required year; 2. The average DBH should reach 25 cm; 3. The harvest priority depends on average DBH, basal area, stem density; 4. Nature considerations: Retain 3-5 high stumps, leave five retained trees for nature regeneration and avoiding damages from browsing and ungulate, cut these trees after 5 years; 5. Retain 10% volume to be buffer zone and nature reservation; 6. Transfer the management type for stands with high conservation values[4, 6-7]; 7. Part of income can be used for regeneration, fencing etc更新
Regeneration27 45.39 S
GA34
GA33
K111.皆伐后样地;2.皆伐后样地继续种植皆伐前的树种及比例;3.白桦采用自然更新的办法;4.更新密度根据瑞典林业局森林更新办法中不同立地条件对应的种植密度进行;5.通过推迟种植时间、整地、选择不同大小,种类的幼苗来降低由于象鼻虫造成的死亡损耗[6];6.建立围栏,防止狩猎和放牧对更新苗的影响;7.将生产力低的区域改为生态保护区
1. Stands after clear cut; 2. Keep the previous tree species and proportion; 3. Keep nature regeneration for birch; 4. Regeneration density will be decided according to Regenerate Act from Swedish Forest Agency; 5. Reduce mortality from pine-weevil attacks by delaying planting, scarification, choosing different seedling type, sizes[6];6. Build fence to avoid game browsing; 7. Transfer stands with low productivity to nature conservation area抚育
Pre-commercial thinning9 13.75 K14
R21
R221.皆伐更新后未经过抚育措施的样地;2.经营期内优势高为3~5 m;3.每公顷株数大于2 500株;4.清理林分内的过量白桦和发展不良的针叶树种
1. Stands without any treatment after regeneration; 2. The dominant tree height is 3-5 m; 3. Stem number is 2 500 per ha; 4. Remove quite a substantial amount of birch and bad quality conifers不采取措施
No implementation34 47.99 S
GA34
GA33
K14
K111.根据预测结果,所需要采取的经营措施在10年内未达到林业法规定,如采伐年龄未达到林业法要求的下限,或在规划期内不需要采取措施的小班,在本次规划中不作具体考虑;2.将经营目标调整为NS或NO的小班
1. According to the predicted result, all treatment should be implemented after 10 years according to the regulations, for example, the age is lower than the required cutting age, or the treatment would be in the next ten-years plan; 2.The objective has been changed to NS or NO表 7 Ostad区生态保护区设置
Table 7. Areas designated for conservation of nature values for Ostad Estate
小班号
Sublot No.面积/hm2
Area/ha立地指数
Site index旧规划目标
Previous objective新规划目标
Current objective原因
Reason1 161 1.01 T18 PG NO 生产力低下Low productivity 1 440 2.93 E22 PF NO 高比例重要阔叶树种High proportion of noble broadleaved species 1 450 0.68 E20 PF NO 高比例重要阔叶树种High proportion of noble broadleaved species 1 950 0.66 E22 PG NO 高比例重要阔叶树种High proportion of noble broadleaved species 2 000 0.78 T18 PF NS 生产力低下Low productivity 2 110 0.34 B20 PF NO 高比例其他阔叶树种High proportion of other broadleaved species 2 120 8.36 G32 PF NS 高比例重要阔叶树种High proportion of noble broadleaved species 2 140 0.44 G32 PF NO 高比例欧洲山毛榉High proportion ofbeech 2 220 4.46 G34 PG NS 高比例重要阔叶树种High proportion of noble broadleaved species 2 240 0.50 E19 PG NO 高比例重要阔叶树种High proportion of noble broadleaved species 2 300 2.22 G32 PF NS 大量重要阔叶树种和一定数量的针叶树种Significant amount of noble and conifers species 2 310 0.21 G35 PG NO 高比例其他阔叶树种High proportion of other broadlead species 2 330 0.28 T10 PG NS 高比例重要阔叶树种High proportion of noble broadleaved species 1 270 1.76 T14 NO NO 经营目的保持不变Management objective unchanged 1 300 1.48 E18 NS NS 1 390 1.24 E18 NO NO 1 400 6.27 E20 NS NS 1 430 0.92 E16 NS NS 2 210 0.85 G32 NS NS 总计Total 35.39 注:G为以云杉林定义的立地指数,T为以赤松定义的立地指数,E为以栎类为代表的重要阔叶树种定义的立地指数,B为以白桦为代表的一般阔叶树种定义的立地指数,数值越高则产量越大。Notes: G is the symbol of site index in spruce forest; T is the symbol of site index in pine forest; E is the symbol of site index in noble broadleaved forest, here means oak; B is the symbol of site index in other broadleaved forest, higher value indicates higher volume. 表 8 造林规划及收益情况(2017—2027年)
Table 8. Summary of silvicultural operations and revenues (SEK) carried out in the plan (2017-2027)
年份Year 更新
Regeneration抚育
Pre-commercial thinning间伐
Thinning皆伐
Clearcut净现值/
瑞典克朗
Net present value (NPV)/
SEK面积/hm2
Area/ha支出/
瑞典克朗
Cost/SEK面积/hm2
Area/ha支出/
瑞典克朗
Cost/SEK面积/hm2
Area/ha净收入/
瑞典克朗
Net income/
SEK面积/hm2
Area/ha净收入/
瑞典克朗
Net income/
SEK2017 0.00 0.00 4.71 5 761.00 9.82 147 668.50 11.37 269 258 111.40 256 571 446.60 2018 5.21 213 916.00 1.72 1 892.00 11.33 20 878.70 11.06 314 008 125.10 284 637 819.30 2019 3.23 134 302.60 6.5 10 355.00 7.66 22 070.60 7.90 204 335 589.60 176 406 869.80 2020 11.06 367 475.00 0 0.00 0 0.00 3.79 237 081 449.30 194 745 172.50 2021 7.90 339 477.40 0.79 948.00 0 0.00 5.53 84 718 083.73 66 112 103.17 2022 7.40 357 841.90 0 0 0 0.00 0.98 36 536 422.42 24 593 769.59 2023 2.90 90 680.70 0 0 3.82 15 739.20 3.38 135 001 375.80 95 889 697.80 2024 3.38 129 102.70 0 0 5.74 34 222.20 0 0.00 -64 218.86 2025 0.00 0.00 0 0 0.49 1 387.00 1.79 15 879 763.16 10 237 130.99 2026 0.00 0.00 0 0 4.40 36 514.60 4.31 95 842 904.56 58 861 646.16 2027 4.31 171 946.60 0 0 0 0.00 5.41 89 034 012.55 51 955 809.55 总计Total 45.39 1 804 742.90 13.75 18 956.00 43.26 278 480.80 55.52 1 481 695 838.00 1 219 947 247.00 -
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