北京大学环境问题外籍专家讲座——新草场生态学.pptx

the new rangeland ecology: a bud that blossomed to a flower 新草场生态学：学科发芽的过程 lynn huntsinger university of california, berkeley main points 要点 understanding of the dynamics of rangeland ecosystems have changed. 对草场生态的多变性有新的认识 the models used in the united states have been shaped by social and economic conditions unique to u.s. history. 美国的草场管理模型纳入社会和经济的变量 understanding rangeland ecological dynamics, and using the right model, is essential for good policy. 了解草场生态系统的多变性以及使用适合的模型决定着政策的成败 outline 汇报 内容 definitions: what is rangeland ecology and why models? 定义：什么是草场生态学？为什么模型？ linear succession model based on succession theory 基于演替的线性演替模式 new rangeland ecology: states and transitions model based on non-equilibrium theory 新草场生态学：基于非平衡理论的状态-过渡模型 influences on development policy 对发展政策产生的影响 rangelands 草场 rangelands: lands that are not cultivated, not artificially irrigated, not timber forests. they include grasslands, deserts, alpine areas, montane meadows, tundra, woodlands, savanna, shrublands. 草场：没有种植，灌溉和用材木的土地，包括草地，沙地，高寒草原 ，山地草甸，冻原，林地，热带草原，灌丛带 about 2/3 of the land surface of the earth central question: what is the impact of management on rangelands? 核心问题：管理对草场带来的影响 grazing：放牧 no grazing：没有放牧 fire：燃烧 weather：天气 seeding, plowing, etc. ：种、耕 we usually manage at the “plant community” scale 平常在植物群落的尺度上进行管理 the “steppe” vegetation type： 高寒草原的植被类型 a needle grass (stipa spp.) grassland ： 针茅属为主的草地 ecosystem models: 生态系统模型 show some of the many interactions among organisms and environment 阐述生物与环境之间的一些关系 help us organize information 整理信息 can help predict management outcomes 预测管理结果 should help to explain the system 说明系统 should help us understand how things work, which interactions are important 了解不同变量之间的关系，提出那些关系相对重要 why do scientists create models?科学家为什么建立模型？ why do managers want models? 管理者为什么需要模型？ -organize information and questions：整理信息和问题 -understand how a system works：认识系统的运作 -predict outcomes of management：预测管理的结果 -test effects of variables：试验变量的影响 what causes vegetation change? 那些因素导致植被的变化？ models, based on theories of what drives vegetation change, are created to “explain” what happens on rangelands, and how rangelands will respond to management. 基于导致植被变化的理论，建立模型来解读草场发生了什么？草场对管理的 反馈？ what explanatory model(s) fits rangelands best? 那些解释模型最适合草场？ models for vegetation change at management and plant community scales 在植物群落与管理尺度上的植被动态模型 succession model 演替模型 succession is the change in an ecosystem or community over time. the time scale is years. 演替指群落或生态系统在时间尺度上的辩护，其时间尺度指年份 the classical model describes plant succession as: 古典模型模型解读植被演替： 1) linear 线性 2) reversible 可逆的 3) predictable 能预测的 4) biotically controlled 靠生物技术可控制的 5) with a stable end point. 稳定的状态 clements: space for time study in the tallgrass prairie 克莱门茨：高杆草原在空间上的时间分析 10 grasslands never plowed 10个从未种耕的草地 10 grasslands plowed 20 years ago 10个种耕20年的草场地 10 grasslands plowed last year 10个去年种耕的草地 10 grasslands plowed 50 years ago 10个种耕50年 以前的草地 a way of studying vegetation change over time 在时间尺度上研究植被变化的方法 (clements, 1916) assemble into “successional sere” 归结到生态演替系列 disturbance : reverses the progression to the endpoint, starts the process over as “secondary succession” 干扰：逆转演替发展到终点，重新开始次级演替 never plowed/plo wed 50 years ago plowed 10 years ago freshly plowed plowed 20 years ago linear, deterministic (clementian) succession for a specific climate 具体气候下的线性的、确定性的演替 succession (plant interactions, competition) disturbance (fire, grazing, plowing) stable, climax, stable, climax, endpoint for endpoint for climateclimate develops like an organism to maturity. linear succession model 线性演替模型 seral stage 1 seral stage 2 seral stage 3 “equilibrium” 4 stable end point “climax”“mid-seral”“pioneer” tall grass prairie (50 years ago or never plowed) taller, perennial grasses (20 years ago) early grasses (10 years ago) pioneer species (just plowed) controversial among scientists, with other ideas promoted, but no big change until the 90s. 科学家之间的争议，直到90年代没有变化 but, a perfect fit to management needs at the time. 但，很好地适应与当时的管理需求 fit the social and ecological conditions of the united states：适应与当时的美国社会和生态的条件 most rangelands owned and managed by the government, needed a “scientific” way to make decisions 大部分草场 都由政府管理拥有和管理，需要“科学性”的决策 first government agency to start managing rangelands established in 1911 clements published in 1916. 第一次 草场管理机构建立与1911，而克莱门茨出版与1916年 use science as a reason for allocating resources among livestock producers 科学作为依据来把资源分配给各畜 牧业生产者 adopted for management 管理者的采取 increasing grazing pressure (disturbance) “climax”“mid-seral”“pioneer” tall grass prairietaller, perennial grasses early grasses pioneer species (just plowed); annuals, weeds carrying capacity # animals allowed used for “range condition” “climax”“mid-seral”“pioneer” increasing grazing pressure measure management outcomes by measuring how similar the species composition is to climax. 利用与测量管理的影响：测量物种的结构与顶级群落的相似性 “degraded”“degraded” “pristine” “pristine” excellentpoorgoodfair condition “rangeland condition” 草场情况 linear-succession based method of assessing rangeland condition was used widely in the west until recently. 基于线性演替模型的方法在西方草场状况研究中常用 climax = “excellent condition” 顶级群落：最好的的状态 early successional stage = “poor condition” 初期延期阶段：不好的状态 management goal: find the right level of grazing to maintain “good” or better condition based on succession theory 管理目标：基于演替理论，需要合适的放牧程度来保持较好的草场状态 the closer to climax, the better the “condition” 离顶级群落越接近，状态越好 condition measured by species composition: “climax” species vs. “pioneer” species 状态评估采取 物种结构：顶级物种与初期物种的比较 establish and regulate fixed “carrying capacity”: number of animals/mu for the year. 建立与规划承载量：每亩草场能养的牲畜数量 for government managers 对于政府的决策者 a way to create rules for herders, allocate use： 建立规则和资源分配的方法 a way to measure affects of management 测量管理影响的方法 predicted management outcomes 预测管理结构 only managers had the “scientific capacity” to measure condition, set stocking rates：只有管理者具有“科学依据 ”来衡量状况，并制定承载率 helped consolidate government authority 帮助统一政府 权利 20th century: four assumptions for rangeland development in u.s. 20世纪：管理美国草场发 展提出四个设想 professional experts should be in charge, need “scientific” management-locals know nothing, they are backward 专家领导管理，需要“科学性”的管理 而当地人无知、落后 technology is the way to solve problems 技术是解决 问题的方法 goal for rangelands is to maximize livestock production at a sustainable carrying capacity草场管 理的目标是基于可持续承载率，畜牧业生产加大化 comprehensive rational planning is key-locals are self-interested and short-sighted 综合理性的规划 是关键当地人目光短浅、自利 outcome: stronger government control management method 管理方法 establish a fixed number of animals for a fixed area: carrying capacity 固定区域里限制牲畜 数量：承载率 divide rangelands into areas used by individual households and regulate carrying capacity to sustain “rangeland condition” 草 场分配到各户来管理承载率，实现可持续 的草场状态 thanks to m. fernndez-gimnez for figure change in land tenure from shared land to individual land land shared land used separately clementian succession: does the model fit arid rangelands? 克莱门茨演替：该模型是否适合用在干旱草场?？ clements research in tall grass prairie 高杆 草原 predictable, high rainfall grasses compete to drive succession clementian succession: does the model fit arid rangelands? 克莱门茨演替： 该模型是否适合用在干旱草场？ “linear deterministic succession” seral stage 1 seral stage 2 seral stage 3 “stable equilibrium” 4 “climax”“mid-seral” “pioneer” excellentpoorgood increasing grazing pressure, disturbance fair range condition a way to predict results of disturbance/grazing “degraded” “pristine” problem i: not linear 问题：非线性 seral stage 1 seral stage 2 seral stage 3 “stable equilibrium” 4 “climax”“mid-seral” “pioneer” reality: there are multiple pathways, and multiple stable states. 现实：多重渠道和多重稳定 状态 “range condition” 草场状态 seral stage 1 seral stage 2 seral stage 3 “stable equilibrium” 4 “climax”“mid-seral” “pioneer” excellentpoorgood increasing grazing pressure, disturbance fair range condition a way to measure management outcomes. 测量管理结构的方法 “degraded” “pristine” = problem ii: “condition” is a value judgment excellentpoorgoodfair reality: each “state” or potential vegetation community, has value. “lower” stages may be more productive, or more biodiverse, than later stages. earlier stages may be more useful to herders, and in some cases, more “natural”. the concept of degradation is highly subjective 退化的观点的是主观性强 change in species? : are there “good” and “bad” species? 物种的变化 ？:是否有“好的”和“不好”的物种 whether a species is good or bad depends on your goals and point of view 物种的好坏取决于个人的目标和观点 linear succession models create “false normative value” 线性演替模型 提出“错的规范价值” change in bare areas? 裸地变化 weather , drought, rodents, or grazing? 天气、干旱、啮齿类动物、还 是放牧 loss of soil? 土壤的变化 influences long term productivity 影响长期的生产 “natural” or caused by management? “自然”的还是管理导致的 some arid lands have flood/drought cycles 有些干旱去有干旱、洪水的 循环 major driver of change is grazing 放牧是变化的主导 seral stage 1 seral stage 2 seral stage 3 “stable equilibrium” 4 “climax”“mid-seral” “pioneer” excellentpoorgood increasing grazing pressure fair reduce grazing to “improve” vegetation state. 减少放牧来提高植被状态 “degraded”“pristine” problem iii: major driver of change is abiotic factors 非生物因素是变化的主导 increasing grazing pressure reducing grazing may not lead to a return to climax state, and heavy grazing may not lead to “degradation”. climate/weather overwhelms impacts of grazing on arid rangelands. 减少放牧并非能重回顶级状态，而大量的放牧压力不会导致“退 化”。在干旱草场，气候、天气的影响比放牧重要 “degraded”“pristine” grazing animal herbivory plant community response weather and climate: wetter, predictable? ecological site: soils, slope, aspect, etc. plant community grazing animal weather and climate: arid, unpredictable? ecological site: soils, slope, aspect, etc. plant community no stabilizing feedbacks, uncoupled system problems with the model: it is not a good fit 模型的问题：不匹配 change can be set off on different trajectories by disturbance, weather conditions, seed availability, etc. and this change may not be reversible, and may lead to an alternate stable state of vegetation. 干扰、天气、种子的利用性等多种因素使变化进入不同的轨道 abiotic factors may be major drivers of system change.非生物 因素也许是系统变化的主因 includes a value judgment: the end state (climax) is “good”, everything else is not so good.包含价值评估：顶级的终点号 ，而其它都不好？ non-climax states have their own set of values for biodiversity, aesthetics, carbon, etc. 非顶级状态都有自己的生物多样性、美 观、碳汇等价值 building a better model. 建立更好的的模型 non-equilibrium theory seeks to explain: 非平衡理论论解读读 biotic interactions may not be the major driver 生 物的相互作用并非主要的驱动因素 multiple possible stable states, not just one climax (clements, etc) 有多重的状态，并非只有一个顶级状态 disturbance, such as grazing and fire, may have a positive role in ecosystems 干扰、包括放牧、燃烧等对生态 系统具有积极作用 management outcomes are not very predictable 管理结果很难预测 non-equilibrium dynamics 非平衡动态 there are many possible “stable” stages of vegetation for a given ecological site. 在摸个生态系统中有多个植被稳定状态 the primary driver of vegetation change is abiotic factors.植被变化主因是非生物因素： not manageable 难以管理 not responsive to grazing 与放牧并非相应的 unpredictable (e.g. rainfall) 难以预测 management must be for uncertainty. a fixed “carrying capacity” cannot be set. 管理必须基于不确定性：很难建立固定的承载率 management model: states and transitions 管理模型：状态-过渡模型 identify an “ecological site”: environmental conditions define a sitesoils, climate, site history. 识别一个生态 系统点：环境特征定义一个点土壤、气候、该点的 历史 identify possible vegetation states 识别可能的植被状态 identify the transitions among states 识别不同状态之 间的过渡 what causes a particular transition? what led to a particular state? 那些因素导致过渡？什么导致特定的 状态 states and transition models must be for specific “ecological sites” based on abiotic factors 状态-过渡模型必须在特定生态系统点，基于 非生物的因素 soils 土壤 climate 气候 aspect, topography 方向、地貌 state and transition models 状态-过渡模型 1. “states”: relatively“states”: relatively stable stable ecosystemecosystem within within temporal temporal scale scale of of interest interest “ “状态状态” ”：在指定：在指定 的时间尺度上的相对稳定的系统的时间尺度上的相对稳定的系统 2. “transitions”: changes 2. “transitions”: changes among among states withinstates within spatial spatial and temporaland temporal scale scale of of interest interest “ “过渡过渡 ” ”：在指定的时空尺度，不同状态的变化：在指定的时空尺度，不同状态的变化 s1s1s2s2 t1 t2 westoby et al. 1989 1 ecological site, 3 states state 1 state 2 s1 s2 why are states stable? 为什么状态是稳定的？ ball and cup diagram for states and transitions transitions threshold (need to cross it for a state change) t1: long drought t2: human action t 1 t 2 states and transition models 状态-过渡模型 based on data, not assumptions 基于数据而不是设想 can incorporate both equilibrium and non-equilibrium dynamics 可以包含平衡与非平衡动态 can be changed as we learn more 随着学习可以变动 states and transitions are site specific 状态-过渡是基于个体案例地 vetter 2005: the debate between equilibrium vs non-equilibrium 平衡与非平衡之间的争议 most arid and semi-arid rangeland systems have both equilibrium and non-equilibrium dynamics depending on scale and site. 基于不同的尺度和案例地， 干旱半干旱草场系统有平衡与非平衡两者的动态 coefficient of variation in rainfall greater than approximately 30% = mostly non-equilibrium, arid lands 降雨量的差异系数大于30%= 大部分是非平衡、干旱 区 coefficient of variation in precipitation 降水量的差异系数 (von wehrden et al. 2012) implications for development policy 发展政策的含义 old: four principles of rangeland development 草场管理的四个原则 professional experts should be in charge, need “scientific” management-locals know nothing, they are backward 专家领导管理，需要“科学性”的管理 而当地人无知、落后 technology is the way to solve problems 技术是解决 问题的方法 goal for rangelands is to maximize livestock production at a sustainable carrying capacity草场管 理的目标是基于可持续承载率，畜牧业生产加大化 comprehensive rational planning is key-locals are self-interested and short-sighted 综合理性的规划 是关键当地人目光短浅、自利 four principles for non-equilibrium systems 非平衡系统的四个原则 local knowledge is site specific and important: culture incorporates long term learning a